一种新型单相倍压整流器的特性分析

提出具有两个辅助双相开关的单相倍压整流电路。其优点是通过两个辅助双相开关控制跨接电容两端电压的不平衡，并能够降低整流器总电容的容量。利用精确状态空间分析法进行了仿真。仿真和实验结果表明，在稳态下能够获得良好的平衡电容电压，使输入电流能在功率因数接近于1的情况下被正弦波化，大大提高了整流器的功率因数。     

垃圾分类背景下城市公共垃圾桶视觉设计研究

目的 对城市公共垃圾桶的造型、色彩、标识符号等进行视觉设计研究.方法 在广泛调研的基础上对城市公共垃圾桶设计的现状进行对比研究.城市公共垃圾桶作为城市公共空间的重要组成部分,不只是一个藏污纳垢的容器,更能体现一个城市的形象和生活品位.在垃圾分类回收的影响下,垃圾桶的造型设计首先应遵循投放简便、省时、省心等功能性设计原则,并在其基础上充分考虑垃圾桶造型的美观设计,设计出富有人情味、具有趣味性的造型,真正实现功能性与艺术性的统一.结论 城市公共垃圾桶色彩设计应该在遵循约定俗成的各类垃圾桶共性色彩的前提下在同一色系中体现色彩的变化.功能性与审美性和谐统一的垃圾桶设计不仅能有助于垃圾分类工作的开展,更能塑造城市形象和传递城市文化.     

金属三片罐空罐检测的样品前处理方法

包装材料同食品类似,在样品检测的过程中会受到多种因素的影响,其中样品前处理条件是整个分析测试环节中的关键因素。通过具体的案例,以模拟物样品中的双酚A类物质为前处理研究目标,对金属三片罐的有害物迁移检测方法进行了详细阐述,完成了体积分数为10%和50%的乙醇及质量分数为3%的乙酸模拟物三大类产品的样品前处理方法研究。     

Case Study – Analysis of Fractured Bottoms of Paint Cans

The purpose of this study was to determine the root cause of fracture in bottoms of rectangular 18 l cans of water‐based acrylic paint used in the building industry and sold in retail. Following a change in the formulation of the inner coating of the cans, fractures developed in the double seams of the can bottoms, which were made of electrolytic chromium/chromium oxide‐coated steel internally coated with pigmented varnish (epoxy melamine). Slight differences were detected in the infrared spectra of both the new and altered varnishes produced with the same base resin. The microanalysis of paint samples collected from both damaged and undamaged cans revealed presence of practically the same elements. The evaluation of the varnished surface of can bottoms revealed depressions in the varnish of all cracked bottoms, inclusive in the curved areas and bottom hook of the double seam, which did not get in direct contact with the paint. However, depressions were not detected in undamaged can bottoms. The metallographic analysis did not reveal significant differences between the microstructures of the metal of cracked or uncracked bottoms. The conclusion was that paint elements got in contact with the steel sheet in the defective spots of the varnished surface, thus starting punctual corrosion that evolved to stress corrosion with ensuing rupture. The stressing agent was the weight of the paint itself or else residual metal stress due to the change in its microstructure caused by the metal‐forming process. Copyright © 2017 John Wiley & Sons, Ltd.     

Inclusion and Bubble in Steel—— A Review

The type, morphology and sources of inclusion in steels, including indigenous and exogenous inclusions, were discussed and reviewed. Indigenous inclusions are deoxidation products or inclusions precipitated during cooling and solidification of steel. Exogenous inclusions arise primarily from the incidental chemical （reoxidation） and mechanical interaction of liquid steel with its surroundings （slag entrainment and erosion of lining refractory）. Types and causes for the nozzle clogging were also summarized. Reasons for bubble formation and bubble size distribution in steels were discussed thereafter. Finally, morphology and causes of inclusion-related defects in continuously cast steel products were reviewed, such as flange cracking in cans, slag spots and line defects on strips.     

某镍基粉末高温合金盘坯的热处理开裂分析

针对某镍基粉末高温合金盘坯在热处理后开裂的问题进行了分析。结果表明:盘坯组织中存在热诱导孔隙缺陷,热诱导孔隙缺陷在盘坯表面形成了微裂纹,降低了材料的抗拉强度。盘坯在热处理过程中,受到残余应力共同作用,其数值超过了材料的抗拉强度导致开裂。该盘坯中的孔隙是由于包套在热等静压过程中漏气造成的,提高包套质量是消除盘坯热诱导孔隙缺陷的关键。     

Kinetics of aluminum can dissolution in sec-butyl alcohol for aluminum sec-butoxide

A kinetic study of dissolution reaction of Al can was conducted for the synthesis of aluminum sec-butoxide (ASB). With the Al can scraps and sec-butyl alcohol (SBA) as reactants, the reaction was examined at the condition of 3 mol SBA/mol Al of stoichiometric ratio, adding 10^− 3 mol HgI₂/mol Al for catalyst and no agitation at the reaction temperature ranging from 80 to 100 °C. After the dissolution of 24 h at 100 ^oC, the reaction gave a 75% yield. A two-stage dissolution mechanism was proposed in which the dissolution rate is determined first by a chemical reaction and then by ash layer diffusion as the previous dissolution kinetics for the synthesis of AIP (Aluminum iso-propoxide) (Yoo, S.-J.,Yoon,H.-S., Jang, H.D., Lee,M.-J., Lee, S.-I.,Hong, S.-T., Park,H.S., 2007a. Dissolution kinetics of aluminum can in isopropyl alcohol for aluminum isopropoxide. Chem. Eng. J. 133, 79–84.). On the basis of the shrinking core model with the shape of flat plate, the first dissolution rate of Al can was controlled by chemical reaction. The concentration of SBA was largely changed during the dissolution reaction because it was added the stoichiometric ratio to the reactor. Therefore it was included as an integral term of the reaction time. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction step was determined to be 200.5 kJ mol^− 1. In the second stage, the dissolution rate is controlled by diffusion control through the ash layer. The apparent activation energy of the second step was determined to be 101.8 kJ mol^− 1.     

基于ARM和CAN总线的双冗余罗经航向变送系统

将CAN总线技术应用于舰船的罗经系统。以LPC2292和CTM1050为核心部件,同时系统采用以及其它的软硬件设计,完成了一套基于ARM和CAN总线的罗经数字变送系统的设计。整个系统能实时、动态地显示航向信息,同时跟踪速度,传输速率,可靠性得到了很大提高。     

基于时间序列的矿井瓦斯涌出量预测方法

由于矿井瓦斯浓度的变化受多种因素共同影响,矿井瓦斯涌出量预测经常出现无法获得一部分变量的情况。针对该问题,提出了一种基于时间序列的矿井瓦斯涌出量预测方法,详细介绍了采用时间序列AR模型对矿井瓦斯涌出量进行预测的具体实现。实验结果表明,该方法对矿井瓦斯涌出量的预测误差率为4.3%,预测比较可靠。     

食品罐头真空度无损检测仪的研制

介绍了一种采用处于同一平面2个同圆心的传感器研制出食品罐头真空度无损检测仪,该仪器利用电涡流工作原理,其旋转环形传感器多次测量罐头盖边缘某一圆周的平均距离;另一传感器测量盖中心的距离,根据2个传感器输出电信号差计算出罐头真空度。本仪器具有测量范围宽(0.025～20MPa)、测量精度高(优于5%)和操作界面友好等优点。