bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow rate measurements in turbulent liquid metal channel flow using Time‐of‐Flight Lorentz force velocimetry
Authors: Jian Dandan , Karcher Christian 
Published: December 2012

AbstractNon‐contact flow control and flow measurements in hot and aggressive metal melts are big challenges in metallurgical applications. Time‐of‐Flight Lorentz force velocimetry (ToF LFV) is an electromagnetic measurement technique to meet these challenges. Our experimental results demonstrate that this method is well suited to measure flow rate in turbulent liquid metal channel flow without knowledge of both melt and magnetic field properties. Moreover, the measured flow profiles are in very good agreement with predictions of numerical simulations using the commercial program Package FLUENT MHD. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sufficient conditions for second order L2‐convergence of the fractional step theta method
Authors: Zanger Florian 
Published: December 2012

AbstractWe consider the fractional step theta time stepping procedure for the non‐stationary incompressible linear Stokes equations in a cylindrical domain (0, T) × Ω, where Ω is a bounded domain in ℝn. Using energy estimates and assuming a certain degree of regularity for the data, we show second order L2‐convergence. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Love's problem for hyperbolic thermoelasticity
Authors: Gawinecki Jerzy August , Rafa Józef , Łazuka Jaroslaw 
Published: December 2012

AbstractIn our paper we investigated the initial‐boundary value problem for elastic layer situated on half space of another elastic medium. In this medium the thermomechanical interactions were taken into consideration. The system of equations with initial‐boundary conditions describes the phenomenon of wave propagation with finite speed. In our problem there are two surfaces ie. free surface and contact surface between layer and half space. On the free surface are setting boundary conditions for normal and tangent surface force. We consider two types of contact between layer and half‐space: rigid contact and slip contact. The initial‐boundary value problem was solved by using integral transformations and Cagniard‐de Hoope methods. From the solution of this problem follows that in layer and half space exist some kind of thermoelastic waves. We investigated moreover the conditions which should be fullfiled for propagation of Rayleigh and Love's type waves on the contact surface between layers and half space. The results obtained in our investigation were used in technical applications especially engineering design and diagnostics of roads and airfields. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On asymptotic behavior for 1‐dimensional functional of Ginzburg‐Landau type with internally‐externally created oscillations of minimizers
Authors: Raguz Andrija 
Published: December 2012

AbstractIn this note we provide a kind of generalization of the well‐known notion of internally (externally, resp.) created oscillations of minimizers of non‐convex integrands in the calculus of variations. As an example, we consider a class of 1‐dimensional Ginzburg‐Landau functionals (the simplest case being considered in the paper G. Alberti, S. Muller: A new approach to variational problems with multiple scales, Comm. Pure Appl. Math. 54, 761–825 (2001)). We describe asymptotic behavior leading to multiple small scale separation as parameter epsilon tends to zero. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Ultra Relativistic Euler Equations
Authors: Abdelrahman Mahmoud , Kunik Matthias , Warnecke Gerald 
Published: December 2012

AbstractWe consider the relativistic Euler equations in isentropic fluids with the equation of state $p = {\rho \over 3}$, which is the ultra‐relativistic limit. We analyze the single shocks. We study the shock interaction, and give explicit example for the non‐backward uniqueness. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Almost Sure Stability Analysis of Parametric Roll in Random Seas Based on Top Lyapunov Exponent
Authors: Dostal Leo , Kreuzer Edwin , Sri Namachchivaya Navaratnam 
Published: December 2012

AbstractStability analysis of the upright position of a ship in random head or following seas is presented. Such seas lead to parametric excitation of roll motion due to periodic variations of the righting lever. The development of simple criteria for the occurrence of parametric induced roll motion in random seas is of major interest for improvement of the international code on intact stability provided by the International Maritime Organization. The stability analysis in random seas is based on the calculation of the top Lyapunov exponent using the fact, that a negative top Lyapunov exponent yields no roll motion. With this findings, roll motion can be excluded for specific sea states. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Analysis of Stochastic Fiber Lay‐Down Models: Geometry and Convergence to Equilibrium of the Basic Model
Authors: Grothaus Martin , Klar Axel , Maringer Johannes , Stilgenbauer Patrik 
Published: December 2012

AbstractThe so‐called fiber lay‐down models arise in the production process of nonwovens. We introduce the generalized version of the basic fiber lay‐down model which can precisely be formulated in abstract form as some manifold‐valued stochastic differential equation. An important criterion for the quality of the nonwoven material is how the solution to the associated Fokker‐Planck equation converges towards its stationary state. Especially, one is interested in determining the speed of convergence. Here we present some results concerning the long‐time behavior by using classical stochastic methods as well as modern analytic methods from the theory of hypocoercivity. Demanding mathematical difficulties arising since the equation is degenerate. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the two‐step method for solving nonlinear equations with nondifferentiable operator
Authors: Shakhno Stepan , Yarmola Halyna 
Published: December 2012

