bluuebunny/crossref_metadata_2025 huggingface dataset:
Power and limitations of electrophoretic separations in proteomics strategies
Authors: Rabilloud Thierry , Vaezzadeh Ali R. , Potier Noelle , Lelong Cécile , Leize‐Wagner Emmanuelle , Chevallet Mireille
Published: December 2008

Proteomics can be defined as the large‐scale analysis of proteins. Due to the complexity of biological systems, it is required to concatenate various separation techniques prior to mass spectrometry. These techniques, dealing with proteins or peptides, can rely on chromatography or electrophoresis. In this review, the electrophoretic techniques are under scrutiny. Their principles are recalled, and their applications for peptide and protein separations are presented and critically discussed. In addition, the features that are specific to gel electrophoresis and that interplay with mass spectrometry (i.e., protein detection after electrophoresis, and the process leading from a gel piece to a solution of peptides) are also discussed. © 2008 Wiley Periodicals, Inc., Mass Spec Rev 28:816–843, 2009
Analysis of p53 mutations in histologically normal lung tissues and lung tumors from non‐small cell lung cancer patients
Authors: Gao Weimin , Mady Hussam H. , Melhem Mona F. , Keohavong Phouthone
Published: December 2008

Our previous study showed a characteristic p53 mutational spectrum in lung tumors from lung cancer patients in the Western Pennsylvania region. To further understand the involvement of p53 mutations in lung tumor development, in this study we compared p53 mutational spectra and distribution between tumor cells taken from lung tumor tissue and histologically normal cells taken from tumor‐surrounding tissue obtained from 122 lung cancer patients [67 adenocarcinomas (ACs) and 55 squamous cell carcinomas (SCCs)]. Overall, mutations were detected in exons 5–8 of the p53 gene in cell samples from 39.3% (48/122) of the patients. Twenty‐four mutations were found among the ACs (35.8%, 24/67) and consisted mostly of G to T transversions at codon 248 in either only the tumor tissue (12 cases, 50%), or only the histologically normal tissue (2 cases, 8.3%), or both tissue types (10 cases, 41.7%). Among the SCCs, 24 mutations of both transition and transversion types were detected at multiple codons in either only the tumor tissue (17 cases, 70.8%), or only the histologically normal tissue (3 cases, 12.5%), or both tissues (4 cases, 16.7%). Overall, the distribution of mutations among the tumor tissue and histologically normal tissue was not significantly different between the ACs and SCCs (P > 0.05). In both groups, the mutations in the histologically normal tissue may be identical to or different from those in the tumor tissue. Therefore, p53 mutations are frequent in tumor‐surrounding histologically normal tissue, and some of them might be involved in lung carcinogenesis. © 2008 Wiley‐Liss, Inc.
Resveratrol addiction: To die or not to die
Authors: Shakibaei Mehdi , Harikumar Kuzhuvelil B. , Aggarwal Bharat B.
Published: December 2008

Resveratrol, a polyphenol derived from red grapes, berries, and peanuts, has been shown to mediate death of a wide variety of cells. The mechanisms by which resveratrol mediates cell death include necrosis, apoptosis, autophagy, and others. While most studies suggest that resveratrol kills tumor cells selectively, evidence is emerging that certain normal cells such as endothelial cells, lymphocytes, and chondrocytes are vulnerable to resveratrol. Cell killing by this stilbene may be mediated through any of numerous mechanisms that involve activation of mitochondria and of death caspases; upregulation of cyclin‐dependent kinase inhibitors, tumor suppressor gene products, or death‐inducing cytokines and cytokine receptors; or downregulation of cell survival proteins (survivin, cFLIP, cIAPs, X‐linked inhibitor of apoptosis protein (XIAP), bcl‐2, bcl‐XL) or inhibition of cell survival kinases (e.g., mitogen‐activiated protein kinases (MAPKs), AKT/phosphoinositide 3‐kinase (PI3K), PKC, EGFR kinase) and survival transcription factors (nuclear factor‐kappaB (NF‐κB), activating protein 1 (AP‐1), HIF‐1α, signal transducer and activator of transcription (STAT3)). Induction of any of these pathways by resveratrol leads to cell death. While cell death is a hallmark of resveratrol, this polyphenol also has been linked with suppression of inflammation, arthritis, and cardiovascular diseases and delaying of aging. These attributes of resveratrol are discussed in detail in this review.
Acoustic modelling by BEM–FEM coupling procedures taking into account explicit and implicit multi‐domain decomposition techniques
Authors: Soares Delfim
Published: December 2008

