基于遗传算法的定位布局优化新方法

在夹具设计过程中,建立了一种定位元件布局确定的新方法.该方法基于模糊评判,考虑候选表面特征类型、表面面积、位置公差等影响因素,确定定位参考面和定位点的数量.以定位误差最小为优化目标通过遗传算法确定定位点的具体位置.最后,通过实例验证该方法优于检验设计,并且能有效提高定性精度.     

Optimal low-thrust transfers between close near-circular coplanar orbits

Four types of optimal solutions are demonstrated to exist for transfers (time of flight is not fixed) between close near-circular coplanar orbits. One solution is realized with the help of fixed orientation of the propulsion system (PS) along a transversal in the orbital coordinate system. Another is reached at fixed orientation of the PS in the inertial coordinate system. The third and fourth types of solutions change the PS orientation in the process of executing the maneuver. Regions of existence are established for all types of solutions, and algorithms for determination of parameters of these maneuvers are suggested. The algorithms were used to calculate parameters of the maneuvers of transfer from a launching orbit to a working Sun-synchronous orbit, and to calculate the maneuvers of supporting the parameters of such an orbit in a specified range.     

柔性SiO2 气凝胶的制备

以甲基三乙氧基硅烷为前驱体,通过溶胶-凝胶法和超临界干燥制备块状柔性SiO2气凝胶.研究了前驱体浓度对材料化学组成、微观结构及柔韧性、热稳定性的影响.结果表明,甲基的存在降低了分子网络的交联密度,赋予了材料柔韧性.随着前驱体浓度降低,微观结构中颗粒堆积紧密程度下降,材料的柔韧性增强;同时分子中硅羟基增多,热稳定性提高.     

Recent advances in the aerothermodynamics of spiked hypersonic vehicles

Among a variety of design requirements, reducing the drag and aeroheating on hypersonic vehicles is the most crucial one. Unfortunately, these two objectives are often conflicting. On one hand, sharp slender forebodies design reduces the drag and ensures longer ranges and more economic flights. However, they are more vulnerable to aerodynamic heating. On the other hand, blunt forebodies produce more drag, however, they are preferred as far as aeroheating is concerned. In addition, in the context of hypersonic vehicles, blunt geometries are preferred over slender ones for practical implications such as higher volumetric efficiency, better accommodation of crew or on-board equipment.In principle, a blunt vehicle flying at hypersonic speeds generates a strong bow shock wave ahead of its nose, which is responsible for the high drag and aeroheating levels. There have been a number of efforts devoted towards reducing both the drag and the aeroheating by modifying the flowfield ahead of the vehicle's nose. Of these techniques, using spikes is the simplest and the most reliable technique. A spike is simply a slender rod attached to the stagnation point of the vehicle's nose. The spike replaces the strong bow shock with a system of weaker shocks along with creating a zone of recirculating flow ahead of the forebody thus reducing both drag and aeroheating.Since their introduction to the high-speed vehicles domain in the late 1940s, spikes have been extensively studied using both experimental facilities and numerical simulation techniques. The present paper is devoted to surveying these studies and illustrating the contributions of the authors in this field. The paper also raises some of the areas in the field that need further investigations.     

3 外涵变循环发动机循环参数匹配模拟

3外涵技术能使发动机涵道比调节范围更宽,使其在所有推力范围和全包线下性能最优。分析了带核心机驱动风扇级（CDFS）的3外涵变循环发动机工作机理,利用稳态性能数值仿真程序,开展了3外涵变循环发动机循环参数匹配模拟研究,得到发动机循环参数取值范围。研究结果表明：3外涵变循环发动机工作范围更广,重点是通过改变其涵道比来实现压比的变化和发动机模态的转变,最终实现3外涵变循环发动机的优越性能。     

Physics of Magnetospheric Variability

Many widely used methods for describing and understanding the magnetosphere are based on balance conditions for quasi-static equilibrium (this is particularly true of the classical theory of magnetosphere/ionosphere coupling, which in addition presupposes the equilibrium to be stable); they may therefore be of limited applicability for dealing with time-variable phenomena as well as for determining cause-effect relations. The large-scale variability of the magnetosphere can be produced both by changing external (solar-wind) conditions and by non-equilibrium internal dynamics. Its developments are governed by the basic equations of physics, especially Maxwell’s equations combined with the unique constraints of large-scale plasma; the requirement of charge quasi-neutrality constrains the electric field to be determined by plasma dynamics (generalized Ohm’s law) and the electric current to match the existing curl of the magnetic field. The structure and dynamics of the ionosphere/magnetosphere/solar-wind system can then be described in terms of three interrelated processes: (1) stress equilibrium and disequilibrium, (2) magnetic flux transport, (3) energy conversion and dissipation. This provides a framework for a unified formulation of settled as well as of controversial issues concerning, e.g., magnetospheric substorms and magnetic storms.     

基于工作过程与行业标准的民航高职专业课程体系的构建与实践

广州民航职业技术学院航空港安全检查专业从职业岗位工作任务分析入手,按完成工作任务的要求来设置课程和实训项目,系统设计了以职业能力和综合素质培养为主体、突出能力目标和安检岗位工作要求的、基于工作过程与行业标准的"课证一体"型的专业课程体系,努力实现知识与应用、理论与实践的有机结合,有效地提高了人才培养的质量。     

基于COM组件的VXI总线ATS现场校准系统软件设计

针对模块式ATS系统规模大、模块多、现场校准需求强烈,校准工作量大的特点,采用COM组件的结构设计了VX I总线ATS现场校准系统软件。基于COM组件的独立性和易于扩展的特点,该校准软件具有良好的扩展性、独立性和可维护性,可以全自动高效地完成校准。最后通过校准实例验证了该校准软件的实用性和高效性。     

无磁金属电导率标块测量系统

介绍了一种基于Ｔｈｏｍｐｓｏｎ－Ｌａｍｐａｒｄ原理的交叉电导率标块测量系统。基准标块的电导率范围为１３％～１００％ＩＡＣＳ，其不确定度为０．０８％，对未知标块传递测量的不确定度为０．１４％＋０．１％ＩＡＣＳ。