AbstractWe study a local and a semilocal convergence of the two‐step method for solving nonlinear equations with a nondifferentiable operator. Its method is based on two methods of order of convergence $1 + \sqrt{2}$. We carry out the numerical research on test problems and do the comparison of obtained results. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
How Competitive is the ADI for Tensor Structured Equations?
Authors: Mach Thomas , Saak Jens 
Published: December 2012

AbstractIn [1] we presented an extension of the alternating direction implicit (ADI) method for the solution of Lyapunov equations

to higher dimensional problems. The vectorized form of the Lyapunov equation is

We considered the generalization of this equation of the form

The tensor train structure is one possible generalization of the low rank factorization we find in the right hand side of (1). Therefor we assume B to be of tensor train structure. We showed that in analogy to the low rank ADI case the solution X can be generated in tensor train structure, too. Further we provided an algorithm that computes X using a generalization of the ADI method.Here we compare our new tensor ADI method with an density matrix renormalization group (DMRG) solver for tensor train matrix equations and with matrix equation solvers to investigate the competitiveness of our new solver. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subspace Iteration Methods in terms of Matrix Product States
Authors: Huckle Thomas , Waldherr Konrad 
Published: December 2012

AbstractWhen dealing with quantum many‐body systems one is faced with problems growing exponentially in the number of particles to be considered. To overcome this curse of dimensionality one has to consider representation formats which scale only polynomially. Physicists developed concepts like matrix product states (MPS) to represent states of interest and formulated algorithms such as the density matrix renormalization group (DMRG) to find such states. We consider the standard Lanczos algorithm and formulate it for vectors given in the MPS format. It turns out that a restarted version which includes a projection onto the MPS manifold gives the same approximation quality as the well‐established DMRG method. Moreover, this variant is more flexible and provides more information about the spectrum. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bounds on the Range of Multivariate Rational Functions
Authors: Garloff Jürgen , Schabert Antek , Smith Andrew P. 
Published: December 2012

AbstractBy utilising the expansion of a polynomial into Bernstein polynomials, we construct bounds for the range of a multivariate rational function over a box. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SPAI Preconditioners for HPC Applications
Authors: Sawyer William , Vanini Carlo , Fourestey Gilles , Popescu Radu 
Published: December 2012

AbstractIterative methods to solve systems of linear equations Ax = b usually require preconditioners M to speed convergence. But the calculation of many preconditioners can be notoriously sequential. The sparse approximate inverse preconditioner (SPAI) has particular potential for high performance computing [1]. We have ported the SPAI algorithm to graphical processing units (GPUs) within NVIDIA's CUSP library [2] for sparse linear algebra. GPUs perform well on dense linear algebra problems where data resides for long periods on the device. Since the underlying minimization problems are independent, they are mapped to separate thread‐blocks, and an optimized QR algorithm implemented using NVIDIA's CUBLAS library is employed on each.Traditionally the challenge has been to determine a sparsity pattern Sp(M) of the preconditioner dynamically [3], which reduces the condition number of MA to a degree where a preconditioned iterative solver such as GMRES becomes computationally viable. Due to the extremely high performance of the GPU, it is possible to consider initial sparsity patterns much denser than have been previously considered. We therefore consider a fixed sparsity patterns to simplify the GPU implementation.We evaluate the performance of the resulting preconditioner on a standard set of sparse matrices, and compare SPAI to other preconditioners. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shape sensitivity analysis in the extended finite element method
Authors: Barthold Franz‐Joseph , Materna Daniel 
Published: December 2012

AbstractThe contribution is concerned with the derivation and implementation of shape sensitivity analysis in the context of the extended finite element method (xfem). Here, the displacement approximation is enhanced in order to model strong and weak discontinuities along the interfaces and cracks. Consequently, sensitivity analysis must be accomplished for the extended formulation based on a sub‐integration technique on sub‐domains of the cut elements. This cumbersome and error‐prone work can be circumvent using a standard treatment of sub‐elements on an appropriately defined sub‐mesh. These modifications guarantee exact analytical sensitivities even for distorted finite element domains. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The bang‐bang funnel controller: An experimental verification
Authors: Hackl Christoph , Trenn Stephan 
Published: December 2012

