bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptive FE Diskretisierung zur Bestimmung der Eigenfrequenzen von Flächentragwerken
Authors: Neumann J. , Schweizerhof K. 
Published: April 2003

AbstractDie Eigenwerte der Bewegungsgleichung in der Strukturdynamik werden numerisch bestimmt. Der Diskretisierungsfehler wird a‐posteriori abgeschätzt. Dieser bildet die Grundlage einer adaptiven Netzverfeinerung. Das Vorgehen wird an einem Beispiel erläutert.
Fundamental Solutions for an Incompressible Model of Porous Continua
Authors: Pryl D. , Schanz M. 
Published: April 2003

AbstractConsidering the dynamic behaviour of semi‐infinite continua, a linear theory is often sufficient. In this case, it is advantageous to use the Boundary Element Method (BEM). One crucial condition to establish a BE formulation is the knowledge of a fundamental solution. For poroelastic constitutive equations, up to now, such a solution has only been available for the case of compressible constituents in Laplace domain. Here, for the first time, the Laplace domain fundamental solutions for incompressible constituents are derived using Hörmanders method. These show that the solutions for the compressible case can be transformed into the incompressible ones by taking the limit of infinite wave speed of the fast compressional wave. Some studies concerning the influence of this infinite wave speed will be shown as well as first results of a BEM calculation.
A Method to Estimate the Inelastic Response in Notched Structures of Anisotropic Materials with Elastic ‐ Perfectly Plastic Behavior
Authors: Mücke Roland , Bernhardi Otto Ernst 
Published: April 2003

AbstractThe fatigue strength of engineering structures is often limited by notches which arise from constructive features or manufacturing defects. The constitutive behavior in notch regions is then characterized by small plastic zones which are contained in an elastic region.To avoid costly plastic calculations, approximate methods have been developed to estimate the inelastic stress‐strain response at the notch tip. One of the first and best known approximate models is that of Neuber which, over the last 40 years, has received considerable attention particularly in connection with fatigue life prediction. Numerous studies have been conducted to the verification and the generalization of the Neuber approach which respect to multiaxiality, cyclic loading and creep conditions. Recently an extension of the Neuber method to anisotropic materials has been proposed in [1] and applied to directionally solidified and single crystal Nickel based superalloys as they are used in high temperature material applications. In this short notice we modify the approach in [1] for the special case of an elastic ‐ perfectly plastic anisotropic material.
Leading edge separation: a comparison between interaction theory and Navier–Stokes computations
Authors: Braun S , Kluwick A , Trenker M 
Published: April 2003

AbstractWe consider the two‐dimensional high/moderate Reynolds‐number flow around a slender airfoil at small angles of attack. Special emphasis is placed on leading edge separation and the associated breakdown of the steady solution of the governing equations. A comparison between the predictions of the viscous/inviscid interaction theory of marginal separation, see e.g. [3], and the results of Navier–Stokes computations with DLR's ‘TAU’–code [2] shows excellent quantitative agreement concerning the location, size of the separation bubble and even the limiting maximum value of the angle of attack, up to which solutions by means of the particular approaches can be found.
Measurement of velocity and concentration in a stream of a helium‐air mixture by hot‐wire/film anemometry
Authors: Mazur O. , Jonáš P. , Šarboch J. , Uruba V. 
Published: April 2003

AbstractA method for simultaneous measurement of instantaneous velocity and concentration values in a stream of the air/helium mixture was suggested. The method applies the hot‐element anemometry principles using dual sensor.
Film flow over strongly undulated bottom profiles at low Reynolds numbers – Experimental study
Authors: Wierschem Andreas , Scholle Markus , Aksel Nuri 
Published: April 2003

AbstractWe study gravity driven films of a Newtonian fluid flowing down sinusoidal bottom profiles. We give experimental evidence of vortices in the film flow under creeping flow conditions down to Reynolds numbers of the order of 10–5. The vortices are created in the valleys of the undulated bottom profile. They are visualized employing a particle image velocimeter with fluorescent tracers. It turns out that the vortices are generated beyond a critical film thickness.
Mathematical and Numerical Study of the 3D Atmospheric Boundary Layer Flows Including Pollution Dispersion
Authors: Benes L. , Bodnar T. , Janour Z. , Kozel K. , Sladek I. 
Published: April 2003