The numerical modelling of interacting acoustic media by boundary element method–finite element method (BEM–FEM) coupling procedures is discussed here, taking into account time‐domain approaches. In this study, the global model is divided into different sub‐domains and each sub‐domain is analysed independently (considering BEM or FEM discretizations): the interaction between the different sub‐domains of the global model is accomplished by interface procedures. Numerical formulations based on FEM explicit and implicit time‐marching schemes are discussed, resulting in direct and optimized iterative BEM–FEM coupling techniques. A multi‐level time‐step algorithm is considered in order to improve the flexibility, accuracy and stability (especially when conditionally stable time‐marching procedures are employed) of the coupled analysis. At the end of the paper, numerical examples are presented, illustrating the potentialities and robustness of the proposed methodologies. Copyright © 2008 John Wiley & Sons, Ltd.
Similarity reductions of a nonlinear model for vibrations of beams
Authors: Bruzón M. S. , Camacho J. C. , Gandarias M. L.
Published: December 2008

In this paper we find exact solutions for a beam equation. We make a full analysis of the symmetry reductions of this equation by using the classical Lie method of infinitesimals. We present some explicit solutions: compacton solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On characteristic polynomials of vertex‐ and edge‐weighted molecular graphs
Authors: Dorninger Dietmar
Published: December 2008

Explicit as well as recursive formulas are derived to determine the characteristic polynomials of arbitrarily weighted molecular graphs and the influence of substitutions of atoms with different weights. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multi‐frequency mode‐locked lasers
Authors: Farnum Edward D. , Kutz J. Nathan
Published: December 2008

A new theoretical model is constructed which describes the operation of multi‐frequency, pulsed mode‐locked laser cavities. The model, which is a combination of multi channel interactions in the canonical master mode‐locking model subject to three different gain models which account for both self‐ and cross‐saturation effects, results in mode‐locking dynamics which qualitatively describe the observed experimental dual‐frequency laser operation. Specifically, the combination of self‐ and cross‐saturation in the gain allows for mode‐locking at two frequencies simultaneously, which can be of significantly different energies and pulsewidths. The model gives a framework for understanding the operation and stability of the increasingly important and timely technology of dual‐ and multi‐frequency mode‐locked laser cavities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Arobust algorithm for parametric model order reduction
Authors: Feng Lihong , Benner Peter
Published: December 2008

A robust algorithm for computing reduced‐order models of parametric systems is proposed. Theoretical considerations suggest that our algorithm is more robust than previous algorithms based on explicit multi‐moment matching. Moreover, numerical simulation results show that the proposed algorithm yields more accurate approximations than traditional non‐parametric model reduction methods and parametric model reduction methods based on explicitly computing moments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GetDP: a general finite‐element solver for the de Rham complex
Authors: Geuzaine Christophe
Published: December 2008

GetDP is a high‐level finite element solver using mixed elements to discretize de Rham‐type complexes in one, two and three dimensions. This paper presents an overview of the structure of GetDP, highlighting the closeness between the organization of data defining a discrete problem and its symbolic mathematical description. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constructing compact Markov processes for correlated workload modeling
Authors: Heindl Armin , Telek Miklós
Published: December 2008

Unnecessarily large submodels aggravate the state‐space explosion problem for large Markov models. The orders of these submodels may multiplicatively flow into the size of the overall model quickly leading to intractable state spaces. To mitigate this effect, compact and correlated Markov processes, in particular Markovian arrival processes (MAPs) of low order, have been developed, which can be used for workload modeling.

Different ways how to construct MAPs from information on marginal moments and the correlation structure are addressed with pointers to the relevant literature. A canonical form for MAPs of second‐order is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scalar shift strategy for accelerating forward iterations on Sm –1
Authors: Shen Hao , Hüper Knut
Published: December 2008

A result on how to accelerate simple forward iteration algorithms on the unit sphere, in the framework of a scalar shift strategy, to achieve local quadratic convergence is developed in this note. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A multiple‐scales solution of the undular hydraulic jump problem
Authors: Jurisits Richard , Schneider Wilhelm , Bae Yee Seok
Published: December 2008

A non‐linear third‐order ODE governing the free surface of an undular hydraulic jump is solved by means of a multiple‐scales analysis. The resulting solutions are compared with direct numerical solutions of the ODE, and good agreement is found. Furthermore, new flow features, which are not evident in the numerical solutions, are revealed by the multiple‐scales solutions. The results of the analysis are also compared with numerical solutions of the full equations of motion and with experimental data, and satisfactory agreement is obtained. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hypertumors in cancer can be caused by tumor phosphorus demand
Authors: Nagy John D.
Published: December 2008

