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Searches for cosmic-ray electron anisotropies with the Fermi Large Area Telescope

Physical Review D 2010年第9期82卷 092003-092003页

作者： M. Ackermann M. Ajello W. B. Atwood L. Baldini J. Ballet G. Barbiellini D. Bastieri K. Bechtol R. Bellazzini B. Berenji E. D. Bloom E. Bonamente A. W. Borgland A. Bouvier J. Bregeon A. Brez M. Brigida P. Bruel R. Buehler T. H. Burnett S. Buson G. A. Caliandro R. A. Cameron P. A. Caraveo S. Carrigan J. M. Casandjian C. Cecchi Ö. Çelik E. Charles A. Chekhtman C. C. Cheung J. Chiang S. Ciprini R. Claus J. Cohen-Tanugi J. Conrad A. Cuoco C. D. Dermer A. de Angelis F. de Palma S. W. Digel G. Di Bernardo E. do Couto e Silva P. S. Drell R. Dubois C. Favuzzi S. J. Fegan W. B. Focke M. Frailis Y. Fukazawa S. Funk P. Fusco D. Gaggero F. Gargano S. Germani N. Giglietto P. Giommi F. Giordano M. Giroletti T. Glanzman G. Godfrey D. Grasso I. A. Grenier J. E. Grove S. Guiriec M. Gustafsson D. Hadasch A. K. Harding K. Hayashi E. Hays R. E. Hughes G. Jóhannesson A. S. Johnson W. N. Johnson T. Kamae H. Katagiri J. Kataoka M. Kerr J. Knödlseder M. Kuss J. Lande L. Latronico S.-H. Lee M. Lemoine-Goumard M. Llena Garde F. Longo F. Loparco M. N. Lovellette P. Lubrano A. Makeev M. N. Mazziotta J. E. McEnery J. Mehault P. F. Michelson T. Mizuno A. A. Moiseev C. Monte M. E. Monzani E. Moretti A. Morselli I. V. Moskalenko S. Murgia T. Nakamori M. Naumann-Godo P. L. Nolan E. Nuss T. Ohsugi A. Okumura N. Omodei E. Orlando J. F. Ormes D. Paneque J. H. Panetta D. Parent V. Pelassa M. Pepe M. Pesce-Rollins F. Piron T. A. Porter S. Profumo S. Rainò R. Rando M. Razzano A. Reimer O. Reimer T. Reposeur J. Ripken S. Ritz M. Roth H. F.-W. Sadrozinski A. Sander T. L. Schalk C. Sgrò J. Siegal-Gaskins E. J. Siskind D. A. Smith P. D. Smith G. Spandre P. Spinelli M. S. Strickman A. W. Strong D. J. Suson H. Takahashi T. Takahashi T. Tanaka J. B. Thayer J. G. Thayer D. J. Thompson L. Tibaldo D. F. Torres G. Tosti A. Tramacere Y. Uchiyama T. L. Usher J. Vandenbroucke V. Vasileiou N. Vilchez V. Vitale A. P. Waite P. Wang B. L. Winer K. S. Wood Z. Yang T. Ylinen G. Zaharijas M. Ziegler W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics University of California at Santa Cruz Santa Cruz California 95064 USA Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Laboratoire AIM CEA-IRFU/CNRS/Université Paris Diderot Service d’Astrophysique CEA Saclay 91191 Gif sur Yvette France Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica “G. Galilei ” Università di Padova I-35131 Padova Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia Italy Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari 70126 Bari Italy Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 Palaiseau France Department of Physics University of Washington Seattle Washington 98195-1560 USA Institut de Ciencies de l’Espai (IEEC-CSIC) Campus UAB 08193 Barcelona Spain INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica I-20133 Milano Italy NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center Greenbelt Maryland 20771 USA Department of Physics and Center for Space Sciences and Technology University of Maryland Baltimore County Baltimore Maryland 21250 USA Space Science Division Naval Research Laboratory Washington D.C. 20375 USA George Mason University Fairfax Virgin

The Large Area Telescope on board the Fermi satellite (Fermi LAT) detected more than 1.6×106 cosmic-ray electrons/positrons with energies above 60 GeV during its first year of operation. The arrival directions of these events were searched for anisotropies of angular scale extending from ∼10° up to 90°, and of minimum energy extending from 60 GeV up to 480 GeV. Two independent techniques were used to search for anisotropies, both resulting in null results. Upper limits on the degree of the anisotropy were set that depended on the analyzed energy range and on the anisotropy’s angular scale. The upper limits for a dipole anisotropy ranged from ∼0.5% to ∼10%.

