bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimente zur Decarboxylierung von Carbonsäuresalzen mit Natriumhydroxid
Authors: Heimann Rebekka , Mühlenschulte Nico , Oldenbürger Dirk , Thegelkamp Anja , Harsch Günther
Published: April 2003

THERMISCHE ZERSETZUNGEN sind geeignet, um eine Beziehung zwischen den Carbonsäuresalzen und den Alkanen herzustellen. In diesem Beitrag wird die Zersetzung von Propionat, Acetat und Malonat mit Natriumhydroxid beschrieben, wobei die beiden letzteren Synthesen zu definierten, mit schulischen Mitteln problemlos identifizierbaren Produkten führen.
Chemiedidaktik und Chemielehrer in der Mitte des 19. Jahrhunderts
Authors: Schmitz‐Wallrafen Norbert
Published: April 2003

MIT DEM AUFBLÜHEN der Realanstalten und der fortschreitenden Etablierung des Faches Chemie rückten auch zunehmend Fragen der Gestaltung von Chemieunterricht in den Vordergrund. Dies soll anhand einiger Dokumente früher Chemiedidaktiker an Schulen in Rheinpreußen und anderer deutscher Länder belegt werden. Dabei wird deutlich, dass viele Fragen heutiger Chemiedidaktik früher schon gestellt und bearbeitet wurden.

Gemeinhin gilt Rudolf Arendt als der Begründer einer Didaktik der Chemie [1, 2], eine These, die vor einiger Zeit von Just [3] noch untermauert wurde. Rudolf Arendt bzw. Ferdinand Wilbrand wird das Verdienst zugeschrieben, den Chemieunterricht in Schulen aus den Fesseln der Stoffsystematik der Hochschulen befreit zu haben. Dies kann jedoch nur eine Teilwahrheit sein, denn es gibt zahlreiche Dokumente in den so genannten Schulprogrammen aus der Zeit vor Arendt, die eine andere Sprache sprechen. Es ist an der Zeit, sie aus ihrem Schattendasein hervorzuholen und einer fachkundigen Öffentlichkeit zur Kenntnis zu bringen, damit sie eine entsprechende Würdigung erfahren. Im Rahmen meiner Arbeit [4] bin ich auf eine Fülle von Hinweisen in dieser Richtung gestoßen, die ich hier nicht alle ausbreiten kann. Zwei Dinge sollen jedoch stellvertretend besonders hervorgehoben werden. Es ist einmal das Wirken von drei Persönlichkeiten im Rheinland, die sich als Lehrer in der didaktischen Aufbereitung des Lehrstoffs in Chemie besonders hervorgetan haben. Dabei tut es ihren Verdiensten keinen Abbruch, dass die Unterlagen in den Archiven nicht immer alle Lebensdaten bereithalten. Des weiteren möchte ich auf eine Reihe von Dokumenten anderer Persönlichkeiten eingehen, die zeigen, dass die Wurzeln einer frühen Didaktik der Chemie nicht auf Rheinpreußen beschränkt waren.

Die Genese des Schulfaches Chemie ist eng mit der Entwicklung der Realanstalten verknüpft. Da ist es naheliegend, bei der Suche nach den Wurzeln einer frühen Didaktik der Chemie bei den Praktikern vor Ort zu beginnen, die sich bei der Konzeption ihres Unterrichts erstmals mit didaktischen Fragestellungen des neuen Faches auseinandersetzen mussten und noch nicht auf einen Fundus anderweitig gesicherter Erkenntnisse zurückgreifen konnten.
Feed additives in animal nutrition: Quantification of a new adrenergic drug by hyphenated techniques
Authors: Bocca Beatrice , Cartoni Claudia , Mattia Michela Di , Fiori Maurizio , Felli Marialinda , Neri Bruno , Russo Mario Vincenzo , Brambilla Gianfranco
Published: April 2003

