Interfacial reaction during fabricating of full Cu3Sn joints in microelectronic packaging

Two copper substrates electroplated with Sn, both consisted of Cu/Sn?+?Sn/Cu structures, but they were bonded over different times in order to investigate the interfacial reaction. The growth morphologies of Cu₆Sn₅ and Cu₃Sn were analysed, respectively. The growth mechanisms for Cu₆Sn₅ and Cu₃Sn were investigated. The results show that the growth of Cu₆Sn₅ is primarily controlled by grain boundary-diffusion. However, the growth Cu₃Sn is controlled by the reaction of Cu-Cu₆Sn₅ at the beginning of the reaction, and then controlled by volume-diffusion as the thickness of the Cu₃Sn layer increases.     

夏县地震台痕量氢气突升异常成因的调查与分析

针对2016年9月~10月山西夏县地震台痕量氢气出现的3次大幅突升变化,按照异常核实的时间相关性、空间相关性、强度相关性和机理相关性原则,对异常进行调查分析、实验,结果表明,山西夏县台痕量氢气大幅度变化系交流电源受干扰导致,非震兆异常,提出观测系统整改意见,以期为地震预测提供可靠的观测资料。     

Effects of halloysite in kaolin on the formation and properties of geopolymers

A kaolin containing 31 wt.% halloysite and a relatively pure kaolin were selected to study the effects of halloysite on the dissolution behavior of precursors and the formation of geopolymers. The Al and Si concentrations in the leached solutions were studied by inductively coupled plasma-optical emission spectrometry (ICP-OES). The reaction process of metakaolin–activator mixtures was monitored by isothermal conduction calorimetry (ICC) while the reaction products were examined by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and mercury intrusion porosity (MIP). Results showed that the halloysite containing kaolin and its metakaolin possessed higher Si and Al dissolution rate than the purer kaolin and its metakaolin. When mixed with sodium silicate activator at 20 °C, the presence of halloysite in kaolin led to a higher geopolymerization rate of metakaolin as reflected by the heat evolution rate. The presence of halloysite improved the reactivity of metakaolin but did not change the geopolymerization pathway under 20 °C air curing and 80 °C steam curing conditions. The products from the two metakaolins had a similar XRD characteristic (i.e. a typically amorphous diffraction). Only a minor difference in the pore distribution and the porosity was found between those products from the two sources of metakaolins.     

近代街区的防火改造与城市发展获益——以日本东京为例

为了防范持续爆发的大火,明治时代的日本政府在东京的人口密集区,设置多条防火带,对沿线的房屋的墙壁屋顶进行防火改造,同时又进行区域屋顶防火改造。由于措施得力,防火改造的任务顺利完成,从而有效地遏制了大面积火灾的发生,也改变了东京的城市面貌。     

企业内部网络的构建

企业内部网络是一个庞大而复杂的系统。企业内部网络的组建多侧重于局域网的设计,对设备的选型、网络拓扑的设计以及实现拓扑的搭建也应该有足够的重视;同时完善网络的组建、服务器的选择及配置、Internet接入技术以及防火墙的使用等亦非常重要。     

落叶松树皮的提取及荧光纳米粒子的制备

以落叶松树皮粉为原料,;利用超声波提取植物多酚,其得率为21.92%,多酚浓度为83.3 mg/g;利用FTIR对其结构进行了确证。采用磷酸法活化处理且制备了落叶松树皮粉活性炭,并以制备的活性炭为原料,在碱性条件制备了粒径约2 nm的水溶性荧光纳米粒子。     

仿真实训在《化工仪表及自动化》教学中的应用

在《化工仪表及自动化》课程的教学过程中,通过合理的安排仿真实训教学内容,加深了学生对本门课程的理解,提高了学生的生产实践应用能力,激发了学生学习主动性,培养了学生的创新意识,获得了令人满意的教学效果。     

Evolution of fabric during undrained cyclic loading

Abstract

Undrained cyclic triaxial tests are performed on specimens of Ottawa sand to study the evolution of fabric during undrained cyclic loading. Isotropic consolidation tests and triaxial drained compression or extension tests are conducted before or after cyclic loading to characterize the state of fabric indirectly. The effects of stress path, cyclic stress ratio, cyclic number, and initial fabric on fabric evolution during undrained cyclic loading are investigated.     

Distillation separation sequence optimization synthesis based on application of adaptive parallel tabu search

Abstract

Distillation separation sequences can be described as binary tree data structures, because of the analogous structures of distillation separation sequences and binary trees, and then by applying graph theory, the change mechanism of neighborhood separation points based on binary trees is built, correspondingly a kind of highly effective, evolutionary neighborhood structure is constructed. For the purpose of researching further tabu search algorithms, adaptive mechanisms and parallel techniques are introduced. That is, according to memory frequency information, the tabu length and the number of candidates are adaptively adjusted, and multitask parallel technology is realized through the arrangement of the search assignments. The example shows that adaptive parallel tabu searches can solve, successfully, large‐scale distillation separation sequence synthesis problems.     

Heat Transfer Characteristics of an Innovative Thermal Protection System Based on Photonic Crystals

In order to protect the internal components of an aircraft from the damage caused by high temperature and heat flux, an effective thermal protection structure must be designed and developed. In this paper, heat transfer characteristics for an innovative thermal protection coating structure are investigated, based on three-dimensional photonic crystals (SiC-3D PCs). The actual system with coating material, containing photonic crystals, is simplified as a macroscopic model of one-dimensional coupled conduction–radiation heat transfer among three layers composed of semitransparent media. Moreover, according to preliminary physical parameters, heat transfer profiles and thermal protection efficiency for the whole system are estimated. In addition, the effect of the photonic crystals part is analyzed.