bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time transformed mixed integer optimal control problems with impacts
Authors: Ringkamp Maik , Ober‐Blöbaum Sina , Leyendecker Sigrid 
Published: October 2016

AbstractThe solutions of mixed integer optimal control problems (MIOCPs) yield optimized trajectories for dynamical systems with instantly changing dynamical behavior. The instant change is caused by a changing value of the integer valued control function. For example, a changing integer value can cause a car to change the gear, or a mechanical system to close a contact. The direct discretization of a MIOCP leads to a mixed integer nonlinear program (MINLP) and can not be solved with gradient based optimization methods at once. We extend the work by Gerdts [1] and reformulate a MIOCP with integer dependent constraints as an ordinary optimal control problem (OCP). The discretized OCP can be solved using gradient based optimization methods. We show how the integer dependent constraints can be used to model systems with impact and present optimized trajectories of computational examples, namely of a lockable double pendulum and an acyclic telescope walker. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Switching time optimization for a PDE constrained optimal control problem of bang‐bang type
Authors: Vossen Georg 
Published: October 2016

AbstractWe consider a well‐known optimal control problem subject to the heat equation where the control variable appears linearly as a boundary control in a Robin type boundary condition. Here, we describe an alternative numerical method to solve the problem by a switching time optimization approach. The method has so far been successfully applied to ODE problems and offers several advantages according to second order sufficient conditions and sensitivity analysis. We discuss theoretical aspects and present numerical results to illustrate the effectiveness of the method. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Disturbance decoupling for descriptor systems by behavioral feedback
Authors: Berger Thomas 
Published: October 2016

AbstractWe study disturbance decoupling for linear descriptor systems. Compared to previous approaches, where state feedback is used, we use the concept of behavioral feedback which allows to study a larger class of systems. We derive geometric characterizations for solvability of the disturbance decoupling problem following the classical approach. Exploiting the freedom in the choice of the behavioral feedback we show that whenever disturbance decoupling can be achieved by behavioral feedback we may additionally achieve autonomous zero dynamics. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some Remarks concerning Flatness and the Parameterization of the System Variables by a Flat Output
Authors: Kolar Bernd , Schöberl Markus , Schlacher Kurt 
Published: October 2016

AbstractFor flat systems, by definition the state‐ and input variables can be parameterized by the flat output and its time derivatives. In the present contribution, for special classes of flat outputs like e.g. flat outputs that only depend on the state, we derive upper bounds for the number of time derivatives that occur in this parameterization. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inner‐Outer Factorization via Lur'e Equations
Authors: Reis Timo , Voigt Matthias 
Published: October 2016

AbstractIn this paper we construct inner‐outer factorizations of transfer functions governed by linear time‐invariant differential‐algebraic systems. This construction is based on the solution of certain Lur’e equations. In contrast to previous work we do not assume any condition apart from behavioral stabilizability of the underlying system realization. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tools for assessing and optimizing the energy requirements of high performance scientific computing software
Authors: Diethelm Kai 
Published: October 2016

AbstractScore‐P is a measurement infrastructure originally designed for the analysis and optimization of the performance of HPC codes. Recent extensions of Score‐P and its associated tools now also allow the investigation of energy‐related properties and support the user in the implementation of corresponding improvements. Since it would be counterproductive to completely ignore performance issues in this connection, the focus should not be laid exclusively on energy. We therefore aim to optimize software with respect to an objective function that takes into account energy and run time. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of glottal flow in surgically changed larynx
Authors: Hundertmark‐Zaušková Anna , Lehmann Ragnar , Hess Markus , Müller Frank 
Published: October 2016

