bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using Swap‐Based Search Trees to obtain Solutions for Resource Constrained Project Scheduling Problems
Authors: Bügler Maximilian , Borrmann André 
Published: December 2014

AbstractThe high level of complexity in modern construction projects causes the problem of scheduling the involved tasks under precedence and resource constraints to be a great challenge. Additionally applications on real construction sites require non linear and non continuous constraints and objective functions. In order to optimize large scale construction sites in practice, this paper proposes a new optimization approach based on creating search trees from swapping and delaying tasks. The convergence of the proposed algorithm is analyzed and its complexity is compared to other available algorithms. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Convergence Analysis of a Two‐Step Modification of the Gauss‐Newton Method
Authors: Iakymchuk Roman , Shakhno Stepan 
Published: December 2014

AbstractWe investigate the convergence of a two‐step modification of the Gauss‐Newton method applying the generalized Lipschitz condition for the first and second order derivatives. The convergence order as well as the convergence radius of the method are studied and the uniqueness ball of solution of the nonlinear least squares problem is examined. Finally, we carry out numerical experiments on a set of well‐known test problems. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Parameter Tuning for Multiclass Support Vector Machines in Machinery Health State Estimation
Authors: Kimotho James Kuria , Sextro Walter 
Published: December 2014

AbstractThe increasing demand for high reliability, safety and availability of technical systems calls for innovative maintenance strategies. The use of prognostic health management (PHM) approach where maintenance action is taken based on current and future health state of a component or system is rapidly gaining popularity in the maintenance industry. Multiclass support vector machines (MC‐SVM) has been identified as a promising algorithm in PHM applications due to its high classification accuracy. However, it requires parameter tuning for each application, with the objective of minimizing the classification error. This is a single objective optimization problem which requires the use of optimization algorithms that are capable of exhaustively searching for the global optimum parameters. This work proposes the use of hybrid differential evolution (DE) and particle swarm optimization (PSO) in optimally tuning the MC‐SVM parameters. DE identifies the search limit of the parameters while PSO finds the global optimum within the search limit. The feasibility of the approach is verified using bearing run‐to‐failure data and the results show that the proposed method significantly increases health state classification accuracy. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Cache‐Aware Implementation of the Spectral Divide‐and‐Conquer Approach for the Non‐Symmetric Generalized Eigenvalue Problem
Authors: Benner Peter , Köhler Martin , Saak Jens 
Published: December 2014

AbstractWe propose a new implementation of the sign function based spectral divide‐and‐conquer method for the generalized non‐symmetric eigenvalue problem. The basic idea is to use the generalized matrix sign function to split the spectrum and the corresponding deflating subspaces and to build a recursive scheme on top of this. The method focuses on an extensive usage of scalable level 3 BLAS operations in order to achieve a good performance on modern computer architectures which makes it computationally superior to current implementations of the classical QZ algorithm. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical example showing that deflations based on rotation leads to higher relative accuracy in QR algorithm
Authors: Mach Thomas , Vandebril Raf 
Published: December 2014

AbstractWe present a numerical example illustrating that the deflation procedure in Francis's implicitly shifted QR algorithm can be improved by a deflation criteria based on the QR decomposition of the upper Hessenberg matrix. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscoelasticity at Large Strain Deformations
Authors: Meyer Arnd , Schmidt Hansjörg 
Published: December 2014

AbstractWe present a theory of viscoelasticity at large strain deformations. Starting from a non‐linear weak formulation, we examine the viscoelastic stress‐strain relation and the linearised system of equations. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Domain decomposition methods for nonlinear transmission conditions
Authors: Gsell Matthias A. F. , Steinbach Olaf 
Published: December 2014

AbstractWe consider the transformation of quasilinear partial differential equations to a coupled system of linear equations, but with nonlinear transmission conditions on the interfaces. After deriving a variational formulation, we will discuss Mortar finite element discretization strategies and present a numerical example. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Actual time integration methods for elastic wave propagation analysis
Authors: Asmus Andreas , Lammering Rolf 
Published: December 2014

AbstractFor the simulation of the interaction of elastic waves in CFRP plates with inhomogeneities and defects the spectral finite element method (SEM) is under investigation. The SEM uses high‐order shape functions which are composed of Lagrange polynomials with nodes at the Gauss‐Lobatto quadrature (GLq) points. In this way we obtain a diagonal mass matrix which makes an explicit time scheme more efficient. In this paper we analyse how actual time integration methods perform in combination with the SEM. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preconditioned defect corrected averaging for parabolic PDEs
Authors: Klöppel Michael , Naumann Andreas , Wensch Jörg 
Published: December 2014

