bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transparency in government communication
Authors: Fairbanks Jenille , Plowman Kenneth D. , Rawlins Brad L. 
Published: January 2007

Abstract
Basic to a successful democracy is the existence of a public informed about government actions. This requires government information to be open and accessible to the public. This study sought to understand how communicators in government value and practice transparency. Constant comparative thematic analysis of 18 semi‐structured interviews of government communicators revealed a transparency model for government communication. This paper outlines that model and identifies practices and structures that promote transparent communication practices.

Copyright © 2007 John Wiley & Sons, Ltd.
Characterisation and Modelling of Piezoceramic Actuator Hystereses
Authors: Bossong Heiko , Lentzen Sven , Schmidt Rüdiger 
Published: January 2007

AbstractPiezoelectric ceramics are often used as actuators in smart structures technology. In the vast majority of papers dealing with this topic only linear constitutive relations are used. However, the electric field‐strain relations of such actuators show hysteretic behaviour, which means that the piezoelectric coupling coefficient is not constant.In this study the hysteresis of a mechanically unconstrained actuator is obtained using the Michelson interferometry. The hysteretic behaviour is modelled by a Preisach model. Using these experimental data, for the modelling of an active structure with embedded piezoelectric actuators the actual coupling coefficient can then be determined with the help of the Preisach model. With this procedure the actuation strain of an embedded actuator, including the physical nonlinearities, can be calculated using the material characteristics obtained for an unconstrained actuator.For an experimental validation of the method outlined above, a Lead Zirconate Titanate (PZT) actuator is characterised experimentally and then glued to a cantilever beam. Then, the tip displacement of the actuated beam is determined experimentally and simulated numerically using the above method. The experimental and numerical results agree reasonably well if the shear lag due to the bonding layer between the actuator and the structure is taken into consideration. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
3D Simulation of Point Defect Migration in Ferroelectrics
Authors: Goy Oliver , Mueller Ralf , Gross Dietmar 
Published: January 2007

AbstractElectric fatigue in functional materials involves a set of phenomena which lead to the degradation of materials with an increasing number of electrical cycles. Ionic and electronic charge carriers, later 0 as point defects, interact with each other and with microstructural elements in the bulk and with interfaces, which can lead to degradation, or finally to mechanical damage and dissociation reactions, see e.g. [1].With this in mind, efforts are made to calculate the fields caused by point defects to simulate their interaction as well as to verify the used material parameters. Here, a material with linear electro mechanical coupling is used. The applied methods are integral transforms (Radon Transform) and a combination of Difference Methods and a Fast Fourier Transform to obtain solutions in an infinite domain and under periodic boundary conditions, respectively. The point defect interaction is studied within the framework of material or configurational forces. These forces are used in combination with reasonable kinetic laws to simulate defect migration, cf. [2]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A hybrid element formulation for electromechanical problems
Authors: Kurzhöfer Ingo , Schröder Jörg 
Published: January 2007

AbstractThe difficulty in the modeling of ferroelectric materials is the coverage of the complicated interactions between electrical and mechanical quantities on the macroscale, which are caused by switching processes on the microscale. In the present work we present an electric hybrid element formulation where the stresses and the electric fields are derived by constitutive relations as presented in [1]. Therefore the displacements, the electric potential and the electric displacements are approximated by bilinear ansatz functions. Applying a static condensation procedure we obtain a modified finite element formulation governed by the degrees of freedoms associated to the displacements and the electric potential. The anisotropic material behavior is modeled within a coordinate‐invariant formulation [6] for an assumed transversely isotropic material [4]. In this context a general return algorithm is applied to compute the remanent quantities at the actual timestep. Resulting hysteresis loops for the ferroelectric ceramics are presented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Variational Based Scale‐Bridging of Inelastic Composites
Authors: Birkle Manuel , Gürses Ercan , Miehe Christian 
Published: January 2007

AbstractThe paper discusses formulations for the theoretical and numerical analysis of inelastic composites with scale separation. The basic underlying structure is a canonical variational setting in the fully nonlinear range based on incremental energy minimization. We focus on formulations of strain–driven homogenization for representative composite aggregates with emphasis on the development of canonical families of algorithms based on Lagrange and penalty functionals to cover alternative boundary constraints of (i.) linear deformations, (ii.) periodic deformations and (iii.) uniform tractions. As a key result, we present a compact matrix formulation for homogenization covering introduced alternative boundary constraints. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From microscopic to macroscopic modelling of cellular materials
Authors: Chatzouridou Anthippi , Ebinger Tobias , Diebels Stefan 
Published: January 2007

