bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mixing symbolic and numerical approaches for the surface‐to‐surface intersection problem
Authors: Fioravanti Mario , Gonzalez‐Vega Laureano 
Published: December 2008

AbstractThis paper shows how the efficiency of the current methodologies applied to the surface‐to‐surface intersection problem can be improved by combining an algebraic/symbolic framework with efficient and robust numerical techniques. The algebraic/symbolic framework is used to translate the computation of resultants, subresultants, discriminants, etc. to one or several generalized eigenvalue problems and SVD computations. The framework requires only the values of the involved polynomials at some set of points, and it will guide the numerical computations, providing thus a certificate of the topological correctness of the output. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Packing cylinders on a cylinder with contact constraints
Authors: Goold Eric , Rakesh Leela 
Published: December 2008

AbstractThe problem of cylinder packing is investigated. The specific problem is to determine the maximum number of congruent cylinders that can be packed around a core cylinder of arbitrary dimensions. The constraint is that their circular face must keep in contact with the core cylinder and there may be no overlapping. Only right circular cylinders are considered. Mathematically, a lower and upper bound is determined. A quantitative result is also found using a modified genetic algorithm. The algorithm was found to reproduce the published results for the top and bottom circular faces of the core which reduces to the problem of packing congruent circles within a circle. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discrete Element Method in der Geotechnik
Authors: Heesen E. , Kreuzer E. 
Published: December 2008

AbstractIn der Discrete Element Method (DEM) werden Böden als Granulat betrachtet, das aus einem System einzelner Partikel besteht, dieüber Kontaktkräfte miteinander in Wechselwirkung stehen und sich gegeneinander verschieben können. In dem hier verwendeten zweidimensionalen Modell werden die Partikel als konvexe unregelmäßige Polygone modelliert. Untersucht wird die Bodenmechanik im Nahfeld der Pfahlinstallation, das Fernfeld wird nicht modelliert. Es wird eine Randbedingung vorgestellt, die das Verhalten der Fernfelds adäquat wiedergibt. Bei der Modellierung zeigt sich, dass es zu deutlichen Spannungsreduktionen im umgebenden Boden kommt. Am Pfahlmantel kommt es zu starken Auflockerungen des Bodens, während andere Bodenbereiche verdichtet werden. Das Verschiebungsfeld während der Pfahlinstallation ist sehr inhomogen und instabil. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscosity in discontinuous Galerkin methods
Authors: Kessler Manuel 
Published: December 2008

AbstractThe Discontinuous Galerkin (DG) discretisation technique proposes a higher order alternative to current state of the art Finite Volume (FV) methods of second order accuracy in space. DG features higher order on unstructured grids without reconstruction, highly local data access patterns and excellent parallelisation properties. However, viscosity does not fit seamlessly into DG, but is indispensable for nearly every technical aeronautical simulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of constrained mechanical systems
Authors: Koutsovasilis Panagiotis , Beitelschmidt Michael 
Published: December 2008

AbstractMotion equations of constrained mechanical Multi Body Systems (MBS) are described by differential and algebraic equations (DAE). Various modeling methods are implemented, while the simulation is based on commercial DAE‐solvers. A comparison study concerning the quality of their results is presented. Issues, such as the importance of DAE‐index, finding a consistent set of initial conditions, the drift‐off phenomenon as well as the application of projection and stabilization techniques are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of PBPK modeling in drug discovery: opportunities and limitations
Authors: Poirier A. , Funk C. , Lavé T. 
Published: December 2008

AbstractDuring drug discovery, considerable resources are required to assess the pharmacokinetic properties of potential drug candidates in vivo in animals and there is interest in optimizing the use of such testing by applying simulation. Physiologically based pharmacokinetic (PBPK) models take in vitro and in silico data inputs to predict concentration versus time profiles before any in vivo experiment is performed. If sufficiently reliable, such simulations could decrease the turnaround time for delivery of information to medicinal chemists during the optimization phase and could also be used to prioritize compounds for the more costly in vivo testing. The mechanistic framework provided by a PBPK model can integrate most of the available predictive data on a compound and provide mechanistic insights into compound properties. Such integrative capabilities and mechanistic insights are not provided by the more commonly used non compartmental or compartmental analysis. However, there are still important processes missing in the models, such as active transport processes, which are the subject of intensive investigation. Thus, mechanistic models integrating active transport processes were developed and are currently being validated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Iterated hard‐thresholding for linear inverse problems with sparsity constraints
Authors: Lorenz Dirk , Bredies Kristian 
Published: December 2008

