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AN ANALYSIS OF THE MOdELING OF STRESS ANd STRAIN FIELdS IN A REAL MICROSTRUC-TURE USING AHYBRId METHOd

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Acta Mechanica Solida Sinica 2002年第3期15卷 277-282页

作者： E.Soppa S.Schmauder MPA Stuttgart UniversityStuttgart D-70569Germany

The distribution of stress and strain fields in a micro-structuralarea of a particle reinforced composite is studied by a combinationof experimental and numerical method (hybrid method). With the ex-perimental values of displacements in a micro-region as the boundaryloading condition, strain and stress fields inside the micro-regionare calculated by the finite element method under tow different kindsof model- ing, namely, as pale stress and plane strain condition. Thedifferences between the two kinds of modeling conditions as appliedto micro-structural areas are discussed.

关键词： particle reinforced composite real microstructure hybrid method deformation and yield- ing

3d-printed miniature spectrometer for the visible range with a 100×100μm^(2) footprint

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Light(Advanced Manufacturing) 2021年第1期2卷 12-22页

作者： Andrea Toulouse Johannes drozella Simon Thiele Harald Giessen Alois Herkommer Institute of Applied Optics(ITO) University of StuttgartPfaffenwaldring 970569 StuttgartGermany Research Center SCoPE University of StuttgartPfaffenwaldring 5770569 StuttgartGermany 4th Physics Institute(PI4) University of StuttgartPfaffenwaldring 5770569 StuttgartGermany

The miniaturisation of spectroscopic measurement devices opens novel information channels for size critical applications such as endoscopy or consumer *** spectrometers in the micrometre size range have been demonstrated,however,these are calibration sensitive and based on complex reconstruction *** we present an angle-insensitive 3d-printed miniature spectrometer with a direct separated spatial-spectral *** spectrometer was fabricated via two-photon direct laser writing combined with a super-fine inkjet *** has a volume of less than 100×100×300μm^(3).Its tailored and chirped high-frequency grating enables strongly dispersive *** miniature spectrometer features a wavelength range of 200 nm in the visible range from 490 nm to 690 *** has a spectral resolution of 9.2±1.1 nm at 532 nm and 17.8±1.7 nm at a wavelength of 633 *** this spectrometer directly onto camera sensors is feasible and can be replicated for use as a macro-pixel of a snapshot hyperspectral camera.

关键词： visible spectral spectrometer

A High Order Sharp-Interface Method with Local Time Stepping for Compressible Multiphase Flows

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Communications in Computational Physics 2011年第1期9卷 205-230页

作者： Angela Ferrari Claus-dieter Munz Bernhard Weigand Institute of Aerodynamics and Gasdynamics University of StuttgartPfaffenwaldring 21D-70569 StuttgartGermany Institute of Aerospace Thermodynamics University of StuttgartPfaffenwaldring 31D-70569 StuttgartGermany

In this paper,a new sharp-interface approach to simulate compressible multiphase flows is *** new scheme consists of a high order WENO finite volume scheme for solving the Euler equations coupled with a high order pathconservative discontinuous Galerkin finite element scheme to evolve an indicator function that tracks the material *** the interface our method applies ghost cells to compute the numerical flux,as the ghost fluid ***,unlike the original ghost fluid scheme of Fedkiw et al.[15],the state of the ghost fluid is derived from an approximate-state Riemann solver,similar to the approach proposed in[25],but based on a much simpler *** formulation leads only to one single scalar nonlinear algebraic equation that has to be solved at the interface,instead of the system used in[25].Away from the interface,we use the new general Osher-type flux recently proposed by dumbser and Toro[13],which is a simple but complete Riemann solver,applicable to general hyperbolic conservation *** time integration is performed using a fully-discrete one-step scheme,based on the approaches recently proposed in[5,7].This allows us to evolve the system also with time-accurate local time *** to the sub-cell resolution and the subsequent more restrictive time-step constraint of the dG scheme,a local evolution for the indicator function is applied,which is matched with the finite volume scheme for the solution of the Euler equations that runs with a larger time *** use of a locally optimal time step avoids the introduction of excessive numerical diffusion in the finite volume *** different fluids have been used,namely an ideal gas and a weakly compressible fluid modeled by the Tait *** tests have been computed to assess the accuracy and the performance of the new high order scheme.A verification of our algorithm has been carefully carried out using exact solutions as well as a comparison with other numerical re

关键词： Sharp interface capturing compressible multiphase flows one-step time-integration time-accurate local time stepping modified ghost fluid method WENO schemes discontinuous Galerkin methods

