Leibniz University of Hanover

About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Computer science. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.

The Theory of Assortative Matching Based on Costly Signals

Abstract: We study two-sided markets with a finite number of agents on each side, and with two-sided incomplete information. Agents are matched assortatively on the basis of costly signals. Asymmetries in signalling activity between the two sides of the market can be explained by asymmetries either in size or in heterogeneity. Our main results identify general conditions under which the potential increase in expected output due to assortative matching (relative to random matching) is offset by the costs of signalling. Finally, we examine the limit model with a continuum of agents and point out differences and similarities to the finite version. Technically, the paper is based on the elegant theory about stochastic order relations among differences of order statistics, pioneered by Barlow and Proschan in 1966 in the framework of reliability theory.

Isogeometric contact: a review

Abstract: This paper reviews the currently available computational contact formulations within the framework of isogeometric analysis (IGA). As opposed to conventional Lagrange discretizations, IGA basis functions feature higher and tailorable inter-element continuity, which translates into evident advantages for the description of interacting surfaces, especially in presence of large displacements and large sliding. This has recently motivated the proposal of several isogeometric contact treatments, based on different ways to incorporate the contact contribution into the variational form of a continuum mechanics problem and to formulate its discretized version. After a brief overview of conventional and isogeometric basis functions as well as conventional contact mechanics approaches, the available isogeometric contact formulations are examined. Attention is paid to the favorable and unfavorable features they share with their finite element counterparts, as well as to the consequences stemming from the use of IGA basis functions. The main needs for future research emerging from the current state of the art are outlined. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Graphical approaches for multiple comparison procedures using weighted Bonferroni, Simes, or parametric tests

Abstract: The confirmatory analysis of pre-specified multiple hypotheses has become common in pivotal clinical trials. In the recent past multiple test procedures have been developed that reflect the relative importance of different study objectives, such as fixed sequence, fallback, and gatekeeping procedures. In addition, graphical approaches have been proposed that facilitate the visualization and communication of Bonferroni-based closed test procedures for common multiple test problems, such as comparing several treatments with a control, assessing the benefit of a new drug for more than one endpoint, combined non-inferiority and superiority testing, or testing a treatment at different dose levels in an overall and a subpopulation. In this paper, we focus on extended graphical approaches by dissociating the underlying weighting strategy from the employed test procedure. This allows one to first derive suitable weighting strategies that reflect the given study objectives and subsequently apply appropriate test procedures, such as weighted Bonferroni tests, weighted parametric tests accounting for the correlation between the test statistics, or weighted Simes tests. We illustrate the extended graphical approaches with several examples. In addition, we describe briefly the gMCP package in R, which implements some of the methods described in this paper.