廊坊市城市居民体育生活方式的调查

本文运用文献法、访谈法、问卷法对廊坊市城市居民体育生活方式状况及影响因素进行调查,分析研究了廊坊市城市居民体育生活方式现状及构建体育生活方式的对策.     

嫦娥一号月球探测卫星技术特点分析

嫦娥一号卫星是我国的第一个月球探测卫星,将飞行至距地球380000km的月球,实现环绕月球对其遥感探测。由于任务目标不同,嫦娥一号卫星将遇到比近地轨道卫星更复杂的空间环境和飞行控制过程,所以必须解决面临的所有新技术问题。文章介绍了嫦娥一号卫星在轨道设计、月食、热设计、制导导航、测控、数传等方面的技术特点及研制验证方法。     

民航机场飞机排放浓度分布模型

按照国际民航组织规定的起飞着陆循环过程,简化飞机在机场起飞降落的活动路线,在原有飞机排放污染物排放指数(EI)计算的基础上,再结合飞机起飞降落过程的燃油流量(F),计算出进近、滑行、起飞、爬升四段路线的排放污染强度.基于高斯点源扩散公式,对其进行积分得线源扩散模型,再对线源扩散模型中的参数进行修正,建立了民航机场飞机排放浓度模型.     

固体火箭发动机喉衬流场及热结构耦合分析

为了准确预示固体火箭发动机喉衬在燃气环境中的烧蚀传热及热结构行为,建立了基于FLUENT流体计算软件和ANSYS结构分析软件的流场及热结构耦合分析模型.由FLUENT采用整场离散、整场求解的方法进行流固耦合烧蚀传热模拟,得到的压强及温度分布导入ANSYS进行结构分析,实现了流场与烧蚀传热的双向耦合以及流场、热到结构的单...     

单轴挠性卫星快速机动试验台

为了验证挠性卫星快速机动控制方法,搭建单轴挠性卫星快速机动试验平台.该平台基于单轴气浮台,令柔性板的挠性频率和刚挠耦合系数与真实卫星的接近.平台充分模拟了卫星在太空中的失重和无阻尼环境,被激发的挠性振动在开环情况下衰减很慢,特别适合挠性卫星姿态快速机动试验.初步的试验包括挠性参数辨识试验和姿态快速机动PD控制试验,仿真结果表明升级后的平台将可以验证快速机动控制方法.     

气动塞式喷管底部压强模型研究

为了解寒式喷管底部压强特点，找出快速、准确计算底部压强的方法，实验研究了不同反压下塞式喷管的底部压强，在认识外界反压对塞式喷管流动作用机理的基础上分析如何确定不同的底部气动状态，将采式喷管底部在不同外界反压下的气动状态划分为“三段”，即底部开放段、底部闭合段和底部由开到闭的过渡段，在各段，底郜压强使用不同的计算方法。把数值模拟、实验研究及塞式喷管底部自身特点结合起求，找出采式喷管底部压强的一般规律，建立了适合于工程应用的底部压强计算模型．结合40％和120％截短塞式喷管的实验数据，验证了底部模型的正确性。塞式喷管底部流动是超声速流的大分离流动，该模型对底部压强的预示比有限差分法具有更高的精度。     

5083铝合金力学性能的球压痕法检测研究

介绍了微压痕法在航空铝合金材料力学性能检测的研究.采用球形压头通过多级循环加载方法得到了5083铝合金材料压痕深度与载荷的关系,将微压痕数据输入经过充分训练的人工神经网络模型,计算出材料力学性能参数和材料应力应变曲线,对压痕法测量得到的材料真应力应变曲线与拉伸试验得到的结果进行了比较.     

基于GEF框架的AFDX网络建模工具的设计与实现

本文提出了基于Eclipse GEF框架的AFDX网络建模方法。该方法应用GEF的MVC结构,以RCP的形式实现了图形化的AFDX网络建模工具,为用户提供了高效的展示和编辑AFDX网络模型的环境。由于建立了基于Eclipse RCP技术的开放性平台,用户可以Eclipse插件的形式将任何新的功能无缝地集成在此平台下,极大地提高了工具的可扩展性。     

Fracture behavior and self-sharpening mechanisms of polycrystalline cubic boron nitride in grinding based on cohesive element method

Unlike monocrystalline cubic boron nitride (CBN), polycrystalline CBN (PCBN) shows not only higher fracture resistance induced by tool-workpiece interaction but also better self-sharpening capability; therefore, efforts have been devoted to the study of PCBN applications in manufacturing engineering. Most of the studies, however, remain qualitative due to difficulties in experimental observations and theoretical modeling and provide limited in-depth understanding of the self-sharpening behavior/mechanism. To fill this research gap, the present study investigates the self-sharpening process of PCBN abrasives in grinding and analyzes the macro-scale fracture behavior and highly localized micro-scale crack propagation in detail. The widely employed finite element (FE) method, together with the classic Voronoi diagram and cohesive element technique, is used considering the pronounced success of FE applications in polycrystalline material modeling. Grinding trials with careful observation of the PCBN abrasive morphologies are performed to validate the proposed method. The self-sharpening details, including fracture morphology, grinding force, strain energy, and damage dissipation energy, are studied. The effects of maximum grain cut depths (MGCDs) and grinding speeds on the PCBN fracture behavior are discussed, and their optimum ranges for preferable PCBN self-sharpening performance are suggested.     

Multi-parameter optimization of machining impeller surface based on the on-machine measuring technique

Selecting the optimal machining parameters for impeller surface is a challenging task in the automatic manufacturing industry, due to its free-form surface and deep-crooked flow channel. Existing experimental methods require lots of machining experiments and off-line tests, which may lead to high machining cost and low efficiency. This paper proposes a novel method of machining parameters optimization for an impeller based on the on-machine measuring technique. The absolute average error and standard deviation of the measured points are used to define the grey relational grade for reconstructing the objective function, and the complex problem of multi-objective optimization is simplified into a problem of single-objective optimization. Then, by comparing the values of the defined grey relational grade in a designed orthogonal experiment, the optimal combination of the machining parameters is obtained. The experiment-solving process of the objective function corresponds to the minimization of the used errors, which is advantageous to reducing the machining error. The proposed method is efficient and low-cost, since it does not require re-clamping the workpiece for off-line tests. Its effectiveness is verified by an on-machine inspection experiment of the impeller blade.