In cancer, tumoral and peritumoral environmental conditions are controlled mostly by the unusual metabolism of malignant cells. For example, tumors typically demand much more phosphorus (P) than normal tissue does, primarily because tumor cells upregulate ribosome biogenesis. Here I use mathematical models to show that this unusual demand for P can lead to a hypertumor, which is a region of highly aggressive cells growing parasitically on the original tumor that can kill all or part of it. Previous work has suggested that hypertumors may develop when a tumor is invaded by an aggressive cell type that fails to secrete angiogenesis factors. In this talk I introduce an entirely different mechanism of hypertumor development. In this case, the aggressive strain upregulates phosphate transporters, leading to increased growth potential, which allows tumor cells to outpace growing blood vessels. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Life, a modern and unified C++ implementation of finite‐element and spectral‐element methods in 1D, 2D and 3D
Authors: Prud'homme Christophe
Published: December 2008

We present a brief overview of Life, a unified framework for finite element and spectral element methods in 1D, 2D and 3D inC++. First, we describe some basic principles, then we focus on the two cornerstones of the library, the polynomial library and FEEL++, aC++ embedded language designed for partial differential equations. The applications range is potentially quite large; at the moment Life is essentially used for the development of new numerical methods and the exhaustive comparisons between standard ones e.g. high order methods, stabilisation methods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Patch dynamics: macroscopic simulation of multiscale systems
Authors: Samaey Giovanni , Kevrekidis Ioannis G. , Roose Dirk
Published: December 2008

We describe a numerical algorithm to perform time integration of a partial differential equation (PDE) which is not available in closed from; instead we are given a more microscopic description of the system behaviour. The proposed methods mimic a macroscopic finite difference (FD) or finite volume (FV) scheme for the unavailable PDE; they extract a macroscopic time derivative (for FD schemes) or flux (for FV schemes) from appropriately initialized, but otherwise unconstrained simulations with the given microscopic model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On large‐scale diagonalization techniques for the Anderson model of localization
Authors: Schenk Olaf , Bollhöfer Matthias , Römer Rudolf A.
Published: December 2008

We propose efficient preconditioning algorithms for an eigenvalue problem arising in quantum physics, namely the computation of a few interior eigenvalues and their associated eigenvectors for large‐scale sparse real and symmetric indefinite matrices of the Anderson model of localization. Our preconditioning approaches for the shift‐and‐invert symmetric indefinite linear system are based on maximum weighted matchings and algebraic multi‐level incomplete LDLT factorizations. These techniques can be seen as a complement to the alternative idea of using more complete pivoting techniques for the highly ill‐conditioned symmetric indefinite Anderson matrices. Our numerical examples reveal that recent algebraic multi‐level preconditioning solvers can accelerate the computation of a large‐scale eigenvalue problem corresponding to the Anderson model of localization by several orders of magnitude. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Covariance analyis for active vehicle suspensions
Authors: Schiehlen Werner , Fehr Jörg , Jung Kim Yun
Published: December 2008

In this paper the covariance analysis will be extended to active suspension systems with skyhook dampers. The covariance matrix of the entire vehicle system follows from an algebraic equation, the so‐called Ljapunov matrix equation, and no integrations are required. An essential prerequisite of the covariance analysis is a white noise input process. This can always be provided by modelling the random vehicle excitation by means of a shape filter. Performance criteria are presented and appropriate design parameters are found by optimization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduced kinematic model of the human spine
Authors: Simonidis Christian , Scharmacher Manuel , Seemann Wolfgang
Published: December 2008

According to the difficulty of marker based motion reconstruction of human torso movements a reduced kinematic formulation of the human spine is introduced, which describes the movement of the first thoracic vertebra in relation to the pelvis. The formulation is for implementation in a multibody model of the human body. As a result the formulation offers convenience in marker based motion capture and motion reconstruction via an optimization based kinematic approach and provides human‐like motion characteristics of torso motion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Basic convergence results for conforming adaptive finite elements
Authors: Morin Pedro , Siebert Kunibert G. , Veeser Andreas
Published: December 2008

We report on a result establishing plain convergence for conforming adaptive finite elements under relatively general assumptions on problem class and adaptive algorithm. Moreover, we indicate some applications and give a sketch of the proof. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the influence of crosswind on the overturning stability of railway vehicles
Authors: Wetzel Christian , Yalamas Claire , Proppe Carsten
Published: December 2008

In recent years modern railway vehicle design shows a trend to faster, lighter and more energy efficient railway systems. These developments unfortunately alter the crosswind stability in a negative manner and so the risk of overturning of railway vehicles during operation in strong winds becomes a critical issue. The risk of overturning is quantified by the probability that a railway vehicle capsizes. To improve the crosswind stability it is very important to know the influence of the design and excitation variables on the wheel unloading of the railway car. Sensitivity coefficients of the design and excitation variables with respect to the probability of failure are calculated and the most influential variables are accentuated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DNS of MHD turbulence in liquid metals based on the least dissipative modes
Authors: Dymkou Vitali , Pothérat Alban
Published: December 2008

