bluuebunny/crossref_metadata_2025 huggingface dataset:
3‐D Modeling of Shock‐induced Precursor Decomposition and Nano‐Particle Growth
Authors: Al‐Hasan N.S. , Schnerr G.H.
Published: February 2009

In the ongoing joint project “Gasdynamically induced nano–particles” (PAK 75/1) a novel method of gas–phase synthesis of nano–particles is being developed [1]. This project is supported by the Deutsche Forschungsgemeinschaft (DFG), the pilotfacility is erected in collaboration with Evonik Degussa, Hanau, Germany. The key features of the new method are the static temperature increase across a stationary shock to provide ignition conditions of the precursor and the subsequent gasdynamic quenching of the particle growth when the desired particle diameter of 10−8m is reached. In this work the decomposition of the precursor, the reactive heat release and the particle growth are coupled with the 3–D transonic flow inside the particle reactor. The simulation results show the effect of shock/boundary layer interactions on the decomposition reaction as well as the effects of the reactive heat release on the shock location and the resulting particle size distribution. The Reynolds number at the shock location is Rex=9·106, the boundary layer thickness is δ=2.2 mm and the pre–shock Mach number is M=1.58. The complex transonic reactive flow within the particle reactor requires a high mesh resolution to resolve the local details of the internal flow problem. In addition, an efficient particle model is required. The formation and growth of the particles are modeled by three separate reactions. The primary reaction is the decomposition of the precursor and the production of monomers. It is modeled by a one step reaction described by an Arrhenius equation. The secondary reaction, the formation of critical nuclei is in our case negligible, because of the high supersaturation ratio of the order of 103 instantly after the primary reaction, where the monomers are already critical nuclei. The tertiary reaction is the particle growth by surface condensation, coagulation and single–aggregation. To simulate the particle growth we apply a local monodisperse bimodal formulation. Thereby, the monodisperse model of Kruis et al. [2] is extended by an additional discrete monodisperse mode for the critical nuclei. This method describes the local particle size due to turbulent mixing, coagulation and coalescence. The coagulation starts in the Knudsen regime Kn ≫ 1 and reaches the continuum regime with particle diameters of the order of 10−8m and a mean free path of the same order of magnitude. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical Solution of Turbine Cascade Flow by Two Equations, EARSM and Bypass Transition Turbulence Models
Authors: Fořt J. , Dobeš J. , Fürst J. , Halama J. , Kozel K. , Louda P. , Příhoda J.
Published: February 2009

This work deals with numerical solution of transonic flow in turbine cascades. We compare results achieved by SST, TNT and EARSM turbulence models and we also present results achieved by two equations turbulence model with an algebraic bypass transition model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Symmetry group analysis and similarity solutions of the CBS equation in (2+1) dimensions
Authors: Gandarias1 M.L. , Bruzon1 M.S.
Published: February 2009

We consider the (2+1)—dimensional integrable Calogero—Bogoyavlenskii—Schiff (CBS) written in a potential form. By using classical Lie symmetries, we consider travelling‐wave reductions with variable velocity depending on the form of an arbitrary function. The corresponding solutions of the (2+1)‐dimensional equation involve arbitrary smooth functions. Consequently the solutions exhibit a rich variety of qualitative behaviours. Indeed by making adequate choices for the arbitrary functions, we exhibit solitary waves and bound states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermodynamics / turbulence analogy modelling dissipating molecular gas flows for high Knudsen numbers
Authors: Groll R. , Rath H. J.
Published: February 2009

Modelling micro channel flows momentum and heat diffusion / convection are recent parameters modelling the molecule velocity distribution. Macroscopic models describe velocity and energy / enthalpie with integrals of mass increments. Using microscopic models motion and forces of a molecular flow have to be computed by models of physical properties, whose are described by statistical power moments of the molecule velocity. Therefore dilute flows have to be investigated in small channels with a mean free path length of molecules higher than the channel width of the the micro channel itself (λ0≥H0). Modelling this process by a continuous flow the boundary conditions have to be modified (e.g. [6]). The present model uses the statistical approximation of the molecule velocity distribution to simulate the behaviour of this discrete flow with a weighted averaged molecule velocity ∼ξi, its standard deviation σ and the characterisic molecule collision rate z. The number density N per volume V near one position is used for the weighting factor averaging method describing the mean molecule velocity. The present model is validated computing Poiseuille and Couette flows with different Knudsen numbers. Showing the advantages of the present model the simulation results are compared with simulation results of the wall–distance depending diffusivity model of Lockerby and Reese [4] and BGK results of a Lattice–Boltzmann simulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical experiments on flow control of near wall turbulence
Authors: Lammers Peter , Jovanovic Jovan , Delgado Antonio
Published: February 2009

