bluuebunny/crossref_metadata_2025_split huggingface dataset:
Problems in practical application of high resolution numerical schemes to internal and external tasks of aerodynamics
Authors: Bosniakov S.M. , Vlasenko V.V. , Glazkov S.A. , Jitenev V.K. , Kazhan E.V. , Quest J. , Mikhailov S.V. 
Published: December 2008

AbstractThis report presents numerical method for solution of aerodynamic tasks on the basis of Reynolds Averaged Navier‐Stokes Equations. The method is applied to simulation of flow around aircraft (including engine‐airframe interference) and to description of flowfield in the wind tunnel (WT) with aircraft model inside. To satisfy growing practical requirements both to accuracy of numerical results and to calculation time, zonal approach is proposed: flow regions with small scales of physical phenomena may be described using implicit scheme, and the rest of the flowfield – using explicit scheme. An example of modeling flow in the test section of European Transonic Windtunnel is shown. Unsteady phenomena around WT slotted walls were obtained. Calculations of noise suppressing nozzles with different geometry are considered. Numerical simulation has allowed to improve the nozzle geometry and to provide essential noise suppression. All presented examples confirm the need in further development of effective and accurate algorithms for practical tasks solution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of tissue anisotropy versus inhomogeneity on the structural behaviour of an elderly human mandible
Authors: Kober C. , Hellmich C. , Erdmann B. , Stübinger S. , Sader R. , Zeilhofer H.‐F. 
Published: December 2008

AbstractWithin the biomechanics of bony organs, individual tissue anisotropy and inhomogeneity are intensively discussed subjects. This paper is dedicated to the impact of a fully anisotropic and inhomogoneous material description on the structural behaviour of an elderly partially edentulous human mandible. Radial, axial, and circumferential trajectories of orthotropic elasticity were reconstructed from kind of inner skeleton derived from the organ's geometry and from coherent structures recognisable from the spatial distribution of the grey values coming from computer tomography (CT). Based on recent micromechanical research driven forward by the second author, CT numbers were transferred into inhomogeneous stiffness tensor components reflecting individual tissue properties. These coefficients were considered as local orthotropic elastic coefficients in reference to coordinate systems formed by the anisotropic trajectories of elasticity. For the sake of a complete anisotropic material description over the whole organ, the tensor components were transformed into a global base frame which allows assembling an overall patient‐specific stiffness matrix. Various sensitivity analysis revealed that the more the anisotropy is considered the more the mandible is spared from loading which indicates kind of mechanical optimality of the mandible with respect to tissue anisotropy. In the opposite, the consideration of individual inhomogeneous tissue properties resulted in intensification of load concentrations due to pathological alterations of the organ which gives rise to the suggestion of self‐energising processes of bone resorption. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid symbolic‐numeric algorithms for computational convex analysis
Authors: Lucet Yves 
Published: December 2008

AbstractComputational convex analysis focuses on developing efficient tools to compute fundamental transforms arising in convex analysis. Symbolic computation tools have been developed, and have allowed more insight into the calculation of the Fenchel conjugate and related transforms. When such tools are not applicable e.g. when there is no closed form, fast transform algorithms perform numerical computation efficiently.However, computing the composition of several transforms is difficult to achieve with fast transform algorithms, which is the case for the recently introduced proximal average operator. We consider the class of piecewise linear‐quadratic functions which, being closed under the most relevant operations in convex analysis, allows the robust and efficient numerical computation of compositions of transforms like the proximal average. The algorithms presented are hybrid symbolic‐numeric: they first compute a piecewise linear‐quadratic approximation of the function, and then manipulate the approximation symbolically. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermomechanical behavior of pseudoelastic NiTi shape memory alloys
Authors: Luig Patrick , Grabe Christian , Bruhns Otto 
Published: December 2008

AbstractThe thermomechanical behavior of polycrystalline Ni‐rich pseudoelastic NiTi shape memory alloys is analyzed. Special focus is on regions within the stress strain diagram which are regarded as linear elastic in common phenomenological material models, i.e. the region between zero stress and the beginning of the pseudoelastic plateau as well as the region within the hysteresis. In both cases, severe temperature changes can be observed. A possible explanation for this effect is twofold: On the one hand, it might be explained by the presence of an R‐phase transformation. On the other hand, unstructured martensite of the B19' phase may form. However, the assumption of a purely thermo‐elastic material behavior in those regions does not seem to hold true in general. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of differential Riccati equations arising in optimal control for parabolic PDEs
Authors: Mena Hermann , Benner Peter 
Published: December 2008