AbstractWe adjust the newly developed bang‐bang funnel controller such that it is more applicable for real world scenarios. The main idea is to introduce a third “neutral” input value to account for the situation when the error is already small enough and no control action is necessary. We present experimental results to illustrate the effectiveness of our new approach in the case of position control of an electrical drive . (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Volumetric Anisotropic Diffusion Computation on GPUs
Authors: Kuijper Arjan , Schwarzkopf Andreas , Kalbe Thomas , Goesele Michael 
Published: December 2012

AbstractWe present an efficient implementation of volumetric anisotropic image diffusion on modern programmable graphics processing units (GPUs). We avoid the computational bottleneck of a time consuming eigenvalue decomposition in ℝ3. Instead, we use a projection of the Hessian matrix along the surface normal onto the tangent plane of the local isodensity surface and solve for the remaining two tangent space eigenvectors. We derive closed formulas to achieve this resulting in efficient GPU code. Our most complex volumetric anisotropic diffusion gains a speed up of more than 600 compared to a CPU solution [1]. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An Estimation Theoretical View on Ambrosio‐Tortorelli Image Segmentation
Authors: Krajsek Kai , Dedovic Ines , Scharr Hanno 
Published: December 2012

AbstractIn this paper, we examine the Ambrosio‐Tortorelli (AT) functional [1] for image segmentation from an estimation theoretical point of view. Instead of considering a single point estimate, i.e. the maximum‐a‐posteriori (MAP) estimate, we adopt a wider estimation theoretical view‐point, meaning we consider images to be random variables and investigate their distribution. We derive an effective block‐Gibbs‐sampler for this posterior probability density function (PDF) based on the theory of Gaussian Markov random fields (GMRF) [2]. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discrete Gradient Flows on surfaces using subdivision
Authors: Grundel Sara 
Published: December 2012

AbstractGradient flows on surfaces play a role in a wide range of applications, for example in biological modelling, computer graphics and shape optimization. We present an approach to compute a discrete gradient flow by using a newly developed C2‐smooth subdivision algorithm. We will briefly present the subdivision algorithm and how we can use it to compute the mean curvature flow. This method can be used similarly for many other gradient flows. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hybrid GPU Accelerated Mesoscopic Particle Simulation
Authors: Fischer Katrin , Ostermeyer Georg‐Peter 
Published: December 2012

AbstractDuring the past few years, the performance enhancement of existing algorithm implementations through massive parallelization on modern graphics processing units (GPUs) based on NVIDIA's Compute Unified Device Architecture (CUDA) has become very popular in a large variety of applications. Particle methods e.g. are dedicated for parallelization because of their basic algorithmic structure. The neighbourhood search, the computation of interaction forces and the final state update via time integration can be parallelized directly among the particles.In order to evaluate the potential of such a GPU implementation compared to the single CPU execution, a parallel and hybrid implementation with OpenMP and CUDA has been developed for a special particle method, the so‐called mesoscopic particle method. This method takes into account mechanical as well as thermodynamical degrees of freedom. On the basis of a hybrid implementation, the performances on different types of execution architectures (sequential on single CPU core, parallel on multi‐core CPU, parallel on GPU) can be determined and compared. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Well‐posedness and Conservativity for Linear Control Systems (Part 1)
Authors: Picard Rainer , Trostorff Sascha , Waurick Marcus 
Published: December 2012

AbstractWe discuss a class of linear control systems in a Hilbert space setting. The aim is to show that these control systems fit in a particular class of evolutionary equations such that the discussion of well‐posedness becomes easily accessible. We exemplify our findings by a system with unbounded control and observation operator. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Uncertainty Quantification in numerical Aerodynamic via low‐rank Response Surface
Authors: Litvinenko Alexander , Matthies Hermann G. 
Published: December 2012

AbstractWith the example from numerical aerodynamic we illustrate how uncertainties in the input data: parameters and computational domain propagate into the solution. The mathematical model is described via a Navier‐Stokes system of equations with a k‐ω turbulence model. The computing domain is the RAE‐2822 airfoil. To reduce storage requirement and computing time, we introduce a low‐rank approximation of the whole set of realisations of the uncertain solution. This approximation allows us to compute a low‐rank approximation of the response surface and then perform post‐processing with a linear complexity and with drastically reduced memory requirements. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approximation of the stochastic Galerkin matrix in the low‐rank canonical tensor format
Authors: Wähnert Philipp , Litvinenko Alexander , Espig Mike , Matthies Hermann G. , Hackbusch Wolfgang 
Published: December 2012

AbstractIn this article we describe an efficient approximation of the stochastic Galerkin matrix which stems from a stationary diffusion equation. The uncertain permeability coefficient is assumed to be a log‐normal random field with given covariance and mean functions. The approximation is done in the canonical tensor format and then compared numerically with the tensor train and hierarchical tensor formats. It will be shown that under additional assumptions the approximation error depends only on smoothness of the covariance function and does not depend either on the number of random variables nor the degree of the multivariate Hermite polynomials. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two model formulations for gradient crystal plasticity
Authors: Klusemann Benjamin , Bargmann Swantje , Svendsen Bob 
Published: December 2012