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Fermi LAT observations of cosmic-ray electrons from 7 GeV to 1 TeV

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Physical Review D 2010年第9期82卷 092004-092004页

作者： M. Ackermann M. Ajello W. B. Atwood L. Baldini J. Ballet G. Barbiellini D. Bastieri B. M. Baughman K. Bechtol F. Bellardi R. Bellazzini F. Belli B. Berenji R. D. Blandford E. D. Bloom J. R. Bogart E. Bonamente A. W. Borgland T. J. Brandt J. Bregeon A. Brez M. Brigida P. Bruel R. Buehler T. H. Burnett G. Busetto S. Buson G. A. Caliandro R. A. Cameron P. A. Caraveo P. Carlson S. Carrigan J. M. Casandjian M. Ceccanti C. Cecchi Ö. Çelik E. Charles A. Chekhtman C. C. Cheung J. Chiang A. N. Cillis S. Ciprini R. Claus J. Cohen-Tanugi J. Conrad R. Corbet M. DeKlotz C. D. Dermer A. de Angelis F. de Palma S. W. Digel G. Di Bernardo E. do Couto e Silva P. S. Drell A. Drlica-Wagner R. Dubois D. Fabiani C. Favuzzi S. J. Fegan P. Fortin Y. Fukazawa S. Funk P. Fusco D. Gaggero F. Gargano D. Gasparrini N. Gehrels S. Germani N. Giglietto P. Giommi F. Giordano M. Giroletti T. Glanzman G. Godfrey D. Grasso I. A. Grenier M.-H. Grondin J. E. Grove S. Guiriec M. Gustafsson D. Hadasch A. K. Harding M. Hayashida E. Hays D. Horan R. E. Hughes G. Jóhannesson A. S. Johnson R. P. Johnson W. N. Johnson T. Kamae H. Katagiri J. Kataoka M. Kerr J. Knödlseder M. Kuss J. Lande L. Latronico M. Lemoine-Goumard M. Llena Garde F. Longo F. Loparco B. Lott M. N. Lovellette P. Lubrano A. Makeev M. N. Mazziotta J. E. McEnery J. Mehault P. F. Michelson M. Minuti W. Mitthumsiri T. Mizuno A. A. Moiseev C. Monte M. E. Monzani E. Moretti A. Morselli I. V. Moskalenko S. Murgia T. Nakamori M. Naumann-Godo P. L. Nolan J. P. Norris E. Nuss T. Ohsugi A. Okumura N. Omodei E. Orlando J. F. Ormes M. Ozaki D. Paneque J. H. Panetta D. Parent V. Pelassa M. Pepe M. Pesce-Rollins V. Petrosian M. Pinchera F. Piron T. A. Porter S. Profumo S. Rainò R. Rando E. Rapposelli M. Razzano A. Reimer O. Reimer T. Reposeur J. Ripken S. Ritz L. S. Rochester R. W. Romani M. Roth H. F.-W. Sadrozinski N. Saggini D. Sanchez A. Sander C. Sgrò E. J. Siskind P. D. Smith G. Spandre P. Spinelli Ł. Stawarz T. E. Stephens M. S. Strickman A. W. Strong D. J. Suson H. Tajima H. Takahashi T. Takahash W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford California 94305 USA Santa Cruz Institute for Particle Physics Department of Physics and Department of Astronomy and Astrophysics University of California at Santa Cruz Santa Cruz California 95064 USA Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Laboratoire AIM CEA-IRFU/CNRS/Université Paris Diderot Service d’Astrophysique CEA Saclay 91191 Gif sur Yvette France Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica “G. Galilei” Università di Padova I-35131 Padova Italy Department of Physics Center for Cosmology and Astro-Particle Physics The Ohio State University Columbus Ohio 43210 USA Istituto Nazionale di Fisica Nucleare Sezione di Roma “Tor Vergata” I-00133 Roma Italy Dipartimento di Fisica Università di Roma “Tor Vergata” I-00133 Roma Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia Italy Centre d’Étude Spatiale des Rayonnements CNRS/UPS BP 44346 F-30128 Toulouse Cedex 4 France Dipartimento di Fisica “M. Merlin” dell’Università e del Politecnico di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari 70126 Bari Italy Laboratoire Leprince-Ringuet École Polytechnique CNRS/IN2P3 Palaiseau France Department of Physics University of Washington Seattle Washington 98195-1560 USA Institut de Ciencies de l’Espai (IEEC-CSIC) Campus UAB 08193 Barcelona Spain INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica I-20133 Milano Italy Department of Physics Royal Institute of Technology (KTH) AlbaNova SE-106 91 Sto

