CuZnAl形状记忆合金相变热力学探讨

本文研究的是Cu－24．5Zn－9．0Al（at％）合金色以程形状记忆弹簧自由状态和约束状态下的热力学性质。通过差热扫描（DSC）的测量，得到正转变时的熵变△S^P－M＝－0．55.mol^-1.K^-1，逆转变时的熵变△S^M－P＝0．56J.mol^-1.K^-1，两者的绝对值十分接近，与熵是一个态函数相符。通过精确测量相变过程中弹簧的电阻变化△R和伸长量△L与温度T的关系，发现与自由状态相比，完全压缩状态以电阻表示的相变点并不变化，外应力影响的是以形变定义的相变点，而且到相变结束时，完全压缩状态的转变分数只有自由状态的82％，即与形变△S1^M－P＝0．24J.mol^-1.k^-1,与形变无关的部分相变的熵变为△S2^M－P＝0．63J.mol^-1.K^-1。     

Triangulation in practice

An evaluation study was designed using a between-method triangulation strategy. Two study teams gathered and analyzed data about the effectiveness of a formal process for long range program planning. One team used a mail questionnaire and the other, on-site open-ended interviews. Initial plans for coordination between the two teams were misguided and, fortunately, were subverted during data collection and analysis. The evaluation strategy and its derailment are discussed in terms of the purposes of triangulation and the forces that work against sensible intentions for coordination in multimethod studies.     

沉淀硬化不锈钢PH15—7Mo的组织结构与强化相

本文用定量金相法和膨胀法研究了 PH15～7Mo 钢中,δ铁素体含量,马氏体转变温度和转变量,板条状马氏体和ε马氏体的生成与热处理制度的关系。用射透电子显微镜和x射线相分析法观察和鉴定了析出相的形貌和晶体结构类型。从而阐明该钢的热处理原理和合理使用的温度范围。认为钢材的强化来源于马氏体组织形态和强化相的沉淀硬化效应,强化相为富 Al 相和 Mo 的碳化物。     

Fe—C合金组织图填写与组织相对量计算

本文研究了Fe—C合金组织图的填写方法及组织组成物相对量的计算方法,提出了“过河搭桥”与“逆推顺算”法的概念,为解决这一问题提供了一种新的途径。     

基于FLUENT的新型三氯化铝反应器散热特性研究

针对三氯化铝反应器内部超温的问题,根据其反应特性,设计了一种新型结构的三氯化铝反应器。该结构有利于反应热的及时排除,并利用FLUENT商业软件模拟了自然对流及强制对流条件下,其反应器内部温度场分布情况。结果表明：该反应器在自然对流条件下,大产量会导致内部超温;而强制对流条件下,可以有效控制反应温度,有利于反应 的正常有效进行,并拟舍得到所需冷却风速和日产量的关系式。通过该研究可有效提高散热效果,在保证产量的同时保证产品质量。     

Standardized Martingale Residuals Applied to Grouped Left Truncated Observations of Dementia Cases

The use of martingale residuals have been proposed for modelchecking and also to get a non-parametric estimate of the effectof an explanatory variable. We apply this approach to an epidemiologicalproblem which presents two characteristics: the data are lefttruncated due to delayed entry in the cohort; the data are groupedinto geographical units (parishes). This grouping suggests anatural way of smoothing the graph of residuals which is to computethe sum of the residuals for each parish. It is also naturalto present a graph with standardized residuals. We derive thevariances of the estimated residuals for left truncated datawhich allows computing the standardized residuals. This methodis applied to the study of dementia in a cohort of old people,and to the possible effect of the concentration of aluminum andsilica in drinking water on the risk of developing dementia.     

Adventures in policy modeling! Operations research in the community and beyond

The literature describing operations research in the community is somewhat of a puzzle. On the one hand, several authors have denigrated the use of traditional operations approaches in addressing community problems, yet several studies document successful applications. Arguing that the operations research mindset is itself a great strength, we will review several examples where operations research methods have been employed creatively to the benefit of the community and beyond.     

影响金属期货价格走势的因素分析

从实证角度检验了影响LME铜和铝价格走势的各种因素,结果表明美国的工业产值指数是影响金属期货价格走势的最主要因素。     

离子束法合成钛铝,镍铝合金的研究

利用从金属蒸汽真空孤离子源引出的强束流钛、镍离子,进行了钛铝、镍铝合金的合成试验研究。研究结果表明,在一定的注入条件下,钛、镍离子的注入能在铝表面形成相应的合金层,离子注入样品的磨损率比未注入样品的明显降低。借助于卢瑟福背散射和X射线衍射分析,我们发现表面合金层中分别形成了Al3Ti、NiTi及Al2O3相,钛在铝中能产生20％以上的原子百分浓度,其深度高达7000。最后,本文还讨论了磨损率降低的原因。     

激光涂敷多种硬质合金的性能及形成机理之研究

叙述了利用一台输出功率为2kW的连续CO_2激光器在20~#钢表面涂敷WC—TiN—SiC—Co和WC—SiC—Co的研究,并对激光处理后的涂敷层进行了物相分析和硬度分布以及耐磨性能的测试。其结果表明:利用高功率激光束可在廉价的碳钢表面实现多种硬质合金的涂敷,其表面的化学成分发生了根本性的改变,机械性能有了极大的提高。同时对涂敷层的形成机理进行了探讨。