bluuebunny/crossref_metadata_2025_split huggingface dataset:
A unified tensorial driving force for phase transitions – calculation of the onset of the transformation
Authors: Oberste‐Brandenburg C. 
Published: April 2003

AbstractThe transformation kinetics during phase transitions in solids are often described by a pair of scalar variables for both the thermodynamic force and flux. Based on the use of the Eshelby‐Tensor as the thermodynamic driving force for the phase‐transition, a tensorial measure is introduced which is used as the associated thermodynamic flux. Based on the assumption that the process maximizes the dissipation, these measures are used to describe the transformation kinetics during the phase transition. The tensorial description reduces to a description with the Gibbs‐energy as the driving force and the mass change of the phases as the thermodynamic flux for a hydrostatic stress state.These considerations serve as the base for a phenomenological material‐law which describes the austenite‐martensite transformation in steels. In order to incorporate the different behavior of the phases, they are modeled independently. The model have been implemented into a finite‐element‐code which allows thermodynamically coupled calculations. A quenching‐test of a cylindrical specimen under biaxial mechanical load is simulated. The influence of the sequence of the change of the thermomechanical load in the stress‐temperature space (temperature→stress vs. temperature→stress) is studied. Furthermore, the influence of the direction of the applied stress is presented.
Simulation des Ausbreitungsverhaltens mikrostrukturell kurzer Ermüdungsrisse
Authors: Schick A. , Fritzen C.‐P. 
Published: April 2003

AbstractEs wird ein Fließstreifenmodell zur Simulation des Stadium‐I‐Risswachstums vorgestellt. Das Randwertproblem wird numerisch über Randelemente gelöst, die auf der Versetzungstheorie basieren. Das Modell kann sowohl geometrisches Rissschließen als auch Lastreihenfolgeeffekte berücksichtigen.
A Thermo‐Mechanical Formulation Describing the Frictional Behavior of Rubber
Authors: Hofstetter K. , Eberhardsteiner J. , Mang H.A. 
Published: April 2003

AbstractIn this paper mechanical and thermal phenomena during the sliding motion of a rubber block on a rough surface are investigated. The presented formulation describes the frictional behavior of rubber on a macroscopic scale. Thus, it is not necessary to consider the roughness of the surface explicitly. Only macroscopic characteristics of the involved solids are required for the contact formulation. For the purpose of parameter identification and model verification, experiments have been carried out. The results from numerical simulations by means of the Finite Element Method (FEM) agree well with the experimental results.
Volumenabhängige hydrostatische Druckbelastung in der nichtlinearen FE‐Analyse
Authors: Rumpel T. , Schweizerhof K. 
Published: April 2003

AbstractFür dünnwandige Schalen‐ und Membranstrukturen ist die Wechselwirkung einer hydrostatischen Druckbelastung mit dem sich durch eine Belastung ergebenden Strukturverformungen sowohl für Stabilitätsbetrachtungen wie auch bei großen Deformationen von entscheidender Bedeutung. Über das Prinzip der virtuellen Arbeit wird die hydrostatische Druckbelastung in die schwache Gleichgewichtsformulierung der elastomechanischen Kräfte eingeführt. Wird für die sich in einem elastischen Behälter befindlichen Flüssigkeit Volumenerhaltung gefordert, so kann die resultierende Spiegelhöhenänderung berechnet werden. Die beschreibenden nichtlinearen Gleichungen sind für eine Lösung mittels Newtonverfahren zu linearisieren. Eine Finite Element Diskretisierung führt auf eine Laststeifigkeitsmatrix und das zugehörige Residuum der volumenabhängigen Druckkraft. Wesentlich ist, das keine Diskretisierung der Flüssigkeit erforderlich ist. An einem numerischen Beispiel wird die Effektivität des Verfahrens vorgestellt.
Identification of the Nonlinear Restoring Force Characteristic of a Rubber Mounting
Authors: Bruns J.‐U. , Lindner M. , Popp K. 
Published: April 2003