We present the results of our analysis of cosmic-ray electrons using about 8×106 electron candidates detected in the first 12 months on-orbit by the Fermi Large Area Telescope. This work extends our previously published cosmic-ray electron spectrum down to 7 GeV, giving a spectral range of approximately 2.5 decades up to 1 TeV. We describe in detail the analysis and its validation using beam-test and on-orbit data. In addition, we describe the spectrum measured via a subset of events selected for the best energy resolution as a cross-check on the measurement using the full event sample. Our electron spectrum can be described with a power law ∝E−3.08±0.05 with no prominent spectral features within systematic uncertainties. Within the limits of our uncertainties, we can accommodate a slight spectral hardening at around 100 GeV and a slight softening above 500 GeV.

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Green supercomputing comes of age

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IT Professional 2008年第1期10卷 17-23页

作者： Feng, Wu-Chun Feng, Xizhou Ge, Rong Department of Computer Science and Electrical and Computer Engineering Virginia Tech. Network Dynamics and Simulation Science Laboratory Virginia Tech. Center for High-End Computing Systems Virginia Tech.

Energy-efficient (green) supercomputing has evolved to improve system reliability and provide better availability and productivity. Green Destiny supercomputing system is a Linux-based cluster that uses low-power components whose performance could be optimized for supercomputing. Low-power supercomputing focuses on energy efficiency at system integration time, selects low-power chips as the building blocks for power reduction and system reliability, and achieves better performance by scaling up to a larger number of processors. Researchers have implemented various power-aware software prototypes for commodity supercomputing starting with cluster of high-performance, high-power processors that support mechanism called dynamic voltage and frequency scaling (DVFS). Various approaches for parallel supercomputing nodes are studied by aiming execution phases that are not on the critical execution path.

关键词： Supercomputers

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Network-centric localization in MANETs based on particle swarm optimization

Network-centric localization in MANETs based on particle swa...

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2008 IEEE Swarm Intelligence Symposium, SIS 2008

作者： Kulkarni, Raghavendra V. Venayagamoorthy, Ganesh K. Miller, Ann Dagli, Cihan H. Real-Time Power and Intelligent Systems Laboratory Department of Electrical and Computer Engineering Missouri University of Science and Technology Rolla MO United States Department of Electrical and Computer Engineering Missouri University of Science and Technology Rolla MO United States Department of Systems Engineering and Engineering Management Missouri University of Science and Technology Rolla MO United States

ISBN: (纸本)9781424427055

There exist several application scenarios of mobile ad hoc networks (MANET) in which the nodes need to locate a target or surround it. Severe resource constraints in MANETs call for energy efficient target localization and collaborative navigation. Centralized control of MANET nodes is not an attractive solution due to its high network utilization that can result in congestions and delays. In nature, many colonies of biological species (such as a flock of birds) can achieve effective collaborative navigation without any centralized control. Particle swarm optimization (PSO), a popular swarm intelligence approach that models social dynamics of a biological swarm is proposed in this paper for network-centric target localization in MANETs that are enhanced by mobile robots. Simulation study of two application scenarios is conducted. While one scenario focuses on quick target localization, the other alms at convergence of MANET nodes around the target. Reduction of swarm size during PSO search is proposed for accelerated convergence. The results of the study show that the proposed algorithm is effective in network-centric collaborative navigation. Emergence of converging behavior of MANET nodes is observed. ©2008 IEEE.