Zilpaterol, (±)‐trans‐4,5,6,7‐tetrahydro‐7‐hydroxy‐6‐(isopropylamino) imidazo [4,5,1‐jk]‐[1]benzazepin‐2(1H)‐one, is an adrenergic agonist drug licensed in Mexico and South Africa as feed additive for cattle at slaughter age. In contrast, the EU legislative framework prohibits the use of beta‐agonists as growth promoters to produce lean meat. In this study, the compound was quantified as its TMS derivative both by gas chromatography‐mass spectrometry (GC‐MS) with a quadrupole detector (QUADR) and by GC‐MS/MS with an ion trap detector (ITD), in Electron Impact (EI) ionization. Subsequently, an extraction and clean‐up procedure for the identification of Zilpaterol in commercial feeds was set up. Different extraction solvents and matrices were considered for their influence on Zilpaterol yield. The analytical method led to good recoveries and limits of detection and quantification in feeds well below the 5–20 μg/g dose proposed for animal nutrition.
Use of different anticoagulants for HPLC separation and quantification of the free amino acid content of plasma
Authors: Avino Pasquale , Campanella Luigi , Russo Mario Vincenzo
Published: April 2003

Amino acid analysis in plasma samples is a very important and difficult task and could represent a useful tool for preventing the occurrence of some diseases (diabetes, cancer, HIV disease). Even though amino acid analysis has been thoroughly investigated, there are still some steps which are not so clear in this analytical procedure, e.g. the coagulation process of the blood to afford plasma and serum. Various anticoagulants are used in clinical chemistry: in this paper we have investigated three commonly used anticoagulants, heparin, EDTA, and sodium citrate. The blood samples have been divided into three portions and each portion treated with a different anticoagulant. The entire analytical procedure (from blood collection to the coagulation all the way to HPLC analysis) has been extensively investigated; the chromatograms and the amino acid recoveries are reported, and the three anticoagulants compared. Finally, the best anticoagulant has been used to analyze glycemic curves of healthy patients: the behavior of essential amino acids in the different blood samples withdrawn has been studied.
Hyphenated techniques of thermal analysis for characterisation of soil humic substances
Authors: Dell'Abate Maria Teresa , Benedetti Anna , Brookes Phil C.
Published: April 2003

Our aim was to investigate the thermal behaviour of humic substances extracted from temperate and tropical soils by means of hyphenated techniques of thermal analysis (e. g. simultaneous thermal analysis DSC/TG coupled with mass spectrometry, MS, for the analysis of evolved gas, EGA) in order (i) to verify whether the chemical composition of isolated humic substances also reflected the differences in microbial parameters previously measured in related soil samples and (ii) to identify suitable indices of thermal stability. Our results show that the investigation of humic substances by thermal methods can provide information on soil organic matter dynamics. Differences in thermal behaviour between the two groups of soils were found. The indices of thermal stability here proposed, IR (index of thermal recalcitrance), and ID (index of thermal decomposability) clearly showed that in humic substances from tropical soils the thermally recalcitrant organic fraction dominated, whilst in temperate humic substances the opposite held. This agrees with previous results on the microbial dynamics and organic matter turnover of the respective soils and indicates that these indices of thermal stability could represent a useful tool in soil environmental quality investigations.
Study of Self‐Assembly of the Lignin Model Compound on Cellulose Model Substrate
Authors: Micic Miodrag , Radotic Ksenija , Jeremic Milorad , Leblanc Roger M.
Published: April 2003

Herein we report a topographical study of the supramolecular organization of enzymatically polymerized lignin model compound – dehydrogenative polymer (DHP) of coniferyl alcohol – on cellulose substrate, using the Environmental Scanning Electron Microscopic (ESEM) technique. A comparison of deposits obtained by bulk polymerization in solution and direct polymerization in the presence of cellulose substrate shows distinct differences in supramolecular organization. DHP polymerized in solution expresses a 3‐D structure with short‐range ordered motifs, while the polymer formed in the presence of cellulose substrate arranges in a single layer compact structure consisting of several domains. Such structures could be described as a two‐dimensional hexagonal close packed lattice(HCPL), with the dimension of unit cell in 1 μm range. The domains have a quite regular structure with few lattice defects, forming a good example of two‐dimensional colloidal crystal. The growth of DHP globules and their assembly into supramolecular structures are interpreted in terms of cooperative electrostatic interaction of polymer precursors, with a framework of cellulose OH groups and interfacial interactions (hydrophilic/hydrophobic) in the course of the structure growth. The results strongly suggest that the carbohydrate matrix in plant cells can serve as a template for lignin structure formation in the plant cell wall.