AbstractThis paper is concerned with the identification of the nonlinear restoring force characteristic of a rubber mounting that is part of an oscillator which is subjected to harmonic force excitation. A linearity test is successfully applied to the experimental data to detect the nonlinear behaviour of the system. It is shown that the results of linear system identification depend on the level of excitation force applied. Furthermore, the frequency response functions of the identified linear models only poorly match the measured ones. In consequence, a parametric nonlinear spring characteristic is introduced into the linear model. It is demonstrated that only one set of parameters is required to explain the system behaviour at different levels of excitation force. Also, each of the measured frequency response functions is matched more closely by the calculated frequency response of the nonlinear model.
Stability analysis of the constant temperature anemometer with frequency depended amplifier gain
Authors: šajn V. , Kosel F. 
Published: April 2003

AbstractIn this paper we are concerned with the stability and the dynamic response of the constant temperature anemometer. The amplifier of the presented hot–wire anemometer has one pole with high time constant, which affect the presented amplifier to behave in the anemometer working frequency bandwidth with the frequency depended gain. For precise description of the anemometer dynamical response the used transfer function of the amplifier is first order of zeros and third order of poles. The hot–wire response to the sine‐wave voltage perturbation was calculated and measured. The root curves of the transfer function were presented.
Large Eddy Simulation of a Compressible Boundary Layer
Authors: El‐Askary W. A. , Meinke M. , Schröder W. 
Published: April 2003

AbstractA large eddy simulation of a compressible boundary layer is performed. To generate an appropriate inflow distribution the rescaling technique for compressible flows is discribed. In this method Morkovin's hypothesis in which the total temperature fluctuations are neglected compared with the static temperature fluctuations is applied to rescale and generate the temperature profile at inlet. This new technique is used for various large eddy simulations of subsonic and supersonic three‐dimensional boundary layers of a flat plate. Simulation results for the time‐averaged mean flow and Reynolds stresses are compared with numerical and analytical data to demonstrate the high quality of the method.
Large‐eddy simulation of compressible rectangular duct flow
Authors: Rembold B. , Kleiser L. 
Published: April 2003

AbstractTurbulent flow inside ducts differs significantly from the statistically one‐dimensional turbulent channel flow due to the additional confining lateral walls. Secondary flows in the corners are found which are known to affect the turbulence structure close to the walls. Most computations have been performed for incompressible or only slightly compressible flows and with square duct geometries (e.g. [1,2]). In the present study we address the effect of the aspect ratio on the flow structure in high subsonic rectangular duct flow using LES. Mean‐flow characteristics are analyzed and compared to square duct and channel flow data. We find good agreement with available incompressible DNS square duct data for low Mach number computations. For aspect ratios as high as five, the mean‐flow profile in the center of the longer side of the duct along the wall normal direction differs distinctively from channel flow for the present Mach 0.7 computations.
Numerical Simulation of Heat Loads in a Cryogenic H2/O2 Rocket Combustion Chamber
Authors: Haarmann T. M. , Koschel W. W. 
Published: April 2003

AbstractA Finite Element solver for a coupled simulation of fluid and structure in an axisymmetric domain is presented. The method employs an explicit solution of the flow and structure variables. The computational domain of the fluid is discretised by unstructured triangles and rectangles while the sturcture domain is discretised by unstructured triangles only. For the purpose of code validation the solution of in total three test cases are shown. One test case deals with the structure only while the other two simulate heat transfer problems with a defined temperature distribution along a boundary wall and coupled conditions. Finally the code is used to simulate the heat load in a cryogenic H2/O2 rocket combustion chamber.
Towards a numerical simulation of a high temperature flow
Authors: Kolman D. , Kozel K. , Louda P. , Sopuch P. 
Published: April 2003

AbstractTwo mathematical models of unsteady plasma flows based on 3D finite volume methods for Navier‐Stokes equations are presented. In the first, cold jet model, the nondimensional NS equations are solved by the artificial compressibility method, and the results include time‐varying velocity fields for different Reynolds numbers. The second formulation is a compressible Stegger‐Warming flux vector splitting scheme that takes into account the non‐perfect character of the plasma fluid. Temperature and composition dependent gas properties are to be evaluated from real data.
Multiscale Considerations for Sound Generation in Low Mach Number Flows
Authors: Fortenbach Roland , Munz Claus‐Dieter 
Published: April 2003