AbstractIn the present contribution the modelling of foam‐like materials is discussed on different scales. Such materials can be foams, sponges, granular media or even hard biological tissues, and their common characteristic is that their macroscopic response is strongly influenced by the iteraction with the cellular microstructure. The individual cells start playing a role when their size becomes on the order of the macroscopic dimensions of the test specimen, leading to size effects, e. g. [1]. To investigate size effects on the macroscale an extended continuum approach is required taking into consideration the microstructural mechanism. Alternatively one can obtain a macroscopic description which includes the microstructural information using a numerical homogenisation procedure. In this way a connection between the discrete quantities of the microscale (e. g. forces) to quantities of an equivalent continuum (e. g. stresses) can be established. The purpose of this study is to investigate the relation between the above mentioned modelling approaches in terms of the involved parameters using procedures of parameter identification. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenisation of elasto‐plastic open‐celled foams
Authors: Demiray S. , Becker W. , Hohe J. 
Published: January 2007

AbstractThe effective yield behaviour of open‐celled metal foams is studied by a micro‐mechanical model. As a surrogate model for the sponge‐like microstructure the simplified Kelvin foam is used. The yield loci in strain space and stress space are constructed by conducting numerical experiments. For the determination of the effective stresses a strain‐energy based homogenisation procedure is adopted. The numerical examples show that the initial yield surface in the normal strain space is similar to a polyhedron with sharp corners. The further evolution of the yield surface is characterized by kinematic and isotropic hardening effects. In addition, the stress yield surface may rotate under certain loading conditions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the simulation of textile reinforced composites and structures
Authors: Haasemann Georg , Ulbricht Volker 
Published: January 2007

AbstractThis paper presents experimental and numerical methods to perform simulations of the mechanical behavior of textile reinforced composites and structures. The first aspect considered refers to the meso‐to‐macro transition in the framework of the finite element (FE) method. Regarding an effective modelling strategy the Binary Model is used to represent the discretized complex architecture of the composite. To simulate the local response and to compute the macroscopic stress and stiffness undergoing small strain a user routine is developed. The results are transfered to the macroscopic model during the solution process.The second aspect concerns the configuration of the fiber orientation and textile shear deformation in complex structural components. To take these deformations which affect the macroscopic material properties into account they are regarded in a macroscopic FE model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fourier Series for Continua with Microstructure
Authors: Kaßbohm S. , Müller W. H. , Silber G. , Feßler R. 
Published: January 2007

AbstractBased on the idea of the Cosserats at the beginning of the 20th century, Mindlin, Tiersten, Toupin, Rivlin, Green, Trostel et al. developed theories for generalized continua in the 1960s. Currently, such theories for continua with microstructure are extended in micromechanics, fluid mechanics, etc. by various scientists. All such theories follow the same purpose of a more precise material description embedded in a continuum theory. In the following article the well‐known Cosseratcontinuum is used for the calulation of strains and stresses in Representative Volume Elements (RVEs) with arbitrary stiffness distribution and periodic boundary conditions. Restricting the problem to small displacements and linear elasticity results in linear equations of motion, that can be solved iteratively by means of Fourier series. It is pointed out that other types of generalized continua can be analyzed in the same manner. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation, Modelling and Analysis of stiffened GFRP‐Samples
Authors: Kreikemeier Janko , Berger Harald , Gröbel Karl‐Heinz , Gabbert Ulrich 
Published: January 2007

AbstractGlasfibre structures feature high potentials for optimization and substitution of conventional materials like steel and aluminum and their alloys. The paper deals with the insertion of glasfibre trusses into thin glasfibre structures to reinforce them. The effective material properties of the glasfibre structures were estimated by experiments and simulations. Furthermore the Young's modulus of the trusses was obtained by bending tests and tension tests. A comparison between bending experiments and bending simulations is given. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transversal walls versus vortex walls in magnetic nanowires
Authors: Kühn Katharina 
Published: January 2007

AbstractIn numeric simulations of magnetic nanowires several groups have observed two different types of reversal modes. It is suggested that the reversal mode corresponds to an energetically optimal domain wall profile. We investigate the energy minimisation problem in different regimes of thickness. When the radius goes to zero, the energy minimisation problem Γ‐converges to a reduced local one dimensional problem. Thus for small radii, minimisers of the energy functional are almost constant on the cross section. This is not the case for big radii. For radius to infinity, a class of magnetisations with a vortex has the optimal energy scaling. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Micromechanical Damage Modelling Of Fibre Reinforced Composites
Authors: Matzenmiller A. , Koester B. 
Published: January 2007

