BEGIN:VCALENDAR
VERSION:2.0
PRODID:researchseminars.org
CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Tomas Roubicek (Math. Inst. Charles University)
DTSTART;VALUE=DATE-TIME:20201012T134000Z
DTEND;VALUE=DATE-TIME:20201012T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/1
DESCRIPTION:Title: The
old Stefan problem in a new mechanical context\nby Tomas Roubicek (Ma
th. Inst. Charles University) as part of Nečas Seminar on Continuum Mecha
nics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Doskar (Czech Technical University)
DTSTART;VALUE=DATE-TIME:20201019T134000Z
DTEND;VALUE=DATE-TIME:20201019T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/2
DESCRIPTION:Title: Mic
romorphic model for mechanical metamaterials\nby Martin Doskar (Czech
Technical University) as part of Nečas Seminar on Continuum Mechanics\n\n
\nAbstract\nMetamaterials\, with their internal composition carefully desi
gned to feature exotic and often counterintuitive properties such as cloak
ing or band gaps\, are the prime example of a pronounced influence of mate
rial’s microstructure on its macroscopic response. Regarding mechanical
responses\, metamaterials have already delivered high stiffness-to-weight
ratio\, negative compressibility\, and tunable auxetic behaviour. These me
chanical metamaterials often rely on internal instability mechanisms that
trigger transformation of their periodic microstructure into predefined pa
tterns\, which introduces strong kinematic coupling among adjacent periodi
c metamaterial cells and leads to significant size and boundary effects. A
s a result\, the standard first-order computational homogenization fails t
o provide an effective model of such metamaterials.\n\nThis talk presents
a micromorphic computational homogenization scheme that has been recently
developed specifically for the instability-driven mechanical metamaterials
. The scheme introduces characteristic deformation patterns at microscale\
, whose magnitudes are communicated across adjacent macroscopic material p
oints by scalar modulation fields\, which are added to the standard contin
uum formulation at the macroscale and for which an additional micromorphic
-like conservation law emerges at macroscale. Consequently\, the presented
scheme captures the above-mentioned size effect and boundary layers and a
ccounts for with spatial mixing of multiple patterns. Combined with the bi
furcation analysis\, the scheme also correctly predicts local to global (i
.e. micro vs. macro) buckling transitions.\n
LOCATION:https://researchseminars.org/talk/NSCM/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Edoardo Mainini (University of Genoa)
DTSTART;VALUE=DATE-TIME:20201026T144000Z
DTEND;VALUE=DATE-TIME:20201026T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/3
DESCRIPTION:Title: Lin
earization of finite elasticity\nby Edoardo Mainini (University of Gen
oa) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nWe sho
w some new results about the linearization of finite elasticity by means o
f Gamma-convergence\, including the incompressible case and pure traction
problems.\n
LOCATION:https://researchseminars.org/talk/NSCM/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Bresciani (TU Vienna)
DTSTART;VALUE=DATE-TIME:20201102T144000Z
DTEND;VALUE=DATE-TIME:20201102T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/4
DESCRIPTION:Title: Lin
earized von Kármán theory for incompressible magnetoelastic plates\n
by Marco Bresciani (TU Vienna) as part of Nečas Seminar on Continuum Mech
anics\n\n\nAbstract\nWe study the asymptotic behavior\, in the sense of Ga
mma-convergence\, of a thin incompressible magnetoelastic plate\, as its t
hickness goes to zero. We focus on the linearized von Kármán regime. The
model features a mixed Eulerian-Lagrangian formulation\, as magnetization
s are defined on the deformed configuration.\n
LOCATION:https://researchseminars.org/talk/NSCM/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daya Reddy (University of Cape Town)
DTSTART;VALUE=DATE-TIME:20201221T144000Z
DTEND;VALUE=DATE-TIME:20201221T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/5
DESCRIPTION:Title: Som
e mathematical aspects of models of strain-gradient plasticity\nby Day
a Reddy (University of Cape Town) as part of Nečas Seminar on Continuum
Mechanics\n\n\nAbstract\nStrain-gradient plasticity has become well establ
ished as an approach to modelling seize-dependent phenomena at the meso- a
nd microscales. This presentation is concerned with a class of models of s
train-gradient plasticity\, which mathematically are formulated as variati
onal inequalities. Conditions for well-posedness are reviewed\, following
which attention is given to some aspects of what is referred to as the dis
sipative model. Though in a sense a natural extension of conventional plas
ticity\, this model possesses some distinctive features\, most particularl
y that the plastic flow relations take a global form. The consequences of
this feature are discussed\, for example\, in relation to determining the
stage at which incipient plastic behaviour takes place. The presentation a
lso treats issues relevant to approximations\, such as the convergence of
predictor-corrector algorithms\, and approximations under conditions of mi
nimal regularity.\n
LOCATION:https://researchseminars.org/talk/NSCM/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Bravin (BCAM Bilbao)
DTSTART;VALUE=DATE-TIME:20201109T144000Z
DTEND;VALUE=DATE-TIME:20201109T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/6
DESCRIPTION:Title: On
some properties for an incompressible\, non-viscous in-out flow in a 2D do
main\nby Marco Bravin (BCAM Bilbao) as part of Nečas Seminar on Conti
nuum Mechanics\n\n\nAbstract\nIn this talk I will present some recent resu
lts on some properties of an in-out flow\nassociated with a perfect two di
mensional fluid. In particular I present existence of\nsolutions in differ
ent classes of regularity and I will conclude with the study of the\nasymp
totic limit of some shrinking sources and sinks. This work is motivated by
a\nquestion left open by Judovic in [2].\nThe system consists of an Euler
type system in a bounded domain with some holes\nwhere non-homogeneous bo
undary conditions are prescribed. I will present how to extend some classi
cal existence results in this setting and then I will consider the case\nw
hen the holes shrink to points. The boundary conditions lead to the creati
on of some\npoint sources and sinks associated with some vortex points in
the limit. Similar type of\nsystems have been already study by Chemetov an
d Starovoitov in [1]\, where a different\napproximation approach was consi
dered.\n\nReferences\n\n[1] Chemetov\, N. V.\, Starovoitov\, V. N. (2002).
On a Motion of a Perfect Fluid in a Domain with Sources and Sinks. Journa
l of Mathematical Fluid Mechanics\, 4(2)\, 128–144.\n\n[2] Judovic\, V.
I. (1964). A two-dimensional non-stationary problem on the flow of an\nide
al incompressible fluid through a given region. (Russian) Mat. Sb. (N.S.)
64 (106)\n562–588\n
LOCATION:https://researchseminars.org/talk/NSCM/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jacopo Ciambella (Sapienza Università di Roma)
DTSTART;VALUE=DATE-TIME:20201116T144000Z
DTEND;VALUE=DATE-TIME:20201116T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/7
DESCRIPTION:Title: Fib
re re-orientation in anisotropic viscoelastic materials\nby Jacopo Cia
mbella (Sapienza Università di Roma) as part of Nečas Seminar on Continu
um Mechanics\n\n\nAbstract\nIn this talk\, we will derive a nonlinear visc
oelastic model for fibre-reinforced materials based on the kinematic assum
ption that the deformation gradient can be multiplicatively decomposed int
o viscous and elastic components\, i.e.\, F=Fe Fv. The model is thermodyna
mically consistent and the evolution equation of the viscous deformation w
ill be derived by combining suitable constitutive prescriptions with balan
ce equations. We will show that\, when external sources are absent\, an Es
helbian-like torque drives the passive reorientation of the fibres. During
the talk\, some issues underlying the definition of anisotropic and inela
stic models will be discussed\, including the evolution of the symmetry gr
oup of the material response due to the inelastic relaxation. Finally\, so
me prototype boundary value problems will be presented with the intent of
highlighting the best experimental procedure to evaluate the constitutive
coefficients of such a model.\n
LOCATION:https://researchseminars.org/talk/NSCM/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giuseppe Tomassetti (Università Roma Tre)
DTSTART;VALUE=DATE-TIME:20201130T144000Z
DTEND;VALUE=DATE-TIME:20201130T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/8
DESCRIPTION:Title: Sha
pe programming of a magnetic elastica\nby Giuseppe Tomassetti (U
niversità Roma Tre) as part of Nečas Seminar on Continuum Mechanics\n\n
\nAbstract\nWe consider a cantilever beam which possesses a possibly non-u
niform permanent magnetization\, and whose shape is controlled by an appli
ed magnetic field. We model the beam as a plane elastic curve and we suppo
se that the magnetic field acts upon the beam by means of a distributed co
uple that pulls the magnetization towards its direction. Given a list of t
arget shapes\, we look for a design of the magnetization profile and for a
list of controls such that the shapes assumed by the beam when acted upon
by the controls are as close as possible to the targets\, in an averaged
sense. To this effect\, we formulate and solve an optimal design and contr
ol problem leading to the minimization of a functional which we study by b
oth direct and indirect methods. In particular\, we prove that minimizers
exist\, solve the associated Lagrange-multiplier formulation (besides non-
generic cases)\, and are unique at least for sufficiently low intensities
of the controlling magnetic fields. To achieve the latter result\, we use
two nested fixed-point arguments relying on the Lagrange-multiplier formul
ation of the problem\, a method which also suggests a numerical scheme. Va
rious relevant open question are also discussed.\n
LOCATION:https://researchseminars.org/talk/NSCM/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charlotte Perrin (CNRS Marseille)
DTSTART;VALUE=DATE-TIME:20201123T144000Z
DTEND;VALUE=DATE-TIME:20201123T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/9
DESCRIPTION:Title: Com
pressible Euler equations under a maximal density constraint\nby Charl
otte Perrin (CNRS Marseille) as part of Nečas Seminar on Continuum Mechan
ics\n\n\nAbstract\nIn this talk\, I will present recent results on solutio
ns to a one-dimensional Euler system coupling compressible and incompressi
ble phases. With this original fluid system we intend to model congestion
(or saturation) phenomena in heterogeneous flows (mixtures\, wave-structur
e interactions\, collective motion\, etc.). Here the compressible-incompre
ssible model will be seen as the limit of a fully compressible Euler syste
m endowed with a singular pressure law. The goal of the talk is to present
theoretical results concerning this singular limit. This is a joint work
with Roberta Bianchini.\n
LOCATION:https://researchseminars.org/talk/NSCM/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tai-Peng Tsai (University of British Columbia)
DTSTART;VALUE=DATE-TIME:20201214T153000Z
DTEND;VALUE=DATE-TIME:20201214T170000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/10
DESCRIPTION:Title: Th
e Green tensor of the nonstationary Stokes system in the half space\nb
y Tai-Peng Tsai (University of British Columbia) as part of Nečas Seminar
on Continuum Mechanics\n\n\nAbstract\nWe prove the first-ever pointwise e
stimates of the (unrestricted) Green tensor and\nthe associated pressure t
ensor of the nonstationary Stokes system in the half-space\, for\nevery sp
ace dimension greater than one. The force field is not necessarily assumed
to\nbe solenoidal. The key is to find a suitable Green tensor formula tha
t maximizes the\ntangential decay\, showing in particular the integrabilit
y of Green tensor derivatives.\nWith its pointwise estimates\, we show the
symmetry of the Green tensor\, which in\nturn improves pointwise estimate
s. We also study how the solutions converge to the\ninitial data\, and the
(infinitely many) restricted Green tensors acting on solenoidal\nvector f
ields. As applications\, we give new proofs of the existence of mild solut
ions of the\nNavier-Stokes equations in Lq\, pointwise decay\, and uniform
ly local Lq spaces in the\nhalf-space.\nThis talk is based on arXiv:2011.0
0134\, a joint work with Kyungkeun Kang\, Baishun\nLai and Chen-Chih Lai.\
n\nThis seminar session will exceptionally start at 16:30.\n
LOCATION:https://researchseminars.org/talk/NSCM/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Arnab Roy (Math. Inst. Czech Academy of Sciences)
DTSTART;VALUE=DATE-TIME:20201207T144000Z
DTEND;VALUE=DATE-TIME:20201207T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/11
DESCRIPTION:Title: Ex
istence of strong solutions for a system of interaction between a compress
ible viscous fluid and a wave equation\nby Arnab Roy (Math. Inst. Czec
h Academy of Sciences) as part of Nečas Seminar on Continuum Mechanics\n\
n\nAbstract\nIn this talk\, we consider a fluid-structure interaction syst
em\nwhere the fluid is viscous and compressible and where the structure i
s\na part of the boundary of the fluid domain and is deformable. The flui
d\nis governed by the barotropic compressible Navier-Stokes system whereas
\nthe structure displacement is described by a wave equation. The\nreferen
ce configuration for the fluid domain is a rectangular cuboid\nwith the el
astic structure being the top face. We use a modified\nLagrangian change o
f variables to transform the moving fluid domain into\nthe rectangular cub
oid and then analyze the corresponding linear system\ncoupling a transport
equation (for the density)\, a heat-type equation\nand a wave equation. T
he corresponding results for this linear system\nand estimations of the co
efficients coming from the change of variables\nallow us to perform a fixe
d point argument and to prove the existence\nand uniqueness of strong solu
tions for the nonlinear system\, locally in\ntime.\n
LOCATION:https://researchseminars.org/talk/NSCM/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Karoline Disser (Universitaet Kassel)
DTSTART;VALUE=DATE-TIME:20210104T144000Z
DTEND;VALUE=DATE-TIME:20210104T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/12
DESCRIPTION:Title: Gl
obal existence and stability for dissipative processes coupled acro
ss volume and surface\nby Karoline Disser (Universitaet Kassel) as pa
rt of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nThe modelling o
f technological and biological processes and devices is\noften characteriz
ed by non-smoothness: material edges and corners\,\nabruptly changing mate
rial properties and a large scope of relevant\ntemporal and spatial scales
. From a PDE point-of-view\, we need to deal\nwith domains of low boundary
regularity\, mixed and dynamic boundary\nconditions\, degeneracy and disc
ontinuity of parameters\, and\, possibly\nafter rescaling\, with the coupl
ing of dynamics across voulme and\nlower-dimensional interfaces or surface
s.\n\nIn this talk\, I want to consider models of non-linear\nreaction-dri
ft-diffusion type in non-smooth and/or volume-surface\nsettings and discus
s their analysis based on the choice of specific\nfunctional analytic sett
ings. The aim is to discuss some aspects of the\ninteraction of thermodyna
mically consistent modelling and the analysis\nof the PDE and to establish
strategies for simultaneously dealing with\nnon-linearity and non-smoothn
ess.\n
LOCATION:https://researchseminars.org/talk/NSCM/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210111T144000Z
DTEND;VALUE=DATE-TIME:20210111T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/13
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210118T144000Z
DTEND;VALUE=DATE-TIME:20210118T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/14
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210125T144000Z
DTEND;VALUE=DATE-TIME:20210125T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/15
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210201T144000Z
DTEND;VALUE=DATE-TIME:20210201T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/16
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/16/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210208T144000Z
DTEND;VALUE=DATE-TIME:20210208T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/17
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/17/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210215T144000Z
DTEND;VALUE=DATE-TIME:20210215T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/18
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/18/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20210222T144000Z
DTEND;VALUE=DATE-TIME:20210222T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/19
DESCRIPTION:Title: No
lecture\nby semester break as part of Nečas Seminar on Continuum Mec
hanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/19/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Easter Monday
DTSTART;VALUE=DATE-TIME:20210405T134000Z
DTEND;VALUE=DATE-TIME:20210405T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/20
DESCRIPTION:Title: No
lecture\nby Easter Monday as part of Nečas Seminar on Continuum Mech
anics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/20/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jiří Outrata (ÚTIA\, Czech Acad. Sci.)
DTSTART;VALUE=DATE-TIME:20210301T144000Z
DTEND;VALUE=DATE-TIME:20210301T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/21
DESCRIPTION:Title: On
the solution of static contact problems with Coulomb friction via the sem
ismooth* Newton method\nby Jiří Outrata (ÚTIA\, Czech Acad. Sci.)
as part of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nThe lectur
e deals with application of a new Newton-type method to the numerical solu
tion of discrete 3D contact problems\nwith Coulomb friction. This method s
uits well to the solution of inclusions and the resulting conceptual algor
ithm exhibits\,\nunder appropriate conditions\, the local superlinear conv
ergence. After a description of the method a new (primal) model\nfor the c
onsidered contact problem\, amenable to the application of the new method\
, will be presented. The second part of\nthe talk is then devoted to an ef
ficient implementation of the general algorithm and to numerical tests. Th
roughout the whole\nlecture\, various tools of modern variational analysis
will be employed.\n
LOCATION:https://researchseminars.org/talk/NSCM/21/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Malte Kampschulte (Charles University)
DTSTART;VALUE=DATE-TIME:20210322T144000Z
DTEND;VALUE=DATE-TIME:20210322T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/22
DESCRIPTION:Title: Mi
nimizing movements and a two-scale method for nonconvex problems involving
inertia\nby Malte Kampschulte (Charles University) as part of Nečas
Seminar on Continuum Mechanics\n\n\nAbstract\nWhen dealing with fully nonl
inear\, nonconvex\, quasistatic (i.e. inertialess) problems in continuum m
echanics\, de Giorgi's method of minimizing movements has long been a stap
le for existence proofs. However by its very nature\, it has always been r
estricted to purely dissipative\, gradient flow-type systems. The aim of t
his talk is to present a new two-scale method\, developed jointly with B.