Self‐assembled lignin model compound on cellulose substrate.

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Self‐assembled lignin model compound on cellulose substrate.
Application of the Weyl–Hörmander calculus to generators of Feller semigroups
Authors: Baldus Frank
Published: April 2003

In this article we apply the S(M, g)–calculus of L. Hörmander and, in particular, results concerning the spectral invariance of the algebra of operators of order zero in ℒ︁(L2(ℝn)) to study generators of Feller semigroups. The core of the article is the proof of the invertibility of λ Id + P for a strongly elliptic operator P in Ψ(M, g) and suitable weight functions M and metrics g. The proof depends highly on precise estimates of the remainder term in asymptotic expansions of the product symbol in Weyl and Kohn–Nirenberg quantization. Due to the Hille–Yosida–Ray theorem and a theorem of Courrège, the result concerning the invertibility of λ Id + P is applicable to obtain sufficient conditions for an operator to extend to a generator of a Feller semigroup. Moreover, we discuss Sobolev spaces adapted to our weight functions and apply our results to study the generator of a subordinate Feller semigroup. As for the Feller semigroups and the subordination in the sense of Bochner, we build on results of N. Jacob and R. L. Schilling.
Organosilicon‐Assisted Transformation of Living Anionic into Living Cationic Polymerization
Authors: Sanji Takanobu , Sunaga Daisuke , Muto Yasuhiro , Sakurai Hideki
Published: April 2003

A novel method is described for transforming an anionic polymerization process into a cationic polymerization process assisted by organosilyl groups. The reaction of the p‐tolyldimethylsilyl end group of polystyrene and trifluoromethanesulfonic acid produced a silyl triflate end group that served as a macroinitiator for the living cationic polymerization of isobutyl vinyl ether. The SiO linkage in the block copolymers underwent specific cleavage by reaction with tetrabutylammonium fluoride.

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Subharmonic motion of floating cranes
Authors: Ellermann K. , Kreuzer E.
Published: April 2003

As an example of the nonlinear phenomena in offshore engineering the subharmonic motion of a floating crane is investigated. This nonlinear behavior was observed in experiments [1] as well as simulations [3] for a periodically forced floating crane. The range of operation, in which initial conditions and disturbances influence the type of motion significantly, are of special interest – as well as bifurcation points, where the dynamics change qualitatively due to a small change of one of the parameters.

Two different mathematical tools for the investigation of these critical ranges are described: The multiple scales method allows for the analysis of the oscillating system in frequency domain. Path following algorithms are applied in the numerical bifurcation analysis. The results of both tools are in good agreement and can assist in the evaluation of operating conditions.
Stability Analysis of A Floating Caliper Disc Brake
Authors: Jearsiripongkul T. , Chakraborty G. , Hagedorn P.
Published: April 2003

In this paper, the onset of the dynamic instability in a .oating caliper disc brake system is studied. The disc is modelled as a .exible rotating plate, the pad is taken as a small mass and a distributed sti.ness, and the motion of the caliper is also taken into consideration. The linearized equations of motion about the equilibrium position are derived assuming a constant braking force. The equations are subsequently discretized with the help of appropriate shape functions. The eigenvalue problem is then solved to detect the onset of instability. The effects of damping on the stability of motion are investigated as well.
Collapse of Keldysh chains and stability boundaries of non‐conservative systems
Authors: Kirillov Oleg
Published: April 2003