AbstractClassical approaches in aeroacoustics are mainly based on analytical solutions of the linear wave equations which are valid in the far field. The sound generation is approximated by source terms obtained from a flow simulation. This procedure designated as the ‘acoustic analogy’ was initiated in the classical work of Lighthill. In order to tackle the sound generation problem at low Mach numbers, we consider a multiple scale asymptotic analysis. As we deal with a fluid flow generating the sound itself, the asymptotic ansatz uses one time scale given by the flow convection, but two space scales due to the difference in fluid and sound velocity. The insight given by this analysis is used to obtain source terms describing the sound generation and perturbation equations for the sound propagation. Numerical results are shown for the example of a co‐rotating vortex pair.
Numerische Simulation der Ausbreitung von Umfangsmoden in axialsymmetrischen Rohren
Authors: Schönwald N. , Schemel C. , Thiele F. , Michel U. 
Published: April 2003

AbstractDie Konstruktion leiser Flugzeuge gewinnt durch den ständig zunehmenden Flugverkehr und der damit einhergehenden Lärmbelastung immer mehr an Bedeutung. Eine wichtige Lärmquelle am Flugzeug, die besonders beim Start eine Rolle spielt, sind die Triebwerke. Durch die Einführung von Nebenstromtriebwerken konnte der Strahllärm der Triebwerke stark reduziert werden. Dies führte aber dazu, dass der durch den Fan verursachte tonale Lärm, der sich durch den Triebwerkseinlauf ausbreitet, zu einer wichtigen Komponente des Triebwerkslärms wurde. Für den Entwurfsprozeß bekommt die numerische Simulation der Schallausbreitung immer größere Bedeutung, da experimentelle Untersuchungen sehr aufwändig sind. Ziel ist die Simulation der Schallausbreitung von der Quelle bis ins Fernfeld mittels spezieller CAA‐Verfahren für axialsymmetrische Rohre.
On Integral Representation Formulae for Biharmonic Functions on the Ball
Authors: Burgeth Bernhard F. 
Published: April 2003

AbstractBiharmonic functions are solutions of the fourth order partial differential equation ΔΔu = 0. A simple method is proposed for deriving integral representation formulae for these functions u on the n‐dimensional ball. Poisson‐type representations in the setting of Hardy Spaces are obtained for biharmonic functions subject to Dirichlet, Riquier and other boundary conditions. The approach exploits algebraic properties of a first order partial differential operator and its resolvent.
Risikoparameter für schwere Herzerkrankungen mittels Auswertung von Langzeit‐EKGs durch Methoden der nichtlinearen Zeitreihenanalyse
Authors: Bach Harriet , Lang Patrick 
Published: April 2003

AbstractBei der Untersuchung von Langzeit‐EKGs bezüglich einer Risikoabschätzung für Plötzlichen Herztod finden in jüngster Zeit neben den etablierten linearen Verfahren (z.B. Standard‐HRV‐Parameter) auch zunehmend Methoden der nichtlineare Zeitreihenanalyse ihre Anwendung. Diese Ansätze zeigen sich hierbei in der erzielten Güte der Risikovorhersage den linearen Methoden oft deutlich überlegen. Im Rahmen dieser Arbeit durchgeführte Untersuchungen zur Bestimmung der Korrelationsdimension von Langzeit‐EKGs führen zum Schluss, dass diese selbst zwar nicht im strengen Sinne bestimmbar ist, die Korrrelationssummenverläufe allerdings sehr wohl zur Risikoklassi fikation geeignet sind. Dazu werden Entscheidungskriterien bestimmt, die eine Unterteilung der Patienten in Risikound Nichtrisikopatienten ermöglichen.
Semi‐Unstructured Grids in the Laser Simulation Program LASCAD
Authors: Altmann K. , Pflaum C. , Seider D. 
Published: April 2003

AbstractAutomatic grid generation is very important in industrial applications. Furthermore, in several applications discretization grids are needed which provide an anisotropic refinement and an accurate approximation of the derivatives of the solution. These requirements are fulfilled by semi‐unstructured grids. In this paper, we report how semi‐unstructured grids are used in the laser simulation program LASCAD [3].
Structure Analysis of Polynomial Modules with Pommaret Bases
Authors: Seiler Werner M. 
Published: April 2003

AbstractWe show how Pommaret bases of submodules of free polynomial modules can be used to extract structural information like the dimension, the depth or the Castelnuovo‐Mumford regularity. In particular, we discuss the syzygy theory of Pommaret bases and its use for the construction of free resolutions.
A Normal Form for Systems of Implicit Ordinary Differential Equations
Authors: Zehetleitner Kurt , Schlacher Kurt , Kugi Andreas 
Published: April 2003

