航天航空中急性缺氧条件下功效改变的研究

受试者为84名男性青年和实验工作人员,在低压舱1500、2500、3000、4000、5000和6000米高度上停留60分钟。每次实验一个高度,总共133人次。实验中,记录了数字记忆、听觉警觉和跟踪操作等多项功效指标。应用统计和模型方法对结果进行了分析,并试用模糊集理论对五种基本功效进行综合评定,得到了急性缺氧下功效改变有意义的结果。这些结果可为飞行员执行飞行任务,航天员在船舱内或穿着航天服在舱外执行任务及制订医学保证方案提供了科学依据。     

低速壁压信息洞壁干扰修正方法两个重要的新改进

本文介绍了对美国洛克希德公司Hackett,J.E.等人研究的壁压信息洞壁干扰修正方法两个重要的新改进。建立了一个简便方法,消除了原方法必须要在模型下游测到壁压的渐近分布,才能进行准确修正的苛刻条件;建立了一个测压试验洞壁干扰的改进修正方法,使测压与测力试验的修正方法一致。文中给出了两组模型的验证结果。本文的两个新改进,消除了壁压信息法应用中的突出难关,不仅拓宽了应用,并大为提高了测力、测压试验洞壁干扰修正的准确性。     

Σ-演算的范畴模型

Σ-演算是并发演算CC的子理论,集中体现CC中的并行运算部分的特征。本文将并发通信系统看作是由状态加变换构成的动态系统,建立了Σ-演算的范畴模型(Categorical ModeI),其基本思想是:把Σ-演算中的公式对应于范畴构造中的对象(Objects),Σ-演算中的推演对应于范畴中的态射(Morphisms),从而通过Σ-演算的结构操作语义自然地得到一种范畴结构。这种方法可以推广到其它并发理论之中,例如网论和逻辑方法(如线性逻辑Linear Logic),从而范畴论可以作为描述并发、通信和非确定性行为的统一的形式化框架。     

壁面摩擦对风洞侧壁干扰的影响

本文研究了摩擦对风洞侧壁干扰的影响。在以Barnwell为代表开展的一系列侧壁干扰研究中,所有工作都未计及摩擦的影响。我们认为,Barnwell等人的这一处理理论上有缺陷。对此,本文用Karman-Pohlhausen方法对侧壁边界层作了分析,指出摩擦对侧壁干扰有不同程度的影响,具体取决于Pohlhausen参数B的大小;B越小,影响越大。Barnwell略去摩擦项的结果只对应于分离边界层情况,而事实上Barnwell处理的是附着边界层。通过这一分析,本文建立了有摩擦影响的侧壁干扰修正的新形式;考虑到多种因素的影响,初步建议参数B按中间值取为B=3～4。最后,就修正参数δ~*的确定作了一定讨论。     

超静超稳卫星碰振动力学建模

针对分离式卫星载荷模块(PM)受到扰动时可能与服务模块(SM)发生碰撞的问题，综合音圈电机反电动势(back-EMF)和柔性线缆动力学的效应，基于牛顿欧拉法建立了分离式卫星(DFP)载荷模块动力学模型。基于Hertz接触理论，推导了分离式卫星碰撞过程中连续接触力模型，并分析了碰撞过程中产生的接触力对载荷模块指向精度和指向稳定度的影响。数值仿真结果表明，碰撞使得载荷模块指向精度和指向稳定度下降5个数量级，碰撞后载荷模块可再次恢复到超静超稳工作状态，恢复时间超过1400 s。本文建立的碰撞模型对研究分离式卫星碰撞规避和碰撞控制具有重要意义。     

Methane pyrolysis in preparation of pyrolytic carbon: Thermodynamic and kinetic analysis by density functional theory

The density functional theory has been successfully applied in analyzing pyrolytic carbon deposition by methane pyrolysis from the view of thermodynamics and kinetics based on a total number of 39 elementary reactions. M06-2X/def2-TZVP level was employed to optimize species structures and locate the transition states. The enthalpy changes and Gibbs free energy changes of all the reactions in the temperature range of 298.15–1800 K were derived with optimized species. Results show that the reacting temperature should be above 1200 K based on the equilibrium constant analysis, which is consistent with the typical reaction temperature adopted in experiments. Potential energy surface profiles report that radical attacking reactions have lower energy barriers than those direct decomposition reactions, especially hydrogen radical attacking reactions. The energy barriers of the first steps, dehydrogenations of methane and ethylene, are 272.4 kJ·mol⁻¹ and 288.9 kJ·mol⁻¹ at 1200 K, which are very close to the experimental activation energy for methane pyrolysis. The most favorable decomposition reaction path is the path of hydrogen radical attacking reactions. The highest energy barrier of the path at 1200 K is 185.7 kJ·mol⁻¹ presented by the C–H bond breaking in ethynyl attacked by hydrogen radical.     

