Cooperative Synchronization in Wireless Networks

Synchronization is a key functionality in wireless network, enabling a wide variety of services. We consider a Bayesian inference framework whereby network nodes can achieve phase and skew synchronization in a fully distributed way. In particular, under the assumption of Gaussian measurement noise, we derive two message passing methods (belief propagation and mean field), analyze their convergence behavior, and perform a qualitative and quantitative comparison with a number of competing algorithms. We also show that both methods can be applied in networks with and without master nodes. Our performance results are complemented by, and compared with, the relevant Bayesian Cram\'er-Rao bounds

Cooperative Simultaneous Localization and Synchronization in Mobile Agent Networks

Cooperative localization in agent networks based on interagent time-of-flight measurements is closely related to synchronization. To leverage this relation, we propose a Bayesian factor graph framework for cooperative simultaneous localization and synchronization (CoSLAS). This framework is suited to mobile agents and time-varying local clock parameters. Building on the CoSLAS factor graph, we develop a distributed (decentralized) belief propagation algorithm for CoSLAS in the practically important case of an affine clock model and asymmetric time stamping. Our algorithm allows for real-time operation and is suitable for a time-varying network connectivity. To achieve high accuracy at reduced complexity and communication cost, the algorithm combines particle implementations with parametric message representations and takes advantage of a conditional independence property. Simulation results demonstrate the good performance of the proposed algorithm in a challenging scenario with time-varying network connectivity.Comment: 13 pages, 6 figures, 3 tables; manuscript submitted to IEEE Transaction on Signal Processin

Two-dimensional finite element models of convective heat transfer in the upper crust — implications for the interpretation of fission-track data

Fission-track (FT) thermochronology is a tool routinely used for studies of surface denudation because of its sensitivity to the low temperatures found in the uppermost part of the crust. FT ages and associated track length distributions are regularly interpreted assuming a steady-state temperature field and only conductive heat transfer. However, application of the method to thermochronological studies based on such interpretations may lead to invalid conclusions, if the temperatures at a certain depth had actually varied with time. For example, the convective transfer of heat by hydrothermal fluids can cause transient thermal events within the upper crust. In particular, fluid circulation along fault zones can result in substantial convective heat transport and cause temperature anomalies in the adjacent rocks (Zuther & Brockamp 1988, Fleming et al. 1998, Lampe & Person 2002, Bächler et al 2003). As a consequence, any refined interpretation of FT data requires a thorough understanding of the upper crustal temperature field and its evolution through time. The main objective of this study is to assess quantitatively how convective heat transport influences the upper crustal temperature field as well as the cooling ages and track length distributions observed in apatite FT data...conferenc

An Interview with Thee Kian Wie:"I am an Indonesian of Chinese origin and am neither better nor worse than any other average Indonesian"

Thee Kian Wie is a prominent economic historian and economist in Indonesia who has known many of Indonesia’s leading economists personally. Despite his retirement in May 2000 and advanced age (74) he is still very active. He publishes several articles per year and visits his office at the Indonesian Institute of Sciences LIPI almost daily, provided he is not somewhere abroad or in Jakarta or somewhere else in Indonesia participating in or delivering a paper at one of the international or national workshops to which he is invited. During his career Thee Kian Wie developed a unique international network and gained a reputation as an expert on Indonesia’s modern economic history and comparative economic, industrial, foreign direct investment, and technological development in East Asia, with particular reference to Indonesia. For many years Thee Kian Wie has also been a kind mediator helping young foreign and Indonesian researchers to find their way to informants and information. He received an honorary doctorate from The Australian National University, Canberra, in December 2004. In 2008 KITLV awarded him an honorary membership. In August 2008 he received the Sarwono Prawirohardjo Award2 from Professor Umar Anggara Jenie, the Head of LIPI, for his achievements in economic research and many years of service to LIPI. Itinerario interviewed him in Leiden in late October 2008 and in early May 2009 in Jakarta.3 The languages we spoke were Dutch and English

Imaging and mapping the impact of clouds on skyglow with all-sky photometry

Artificial skyglow is constantly growing on a global scale, with potential ecological consequences ranging up to affecting biodiversity. To understand these consequences, worldwide mapping of skyglow for all weather conditions is urgently required. In particular, the amplification of skyglow by clouds needs to be studied, as clouds can extend the reach of skyglow into remote areas not affected by light pollution on clear nights. Here we use commercial digital single lens reflex cameras with fisheye lenses for all-sky photometry. We track the reach of skyglow from a peri-urban into a remote area on a clear and a partly cloudy night by performing transects from the Spanish town of Balaguer towards Montsec Astronomical Park. From one single all-sky image, we extract zenith luminance, horizontal and scalar illuminance. While zenith luminance reaches near-natural levels at 5km distance from the town on the clear night, similar levels are only reached at 27km on the partly cloudy night. Our results show the dramatic increase of the reach of skyglow even for moderate cloud coverage at this site. The powerful and easy-to-use method promises to be widely applicable for studies of ecological light pollution on a global scale also by non-specialists in photometry.Comment: 13 pages, 7 figure

