bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation on an atmospheric pressure dielectric barrier discharge infrared image converter
Authors: Schmiedel A , Ye F , Fischer C , Viöl W
Published: January 2007

In this paper the possibility is investigated to utilise an atmospheric pressure dielectric barrier glow discharge in nitrogen to convert infrared radiation to the visible spectral range (VIS). In principle, it belongs to the thermal detectors. The converter cell consists of a plan-parallel arrangement of electrodes. One electrode acts simultaneously as the infrared transparent window and the other electrode is performed transparency in the VIS to observe the discharge. The effect mainly depends on an increasing electron desorption rate from the dielectric surface by the infrared radiation, which involves a higher brightness of the discharge. In the investigation a working range was figured out from 1.5 mJ cm-2 up to 0.6 J cm-2 and the time of reaction is less than 1/100 s. One possible application is the analysis of the spatial intensity distribution of a carbon dioxide laser beam. The spatial resolution was identified to be at least 3 to 4 lines per millimeter.
Unitizations of double-ring structure and Erbium-doped waveguide amplifier for stable and tunable fiber laser
Authors: Chou S-Y , Yeh C-H , Chi S
Published: January 2007

We propose and demonstrate experimentally a single-longitudinal-mode (SLM) fiber double-ring laser using an Erbium-doped waveguide amplifier (EDWA), polarization controller (PC), and a fiber Fabry-Perot tunable filter (FFP-TF) into the ring cavity. In addition, the output power, side-mode suppression ratio (SMSR), and the stabilities of power and wavelength of the laser also are investigated.
Accuracy of medicare claims data in identifying Parkinsonism cases: Comparison with the medicare current beneficiary survey
Authors: Noyes Katia , Liu Hangsheng , Holloway Robert , Dick Andrew W.
Published: January 2007

Study Purpose

Administrative databases are commonly used to examine use of healthcare service, with researchers relying on diagnostic codes to identify medical conditions. This study evaluates the accuracy of administrative claims in identifying Parkinsonism cases compared to the self‐reported Parkinson's disease (PD).

Methods

The reference cases were identified based on the self‐reported PD status and the use of PD drugs collected by the 1992–2000 Medicare Current Beneficiary Survey that contained 72,922 observations from 30,469 individuals. Using ICD‐9 CM, cases with PD were extracted from the corresponding Medicare claims. We compared prevalence of PD obtained using different types of claims.

Results

The sensitivities were the highest when all claims were used (66%). All the specificities were greater than 99%. When drug use information was included in the gold standard, the sensitivities became lower, while the specificities and positive predictive values (PPVs) increased. Using more diagnostic codes improved the sensitivity of the identification process but reduced PPVs.

Conclusions

Administrative claims can provide fairly accurate and practical approach to “rule in” patients with PD. Depending on the purpose of evaluation, researchers may consider using more categories of claims to improve the sensitivity of the identification algorithm or use fewer diagnoses to minimize number of false positive cases. © 2006 Movement Disorder Society
Rat model of Parkinson's disease with bilateral motor abnormalities, reversible with levodopa, and dyskinesias
Authors: Paillé Vincent , Henry Vincent , Lescaudron Laurent , Brachet Philippe , Damier Philippe
Published: January 2007

Parkinson's disease (PD) is characterized by the bilateral degeneration of the midbrain dopamine‐containing neurons with the most severe lesion in the posterolateral part of the substantia nigra pars compacta (SNpc). In humans, such lesions lead to specific motor abnormalities (i.e., akinesia, rigidity, and tremor) that are greatly improved by levodopa treatment. After a few years, the beneficial effect of the treatment is frequently offset by the development of dyskinesias. To improve treatment strategies, an animal model showing most of the histological and clinical characteristics of the human disease is mandatory. Ten rats received a bilateral injection of small doses of 6‐OHDA in the medial forebrain bundle (MFB) and were compared with five sham‐lesioned rats. The 6‐OHDA‐lesioned rats progressively developed abnormal motor behavior (assessed by the stepping test) compared with the sham‐lesioned rats. The lesioned rats greatly improved under levodopa treatment, but developed concomitant dyskinesias. All 6‐OHDA‐lesioned animals had bilateral partial lesions of the SNpc, with the most severe lesion being in its posterolateral part. There was a significant correlation between the severity of the dopaminergic cell loss and the severity of the levodopa‐induced dyskinesias. These rats constitute an interesting model of PD, sharing some of the main characteristics of the human disease. © 2006 Movement Disorder Society
Vitamin D and Parkinson's disease—A hypothesis
Authors: Newmark Harold L. , Newmark Jonathan
Published: January 2007