Can Quick Release Experiments Reveal the Muscle Structure？ A Bionic Approach

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Journal of Bionic Engineering 2012年第2期9卷 211-223页

作者： d. F. B. Haeufle M. Gunther R. Blickhan S. Schmitt Institute of Sports and Exercise-Science University of Stuttgart Allmandring 28 D-70569 Stuttgart Germany stuttgart Research Centre for Simulation Technology （SRC SimTech） University of Stuttgart Pfaffenwaldring 7a D-70569 Stuttgart Germany Institute of Motion Science Friedrich-Schiller-University Seidelstraβe 20 D-07749 Jena Germany

The goal of this study was to understand the macroscopic mechanical structure and function of biological muscle with respect to its dynamic role in the contraction. A recently published muscle model, deriving the hyperbolic force-velocity relation from first-order mechanical principles, predicts different force-velocity operating points for different load situations. With a new approach, this model could be simplified and thus, transferred into a numerical simulation and a hardware experiment. Two types of quick release experiments were performed in simulation and with the hardware setup, which represent two extreme cases of the contraction dynamics： against a constant force （isotonic） and against an inertial mass. Both experiments revealed hyperbolic or hyperbolic-like force-velocity relations. Interestingly, the analytical model not only predicts these extreme cases, but also additionally all contraction states in between. It was possible to validate these predictions with the numerical model and the hardware experiment. These results prove that the origin of the hyperbolic force-velocity relation can be mechanically explained on a macroscopic level by the dynamical interaction of three mechanical elements. The implications for the interpretation of biological muscle experiments and the realization of muscle-like bionic actuators are discussed.

关键词： force-velocity relation isotonic quick release proof of concept artificial muscle

An Effective 3d-CFd Methodology for the Complementary Virtual development of Alternative Fuels and Engine Concepts

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同济大学学报（自然科学版） 2024年第S01期52卷 1-8页

作者： Robin SCHMELCHER Thomas GAL Mario PIPOLO Cristian TORTORELLA Antonino VACCA Edoardo ROSSI Francesco CUPO Marco CHIOdI AndréCASAL KULZER Institute of Automotive Engineering(IFS) University of Stuttgart70569 StuttgartGermany Research Institute for Automotive Engineering and Powertrain Systems stuttgart(FKFS) 70569 StuttgartGermany

With the aim of reducing the cost of developing internal combustion engines,while at the same time investigating different geometries,layouts and fuels,3d-CFd-CHT simulations represent an indispensable part for the development of new *** tools are increasingly used by manufacturers,as a screening process before building the first *** paper presents an innovative methodology for virtual engine *** 3d-CFd tool QuickSim,developed at FKFS,allows both a significant reduction in computation time and an extension of the simulated domain for complete engine *** is possible thanks to a combination of coarse meshes and self-developed internal combustion engine models,which simultaneously ensure high *** present work demonstrates the capabilities of this innovative methodology for the design and optimization of different engines and fuels with the goal of achieving the highest possible combustion efficiencies and pollutant *** analysis focuses on the influence of different fuels such as hydrogen,methanol,synthetic gasolines and methane on different engine geometries,in combination with suitable injection and ignition systems,including passive and active *** operations as well as knock reduction are discussed,particularly for methane and hydrogen ***,it is shown how depending on the chosen fuel,an appropriate ad-hoc engine layout can be designed to increase the indicated efficiency of the respective engines.

关键词： eFuels methane methanol hydrogen CO_(2)reduction virtual development 3d-CFd

Reconstruction of Complex Materials by Integral Geometric Measures

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Journal of Materials Science & Technology 2002年第2期18卷 155-158页

作者： Klaus R.MeckeMax-Planck-Institut fur Metallforschung, Heisenbergstr.1, d-70569 stuttgart, Institut fur Theoretische und Angewandte Physik, Fakultat fiir Physik Universitat stuttgart, Pfaffenwaldring 57, d-70569 stuttgart, Germany [ Manuscript received Nov Fakultat fur Phys. Univ. stuttgart D-70569Stuttgart Pfaffenwaldring 57 Germany

The goal of much research in computational materials science is to quantify necessary morphological information and then to develop stochastic models which both accurately reflect the material morphology and allow one to estimate macroscopic physical properties. A novel method of characterizing the morphology of disordered systems is presented based on the evolution of a family of integral geometric measures during erosion and dilation operations. The method is used to determine the accuracy of model reconstructions of random systems. It is shown that the use of erosion/dilation operations on the original image leads to a more accurate discrimination of morphology than previous methods.

