A Low-Cost Robust Distributed Linearly Constrained Beamformer for Wireless Acoustic Sensor Networks with Arbitrary Topology

We propose a new robust distributed linearly constrained beamformer which utilizes a set of linear equality constraints to reduce the cross power spectral density matrix to a block-diagonal form. The proposed beamformer has a convenient objective function for use in arbitrary distributed network topologies while having identical performance to a centralized implementation. Moreover, the new optimization problem is robust to relative acoustic transfer function (RATF) estimation errors and to target activity detection (TAD) errors. Two variants of the proposed beamformer are presented and evaluated in the context of multi-microphone speech enhancement in a wireless acoustic sensor network, and are compared with other state-of-the-art distributed beamformers in terms of communication costs and robustness to RATF estimation errors and TAD errors

An Analysis of the Representations of the Mapping Class Group of a Multi-Geon Three-Manifold

It is well known that the inequivalent unitary irreducible representations (UIR's) of the mapping class group $G$ of a 3-manifold give rise to ``theta sectors'' in theories of quantum gravity with fixed spatial topology. In this paper, we study several families of UIR's of $G$ and attempt to understand the physical implications of the resulting quantum sectors. The mapping class group of a three-manifold which is the connected sum of $\R^3$ with a finite number of identical irreducible primes is a semi-direct product group. Following Mackey's theory of induced representations, we provide an analysis of the structure of the general finite dimensional UIR of such a group. In the picture of quantized primes as particles (topological geons), this general group-theoretic analysis enables one to draw several interesting qualitative conclusions about the geons' behavior in different quantum sectors, without requiring an explicit knowledge of the UIR's corresponding to the individual primes.Comment: 52 pages, harvmac, 2 postscript figures, epsf required. Added an appendix proving the semi-direct product structure of the MCG, corrected an error in the characterization of the slide subgroup, reworded extensively. All our analysis and conclusions remain as befor

Het effect van werk op de criminele carrière van jeugdige zedendelinquenten

In this paper delinquent development from age 12 to 29 of 498 juvenile sex offenders is analyzed. Fixed and random effects models are used to determine the effect of employment and of the stability of employment on the criminal career. We first show that juvenile sex offenders have limited access to the labor market, with stagnating participation rates from age 25 on, many different and short contracts. In spite of this, employment reduces offending, and having stable employment has an additional reducing effect on crime. We also looked at three types of sex offenders (child abusers, peer abusers and group offenders), who have a different background and for whom therefore effects could differ. We found no difference for offender types in the effect of employment on offending. The effects of employment stability, however, were due to only child abusers experiencing significant effects of continuity. We conclude that for juvenile sex offenders employment impacts similarly on offending as was found in previous studies among high-risk groups. Met behulp van een fixed- en random-effectsmodel onderzochten wij het effect van werk op de criminele carrière van 498 jeugdige zedendelinquenten van 12 tot gemiddeld bijna 29 jaar. Wij laten allereerst zien dat de transities van jeugdige zedendelinquenten naar de arbeidsmarkt beperkt zijn: vanaf 25 jaar stagneert participatie, en veel jeugdige zedendelinquenten werken in wisselende en korte contracten. Desondanks vonden wij zowel voor het hebben als voor de continuïteit van een baan een significant remmend effect op delinquentie. Gezien de verschillen in probleemachtergrond onderzochten wij vervolgens of deze effecten verschillen voor diverse typen zedendelinquenten (kindmisbruiker, leeftijdgenootmisbruiker en groepsdader). Wij vonden dat de effecten niet verschilden. Het additioneel dempend effect van werkcontinuïteit werd alleen gevonden bij de kindmisbruikers: bij deze groep zien we dat de kans op criminaliteit bij langere contractduur verder afneemt. Wij concluderen dat - net als in andere hoogrisicogroepen - werk bij jeugdige zedendelinquenten een remmend effect heeft op de criminele carrière

Permeability characteristics of human endothelial monolayers seeded on different extracellular matrix proteins.

OBJECTIVE: To investigate whether endothelial monolayer permeability changes induced by inflammatory mediators are affected by the extracellular matrix protein used for cell seeding. METHODS: Human umbilical venular endothelial cells (HUVEC) were grown to confluent monolayers on membranes coated with either collagen, fibronectin or gelatin. The permeability to albumin and dextran was then assessed, both under normal conditions and after treatment with tumor necrosis factor-alpha (TNF-alpha) and bacterial lipopolysaccharide (LPS). RESULTS: With any of the three protein coatings, tight junctions were formed all over the monolayers. The permeability of the coated membranes to albumin and dextran was reduced strongly by confluent monolayers; the relative reduction was similar for the three matrix proteins used. Pre-incubation of the monolayers with either TNF-alpha or LPS increased permeability dose dependently. However, the relative increase due to either treatment was independent of the protein used for membrane coating. CONCLUSION: The extracellular matrix protein used for initial seeding of endothelial cultures plays a minor role in determining the permeability changes induced in HUVEC monolayers by inflammatory mediators

Cyclic Statistics In Three Dimensions

While 2-dimensional quantum systems are known to exhibit non-permutation, braid group statistics, it is widely expected that quantum statistics in 3-dimensions is solely determined by representations of the permutation group. This expectation is false for certain 3-dimensional systems, as was shown by the authors of ref. [1,2,3]. In this work we demonstrate the existence of ``cyclic'', or $Z_n$, {\it non-permutation group} statistics for a system of n > 2 identical, unknotted rings embedded in $R^3$. We make crucial use of a theorem due to Goldsmith in conjunction with the so called Fuchs-Rabinovitch relations for the automorphisms of the free product group on n elements.Comment: 13 pages, 1 figure, LaTex, minor page reformattin