AbstractThe numerical analysis of engineering structures is usually based upon the assumption of a homogeneous as well as a continuous medium. Macroscopic homogeneity is maintained also for heterogeneous, fibre reinforced composite structures by replacing the inhomogeneous medium through a model of a mathematically homogenized material. The constitutive behaviour is then described in terms of volume averaged quantities that smear the heterogeneities of the microscale. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a Sachs bound for stress‐induced phase transformations in polycrystalline shape memory alloys
Authors: Schlömerkemper Anja 
Published: January 2007

AbstractIn earlier work [3], a Sachs and a Taylor bound on the transformation yield stress in shape memory polycrystals were derived in the context of a variational model. The aim of this article is to compare the Sachs with the Taylor bound for cubic‐toorthorhombic phase transformations under biaxial loading, where the material parameters are chosen explicitly (CuAlNi). It turns out that the gap between the two bounds can be quite large depending on the underlying texture and the loading direction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From particle dynamics to micropolar media: a localization study
Authors: Scholz B. , Ehlers W. 
Published: January 2007

AbstractGranular materials show a complex stress‐strain behavior depending on the stress state and the load history. In case of biaxial tests and compaction loading situations, one furthermore observes localization effects, e. g., by the formation of shear bands. For the simulation of such a material behavior two different methods can be applied. Firstly, the microscopic model which means the direct modeling of the single material grains on the basis of the Molecular Dynamic methods. The second one is a macroscopic approach, whereby, the fundamental effect on the microscale, the rotations of the single grains, are considered by use of the micropolar or Cosserat theory. The intend of this contribution is to demonstrate that the Cosserat theory is a physical correct way for the description of granular materials. Therefore, it will be shown that in both methods the occurrence of localization zones (shear bands) is connected with the appearance of curvatures in the material combined with couple stresses, which indicates a Cosserat material. The required curvature and couple stress tensors are obtained in the macroscopic theory as a direct result of the computation, whereas by use of the microscopic theory the translations and rotations as well as contact forces are obtained as the direct result. Thus, homogenization methods basing on an appropriate Representative Elementary Volume (REV) are required. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homogenization for rate‐independent systems
Authors: Timofte Aida , Mielke Alexander 
Published: January 2007

AbstractThis paper is devoted to the homogenization for a class of rate‐independent systems described by the energetic formulation. The associated nonlinear partial differential system has periodically oscillating coefficients, but has the form of a standard evolutionary variational inequality. Thus, the model applies to standard linearized elastoplasticity with hardening. Using the recently developed methods of two‐scale convergence, periodic unfolding and the new introduced one, periodic folding, we show that the homogenized problem can be represented as a two‐scale limit which is again an energetic formulation, but now involving the macroscopic variable in the physical domain as well as the microscopic variable in the periodicity cell. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Particle‐Laden Flow Simulation in a Cyclone Separator
Authors: Shalaby Hemdan , Wozniak Klaus , Wozniak Günter 
Published: January 2007

AbstractThe particle‐laden flow of a cyclone separator for industrial applications at a Reynolds number of Re = 140, 000 has been studied numerically. Due to the nature of cyclone flows, which exhibit highly curved streamlines and anisotropic turbulence, we used the advanced turbulence model Large Eddy Simulation (LES). Our LES reveals qualitative agreement with experimental data, but requires higher computer capacity and longer running times compared to other turbulence models. The results of the continuous phase flow computations were generated first and served as a basis for modeling the behavior of solid particles in the separator. Modeling of the solid particle motion in the cyclone was performed applying a one‐way coupling between the gas flow field and the particles. The cyclone separation efficiency and particle trajectories have been studied in detail. Separation efficiency results show satisfying agreement between LES data and experimental results. It turned out that the particle cut‐off diameter for a particle material density of 2500 kg/m3 is approximately 1.3 μm. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical methods for 2‐D flow of flapping airfoil
Authors: Dumitrache Alexandru 
Published: January 2007

AbstractTo study the physics of the flow of flapping flight, a numerical model for the two‐dimensional flow around an airfoil undergoing prescribed oscillatory motions in a viscous flow is described. The model is used to examine the flow characteristics and power coefficients of a symmetric airfoil heaving sinusoidally over a range of frequencies and amplitudes. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of eddies on heat transfer in Couette flow
Authors: Scholle M. , Aksel N. 
Published: January 2007

AbstractUnder creeping flow conditions, we consider the steady Couette flow of a Newtonian fluid between two plates, one of them planar, the other one with a sinusoidal profile. Recent analytical studies on the velocity field revealed the formation of kinematically induced eddies in the valleys of the plate topography and the influence of these eddies on drag force and flow rate. The influence of these eddies on the convective heat transfer is the subject of our paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Über die exzentrische Zylinderspaltströmung bei engen Spaltweiten
Authors: Stücke Peter , Schwarz Mike , Scurtu Nicoleta , Egbers Christoph 
Published: January 2007

