半球动压马达转子端面垂直度检测装置

在半球动压马达转子端面垂直度的工序中,检测一直是影响生产效率的重要瓶颈问题,因没有理想的检测手段,目前只能依赖三坐标仪进行检测.因检测频繁、测点多、耗时长,极大地影响了生产效率.介绍了一种基于光学检测原理研制的端面垂直度检测装置,工程实际应用结果表明,它具有检测精度高、操作简便、时间短的特点,极大地提高了检测效率,在提高生产效率方面具有重大的实际意义.     

Delineation of possible influence of solar variability and galactic cosmic rays on terrestrial climate parameters

The present paper has investigated the associations of solar activity (SA), represented by total solar irradiance (TSI), galactic cosmic rays (GCR) and terrestrial climate parameters in particular the global cloudiness and global surface temperature. To that end, we have analysed thirty five years (1983–2018) data of these parameters and have applied the Granger-causality test in order to assess whether there is any potential predictability power of one indicator to the other. The correlations among the involved parameters are tested using Vector Auto Regression (VAR) model and variance decomposition method. As a result of the above analysis, we have found that the TSI is an important factor and has contributed about 8.77 ± 0.42% in the cosmic ray intensity variations. In case of cloud cover variations, the other three parameters (TSI, cosmic ray and global surface temperature) have played a significant role. Further, the TSI changes have contributed 1.68 ± 0.03% fluctuations in the variance of the cloud cover while the cosmic ray intensity and global surface temperature have contributed about 4.89 ± 0.08% and 10.87 ± 1.41% respectively. In case of the global surface temperature anomaly both TSI and cloud covers have contributed about 5.07 ± 0.47% and 14.42 ± 2.13% fluctuations respectively. Additionally, we have also assessed the impact of internal climate oscillations like multivariate ENSO index (MEI), north Atlantic oscillations (NAO) and quasi biennial oscillations (QBO) on cloud cover variations. The contribution of these internal oscillations e.g. ENSO, NAO and QBO in cloud cover variation were reported as 7.48 ± 1.02%, 5.51 ± 0.16% and 1.36 ± 0.43% respectively.     

太空中的PM2.5——太阳系尘埃动力学研究进展

对太阳系尘埃动力学所涉及到的基本内容进行概述，包括尘埃的种类、成分、尺寸、密度、形状和生命周期。介绍了近年来在尘埃的来源与生成机制方面的力学过程、主要理论、模型与方法，包括冲击溅射、表面喷射、风化、滑坡、质量脱落、旋转断裂等，阐述了尘埃的充电过程与磁场环境，简要概述了航天任务的尘埃探测结果，介绍了尘埃受力模型、单个尘埃颗粒的运动以及大量尘埃的分布特征、动力学现象及内在规律方面的最新研究结论。最后对太阳系尘埃动力学领域的未来发展趋势进行了展望。     

云制造资源服务化封装与服务发现研究

为屏蔽制造资源的复杂性和异构性,实现异地、异构的制造资源整合与共享,向用户提供统一资源服务调用接口,分析云制造资源池业务流程和云制造资源组织模式,并提出以模块化的方式描述资源管理信息.在此基础上,构建制造资源的本体语义模型,使用OWL(Contology Web Language for Services),进行形式化描述;使用描述模版库和资源—服务映射器,实现资源服务化封装操作的简单化、自动化和规范化;使用OWL-S对制造云服务进行形式化描述,提供简便的服务注册、发布操作.采用基于语义相似度的服务搜索和匹配方法,并将云制造服务语义细分为功能语义、服务质量语义、数据语义和执行语义,使服务匹配快速、准确.     

混合小推力航天器轨道保持高性能滑模控制

针对采用太阳帆、太阳电混合小推力推进的航天器，研究了其在日心悬浮轨道的保持控制问题。为解决已有控制方法中未综合考虑内部未建模动态和外部未知扰动的问题，以及进一步提高系统控制性能，设计了一种高性能滑模控制策略。首先，考虑模型不确定性，建立了混合小推力航天器在日心悬浮轨道柱面坐标系的动力学方程；其次，基于改进型条件积分滑模面和径向基（RBF）神经网络设计了控制律，结合自适应方法在线估计不确定参数；接着，将求取的虚拟控制量在推进剂最优条件下转换成实际控制量，即太阳帆姿态角和太阳电推进力；最后，数值仿真验证了上述设计方法提高了系统鲁棒性，减小了轨道位置超调，并且混合推进相比于单一太阳帆推进，在更短收敛时间内控制精度提高了4个数量级，相比于单一太阳电推进，一年可以节省约89.6%的推进剂。     