Designing Tablet Banking Apps for High-Net-Worth Individuals: Specifying Customer Requirements with Prototyping

Private banks with high-net-worth customers see a great potential in mobile information technology to provide more transparency in the advisory process. Previous literature has mainly focused on gathering requirements with regard to mobile banking applications targeted for retail customers or with regard to advisory services in physical proximity. This paper focuses on an mFAS which is designed for the private banking customer segment and facilitates location-independent customer relationships on a tablet. Furthermore, we specify previously established requirements with the Requirements Abstraction Model. In this study, we evaluated the requirements with a focus group involving seven domain experts. The results of this workshop suggest that most of the specified requirements meet the recommended practice for requirements specification. However, the experts only partly agreed that the presented requirements meet the completeness criterion, which guides future research endeavors

Evolution of the Tamtsag Basin / NE-Mongolia — part II: structure and hydrocarbon potential

The Tamtsag basin in NE Mongolia is part of a widespread basin system which formed during Late Jurassic and Cretaceous times (Graham et al. 2001, Qing-Ren et al. 2003). It is filled with continental sediments and volcanics which can reach up to 4km in thickness. Rifting and subsequent basin inversion led to a complex basin geometry characterized by several horst and graben structures. The geodynamic causes for regional basin formation are discussed controversially and several hypothesis ranging from orogenic collapse via subduction rollback to collision-induced rifting have been put forward. Scientific research on the Mesozoic basins in Mongolia has so far concentrated on the East Gobi basin to the southwest (Graham et al. 2001, Prost 2004, Johnson et al. 2004) and some work has also been published on the Hailar Basin (Qing-Ren et al. 2003), the northeastward continuation of the Tamtsag Basin into China. Fundamental data on the fill and tectonics of the Tamtsag Basin in between is still missing. This is partly due to poor exposure as most of the basin fill is covered by Cenozoic sediments and only locally, near the borders faults, rocks are accessible for surface investigations. However, recent discoveries of oil in the Tamtsag and Hailar Basins have resulted in intense exploration activity and a strong interest in the area. This contribution describes the results of a field campaign in Fall 2005 focusing on the structure and hydrocarbon potential while a companion paper (Geerdts et al. this volume) deals with the fill of the Tamtsag Basin.conferenc

Evolution of the Tamtsag Basin / NE-Mongolia — part I: basin fill

The Tamtsag Basin in NE Mongolia is part of a widespread basin system which formed during Late Jurassic and Cretaceous times (Graham et al. 2001, Qing-Ren et al. 2003). It is filled with continental sediments and volcanics which can reach up to 4 km in thickness. Rifting and subsequent basin inversion led to a complex basin geometry characterized by several horst and graben structures. The geodynamic causes for regional basin formation are discussed controversially and several hypothesis ranging from orogenic collaps via subduction rollback to collision-induced rifting have been put forward. Scientific research on the Mesozoic basins in Mongolia has so far concentrated on the East Gobi Basin to the south (Graham et al 2001, Prost 2004, Johnson 2004) and some work has also been published on the Hailar Basin (Qing-Ren et al. 2003), the northeastward continuation of the Tamtsag Basin into China. Fundamental data on the fill and tectonics of the Tamtsag Basin in between is still missing. This is partly due to poor exposure as most of the basin fill is covered by Cenozoic sediments and only locally, near the bordering faults, rocks are accessible for surface investigations. However, recent discoveries of oil in the Tamtsag and Hailar Basins have resulted in intense exploration activity and a strong interest in the area. This contribution describes the results of a field campaign in fall 2005 focusing on the basin fill while a companion paper (Davaa et al. this volume) deals with the basin structure and hydrocarbon potential of the Tamtsag Basin.conferenc

Felsmechanische Untersuchungen am Hauptrogenstein (bjHR) der Vorbergzone des südlichen Oberrheingrabens

Der Hauptrogenstein ist im Ober- Bajocium, im Braunen Jura(bjHR), gebildet worden. Im Bereich des südlichen Oberrheingrabens ist der Hauptrogenstein als hellgrauer bis hellbräunlicher, schräggeschichteter bis massiger Kalkoolith ausgebildet. Die Gesamtmächtigkeiten dieser durch Mergelbänke und Schill-Lagen gegliederten Einheit reichen von 40m bis ca. 80 m. Durch mehrere große Steinbrüche der Kalkindustrie ist der Hauptrogenstein in der Vorbergzone hervorragend aufgeschlossen. Mit Uniaxial- und Triaxialexperimenten sollen felsmechanische Kennwerte für den Hauptrogenstein bestimmt werden, auch in Hinblick auf die mögliche zukünftige Nutzung als Heisswasseraquifer für die Gewinnung geothermischer Energie.conferenc