AbstractThe numerical treatment of linear‐quadratic regulator problems on finite time horizons for parabolic partial differential equations requires the solution of large‐scale differential Riccati equations (DREs). Typically the coefficient matrices of the resulting DRE have a given structure (e.g. sparse, symmetric or low rank). Here we discuss numerical methods for solving DREs capable of exploiting this structure. These methods are based on a matrix‐valued implementation of the BDF methods. The crucial question of suitable stepsize and order selection strategies is also addressed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust a‐posteriori error control of Cahn‐Hilliard type equations with elasticity
Authors: Bartels Sören , Müller Rüdiger 
Published: December 2008

AbstractPhase separation of an initially homogeneous mixture into two different phases can be modeled on a mesoscopic scale by the Cahn‐Hilliard equation. The interface thickness between the pure phases enters as a small parameter γ into this mass conserving fourth order semilinear parabolic equation. Numerical analysis is well established for a fixed parameter size, but error estimates depend exponentially on γ–1 and thus become useless if γ → 0. We consider the case, that elastic stresses due to a lattice misfit become important and the equation has to be coupled to a system of linear elasticity. Applications include e. g. the simulation of Sn‐Cu alloys for the production of lead free solder or Ni‐Al alloys used for rotor blade surfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An iterative optimum‐optimorum theory for the design of a globally optimal shape
Authors: Nastase A. 
Published: December 2008

AbstractIn some previous papers, the author has developed the optimum‐optimorum theory, which solves an enlarged variational problem with free boundaries, inside of a class of flying configurations (FCs), defined by some chosen common properties. This optimization strategy was used by the author for the inviscid, aerodynamical, global optimal design of three models, namely, Adela, a delta wing alone and of two fully‐integrated wing‐fuselage FCs, namely, Fadet I and Fadet II, which have all high values of L/D (lift to drag). A further enlargement of the optimization strategy is developed here, in form of an iterative optimum‐optimorum theory, which uses the inviscid global optimized FC's shape as first step of iteration and the own developed reinforced Navier‐Stokes solutions up the first computational checking and up the second step of iteration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combining modeling, simulation, optimization and analysis under a unique framework
Authors: Serna S. Pena , Stork A. 
Published: December 2008

AbstractThe virtual engineering design process is based on several phases and every phase is supported by special concepts, representations and tools. This process is complex and the transition and communication between phases is difficult because of conversions and transformations. Embodiment is the phase, which more time requires, in order to produce a definitive layout from the concept, hence, we are designing and developing a unique framework where the embodiment phase can be performed, integrated and combined without transformations and conversions. This approach will support the engineers with advanced techniques on modeling meshes, conceptual simulations and real time optimization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitivity analysis for indirect measurement and profile reconstruction in scatterometry
Authors: Groß Hermann , Rathsfeld Andreas 
Published: December 2008

AbstractTo control the design and manufacturing of lithographic masks a fast and non‐destructive measurement technique is needed. In scatterometry the mask is illuminated by plane waves from various directions, the scattered light is measured, and the geometry of the mask surface is reconstructed from the measured data. The quality of reconstruction surely depends on the angles of incidence, on the wave lengths and/or the number of propagating scattered wave modes. Optimizing the conditioning of some Jacobian matrices, we develop a sensitivity analysis to find an optimal measurement configuration for scatterometry. Our first important test geometry is a simple periodic line‐space structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of the dynamic problem of the elasticity theory in arbitrary shaped plane domain
Authors: Ribacova Galina 
Published: December 2008

AbstractThe numerical method for solving the dynamical problems of the theory of elasticity in two‐dimensional arbitrary shaped regions is proposed. The developed method consists of two main stages. The first one deals with the numerical grid generation. The method for creating the regular two dimensional grids based on equations of longitudinal plate deformation is presented. The last problem is solved numerically by means of finite difference method with the posterior using of the iteration process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SPSA for oil‐parameter estimation and reservoir management
Authors: Rodriguez A. , Klie H , Wheeler M. 
Published: December 2008

AbstractIn this paper we implement and test the Simultaneous Perturbation Stochastic Approximation method (SPSA) in order to perform parameter estimation or history matching in reservoir simulation. The SPSA algorithm allows the determination of descent directions with very few forward model evaluations no matter the number of parameters. We test this approach for the estimation of transmissibilities for a single‐phase flow problem in very heterogeneous environments. The global properties of SPSA allow the determination of reasonable good inverse solutions which is demonstrated through numerical experiments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contact area of solid bodies: calculations compared to measured results
Authors: Sick J.‐H. , Ostermeyer G.‐P. 
Published: December 2008

AbstractA novel attempt is made to directly measure the contact area of solid bodies by relating it to the electrical contact resistance. This method was used by F. P. Bowden and D. Tabor in the 1930s already. We confined the setup by use of low conductive thin film coatings. This way it is possible to point out the influence of contact area in contrast to incidental contaminations. By use of wear resistant coatings it will be possible to measure the contact area in sliding contacts as well. New measurements and calculations are compared with the original setup and model for contact resistance and contact area, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal design of a 2 DOF parallel robot
Authors: Stan S.‐D. , Maties V. , Balan R. 
Published: December 2008