In this paper we demonstrate by means of direct numerical simulations (DNS) of channel flow with surface structuring or modified boundary conditions how turbulence can be controlled by influencing the anisotropy state of near wall turbulence. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional turbulent boundary layer on wind turbine blades
Authors: Dumitrescu Horia , Cardos Vladimir
Published: February 2009

The momentum integral technique for predicting the boundary–layer growth in three–dimensional flow has been extended to include the entrainment equation as the closure model. Special attention has been devoted to those terms in the differential equations that change the boundary–layer structure from that of cvasi two–dimensional steady flow, at outboard locations, to a tree–dimensional flow pattern. It is concluded that the stall is delayed due to the boundary–layer reattachment at inboard sections in conjunction with the onset of a spanwise vortex like structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct numerical simulation of single gas bubbles in pure and contaminated liquids
Authors: Lakshmanan Peter , Ehrhard Peter
Published: February 2009

Disperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break–up or coalescence in different systems can be crucial for the process design. Hence, knowing the fundamental behaviour of a single bubble appears mandatory for the examination of bubble swarms and for the Euler–Lagrange or Euler–Euler modelling of disperse systems. In the present work a level–set–based volume–tracking method is implemented into the CFD–code OpenFOAM to follow the free interface of a single bubble. The volume–tracking method is coupled with a transport model for surfactants on the interface, including adsorption and desorption processes. The dependency of surface tension on the local surfactant concentration on the interface is modelled by a non–linear (Langmuir) equation of state. Marangoni forces, resulting from surface tension gradients, are included. The rise of a single air bubble (i) in pure water and (ii) in the presence of surfactants of different strengths is simulated. The results show good agreement with available correlations from literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of local particle accumulation in disperse flows with kinematic singularities
Authors: Lebedeva N.A. , Osiptsov A.N.
Published: February 2009

The aim of the study is to model the formation of local particle accumulation zones near several typical kinematic singularities. The flows considered are: (i) a steady two–dimensional flow with localized vorticity of the Kelvin cat's eye type (vortex in a mixing layer), (ii) a steady axisymmetric flow formed by a vortex filament normal to a plane in viscous fluid (simple model of tornado), (iii) a neighbourhood of a zero acceleration point in two–dimensional unsteady (harmonic) flow. From parametric numerical calculations, we investigated the inertial mechanisms of forming local particle accumulation zones and found the threshold values of governing parameters separating qualitatively different particle velocity and density patterns. In particular, it is shown that the zero–acceleration point can either “attract” or “scatter” the particles. Zones of concentrated vorticity are typically devoid of particles. In the tornado–like flow, an axisymmetric “cup‐shaped” particle accumulation region is formed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advances in Numerical Prediction of Extrusion Tools used for Fabrication of Rubber Profiles
Authors: Müllner Herbert W. , Wieczorek André , Fidi Wolfgang , Eberhardsteiner Josef
Published: February 2009

This contribution is focussed on numerical simulations of realistic extrusion tools of rubber profiles. The underlying material parameters provided by material characterization procedure which is based on capillary–experiments in combined with die swell measurements. The simulations were performed with the CFD program POLYFLOW under usage of an inverse calculation approach. The validation of these simulations is performed by comparison predicted andf measured dimensions of the already fabricated tools. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial Instability Of Two‐Phase Mixing Layers
Authors: Otto Thomas , Rossi Maurice , Boeck Thomas
Published: February 2009

The initial stage of liquid atomization by a fast gas stream is considered by means of spatial stability analysis of two–phase shear layers. We solve the viscous linear stability problem for parallel flow modelled by error–function profiles. The unstable modes known from temporal theory are recovered in the convectively unstable case for fluid properties close to the air/water system. The most unstable wavelength depends only weakly on the absolute velocity relative to the laboratory system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the effects of compressibility in marginally separated flows
Authors: Scheichl Stefan , Kluwick Alfred
Published: February 2009