Benešová and S. Schwarzacher\, which allows to add inertial\, conservati
ve effects by using the minimizing movements method as a stepping stone to
solve an approximative time-delayed problem in the same nonlinear\, nonco
nvex state space. Using a flow-map approach\, this method is not only able
to cope with problems in Lagrangian\, but also with those in Eulerian and
even mixed formulations. While the method itself is quite general\, we wi
ll illustrate its application at several examples involving solids\, fluid
s and their interaction.\n
LOCATION:https://researchseminars.org/talk/NSCM/22/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eitan Tadmor (University of Maryland\, College Park)
DTSTART;VALUE=DATE-TIME:20210329T134000Z
DTEND;VALUE=DATE-TIME:20210329T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/23
DESCRIPTION:Title: Em
ergent behavior in swarming hydrodynamics\nby Eitan Tadmor (University
of Maryland\, College Park) as part of Nečas Seminar on Continuum Mechan
ics\n\n\nAbstract\nI will discuss recent developments in our study of swar
ming \ndynamics.\nA main question of interest is the emergent behavior whi
ch we \ncharacterize by\nspectral analysis\, covering different classes of
long-range and \nshort-range communication kernels.\nThese include examp
les of metric-based and topologically-based kernels\, \nand kernels derive
d from a unified paradigm of anticipation.\nIn the canonical case of metri
c-based short-range kernels\, we derive \nlower-bounds on the spectral gap
\,\nindependent of thermal equilibrium (no closure for the pressure)\, whi
ch \nyield an emergent behavior of non-vacuous smooth solutions.\nThe latt
er are known to exist in one- and two space dimensions and we \nsettle th
e question of existence for arbitrary dimension.\n
LOCATION:https://researchseminars.org/talk/NSCM/23/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Antonio J. Gil (University of Swansea\, UK)
DTSTART;VALUE=DATE-TIME:20210308T144000Z
DTEND;VALUE=DATE-TIME:20210308T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/24
DESCRIPTION:Title: On
the use of mixed formulations for computational polyconvexity and multi
-variable convexity\nby Antonio J. Gil (University of Swansea\, UK) as
part of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nThe computat
ional modelling of large strain multi-physics problems is nowadays an area
of intensive research by numerous scientists. Among problems of this kind
\, two pressing applications underpin the motivation behind this presentat
ion. On the one hand\, the in-silico design of highly flexible dielectric
elastomers for soft robotics applications and\, on the other hand\, the re
alistic simulation of the electromechanical interactions of the cardiac mu
scle from the physiological and pathological standpoints. In both applicat
ions\, the requirement for extremely accurate and stable results at\, poss
ibly\, large values of the field variables (i.e. strains and electric/card
iac potential) proves very challenging from the computational point of vie
w.\nThe presentation starts by revisiting the now well-accepted requiremen
t of polyconvexity (a sufficient condition for rank-one convexity) in the
case of reversible hyperelasticity\, where the strain energy functional is
described by a convex combination of the minors of the deformation gradie
nt tensor. We then extend this concept to the case of energies which depen
d on non-strain based variables\, for instance\, other physical measures s
uch as the electric displacement\, leading to the introduction of a new co
mputational paradigm\, Multi-Variable Convexity. Crucially\, this new defi
nition of the internal energy enables ellipticity to be extended to the en
tire range of deformations and electric fields and\, thus\, spurious numer
ical instabilities can then effectively be removed from the model whilst m
aintaining real physical instabilities.\nThe polyconvexity of the energy f
unctional with respect to its set of arguments guarantees the definition o
f well-posed counterpart work conjugates\, where a one to one (invertible)
relationship can be established. This ensures the existence of alternativ
e energy potentials via the use of partial or total Legendre transforms an
d opens up the possibility for new extended Hu–Washizu-type variational
principles in terms of using various interpolation spaces for the differen
t unknown fields\, leading to enhanced type of formulations. A series of e
xamples will be presented demonstrating the potential of this new paradigm
when coupled with the use of Finite Element type discretisation technique
s.\n
LOCATION:https://researchseminars.org/talk/NSCM/24/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Adrian Muntean (Karlstadt University)
DTSTART;VALUE=DATE-TIME:20210426T134000Z
DTEND;VALUE=DATE-TIME:20210426T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/25
DESCRIPTION:Title: Do
es vesicle micro-dynamics enhance the signaling among plants macro-transpo
rt? Multiscale discussions around a model problem\nby Adrian Muntean (
Karlstadt University) as part of Nečas Seminar on Continuum Mechanics\n\n
\nAbstract\nWe study a transport problem for signaling among plants in the
context of measure-valued equations. We report on preliminary results con
cerning the modeling and mathematical analysis of a reaction-diffusion sce
nario involving the macroscopic diffusion of signaling molecules enhanced
by the presence of a finite number of microscopic vesicles - pockets with
own dynamics able to capture and release signals as a relay system. The c
oupling between the macroscopic and microscopic spatial scales relies on t
he use of a two-scale transmission condition and benefits of the posing of
the problem in terms of measures. Mild solutions to our problem will turn
to exist and will also be positive weak solutions. A couple of open quest
ions at the modeling\, mathematical analysis\, and simulation levels will
be pointed out. This is a joint work with Sander Hille (Leiden\, NL) and i
s supported financially by the KVA’s G. S. Magnussonsfond.\n
LOCATION:https://researchseminars.org/talk/NSCM/25/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valerio Pagliari (TU Vienna)
DTSTART;VALUE=DATE-TIME:20210412T134000Z
DTEND;VALUE=DATE-TIME:20210412T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/26
DESCRIPTION:Title: Co
nvergence of nonlocal geometric flows to anisotropic mean curvature motion
\nby Valerio Pagliari (TU Vienna) as part of Nečas Seminar on Continu
um Mechanics\n\n\nAbstract\nWe consider the Cauchy problem for motions by
nonlocal curvature\, whose \nwell-posedness may be established in the fram
ework of viscosity solutions.\nWe show that a suitable rescaling of the no
nlocal curvature induces a \nlocalisation effect\, that is\, as the scalin
g parameter tends to 0\,\nwe retrieve an anisotropic mean curvature functi
onal. From this fact\, \nthanks to the theory of geometric barriers by De
Giorgi\,\nwe prove that the solutions to the rescaled nonlocal motions loc
ally \nuniformly converge to the solution of the local flow.\nThe talk is
based on joint work with A. Cesaroni (Padova).\n
LOCATION:https://researchseminars.org/talk/NSCM/26/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Denis Bonheure (Université Libre de Bruxelles)
DTSTART;VALUE=DATE-TIME:20210510T134000Z
DTEND;VALUE=DATE-TIME:20210510T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/27
DESCRIPTION:Title: Eq
uilibrium configuration of a rectangular obstacle immersed in a channel fl
ow\nby Denis Bonheure (Université Libre de Bruxelles) as part of N
ečas Seminar on Continuum Mechanics\n\n\nAbstract\nFluid flows around an
obstacle generate vortices which\, in turn\, generate lift forces on the o
bstacle. Therefore\, even in a perfectly symmetric framework equilibrium p
ositions may be asymmetric. We show that this is not the case for a Poiseu
ille flow in an unbounded 2D channel\, at least for small Reynolds number
and flow rate. We consider both the cases of vertically moving obstacles a
nd obstacles rotating around a fixed pin.\nJoint work with P.G. Galdi and
F. Gazzola\n
LOCATION:https://researchseminars.org/talk/NSCM/27/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Maria Neuss-Radu (University of Erlangen-Nuremberg)
DTSTART;VALUE=DATE-TIME:20210524T134000Z
DTEND;VALUE=DATE-TIME:20210524T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/28
DESCRIPTION:Title: Ho
mogenization of a reaction-diffusion-advection problem in an evolving mic
ro-domain and including nonlinear boundary conditions\nby Maria Neuss-
Radu (University of Erlangen-Nuremberg) as part of Nečas Seminar on Conti
nuum Mechanics\n\n\nAbstract\nWe consider a reaction-diffusion-advection p
roblem in a \nperforated medium\, with nonlinear reactions in the bulk and
at the \nmicroscopic boundary\, and slow diffusion scaling. The microstru
cture \nchanges in time\; the microstructural evolution is known a priori.
The \naim of the paper is the rigorous derivation of a homogenized model.
We \nuse appropriately scaled function spaces\, which allow us to show \n
compactness results\, especially regarding the time-derivative and we \npr
ove strong two-scale compactness results of Kolmogorov-Simon-type\, \nwhic
h allow to pass to the limit in the nonlinear terms. The derived \nmacrosc
opic model depends on the micro- and the macro-variable\, and the \nevolut
ion of the underlying microstructure is approximated by time- and \nspace-
dependent reference elements. This is a joint work with Markus \nGahn (Uni
versity of Heidelberg) and Iuliu Sorin Pop (Hasselt \nUniversity).\n
LOCATION:https://researchseminars.org/talk/NSCM/28/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Patrick Dondl (University of Freiburg)
DTSTART;VALUE=DATE-TIME:20210315T144000Z
DTEND;VALUE=DATE-TIME:20210315T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/29
DESCRIPTION:Title: En
ergetic bounds for paperboard delamination under bending\nby Patrick D
ondl (University of Freiburg) as part of Nečas Seminar on Continuum Mecha
nics\n\n\nAbstract\nPaperboard is an engineering material consisting of a
number of separate sheets of paper\, that have been bonded together. Exper
imental evidence shows that paperboard undergoing bending develops phenome
nologically plastic hinges. We consider a nonlinearly elastic mathematical
model for paperboard\, allowing debonding of the sheets at a given cost p
er unit area. Analysis of our model predicts a number of different regimes
\, including somewhere bending is concentrated in delaminated hinges\, whe
re the mid-plane of each individual layer may deform isometrically. This i
s joint work with Sergio Conti (Bonn) and Julia Orlik (Kaiserslautern).\n
LOCATION:https://researchseminars.org/talk/NSCM/29/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Summer break
DTSTART;VALUE=DATE-TIME:20210607T134000Z
DTEND;VALUE=DATE-TIME:20210607T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/30
DESCRIPTION:Title: We
'll meet again in October 2021\nby Summer break as part of Nečas Semi
nar on Continuum Mechanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/30/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Březina (TU Liberec)
DTSTART;VALUE=DATE-TIME:20210503T134000Z
DTEND;VALUE=DATE-TIME:20210503T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/31
DESCRIPTION:Title: Co
ntinuum-fracture approach to modelling crystalline rock\nby Jan Březi
na (TU Liberec) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbst
ract\nWe start with a statistical description of the fracture networks in
real (crystalline) rocks and related heterogeneous material properties. Ne
xt\, we shall present continuum-fracture (CF) approach to the description
of the processes in real rock. CF description has been consistently applie
d in the Flow123d simulator of THMC proceses. We will summarize simulated
processes\, numerical schemes\, and software tools. Finally\, we present p
articular applications in the safety of deep nuclear waste repositories an
d the efficiency of enhanced geothermal systems.\n
LOCATION:https://researchseminars.org/talk/NSCM/31/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Stebel (TU Liberec)
DTSTART;VALUE=DATE-TIME:20210517T134000Z
DTEND;VALUE=DATE-TIME:20210517T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/32
DESCRIPTION:Title: Co
ntinuum-fracture models of porous media processes: derivation and analysis
\nby Jan Stebel (TU Liberec) as part of Nečas Seminar on Continuum Me
chanics\n\n\nAbstract\nMathematical modelling of heterogeneous materials s
uch as granitic rocks requires special treatment of fractures. We present
the derivation of the so-called continuum-fracture model for two types of
problems: advection-diffusion process (e.g. transport of contaminants or h
eat) and hydro-mechanical coupling based on Biot’s theory. For the hydro
-mechanical problem we distinguish the linear case and the case of contact
and shear-dilation conditions at fractures. Existence of weak solutions
is established. The problem is discretized by the finite element method an
d solved using the so-called fixed-stress iterative splitting whose conver
gence is analyzed.\n
LOCATION:https://researchseminars.org/talk/NSCM/32/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Milan Pokorný (Mathematical Institute\, Charles Universiy)
DTSTART;VALUE=DATE-TIME:20210531T134000Z
DTEND;VALUE=DATE-TIME:20210531T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/33
DESCRIPTION:Title: Ho
mogenization of Navier--Stokes--Fourier system in domains with tiny holes<
/a>\nby Milan Pokorný (Mathematical Institute\, Charles Universiy) as par
t of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nWe consider the
compressible Navier--Stokes--Fourier system in a domain with large number
of holes. Under the assumption that the holes are sufficiently small\, tog
ether with certain standard assumptions on the adiabatic exponent and the
behaviour of the heat conductivity\, we show that if passing simultaneousl
y with the number of holes to infinity and their size to zero\, in the lim
it we obtain again solution to the compressible Navier--Stokes--Fourier sy
stem in the domain without holes. The result holds both for the steady and
evolutionary problem. It is a joint work with Yong Lu (Nanjing University
) and Emil Skříšovský (Charles University\, Prague).\n
LOCATION:https://researchseminars.org/talk/NSCM/33/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuel Friedrich (University of Muenster)
DTSTART;VALUE=DATE-TIME:20210419T134000Z
DTEND;VALUE=DATE-TIME:20210419T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/34
DESCRIPTION:Title: Em
ergence of rigid polycrystals from atomistic systems\nby Manuel Friedr
ich (University of Muenster) as part of Nečas Seminar on Continuum Mechan
ics\n\n\nAbstract\nWe investigate the emergence of rigid polycrystalline s
tructures from atomistic particle systems. The atomic interaction is gover
ned by a suitably normalized pair interaction energy\, where the `sticky d
isk’ interaction potential models the atoms as hard spheres that interac
t when they are tangential. The discrete energy is frame invariant and no
underlying reference lattice on the atomistic configurations is assumed. B
y means of Gamma-convergence\, we characterize the asymptotic behavior of
configurations with finite surface energy scaling in the infinite particle
limit. The effective continuum theory is described in terms of a piecewis
e constant field delineating the local orientation and micro-translation o
f the configuration. The limiting energy is local and concentrated on the
grain boundaries\, i.e.\, on the boundaries of the zones where the underly
ing microscopic configuration has constant parameters. The corresponding s
urface energy density depends on the relative orientation of the two grain
s\, their microscopic translation misfit\, and the normal to the interface
. Joint work with Leonard Kreutz (Münster) and Bernd Schmidt (Augsburg).\
n
LOCATION:https://researchseminars.org/talk/NSCM/34/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Zeman (Faculty of Civil Engineering\, Czech Tech. Uni.)
DTSTART;VALUE=DATE-TIME:20211004T134000Z
DTEND;VALUE=DATE-TIME:20211004T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/35
DESCRIPTION:Title: De
signing optimal reinforcement for high-performance composite tubes with se
midefinite programming\nby Jan Zeman (Faculty of Civil Engineering\, C
zech Tech. Uni.) as part of Nečas Seminar on Continuum Mechanics\n\nLectu
re held in K3 Karlin.\n\nAbstract\nFueled by their excellent stiffness-to-
weight ratio and the availability of mature manufacturing technologies\, f
ilament wound carbon fiber reinforced polymers represent ideal materials f
or thin-walled laminate structures. However\, their strong anisotropy redu
ces structural resistance to wall instabilities under shear and buckling.
Increasing laminate thickness degrades weight and structural efficiencies
and the application of a dense internal core is often uneconomical and lab
or-intensive. In this contribution\, we introduce a convex linear semidefi
nite programming formulation for truss topology optimization to design an
efficient non-uniform lattice-like internal structure. The internal struct
ure not only reduces the effect of wall instabilities\, mirrored in the in
crease of the fundamental free-vibration eigenfrequency\, but also keeps w
eight low\, secures manufacturability using conventional three-dimensional
printers\, and withstands the loads induced during the production process
. We showcase a fully automatic procedure in detail for the design\, proto
type manufacturing\, and verification of a simply-supported composite mach
ine tool component\, including validation with roving hammer tests. The re
sults confirm that the 3D-printed optimized internal structure almost doub
les the fundamental free-vibration eigenfrequency\, allowing to increase t
he working frequency of the machine tool\, even though the ratio between e
lastic properties of the carbon composite and the ABS polymer used for 3D
printing exceeds two orders of magnitude.\n
LOCATION:https://researchseminars.org/talk/NSCM/35/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hanuš Seiner (Inst. of Thermomechanics\, CAS)
DTSTART;VALUE=DATE-TIME:20211018T134000Z
DTEND;VALUE=DATE-TIME:20211018T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/36
DESCRIPTION:Title: La
ndau-energy landscape reconstruction for a Ni-Fe-Ga(Co) Shape Memory Alloy
\nby Hanuš Seiner (Inst. of Thermomechanics\, CAS) as part of Nečas
Seminar on Continuum Mechanics\n\n\nAbstract\nIn the framework of continuu
m mechanics\, the thermo-mechanical behavior of shape memory alloys is oft
en described using the Landau-theory approach\, where the multi-well free
energy density of the crystal is approximated by a polynomial with the req
uired number of minima and energy barriers. Here we show how the energy la
ndscape (in the strain-temperature space) can be reconstructed from experi
ments\, and how accurately this energy is approximated by the Landau-theor
y ansatz. Elastic behavior of single crystals of Ni-Fe-Ga(Co) ferromagneti
c shape memory alloys is studied in a broad temperature range. Using tensi
le stress-strain measurements and ultrasonic characterization\, we prove t
hat austenite and martensite phases of the given alloy exhibit strongly no
n-linear elastic responses\, and we utilize the non-linear stress-strain d
ata for constructing an energy function describing the observed behavior i
n the context of the Landau theory. We discuss the implications of the con
structed model\, focusing in particular to the so-called critical point in
the energy landscape\, where the austenite-martensite transition becomes
weakly second-order.\n
LOCATION:https://researchseminars.org/talk/NSCM/36/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Katharina Brazda (University of Vienna)
DTSTART;VALUE=DATE-TIME:20211025T134000Z
DTEND;VALUE=DATE-TIME:20211025T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/37
DESCRIPTION:Title: Mu
ltiphase biological membranes\nby Katharina Brazda (University of Vien
na) as part of Nečas Seminar on Continuum Mechanics\n\nLecture held in K3
Karlin\, Sokolovska 83\, Praha 8.\n\nAbstract\nBiological membranes are t
hin layers of lipid molecules. Mechanically\,\nthey can be described as in
compressible viscous fluid surfaces with\nbending elasticity. The equilibr
ium shapes of homogeneous membranes\nminimize the Canham-Helfrich energy u
nder area and enclosed volume\nconstraints. In particular\, this variation
al model explains the typical\nbiconcave shape of human red blood cells. C
onfigurations of\nheterogeneous biomembranes also feature an intriguing co
upling effect\nbetween composition and geometry\, which originates from th
eir inherent\nfluidity. In this talk\, we introduce these models and prese
nt an\nexistence result for multiphase membranes with sharp phase interfac
es\,\nobtained in the framework of oriented curvature varifolds.\n
LOCATION:https://researchseminars.org/talk/NSCM/37/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Filippo Riva (University of Pavia)
DTSTART;VALUE=DATE-TIME:20211011T134000Z
DTEND;VALUE=DATE-TIME:20211011T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/38
DESCRIPTION:Title: In
ertial Balanced Viscosity solutions to rate-independent systems\nby Fi
lippo Riva (University of Pavia) as part of Nečas Seminar on Continuum Me
chanics\n\n\nAbstract\nRate-independent evolutions frequently occur in mec
hanics when \nthe problem\nunder consideration presents such small rate-de
pendent effects\, as \ninertia or viscosity\, that can be neglected. If th
e driving potential \nenergy is nonconvex any (reasonable) solution necess
arily exhibits \ntime-discontinuities. To describe the behaviour of the ju
mps\, in the \nlast decades the notions of Energetic and Balanced Viscosit
y solutions \nhave been developed\, the latter as a refinement of the form
er. While for \nEnergetic solutions the cost at jumps is described only in
terms of the \nrate-independent dissipation potential\, in the case of Ba
lanced \nViscosity solutions it arises from a suitable coupling between th
is \ndissipation potential and a smaller and smaller viscosity potential\,
\nwhich is reminiscent of an original presence of viscous damping.\nIn th
is talk we present a novel notion of solution to rate-independent \nsystem
s\, named Inertial Balanced Viscosity (IBV) solution\, which in \naddition
takes into account small inertial effects. Differently from the \npreviou
s cases\, now the jump cost turns out to be rate-dependent. In \nfinite di
mension\, we show how IBV solutions can be obtained as a \nvanishing inert
ia and viscosity limit of dynamic evolutions\, and we \nintroduce a multis
cale Minimizing Movements algorithm which can be used \nto build such solu
tions.\nThis is a joint work with G. Scilla and F. Solombrino.\n
LOCATION:https://researchseminars.org/talk/NSCM/38/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jonathan Bevan (University of Surrey\, GB)
DTSTART;VALUE=DATE-TIME:20211108T144000Z
DTEND;VALUE=DATE-TIME:20211108T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/39
DESCRIPTION:Title: In
terior 'buckling' and non-uniqueness in a class of incompressible variatio
nal problems\nby Jonathan Bevan (University of Surrey\, GB) as part of
Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nThe talk is about a
class variational problems whose associated energies $E_{\\eps}$ can be th
ought of as perturbations of the Dirichlet energy. These energies have co
untably many pairs of planar\, measure-preserving stationary points $u^n_{
\\pm}$ with the properties that (a) $E_{\\eps}(u^n_+)=E_{\\eps}(u^n_-)$ an
d (b) the maps $u^n_{\\pm}$ cause `buckling' at the centre $0$ of the unit
ball $B$ in $\\mathbb{R}^2$ while acting as the identity on $\\partial B$
. Numerical calculations show that $n$ can be treated as a proxy for the
`number of buckles' that occur at $0$\, and that\, as one might expect\,
$E_{\\eps}(u^n_{\\pm})$ increases as $n$ does. This is joint work with J.
