Improving the solidification structure of commercially pure aluminium with electropulse acting on liquid metal

The effect of electropulse on the solidification structure of commercially pure aluminium was studied. The orthogonal array L9 was used to determine the effect of three process parameters of electropulse modification (EPM), which were pulse current intensity, pulse frequency, and treating time. For each factor, three levels were chosen to cover the experimental region. According to the experimental results, the solidification structure of commercially pure aluminium was modified from large grains with columnar crystals to finer grains with equiaxed crystals, by allowing the electropulse to act on liquid aluminium. However, the solidification structures could be refined differently at different EPM parameters. Certain EPM parameters should be selected to get the optimum solidification structure. Among the three parameters, pulse frequency was the most important factor influencing the solidification structure, the secondary factor was current intensity, and treating time was the third one. The optimum parameters were the pulse frequency of 5 Hz, the current intensity of 68 A, and the treating time of 10 s.     

高层建筑结构选型影响因素分析

现今,越来越多的高层建筑建筑伫立于城市之中,要想在建筑行业得到利益与名义的双丰收,光靠地皮的价位是远远不够的,更重要的是建筑结构选型的标新立异、材料施工的安全保障和后期服务的全面到位。下面,就高层建筑结构选型这一问题进行具体探究。     

基于Hadoop企业私有云存储平台的构建

针对企业级用户面临文件和数据量的指数级增长,现有的文件存储设施不能适应业务增长问题,提出基于Hadoop构建企业私有云存储平台,通过采用Linux集群技术、分布式文件系统和云计算框架,实现海量数据存储和高速数据处理业务。比较了私有云存储和传统存储模式,分析了私有云存储技术优势和可行性,提出企业私有云存储架构模型。分析结果表明:企业私有云存储平台适用于关键业务应用、在线事务处理,满足企业对海量数据存储、数据规模易扩展性的要求。     

X-ray illumination of the ejecta of supernova 1987A

When a massive star explodes as a supernova, substantial amounts of radioactive elements--primarily (56)Ni, (57)Ni and (44)Ti--are produced. After the initial flash of light from shock heating, the fading light emitted by the supernova is due to the decay of these elements. However, after decades, the energy powering a supernova remnant comes from the shock interaction between the ejecta and the surrounding medium. The transition to this phase has hitherto not been observed: supernovae occur too infrequently in the Milky Way to provide a young example, and extragalactic supernovae are generally too faint and too small. Here we report observations that show this transition in the supernova SN 1987A in the Large Magellanic Cloud. From 1994 to 2001, the ejecta faded owing to radioactive decay of (44)Ti as predicted. Then the flux started to increase, more than doubling by the end of 2009. We show that this increase is the result of heat deposited by X-rays produced as the ejecta interacts with the surrounding material. In time, the X-rays will penetrate farther into the ejecta, enabling us to analyse the structure and chemistry of the vanished star.     

我国农村土地制度面临的困境与出路

农村人地之间的矛盾一直制约着农村经济和社会的发展。要确立科学合理、稳定长久的农村土地制度，建立真正意义上的农村土地市场，充分调动农民的生产积极性，必须对面临的困境进行分析，实行农村土地农民所有的制度，赋予农民土地所有权。     

利用传输线模型分析动态电路

本文详细介绍了利用传输线模型(Transmission Line Model)进行电路分析的基本原理,并给出分析一阶动态电路的实际算例.     

取代苯甲酸晶体结构的研究——Ⅲ.对位溴代苯甲酸的晶体结构

对位溴代苯甲酸ｐ－ＢｒＣ６ Ｈ５ＣＯＯＨ晶体属单斜晶系,空间群是 Ｃ５２ｈ－Ｐ２１ ／ｃ;晶胞参数为：ａ＝３．９５Ａ,ｂ＝６．１４ａ,ｃ＝２９．４Ａ, β＝９４．４５’;晶胞中含四个分子。这四个分子两两地通过羧基间所形成的氢键（Ｏ－Ｈ…Ｏ＝２．６５Ａ）结合成为具有对称心的双聚分子。羧基和苯环基本上共面。双聚分子的长轴差不多就在（１０２ ）面上,与ｂ轴的交角为５４°１２’;它的平面绕着分子长轴偏离（１０２ ）面的角度为２８°１２’。     

桂林市四湖水系水环境现状及水质评价

为了进一步监测、控制以及优化桂林市四湖景区的水环境,明确该湖区水环境变化特征以及主要影响因子,分析2008年春、夏季四湖水系的10个样点监测数据,采用因子分析法的主成分分析方法,结合水质标识指数,研究该湖区水质状况及变化趋势.结果从时间变化上看,春夏季水质较好且变化不大,春季的水质稍优于夏季;从四湖水质受控因子上看,春夏季四湖水的第一主成分都为营养盐,它对水质影响最大,是控制治理的主因子.     

高速多通道CCD信号并行处理系统

为解决目前很多高速CCD(Charge Coupled Device)应用系统数据输出路数多,数据率高的问题,提出一种并行处理高速多通道CCD信号的系统架构,阐述了该系统的架构组成和实现方案,并对设计要点进行了分析.该系统采用FPGA(Filed Programmble Gate Array),时分复用,LVDS(Low Voltage Differential Signal)和SCSI(Small Computer System Interface)存储等技术.研究结果表明,该设计具有较好的稳定性,灵活性和通用性等,并已成功应用于某8通道高速TDICCD(Time Delay Integration Charge Couple Device)成像系统的设计中,数据率高达1.28 Gbit/s.     

Development and study on automatic balancer based on counter weight by magnetic force

Rotating machines are very sensitive to mass unbalance which has a harmful effect on its running accuracy and service life. Therefore,a variety of dynamic balancing methods and devices are studied to reduce the vibration caused by mass unbalance. On-line active balancing is a new balancing procedure which is more convenient and precise than the previous methods. In this paper,an electromagnetic balancer based on ring coils and permanent magnets is presented. The balancer has a simple structure and the self-locking function without clutch,and transfers power by the non-contact electromagnetic field. In order to justify the rationality of its design,a two-dimension(2D) electromagnetic finite element model is conducted to verify that this magnetic circuit has no flux leakage and saturation. A three-dimension (3D) 1/10 model of the balancer is built to obtain the self-locking torque and driving torque. Based on the research work above,an electromagnetic balancer is developed. By testing the balancer using COCO80,it is verified effective to reduce the rotor unbalance at the speed of 1300 r/min.