Relation between hardness and compressive strength of polymer concrete

Experimental studies were made of the influence of mixing and casting techniques and of curing time upon the compressive strength and hardness of methyl methacrylate based polymer concrete. The Rockwell K and F scales were found to be suitable for the hardness determinations. Over a wide range of hardness and strength values, the average compressive strength (f_c) varied linearly with the average hardness (R_K) according to the relation f_c (psi) = 560 R_K - 12000, irrespective of casting and curing variables. The weaker materials exhibited greater variations in hardness. Hardness testing is found to provide a meaningful and convenient method for evaluating the quality of polymer concrete.     

INTEGER analysis of two-dimensional polygonal objects

A consistent modelling scheme for digital images is presented, with the grey-level raster image as input and the list-oriented polygonal image as output. The output information consists of two parts: The metric of the polygonal object, represented by coordinates of marked positions, and the global topology, which takes the form of a two-dimensional topologic order. The central problem, which has to be solved, is to select a digital polygon, approximating a digital arc such that the essential feature of the arc is represented at a predefined precision level. The proposed algorithm uses simple incremental calculations of INTEGER quantities to solve the problem.     

On the deformation of circular cylindrical rubber bars under axial thrust

Summary The axisymmetric bulging of circular cylindrical rubber bars under end thrust is investigated. The results for different forms of the strain energy function are compared with experimental results.With 2 Figures     

Computation of nonlinear functionals in particle methods

We consider the numerical computation of nonlinear functionals of distribution functions approximated by point measures. Two methods are described and estimates for the speed of convergence as the number of points tends to infinity are given. Moreover, numerical results for the entropy functional are presented.     

Analysis of ink flow in a mimeograph printer based on the mechanics of fluid-filled poroelastic solids

Summary To understand some main ink flow mechanisms in a mimeograph printer, the continuum mechanics theory of fluid-saturated porous solids is applied to analyze the ink flow through screens and a printing master, which are modeled by a fluid-filled poroelastic single layer. The layer is assumed to be pressed by a press roller from below and to be subjected from above to the hydrodynamic lubrication pressure induced between a printing drum and an ink roller. Nonlinear elasticity of the layer and dependence of the permeability on its deformation are taken into account. The numerical results show some important results: e.g., squeezing-out of the ink from the layer by the layer compaction by the press roller plays an important role, especially for the case where the compression duration is small in comparison with the characteristic time of the ink-filled poroelastic layer.     

Traditional organizations and crisis management in transition—Organizational perspectives on new dynamics of independent civil engagement

Digitalization and the trend towards more short‐term and project‐oriented social engagement have had a direct impact on traditional crisis management. This societal change has supported the evolution of new types of volunteers who use low‐threshold potentials to organize and maintain support independently. Traditional institutions like the German Red Cross are challenged to deal with these rapid changes regarding their own organizational culture in relation to the new phenomenon of so‐called unaffiliated volunteers. This paper investigates how unaffiliated volunteers influence and change the organizational culture of German disaster management by analysing and reflecting organizational adaptation processes in the aftermath of the German floods in 2013, the storm events in the west of Germany in 2014 and the refugee relief mission in 2015–2016. Therefore, semi‐structured interviews with experts of the German Red Cross were held to analyse their reactions towards unaffiliated Volunteers during the Floods in 2013 and the refugee relief missions, and further focus group interviews were conducted to validate the extracted results. Findings suggest that among professionals and leading entities in the German Red Cross, a process of rethinking has emerged, recognizing the importance and necessity to open up organizational structures for the collaboration and coordination of unaffiliated volunteers.     

A route to chaos in a nonlinear oscillator with delay

Summary The paper presents an analysis of the transition from regular to chaotic motion in a Van der Pol-Duffing's oscillator with delay after a Hopf bifurcation. The conditions for the occurrence of the Hopf bifurcation have been determined by means of the approximate method. For the parameters near the bifurcation point a computer simulation of the vibrating system had been performed and the evolution of the system from regular motion to chaos has been analysed at the decrease of the value of the dimensionless damping coefficient.With 2 Figures     

The incorporation of yield surface distortion into a unified constitutive model,part 2: Predictive capabilities

Summary The MATMOD-4V-DISTORTION model has been derived [1] with the intent of improving the MATMOD-4V model by adding the capability to predict distortions of small strain offset yield surfaces. This model is compared against a variety of experimental data to verify its behavior. Model simulations are compared with experimental data for proportional and nonproportional prestress histories and the effect of yield definition is also investigated. Finally, the same model which predicts a flattening of the yield surface in space is used to predict a rotation of the yield surface in ₁-₂ coordinates.With 9 Figures     

Stromdichte- und Magnetfeldverteilung bei einer Anordnung aus Platten und vielen parallelen Stromleitern

Übersicht Die vorliegende Arbeit befaßt sich mit der gesamten Stromdichte- und Magnetfeldverteilung in vielen flachen leitenden Platten konstanter Permeabilität, die bei einer Anordnung aus diesen Platten und vielen parallelen stromführenden Leitern angeordnet in mehreren Lagen entsteht. Unter Anwendung der Maxwellschen Differentialgleichungen und durch Einführung des Vektorpotentials werden allgemeine Gleichungen für die Komponenten der magnetischen Induktion im zweidimensionalen Feldraum aufgestellt. Die Stromdichteverteilung in den leitenden Platten, in denen Wirbelströme entstehen, wird aus dem Vektorpotential hergeleitet. Zunächst werden die Platten unendlich lang angenommen und die entsprechenden Gleichungen in Integralform aufgestellt, für deren Lösung die Gauss-Laguerresche Methode angewandt wird. Dann werden die Platten beiderseits durch Eisenwände begrenzt, womit die Gleichungen unter Berücksichtigung der Randbedingungen in Summenform ausgedrückt werden.

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Distribution of current and magnetic field density in flat conductive plates in an array composed from plates and many parallel conductors

Contents In the present research work the overall distribution of current and magnetic field density in many flat plates of constant magnetic permeability has been investigated, which applies to an array composed from the flat plates and many parallel conductors installed in many layers. Use of Maxwell's differential equations and vector potential results in general equations for the components of magnetic density in two dimensional field space. The distribution of current density in the conductive plates, where eddy currents are taken into account, is obtained from the vector potential. Initially the flat plates are considered being of infinite length, and with appropriate arrangement of the boundary conditions, the model applies to flat plates limited to both sides by iron partitions. Examples are given for both cases, where for the plates of infinite length the Gauss-Laguerre method is applied.

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Liste der Symbole A Vektorpotential - B Magnetische Induktion - I ₁ Stromstärke eines Leiters - N ₁ Anzahl der parallelen Leiter - N ₂ Anzahl der parallelen Platten - Permeabilität des Plattenmaterials - _r Relative Permeabilitätskonstante des Plattenmaterials - Leitfähigkeit - b Breite des Hauptstreukanals - i Stromdichte der Platten samt Wirbelströme - h ₁ Höhe der Leiter - a ₁ Breite der Leiterlagen - a Plattendicke - s Breite des Nebenstreukanals - c Abstand der letzten Platte von der Eisenwand - g Plattenhöhe - x, z, , Dimensionen - Q, K Integrationskonstanten - k ganze Zahl