Microstructural evolution of AS21X HPDC alloy during thermal treatment

Abstract

The microstructure of a High Pressure Die Cast Magnesium (HPDC) AS21X alloy was investigated after various heat treatments. The material, supplied in the as cast state, consisted of Mg-α grains separated by intermetallic particles such as Mg₁₇Al₁₂, Mg₂Si and Al–Mn. The alloy was subjected to solution treatment at 415° C for times ranging from 0.5 to 48 h and to aging to assess grain growth stability and precipitation hardening. Light microscopy showed that Mg-α grains increase slightly in size whereas intermetallic particles do not disappear but assume a more rounded shape. Static precipitation and/or dissolution were followed by electrical conductivity, hardness measurements and X-ray diffractometry. Tensile properties at room temperature were evaluated on both the as cast and solution treated samples. Density was used as an indicator of porosity to explain the scatter in elongation to fracture data. Study of the fracture surfaces revealed the morphology of porosity and the otherwise ductile fracture failure mechanism.     

Cross-sectional distortion behaviors of thin-walled rectangular tube in rotary-draw bending process

The cross-sectional distortion usually appears during rotary-draw bending process of thin-walled rectangular tube with small bending radius.To study the cross-sectional distortion of the tube,a three-dimensional finite-element model of the process was developed based on ABAQUS/Explicit code and its reliability was validated by experiment.Then,the cross-sectional distortion behaviors of the tube were investigated.The results show that a zone of larger circumferential stress appears on the tube when bending angle reaches 30°.And in the larger circumferential stress zone,the sagging phenomenon is produced obviously.The maximum cross-sectional distortion is located in the larger circumferential stress zone and the angle between the plane of maximum cross-sectional distortion and the bending reference plane is about 50°.The position of the maximum cross-sectional distortion keeps almost unchanged with the variation of the clearances between dies and tube.     

氧—乙炔火焰钎焊在LF21铝合金上的应用

从铝钎焊机及具体工艺操作方面进行阐述，解决了LF21防锈铝用氧－乙烯火焰作为热源进行钎焊的工艺问题。     

NAM模型与水资源配置模型耦合研究

选取汉江作为示范流域,基于MIKE BASIN软件构建了汉江流域水资源配置模型,介绍了该系统的重要特征,探讨了系统内部各组成部分间相互联系;将所建模型与NAM模型的预测结果进行耦合,并分析了2006年皇庄以上汉江流域水资源供需平衡.结果表明:汉江流域内(至皇庄)生活用水、工业用水基本满足要求;农业灌溉、河道内生态用水缺水率为35.8%、25.7%,整体缺水率为22.2%.     

连续出矿与大块物料振动输送机的发展概况

在对连续出矿和连续运搬设备进行介绍的基础上，对大块物料矿用振动输送机的国内外研制概况和发展方向进行了论述。指出它是２１世纪一种很有发展前途的新型矿山设备。     

低频采油技术及应用效果

介绍了低频采油技术的作用机理及其基本作业参数的选择，以两口采油井和一口注水井的低频脉冲处理情况为例，分析了其作用效果及孤东油田适合于低频处理的注、采井的油藏条件。     

Diminazene Aceturate Stabilizes Atherosclerotic Plaque and Attenuates Hepatic Steatosis in apoE-Knockout Mice by Influencing Macrophages Polarization and Taurine Biosynthesis

Atherosclerosis and nonalcoholic fatty liver disease are leading causes of morbidity and mortality in the Western countries. The renin–angiotensin system (RAS) with its two main opposing effectors, i.e., angiotensin II (Ang II) and Ang-(1–7), is widely recognized as a major regulator of cardiovascular function and body metabolic processes. Angiotensin-converting enzyme 2 (ACE2) by breaking-down Ang II forms Ang-(1–7) and thus favors Ang-(1–7) actions. Therefore, the aim of our study was to comprehensively evaluate the influence of prolonged treatment with ACE2 activator, diminazene aceturate (DIZE) on the development of atherosclerotic lesions and hepatic steatosis in apoE^−/− mice fed a high-fat diet (HFD). We have shown that DIZE stabilized atherosclerotic lesions and attenuated hepatic steatosis in apoE^−/− mice fed an HFD. Such effects were associated with decreased total macrophages content and increased α-smooth muscle actin levels in atherosclerotic plaques. Moreover, DIZE changed polarization of macrophages towards increased amount of anti-inflammatory M2 macrophages in the atherosclerotic lesions. Interestingly, the anti-steatotic action of DIZE in the liver was related to the elevated levels of HDL in the plasma, decreased levels of triglycerides, and increased biosynthesis and concentration of taurine in the liver of apoE^−/− mice. However, exact molecular mechanisms of both anti-atherosclerotic and anti-steatotic actions of DIZE require further investigations.     

On the optimal production and location of a labor-managed firm

This paper endeavors to introduce space into the theory of the Labor-Managed firm (LMF) and to investigate its optimal production and location decisions. It is shown that the degree of returns to scale plays a key role in the determination of optimal production and location for an LMF, in particular, that the optimal location of an LMF is farther away from (closer to) the market as compared to a profit-maximizing firm (PMF) if the production function is of increasing (decreasing) returns to scale. We also demonstrate that the optimum location of an LMF moves closer towards the market as demand increases, regardless of whether the production function is of increasing or decreasing returns to scale. This finding is in sharp contrast with that in a capitalist economy. Received: February 2000/August 2000     

Firm relocation decisions in The Netherlands: An ordered logit approach

This article explores the determinants of firm migration in The Netherlands. First, based on the existing literature a theoretical framework is developed. Second, based on aggregate data firm relocation processes in The Netherlands are discussed in terms of numbers, sectoral composition, origins and destinations (regions), distance moved and employments effects. In the third part a formal model will be tested using individual data of firms. The relocation decisions of individual firms will be related to firm and location characteristics by means of an ordered logit model. The results indicate that the decision to relocate is mainly determined by firm internal factors and to a lesser extent by site related factors. Received 1 July 1999 / Accepted 28 November 1999