射频超导腔用高纯铌材制备

采用高真空电子束炉不少于3次熔炼的方式制备了大规格高纯铌铸锭。高纯铌铸锭的纯度达到99.99%,剩余电阻率比值(residual resistivity ratio,RRR)稳定地大于300,满足了射频超导腔用高纯铌材料的要求。高纯铌铸锭的RRR值主要受H、N、O、C等间隙元素的影响,随着熔炼次数的增加,气体元素可有效去除,RRR值也稳步增长。高纯铌化学元素的检测精度不能完全与RRR值对应,应结合两参数来评价高纯铌铸锭的品质。     

Unfriend or ignore tweets?: A time series analysis on Japanese Twitter users suffering from information overload

In recent years, with increased opportunities to post content on social media, a number of users are experiencing information overload in relation to social media use. This study addresses how Japanese Twitter users suffering from information overload cope with their stress, focusing on two actions: (1) The “unfriending” activities and (2) The changes in tweet processing methods. Objective data, such as numbers of friends, were collected through Twitter's open Application Programming Interfaces (APIs), and subjective data, such as perceived information overload and tweet processing methods, were collected through a web-based survey as a panel dataset (n = 778). The results demonstrated that although users experience information overload, they continue to increase their number of friends, and that the users who experience information overload modify their usage habits to avoid seeing all received tweets. In short, users do not choose a strategy to reduce the absolute number of received tweets, but only a strategy that involves changing the processing method of the received tweets.     

超导铌材剩余电阻率的测量

基于超导铌材剩余电阻率的物理定义,分析超导铌材剩余电阻存在的原理,然后选择符合精度要求的测试设备,研究设备的接线方法,进行物理连接;通过使用DESY实验室提供的标样进行重复测量,验证了该测量系统的可靠性.该系统可以应用于超导铌材的生产领域,履行在线质量预警以及产品检验等任务,能够提高超导铌材及其相关产品的生产效率,降低不良品的产生.经试验测量结果表明,该测量系统误差小于5%,能够满足超导铌材工业生产的检测需要.     

校平工艺对RRR300超导铌板性能的影响

研究了校平工艺对RRR300超导铌板横纵向力学性能的影响,结果表明:随着校平辊缝的减小,校平次数增加,屈服强度明显增加,硬度增加;材料整体主体组织无明显变化,但表层有晶粒状态改变的趋势。     

基于三分支非均匀分布球面并联机构腰关节的运动学传递性能分析

把基于三分支非均匀分布球面并联机构应用于新型拟人腰关节,可以很大程度改善现有拟人腰关节的性能.为满足该拟人腰关节的性能要求,对其结构进行了运动学传递性能计算与分析,选取了一组合理的设计几何参数,从而使其基本能满足腰关节对工作空间的要求.通过分析腰关节的运动学传递性能,定义了角度传递性能评价指标,并研究了评价指标如何提高全域角速度传递性能.     

准一维NbSe3单晶的制备及其输运特性

用气相输运法制备了准一维结构的NbSe3单品，并研究了其剩余电阻率与杂质的关系．在电子扫描电镜(SEM)下观测了NbSe3单品的表面形貌，末见亚微米尺寸的缺陷．NbSe3单品的电阻温度与温度的关系(ρ-T)曲线表明，NbSe3样品分别在Tp1＝145K和Tp2＝57K经历两次Peierls相变，剩余电阻比RRR高于200．根据对不同样品的ρ-T曲线的研究指出，以前的文献用剩余电阻比估计杂质浓度ni的方法是一个错误，并提出了改进措施。     

一种超导铌板制备工艺研究

本文对RRR300超导铌板制备工艺进行了探究,设计了包括锻造工艺、轧制工艺、热处理工艺在内的3个工艺方案,并在900℃/60 min和950℃/60 min两个成品热处理工艺条件下,测试了RRR300超导铌板的RRR值、微观组织与机械性能。最终确定了工艺方案2为最优工艺,可制备出RRR值300,硬度≤50HV、抗拉强度在140~175 MPa、屈服强度确定在50~75 MPa、延伸率≥50%、晶粒度在G=5.5~6.0级的超导铌板,并可应用于工业化生产。     

Structural, magnetic and electrical properties of Fe/Cu/Fe films

A set of sandwich films in the configurations, Fe(200 nm)/Cu(t)/Fe(200 nm); t = 20 nm, 40 nm, 60 nm, 80 nm, 100 nm and 200 nm have been grown using thermal and electron beam gun evaporation techniques at a temperature of 473 K, under high vacuum conditions. The structure and crystallite sizes of the films were investigated by grazing incidence X-ray diffraction (GIXRD). The microstructure was examined by scanning electron microscope (SEM) studies. Average grain size and surface roughness were determined by atomic force microscope (AFM). The room temperature magnetization as a function of field has been measured using the vibrating sample magnetometer (VSM). The results revealed the existence of antiferromagnetic (AF) coupling between Fe layers through an interfacer Cu layer. The strength of AF coupling was observed to be increasing with increasing t and became maximum for t = 60 nm and, decreases for further increase in t. The behavior of coercive field with t indicated softness of the films. The low temperature electrical resistivity in the range from 4.2 K to 300 K has been measured. The residual resistance ratio, RRR and the temperature coefficient, TCR were determined. The power laws for the resistivity variation with temperature have been established. This is for the first time that a set of sandwich films in the present configurations were investigated for structural, magnetic and electrical properties and, the power laws for resistivity variation at low temperature have been established.     

油气勘探开发投资比例与储量接替率关系探讨

当前,储量接替率已经成为衡量国际大油公司发展潜力的重要标志之一,而保持合理的勘探开发投资比例是储量接替率增长的内在因素。1991年以来全球持续增长的勘探开发投资推动了产量的增长,而2000年以来勘探投资的不足削弱了增储上产的基础。通过分析1991年以来世界原油价格从低向高一个完整周期内全球、典型地区以及世界主要石油公司的勘探开发投资比例与储采平衡的关系,认为勘探投资占上游投资比例维持在20%以上,有利于保持储采平衡,如能达到25%~30%,有利于石油公司储量接替率保持长期稳定和可持续发展,一旦低于20%,可能导致储采失衡。