AbstractAccording to clinical experience the shape of the larynx seems to have a significant impact on the airflow degree and breathing pattern. In this study we perform a set of numerical experiments simulating the glottal flow in surgically changed larynx, where the vocal folds or false vocal are modified. We are aiming to find an optimal geometry of the larynx in terms of easiness for breathing. To this goal we numerically solve the system for weakly compressible Navier–Stokes equations using the finite element method and we compare the airflow resistance and the volumetric flow rate for the set of geometries for inspiration as well as expiration. We discuss the optimal geometry with respect to the quality of breathing. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hybrid weakly nonconforming discretization for linear elasticity
Authors: Krämer Julian , Wieners Christian , Wohlmuth Barbara , Wunderlich Linus 
Published: October 2016

AbstractWe introduce a hybridizable discretization for problems of linear elasticity, based on a flexible weak coupling of the displacement and the normal stress across the inner element boundaries. The dual variables of the Lagrange multiplier are introduced as hybrid trace variables. A reduction of the equation system to these variables allows for an efficient parallel implementation. The performance of an adaptive choice of the hybrid degrees of freedom is demonstrated by a numerical example with a corner singularity. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multirate finite step methods for linear acoustics
Authors: Naumann Andreas , Wensch Jörg 
Published: October 2016

AbstractMany processes contain phenomena on different time scales, leading to model equations with fast and small parts. There are several approaches to solve these equations, like additive Runge Kutta methods or multirate infinitesimal steps methods (MIS). Both methods make use of the additive splitting of the ODE in fast and small parts. The multiple infinitesimal step method integrates the slow part with a large macro stepsize, whereas the fast terms are solved with several smaller steps of a simpler method. The order conditions of a MIS method are derived under the assumption of the exact integration of the fast parts.We develop the multirate finite step methods (MFS). These methods are derived from the MIS methods, by taking a simple small scale integrator for the fast terms. This small scale integrator uses the same number of steps in each stage. With these assumptions, we derive the order conditions, such that the order is independent in the number of small steps. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Kinetic energy preserving DG schemes based on summation‐by‐parts operators on interior node distributions
Authors: Ortleb Sigrun 
Published: October 2016

AbstractIn this work, a kinetic energy preserving DG scheme in one space dimension using Gauss‐Legendre nodes is presented. Stability problems will be demonstrated when using interface terms that are derived from the Lobatto nodes within the Gauss‐Legendre skew‐symmetric DG formulation. However, combined with correct interface terms, the skew‐symmetric DG scheme constructed on Gauss‐Legendre nodes is expected to yield higher accuracy compared to its Gauss‐Lobatto counterpart. This advantage is demonstrated in the case of viscous compressible flow computation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Automated Generation of Performance Values for Algorithmic Differentiation
Authors: Sagebaum Max , Albring Tim , Gauger Nicolas R. 
Published: October 2016

AbstractThe transition from simulation software to optimization software is often quite cumbersome and error prone. With Algorithmic Differentiation(AD) a semi automatic transition can be achieved, but most of the times the performance characteristics of the modified software are not clear in advance. Therefore the performance model from Griewank is tested against real world examples and an automated measurement for the performance characteristics of the hardware is proposed. This enables a more accurate calculation of the performance characteristics of the modified software. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled Thermo‐Mechanical and Wear Effects on the Analysis of High Speed Railway Brake Systems
Authors: Srisupattarawanit T. , Schiefer F. , Ostermeyer G.‐P. 
Published: October 2016

AbstractThe high speed railway brakes transfer a large amount of kinetic energy into heat. The temperature during a brake operation could reach values higher than 90 °C. The dynamics of the brake system is rather complicated with respect to the multiphysical phenomena. In this paper, the thermo‐mechanical coupling are investigated combined with the loos of brake material due to wear. The coupled model is discretized by conventional finite element method. Different coupled algorithms have been tested. Various scenarios have been simulated and shown reasonable results. The temperature and deformation on pad and disc, especially the thermal deformation of disc the so–called coning effect can also be prescribed with this coupled multiphysics model. Furthermore, the tapered wear on brake pads is also discussed as a requirement of railway brake design in terms of durability. Thereby, the Ehlers's model is normally used to minimize tapered wear by selecting an adequate point of applied braking force. An extended Ehlers's model is also presented here, which concerns wear effect based on Archard's model. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Perturbations of positive strongly continuous semigroups on AM spaces
Authors: Wintermayr Jens 
Published: October 2016

