Numerical investigation on adiabatic film cooling effectiveness and heat transfer coefficient for effusion cooling over a transverse corrugated surface

Three-dimensional numerical computations are conducted to investigate the effects of the blowing ratio and corrugation geometry on the adiabatic film cooling effectiveness as well as the heat transfer coefficient over a transverse corrugated surface. It is noticeable that the adiabatic wall temperature on the wavy valley of the transverse corrugated surface is relatively lower than that on the wavy peak. Surface corrugation has a relatively obvious influence on the laterally-averaged adiabatic film cooling effectiveness in the region where the effusion film layer is developed, but has little influence in the front region. Compared to a flat surface, the transverse corrugated sur-face produces a smaller adiabatic film cooling effectiveness and a higher heat transfer coefficient ratio. The effusion cooling difference between the flat and corrugated surfaces behaves more obvi-ously under a small aspect ratio of the wavy corrugation.     

军用油料调运优化中的参数值修改法

编制军用油料调运计划，要涉及众多参数，关系错综复杂，绝大多数情况下难以同时实现所有期望目标，因此有必要对有关参数值进行合理修改。通过建立军用油料调拨运输的二部图，针对二部图，证明了能使发点发量发送完毕的定理，从而得到可对有关参数值进行合理修改的方法，为进一步应用线性规划法优化油料调运计划奠定了基础。该方法原理简单、操作方便，适于计算机编程。     

高速冲击下块体金属玻璃动力学响应的实验研究

块体金属玻璃具有极高的力学强度,存在潜在的军事应用价值,实现其应用的关键在于认识材料在高应变率下的动力学行为特性。为此,利用飞片驱动速度可达3．5km／s的电炮加载装置,对一种新制备的锆基块体金属玻璃的动力学响应进行了实验研究。实验中,基于高精度DPS激光干涉仪测得的样品／窗口界面粒子速度波剖面,获得了新材料在应变率约为10^5／s下的冲击响应特性参数。在加载压力15～25GPa范围下,确定的Hugoniot弹性极限约为2．4GPa,线性拟合得到的冲击Hugoniot关系为Ds=（4．4±0．1）＋（0．58±0．08）up。     

Sensor selection of helicopter transmission systems based on physical model and sensitivity analysis

In the helicopter transmission systems, it is important to monitor and track the tooth damage evolution using lots of sensors and detection methods. This paper develops a novel approach for sensor selection based on physical model and sensitivity analysis. Firstly, a physical model of tooth damage and mesh stiffness is built. Secondly, some effective condition indicators(CIs) are presented, and the optimal CIs set is selected by comparing their test statistics according to Mann–Kendall test. Afterwards, the selected CIs are used to generate a health indicator(HI)through sen slop estimator. Then, the sensors are selected according to the monotonic relevance and sensitivity to the damage levels. Finally, the proposed method is verified by the simulation and experimental data. The results show that the approach can provide a guide for health monitoring of helicopter transmission systems, and it is effective to reduce the test cost and improve the system's reliability.     

载人月球软着陆任务紧急中止轨道分析与设计

针对载人月球软着陆进程中,由载人飞船发动机失效引起的任务中止问题,首先分析主发动机失效可能引起的撞月轨道、环绕轨道、逃逸轨道等轨道类型及其特点;然后分析了中止任务执行的前提条件及中止过程的导航制导要求,在此基础上,考虑二体模型,提出普适的共面软着陆中止轨道计算方法;最后,在考虑登月飞船生保系统时间限制条件下,给出下降级主发动机失效情况下,撞月轨道的中止仿真算例。仿真结果表明,该方法可以实现登月飞船软着陆制动故障情形下的任务中止,能够确保飞船安全返回环月轨道。     

Present-day crustal movement of the Chinese mainland based on Global Navigation Satellite System data from 1998 to 2018

A total of more than 260 continuous stations and 2000 campaign stations from the Crustal Movement Observation Network of China (CMONOC) project, covering the Chinese mainland and its surrounding areas during the period of 1998–2018, are processed using the Bernese Global Navigation Satellite System (GNSS) software via a state-of-the-art method. We obtain the coordinate time series of all the stations given in the reference frame ITRF2014, estimate the coseismic deformation, and remove outliers. Lastly, we present the latest, most complete, and most accurate contemporary horizontal velocity field with respect to the stable Eurasian plate, irrespective of the postseismic deformations. This study shows that the signal of tectonic movement in Western China is stronger than that in Eastern China particularly in the Tibetan Plateau, with a rate of 18–32?mm/a. Moreover, the signal decays sharply from south to north. However, North China and South China move coherently to the ESE direction mostly at a rate of 4–10?mm/a and have not experienced any abrupt velocity gradients in their interiors. Meanwhile, Northeast China has the lowest velocity of only 2–4?mm/a in addition to the coastal areas that have slightly larger velocities. The densified and continuous observation of GNSS stations are of great significance to the study of the present-day crustal movement and tectonic deformation characteristics of the Chinese mainland. This would help to provide better constraints on the kinematics and dynamics of the region.     

钢筋混凝土梁抗弯刚度公式修正及研究

使用过程中梁的刚度会发生退化,从而影响其使用性能.根据钢筋混凝土的基本性能,分析了各种损伤对刚度退化的影响因素,认为裂缝对刚度的影响最为直接也最为明显.进而从数学角度、物理意义角度对现行规范刚度公式进行分析,并提取出裂缝对刚度退化的影响参数--受拉钢筋应变不均匀系数φ.选择裂缝平均间距和裂缝开展高度作为裂缝统计参数,通过ANSYS有限元软件模拟和分析,建立了关于裂缝统计参数的抗弯刚度修正公式.     

缓冲气囊展开与缓冲着陆过程的仿真分析

文章基于显式有限元模型,采用控制体积法对缓冲气囊的展开及缓冲过程进行仿真分析。首先对单个球形气囊进行折叠展开过程模拟,之后依据NASA"猎户座"缓冲着陆器的缩比模型,建立了一个用以评估气囊着陆衰减系统的LS-DYNA有限元模型。分别研究了缓冲着陆器正碰和侧碰对缓冲气囊压力、着陆器的加速度和运动的影响。并与文献进行对比验证,计算结果表明数值模拟的正确性。     

提升基础研究平台能力,支撑液体动力技术创新发展

从基础理论与设计准则创建、提高产品质量与可靠性、支撑关键技术攻关及引领技术创新发展等层面论述了液体动力技术基础研究的重要性。介绍了俄罗斯、美国、欧洲及日本等相关领域的发展概况,并与国内基础研究情况进行了比较。从优化整合资源、创新体制机制、强化队伍建设及增加研究经费等方面,提出了提升我国液体动力技术基础研究平台能力的对策。     

实现结构轻量化的新型平流层飞艇研究进展

平流层飞艇具有极高的实用价值,是国内外临近空间开发的研究热点。和中低空常规飞艇相比,由于单位体积所提供的浮力大大降低,使得平流层飞艇设计时存在艇体体积、阻力和重量之间的循环关系,飞艇结构轻量化成为平流层飞艇研发的首要课题,受到了各国研究机构的高度重视。本文对目前实现平流层飞艇结构轻量化的主要方法和技术进行了整理,给出了利用这些方法实现结构轻量化的平流层飞艇研究进展,比较了这些方法的优势和不足,并对新型的平流层展开飞艇技术进行了分析。分析结果认为改进蒙皮材料性能、改变飞艇的结构形式和利用新型的空中展开飞艇将是平流层飞艇实现结构轻量化的主要手段,新型空中展开飞艇能够有效地实现结构轻量化,具备较好的发展潜力。