Parkinson's disease (PD), a common disease of the elderly, is a movement disorder characterized by tremor, akinesia, and loss of postural reflexes, leading to immobility and frequent falls. It results from selective loss (death) of dopaminergic neurons in the substantia nigra region of the brain, largely developed prior to clinical diagnosis, and continuous after diagnosis, despite use of current therapeutic modalities. In PD in the United States the cause and mechanism of continued neuron cell death in the substantia nigra is currently unknown. We hypothesize, based upon several lines of evidence, that documented chronically inadequate vitamin D intake in the United States, particularly in the northern states and particularly in the elderly, is a significant factor in the pathogenesis of PD. This hypothesis implies that dietary aid for prevention and therapy for PD is possible. © 2006 Movement Disorder Society
Testosterone not associated with violent dreams or REM sleep behavior disorder in men with Parkinson's
Authors: Chou Kelvin L. , Moro‐De‐Casillas Maria L. , Amick Melissa M. , Borek Leora L. , Friedman Joseph H.
Published: January 2007

We examined the relationship between testosterone levels, violent dreams, and REM sleep behavior disorder (RBD) in 31 men with Parkinson's disease (PD): 12 with clinical RBD and 19 without. All PD patients with clinical RBD experienced violent dreams, but none of the 19 non‐RBD patients reported violent dreams. While dream content appears to be more aggressive in PD patients with clinical RBD, the presence of violent dreams or clinical RBD is not associated with testosterone levels in men with PD. © 2006 Movement Disorder Society
Midbrain sonography in patients with essential tremor
Authors: Stockner Heike , Sojer Martin , K Klaus Seppi , Mueller Joerg , Wenning Gregor K. , Schmidauer Christoph , Poewe Werner
Published: January 2007

Several studies have reported an increased risk to develop Parkinson's disease (PD) in essential tremor (ET) populations. Hyperechogenicity of the substantia nigra (SN) is a common transcranial sonography (TCS) finding in PD and has been suggested as a PD risk‐marker in nonparkinsonian subjects. This study compared SN areas of 44 ET patients with 100 controls and 100 PD patients. Sixteen percent of ET patients had SN hyperechogenicity as compared with 3% of controls and 75% of PD patients. These findings might correspond to an increased risk of ET patients to develop PD. Long‐term follow‐up will show if those with hyperechogenic SN develop PD, while these without will not. © 2006 Movement Disorder Society
Impact of varying pulse frequency and duration on muscle torque production and fatigue
Authors: Gregory Chris M. , Dixon Warren , Bickel C. Scott
Published: January 2007

Neuromuscular electrical stimulation (NMES) involves the use of electrical current to facilitate contraction of skeletal muscle. However, little is known concerning the effects of varying stimulation parameters on muscle function in humans. The purpose of this study was to determine the extent to which varying pulse duration and frequency altered torque production and fatigability of human skeletal muscle in vivo. Ten subjects underwent NMES‐elicited contractions of varying pulse frequencies and durations as well as fatigue tests using stimulation trains of equal total charge, yet differing parametric settings at a constant voltage. Total charge was a strong predictor of torque production, and pulse trains with equal total charge elicited identical torque output. Despite similar torque output, higher‐ frequency trains caused greater fatigue. These data demonstrate the ability to predictably control torque output by simultaneously controlling pulse frequency and duration and suggest the need to minimize stimulation frequency to control fatigue. Muscle Nerve, 2007
Severity, type, and distribution of myotonic discharges are different in type 1 and type 2 myotonic dystrophy
Authors: Logigian Eric L. , Ciafaloni Emma , Quinn L. Christine , Dilek Nuran , Pandya Shree , Moxley Richard T. , Thornton Charles A.
Published: January 2007

To characterize and compare electrical myotonia in myotonic dystrophy type 1 (DM1) and type 2 (DM2), 16 patients with genetically confirmed DM1 and 17 patients with DM2 underwent standardized concentric needle electromyography of deltoid, biceps, extensor digitorum communis, first dorsal interosseous, tensor fascia lata (TFL), vastus lateralis (VL), tibialis anterior, and thoracic paraspinal muscles. Eight needle insertions per muscle were made by electromyographers blinded to DM type who recorded the presence and type of myotonia (e.g., classic waxing–waning or less specific waning discharges). Manual muscle testing was performed by a physical therapist. Overall, myotonia was more elicitable in DM1 than DM2; only in VL and TFL was myotonia more elicitable in DM2 than DM1. The major type of myotonia was waxing–waning in DM1, and waning in DM2. Four DM2 (24%), but no DM1 patients had only waning myotonia. In the arms, myotonia was distally predominant in both DM1 and DM2. In the legs, it was distally predominant in DM1, but both proximal and distal in DM2. The severity of myotonia was positively correlated with muscle weakness and with the presence of waxing and waning discharges in DM1, but with neither in DM2. Thus, myotonia is qualitatively and quantitatively different in DM1 than DM2. Except for proximal leg muscles, myotonia is more evocable in DM1 than DM2. It tends to be waxing–waning in DM1 but waning in DM2, thus making electrodiagnosis of DM2 more challenging. Its severity correlates with muscle weakness and the presence of waxing–waning discharges in DM1 but not DM2. Muscle Nerve, 2007
Delamination Analysis of UD Composites Using Interface Elements
Authors: Balzani Claudio , Wagner Werner
Published: January 2007