Deane.\n
LOCATION:https://researchseminars.org/talk/NSCM/39/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Daniel Campbell (Universita Hradec Králové)
DTSTART;VALUE=DATE-TIME:20211129T144000Z
DTEND;VALUE=DATE-TIME:20211129T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/40
DESCRIPTION:Title: Cl
osures of planar BV homeomorphisms and the relaxation of functionals with
linear growth\nby Daniel Campbell (Universita Hradec Králové) as par
t of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nMotivated by rel
axation results of Kristensen and Rindler\, and of Benešová\, Krömer an
d Kružík for BV maps\, we study the class of strict limits of BV planar
homeomorphisms. We show that\, although such maps need not be injective an
d are not necessarily continuous on almost every line\, the class has a re
asonable behavior expected for limit of elastic deformations. By a charact
erization of the classes of strict and area-strict limits of BV homeomorph
isms we show that these classes coincide. \n\nThis is based on joint works
with S. Hencl\, A. Kauranen and E. Radici.\n
LOCATION:https://researchseminars.org/talk/NSCM/40/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ulisse Stefanelli (University of Vienna)
DTSTART;VALUE=DATE-TIME:20211122T144000Z
DTEND;VALUE=DATE-TIME:20211122T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/41
DESCRIPTION:Title: Ex
istence results for a morphoelastic model\nby Ulisse Stefanelli (Unive
rsity of Vienna) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbs
tract\nI will report on a recent work in collaboration with Elisa Davoli (
TU Wien) and Katerina Nik (University of Vienna) on a three-dimensional qu
asistatic morpholelastic model. The mechanical response of the body and it
s growth are modeled by an interplay of hyperelastic energy minimization a
nd growth dynamics. A first existence result is obtained by regularization
and time-discretization\, also taking advantage of an exponential-update
scheme. We then allow the growth dynamics to depend on an additional scala
r field\, say a nutrient\, and formulate an optimal control problem. Event
ually\, we tackle the existence of coupled morphoelastic and nutrient solu
tions\, when the latter is allowed to diffuse and interact with the growin
g body.\n\nThe preprint is available as arXiv:2110.05566.\n
LOCATION:https://researchseminars.org/talk/NSCM/41/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tomáš Roubíček (Math. Inst. of Charles University)
DTSTART;VALUE=DATE-TIME:20211101T144000Z
DTEND;VALUE=DATE-TIME:20211101T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/42
DESCRIPTION:Title: Vi
sco-plastic elastodynamics and poro-elastodynamics at large deformations b
y Eulerian approaches\nby Tomáš Roubíček (Math. Inst. of Charles U
niversity) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\
nTwo models of hardening-free plasticity at large deformations\nwill be pr
esented in Eulerian rate formulation based on two\nstandard concepts\, Gre
en-Naghdi additive decomposition\nand Kroner-Lee-Liu multiplicative decomp
osition of the\ntotal strain. Extension towards poroelasticity and\nthermo
dynamics will be outlined\, too.\n
LOCATION:https://researchseminars.org/talk/NSCM/42/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Philipp Reiter (TU Chemnitz)
DTSTART;VALUE=DATE-TIME:20211115T144000Z
DTEND;VALUE=DATE-TIME:20211115T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/43
DESCRIPTION:Title: Sy
mmetric elastic knots\nby Philipp Reiter (TU Chemnitz) as part of Neč
as Seminar on Continuum Mechanics\n\n\nAbstract\nMinimizing the bending en
ergy within knot classes leads to the concept \nof elastic knots. Motivate
d by numerical experiments we prescribe \ndihedral symmetry and establish
existence of dihedrally symmetric \nelastic knots for knot classes admitti
ng this type of symmetry. Among \nother results we prove that the dihedral
elastic trefoil is the union of \ntwo circles that form a (planar) figure
-eight. We also discuss some \ngeneralizations and limitations regarding o
ther symmetries and knot classes.\n\nThis is joint work with Alexandra Gil
sbach and Heiko von der Mosel.\n
LOCATION:https://researchseminars.org/talk/NSCM/43/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stanislav Sysala (Institute of Geonics\, Cz. Acad. Sci.)
DTSTART;VALUE=DATE-TIME:20211206T144000Z
DTEND;VALUE=DATE-TIME:20211206T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/44
DESCRIPTION:Title: Sa
ddle-point problems with bilinear Lagrangian and convex constraints: anal
ysis\, numerical solution and applications\nby Stanislav Sysala (Insti
tute of Geonics\, Cz. Acad. Sci.) as part of Nečas Seminar on Continuum M
echanics\n\n\nAbstract\nThe first part of the talk is concerned with an ab
stract inf-sup problem \ngenerated by a bilinear Lagrangian and convex con
straints. The \nconditions that guarantee no gap between the inf-sup and r
elated sup-inf \nproblems are studied. A particular attention is devoted t
o the inf-sup \ncondition defined for convex cones in function spaces. Nex
t\, a \nregularization method convenient for solving the inf-sup problem i
s \nanalyzed and a computable majorant of the critical (inf-sup) value is
\nderived for purposes of a posteriori error analysis of numerical \nresul
ts. The second part of the talk is devoted to applications of the \nabstra
ct framework to continuum mechanics. In particular\, examples of \nlimit l
oad problems and similar ones arising in classical plasticity\, \ngradient
plasticity and delamination are introduced. The presented \nresults follo
w from the joint work with Daya B. Reddy\, Sergey Repin and \nJaroslav Has
linger.\n
LOCATION:https://researchseminars.org/talk/NSCM/44/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Amrita Gosh (University of Bonn)
DTSTART;VALUE=DATE-TIME:20211213T144000Z
DTEND;VALUE=DATE-TIME:20211213T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/45
DESCRIPTION:Title: On
Shikhmurzaev’s approach to the Contact Line Problem\nby Amrita Gosh
(University of Bonn) as part of Nečas Seminar on Continuum Mechanics\n\n
\nAbstract\nI will discuss the general moving contact line problem\, arisi
ng from many fluid mechanics\nphenomena. The classical formulation of this
model with the no-slip (Dirichlet) boundary\ncondition for velocities at
the liquid-solid interface gives rise to a non-integrable singularity\nof
the shear stress\, which is known as the ”moving contact line paradox”
. Y. Shikhmurzaev\nproposed (1993) a different approach to solve this issu
e. This approach\, apart from the\nclassical conservation equations\, form
ulates the boundary conditions for the equations in\nthe bulk phases in an
elaborate way\, which can be viewed as a generalization of the existing\n
models in the literature\, although generated from a different underlying
theory. After giving\nan overview of this model\, I would like to derive a
thin film approximation of Shikhmurzaev’s\nmodel to compare with the ot
her solution model of the contact line problem.\n
LOCATION:https://researchseminars.org/talk/NSCM/45/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christmas break (Christmas break)
DTSTART;VALUE=DATE-TIME:20211227T144000Z
DTEND;VALUE=DATE-TIME:20211227T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/46
DESCRIPTION:Title: Ch
ristmas break\nby Christmas break (Christmas break) as part of Nečas
Seminar on Continuum Mechanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/46/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Christmas break (Christmas break)
DTSTART;VALUE=DATE-TIME:20211220T144000Z
DTEND;VALUE=DATE-TIME:20211220T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/47
DESCRIPTION:Title: Ch
ristmas break\nby Christmas break (Christmas break) as part of Nečas
Seminar on Continuum Mechanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/47/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Karel Tůma (Mathematical Institute\, Charles University)
DTSTART;VALUE=DATE-TIME:20220103T144000Z
DTEND;VALUE=DATE-TIME:20220103T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/48
DESCRIPTION:Title: Fi
nite strain phase-field model for martensitic transformation: Large-scale
finite element simulations\nby Karel Tůma (Mathematical Institute\, C
harles University) as part of Nečas Seminar on Continuum Mechanics\n\n\nA
bstract\nMartensitic transformation is a first-order solid-solid diffusion
less transformation that occurs between the parent phase (austenite) and t
he product phase (martensite) and is characterized by the microstructure e
volution\, which is accompanied by the formation\, propagation\, and annih
ilation of the interfaces. In shape memory alloys\, the microstructure evo
lution is the mechanism behind the properties such as pseudoelasticity and
shape memory effect. In general\, due to the incompatibility between aust
enite and a single variant of martensite\, the martensitic transformation
is realized via the formation of complex twinning microstructure. \nA rece
ntly developed phase-field model for multivariant martensitic transformati
on is implemented using the finite element method and used to compute larg
e-scale simulations reaching 150 million degrees of freedom. The computat
ional problems are quite expensive due to the fact that high mesh density
is needed to capture the detailed microstructure\, see attached figure. Ou
r implementation has shown robustness and good parallel scaling performanc
e. Having this model\, the goal is to perform a systematic investigation o
f the effect of crystal lattice orientation and material anisotropy on the
indentation-induced microstructure evolution in CuAlNi shape memory alloy
. To our knowledge\, such a comprehensive high-resolution microstructure-b
ased modeling study has not been reported before. This is a joint work wit
h M. Rezaee-Hajidehi\, S. Stupkiewicz\, J. Hron and P. Farrell.\n
LOCATION:https://researchseminars.org/talk/NSCM/48/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20220110T144000Z
DTEND;VALUE=DATE-TIME:20220110T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/49
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/49/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20220117T144000Z
DTEND;VALUE=DATE-TIME:20220117T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/50
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/50/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20220124T144000Z
DTEND;VALUE=DATE-TIME:20220124T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/51
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/51/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20220131T144000Z
DTEND;VALUE=DATE-TIME:20220131T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/52
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/52/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20220207T144000Z
DTEND;VALUE=DATE-TIME:20220207T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/53
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/53/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sabrine Chebbi (University of Tunisia\, El MANAR\, UTM)
DTSTART;VALUE=DATE-TIME:20220221T144000Z
DTEND;VALUE=DATE-TIME:20220221T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/54
DESCRIPTION:Title: Th
e Energy decay rate of 1D and 2D Timoshenko systems. Theoretical analysis
and numerical simulation\nby Sabrine Chebbi (University of Tunisia\,
El MANAR\, UTM) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbs
tract\nWe focus on the behavior of the solutions of the Timoshenko systems
\nin dimensions 1 and 2 using the lower bound estimates of the energy. We\
nstudy a nonlinear damped one-dimensional thermo-elastic Timoshenko system
\nwhere the heat flux is given by the Cattaneo’s law. After deriving the
strong\nlower energy estimates\, we show the optimality for some explicit
examples.\nFurthermore\, we discuss the well-posedness and the decay rate
of the energy\nof the Mindlin-Timoshenko plate equations subject to a non
linear dissipation\nacting on the rotation angles’equations. Later\, we
perform a numerical sim-\nulation of the one-dimensional Timoshenko system
\, our approach is based\non adequate use of the finite element and the fi
nite difference methods\ngiving rise to a new scheme which characterizes t
he asymptotic behavior of\nthe discrete energy.\n
LOCATION:https://researchseminars.org/talk/NSCM/54/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giusy Mazzone (Queen's University)
DTSTART;VALUE=DATE-TIME:20220502T134000Z
DTEND;VALUE=DATE-TIME:20220502T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/55
DESCRIPTION:Title: On
partially dissipative systems\nby Giusy Mazzone (Queen's University)
as part of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nIn this ta
lk\, we will investigate the dynamics of three mechanical systems: a rigid
body with a damper\, a system of rigid bodies with a fluid-filled gap\, a
nd a harmonic oscillator in a fluid-filled pipe. The equations governing t
he motion of these systems are “partially dissipative”\, in that there
exists an energy functional that decreases along the trajectories\, while
other physical variables are conserved or even excited during the motion.
The objective of our investigations is to describe the “stabilization p
roperties” of the systems. By “stabilization” we mean either converg
ence of each trajectory to a stationary solution or the existence of perio
dic solutions to the governing equations corresponding to forces with arbi
trary frequencies.\n
LOCATION:https://researchseminars.org/talk/NSCM/55/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Petr Pelech (WIAS Berlin)
DTSTART;VALUE=DATE-TIME:20220307T144000Z
DTEND;VALUE=DATE-TIME:20220307T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/56
DESCRIPTION:Title: Pe
nrose-Fife model with activated phase transformation - Existence and effec
tive model for slow-loading regimes.\nby Petr Pelech (WIAS Berlin) as
part of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nWe study a no
n-autonomous system of two evolutionary PDEs\, an enhanced version of the
Penrose-Fife model introduced in 1990\, which first in history coupled the
Allen-Cahn phase-field equation with thermal effects in a thermodynamical
ly consistent way. In our work we consider an activated phase transformati
on which makes the phase-field equation non-linear in time derivative\; it
contains an additional term that describes also the Coulomb dry friction
and whose analogues appear in rate-independent models of plasticity or dam
age. Apart from proving the existence of solutions of the system\, we inve
stigate its effective behavior for the so-called slow-loading regimes. The
re the internal time-scale introduced by phase-field viscosity and thermal
conductivity is much smaller than the time-scale of the loading\, an exte
rnal force acting on the system. Hence the system stays almost in its equi
librium described by the static solution. However\, the limit of solutions
(as the ratio of the time scales tends to zero) may not be characterized
by the corresponding rate-independent model where the viscous-like terms h
ave been dropped. The reason is that the phase transformation is driven by
a non-convex thermodynamic potential and hence the solutions may develop
jumps in the limit. In order to resolve the jump's detailed trajectory\, a
long which the viscous effects play a crucial role\, we use the so-called
Balanced-Viscosity (BV) solutions introduced by Efendiev and Mielke in 200
6. This work is a collaboration with Matthias Liero and Alexander Mielke f
rom WIAS Berlin.\n\nPenrose O.\, Fife P. C. - Thermodynamically Consistent
Models of Phase-Field Type for the Kinetics of Phase Transitions (1990)\n
\nSprekels J.\, Zheng S. M. - Global smooth solutions to a thermodynamical
ly consistent model of phase-field type in higher space dimensions (1993)\
n\nEfendiev M.\, Mielke A. - On the rate-independent limit of systems wit
h dry friction and small viscosity (2006)\n\nMielke A.\, Roubicek T. - Rat
e-independent Systems Theory and Application (2015)\n
LOCATION:https://researchseminars.org/talk/NSCM/56/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Easter Monday
DTSTART;VALUE=DATE-TIME:20220418T134000Z
DTEND;VALUE=DATE-TIME:20220418T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/57
DESCRIPTION:Title: No
lecture\nby Easter Monday as part of Nečas Seminar on Continuum Mech
anics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/57/
END:VEVENT
BEGIN:VEVENT
SUMMARY:George Avalos (UNIVERSITY of NEBRASKA–LINCOLN)
DTSTART;VALUE=DATE-TIME:20220516T134000Z
DTEND;VALUE=DATE-TIME:20220516T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/58
DESCRIPTION:Title: Co
ncerning the strong and uniform decay of solutions to coupled fluid/multi
layered structure PDE dynamics\nby George Avalos (UNIVERSITY of NEBRA
SKA–LINCOLN) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbstr
act\nIn this talk\, we will discuss our recent work on a certain\n multila
yered structure-fluid interaction (FSI) which arises in the\n modeling of
vascular blood flow. The coupled PDE system under our\n consideration math
ematically accounts for the fact that mammalian\n veins and arteries are t
ypically composed of various layers of\n tissues: each layer will generall
y manifest its own intrinsic material\n properties\, and will moreover be
separated from the other layers by\n thin elastic laminae. Consequently\,
the resulting modeling FSI system\n will manifest an additional PDE\, whic
h evolves on the boundary\n interface\, so as to account for the thin elas
tic layer. (This is in\n contrast to the FSI PDE’s which appear in the l
iterature\, wherein\n elastic dynamics are largely absent on the boundary
interface.) As\n such\, the PDE system will constitute a coupling of 3D fl
uid-2D\n elastic-3D elastic dynamics. For this multilayered FSI system\, w
e will\n in particular present results of strong stability for finite ener
gy\n solutions\, and polynomial decay for sufficiently regular solutions.\
n This is joint work with Pelin Güven Geredeli and Boris Muha.\n
LOCATION:https://researchseminars.org/talk/NSCM/58/
END:VEVENT
BEGIN:VEVENT
SUMMARY:summer break
DTSTART;VALUE=DATE-TIME:20220523T134000Z
DTEND;VALUE=DATE-TIME:20220523T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/59
DESCRIPTION:Title: We
will continue on Monday\, October 3\, 2022\nby summer break as part o
f Nečas Seminar on Continuum Mechanics\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/59/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Václav Mácha (Inst. of Mathematics\, Czech Academy of Sciences)
DTSTART;VALUE=DATE-TIME:20220228T144000Z
DTEND;VALUE=DATE-TIME:20220228T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/60
DESCRIPTION:Title: Fl
uids in moving domains\nby Václav Mácha (Inst. of Mathematics\, Czec
h Academy of Sciences) as part of Nečas Seminar on Continuum Mechanics\n\
n\nAbstract\nWe present several results concerning the flow of a\n compres
sible heat-conducting fluid in a moving domain. We discuss the\n existence
of a weak solution. Next\, we tackle the low-Mach number\n limit and we d
educe the target system for the low-stratification case.\n The talk is bas
ed on results obtained in collaboration with O. Kreml\,\n S. Nečasová an
d A. Wroblewska-Kaminska\n
LOCATION:https://researchseminars.org/talk/NSCM/60/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Justyna Ogorzaly (Jagiellonian University)
DTSTART;VALUE=DATE-TIME:20220404T134000Z
DTEND;VALUE=DATE-TIME:20220404T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/61
DESCRIPTION:Title: Va
riational-Hemivariational Inequalities with Applications to Contact Mechan
ics\nby Justyna Ogorzaly (Jagiellonian University) as part of Nečas S
eminar on Continuum Mechanics\n\n\nAbstract\nWe will present the existence
and uniqueness results for the\nspecial classes of nonlinear variational-
hemivariational inequalities.\nThen\, we will consider concrete contact pr
oblems and we will show how\nthese problems lead to the different type of
variational-hemivariational\ninequalities.\n
LOCATION:https://researchseminars.org/talk/NSCM/61/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Henrik Schumacher (TU Chemnitz)
DTSTART;VALUE=DATE-TIME:20220509T134000Z
DTEND;VALUE=DATE-TIME:20220509T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/62
DESCRIPTION:Title: Re
pulsive Curves and Surfaces\nby Henrik Schumacher (TU Chemnitz) as par
t of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nFunctionals that
penalize bending or stretching of a surface play a key role in geometric
and scientific\ncomputing\, but to date have ignored a very basic requirem
ent: in many situations\, surfaces must not pass\nthrough themselves or ea
ch other. This paper develops a numerical framework for optimization of su
rface\ngeometry while avoiding (self-)collision. The starting point is the
tangent-point energy\, which effectively pushes\napart pairs of points th
at are close in space but distant along the surface. We develop a discreti
zation of\nthis energy for triangle meshes and introduce a novel accelerat
