bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐order finite elements compared to low‐order mixed element formulations
Authors: Netz T. , Düster A. , Hartmann S. 
Published: June 2013

AbstractHigh‐order finite elements are commonly compared with linear element formulations showing that, in terms of the relation between computational time and achievable accuracy, linear element formulations are inferior to high‐order elements. On the other hand, the finite element community follows the h‐version approach due to its simplicity in implementation. This article compares high‐order finite elements based on hierarchic shape functions with low‐order mixed element formulations using finite strain hyperelasticity. These comparisons are conducted from the point of view of both accuracy and efficiency as well as highly deformed structures. It also investigates improvements to minimize the overall computational effort such as parallelizing the element assemblage procedure, choosing a starting vector estimator for Newton's method, and investigating the Newton‐Chord method. The advantages and disadvantages of both finite element approaches are also discussed.
Photoelastic‐numerical treatment of Beltrami‐Michell boundary value problems
Authors: Rezini D. , Tamine T. 
Published: June 2013

AbstractOne of the main challenges of using photoelasticity has always been its complexity to determining all stress components, for it provides an unfinished solution. Indeed, the use of the Beltrami‐Michell Boundary Value Problem remains of practical interest for the study of the stress‐separation, when complemented by the photoelasticity analysis to acquire the Dirichlet conditions. The synergy of both is enhanced with the use of Finite Difference Method to work out a photoelastic‐numerical hybrid method for stress analysis under plane conditions. On the other hand, while for photoelasticity specially, annular disks under diametral compressive load are usually used as standard models allowing to check the performance of any developed method; because theoretical solutions exist. A comprehensive study has been carried out to show the photoelastic‐numerical method in order to investigate the in‐plane stress distribution using isochromatic values only on the boundaries of an annular object subjected to diametral compression. Compared with a reference work, the obtained results are more than concluding. The method is fast in the analysis for a low cost.
Hysteresis models and gravity fingering in porous media
Authors: Rätz A. , Schweizer B. 
Published: June 2013

AbstractWe study flow problems in unsaturated porous media. Our main interest is the gravity driven penetration of a dry material, a situation in which fingering effects can be observed experimentally and numerically. The flow is described by either a Richards or a two‐phase model. The important modelling aspect regards the capillary pressure relation which can include static hysteresis and dynamic corrections. We report on analytical existence and instability results for the corresponding models and present numerical calculations. We show that fingering effects can be observed in various models and discuss the importance of the static hysteresis term.
Model reduction of an elastic crankshaft for elastic multibody simulations
Authors: Nowakowski C. , Kürschner P. , Eberhard P. , Benner P. 
Published: June 2013

AbstractSystem analysis and optimization of combustion engines and engine components are increasingly supported by digital simulations. In the simulation process of combustion engines multi physics simulations are used. As an example, in the simulation of a crank drive the mechanical subsystem is coupled to a hydrodynamic subsystem. As far as the modeling of the mechanical subsystems is concerned, elastic multibody systems are frequently used. During the simulation many equations must be solved simultaneously, the hydrodynamic equations as well as the equations of motion of each body in the elastic multibody system. Since the discretization of the elastic bodies, e.g with the help of the finite element method, introduces a large number of elastic degrees of freedom, an efficient simulation of the system becomes difficult. The linear model reduction of the elastic degrees of freedom is a key step for using flexible bodies in multibody systems and turning simulations more efficient from a computational point of view. In recent years, a variety of new reduction methods alongside the traditional techniques were developed in applied mathematics. Some of these methods are reviewed and compared for reducing the equations of motion of an elastic body used in multibody systems. The special focus of this work is on balanced truncation model order reduction, which is a singular value based reduction technique using the Gramian matrices of the system. We investigate a version of this method that is adapted to the structure of a special class of second order dynamical systems which is important for the particular application discussed here. The simulation of a crank drive with a flexible crankshaft is taken as technically relevant example. The results are compared to other methods like Krylov approaches or modal reduction.
Numerical investigation of 1D continuum dynamical models of discrete chain
Authors: Andrianov I.V. , Starushenko G.A. , Weichert D. 
Published: June 2013