3-UPS/S并联转台球铰链的优化研究

受球铰链最大转角的影响,并联机构的最大倾角通常在30°左右。3-UPS/S并联转台的大倾角要求,需要有大转角空间的球铰链。本文首先建立了转台球铰链的无量纲模型,运用二维空间搜索的方法得到了最优的球铰链法线和球铰链最大转角。然后研究了转台参数对球铰链最大转角的影响,并选择了合适的转台初始角度。针对转台的大运动空间要求,对转台的参数和球铰链的参数进行了优化设计,最后对球铰链的转角和转台的运动空间进行了验证。为物理样机的设计制造提供了依据。     

Building components for an outpost on the Lunar soil by means of a novel 3D printing technology

3D-printing technologies are receiving an always increasing attention in architecture, due to their potential use for direct construction of buildings and other complex structures, also of considerable dimensions, with virtually any shape. Some of these technologies rely on an agglomeration process of inert materials, e.g. sand, through a special binding liquid and this capability is of interest for the space community for its potential application to space exploration. In fact, it opens the possibility for exploiting in-situ resources for the construction of buildings in harsh spatial environments. The paper presents the results of a study aimed at assessing the concept of 3D printing technology for building habitats on the Moon using lunar soil, also called regolith. A particular patented 3D-printing technology – D-shape – has been applied, which is, among the existing rapid prototyping systems, the closest to achieving full scale construction of buildings and the physical and chemical characteristics of lunar regolith and terrestrial regolith simulants have been assessed with respect to the working principles of such technology. A novel lunar regolith simulant has also been developed, which almost exactly reproduces the characteristics of the JSC-1A simulant produced in the US. Moreover, tests in air and in vacuum have been performed to demonstrate the occurrence of the reticulation reaction with the regolith simulant. The vacuum tests also showed that evaporation or freezing of the binding liquid can be prevented through a proper injection method. The general requirements of a Moon outpost have been specified, and a preliminary design of the habitat has been developed. Based on such design, a section of the outpost wall has been selected and manufactured at full scale using the D-shape printer and regolith simulant. Test pieces have also been manufactured and their mechanical properties have been assessed.     

Grindability and Surface Integrity of Cast Nickel-based Superalloy in Creep Feed Grinding with Brazed CBN Abrasive Wheels

The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters (i.e. wheel speed, workpiece speed and depth of cut) on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride (CBN) abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardness and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 °C is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm³. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the burn-free and crack-free ground surface.     

Tool Life and Surface Integrity in High-speed Milling of Titanium Alloy TA15 with PCD/PCBN Tools

Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high process temperature as well as rapidly increasing tool wear. The conventional tool materials are not able to maintain their hardness and other mechanical properties at higher cutting temperatures encountered in high speed machining. In this work, the new material tools, which are polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) tools, are used in high-speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy. The performance and wear mechanism of the tools are investigated. Compared to PCBN tool, PCD tool has a much longer tool life, especially at higher cutting speeds. Analyses based on the SEM and EDX suggest that attrition, adhesion and diffusion are the main wear mechanisms of PCD and PCBN tools in high-speed milling of TA15. Oxidation wear is also observed at PCBN tool/workpiece interface. Roughness, defects, micro-hardness and microstructure of the machined surface are investigated. The recorded surface roughness values with PCD/PCBN tools are bellow 0.3 μm at initial and steady cutting stage. Micro-hardness analysis shows that the machined surface hardening depth with PCD and PCBN tools is small. There is no evidence of sub-surface defects with PCD and PCBN tools. It is concluded that for TA15 alloy, high-speed milling can be carried out with PCD/PCBN tools.     

小展弦比飞翼布局作战飞机可控性设计方法

 飞翼布局飞机取消了常规布局飞机采用的安定面和操纵面,由此引起其可控性设计的诸多新问题。以某小展弦比飞翼布局作战飞机为例,利用风洞试验结果研究了几种典型新型操纵面的操纵新机理及不同飞行条件下的操纵效能等。基于可控性设计的要求,估算了该飞翼构型作战使用所需的三轴最大控制力矩系数。通过引进舵容量的概念提出了新型操纵面的参数化设计方法,最后对这一新布局方案进行了可控性评估,为飞翼布局飞机概念设计阶段的新型操纵面布置和设计提供了一种实用的方法。