For an accurate simulation of the mechanical behavior of laminated composites, several fracture modes should be considered. This work focuses on the numerical treatment of delamination within the framework of the finite element method. An interface element is presented which is written in terms of stress‐strain relationships. The constitutive law is mainly inspired by publications of De‐Andrés et al. [1] and Ortiz & Pandolfi [2]. A Smith‐Ferrante type cohesive free energy function is edited in a way that only tensile normal stresses trigger interlaminar damage. Furthermore, an additional penalty term avoids the interpenetration of the crack faces. The simulation of a DCB test shows the performance and the applicability of the model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The peridynamic model in non‐local elasticity theory
Authors: Emmrich Etienne , Weckner Olaf
Published: January 2007

The peridynamic model is described and an overview of some recent results concerning the analysis of the peridynamic equation of motion is given. Moreover, its numerical solution is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of an elastic contact problem with damage
Authors: Fernández José R. , Campo Marco
Published: January 2007

In this work, we consider a mathematical model for the quasistatic contact problem between an elastic body and a deformable obstacle, including the effect of the damage of the material, within the framework of the small deformation theory. The numerical analysis of the variational problem is provided using the finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivatives. Finally, a two‐dimensional numerical problem is presented to show the performance of the method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust Algorithm for Brittle Fracture based on Energy Minimization
Authors: Gürses Ercan , Miehe Christian
Published: January 2007

The paper outlines a variational formulation of brittle fracture in solids and considers its numerical implementation by a distinct finite element method. The starting point is a variational setting of fracture mechanics that recasts a monotonic quasistatic fracture process into a sequence of incremental minimization problems. The proposed implementation introduces discretized crack patterns with material‐force‐driven incremental crack‐segment releases. These releases of crack segments constitute a sequence of positive definite subproblems with successively decreasing overall stiffness, providing an extremely robust algorithmic setting in the postcritical range. The formulation is embedded into accompanying r‐adaptive crack‐pattern reorientation procedures with material‐force‐based indicators, providing reorientations of elements at the crack‐tip. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On some relations between different interface crack models
Authors: Loboda Volodymyr , Herrmann Klaus
Published: January 2007

Exact analytical solutions for an interface crack with an artificial contact zone in isotropic, anisotropic and piezoelectric materials have been analyzed and their comparison with the correspondent classical results has been performed. This analysis showed the way of a presentation of the main results for an artificial contact zone model in the manner very similar to the classical model, and due to this phenomenon the essential simplification of the investigation of the contact zone model has been attained. The application of the obtained results to interface cracks in anisotropic and piezoelectric bimaterials can be demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical aspects of the XFEM — The XFEM p–Version
Authors: Peters Markus , Hackl Klaus
Published: January 2007

The XFEM is known to approximate the displacements and stresses around a crack tip in a very efficient way. But as we will present in this paper we have to deal with a phenomenon coming along with this method that compels us to use higher order shape functions for those elements that are enriched by the crack tip functions.

For the computation of the stress–intensity–factors we are using a J–integral over a circular domain Ω. The accuracy of the results depend on

• the radius of Ω

• the number of elements used in the XFEM computation

• the number of nodes which were enriched by the crack tip functions (number of layers) and

• the shape functions which were used for the standard FE term

For more information about the XFEM we refer to [1]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Thermal Impact Welded Lightweight Structures
Authors: Utzinger Johannes , Menzel Andreas , Kuhl Ellen , Steinmann Paul
Published: January 2007

In the field of composites, welding of lightweight structures consisting of metal/fibre‐reinforced polymers is a very seminal issue, concerning for example the automotive industry. The theoretical and numerical modelling as well as the simulation of the mentioned composites is a crucial and integrating subarea. By using various material laws in a traction‐separation context, different experimental and analytical methods must be consulted to verify the mesomechanical models. In this contribution we discuss a characterisation of interfacial elasto‐plasticity with Lemaitre‐damage, which has been applied to model thermal impact welded single lap tensile specimens. Then, numerical and experimental results are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient crack growth analyzes by combining fast methods for BEM
Authors: Weber W. , Kolk K. , Kuhn G.
Published: January 2007