Eigenvalue problems for non‐selfadjoint linear differential operators smoothly dependent on a vector of real parameters are considered. Bifurcation of eigenvalues along smooth curves in the parameter space is studied. The case of a multiple eigenvalue with the Keldysh chain of arbitrary length is investigated. Explicit expressions describing bifurcation of eigenvalues are found. The obtained formulae use eigenfunctions and associated functions of the adjoint eigenvalue problems as well as the derivatives of the differential operator taken at the initial point of the parameter space. These results are important for the stability theory and sensitivity analysis of non‐conservative systems. Mechanical examples are considered and discussed in detail.
Internal stabilization of standard sampled‐data systems
Authors: Lampe B. P. , Rosenwasser E. N.
Published: April 2003

The paper presents necessary and sufficient conditions under which for a standard sampled‐data system there exists a digital controller, that ensures the internal stability of the system. For the case of stabilizability a general expression for the set of all stabilizing controllers is given. The stabilizability conditions are formulated as divisibility of certain polynomials, controllability and observability concepts are not used.
On the Optimal Stabilisation for a set of Programmed Motions of the Bilinear Control System
Authors: Smirnov N. V. , Smirnov T. E.
Published: April 2003

During recent years there has been considerable interest in using bilinear systems [1, 2] as mathematical models to represent the dynamic behavior of a wide class of engineering, biological and economic systems. Moreover, there are some methods [3] which may approximate nonlinear control systems by bilinear systems. For the first time Zubov has proposed a method of stabilization control synthesis for a set of programmed motions in linear systems [4]. In papers [5, 6] this method has been developed and used to solve the same problem for bilinear systems.

In the present paper the following problems are considered. First, synthesis of nonlinear control as feedback under which the bilinear control system has a given set of programmed and asymptotic stable motions. Because this control is not unique, the second problem concerns optimal stabilization. In this paper a method for the design of nonlinear optimal control is suggested. This control is constructed in the form of a convergent series. The theorem on the sufficient conditions to solve this problem is represented.
Motion planning and boundary control for a rotating Timoshenko beam
Authors: Woittennek Frank , Rudolph Joachim
Published: April 2003

Motion planning and boundary control for a rotating Timoshenko beam is presented. Parameterizing the system trajectories by a so‐called flat output, transitions from rest to rest can be achieved in a prescribed finite time.
Model Based Trajectory Control of an Overhead Travelling Crane
Authors: Aschemann H. , Sawodny O. , Hofer E.P.
Published: April 2003

Until now, most papers concerning control of overhead travelling cranes have only focussed on position control of the translational degrees of freedom, see for example [1], [3], [4], and [5]. With more advanced robotic applications envisaged, however, there is a demand for both trajectory control in six degrees of freedom and active damping of the weakly damped load oscillations due to the rope suspension [2]. Hence, a model based trajectory control is presented for an overhead travelling crane that has been upgraded with an orientation unit providing three additional axes. Starting from a central multibody model, decentralised design models are derived for each crane axis. By this, couplings between the axes are identified and appear as disturbance inputs in these decentralised design models. Each decentralised axis controller consists of linear state feedback, feedforward control, and observer based disturbance compensation and is derived in symbolic form. This allows for an adaptation of the complete control structure employing the gain scheduling technique with respect to varying system parameters like rope length and load mass. Couplings between the crane axes are compensated by feedforward control, whereas the e.ects of nonlinear friction forces are counteracted by combination of feedforward control and disturbance estimation. Experimental results, taken at a 5 t ‐ bridge crane, show the bene.ts of the proposed control scheme as regards control performance and steady‐state accuracy.
An Elastic Model of a Metal V‐Belt CVT
Authors: Bullinger M. , Pfeiffer F.
Published: April 2003

A simulation model has been developed to determine the behaviour of power transmission of a metal pushing V‐belt CVT at steady states. This allows to calculate the characteristics of forces and permits to evaluate the necessary pulley thrust, the maximum transmittable torque and the efficiency. Therefor the pulley and shaft deflection and the unilateral constraints of contacts must be modelled properly. The dynamics of the belt is specified by separate longitudinal and transversal approaches. The transversal dynamics is modelled continuously applying a Ritz‐approach based on B‐Splines. The longitudinal dynamics is described with Lagrange coordinates. So discontinuous effects as separation of elements can be modelled by continuous shape functions. Concluding, the obtained results of the presented simulation model are compared with measurements published by Doshisha University [2].
Coupled Multibody‐Aerodynamic Simulation of High‐Speed Trains Manoeuvres
Authors: Carrarini A.
Published: April 2003

