Stability of marginally outer trapped surfaces and existence of marginally outer trapped tubes

The present work extends our short communication Phys. Rev. Lett. 95, 111102 (2005). For smooth marginally outer trapped surfaces (MOTS) in a smooth spacetime we define stability with respect to variations along arbitrary vectors v normal to the MOTS. After giving some introductory material about linear non self-adjoint elliptic operators, we introduce the stability operator L_v and we characterize stable MOTS in terms of sign conditions on the principal eigenvalue of L_v. The main result shows that given a strictly stable MOTS S contained in one leaf of a given reference foliation in a spacetime, there is an open marginally outer trapped tube (MOTT), adapted to the reference foliation, which contains S. We give conditions under which the MOTT can be completed. Finally, we show that under standard energy conditions on the spacetime, the MOTT must be either locally achronal, spacelike or null.Comment: 33 pages, no figures, typos corrected, minor changes in presentatio

Feature and viewpoint selection for industrial car assembly

Abstract. Quality assurance programs of today’s car manufacturers show increasing demand for automated visual inspection tasks. A typical example is just-in-time checking of assemblies along production lines. Since high throughput must be achieved, object recognition and pose estimation heavily rely on offline preprocessing stages of available CAD data. In this paper, we propose a complete, universal framework for CAD model feature extraction and entropy index based viewpoint selection that is developed in cooperation with a major german car manufacturer

Electricity demand modeling of German data centers: Dealing with uncertainities

Der steigende Energiebedarf für den Betrieb von Rechenzentren und die damit verbundenen CO2-Emissionen stellen in den letzten Jahren eine große Herausforderungen im Rahmen von Green IT dar. Vor diesem Hintergrund wurde der Strombedarf von Rechenzentren in Deutschland für die Jahren 1998-2008 unter der besonderen Berücksichtigung einer Unsicherheitsanalyse modelliert. Online-Version im Universitätsverlag der TU Berlin (www.univerlag.tu-berlin.de) erschienen.Concerns about data centers’ soaring energy consumption and associated CO2 emissions have emerged in recent years. The aim of this study is to analyze the nationwide impact of data centers on electricity demand in Germany for the period of 1998-2008, including uncertainity analysis. Online-Version published by Universitätsverlag der TU Berlin (www.univerlag.tu-berlin.de

Winter Active Bumblebees (Bombus terrestris) Achieve High Foraging Rates in Urban Britain

Background: Foraging bumblebees are normally associated with spring and summer in northern Europe. However, there have been sightings of the bumblebee Bombus terrestris during the warmer winters in recent years in southern England. But what floral resources are they relying upon during winter and how much winter forage can they collect? Methodology/Principal Findings: To test if urban areas in the UK provide a rich foraging niche for bees we set up colonies of B. terrestris in the field during two late winter periods (2005/6 & 2006/7) in London, UK, and measured their foraging performance. Fully automatic radio-frequency identification (RFID) technology was used in 2006/7 to enable us to record the complete foraging activity of individually tagged bees. The number of bumblebees present during winter (October 2007 to March 2008) and the main plants they visited were also recorded during transect walks. Queens and workers were observed throughout the winter, suggesting a second generation of bee colonies active during the winter months. Mass flowering shrubs such as Mahonia spp. were identified as important food resources. The foraging experiments showed that bees active during the winter can attain nectar and pollen foraging rates that match, and even surpass, those recorded during summer. Conclusions/Significance: B. terrestris in the UK are now able to utilise a rich winter foraging resource in urban parks and gardens that might at present still be under-exploited, opening up the possibility of further changes in pollinato

Bewertung von Kennzahlen und Kennzahlensystemen zur Beschreibung der Energieeffizienz von Rechenzentren

Eine Vielzahl von verschiedenen Energieeffizienz-Kennzahlen für Rechenzentren (RZ) wurde in den letzten Jahren veröffentlicht und diskutiert. Mit einer Übersicht über die aktuellen Kennzahlen und Kennzahlensysteme soll dieser Artikel einen Beitrag zur Beantwortung der folgenden Fragen für RZ-Verantwortliche und RZ-Betreiber leisten: Was können die aktuellen Kennwerte und was können sie nicht? Was muss man beachten, wenn man diese Kennwerte berechnet und sich mit anderen RZ vergleichen möchte? Dazu werden verschiedene Kriterien zur Bewertung der Energieeffizienzkannzahlen definiert und auf die Systeme angewandt. Online erschienen im Universitätsverlag der TU Berlin (www.univerlag.tu-berlin.de) ISBN 978-3-7983-2432-

Local existence of dynamical and trapping horizons

Given a spacelike foliation of a spacetime and a marginally outer trapped surface S on some initial leaf, we prove that under a suitable stability condition S is contained in a ``horizon'', i.e. a smooth 3-surface foliated by marginally outer trapped slices which lie in the leaves of the given foliation. We also show that under rather weak energy conditions this horizon must be either achronal or spacelike everywhere. Furthermore, we discuss the relation between ``bounding'' and ``stability'' properties of marginally outer trapped surfaces.Comment: 4 pages, 1 figure, minor change