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891.
A. V. Bagrov A. A. Barabanov L. V. Vernigora P. A. Vyatlev M. B. Martynov K. M. Pichkhadze V. K. Sysoev 《Cosmic Research》2013,51(5):379-387
We consider the principles of constructing measurement schemes with optical autonomous laser diode beacons for space and ground objects. The structure, functional scheme, and cyclogram of operation of such beacons are described. Possible scenarios of application of the beacons for providing high-precision localization of space and ground devices are analyzed. 相似文献
892.
893.
Has the current US space policy improved the USA's overall strategic position? Does it affect favorably international partnerships? These questions are examined in terms of security, political economy, and influence. In today's context, where there are more space players, more options, more potential for unintended consequences, and higher stakes, unilateral action is more limited in its effectiveness than in earlier times. Surveying current US space policy, it is not clear that data-driven, analytically based decisions are being made to affect positively national independence, innovation, market creation, and international perceptions of the USA as a trustworthy partner. More promising are the steps taken to bolster a predictable space operational environment and economic competitiveness. Ultimately, in order to achieve American excellence and leadership, a ‘closed loop’ on the policy system is needed, to gauge regularly and systematically whether the US is achieving the desired national outcomes. 相似文献
894.
For pt.I, see ibid., vol.28, no.3, p.829-840 (1992). In the central-limit control (CLC), the multiloop controls are employed to regulate the output voltage and track the central weighted current, thus equalizing the output current of each converter module (CM). The current distribution error (CDE) between the output current of each CM is used as a criterion in judging system performance. The prediction and simulation results of this control scheme are illustrated. When incorporated with the maximum current limit, the proposed control method can determine the number of required converters in the active state for each load condition. As a result, the efficiency of a system can be increased significantly. A comparison between the performances of the system under master-slave control (MSC) and CLC is given 相似文献
895.
Y Kumei R Shimokawa K Toda Y Kawauchi K Makita M Terasawa K Ohya H Shimokawa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):783-788
Hypergravity (2G) exposure elevated the nociceptive threshold (pain suppression) concomitantly with evoked neuronal activity in the hypothalamus. Young Wistar male rats were exposed to 2G by centrifugal rotation for 10 min. Before and after 2G exposure, the nociceptive threshold was measured as the withdrawal reflex by using the von Frey type needle at a total of 8 sites of each rat (nose, four quarters, upper and lower back, tail), and then rats were sacrificed. Fos expression was examined immunohistochemically in the hypothalamic slices of the 2G-treated rats. When rats were exposed to 2G hypergravity, the nociceptive threshold was significantly elevated to approximately 150 to 250% of the 1G baseline control levels in all the examination sites. The 2G hypergravity remarkably induced Fos expression in the paraventricular and arcuate nuclei of the hypothalamus. The analgesic effects of 2G hypergravity were attenuated by naloxone pretreatment. Data indicate that hypergravity induces analgesic effects in rats, mediated through hypothalamic neuronal activity in the endogenous opioid system and hypothalamo-pituitary-adrenal axis. 相似文献
896.
R Shimura K Ijiri R Mizuno S Nagaoka 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):803-808
We studied the effects of accumulated nitrate in water on the spawning, hatching and development of medaka using a simple nitrifying filter and a combined filter having both nitrifying and denitrifying capabilities. A nitrate concentration of 100 mg NO3(-)-N/L was clearly of lethal toxicity to fish when they were exposed to nitrate in both adult and the growing phases. A nitrate concentration of 75 mg NO3(-)-N/L reduced the fertilization rate, delayed the hatching time and reduced the hatching rate of the eggs laid by adults and decreased the growth rate of juveniles. In addition, nitrate accumulations as low as 50 mg NO3(-)-N/L remarkably retarded spawning and lowered the number of eggs laid by fish exposed in the juvenile phase. The effects on the reproduction system may be initiated by a low concentration, approximately 30 mg NO3(-)-N/L. 相似文献
897.
K M Deeley M L Duldig J E Humble 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,30(4):1049-1052
The relativistic solar particle event of 4 May 1960, resulting in a cosmic ray ground level enhancement, occurred well before modern analysis techniques were available. We have located surviving data from 23 neutron monitors and have used these to estimate the spectrum, mean arrival direction and particle pitch angle distribution as the event progressed. We find that the apparent particle arrival direction was at equatorial latitudes, over northern South America, in contrast to contemporary analyses that proposed it to be over North America. Our modified power law spectra are broadly consistent with earlier results. Data from stations above sea level need to be corrected for altitude using a two-attenuation length technique. The standard method involves comparison of data from two relatively close stations at significantly different altitude. We have shown that this method may be unreliable in cases, such as this, of quite sharp anisotropy. 相似文献
898.
Multiple model adaptive estimation (MMAE) with filter spawning is used to detect and estimate partial actuator failures on the VISTA F-16. The truth model is a full six-degree-of-freedom simulation provided by Calspan and General Dynamics. The design models are chosen as 13-state linearized models, including first order actuator models. Actuator failures are incorporated into the truth model and design model assuming a "failure to free stream." Filter spawning is used to include additional filters with partial actuator failure hypotheses into the MMAE bank. The spawned filters are based on varying degrees of partial failures (in terms of effectiveness) associated with the complete-actuaton-failure hypothesis with the highest conditional probability of correctness at the current time. Thus, a blended estimate of the failure effectiveness is found using the filters' estimates based upon a no-failure hypothesis, a complete actuator failure hypothesis, and the spawned filters' partial-failure hypotheses. This yields substantial precision in effectiveness estimation, compared with what is possible without spawning additional filters, making partial failure adaptation a viable methodology. 相似文献
899.
This study was initially undertaken to understand how commonalities among the application of proven automation processes such as aircraft control, nuclear power generation, auto manufacturing, etc. could be applied to spacecraft operations at NASA. These industries applied automation to reduce human repetitive task and mitigate risk, rather than create complete "lights out" operations as was the goal at NASA. 相似文献
900.
In 2003, geomagnetic activity was found to be considerably higher than in any other year of the current solar cycle. This was caused by the time coincidence of large low-latitude coronal holes and a significant burst of the flare and eruptive activity of the Sun. The features of recent intensification of the activity are discussed, and the long-period behavior of indices of the geomagnetic activity in the 23rd and previous cycles is compared. The large magnetic storms in October–November 2003 are analyzed in more detail.Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 563–573.Original Russian Text Copyright © 2004 by Belov, Gaidash, Ivanov, Kanonidi. 相似文献