AbstractModelling physical systems with fast moving components leads to PDEs with highly oscillatory sources. Often, the time scale of the oscillation is much below the scale of the interesting variables. Time integrators must follow the scale of the fast motion, leading to long simulation times. For mechanical systems, methods like heterogeneous multiscaling and stroboscopic averaging are quite satisfactory. In case of semidiscretized PDEs, their advantage is limited. Here, we derive a smooth source term which generates a solution that coincides with the solution of the oscillatory system in stroboscopic points. The derivation involves the solution of a linear system with the solution operator of the PDE being the linear operator. Several preconditioners are developed and compared for those systems. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Residual‐based a posteriori error control for Space‐time finite element approximations of parabolic optimal control problems
Authors: Gong Wei , Hinze Michael , Zhou Zhaojie 
Published: December 2014

AbstractIn this paper we investigate a space‐time finite element approximation of parabolic optimal control problems. The first order optimality conditions are transformed into an elliptic equation of fourth order in space and second order in time involving only the state or the adjoint state in the space‐time domain. We derive a priori and a posteriori error estimates for the time discretization of the state and the adjoint state. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control of Large Deformation Elasticity by Fiber Tension
Authors: Günnel Andreas , Herzog Roland 
Published: December 2014

AbstractObject of our interest is an elastic body Ω ⊂ ℝ3 which we can deform by applying a tension along certain given short fibers inside the body. The deformation of the body is desribed by a hyperelastic model with polyconvex energy density and a special energy functional for the tension along the fibers. We seek to apply (possibly large) deformations to the body so that a desired shape is obtained. To this end, we formulate an optimal control problem for the fiber tension field. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proper orthogonal decomposition in sparse optimal control of some reaction diffusion equations using model predictive control
Authors: Ryll Christopher , Tröltzsch Fredi 
Published: December 2014

AbstractWe investigate optimal sparse control problems for reaction diffusion equations with non‐monotonous cubic non‐linearities. In particular, we consider the Schlöl equation as well as the FitzHugh‐Nagumo system. In these models, the solutions form pattern of traveling wave fronts or spiral waves. To control them turns out to be very challenging and computational difficult. The needed computational times are enormous. The use of sparse optimal control techniques was surprisingly very helpful. On the one hand the optimal control becomes sparse and on the other hand we achieve our control goals with satisfying accuracy for much less computational time then before. Trying to decrease it even more by POD model reduction does not work sufficiently well since too many POD modes are needed to approximate the solutions satisfactorily. Our second approach is the application of model predictive controls. This technique performs very well for the control aim of following a desired trajectory. An additional use of POD model reduction for each ‐ now very small ‐ time horizon yields even better results in computational time with a marginal loss of precession. This result holds for optimal controls as well as for optimal sparse controls. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Real‐time Model Predictive Control of a Pendulum
Authors: Schnelle Fabian , Eberhard Peter 
Published: December 2014

AbstractIn this work, a model predictive approach is applied on a mechanical system with a view on a real‐time capable implementation. The mechanical system is represented by a pendulum, which consists of a sphere at the end of a long, thin rod. The rod is mounted on gimbals on a cross table, which can be moved by two DC motors. The control objective is trajectory tracking of the sphere, which can be realized by the control of these motors. In this work, linear model predictive control techniques are designed for the pendulum and are simulatively compared with regard to an accurate trajectory tracking and a real‐time capable algorithm. A linear time‐invariant approach is implemented on the experiment. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Trajectory generation with rich information content
Authors: Mayr Simon , Grabmair Gernot 
Published: December 2014

AbstractOften, trajectories for mechanical systems are generated solving some optimization problem. Common approaches include time‐optimal, energy optimal, etc., motion profiles. In order to decrease mechanical wear of real plants this profiles provide, e.g., a smooth movement (rest‐to‐rest) in accordance with restrictions in jerk, acceleration and velocity. There exists a number of methods, to calculate for a given trajectory the plant feed forward action and to design stabilizing controllers. In case of parameter uncertainty the control law often exhibits some adaptive part. Unfortunately, smooth trajectories tend to contain insufficient excitation for adaption and/or identification. Therefore, we propose to consider some measure for the information content concerning some unknown parameters in the trajectory optimization problem. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discrete mechanics and mixed integer optimal control of dynamical systems
Authors: Ringkamp Maik , Ober‐Blöbaum Sina , Leyendecker Sigrid 
Published: December 2014