The combination of fast methods for the boundary element method (BEM) for efficient crack growth analyzes is presented. Due to the nonlinearity of fatigue crack growth an incremental procedure has to be applied. Within each increment a stress analysis is needed. Based on the asymptotic stress field the stress intensity factors (SIFs) are calculated by an extrapolation method. Then, a new crack front is determined by a reliable 3D crack growth criterion. Finally, the numerical model has to be updated for the next increment. The time dominant factor in each increment is the computation of the stress field. Due to the stress concentration problem the BEM is utilized. To speed‐up the calculation several independent fast methods are exploited. An algebraic technique is the adaptive cross approximation (ACA) method which is acting on the system matrix itself. The application of the substructure technique leads to a blockwise band matrix and therefore to reduced memory requirements. Further savings in memory and computation time are reached by modelling cracks with the dual discontinuity method (DDM) and using the ACA method in each substructure. The efficiency of the combined methods is shown by a complex industrial example. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic stability of a porous rectangular plate
Authors: Debowski Daniel , Magnucki Krzysztof
Published: January 2007

The study is devoted to a axial compressed porous‐cellular rectangular plate. Mechanical properties of the plate vary across is its thickness which is defined by the non‐linear function with dimensionless variable and coefficient of porosity. The material model used in the current paper is as described by Magnucki, Stasiewicz papers. The middle plane of the plate is the symmetry plane. First of all, a displacement field of any cross section of the plane was defined. The geometric and physical (according to Hook's law) relationships are linear. Afterwards, the components of strain and stress states in the plate were found. The Hamilton's principle to the problem of dynamic stability is used. This principle was allowed to formulate a system of five differential equations of dynamic stability of the plate satisfying boundary conditions. This basic system of differential equations was approximately solved with the use of Galerkin's method. The forms of unknown functions were assumed and the system of equations was reduced to a single ordinary differential equation of motion. The critical load determined used numerically processed was solved. Results of solution shown in the Figures for a family of isotropic porous‐cellular plates. The effect of porosity on the critical loads is presented. In the particular case of a rectangular plate made of an isotropic homogeneous material, the elasticity coefficients do not depend on the coordinate (thickness direction), giving a classical plate. The results obtained for porous plates are compared to a homogeneous isotropic rectangular plate. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling of 3D Boundary Elements with Curved Finite Shell Elements
Authors: Helldörfer Bastian , Haas Michael , Kuhn Günther
Published: January 2007

The mixed‐dimensional coupling of finite shells and 3D boundary elements is presented. A stiffness formulation for the boundary element domain is generated by the Symmetric Galerkin Boundary Element Method and is assembled to the global finite element system. Multipoint constraints are derived in an integral sense by equating the work at the coupling interface. They are evaluated numerically during the analysis and avoid spurious stress concentrations also for curved interfaces. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chaotic vibrations in nonlinear problems of bar structures
Authors: Koszela P. , Napiorkowska‐Alykow M.
Published: January 2007

In the response of nonlinear mathematical models which describe vibrations of structural elements one could observe an irregular behaviour which is called chaos. Loss of the information on initial states in deterministic dynamical systems after a short time of theirs evolution, increasing amplitudes of displacements, velocities and accelerations, sensitive dependency on initial conditions makes chaos dangerous phenomenon in mechanics of construction. In this article quantitative (bifurcation diagrams, Poincare sections and Fourier power spectrum analysis) identication methods of the chaotic dynamics in geometrically nonlinear model of one DOF Mises truss are shown. Main goal of this article is to show and verify dangerous influence of chaos (in the engineering sense) on the analyzed structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability problems of textile wound structures
Authors: Kyosev Yordan , Reinbach Ingo , Gries Thomas
Published: January 2007

Mathematical model for calculation of the stress‐strain behavior of the wound package is presented. It uses the split of the body of cylindrical layers with finite thickness under assumption for orthotropic, linear elastic behavior of the single layers. The numerical results demonstrate, that in certain cases the windings and layers lose their tension forces, where the winding package loses its stability. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite strain model for contact interface in forming processes
Authors: Luege Mariela , Luccioni Bibiana M.
Published: January 2007

A phenomenological rate and state‐variable friction law for the continuous sliding under lubricated and dry conditions, as it occurs in metal forming processes, is presented in this paper. The contact model is developed within the framework of continuum thermodynamics of irreversible processes with internal variables and for large strains assuming the contact area as a material surface. The model reproduces the experimental boundary friction map obtained by Luengo et al [1]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coherence of Structural Optimization and Configurational Mechanics
Authors: Materna Daniel , Barthold Franz‐Joseph
Published: January 2007

This contribution is concerned with the similarities of structural optimization and configurational mechanics. In structural optimization sensitivity analysis is used to obtain the sensitivity of continuum mechanical functions with respect to variations of the material body, i.e. the reference configuration. In the same manner in configurational mechanics we are interested in changes of the material body, e.g. crack propagation or phase transition problems. Consequently, variational design sensitivity analysis and the numerical techniques from structural optimization are applicable to problems fromconfigurational mechanics. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Symmetric and Asymmetric Underplatform Dampers for Turbine Blades
Authors: Panning Lars
Published: January 2007

