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25 October 1986, Volume 6 Issue 05 Previous Issue    Next Issue

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A PERFORMANCE ANALYSES FOR PCM/PPK TELEMETRY SYSTEM Cheng Bing zhang, Jiang Chang 1986, 6 (05):  1-8.  Abstract ( 2173 )   Save PCM/PPK telemefry system is a multiple-signal digital communication system whose structure is very simple. In this paper, utilizing the feature that codes transmitted by PCM/PPK are group codes, the bit error probability P_b is analysed and calculated under the various transmission stares, and the transmission error is analysed as the distribution of the prior probability is uniform. The results show that the PCM/PPK is very efficient telemetry system. Related Articles | Metrics

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LARGE AIR HYDROSTATIC BEARING OF THE AEROSPACE VERTICAL DYNAMIC BALANCING MACHINE WITH HARD SUPPORT Zhang Zhu 1986, 6 (05):  9-19.  Abstract ( 2006 )   Save In order to meet the pressing need of the aeroscientific experments, this paper presents an air hydrostatic bearing of the low speed and the high torque stiffness. on the structural characteristics and the reliability, the paper briefly analyzes this type of bearing. We adopt the opposite bearing with two-row throttle to greatly raise the rigidity for satisfying the special requirements of the new type of vertical dynamic balancing machine with the hard support, that is: low noise, low turning speed and great stiffness of the support system. Limiting strictly the mass specific parametere of the satellites within a certain testing precision range, and assuring the attitude stability of communication satellites in space flight are the indispensable technical means of successful running of the communication satellites. The practice has proved that such kind of the method of designing is accurate and reliable for satisfying the requirements of a certain urgent engineering. It fills up the gaps in the fields of experimental equipments in China and opens up a new area in the application of the air hydrostatic bearing. Related Articles | Metrics

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IDENTIFICATION OF SPACECRAFT STRUCTURAL MODAL PARAMETER BASED ON TRANSFER FUNCTION WHICH IS OBTAINED BY MEANS OF SINGLE POINT PSEUDO-RANDOM EXCITATION Yi Jinzeng 1986, 6 (05):  20-29.  Abstract ( 2267 )   Save The Paper presents method for identification spacecraft structural modal parameter based on transfer functions which is obtained by means of single point pseudo-random excitation, some problems in test and data reduction were also discussed. Related Articles | Metrics

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ON NEAR-EARTH SPACE RESOUECES AND SOUNDING ROCKETS Song Zhong-bao Li Da-yao 1986, 6 (05):  30-35.  Abstract ( 1895 )   Save This paper reviews near-earth space resources and the development of sounding rockets, explains the special and important part which the sounding rockets play in exploring and using the near-earth space resourses. Related Articles | Metrics

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THE PRESENT AND DEVELOPMENT OF METEOROLOGICAL SATELLITE Xu Jianping 1986, 6 (05):  36-45.  Abstract ( 2089 )   Save This paper describes the present and development of meteorological Satellites. This paper summarizes the developping direction in remote sensors, data collection, data dissemination, orbit and attitude, and comprehen-sive utilization. The U. S. A-NOAA polar orbit satellite will use the Advanced Microwave sounding Unit to do vertical sounding. The U.S.A geostationary meteorological satellite GOES-NEXT will use the sensors similar to the AVHRR and HIRS now using in NOAA satellites. Author emphosises that the three-axials attitude stabilization is the developping direction in geostationary meterological satellite. Related Articles | Metrics

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MEASUREMENT OF RADIOMETRIC TEMPERATURE OF TERRESTRIAL OBJECTS BY 2—CM MICROWAVE RADIOMETER Luo Mingxue Sun Fuzeng Zhang Guangjie Guo Huizhen 1986, 6 (05):  46-53+64.  Abstract ( 2150 )   Save In this paper, the priniples of the measurement for terrestrial objects by 2-CM microwave radiometer and its system characteristics are discussed. The measured results of radiometric temperature of a few typical terrestrial oblects by scallop scanning mothed are reported. Objects radiometric ISO-temperature curves are obtaind by scallop scanning toothed. It is shown that according ISO-temperature curves obtained is suffeient for the identification of the object's site of research. Related Articles | Metrics

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DETECTION AND CORRECTION OF THE CHANNEL BIT ERRORS FOR DIGITAL IMAGE TRANSMISSION SYSTEMS Li Wenxin Liu Chengxi 1986, 6 (05):  54-63.  Abstract ( 1921 )   Save The effects of the channel bit error on the reconstructed images of the Differential Pulse Code Modulation (DPCM) systems are analysed in this paper. Based on this analysis, an error detection algorithm, which is suitable for the One—dimensionaL DPCM systems, is proposed with mathematical analysis and experiments. It is shown from the results that the origin of the erroreous pixel within a scan line can be detected accurately by the algorithm under some certain conditions without adding any auxiliaries to the DPCM encoders. Furthermore, the algorithm may be fast implemented in digital computers due to its simplicity and recursive property. The experiments also demonstrate that comfining this algorithm with the correction method of line replacement is effective in improving the quality of the DPCM reconstructed image which contains the channel bit error effects. Related Articles | Metrics

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THE RELIABILITY OF THE n:k CROSS—STR APPING REDUNDANCY SYSTEM Liao Jiongsheng(Beijing Institute of Control Engineering) 1986, 6 (05):  65-68.  Abstract ( 1765 )   Save The reliability of TWTA is a central issue in the field of communication and broadcast satellite. In order to increase the reliability, the TWTA redundancy can be introduced. It can be shown that the cross-strapping redundancy is better than the redundancy individually for each channel. In this paper, the formule for the reliability of n:k "cold" cross-strappinp redundancy system is discussed, and that of n : k "warm" cross-strapping redundancy system and its approximete form when η≤0.1λ are prfsented. Related Articles | Metrics