AbstractThis contribution deals with the application of computer algebra based methods to the analysis of dynamic systems described by implicit ordinary differential equations. This type of system defines a submanifold of a certain jet space. We solve the problem whether this submanifold admits a parametrization by an explicit system, i.e. any solution of the original system is a solution of the explicit one and vice versa. Since this approach requires the formal integrability of the implicit system, a sketch of an algorithm for the computation of the formally integrable system is presented.
Nonparametric changepoint detection for time series
Authors: Franke J. , Kroisandt G. 
Published: April 2003

AbstractWe consider time series which change their structure repeatedly between a finite number of states, and we discuss algorithms to detect the changepoints for two particular situations. In the first case, the observed time series is a nonparametric autoregression of order p and the autoregression function changes sometimes. Here, we use a system of neural networks to estimate the autoregression functions and to detect the changepoints. In the second case, the time series is a piecewise linear process with stable innovations, where we assume that the various processes represent different dominating local frequencies, and we use wavelet packet coefficients to detect the changepoints.
Quadrature rules for qualocation
Authors: Junges Michael , Schneider Claus 
Published: April 2003

AbstractQualocation is a method for the numerical treatment of boundary integral equations on smooth curves which was developed by Chandler, Sloan and Wendland (1988‐2000) [1,2]. They showed that the method needs symmetric J–point–quadrature rules on [0, 1] that are exact for a maximum number of 1–periodic functions$$ G _{\alpha} (x) \ggleich \sum ^{\infty} _{k=1} k ^{-\alpha} \cos (2 \pi kx), \qquad \alpha > {1 \over {2}}. $$The existence of 2–point–rules of that type was proven by Chandler and Sloan. For J ∈ {3, 4} such formulas have been calculated numerically in [2]. We show that the functions Gα form a Chebyshev–system on [0, 1/2] for arbitrary indices á and thus prove the existence of such quadrature rules for any J.
Performance prediction of concentrator solar cells and modules from darkI–Vcharacteristics
Authors: Antón I. , Sala G. , Heasman K. , Kern R. , Bruton T. M. 
Published: April 2003

AbstractThe indoor performance of concentrator solar cells and modules at operating conditions is a complex task, owing to the required illumination and temperature conditions, and even more so during extensive procedures, such as on a production line. The solution proposed throughout this paper consists of predicting the illuminationI–Vcharacteristic of the solar cells, with the darkI–Vcurve and the photogenerated current as the only input data. As well as this, the technology‐dependent components of the series resistance are obtained from the dark characteristics for quality control. Theory and experiments on several types of concentrator cell have been carried out to validate the method. The equipment to be used on a production line has been developed by IES and used by BP Solar to test up to 25 000 cells and 2000 modules for the 480 kWppower plant using the EUCLIDESTMconcentrator. Copyright © 2003 John Wiley & Sons, Ltd.
Dynamic battery model for photovoltaic applications
Authors: Guasch D. , Silvestre S. 
Published: April 2003

AbstractThe main purpose of this paper is to offer a useful battery model for simulation of stand‐alone photovoltaic applications. At present, many models for battery behaviour simulation are available. Owing to the complex response of this element, these models are mainly concerned with stationary working point conditions. This paper presents an enhancement of a generic battery model, achieving a dynamic battery model for photovoltaic applications. It includes the use of automatic parameter extraction techniques and the solving of numerical calculation problems. It also introduces some new concepts, such as the maximum available capacity and the level of energy. Finally, a battery state of health estimation, has been added to complete the battery behaviour description, including non‐ideal effects, such as battery capacity reduction and self‐discharging current. Copyright © 2003 John Wiley & Sons, Ltd.
Multi‐component immunoaffinity subtraction chromatography: An innovative step towards a comprehensive survey of the human plasma proteome
Authors: Pieper Rembert , Su Qin , Gatlin Christine L. , Huang Shih‐Ting , Anderson N. Leigh , Steiner Sandra 
Published: April 2003