AbstractThis paper is devoted to the numerical analysis of the various continuum models of a 1D discrete media. Namely, we consider intermediate, quasi‐continuum, and improved quasi‐continuum models. The analysis of various receptions of continualization in a linear case is carried out. For this purpose, we consider the solution in the form of a traveling wave caused by the initial perturbation. The solution is obtained by Fourier transformation inverted numerically. Then we compare solutions of discrete and continuum models for wave velocity. Numerical calculations show that all the above described nonlocal theories qualitatively equally well describe the propagation of waves in a discrete media. The disadvantage of intermediate continuum model is the high order of differential equation. For finite chain this leads to the need for the formulation of boundary conditions that do not follow naturally from the source of the problem. The quasi‐continuum approximation yields results practically identical with those obtained on the basis of improved quasi‐continuum approximation. The most accurate approximation of a discrete medium gives improved quasi‐continuum approximation. The advantage of improved quasi‐continuum approximation is manifested in those cases where you need to describe the high modes of oscillation of the discrete finite chain.
Scattering of plane acoustic waves by a circular semi‐infinite pipe with a rigid end face placed axially in an infinite circular duct
Authors: Yanaz Çınar Ö. 
Published: June 2013

AbstractIn this paper, the propagation of acoustic waves along a duct system, where a semi‐infinite circular rigid pipe with a rigid end face is placed axially inside an infinite circular rigid pipe is analyzed rigorously. First, direct Fourier transform is applied and the problem is reduced into the solution of a modified Wiener‐Hopf equation of the second type from which the reflection and transmission coefficients are determined. Then the bifurcated circular waveguide problem is solved by applying direct Fourier transform again to reduce the problem into the solution of a Wiener‐Hopf equation and the resulting transfer coefficients are taken into account when applying the building block method. Building block method is one of the scattering matrix techniques where reflection and transmission characteristics of each discontinuity in a duct are first determined independently and then taken into account as scattering matrices in order to analyze the original problem. At the end of the analysis, numerical results are presented comparing two approaches of formulation and illustrating the effects of the radii of the pipes and frequency.
Sharp conditions of global existence for second‐order derivative nonlinear Schrödinger equations with combined power‐type nonlinearities
Authors: Xu Runzhang , Xu Chuang 
Published: June 2013

AbstractWe undertake a comprehensive study of the Cauchy problem of a class of second‐order derivative nonlinear Schrödinger equations with combined power‐type nonlinearities. Using the potential theory and the concavity method, we construct a variational problem and two invariant manifolds. Furthermore, we give sharp conditions of global existence and blowup.
Prandtl‐Tomlinson model: History and applications in friction, plasticity, and nanotechnologies
Authors: Popov V.L. , Gray J.A.T. 
Published: June 2013

AbstractOne of the most popular models widely used in nanotribology as the basis for many investigations of frictional mechanisms on the atomic scale is the so‐called Tomlinson model consisting of a point mass driven over a periodic potential. The name “Tomlinson model” is, however, historically incorrect: The paper by Tomlinson from the year 1929 which is often cited in this context did not, in fact, contain the model known as the “Tomlinson model” and suggests, instead, an adhesive contribution to friction. In reality, it was Ludwig Prandtl who suggested this model in 1928 to describe the plastic deformation in crystals and dry friction. Staying in line with some other researchers, we call this model the “Prandtl‐Tomlinson model,” although the model could simply and rightly be dubbed the “Prandtl model.” The original paper by Ludwig Prandtl was written in German and was not accessible for a long time for the largest part of the international tribological community. The present paper is a historical introduction to the English translation of the classical paper by Ludwig Prandtl. It gives a short review of the model as well as its properties, applications, and extensions from the contemporary viewpoint.
Simulation of the abrasive flow machining process
Authors: Schmitt J. , Diebels S. 
Published: June 2013

