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971.
The paper by Koc and Chen (1994) includes new formulas for computational complexity, but the method itself is already known and has dubious numerical stability. A poorly conditioned example is shown 相似文献
972.
An optimal load allocation approach is presented for measurement and data reporting in wireless sensor networks with a single level tree network topology. The measurement problem investigated involves a measurement space, part of which can be sampled by each sensor. We seek to optimally assign sensors part of the measurement space to minimize reporting time and energy usage. Three representative measurement and reporting strategies are studied. This work is novel as it considers, for the first time, the measurement capacity of processors and assumes negligible computation time which is radically different from the traditional divisible load scheduling research to date. Aerospace applications include satellite remote sensing and monitoring and sensor networks deployed and monitored from the air. 相似文献
973.
Portell J. Luri X. Garcia-Berro E. 《IEEE transactions on aerospace and electronic systems》2006,42(2):421-435
Gaia is the most ambitious space astrometry mission currently envisaged and is a technological challenge in all its aspects. We describe a proposal for the payload data handling system of Gaia, as an example of a high-performance, real-time, concurrent, and pipelined data system. This proposal includes the front-end systems for the instrumentation, the data acquisition and management modules, the star data processing modules, and the payload data handling unit. We also review other payload and service module elements and we illustrate a data flux proposal. 相似文献
974.
L. Prech Z. Nemecek J.
afrnkov J.
imunek V. Truhlík N. M. Shutte 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(12):33-36
The paper is based on the electron and ion energy spectra measurement on board the main spacecraft of the APEX mission. During the active phase of the experiment an intense electron beam was emitted from the main satellite. The basic cycle of the electron injection is formed by current pulses of different frequencies, duration and intensity. The spacecraft potential changes due to the gun operation were compensated by a low energy Xe plasma generator. The data show that the response of the environment to the beam emission depends not only on injection parameters but on the spacecraft position and orientation with respect to the magnetic field as well. The typical response is an increase of the intensity of the low energy (less than 1 keV) electrons in all directions. In addition, strong field aligned fluxes of electrons and/or ions are observed with energies below the gun energy. An attempt to classify different types of response and to find possible mechanisms which can explain the observed phenomena is made in the present paper. 相似文献
975.
DNA fragmentation by charged particle tracks. 总被引:1,自引:0,他引:1
B Stenerlow E Hoglund J Carlsson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):859-863
High-LET (linear energy transfer) charged particles induce DNA double-strand breaks (DSB) in a non-random fashion in mammalian cells. The clustering of DSB, probably determined by track structure as well as chromatin conformation, results in an excess of small- and intermediate-sized DNA fragments. DNA fragmentation in normal human fibroblasts (GM5758) was analyzed by pulsed-field gel electrophoresis after irradiation with photons (60Co) or 125 keV/micrometers nitrogen ions. Compared to conventional DSB analysis, i.e. assays only measuring the fraction of DNA smaller than a single threshold, the relative biological effectiveness (RBE) for DSB induction increased with 100%. Further, the size distribution of DNA fragments showed a significant dependence on radiation quality, with an excess of fragments up to 1 Mbp. Irradiation of naked genomic DNA without histone proteins increased the DSB yields 25 and 13 times for photons and nitrogen ions, respectively. The results suggest possible roles of both track structure and chromatin organization in the distribution of DNA double-strand breaks along the chromosome. 相似文献
976.
Daniel Gómez 《Space Science Reviews》2006,122(1-4):231-238
977.
978.
R J White J B Bassingthwaighte J B Charles M J Kushmerick D J Newman 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(1):7-16
Today, the tools are in our hands to enable us to travel away from our home planet and become citizens of the solar system. Even now, we are seriously beginning to develop the robust infrastructure that will make the 21st century the Century of Space Travel. But this bold step must be taken with due concern for the health, safety and wellbeing of future space explorers. Our long experience with space biomedical research convinces us that, if we are to deal effectively with the medical and biomedical issues of exploration, then dramatic and bold steps are also necessary in this field. We can no longer treat the human body as if it were composed of muscles, bones, heart and brain acting independently. Instead, we must lead the effort to develop a fully integrated view of the body, with all parts connected and fully interacting in a realistic way. This paper will present the status of current (2000) plans by the National Space Biomedical Research Institute to initiate research in this area of integrative physiology and medicine. Specifically, three example projects are discussed as potential stepping stones towards the ultimate goal of producing a digital human. These projects relate to developing a functional model of the human musculoskeletal system and the heart. 相似文献
979.
Ts P Dachev E G Stassinopoulous B T Tomov Pl G Dimitrov Yu N Matviichuk V A Shurshakov V M Petrov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,32(1):67-71
The LIULIN-3M instrument is a further development of the LIULIN dosimeter-radiometer, used on the MIR spacestation during the 1988-1994 time period. The LIULIN-3M is designed for continuous monitoring of the radiation environment during the BION-12 satellite flight in 1999. A semiconductor detector with 1 mm thickness and cm2 area is contained in the instrument. Pulse high analysis technique is used to determine the energy losses in the detector. The final data from the instrument are the flux and the dose rate for the exposure time and 256 channels of absorbed dose spectra based on the assumption that the particle flux is normal to the detector. The LIULIN-3M instrument was calibrated by proton fluxes with different energies at the Indiana University Cyclotron Facility in June 1997 and had been used for radiation measurements during commercial aircraft flights. The calibration procedure and some flight results are presented in this paper. 相似文献
980.
J.C. Cretenet 《Acta Astronautica》1985,12(11):949-958
The presence of Europe in the future developments of spatial programs, which are foreseen, for the 1990s and further, needs the availability of vehicles, modules and all related technologies adapted to operational use of low earth orbit station.The manned HERMES vehicle shall be part of the in-orbit infrastructure realized either in the European context or in cooperation between Europe and the United States.The main mission for this vehicle will be to run a shuttle with the station that means transport and change of the crews, its safe return in abort condition and cargo transport of consumable and experimental equipment.Secondary missions could be servicing on automatic platform, making autonomous scientific experiments. Lastly, the vehicle, by means of its on-board propulsion capability, could be used to accomplish in-orbit tow and assembly missions.Studies which are undertaken now about the vehicle are devoted to the aerodynamic shape (research of a compromise between aerothermic and overall fitting), the system (functional architecture, ground and flight configuration); further works dealing with technology are presently on hand in the field of thermal protection, aerodynamics, power generation with a high massic yield. 相似文献