Evaluation of the contribution of different types of galaxies to the cosmic diffuse background based on γ-ray observations

The relative contribution to the γ-ray background of different types of sources, namely Seyfert Galaxies, Quasars, BL Lac objects, radio galaxies and field galaxies is estimated under the hypothesis that the cosmic diffuse flux is the result of a superposition of many unresolved galaxies. The γ-ray data indicate that the Seyfert volume emissivity matches that of the diffuse background at few hundred keV and exceeds it at higher energies by as much as a factor of about 4. Whilst normal galaxies contribute less than 0.1%, BL Lac objects, Quasars and Radio Galaxies may contribute as much as 5–10% each, even without significant evolution. In this paper we explore different ways of reconciling the observational data on active galaxies with the measured diffuse background level.     

非晶态镍磷合金电沉积的研究

研究了亚磷酸—镍盐型电解液中主要工艺因素对电沉积非晶态镍磷合金的影响。结果表明,亚磷酸与氯化镍浓度比的影响最明显,该比值小于1:3时,难于形成非晶态镀层。随该比值增加,电沉积速度降低而镀层含磷量增大。镀液pH值和阴极电流密度增大时,镀层含磷量降低,不利于非晶结构的形成。从磷的阴极析出机理及其与析氢反应的相关性讨论了上述实验结果。     

临近空间非弹道式目标HTV-2跟踪滤波与预报问题

近年来各国均开始重视临近空间高超声速飞行器的发展,其中以X-51A和HTV-2高超声速飞行器飞行试验相继成功为代表。本文概述了目前高超声速飞行器跟踪滤波与预报领域存在的难点问题,然后对坐标系进行了定义,并设计了HTV-2(Hypersonic Technology Vehicle-2)质心运动方程及跟踪滤波器,介绍了HTV-2弹道预估原理,最后使用卡尔曼滤波方法进行了仿真计算,并对相关参数的选取进行了分析。仿真结果得出使用卡尔曼滤波算法跟踪滤波效果较好,对工程应用有一定的借鉴意义。     

载人机动装置救援轨迹优化设计

本文研究宇航员携带舱外机动装置（ＭＭＵ）进行舱外飞行，营救脱离空间站的目标，随后返回空间站的Ｈｉｌｌ制导方法。根据最小燃料指标，精度要求和时间约束，优化设计ＭＭＵ出舱营救脱离空间站的宇航员或其它装置的飞行轨迹。求出１７种典型情况下的最小燃料解，提出了救援轨迹设计准则。本文分析了ＭＭＵ交会目标过程中，导航和控制误差对Ｈｉｌｌ制导瞄准误差的影响，提出了用多脉冲Ｈｉｌｌ制导按标称最优轨迹飞行的设计方案，     

飞行实测数据相容性检验的三步法

本文指出了１９７７年Ｋｌｅｉｈ首先建立后被各国所广泛采用的相容性检验数学模型存在的局限性，详细地分析了其在飞行实测数据应用中的缺点及其适用性。给出了新的飞行数据鲁棒相容性检验三步法，采用数值稳定的快速三角化平方根分解滤波算法进行参数估计，仿真及实际应用五实了本文有效性。     

有限推力下相对绕飞轨道的直接形成

提出了一种有限推力下主动航天器在完成轨道转移的同时形成相对目标航天器绕飞的方法。根据以改进春分点轨道根数表示的非奇异轨道摄动方程,用变分方法将问题转化为经典的最优控制,由相对运动动力学获得主动航天器实现绕飞须满足的终端约束条件,再用非线性规划求解。给出了求解模型。理论分析和仿真结果表明,该方法理论上可行,但为减少干扰产生的偏差,还需对绕飞形成过程中的导引率进行研究。     

压电自适应桁架结构控制一体化设计

针对压电自适应桁架结构,建立了含有主动元件位置的结构控制一体化设计数学模型,以结构重量作为目标函数,以结构静、动态响应作为约束函数,同时优化结构设计参数、控制参数和主动元件的位置。提出一种解决混合变量一体化设计问题的新方法,该方法将近似概念、遗传算法和对偶法相结合。首先采用组合多点近似函数建立原问题的序列近似问题,再对近似问题中的(0,1)离散变量和连续变量采用遗传算法和对偶方法分别寻优的分层优化策略。算例表明本文方法由于遗传算法只用于求解近似问题,因此只需要很少的结构分析次数就能得到最优解或近似最优解。     

一种波瓣混合器超级燃烧室的掺混特性

为了使涡轮基组合循环发动机超级燃烧室的涡扇涵道和冲压涵道两股气流具有高效低阻的掺混特性,设计了一种结构简单的方形波瓣混合器.用数值模拟方法对该方形波瓣混合器与常规混合器进行了比较分析,结果表明方形波瓣混合器具有与菊花型波瓣混合器相似的流向涡高效低阻掺混特性.进行混合器结构参数变化对掺混特性的影响研究发现扩张角对方形波瓣混合器的热混合效率的影响起主要作用,而出口高度的影响不大;当方形波瓣混合器的波长比为1.0时,方形波瓣混合器具有高效低阻的掺混特性.     

透明件强度设计应考虑材料的综合性能

就飞机座舱盖透明件的使用条件，强度设计，对透明件材料性能的要求以及国内外材料选择的经验进行了介绍，说明舱盖强度设计材料的选择考虑透明材料的综合性能，既要满足静强度条件下的力学性能，又要满足飞机长期外场使用的要求。     

Electrochemical machining of a convex strips structure on a revolving part by using site directed power interruption

Revolving parts with complex surface structures are widely used in machinery and mechanical equipment. The ECM process provides its adequacy to cut hard materials with different shapes, and its applications are widely increased, due to its outstanding advantages. In this paper, a new method for machining a convex strips structure on a cylinder by using site directed power interruption(SDPI) in the ECM process is presented. A variable correction value of the power-off time was defined and optimized to obtain the ideal interval for better machining accuracy and stability.The electric field distribution and the simulated convex profiles show that the stray current density can be reduced effectively by using the proposed method. The correction value has an important influence on the machining accuracy. A suitable correction value in the range of 0.6–1.2 s can effectively improve the machining accuracy of the convex strips structure. Experiments were also conducted to verify the proposed method. Results have confirmed that the stray corrosion on the convex strips surface is significantly reduced and the machining accuracy of convex strips structure is remarkably improved by using the proposed method with a suitable correction value in the ECM process. Finally, a convex strip with a height of 2 mm on a thin-wall revolving part was also produced successfully using a correction value of 0.9.