AbstractIn order to discover novel protein markers indicative of disease processes or drug effects, the proteomics technology platform most commonly used consists of high resolution protein separation by two‐dimensional electrophoresis (2‐DE), mass spectrometric identification of proteins from stained gel spots and a bioinformatic data analysis process supported by statistics. This approach has been more successful in profiling proteins and their disease‐ or treatment‐related quantitative changes in tissue homogenates than in plasma samples. Plasma protein display and quantitation suffer from several disadvantages: very high abundance of a few proteins; high heterogeneity of many proteins resulting in long charge trains; crowding of 2‐DE separated protein spots in the molecular mass range between 45–80 kD and in the isoelectric point range between 4.5 and 6. Therefore, proteomic technologies are needed that address these problems and particularly allow accurate quantitation of a larger number of less abundant proteins in plasma and other body fluids. The immunoaffinity‐based protein subtraction chromatography (IASC) described here removes multiple proteins present in plasma and serum in high concentrations effectively and reproducibly. Applying IASC as an upfront plasma sample preparation process for 2‐DE, the protein spot pattern observed in gels changes dramatically and at least 350 additional lower abundance proteins are visualized. Affinity‐purified polyclonal antibodies (pAbs) are the immunoaffinity reagents used to specifically remove the abundant proteins such as albumin, immunoglobulin G, immunoglobulin A, transferrin, haptoglobin, α‐1‐antitrypsin, hemopexin, transthyretin, α‐2‐HS glycoprotein, α‐1‐acid glycoprotein, α‐2‐macroglobulin and fibrinogen from human plasma samples. To render the immunoaffinity subtraction procedure recyclable, the pAbs are immobilized and cross‐linked on chromatographic matrices. Antibody‐coupled matrices specific for one protein each can be pooled to form mixed‐bed IASC columns. We show that up to ten affinity‐bound plasma proteins with similar solubility characteristics are eluted from a mixed‐bed column in one step. This facilitates automated chromatographic processing of plasma samples in high throughput, which is desirable in proteomic disease marker discovery projects.
Use of serological proteomic methods to find biomarkers associated with breast cancer
Authors: Rui Zhao , Jian‐Guo Ji , Yuan‐Peng Tong , Hai Pu , Bing‐Gen Ru 
Published: April 2003

AbstractNew technologies for the detection and therapy of early stage breast cancer are urgently needed. Pathological changes in breast might be reflected in proteomic patterns in serum. A proteomic tool was used to identify proteomic patterns in serum that distinguishes neoplastic from non‐neoplastic disease within the breast. Preliminary results derived from the serum analysis from 54 unaffected women and 76 petients with breast cancer were analyzed by two‐dimensional (2‐D) electrophoresis and matrix‐assisted laser desorption/ionization‐time of flight mass spectrometry, HSP27 was found up‐regulated while14‐3‐3 sigma was down‐regulated in the serum of breast cancer patients. The two protein biomarkers were then used to classify an independent set of 104 masked serum samples. The results showed that the protein pattern on 2‐D gels can completely segregate the serum of breast cancer from non‐cancer. The discriminatory pattern correctly identified all 69 breast cancer cases in the masked set. Of the 35 cases of non‐malignant disease, 34 were recognized as non‐cancer. These findings justify a prospective population‐based assessment of proteomic technology as a screening or diagnostic tool for breast cancer in high‐risk and general populations. These two protein biomarkers could also be used as targets for further study in drug design and breast cancer therapy.
Proteins from bovine tissues and biological fluids: Defining a reference electrophoresis map for liver, kidney, muscle, plasma and red blood cells
Authors: Talamo Fabio , D'Ambrosio Chiara , Arena Simona , Del Vecchio Prisco , Ledda Luigi , Zehender Goffredo , Ferrara Lino , Scaloni Andrea 
Published: April 2003

AbstractA number of high resolution two‐dimensional electrophoresis (2‐DE) reference maps for bovine tissues and biological fluids have been determined for animals in basal state. Among the 1863 distinct protein features detected in samples of liver, kidney, muscle, plasma and red blood cells, 509 species were identified and associated to 209 different genes. Difficulties in the identification were related to the poorly characterized Bos taurus genome and were solved by a combined matrix‐assisted laser desorption/ionisation‐mass spectrometry and liquid chromatography‐electrospray ionization tandem mass spectrometry approach. The experimental output allowed us to establish a 2‐DE database accessible through the World Wide Web network at the URL address (http://www.iabbam.na.cnr.it/Biochem). These reference maps may serve as a tool in future veterinary medical studies aimed at the evaluation of changes in protein repertoire for altered animal physiological conditions and infectious diseases, to the definition of molecular markers for novel diagnostic kits and vaccines, as well as the characterization of protein modifications in bovine materials following technological processes used in the food industry.