ion scheme based on a fractional Sobolev inner\nproduct. In contrast to si
milar schemes developed for curves (cf. [2])\, we avoid the complexity of
building a\nmultiresolution mesh hierarchy by decomposing our precondition
er into two ordinary Poisson equations\, plus\nforward application of a fr
actional differential operator. We further accelerate this scheme via hier
archical\napproximation and describe how to incorporate a variety of const
raints (on area\, volume\, etc.). Finally\, we\nexplore how this machinery
might be applied to problems in mathematical visualization\, geometric mo
deling\,\nand geometry processing.\nJoint work with: Chris Yu\, Caleb Brak
ensiek\, Keenan Crane\nReferences\n[1] C. Yu\, C. Brakensiek\, H. Schumach
er\, and C. Keenan Repulsive Surfaces. ACM Trans. Graph.\, 40(6):1–19\,\
n2021.\n[2] C. Yu\, H. Schumacher\, and C. Keenan Repulsive Curves. ACM Tr
ans. Graph.\, 40(2):1-21\, 2021.\n
LOCATION:https://researchseminars.org/talk/NSCM/62/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marta Zoppello (DISMA\, Politecnico di Torino)
DTSTART;VALUE=DATE-TIME:20220328T134000Z
DTEND;VALUE=DATE-TIME:20220328T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/65
DESCRIPTION:Title: N-
link swimmers swimming alone or in pairs\nby Marta Zoppello (DISMA\, P
olitecnico di Torino) as part of Nečas Seminar on Continuum Mechanics\n\n
\nAbstract\nThis talk presents two models of swimmers immersed in a low Re
ynolds number fluid\,\nboth of them involving the so-called N -link swimme
r. The first one studies the 3-dimensional N-link swimmer swimming alone [
1]\, the second focuses on two planar 2-link swimmers\nswimming together [
2]. Both models rely on Resistive Force Theory\, which is a good approxima
tion of hydrodynamic forces at low Reynolds number for slender swimmers an
d allows us to cast the equations of motion as ODEs. These equations can b
e seen as control systems\nwhere the controls are the velocity of deformat
ion of the swimmers.\nWe prove that the 3 dimensional N -link swimmer is f
ully controllable and we show the existence of optimal controls for some c
ost functionals. Regarding the coupled swimmers\, even\nif\, taken singula
rly\, they are non-controllable units (because of Purcell’s celebrated S
callop Theorem)\, we prove that taking into account the hydrodynamic inter
action they can achieve a net motion after a periodic sequence of shape ch
anges. Moreover\, under suitable\napproximations\, we are able to optimize
the displacement.\n\n\n[1] R. Marchello\, M\, Morandotti\, H. Shum\, M. Z
oppello.\nThe N -link swimmer in three dimensions: controllability and opt
imality results.\nAccepted for publication in Acta Applicandae Mathematica
e (2022)\n\n\n[2] M. Zoppello\, M. Morandotti\, H. Gadˆelha.\nControlling
non-controllable scallops.\nSubmitted.\n
LOCATION:https://researchseminars.org/talk/NSCM/65/
END:VEVENT
BEGIN:VEVENT
SUMMARY:summer break
DTSTART;VALUE=DATE-TIME:20220523T134000Z
DTEND;VALUE=DATE-TIME:20220523T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/67
DESCRIPTION:by summer break as part of Nečas Seminar on Continuum Mechani
cs\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/67/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bangwei She (Inst. of Mathematics\, Czech Academy of Sciences)
DTSTART;VALUE=DATE-TIME:20220321T144000Z
DTEND;VALUE=DATE-TIME:20220321T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/68
DESCRIPTION:Title: On
convergence of numerical solutions for the compressible MHD system\nb
y Bangwei She (Inst. of Mathematics\, Czech Academy of Sciences) as part o
f Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nWe study a general
convergence theory for the analysis of numerical\n solutions to a magnetoh
ydrodynamic system describing the time\n evolution of compressible\, visco
us\, electrically conducting fluids.\n \n First\, we introduce the concept
of consistent approximation mimicking\n the density positivity\, energy s
tability\, and consistency of a\n suitable numerical approximation. Furthe
r\, we introduce the concept of\n dissipative weak solution\, which can be
obtained as the weak limit of\n the consistent approximation. Here\, by
“dissipative" we mean that\n the energy inequality contains energy defec
ts that control the\n oscillations in the momentum equation.\n \n Next\, b
y using the relative energy functional\, we prove the\n dissipative weak-s
trong uniqueness principle\, meaning that a\n dissipative weak solution co
incides with a classical solution of the\n same problem as long as the lat
ter exists. This indicates that a\n consistent approximation converges unc
onditionally to the classical\n solution. As a summary\, we built a nonlin
ear variant of the Lax\n equivalence theory for the compressible MHD syste
m.\n \n Finally\, to show the application of the convergence theory\, we p
ropose\n two numerical methods. We show that the numerical solutions prese
rve\n the positivity of density and stability of the total energy. Then by
\n using the a priori estimates derived from the energy estimates we\n pro
ve that the numerical methods are consistent. Consequently\, our\n numeric
al methods belong to the class of consistent approximation.\n Applying the
prebuilt convergence theory\, we conclude that the\n solutions of our num
erical methods converge to i) the dissipative\n weak solution\; ii) the c
lassical solution as long as the classical\n solution exists. As a byprodu
ct of the first convergence\, we prove the\n global in-time existence of t
he dissipative weak solution.\n
LOCATION:https://researchseminars.org/talk/NSCM/68/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Barbora Benešová (Charles University)
DTSTART;VALUE=DATE-TIME:20220425T134000Z
DTEND;VALUE=DATE-TIME:20220425T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/69
DESCRIPTION:Title: A
model for polycrystalline Ni-Ti shape-memory alloys including plasticity\nby Barbora Benešová (Charles University) as part of Nečas Seminar o
n Continuum Mechanics\n\n\nAbstract\nIn this talk\, I will discuss the int
erplay between the martensitic transformation and the plastic deformation
in polycrystalline NiTi- alloys. I will then propose a phenomenological\,
macroscopic model capturing both effects within the generalized standard m
aterials modelling framework. Special attention will be paid to distinguis
hing dependent and independent processes and their accurate modelling. Thi
s is a joint work with Miroslav Frost\, Martin Kružík\, Petr Sedlák and
Hanuš Seiner.\n
LOCATION:https://researchseminars.org/talk/NSCM/69/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rufat Badal (University of Erlangen)
DTSTART;VALUE=DATE-TIME:20220214T144000Z
DTEND;VALUE=DATE-TIME:20220214T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/70
DESCRIPTION:Title: No
nlinear and Linearized Models in Thermoviscoelasticity\nby Rufat Badal
(University of Erlangen) as part of Nečas Seminar on Continuum Mechanics
\n\n\nAbstract\nWe consider a quasistatic nonlinear model in thermoviscoel
asticity at a finite-strain setting in the Kelvin’s-Voigt’s rheology w
here both the elastic and viscous stress tensors comply with the principle
of frame indifference under rotations. The force balance is formulated in
the reference configuration by resorting to the concept of nonsimple mate
rials whereas the heat transfer equation is modeled by the Fourier law in
the deformed configurations. Weak solutions are obtained by means of a sta
ggered in-time discretization where the deformation and the temperature ar
e updated alternatingly. Our result refines a recent work by Mielke & Roub
íček [1] since our approximation does not require any regularization of
the viscosity term. Afterwards\, we focus on the case of deformations near
the identity and small temperatures\, and we show by a rigorous lineariza
tion procedure that weak solutions of the nonlinear system converge in a s
uitable sense to solutions of a system in linearized thermoviscoelasticity
. The same property holds for time-discrete approximations and we provide
a corresponding commutativity result.\n\n[1] Mielke A.\, Roubíček T.: Th
ermoviscoelasticity in Kelvin-Voigt rheology at large strains. (2020)\n
LOCATION:https://researchseminars.org/talk/NSCM/70/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michele Ruggeri (University of Strathclyde)
DTSTART;VALUE=DATE-TIME:20220314T144000Z
DTEND;VALUE=DATE-TIME:20220314T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/71
DESCRIPTION:Title: Th
e Landau-Lifshitz-Gilbert equation with Dzyaloshinki-Moriya interaction: n
umerical aspects\nby Michele Ruggeri (University of Strathclyde) as pa
rt of Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nThe talk will b
e split into two parts.\nIn the first one\, we discuss the numerical appro
ximation of the Landau-Lifshitz-Gilbert equation\n(LLG) for the case in wh
ich the energy (and\, hence\, the effective field appearing in LLG) includ
es\nthe Dzyaloshinki-Moriya interaction (DMI)\, the fundamental ingredient
for the enucleation and stability\nof chiral magnetic skyrmions. In the s
econd part\, we discuss a limiting model for micromagnetic thin\nfilms in
the presence of bulk DMI\, where we focus on the limiting behavior of the
magnetization\nas the thickness of the film goes to zero. We show that the
reduced model unveils some physics\nand discuss its practical implication
s for computations. The results presented in the talk have been\nobtained
together with Giovanni Di Fratta (University of Naples Federico II)\, Elis
a Davoli\,\nCarl-Martin Pfeiler\, and Dirk Praetorius (TU Wien).\n
LOCATION:https://researchseminars.org/talk/NSCM/71/
END:VEVENT
BEGIN:VEVENT
SUMMARY:---
DTSTART;VALUE=DATE-TIME:20220411T134000Z
DTEND;VALUE=DATE-TIME:20220411T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/72
DESCRIPTION:by --- as part of Nečas Seminar on Continuum Mechanics\n\nAbs
tract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/72/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Rita Ferreira (King Abdullah University of Science and Technology)
DTSTART;VALUE=DATE-TIME:20221031T144000Z
DTEND;VALUE=DATE-TIME:20221031T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/73
DESCRIPTION:Title: St
ructural changes in nonlocal denoising models arising through bi-level par
ameter learning\nby Rita Ferreira (King Abdullah University of Science
and Technology) as part of Nečas Seminar on Continuum Mechanics\n\n\nAbs
tract\nIn this talk\, we will discuss a unified framework based on bi-leve
l optimization schemes to deal with parameter learning in the context of i
mage processing. The goal is to identify the optimal regularizer within a
family depending on a parameter in a general topological space. Of particu
lar interest is the non-compact parameter domains case\, which is relevant
\, for instance\, when the commonly used box constraints are disregarded.
To overcome this lack of compactness\, we propose a natural extension of t
he upper-level functional to the closure of the parameter domain via Gamma
-convergence\, which captures possible structural changes in the reconstru
ction model at the edge of the domain. Under two main assumptions\, Mosco
-convergence of the regularizers and uniqueness of minimizers of the lower
-level problem\, we prove that the extension coincides with the relaxation
\, thus admitting minimizers that relate to the parameter optimization pro
blem of interest. To conclude\, we apply this abstract framework to invest
igate four practically relevant models in image denoising\, all featuring
nonlocality\; moreover\, the associated families of regularizers exhibit q
ualitatively different parameter dependence\, describing a weight factor\,
an amount of nonlocality\, an integrability exponent\, and a fractional o
rder\, respectively. \nThis talk is based on a joint work with Elisa Davol
i\, Carolin Kreisbeck\, and Hidde Schönberger.\n
LOCATION:https://researchseminars.org/talk/NSCM/73/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lennart Machill (University of Muenster\, Germany)
DTSTART;VALUE=DATE-TIME:20221010T134000Z
DTEND;VALUE=DATE-TIME:20221010T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/74
DESCRIPTION:Title: On
e-dimensional viscoelastic von Kármán theories\nby Lennart Machill (
University of Muenster\, Germany) as part of Nečas Seminar on Continuum M
echanics\n\n\nAbstract\nWe derive an effective one-dimensional limit from
a three-dimensional Kelvin-Voigt model for viscoelastic thin-walled beams\
, in which the elastic and the viscous stress tensor comply with a frame-i
ndifference principle. The limiting system of equations comprises stretchi
ng\, bending\, and twisting both in the elastic and the viscous stress. It
coincides with the model already identified via [Friedrich-Kružík '20]
and [Friedrich-Machill '22] by a successive dimension reduction\, first fr
om 3D to a 2D theory for von Kármán plates and then from 2D to a 1D theo
ry for ribbons. Our arguments rely on the static Gamma-convergence in [Fre
ddi-Mora-Paroni '13]\, on the abstract theory of metric gradient flows\, a
nd on evolutionary Gamma-convergence by Sandier and Serfaty.\n
LOCATION:https://researchseminars.org/talk/NSCM/74/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Elvira Zappale (University of Rome - I\, Sapienza)
DTSTART;VALUE=DATE-TIME:20221121T144000Z
DTEND;VALUE=DATE-TIME:20221121T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/75
DESCRIPTION:Title: Va
riational formulation for hierarchies of structured deformations\nby E
lvira Zappale (University of Rome - I\, Sapienza) as part of Nečas Semina
r on Continuum Mechanics\n\n\nAbstract\nThe mechanical theory of first ord
er structured deformations formulated in [2] enriches the purely macroscop
ic field theory of non-linear elasticity by taking into account the effect
s of disarrangements that occur at a single submacroscopic level. In [1] a
variational formulation for this theory has been successfully provided in
the context of special fields of bounded variation.\nTaking into account
that many natural and man-made physical systems have a rich enough geometr
ical structure to permit the identification of hierarchies consisting of m
ore than one physically meaningful submacroscopic level\, the mechanical t
heory of structured deformations has been enriched in [3]. This talk aims
at presenting a variational framework of these latter theoretical setting
s.\n\n\nReferences:\n\n[1] R. Choksi and I. Fonseca: Bulk and interfacial
energy densities for structured deformations of continua. Arch. Rational M
ech. Anal. 138 (1997)\, 37-103.\n\n\n[2] G. Del Piero and D. -R. Owen: Str
uctured deformations of continua: Arch. Ration. Mech. Anal. 124 (1993)\, 9
9-155.\n\n[3] L. Deseri and D. R. Owen: Elasticity with Hierarchical Disar
rangements: A Field Theory That Admits Slips and Separations at Multiple S
ubmacroscopic Levels: J.of Elasticity Vol- 135 (2019) Issue 1-2\, 149-180.
\n\nJoint project with Ana Cristina Barroso\, José Matias\, Marco Morando
tti & David Owen\n
LOCATION:https://researchseminars.org/talk/NSCM/75/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Martin Horák (Faculty of Civil Engineering\, CTU\, ÚTIA AVČR)
DTSTART;VALUE=DATE-TIME:20221003T134000Z
DTEND;VALUE=DATE-TIME:20221003T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/76
DESCRIPTION:Title: Ef
ficient formulation of a two-dimensional geometrically exact Bernoulli bea
m\nby Martin Horák (Faculty of Civil Engineering\, CTU\, ÚTIA AVČR
) as part of Nečas Seminar on Continuum Mechanics\n\nLecture held in K3 K
arlin\, Sokolovska 83\, Praha 8.\n\nAbstract\nIn this talk\, I will focus
on a two-dimensional geometrically exact formulation of a Bernoulli beam.\
nThe formulation is based on the integrated form of equilibrium equations\
, which are combined with the\nkinematic equations and generalized materia
l equations\, leading to a set of three first-order differential\nequation
s. These equations are then discretized by finite differences and the boun
dary value problem is\nconverted into an initial value problem using a tec
hnique inspired by the shooting method. The accuracy of\nthe numerical app
roximation is conveniently increased by refining the integration scheme on
the element\nlevel while the number of global degrees of freedom is kept
constant\, which leads to high computational\nefficiency. The element has
been implemented into an open-source finite element code. I will show a\nf
avorable comparison with standard beam elements formulated in the finite-s
train framework and with\nanalytical solutions. Several extensions of the
proposed approach\, including curved initial geometry\, follower pressure
load\, and beam-to-beam contact will be also discussed. This is joint wor
k with M. Jirásek and E. La Malfa Ribolla.\n\n\nREFERENCES\n\n\n[1] Jirá
sek\, M.\,La Malfa Ribolla\, E.\, and Horák\, M. Efficient finite differe
nce formulation of a ge-ometrically nonlinear beam element. International
Journal for Numerical Methods in Engineering\,(2021) 122:7013–7053.\n\n\
n[2] Horák\, M.\, La Malfa Ribolla\, E.\, and Jirásek\, M. Efficient for
mulation of a two-noded geometrically exact curved beam element. Internati
onal Journal for Numerical Methods in Engineering\, (2022)\, accepted for
publication.\n
LOCATION:https://researchseminars.org/talk/NSCM/76/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bohumír Bastl (University of West Bohemia)
DTSTART;VALUE=DATE-TIME:20221024T134000Z
DTEND;VALUE=DATE-TIME:20221024T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/77
DESCRIPTION:Title: Nu
merical simulation of incompressible fluid flow with the help of isogeomet
ric analysis\nby Bohumír Bastl (University of West Bohemia) as part o
f Nečas Seminar on Continuum Mechanics\n\n\nAbstract\nIsogeometric analys
is is a relatively recently introduced concept for numerical\nsolving of p
artial differential equations which bridges the gap between\ngeometric mod
elling and numerical simulation/analysis.\n\nIn this talk\, the isogeometr
ic analysis is used for numerical simulation of\nincompressible fluid flow
. We give an overview of the method which shares many\nfeatures with Finit
e Element Method\, but different meshes and basis functions\nalso lead to
significant differences. We present advantages and drawbacks of the\nmetho
d which we have encountered during development of incompressible turbulent
\nflow solver and we focus on our results concerning isogeometric mesh gen
eration\,\nstabilization methods and solving systems of linear equations i
n this context.\n
LOCATION:https://researchseminars.org/talk/NSCM/77/
END:VEVENT
BEGIN:VEVENT
SUMMARY:John Simon (Institute of Mathematics\, Czech Academy of Sciences)
DTSTART;VALUE=DATE-TIME:20221114T144000Z
DTEND;VALUE=DATE-TIME:20221114T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/78
DESCRIPTION:Title: A
NAIVE FORMULATION OF MAXIMIZING THE COMPUTATIONAL CAPABILITY OF THE TWIN V
ORTEX COMPUTER VIA SHAPE OPTIMIZATION\nby John Simon (Institute of Mat
hematics\, Czech Academy of Sciences) as part of Nečas Seminar on Continu
um Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and Phys
ics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nPhysica
l reservoir computing is a new computational paradigm based on recurrent n
eural networks\nwhere instead of optimizing nodal connection of the intern
al network\, one gets to utilize the nonlinear behavior of\nphysical syste
ms and gets to focus on optimizing a minimal number parameters. In 2021\,
Goto et al [1] investigated\na physical reservoir computer in the context
of a flow past a cylinder and shown that the computer’s computational\nc
apability is maximized at the bifurcation point between the generation of
twin vortex and the onset of Karman vortex.\nIn this exposition\, the auth
ors illustrated how the the dynamics of twin vortex affects the ability of
the computer to\naccomplish certain tasks. In particular\, they have show
n that the length of the twin vortex is directly proportional to\nthe perf
ormance.\nIn this talk\, a shape optimization problem that aims to increas
e the said capability will be presented. The op-\ntimization problem is a
naive formulation by maximizing two types of functional which has been his
torically used a\nquantifiers of vortex\, namely\, the L2-norm of the curl
of the velocity and the positivity of the determinant of the velocity\ngr
adient. The optimization problem is regularized by a perimeter functional
which acts as a Tikhonov regularizer. A\nvolume constraint is also imposed
\, which — together with the regularizer — prevents possible topologic
al changes in\nthe domain. The analysis of this problem includes existence
analysis of the governing state\, establishing the existence\nof shape so
lutions\, and sensitivity of the objective functional with respect to doma
in perturbation. We shall then utilize\nthe results of the sensitivity ana
lysis to a gradient descent-type algorithm for numerical illustrations.\n\
n[1] K. Goto\, K. Nakajima\, and H. Notsu\, Twin vortex computer in fluid
flow\, New J. Phys.\, 23 (2021)\, p. 063051\,\nhttps://doi.org/doi.org/10.
