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791.
Cumulative probability distributions such as occur in radar detection problems are approximated by a new version of the saddlepoint method of evaluating the inverse Laplace transform of the moment-generating function. When the number of radar pulses integrated is large, the approximation of lowest order yields good accuracy in the tails of the distributions, yet requires much less computation than standard recursive methods. Greater accuracy can be achieved upon summing the residual series by converting it to a continued fraction. The method is applied to evaluating the error-function integral and the Mth-order Q function, and to approximating the inverse of the chi-squared distribution. Cumulative distributions of discrete random variables, needed for determining error probabilities in optical communication receivers that involve counting photoelectrons, can be approximated by a simple modification of the method, which is here applied to the Laguerre distribution. 相似文献
792.
793.
794.
Johnson WH 《Acta Astronautica》1975,2(1-2):23-30
The early orbital flights, although undertaken with considerable confidence, involved some uncertainty because of the impossibility of simulating under terrestrial conditions all of the conditions encountered in space. However, space-flight achievements by both the American astronauts and Soviet cosmonauts have firmly established that man, if appropriately selected, trained, and protected by suitable life-support systems, can perform efficiently for long periods of time in the hostile environment of space. We know that the side effects of vestibular origin pose important problems in space exploration, and the neurophysiological effects of any extensive, rapid adaptation processes in subgravity states have enabled a better understanding of man's compensatory capabilities. With the successful establishment of orbiting research laboratories, an unparalleled opportunity exists that will undoubtedly enable better understanding of the role played by gravity in normal terrestrial activity, not only as it affects our vestibular physiology, but also as it may or may not concern other systems and at different organizational levels in the body. 相似文献
795.
796.
Radio direction finders based on the principles of interference measurement provide increased angular resolution as the number of bearing ambiguities increase. In spite of the diversity of interference direction finder design, the resolution of bearing ambiguities reduces to a simple relative phase measurement on crossed baselines less than ?/2 long. This principle is applied in a review of current interference direction finder (DF) designs from the Adcock to the multiwavelength interferometer including both analog and digital bearing computation and display. Analysis shows that simple digital logic circuits may be used to resolve bearing ambiguities in multichannel DF rather than the "sense" displays of conventional analog design. This technique has the advantage of keeping direction finding and sense finding functions simultaneous but separate so that the DF information is not degraded by the injection of the ambiguity resolving sense signal. 相似文献
797.
W. I. Axford 《Space Science Reviews》1968,8(3):331-365
Observations bearing on the nature and properties of the interplanetary plasma are reviewed, and consideration is given to possible fruitful directions for further work. The observations are classified according as they involve traditional (comet tail, optical, geomagnetic, cosmic ray), radio (solar noise, radar, radio-source scattering and scintillation, space-probe transmission) or direct (space-probe) measurements. A fairly complete set of references up to September 1967 is given for the cases of comet tail, radar, radio-source scattering and scintillation, and space-probe measurements.An important development concerns observations of the composition of the solar wind. High-resolution measurements of the positive ion energy per charge spectra have been made using the Vela-3 satellites (Bame
et al., 1968). Ionic components other than H+ and He++ have been detected, notably the various ions of oxygen, O+5, O+6, O+7, (Hundhausen
et al., 1968). A promising technique for unambiguously distinguishing H+ and He++ ions, based on velocity as well as energy per unit charge, has been flown successfully on the satellite IMP-F by Ogilvie and Williamson (1968).This research was supported by the Advanced Research Projects Agency (Project DEFENDER) and was monitored by the U.S. Army Research Office — Durham under Contract DA-31-124-ARO-D-257. 相似文献
798.
799.
The Goddard Experiment Package will measure the ultraviolet spectral emittance of stars and nebulae. It has a spectral resolution of 2 ? in the 1050-? to 4000-? band. The telescope has a 38-inch clear aperture and automatically reduces the spectral data to digital form. Guidance accuracy is 1 of second arc. 相似文献
800.
Henderson IW 《Journal of the British Interplanetary Society》1989,42(7):363-366
Under conditions of microgravity severe alterations in body fluid composition and volume take place largely as a result of "cardiothoracic pooling" or headward shift of blood. Inappropriate endocrine, renal and cardiovascular responses result from the "misreading" of homeostatic signals by physiological receptors to produce an as yet incompletely defined syndrome under microgravitational conditions. 相似文献