AbstractThe purpose of the current work is the formulation of two different (algorithmic) models for multiscale inelastic materials whose behavior is influenced by the evolution of inelastic microstructure and the corresponding material or internal lengthscales. The two models are compared with each other, depending in particular on how the inelastic deformation and dislocation density are modeled. The work is a first extension of the investigation in Klusemann et al. [1] to two‐dimensions. In the first model, the corresponding displacement and inelastic local deformation are modeled as global via weak field relations, and the dislocation density is a local quantity and solved for via a strong field relation. In the second model, displacement and dislocation density are modeled as global, and the inelastic deformation as local, in this sense. The influence for the modeling results is discussed. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Production simulation by means of a structure tensor‐based framework of anisotropic plasticity
Authors: Vladimirov Ivaylo N. , Reese Stefanie 
Published: December 2012

AbstractIn this work, we discuss a hyperelasticity‐based concept of finite strain plasticity with combined hardening using evolving structure tensors to represent the evolution of elastic and plastic anisotropy. By defining the Helmholtz free energy density and the yield surface as functions of the evolving structure tensors, we are able to describe both evolving elastic and plastic anisotropy, respectively. The model considers also nonlinear kinematic and isotropic hardening and is derived from a thermodynamic framework based on the multiplicative split of the deformation gradient. Exploiting the dissipation inequality leads to the important result that the model includes only symmetric tensor‐valued internal variables. Evolution of anisotropy is investigated by means of simulations of cylindrical deep drawing of metal sheets. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduction of Plasticizer Leaching from PVC by Barrier Coatings Deposited Using DBD Processes at Atmospheric Pressure
Authors: Barreto Mercedes Cerezuela , Borris Jochen , Thomas Michael , Hänsel Renate , Stoll Michael , Klages Claus‐Peter 
Published: December 2012

AbstractBarrier coatings against plasticizer leaching are deposited on flexible polyvinylchloride (PVC) films typically used in flooring or in the automotive industry. Octamethylcyclotetrasiloxane (OMCTS) and hexamethyldisiloxane (HMDSO) are plasma polymerized using plasma‐activated CVD (PA‐CVD) based on an atmospheric pressure (AP) dielectric barrier discharge (DBD). A reduction in plasticizer leaching higher than 80% is achieved with these coatings. The effect of the monomer flow rate, discharge power, and oxygen flow rate on the barrier efficiency is investigated. The coating composition of the best barrier coating has been identified and the long‐time barrier efficiency in contact with an organic solvent has been studied. magnified image
A Relict Pronival (Protalus) Rampart in the Tararua Range, North Island, New Zealand
Authors: Brook Martin S. , Williams Jacob 
Published: December 2012

ABSTRACTDebris ridges in New Zealand are routinely assumed to be ‘moraines’ and used as key Southern Hemisphere paleoclimatic sites without detailed evaluation of ridge origin. Here we assess the origin of a debris ridge adjacent to Dundas Ridge in the Tararua Range, North Island, New Zealand, through measurements of ridge morphology and sedimentary properties. The ridge has a steep c. 35° distal slope (height 18 m), compared with the c. 19° proximal slope (height 6 m), and on all transects the distal slopes contain the coarsest material (median b‐axis clast widths of 0.18‐0.25 m), compared to distal samples (0.34‐0.37 m). Clast shape (C40 range 40‐60%) and angularity (RA>65%) indicate typically angular and ‘slabby’ clasts, and along with the lack of fines, and the ca. 40‐m‐distance between the ridge crest and the foot of the backwall, lead us to reject a glacial (moraine) origin for the ridge. The single ridge morphology precludes a protalus rock glacier origin, while the lack of a broad hillslope scar and debris apron beyond the ridge excludes a landslide origin. Instead, we interpret the ridge as a pronival (protalus) rampart formed by supranival debris supply–from the ca. 200 m‐high southeastern slopes of Dundas Ridge–across a snowbed. Re‐distribution of snow by prevailing westerlies from Mt Dundas Ridge into the basin would have nourished the snowbed, which is likely to have formed during the interval 24‐18 ka BP, when a minor alpine‐style glaciation affected sectors of the Tararua Range. This is the first pronival rampart detailed in New Zealand, raising the possibility that debris ridges of pronival origin may also be present elsewhere in New Zealand's mountains. Copyright © 2012 John Wiley & Sons, Ltd.