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25 February 2000, Volume 20 Issue 01 Previous Issue    Next Issue

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The Modal Force Rule of Point Piezoelectric Actuator Place Optimization on Intelligent Beam and Frame Li Bin (Logistic Engineering College,Chongqing 400041) Li Yugang Yin Xuegang Huang Shanglian (Intelligent Structure Research Center of Chongqing University,Chongqing 400044) 2000, 20 (01):  .  Abstract ( 1609 )   Save The conclusion is given that the modal control forces produced by point piezoelectric actuators on flexible beam and frame are direct proportion to the modal strains at the places pasted piezoelectric flakes,based on modal control theory and Euler Bernoulli point force model of point piezoelectric actuator.According to the conclusion,the maximal modal force rule of point piezoelectric actuator place optimization has been put out that point piezoelectric actuator should be placed at the position where each order modal strain is maximal.The computer emulating results of intelligent flexible beam and frame show that the rule is correct and effective. Related Articles | Metrics

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Discussion on the Sampling of CCD Cameras Jiao Binliang Wang Zhaohui (Xi'an Institute of Space Radio Technology,Xi'an 710000) 2000, 20 (01):  .  Abstract ( 1447 )   Save The sampling of CCD cameras is discussed.The relation between optical sampling and circuit sampling is analysed.Some suggestions on the design of sampling circuit are presented. Related Articles | Metrics

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An Experimental Digital Multiplexer/Demultiplexer Using Frequency Synthesiser Wang Sheng Lu Chunjie Yang Suze (Beijing Institute of Satellite Information Engineering,Beijing 100080) 2000, 20 (01):  .  Abstract ( 1775 )   Save A method of implementing justification in digital multiplexer/demultiplexer using frequency synthesizer is analyzed in detail.Comparing with classical way (e.g.positive justification or positive/negative justification),the logical design is simple and the implementation is easier.This way is effective. Related Articles | Metrics

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Calibration Method of Scanning Radiometer on FY-2 Satellite in Orbit Rong Zhiguo (National Satellite Meteorology Center,Beijing 100081) 2000, 20 (01):  .  Abstract ( 1955 )   Save The calibration on FY-2 in orbit is the key to the quantify analysis with the image of meteorological satellite.The calibration method of FY-2's visible,infrared and vapor channels in orbit is shown.The process of electric calibration and black body calibration of the channels in orbit is introduced.The result indicates that the infrared channel calibration curveis highly similar to the curve in the labortory. Related Articles | Metrics

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Effect of Baffles on Sloshing Modulated Forces and Torques Responsed to Input Orbital Accelerations in Microgravity Pan Hailin (Beijing Institute of Control Engineering,Beijing 100080) Hong Ruzhen (The University of Alabama in Huntsville USA) 2000, 20 (01):  .  Abstract ( 1565 )   Save The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations with partially filled rotating fluids applicable to a full scale Gravity Probe B Spacecraft dewar tank with and without installing a baffle board have been investigated.Results of slosh wave excitation along the liquid vapor interface is induced by jitter acceleration dominated orbital acceleration which provide a torsional moment with an up and down movement of bubble oscillations in the rotating dewar.Fluctuations of fluid stress forces and fluid stress moment (torque) exerted on the dewar wall of container caused by slosh wave excitation driven by the orbital acceleration are also investigated.As viscous force between liquid solid interface,and surface tension force between liquid vapor solid interface can greatly contribute to the damping effect of slosh wave excitation,rotating dewar installed with baffle provides more areas of liquid solid and liquid vapor solid interface than that of rotating dewar without installing baffle.Results show that damping effect provided by baffle reduces the amplitudes of force and moment feedback from the fluids to the container,in particular,the components of fluctuations transverse to the direction of baffle boards. Related Articles | Metrics

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Study on Dynamics of a Rigid flexible Coupling System with Backlash Hinges Li Tieshou Gou Xingyu (Beijing Institute of Control Engineering,Beijing 100080) 2000, 20 (01):  .  Abstract ( 1683 )   Save Dynamical modeling and simulation of a symmetric rigid flexible coupling system with hinge backlashes are studied.The rigid beam is simplified as a thin cantilever with a lumped mass in the free end.A new concept——bi rigidity of a thin beam is put forward at first.Then,based on the analyzing of the kinematic relationship,the dynamical model with five degrees of freedom of the coupling system is derived by using d'Alambert principle.The anti symmetric initial value response of the system is discussed in detail.It shows that there are one kind of vibration with low frequency and two kinds of vibrations with high frequencies in the response.Because of the vibrations,a small enough step must be used in simulation to obtain reliable numerical solutions.Simulations show that the frequency of the former would decrease with the backlash angles appearing and increasing. Related Articles | Metrics