A co‐simulation MBS/CFD was implemented to investigate the effects of unsteady aerodynamic loads on the driving dynamics of high speed trains during common manoeuvres in absence of cross wind. A linear aerodynamic model, the panel method, was applied to the computation of the flow around the driving trailers and the multibody simulation program SIMPACK simulated the dynamic response of the vehicles to the resulting aerodynamic loads.
Rekursive Lösung der Bewegungsgleichung von Mehrkörperketten mit Microcontrollerketten
Authors: Ferrara P. , Bremer H.
Published: April 2003

Bei der Erstellung von Bewegungsgleichungen für Mehrkörpersysteme wird man mit einer grundlegenden Schwierigkeit konfrontiert: die dabei entstehenden Matrizen wachsen schnell zu unhandlicher und unübersichtlicher und damit fehleranfälliger Größe an. Eine numerische Lösung ist durch die Inversion der Massenmatrix zwar auf den aktuellen PC's, aber nicht auf kleineren Microcontrollern möglich. Genau diese werden in der mobilen Robotik (Serviceroboter, Krabbeltiere, intelligente Prothesen,…) zunehmend häufiger eingesetzt. In dieser Arbeit wird ein modulares Konzept für die Lösung der Bewegungsgleichung auf solchen kleinen Rechnern vorgestellt.
Model Based Control of a Parallel Robot – A Comparison of Control Algorithms
Authors: Hahn Hubert
Published: April 2003

In this contribution the control behavior of a special construction of a parallel robot, called multi‐axes test facility, is investigated. After a brief discussion of the different tasks of the robot the construction of the robot is briefly presented. To solve the tasks, different control algorithms are derived based on model equations of different complexity of the robot. Depending on the task to be performed by the robot, the controllers compensate the kinematic and/or kinetic coupling of the degrees of freedom of the robot, stabilize the system and achieve the desired spatial motion of each degree of freedom as well as sufficient robustness with respect to parameter uncertainties and load variations. A few results obtained in computer simulations and laboratory experiments are presented and judged with respect to the quality of control, the closeness to reality of the computer simulations, and the amount of costs and work needed to realize the different solutions.
Development of a Toolbox for Model‐Based Real‐Time Simulation and Analysis of Legged Robots
Authors: Alexander Helm , Hardt Michael , von Stryk Oskar , Höpler Robert
Published: April 2003

Multibody systems such as legged robots require sophisticated and efficient methods for their modeling, control and simulation. This paper discusses the development of a software library based on modern tools such as C++, OpenGL and XML for highly efficient dynamics modeling. A primary focus lies on modularity permitting its easy extensibility in connection with different actuation and contact models, optimization algorithms, localized and centralized on‐line control schemes as well as animation and simulation environments.
Simulation of Multibody Systems with Nonholonomic Constraints
Authors: Kielau G. , Maißer P.
Published: April 2003

The paper deals with the nonholonomic multibody system dynamics from a point of view resulting from some present applications in high‐tec areas like high‐speed train technology or biomechanics of some disciplines in high‐performance sports. A formulation of nonholonomic constraints which are linear related to generalized velocities is based on a derivative‐free approach for generating Lagrangian motion equations of multibody systems with kinematical tree structure as well as for constrained multibody systems. This has been done by using di.erential‐geometric concepts in a Riemannian space. The ideas are illustrated by the classical edge condition on double‐curved surfaces. The surfaces are described by C2‐vector functions, for example by NURBS‐approximation. As an example a bobsleigh is regarded moving on a double‐curved surface.
Verallgemeinerung der kinematischen Modelle integrierter Navigationssysteme
Authors: Wagner J.F.
Published: April 2003

