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251.
252.
Delcam亚洲技术峰会于2010年10月19~21日在印度西部重要的工业城市浦那市举行,来自亚洲11个国家和地区的Delcam公司代表、当地用户代表以及媒体记者100余人参加了本次技术峰会。 相似文献
253.
Lorna M. Small Michael J. Rycroft Shaun Quegan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(4):41-46
The realistic model of Quegan et al. has been used to investigate the convection paths of ionospheric plasma at 300 km altitude, for different polar cap radii and in both hemispheres. Taking the Northern magnetic dip pole to be at a co-latitude of 11° and the Southern magnetic dip pole at a co-latitude of 23°, these paths are presented in a Sun-Earth frame, with the position of the Earth's axis fixed as it is on 21 March, as polar plots centred on the magnetic pole. There are marked hemispheric differences between 13 and 23 L.T., particularly near the stagnation region at 18 to 21 L.T., but only minor differences between 00 and 12 L.T., when the radius of the polar cap exceeds 12°. For a smaller polar cap, the differences between the hemispheres are small at all local times. The time taken to perform a complete circuit is most dependent on the polar cap radius, and most variable - between 15 and 36 h - for convection paths starting near 60° latitude. The time that plasma convecting from noon to near midnight across the Northern polar cap spends within the 10° co-latitude circle increases from 6 h, for a polar cap radius of 10°, to 11.5 h at 17°. These results are compared and contrasted with other model calculation results and with some ground-based and satellite observations of plasma densities at high latitudes. 相似文献
254.
Stelios Charalambides Garry E. Hunt Michael J. Rycroft Robert J. Murgatroyd David W.S. Limbert 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(6):127-132
We present the results of a study of anomalies, which are defined as differences of seasonal means from the data set seasonal means, in the Earth's radiation budget from the analysis of nine years of ten day mean observations derived from the NOAA polar orbiter satellites for the period, 1974–1983. We estimate that the standard deviation in the outgoing longwave flux for this period is less than 12 Wm?2 and typically 7 Wm?2. The results show that there are several geographical areas for which the standard deviation is in excess of 20 Wm?2; in such regions the radiation budget anomalies exceeded these due to natural atmospheric variability. In this paper we discuss the relationship of these anomalies with climatic change. 相似文献
255.
Michael Schulz 《Space Science Reviews》1975,17(2-4):481-536
This review covers the major developments in radiation-belt phenomenology of the past four years (1970–1973). This has been a period characterized by consolidation and refinement of ideas and measurements related to geomagnetically trapped particles. Significant progress has been made in understanding ion and electron pitch-angle distributions within the context of radial diffusion and pitch-angle diffusion, respectively. Comparison of alpha-particle and proton distributions has helped to clarify the relative strengths of known radial-diffusion mechanisms. Careful measurements have indicated the directional flux of cosmic-ray-albedo neutrons, which constitute (through beta decay) a major source of high-energy ( 20 MeV) inner-belt protons. Inclusion of radial-diffusion and geomagnetic-secular effects has brought the theory of the inner proton belt into reasonable agreement with observation. At very lowL values (L 1.2) atmospheric collisions have been found to facilitate the radial transport of 40 keV protons and 2 MeV electrons. The plasmapause has been identified as an important boundary for plasma instabilities (wave-particle interactions) that lead to particle precipitation and red-arc excitation. Suggestions have followed for artificially simulating such plasmaspheric effects by magnetospheric injection of cold barium or lithium plasma. 相似文献
256.
F. Perotti A. Della Ventura G. Villa R.C. Butler G. Di Cocco R.E. Baker J.N. Carter A.J. Dean R.I. Hayles 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(4):117-119
During a balloon flight of the MISO telescope on 1980 May 17, the Crab Nebula and the Seyfert galaxy NGC 4151 were studied over the photon energy range 0.03 –16 MeV. The photon spectrum of the Crab Nebula was measured up to ~ 2 MeV. No gamma-ray emission from NGC 4151 was detected on this occasion. 相似文献
257.
258.
As part of the DOD Logistics Research and Development Program, the Navy is embarking on the development of an Integrated Diagnostics Support System. This System is composed of a number of diagnostic design tools, which are aimed at automating the diagnostic design process. When completed, the tools will be utilized in a comprehensive integrated diagnostic demonstration project applied to a Naval weapon system. The last three years have been characterized by increasing attention given to the definition, implementation, and evaluation of integrated diagnostics concepts. Integrated diagnostics is a structured process which maximizes the effectiveness of diagnostics by integrating pertinent elements, such as testability, automatic and manual testing, training, maintenance aiding, personnel and computer-aided engineering as a means for providing a cost-effective capability to detect and unambiguously isolate all faults known or expected to occur in weapon systems and equipment, and to satisfy weapon system mission requirements. 相似文献
259.
Michael Paluszek 《Acta Astronautica》1983,10(4):163-178
The Space Shuttle Orbiter will be used as an orbital base for near-term space operations. Its payloads will range from compact satellites to large, flexible antennas. This paper addresses the problem of the dynamics and control of the Orbiter with a flexible payload. Two different cases are presented as examples. The first is a long, slender beam which might be used as an element in a large orbiting structure. The second is a compact satellite mounted on a spin table in the Orbiter payload bay. The closed loop limit cycles are determined for the first payload and the open loop eigenvalues are calculated for the second. Models of both payloads are mechanized in a simulation with the Shuttle on-orbit autopilot. The vehicle is put through a series of representative maneuvers and its behavior analyzed. The degree of interaction for each payload is determined and strategies are discussed for its reduction. 相似文献
260.
Michael Simpson 《Space Policy》2005,21(2):165-166
The ISU held its 9th annual symposium in Strasbourg from 30 November to 2 December 2004, with the theme ‘Civil, Commercial and Security Space: What will drive the Next Decade?’ Speakers from industry, academe, space agencies, international organizations and the military presented a range of views on where the different sectors that make up space activity might be headed and, on the final day, sectoral discussion groups attempted to draw together some of the themes that had emerged. This report is an edited version of ISU President Michael Simpson's closing speech, in which he summed up the findings of the discussion groups. The growing importance of user demand was considered likely to present the biggest change to the way space activity is carried out. 相似文献