Friction damping devices like underplatform dampers are widely used in turbomachinery applications to reduce vibration amplitudes and to increase lifetime and reliability of the bladed disk. Nowadays, in practical applications, a variety of different underplatform damper geometries is applied. Nevertheless, a detailed study of the in.uence of the geometric and dynamic properties of the damper is still not available. Within this paper the most frequently applied damper types like cylindrical and wedge as well as asymmetrical dampers are investigated and compared to each other with respect to their effectiveness. Especially the in.uence of the damper geometry on the resonance frequency and vibration amplitude is pointed out. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational Approaches in the Beam Theory
Authors: Vasily Saurin , Georgy Kostin
Published: January 2007

Equations governing the stress‐strain state of an elastic beam are derived on the basis of the method of the integro‐differential relations (IDR). The influence of Poisson's ratio and shear modulus on the stiffness characteristics of an elastic beam with a rectangular cross section is investigated. Explicit expressions are obtained for the stress fields in an isotropic or anisotropic beam for an arbitrary type of loading. A system of differential equations for displacement fields in these beams is presented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Size Effects at Corners of Anisotropic Material Discontinuities
Authors: Wigger Hubertus Michael , Becker Wilfried
Published: January 2007

Reinforcement patches of composite laminates often possess corners due to design and manufacturing necessities. Hence, the patches reconstitute the demanded effective strength or stiffness in the region considered but at their boundaries also constitute a source for stress localizations. The complex potential method is a means for the investigation of such stress localizations. With the help of appropriate complex potentials the mechanical in‐plane fields around the reinforcement corner can be expressed as series representations. A first analysis step is to obtain the exponents and corresponding modes which cause singular behavior of the membrane forces. Then, the determination of appropriately defined generalized membrane force intensity factors is used to show whether and how the singularity exponents are in effect. On this basis it is possible to deduce what impact a specific loading condition or the reinforcement corner's material combination and geometry have on the character of the singularity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contact of fractal surfaces – Experimental and numerical results
Authors: Willner Kai , Görke Daniel
Published: January 2007

Measurements of rough surfaces show that the roughness topography can be described as a fractal over several length scales. A suitable description is then given by a discrete structure function. For a large class of typical surfaces measured structure functions can be approximated by a three‐parameter function, employing the rms‐value of the roughness, a transition length between fractal behavior at high wavenumbers and stationary behavior at low wavenumbers, and the fractal dimension in the fractal region, respectively, as intrinsic parameters to describe an isotropic rough surface.

To study the normal contact behavior of such fractal surfaces numerically, the first author presented in [1] a numerical model which allows to describe the elasto‐plastic normal contact of isotropic fractal surfaces. This model is now tested against experimental data which are obtained from contact tests of several aluminum specimens. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear flexural vibrations of composite shallow open shells
Authors: Adam Christoph
Published: January 2007

This paper addresses geometrically nonlinear flexural vibrations of open doubly curved shallow shells composed of three thick isotropic layers. The layers are perfectly bonded, and thickness and linear elastic properties of the outer layers are symmetrically arranged with respect to the middle surface. The outer layers and the central layer may exhibit extremely different elastic moduli with a common Poisson's ratio ν. The considered shell structures of polygonal planform are hard hinged supported with the edges fully restraint against displacements in any direction. The kinematic field equations are formulated by layerwise application of a first order shear deformation theory. A modification of Berger's theory is employed to model the nonlinear characteristics of the structural response. The continuity of the transverse shear stress across the interfaces is specified according to Hooke's law, and subsequently the equations of motion of this higher order problem can be derived in analogy to a homogeneous single‐layer shear deformable shallow shell. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wirkung von Störungen auf die Stabilität von Seilschwingungen
Authors: Aps Ulrich , Thalheim Jens‐Uwe , Heinen Anton
Published: January 2007

Instabilitätserscheinungen bei Seilen lassen sich numerisch simulieren durch Aufbringen einer sehr kleinen Störverschiebung auf die Grundschwingung. Es werden die Auswirkungen unterschiedlicher Störeinflüsse untersucht. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hoisting Manipulation for Flying Cranes
Authors: Bockstedte Andreas , Kreuzer Edwin
Published: January 2007

A control strategy for hoisting drives of crane systems is discussed. Based on modal coupling control, the desired hoisting velocity is manipulated by superposition of a suitably modulated motion in order to suppress the so–called spaghetti–problem of hoisting–induced pendulations. For a 3–dimensional multibody system featuring the flying–crane –concept the extension of this control strategy to more complicated systems is exemplified. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rolling Contact Problem with the Generalized Coulomb Friction
Authors: Chudzikiewicz Andrzej , Myslinski Andrzej
Published: January 2007