AbstractThe paper presents a mathematical and numerical investigation of the atmospheric boundary layer (ABL) flow over 3D complex terrain part of which is represented by the real topography of the Krkonose mountains located in the Czech Republic. The flow is supposed to be turbulent, non‐stratified, viscous, incompressible and stationary. Two mathematical models have been formulated. The first model is based upon the RANS equations in the conservative form and the second one uses the Boussinesq approximation of RANS equations and takes the non‐conservative form. Also pollution dispersion over the complex 3D terrain has been considered in both models. The problem closure is achieved by an algebraic turbulence model and given boundary conditions.
Modeling and Numerical Simulation of Cavitation for Compressible Liquid Flow
Authors: Berg A. , Iben U. , Meister A. 
Published: April 2003

AbstractA method for the numerical simulation of cavitation phenomena based on the thermodynamic properties of liquid and steam is described. Thereby, a homogeneous cavitation model using a fully compressible discretization technique is considered. The ability of the scheme is proven by numerical experiments.
Multifrequency Analysis for the Helmholtz Equation
Authors: Köhl M. , Rjasanow S. 
Published: April 2003

AbstractThis paper is a brief review of a new numerical method for the multifrequency analysis of the three‐dimensional Helmholtz equation. We describe the principles of this method which is based on the identity of the Fourier transform with respect to the wave number. Some numerical examples for the solution were presented at the oral session.
The Noise Prediction Model SATIN
Authors: Ostertag J. , Wagner S. 
Published: April 2003

AbstractThis paper presents the noise prediction model SATIN (Statistical Approach to Turbulence Induced Noise) which is based on Lighthill's acoustic analogy. It allows to predict both, the far‐field noise radiation as well as near‐field wall‐pressure fluctuations. Far‐field noise radiation may result from the scattering of wall‐pressure fluctuations at geometrical discontinuities and is therefore important for many practical problems. Within this paper, we focus on the calculation of far‐field noise radiation.The required input values of SATIN are local properties of turbulence, namely the turbulent kinetic energy and the integral length scale which can be obtained by steady solutions of the Reynolds‐averaged Navier‐Stokes equations with a two equation turbulence model. It is assumed that the turbulence is axisymmetric and homogenous, which is taken into account by introducing two anisotropy parameters.The validation of SATIN is done for trailing‐edge noise originating from a thin flat plate using measurements of a phased array. As expected, the anisotropic formulation of SATIN improves the prediction quality considerably compared to isotropic turbulence.
Diffusive mixing of the phase in pattern forming systems
Authors: Schneider Guido 
Published: April 2003

AbstractIt is the purpose of this paper to state two theorems which haven't been stated explicitely before, namely the diffusive stability of spatially periodic traveling wave solutions and the diffusive mixing of the phase for Turing pattern. Although true for general systems, the results are only formulated for the Taylor‐Couette problem, a paradigm of pattern forming systems.
Parameter Identification Based on First Order Approximation Neural Networks
Authors: Pichler Bernhard , Mang Herbert A. 
Published: April 2003

AbstractConstitutive models for structural analyses contain material parameters. Usually not all of them can be determined a priori with sufficient accuracy. They must be set such that numerical results agree with available measurements as well as possible. Hence, an inverse problem must be solved. In order to keep the number of the required numerical calculations for parameter identification as small as possible, back analyses are performed iteratively. In each iteration step, a backpropagation artificial neural network (BPANN) is trained to approximate results of already performed numerical analyses. In this paper the classical zero‐order training algorithm is extended in order to obtain first‐order approximation neural networks. Based on the trained BPANN, a prognosis of optimal parameters can be obtained.
Stochastic Response of a Continuous System with Stochastic Surface Irregularities to an Accelerated Load
Authors: Schenk C.A. , Bergman L.A. 
Published: April 2003

