bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermofluiddynamics in liquid media during biotechnological processes under high pressure
Authors: Rauh C. , Delgado A. 
Published: February 2009

AbstractIn bio/ chemical engineering high pressure (HP) processing up to several GPa represents a novel technique to selectively influence (bio–)chemical reactions resulting from temperature and pressure sensitivities differing between the occuring reactions. Therefore, thermofluiddynamical effects leading to inhomogeneous process conditions (pressure, temperature) show an important influence on the process results. To predict and improve mass, momentum and energy transport within the HP vessel and the impact on desired chemical reactions spatiotemporal numerical simulations are a useful tool in process analysis and design. The present contribution deals with mathematical modelling of the enzyme inactivation in HP processing of liquid biotechnological media. For the first time a transport equation for the scalar quantity “enzyme activity” is deduced. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flare gas extraction by a Laval nozzle
Authors: Steinrück Herbert , Kornfeld Matthias , Braun Stefan 
Published: February 2009

AbstractIt is proposed to use a double Laval nozzle as ejector pump to extract flare gas from compressor packings. The efficiency and stability of possible operating points will be discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transmission of sound in a wedge‐shaped layer of fluid with a rigid bottom
Authors: Borejko Piotr 
Published: February 2009

AbstractThe theory of generalized rays is applied to the problem of determining the exact shape of the pressure pulse received at very large ranges, in the case of a sound source in a 3° perfect wedge of fluid. The time variation of the pressure at the point source is assumed to be given by a Heaviside unit function H(t). It is found that horizontal refraction and backscattering have a pronounced effect on the overall appearance of the received pulse: at very large down–slope (normal to the apex line) ranges, the shape of the received pulse does not change much, while, at very large cross–slope (parallel to the apex line) ranges, it changes drastically. Thus, in a 3° perfect wedge of fluid, long–range down–slope propagation (exclusively affected by backscattering) seems to be nondispersive, but long–range cross–slope propagation (affected by horizontal refraction and backscattering) seems to be highly dispersive. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generation and dissipation of ocean surface waves
Authors: Ellermann Katrin 
Published: February 2009

AbstractOcean surface waves constitute one of the most important sources of external forces that act on ships and offshore structures. Most ocean waves are generated by wind, but various other effects such as currents, ground and coastal topology, breaking and wave–wave interaction have an influence on the growth and dissipation of wave energy at specific frequency ranges. These water waves are inherently random in nature and their exact shape is difficult to describe, even when confining the described area to a small range. While many different approaches exist to describe the spectral characteristics of ocean waves, some of the processes which affect the generation of waves are still poorly understood. This paper addresses some techniques which serve to describe seaway spectra with respect to the subsequent analysis of dynamic mechanical systems in the ocean such as ships, platforms and pipelines. Advantages and limits of the different approaches are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dissipation‐induced subcritical flutter in the acoustics of friction
Authors: Kirillov1 Oleg N. 
Published: February 2009

AbstractWe consider a gyroscopic system under the action of small dissipative and non–conservative positional forces, which has its origin in the models of rotating elastic bodies of revolution in frictional contact such as the singing wine glass or the squealing disc/drum brakes. The spectrum of the unperturbed gyroscopic system forms a spectral mesh in the plane ‘frequency versus gyroscopic parameter’ with double semi–simple purely imaginary eigenvalues at the nodes. In the subcritical range of the gyroscopic parameter the eigenvalues involved into the crossings have the same Krein signature and thus their splitting due to changes in the stiffness matrix, which break the rotational symmetry of the body, cannot produce complex eigenvalues and, therefore, flutter. We establish that perturbation of the gyroscopic system by the dissipative forces with the indefinite matrix can lead to the subcritical flutter instability even if the rotational symmetry is destroyed. With the use of the perturbation theory of multiple eigenvalues we explicitly find the linear approximation to the domain of the subcritical flutter, which turns out to have a conical shape. The orientation of the cone in the three dimensional space of the parameters, corresponding to gyroscopic, damping, and potential forces, is determined by the sign of an explicit expression involving the entries of both the damping and potential matrices. With the use of a time–dependent coordinate transformation we demonstrate that the conical zones of flutter for the original autonomous system coincide with the zones of the subcritical parametric resonance of the rotationally symmetric flexible body with the load moving in the circumferential direction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Simulation of Elastic Waves Propagation in Anisotropic Media
Authors: Lisitsa Vadim , Lys Egor 
Published: February 2009

AbstractThe paper deals with finite–difference (f‐d) approach to simulation of elastic waves' propagation in anisotropic elastic media with general symmetry. Any implementation of this approach claims resolution of two key problems:

construction of an effective f‐d scheme itself; we propose to use the Lebedev's scheme (LS) being a natural generalization of Virieux staggered grid scheme (VS) widely used for isotropy; we prove that LS possesses better dispersion properties in comparison with well known Rotated Staggered Grids Scheme (RSGS).

stable domain distension. The Perfectly Matched Layers(PML) useful for isotropic problems can be unstable in the case of anisotropy. Lebedev scheme allows one to use Optimal Grids (OG) which gives a possibility to implement efficient and low cost domain distension.

(© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localization of acoustic sources in subsonic jets
Authors: Obrist Dominik , Kleiser Leonhard 
Published: February 2009

AbstractThe sound in the acoustic far–field of a round jet is generated by a multitude of unsteady flow structures with different length and time scales. Most likely, different components of the noise spectrum are created by different structures in the jet which emit sound in different directions. Based on Lighthill's acoustic analogy, we present a method for relating flow structures of the jet with far–field noise spectra and their associated directivity patterns. The method allows to determine what kind of noise (with respect to frequency and emission direction) is generated at a given streamwise location. We illustrate the method with numerical results for a round isothermal jet. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Coupled FE‐BE Analysis of Smart Lightweight Structures for Active Noise and Vibration Control
Authors: Ringwelski Stefan , Gabbert Ulrich 
Published: February 2009

AbstractOver the past years much research and development has been done in the area of active control in order to improve the acoustical and vibrational properties of thin–walled lightweight structures. An efficient technique for actively reducing the structural vibration and sound radiation is the application of smart structures. In smart structures piezoelectric materials are often used as actuators and sensors. The design of smart structures requires fast and reliable simulation tools. Therefore, the purpose of this paper is to present a coupled finite element–boundary element formulation, which enables the modeling of piezoelectric smart lightweight structures.The paper describes the theoretical background of the coupled approach in which the finite element method (FEM) is applied for the modeling of the passive vibrating shell structure as well as the surface attached piezoelectric actuators and sensors. The boundary element method (BEM) is used to characterize the corresponding sound field. In order to derive a coupled FE–BE formulation additional coupling conditions are introduced at the fluid–structure interface. Since the resulting overall model contains a large number of degrees of freedom, the mode superposition method is employed to reduce the size of the FE submodel. To validate the accuracy of the proposed approach, numerical simulations are carried out in the frequency domain and the results are compared with analytical reference solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shape optimization for the Helmholtz equation
Authors: Seifrt František , Leugering Günter , Rohan Eduard 
Published: February 2009

AbstractThe aim of our work is to develop optimal dielectric composite structures with specific qualities. The task is to design interfaces of given material components such that the originated structure attains certain optical properties. Propagation of the electromagnetic waves in the composite is described by the Helmholtz equation. Success of the structure is enumerated by the objective function which is to be minimized. Interfaces of the given materials are parametrized by the cubic B–spline curves. The design variables are afterwards the positions of B–spline control points. For objective function evaluation one forward computation of the Helmholtz equation is needed. To get the sensitivity of the objective function we solve the backward (adjoint) equation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of micromachining of C45 steel by single abrasive grain
Authors: Chodor Jaroslaw , Kukielka Leon 
Published: February 2009

AbstractGrinding is a very complicated processing. To increase quality of product and minimize the cost of abrasive machining, we should know physical phenomena which exist during the process. The first step to solution of this problem is analysis of machining process with a single abrasive grain. In the paper [1] the thermo–mechanical models of this process are presented, but in this work attention is concentrated on chip formation and his separation from object for different velocity of abrasive grain. The phenomena on a typical step time were described using step–by–step incremental procedure, with updated Lagrangian formulation. Then, the finite elements methods (FEM) and dynamic explicit method (DEM) were used to obtain the solution. Application was developed in the ANSYS system, which makes possible a complex time analysis of the physical phenomena – states of: displacements, strains and stress. Numerical computations of the strain have been conducted with the use of two methodologies. The first one requires an introduction of boundary conditions for displacements in the contact area determined in modeling investigation, while the second – a proper definition of the contact zone, without the necessity to introduce boundary conditions in the contact area. Examples of calculations for the intensity of stress in the surface layer zones were presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homotopic Arnold tongues deformation of the MHD α2‐dynamo
Authors: Günther Uwe , Kirillov Oleg N. 
Published: February 2009