This paper deals with the numerical solution of the wheel ‐ rail rolling contact problems. The unilateral dynamic contact problem between a rigid wheel and a viscoelastic rail lying on a rigid foundation is considered. The contact with the generalized Coulomb friction law occurs at a portion of the boundary of the contacting bodies. The Coulomb friction model where the friction coefficient is assumed to be Lipschitz continuous function of the sliding velocity is assumed. Moreover Archard's law of wear in the contact zone is assumed. This contact problem is governed by the evolutionary variational inequality of the second order. Finite difference and finite element methods are used to discretize this dynamic contact problem. Numerical examples are provided. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Track–Monitoring of Wheel–Rail–Systems
Authors: Glösmann Philipp , Kreuzer Edwin
Published: January 2007

Inspection and maintenance of railway networks is a complex and expensive task. Special measurement vehicles are used to record the geometrical properties of railway lines within required time intervals. Due to the extent of measurement data the quality of railway track is evaluated considering only a few parameters. Although safety and comfort of wheel–rail–systems depend on the dynamical behavior, current inspection vehicles are not equipped to measure dynamic properties.

In this paper, we will discuss a novel approach to evaluate the quality of railway tracks based on wheel–rail dynamics: Wheelset dynamics of subway trains are analyzed by Karhunen–Loève Transformation to extract the principal dynamics from the collected measurement data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial Random Material Property Model for Vibration of Composites
Authors: Machina Gangadhar , Zehn Manfred W.
Published: January 2007

Investigation of vibration and buckling of thin walled composite structures is very sensitive to parameters like uncertain material properties and thickness imperfections. Because of the manufacturing process and others, thin walled composite and other structures show uncertainties in material properties, and other parameters which cannot be reduced by refined discretization. These parameters are mostly spatial distributed in nature. Here I introduce a semivariogram type material property model to predict the spatial distributed material property (like young's modulus) over the structure. The computation of semivariogram parameters needs the local material properties over a prespecified gird. The material properties at each grid have been obtained by considering a statistically homogeneous representative volume element (RVE) at each gird. According to random nature of the spatial arrangement of fibers, the statistically homogeneous RVE is obtained using image processing. The effective material properties of the RVE have been obtained numerically with the help of periodic boundary condition. The methodology is applied to a composite panel model and modal analysis has been carried. The results of the modal analysis (eigen values and mode shapes) are compared with experimental modal analysis results which are in good agreement. Using the presented material property model we can better predict the vibration characteristics of the thin walled composite structures with the inherent uncertainties. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of critical motions of floating structures
Authors: Pick Marc‐André , Kreuzer Edwin , Wagner Jörg
Published: January 2007

Validation of numerical methods for describing the motion of a ship in sea conditions by adequate experiments is a major research field in ocean engineering. For the development of a method for the systematic determination of critical and safe operational conditions and for the classification of capsize scenarios bifurcation analyses are performed. The computational effort for these analyses is enormous using a full model describing the nonlinear dynamics of a floating body. Therefore, a method for model reduction is currently being developed at the Institute of Mechanics and Ocean Engineering at TUHH. Bases for the validation of this new method are experiments conducted in the institute's wave tank. The determination of position and attitude of the body is performed with an integrated measurement system: An inertial measurement unit and a video system are combined using an extended Kalman Filter. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibration Analysis in Mechanical and Medical Engineering
Authors: Reicke L. , Kröger M.
Published: January 2007

This contribution gives an introduction to time‐frequency analysis. A comparison of the basic principles of linear timefrequency analysis explains, in what kind of applications the short‐time fourier transform (STFT) is superior to wavelet transforms. Subsequently, the STFT is performed on signals of mechanical and medical origin to illustrate its potential with regard to vibration analysis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐Dimensional Simulation of a Circulating Monocable Ropeway
Authors: Renezeder Hans C. , Steindl Alois , Troger Hans
Published: January 2007

We investigate the practically interesting case of ‘sag‐oscillations’ of circulating monocable ropeways using a simple but very instructive three‐dimensional Finite Element model with two cable spans and discuss the qualitative results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Paper Machine Roll Contact with Beating Vibrations
Authors: Yuan L. , Järvenpää V.‐M.
Published: January 2007

Beating vibration phenomenon observed in paper machine roll units is studied. An analytical model of a roll system is described and an expression for the beating frequency is derived. Numerical results are compared to measurements and conclusions are made based on the observations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibration Analysis of Gyroscopic Systems
Authors: Zwiers U. , Braun M.
Published: January 2007

