离心压气机无叶扩压段流路控制扩稳机理

为寻求叶轮-扩压器间无叶扩压段流路控制的扩稳机理,选取某离心压气机为研究对象,利用数值模拟的方法,通过流场分析解释其失速机理,并在此基础上重新设计无叶扩压段机匣结构,探讨一种有效流路控制扩稳方式.分析结果表明:将无叶扩压段机匣结构设计为先收缩后扩张型后,离心压气机稳定工作范围提高了2.8%,但绝热效率有所降低.      

天基空间目标监视的短弧段定轨技术

利用两个短弧段的天基测角资料实现对空间目标的轨道确定是天基空间目标监视系统需解决的重要问题之一。提出利用二体轨道的角动量和能量守恒方程计算空间目标初轨的新方法,该方法将短弧段的主要测量信息表示为弧段属性,由两个短弧段的弧段属性建立守恒方程,采用变量替换法求解守恒方程获得多个初轨,通过方差分析从中选择合适的初轨。针对轨道改进中的迭代发散和收敛于局部极小点的问题,提出了选取多个迭代初值进行轨道改进的采样方法。仿真结果表明,初轨确定算法是可行的,轨道改进能成功解算最小二乘轨道。     

流量调节器研制中的主要问题及结构改进

介绍了一种用于液氧／煤油发动机的流量调节器的结构、原理。在调节器研制中出现的主要问题有滑阀卡滞、主级工况的负载特性存在负差率、转级活塞不能复位等。根据调节器的工作条件,运用静力学原理,分析了产生的原因,提出了改进方法,并进行了试验验证。试验结果表明：结构改进后的调节器工作可靠性得到了明显提高。     

加强高校教师人文素养的探究

振兴民族的希望在教育,振兴教育的希望在教师。高校教师人文素养的高低直接关系到高校素质教育的成功与否。因此解读高校教师人文素养的内涵,剖析高校教师人文素养的缺失及成因,着力提升高校教师自身的人文素养已成为深化教育改革、全面推进素质教育的当务之急。     

河北省外贸企业应对技术性贸易壁垒的对策研究

技术性贸易壁垒一方面严重制约了河北省对外贸易的正常发展,同时也给河北省的对外贸易带来难得的发展机遇。对于一个个市场主体而言,技术进步是突破技术性贸易壁垒制约的关键,市场多元化是突破技术性贸易壁垒制约的重要方法。     

铝合金车轮的现状与发展

摩托车铝合金车是８０年代末发展起来的新产品，目前已形成一个规模齐全的新兴行业。本文介绍了铝合金车轮行业的现实状况，并提出了发展思路。     

Characteristics of surface and subsurface of formed thread parts by axial-infeed thread rolling process

The thread rolling process has been widely applied to manufacture high-performance thread parts. In this process, the evolutions of surface and subsurface are frequently introduced, which affect the working performance of manufactured parts. In this study, an axial-infeed thread rolling process (ATRP) is employed, and the macro-meso surface characteristics under different lubrications and operating conditions are investigated. Moreover, the distributions of microstructure and hardness on the subsurface of formed tooth are analyzed in detail, along with the study of stress state and yield strength change. It is found that the MoS₂ grease is more effective in reducing the surface roughness and defects than the lubrication oil and water-base graphite during the ATRP process. Increasing rolling speed improves the quality of surface morphology and can reduce the surface roughness. On the subsurface of bottom and flank, intensive shear stress occurs in a narrow region, resulting in the elongation and refinement of the grains and increasing the low angle grain boundary fraction. Based on the grain size and plastic strain, the yield strength is predicted. The maximum yield strength and hardness on the bottom of formed tooth are improved by 41.2% and 39.4%, respectively.     

Performance improvement of licklider transmission protocol in complex deep space networks based on parameter optimization

A reasonable parameter configuration helps improve the data transmission performance of the Licklider Transmission Protocol (LTP). Previous research has focused mainly on parameter optimization for LTP in simplified scenarios with one to two hops or multihop scenarios with a custody mechanism of the Bundle Protocol (BP). However, the research results are not applicable to communications in Complex Deep Space Networks (CDSNs) without the custody mechanism of BP that are more suitable for deep space communications with LTP. In this paper, we propose a model of file delivery time for LTP in CDSNs. Based on the model, we propose a Parameter Optimization Design Algorithm for LTP (LTP-PODA) of configuring reasonable parameters for LTP. The results show that the accuracy of the proposed model is at least 6.47% higher than that of the previously established models based on simple scenarios, and the proposed model is more suitable for CDSNs. Moreover, the LTP parameters are optimized by the LTP-PODA algorithm to obtain an optimization plan. Configuring the optimization plan for LTP improves the protocol transmission performance by at least 18.77% compared with configuring the other parameter configuration plans.