Quantitative assessment and visualization of flight risk induced by coupled multi-factor under icing conditions

Aircraft icing has been proven to be one of the most serious threats to flight safety. During the analysis of flight risk under icing conditions, quantitative assessment and visualization of flight risk are quite essential as they provide safe manipulation strategies in intricate conditions. However, they are rarely studied. Since the icing flight accidents are the result of the coupling of multiple unfavorable factors, in present study, we have proposed a method to quantitatively assess flight risk induced by multi-factor coupling under icing conditions by Monte-Carlo simulation and multivariate extreme value theory. The results demonstrate that the flight risk probability increases with the rise of unfavorable factors. Besides, a flight risk visualization method named flight safety window has been presented to build the flight risk distribution cloud maps in different complex conditions. The cloud maps show that the icing would give rise to atrophy of the safety scope, and the consequence would be even more severe when coupled with other more unfavorable factors. The proposed methods in this study would be useful in flight risk analysis under icing conditions and can enhance the pilot's situational awareness in selecting correct strategies within the safety zone to avoid unsafe manipulation.     

电动式磁悬浮动量球电磁场耦合分析

本文针对电动式磁悬浮动量球(Electrodynamic suspension reaction sphere, EDSRS)的电磁场耦合进行分析，采用定子绕组的感应电动势评判耦合强度，提出了耦合强度评判指标，作为EDSRS的结构设计约束，以降低电磁场耦合的影响。首先，结合EDSRS的具体结构特点，对多定子之间的电磁场耦合问题进行分析，采用定子电磁场在另一个定子绕组中产生的感应电动势评判耦合强度。然后，对感应电动势产生规律进行分析，提出了耦合强度评判指标，并基于所提评判指标，建立了耦合约束验证流程，作为EDSRS的结构设计约束，最后，通过有限元仿真和实验验证了上述电磁场耦合分析。     

商务英语模糊语语境顺应性研究

商务英语是国际商务活动的重要语言载体。模糊语在商务英语中有着不可替代的语用功能。以商务活动中的内部沟通语境和对外沟通语境为视角,对在这两种语境下商务英语模糊语的应用规律进行分析研究,应用顺应性理论对其进行解释,阐明在实际应用中应遵循这些规律,做到＂内外有别＂。对准确使用商务英语,提高商务沟通效率以及促进商务英语的教学等方面都有重要的意义。     

Evasion guidance algorithms for air-breathing hypersonic vehicles in three-player pursuit-evasion games

In practical combat scenario, the cooperative intercept strategies are often carefully designed, and it is challenging for the hypersonic vehicles to achieve successful evasion. Based on the analysis, it can be found that if several Successive Pursuers come from the Same Direction (SPSD) and flight with a proper spacing, the evasion difficulty may increase greatly. To address this problem, we focus on the evasion guidance strategy design for the Air-breathing Hypersonic Vehicles (AHVs) under the SPSD combat scenario. In order to avoid the induced influence on the scramjet, altitude and speed of the vehicle, the lateral maneuver and evasion are employed. To guarantee the remnant maneuver ability, the concept of specified miss distance is introduced and utilized to generate the guidance command for the AHV. In the framework of constrained optimal control, the analytical expression of the evasion command is derived, and the constraints of the overload can be ensured to be never violated. In fact, by analyzing the spacing of the pursers, it can be classified whether the cooperative pursuit is formed. For the coordination-unformed multiple pursers, the evasion can be achieved lightly by the proposed strategy. If the coordination is formed, the proposed method will generate a large reverse direction maneuver, and the successful evasion can be maintained as a result. The performance of the proposed algorithms is tested in numerical simulations.