We investigate numerically the incompressible Navier‐Stokes equations under an externally imposed magnetic field. The results obtained for the simplified geometry of a three dimensional periodic box and show a lower computational complexity and stronger relationship between the physical reality and its numerical representation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MR image reconstruction from undersampled data by using the iterative refinement procedure
Authors: He Lin , Chang Ti‐Chiun , Osher Stanley , Fang Tong , Speier Peter
Published: December 2008

Magnetic resonance imaging (MRI) reconstruction from sparsely sampled data has been a difficult problem in medical imaging field. We approach this problem by formulating a cost functional that includes a constraint term that is imposed by the raw measurement data in k‐space and the L1 norm of a sparse representation of the reconstructed image. The sparse representation is usually realized by total variational regularization and/or wavelet transform. We have applied the Bregman iteration to minimize this functional to recover finer scales in our recent work. Here we propose nonlinear inverse scale space methods in addition to the iterative refinement procedure. Numerical results from the two methods are presented and it shows that the nonlinear inverse scale space method is a more efficient algorithm than the iterated refinement method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The numerical analysis of the trapezoidal thread rolling process
Authors: Kukielka Krzysztof , Kukielka Leon
Published: December 2008

The thread rolling is difficult technological process. Improve quality and contemporary reduce manufacture cost of the trapezoidal thread requires acquaintances of physical phenomena observed in the contact zone between rolls and deform work‐pieces. Therefore, in this paper the physical and mathematical models of deformations (displacements and strains) and stress in the cold process of trapezoidal thread rolling, were developed. The process is considered as a geometrical and physical non‐linear, initial as well as boundary value problem. The phenomena on a typical incremental step were described using a step‐by‐step incremental procedure, with an updated Lagrangian formulation. The state of strains was described by Green‐Lagrange's tensor, while the state of stress by the second symmetrical Pioli‐Kirchhoff's tensor. The object was treated as an elastic (in the reversible zone) and visco‐plastic body (in non‐reversible zone) with mixed hardening. The variational equation of motion in three dimensions for this case was proposed. Then, the finite elements methods (FEM) and dynamic explicit method (DEM) were used to obtain the solution. The application developed for in the ANSYS programme, which provides a complex time analysis for displacement, strains and stresses occurring in the object. The recommendations concern modeling the trapezoidal thread rolling process, where reduce degrees of freedom in numerical model is very important and provide convergence calculated results for maximum stress and strain values in the thread surface layer, were elaborated. The influence a various process conditions on the states deformation and stress for examples calculations, were presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Negative specific heat in a quasi‐2D vortex system
Authors: Andersen Timothy D. , Lim Chjan C.
Published: December 2008

Negative specific heat is a dramatic phenomenon where processes decrease in temperature when adding energy. It has been observed in gravo‐thermal collapse of globular clusters. We now report finding this phenomenon in bundles of nearly parallel, periodic, single‐sign generalized vortex filaments in the electron magnetohydrodynamic (EMH) model for the unbounded plane under strong magnetic confinement. We derive the specific heat using a steepest descent method and a mean field property. Our derivations show that as temperature increases, the overall size of the system increases exponentially and the energy drops. The implication of negative specific heat is a runaway reaction, resulting in a collapsing inner core surrounded by an expanding halo of filaments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Semi‐analytical modelling of cracks with interacting faces in isotropic materials under harmonic load
Authors: Menshykov Oleksandr V. , Mykhailova Iryna I. , Guz Igor A.
Published: December 2008

The present work is devoted to the investigation of the contact interaction of the faces of cracks located in the homogeneous, isotropic, linearly elastic 3‐D medium under a harmonic loading. The Signorini contact constraints are imposed and the friction is governed by the Coulomb law. The problem is solved by the method of the boundary integral equations with the use of the iterative procedure. The dependence of the stress intensity factors on the friction coefficient and parameters of the incident wave parameters (frequency, angle of incidence, etc.) is studied. Numerical results are compared with those obtained without allowance for the contact interaction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal singular control for quasi‐linear systems with small parameters
Authors: Popescu Mihai
Published: December 2008

The present study deals with the general case of the quasi‐linear command systems with a small parameter. We shall determine an approximate solution of the problem of optimum which minimizes the class of the quadratic functionals in a non‐specified final time. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of viscoelastic systems under stochastic excitation
Authors: Potapov Vadim
Published: December 2008

An effective method for the investigation of the stability for viscoelastic systems under a parametric stochastic excitation is proposed. The parametric force is assumed in the form of a Gaussian stationary colored noise. The method is based on the simulation of random processes, the numerical solution of differential equations, describing the perturbed motion of the considered system, and the calculation of top Liapunov exponents. The considered method makes it possible to estimate the almost sure stability and the stability with respect to statistical moments of the different order. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multirate models for simulating a colpitts oscillator
Authors: Pulch Roland
Published: December 2008

