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501.
The local radiation belts of the Sun are defined as giant quasi-stationary coronal and heliospheric traps for solar cosmic rays. These traps are formed by loop magnetic fields, both solar and interplanetary. Using observational data, some experimental examples of the local radiation belts of the Sun are considered. The hypotheses on the origin of energetic particles in the outer heliosphere and on the local radiation belts of the Sun are discussed. 相似文献
502.
P. R. Goode L. V. Didkovsky K. G. Libbrecht M. F. Woodard 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,29(12):1-1898
Solar oscillations provide the most accurate measures of cycle dependent changes in the sun, and the Solar and Heliospheric Observatory/Michelson Doppler Imager (MDI) data are the most precise of all. They give us the opportunity to address the real challenge — connecting the MDI seismic measures to observed characteristics of the dynamic sun. From inversions of the evolving MDI data, one expects to determine the nature of the evolution, through the solar cycle, of the layers just beneath the sun's surface. Such inversions require one to guess the form of the causal perturbation — usually beginning with asking whether it is thermal or magnetic. Matters here are complicated because the inversion kernels for these two are quite similar, which means that we don't have much chance of disentangling them by inversion. However, since the perturbation lies very close to the solar surface, one can use synoptic data as an outer boundary condition to fix the choice. It turns out that magnetic and thermal synoptic signals are also quite similar. Thus, the most precise measure of the surface is required.
We argue that the most precise synoptic data come from the Big Bear Solar Observatory (BBSO) Solar Disk Photometer (SDP). A preliminary analysis of these data implies a magnetic origin of the cycle-dependent sub-surface perturbation. However, we still need to do a more careful removal of the facular signal to determine the true thermal signal. 相似文献
503.
Most utility power quality problems are caused by sags, surges, and momentary outages which last from several cycles to several seconds. Modern loads are very sensitive to these short duration glitches resulting in major losses in revenue through system down-time and loss of product from work in process. Many of these problems are caused by normal transients as equipment and factories go on-line or shut down. Others are caused by lightening strikes and faults on the distribution system. Although power utility companies attempt to minimize the interruptions through filtering and system management, power quality problems continue to cost American industry billions of dollars a year. Batteries have been used for many years in uninterruptible power supplies (UPS) to protect critical loads. However, because many new facilities have a network of broadly distributed critical loads, a UPS on the order of one to several megawatts is needed to support the total plant rather than several small kilowatt installations. This paper reports on the implementation of such a utility scale power quality management system 相似文献
504.
Scoles D.L. Hayden J.W. Pickett D.F. Jr. Rao G.M. 《Aerospace and Electronic Systems Magazine, IEEE》1996,11(7):27-30
A nickel cadmium cell system which utilizes a polypropylene separator impregnated with polybenzimadazole, and which shows promise of providing an aerospace battery with performance equivalent to Super NiCd, and yet is more cost effective, is described. Background information, cell construction information, detailed test program information and data, and status of qualification are given 相似文献
505.
On phased-array radar tracking and parameter control 总被引:1,自引:0,他引:1
Based on a simple model of a ground-based phased-array radar used for a multiple-target surveillance task, beam scheduling, positioning, and radar parameters like signal-to-noise ratio, track sharpness, and detection threshold have been optimized with respect to the radar/computer load induced by tracking. From this the minimum energy necessary for track maintenance during surveillance can be derived 相似文献
506.
A space-based radar system concept is described that can provide continuous world-wide, all-weather, day-night observation and tracking of ships, aircraft, vehicles and ground facilities of interest. The system employs a constellation of radar satellites in low-earth orbit to provide continuous world-wide target access. The radars employ reflector antennas, TWT transmitters and high frequency (e.g., X band) to achieve long range with relatively low weight, complexity and cost. The radars operate in moving-target-detection (MTD) and synthetic-aperture-radar (SAR) spotlight imaging modes to observe moving and fixed targets, respectively. The system could support a wide range of military, intelligence, law-enforcement and civilian missions 相似文献
507.
To cancel clutter, both medium-PRF waveforms which are ambiguous in both range and Doppler and high-PRF waveforms which are ambiguous in range but unambiguous in ambiguities, a previous paper has shown that superior results for a single target can be achieved by using a clustering algorithm. Here, the problem of multiple targets is considered. A maximum likelihood (ML) technique which incorporates the clustering algorithm is developed for the multiple target problem. Simulation results show that four targets which have the same speed but are at different ranges can be resolved by using a medium-PRF waveform and employing the ML resolution technique 相似文献
508.
Alexander G. Kosovichev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(6):830-837
Solar and stellar activity is a result of complex interaction between magnetic field, turbulent convection and differential rotation in a star’s interior. Magnetic field is believed to be generated by a dynamo process in the convection zone. It emerges on the surface forming sunspots and starspots. Localization of the magnetic spots and their evolution with the activity cycle is determined by large-scale interior flows. Thus, the internal dynamics of the Sun and other stars hold the key to understanding the dynamo mechanism and activity cycles. Recently, significant progress has been made for modeling magnetohydrodynamics of the stellar interiors and probing the internal rotation and large-scale dynamics of the Sun by helioseismology. Also, asteroseismology is beginning to probe interiors of distant stars. I review key achievements and challenges in our quest to understand the basic mechanisms of solar and stellar activity. 相似文献
509.
J Huttermann A Schaefer G Kraft 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1989,9(10):35-44
Free radical formation after heavy-ion bombardment was studied in solid, polycristalline pellets of DNA-constituents by analysing the dose-yield curves and the spectra obtained by ESR-spectroscopy at low (< 100 K) and ambient temperatures. The dose-yield curves were found to correlate with those found after X-irradiation but shifted to higher doses and lower saturation concentrations. The corresponding radical yields (per 100 eV) exhibit values which are one to two orders of magnitudes lower. The structural aspects as revealed from powder ESR-spectra gave a complex inter-relation between substance, LET, dose and irradiation temperature, which is discussed in terms of mechanistic models. 相似文献
510.
S. Seetha M.C. Ramadevi V.C. Babu M.R. Sharma N.S.R. Murthy B.N. Ashoka K.C. Shyama R. Kulkarni G. Meena P. Sreekumar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2006,38(12):2995-2998
The Scanning Sky Monitor is one of the experiments onboard the ASTROSAT, an Indian multiwavelength astronomy satellite mission. This experiment will detect and monitor X-ray transients in the energy band 2–10 keV. It is similar in design to the ASM on RXTE. It consists of position-sensitive proportional counters with one-dimensional mask. We describe the configuration of the experiment. We also discuss some of the results obtained using a detector which has already been fabricated and tested in our laboratory. 相似文献