Shanghai Institute of Mechanical and Electrical Engineering
Shanghai Institute of Mechanical and Electrical Engineering
Duan K.,Henan University of Urban Construction |
Wei Y.,Shanghai Institute of Mechanical and Electrical Engineering |
Li X.,CAS Institute of Electronics
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2016
The impact of the transversal velocity of the thermal electrons and the anode aperture on the electron beam spreading in Pierce-type electron gun was mathematically modeled, theoretically analyzed and experimentally measured, to get a more realistic correction of the electron beam spread curve. The calculated results show that the widely-accepted normal deviation σ of the thermal electrons keeps on significantly widening the spreading in the formation of the electron beam, resulting in a fairly large discrepancy between the calculated and measured results. In the newly-formulated model, thermal velocity dominates in the beam convergence; whereas the space charge plays a dominant role in the beam divergence in ignorance of the normal deviation σ. Based on the new model, the beam spread curve was calculated. The results show that the new model outperforms the conventional one because of a better agreement between the predicted and measured beam spread curves. © 2016, Science Press. All right reserved.
Lu Z.,Nanjing University of Aeronautics and Astronautics |
Xiao T.,Nanjing University of Aeronautics and Astronautics |
Li Z.,Nanjing University of Aeronautics and Astronautics |
Zhang Z.,Shanghai Institute of Mechanical and Electrical Engineering |
And 3 more authors.
Journal of Spacecraft and Rockets | Year: 2017
This paper presents an investigation of water-impact characteristics of a space capsule model with various initial pitching angles using an in-house smoothed particle hydrodynamics solver. By solving the governing equations coupled with six degree-of-freedom equations, the strong interaction between the space capsule and water is properly modeled with the kinematic dynamics and hydrodynamics accurately captured. The ditching events of the capsule model with different initial pitching angles were simulated, the computation of which was set up based on a time-stepsize refinement study with results compared to documented experimental data. The well-Agreed-upon results indicate that the initial pitching angle had a noticeable effect on both the normal and longitudinal loads due to the specific geometric characteristics and the appearance of a negative pressure region and that the accelerations became and remained a steady value when the initial pitching angle exceeded 33 deg. In this case, the pressure distribution on the belly of the capsule was also apparently influenced during water impact, which was demonstrated by two different trend of loads. One is that the smaller the initial angle, the higher the pressure to which the probe points were subject, and the other is that the maximum value of pressure experienced increasing and changed to decreasing later. Also, a noticeable nosedown pitching and a significant splashing jet caused by the impact of the capsule leading edge on the water were demonstrated particularly.
Wei Y.-X.,Shanghai Institute of Mechanical and Electrical Engineering |
Wei Y.-X.,CAS Institute of Electronics |
Liu S.-Q.,CAS Institute of Electronics |
Li X.-X.,CAS Institute of Electronics |
And 3 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015
In this paper, a new compact retarding field energy analyzer (RFEA) is designed for diagnosing electron beams of a K-band space travelling-wave tube (TWT). This analyzer has an aperture plate to sample electron beams and a cylindrical electrode to overcome the defocusing effects. The front end of the analyzer constructed as a multistage depression collector (MDC) structure is intended to shape the field to prevent electrons from being accelerated to escape. The direct-current (DC) beams of the K-band space TWTs with the removing MDC can be investigated on the beam measurement system. The current density distribution of DC beams is determined by the analyzer, while the anode voltage and helix voltage of the TWTs are 7000 V and 6850 V, respectively. The current curve's slope effect due to the reflection of secondary electrons on the copper collector of the analyzer is discussed. The experimental analysis shows this RFEA has a good energy resolution to satisfy the requirement of beam measurement. © 2015 Elsevier B.V. All rights reserved.
Chen J.,Beihang University |
Liang J.,Beihang University |
Wang T.,Beihang University |
Zhang T.,Beihang University |
And 2 more authors.
Proceedings of the International Offshore and Polar Engineering Conference | Year: 2014
Arobotic rover harvesting energy from wind and sun was designed to roam and supersede humans to complete scientific missions in Antarctica. Specific terrains, temperature, wind & solar availability and wind resistance in Antarctica were taken into consideration. In energy, the rover need consume much more to travel than it harvests. A fuzzy logic approach in power management was developed to make improvements. Using an energy harvest-manage-consume simulator, both the fuzzy approach and the simple approach were tested. Results showed the fuzzy approach made the rover travel 296% longer and 11% farther than the simple approach did. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).
Zhang H.,Control and Simulation Center |
Zhang Y.,Shanghai Institute of Mechanical and Electrical Engineering |
Zhao H.,Control and Simulation Center
Xitong Fangzhen Xuebao / Journal of System Simulation | Year: 2015
Gyrowheel has the advantage of small size, light weight by its high level of system integration, and it has been attempted to be applied in micro-satellite attitude control system. A linear dynamics model of GyroWheel was built, and then pole-zero analysis was carried out to obtain its basic dynamic characteristics which is different with dynamic tuned gyros (DTG). It is indicated that gyrowheel has two feature frequencies in addition to the precession and nutation frequencies outside. The correctness of the analytical model is proved by the ADAMS model and its simulation. The controlled object characteristic analysis foundation is so provided for gyrowheel to be applied in the attitude control system. ©, 2015, Chinese Association for System Simulation. All right reserved.
