Material modelling of a sheet-layered lamination stack by homogenization

In electrical machines, sheet-layered lamination stacks play an important role for the mechanical behavior of the system. Especially the interlayer between individual sheets and their interaction have a severe influence on the structure. In the context of performance and computational effort, it is desirable to avoid a full FE simulation of a lamination stack with every single sheet. Therefore, homogenization techniques are presented to identify a transversely isotropic surrogate material model, while Zero-Thickness elements are utilized during this process to cover the interplay of single sheets. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations of the influence of geometrical irregularities and roughness on the normal contact stiffness of joints

Conducting experiments is necessary to determine the normal contact stiffness of rough surfaces. In compression tests the interface of specimen pairs is loaded in normal direction and the deflection is measured by extensometers with strain gages. The results can be used for example to describe the contact behaviour of joints in finite element analyses. It is shown that geometrical irregularities which are superposed by the surface roughness have a large influence on the elastic deformation of a joint and on the determination of the contact stiffness. They can be characterized by a skewed and a waved form of the surface with wavelengths which are larger than the surface roughness. In the experimental setup several different surfaces are compressed. In addition, the influence of the size of the contact area on the deformation of a joint is analysed. The results of the normal contact tests are compared with numerical simulations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The influence of the node criticality relation on some measures of component importance

For different reliability importance measures we prove that the criticality relation between nodes can completely determine the most important component in a system. In particular, we prove that in k-out-of-n systems, the ranking of component reliabilities determines the ranking of component importance for, at least, three different reliability importance measures.     

The influence of the stiffness of reinforcing elements on the deformed state of shells with a hole

We propose a method of experimental estimation of the influence of the stiffness of elements that reinforce the contour of a hole on the deformed state of shells under surface pressure. We obtain the experimental data for the deflections on the contour of a lateral hole in a cylindrical shell as a function of the stiffness characteristics and the caps. We compare the results of experiments with numerical computations and give an analysis of the theoretical and experimental data obtained. Three figures. Bibliography: 5 titles. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 22, pp. 67–71, 1991.     

Effects of the urban environment on the trajectories of stack plumes

A numerical model for plume rise is used, together with a model of the urban mixing layer, to study the effects of the inhomogeneous temperature structure of the city of Leeds on the trajectory of effluent plumes. Consideration is given to chimney location, source strength, city topography, areal sources, wind speed and rural ground level temperatures.     

Analysis of the stator/rotor-contact in a two stators hybrid transducer type ultrasonic motor

This paper presents the procedure to understand the contact mechanism of the hybrid transducer type piezoelectric ultrasonic motor with two stators by using finite element analysis. First, the vibration mode of a stator will be calculated and analyzed using the commercial finite element program package ANSYS. The computed resonance frequencies of the stator will be presented in the frequency domain, in term of input admittance analysis. After that the distribution of the elliptic path of motion of a particle on the stator surface area will be studied. Finally, the contact condition between the stator and the rotor will be addressed in the computation. The normal displacement, normal velocity and tangential velocity of a point on stator surface area will be calculated. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the average oscillation of a stack

Evaluating a binary tree in postorder we assume that in one unit of time zero or two nodes are removed from the top of the stack and one node is stored in the stack. The oscillation of the stack can be described by a functionf wheref(t) is the number of nodes in the stack aftert units of time. In this paper we shall first derive several new enumeration results concerning planted plane trees. In the second part we shall prove, that the average number of maxima (MAX-turns) and minima (MIN-turns) of the functionf isn/2 andn/2—1, respectively, provided that all binary trees withn leaves are equally likely. Finally, we shall compute for largen and fixedj the average increase (decrease) of the length of the stack between thej-th MIN-turn and (j+1)-th MAX-turn (between thej-th MAX-turn and thej-th MIN-turn). This result implies that the average oscillation of the stack can be described by the functionf(j)=4√j/π−(−1) ^j +O(1/√j) for largen and fixed turn-numberj.     

A note on the stack size of regularly distributed binary trees

Assume that in one unit of time a node is stored in the stack or is removed from the top of the stack during postorder-traversing of a binary tree. If all binary trees are equally likely the average stack size aftert units of time and the variance is computed as a function of the proportion=t/n.Part of this paper was presented at the 6th Colloquium on Automata, Languages and Programming, ICALP' 79, July 1979.     

