An iterative method of evaluation of elastic-plastic deflections of hyperstatic framed structures

Summary The concept of substitutive concentrated elastic-plastic rotations, replacing actual elasticplastic zones is used, together with an iterative method of determination of the bending moment distribution to simplify the evaluation of elastic-plastic deflections of hyperstatic beams and frames.

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Eine iterative Methode der Auswertung von elastisch-plastischen Verschiebungen für statisch unbestimmte Rahmen

Übersicht Die Idee von fiktiven Ersatzrotationen, welche die tatsächlichen elastisch-plastischen Zonen modelliert, wird mit einer iterativen Methode kombiniert, um eine relativ einfache Bestimmung von Biegemomentenfeldern in statisch unbestimmten Balken und Rahmen zu ermöglichen. Die resultierenden Verschiebungen, ergeben sich mit ausreichender Genauigkeit.

     

Effects of pressure on optical F-bands in rubidium halides

High pressure optical absorption measurements have been made on additively colored RbCl and RbBr at pressures up to 10 kbar and on electrolytically colored Rbl up to 4 kbar. The pressure dependence of the F-band produced in RbCl by x-irradiation in the s.c. phase is also reported. Effects of the pressure induced structure transformation in these salts are described. F-band pressure shifts are related to a semi-empirical treatment which takes account of relative ion sizes. A new Ivey law for F-centers in host crystals having the s.c. structure is presented. This relation is established using all available F-band data including those for salts transformed to the s.c. structure by the application of high pressure.     

Wechselnde Bindungen in einem Zweikörpersystem mit trockener Reibung

Übersicht Betrachtet wird ein zwangserregtes Zweikörpersystem mit wechselnden Bindungen infolge trockener Reibung. Stationäre Bewegungen werden als Grenzfall instationärer Einschwingvorgänge berechnet. Abhängig von den Systemparametern ergeben sich drei typische Bewegungsformen. Ihnen entsprechen dauernde Haftzustände, wechselnde Haft-Gleitzustände oder dauernde Gleitzustände an der Berührfläche beider Körper.

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Intermittant constraints in a two-body-system with dry friction

Summary An externally excited two-body-system with intermittant constraints due to dry friction is considered. Stationary motions are calculated as limit cases of instationary transients. Depending on the parameters of the system, three typical modes are of interest. These correspond to permanent sticking, slipstick behaviour, or to permanent slipping in the contact surface of the bodies, respectively.

     

W-Gleitgleitkinematik

The following gives some starting elements of a theory, which the author calls glide-glide-kinematics and which goes far beyond the kinematics of helical motion in ℝ ⁿ , which was studied up to now. We are mainly concerned here with “angle-preservering glide-glide-kinematics”, generalising (and giving as well some idea of) the distance-preservering glide-glide-kinematics, which we develop in a forthcoming book ([5]) in detail.      

The ground state for sticky disks

It is proven that the ground state of the two-dimensional sticky potential is the triangular lattice.Research supported in part by NSF grant MCS 78-01520-A01.     

Riemann-measurable selections

LetX be a Polish space equipped with a σ-finite regular Borel measure μ. IfE is a metric space andF a set-valued function:X → 2 ^E with complete values, and ifF is lower semicontinuous at almost all points ofX, we prove that there exists a Riemann-measurable selections ofF.     

Comparison of simulations and data from a seismo-acoustic tank experiment

A tank experiment was carried out to investigate underwater sound propagation over an elastic bottom in flat and sloping configurations. The purpose of the experiment was to evaluate range-dependent propagation models with high-quality experimental data. The sea floor was modeled as an elastic medium by a polyvinyl chloride slab. The relatively high rigidity of the slab requires accounting for shear waves in this environment. Acoustic measurements were obtained along virtual arrays in the water column using a robotic apparatus. Elastic parabolic equation solutions are in excellent agreement with data.     

Prediction of the acoustic behavior of a parallel assembly of hollow cylinders

In this paper, an approach to predict the sound absorption coefficient and sound transmission loss of a parallel assembly of hollow cylinders is presented. This approach is based on image processing and the Parallel Transfer Matrix Method (PTMM) using four Johnson–Champoux–Allard effective fluids. First, effective parameters of each fluid are identified using geometrical considerations and numerical simulations. Then, the approach is validated for a stack of uniform plastic straws, and used to model a natural stack of non-uniform switchgrass straws. Finally, two parametric studies are conducted to evaluate the effects of the geometric parameters of the straws on the acoustic behavior of their stack. It is shown that there are optimal parameters that maximize the acoustic behavior at specific frequencies.     

Which sets are images of disk-algebra functions?

We give a characterization of those compact sets in the plane with finitely many holes that are images of disk-algebra functions. We also show that the image of the closed unit disk via a polynomial is, in general, not polynomially convex.