Bei integrierten Navigationssystemen spielt die Modellvorstellung über die Kinematik des jeweils betreffenden Fahrzeugs eine zentrale Rolle. Eingang finden die kinematischen Modelle in die Gleichungen eines erweiterten Kalman‐Filters, das die Zustandsgrößen des betrachteten Fahrzeugs z. B. für Regelungszwecke schätz und Messsignale von Inertialsensoren sowie von Struktursensoren und äußeren Vermessungseinrichtungen zusammenführt.
A Nonlinear Sandwich Shell Theory Accounting for Transverse Core Compressibility
Authors: Hohe J. , Librescu L.
Published: April 2003

The present study is concerned with an advanced theory of sandwich shells with transversely compressible core. The model is based on the standard Kirchhoff‐Love hypothesis for the face sheets and a third‐order displacement expansion for the core. Consistent equations of motion and boundary conditions are derived by means of Hamilton's variational principle. The model is applied to a postbuckling analysis of cylindrical shells under axial compression.
Analyse von Spannungslokalisierungen in Mehrschichtverbunden mittels der Rand‐Finite‐Elemente‐Methode
Authors: Lindemann J. , Becker W.
Published: April 2003

Die Rand‐Finite‐Elemente‐Methode wird als Randdiskretisierungsverfahren vorgestellt, das vorteilhaft zur Analyse von Spannungskonzentrationen in Mehrschichtverbunden eingesetzt werden kann. Wie auch in anderen Situationen ergibt sich für den Fall eines transversalen Matrixrisses eine gute übereinstimmung mit vergleichenden Finite‐Elemente‐Analysen.
Boundary integral equation method in rolling contact problems involving roughness, wear and frictional heating
Authors: Pauk Volodymyr , Zastrau Bernd
Published: April 2003

The method of boundary integral equations is developed to the solution of the rolling contact problems for rough bodies. A model of boundary roughness is proposed. The method permits to involve wear and frictional heating due to the slip in rolling contact.
Rate‐type Model for electro‐rheological Material Behaviour consistent with Extended Thermodynamics: Application to a steady viscometric flow
Authors: Sadiki A. , Balan C.
Published: April 2003

Based on extended thermodynamics, a class of rate‐type constitutive equations for electrorheological materials is presented. It is shown unlike many recent works using standard methods of continuum mechanics, that this approach, which consists in postulating expressions which relate the time derivative of the Cauchy stress to the motion, takes well account of the viscoelastic‐plastic effects as well as the coupling between the motion and the electric field. By considering special cases it turns out that the derived nonlinear algebraic model embeds a variety of existing differential models in the literature. The accuracy of the model is illustrated by considering a steady shear flow in which the electric field is applied perpendicularly to the flow direction. Analytical solutions with various parameter variations are obtained and discussed. The model predicts well the behaviour associated with material instabilities observed in viscometric flows for which the existence of the yield stress is required as confirmed by many experiments.
An Elasto‐Plastic Formulation of a Soil‐Foundation Interface
Authors: Ehlers Wolfgang , Blome Peter
Published: April 2003

In this paper, a special interface formulation for the continuum mechanical description of the contact zone between soil and geotechnical foundation is presented. The proposed model is based on the Theory of Porous Media (TPM), a consistent approach to describe geomaterials in a macroscopic frame [1]. Assuming quasi‐static conditions, strains in the porous soil body are due to an elasto‐plastic work‐hardening model, whereas the constitutive properties of the interface are based on the continuous elasto‐plastic behaviour of the soil body and on the failure kinematics of the contact zone. Using the FE method, a 3‐d initial‐boundary‐value problem of a soil‐foundation interaction is discussed with a close look on the occurring localization phenomenon.
On the formulation and finite element implementation of anisotropic multiplicative finite strain elastoplasticity
Authors: Eidel B. , Gruttmann F.
Published: April 2003

