Characters of multicomponent lead-free solders

In the process of electronic packaging, such as flip chip technology, under bump metallization (UBM) can be consumed gradually by solder during soldering. Then dissolution of Ni, Au and Cu from UBM into the solder may change the original solder to a multicomponent one especially under the trend of miniaturization. It is quite necessary to evaluate the properties of the multicomponent solders that have new composition after soldering. In this study, the microstructure, thermal and mechanical properties of five types of multicomponent lead-free solders, i.e. Sn–2Cu–0.5Ni, Sn–2Cu–0.5Ni–0.5Au, Sn–3.5Ag–0.5Ni, Sn–3.5Ag–1Cu–0.5Ni and Sn–3.5Ag–2Cu–0.5Ni (all in wt% unless specified otherwise) were investigated. Comparison with eutectic Sn–0.7Cu, Sn–3.5Ag and Sn–3.5Ag–0.7Cu solders was made. There was no obvious difference of the melting point between the multicomponent lead-free solders and the eutectic ones. For Sn–2Cu–0.5Ni solder, Cu₆Sn₅ and (Cu,Ni)₆Sn₅ intermetallic compounds (IMCs) formed. In the case of Sn–2Cu–0.5Ni–0.5Au, besides (Cu,Ni)₆Sn₅, (Cu,Au)₆Sn₅ and (Cu,Ni,Au)₆Sn₅ were also observed. The IMCs formed in Sn–3.5Ag–0.5Ni solder were Ag₃Sn and Ni₃Sn₄. In both Sn–3.5Ag–1Cu–0.5Ni and Sn–3.5Ag–2Cu–0.5Ni solders, Ag₃Sn and (Cu,Ni)₆Sn₅ were detected. The mechanism for the formation of the IMCs was discussed. Tensile test was also conducted. The fractography indicated that all of the multicomponent lead-free solders exhibited a ductile rupture.     

道路施工机群智能化管理系统的设计及开发

以高等级公路施工机群管理为背景,研究和开发了智能化公路工程机械机群管理系统,描述了系统的体系结构设计,组成系统的各级中心站的设计以及功能,以及监控系统的核心功能,包括资源配置功能、监控调度功能及故障诊断功能等。本文所描述的系统是计算机智能化信息采集及控制在一个新的行业领域的应用,并针对问题的特殊性,设计并实现了实时监控及动态优化调度的功能和算法。     

高取代度氰乙基纤维素与二醋酸纤维素共混中空纤维纳滤膜的研制

采用高取代度氰乙基纤维素与二醋酸纤维素共混为膜材料,丙酮、二氧六环混合溶剂,以有机醇为主、加入适量其他添加剂为致孔剂,通过冰水凝胶浴干湿法纺丝,制得性能良好的中空纤维纳滤膜,该膜在给水质量浓度1 800 mg/L、操作压力为0.6 MPa、水温25℃条件下,对二价盐CaCl2、一价盐NaCl的水溶液的脱盐率分别大于90%和小于60%,水通量均大于3.5 mL/(cm2.h).还讨论了膜液的组成和纺丝条件对膜性能的影响.     

三种绝缘子材料的分析及其研究进展

论述了绝缘子对于电力系统稳定运行的重要意义.详细介绍了陶瓷绝缘子、玻璃绝缘子以及复合绝缘子所用材料的化学组成与结构.根据其化学组成的不同对各绝缘子进行了分类介绍,并分析了化学组成对于绝缘子电气性能与机械性能的影响.介绍了外部作用对于绝缘子性能的影响,尤其详细描述了电晕、紫外线等外力作用对硅橡胶绝缘子化学结构的影响及其机理.     

超临界流体干燥法制备钡铁氧体超细粉末──Ⅱ.红外吸收光谱的研究

对钡铁氧体的水凝胶、醇凝胶以及气凝胶的红外光谱进行了初步的观察，同时对不同焙烧温度及时间所得粉末的红外吸收光谱进行了考察。联系X-射线衍射结果，对钡铁氧体粉末的形成过程有了更进一步的认识。     

模糊强半预开集和模糊强半预连续性(英文)

本文引入并讨论模糊拓扑空间中的模糊强半预开集和模糊强半预连续映射及其基本性质     

Fullerene材料的现状与发展趋势

富勒烯（Ｆｕｌｅｒｅｎｅ）和碳纳米管（ＣＮＴ）可能是本世纪末材料科学领域最重大的发现之一。进入９０年代以来，其制备方法、物化特性及可能的应用领域等成为人们的研究热点，并对材料物理、微电子、介观量子效应等众多科研领域产生了重大的冲击。根据目前进展，富勒烯／碳纳米管的应用研究很可能首先在ＣＮＴ缺陷研究、分子工具（Ｍｏｌｅｃｕｌａｒｔｏｏｌｓ）、纳米装置（Ｎａｎｏ－ｄｅｖｉｃｅ）应用和新一代贮能材料等方面取得突破。     

云南省铟资源的合理开发

介绍了我国金属铟的资源、生产现状、应用及市场情况,论述了云南铟的资源及铟产业现状,对今后铟产业可持续发展提出建议。     

制冷空调系统水平管降膜蒸发研究

在制冷剂面临严峻的环境保护控制要求的背景下,研究表明,降膜蒸发由于其较低的制冷剂充注量在制冷空调行业具有重大的应用潜力。本文主要从降膜蒸发管外液膜的流动模式和强化传热2个方面,对水平管降膜蒸发的国内外研究现状进行研究分析。分析表明,管外液膜存在滴状流、射（柱状）流和片状流等模式,而且强化传热须区分高低热流密度情况。为了进一步探究降膜蒸发的机制,从换热和可视化的角度开展强化管外降膜蒸发的特性实验研究。     

Truly Concomitant and Independently Expressed Short‐ and Long‐Term Plasticity in a Bi2O2Se‐Based Three‐Terminal Memristor

Concomitance of diverse synaptic plasticity across different timescales produces complex cognitive processes. To achieve comparable cognitive complexity in memristive neuromorphic systems, devices that are capable of emulating short‐term (STP) and long‐term plasticity (LTP) concomitantly are essential. In existing memristors, however, STP and LTP can only be induced selectively because of the inability to be decoupled using different loci and mechanisms. In this work, the first demonstration of truly concomitant STP and LTP is reported in a three‐terminal memristor that uses independent physical phenomena to represent each form of plasticity. The emerging layered material Bi₂O₂Se is used for memristors for the first time, opening up the prospects for ultrathin, high‐speed, and low‐power neuromorphic devices. The concerted action of STP and LTP allows full‐range modulation of the transient synaptic efficacy, from depression to facilitation, by stimulus frequency or intensity, providing a versatile device platform for neuromorphic function implementation. A heuristic recurrent neural circuitry model is developed to simulate the intricate “sleep–wake cycle autoregulation” process, in which the concomitance of STP and LTP is posited as a key factor in enabling this neural homeostasis. This work sheds new light on the development of generic memristor platforms for highly dynamic neuromorphic computing.