Motion trajectory prediction model of hydrogen leak and diffusion in a stable thermally-stratified environment

The motion trajectory of hydrogen leakage is an essential safe issue for the application of hydrogen energy. A dimensionless fast-running motion trajectory prediction model is proposed to predict the dispersion characteristics of the buoyant jet of hydrogen leakage for the accident. The impact of different leakage angles, leakage velocity and thermal stratification of ambient air on hydrogen leakage behavior was analyzed. The new developed model was verified by experimental results in literatures. Leakage hydrogen can flow upwards freely in a uniform environment. However, it shows an oscillating trajectory at a certain height in a thermally stratified environment, which is so called “locking phenomenon”. The trajectory of hydrogen leakage is upward and hydrogen gathers at the top of the space to form stratification in a uniform environment, while the hydrogen leakage shows an oscillating trajectory at a certain height in a thermal stratification environment. With the increase of Froude number Fr, it shows that the stable height and maximum height of the leakage airflow have a trend of rising first and then falling in a thermally stratified environment. The findings are expected to give guidance in real-world situations, for example, a larger Fr value and a larger temperature gradient can lead to a decrease in the stable height in the thermally stratified environment. It is found that the fitting of the stable height with different temperature gradients satisfies the power function relationship. This work is expected to be helpful for reducing hydrogen leakage accumulation and explosion risk.     

Study on the non-uniform contact during ELID groove grinding

This paper introduces the potential feasibility that ELID (electrolytic in-process dressing) grinding replaces superfinishing in bearing manufacturing, but ELID grinding will bring new challenges. Different regions present distinguish surface profile due to the non-uniform contact in ELID groove grinding. However, few reports explaining the non-uniform contact are available. This article explores the mechanisms of the non-uniform contact during ELID groove grinding. Experiments on the non-uniform contact between bearing raceway and grinding wheel have been carried out under different conditions. The results show that non-uniform contact exists in ELID groove grinding process and it exerts influence on the profile of the raceway surface. Non-uniform contact influences the Rsk and Rku value all the time, but it influences the Ra value occasionally. Improvement strategies of eliminating the non-uniform contact are also discussed based on the experimental study.     

光电平台无角位移减振机构运动分析

分析了光电平台的工作环境和角振动对成像质量的影响，应用空间机构学原理和减振理论，设计了一种既具减振功能又能抑制角位移的无角位移减振机构。对减振机构的减振机理及运动特性进行了分析，并利用三维建模软件和MSC．Visual Nastran 4D仿真分析软件对该减振机构进行了三雏实体仿真分析，通过输出的仿真数据及曲线检验无角位移减振原理的正确性。     

MIM隧道发光结的负阻现象

本文介绍了薄膜隧道发光结的基本结构、发光机理，阐述了其Ｉ－Ｖ特性中的负阻现象。简单介绍了ＭＩＭ结构负阻的几种解释，根据热像仪照片和低温测试结果分析，再结合Ｄｅａｒｍａｌｅｙ导电模型，我们提出了ＭＩＭ负阻的物理模型，理论与实验符合较好，最后分析了负阻现象的应用前景。     

有限区间信号边界效应问题的研究

研究了截断信号边界的“吉布斯”现象及数字滤波器相位特性对有限区间信号滤波处理的影响，在阐明了有限区间信号处理中边界效应物理本质的基础上，探讨了数字信号处理中通常所采用的边界处理方法的有效性问题，提出了一种命名为端值延拓法的新的边界处理方法，通过比较分析和实例验证表明这种方法的优越性，文中以零相位数字滤波及运用MALLAT算法对有限区间信号进行小波分解与重构为实例，介绍了其边界效应问题及解决方案，取得了很好的效果。     

Nucleation Mechanism for Bainite

Based on the experimental results that solute-depleted zone was observed in Cu-28Zn-4AI (mass fraction) at 523 K, AG is calculated as a positive according to the thermodynamic criteria for the spinodal decomposition of a ternary systems. So, the solute-depleted zone cannot be formed by spinodal decomposition. Dislocation density required by the formation of solute-depleted zone is estimated greater than 7.89×109 cm-2, according to the segregation of solute atoms around dislocations, which is not consistent with the practical situation for the alloy at 523 K. Associated with the internal friction experimental fact that internal friction peaks appear within the incubation for bainitic transformation in Cu-Zn-AI alloy, the equilibrium temperature, TO, is evaluated as 433 K for solute-depleted Cu-25Zn-3.4AI, which is lower than the experimental temperature 523 K. Thus, nucleation by shear mechanism is impossible in this circumstance. Therefore, it is concluded that, like bainite in steels and Ag-Cd, bainite in     

非关联双模场对Kerr介质中电子绝热跃迁转移现象的影响

本文研究了充满Kerr介质的高Q腔中非关联双模相干态场与级联三能级原子非共振相互作用情况下,电子的绝热跃迁转移现象与非关联场之间的关系。数值计算显示:级联三能级原子在与非关联双模相干态的相互作用下,该现象依然存在,但呈现不同于原子与关联场相互作用的新特征。     

小梁现象的社会经济思考

以山西省河津市小梁乡为代表,研究了因建筑业的发展壮大而产生的社会经济空心化现象,分析了其形成原因,并提出了解决措施,以期引起大家对这一社会经济现象的关注,开展更深层次的研究。     

国产掘进机在龙门滩引水隧洞施工中的应用

在长隧洞的施工中，采用掘进机施工的工程越来越多，特别是国外掘进机的引进，加快了长隧洞工程的开发。而国产掘进机由于其性能和材质方面的原因，存在着一定的技术缺陷．通过国产SJ-45型掘进机在龙门滩工程的施工应用，分析和总结了SJ-45型掘进机的机械性能和存在的技术问题及处理结果，以利于国产掘进机的科研、生产和施工。     

钻井液振动筛叠层筛网透筛率的研究

从理论上详细论述了钻井液振动筛叠层筛网对固相颗粒分离的影响 ,首次提出用透筛率的概念定量地描述这一影响 ,并进行了实例计算。研究表明 ,当上下层筛网随机叠加时对透筛率的影响有以下几种情况 :(1)当上下层筛网开孔尺寸相除的余数为零 ,任意组合叠层筛网的透筛率分别为某一常数 ;(2 )上层筛网目数一定时 ,下层筛网目数越大 ,则透筛率越小 ;(3)上下层筛网的目数相差越小 ,透筛率越小 ;(4 )任意目数的上下层筛网随机叠加后 ,其透筛率仅在一个小范围内变化 ,因此任一叠层筛网有其固有的透筛率属性。