AbstractWe describe an iterative algorithm for the minimization of Tikhonov type functionals which involve sparsity constraints in form of ℓp ‐penalties which have been proposed recently for the regularization of ill‐posed problems.In contrast to the well‐known algorithm considered by Daubechies, Defrise and De Mol, it uses hard instead of soft thresholding. This hard thresholding algorithm is based on the generalized conditional gradient method. General results on the convergence of the generalized conditional gradient method enable us to prove strong convergence of the iterates. Furthermore we are able to establish convergence rates of O (n–1/2) and O (λn) for p = 1 and 1 < p ≤ 2 respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A software engineering for numerical simulation of 2D non‐stationary real MGD flows
Authors: Maglione L. S. , Elaskar S. A. , Brito H. H. , Dean R. A. , Lifschitz1 L. A. 
Published: December 2008

AbstractThe study of flows in which an electrically conducting gas moves in a magnetic field is known as magnetogasdynamics or MGD for short. Computational MGD represents one of the most promising interdisciplinary computational technologies for aerospace design. At the present, in Argentina, an ablative magnetoplasmadynamic thruster (AMPD) is being developed as a native propulsion option for satellite and, particularly, microsatellite orbit and/or attitude control. A MGD model is generally based on the assumption that plasma can be regarded as a continuum and thus may be characterized by relatively few macroscopic quantities. A model for a flow affected by electromagnetic forces includes the full set of Maxwell's equations coupled with the Navier‐Stokes equations. The real MGD equations constitute a parabolic‐hyperbolic partial differential system. In addition the ideal part of the MGD equations is nonconvex and as consequence the wave structure is more complicated than for the Euler equations. A software tool was developed which by using structured meshes solves 2D, time‐dependent, viscous and resistive MGD flows. In this case, the numerical approach consists of an approximate Riemann solver coupled with the TVD scheme proposed by Yee. The eigensystem introduced by Powell and the normalization of the eigenvectors presented by Zarachay et al. have also been used. To check accuracy, the computational code has been applied in the simulation of a Riemann problem introduced by Brio and Wu. Also results in the simulation of the Hartmann flow are shown. The results obtained are in good agreement with those reported by other authors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of the material symmetries with anisotropic damage evolution due to a growing mixed‐mode crack
Authors: Molla‐Abbasi K. , Schuette H. 
Published: December 2008

AbstractA numerical study of a growing mixed‐mode internal crack in a unit cell was undertaken with the help of a finite element simulation. The model enables us to measure the components of the elastic compliance tensor modified by damage as the crack grows, showing the evolution of the anisotropic damage and the evolution of the type of material symmetries. The evolution of the elasticity tensor shows that the damage associated with a growing elliptical crack changes the virgin isotropic properties into orthotropic ones and by crack growth the axes of orthotropic symmetry, initially aligned with the local coordinates of the crack, rotate towards the principle loading axes. Crack propagation is simulated using the stepwise method, which consists of the succession of straight segments and crack growth is governed by the principle of maximum driving force which is a direct consequence of the variational principle of a cracked body in equilibrium and considers the effect of all three stress intensity factors. Without any ad hoc assumption, the crack growth rate is calculated using its thermodynamic duality with the local maximum driving force. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient reconstruction of functions on the sphere from scattered data
Authors: Keiner Jens , Kunis Stefan , Potts Daniel 
Published: December 2008

AbstractMotivated by the fact that most data collected over the surface of the earth is available at scattered nodes only, the least squares approximation and interpolation of such data has attracted much attention, see e.g. [1, 2, 5]. The most prominent approaches rely on so‐called zonal basis function methods [16] or on finite expansions into spherical harmonics [12, 14]. We focus on the latter, i.e., the use of spherical polynomials since these allow for the application of the fast spherical Fourier transform, see for example [8, 9] and the references therein. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Representation of the linear viscoelastic behaviour of wood with a constitutive theory based on fractional time derivatives
Authors: Ranz T. , Lion A. 
Published: December 2008

AbstractLike many other materials used in mechanical and civil engineering, wood shows a pronounced history‐dependent mechanical material behaviour. Due to its anisotropy its rheological behaviour is strongly dependent on the direction. In this research project, the material behaviour is represented with a phenomenological theory of anisotropic fractional viscoelasticity. In order to identify the material functions and parameters, the time‐dependent creep compliances are measured in three orthogonal directions under tension and shear. As a result of the developed constitutive approach, the experimentally observed creep data is described by several power functions. In the second part of the presentation, some differences between classical models of viscoelasticity which are based on Kelvin‐Voigt or Maxwell elements and the fractional approach are presented. The assets and drawbacks with respect to wood are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations of yield stress in ferrofluids with a stress controlled rheometer
Authors: Shahnazian H. , Odenbach S. 
Published: December 2008