AbstractMixed integer optimal control problems are a generalization of ordinary optimal control problems that include additional integer valued control functions. The integer control functions are used to switch instantaneously from one system to another. We use a time transformation (similar as in [1]) to get rid of the integer valued functions. This allows to apply gradient based optimization methods to approximate the mixed integer optimal control problem. The time transformation from [1] is adapted such that problems with distinct state domains for each system can be solved and it is combined with the direct discretization method DMOC [2,3] (Discrete Mechanics and Optimal Control) to approximate trajectories of the underlying optimal control problems. Our approach is illustrated with the help of a first example, the hybrid mass oscillator. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational integrators for nonlinear electric circuits
Authors: Ober‐Blöbaum Sina , Lindhorst Henning 
Published: December 2014

AbstractThe variational framework for linear electric circuits introduced in [1] is extended to general nonlinear circuits. Based on a constrained Lagrangian formulation that takes the basic circuit laws into account the equations of motion of a nonlinear electric circuit are derived. The resulting differential‐algebraic system can be reduced by performing the variational principle on a reduced space and regularity conditions for the reduced Lagrangian are presented. A variational integrator for the structure‐preserving simulation of nonlinear electric circuits is derived and demonstrated by numerical examples. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solution of Descriptor Lur'e Equations via Even Matrix Pencils
Authors: Reis Timo , Voigt Matthias 
Published: December 2014

AbstractDescriptor Lur’e equations are an important tool for the solution of linear‐quadratic optimal control problems for differential‐algebraic systems. In this article we discuss how one can construct all solutions of these equations by the deflating subspaces of associated even matrix pencils. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Observer Design for Multirate Sampled‐Data Systems
Authors: Voigt Thorsten , Konigorski Ulrich 
Published: December 2014

AbstractThis contribution deals with the observer design for linear multirate sampled systems. The proposed algorithm is fea‐tured by a time‐invariant modelling approach. It is shown that a multirate state observer can be derived by gradually building up the observer gain matrix by means of optimization based design methods in combination with a pole placement observer design. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Open‐loop control of parameter‐dependent discrete‐time systems
Authors: Scherlein Barbara , Schönlein Michael , Helmke Uwe 
Published: December 2014

AbstractWe consider parameter‐dependent linear time‐invariant discrete‐time single input systems, where the system matrix and the input vector are assumed to depend continuously on a parameter varying over a compact interval. We face the problem of steering the zero state simultaneously arbitrarily close towards a given continuous family of desired terminal states with a finite parameter independent open‐loop input sequence. Starting from existing sufficient conditions, which include simplicity of the eigenvalues of the system matrices, we examine the case of multiple eigenvalues. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parallel time integration with multigrid
Authors: Falgout Robert , Friedhoff Stephanie , Kolev Tzanio , MacLachlan Scott , Schroder Jacob B. 
Published: December 2014

AbstractWith current trends in computer architectures leading towards systems with more, but not faster, processors, faster time‐to‐solution must come from greater parallelism. We present a family of truly multilevel approaches to parallel time integration based on multigrid reduction (MGR) principles. The resulting multigrid‐reduction‐in‐time (MGRIT) algorithms are non‐intrusive approaches, which directly use an existing time propagator and, thus, can easily exploit substantially more computational resources then standard sequential time‐stepping. Furthermore, we demonstrate that MGRIT offers excellent strong and weak parallel scaling up to thousands of processors for solving diffusion equations in two and three space dimensions. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Implementing a discontinuous Galerkin method for the compressible, inviscid Euler equations in the DUNE framework
Authors: Gallego‐Valencia Juan Pablo , Löbbert Johannes , Müthing Steffen , Bastian Peter , Klingenberg Christian , Xia Yinhua 
Published: December 2014

AbstractA discontinuous Galerkin scheme was implemented in the DUNE framework to solve the compressible, inviscid Euler equations in a multi‐dimensional Cartesian grid. It uses a HLLC Riemann solver for the numerical fluxes in the interfaces, a total variation bounded limiter to handle discontinuities, a positivity preserving limiter for near vacuum conditions, and adaptive mesh refinement (AMR). (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An adaptive moving mesh approach for hyperbolic conservation laws on time‐dependent domains
Authors: Schiessl Stefan , Marheineke Nicole , Arne Walter , Wegener Raimund 
Published: December 2014

AbstractThe general idea of moving mesh approaches is to improve the approximation quality and the numerical performance by redistributing a fixed number of discretization points. This is called rrefinement. The classical approaches are applied to partial differential equations on fixed domains. An extension to time‐dependent (expanding) domains is presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reducing of birefringence of [111]‐cut crystal rod using side‐pumping and suitable crystal rotation
Authors: Graupeter Thomas , Pflaum Christoph 
Published: December 2014