AbstractDuring the last decade the abrasive flow machining process became an accepted technique to smooth and to round inner edges in badly contactable regions of complex geometries, e.g. grooves in rails of common rail systems. The process is based on the flow of a highly viscous silicone oil which is charged by abrasive particles. This leads to an efficient rounding of the egdes. In the present article a material model for the non‐Newtonian behaviour of the abrasive paste is proposed, the material parameters are identified according to experiments and, finally, a simulation of the abrasive flow machining process is presented based on a model implementation in the software package COMSOL Multiphysics®.
From fractal media to continuum mechanics
Authors: Ostoja‐Starzewski M. , Li J. , Joumaa H. , Demmie P.N. 
Published: June 2013

AbstractThis paper presents an overview of modeling fractal media by continuum mechanics using the method of dimensional regularization. The basis of this method is to express the balance laws for fractal media in terms of fractional integrals and, then, convert them to integer‐order integrals in conventional (Euclidean) space. Following an account of this method, we develop balance laws of fractal media (continuity, linear and angular momenta, energy, and second law) and discuss wave equations in several settings (1d and 3d wave motions, fractal Timoshenko beam, and elastodynamics under finite strains). We then discuss extremum and variational principles, fracture mechanics, and equations of turbulent flow in fractal media. In all the cases, the derived equations for fractal media depend explicitly on fractal dimensions and reduce to conventional forms for continuous media with Euclidean geometries upon setting the dimensions to integers. We also point out relations and potential extensions of dimensional regularization to other models of microscopically heterogeneous physical systems.
Global well‐posedness of the aggregation equation with supercritical dissipation in Besov spaces
Authors: Wu G. , Zhang Q. 
Published: June 2013

AbstractIn this paper, we study the supercritical aggregation equation. We prove the global well‐posedness for small initial data lying in Besov spaces and the local well‐posedness for arbitrary initial data. The Fourier localization technique and the Littlewood‐Paley theory are the main tools used in the proof.
Finite element modeling of Kirchhoff‐Love shells as smooth material surfaces
Authors: Vetyukov Yu. 
Published: June 2013

AbstractWe consider large deformations of curved thin shells in the framework of a classical Kirchhoff‐Love theory for material surfaces. The geometry of the element is approximated via the position vector and its derivatives with respect to the material coordinates at the four nodes, and C1 continuity of the surface over the interfaces between the elements is guaranteed. Theoretical background provides certainty concerning the boundary conditions, the range of applicability of the model, extensions to multi‐field problems, etc. Robust convergence and accuracy of the resulting simple numerical scheme is demonstrated by the analysis of benchmark problems in comparison with other solutions.
Layer potential analysis for a Dirichlet‐transmission problem in Lipschitz domains in ℝn
Authors: Fericean D. , Wendland W.L. 
Published: June 2013

AbstractIn this paper we obtain the existence and uniqueness in some Sobolev and Lp spaces for a Dirichlet‐transmission problem for the Stokes and Brinkman equations on Lipschitz domains in ℝn, n > 3. In the particular case n = 3 this problem describes the Stokes flow of a viscous incompressible fluid past a porous particle and in presence of a solid core. The flow within the porous particle is described by the Brinkman equation. In order to obtain the desired existence and uniqueness result, we use an indirect boundary integral formulation based on the layer potential theory for both Brinkman and Stokes equations. Some special cases, which refer to the Stokes flow past a porous particle with large permeability, respectively low permeability, are also analyzed.
Refined modeling of composite plates with in‐plane heterogeneity
Authors: Lee C.‐Y. , Yu W. , Hodges D.H. 
Published: June 2013