关键词： Multipurpose robots

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Fast Discovery of Spectrum Opportunities in Cognitive Radio Networks

Fast Discovery of Spectrum Opportunities in Cognitive Radio ...

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IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks, DySPAN

作者： Hyoil Kim Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

We address the problem of rapidly discovering spectrum opportunities for seamless service provisioning for secondary users (SUs) in cognitive radio networks (CRNs). Specifically, we propose an efficient sensing-sequence that incurs a small opportunity-discovery delay by considering (1) the probability that a spectrum band (or a channel) may be available at the time of sensing, (2) the duration of sensing on a channel, and (3) the channel capacity. We derive the optimal sensing-sequence for channels with homogeneous capacities, and a suboptimal sequence for channels with heterogeneous capacities for which the problem of finding the optimal sensing-sequence is shown to be NP-hard. To support the proposed sensing-sequence, we also propose a channel-management strategy that optimally selects and updates the list of backup channels. A hybrid of maximum likelihood (ML) and Bayesian inference is also introduced for flexible estimation of ON/OFF channel-usage patterns and prediction of channel availability when sensing produces infrequent samples. The proposed schemes are evaluated via in-depth simulation. For the scenarios we considered, the proposed suboptimal sequence is shown to achieve close-to-optimal performance, reducing the opportunity-discovery delay by up to 47% over an existing probability-based sequence. The hybrid estimation strategy is also shown to outperform the ML-only strategy by reducing the overall opportunity-discovery delay by up to 34%.

关键词： Sensors Channel capacity Delay Algorithm design and analysis Availability Channel estimation Maximum likelihood estimation

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BD-LZW picture compression algorithm for WSN system

BD-LZW picture compression algorithm for WSN system

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2008 3rd International Conference on Pervasive computing and Applications, ICPCA08

作者： Jinlan, Zhan Qingguo, Zhou Shuwei, Bai Li, Cuihual Bin, Hu Li, Lian Department of Computer Science Video and Image Processing Lab Xiamen University China Engineering Research Center of Open Source Software and Real-time System Ministry of Education Department of Information Science and Engineering Lanzhou University China Department of Computing University of Central England United Kingdom

ISBN: (纸本)9781424420209

In the paper, a new parallel LZW-Like algorithm, bidirectory LZW algorithm (BD-LZW) will be interpreted The new algorithm can be used in data compression/decompression system which runs on multi-microprocessor system, such as CELL, which the algorithm will be implemented on. Different from the conventional parallel LZW algorithm with one input directory, BD-LZW algorithm allows two threads reading characters from two ends of string. By this method, the data can be partitioned for compression/decompression loading between two threads fairly and easily. The most important is the compression performance can be improved by the new algorithm. Comparing running time, it's lower 10% than conventional parallel LZW (P-LZW) algorithm when there are two threads running on CELL architecture. © 2008 IEEE.

关键词： Compression algorithms Wireless sensor networks Yarn Partitioning algorithms Image coding Data compression Video compression Image processing computer science Open source software

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real-time mobile robot teleoperation via Internet based on predictive control

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中国高等学校学术文摘·机械工程 2008年第3期3卷 299-306页

作者： Shihua WANG Bugong XU YunHui LIU Yeming ZHOU Laboratory of Real-Time Control Through Internet and Fieldbuses College of Automation Science and Engineering South China University of Technology Guangzhou 510640 China Naval Arms Command Academy of Guangzhou Guangzhou 510430 China Laboratory of Real-Time Control Through Internet and Fieldbuses College of Automation Science and Engineering South China University of Technology Guangzhou 510640 China Naval Arms Command Academy of Guangzhou Guangzhou 510430 China Department of Automation and Computer Aided Engineering The Chinese University of Hong Kong Shatin N.T. HK China

A remote control system that can control a mobile robot in real time via the internet is proposed. To compensate for the network delay and counteract its impact on the teleoperation system, a predictive control scheme based on the modified Smith predictor proposed is selected. To ensure the stability and transparency of the system, a dynamic model manager is designed based on the information exchange between the sensors at the mas-ter and slave sides. To precisely predict the time delay, a new timer synchronization algorithm is proposed. To decrease delay- jitter, a new data buffer scheme is per-formed. Force feedback and a virtual predictive display are introduced to enhance the real-time efficiency of tele-operation. The usefulness and effectiveness of the pro-posed method and system are proven by teleoperation experiments via the internet over a long distance.