AbstractThe beam quality and output power of high power solid‐state lasers is influenced by birefringence. Inhomogeneous distribution of the thermal field inside the laser crystal rod occurs due to non‐uniform absorption of the pump light inside the crystal and a heat sink only at boundaries. Due to the photoelastic effect, this distribution leads to inhomogeneous thermal strains and birefringence inside the rod. Plane stress and plane strain assumptions for an axially symmetric pumped crystal have been used formerly for analytical models for calculating the birefringence. This model leads in case of an [111]‐cut crystal to an axially symmetric birefringence pattern. However, the shear strains in the axial‐radial plane are neglected in this former models using plane stress and plane strain assumptions. This shear strains are taken into account by full 3D numerical calculations. A threefold symmetry pattern due to the anisotropic behaviour of the photoelastic tensor, which is contradictory to the ideal use of a radial or azimuthal polarized beam, is shown by results of the birefringence simulation. A laser rod pumped at three sides with threefold symmetry is analysed in order to reduce the effect of birefringence. In this case the absorption is not axially symmetric anymore. Within the crystal in regions where pumping is stronger, the pump light absorption and consequently the temperature, the strains and birefringence are higher. The degree of three‐fold symmetry of birefringence will be reduced, if the region having a low birefringence due to the photoelastic effect is more strongly pumped than the rest of domain. This means the birefringence is affected by the rotation of crystal around its [111]‐axis. By an optimal rotation with respect to the edges of the crystal, smallest birefringence can be obtained. For generating radial or azimuthal polarizations, the output beam of this laser device is therefore more suitable. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Error estimates for the Ginzburg‐Landau approximation: an overview and recent results
Authors: Schneider Guido , Zimmermann Dominik 
Published: December 2014

AbstractWe consider quasilinear parabolic systems posed on the real line with a spatially homogeneous ground state which becomes unstable via a Hopf‐, Turing‐, or Turing‐Hopf instability. Then close to the first instability via multiple scaling analysis a Ginzburg‐Landau equation can be derived in order to describe bifurcating solutions which are slow modulations in time and space of the most unstable modes. We give an overview about the mathematical justification and explain recent error estimates. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Convergence of 2D‐Schrödinger operators with local scaled short‐range interactions to a Hamiltonian with infinitely many δ‐point interactions
Authors: Behrndt Jussi , Holzmann Markus , Lotoreichik Vladimir 
Published: December 2014

AbstractWe prove, that a Hamiltonian with infinitely many δ‐point interactions in the plane can be approximated in the norm resolvent sense by a family of Schrödinger operators with regular, local scaled short‐range potentials. Similar well known results from the 1D and the 3D case are complemented thereby. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kernel estimates for perturbations of positive semigroups
Authors: Seifert Christian 
Published: December 2014

AbstractGiven a positive C0‐semigroup T0 on L2(Ω, m) with a kernel k0, where (Ω, m) is a σ‐finite measure space, we study a suitably perturbed semigroup T and prove existence of a kernel k for T and an estimate of the k in terms of k0. In this way we extend a heat kernel estimate proven by Barlow, Grigor’yan and Kumagai [4] for Dirichlet forms perturbed by jump processes. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of potential flow using the soap film analogy – a historical review
Authors: Heitkam Sascha , Ihlenfeld Horst , Fröhlich Jochen 
Published: December 2014

AbstractThe soap film analogy is a tool for analysing potential flow in complex geometries. It has been used around 1960 in Dresden to investigate the flow in high‐pressure turbine cascades. The present paper briefly reviews the technique and reports on the comparison between historical results, achieved with the soap film analogy, and numerical simulations. It illustrates the capabilities of the method and the historical progress made since then. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A one shot method for divertor target shape optimization
Authors: Dekeyser Wouter , Reiter Detlev , Baelmans Martine 
Published: December 2014

AbstractShape optimization methods, as commonly applied in aerodynamic design applications, have recently been adapted for use in nuclear fusion divertor target design. The resulting algorithms are very efficient compared to the standard use of numerical edge plasma simulations as analysis tools only. In this paper, we highlight some numerical aspects of the underlying algorithm, focusing on a correct, nine‐point discretization of the fluxes and the need for an adjoint pressure correction equation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical Description and Algorithmization of Expert Knowledge for the Support of the Topology Optimization of Crashworthiness Structures
Authors: Ortmann Christopher , Schumacher Axel 
Published: December 2014

AbstractThis contribution deals with the mathematical description and algorithmization of expert knowledge so that this expert knowledge can be used within automatic optimization procedures with a focus on the topology optimization of crashworthiness structures. Up to now, a purely mathematical topology optimization of crashworthiness structures is not possible. The reasons for that are the nonlinearities coming from the large displacements and rotations, contact phenomena and complex material behaviour (e.g. plasticity, failure and strain rate dependency). One approach to overcome these problems by using heuristics based on expert knowledge and an application example are shown in this contribution. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)