AbstractThis paper is aimed at presenting a study on the optimization of the Biglide mini parallel robot, which comprises two‐degree‐of‐freedom (DOF) mini parallel robots with constant struts. The robot workspace is characterized and the inverse kinematics equation is obtained. In the paper, design optimization is implemented with Genetic Algorithms (GA) for optimization considering transmission quality index and workspace. Here, intended to show the advantages of using the GA, we applied it to a multicriteria optimization problem of 2 DOF mini parallel robot. Genetic algorithms (GA) are so far generally the best and most robust kind of evolutionary algorithms. A GA has a number of advantages. It can quickly scan a vast solution set. Bad proposals do not affect the end solution negatively as they are simply discarded. The obtained results have shown that the use of GA in such kind of optimization problem enhances the quality of the optimization outcome, providing a better and more realistic support for the decision maker. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diffusion‐wave phenomena
Authors: Stojanović Mirjana , Gorenflo Rudolf 
Published: December 2008

AbstractWe announce the forthcoming papers [4] and [5] in which we prove the existence and the uniqueness, find properties, asymptotic and regularity of the solution to diffusion‐wave phenomena. We give explicit solutions for 1, 2, …, n ‐term time fractional diffusion‐wave equations. For the distributed order equation and for the equation with n‐term time fractional derivatives, we prove that the first fundamental solution is always a probability density for x ∈ R. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inversion‐based trajectory planning for the heat equation with temperature‐dependent parameters and radiation boundary conditions
Authors: Utz Tilman , Meurer Thomas , Wild Daniel , Kugi Andreas 
Published: December 2008

AbstractThis contribution is concerned with the trajectory planning for the nonlinear heat equation with radiation boundary conditions (BCs). For this, the infinite‐dimensional model is spatially discretized using finite differences. The discretized finite‐dimensional model serves as a basis for a flatness‐based feedforward control design. In the case of constant physical parameters, it is shown that the thus obtained feedforward controller converges to the feedforward controller for the original infinite‐dimensional problem in the limit as the discretization step size tends to zero. In the case of temperature‐dependent parameters, simulation results illustrate the convergence behavior. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hybrid optimization approach for automated parameter estimation problems
Authors: Argáez M. , Klie H. , Quintero C. , Velázquez L. , Wheeler M. 
Published: December 2008

AbstractWe present a hybrid optimization approach for solving automated parameter estimation models. The hybrid approach is based on the coupling of the Simultaneous Perturbation Stochastic Approximation (SPSA) [1] and a Newton‐Krylov Interior‐Point method (NKIP) [2] via a surrogate model. The global method SPSA performs a stochastic search to find target regions with low function values. Next, we generate a surrogate model based on the points of regions on which the local method NKIP algorithm is applied for finding an optimal solution. We illustrate the behavior of the hybrid optimization algorithm on one testcase. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Projection acceleration of Krylov solvers
Authors: Vuik C. , Tang J.M. , Nabben R. 
Published: December 2008

AbstractIn many applications it appears that the initial convergence of preconditioned Krylov solvers is slow. The reason for this is that a number of small eigenvalues are present. After these bad eigenvector components are approximated, the fast superlinear convergence sets in. A way to have fast convergence from the start is to remove these components by a projection. In this paper we give a comparison of some of these projection operators. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive detection of distribution changes in medical information systems
Authors: Xue Xinjian Jack 
Published: December 2008

AbstractThe number of messages received by a medical information system was modelled as the signal in a stochastic process. Algorithms were developed for detecting changes of mean and variance and reporting the changes of status from normal to abnormal (upward edge), and vice verse (downward edge) under the assumption that the signal was distributed independently and normally in a series of time intervals. System tests have shown that the performance of the fault detecting and reporting in non‐holiday days is generally satisfactory for all laboratory data feeds. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exploiting statistical properties of wavelet coefficient for face detection and recognition
Authors: Al‐Jawad Naseer 
Published: December 2008