AbstractOne of the most important properties of ferrofluids is the strong change of viscosity when subject to an applied magnetic field – the so called magnetoviscous effect. The rheological experiments as well as theoretical studies correlate this effect with the appearance of chain‐like structures of magnetic particles due to the strong interparticle interaction in presence of a magnetic field. Furthermore, viscoelastic effects or other non‐Newtonian features, like yield stress in ferrofluids, can theoretically be described with these structures under the influence of the magnetic field. In earlier experiments, when a shear rate controlled rheometer has been used, yield stress could not be investigated directly. A field dependent yield stress could only be estimated in ferrofluids. For direct yield stress investigations, a dedicated stress controlled rheometer is needed, so that the yield stress and its dependence on the magnetic field can be investigated directly. This paper presents investigations of yield stress and its dependence on the magnetic field strength as well as on volume concentration of large magnetic particles. In order to get more information about the structure formed by the particles, variation of gap thickness of the shear cell for the yield stress experiments has been used. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Well‐posedness, stability and numerical results for the thermoelastic behavior of a coupled joint‐beam PDE‐ODE system modeling the transverse motions of the antennas of a space structure
Authors: Cliff Eugene M. , Herdman Terry L. , Liu Zhuangyi , Spies Ruben D. 
Published: December 2008

AbstractA mathematical model for both axial and transverse motions of two beams with cylindrical cross‐sections coupled through a joint is presented and analyzed. The motivation for this problem comes from the need to accurately model damping and joint dynamics for the next generation of inflatable/rigidizable space structures. Thermo‐elastic damping is included in the two beams and the motions are coupled through a joint which includes an internal moment. Thermal response in each beam is modeled by two temperature fields. The first field describes the circumferentially averaged temperature along the beam, and is linked to the axial deformation of the beam. The second describes the circumferential variation and is coupled to transverse bending. The resulting equations of motion consist of four, second‐order in time, partial differential equations, four, first‐order in time, partial differential equations, four second order ordinary differential equations, and certain compatibility boundary conditions. The system is written as an abstract differential equation in an appropriate Hilbert space, consisting of function spaces describing the distributed beam deflections and temperature fields, and a finite‐dimensional space that projects important features at the joint boundary. Semigroup theory is used to prove that the system is well‐posed, and that with positive damping parameters the resulting semigroup is exponentially stable. Steady states are characterized and several numerical approximation results are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact controllability of a semilinear thermoelastic system with control and nonlinearity in thermal component only
Authors: Tomar Nutan Kumar , Sukavanam N. 
Published: December 2008

AbstractA result concerning the exact controllability of semilinear thermoelastic system, in which the control and nonlinear term occurs solely in the thermal equation, is derived under the influence of rotational inertia and Lipschitz nonlinearity, subject to the clamped/Dirichlet boundary conditions. In the proof we make use the result given by Avalos G. [Differential and Integral Equations, 13 (2000), 613‐630] which states that the corresponding linear system is exact controllable. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Undergraduate computational science and engineering education: A SIAM Working Group Report
Authors: Turner Peter R , Vakalis Ignatios 
Published: December 2008

AbstractComputational Science and Engineering (CSE) is a rapidly growing multidisciplinary area with connections ot the sciences, engineering, mathematics and computer science. CSE is a legitimate and important academic enterprise, even if it is yet to be formally recognized by a number of institutions. The undergraduate arena is the most important segment of the educational pipeline, since it prepares teachers for the high school environment, invigorates students to pursue graduate studies in cutting edgetechnical fields, and produces a vast number of future employees for industry and the “knowledge‐based” economy. Thus it is critical that CSE curricula and programs are a viable option for every undergraduate student. This presentation introduces the SIAM Working Group report on undergraduate CSE education. The particular focus here is on background and the varying nature of programs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Re‐entrant corner flow of Phan‐Thien‐Tanner fluids
Authors: Evans J.D. , Sibley D.N. 
Published: December 2008

AbstractResults are described for the planar flow of Phan‐Thien‐Tanner (PTT) fluids around re‐entrant corners. A stress singularity similar to the Upper Convected Maxwell (UCM) model is obtained, namely O (r–2(1–α)) where r is the radial distance from the corner and π /α the corner angle. However, the stream function vanishes at the slower rate O (r(1+α)α ) compared to O (r(3–α)α ) for UCM – this feature being a consequence of the shear thinning property of the PTT model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient HOC scheme for transient convection‐diffusion‐reaction equations with discontinuous coefficients and singular source terms
Authors: Ray Rajendra K , Kalita Jiten C , Dass Anoop K 
Published: December 2008

AbstractIn this paper, we propose a new methodology for numerically solving one‐dimensional (1D) transient convection‐diffusion‐reaction equations with discontinuous coefficients and singular source terms on nonuniform space grids. This Higher Order Compact (HOC) formulation is at least third order accurate at regular grid points and exactly third order accurate at points just next to the discontinuity. We conduct numerous numerical studies on a number of problems and compare our results with those obtained with immersed interface and other well‐known methods. In all cases our formulation is found to produce better results on relatively coarser grids. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subgroup structure of bifurcation equations with crystallographic group symmetry
Authors: Makeev Oleg , Loginov Boris 
Published: December 2008