A constitutive model for orthotropic elastoplasticity at finite plastic strains is presented and aspects of its numerical implementation are addressed. The constitutive equations are related to the plastic intermediate configuration, which is introduced by F = Fe Fp. Isotropic tensor functions are used for the description of orthotropic material response in the elasticity law and the yield function. The latter is formulated in terms of the Mandel stress tensor.
Parameter Identification for Inelastic Constitutive Models
Authors: Harth Tobias
Published: April 2003

The identification of material parameters of constitutive models is based on identification experiments. Since even specimens from the same lot show high deviations in the experimental data, the identification of the material parameters leads to different results for one and the same material. The number of identification experiments is usually not large enough for a statistical analysis of the deviations in the identified parameters. In order to overcome this problem we present a method of stochastic simulation which is based on time series analysis for generating artificial data with the same stochastic behaviour as the experimental data. The stochastic simulations allow an investigation of the confidence in the fits of the material parameters. We validate the stochastic simulations by comparing the results of the parameter identification from experimental data with the results from artificial data. The presented simulation method applied here turns out to be a suitable tool for generating artificial data for various kinds of analysis purposes. However, it is very important to take into account that the machines which perform the experiments do not maintain constant strain rates in the loading history of the tension and cyclic experiments.
Parameteridentifikation inelastischer Lotwerkstoffmodelle mittels experimenteller und numerischer Analyse
Authors: Nguyen v.S. , Herrmann K.P. , Müller W.H.
Published: April 2003

Die Bestimmung der Materialparameter des Lotwerkstoffmodells spielt eine wichtige Rolle für die Modellierung des Materialverhaltens. Dabei enthalten die Lotwerkstoffmodelle sowohl elastisch‐plastische als auch viskoplastische Materialparameter. Die Identifikation der Modellparameter anhand der Versuchsergebnisse stellt eine inverse Problemstellung dar. Zur Lösung des inversen Problems werden nichtlineare Optimierungsverfahren verwendet. Es handelt sich um die Fehlerminimierung zwischen experimentell bestimmten Meßkurven und simulierten Kurven. Anhand von Small‐Punch‐Testversuchen wird die Parameteridentifikation an Zinn‐Blei‐Lot SnPb37 unter Benutzung der Finiten Elemente Methode und des nichtlinearen Optimierungsverfahrens vorgenommen.
On the role of energy in chip formation
Authors: Nachname Martin Bäker
Published: April 2003

The implicit code ABAQUS/Standard is used to simulate the formation of continuous and segmented chips. Using the described model, the idealized process of friction‐less machining of an elastic ideally‐plastic material is studied. It is shown that Merchant's classical shear angle relation does not hold, as chip formation does not minimize the energy as assumed by Merchant. The model is also used to study segmented chip formation using a realistic material law for the Titanium alloy Ti6Al4V at high cutting speeds.
A Domain Decomposition Method for Frictional Contact Problem
Authors: Lotfi A. , Kiss B.
Published: April 2003

The bilateral or unilateral contact problem with Coulomb friction between two elastic bodies is considered [1]. An algorithm is introduced to solve the resulting finite element system by a non‐overlapping domain decomposition method. The global problem is transformed to a smaller problem on the contact surface. The solution is obtained by using a successive approximation method, in each step of this algorithm we solve two intermediate problems the first with prescribed tangential pressure and the second with prescribed normal pressure.
Adaptive FE Diskretisierung zur Bestimmung der Eigenfrequenzen von Flächentragwerken
Authors: Neumann J. , Schweizerhof K.
Published: April 2003

Die 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

Considering 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

The 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

We 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

A 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

We 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

The 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

A 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

This 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

This 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

It 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

Constitutive 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

The 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

New 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.
Parallel Solution of Stochastic PDEs
Authors: Keese Andreas , Matthies Hermann G.
Published: April 2003

A stochastic partial differential equation is discretized by stochastic spectral finite elements. The resulting large linear system is solved by parallel iterative solvers, exploiting various forms of parallelism.
Error expansion for a first‐order upwind difference scheme
Authors: Linss Torsten
Published: April 2003

A 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

In 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

The 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

In 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

A 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

Although 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

Protein‐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.