Mechanical structures which can vibrate about a state of mean rotation or translation may constitute gyroscopic dynamic systems that are related by the mathematical similarity of their governing equations of motion. Considering as examples a rotating circular ring and an axially travelling string, the analogy of those systems is demonstrated. The linear vibrations obtained by superposing small perturbations on the stationary solution are analyzed. Assuming time‐varying speeds, the effect of non‐constant stress resultants on the dynamic stability of gyroscopic systems is investigated and the results are compared to those found in literature where the stress resultants of axially moving continua are commonly taken as constant. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parameteridentification of Hostun‐Sand and Shear‐Band Simulation of Landsliding
Authors: Avci O. , Ehlers W.
Published: January 2007

The simulation of deformation process of landsliding needs the knowledge of the very complex behaviour of granular materials, e. g., sand. The triax experiments on sand show a highly non‐linear elasto‐plastic material behaviour. Therefore, it is necessary to use a yield criteria, e. g., single‐surface yield criteria with isotropic hardening and non‐associated plastic potential, which satisfies adequately the requirements of the material properties.

This kind of material behaviour can be described by an elasto‐plastic material law in the frame of Theory of Porous Media, which is implemented in the FE tool PANDAS. By means of the data of Hostun‐Sand, the material parameters of the singlesurface yield criteria are determined by use of a optimization algorithm, namely Sequential Quadratic Programming (SQP) a gradient based optimization method, which is coupled with PANDAS. Using this optimized material parameters, a simulation of a initial boundary‐value problem of landsliding is presented. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and Simulation of the Portevin‐Le Chatelier Effect
Authors: Bertram Albrecht , Böhlke Thomas , Brüggemann Carina , Estrin Yuri , Lebyodkin Mikhail
Published: January 2007

During deformation of an Al‐Mg alloy (AA5754) dynamic strain aging occurs in a certain range of temperatures and strainrates. An extreme manifestation of this phenomenon, usually referred to as the Portevin‐Le Chatelier (PLC) effect, consists in the occurrence of strain localisation bands accompanied with discontinuous yielding. The PLC effect stems from dynamic dislocation‐solute interactions and results in negative strain‐rate sensitivity of the flow stress. The PLC effect is detrimental to the surface quality of sheet metals and also affects the ductility of the material. Since the appearance of the effect strongly depends on the triaxiality of the stress state, three‐dimensional finite element simulations are necessary in order to optimize metal forming operations. We present a geometrically nonlinear material model which reproduces the main features of the PLC effect. The material parameters were identified based on experimental data from tensile tests. Special emphasis was put on the critical strain for the onset of PLC effect, ε c , and the statistical characteristics of the stress drop distribution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of strain induced austenite‐martensite transformation
Authors: Bontcheva Nikolina , Petrov Peter , Petzov Georgi , Parashkevova Ludmils
Published: January 2007

Grain refinement due to phase transformation is an effective method for improving the mechanical properties of steel. An approach is proposed in the present work based on the FEM, for numerical simulation of the microstructure evolution as a result of hot rolling and subsequent cold torsion. Grain refinement in 304 stainless steel at four different technological schedules is considered. Results of numerical simulation are compared with experimental data. Coupling of the thermoplastic deformation with microstructure evolution is realized. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Materialmodelling of shape memory alloys in range of large deformations
Authors: Christ Daniel , Reese Stefanie
Published: January 2007

In this contribution we present a finite deformation material model for SMA which includes the effect of pseudoelasticity. The model's structure is similiar to a Frederick‐Armstrong type hardening model for elastoplasticity. A special algorithm has been developed to incorporate the concept into a FE code. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dual reciprocity BEM for dynamic piezoelectricity
Authors: Dziatkiewicz Grzegorz , Fedelinski Piotr
Published: January 2007

The piezoelectric phenomenon is widely utilized in many devices. An analysis of piezoelectric devices requires a solution of coupled mechanical and electrical partial differential equations. In this paper the boundary element method (BEM) is implemented to solve the eigenvalue two‐dimensional problem of linear piezoelectricity. The piezoelectric material is modeled as: homogenous, transversal isotropic, linear elastic and dielectric. The numerical solution by the BEM requires fundamental solutions,which are derived using the Stroh formalism. The mass matrix of piezoelectric is computed by the dual reciprocity BEM. A numerical example shows that the dual reciprocity BEM formulation allows to analyze accurately dynamic problems of linear piezoelectricity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational Material Forces in Micromorphic Continua
Authors: Hirschberger C. Britta , Kuhl Ellen , Steinmann Paul
Published: January 2007

