METHIS: Mercury thermal infrared spectrometer

The BepiColombo mission to Mercury is devoted to the thorough exploration of Mercury and its environment, with the aim to understand the processes of planetary formation and evolution in the hottest part of the protoplanetary nebula. This mission represents an unique opportunity for the European community to extend the understanding of the Solar Nebula evolution from its outer edge – ideally represented by comets – to its inner and warmer edge. Obviously this exploration asks for a detailed knowledge of the main constituents of the matter present in the different Solar System areas. Spectroscopy is a powerful tool to acquire this knowledge. We have participated with a large consortium of European researchers to the development of the Rosetta imaging spectrometer. We propose here to use our experience to develop a newly designed spectrometer to investigate the mineralogical composition of the Mercurial surface. Given the particular thermodynamical situation of the Mercurial surface, we have developed a concept that combines a medium IR low spectral resolution imager with a moderate spectral resolution NIR point spectrometer. The main goal of METHIS is to provide the mineralogical characterisation of the surface with sufficient spectral resolution in a scientifically diagnostic spectral range.     

Robust and efficient computation of turbulent flows around civil transport aircraft at flight Reynolds numbers

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.     

基于线性矩阵不等式的电传飞机人机闭环系统稳定域

 针对静不稳定电传飞机作动器速率限制环节引起的Ⅱ型驾驶员诱发振荡(PIO)严重威胁飞机飞行安全的问题,研究了考虑作动器速率限制因素的人机闭环系统稳定域。引入增广状态变量分离速率限制环节,建立了人机闭环系统饱和非线性模型。为得到尽可能大的人机闭环系统稳定域估计,首先将稳定域求解问题转化为凸优化问题,再通过Schur补引理将其转化为线性矩阵不等式的求解问题,最终得到了人机闭环系统椭球体稳定域估计的一般算法。时域仿真研究表明:所估计的稳定域略微保守但不冒进,静不稳定电传飞机的Ⅱ型PIO是一种发散很快的振荡而非极限环振荡,驾驶员操纵增益以及作动器速率限制值是影响稳定域的重要因素。稳定域法物理意义清晰、结果直观,可用于非线性人机闭环系统稳定性的评估。     

Extensions in adaptive model tracking with mitigated passivity conditions

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.     

Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

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.     

涡轴发动机稳定性实验研究

为了评定涡轴发动机的稳定性,采用了可移动插板式压力畸变发生器评定方法对其稳定性进行评定,通过分析喘振时的压力信号,得到了临界状态下的各种参数和临界畸变指数,在此基础上间接地比较了四台发动机的稳定性的好坏,并且发现该发动机由于离心压气机首先失稳从而引起发动机喘振,且低转速下对喘振的容忍能力要高于高转速状态,这些结论可以作为该型涡轴发动机改进和设计使用的参考依据.     

中国行政垄断现象及法律规制研究

近年来,在我国由计划经济体制向市场经济体制转轨的过程中,长期存在的计划经济所产生的惯性使政府利用其公共权力限制市场竞争,在众多经济部门建立垄断企业,比如铁路、电信、石油、银行等部门,由此出现了行政垄断现象,并愈演愈烈.转型时期,以地方保护和市场分割为主要表现形式的行政垄断扭曲了市场良性竞争关系,降低了资源配置效率,不利于经济的发展.因此,在转型时期,行政垄断的治理、政府管制的改革以及法律制度的规制都成为社会各界普遍关注的问题.文章拟就转型时期的行政垄断现象及法律规制方面的对策进行较为全面的剖析,以期有利于我国在该领域改革实践的深入.     

风雪运动数值模拟中自保持平衡边界条件研究

在目前风场自保持性研究的基础上,结合等效物理粗糙高度,给出一类近似满足自保持性的用于风雪运动数值模拟的边界条件.首先结合低温风洞实验室的风雪实验数据,把文献的方法应用于风雪运动数值模拟中.经对比验算发现,文献的方法应用于风雪数值模拟中不能很好满足自保持性.为了进一步满足自保持性要求,引入等效物理粗糙高度,建立起雪跃移高度与等效物理粗糙高度的关系.结果表明:通过引入等效物理粗糙高度,边界条件的自保持特性得到了进一步的提高.最后对该方法的应用进行了推广验证.     

Determination of crustal deformations based on GPS observing-session duration in Marmara region,Turkey

This paper reports on the estimation of changes of a GPS-based crustal deformation field as function of the observing session duration. This investigation was carried out on the Marmara Continuous GPS Network (Marmara region) by using GPS data collected on a set of 10 stations during the period 2002.50–2005.47 The GPS observations were processed in the ITRF 2005 reference frame using Bernese v5.0 software.