AbstractWe give a definition for positivity on an extrapolation space for positive strongly continuous semigroups. We prove a perturbation result on AM spaces for positive semigroups by positive operators. Finally, we give an example for this kind of perturbations. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dichotomy properties of Hamiltonians for linear systems in extrapolation spaces
Authors: Wyss Christian 
Published: October 2016

AbstractFor the Hamiltonian operator matrix from systems theory the existence of invariant subspaces corresponding to the spectrum in the right and left half‐plane is shown. The control and observation operators are unbounded in the sense that they map into extrapolation spaces, thereby allowing for PDE systems with control and observation on the boundary. The invariant subspaces are then used to construct solutions of the corresponding Riccati equation. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tree forcings and sharps
Authors: Castiblanco Fabiana , Schlicht Philipp 
Published: October 2016

AbstractThe Levy‐Solovay theorem and its variants show that various large cardinals are preserved under small forcings. We study the preservation of consequences of large cardinals under proper forcings. In particular, we consider the preservation of the statement that every real has a sharp for classical tree forcings. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
No large sets which can be translated away from every Marczewski null set
Authors: Brendle Jörg , Wohofsky Wolfgang 
Published: October 2016

AbstractThere is no set of size continuum which is “s0‐shiftable”, i. e., which can be translated away from every set in the Marczewski ideal s0 (where a set of reals is in s0 if for every perfect set there is a perfect subset disjoint from it). (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization of Cahn–Hilliard‐type equations with unbounded potentials
Authors: Liero Matthias , Reichelt Sina 
Published: October 2016

AbstractIn this note we recall two approaches to evolutionary Γ‐convergence for classical gradient systems: evolutionary variational inequalities versus energy‐dissipation principles. Following [1] we apply both approaches to homogenize Cahn–Hilliard‐type equations with rapidly oscillating coefficients and quite general potential. Here the focus is on the Γ‐convergence of the energy functional, which we prove without assuming any growth conditions for the convex part of the potential. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physiological loading of cartilage replacement materials in a bioreactor environment
Authors: Fuhrmann‐Nelles Nadine , Willenberg Wolfgang , Stoffel Marcus , Markert Bernd 
Published: October 2016

AbstractTrying to replace injured cartilage by implants is a common practice in biomedical engineering. These implants can be non‐seeded or seeded with human cartilage cells. To initiate cell multiplication and oriented cell growth in cell seeded implants, the implants are cultivated and usually stimulated electrically or mechanically in a bioreactor before implanting.In the present study, a knee testing bench combined with a bioreactor environment is developed. Doing so, it is possible to stimulate such implants controlled in a physiologically consistent, multi‐dimensional way. The implants are placed in a recreated human knee joint and stimulated with several physiological load cycles of reproduced walking. After some days, the implanted material can be removed and mechanically and biologically evaluated in cooperation with the RWTH Aachen University Hospital.The new experimental set‐up enables us for the first time to study the remodelling effect, the efficiency of the preconditioning as well as the influence of the body‐conformable load on the material. Furthermore, the need of cell colonisation in the implants shall be investigated. To understand the correlation between tissue remodelling and mechanical load history, the experiment is also numerically investigated, based on a geometrically realistic FE model of the recreated human knee and appropriate material models for the involved structures. Doing so, the strains and stresses, as well as the shear forces in the implant can be evaluated. The results will be compared to experimental data. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conservation properties of higher order time stepping schemes based on variational integrators
Authors: Bartelt Matthias , Groß Michael 
Published: October 2016