The micromorphic continuum theory is used to describe materials with significant microstructure which thus exhibit scaledependence (see e.g. [1], [2] [3]). Microcontinua are assumed to be attached to each physical point and may experience both stretch and rotation which are affine throughout the microcontinuum, nevertheless kinematically independent from the deformation on the macroscale. The additional kinematical quantities which account for the micro‐deformation yield additional stresses and contributions to the balance of momentum. Additionally to the common finite‐element approximation which here is a coupled problem to be solved for macro‐ and the micro‐quantities, we apply the method of material forces, cf. [4], [5]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling and simulation of extrusion of aluminum alloys
Authors: Kayser Tobias , Hortig Christian , Svendsen Bob
Published: January 2007

The purpose of this work is the modeling and simulation of the material behavior of aluminum alloys during extrusion, cooling and metal forming processes. In particular, the alloys of the 6000 series (Al‐Mg‐Si) and 7000 series (Al‐Zn‐Mg) are relevant here. Under the corresponding conditions, their behavior is controlled mainly by dynamic recovery during the extrusion and static recrystallization during cooling. The current material model is based on the role of the energy stored in the material during extrusion as the driving force for microstructural evolution. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experiments and Identifications for Finite Polymer Inelasticity
Authors: Méndez Joel , Göktepe Serdar , Miehe Christian
Published: January 2007

The constitutive theories intended to quantitatively account for the complicated material response exhibited by polymers include, in general, adjustable material parameters. These must be identified from experimental data obtained from the material under consideration. This contribution presents the complete procedure studying the behavior of polymers at large strains in three basic steps: i) Accomplishment of homogeneous and 3‐D inhomogeneous experiments under different deformation conditions. ii) Identification of the material parameters of a constitutive model by means of gradient–based optimization methods with respect to the homogeneous experimental data. iii) Validation of the identified material parameters by comparing 3‐D FE simulations to the inhomogeneous experimental data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Rate Dependent Plasticity of Polymers
Authors: Shaban Ahmed , Mahnken Rolf
Published: January 2007

Polycarbonate is an amorphous polymer which exhibits nonlinear deformation before failure. It shows a pronounced strength‐differential effect between compression and tension. Strain rate influences the mechanical response of the polycarbonate. In particular, the yield stress is increased with increasing strain rate. The concept of stress mode dependent weighting function is used in the proposed model to simulate the asymmetric effects for different loading speeds. In this concept, an additive decomposition of the flow rule is assumed into a sum of weighted stress mode related quantities. The characterization of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the mode angle, such that stress mode dependent scalar weighting functions can be constructed. The resulting evolution equations are updated using a backward Euler scheme and the algorithmic tangent operator is derived for the finite element equilibrium iteration. The numerical implementation of the resulting set of constitutive equations is used in a finite element program for parameter identification. The proposed model is verified by showing a good agreement with the experimental data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the Springback of Sheet Metals at Large Deformations
Authors: Vladimirov Ivaylo N. , Reese Stefanie
Published: January 2007

Sheet metal forming simulations are increasingly replacing traditional build‐and‐break prototyping because they provide a less expensive and more rapid way to speed up product design time while improving quality and performance. Sheet metal is subjected to stretching, bending and unbending during forming, and an accurate prediction of the formability and springback of the sheet necessitates the use of an appropriate constitutive model.

Use of isotropic hardening alone has been identified as a source of inaccurate springback prediction. In order to be able to describe the cyclic hardening behaviour and the Bauschinger effect, a large‐deformation elasto‐plastic material model with non‐linear kinematic hardening is discussed in the present work. The model is derived from a thermodynamical framework and is based on the multiplicative split of the deformation gradient. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibrations and heating of inelastic solids under harmonic loading
Authors: Zhuk Yaroslav
Published: January 2007

Two problem statements for the investigation of the thermomechanical behavior of inelastic materials under harmonic loading are developed. The “complete” problem statement consists of universal balance equations of thermodynamics and constitutive equations derived from the general thermodynamic theory of viscoplastic solids with internal state variables. An approximate problem statement is derived by the application of modified harmonic linearizing technique to the complete system of equations. Thereby the subsystem of mechanical equations is formulated in the complex‐value form and material properties are described by means of amplitude‐dependent complex‐value moduli. The problems of vibration and dissipative heating of physically nonlinear solids are formulated. The main thermomechanical characteristics are analyzed for some classes of problems. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparative isolation and purification of geniposide from gardenia fruits by centrifugal partition chromatography
Authors: Kim Chul Young , Kim Jinwoong
Published: January 2007

The iridoid glycoside, geniposide was purified by centrifugal partition chromatography (CPC) with a two‐phase solvent system composed of ethyl acetate:isopropanol:water (3:2:5, v/v) from an 80% methanolic extract of fruits of Gardenia jasminoides. Preparative CPC yielded 56.2 mg of geniposide in a one‐step separation of 500 mg of extract, with a purity of 95% as determined by HPLC. Isolated geniposide was identified from its 1H‐NMR, 13C‐NMR and MS spectra. Copyright © 2006 John Wiley & Sons, Ltd.