A model based on multirate partial differential algebraic equations yields an efficient numerical simulation of electric circuits in radio frequency applications. Considering frequency modulation, free parameters of the model are determined appropriately by a minimisation strategy. We apply the multirate approach to simulate a modified version of a Colpitts oscillator, which exhibits frequency modulation at widely separated time scales. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interval techniques for enclosures of regions of reachability and controllability and for guaranteed state and parameter estimation of dynamical systems
Authors: Rauh Andreas , Kletting Marco , Hofer Eberhard P.
Published: December 2008

Interval techniques are a powerful means for calculation of enclosures of the regions of reachability and controllability of dynamical systems with uncertainties during analysis and design of controllers. In this contribution, both discrete‐time and continuous‐time dynamical systems are considered. Using suitable algorithms, guaranteed state enclosures can be determined for systems with uncertain parameters, uncertain initial conditions, nonlinearities, and time‐varying characteristics.

Although both uncertain system parameters and bounded control variables are assumed to be represented by interval boxes in the following, they have to be distinguished in reachability and controllability analysis. Typically, robustness specifications for controllers of dynamical systems are given in terms of bounds on the system's time response which must not be violated for any possible operating condition. Hence, reachability as well as controllability of states have to be proven for all possible parameter values but for at least one admissible control sequence.

Robust control strategies for nonlinear systems usually rely on knowledge of all current states. However, the complete state vector is not always directly accessible for measurement. In this case, observers are applicable to reconstruct non‐measurable state variables. Furthermore, they can reduce the uncertainties of the measured quantities by model‐based recursive computation of estimates and fusion of information gathered by different measurement devices. If guaranteed bounds of all uncertain parameters of a dynamical system (including the sensor characteristics) and conservative bounds of all disturbances can be specified, the presented interval observer provides guaranteed enclosures of all reachable states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled CFD analysis of hot gas and coolant flow in effusion‐cooled combustion chambers
Authors: Riccius Jörg , Gernoth Andreas , Greuel Dirk
Published: December 2008

Three different coupled CFD analyses of the hot gas and the coolant flow in effusion‐cooled combustion chambers are shown. The common feature of these CFD analyses are the following principles:

• solution of the Navier Stokes equations

• multi species analysis including hot gas (steam) and coolant (hydrogen)

• compressible flow

• ideal gas

• distributed resistance according to Forchheimer in the combustion chamber wall

The differences between these models are given in the following table:

image

The detailed analysis of the combustion itself is avoided by defining the injector plate of the combustion chamber (left boundaries of the colour plots in figure 2) as an inlet of the by‐product of the combustion (steam). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled time‐domain analysis with boundary and finite elements
Authors: Rüberg Thomas , Schanz Martin
Published: December 2008

A methodology for the combination of boundary and finite element discretizations for the numerical analysis of time‐dependent problems is presented. The interface conditions arising from the partitioning of the problem are incorporated in a weak form by means of Lagrange multiplier fields and, therefore, allow for nonconform interface discretizations. The resulting system matrices have the same saddle point structure as in the FETI method. Possible applications of the proposed method are the dynamic analysis of soil‐structure interaction and similar wave propagation phenomena in unbounded media. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A nonlinear finite element framework for flexible multibody dynamics
Authors: Sänger Nicolas , Betsch Peter
Published: December 2008

We present a uniform treatment of rigid body dynamics and nonlinear structural dynamics. The advocated approach is based on a rotationless formulation of rigid bodies, nonlinear beams and shells. In this connection, the specific kinematic assumptions are taken into account by the explicit incorporation of holonomic constraints. This approach facilitates the straightforward extension to flexible multibody dynamics by including additional constraints due to the interconnection of rigid and flexible bodies. We further address the design of energy‐momentum schemes for the stable numerical integration of the underlying finite‐dimensional Hamiltonian systems.

To demonstrate the superior numerical performance of the proposed methodology, the numerical examples deals with a multibody system containing both rigid and flexible bodies undergoing large deformations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cyclic martensitic phase transformation of monocrystals at finite strains
Authors: Sagar Gautam , Stein Erwin
Published: December 2008

Based on Bain's principle, a C1‐continuous thermo‐mechanical micro‐macro constitutive model for martensitic phase transformation (PT) of monocrystals at finite strains and hyperelastic free energy function is used. It is represented by a unified non‐convex Lagrangian variational functional. The convexification problem is solved here by generalizing the explicit form of the lower Reuss bound for small strains given in [1] to finite strains. Abaqus is used for implementation of 3D finite elements in space, via UMAT‐interface which requires Jaumann rate of Kirchhoff stress tensor. Deterministic validation of the model is presented by comparing verified numerical results with experimental data for Cu82Al14Ni4[6] for quasiplastic PT. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Tamir's algorithm for solving the nonlinear complementarity problem
Authors: Schäfer Uwe
Published: December 2008