AbstractFor stationary and Andronov‐Hopf bifurcation with symmetry of highest crystalline classes of basic syngonies of symmorphic crystallographic groups as semidirect products of translations on basic directions and point symmetry of lattice the subgroup structure of relevant bifurcation equations and bifurcating solutions dual to subgroup structure of such symmetry is investigated. Applications to phase transitions in physics are considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ein Ansatz zur Beschreibung der dreidimensionalen Topographiedynamik bei Bremsvorgängen
Authors: Müller M. , Ostermeyer G.‐P. 
Published: December 2008

AbstractDie Dynamik in der Grenzschicht zwischen Bremsbelag und Bremsscheibe ist während eines Bremsvorganges durch eine komplexe Wechselwirkung zwischen Reibung und Verschleiß charakterisiert. Um explizite Aussagen über globale Verschleißraten oder laterale Anregungsmechanismen zu erhalten, ist ein Modell eines Zellulären Automaten auf eine dreidimensionale Topographiebeschreibung erweitert worden. Zur Verifizierung und Quantifizierung werden identische Bremssysteme mit unterschiedlicher Belastungsgeschichte optisch untersucht. Die daraus gewonnenen Daten der Oberflächentopographie werden in diesem Paper den Ergebnissen aus der Simulation gegenübergestellt und interpretiert. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Bogolubov generating functional method in statistical physics and the Wigner transform (Poster Presentation)
Authors: Prykarpatsky Anatoliy K. , Bogolubov Nikolai N. 
Published: December 2008

AbstractWe show that the N.N. Bogolubov generating functional method is a very effective tool for studying distribution functions of both equilibrium and non equilibrium states of classical many‐particle dynamical systems. In some cases the Bogolubov generating functionals can be represented by means of infinite Ursell‐Mayer diagram expansions, whose convergence holds under some additional constraints on statistical system. The classical Bogolubov idea [1] to use the Wigner density operator transformation for studying the non equilibrium distribution functions is developed and new analytic non‐stationary solution to the classical N.N. Bogolubov evolution functional equation is constructed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical notation and the use of functions (Poster Presentation)
Authors: Thielemann Henning 
Published: December 2008

AbstractIn contrast to natural languages, mathematical notation is accepted as being exceptionally precise. It shall make mathematical statements unambiguous, it shall allow formal manipulation, it is model for programming languages, computer algebra systems and machine provers. However, what is traditional notation and is it indeed as precise as expected?We discuss some examples of notation which require caution. How are they adapted in computer algebra systems? Can we improve them somehow? What can we learn from functional programming? (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Olga Taussky, a torchbearer for mathematics and teacher of mathematicians
Authors: Uhlig Frank 
Published: December 2008

AbstractOlga Taussky‐Todd's mathematical and personal life (1906‐1995), her achievements and obstacles, her scientific reasoning and teaching all have served as inspiration to many mathematicians. We describe her role in the mathematics world of the previous century as a torchbearer for mathematics and mathematicians, bearing the “torch of scientific truth” that burns inside of mathematics and its applications. Besides her many deep math contributions – too many to elaborate – she excelled at distilling and presenting mathematical concepts and ideas in her work and gave us many visionary papers and math talks. By sharing her mathematical vision freely she has inspired many of us. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of bond ratings using statistical and neural networks techniques
Authors: Alam S. 
Published: December 2008

AbstractQuantitative models have been developed to predict bond ratings of firms in the Indian manufacturing sector, using financial leverage, profitability, asset management ability, stability and market sensitivity of the firm, which totally involved 16 variables. These 16 independent variables are first reduced to seven orthogonal variables using principal component analysis. Then these variables are used to build three types of models, namely Multiple Discriminant Analysis (MDA), Multinomial Logistic Regression (MLR) and Artificial Neural Networks (ANN). Based on both in‐sample classification and out‐sample validation it is found that both MLR and ANN models are superior to MDA, with little difference in performance between themselves. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Teaching computational science with computer algebra
Authors: Gander Walter 
Published: December 2008

AbstractComputer algebra systems can be used to generate algorithms for numerical computations. We have computed and shown examples in [1] and more recently in [2]. In this paper we emphasize the teaching aspect and use essentially the capability of computer algebra system to construct and manipulate the interpolating polynomial and to compute a series expansion of a function. We automatically generate formulas for integration with error terms and also generate multi‐step methods for integrating differential equations. Furthermore we discuss the use of multiple precision. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)