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The Dual-Modulation Compound System in Reentry Telemetry Zhang Jian (China Academy of Engineering Physics,Mianyang 621900) 2000, 20 (01):  .  Abstract ( 1780 )   Save The dual modulation compound system (DMCS) in reentry telemetry is analyzed.In this system,two kinds of modulation,Pulse Position Keying/On Off Keying (PPK/OOK) and Pulse Code Modulation/Frequency Modulation (PCM/FM) are employed simultaneously.The conclusion shows DMCS can obviously improve the channel capacity compared with that of PPK/OOK system. Related Articles | Metrics

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Modifying S/DB to Improve the Image Matching Precision of the FY-2A Satellite Zhou Jiafeng (National Satellite Meteorological Center,Beijing 100081) 2000, 20 (01):  .  Abstract ( 1550 )   Save The stepping of the VISSR of the FY-2A Meteorological Satellite changes its spin period.As a result,the image matching precision is deteriorated.Based on the movement rule of the VISSR,this paper presents a method to balance the system error in advance by modifying S/DB (Synchronizer/Data Buffer),which can improve the image matching precision trebly and hence intensify the tracking function of S/DB,reaching the international level of the advanced geostationary satellites.This technique is effective in application. Related Articles | Metrics

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Hybrid Coordinate Dynamic Modeling of Flexible Spacecraft in Terms of System Modes Miao Bingqi (Zhejiang University of Technology,Hangzhou 310014) Qu Guangji (Beijing Institute of Spacecraft System Engineering,Beijing 100086) 2000, 20 (01):  .  Abstract ( 1874 )   Save The dynamic equations of flexible spacecraft are derived by introducing a moving coordinate frame.Choosing body frame as moving coordinate frame,the vehicle system modes are obtained by solving the eigenvalue problem of the derived dynamic equations.The hybrid coordinate dynamic equation are then acquired by describing deformation with system modes.It is noted that there is on inertial coupling from the rigid coordinate in the elastic equation and the rigid coordinate direct reflects the rigid motion of spacecraft in contrast to using free modes.Finally,two illustrative examples are given. Related Articles | Metrics

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Analysis of the Temperature of Protuberance on the Surface of Thermal Layer and Inner Complex Structure Tang Gongyue Wu Guoting (Beijing Institute of Spacecraft System Engineering,Beijing 100086) 2000, 20 (01):  .  Abstract ( 1575 )   Save Local overheat causing by the protuberance on the surface of reentry spacecraft in the condition of hypersonic and supersonic flow is discussed briefly.Using the pre processing and after processing software ARIES and calculation program NASTRAN,the distributions of temperature on the protuberance under the test thermal environment and trajectory thermal environment condition are calculated respectively.Then the result of calculation are compared with the result of the test and they are very identical,which is proved that the way treating local overheat causing by the protuberance is practicable and advanced. Related Articles | Metrics

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Research on GPS Interferometry Pointing Determination Wang Zhong Ren Suping (Chengdu Institute of Meteorology,Chengdu 610041) 2000, 20 (01):  .  Abstract ( 1663 )   Save According to the basic principles of GPS interferometry,this paper discusses the pointing problem of the rigid platform.With the observed carrier phasses of multi antenna linear array from multiply GPS satellites,the pointing estimation problem (including azimuth and elevation) is solved using the likelihood methods.The measured phase noise is assumed Gauss distributed,simulation results show the RMS reached 0 1° Related Articles | Metrics

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Structure of Guidance Pattern Based on Primary Bright Star Lin Tao Liu Ruikuan Jia Xiaoguang Qian Guohui (Harbin Institute of Technology,Harbin 150001) 2000, 20 (01):  .  Abstract ( 1576 )   Save The selection of guide primary star and the building of guidance pattern,based on primary bright star,are derived by calculating the optimal solution of multiple variables which are restricted to inequality condition.Experiments demonstrate that the structure of guidance pattern doesn't lost the necessary guide star pairs and reduces obviously the storage capacity of on board guide pattern database. Related Articles | Metrics

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Quartz Accelerometers Used in Space Frecture Characterization Research Jia Cuihong (Fujian Teachers' University,Fuzhou 350007) Xue Datong (Lanzhou Institute of Physics,Lanzhou 730000) 2000, 20 (01):  .  Abstract ( 1838 )   Save Quartz accelerometers used in space are made of fused quartz glass.It is the most important characterization.Their springy supports are easily fragile because of bad conditions in space,such as vibration,shock,changing temperature between high and low.Experiments on their fracture characterization are made and many important data or results are obtained. Related Articles | Metrics