Some comments concerning Tamir's algorithm for solving the nonlinear complementarity problem are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time variant Hamiltonian control systems – a covariant approach
Authors: Schöberl Markus
Published: December 2008

In this contribution we present an intrinsic description of time variant Hamiltonian control systems. This formulation is based on the splitting of the state bundle and the use of appropriate covariant derivatives, which guarantees that the structure of the equations is invariant with respect to time variant coordinate transformations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Least‐squares mixed finite elements with applications to anisotropic elasticity and viscoplasticity
Authors: Schwarz Alexander , Schröder Jörg
Published: December 2008

The objective of this work is to discuss a least‐squares finite element method with applications to physically nonlinear and anisotropic constitutive equations at small strains. The L2‐norm minimization of the residuals of the given first order system of differential equations leads to a functional, which is a two field formulation in the displacements and the stresses, see e.g. Cai & Starke [1]. These functionals provide the foundation for the formulations of the related least‐squares mixed finite elements. A main focus of the presentation lies on the extension of plane elasticity to anisotropic or nonlinear material behavior. In this context transversely isotropic elasticity and viscoplasticity is considered. Finally a numerical example is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the homogenization of the Buckley‐Leverett equation including trapping effects at the micro scale
Authors: Schweizer Ben , Pop Iuliu Sorin
Published: December 2008

We consider a simplified, one dimensional model for two‐phase (oil/water) flow in a porous medium. The medium consist of alternating homogeneous blocks separated by interfaces, where trapping effects may occur. Two effective models are derived in [2] and [7]. In this paper we show that the two models are equivalent. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiresolution schemes for an extended clarifier‐thickener model
Authors: Bürger Raimund , Ruiz Ricardo , Schneider Kai , Sepúlveda Mauricio
Published: December 2008

A fully adaptive finite volume multiresolution scheme for one‐dimensional strongly degenerate parabolic equations with discontinuous flux modelling an extended clarifier‐thickener, is presented. The numerical scheme is based on a finite volume discretization using the approximation of Engquist‐Osher for the flux and explicit time stepping. Cell averages multiresolution scheme speeds up CPU time and memory requirements. A particular feature of our scheme is the storage of the multiresolution representation of the solution in a dynamic graded tree. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A semi‐adaptive split‐cosine scheme for the sine‐Gordon equation
Authors: Sheng Q.
Published: December 2008

This talk concerns the numerical solution of the nonlinear sine‐Gordon equation in rectangular large‐area Josephson junctions. An application of the adaptive method of lines leads to a system of second‐order nonlinear ordinary differential equations. The system is approximated by a nonlinear recurrence relation. Strang's splitting is then introduced for establishing a highly effective and stable semi‐adaptive scheme. The novel new method offers an efficient way in the solitary wave solution approximations. A stability analysis is presented. Straightforward numerical demonstrations on ring solitons up to higher time levels are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stochastic oscillations in circuit simulation
Authors: Sickenberger Thorsten , Winkler Renate
Published: December 2008

We consider the simulation of noisy electronic circuits with oscillatory solutions. For their transient noise simulation we use variable step‐size two‐step schemes for stochastic differential‐algebraic equations. The performance of these methods in combination with a suitable step‐size control strategy is illustrated by an industrial test application. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of stress intensity factors in a plane homogeneous anisotropic solid
Authors: Steigemann Martin , Fulland Markus , Specovius‐Neugebauer Maria , Richard Hans A.
Published: December 2008

The accurate computation of stress intensity factors (SIFs) plays a decisive role in the determination of crack paths. The calculation of SIFs with the help of singular weight functions leads to pure Neumann problem for anisotropic elasticity in a plane domain with a crack. We present a method to overcome the specific numerical difficulties which arises while calculating these solutions with Finite Element methods. the accuracy and advantage of this method are shown by a numerical example, the calculation of SIFs of a compact tension specimen. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hopf bifurcations of travelling waves in a brake‐like system
Authors: Steindl Alois
Published: December 2008

We consider a system composed of an elastic tube, which is fixed at the outer boundary and in frictional contact with a rigid cylinder, rotating inside the tube about the common axis. Under the assumption of Coulomb's friction law at the contact surface between the two bodies several types of rotating slip‐stick and also slip‐stick‐separation travelling waves with different wave numbers can be observed.