AbstractThis paper deals with higher order accurate variational integrators for finite element systems. The variational integrator (VI) is based on higher order LAGRANGE polynomials as shape functions and a higher order GAUSSIAN quadrature rule. The goals of this paper are to implement a discrete gradient to preserve the balance of total energy and fulfill the constraints with the LAGRANGE multiplier method and a NEWTON‐COTÊS quadrature rule. We show the calculation of bearing forces from the LAGRANGE multipliers, which are essential for the balance of total linear momentum and the balance of total angular momentum. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some heuristics about the ecosystem of mathematics research data
Authors: Teschke Olaf 
Published: October 2016

AbstractLike in other sciences, research data play a growing role in mathematics, but in contrast to classical objects like measurements in physics they are much more heterogeneous. They may take the shape of abstract objects like the collection of integer sequences in OEIS, algorithms and their implementations as mathematical software, libraries of test problems or statistical data. From an infrastructure viewpoint, which aims at sustainable and connected data repositories which facilitate researchers to use existing information efficiently, it is essential to define an appropriate framework that allows not just storage but also connection and retrieval of the various types of data. Recently, there have been promising attempts to define standards for mathematical software, but the general task remains a big challenge, which is also addressed within the recently initiated GDML working group of the IMU. This is especially important in the fields of applied mathematics where research is often connected to research data originating from applications. The goal of this talk is a first attempt to analyse the diverse ecosystem of research data based on reference data from zbMATH. This approach has worked quite well for mathematical software, resulting in the formation of the swMATH database. Though reference data involve always a bias, the collected information of about 16 million reference data in zbMATH may be useful to identify the recent needs of researchers in different fields pertaining mathematical research data, and we discuss several aspects of such an analysis. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rheological and thermal stability of novel weak gels based on sulfonated polyacrylamide/scleroglucan/chromium triacetate
Authors: Alvand Ehsan , Aalaie Jamal , Hemmati Mahmood , Sajjadian Vali Ahmad 
Published: October 2016

AbstractThe present study deals with weak gels based on sulfonated polyacrylamide (SPA)/scleroglucan (SC)/Cr3+ with an exceptional thermal stability in electrolyte media. The rheological results showed that on increasing the SC concentration the shear viscosity and storage modulus of the SPA/SC/Cr3+ system were increased and the dependence of the storage modulus on frequency became weaker. The yield stress of the SPA/SC/Cr3+ system was higher than that of the corresponding SPA/SC system. The thermochemical stability increased with increasing relaxation time. The SPA/SC/Cr3+ semi‐interpenetrating network exhibited the lowest viscosity loss in electrolyte media; therefore this system may be a potential candidate for enhanced oil recovery applications. © 2016 Society of Chemical Industry
Finite frequency fault detection for networked systems with access constraint
Authors: Long Yue , Park Ju H. , Ye Dan 
Published: October 2016

SummaryThis paper addresses a fault detection strategy in finite frequency domain for networked system with communication constraints and packet loss. The considered communication constraint is that only one data packet can gain into the networks at each time‐slot, and the fault detection filters complete the task with only partially available measurements. With consideration of the data packet loss and the stochastic scheduling protocol, a nonhomogeneous Markov jump system is firstly derived to describe the networked systems. For this class of systems, the generalized Kalman–Yakubovic–Popov lemma‐based finite frequency fault detection filter design methods are invalid. To tackle this problem, a new mode‐dependent lemma is developed to capture the system performance in finite frequency domain. Further, a set of fault detection filters are designed corresponding to the accessed nodes accordingly. Finally, an example is given to show the effectiveness of the proposed fault detection approach. Copyright © 2016 John Wiley & Sons, Ltd.
Influence of Different Kinds of Music on Walking in Children
Authors: Reychler Gregory , Fabre Justine , Lux Amandine , Caty Gilles , Pieters Thierry , Liistro Giuseppe 
Published: October 2016

Abstract

Purpose:
The aim of this study was to evaluate the effect of different kinds of music on submaximal performance and exercise tolerance in healthy children by means of the 6-minute walking test (6MWT) and to explore the influence of gender.

Design:
Cross-over study.