AbstractWe consider a mean–field α2–dynamo with helical turbulence parameter α(r)=α0+γΔα(r) and a boundary homotopy with parameter β∈[0,1] interpolating between Dirichlet (idealized, β=0) and Robin (physically realistic, β=1) boundary conditions. It is shown that the zones of oscillatory solutions at β=1 end up at the diabolical points for β=0 under the homotopic deformation. The underlying network of the diabolical points for β=0 substantially determines the choreography of eigenvalues and thus the character of the dynamo instability for β=1. Using perturbation theory we derive the first–order approximations to the resonance (Arnold's) tongues in the α0βγ‐space, which turn out to be cones in the vicinity of the diabolical points, selected by the Fourier coefficients of Δα(r). The space orientation of the 3D tongues is determined by the Krein signature of the modes involved in the diabolical crossings at the apexes of the cones. The Krein space induced geometry of the resonance zones explains the subtleties in finding α‐profiles leading to oscillatory dynamos, and it explicitly predicts the locations of the spectral exceptional points, which are important ingredients in the recent theories of polarity reversals of the geomagnetic field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hyperelliptic functions and geodesic equations
Authors: Hackmann Eva , Lämmerzahl Claus 
Published: February 2009

AbstractA method for solving geodesic equations in Schwarzschild–de Sitter space–times and higher dimensional Schwarzschild space–times is presented. The solutions are derived from Jacobi's inversion problem on a Riemann surface of genus 2 restricted to the set of zeros of the theta function, which is called a theta–divisor. In its final form, the solutions are given in terms of derivatives of Kleinian sigma functions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectrum asymptotics for the linearized thin film equation
Authors: Kitavtsev G. , Recke L. , Wagner B. 
Published: February 2009

AbstractIn this paper we describe linear stability properties for the special type of thin film equation corresponding to a presence both destabilizing van der Waals and stabilizing Born forces in the intermolecular interactions. The final stage of the evolution described by such type equation is characterized by the slow–time coarsening dynamics after formation of an array of droplets. Finally the dynamics converges to one stationary droplet. We derive analytically the asymptotics for the spectrum of the thin film equation linearized at one droplet steady state with respect to small parameter ϵ (describing the form of droplet) tending to zero. This asymptotics is confirmed by numerical investigations as well. The analytical approach can be applied also for the investigation for the spectrum of the thin film equation linearized at an array of droplets. Our results considerably extend the ones derived in [4]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Numerical Analysis of the External Round Thread Rolling
Authors: Kukielka Krzysztof , Kukielka Leon 
Published: February 2009

AbstractThe papers [1] describe modeling of the contact problem in the external thread rolling process. This paper shown an application of obtained model for the thread with round outline. The mathematical model of process, were presented. The variational and finite element method, were used. The algorithm of numerical analysis in ANSYS system, were elaborated. Numerical computions of displacements, strains and stresses have been conducted without the necessity to introduce boundary condition in the contact zone – a proper definition of the contact zone by single surface auto 2D. Exemplary results of numerical analysis for various condition of the process realization in the discretized model has been presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solution multiplicity of circular plate
Authors: Marko Lubomir 
Published: February 2009

AbstractWe deal with the number of solutions for the system of von Kármán equations for a thin elastic circular plate of constant thickness. The plate is subjected to a uniform compressive thrust along its edge in the midplane of the plate. The thrust is proportional to a real parameter λ. We assume rotationally symmetric case. Let λ1<λ3<…λn… be the critical values of the real parameter. For λ∈[λn,λn+1] the multiplicity of solutions in dependence of parameter λ is analyzed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence and uniqueness results for a class of nonlinear differential systems with second‐order differences
Authors: Luca‐Tudorache Rodica 
Published: February 2009

AbstractIn a real Hilbert space we investigate the existence, uniqueness and asymptotic properties of the strong and weak solutions to an infinite nonlinear differential system with second–order differences, subject to an extreme condition and initial data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystallization problem with symmetries of composite lattices in statistical crystal theory as bifurcational symmetry breaking problem
Authors: Makeev Oleg , Loginov Boris 
Published: February 2009

AbstractBifurcation theory methods under group symmetry conditions are applied to crystallization problem with composite lattices in statistical crystal theory. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of shot peening on surfaces in Ansys application
Authors: Szyc Marcin , Kukielka Leon 
Published: February 2009