Borel-Weil-Bott theory on the moduli stack of G-bundles over a curve

Let G be a semi-simple group and M the moduli stack of G-bundles over a smooth, complex, projective curve. Using representation-theoretic methods, I prove the pure-dimensionality of sheaf cohomology for certain “evaluation vector bundles” over M, twisted by powers of the fundamental line bundle. This result is used to prove a Borel-Weil-Bott theorem, conjectured by G. Segal, for certain generalized flag varieties of loop groups. Along the way, the homotopy type of the group of algebraic maps from an affine curve to G, and the homotopy type, the Hodge theory and the Picard group of M are described. One auxiliary result, in Appendix A, is the Alexander cohomology theorem conjectured in [Gro2]. A self-contained account of the “uniformization theorem” of [LS] for the stack M is given, including a proof of a key result of Drinfeld and Simpson (in characteristic 0). A basic survey of the simplicial theory of stacks is outlined in Appendix B. Oblatum 17-XII-1996 & 26 VI-1997     

On the motivic class of the stack of bundles

Let G be a split connected semisimple group over a field. We give a conjectural formula for the motivic class of the stack of G-bundles over a curve C, in terms of special values of the motivic zeta function of C. The formula is true if C=P¹ or G=SLn. If k=C, upon applying the Poincaré or called the Serre characteristic by some authors the formula reduces to results of Teleman and Atiyah-Bott on the gauge group. If k=Fq, upon applying the counting measure, it reduces to the fact that the Tamagawa number of G over the function field of C is |π₁(G)|.     

On the derived category of quasi-coherent sheaves on an Adams geometric stack

Let $\mathsf{X}$ be an Adams geometric stack. We show that $\mathsf{D}({\mathsf{A}}_{\mathsf{qc}}(\mathsf{X}))$, its derived category of quasi-coherent sheaves, satisfies the axioms of a stable homotopy category defined by Hovey, Palmieri and Strickland in [13]. Moreover we show how this structure relates to the derived category of comodules over a Hopf algebroid that determines $\mathsf{X}$.     

Analysis of an industrial component commonality problem

We discuss a case study of an industrial production-marketing coordination problem involving component commonality. For the product line considered, the strategic goal of the company is to move from the current low volume market to a high volume market. The marketing department believes that this can be achieved by substantially lowering the end products’ prices. However, this requires a product redesign to lower production costs in order to maintain profit margins. The redesign decision involves grouping end products into families. All products within one family use the same version of some components. This paper fits in the stream of recent literature on component commonality where the focus has shifted from inventory cost savings to production and development cost savings. Further, we consider both costs and revenues, leading to a profit maximization approach. The price elasticity of demand determines the relationship between the price level and number of units sold. Consequently, we integrate information from different functional areas such as production, marketing and accounting. We formulate the problem as a net-present-value investment decision. We propose a mixed integer nonlinear optimization model to find the optimal commonality decision. The recommendation based on our analysis has been implemented in the company. In addition, the application allows us to experimentally validate some claims made in the literature and obtain managerial insights into the trade-offs.     

Components of the stack of torsion-free sheaves of rank 2 on ruled surfaces

Supported in part by NSA research grant MDA904-92-H-3009     

Effect of strainrate on the stiffness of polyamide gear teeth

Mechanics of Composite Materials -     

Analysis and comparison of several component mode synthesis methods on one-dimensional domains

O Summary Component mode synthesis methods enable to compute the eigenpairs of a differential operator on a domain that can be subdivided in different subdomains on each of which the eigenpairs of the same operator are assumed to be partially known. Error estimates are given for several of these methods applied to second order elliptic operators on one-dimensional domains. They are partly tied to an argument which is called here asymptotic hidden regularity of eigenfunctions of an elliptic operator.     

Novel design model for the stator currents subsystem of induction motors

The stator currents subsystem is a vital element of many high-performance induction motor control schemes. While there are several control techniques available for this subsystem, traditional linear controllers are still widely used because of its simplicity and proven effectiveness. However, the traditional simplified design-model lacks important information, necessary for the design of high-performance and robust controllers. In this article a novel design-model intended for linear controller formulation and evaluation is developed. This new mathematical representation captures several elements which are missing in the traditional representation, maintaining at the same time a similar level of simplicity. Along the derivation of this new representation several models of decreasing complexity and comprehensiveness are also presented together with a critical classification. This classification is intended to aid the designer in choosing the appropriate mathematical representation for specific purposes. Finally, the article is accompanied with experimental findings which illustrate the use of the proposed model.     

环境因素对独立学院办学效益的影响——基于DEA的实证分析

为提高独立学院教育资源配置效率,基于数据包络分析理论,构建了独立学院相对办学效益测评指标体系及模型,将独立学院所在地区经济、人口和母体高校声誉等环境因素视为不可控投入要素纳入其中,分析了这些环境因素对45所独立学院办学效益的影响,得出了一个有趣的结论:即使环境因素对独立学院的办学效益不起主要作用,但是,可能会显著影响其投入与产出的改进量.