ML40Cr钢动态再结晶行为的研究

使用Gleeble-1500热模拟试验机,在不同变形条件下进行单道次压缩试验,并通过计算机和绘图仪输出压缩过程的应力-应变曲线。根据该曲线分析了变形温度、变形速度和变形程度对ML40Cr钢动态再结晶行为的影响;并且根据试验得到的应力-应变曲线做出了再结晶图,为研究ML40Cr钢的动态再结晶提供了依据。     

覆膜种植对重金属在蔬菜中的含量和形态影响与评价

以莴苣为研究对象,通过不同种植状态对比,研究了覆膜栽培方式对莴苣茎和叶片中Cu、Fe、Cd总量和形态的影响及评价。覆膜栽培方式促进了土壤有机质的矿化改变了重金属向莴苣迁移的行为。覆膜方式对莴苣茎和叶中Cu的总量影响很小,但显著增加了莴苣茎中的Cd含量,降低了叶片中Fe的含量,平均增值为0.2 mg/kg和-150 mg/kg。形态分析结果表明覆膜栽培使得莴苣茎中的Fe II向Fe III转化,降低了其在茎中的生物活性,由此导致叶片部位总Fe以及Fe III和Fe IV的减少。覆膜组茎中Cd的活性并没有改变,其总Cd的增加归功于活性最低的Cd IV含量的增加;而叶片中显著增加的CdI形态由于占总量的比例很少,因此覆膜组叶片中总Cd并没有显著增加。两种栽培方式下的莴苣叶中Cd总量均超标,存在食品安全问题,但以每日最大允许摄入量作为参考,3种元素的人均日暴露量均低于ADI值2.4 mg/d、42 mg/d、0.06 mg/d。覆膜栽培方式对人体莴苣叶摄入量贡献率的影响较大,使Fe的贡献率降低了13.1%,而Cd的贡献率增加了6.53%,即增加了摄入镉的潜在风险。     

Response sensitivity analysis of the dynamic milling process based on the numerical integration method

As one of the bases of gradient-based optimization algorithms, sensitivity analysis is usually required to calculate the derivatives of the system response with respect to the machining parameters. The most widely used approaches for sensitivity analysis are based on time-consuming numerical methods, such as finite difference methods. This paper presents a semi-analytical method for calculation of the sensitivity of the stability boundary in milling. After transforming the delay-differential equation with time-periodic coefficients governing the dynamic milling process into the integral form, the Floquet transition matrix is constructed by using the numerical integration method. Then, the analytical expressions of derivatives of the Floquet transition matrix with respect to the machining parameters are obtained. Thereafter, the classical analytical expression of the sensitivity of matrix eigenvalues is employed to calculate the sensitivity of the stability lobe diagram. The two-degree-of-freedom milling example illustrates the accuracy and efficiency of the proposed method. Compared with the existing methods, the unique merit of the proposed method is that it can be used for analytically computing the sensitivity of the stability boundary in milling, without employing any finite difference methods. Therefore, the high accuracy and high efficiency are both achieved. The proposed method can serve as an effective tool for machining parameter optimization and uncertainty analysis in high-speed milling.     

A novel method to prepare poly(vinyl alcohol) water-soluble fiber with narrowly dissolving temperature range

Poly(vinyl alcohol) (PVA) is an important water-soluble polymer. In this study, a novel method has been developed for preparing water-soluble PVA fiber with narrowly dissolving temperature range via wet spinning of partly acetalized PVA. The structures and properties of the fiber were characterized by IR, ¹H-NMR, DSC, WAXD, tensile strength tester, etc. IR and NMR spectra showed that acetal groups were successfully generated on the lateral chains of PVA with the catalysis of acid. As a small quantity of CH₂O was added, the introduction of the acetal group could reduce both the hydrophilicity of amorphous region and the crystallinity of PVA water-soluble fiber, and hence narrowed the dissolving temperature range of fiber. However, the dissolving temperature range was broadened with a further increase of CH₂O amount, because of the large decrease of crystallinity and crystallite perfection. When the CH₂O added amount reached up to 20%, the acetalized PVA was completely insoluble, so that the spinning process could not be carried out. The breaking strengths of most acetalized fibers were beyond 4 cN/dtex, which satisfied the ordinary use of industrial and domestic field. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Accommodation of China’s Industrial Heritage in Urban Conservation Practices (Ⅱ)

In recent years, the conservation of industrial heritage in China has gained increasing attention within the broader context of urban conservation practices. For both policy-makers and scholars, accommodating this industrial heritage will emerge as a pertinent issue for consideration as a growing number of industrial architectural legacies dating from the Republican and Maoist eras come under (re)development pressures. This paper thus traces the development of industrial heritage conservation practices in China and discusses several dilemmas intrinsic to this type of conservation, including issues of authenticity, representativeness, and distinction. Based on comparative case studies from China and other international precedents, this paper also seeks to illustrate the different approaches that could be pursued while still attaining a balance between competing interests and claims.     

丰满水电站重建工程三期独立运行计算机监控系统设计方案

正1概述丰满水电站始建于1937年的伪满时期,1943年第一台机组发电,1953年大坝建成,1959年一期机组(552.5 MW)全部投产,并在20世纪90年代陆续扩建了二期、三期厂房。丰满水电站总装机容量为1 002.5 MW,丰满水电站在东北电力系统中担负着发电、调峰、调频、事故备用等任务,是东北电力系统中的主力调峰电源和事故备用电源。由于工程建设于特殊性的历史时期,大坝设计与施工存在严     

Adsorption Behavior of Halogenated Anesthetic and Water Vapor on Cr‐Based MOF (MIL‐101) Adsorbent. Part I. Equilibrium and Breakthrough Characterizations

A synthesized chromium‐based metal organic framework (Cr‐MOF) was used for the adsorption of halogenated anesthetics, i.e., sevoflurane (SF). Adsorption isotherm and breakthrough experiments involving SF (reference sorbate) and water vapor were measured at 298 K and atmospheric pressure on both Cr‐MOF and a commercially used reference adsorbent. The Cr‐MOF MIL‐101 showed a significantly higher SF adsorption capacity and much higher selectivity relative to water vapor compared to the reference adsorbent. Binary‐mixture breakthrough tests demonstrated a “roll‐up effect” for SF on the reference adsorbent while no such effect was observed on MIL‐101.     

湖北利川福宝山盆地三叠统含盐层系中盐溶角砾岩的特征及其成因意义

福宝山盆地位于川东-鄂西地区,是中国东部重要的含盐层系盆地,共包含4个含盐层系,分别为嘉陵江组二段、四段、五段和巴东组一段。由于受到地表水的溶蚀和淋滤,岩溶塌陷普遍发育,构成呈层分布的盐溶角砾岩带。该区盐溶角砾岩可分为3种类型,碳酸盐质盐溶角砾岩、泥质盐溶角砾岩和杂砾盐溶角砾岩。盐溶角砾岩的成因指示了其成盐环境,为寻找地下盐类矿床指明方向。     

中国美容医疗设备及其技术进展

近些年随着人们生活水平的提高,中国人在美容方面的需求不断加大,使得医学美容行业的发展极具活力,与之相应的美容医疗设备及技术的未来市场容量将非常可观。