1088/1367-2630/ac024d.\n
LOCATION:https://researchseminars.org/talk/NSCM/78/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jiří Mikyška (Faculty of Nuclear Sciences and Physical Engineer
ing\, Czech Tech. University)
DTSTART;VALUE=DATE-TIME:20221017T134000Z
DTEND;VALUE=DATE-TIME:20221017T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/79
DESCRIPTION:Title: An
alternative model of multicomponent diffusion based on a combination of t
he Maxwell-Stefan theory and continuum mechanics.\nby Jiří Mikyška
(Faculty of Nuclear Sciences and Physical Engineering\, Czech Tech. Univer
sity) as part of Nečas Seminar on Continuum Mechanics\n\nLecture held in
Room K3\, Faculty of Mathematics and Physics\, Charles University\, Sokol
ovská 83 Prague 8..\n\nAbstract\nI will present a theory of multicompone
nt mixtures that do not employ any splitting of component fluxes\ninto con
vective and diffusive parts. Instead\, momentum balance is formulated indi
vidually for each\ncomponent in which both 1) viscous friction within a co
mponent\, and 2) momentum exchange among different\ncomponents\, are taken
into account. While viscous friction is described using the Newtonian str
ess\ntensor\, the Maxwell-Stefan theory is used to describe the momentum e
xchange among different components.\nWhen the viscosity is neglected\, the
model of an ideal mixture of ideal gases leads to a hyperbolic system of\
nconservation laws. For the non-ideal mixtures\, we obtain the first-order
system in a non-conservative form.\nA simplified version of the model is
discretized using a combination of the finite volume method and the\nmixed
-hybrid finite element method. Numerical examples are provided to show the
typical behavior of the\nsolution of the model equations.\n
LOCATION:https://researchseminars.org/talk/NSCM/79/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dallas Albritton (Princeton University)
DTSTART;VALUE=DATE-TIME:20221205T144000Z
DTEND;VALUE=DATE-TIME:20221205T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/80
DESCRIPTION:Title: No
n-uniqueness of Leray solutions to the forced Navier-Stokes equations\nby Dallas Albritton (Princeton University) as part of Nečas Seminar on
Continuum Mechanics\n\nLecture held in Institute of Mathematics\, Žitn
á 25\, Praha 1\, library.\n\nAbstract\nIn a seminal work\, Leray demonstr
ated the existence of\nglobal weak solutions to the Navier-Stokes equation
s in three\ndimensions. Are Leray's solutions unique? This is a fundamenta
l\nquestion in mathematical hydrodynamics\, which we answer in the\nnegati
ve within the `forced' category\, by exhibiting two distinct\nLeray soluti
ons with zero initial velocity and identical body force.\n\nThis is joint
work with Elia Brué and Maria Colombo.\n
LOCATION:https://researchseminars.org/talk/NSCM/80/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20230109T144000Z
DTEND;VALUE=DATE-TIME:20230109T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/81
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/81/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20230116T144000Z
DTEND;VALUE=DATE-TIME:20230116T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/82
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/82/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20230123T144000Z
DTEND;VALUE=DATE-TIME:20230123T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/83
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/83/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20230130T144000Z
DTEND;VALUE=DATE-TIME:20230130T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/84
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/84/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semester break
DTSTART;VALUE=DATE-TIME:20230206T144000Z
DTEND;VALUE=DATE-TIME:20230206T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/85
DESCRIPTION:by semester break as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/85/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cy Maor (Hebrew University of Jerusalem)
DTSTART;VALUE=DATE-TIME:20230320T144000Z
DTEND;VALUE=DATE-TIME:20230320T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/86
DESCRIPTION:Title: No
n-Euclidean elasticity: shape transitions in non-Euclidean ribbons\nby
Cy Maor (Hebrew University of Jerusalem) as part of Nečas Seminar on Con
tinuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and
Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nMan
y bodies in nature that undergo inhomogeneous growth/shrinkage become "pre
-strained"\; that is\, they are stressed even in the absence of external f
orces. They are typically modeled by having an intrinsic non-flat metric\,
giving rise to non-Euclidean elasticity.\nOf particular interest are thin
bodies: shell-like\, rod-like or ribbon-like bodies (e.g.\, leaves or sup
ramolecular assemblies)\, which exhibit interesting energy-driven patterns
. In this talk I will describe the model of non-Euclidean elasticity\, and
then focus on thin bodies\, the relations between their intrinsic curvatu
re and their elastic behavior\, and specifically on shape transitions in n
on-Euclidean ribbons.\n
LOCATION:https://researchseminars.org/talk/NSCM/86/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Easter Monday
DTSTART;VALUE=DATE-TIME:20230410T134000Z
DTEND;VALUE=DATE-TIME:20230410T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/87
DESCRIPTION:by Easter Monday as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/87/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Holiday
DTSTART;VALUE=DATE-TIME:20230501T134000Z
DTEND;VALUE=DATE-TIME:20230501T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/88
DESCRIPTION:by Holiday as part of Nečas Seminar on Continuum Mechanics\n\
nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles U
niversity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/88/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Holiday
DTSTART;VALUE=DATE-TIME:20230508T134000Z
DTEND;VALUE=DATE-TIME:20230508T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/89
DESCRIPTION:by Holiday as part of Nečas Seminar on Continuum Mechanics\n\
nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles U
niversity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/89/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Petr Sváček (Faculty of Mechanical Engineering\, CTU)
DTSTART;VALUE=DATE-TIME:20230522T134000Z
DTEND;VALUE=DATE-TIME:20230522T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/90
DESCRIPTION:Title: On
Application of Finite Element Method for Fluid-Structure-Acoustic Interac
tions Related to Human Phonation Process\nby Petr Sváček (Faculty of
Mechanical Engineering\, CTU) as part of Nečas Seminar on Continuum Mech
anics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, C
harles University\, Sokolovská 83 Prague 8..\n\nAbstract\nHuman voice is
created by a complex process consisting of mutual\ninteractions of flowin
g air\, vibrating vocal folds and the sound propagation\nthrough the vocal
tract. The fundamental sound is created by the mutual\ninteraction of the
flowing air with vibrations of vocal folds(VFs). The\narising fundamenta
l sound is enriched by aeroacoustic sound sources and\npropagated through
the vocal tract. In this talk\, mathematical models of a\nsimplified fluid
-structure-acoustic interaction problem shall be\,\nnumerically discretize
d and numerical results will be presented. In\nparticular the deformation
of an elastic body representing the model of\nvocal folds will be consider
ed in the interaction with the complex fluid\nflow and aeroacoustics. In p
articular the attention will be paid to several\nimportant issues of such
a modelling as the inclusion of the VFs contact\,\nchoice of suitable boun
dary conditions\, the influence of pre-stressed vocal\nfold on the fundame
ntal frequency\, etc. For the flow model the realization\nof the variation
al multiscale method is discussed. The numerical\napproximation of the pro
blem is presented and numerical results are shown.\n
LOCATION:https://researchseminars.org/talk/NSCM/90/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xmas
DTSTART;VALUE=DATE-TIME:20221226T144000Z
DTEND;VALUE=DATE-TIME:20221226T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/91
DESCRIPTION:Title: no
talk\nby Xmas as part of Nečas Seminar on Continuum Mechanics\n\nLec
ture held in Room K3\, Faculty of Mathematics and Physics\, Charles Unive
rsity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/91/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabriel Pathó (Dlubal Software CS)
DTSTART;VALUE=DATE-TIME:20221107T144000Z
DTEND;VALUE=DATE-TIME:20221107T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/92
DESCRIPTION:Title: Co
nstitutive modelling of masonry for civil engineering\nby Gabriel Path
ó (Dlubal Software CS) as part of Nečas Seminar on Continuum Mechanics\n
\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles
University\, Sokolovská 83 Prague 8..\n\nAbstract\nWe discuss the macros
cale modeling of masonry consisting of brick and mortar as a brittle mater
ial and its implementation in the commercial software RFEM 6 which is conv
enient for practical civil engineers and complies with both Eurocode 6 and
available test data.\n
LOCATION:https://researchseminars.org/talk/NSCM/92/
END:VEVENT
BEGIN:VEVENT
SUMMARY:cancelled
DTSTART;VALUE=DATE-TIME:20221128T144000Z
DTEND;VALUE=DATE-TIME:20221128T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/93
DESCRIPTION:Title: se
minar is cancelled\nby cancelled as part of Nečas Seminar on Continuu
m Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physi
cs\, Charles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/93/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Michael Růžička (University of Freiburg)
DTSTART;VALUE=DATE-TIME:20221205T161000Z
DTEND;VALUE=DATE-TIME:20221205T171000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/94
DESCRIPTION:Title: Ex
istence proofs for pseudomonotone parabolic problems\nby Michael Růž
ička (University of Freiburg) as part of Nečas Seminar on Continuum Mech
anics\n\nLecture held in Institute of Mathematics\, Žitná 25\, Praha 1\
, library.\n\nAbstract\nIn the talk we discuss nonlinear parabolic problem
s which \ncontain a pseudomonotone operator. A new notion of Bochner pseud
omonotonicity is introduced and \napplied. Extensions to quasi non-conform
ing and non-conforming Bochner pseudomonotonicity yield\nconvergence proo
fs for fully discrete Rothe–Galerkin schemes in the framework of discre
tely divergence free FE and DG methods.\n\nReferences\n[1] E. Baumle and M
. Růžička: Note on the existence theory for evolution \nequations with
pseudomonotone operators\, Ric. Mat.\, 2017.\n\n[2] S. Bartels\, M. Růži
čka: Convergence of fully discrete implicit and \nsemi-implicit approxima
tions of singular parabolic equations\, SIAM J. Numer. Anal.\, 2020.\n\n[3
] A. Kaltenbach\, M. Růžička: Note on the existence theory for \npseudo
-monotone evolution problems\, J. Evol. Equ.\, 2021.\n\n[4] L.C. Berselli\
, A. Kaltenbach\, M. Růžička: Analysis of fully \ndiscrete\, quasi non-
conforming approximations of evolution equations and applications\, Math.
Models \nMethods Appl. Sci.\, 2021.\n\n[5] A. Kaltenbach\, M. Růžička:
Analysis of fully discrete\, non-conforming approximation of evolution eq
uations and applications\, in preparation\, 2022.\n
LOCATION:https://researchseminars.org/talk/NSCM/94/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sourav Mitra (Institute of Mathematics\, Czech Academy of Sciences
)
DTSTART;VALUE=DATE-TIME:20221212T144000Z
DTEND;VALUE=DATE-TIME:20221212T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/95
DESCRIPTION:Title: Ex
istence of a weak solution for a compressible multicomponent fluid-structu
re interaction problem\nby Sourav Mitra (Institute of Mathematics\, Cz
ech Academy of Sciences) as part of Nečas Seminar on Continuum Mechanics\
n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles
University\, Sokolovská 83 Prague 8..\n\nAbstract\nI will speak about o
ur recent work on the analysis of a system of PDEs governing the interacti
on between two compressible mutually noninteracting fluids and a shell of
Koiter type encompassing a time-dependent 3D domain filled by the fluids.
The dynamics of the fluids is modeled by compressible\nNavier-Stokes equat
ions with a physically realistic pressure depending on the densities of bo
th fluids. The shell constitutes the boundary of the fluid domain\, and it
possesses a non-linear\, non-convex Koiter energy (of a quite general for
m). We are interested in the existence of a weak solution to the system\nu
ntil the time-dependent boundary approaches a self-intersection. We first
prove a global existence result (until a degeneracy occurs) when the adiab
atic exponents solve max{γ\, β} > 2 and min{γ\, β} > 0\, and further\,
the densities are comparable. Next\, with a slightly extra regularity ass
umption on the\ninitial structural displacement\, we extend our global exi
stence result to the case max{γ\, β} ≥ 2 and min{γ\, β} > 0.\nIn the
first part of the talk\, I will try to introduce the classical theory on
the existence of weak solutions for compressible mono-fluid models. Next\,
I will talk about our work on the multi-component FSI problem. This is jo
int work with M. Kalousek and Š. Nečasová.\n
LOCATION:https://researchseminars.org/talk/NSCM/95/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nilasis Chaudhuri (Imperial College London)
DTSTART;VALUE=DATE-TIME:20221219T144000Z
DTEND;VALUE=DATE-TIME:20221219T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/96
DESCRIPTION:Title: Na
vier--Stokes--Fourier system with Dirichlet boundary conditions for temper
ature\nby Nilasis Chaudhuri (Imperial College London) as part of Neča
s Seminar on Continuum Mechanics\n\n\nAbstract\nIn this talk\, we consider
the Navier--Stokes--Fourier system\,\ndescribing the motion of a compress
ible\, viscous\, and heat conducting\nfluid in a bounded domain $\\Omega \
\subset R^d$\, $d =2\,3$\, with general\nnon-homogeneous Dirichlet boundar
y conditions for the absolute\ntemperature. We introduce a new concept of
weak solution based on the\nsatisfaction of the entropy inequality togethe
r with a balance law for\nthe ballistic energy. We show the existence of g
lobal-in-time weak\nsolutions\, as well as the weak--strong uniqueness pri
nciple.\n
LOCATION:https://researchseminars.org/talk/NSCM/96/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jiří Outrata (Czech Academy of Sciences\, Institute of Informati
on Theory and Automation)
DTSTART;VALUE=DATE-TIME:20230102T144000Z
DTEND;VALUE=DATE-TIME:20230102T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/97
DESCRIPTION:Title: On
the application of the SCD semismooth* Newton method to variational inequ
alities of the second kind\nby Jiří Outrata (Czech Academy of Scienc
es\, Institute of Information Theory and Automation) as part of Nečas Sem
inar on Continuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathe
matics and Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAb
stract\nThe first part of the lecture deals with a description of the SCD
(subspace containing\nderivative) mappings and the SCD semismooth* Newton
method for the solution of general\ninclusions. This method is then applie
d to a class of variational inequalities of the second\nkind. As a result\
, one obtains an implementable algorithm exhibiting a locally superlinear\
nconvergence. Finally\, we demonstrate the efficiency of a globalized vers
ion of this method\nvia a Cournot-Nash equilibrium in which the objectives
of the players (firms) are nonsmooth\ndue to the presence of the so-calle
d cost of change. The problem is modeled as a variational\ninequality of t
he second kind and\, to test the performance of the applied method\, one a
dmits\nreally large numbers of players and produced commodities.\nJoint wo
rk with: Helmut Gfrerer and Jan Valdman.\n
LOCATION:https://researchseminars.org/talk/NSCM/97/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Malte Kampschulte (Faculty of Mathematics and Physics\, Charles Un
iversity)
DTSTART;VALUE=DATE-TIME:20230213T144000Z
DTEND;VALUE=DATE-TIME:20230213T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/98
DESCRIPTION:Title: Se
lf-contact for inertial problems in continuum mechanics\nby Malte Kamp
schulte (Faculty of Mathematics and Physics\, Charles University) as part
of Nečas Seminar on Continuum Mechanics\n\nLecture held in Room K3\, Fac
ulty of Mathematics and Physics\, Charles University\, Sokolovská 83 Pra
gue 8..\n\nAbstract\nThere are many theories about elastic collisions of s
olids and the resulting inertial evolution. What unifies most of them is t
hat they involve some phenomenological assumption. The aim of this talk is
to present a recent result which shows that for the self-collision of ela
stic bulk solids\, it is in fact sufficient to consider matter non-interpe
netration. Based only on this\, we are able to derive existence of weak so
lutions including contact with obstacles and self-contact for arbitrary la
rge times and for large deformations. Additionally we are able to precisel
y characterize the contact forces as a vector-valued measure. This is base
d on joint works with A. Češík\, and G. Gravina.\n
LOCATION:https://researchseminars.org/talk/NSCM/98/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ivan Gudoshnikov (Institute of Mathematics\, Czech Academy of Scie
nces)
DTSTART;VALUE=DATE-TIME:20230220T144000Z
DTEND;VALUE=DATE-TIME:20230220T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/99
DESCRIPTION:Title: El
astoplasticity with softening in spring network models: a state-dependent
sweeping process approach\nby Ivan Gudoshnikov (Institute of Mathemat
ics\, Czech Academy of Sciences) as part of Nečas Seminar on Continuum Me
chanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\,
Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nSoftening pl
asticity and Gurson model of damage in particular lead to ill-posed mathem
atical\nproblems due to the loss of monotonicity. Multiple co-existing sol
utions are possible when softening\nelements are coupled together\, and so
