The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform

D. Christ - One of the best experts on this subject based on the ideXlab platform.

  • Finite element-based multi-phase modelling of shape memory polymer stents
    Computer Methods in Applied Mechanics and Engineering, 2010
    Co-Authors: Stefanie Reese, Markus Böl, D. Christ
    Abstract:

    Abstract In the western hemisphere almost the half of all events of death are caused by cardiovascular diseases, e.g. strokes and heart attacks. The latter are consequences of arteriosclerosis leading to abnormal deposits (plaque) in blood vessels. In order to avoid the serious symptoms discussed in the above or to hold affected blood vessels open, tubular structures made of metallic or polymeric materials (stents) are implanted. In the paper we discuss the modelling of a new kind of stents, so-called shape memory polymer (SMP) stents. The first part of the paper is devoted to the thermo-mechanical modelling of these materials. Aspects as the transition from entropy to Energy Elasticity are included. The constitutive equations are derived in the framework of large strains. We follow both, a purely macroscopic as well as a micromechanically motivated approach. In the second part of the work representative examples based on realistic stent structures are used to validate the model.

Olaf Hinrichsen - One of the best experts on this subject based on the ideXlab platform.

  • Development of a methodology for numerical simulation of non-isothermal viscoelastic fluid flows with application to axisymmetric 4:1 contraction flows
    Chemical Engineering Journal, 2012
    Co-Authors: Florian Habla, Alexander Woitalka, Stefanie Neuner, Olaf Hinrichsen
    Abstract:

    In this work we focus on developing a methodology for the free-to-use software OpenFOAM (R) to simulate non-isothermal viscoelastic flows, which is generally applicable to any mesh type and geometry. The methodology is validated by simulating non-isothermal viscoelastic flows in 4:1 axisymmetric contractions, in which the viscoelastic fluid is governed by the Oldroyd-B constitutive equation. The thermorheological modeling may vary between pure Energy Elasticity and entropy Elasticity depending on a predetermined split coefficient. The temperature-dependent viscosity and relaxation time are modeled using the WLF (Williams-Landel-Ferry) relation. The governing equations are discretized in OpenFOAM (R) using a collocated finite volume method. The DEVSS technique is employed for stabilization of the numerical algorithm at high Deborah numbers. An extrapolation method is proposed for the viscoelastic stress on solid walls, which is subsequently being evaluated regarding accuracy and stability. Next, flows in axisymmetric 4:1 contractions with a temperature jump at the contraction are simulated, similar to the studies of Wachs and Clermont (2000) [24] The influence of the Deborah number and the temperature jump on the flow behavior, such as the vortex length, is examined. Furthermore, the asymptotic behavior at the singularity is examined for different Deborah numbers. (C) 2012 Published by Elsevier B.V.

Wolfgang Lehner - One of the best experts on this subject based on the ideXlab platform.

  • Energy Elasticity on heterogeneous hardware using adaptive resource reconfiguration live
    International Conference on Management of Data, 2016
    Co-Authors: Annett Ungethum, Thomas Kissinger, Williwolfram Mentzel, Dirk Habich, Wolfgang Lehner
    Abstract:

    Energy awareness of database systems has emerged as a critical research topic, since Energy consumption is becoming a major limiter for their scalability. Recent Energy-related hardware developments trend towards offering more and more configuration opportunities for the software to control its own Energy consumption. Existing research so far mainly focused on leveraging this configuration spectrum to find the most Energy-efficient configuration for specific operators or entire queries. In this demo, we introduce the concept of Energy Elasticity and propose the Energy-control loop as an implementation of this concept. Energy Elasticity refers to the ability of software to behave Energy-proportional and Energy-efficient at the same time while maintaining a certain quality of service. Thus, our system does not draw the least Energy possible but the least Energy necessary to still perform reasonably. We demonstrate our overall approach using a rich interactive GUI to give attendees the opportunity to learn more about our concept.

  • SIGMOD Conference - Energy Elasticity on Heterogeneous Hardware using Adaptive Resource Reconfiguration LIVE
    Proceedings of the 2016 International Conference on Management of Data, 2016
    Co-Authors: Annett Ungethum, Thomas Kissinger, Williwolfram Mentzel, Dirk Habich, Wolfgang Lehner
    Abstract:

    Energy awareness of database systems has emerged as a critical research topic, since Energy consumption is becoming a major limiter for their scalability. Recent Energy-related hardware developments trend towards offering more and more configuration opportunities for the software to control its own Energy consumption. Existing research so far mainly focused on leveraging this configuration spectrum to find the most Energy-efficient configuration for specific operators or entire queries. In this demo, we introduce the concept of Energy Elasticity and propose the Energy-control loop as an implementation of this concept. Energy Elasticity refers to the ability of software to behave Energy-proportional and Energy-efficient at the same time while maintaining a certain quality of service. Thus, our system does not draw the least Energy possible but the least Energy necessary to still perform reasonably. We demonstrate our overall approach using a rich interactive GUI to give attendees the opportunity to learn more about our concept.

R. V. Kukta - One of the best experts on this subject based on the ideXlab platform.

  • Surface Energy, Elasticity and the homogenization of rough surfaces
    Journal of the Mechanics and Physics of Solids, 2013
    Co-Authors: P. Mohammadi, Liping Liu, Pradeep Sharma, R. V. Kukta
    Abstract:

    Abstract The concept of surface Energy is widely used to understand numerous aspects of material behavior: fracture, self-assembly, catalysis, void formation, microstructure evolution, and size-effect exhibited by nanostructures. Extensive work exists on deriving homogenized constitutive responses for macroscopic composites—relating effective properties to various microstructural details. In the present work, we focus on homogenization of surfaces. Indeed, elucidation of the effect of surface roughness on the surface Energy, stress, and elastic behavior is relatively under-studied and quite relevant to the behavior of both nanostructures and bulk material where surfaces are involved in some form or fashion. We present derivations that relate both periodic and random roughness to the effective surface elastic behavior. We find that the residual surface stress is hardly affected by roughness while the superficial elastic properties are dramatically altered and, importantly, they may also change sign—this has significant ramifications in the interpretation of sensing based on frequency measurement changes. Interestingly, even if the bare surface has a zero surface Elasticity modulus, roughness is seen to endow it with one. Using atomistic calculations, we verify the qualitative validity of the obtained theoretical insights. We show, through an illustrative example, that the square of resonance frequency of a cantilever beam with rough surface can decrease almost by a factor of two compared to a flat surface.

Giseop Kwak - One of the best experts on this subject based on the ideXlab platform.