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25 June 1988, Volume 8 Issue 03 Previous Issue    Next Issue

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APPLICATION OF DIFFERENTIAL TECHNOLOGY IN TWO-GEOSTATIONARY SATELLITE POSITIONING AND COMMUNICATION SYSTEM Tang Jianmin,Wang Li, and Liu Zhikui 1988, 8 (03):  .  Abstract ( 2106 )   Save Radio Determination Satellite Service is one of the second generation satellite navigation-position fixing systems which posseses high accuracy in position within 10m. Spread-spectrum PN code ranging and differential Posi tioning technology are used to make it possible to reach such accuracy. Errors, such as ionospheric delay variations, satellite ephemeric errors and the shape uncertainty of the earth (the geoid) can be largly compensated by using differential technology.The differential technology and system accuracy analysis are described in this paper. Related Articles | Metrics

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RESEARCH ON ASYMPTOTICAL CHARACTERISTIC OF TEMPERATURE FIELD FOR RADIATIVE THERMAL EXCHANGE SYSTEM Li Dazhi, Li Dayao 1988, 8 (03):  .  Abstract ( 1530 )   Save This paper deals with the asymptotical characteristic of temperature field for the radiative thermal exchange system. The problem is closely related to the thermal simulation test of an artifical satellite with periodic heat source. Based upon the work of this paper, the effective methods described in references[1, 2] can be improved further. Related Articles | Metrics

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MINIMUM ALTITUDE VARIATION ORBIT Yang Weilian (Institute of spacecraft systems engineerjng) 1988, 8 (03):  .  Abstract ( 1759 )   Save Some earth observation satellites require minimum altitude variation in certain areas in order to provide satellites with optimal range at which onboard remote sensing devices operate, so that images can be sharp and with near constant scale. In this paper conditions for such a kind of orbits, the minimum altitude variation orbits, are derived and related parameters are given. Related Articles | Metrics

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ROBUST SPEECH RECOGNITION TECHNIQUE Zhang Pengfei, Qian Hongyu 1988, 8 (03):  .  Abstract ( 1618 )   Save Background noise acoustically adding to speech can degrade the performance of digital environments for applications such as speech comperession and recognition. In this paper we are primarily interested in those situation for which it is known that the noise distribution is nearly normal.We take the noise probability density function (p. d. f) to be the form.As f(x)=(1-ε)g(x)+εh(x) where g(x) is the normal p.d.f,A(x) is an arbitrary symmetric p.d.f,and ε is constant where 0<ε<1. By means of robust estimation,we give the construction of robust M-estimation adding effective function in linear Predictive residue. In ordar to reduce the deviation of estimated parameters of noisy speech, we present a procedure for estimating the robust M and give the experiment data and results. Related Articles | Metrics

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THE CONDITIONAL EQUATION AND ITS WEIGHTING COEFFICIENTS OF THE DIFFERENTIAL ORBIT IMPOROVEMENT USING CONCENTRATED DATA OF THE DIRECTION OBSERVATION Lu Benkui, Rong Pengzhi (Purple Mountain Observatory, Academia Sinica) 1988, 8 (03):  .  Abstract ( 1493 )   Save Making the use of the fact that the rate of the direction observation can be obtained with aid of the information of concentrated data of the direction observation, in this paper a new method of improving the orbit determination, is presented, which can set up the conditional equations of both the direction observation and its rate simultaneously, and calculate their weighting coefficients as well. The method is believed to be useful for some practical and routine work to improve the accuracy of the orbit determination. Related Articles | Metrics

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PERMANENT DISTORTIONS AND IT'S PREDICTION OF SATELLITE COMPONENTS MADE OF COMPOSITE MATERIALS DURING THERMAL CYCLING TEST IN VACUUM Li Liqiang Chen Weijun Qiu Ruiyuan (Beijing Institute of Environmental Test Engineering) 1988, 8 (03):  .  Abstract ( 1963 )   Save This paper describes a thermal cycling test in vacuum of antenna paraboloidal reflector, small model and specimen, made of two carbon fibre sheets and one aluminum honeycomb core and gives the approach for predi- cting the permanent distortions. During thirty thermal cycles between -144℃ and +117℃ the temperature distribution and corresponding distortions were measured and some experimental data and diagram were given.On the basis of relationship between permanent distortion and thermal cycling number, we present mathematical model in terms of power function. Using this model the permanent distortion and work life in long term under thermal cycling can be predicted based on a few test data. Related Articles | Metrics

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THE DOUBLE SINGLE-CHIP-MICROCOMPUTER PARALLEL SYSTEM Gao Lijun (Beijing Institute of Satellite Information Engineering) 1988, 8 (03):  .  Abstract ( 1626 )   Save The Paper puts forward a programme of a kind of double single-chipmicrocomputer parallel processing controller as the definition on properties of a ordinary process computer has stood in the way of the applications of modern control algorithm on the field of industrial process control, It divides the control algorithm appraciately on the two single-chip-microcomputer so as to apply various complex control algorithm on industrial control system. And the pole assignment self-tunning regulator algorithm has come into use in this system, The experiment shows that its real-time processing ability is more powerful than the ordinary one, The system is based on the MCS-51 family single chip microcomputer. Related Articles | Metrics