RH真空系统测试技术分析

详述了RH真空精炼炉中真空系统各种设备的功能,对真空度测量和泄漏量测试进行了说明,并分析了真空系统出现故障的原因。分析结果对于正确判断真空度故障的发生部位,全面掌控真空系统的运行状态,具有重要的现实意义。     

真空断路器的绝缘性能

对真空断路器的电气性能进行分析,找到了影响真空断路器绝缘性能的原因,提出了一些提高真空断路器的绝缘性能的办法。提高真空断路器的绝缘性能,有助于它在高电压使用领域发展,也利于输电系统的运行。     

提高汽轮机组真空系统严密性的经验

通过对包头东华电厂机组凝结器真空低的原因分析,得出包头东华电厂机组真空低的主要原因为凝汽器本体疏水扩容器泄露及与真空系统直接相连的部分放空气门未关闭,并针对类似原因引起凝结器真空低提出应对措施,提高机组运行中真空,以提高机组的安全经济性。     

粤东梅州与东南亚真空教的关系初探

真空教是近代赣南客家地区新兴的一个教门,在数十年的时间里迅速传到中国的10多个省份并远播新加坡、马来西亚等东南亚国家。粤东梅州被誉为"世界客都"、"华侨之乡",有着丰富多彩的民间宗教文化,有许多粤东籍华侨在真空教盛行的东南亚各国安居,那么,真空教是何时传入粤东的?粤东与东南亚真空教道坛又有着怎样的关联?文章结合在梅州的田野调查与前人的研究成果对此作一分析与探讨。     

真空预压法在海相淤泥处理工程中的应用

结合一个真空预压处理人工湖海相淤泥地基的工程实例,通过对真空预压施工工艺流程及监测数据的分析,得出结论:对于海相淤泥地基,真空预压加固法是行之有效的地基处理方法,其加固效果和经济效益明显.加固后固结度和工后沉降量都达到了设计预期的目的.     

真空——以太物质

真空并非空无一物的虚空,真空是很复杂的物理空间,真空是物质存在的一种形式,是一种以太物质。     

在低温条件下SGM308真空助力管结冰问题及解决方案探究

针对SGM308真空助力系统在低温条件下结冰问题,进行了原因分析和相关实验验证,确定EGR除冰模式标定引发析水量过多和真空助力管处温度场过低是导致结冰的主要原因。因此,提出了修改除冰模式标定策略和增加真空管保温护套的解决方案,最后对解决方案进行了验证,结果表明此方案可以有效降低92%的析水量并将真空助力管内温度增加8℃以上,真空助力系统结冰问题得到解决。     

自然界厌恶真空

人们早就知道,只要抽去水管里的空气,形成真空,水就会沿着水管往上流。亚里士多德为了解释抽水现象,说了一句名言——自然界厌恶真空。这句话的意思是:大自然是不会让真空存在的,一旦出现真空就让水来填补,于是,水就被抽上去了。真空出现在哪里,水就跟到哪里。     

真空——以太物质

真空并非空无一物的虚空,真空是很复杂的物理空间,真空是物质存在的一种形式．是一种以太物质。     

巧用真空表诊断汽车发动机故障

当前,维修技术人员越来越重视示波器、发动机综合分析仪等相对复杂检测设备的使用;却常常忽略真空表这样一种简单而又实用的检测工具。实际上,借助真空表对发动机的性能与故障进行分析,可以给维修诊断工作带来很多方便。如何巧用真空表诊断汽车故障,成为当前汽车维修技术人员积极探讨的问题。     

烧结温度对WC-16TiC-4TaC-9Co硬质合金微观组织与性能的影响

选用WC、（W,Ti）C、TaC和Co粉配制WC-16TiC-4TaC-9Co合金混合料,经球磨后压制压坯,在1 410℃、1 430℃和1 450℃温度下真空烧结.测试烧结试样的性能,采用扫描电子显微镜（SEM）观察其微观形貌.结果表明：随着烧结温度升高,合金晶粒尺寸明显长大.1 450℃真空烧结的试样综合性能较好,WC平均尺寸为0.7μm,（W,Ti,Ta）C平均尺寸为3μm.     

关于真空Einstein方程所容许的群定理

一般情形下探求真空Einstein方程的精确局部不变解问题在数学物理中一直是人们关注的焦点。人们发现可以依据李变换群的延拓群概念,将运用纤维丛方法已经解决的延拓群算子中的系数问题作为引理,着重分析并求出真空Einstein方程所容许的群是解决上述问题的关键。     

Non-formation of vacuum states for Navier-Stokes equations with density-dependent viscosity

We consider the Cauchy problem, free boundary problem and piston problem for one-dimensional compressible Navier-Stokes equations with density-dependent viscosity. Using the reduction to absurdity method, we prove that the weak solutions to these systems do not exhibit vacuum states, provided that no vacuum states are present initially. The essential re- quirements on the solutions are that the mass and energy of the fluid are locally integrable at each time, and the Lloc1-norm of the velocity gradient is locally integrable in time.     

