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BEGIN:VEVENT
SUMMARY:Tomas Roubicek (Math. Inst. Charles University)
DTSTART;VALUE=DATE-TIME:20201012T134000Z
DTEND;VALUE=DATE-TIME:20201012T151000Z
DTSTAMP;VALUE=DATE-TIME:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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:20220528T073633Z
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
END:VCALENDAR