If the angle of attack α of a slender airfoil reaches a critical value αs flow separation is known to occur at the upper surface. Further increase of α initially leads to the formation of a short laminar separation bubble which has an extremely weak influence on the external flow field — a phenomenon known as marginal separation — but then rather rapidly causes a severe change of the flow behaviour (leading edge stall). According to the asymptotic theory of marginal separation holding in the limit of large Reynolds numbers t→∞ the flow in the neighbourhood of the separation bubble is governed by an integro–differential equation exhibiting a single controlling parameter Γ which relates the angle of attack to the Reynolds number, with a value Γs corresponding to αs. Numerical investigations have shown that solutions to this equation exist up to a critical value Γc>Γs only and this has been taken as an indication that a substantial change of the flow field must take place if Γ exceeds Γc. In the case of unsteady three–dimensional perturbations of a two–dimensional steady marginally separated boundary layer in the limit Γ→Γc, the (generalized form of the) integro–differential equation reduces to a nonlinear diffusion equation of Fisher type. This asymptotic description serves as a basis for the investigations concerning compressibility effects, also in respect of the mechanism through which the hydromechanic motion inside the boundary layer could be transformed into aerodynamic sound. A modified interaction equation is obtained, which in addition to Γ, contains the Mach number at the point of separation as a second controlling parameter. The unsteady changes of the boundary layer displacement thickness in the limit ΔΓ=Γc−Γ→0, again governed by Fisher's equation, then are identified to act as a quadrupole source for sound radiation. The most surprising outcome is the fact that in the three–dimensional case, the second derivative with respect to the lateral direction contained in the Fisher equation changes its sign and becomes negative if the Mach number exceeds a certain value. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of Thermal Convection in an Inclined Narrow Cavity
Authors: Wu J. , Rubes D. , Heiland H.G. , Wozniak G.
Published: February 2009

In order to adapt to the rapid progress in fabricating and utilizing micro electromechanical systems, the investigation of the fluid behaviour in small volumes is of fundamental importance as far as heat and mass transfer are concerned. After the experimental exploration in a small vertical gap with a temperature gradient [1], subsequently the investigation of thermal convection in an inclined narrow cavity is followed experimentally. The gap volume is 6 × 24 × 17 mm3 with a width of 6 mm. Liquid crystal tracer particles are used for measuring the temperature and velocity distribution of the fluid. The measurement results are presented and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Aerodynamic and aeroacoustic phenomena due to non‐uniform flow of wind turbines
Authors: Dumitrache Alexandru , Dumitrescu Horia , Cardos Vladimir
Published: February 2009

Stall control and pitch control are the most commonly used methods of regulating power. However, through the opportunities presented by the flexible (or teetered) hub of a two–bladed teetered rotor one can also utilize yaw control to regulate power. This is achieved by adjusting the capture area of the rotor disk relative to the prevailing wind direction. This paper presents the aerodynamic and aeroacoustic results obtained from theoretical models for a rotor when is yawed to the undisturbed flow. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the absorption coefficient and material boundaries distribution on the acoustic pressure in the room with rigid walls
Authors: Blazejewski Andrzej , Krzyzynski Tomasz
Published: February 2009

In the paper a problem of distribution of an acoustic absorption materials on room's boundaries has been presented. A room with a harmonic sound source inside has been considered. A pressure distribution was described using modal analysis assumptions. Usually, most of real rooms have enough high boundaries' impedance (absorption coefficient), therefore the modal coupling can be neglected. Hence, pressure can be represented by a sum over a set of room's eigenfunctions and time components i.e. the modal amplitudes. Amplitudes are dependent of eigenfrequencies ωn, damping coefficients rn and a source function Qn. Conducting analysis of the modal amplitude function, in relation to ωn and rn, an optimal acoustical damping can be obtained. Taking triple criteria objective function into consideration, absorbtion material optimal distribution on boundaries has been found. In order to find minimum of the objective function genetic algorithm was used. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Forced stationary gas‐structure interaction vibrations in a rectangular parallelepiped tank
Authors: Gavrilova E.
Published: February 2009

A closed rigid rectangular parallelepiped tank is filled with gas and a part of one of its walls is a thin linearly elastic rectangular plate. The problem about the determination of the forced stationary vibrations of the obtained gas–structure interaction system under the action of a source is considered. The method of the crossed strips of Warburton and the Bubnov–Galerkin method are used to create a method of investigation of the dynamic behavior of this gas–structure interaction system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonance excitation and mode selection in smart structures with piezoelectric patch actuators
Authors: Glushkov E.V. , Glushkova N.V. , Kvasha O.V. , Seemann W.
Published: February 2009

A system of piezoelectric flexible patch actuators bonded to an elastic layered substrate is considered. An integral equation based model for the smart structure under consideration has been developing. The rigorous solution to the patch–substrate dynamic contact problem extends the range of the model's utility far beyond the bounds of conventional simplified models that rely on plate, beam or shell equations for the waveguide part. The developed approach provides the possibility to reveal the effects of resonance energy radiation associated with higher modes that would be inaccessible using models accounting for the fundamental modes only. Algorithms that correctly account for the mutual wave interaction among the actuators via the host medium, for selective mode excitation in a layer as well as for body waves directed to required zones in a half–space, have also been elaborated and implemented in computer code. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Scattering of acoustic waves by inhomogeneous obstacles
Authors: Morro Angelo , Caviglia Giacomo
Published: February 2009

The scattering of acoustic waves, produced by a continuously–stratified layer, is investigated through a Volterra integral formulation in the Fourier–transform domain. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inversion of seismic data: sensitivity and stability via SVD analysis
Authors: Silvestrov Ilya
Published: February 2009

The problem of recovery of seismic parameters of the media via wavefield produced by array of sources and recorded by array of receivers is considered in this work. In order to invert these data and recover elastic parameters one can use the optimization technique based on the gradient–like or Newton–like methods. In seismic applications this approach is known as “Full waveform inversion”. According to it we search for solution which minimizes mean–square deviation of the observed wavefield from the computed one for current values of elastic parameters. Surely convergence is governed by the properties of the Frechet derivative of nonlinear operator that maps medium parameters to the observed data. Thus studying these properties is an important step before development the numerical methods and algorithms of this inversion.

