Distribution of the reflection eigenvalues of a weakly absorbing chaotic cavity

The scattering-matrix product SS+ of a weakly absorbing medium is related by a unitary transformation to the time-delay matrix without absorption. It follows from this relationship that the eigenvalues of SS+ for a weakly absorbing chaotic cavity are distributed according to a generalized Laguerre ensemble.Comment: 4 pages, 1 figure, to appear in Physica E (special issue on Dynamics of Complex Systems

The Old and the Stubborn? Firm Characteristics and Relocation in the Netherlands

This study gives some insight into the relationships between the spatial environment, firm characteristics and long term existence of firms in the Netherlands. A logit model is employed to investigate the locational difference of firms, considering firm characteristics such as age, size, region and network. The main findings are that (long-term) continuation of the location and firm size are positively associated with long-term existence of firms

A modified version of frozen percolation on the binary tree

We consider the following, intuitively described process: at time zero, all sites of a binary tree are at rest. Each site becomes activated at a random uniform [0,1] time, independent of the other sites. As soon as a site is in an infinite cluster of activated sites, this cluster of activated sites freezes. The main question is whether a process like this exists. Aldous [Ald00] proved that this is the case for a slightly different version of frozen percolation. In this paper we construct a process that fits the intuitive description and discuss some properties.Comment: 19 pages, 2 figure

Food systems research in Ethiopia: 25 priority questions identified

Poster prepared for a share fair, Addis Ababa, May 201

Design principles for six degrees-of-freedom MEMS-based precision manipulators

In the future, the precision manipulation of small objects will become more and more important for appliances such as data storage, micro assembly, sample manipulation in microscopes, cell manipulation, and manipulation of beam paths by micro mirrors. At the same time, there is a drive towards miniaturized systems.\ud Therefore, Micro ElectroMechanical Systems (MEMS), a fabrication technique enabling micron sized features, has been researched for precision manipulation. MEMS devices comprise micro sensors, actuators, mechanisms, optics and fluidic systems. They have the ability to integrate several functions in a small package. MEMS can be commercially attractive by providing cost reduction or enabling new functionality with respect to macro systems. Combining design principles, a mature design philosophy for creating precision machines, and MEMS fabrication, a\ud technology for miniaturization, could lead to micro systems with deterministic behavior and accurate positioning capability. However, in MEMS design trade-offs\ud need to be made between fabrication complexity and design principle requirements.\ud Therefore, the goal of this research has been twofold:\ud 1. Design and manufacture a 6 Degrees-of-Freedom (DOFs) MEMS-based manipulator with nanometer resolution positioning.\ud 2. Derive principle solutions for the synthesis of exact kinematic constraint design and MEMS fabrication technology for multi DOFs precision manipulation in the\ud micro domain

Magnetic-field symmetries of mesoscopic nonlinear conductance

We examine contributions to the dc-current of mesoscopic samples which are non-linear in applied voltage. In the presence of a magnetic field, the current can be decomposed into components which are odd (antisymmetric) and even (symmetric) under flux reversal. For a two-terminal chaotic cavity, these components turn out to be very sensitive to the strength of the Coulomb interaction and the asymmetry of the contact conductances. For both two- and multi-terminal quantum dots we discuss correlations of current non-linearity in voltage measured at different magnetic fields and temperatures.Comment: 9 pages, 4 figure

Two distance-regular graphs

We construct two families of distance-regular graphs, namely the subgraph of the dual polar graph of type B_3(q) induced on the vertices far from a fixed point, and the subgraph of the dual polar graph of type D_4(q) induced on the vertices far from a fixed edge. The latter is the extended bipartite double of the former