AbstractThis article is concerned with the mechanical behavior of heterogeneous composite plates with elastic moduli and layered geometries varying through the thickness direction and periodically along the in‐plane directions. By using the concept of decomposition of the rotation tensor, we first formulate the three‐dimensional elastic problem in an intrinsic form for application to the geometrically nonlinear problem. The variational asymptotic method is then exercised, leading to simultaneous homogenization and dimensional reduction to construct an effective and simple model suitable for plates with in‐plane periodicity. In particular, having obtained the refinement terms up to the second order, we develop a refined plate model, namely a generalized Reissner‐Mindlin model that is capable of capturing the transverse shear deformations. In order to deal with realistic and complex plate geometries and constituent materials efficiently and conveniently, the proposed model is implemented into a single unified formulation suitable for incorporation into a commercial analysis package. Numerical results computed herein for a few examples are compared to similar results available in the literature to demonstrate the application and performance of the present model.
Adaptive fuzzy sliding mode control of a chaotic pendulum with noisy signals
Authors: Bessa W.M. , de Paula A.S. , Savi M.A. 
Published: June 2013

AbstractChaotic response is related to a dense set of unstable periodic orbits (UPOs) and the system often visits the neighborhood of each one of them. Moreover, chaos has sensitive dependence to initial conditions, which implies that the system evolution may be altered by small perturbations. Chaos control is based on the richness of chaotic behavior and may be understood as the use of tiny perturbations for the stabilization of an UPO enclosed in a chaotic attractor. It makes this kind of behavior to be desirable in a variety of applications, since one of these UPOs can provide better performance than others in a particular situation. In this work, an adaptive fuzzy sliding mode controller is combined with the close return method for the stabilization of UPOs in a chaotic pendulum. The adaptive fuzzy inference system is embedded in a smooth sliding mode controller to cope with both structured and unstructured uncertainties. Since noise contamination is unavoidable in experimental data acquisition, this work also investigates the effect of noisy signals on the used control law, verifying their influence on the system stabilization and on the required control action. Numerical results are presented in order to illustrate the ability of the proposed control scheme to track UPOs even in the presence of modeling inaccuracies and noisy input signals.
On the bending of plates in the electromagnetic theory of microstretch elasticity
Authors: Galeş C. , Baroiu N. 
Published: June 2013

AbstractThis paper deals with the electromagnetic theory of microstretch elasticity. The full dynamic theory, which describes the interaction of electromagnetic fields with piezoelectric bodies, called piezoelectromagnetism, is considered. First, we derive the equations governing the bending theory of thin piezoelectromagnetic microstretch plates. Then, the boundary‐initial value problem is formulated and a uniqueness result is presented. Finally, the effects of a concentrated charge density in an infinite plate are studied.
The two‐component Camassa‐Holm system in weighted Lp spaces
Authors: Kohlmann M. 
Published: June 2013

AbstractWe present some new persistence results for the non‐periodic two‐component Camassa‐Holm (2CH) system in weighted Lp spaces. Working with moderate weight functions that are commonly used in time‐frequency analysis, the paper generalizes some recent persistence results for the Camassa‐Holm equation [2] to its supersymmetric extension. As an application we discuss the spatial asymptotic profile of solutions to 2CH.
Quasistatic adhesive contact of visco‐elastic bodies and its numerical treatment for very small viscosity
Authors: Roubíček T. , Panagiotopoulos C.G. , Mantič V. 
Published: June 2013

AbstractAn adhesive unilateral contact of elastic bodies with a small viscosity in the linear Kelvin‐Voigt rheology at small strains is scrutinized. The flow‐rule for debonding the adhesive is considered rate‐independent and unidirectional, and inertia is neglected. The asymptotics for the viscosity approaching zero towards purely elastic material involves a certain defect‐like measure recording in some sense natural additional energy dissipated in the bulk due to (vanishing) viscosity, which is demonstrated on particular 2‐dimensional computational simulations based on a semi‐implicit time discretisation and a spacial discretisation implemented by boundary‐element method.
The Y‐junction of quantum waveguides
Authors: Nazarov S.A. , Ruotsalainen K. , Uusitalo P. 
Published: June 2013