AbstractThe problem of calculating the second moment characteristics of the response of a general class of nonconservative linear distributed parameter systems with stochastically varying surface roughness, excited by a moving concentrated load, is investigated. In particular the case of an accelerated load is discussed. The surface roughness is modeled as a Gaussian stationary second order process. For the stochastic representation of the surface roughness a orthogonal series expansion of the covariance kernel, the so called Karhunen‐Loéve expansion, is applied. The resulting initial/boundary value problem is transformed by eigenfunction expansion into the modal state space. Second moment characteristics of the response are determined numerically by direct integration using a Runge‐Kutta method.
Optimization Strategies for Optimization Procedures and Algorithms
Authors: Simeliene N. 
Published: April 2003

AbstractNew theory of circle patterns (or packing) is now well developed. Uniformization result, the circle packing theorem [1], is based on analytic functions, while Doyle spirals are analoques of entire functions.Doyle constructed entire immersed hexagonal circle patterns analoques to the exponential map and conjectured that these immersed packings which came to be known as Doyle spirals, are the only entire immersed hexagonal circle packings [2, 3].Schramm had found that a framework of circle patterns based on the square grid which is called SG patterns, is more tractable than the traditional hexagonal patterns [4].We present a new approach concerned with a theory of discrete multistage optimization [5, 6]. Optimization strategies for optimization procedures are good tools for modelling. Consequently calculations are not far from empirical observations and experimental results. This clearly demonstrates the broad interest in our field and the role which mathematical modelling and analysis is expected to play with regard to the solution of the challenging problems that we are facing at the beginning of this millennium.
Error expansion for a first‐order upwind difference scheme
Authors: Linss Torsten 
Published: April 2003

AbstractA singularly perturbed convection‐diffusion problem is considered. The problem is discretized using a simple firstorder upwinded difference scheme on general meshes. We derive an expansion of the error of the scheme that allows us to give error bounds in the discrete maximum norm, uniformly with respect to the perturbation parameter, for both a defect correction method and the Richardson extrapolation technique. This generalizes and simplifies results obtained in earlier publications [2], [8].
Extended Kaczmarz‐like methods with oblique projections
Authors: Popa C. 
Published: April 2003

AbstractIn this paper we describe two “sparse preconditioning” techniques for accelerating the convergence of Kaczmarzlike algorithms. The first method, uses projections with respect to the “energy scalar product” generated by an appropriate symmetric and positive definite matrix. The second one starts from some recent results of Y. Censor and T. Elfving on “sparsity pattern oriented” (SPO) oblique projections and uses an “algebraic multigrid interpolationlike” construction of the (SPO) family. Numerical experiments are described on a system comming from a bioelectric field simulation problem.
Semidiscretisation Methods for Quasi‐periodic Solutions
Authors: Schilder F. , Vogt W. 
Published: April 2003

AbstractThe aim of our approach is a reliable numerical approximation of quasi‐periodic solutions of periodically forced ODEs without using a‐priori transformations into new coordinates [1]. The invariant torus is computed as a solution of a special invariance equation. In the case of two basic frequencies this system can be solved by semidiscretisation, which transforms the system into a higher dimensional autonomous ODE system with periodic solutions.
QMC Methods for the solution of delay differential equations
Authors: Kainhofer R. , Tichy R.F. 
Published: April 2003

AbstractIn this paper we will discuss the application of so‐called Runge Kutta Quasi‐Monte Carlo (RKQMC) methods (as proposed by Lécot, Koudiraty, Coulibaly, and Stengle) to heavily oscillating di.erential equations. The delayed argument is approximated by Hermite interpolation which transforms the equation into an ordinary differential equation so that the RKQMC methods can be applied. We will give a short discussion of this method and its advantages as well as its drawbacks, and give some more numerical results.
Natural convection in porous media ‐ a meshless solution of the Brinkman extended Darcy model
Authors: Perko Janez , Šarler Božidar , Kuhn Günther 
Published: April 2003

AbstractA numerical study is performed on steady natural convection inside a differentially heated square cavity. The cavity is filled with porous media which exhibits the Brinkman extended Darcy behavior. The solution procedure for coupled mass, momentum, and energy equations is based on primitive variables and RBF collocation method with r7 function. Numerical examples include calculations at filtration with Rayleigh number 100, and Darcy numbers 10–3 and 10–5. The solution is compared with reference results of the fine‐grid finite volume method.
Bacterial glycoproteins: Functions, biosynthesis and applications
Authors: Upreti Raj K. , Kumar Manoj , Shankar V. 
Published: April 2003