lutions cannot be continued beyond the point of complete\nfailure of a mat
erial. Moreover\, spatially continuous models with softening suffer from l
ocalization\nof strains and stresses to measure-zero submanifolds.\nWe for
mulate a problem of quasistatic evolution of elasto-plastic spring network
s (Lattice Spring\nModels) with a plastic flow rule which describes linear
hardening\, linear softening and perfectly\nplastic springs in a uniform
manner. The fundamental kinematic and static characteristics of the\nnetwo
rk are described by the rigidity theory and structural mechanics.\nTo solv
e the evolution problem we convert it to a type of a differential quasi-va
riational inequality known as the state-dependent sweeping process. We pro
ve the existence of solution to the\nassociated time-stepping problem (imp
licit catch-up algorithm)\, and the estimates we obtain imply\nthe existen
ce of a solution to the (time-continuous) sweeping process.\nUsing numeric
al simulations of regular grid-shaped networks with softening we demonstra
te\nthe development of non-symmetric shear bands. At the same time\, in to
y examples it is easy to\nanalytically derive multiple co-existing solutio
ns\, appearing in a bifurcation which happens when\nthe parameters of the
networks continuously change from hardening through perfect plasticity to\
nsoftening.\n
LOCATION:https://researchseminars.org/talk/NSCM/99/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pei Su (Charles University\, Faculty of Mathematics and Physics)
DTSTART;VALUE=DATE-TIME:20230227T144000Z
DTEND;VALUE=DATE-TIME:20230227T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/100
DESCRIPTION:Title: A
symptotic analysis of the system describing a small moving rigid body in v
iscous incompressible fluid\nby Pei Su (Charles University\, Faculty o
f Mathematics and Physics) as part of Nečas Seminar on Continuum Mechanic
s\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charl
es University\, Sokolovská 83 Prague 8..\n\nAbstract\nWe consider the in
teraction between a viscous incompressible fluid and a\nsmall rigid body\,
which is immersed in the fluid. The fluid is modeled by\nthe 3D Navier-St
okes equations. The motion of the body obeys the conservation of linear an
d angular momentum. We assume that the density of the\nbody is constant wh
ich is independent of the size of the body ε. Based on\nthe L\np − L\nq
\nestimate of the so-called fluid-structure semigroup\, we obtain a\nunifo
rm estimate for the velocity of the body. In particular\, we show that\nth
ese estimates are ε-invariant. This help us to construct an approximation
\nsequence of the test functions of the fluid-body system. We prove that t
he solution of the fluid-body system\, in appropriate sense\, converges to
a solution\nof the Navier-Stokes equations as ε → 0.\nThis is a joint
work with Jiao He (Univerist´e Paris-Sud).\n
LOCATION:https://researchseminars.org/talk/NSCM/100/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Edoardo Mainini (University of Genoa)
DTSTART;VALUE=DATE-TIME:20230306T144000Z
DTEND;VALUE=DATE-TIME:20230306T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/101
DESCRIPTION:Title: S
tability conditions for the linearization of pure traction problems of fin
ite elasticity.\nby Edoardo Mainini (University of Genoa) as part of N
ečas Seminar on Continuum Mechanics\n\nLecture held in Room K3\, Faculty
of Mathematics and Physics\, Charles University\, Sokolovská 83 Prague
8..\n\nAbstract\nWe discuss the linearization of finite elasticity by mean
s of Gamma-convergence for the case of pure traction problems. For hyperel
astic bodies subject to equilibrated force fields\, the limit energy can b
e different from the global energy of linear elasticity subject to the sam
e force field. However\, under a suitable curl constraint\, we show that t
he linear elastic equilibrium can be obtained as limit of local minimizers
of finite elasticity. This is joint work with Roberto Ognibene and Danilo
Percivale.\n
LOCATION:https://researchseminars.org/talk/NSCM/101/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Monika Balaszová (Facaulty of Mathematics and Physics\, Charles U
niversity)
DTSTART;VALUE=DATE-TIME:20230515T134000Z
DTEND;VALUE=DATE-TIME:20230515T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/102
DESCRIPTION:Title: D
iscontinuous Galerkin method for problems in time-depend domains – theor
y and applications\nby Monika Balaszová (Facaulty of Mathematics and
Physics\, Charles University) as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\n\nAbstract\nMost of the the
oretical mathematical results on the solvability and numerical analysis of
nonstationary partial differential equations are obtained under the assum
ption that a space domain is independent of time. However\, problems in ti
me-dependent domains are important in a number of areas of science and tec
hnology. This is particularly the case of fluid-structure interaction prob
lems\, when the flow is solved in a domain deformed due to the coupling wi
th an elastic structure. There are various approaches to the solution of p
roblems in time-dependent domains\, a very popular technique is the arbitr
ary Lagrangian-Eulerian (ALE) method. In this talk we present an ALE versi
on of the space-time discontinuous Galerkin method\, which is based on pie
cewise polynomial approximations over finite element meshes\, in general d
iscontinuous on interfaces between neighbouring elements. We show that the
proposed method is numerically unconditionally stable and demonstrate its
robustness on a numerical solution of the nonlinear elasticity benchmark
problem. The developed method is also applied to the numerical simulation
of air flow in a simplified model of human vocal tract and flow induced vo
cal folds vibrations.\n
LOCATION:https://researchseminars.org/talk/NSCM/102/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Florian Oschmann (Institute of Mathematics AS CR)
DTSTART;VALUE=DATE-TIME:20230313T144000Z
DTEND;VALUE=DATE-TIME:20230313T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/103
DESCRIPTION:Title: S
ome insides in homogenization of compressible Navier-Stokes equations\
nby Florian Oschmann (Institute of Mathematics AS CR) as part of Nečas Se
minar on Continuum Mechanics\n\nLecture held in Room K3\, Faculty of Math
ematics and Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nA
bstract\nWe investigate the homogenization of the two- and\nthree-dimensio
nal unsteady compressible Navier-Stokes equations\, and\nshow (i) the conv
ergence result for the 2D case\, and (ii) a better lower\nbound for the ad
iabatic exponent occurring in the pressure law for the\n3D case. The latte
r will be covered with two different proofs. Lastly\,\nwe briefly discuss
the optimality of the achieved bounds for the\nadiabatic exponent in terms
of the underlying space-time dimension. This\nis joint work with Šárka
Nečasová (CAS) and Milan Pokorný\n(Charles University).\n
LOCATION:https://researchseminars.org/talk/NSCM/103/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Morandotti (Politecnico di Torino)
DTSTART;VALUE=DATE-TIME:20230403T134000Z
DTEND;VALUE=DATE-TIME:20230403T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/104
DESCRIPTION:Title: S
emi-discrete modeling of systems of disclinations and dislocations\nby
Marco Morandotti (Politecnico di Torino) as part of Nečas Seminar on Con
tinuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and
Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nDis
clinations in crystalline materials are point defects that are responsible
for rotational kinematic incompatibility. They are characterised by the s
o-called Frank angle\, measuring the severity of the lattice mismatch. In
a two-dimensional medium under the assumption of plain strain\, the Airy s
tress function can be used to translate the measure of incompatibility int
o a fourth-order PDE with measure data. \n\nWe propose a variational model
for disclinations in two-dimensional materials by means of the core-radiu
s approach. Moreover\, we identify a good scaling regime in which we study
the effective behaviour of dipoles of disclinations (of opposite signs)\,
thus validating analytically the results obtained in [Eshelby\, 1966]: a
dipole of plane disclinations generates an edge dislocation with Burgers v
ector perpendicular to the dipole axis. Finally\, we study the energy of a
system of a finite number of dipoles of disclinations and recover the res
ults of [Cermelli-Leoni\, 2005] for edge dislocations.\n\n \n\nThis is wor
k in collaboration with Pierluigi Cesana (Kyushu University) and Lucia De
Luca (CNR Rome).\n
LOCATION:https://researchseminars.org/talk/NSCM/104/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Franco Tomarelli (Politecnico di Milano)
DTSTART;VALUE=DATE-TIME:20230424T134000Z
DTEND;VALUE=DATE-TIME:20230424T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/105
DESCRIPTION:Title: P
ure traction and Signorini problem between linear and finite elasticity\nby Franco Tomarelli (Politecnico di Milano) as part of Nečas Seminar o
n Continuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics
and Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract
\nA limit elastic energy for pure traction problem is derived from re-scal
ed nonlinear energies of a\nhyper-elastic material body subject to an equi
librated force field.\nWe show that the strains of minimizing sequences as
sociated to re-scaled nonlinear energies weakly\nconverge\, up to subseque
nces\, to the strains of minimizers of a limit energy.\nThe limit energy f
unctional exhibits a gap that makes it different from the classical linear
elasticity\nfunctional. Nevertheless a suitable compatibility condition e
ntails the coincidence of related minima\nand minimizers\, hence the rigor
ous validation of linear elasticity. Strong violation of this condition\np
rovides a limit energy which is unbounded from below\, while a mild violat
ion may produce\nunboundedness of strains and a limit energy which has inf
initely many extra minimizers which are\nnot minimizers of standard linear
elastic energy. As a consequence\, a rigorous validation of linear\nelast
icity fails for compressive force fields that infringe such a compatibilit
y condition.\nThis phenomenon has relevant consequences also on the valida
tion of the Signorini problem in\nlinear elasticity: there are loads pushi
ng the body against the obstacle\, but unfit for the geometry of\nthe whol
e system body-obstacle\, so that the corresponding variational limit turns
out to be different\nfrom the classical Signorini problem. However\, if t
he force field acting on the body fulfils an\nappropriate geometric admiss
ibility condition\, we can show coincidence of related solutions.\nThe asy
mptotic analysis provides a sharp and rigorous variational justification o
f the unilateral\nproblem in linear elasticity\, together with an accurate
analysis of the unilateral constraint.\nThese results were obtained in a
joint research with Francesco Maddalena (Politecnico di Bari) and\nDanilo
Percivale (Università di Genova).\n
LOCATION:https://researchseminars.org/talk/NSCM/105/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Manuel Friedrich (University of Erlangen)
DTSTART;VALUE=DATE-TIME:20230327T134000Z
DTEND;VALUE=DATE-TIME:20230327T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/106
DESCRIPTION:Title: F
inite crystallization via stratification\nby Manuel Friedrich (Univers
ity of Erlangen) as part of Nečas Seminar on Continuum Mechanics\n\nLectu
re held in Room K3\, Faculty of Mathematics and Physics\, Charles Univers
ity\, Sokolovská 83 Prague 8..\n\nAbstract\nIn this talk\, I present a n
ew technique to prove two-dimensional\ncrystallization results in the squa
re lattice for finite particle\nsystems. We consider configurational energ
ies featuring two-body\nshort-ranged particle interactions and three-body
angular potentials\nfavoring bond-angles of the square lattice. To each co
nfiguration\, we\nassociate its bond graph which is then suitably modified
by identifying\nchains of successive atoms. This method\, called stratifi
cation\, reduces\nthe crystallization problem to a simple minimization tha
t corresponds to\na proof via slicing of the isoperimetric inequality in l
1. Based on\njoint work with Leonard Kreutz.\n
LOCATION:https://researchseminars.org/talk/NSCM/106/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Katerina Nik (University of Vienna)
DTSTART;VALUE=DATE-TIME:20230417T134000Z
DTEND;VALUE=DATE-TIME:20230417T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/107
DESCRIPTION:Title: A
nalysis of a three-dimensional model for MEMS with a hinged upper plate\nby Katerina Nik (University of Vienna) as part of Nečas Seminar on Con
tinuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and
Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nAn
idealized electrostatic microelectromechanical system (MEMS) consists of a
rigid ground plate above which a thin elastic plate is suspended. The ela
stic plate is assumed to be hinged on its boundary. Applying a voltage dif
ference between the two plates induces a Coulomb force that deforms the el
astic plate. The corresponding mathematical model couples a fourth-order p
arabolic equation for the vertical deformation of the elastic plate to the
harmonic electrostatic potential in the free domain between the two plate
s. In this talk\, I will present some recent results on local and global w
ell-posedness of the model as well as on existence and non-existence of st
ationary solutions.\n
LOCATION:https://researchseminars.org/talk/NSCM/107/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Semester break
DTSTART;VALUE=DATE-TIME:20230529T134000Z
DTEND;VALUE=DATE-TIME:20230529T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/108
DESCRIPTION:Title: W
e'll go on in October 2023\nby Semester break as part of Nečas Semina
r on Continuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathemat
ics and Physics\, Charles University\, Sokolovská 83 Prague 8..\nAbstrac
t: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/108/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semestr break
DTSTART;VALUE=DATE-TIME:20230904T134000Z
DTEND;VALUE=DATE-TIME:20230904T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/109
DESCRIPTION:by semestr break as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/109/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semestr break
DTSTART;VALUE=DATE-TIME:20230911T134000Z
DTEND;VALUE=DATE-TIME:20230911T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/110
DESCRIPTION:by semestr break as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/110/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semestr break
DTSTART;VALUE=DATE-TIME:20230918T134000Z
DTEND;VALUE=DATE-TIME:20230918T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/111
DESCRIPTION:by semestr break as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/111/
END:VEVENT
BEGIN:VEVENT
SUMMARY:semestr break
DTSTART;VALUE=DATE-TIME:20230925T134000Z
DTEND;VALUE=DATE-TIME:20230925T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/112
DESCRIPTION:by semestr break as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/112/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Angkana Rüland (University of Bonn)
DTSTART;VALUE=DATE-TIME:20231002T134000Z
DTEND;VALUE=DATE-TIME:20231002T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/113
DESCRIPTION:Title: R
igidity and Flexibility in the Modelling of Shape-Memory Alloys\nby An
gkana Rüland (University of Bonn) as part of Nečas Seminar on Continuum
Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics
\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nIn the mod
elling of shape-memory alloys\, a striking dichotomy between rigid and fle
xible behaviour emerges: On the one hand\, in many physically relevant set
tings\, exactly stress-free structures of sufficiently high regularity can
be shown to satisfy the kinematic compatibility conditions given by the c
haracteristics of the compatibility equations. The solutions are rigid. On
the other hand\, when dropping these regularity conditions\, the method o
f convex integration shows that a plethora of wild\, irregular solutions e
xist which do not satisfy the kinematic conditions in general. These solut
ions can approximate a large class of boundary data and are thus flexible.
In this talk\, I discuss an approach towards investigating this dichotomy
in more detail based on scaling laws. For a class of simplified models\,
we show that the complexity of the microstructure is captured by these sca
ling laws both in settings with displacement and with nucleation boundary
conditions.\n\nThe talk is based on joint work with P. Cesana\, F. Della P
orta\, J. M. Taylor\, A. Tribuzio\, Ch. Zillinger\, B. Zwicknagl.\n
LOCATION:https://researchseminars.org/talk/NSCM/113/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Illia Donhauzer (La Trobe University)
DTSTART;VALUE=DATE-TIME:20231009T134000Z
DTEND;VALUE=DATE-TIME:20231009T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/114
DESCRIPTION:Title: L
imit theorems for multifractal products of random fields\nby Illia D
onhauzer (La Trobe University) as part of Nečas Seminar on Continuum Mech
anics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, C
harles University\, Sokolovská 83 Prague 8..\n\nAbstract\nThe talk is ab
out random functions with changing local regularity\n exponent (multifract
al processes and multifractal fields in multidimensional\n cases). This ty
pe of random function has been observed in various areas\n including commu
nication systems\, precipitation fields\, econometrics\, and so\n on. The
goal of this talk is to present new results in the modeling of\n multifrac
tal random functions. One of the possible approaches to obtain\n multifrac
tal random functions is as limits of multifractal products of\n random fun
ctions (roughly speaking\, integrals of infinite products of random\n func
tions). In the talk\, I will show new results on the existence of those\n
limits in the spaces Lq as well as new results on the rate of convergence.