Method:
Ninety-seven children performed 6MWT in four conditions (without music, with their preferred music, with slow and with fast music). Distance, cardio-respiratory parameters, perceived exertion rate, and amount of dyspnea were measured.

Findings:
Walked distance depended on the kind of music (p = .022). To listen to fast music promoted a longer distance when compared with slow music. Walked distance was not influenced by gender (p = .721) and there was no interaction between music and gender for walked distances (p = .069). The other parameters were not modified by music and gender.

Conclusion:
Music influences submaximal performances without modifying exercise tolerance in healthy children.

Clinical Relevance:
Music does modify submaximal performance in children.
Solely Biomass‐Derived Polyethylene Terephthalate (PET): Conversion of Bio‐based Isoprene and Acrolein to p‐Xylene and Terephthalic Acid
Authors: Wang Fei , Tong Zhaohui 
Published: October 2016

AbstractThere exist significant challenges in the synthesis of solely biomass‐derived p‐xylene and terephthalic acid (TPA), the monomer precursors of polyethylene terephthalate (PET). Herein, we describe a flexible synthetic route to prepare either p‐xylene or TPA from biomass‐derived isoprene and acrolein, which avoids harsh reaction conditions such as high pressure or extreme low temperature. The route starts from 4‐methyl‐cyclohex‐3‐enecarbaldehyde, the product of Diels‐Alder reaction of isoprene and acrolein. Then p‐xylene was successfully obtained by subsequent reduction and aromatization reactions using either environment‐friendly solvents or in neat. In addition, this route was further modified for a process to prepare both p‐xylene and TPA. By using the same intermediate after Diels‐Alder reaction, an aromatization reaction was followed by a reduction to p‐xylene or an oxidation to directly TPA in an overall yield of 32% over three steps.
Computational Study of Cu–Containing Artificial DNA: Twist Angle Dependence of Magnetism
Authors: Orimoto Yuuichi , Aoki Yuriko 
Published: October 2016

AbstractThe magnetic properties of a copper‐containing artificial DNA (a 2,6‐dipicolinate−Cu(II)−pyridine complex‐based artificial DNA) were theoretically investigated at the ab initio molecular orbital (MO) theory level from the standpoint of the relationship between the twist angle about the DNA chain axis and its high‐spin (HS) stability. It was found that HS stability gradually increased with increasing twist angle at the Hartree‐Fock level. Consideration of the electron correlation effects using a perturbation theory emphasized on the twist angle dependence of HS stability (leading to an increase in the magnetic contrast for the twist angle). Detailed analyses based on MOs revealed that the trend in HS stability is related to the twist angle dependence of the delocalization of singly occupied MOs for the highest spin state and that of the highest doubly occupied MO for the lowest spin state.
Magnetic Responsive Polymer Nanocomposites with In–situ Tunable Anisotropy by Magnetic Self‐Organization
Authors: Zhang Kai , Wang Ming , Shi Yu‐Dong , Chen Yi‐Fu , Zeng Jian‐Bing , Huang Jin 
Published: October 2016

AbstractThe tunable magnetic response has rarely been achieved in conventional magnetic responsive polymer nanocomposites (MRPNCs). Here we show a new approach to offer effective rules for designing novel MRPNCs with in‐situ tunable magnetic anisotropy which are self‐organized in a low magnetic field via controlling the self‐organization temperature between the melting points of isotactic polypropylene (iPP) and poly(ϵ‐caprolactone) (PCL), and magnetic ferroferric oxide (Fe3O4) nanoparticles selectively dispersing in PCL with low melting temperature. The iPP/PCL/Fe3O4 nanoparticles with magnetic anisotropy not only exhibit tunable rotation behavior, but also show tunable mechanical enhancement. The deflection force, tensile strength and Young modulus of the iPP/PCL/Fe3O4 nanocomposites with 10 wt% Fe3O4 particles with magnetic anisotropy show nearly 3.2, 3.2 and 2.7 times higher than that of the samples with random dispersion of magnetic nanoparticles, respectively.