473 research outputs found
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 sĂĽdlichen Oberrheingrabens
Der Hauptrogenstein ist im Ober-
Bajocium, im Braunen Jura(bjHR),
gebildet worden. Im Bereich des sĂĽdlichen
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 groĂźe SteinbrĂĽche
der Kalkindustrie ist der Hauptrogenstein
in der Vorbergzone hervorragend
aufgeschlossen. Mit Uniaxial- und
Triaxialexperimenten sollen felsmechanische
Kennwerte fĂĽr den Hauptrogenstein
bestimmt werden, auch in Hinblick
auf die mögliche zukünftige Nutzung als
Heisswasseraquifer fĂĽr die Gewinnung
geothermischer Energie.conferenc
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