For a simple case it can be shown that this derivative is a compact operator so implementation of any Newton–like approach is connected with necessity to resolve ill–posed problem of resolution of the first–order linear integral operational equation. In order to study the main peculiarities of this operator Singular Value Decomposition is applied. Two acquisition systems are dealt with – the offset vertical seismic profiling and cross–well tomography. Numerical results for realistic media are presented and the main differences of inverse problems for these two acquisition are shown. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The numerical analysis of burnishing rolling process with taking into account inaccuracy of surface preparation in previous treatment
Authors: Kuakowska Agnieszka , Kukielka Leon
Published: February 2009

In the paper the numerical analysis of burnishing rolling process with taking into account inaccuracy of surface preparation in previous treatment are shown. The researches were realized in two stages, in the first one outline of asperities was prepared in turning process. The ranges of outline deviation (height and distance) of triangular asperity after turning are shown as the result. In the second one the numerical analysis of burnishing rolling with different outline deviation were made. The application in ANSYS was elaborated. To solve problem explicit method was used. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Poincaré‐Andronov‐Hopf bifurcation with hyperbolic rotation symmetry
Authors: Konopleva Irina , Loginov Boris , Makeev Oleg , Rousaky Youri
Published: February 2009

For differential equations in Banach spaces with degenerate Fredholm operator at the derivative the general theorem about group symmetry inheritance by the relevant Lyapounov–Schmidt branching equation allows to construct its general form on admitted group symmetry. Here the solving of this problem is illustrated on the examples of the presence of SH(2) and H(2) symmetries. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of embossing process of regular inequalities with triangular outline
Authors: Patyk Radoslaw , Kukielka Leon
Published: February 2009

The paper presents the numerical analysis of plastic formation process of regular inequalities of surface with triangular outline. The physical and mathematical models of deformations (displacements and strains) and stress in the process were worked out. The process is considered as a geometrical and physical non–linear problem with unknown boundary conditions. The computer analyses were conducted with the use of Finite Elements Method (FEM). The solution of problem was conducted with use of updated Lagrangian description. In simulations material model of elasto/visco – plastic (E/VP) was used. The solution of variational equation of movement object was conducted applying the explicit method. The results of simulation are basis to projection of new technological operation – plastic formation of regular inequalities with triangular outlines as previous burnishing rolling process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence for an energetic problem in contact mechanics with dry friction
Authors: Schmid Florian
Published: February 2009

A simplified contact problem with dry friction is considered for a non–linear elastic system with two degrees of freedom. The simplification consits in neglecting kinetic energies or equivalently inertial forces. By proving existence it is shown under which conditions such simplifications are justifiable. The main focus is on the influence of a curved obstacle surface on the question of existence. The friction is modelled according to the Coulomb law and the coefficient of friction may vary along the obstacle surface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On wellposedness in nonlinear acoustics
Authors: Kaltenbacher Barbara , Lasiecka Irena , Veljović Slobodan
Published: February 2009

Motivated by a medical application from lithotripsy, we study the initial–boundary value problem given by Westervelt equation

in a bounded domain Ω. This models the nonlinear evolution of the acoustic pressure u excited at a part Γ0 of the boundary. Along with the excitation given by Neumann boundary condition as in (1), we also consider the Dirichlet type of excitation. Whereas shock waves are known to emerge after a sufficiently large time interval for appropriate initial and boundary conditions, we here prove existence and uniqueness as well as stability of a solution u for small data g, u0 and u1 or short time T, using a fixed point argument. Moreover we extend the result to the more general model given by the Kuznetsov equation

for the acoustic velocity potential ψ.
(© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
DNS of stochastically forced laminar plane Couette flow
Authors: Khujadze G. , Oberlack M. , Chagelishvili G.
Published: February 2009