AbstractWavelet transforms (WT) are widely accepted as an essential tool for image processing and analysis. Image and video compression, image watermarking, content‐base image retrieval, face recognition, texture analysis, and image feature extraction are all but few examples. It provides an alternative tool for short time analysis of quasi‐stationary signals, such as speech and image signals, in contrast to the traditional short‐time Fourier transform. The Discrete Wavelet Transform (DWT) is a special case of the WT, which provides a compact representation of a signal in the time and frequency domain. In particular, wavelet transforms are capable of representing smooth patterns as well anomalies (e.g. edges and sharp corners) in images. We are focusing here on using wavelet transforms statistical properties for facial feature detection, which allows us to extract the image facial feature/edges easily. Wavelet sub‐bands segmentation method been developed and used to clean up the non‐significant wavelet coefficients in wavelet sub‐band (k) based on the (k‐1) sub‐band. Moreover, erosion which is considered as one of the fundamental operation in morphological image processing, been used to reduce the unwanted edges in certain directions. For face detection, face template profiles been built for both the face and the eyes for different wavelet sub‐band levels to achieve better computational performance, these profiles used to match the extracted profiles from the wavelet domain of the input image using the Dynamic Time Warping technique DTW. The DTW smallest distance allows identifying the face and the eyes location. The performance of face features distances and ratio has been also tested for face verification purposes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure formation and phase behaviour in ferrofluid monolayers: theory and computer simulations
Authors: Cerdà Juan J. , Kantorovich Sofia , Holm Christian 
Published: December 2008

AbstractIn order to investigate the peculiarities brought by the quasi‐2D geometry into the aggregation processes in ferrofluids, a combination of density functional theory (DFT), and molecular dynamics (MD) simulations is presented. The microstructure formation and the phase behaviour of monodisperse ferrofluid monolayers is studied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A ranking for the nodes of directed graphs based on game theory (Poster Presentation)
Authors: Amer Rafael , Giménez José Miguel , Magãna Antonio 
Published: December 2008

AbstractWe introduce a value that allows us to emphasize the importance of each player in a cooperative game when the cooperation possibilities are limited according to the links of an oriented network. The proposed concept of accessibility tries to conjugate the marginal contributions of each node as a game player with the cooperation geometry imposed by the directed graph that models the network. As a consequence, it is possible to offer a ranking for the nodes of directed graphs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Out‐of‐plane displacement measurement near the crack tip during a crack propagation: Validation of a 3D formulation for a specimen in PMMA loaded in mode I.
Authors: Hédan S. , Valle V. , Cottron M. , Brémand F. 
Published: December 2008

AbstractThe fundamental aim of this study is the determination zone of the 3D effects and the transient one at the vicinity of the crack tip during a crack propagation in brittle materials (PMMA) using an optical method (Michelson interferometer). With the obtained interferograms, we can extract the phase (thus the relief) by using a new numerical approach based on the principle of images correlation between real fringes and virtual fringes. Different dynamic tests are realized by a plate loaded in mode I under a constant loading. We compare the obtained data with the two‐dimensional theory of Westergaard (plane stress hypothesis) [1]. With the divergence is established, we propose a new 3D formulation, based on a formulation employed for static crack, which takes into account 3D and transient effects. For the static cracks, the 3D effects relate to a presence of the state of three‐dimensional stresses. However in dynamics, the transient effects appear and are related to the crack propagation velocity. The 3D effects and transient effects lead to results equivalent to experimental ones in terms of displacement but are completely different to results given by the two‐dimensional theory near the crack tip. It is possible to quantify the zone when the plane stress hypothesis is not valid according to the crack propagation speed V. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Andronov–Hopf bifurcation and group symmetry for differential equations non‐resolved under derivative
Authors: Loginov Boris , Makeev Oleg , Konopleva Irina , Rousak Yu. 
Published: December 2008

AbstractFor the differential equations in Banach spaces non‐resolved under derivative on the base of general theorem about group symmetry inheritance by relevant A.M. Lyapounov and E. Schmidt branching equations the possibilities of the reduction (dimension lowering) of the potential type branching equations are studied. As corollaries the results about general form of branching equations with rotational symmetries for evolution equation with degenerate Fredholm operator at the derivative are established. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Automatic adaptation of an integration formula in thickness direction for solid‐shell elements
Authors: Michaloudis Georgios , Schweizerhof Karl 
Published: December 2008

AbstractIn the simulation of shell problems in which plastic stresses in thickness direction are developed, the necessity of a more accurate integration through thickness using more integration points e.g. Gauss points becomes obvious, often increasing respectively the computational time and effort. A new algorithm is proposed for the automatic adaptation of the integration formula in thickness direction during the computation. Simple engineering criteria are found to define the time‐point and the regions to increase the number of integration points. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A coupled MD–FE approach for contact at microscopic length–scales (Poster Presentation)
Authors: Helmich Tobias , Nackenhorst Udo 
Published: December 2008

AbstractContact at very tiny length–scales is characterized by atomic force interaction. A technical application of interest is the atomic force microscope (AFM). A coupled molecular dynamics (MD) – finite element (FE) approach is outlined to tackle the multi–scale problem by numerical simulation. Guidelines for the spatial discretization are derived from convergence studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)