铝对钨活化烧结样品组织和性能分析

选用纯钨粉和纯铝粉通过实验方法探讨铝对钨的活化烧结行为,采用高真空钽加热炉进行烧结,应用扫描电镜(SEM)分析了样品组织形貌,并用洛氏硬度计和水静法等方法测试、分析了样品的硬度和密度等性能。结果表明,A l的加入使钨的烧结过程由固相烧结转为液相烧结,从而起到活化烧结作用;相同成分下,随着烧结温度的提高,烧结体的致密度、硬度提高;相同烧结工艺,随着含铝量的增加,烧结体的致密度降低、硬度提高。相比较而言,最佳的烧结工艺应选择在真空中以1 600℃烧结0.5h,最佳的成分应选择钨中掺杂0.99%的铝元素。     

Consolidation behavior of Tianjin dredged clay using two air-booster vacuum preloading methods

This paper presents model tests(macro aspect) and microstructure tests(micro aspect) for investigating the consolidation behavior of Tianjin dredged clay using the prefabricated vertical drain air-booster vacuum preloading(PAVP) and tube air-booster vacuum preloading(TAVP) methods. The mechanism of air-booster vacuum preloading(AVP) using a spring-like system is explained. The main difference between these two methods is the air-boosting equipment. A new anticlogging air-booster prefabricated vertical drain(PVD) is used in the PAVP technique and a self-designed air-booster tube is used in the TAVP technique. In the model tests, a comparison of the variables that are monitored during reinforcement(vacuum pressure, surface settlement, water discharge, and pore-water pressure) and after reinforcement(water content, dry density, and vane shear strength) is conducted. The results indicate that the consolidation behavior of Tianjin dredged clay using the PAVP method is better than that using the TAVP method. PAVP more efficiently mitigates the issue of water-draining PVD clogging and significantly accelerates drainage consolidation. In addition, in the microstructure tests, a comparison of the variables that are monitored after reinforcement(via scanning electron microscopy(SEM) and mercury intrusion porosimetry(MIP)) is conducted, and the results further explain the model test results.     

Randomized Response Analysis in Mplus

This article describes a technique to analyze randomized response data using available structural equation modeling (SEM) software. The randomized response technique was developed to obtain estimates that are more valid when studying sensitive topics. The basic feature of all randomized response methods is that the data are deliberately contaminated with error. This makes it difficult to relate randomized responses to explanatory variables. In this tutorial, we present an approach to this problem, in which the analysis of randomized response data is viewed as a latent class problem, with different latent classes for the random and the truthful responses. To illustrate this technique, an example is presented using the program Mplus.     

定常零压等熵流的三片常数的黎曼问题

研究二维定常零压等熵流带有三个常状态作为初值的黎曼问题．借助于特征分析方法，在适当的广义Ranine-Hugoniot条件和熵条件下，得到狄拉克激波与真空、接触间断之间相互作用的结果，建立了四种不同的唯一的黎曼解结构。     

Sensitivity Analysis of Multiple Informant Models When Data Are Not Missing at Random

Missing data are common in studies that rely on multiple informant data to evaluate relationships among variables for distinguishable individuals clustered within groups. Estimation of structural equation models using raw data allows for incomplete data, and so all groups can be retained for analysis even if only 1 member of a group contributes data. Statistical inference is based on the assumption that data are missing completely at random or missing at random. Importantly, whether or not data are missing is assumed to be independent of the missing data. A saturated correlates model that incorporates correlates of the missingness or the missing data into an analysis and multiple imputation that might also use such correlates offer advantages over the standard implementation of SEM when data are not missing at random because these approaches could result in a data analysis problem for which the missingness is ignorable. This article considers these approaches in an analysis of family data to assess the sensitivity of parameter estimates and statistical inferences to assumptions about missing data, a strategy that could be easily implemented using SEM software.     

Editor's note

This article provides a didactic example and application of new developments in structural equation modeling (SEM) that allow for the modeling of multilevel data. Such data often arise naturally from organizational structures in which within‐group units (employees, students, etc.) are observed in larger between‐group units (firms, schools, etc.) The article begins with an overview of the basic ideas of SEM and multilevel linear regression. The synthesis of both methods developed by Muthéin (1994) is then presented in the simple case of a multilevel path analysis model, in which the variations in within‐group level intercepts are modeled as a function of between‐group variables following their own path model. An application motivated by a real problem in the field of education that focuses on validating indicators of the quality of science education in the United States follows. The results show that it is possible to statistically capture the salient complexities of organizations through the application of multilevel SEM. The article concludes with a discussion of the utility of multilevel SEM for organizational studies.     

Experimental Research of DLC Film Deposited by Filtered Vacuum Arc Evaporation

本文研究了过滤式阴极电弧沉积方法获得的类金刚石薄膜．实验研究电弧的稳定性和探针电流与沉积参数的关系，并系统研究了膜层的性能．膜层的摩擦性能也得到了研究．