\n The developed methodology is also applied to multidimensional multifrac
tal\n measures. Finally\, I will show a new class of examples of geometric
\n φ-sub-Gaussian random functions when the general assumptions have a si
mple\n form and can be expressed in terms of covariance functions only.\n
LOCATION:https://researchseminars.org/talk/NSCM/114/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Kerrek Stinson (University of Bonn)
DTSTART;VALUE=DATE-TIME:20240108T144000Z
DTEND;VALUE=DATE-TIME:20240108T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/115
DESCRIPTION:Title: R
egularity for minimizers of the Griffith fracture energy\nby Kerrek St
inson (University of Bonn) as part of Nečas Seminar on Continuum Mechanic
s\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charl
es University\, Sokolovská 83 Prague 8..\n\nAbstract\nThe Griffith crite
rion says that the energy to crack a brittle\nelastic material is proporti
onal to the length of the crack. Understanding\nthe regularity of minimize
rs requires unraveling the complex interplay of\nbulk (elastic) and surfac
e (crack) energies in the vectorial setting of\nlinearized frame indiffere
nce. In dimension 2\, we prove that the crack of a\nminimizer is given by
a $C^{1\,\\alpha}$ surface outside of a singular set of\npoints that has d
imension strictly less than 1\, analogous to results for the\nscalar Mumfo
rd-Shah functional. Joint work with Manuel Friedrich (FAU) and\nCamille La
bourie (UPS).\n
LOCATION:https://researchseminars.org/talk/NSCM/115/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Valentin Calisti (Institute of Mathematics\, Czech Academy of Scie
nces)
DTSTART;VALUE=DATE-TIME:20231030T144000Z
DTEND;VALUE=DATE-TIME:20231030T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/116
DESCRIPTION:Title: M
inimization of blood damage induced by non-Newtonian fluid flows in moving
domains\nby Valentin Calisti (Institute of Mathematics\, Czech Academ
y of Sciences) as part of Nečas Seminar on Continuum Mechanics\n\nLecture
held in Room K3\, Faculty of Mathematics and Physics\, Charles Universit
y\, Sokolovská 83 Prague 8..\n\nAbstract\nMany engineering works are int
erested in the parametric optimization of\nblood pumps to minimize hemolys
is (destruction of red blood cells).\nIn order to generalize this approach
\, we study the shape continuity of a\ncoupled system of PDEs modeling blo
od flows and hemolysis evolution in\nmoving domains\, governed respectivel
y by generalized Navier-Stokes and\ntransport equations.\n\nFirst\, the sh
ape continuity of the blood flow solutions is shown. This\ndevelopment\, w
hich extends the one led in (Sokolowski\, Stebel\, Evol.\nEqu. Control The
ory\, 2014) to the case of shear thinning fluids\, is\nbased on the recent
progress made in (Nägele\, Ružička\, J. Differential\nEquations\, 2018
)\, adapted to the present framework of a sequence of\nconverging moving d
omains.\n\nAfter calculating blood flows solutions\, the velocity and stre
ss fields\nare used as coefficients and r.h.s for the transport equation g
overning\nthe evolution of the hemolysis rate. From this\, the shape conti
nuity of\nthe hemolysis rate is also proved.\n\nFinally\, these results al
low to show the existence of minimum for a\nclass of shape optimization pr
oblems based on the minimization of the\nhemolysis rate\, in the framework
of moving domains.\n
LOCATION:https://researchseminars.org/talk/NSCM/116/
END:VEVENT
BEGIN:VEVENT
SUMMARY:CANCELLED
DTSTART;VALUE=DATE-TIME:20231211T144000Z
DTEND;VALUE=DATE-TIME:20231211T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/117
DESCRIPTION:by CANCELLED as part of Nečas Seminar on Continuum Mechanics\
n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles
University\, Sokolovská 83 Prague 8..\n\nAbstract\nWe discuss the stabi
lity of objective structures of interacting atoms that form a far-reaching
generalization of crystal lattices. To this end\, we use methods from har
monic analysis to set up a second derivative test of the configurational e
nergy at equilibria\, a key point being the identification of a carefully
chosen seminorm with respect to which coercivity is estimated. In particul
ar\, a novel discrete Korn-type inequality is established in the setting o
f objective structures. We also provide an efficient algorithm to check fo
r atomistic stability\, which we illustrate numerically for a general carb
on nanotube. (This is joint work with M. Steinbach\, Augsburg).\n
LOCATION:https://researchseminars.org/talk/NSCM/117/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anastasia Molchanova (University of Vienna)
DTSTART;VALUE=DATE-TIME:20231204T144000Z
DTEND;VALUE=DATE-TIME:20231204T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/118
DESCRIPTION:Title: V
ariational Model of a Hyperelastic Capacitor\nby Anastasia Molchanova
(University of Vienna) as part of Nečas Seminar on Continuum Mechanics\n\
nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles U
niversity\, Sokolovská 83 Prague 8..\n\nAbstract\nThis talk discusses an
interplay between elastic deformations and electrostatic capacitance for
charged elastic materials. We consider a variational model\, where electro
elastic energy involves coupling elastic response and electrostatics using
a capacitary term naturally defined in Eulerian coordinates. The ensuing
electroelastic energy is then of mixed Lagrangian-Eulerian type. We study
the continuity properties of the capacitary terms under the convergence of
the deformations and prove the existence of minimizers.\n
LOCATION:https://researchseminars.org/talk/NSCM/118/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jiří Zeman (Faculty of Mathematics and Physics\, Charles Univers
ity)
DTSTART;VALUE=DATE-TIME:20231106T144000Z
DTEND;VALUE=DATE-TIME:20231106T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/119
DESCRIPTION:Title: B
ending-torsion theories for elastic and brittle nanowires as Gamma-limits
of atomistic models\nby Jiří Zeman (Faculty of Mathematics and Physi
cs\, Charles University) as part of Nečas Seminar on Continuum Mechanics\
n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles
University\, Sokolovská 83 Prague 8..\n\nAbstract\nNanotechnology has r
anked among paradigm-shifting and the fastest growing research areas over
the last 30 years. To benefit from the wide application prospects of engin
eered nanoworld objects\, it is important to study their mechanical respon
se\, which often differs from that of macroscopic bodies\, though (because
of size or structure effects for example). In particular\, there exist ro
d-like structures in nanoengineering which are long enough in one directio
n for continuum theories to be applicable\, but in the perpendicular direc
tion\, they have a diameter on the scale of tens to hundreds of atoms. In
this talk\, derivation of nonlinear continuum models for thin and ultrathi
n rods will be presented. We start from a 3D crystalline lattice with shor
t-range interactions and study simultaneous limits of vanishing rod thickn
ess and interatomic distance. Gamma-convergence especially yields a novel
theory for inextensible rods that undergo bending\, torsion\, and brittle
fracture. New discrete and surface terms appear in the limiting energy fun
ctional\, whose fracture part is expressed by an implicit cell formula tha
t covers different modes of fracture\, including (complete) cracks\, folds
and torsional cracks. Joint work with Bernd Schmidt (Augsburg).\n
LOCATION:https://researchseminars.org/talk/NSCM/119/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Stefano Almi (University of Naples)
DTSTART;VALUE=DATE-TIME:20231127T144000Z
DTEND;VALUE=DATE-TIME:20231127T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/120
DESCRIPTION:Title: S
train gradient plasticity and multi-well potentials\nby Stefano Almi (
University of Naples) as part of Nečas Seminar on Continuum Mechanics\n\n
Lecture held in Room K3\, Faculty of Mathematics and Physics\, Charles Un
iversity\, Sokolovská 83 Prague 8..\n\nAbstract\nI will present a strain
-gradient plasticity model obtained as\n$\\Gamma$-limit of a nonlinear fin
ite dislocation model characterised by\na multiple-well potential and a si
ngular perturbation term accounting\nfor the divergence of the strain fiel
d. The analysis builds upon a new\nquantitative rigidity estimate for inco
mpatible fields in presence of a\nmultiwell elastic energy\, showing that
the $L^{1^{*}}$-distance of a\nstrain field from a single well is controll
ed in terms of the\n$L^{1^{*}}$-distance from a finite set of wells\, of c
url $\\beta$\, and\nof ${\\rm div} \\beta$. This is a joint work with Dari
o Reggiani (Scuola\nSuperiore Meridionale) and Francesco Solombrino (Unive
rsity of Naples\nFederico II).\n
LOCATION:https://researchseminars.org/talk/NSCM/120/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xmas
DTSTART;VALUE=DATE-TIME:20231225T144000Z
DTEND;VALUE=DATE-TIME:20231225T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/121
DESCRIPTION:by Xmas as part of Nečas Seminar on Continuum Mechanics\n\nLe
cture held in Room K3\, Faculty of Mathematics and Physics\, Charles Univ
ersity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/121/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Raffaele Grande (Czech Academy of Sciences\, Institute of Informat
ion Theory and Automation)
DTSTART;VALUE=DATE-TIME:20231023T134000Z
DTEND;VALUE=DATE-TIME:20231023T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/122
DESCRIPTION:Title: S
tochastic control problems and a convergence result for horizontal mean cu
rvature flow\nby Raffaele Grande (Czech Academy of Sciences\, Institut
e of Information Theory and Automation) as part of Nečas Seminar on Conti
nuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and Ph
ysics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nThe e
volution by horizontal mean curvature flow was broadly studied for its app
lications in neurogeometry and in image processing (e.g. Citti-Sarti model
). It represents the contracting evolution of a hypersurface embedded in a
particular geometrical setting\, called sub-Riemannian geometry\, in whic
h only some curves (called horizontal curves) are admissible by definition
. This may lead to the existence of some points of the hypersurface\, call
ed characteristic\, in which is not possible to define the so-called horiz
ontal normal. To avoid this problem\, it is possible to use the notion of
Riemannian approximation of a sub-Riemannian geometry applied to the horiz
ontal mean curvature flow.\n\nI will show the connection between the evolu
tion of a generic hypersurface in this setting and the associated stochast
ic optimal control problem. Then\, I will show some results of asymptotic
optimal controls in the Heisenberg group and use them to show later a conv
ergence result between the solutions of the approximated mean curvature fl
ow and the horizontal ones. This is from some joint works with N. Dirr and
F. Dragoni.\n
LOCATION:https://researchseminars.org/talk/NSCM/122/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Tomáš Bodnár (Faculty of Mechanical Engineering\, Czech Technic
al University)
DTSTART;VALUE=DATE-TIME:20231016T134000Z
DTEND;VALUE=DATE-TIME:20231016T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/123
DESCRIPTION:Title: O
n the estimation of blood hemolysis index from viscoelastic stretch model<
/a>\nby Tomáš Bodnár (Faculty of Mechanical Engineering\, Czech Technic
al University) as part of Nečas Seminar on Continuum Mechanics\n\nLecture
held in Room K3\, Faculty of Mathematics and Physics\, Charles Universit
y\, Sokolovská 83 Prague 8..\n\nAbstract\nThis contribution presents an
alternative way of estimating the blood damage\nhemolysis index using the
viscoelastic stretch tensor. This tensor is obtained\nby solving a set of
coupled partial differential equations describing the\nrheology of shear-t
hinning viscoelastic fluid. The main advantage of the chosen\napproach is
that the already calculated and known stretch tensor is just reused\nand p
ostprocessed to assess the local deformation of red blood cells\, that can
\nin certain cases lead to degradation of the cell membranes and consequen
t\nrelease of hemoglobin. The algorithm of solving the viscoelastic stretc
h tensor\nequations and hemolysis index postprocessing will be outlined an
d discussed in\ndetail. Some initial numerical simulations for an axisymme
tric idealized\nstenosed blood vessel\, obtained using an in-house finite-
volume solver\, will be\npresented.\n
LOCATION:https://researchseminars.org/talk/NSCM/123/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Bresciani (Department of Mathematics\, University of Erlange
n)
DTSTART;VALUE=DATE-TIME:20231113T144000Z
DTEND;VALUE=DATE-TIME:20231113T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/124
DESCRIPTION:Title: C
ANCELED\nby Marco Bresciani (Department of Mathematics\, University of
Erlangen) as part of Nečas Seminar on Continuum Mechanics\n\nLecture hel
d in Room K3\, Faculty of Mathematics and Physics\, Charles University\,
Sokolovská 83 Prague 8..\n\nAbstract\nWe study a variational model for f
erromagnetic elastomers featuring a mixed Eulerian-Lagrangian formulation.
The magnetic variable is defined on the deformed configuration\nin the ac
tual space and the saturation constraint involves the Jacobian determinant
of\ndeformations.\nFirst\, in the case for purely elastic materials\, we
discuss the existence of equilibrium\nconfigurations and we investigate th
e model under quasistatic evolution in the rate-independent setting. Subse
quently\, we address the extension of the existence theory for\nthe static
problem to a framework allowing for cavitation.\nThe talk is partly based
on joint work with Manuel Friedrich (FAU Erlangen-Nuernberg)\nand Carlos
Mora-Corral (Universidad Autonoma de Madrid).\n
LOCATION:https://researchseminars.org/talk/NSCM/124/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jaroslav Kruis (Department of Mechanics\, Faculty of Civil Enginee
ring\, Czech Technical University)
DTSTART;VALUE=DATE-TIME:20231120T144000Z
DTEND;VALUE=DATE-TIME:20231120T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/125
DESCRIPTION:Title: H
ydro-thermo-mechanical simulation of deep geological repository of radioac
tive waste\nby Jaroslav Kruis (Department of Mechanics\, Faculty of Ci
vil Engineering\, Czech Technical University) as part of Nečas Seminar on
Continuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics
and Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\
nPossible variants of deep geological repository will be introduced. Selec
ted\nengineering problems connected with the deep repositories will be sum
marized\nand the appropriate mathematical models and numerical methods for
their\nsolution will be described. The first problem is heat transfer cau
sed by the\nradioactive waste in steel-based containers of length about 5
meters. The\nsizes of studied domain are approximately one kilometer and t
he investigated\nperiod is thousands of years long. A combination of suita
ble numerical\nmethods has to be used in order to finish the numerical sim
ulations in\nreasonable time. The second problem is thermo-hydro-mechanica
l (THM)\nanalysis of a system container-bentonite layer-surrounding rock m
assif. It\nis based on the balance equation of momentum\, mass and energy
together with\nvarious constitutive relationships. The THM analysis is for
mulated for 2D\nand 3D.\n
LOCATION:https://researchseminars.org/talk/NSCM/125/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Xmas
DTSTART;VALUE=DATE-TIME:20231218T144000Z
DTEND;VALUE=DATE-TIME:20231218T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/126
DESCRIPTION:by Xmas as part of Nečas Seminar on Continuum Mechanics\n\nLe
cture held in Room K3\, Faculty of Mathematics and Physics\, Charles Univ
ersity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/126/
END:VEVENT
BEGIN:VEVENT
SUMMARY:New Year
DTSTART;VALUE=DATE-TIME:20240101T144000Z
DTEND;VALUE=DATE-TIME:20240101T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/127
DESCRIPTION:by New Year as part of Nečas Seminar on Continuum Mechanics\n
\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles
University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/127/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Leon Happ (TU Wien)
DTSTART;VALUE=DATE-TIME:20240311T144000Z
DTEND;VALUE=DATE-TIME:20240311T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/128
DESCRIPTION:Title: E
xtension operators for homogenization that preserve target manifold constr
aints\nby Leon Happ (TU Wien) as part of Nečas Seminar on Continuum M
echanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\
, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nMotivated b
y homogenization problems in micro-magnetics and plasticity\, we study the
existence of extension operators for W^{1\,p} Sobolev maps on periodicall
y perforated domains\, where the maps are only allowed to range in some pr
escribed Riemannian manifold. For applications\, one demands that separate
L^p bounds for the extension and its gradient\, independent of the scale
of the perforations\, hold. We stress that the main novelty of our work li
es in the fact that all functions are subject to a manifold constrained in
the target space. The challenge is then to find an extension operator pre
serving this feature. It turns out that this is a problem sitting right at
the interface between analysis and algebraic topology.\n\nThe unconstrain
ed case was famously treated in an influential paper by E. Acerbi\, V. C.
Piat\, G. Dal Maso\, and D. Percivale from 1992\, providing a positive ans
wer for all p except infinity. However\, as soon as one starts to include
manifold constraints\, the existence problem of extensions becomes highly
sensitive towards the relation between p and d and calls for a case differ
entiation. It can be shown that\, due to Sobolev embeddings\, for p bigger
or equal than d the question whether every Sobolev function on a perforat
ed domain possesses an extension reduces to a similar question for continu
ous functions. This is a problem well studied in algebraic topology and\,
in theory\, there are tools available to determine its answer.\n\nThese ob
servations lead us to focus on the case that p is smaller than d (e.g.\, i
n the physically relevant instance that p=2\, d=3). Then\, for p>1\, we ca
n indeed proof the existence of an extension operator as described above\,
and under the additional assumption that the target manifold is [p-1] con
nected (where [] is the floor function)\, meaning that the first [p-1] fun
damental groups of N are trivial. The proof builds upon the already allude
d result by E. Acerbi\, V. C. Piat\, G. Dal Maso\, and D. Percivale\, comb
ining it with an appropriate retraction onto the target manifold\, firstly
suggested by R. Hardt and F.-H. Lin in 1987\, and originating again from
algebraic topology. It is important to note that the extension operator wi
ll not be linear. Already the target manifold constraint is not compatible
with linearity. \n\nIn my talk\, I will put a special emphasis on illumin
ating the [p-1]-connectedness condition that arises from the construction
of the retraction onto N. The same assumption is already well-known in the
context of the Sobolev functions between manifolds\, where\, for instance
\, it determines the surjectivity of the trace operator. This is only one
example of a deeper connection that I will unveil.\n
LOCATION:https://researchseminars.org/talk/NSCM/128/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Morandotti (Politecnico di Torino)
DTSTART;VALUE=DATE-TIME:20240219T144000Z
DTEND;VALUE=DATE-TIME:20240219T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/129
DESCRIPTION:Title: F
rom game theory to the control of multi-agent systems\nby Marco Morand
otti (Politecnico di Torino) as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\n\nAbstract\nMotivated by the
analysis of evolutive systems of agents with strategies\, we enrich the s
tructure of the celebrated replicator equation to include more realistic s
cenarios suitable for game-theoretic applications. In this context\, non-l
inear continuity equations arise to describe the evolution of the mean-fie
ld limit of such systems. Starting from simple cases\, we discuss more sop
histicated models\, which include the interplay between the evolution of t
he position of the players and the evolution of their strategies\; the add
ition of a control factor that models the presence of a policy maker in mu
lti-population dynamics\, together with the rise and fall of leadership\;
the effects of an entropic regularisation in the system\, as well as that
of fluctuations.\n\nWe present the derivation of these equations\, togethe
r with some well-posedness results.\n
LOCATION:https://researchseminars.org/talk/NSCM/129/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Bernd Schmidt (University of Augsburg)
DTSTART;VALUE=DATE-TIME:20240226T144000Z
DTEND;VALUE=DATE-TIME:20240226T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/130
DESCRIPTION:Title: O
n the Stability of Objective Structures\nby Bernd Schmidt (University
of Augsburg) as part of Nečas Seminar on Continuum Mechanics\n\nLecture h
eld in Room K3\, Faculty of Mathematics and Physics\, Charles University\
, Sokolovská 83 Prague 8..\n\nAbstract\nWe discuss the stability of obje
ctive structures of interacting atoms that form a far reaching generalizat
ion of crystal lattices. To this end\, we use methods from harmonic analys
is to set up a second derivative test of the configurational energy at equ
ilibria\, a key point being the identification of a carefully chosen semin
orm with respect to which coercivity is estimated. In particular\, a novel
discrete Korn type inequality is established in the setting of objective
structures. We also provide an efficient algorithm to check for atomistic
stability which we illustrate numerically for a general carbon nanotube. (
This is joint work with M. Steinbach\, Augsburg)\n
LOCATION:https://researchseminars.org/talk/NSCM/130/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Marco Bresciani (University of Erlangen)
DTSTART;VALUE=DATE-TIME:20240415T134000Z
DTEND;VALUE=DATE-TIME:20240415T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/131
DESCRIPTION:Title: V
ariational models with Eulerian-Lagrangian formulation allowing for materi
al failure\nby Marco Bresciani (University of Erlangen) as part of Ne
čas Seminar on Continuum Mechanics\n\nLecture held in Room K3\, Faculty