Background of three dimensional hydrodynamic/vortical fluctuations in a stochastically forced, laminar, incompressible, plane Couette flow is simulated by direct numerical simulations (DNS). It was found that the fluctuating field has well pronounced peculiarities: (i) The hydrodynamic fluctuations exhibits non–exponential, transient growth; (ii) Streamwise non–constant fluctuations with the characteristic length scale of the order of the channel width are predominant in the fluctuating spectrum; (iii) Existence of coherent structures in the fluctuating background; (iv) Stochastic forcing breaks the spanwise reflection symmetry (inherent to the linear and full Navier–stokes equations in a case of the Couette flow) and inputs an asymmetry on dynamical processes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A sub‐feasible correction step for non‐linear programming methods with equality constraints
Authors: Nikolayzik Tim , Büskens Christof
Published: February 2009

Due to the sparsity of large–scale optimazation problems it can be useful to use the exact hessian matrix instead of update techniques for solving nonlinear optimization problems. Herewith it is possible to use techniques of the parametric sensitivity analysis to improve the feasibility of the NLP–problem in each iteration step of a solver. The main idea is to treat the measurable error between the general nonlinear equality constraints and the linear approximations inside the QP subproblems as a linear perturbation in the constraints. By special real–time optimization approximations this error can be reduced nearly without any extra computational costs. First results will be presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficiency and Applications
Authors: Postolică Vasile
Published: February 2009

This research work is concerned with the usual concepts of the efficiency and optimization. After a short introduction, we give some questions on the notion of the efficiency and we emphasize the Pareto optimality as one of the illustrative examples.We present the efficiency and optimization in the infinite dimensional vector spaces following also our recent results concerning the most general concept of approximate efficiency, as a natural generalization of the efficiency, with implications and applications in vector optimization and the new link between the approximate efficiency and the strong optimization by the full nuclear cones. An important extension of our coincidence result between the efficient points sets and the Choquet boundaries is developed . In this way, the efficiency is connected with Potential theory through the agency of optimization and conversely. Several pertinent references conclude the study. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analyse des Penalty‐Faktors in SIMP‐Methode in Bezug auf die Konvergenz der Lösung
Authors: Kutylowski Ryszard , Szwechlowicz Marek
Published: February 2009

In vorliegender Arbeit wurde das Problem des Penalty–Faktors in der SIMP–Methode in Bezug auf Geschwindigkeit und Konvergenz der Lösung analysiert. Der Penalty–Faktor tritt in der Formel zur Berechnung des Elastizitätsmoduls auf [1]. Man hat diese Aufgabe unternommen, weil es in der Literatur an Beweisen fehlt, die durch eine ausführliche Analyse des angenommenen Wertespin der Formel zur Berechnung des Elastizitätsmoduls belegt wären (1). Beim Formulieren des Problems der Topologieoptimierung wurde die Nachgiebigkeit einer Struktur als Zielfunktional angenommen. Man hat optimale Topologie gesucht, indem man die Nachgiebigkeit einer Struktur bei der Einschränkung der Körpermasse minimalisierte. Mit der FEM–Anwendung wurden Berechnungen für verschiedene Potenzenpdurchgeführt, das heißt, die so genannten “benchmarks” wurden analysiert. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On solution of total least squares problems with multiple right‐hand sides
Authors: Hnětynková Iveta , Plešinger Martin , Strakoš Zdeněk
Published: February 2009

Consider a linear approximation problem AX≈B with multiple right–hand sides. When errors in the data are confirmed both to B and A, the total least squares (TLS) concept is used to solve this problem. Contrary to the standard least squares approximation problem, a solution of the TLS problem may not exist. For a single (vector) right–hand side, the classical theory has been developed by G.H. Golub, C.F. Van Loan [2], and S. Van Huffel, J. Vandewalle [4], and then complemented recently by the core problem approach of C.C. Paige, Z. Strakoš [5,6,7]. Analysis of the problem with multiple right–hand sides is still under development. In this short contribution we present conditions for the existence of a TLS solution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the efficient update of the Singular Value Decomposition
Authors: Stange Peter
Published: February 2009

We introduce a new method for updating the singular value decomposition subject to a rank–one modification. Using the secular equation and exploiting arising matrix structures our algorithm has a computational complexity of O(n2log2n). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient computation of non‐isothermal highly viscous incompressible flow
Authors: Kopecz Stefan , Meister Andreas , Ouazzi Abderrahim , Turek Stefan , Wünsch Olaf
Published: February 2009

We consider the numerical solution of the non–isothermal incompressible Navier–Stokes equations using a discrete projection method. The computation of velocity and temperature subproblems is carried out on different meshes chosen with respect to the physical behavior of these quantities. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
FETI‐DP Methods for P‐Elasticity
Authors: Klawonn Axel , Neff Patrizio , Rheinbach Oliver , Vanisy Stefanie
Published: February 2009

A FETI–DP method is introduced for the problem of linear P–elasticity which arises from linear elasticity by the introduction of a matrix P and which is motivated by micromorphic models. Numerical results as well as a condition number estimate are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advanced Optimal Feedback Control for Tracking of Real‐Life Applications
Authors: Stach Ramona , Büskens Christof , Tietjen Jan
Published: February 2009

