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541.
Rajat Acharya Bijoy Roy M.R. Sivaraman Ashish Dasgupta 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
It is important to use models developed specifically for the equatorial ionospheric estimation for real-time applications, particularly in Satellite Navigation. This work demonstrates a methodology for improved predictions of VTEC in real time using the model developed for the equatorial ionosphere by the authors. This work has been done using TEC data of the low solar activity period of 2005 obtained using dual frequency GPS receivers installed under the GAGAN project of ISRO. For the purpose, the model is first used in conjunction with Kriging technique. Improvement in accuracy is observed when compared with the estimations from the model alone using the measurements as true reference. Further improvement is obtained by Bayesian combination of these estimates with independent Neural Network based predictions. Statistical performance of improvement is provided. An improvement of ∼1 m in confidence level of estimation of VTEC is obtained. 相似文献
542.
543.
R. R. Brown 《Space Science Reviews》1966,5(3):311-387
The present experimental knowledge of electron precipitation in the auroral zone is summarized, using observations primarily
from riometer, balloon, rocket and satellite studies. This includes the association of electron precipitation events with
aurora, magnetic disturbances as well as temporal and spatial aspects of the particle bombardment. 相似文献
544.
545.
The possibility of using solar sails in Earth orbit is investigated. The characteristic parameters of a solar sail consisting of six spheres attached by mutually orthogonal long rods are estimated. 相似文献
546.
T Naitoh M Yamashita A Izumi-Kurotani I Takabatake R J Wassersug 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2000,25(10):2015-2018
Amphibians possess the ability to vomit in response to a variety of stimuli that provoke emesis in mammals. Pharmacological studies have establish that the ejection of gastric contents and the basic mechanism for vomiting have been phylogenetically conserved among these tetrapods. As part of on-going comparative studies on emesis in vertebrates, we previously documented that some postmetamorphic anurans and salamander larvae experience motion-induced emesis when exposed to the provocative stimulus of parabolic aircraft flight. However, more recent experiments suggest that there are strict conditions for inducing emesis in amphibians exposed to parabolic flight and that amphibians are not as sensitive to this stimulus as mammals. Further studies on emesis in lower vertebrates may help us understand the processes that cause emesis in abnormal gravitational regimes. 相似文献
547.
The Monitor-E spacecraft executed uncontrolled flight due to emergency situation, no telemetry information on parameters of the spacecraft’s
attitude motion being available. So, the problem arose to determine the spacecraft’s rotational motion from the accessible
indirect information—the electric current provided by solar batteries. In this paper the integrated statistical technique
is described, that allows one to solve this problem. The values of current, obtained over the time interval some tens of minutes
long, have been processed simultaneously by the least squares method using the integration of the equations of spacecraft’s
rotational motion. As a result of processing, the initial conditions of motion were estimated, and the spacecraft’s moments
of inertia were updated, as well as the angles, specifying solar batteries position in the spacecraft-fixed coordinate system.
The results of processing of 12 data sets are presented, which allowed us to reconstruct the actual rotational motion of the
spacecraft. 相似文献
548.
Purpose of the work is to analyze and to summarize the data of investigations into human hemodynamics performed over 20 years aboard orbital stations Salyut-7 and Mir with participation of 26 cosmonauts on space flights (SF) from 8 to 438 days in duration. The ultrasonic techniques and occlusive plethysmography demonstrated dynamics of changes in the cardiovascular system during SF of various durations. The parameters of general hemodynamics, the pumping function of the heart and arterial circulation in the brain remained stable in all the space flights; however, there were alterations in peripheral circulation associated with blood redistribution and hypovolemie in microgravity. The anti-gravity distribution of the vascular tone decayed gradually as unneeded. The most considerable changes were observed in leg vessels, equally in arteries (decrease in resistance) and veins (increase in maximum capacity). The lower body negative pressure test (LBNP) revealed deterioration of the gravity-dependent reactions that changed for the worse as SF duration extended. The cardiovascular deconditioning showed itself as loss of descent acceleration tolerance and orthostatic instability in the postflight period. 相似文献
549.
550.
Peebles Peyton Z. Berkowitz R. S. 《IEEE transactions on aerospace and electronic systems》1968,(6):845-854
The problem of determining target parameters of a known number of radar targets falling in the same range-Doppler-angle-angle resolution cell is examined for the noise-free case. The required minimum number of radar beams is determined, based upon approximating the beam patterns by a Taylor series expansion, both for the general problem and for factorable beams. Signal processors for target position estimation are developed for the two-target case and equations are presented for the general case. 相似文献