关键词： teleoperation internet robots predictive con-trol delay algorithm

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Comparison of DE and PSO for generator maintenance scheduling

Comparison of DE and PSO for generator maintenance schedulin...

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IEEE Swarm Intelligence Symposium, SIS

作者： Y. Yare G. K. Venayagamoorthy Real-Time and Intelligent Systems Laboratory Department of Electrical and Computer Engineering Missouri University of Science and Technology Rolla MO USA

This paper presents a comparison of a differential evolution (DE) algorithm and a modified discrete particle swarm optimization (MDPSO) algorithm for generating optimal preventive maintenance schedules for economical and reliable operation of a power system, while satisfying system load demand and crew constraints. The DE, an evolutionary technique and an optimization algorithm utilizes the differential information to guide its further search, and can handle mixed integer discrete continuous optimization problems. Discrete particle swarm optimization (DPSO) is known to effectively solve large scale multi-objective optimization problems and has been widely applied in power systems. Both the DE and MDPSO are applied to solve a multi-objective generator maintenance scheduling (GMS) optimization problem. The two algorithms generate feasible and optimal solutions and overcome the limitations of the conventional methods including extensive computational effort, which increases exponentially as the size of the problem increases. The proposed methods are tested, validated and compared on the Nigerian power system.

关键词： Power system reliability Scheduling algorithm Particle swarm optimization Power systems Power generation Preventive maintenance Power system economics Power generation economics Large-scale systems Processor scheduling

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CARBON REDUCTION POTENTIAL WITH INTELLIGENT CONTROL OF POWER SYSTEMS

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IFAC Proceedings Volumes 2008年第2期41卷 13952-13957页

作者： Ganesh K. Venayagamoorthy Gabriele Braband Real-Time Power and Intelligent Systems Laboratory Department of Electrical and Computer Engineering Missouri University of Science and Technology Rolla MO 65409 USA Simmons & Simmons Dusseldorf Germany

Climate change caused by anthropogenic greenhouse gas (GHG) emissions such as carbon dioxide (CO 2 ) is now widely accepted as a real condition that has potentially serious consequences for human society and industries need to factor this into their strategic plans. One salient planning assumption is that energy - essential for every activity - will become more expensive relative to other inputs. Economic growth does not have to be linked to an increase of GHG emissions and can be attained in addition to the usage of renewable energy sources by using energy efficiency technologies for power system generation, transmission, and distribution. The development of intelligent energy-efficient control technologies will both soften negative effects of the climate change on the economy and enhance energy security. This paper outlines the significant carbon reduction potential with intelligent control and optimization techniques applied to power system generation and transmission systems with and without wind farms.

关键词： Intelligent control Economics Emissions Optimization Power systems

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Software architecture of the Autonomous Mobile Outdoor Robot AMOR

Software architecture of the Autonomous Mobile Outdoor Robot...

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IEEE Symposium on Intelligent Vehicle

作者： Klaus-Dieter Kuhnert Institute of Real-Time Learning Systems Department of Electrical Engineering and Computer Science University of Siegen Germany

Even if outdoor robotics is gaining increasing interest, universal systems are rare to find up to now. One of them is the autonomous mobile outdoor robot (AMOR), which operates in rough terrain under arbitrary weather condition. This paper presents its software architecture and some performance figures. The whole system is designed by a modular and layered paradigm, to allow for easy reconfiguration and adaptation to new tasks. Elementary behaviours act as the fundament, which delivers the basic abilities and secures the robot. Model based components are utilized for more intelligent tasks like obstacle avoidance and local/global path planning. Robust operation in complex terrain is achieved by combining a multitude of sensors. The software architecture unifies them by introducing a virtualisation layer, which hides all hardware specific consideration from the application programmer. This way the overall system configuration can be easily adapted to the actual task without changing the high level software. Above the medium layer an object oriented system has been implemented, that is able to localise, navigate and avoid obstacles in rough terrain. The overall performance of the system has been proven by winning the first price in autonomous driving in the European Land Robot Trial (ELROB 2007) for urban and non-urban terrain. Details of the performance are given in the results.

关键词： Vehicles

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