Calculating the open–loop solution of an optimal control problem is just the first step to cope with the practical realization of real life applications. Feedback controllers, like the classical Linear Quadratic Regulator (LQR), are needed to compensate pertubations appearing in reality. Although these controllers have proven to be a powerful tool in many applications and to be robust enough to countervail most differences between simulation and practice, they are not optimal if disturbances in the system data occur. If these controllers are applied in a real process, the possibility of data disturbances force recomputing the feedback control law in real–time to preserve stability and optimality, at least approximately. For this purpose, variations of the classical closed–loop controller with the extention to a trackingtype controller are analysed by means of an industrial application of container cranes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parameter Identification in Radio‐Frequency Ablation
Authors: Tiesler Hanne , Bueskens Christof , Preusser Tobias
Published: February 2009

The prediction of the temperature profile for radio frequency ablation—a minimal form of tumor treatment—depends on a variety of material parameters (e.g. electric and thermal conductivities) as the coefficients of a system of partial differential equations. We discuss a basic model for the identification of such material parameters from measured temperature data, which bases on an objective function of tracking type which is constrained by the system of PDE. After the discretization of the PDE system with a standard finite element method we optimize the discrete system with an SQP solver. Numerical results are shown for a test scenario consisting of an artificial tumor and artificially generated target temperature profile. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Necessary conditions of optimality in quasilinear systems with delays
Authors: Tsintsadze M. , Tsintsadze Z.
Published: February 2009

The optimal control problem for the processes described with quasilinear system of differential equations in presence of mixed restrictions on phase and control variables in case of delays on both variables is considered. Using the Lagrange principle of taking restrictions off necessary conditions of optimality for such kind of systems are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive FEM for PDE Constrained Optimization with Pointwise Constraints on the Gradient of the State
Authors: Wollner Winnifried
Published: February 2009

We are concerned with an interior penalty method for an optimal control problem with an elliptic PDE constraint and additional pointwise constraints on the gradient of the state variable. We will derive an estimator that gives qualitative information about the error in the cost functional due to the interior penalty parameter and for the discretization of the PDE. These can be used to balance the error contributions of both types of errors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechatronic Design of the 2 DOF PRRRP Parallel Robot
Authors: Besoiu S. , Mătieş V. , Stan S.‐D.
Published: February 2009

Mechatronics consists in integration of three fields in engineering: mechanics, electronics and information technology. The paradigm of mechatronics is the integration concept, being the first step in the design of complex mechatronic systems. The need for an integrated approach to the design of complex engineering system involving electronic engineering, mechanical engineering and computing has led to the growth of the concept of mechatronics. The paper presents details regarding the integration process for the kinematic axis in mechatronic. The example of the positioning system based on dc motor and screw–nut transmission is analysed. This actuator is further used for driving a 2 DOF PRRRP parallel robot. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant Excitation of a Composite Beam
Authors: Rudolf Christian , Seemann Wolfgang
Published: February 2009

Phase–locked loops are widely used within communication technology for synchronizing signals by tracking their phases. Their functional principle can be applied for maintaining the resonant excitation of a beam whose eigenfrequency changes over time and, thus, representing an alternative excitation method for the adaptronic strut for machine tools shown in [1]. In this contribution an experimental set–up for resonant excitation of a composite beam is introduced. A particle is mounted on the beam, its position and mass are are adjustable to modify the eigenfrequency of the beam. The simulation results of the analytical examination of the test–rig are compared with the experimental results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inversion‐Based Feedforward Control for the Transient Shaping of a Piezo‐Actuated Cantilevered Kirchhoff Plate
Authors: Schröck Johannes , Meurer Thomas , Kugi Andreas
Published: February 2009

Nowadays piezoelectric actuators are successfully applied for vibration suppression in structural mechanics. The progress in material and actuator development allows to put focus also on novel applications. In this contribution, a systematic approach for inversion–based feedforward control and motion planning is presented for the realization of a transient deflection profile of a cantilevered piezo–actuated plate modeling an adaptive wing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recursive Control of a 7 dof Robotic Arm
Authors: Simonidis Christian , Seemann Wolfgang
Published: February 2009

This paper provides a short insight into tracking control of uncertain nonlinear plants with the focus on ease of application and simple parameter tuning. The advanced control scheme is based on recursive control laws which have been shown in the last decades to be efficient in control of robotic motion. The algorithm is recursive rapidly convergent and robust. The development of humanoid robotic arms within the collaborative research center (CRC588) requires a class of easy implementable and robust nonlinear controllers to accomplish manipulation tasks in permanently alternating scenarios. The ability of the controller is tested by simulation for several robotic arms with increasing dof and variable end–effector mass for given human arm movements provided from a motion capture system. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability Analysis of an Orbiting Plate with Finite Elements
Authors: Steiner Wolfgang
Published: February 2009

This paper contributes to the analysis of rotating equilibria of non–driven systems (sometimes called relative equilibria), which are characterized by the fact that their angular momentum is conserved and non–zero. Interesting applications are usually found in space dynamics, in particular if large earth orbiting structures such as the space elevator are considered.