of Mathematics and Physics\, Charles University\, Sokolovská 83 Prague 8
..\n\nAbstract\nWe investigate the existence of minimizers of variational
models with Eulerian-Lagrangian\nformulations. Similar models arise natura
lly in many multi-physics problems such as\nthe modeling of nematic and fe
rromagnetic elastomers. We consider energy functionals\ndepending on the d
eformation of a body\, defined on its reference configuration\, and an\nEu
lerian map defined on the unknown deformed configuration in the actual spa
ce. Our\nexistence theory moves beyond the purely elastic setting and acco
unts for material failure\nby addressing free-discontinuity problems where
both deformations and Eulerian fields are\nallowed to jump. To do so\, we
build upon the work of Henao and Mora-Corral regarding\nthe variational m
odeling of cavitation and fracture in nonlinear elasticity. Two main\nsett
ings are considered by modeling deformations as Sobolev and SBV -maps\, re
spectively.\nThe regularity of Eulerian maps is specified in each of these
two settings according to the\ngeometric and topological properties of th
e deformed configuration. Effectiveness and\nlimitations of the theory are
illustrated by means of explicit examples.\nThe talk is based on joint wo
rk with Manuel Friedrich (FAU Erlangen-Nuremberg) and\nCarlos Mora-Corral
(Universidad Autonoma de Madrid).\n
LOCATION:https://researchseminars.org/talk/NSCM/131/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giovanni Fantuzzi (University of Erlangen)
DTSTART;VALUE=DATE-TIME:20240513T134000Z
DTEND;VALUE=DATE-TIME:20240513T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/132
DESCRIPTION:Title: M
oment-Sum-of-Squares relaxations for variational problems\nby Giovanni
Fantuzzi (University of Erlangen) as part of Nečas Seminar on Continuum
Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics
\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nMoment-Sum
-of-Squares (moment-SOS) relaxations are an established technique to compu
te converging sequences of lower bounds on the global minimum of finite-di
mensional polynomial optimization problems. In this talk\, I will discuss
two recent extensions of moment-SOS relaxations to infinite-dimensional va
riational problems\, where a (possibly nonconvex) integral functional is t
o be minimized over functions from a Sobolev space. The first extension op
timizes so-called "null Lagrangian translations" and returns certified low
er bounds on the global minimum of the variational problem. The second ext
ension\, instead\, produces upper bounds by approximating minimizers of fi
nite element discretizations of the variational problem. Conditions that e
nsure the convergence of these upper and lower bounds to the desired globa
l minimum will be discussed\, and current gaps between theory and practice
will be illustrated by means of examples.\n
LOCATION:https://researchseminars.org/talk/NSCM/132/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hywel Normington (University of Strathclyde)
DTSTART;VALUE=DATE-TIME:20240422T134000Z
DTEND;VALUE=DATE-TIME:20240422T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/133
DESCRIPTION:Title: A
decoupled\, convergent and fully linear algorithm for the Landau-Lifshitz
-Gilbert equation with magnetoelastic effects\nby Hywel Normington (Un
iversity of Strathclyde) as part of Nečas Seminar on Continuum Mechanics\
n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Charles
University\, Sokolovská 83 Prague 8..\n\nAbstract\nThe mechanical and m
agnetic properties of ferromagnetic materials are strongly coupled. Applyi
ng a stress to a ferromagnetic material changes the magnetic state\, and a
pplying a magnetic field deforms it. These fall collectively under the phe
nomena of "magnetostriction". We consider the coupled system of the Landau
-Lifshitz-Gilbert (LLG) equation and conservation of momentum to describe
magnetostrictive processes. For this nonlinear system of time-dependent pa
rtial differential equations\, we present a decoupled and unconditionally
convergent integrator based on linear finite elements in space and a one-s
tep method in time. Compared to previous works on this problem\, for our m
ethod\, we prove a discrete energy law that mimics that of the continuous
problem. Moreover\, we do not employ a nodal projection to impose the unit
-length constraint on the discrete magnetization\, so that the stability o
f the method does not require weakly acute meshes. Furthermore\, our integ
rator and its analysis hold for a more general setting\, including body fo
rces and traction\, and a more general representation of the magnetostrain
.\n\nH. Normington and M. Ruggeri\, A decoupled\, convergent and fully lin
ear algorithm for the Landau--Lifshitz--Gilbert equation with magnetoelast
ic effects.\n(under review)\,\nhttps://arxiv.org/abs/2309.00605v2\n
LOCATION:https://researchseminars.org/talk/NSCM/133/
END:VEVENT
BEGIN:VEVENT
SUMMARY:break
DTSTART;VALUE=DATE-TIME:20240129T144000Z
DTEND;VALUE=DATE-TIME:20240129T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/134
DESCRIPTION:by break as part of Nečas Seminar on Continuum Mechanics\n\nL
ecture held in Room K3\, Faculty of Mathematics and Physics\, Charles Uni
versity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/134/
END:VEVENT
BEGIN:VEVENT
SUMMARY:break
DTSTART;VALUE=DATE-TIME:20240205T144000Z
DTEND;VALUE=DATE-TIME:20240205T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/135
DESCRIPTION:by break as part of Nečas Seminar on Continuum Mechanics\n\nL
ecture held in Room K3\, Faculty of Mathematics and Physics\, Charles Uni
versity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/135/
END:VEVENT
BEGIN:VEVENT
SUMMARY:break
DTSTART;VALUE=DATE-TIME:20240212T144000Z
DTEND;VALUE=DATE-TIME:20240212T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/136
DESCRIPTION:by break as part of Nečas Seminar on Continuum Mechanics\n\nL
ecture held in Room K3\, Faculty of Mathematics and Physics\, Charles Uni
versity\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/136/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Jan Scherz (University of Wuerzburg)
DTSTART;VALUE=DATE-TIME:20240408T134000Z
DTEND;VALUE=DATE-TIME:20240408T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/137
DESCRIPTION:Title: W
eak Solutions to Mathematical Models of the Interaction between Fluids\, S
olids and Electromagnetic Fields\nby Jan Scherz (University of Wuerzbu
rg) as part of Nečas Seminar on Continuum Mechanics\n\nLecture held in Ro
om K3\, Faculty of Mathematics and Physics\, Charles University\, Sokolov
ská 83 Prague 8..\n\nAbstract\nWe prove the existence of weak solutions
to two systems of PDEs modeling interactions between fluids\, solids and e
lectromagnetic fields. The first problem we consider describes the motion
of an insulating rigid body through an electrically conducting incompressi
ble fluid. The existence of weak solutions to this problem is achieved via
a time discretization and an application of the Brinkman penalization. Th
e second considered problem deals with the evolution of the deformation an
d the magnetization of a magnetoelastic material and is solved via an appl
ication of De Giorgi's minimizing movements scheme.\n
LOCATION:https://researchseminars.org/talk/NSCM/137/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Easter Monday
DTSTART;VALUE=DATE-TIME:20240401T134000Z
DTEND;VALUE=DATE-TIME:20240401T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/138
DESCRIPTION:Title: n
o talk\nby Easter Monday as part of Nečas Seminar on Continuum Mechan
ics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Cha
rles University\, Sokolovská 83 Prague 8..\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/138/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eduard Rohan (University of West Bohemia\, Pilsen)
DTSTART;VALUE=DATE-TIME:20240325T144000Z
DTEND;VALUE=DATE-TIME:20240325T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/139
DESCRIPTION:Title: H
omogenization based model of flows in piezoelectric porous metamaterials d
riven by peristaltic deformation\nby Eduard Rohan (University of West
Bohemia\, Pilsen) as part of Nečas Seminar on Continuum Mechanics\n\nLect
ure held in Room K3\, Faculty of Mathematics and Physics\, Charles Univer
sity\, Sokolovská 83 Prague 8..\n\nAbstract\nThe seminar talk is devoted
to the multiscale modelling of an electroactive porous material intended
for fluid transport. Its functionality is based on the peristaltic flow wh
ich is induced by deforming pore walls. This phenomenon is of a great impo
rtance in physiology and biomechanics\, however\, as a driving mechanism o
f fluid transport\, it presents and important and challenging issue in the
design of smart ``bio-inspired'' materials. We consider locally periodic
porous structures saturated by a Newtonian fluid. The peristaltic deforma
tion wave of the microchannels is induced by a convenient local control of
piezoelectric segments. Several issues related to the construction of a c
omputationally efficient two-scale metamaterial model within the homogeniz
ation framework will be presented. We consider relatively small deformatio
n which enables to use the linear kinematic framework. The poro-piezoelect
ric model derived in [1] is extended for the viscous fluid flow while resp
ecting the inertia effects in both the phases. Using the homogenization ba
sed on the classic asymptotic analysis\, cell problems (at the microlevel)
are obtained which provide characteristic responses of the microstructure
s with respect to macroscopic strains\, fluid pressure and electric potent
ials. These responses are needed to compute the effective (homogenized) pa
rameters of the macroscopic problem which depend on the microconfiguration
. The numerical studies demonstrate that such a linear model cannot captur
e the desired pumping effect of the homogenized continuum. To achieve this
functionality of the model\, it is necessary to account for the nonlinear
ity associated with deformation-dependent microconfigurations. To avoid hu
rdles associated with a fully nonlinear two-scale model\, we apply a linea
rization procedure based on the sensitivity analysis of the local characte
ristic responses with respect to the deformation induced by the macroscopi
c quantities. In this way\, by virtue of the methodology introduced in [2]
\, we get first-order expansions of all the homogenized coefficients. The
dynamic effects lead to the macroscopic flow model in a convolution form.
For this option\, a special treatment of the deformation-dependent dynamic
permeability is needed. Numerical examples illustrate efficiency of the p
roposed computational approach [3].\n\n\n[1] E. Rohan\, V. Lukeš. On mode
lling nonlinear phenomena in deforming heterogeneous media using homogeniz
ation and sensitivity analysis concepts. Applied Mathematics and Computati
on (2015) 267:583-595.\n\n[2] E. Rohan\, V. Lukeš. Homogenization of the
fluid-saturated piezoelectric porous media. Int. Jour. Solids and Structur
es (2018) 147:110-125.\n\n[3] E. Rohan\, V. Lukeš. Homogenization of peri
staltic flows in piezoelectric porous media. (2023) arXiv:2304.05393v1\, h
ttps://doi.org/10.48550/arXiv.2304.05393\n
LOCATION:https://researchseminars.org/talk/NSCM/139/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chiara Gavioli (Czech Technical University\, Prague)
DTSTART;VALUE=DATE-TIME:20240429T134000Z
DTEND;VALUE=DATE-TIME:20240429T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/140
DESCRIPTION:Title: A
model for lime consolidation of porous solids\nby Chiara Gavioli (Cze
ch Technical University\, Prague) as part of Nečas Seminar on Continuum M
echanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\
, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nWe present
the first mathematical 3D model describing the process of filling the pore
s of a building material with a water-lime-mixture\, with the goal to impr
ove the consistency of the porous solid. Chemical reactions produce calciu
m carbonate which glues the solid particles together at some distance from
the boundary and strengthens the whole structure. The model consists of a
reaction-diffusion system with a nonlinear non-smooth boundary condition\
, coupled with the mass balance equations for the chemical reaction. The m
ain result consists in proving that the system has a solution for each ini
tial data from a physically relevant class. A 1D numerical test shows a qu
alitative agreement with experimental observations.\nThis is a joint work
with B. Detmann (Universität Duisburg-Essen)\, P. Krejčí\, J. Lamač\,
and Y. Namlyeyeva (Czech Technical University Prague).\n
LOCATION:https://researchseminars.org/talk/NSCM/140/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Johannes Zimmer (Technical University of Munich)
DTSTART;VALUE=DATE-TIME:20240506T134000Z
DTEND;VALUE=DATE-TIME:20240506T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/141
DESCRIPTION:Title: D
eriving a GENERIC system from a Hamiltonian system\nby Johannes Zimmer
(Technical University of Munich) as part of Nečas Seminar on Continuum
Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics
\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\nWe reconsi
der the problem of coarse-graining infinite-dimensional Hamiltonian dynami
cs to obtain a macroscopic system that includes dissipative mechanisms. In
particular\, we study the thermodynamical implications concerning Hamilto
nians\, energy\, and entropy and the induced geometric structures. The Ham
iltonian model is described by a unitary group\, and is time-reversible. T
he coarse-grained description includes dissipative effects\, is described
by a contraction semigroup\, and is thus irreversible. The concepts of dil
ations and contractions will be described as they provide a link between d
issipative semigroups and unitary groups. The coarse-grained version will
be shown to have GENERIC (General Equations for Non-Equilibrium Reversible
Irreversibe Coupling) structure\, with conserved energy\, nondecreasing e
ntropy and an Onsager operator describing the dissipation.\n\n This is joi
nt work with Alex Mielke and Mark Peletier.\n
LOCATION:https://researchseminars.org/talk/NSCM/141/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Giuseppe Tomassetti (University of Roma Tre)
DTSTART;VALUE=DATE-TIME:20240318T144000Z
DTEND;VALUE=DATE-TIME:20240318T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/142
DESCRIPTION:Title: A
mechanical model of ocular bulb vibrations and implications for acoustic
tonometry\nby Giuseppe Tomassetti (University of Roma Tre) as part of
Nečas Seminar on Continuum Mechanics\n\nLecture held in Room K3\, Facult
y of Mathematics and Physics\, Charles University\, Sokolovská 83 Prague
8..\n\nAbstract\nWe propose a comprehensive mechanical model of ocular bu
lb vibrations and discuss its implications for acoustic tonometry. The mod
el describes the eye wall as a spherical\, pre-stressed elastic shell cont
aining a viscoelastic material and accounts for the interaction between th
e elastic corneoscleral shell and the viscoelastic vitreous humor. We inve
stigate the natural frequencies of the system and the corresponding vibrat
ion modes\, expanding the solution in terms of scalar and vector spherical
harmonics. From a quantitative point of view\, our findings reveal that t
he eyebulb vibration frequencies significantly depend on IOP. This depende
ncy has two origins: "geometric" stiffening\, due to an increase of the pr
e-stress\, and "material" stiffening\, due to the nonlinearity of the stre
ss-strain curve of the sclera. The model shows that the second effect is b
y far dominant. We also find that the oscillation frequencies depend on oc
ular rigidity\, but this dependency is important only at relatively large
values of IOP. Thus close to physiological conditions\, IOP is the main de
terminant of ocular vibration frequencies. The vitreous rheological proper
ties are found to mostly influence vibration damping. This study contribut
es to the understanding of the mechanical behavior of the eye under dynami
c conditions and thus has implications for non-contact intraocular pressur
e measurement techniques\, such as acoustic tonometry. The model can also
be relevant for other ocular pathological conditions\, such as traumatic r
etinal detachment\, which are believed to be influenced by the dynamic beh
avior of the eye.\n
LOCATION:https://researchseminars.org/talk/NSCM/142/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Václav Mácha (Institute of Mathematics\, Czech Academy of Scienc
es)
DTSTART;VALUE=DATE-TIME:20240304T144000Z
DTEND;VALUE=DATE-TIME:20240304T161000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/143
DESCRIPTION:Title: A
NALYSIS OF A SYSTEM MODELLING THE INTERACTION BETWEEN THE MOTION OF PISTON
-SPRING AND A VISCOUS GAS\nby Václav Mácha (Institute of Mathematics
\, Czech Academy of Sciences) as part of Nečas Seminar on Continuum Mecha
nics\n\nLecture held in Room K3\, Faculty of Mathematics and Physics\, Ch
arles University\, Sokolovská 83 Prague 8..\n\nAbstract\nWe are concerne
d with a one-dimensional flow of a compressible\nfluid which may be seen\n
as a simplification of the flow of fluid in a long\, thin pipe. We assume\
nthe pipe is on one side\,\nending by a spring. The other side of the pipe
is left open – there\, we\nassume either inflow or outflow\nboundary co
nditions. Such a situation can be understood as a toy model for\nhuman lun
gs. We tackle\nthe question of uniqueness and the existence of a strong so
lution for a\nsystem modeling the above process\,\nspecial emphasis is lai
d upon the estimate of the maximal time of\nexistence.\nThis is a joint wo
rk with Sabrine Chebbi and Šárka Nečasová\n
LOCATION:https://researchseminars.org/talk/NSCM/143/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pavel Krejčí (Czech Technical University in Prague\, Faculty of
Civil Engineering)
DTSTART;VALUE=DATE-TIME:20240520T134000Z
DTEND;VALUE=DATE-TIME:20240520T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/144
DESCRIPTION:Title: H
ysteresis in porous media\nby Pavel Krejčí (Czech Technical Universi
ty in Prague\, Faculty of Civil Engineering) as part of Nečas Seminar on
Continuum Mechanics\n\nLecture held in Room K3\, Faculty of Mathematics a
nd Physics\, Charles University\, Sokolovská 83 Prague 8..\n\nAbstract\n
We propose a model for fluid diffusion in partially saturated porous media
taking\ninto account saturation-dependent permeability as well as hystere
sis effects in the pressure saturation relation. The resulting mathematica
l problem leads to a diffusion equation for\nthe pressure in an N-dimensio
nal domain with a Preisach hysteresis operator under the time\nderivative
and in the diffusion coefficient. The problem is doubly degenerate in the
sense\nthat the saturation range is bounded\, and no a priori control of t
he time derivative of the\npressure is available. We discuss the condition
s for existence and uniqueness of a solution\nto the problem with or witho
ut gravity effects in appropriate function spaces\, as well as the\nquesti
on of bounded speed of propagation. This is a joint work with Chiara Gavio
li.\n
LOCATION:https://researchseminars.org/talk/NSCM/144/
END:VEVENT
BEGIN:VEVENT
SUMMARY:summer break
DTSTART;VALUE=DATE-TIME:20240527T134000Z
DTEND;VALUE=DATE-TIME:20240527T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/145
DESCRIPTION:Title: W
e'll continue on September 30\, 2024\nby summer break as part of Neč
as Seminar on Continuum Mechanics\n\nLecture held in Room K3\, Faculty of
Mathematics and Physics\, Charles University\, Sokolovská 83 Prague 8..
\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/NSCM/145/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Matteo Negri (University of Pavia)
DTSTART;VALUE=DATE-TIME:20241021T134000Z
DTEND;VALUE=DATE-TIME:20241021T151000Z
DTSTAMP;VALUE=DATE-TIME:20240715T175123Z
UID:NSCM/146
DESCRIPTION:Title: R
ate-independent evolutions in phase-field fracture generated by equilibriu
m configurations\nby Matteo Negri (University of Pavia) as part of Ne
čas Seminar on Continuum Mechanics\n\nInteractive livestream: https://ces
net.zoom.us/j/94319936814?pwd=Y0pRL0FpWEhhQ1U4TzZGc2FDQVM4Zz09\nView-only
livestream: https://www.youtube.com/channel/UCn9vmevniyXXLEr7VBp5cCQ\nLect
ure held in Room K3\, Faculty of Mathematics and Physics\, Charles Univer
sity\, Sokolovská 83 Prague 8..\n\nAbstract\nIn the phase-field approach
\, and in other regularized fracture models\, rate-independent (quasi-stat
ic) evolutions are usually obtained by means of time-discrete schemes\, pr
oviding at each time an equilibrium configuration of the system. Numerica
lly\, equilibria are computed by descent methods for the free energy (e.g.
staggered\, monolithic etc.) endowed with a suitable irreversibility cons
traint on phase-field parameter (e.g. monotonicity in time). The time-con
tinuous limit evolution is characterized in terms of evolutionary variatio
nal inequalities and in terms of Griffith's criterion. The study of the li
mit evolution reveals a couple of propagation regimes: stable (or steady s
tate) and unstable (or catastrophic). In the stable regime the evolution i
s simultaneous (in displacement and phase field parameter) and satisfies G
riffith's criterion in terms of toughness and phase field energy release r
ate. In the unstable regime the evolution is not necessarily simultaneous
and may not satisfy Griffith's criterion. Energy identity holds in general
with an instantaneous drop of energy in unstable times. The monotonicity
constraint turns out to be fully thermodynamically consistent along the wh
ole evolution. Technically\, the proof relies on: (a) the strong convergen
ce of the phase field parameter\, (b) Kuratowski convergence of parametriz
ed discrete times\, (c) the limit of the power identity. The result is ver
y general since it works independently of the scheme employed in the incre
mental problem\, it holds for instance for AT1 and AT2 energies\, in plane
strain and plane stress settings. Numerically\, we compare energies\, ene
rgy release rates and evolutions computed in the sharp crack and in the ph
ase field setting for a couple of reference benchmarks: the double cantile
ver beam (for steady state propagation) and the single edge notch under te
nsion (for unstable propagation).\n
LOCATION:https://researchseminars.org/talk/NSCM/146/
URL:https://cesnet.zoom.us/j/94319936814?pwd=Y0pRL0FpWEhhQ1U4TzZGc2FDQVM4Z
z09
URL:https://www.youtube.com/channel/UCn9vmevniyXXLEr7VBp5cCQ
END:VEVENT
END:VCALENDAR