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761.
本文提出一种基于混响室平台将电磁环境和自然环境结合的综合试验箱集成技术,该试验箱集成了环境试验条件和电磁辐射敏感度试验条件,可以在高低温、湿热、温度循环、温度冲击等多种环境条件下同时对电子设备施加电磁辐射干扰,考核电子设备在同施加环境应力和电磁应力的复杂条件下的适应性。经过设计、建造和测试,该集成技术满足各项预期指标并容易进行推广,可进一步降低设备试验成本。 相似文献
762.
E.J. Iles L. McCallum J.E.J. Lovell J.N. McCallum 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(3):962-973
As we move into the next era of geodetic VLBI, the scheduling process is one focus for improvement in terms of increased flexibility and the ability to react with changing conditions. A range of simulations were conducted to ascertain the impact of scheduling on geodetic results such as Earth Orientation Parameters (EOPs) and station coordinates. The potential capabilities of new automated scheduling modes were also simulated, using the so-called ‘dynamic scheduling’ technique. The primary aim was to improve efficiency for both cost and time without losing geodetic precision, particularly to maximise the uses of the Australian AuScope VLBI array.We show that short breaks in observation will not significantly degrade the results of a typical 24?h experiment, whereas simply shortening observing time degrades precision exponentially. We also confirm the new automated, dynamic scheduling mode is capable of producing the same standard of result as a traditional schedule, with close to real-time flexibility. Further, it is possible to use the dynamic scheduler to augment the 3 station Australian AuScope array and thereby attain EOPs of the current global precision with only intermittent contribution from 2 additional stations. We thus confirm automated, dynamic scheduling bears great potential for flexibility and automation in line with aims for future continuous VLBI operations. 相似文献
763.
Jianguo Cai Meng Li Yuanyuan Li Yifan Ding Jian Feng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(10):3343-3353
Miura-ori is a rigid origami structure utilized in the packaging of deployable solar panels for use in space or in the folding of maps. It's pattern can largely reduce the membrane stress and improve the work efficiency. Inspired by origami structures, we numerically and experimentally studied a scalable solar sail structure. As an improvement of the existing membrane simulations, a variable Poisson's ratio model considering the wrinkling effect of the membrane was introduced. We focused on a quadrant shape and studied how its geometry parameters and initial imperfections affect the membrane mechanical behavior. We also designed and fabricated a pantographic mechanism as an origami membrane actuator. In addition, design protocols of deployment applied to a scalable gossamer structure were proposed. 相似文献
764.
Peter Plötner Markus Czupalla Anton Zhukov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The Virtual Habitat (V-HAB), is a Life Support System (LSS) simulation, created to perform dynamic simulation of LSS’s for future human spaceflight missions. It allows the testing of LSS robustness by means of computer simulations, e.g. of worst case scenarios. 相似文献
765.
This work aims at providing numerical methods that enable the robust and efficient simulation of turbulent flows around civil transport aircraft configurations at flight Reynolds numbers. Robustness problems related to the multigrid treatment of advanced transport equation turbulence models have been identified preventing convergence of simulations at high or flight Reynolds numbers. Therefore the application of multigrid to the turbulence equations is omitted while the multigrid treatment of the mean flow equations stays unchanged. Moreover, a fully implicit time integration scheme – a DDADI approach – is applied to the turbulence equations. The new approach raised robustness to a sufficient level to converge viscous computations at flight Reynolds numbers. Furthermore, the convergence speed of aerodynamic coefficients for three dimensional applications has also been improved significantly. 相似文献
766.
Itzhak BARKANA 《中国航空学报》2013,26(1):136-150
Feasibility of nonlinear and adaptive control methodologies in multivariable linear timeinvariant systems with state space realization {A, B, C} has apparently been limited by the standard strict passivity (or positive realness) conditions that imply that the product CB must be positive definite symmetric. More recently the symmetry condition has been mitigated, requiring instead that the not necessarily symmetric matrix CB be diagonalizable and with positive real eigenvalues. However, although the mitigated conditions are useful in proving pure stabilizability with Adaptive Controllers, the Model Tracking question has remained open and counterexamples seem to demonstrate total divergence of standard model reference adaptive controllers when the regular passivity conditions are not fully satisfied. Therefore, this paper further extends the previous results, showing that the new passivity conditions do guarantee stability with adaptive model tracking. Examples show how the new conditions solve the case of flexible structures with unknown parameters when perfect collocation is not possible. Also, the so-called counterexamples become simple, well-behaved, examples. 相似文献
767.
To investigate the longitudinal motion stability of aircraft maneuvers conveniently, a new stability analysis approach is presented in this paper. Based on describing longitudinal aerodynamics at high angle-of-attack (a < 50 ) motion by polynomials, a union structure of two-order differential equation is suggested. By means of nonlinear theory and method, analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight. Applying the theories of bifurcations, many kinds of bifurcations, such as equilibrium, Hopf, homoclinic (heteroclinic) orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived. The bifurcation curves divide the parameter plane into several regions; moreover, the complete bifurcation diagrams and phase portraits in different regions are obtained. Finally, our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium. The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack. 相似文献
768.
769.
770.
J. Rodriguez V. Lapuerta A. Laveron-Simavilla M. Cordero-Gracia 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
An experiment in microgravity conditions aboard the TEXUS-23 mission was performed to obtain the deformation up to breakage of a cylindrical liquid column in isorotation around an eccentric axis. In previous work, breakage rotation speed was predicted by a numerical method. This method was validated by comparison with analytical and experimental results. The non-symmetric breakage of the liquid column observed in the experiment, however, was not explained by the combined effect of rotation and eccentricity. 相似文献