AbstractAlthough widely distributed in eukaryotic cells glycoproteins appear to be rare in prokaryotic organisms. The prevalence of the misconception that bacteria do not glycosylate their proteins has been a subject matter of discussion for a long time. Glycoconjugates that are linked to proteins or peptides, generated by the ribosomal translational mechanism have been reported only in the last two to three decades in a few prokaryotic organisms. Most studied prokaryotic glycoproteins are the S‐layer glycoproteins of Archeabacteria. Apart from these, membrane‐associated, surface‐associated, secreted glycoproteins and exoenzymes glycoproteins are also well documented in both, Archea and Eubacteria. From the recent literature, it is now clear that prokaryotes are capable of glycosylating proteins. In general, prokaryotes are deprived of the cellular organelles required for glycosylation. In prokaryotes many different glycoprotein structures have been observed that display much more variation than that observed in eukaryotes. Besides following similar mechanisms in the process of glycosylation, prokaryotes have also been shown to use mechanisms that are different from those found in eukaryotes. The knowledge pertaining to the functional aspects of prokaryotic glycoproteins is rather scarce. This review summarizes developments and understanding relating to characteristics, synthesis, and functions of prokaryotic glycoproteins. An extensive summary of glycosylation that has been reported to occur in bacteria has also been tabulated. Various possible applications of these diverse biomolecules in biotechnology, vaccine development, pharmaceutics and diagnostics are also touched upon.
Protein‐protein interactions as a target for drugs in proteomics
Authors: Archakov Alexander I. , Govorun Vadim M. , Dubanov Alexander V. , Ivanov Yuri D. , Veselovsky Alexander V. , Lewi Paul , Janssen Paul 
Published: April 2003

AbstractProtein‐protein interactions play a central role in numerous processes in the cell and are one of the main fields of functional proteomics. This review highlights the methods of bioinformatics and functional proteomics of protein‐protein interaction investigation. The structures and properties of contact surfaces, forces involved in protein‐protein interactions, kinetic and thermodynamic parameters of these reactions were considered. The properties of protein contact surfaces depend on their functions. The contact surfaces of permanent complexes resemble domain contacts or the protein core and it is reasonable to consider such complex formation as a continuation of protein folding. Characteristics of contact surfaces of temporary protein complexes share some similarities with active sites of enzymes. The contact surfaces of the temporary protein complexes have unique structure and properties and they are more conservative in comparison with active site of enzymes. So they represent prospective targets for a new generation of drugs. During the last decade, numerous investigations were undertaken to find or design small molecules that block protein dimerization or protein(peptide)‐receptor interaction, or, on the contrary, to induce protein dimerization.
Hepatic protein expression of lean mice and obese diabetic mice treated with peroxisome proliferator‐activated receptor activators
Authors: Edvardsson Ulrika , Brockenhuus von Löwenhielm Helena , Panfilov Oleg , Nyström Ann‐Christin , Nilsson Fredrik , Dahllöf Björn 
Published: April 2003

AbstractThe peroxisome proliferator‐activated receptors (PPARs) are ligand‐activated transcription factors that modulate lipid and glucose homeostasis. In the clinic, PPARα and PPARγ agonists are used to treat hypertriglyceridemia and insulin resistance of diabetes, respectively. To gain further insight into the molecular mechanisms underlying the therapeutic actions of these drugs, we have by two‐dimensional electrophoresis and mass spectrometry performed a comparative analysis of the hepatic protein expression profiles of lean and obese (ob/ob) mice, and obese mice treated with WY14,643 (PPARα agonist) or rosiglitazone (PPARγ agonist). We found that livers from obese mice displayed higher levels of enzymes involved in fatty acid oxidation and lipogenesis compared to lean mice and these differences were further amplified by treatment with both PPAR activators. WY14,643 normalized the expression levels of several enzymes involved in glycolysis, gluconeogenesis and amino acid metabolism in the obese mice to the levels of lean mice, whereas rosiglitazone partially normalized levels of enzymes involved in amino acid metabolism. In summary, a classical proteomics approach was successfully used to characterize differences at the hepatic proteome level between lean and obese diabetic mice, to map metabolic pathways affected by treatment, and to discriminate between effects caused by treatment with agonists of the closely related PPARα and PPARγ receptors.
Stress protein flux during recovery from simulated ischemia: Induced heat shock protein 70 confers cytoprotection by suppressing JNK activation and inhibiting apoptotic cell death
Authors: Kumar Yadunanda , Tatu Utpal 
Published: April 2003