AbstractA planar quantum waveguide is composed from two semi‐strips of width 1 and a semi‐strip of width H and the angle between strips is 2π/3. The spectrum of the Dirichlet problem in this waveguide is investigated. In particular, it is proved that there exists a critical width H* for which the discrete spectrum is non‐empty for any H ≤ H* and conversely is empty for any H ≥ H*. The critical width is estimated to be approximately H* ≈︁ 1.25. Furthermore, the eigenvalue in the discrete spectrum is unique for 0 ≤ H
≤ H*.
LGBT Community, Social Network Characteristics, and Smoking Behaviors in Young Sexual Minority Women
Authors: Johns Michelle Marie , Pingel Emily S. , Youatt Emily J. , Soler Jorge H. , McClelland Sara I. , Bauermeister Jose A. 
Published: June 2013

AbstractSmoking rates among young sexual minority women (YSMW) are disproportionately high as compared to heterosexual populations. While this disparity has commonly been attributed to the sexual minority stress process, little empirical work has explored what may protect YSMW from high rates of smoking. Using data (N = 471) from a cross‐sectional study designed to investigate YSMW's (age 18–24) smoking behaviors and correlates; we explore the relationship of LGBT community connections, YSMW's social network characteristics, and stress to smoking behaviors (i.e., status, frequency, amount). Through this analysis, we find support for LGBT community connection as well as friendships with other sexual minorities as protective in relation to YSMW's smoking behaviors. We discuss the implications of our results, highlighting the need for future longitudinal research and interventions designed to bolster YSMW's connections to the LGBT community and their social networks.
Intrahousehold Resource Allocation: Do Parents Reduce or Reinforce Child Ability Gaps?
Authors: Frijters Paul , Johnston David W. , Shah Manisha , Shields Michael A. 
Published: June 2013

Abstract
Do parents invest more or less in their high-ability children? We provide new evidence on this question by comparing observed ability differences and observed investment differences between siblings living in the United States. To overcome endogeneity issues, we use sibling differences in handedness as an instrument for cognitive ability differences. We find that parents invest more in high-ability children, with a 1 standard deviation increase in child cognitive ability increasing parental investments by approximately one-third of a standard deviation. Consequently, differences in child cognitive ability are enhanced by differential parental investments.
A randomized controlled trial on the value of misoprostol for the treatment of retained placenta in a low‐resource setting
Authors: van Beekhuizen Heleen J. , Tarimo Vincent , Pembe Andrea B. , Fauteck Heiner , Lotgering Fred K. 
Published: June 2013

AbstractObjectiveTo evaluate the efficacy and safety of misoprostol among patients with retained placenta in a low‐resource setting.MethodsA prospective, multicenter, randomized, double‐blind, placebo‐controlled trial was carried out in Tanzania between April 2008 and November 2011. It included patients who delivered at a gestational age of 28 weeks or more and had blood loss of 750 mL or less at 30 minutes after delivery. Sublingual misoprostol (800 μg) was compared with placebo as the primary treatment. Power analysis showed that 117 patients would be required to observe a reduction of 40% in the incidence of manual removal of the placenta (MRP; P = 0.05, 80% power), the primary outcome. The secondary outcomes were blood loss and number of blood transfusions.ResultsInterim analysis after recruitment of 95 patients showed that incidence of MRP, total blood loss, and incidence of blood transfusions were similar in the misoprostol (MRP, 40%; blood loss, 803 mL; blood transfusion, 15%) and placebo (MRP, 33%, blood loss 787 mL, blood transfusion, 23%) groups. The trial was stopped because continuation would not alter the interim conclusion that misoprostol was ineffective.ConclusionTreatment with misoprostol was found to have no clinically significant beneficial effect among women with retained placenta.Clinical Trial Registration: Current Controlled Trials ISRCTN16104753