For flexible structures relative equilibria can be found with Finite Element software packages. However, in this case the stability analysis is a non–trivial task since one usually has only limited account to the internal data of commercial FE solvers. Therefore, in [5] a new finite element based stability test was developed and applied to one–dimensional structural elements. Here, we consider a large–scale flexible plate orbiting around the earth in order to demonstrate that this method works well also for two dimensional shell–elements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flatness of boundary coupled second order partial differential equations
Authors: Woittennek Frank , Mounier Hugues
Published: February 2009

We sketch algebraic and trajectory related controllability results for systems described by boundary coupled partial differential equations of second order in one spatial dimension. Those systems may be described by modules over a Bézout domain ℛℚ generated by particular Mikusinski–Operators with compact support. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of nonlinear multiresolution analysis
Authors: Harizanov Stanislav
Published: February 2009

Stability of nonlinear subdivision and multiresolution has recently been addressed in [1]. Here we give applications to convexity/monotonicity preserving schemes introduced in [2], [3]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Topology‐Preserving Geodesic Active Contours for Segmentation of High Content Fluorescent Cellular Images
Authors: Lorenz Dirk A. , Maass Peter , Preckel Hartwig , Trede Dennis
Published: February 2009

In this paper a method for segmentation of fluorescent cellular images is introduced, which uses geodesic active contours. After segmentation of the nuclei by a thresholding algorithm, the appropriate whole cells are detected by inflation of the nuclei masks and gradient information. Because the implicit level set formulation provides topological changes and the topology of the nuclei and the whole cells is equal, a topology–preserving modification is necessary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of electromagnetically influenced plasma flows using discontinuous Galerkin methods
Authors: Brußies Eva , Stiller Jörg , Grundmann Roger
Published: February 2009

We study several model cases to find possibilities to control the plasma flow by alternating magnetic fields, in particular travelling and high frequency (HF) fields, using numerical simulations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flow stabilisation by Dirichlet boundary control
Authors: Schneider René , Rothaug Tobias , Benner Peter
Published: February 2009

Re–attachment of separated flow is investigated for the model problem of a backward facing step at moderate Reynolds number (up to 400), where the length of the detachment zone is reduced by blowing in (or sucking out) fluid through a nozzle below the step. Both optimal feed forward control as well as a simple feedback control are considered, with surprisingly good results obtained by a very simple (non–optimal) linear feedback controller. Numerical results are shown. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the addendum modification at helical gears, at the points where the meshing starts and ends, based on the relative velocity equalization criterion
Authors: Antal Tiberiu Alexandru , Antal Adalbert , Arghir Mariana
Published: February 2009

The paper gives a new method for the determination of the specific addendum modifications at helical gears. The method is based on the equalization of the relative velocities at the points where the meshing of the teeth begins and ends. The numerical values were obtained for some given gears using MathCAD. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mass Conservative Approximation of Single and Two Phase Flow in Porous Media
Authors: Bause Markus
Published: February 2009

In this paper a new error estimate for a multi point flux approximation (MPFA) control volume method on triangular meshes for approximating flow in porous media is presented. The scheme is mass conservative and has shown to simulate reliably flows with discontinuous permeability tensors and on irregular grids which is the major challenge in hydrological engineering. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generative Programming in Scientific Computing
Authors: Jürgens Dominik
Published: February 2009

The complexity of simulation software increases because the simulated phenomena get more complex and massively parallel machines have to be used. Other reasons are the consideration of new technologies like the computational Grid and the integration of simulation programs into more complex applications. Therefore the development of future scientific software requires implicitly a step towards separation of concerns beyond the possibilities of classical programming techniques. An important integration problem in the context of scientific computing is the coupling of independently simulated phenomena, where different programs simulate only a part of a more complex coupled system. Numerical methods for the coupling of simulators like Lagrangian–multipliers based or staggered methods are in common use. Many problems which appear in practice of simulator coupling are not mathematical, but of more technical nature. That results in the current situation where code for the coupling of simulations is not implemented in a reusable way. New approaches to separation of concerns like aspect oriented and generative techniques may help to overcome these issues. As our vision we discuss the idea of a domain specific language (DSL) for coupled simulations. We present a review on methods, paradigms, theories and tools which aim at the development of coupled simulations with a generative approach. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solving fluid‐structure interaction problems using strong coupling algorithms with the component template library (CTL)
Authors: Rang Joachim , Krosche Martin , Niekamp R. , Matthies Hermann G.
Published: February 2009

