258 research outputs found
The relaxed-polar mechanism of locally optimal Cosserat rotations for an idealized nanoindentation and comparison with 3D-EBSD experiments
The rotation arises as the unique orthogonal
factor of the right polar decomposition of a given
invertible matrix . In the context of nonlinear elasticity
Grioli (1940) discovered a geometric variational characterization of as a unique energy-minimizing rotation. In preceding works, we have
analyzed a generalization of Grioli's variational approach with weights
(material parameters) and (Grioli: ). The
energy subject to minimization coincides with the Cosserat shear-stretch
contribution arising in any geometrically nonlinear, isotropic and quadratic
Cosserat continuum model formulated in the deformation gradient field and the microrotation field . The corresponding set of non-classical energy-minimizing
rotations represents a new relaxed-polar mechanism.
Our goal is to motivate this mechanism by presenting it in a relevant setting.
To this end, we explicitly construct a deformation mapping
which models an idealized nanoindentation and compare the corresponding optimal
rotation patterns with experimentally
obtained 3D-EBSD measurements of the disorientation angle of lattice rotations
due to a nanoindentation in solid copper. We observe that the non-classical
relaxed-polar mechanism can produce interesting counter-rotations. A possible
link between Cosserat theory and finite multiplicative plasticity theory on
small scales is also explored.Comment: 28 pages, 11 figure
Regularity for a geometrically nonlinear flat Cosserat micropolar membrane shell with curvature
We consider the rigorously derived thin shell membrane -limit of a
three-dimensional isotropic geometrically nonlinear Cosserat micropolar model
and deduce full interior regularity of both the midsurface deformation
and the orthogonal microrotation
tensor field . The only further
structural assumption is that the curvature energy depends solely on the
uni-constant isotropic Dirichlet type energy term . We use Rivi\`ere's
regularity techniques of harmonic map type systems for our system which couples
harmonic maps to with a linear equation for . The additional
coupling term in the harmonic map equation is of critical integrability and can
only be handled because of its special structure
Jointly they edit: examining the impact of community identification on political interaction in Wikipedia
In their 2005 study, Adamic and Glance coined the memorable phrase "divided
they blog", referring to a trend of cyberbalkanization in the political
blogosphere, with liberal and conservative blogs tending to link to other blogs
with a similar political slant, and not to one another. As political discussion
and activity increasingly moves online, the power of framing political
discourses is shifting from mass media to social media. Continued examination
of political interactions online is critical, and we extend this line of
research by examining the activities of political users within the Wikipedia
community. First, we examined how users in Wikipedia choose to display (or not
to display) their political affiliation. Next, we more closely examined the
patterns of cross-party interaction and community participation among those
users proclaiming a political affiliation. In contrast to previous analyses of
other social media, we did not find strong trends indicating a preference to
interact with members of the same political party within the Wikipedia
community. Our results indicate that users who proclaim their political
affiliation within the community tend to proclaim their identity as a
"Wikipedian" even more loudly. It seems that the shared identity of "being
Wikipedian" may be strong enough to triumph over other potentially divisive
facets of personal identity, such as political affiliation.Comment: 33 pages, 5 figure
Novel -conforming finite elements for the relaxed micromorphic sequence
In this work we construct novel -conforming
finite elements for the recently introduced relaxed micromorphic sequence,
which can be considered as the completion of the -sequence with respect to the -space. The elements respect -regularity and
their lowest order versions converge optimally for -fields. This work introduces a
detailed construction, proofs of linear independence and conformity of the
basis, and numerical examples. Further, we demonstrate an application to the
computation of metamaterials with the relaxed micromorphic model
Transitional cluster dynamics in a model for delay-coupled chemical oscillators
Cluster synchronization is a fundamental phenomenon in systems of coupled
oscillators. Here, we investigate clustering patterns that emerge in a
unidirectional ring of four delay-coupled electrochemical oscillators. A
voltage parameter in the experimental set-up controls the onset of oscillations
via a Hopf bifurcation. For a smaller voltage, the oscillators exhibit simple,
so-called primary, clustering patterns, where all phase differences between
each set of coupled oscillators are identical. However, upon increasing the
voltage, additional secondary states, where phase differences differ, are
detected. Previous work on this system saw the development of a mathematical
model that explains how the existence, stability, and common frequency of the
experimentally observed cluster states can be accurately controlled by the
delay time of the coupling.
In this study, we revisit the mathematical model of the electrochemical
oscillators to address open questions by means of bifurcation analysis. Our
analysis reveals how the stable cluster states, corresponding to experimental
observations, lose their stability via an assortment of bifurcation types. The
analysis further reveals a complex interconnectedness between branches of
different cluster types; in particular, we find that each secondary state
provides a continuous transition between certain primary states. These
connections are explained by studying the phase space and parameter symmetries
of the respective states. Furthermore, we show that it is only for a larger
value of the voltage parameter that the branches of secondary states develop
intervals of stability. Otherwise, for a smaller voltage, all the branches of
secondary states are completely unstable and therefore hidden to
experimentalists.Comment: 13 pages, 14 figure
The Role of Application Portfolio Management in Application Services Outsourcing: Explicating Variations in Application Portfolio Management among Outsourcing Gestalts
Prior research has identified different outsourcing strategy types most likely to succeed, described by the outsourcing extent, the contract type, and duration. Each of the strategy types serves a particular outsourcing outcome. Since application portfolio management pursues improvement and optimization in the application landscape, it supports and enables decisions in the field of application services outsourcing. The aim of our research is to investigate the varying role of application portfolio management (APM) for different application services outsourcing strategies. Therefore, we conducted case study research with eleven large German and Swiss companies. In order to identify the varying role of APM, we compared the behaviors of the companies successfully applying particular strategy types, analyzing the differences in APM capabilities, application portfolio structure, and the influence of application characteristics. The results reveal that the companies applying different strategies vary in the extent to which APM is implemented in an organization
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