AbstractMultiple stress proteins are recruited in response to stress in living cells. There are limited reports in the literature analyzing multiple stress protein shifts and their functional consequences on stress response. Using two‐dimensional electrophoresis we have analyzed shifts in stress protein profiles in response to energy deprivation as a model of ischemic injury to kidneys. A group of chaperones and stress‐induced mitogen activated protein (MAP) kinases were analyzed. In addition to examining stress protein induction and phosphorylation we have also examined the mechanism of cytoprotection by heat shock protein 70 (Hsp70). Our results show that, of the different stress proteins examined, only binding protein (BiP) and Hsp70 were significantly induced upon energy deprivation. Other stress proteins, including Hsp27, calnexin, Hsp90 and ERp57 showed alterations in their phosphorylation profiles. Three different MAP kinases, namely p38, extracellular signal regulated kisase and c‐jun N‐terminal kinase (JNK) were activated in response to energy deprivation. While JNK activation was linked to apoptosis, activated‐p38 was involved in phosphorylation of Hsp27. Study of inhibitors of Hsp70 induction or pre‐induction of Hsp70 indicated that induced Hsp70 was involved in the suppression of JNK activation thereby inhibiting apoptotic cell death. Our results provide important insights into the flux in stress protein profiles in response to simulated ischemia and highlight the antiapoptotic, cytoprotective mechanism of Hsp70 action.
Use of a sensitive EnVision™+‐based detection system for Western blotting: avoidance of streptavidin binding to endogenous biotin and biotin‐containing proteins in kidney and other tissues
Authors: Banks Rosamonde E. , Craven Rachel A. , Harnden Patricia A. , Selby Peter J. 
Published: April 2003

AbstractWestern blotting remains a central technique in confirming identities of proteins, their quantitation and analysis of various isoforms. The biotin‐avidin/streptavidin system is often used as an amplification step to increase sensitivity but in some tissues such as kidney, “nonspecific” interactions may be a problem due to high levels of endogenous biotin‐containing proteins. The EnVision™ system, developed for immunohistochemical applications, relies on binding of a polymeric conjugate consisting of up to 100 peroxidase molecules and 20 secondary antibody molecules linked directly to an activated dextran backbone, to the primary antibody. This study demonstrates that it is also a viable and sensitive alternative detection system in Western blotting applications.
Non-compact lamination convex hulls
Authors: Kolář Jan 
Published: April 2003

For K a compact set of

m\times n

matrices, let

L(K)

denote the lamination convex hull of

K

.

We give an example of a compact set

K

of symmetric two by two matrices such that

L(K)

is not compact, and similar examples for separate convexity in

\mathbb{R}^{3}

and bi-convexity in

\mathbb{R}^{2} \times \mathbb{R}

. Furthermore we show that function

\tilde L

, where

\tilde L(K) = \overline{L(K)}

, is not upper semi-continuous with respect to Hausdorff metric on the space of all compact sets

K

of diagonal

3\times 3

matrices.

Résumé

Si K est un ensemble compact des matrices du type

m\times n

,

L(K)

) signifie le plus petit ensemble lamineusement convexe contenant

K

. (Un ensemble

K

est lamineusement convexe si

[a,b]\subset K

pour tous

a,b\in K

tels que

a−b

est une matrice de rang 1.)

Nous démontrons qu’il y a

K

, un ensemble compact des matrices symétriques d’ordre 2 tel que

L(K)

ne soit pas compact. Nous présentons aussi des exemples similaires pour convexité séparée dans

\mathbb{R}^{3}

et bi-convexité dans

\mathbb{R}^{2} \times \mathbb{R}

. En plus, nous démontrons que l’application

\tilde{L}:K\mapsto \overline{L(K)}

n’est pas semi-continue superieurement sur l’espace des ensembles compacts de matrices diagonales d’ordre 3 muni de la métrique de Hausdorff.