For a wide range of parameters the linearized system has unstable complex eigenvalues, which cause high frequency oscillations and unpleasant squeal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stick‐slip‐separation waves in a rotating shaft‐bush system
Authors: Teufel Andreas , Troger Hans
Published: December 2008

We consider an elastic annular bush fitted to a rigid rotating shaft with a diameter mismatch. The formation of stick‐slip, slip‐separation and stick‐slip‐separation waves due to dynamic friction acting between the bush and the shaft is studied. Numerically, we calculate the loci of non‐smooth bifurcations in the parameter space for rotating mode‐1 waves on the shaft‐bush interface, varying the angular velocity and the static coefficient of friction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Upscaling in nonlinear thermal diffusion problems
Authors: Timofte Claudia
Published: December 2008

The aim of this paper is to study the homogenization of a nonlinear problem arising in the modelling of thermal diffusion in a two‐component composite. We consider, at the microscale, a periodic structure formed by two materials with different thermal properties. We assume that we have nonlinear sources and that at the interface between our two materials the flux is continuous and depends in a nonlinear way on the jump of the temperature field. We shall be interested in describing the asymptotic behavior, as the small parameter which characterizes the sizes of our two regions tends to zero, of the temperature field in the periodic composite. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Algorithm and MATLAB package for some nonlinear 2D evolution equations
Authors: Trif Damian
Published: December 2008

We will present LiScM2, a MATLAB package for numerical solutions of some partial differential evolution equations of the form ut + Lu = N (u, ∇u), with boundary and initial conditions, where L is a 2D linear elliptic operator (Laplace operator for this version) and N is a nonlinear part. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Regularized Kalman filtering in dynamic SPECT
Authors: Celler A. , Qranfal J. , Trummer M.R.
Published: December 2008

This paper presents an algorithm for reconstructing a dynamic SPECT image. Projections of a time‐dependent activity are acquired in discrete time frames. This leads to a highly underdetermined set of equations for the images corresponding to each time frame. We reconstruct these images using a Kalman filter algorithm which helps is processing the time‐varying information, To obtain meaningful results a positivity constraint must be enforced. Due to the ill‐posedness of the problem, regularization is required. We compared Tikhonov and total bounded variation regularization schemes, and found the latter to be more effective, producing superior results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
About weak resolvability of initial‐boundary value problem for Foight model of liquid motion in domain with time‐dependent boundary
Authors: Turbin Mikhail V. , Zvyagin Victor G.
Published: December 2008

We prove the existence and uniqueness of a weak solution of the initial‐boundary value problem for the Foight model of liquid motion in a domain with time‐dependent boundary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nash‐equilibrium conditions for strategic games
Authors: Ungureanu Valeriu
Published: December 2008

The notion of the Lagrange vector‐function is considered for strategic mono and multi criteria games. Nash and Pareto‐Nash equilibrium conditions are studied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High order upwind scheme for modelling turbulent shallow water flow in hydraulic structures
Authors: Vázquez‐Cendón María‐Elena , Cea Luis
Published: December 2008

An unstructured finite volume model for quasi‐2D free surface flow with wet‐dry fronts and turbulence modelling is presented. The convective flux is discretised with either a an hybrid second‐order/first‐order scheme, or a fully second order scheme, both of them upwind Godunov's schemes based on Roe's average. The hybrid scheme uses a second order discretisation for the two unit discharge components, whilst keeping a first order discretisation for the water depth [2]. In such a way the numerical diffusion is much reduced, without a significant reduction on the numerical stability of the scheme, obtaining in such a way accurate and stable results. It is important to keep the numerical diffusion to a minimum level without loss of numerical stability, specially when modelling turbulent flows, because the numerical diffusion may interfere with the real turbulent diffusion.

In order to avoid spurious oscillations of the free surface when the bathymetry is irregular, an upwind discretisation of the bed slope source term [4] with second order corrections is used [2]. In this way a fully second order scheme which gives an exact balance between convective flux and bed slope in the hydrostatic case is obtained. The k – ε equations are solved with either an hybrid or a second order scheme.

In all the numerical simulations the importance of using a second order upwind spatial discretisation has been checked [1]. A first order scheme may give rather good predictions for the water depth, but it introduces too much numerical diffusion and therefore, it excessively smooths the velocity profiles. This is specially important when comparing different turbulence models, since the numerical diffusion introduced by a first order upwind scheme may be of the same order of magnitude as the turbulent diffusion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combinatorial preconditioners for scalar elliptic finite‐element problems
Authors: Avron Haim , Chen Doron , Shklarski Gil , Toledo Sivan
Published: December 2008

We present a new preconditioner for linear systems arising from finite‐elements discretizations of scalar elliptic partial differential equations. The solver is based on building a symmetric diagonally dominant (SDD) approximation of the stiffness matrix K. The approximation is built by approximating each element inside the collection {Ke } of element matrices by an SDD matrix Le. The SDD approximation L is built by assembling the collection {Le }. We then sparsify L using a graph algorithm, and use the sparsified matrix as a preconditioner. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Laminar separation bubbles from a high Reynolds‐number asymptotic point of view
Authors: Braun Stefan
Published: December 2008