In this note fluid–structure interaction problems are treated with a partitioned approach where the different solvers are transformed into software components which communicate with the help of the component template library (CTL). The implementation is explained and a numerical result shows the advantages of the numerical method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vitamin E. Alles ist im Fluss
Authors: Holzgrabe Ulrike
Published: February 2009

Die Literatur über die Chemie, Physiologie, Biochemie und den therapeutischen Einsatz von Vitamin E ist unübersehbar. Erst kürzlich haben wir den antioxidativen Wirkmechanismus von Tocopherol vollständig verstanden. Weniger wissen wir über seine physiologischen Wirkungen und damit auch über den möglichen Einsatz in Prävention und Therapie von Krankheiten wie Krebs, kardiovaskulären Erkrankungen oder Rheuma. Große Metaanalysen haben keine Vorteile aufgezeigt, ja sogar eine leichte Erhöhung der Mortalität ergeben, so dass bei der Supplementierung mit hohen Dosen Vitamin E Vorsicht geboten ist.
Vitamine in der Dermatologie. Etablierte Therapien bei Hautkrankheiten
Authors: Krauss Jürgen , Knorr Veronika
Published: February 2009

Der Einsatz von Vitaminen wie Vitamin E, Vitamin A oder Dexpanthenol in der Dermatologie ist allgegenwärtig. Ihr Nutzen bei verschiedenen Hauterkrankungen oder kosmetischen Problemen wird teilweise kontrovers diskutiert. Zurzeit finden sich nur wenige vitaminhaltige Externa in der Roten Liste und aus Sicht der Dermatologen wird auch die innerliche Anwendung in den meisten Fällen nicht unkritisch beurteilt. Dagegen haben Vitamin‐Derivate in der Therapie von Hauterkrankungen ihren Siegeszug angetreten und sind heute unverzichtbarer Teil der Dermatopharmakologie.
De novo balanced chromosome rearrangements in prenatal diagnosis
Authors: Giardino Daniela , Corti Cecilia , Ballarati Lucia , Colombo Daniela , Sala Elena , Villa Nicoletta , Piombo Giuseppe , Pierluigi Mauro , Faravelli Francesca , Guerneri Silvana , Coviello Domenico , Lalatta Faustina , Cavallari Ugo , Bellotti Daniela , Barlati Sergio , Croci Gianfranco , Franchi Fabrizia , Savin Elisa , Nocera Gianfranco , Amico Francesco Paolo , Granata Paola , Casalone Rosario , Nutini Lucia , Lisi Ermanna , Torricelli Francesca , Giussani Ursula , Facchinetti Barbara , Guanti Ginevra , Di Giacomo Marilena , Susca Francesco Paolo , Pecile Vanna , Romitti Lorenza , Cardarelli Laura , Racalbuto Erika , Police Maria Adalgisa , Chiodo Francamaria , Rodeschini Ornella , Falcone Patrizia , Donti Emilio , Grimoldi Maria Grazia , Martinoli Emanuela , Stioui Sabine , Caufin Daniele , Lauricella Salvatrice Antonia , Tanzariello Salvatrice Antonella , Voglino Gianfranco , Lenzini Elisabetta , Besozzi Marco , Larizza Lidia , Dalprà Leda
Published: February 2009

Objective

We surveyed the datasheets of 29 laboratories concerning prenatal diagnosis of de novo apparently balanced chromosome rearrangements to assess the involvement of specific chromosomes, the breakpoints distribution and the impact on the pregnancy outcome.

Method

By means of a questionnaire, data on 269.371 analyses performed from 1983 to 2006 on amniotic fluid, chorionic villus and fetal blood samples were collected.

Results

A total of 246 balanced anomalies were detected at frequencies of 72% for reciprocal translocations, 18% for Robertsonian translocations, 7% for inversions and 3% for complex chromosome rearrangements. The total frequencies of balanced rearrangements were 0.09%, 0.08% and 0.05% on amniotic fluid, chorionic villus and fetal blood samples.

Conclusion

A preferential involvement of chromosomes 22, 7, 21, 3, 9 and 11 and a less involvement of chromosomes X, 19, 12, 6 and 1 was observed. A nonrandom distribution of the breakpoints across chromosomes was noticed. Association in the location of recurrent breakpoints and fragile sites was observed for chromosomes 11, 7, 10 and 22, while it was not recorded for chromosome 3. The rate of pregnancy termination was about 20%, with frequencies decreasing from complex chromosomal rearrangements (33%), reciprocal translocations (24%) to inversions (11%) and Robertsonian translocations (3%). Copyright © 2009 John Wiley & Sons, Ltd.