AbstractABSTRACT: Paper presents the posibility to application of Finite Element Method (FEM) to analysis of strain and stress states in surface layer of object. The application in Ansys/Ls – Dyna programme using incremental procedure in updated Lagrangian formulation was developed. Examples of calculations of influence of different distance of leaving traces for the strain and stress field in the surface layer zone were presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dependence of accuracy of ESPRIT estimates on signal eigenvalues: the case of a noisy sum of two real exponentials
Authors: Alexandrov Theodore , Golyandina Nina , Timofeyev Alexey 
Published: February 2009

AbstractThis paper is devoted to estimation of parameters for a noisy sum of two real exponential functions. Singular Spectrum Analysis is used to extract the signal subspace and then the ESPRIT method exploiting signal subspace features is applied to obtain estimates of the desired exponential rates. Dependence of estimation quality on signal eigenvalues is investigated. The special design to test this relation is elaborated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Component‐Based Software Realisations of Monte Carlo and Stochastic Galerkin Methods
Authors: Krosche Martin , Matthies Hermann G. 
Published: February 2009

AbstractIn this paper we present a component–based software realisation of the Monte Carlo and Stochastic Galerkin methods for simulating stochastic models with uncertain parameters described by random fields. The system supports parallel and distributed computations and focuses on the reusability and extensibility of the provided components and frameworks. Third–party software is interfaced to avoid cost–intensive reimplementations. The mentioned schemes are compared with respect to their convergence by considering a stationary groundwater flow model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Evaluation of Functionals based on Variance Minimisation
Authors: Pajonk Oliver , Niekamp Rainer , Matthies Hermann G. 
Published: February 2009

AbstractNumerically evaluating the effect of a functional on a function is a very common task in scientific computing. The definite integral of a function over a domain is an example, differentiating a function in a certain point into a certain direction is another one.We developed a generic method to compute the effect of a functional using a linear approximation formula. The method is designed to generate the nodes and weights needed to approximate different functionals using a single set of tools: it regards the target function as a stochastic field and uses a user–defined covariance function for this field to minimise the error made by the approximation formula.The resulting formulas are optimal in an average case sense: all possible realisations of this stochastic field are taken into account while computing the solution. This results in nodes and weights that evaluate the target functional applied to any realisation with a minimised average error. The space of all realisations of such a stochastic field can be of infinite dimension whereas classical approaches often only consider a finite dimensional space of functions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topology Optimization of 3D Elastic Structures Using Boundary Elements
Authors: Bertsch Christine , Cisilino Adrián P. , Langer Sabine , Reese Stefanie 
Published: February 2009

AbstractA numerical approach for the topological optimization of 3D linear elastic problems using boundary elements and the topological derivative is presented in this work. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From Inviscid to Viscous Aerodynamical Global Optimal Shape's Design
Authors: Nastase1 A. 
Published: February 2009

AbstractThe refinement of the global aerodynamical optimal design (OD) of the shape of a flying configuration (FC) can be performed by improving of the start solutions for the optimization and/or of the optimization strategy itself. The proposed strategy is the own developed iterative optimum–optimorum theory. The study is here focused on the further improvement of her new, original, reinforced, zonal, spectral solutions for the partial–differential equations (PDEs) of the three–dimensional compressible Navier–Stokes layer (NSL), which govern the flow over the FCs, in subsonic and supersonic flow. These NSL's solutions, which are good suited for the computation and, especially, for the global optimal design, use the analytical potential solutions of the flow over the same FC twice: firstly as outer flow, at the NSL's edge (instead of the parallel flow used by Prandtl in his boundary layer theory) and, secondly, the velocity's components are products between the corresponding potential velocities and polynomial expansions with arbitrary coefficients, which are used to satisfy the NSL's PDEs. The use of analytical elliptical potential solutions leads to subsonic and the use of hyperbolical potential solutions leads to supersonic stabilized and rapid convergent NSL's solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization under consideration of uncertain input quantities
Authors: Pannier Stephan , Sickert Jan‐Uwe , Graf Wolfgang 
Published: February 2009

AbstractThis contribution presents an approach to account for imprecise data within an optimization task in view of engineering applications. In order to specify imprecise data the concept of imprecise probabilities is utilized, applying the generalized uncertainty model fuzzy randomness. Considering the fact, that the uncertainty affects both the objective function and the constraints, the optimum and the respective design is obtained imprecise. In view of decision making for engineering applications the optimization is converted to account for information reducing methods, e.g. determination of failure probabilities, defuzzification and robustness assessment. The introduced methods and algorithms are focused on a numerical treatment to solve nonlinear industry–sized problems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)