Zum ebenen plastischen Fließen der porigen Metalle

Übersicht In der vorliegenden Arbeit wird ein Gleichungssystem der Theorie des ebenen plastischen Fließens der porigen Metalle präsentiert. Im Gegensatz zur Theorie ideal plastischer Materialien sind die Gleichungen für die Komponenten des Spannungstensors und die Geschwindigkeitsgleichungen durch die Porosität gekoppelt. Eine Anwendungsmöglichkeit der Charakteristikenmethode wird diskutiert. Eine Linearisierung der Fließbedingung wird eingeführt und drei Randwertprobleme werden betrachtet.

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Plane plastic flow of porous metals

Summary In the paper a system of the equations for the theory of plane plastic flow of porous metals is introduced. As distinct from ideal plasticity the stress tensor and the strain rate tensor are coupled by means of a porosity function. It is discussed wether or not the method of characteristics may be used in order to solve the system. A linearization of the yield condition is introduced and three boundary value problems are investigated.

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Herrn Prof. Dr. Th. Lehmann zum 60. Geburtstag gewidmet     

The empirical process of a short-range dependent stationary sequence under Gaussian subordination

Summary Consider the stationary sequenceX ₁=G(Z ₁),X ₂=G(Z ₂),..., whereG(·) is an arbitrary Borel function andZ ₁,Z ₂,... is a mean-zero stationary Gaussian sequence with covariance functionr(k)=E(Z ₁ Z _k+1) satisfyingr(0)=1 and _k=1 |r(k)| ^m < , where, withI{·} denoting the indicator function andF(·) the continuous marginal distribution function of the sequence {X _n }, the integerm is the Hermite rank of the family {I{G(·) x} –F(x):xR}. LetF _n (·) be the empirical distribution function ofX ₁,...,X _n . We prove that, asn, the empirical processn ^1/2{F _n (·)-F(·)} converges in distribution to a Gaussian process in the spaceD[–,].Partially supported by NSF Grant DMS-9208067     

Simultaneous determination of mexiletine and four hydroxylated metabolites in human serum by high-performance liquid chromatography and its application to pharmacokinetic studies.

A high-performance liquid chromatographic method has been developed for the simultaneous determination of mexiletine and its four hydroxylated metabolites in human serum. The method involves a single-step extraction of mexiletine, hydroxymethylmexiletine, p-hydroxymexiletine and their corresponding alcohols with diisopropyl ether-dichloromethane-propan-2-ol (2.5:1.5:0.5, v/v). Separation of the compounds on a deactivated Supelcosil LC8-DB column is accomplished by high-performance liquid chromatography with ultraviolet detection at 203 nm. Overall the recovery of each compound is reproducible and greater than 75%. The lower limit of detection is 2 ng/ml for mexiletine and its metabolites. The application of the method is shown by measuring the concentrations in serum of mexiletine and its metabolites over 24 h in a healthy volunteer after a single intravenous injection of the drug and by monitoring serum concentrations in patients receiving long-term treatment by mouth of the drug.     

Random Subspace Method for high-dimensional regression with the <Emphasis FontCategory="NonProportional">R</Emphasis> package <Emphasis FontCategory="NonProportional">regRSM</Emphasis>

Model selection and variable importance assessment in high-dimensional regression are among the most important tasks in contemporary applied statistics. In our procedure, implemented in the package regRSM, the Random Subspace Method (RSM) is used to construct a variable importance measure. The variables are ordered with respect to the measures computed in the first step using the RSM and then, from the hierarchical list of models given by the ordering, the final subset of variables is chosen using information criteria or validation set. Modifications of the original method such as the weighted Random Subspace Method and the version with initial screening of redundant variables are discussed. We developed parallel implementations which enable to reduce the computation time significantly. In this paper, we give a brief overview of the methodology, demonstrate the package’s functionality and present a comparative study of the proposed algorithm and the competitive methods like lasso or CAR scores. In the performance tests the computational times for parallel implementations are compared.     

Magnetic behavior,transport properties and nanocrystallization of melt-spun YxCe50 − xCu42Al8 (0 ≤ x ≤ 50) amorphous system

Amorphous Y_xCe_50 ? xCu₄₂Al₈ (0 ≤ x ≤ 50) ribbons prepared by melt-spinning on the Cu wheel were subjected to X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and to the measurements of magnetization and resistivity in the temperature range from 1.7 to 300 K. Effective activation energies, characteristic crystallization temperatures and enthalpies of as-quenched alloys have been determined. Two stages of crystallization have been observed in most samples (except shallow effects in Ce₅₀Cu₄₂Al₈). The activation energies have been calculated from the Kissinger relation to be 247 ± 18 and 570 ± 56 kJ/mol for Y₂₅Ce₂₅Cu₄₂Al₈ and Y₅₀Cu₄₂Al₈, respectively. The absence of the endothermic effect for x = 50, usually associated with a glass transition, below the primary crystallization event, indicates the presence of dispersed polyamorphous packing with a wide range of local glass transitions. The magnetization versus temperature plot for Y₂₅Ce₂₅Cu₄₂Al₈ points to a magnetic ordering at temperatures considerably below 50 K. This observation has been confirmed by the temperature dependence of resistivity, which exhibits a singularity at the same temperature. Moreover, a negative temperature coefficient of resistivity, characteristic of disordered systems, was observed. The electrical resistivity in the Y₂₅Ce₂₅Cu₄₂Al₈ amorphous alloy is governed by the weak localization of electrons.     

Verformung von gummi-flachriemen bei komplexem belastungszustand

Übersicht In dieser Arbeit wird die Formänderung eines durch Gewebe verstärkten Gummi-Flachriemens unter einem komplexen Belastungszustand behandelt. Die Annahme eines nichtlinear-elastischen Werkstoffs ermöglicht die effektive Bestimmung der uns interessierenden Abmessungen des deformierten Riemenquerschnitts und auch der Spannungsverteilungen sowohl im Gummi als auch in der Gewebeschicht. Die vorgestellte Annahme bildet eine neue genauere Methode für die Auslegungsberechnungen von Riementrieben.

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Deformation of a flat rubber belt in complex loading state

Summary The paper deals with the deformation process of a flat rubber belt reinforced with a cord layer and loaded by a complex loading state. Assuming non-linear elastic material enables us to effectively determine the cross-sectional dimensions of the deformed belt as well as the stress distribution both in the rubber and in the cord layer.This approach presents a new, more accurate calculation method for belt transmissions design.

     

Asymptotic Distributions of Empirical Interaction Information

Methodology and Computing in Applied Probability - Interaction Information is one of the most promising interaction strength measures with many desirable properties. However, its use for...