Classical boundary layer theory proved to lose its validity if flow separation is encountered. However, introduction of the triple deck concept – i.e. allowing for the displacement effect of the viscous boundary layer to interact locally with the induced pressure (disturbances) in the outer inviscid flow regime – led to a successful description of ‘short’ laminar separation bubbles in various fundamental flow problems. Here we want to focus on situations which share the following distinctive feature: two‐dimensional steady state solutions of the underlying interaction equations exist in a limited range of values of a parameter controlling the conditions leading to separation only. Furthermore, these solutions turn out to be non‐unique in the vicinity of the limiting critical value of this parameter. Typical examples include leading edge separation, smooth backward facing step flow, channel flow with suction (cases of so‐called marginal separation) and subsonic expansion ramp flow, asymmetric trailing edge separation (classical triple deck flows). More recent investigations which take into account (local) unsteady, three‐dimensional and flow control device effects and concentrate on near critical flows indicate that (i) exceeding the critical value of the controlling parameter is associated with self‐sustained vortex shedding (time periodic bubble ‘bursting’ even in the absence of external disturbances), (ii) coherent structure formation caused by bubble bursting events turns out to be essentially self‐similar, (iii) the high sensitivity of the separated flow region with respect to external disturbances allows for effective application of (optimized) flow control devices in order to force or delay the transition process to turbulent boundary layer flow. The aim of the presentation is to deliver insight into the power of modern asymptotic analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic analysis of porous materials: Numerical simulation with an adaptive space‐time FEM
Authors: Chen Z. , Diebels S. , Steeb H.
Published: December 2008

We investigated a space‐time Galerkin method applied to the dynamic analysis of fully‐saturated porous material. The governing set of equations are derived from the well‐studied Theory of Porous Media (TPM). The numerical scheme consists of a coupled finite element discretization in the space‐time domain. Discontinuous approximations of the primary variables in time are employed. A natural flux treatment is applied in time to impose the consistency between the adjacent time intervals. A simple space‐time decoupled adaptive strategy based on the “jumps” in time and the ZZ error indicator in space is investigated. Numerical experiments demonstrate the efficiency and reliability of the proposed approach. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of chip formation during machining for different value of failure strain
Authors: Chodor Jaroslaw , Kukielka Leon
Published: December 2008

Grinding is a very complicated processing. To increase quality of product and minimize the cost of abrasive machining, we should know physical phenomena which exist during the process. The first step to solution of this problem is analysis of machining process with a single abrasive grain. In the papers [1, 2] the thermo‐mechanical models of this process are presented, but in this work attention is concentrated on chip formation and his separation from object. The influence of failure strain εf on states of strain and stress in surface layer during machining is explained. The phenomena on a typical incremental step were described using step‐by‐step incremental procedure, with updated Lagrangian formulation. Then, the Finite Element Method (FEM) and Dynamic Explicit Method (DEM) were used to obtain the solution. Application was developed in the ANSYS system, which makes possible a complex time analysis of the physical phenomena: states of displacements, strains and stress. Numerical computations of the strain have been conducted with the use of two methodologies. The first one requires an introduction of boundary conditions for displacements in the contact area determined in modeling investigation, while the second – a proper definition of the contact zone through the introduction of finite elements of TARGET and CONTACT types, without the necessity to introduce boundary conditions. This model includes variational equations of the object's motion and deformation. Examples of calculations for the displacement, strain and stress field in the surface layer zones were presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weak coupling in function space: a unifying coupling approach for multiscale simulations
Authors: Fackeldey Konstantin , Krause Rolf
Published: December 2008

In multiscale simulations, often on the micro‐ and the macro scale different discretization are used in order to capture the different behavior of the materials under consideration on the respective scales. Using, e.g., molecular dynamics (MD) on the micro scale and finite elements (FE) in the macro scale, values in the phase space ℝd (MD) have to be correlated with the values from the FE‐simulation in the Sobolev space H1. Here, we present a new coupling approach which gives rise to a stabilizing new scale transfer operator. Our construction allows moreover for a unifying theoretical description of already existing coupling methods. The key idea is to construct the transfer operator by assigning a partition of unity to the molecular degrees of freedom, thus giving rise to a fully function space based treatment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust controllability of linear systems: Analysis and application to pursuit problems
Authors: Glizer Valery Y. , Turetsky Vladimir
Published: December 2008

Robust controllability conditions for a linear uncertain system are derived. A class of transferring strategies is obtained. A robust controllability set, respecting a given control constraint, is constructed. An application example is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)