关键词： Porous media Integral geometry Morphology Erosion dilation Minkowski functionals Reconstruction

Local discontinuous-Galerkin Schemes for Model Problems in Phase Transition Theory

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Communications in Computational Physics 2008年第9期4卷 860-893页

作者： Jenny Haink Christian Rohde Fachbereich Mathematik-IANS Universitat StuttgartPfaffenwaldring 57D-70569 StuttgartGermany.

Local discontinuous Galerkin(LdG)schemes in the sense of[5]are a flexible numerical tool to approximate solutions of nonlinear convection problems with complicated dissipative *** terms frequently appear in evolution equations which describe the dynamics of phase changes in ***-vapour mixtures or in elastic *** report on results for one-dimensional model problems with dissipative terms including third-order and convolution *** entropy inequalities and L2-stability results are proved for those model *** is common in phase transition theory the solution structure sensitively depends on the coupling parameter between viscosity and *** avoid spurious solutions due to the counteracting effect of artificial dissipation by the numerical flux and the actual dissipation terms we introduce Tadmors’entropy conservative *** numerical experiments underline the reliability of our approach and also illustrate interesting and(partly)new phase transition phenomena.

关键词： Conservation laws discontinuous-Galerkin method dynamical phase boundaries Tadmor flux convolution operator.

dNA-assembled bimetallic plasmonic nanosensors

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Light(Science & Applications) 2014年第1期3卷 1-4页

作者： Na Li Andreas Tittl Song Yue Harald Giessen Chen Song Baoquan ding Na Liu National Center for Nanoscience and Technology Beijing 100190China th Physics Institute and Research Center Scope University of StuttgartD-70569 StuttgartGermany Max Planck Institute for Intelligent Systems D-70569 StuttgartGermany

Plasmonic hybrid nanomaterials are highly desirable in advanced sensing *** components in these materials undertake distinct roles and work *** material component may act as an efficient light concentrator and optical probe,whereas another provides specific chemical or biological *** this work,we present dNA-assembled bimetallic plasmonic nanostructures and demonstrate their application for the all-optical detection of ***(Au)nanorods are functionalized with dNA strands,which serve both as linkers and seeding sites for the growth of palladium(Pd)nanocrystals and facilitate reliable positioning of Pd satellites around an Au nanorod at an ultrashort spacing in the nanometer ***-field scattering spectra of single Au–dNA–Pd nanorods were recorded during controlled cycles of hydrogen gas exposure,and an unambiguous concentration-dependent optical response was *** method enables,for the first time,the all-optical detection of hydrogen-induced phase-change processes in sub-5-nm Pd nanocrystals at the single-antenna *** substituting the Pd satellites with other functional materials,our sensor platform can be extended to plasmonic sensing of a multitude of chemical and biological reagents,both in liquid and gaseous phases.

关键词： dNA self-assembly hydrogen sensing palladium plasmonics

Visual analytics tool for the interpretation of hidden states in recurrent neural networks

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Visual Computing for Industry,Biomedicine,and Art 2021年第1期4卷 233-245页

作者： Rafael Garcia Tanja Munz daniel Weiskopf VISUS University of Stuttgart70569 StuttgartGermany

In this paper,we introduce a visual analytics approach aimed at helping machine learning experts analyze the hidden states of layers in recurrent neural *** technique allows the user to interactively inspect how hidden states store and process information throughout the feeding of an input sequence into the *** technique can help answer questions,such as which parts of the input data have a higher impact on the prediction and how the model correlates each hidden state configuration with a certain *** visual analytics approach comprises several components:First,our input visualization shows the input sequence and how it relates to the output(using color coding).In addition,hidden states are visualized through a nonlinear projection into a 2-d visualization space using t-distributed stochastic neighbor embedding to understand the shape of the space of the hidden *** are also employed to show the details of the evolution of the hidden state ***,a time-multi-class heatmap matrix visualizes the evolution of the expected predictions for multi-class classifiers,and a histogram indicates the distances between the hidden states within the original *** different visualizations are shown simultaneously in multiple views and support brushing-and-linking to facilitate the analysis of the classifications and debugging for misclassified input *** demonstrate the capability of our approach,we discuss two typical use cases for long short-term memory models applied to two widely used natural language processing datasets.

关键词： Visual analytics Visualization Machine learning Classification Recurrent neural networks Long shortterm memory Hidden states Interpretability Natural language processing Nonlinear projection