AbstractEs werden die Strömungsverhältnisse im Ringspalt zweier koaxial angeordneter Zylinder mit den Mitteln der Strömungsvisualisierung untersucht. Dabei wird der Übergangsbereich von laminarer Couette‐Strömung zu Taylor‐Wirbel‐Strömung bei konzentrischer und exzentrischer Anordnung der Zylinder und relativen Spaltweiten von unter 0.1 untersucht. Bei konzentrischer Zylinderanordnung kann die Stabilitätsgrenze der laminaren Couette‐Strömung für Reynolds‐Zahlen von 150 bis 400 bestätigt werden. Bei exzentrischer Anordnung der Zylinder ändern sich die Strömungsverhältnisse grundlegend. Mit zunehmender Exzentrizität verschiebt sich die Stabilitätsgrenze zu höheren Reynolds‐Zahlen. In Abhängigkeit von der Reynolds‐Zahl bilden sich Taylor‐Wirbel bei bestimmten Exzentrizitäten nur im konvergenten Teil des Spaltes. Der Bereich um die engste Spaltweite ist dann frei von Taylor‐Wirbeln. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling of Newtonian and Non‐Newtonian Incompressible Fluid Flow
Authors: Vimmr Jan 
Published: January 2007

AbstractThis paper deals with numerical simulation of steady laminar incompressible Newtonian and non‐Newtonian fluid flow. The viscosity of non‐Newtonian fluid is modelled using the fluid power law. The mathematical model is described by the non‐linear conservative system of the incompressible Navier‐Stokes equations that is solved using the explicit two‐step MacCormack scheme with artificial viscosity together with the pseudo‐compressibility method. The spatial discretization is performed by the cell‐centred finite volume method on a structured quadrilateral grid. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Perceived disability, fatigue, pain and measured isometric muscle strength in patients with post‐polio symptoms
Authors: Lygren Hildegunn , Jones Kari , Grenstad Torunn , Dreyer Vibeke , Farbu Elisabeth , Rekand Tiina 
Published: January 2007

AbstractBackground and Purpose. Several years after the acute polio illness, patients may develop new post‐polio symptoms. The purpose of the present study was to evaluate patients with post‐polio symptoms with regard to perceived fatigue, functional ability, muscle strength, pain and with regard to measured physical fitness and isometric muscle strength. In addition, the relationship between the results of these subjective and objective measurements was investigated. Method. This was a prospective cross‐sectional study in which 32 patients with post‐polio symptoms were included. Main outcome measures were the Fatigue Severity Scale (FSS), the Disability Rating Index (DRI), pain intensity, pain distribution, self‐reported and measured muscle strength and oxygen uptake. Results. A marked reduction in isometric muscle strength compared to normal data, high scores in fatigue, widespread pain, low oxygen uptake and difficulties in performing some daily activities were found. Self‐reported general muscle strength, pain intensity and pain distribution correlated significantly with patients' perceived fatigue and function at the activity level. There was no significant correlation between self‐reported and measured results except for that found between isometric muscle strength in the legs and patients' perceived general muscle strength and oxygen uptake. Conclusions. Evaluation of pain intensity, pain distribution, perceived muscle strength, fatigue and ability to perform daily tasks reveals important aspects of health status in patients with post‐polio symptoms. Reduction in isometric muscle strength was not reflected in those tests or in reported symptoms, and should be monitored independently using a sensitive assessment tool. Accurate screening of isometric muscle strength in isolated muscle groups contributes to therapeutic management in making a functional diagnosis at the level of body function and structure when designing specific training programmes and in motivating patients. An evaluation combining self‐reports with sensitive muscle strength measures provide supplementary information and is appropriate for evaluating these patients in physiotherapy practice. Copyright © 2007 John Wiley & Sons, Ltd.
Architecture of cylinders with implications for materials with negative Poisson ratio
Authors: Pikhitsa Peter V. 
Published: January 2007

AbstractIt is known that auxetic properties (for example, negative Poisson ratios, that is, when a solid experiences lateral expansion under stretching instead of lateral contraction) start showing themselves in materials where there is a certain kind of geometrical orientational correlations between “rigid” constituents. Properly arranged orientational degrees of freedom of building blocks govern the characteristic distances in auxetic materials and thus determine the way in which the materials contract or expand. Very often the building blocks are filamentous. We suggest a way to arrange filamentous objects into highly interwoven regular structures which may exhibit auxetic properties with negative Poisson ratio. Our purely geometrical consideration can be extended to an irregular positional arrangement. This implies that a solid of sufficiently dense “random” arrangements of filaments (for example, “wool” of nanowires or of carbon nanotubes) may become auxetic. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)