Zhang W.,Northwestern Polytechnical University |
Zhai J.,Northwestern Polytechnical University |
Liu X.,Northwestern Polytechnical University |
Liu X.,Shanghai Institute of Mechanical and Electrical Engineering |
Ye Z.,Northwestern Polytechnical University
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2014
A low frequency high power synthetic jet actuator is designed to study the effects of the synthetic jet near the trailing edge of NACA0015 airfoil. The effect of the spout speed, frequency and other parameters on the aerodynamic loads can be studied by changing the ground cylinder stroke or the operating frequency of the motor. The experimental results show that the interaction of the synthetic jet with the upstream can modify the aerodynamic loads obviously. If one jet works, the loads amplitude in the “blowing” process is about 3 times of that in the “sucking” process. Moreover, when two jets work, the amplitudes of lift and moment coefficients are not simply the sum of relevant amplitudes of the one jet case, but lie between the amplitudes of one jet work and two jets work sum. The amplitudes of the lift and momentum coefficients show a good proportional relation to the amplitude of the jet velocity, and the amplitudes of the loads decrease with the increase of the reduced frequency. When the stroke of the synthetic jet is fixed, changing the rotate speed of the servomotor, there is a linear relation between the amplitude of the loads coefficients and the rotate speed. ©, 2014, Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics. All right reserved.
Liu X.-B.,Northwestern Polytechnical University |
Liu X.-B.,Shanghai Institute of Mechanical and Electrical Engineering |
Zhang W.-W.,Northwestern Polytechnical University |
Zhai J.,Northwestern Polytechnical University |
Ye Z.-Y.,Northwestern Polytechnical University
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2013
In order to study the characteristics of the synthetic jet near the trailing edge of an airfoil, an experimental project in wind tunnel is designed for a NACA0015 airfoil. It contains the design of the experimental model, the design of low frequency high power synthetic jet actuator and the method of measurement. The experimental results show that when the speed of the servo-motor runs up to an appropriate rotational speed, the synthetic jet works well. By adjusting the ground cylinder stroke and the operating frequency of the motor, the effect of the spout speed, frequency and other parameters on the aerodynamic loads can be studied. For the two-dimensional test section, a two-dimensional strain balance is designed to measure the dynamic lift and moment. The present experimental project operates successfully in the wind tunnel. It shows that when the frequency of synthetic jet is 3 Hz, the amplitude of lift coefficient is approximate 0.16 which is equal to the value of the experimental airfoil at 1.5 deg angle of attack. So, a synthetic jet actuator of low frequency and high power can supply a large force to control the aeroelastic problem. The new action provides a new way for future aircraft aeroelastic stability control.
Chen H.,Harbin Engineering University |
Xia X.,Shanghai Institute of Mechanical and Electrical Engineering |
Gong L.,Harbin Engineering University
Chinese Control Conference, CCC | Year: 2016
This paper deals with the state filtering problem of nonlinear state-space functions with partial parameters unknown. A novel filtering algorithm is proposed based on a modified maximum likelihood method. Using a new likelihood probabilistic function, we obtain a two-stages strategy of Expectation and Maximization (EM) with the help of Monte Carlo method. The convergence of EM parameter updating strategy is verified theoretically and the proposed algorithm is an iterative process of these two stages. Here we use modified maximum likelihood method for parameter identification and particle filtering method for state estimation at current time moment. The proposed algorithm no longer uses all the observed values for iteration but only the current observed values, so it is simple for calculation and has advantages for application to online parameters identification. Simulation result proves that the proposed algorithm works effectively. © 2016 TCCT.
Hong Z.-H.,Shanghai Institute of Mechanical and Electrical Engineering |
Zhang L.,Shanghai Institute of Mechanical and Electrical Engineering |
Lu Z.-F.,Shanghai Institute of Mechanical and Electrical Engineering |
Wu Y.,Shanghai Institute of Mechanical and Electrical Engineering |
Li Y.-H.,Shanghai Institute of Mechanical and Electrical Engineering
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013
An inter-mode interference sensor based on biconical taped micro/nano optical fibers is presented. And the structural parameters of the sensor are optimized. The device sensitivity has been simulated by the finite element method with commercial software. © 2013 SPIE.
Yin S.,Shanghai Institute of Mechanical and Electrical Engineering |
Pan H.,Shanghai Institute of Mechanical and Electrical Engineering |
Wang Z.,Shanghai Institute of Mechanical and Electrical Engineering |
Wu Z.,Shanghai Institute of Mechanical and Electrical Engineering
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2015
For the recent progress in semiconductor, and the development in sensitivity of uncooled infrared imaging device, uncooled IR seeker is applied on the air-to-surface missile, but none of surface- to-air. Because of its short flying time and a nearer distance, uncooled IR seeker is used on Terminal Defence Misslie. Also there are some practical points needing to be researched in deep. There are some key points on the air-to-surface like anti-aircraft. First of all, the different bands it works lead to a different target or background characteristics, affecting the acquired distance; There is a longer integration time constant of uncooled IR detector compared with the cooled, it is hard to track high maneuvering targets; Finally, the aerodynamic heating on the seeker dome will cause severe thermal radiation effect on the detection system in the aerodynamic thermal environment, because of the long-wave IR band and the long time flying. If such problem can be solved favorably, uncooled IR seeker will be applied quickly on Terminal Defence Misslie, and this research will provide a reference. ©, 2015, Chinese Society of Astronautics. All right reserved.