Low-cycle fatigue behavior of Sn-Ag, Sn-Ag-Cu, and Sn-Ag-Cu-Bi lead-free solders

Low-cycle fatigue (LCF) tests on as-cast Sn-3.5Ag, Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-1Bi, and Sn-3Ag-0.5Cu-3Bi solders was carried out using a noncontact strain-controlled system at 20°C with a constant frequency of 0.1 Hz. The addition of Cu does not significantly affect the fatigue life of eutectic Sn-Ag solder. However, the fatigue life was significantly reduced with the addition of Bi. The LCF behavior of all solders followed the Coffin-Manson relationship. The fatigue life of the present solders is dominated by the fracture ductility and can be described by the ductility-modified Coffin-Manson’s relationship. Steps at the boundaries of dendrite phases were the initiation sites for microcracks for Sn-3.5Ag, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-1Bi solders, while for Sn-3Ag-0.5Cu-3Bi solder, cracks initiated along both the dendrite boundaries and subgrain boundaries in the dendrite phases. The linking of these cracks and the propagation of cracks inside the specimen occurred both transgranularly through eutectic phases and intergranularly along dendrite boundaries or subgrain boundaries.     

从供应商受益角度研究国际供应链合作关系

首先指出从供应商受益角度对国际供应链合作关系进行研究的重要意义，接着对国际供应链合作关系的起源及其概念界定进行了综合分析；其次对国际供应链战略伙伴关系下的供应商受益进行了相关研究结论的综合，并对我国供应商参与国际供应链合作的实际受益进行分析，然后将两者进行了比较，最后综合全文探讨得出本文研究的结论。     

Models and observations of fcc/bcc interfaces

Whereas models of the structure and periodicity of CSL or near CSL high angle grain boundaries are relatively well developed and have been to some extent verified by experiment, the nature of more general (e.g. fcc/bcc) interfaces is very imperfectly understood. One of the major differences between homo- and heterophase boundaries is the occurrence, in the latter case, of reproducible orientation relationships due to the crystallographic requirements of phase transformation (e.g. a glissile interface for martensitic growth, low energy interfaces for classical nucleation). A review is given of the relationships commonly observed to obtain between fcc and bcc crystals (as well as ordered phases based upon these structures). Within a given relationship, it is possible to use models of the available interfaces to predict their dislocation content; the success of the various approaches is considered. It is shown that the dislocation arrays identified on fcc/bcc boundaries are consistent with the occurrence of a primary structural relaxation, but that the latter does not appear to be complete. Possible reasons for this are discussed, together with the extent to which secondary structural models may be applicable. Attempts to rationalize the observed orientation relationships and morphologies are discussed, and it is pointed out that these all rely on searches for situations of minimum primary misfit, but that the way in which the latter is quantified determines the results of the analyses. Nevertheless, the implication is that the primary misfit does appear to determine the actual behaviour, though no structural or mechanistic conclusions can safely be drawn from this observation.     

Perceived effectiveness of filial therapy for a Jamaican mother: A qualitative case study.

Although filial therapy has traditionally been viewed as suitable for children of diverse cultures, there is limited research to support this perspective. This qualitative case study examined the perceived effectiveness of filial therapy for a Jamaican mother and the perceived effect on the mother-child relationship. Findings indicate that some aspects of filial therapy are congruent with the parenting practices and values of this Jamaican mother. The mother reported an increase in empathy, a heightened awareness of her child's needs, and a stronger relationship with her child. She expressed some difficulty with limit setting and tracking skills taught as part of the model. Future research directions include further examination of the compatibility of filial therapy with other Jamaican parents and the effectiveness of group filial therapy with Jamaican parents or other parents of Caribbean descent. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

非牛顿流体在气液搅拌槽内强制流动传热特征研究

为了确定非牛顿流体气流搅拌流动传热特征，对气体有效分散区域（载点）提出了无因次准数关联式，并就两种不同叶轮搅拌的通气管外传热系数作了比较。     

Defensive allomones in three species ofHypselodoris (gastropoda: Nudibranchia) from the Cantabrian sea

ThreeHypselodoris species,H. villafranca, H. cantabrica, and H. tricolor, have been studied in order to further investigate the defensive strategies of Chromodorididae mollusks from Iberian coasts. All animals possess large amounts of furanosesquiterpenoids, probably derived from their diet of sponges. The products are transferred and stored in specific sites of the mantle (mantle dermal formations, MDFs) to be used as chemical deterrents against predators. Chemical analysis of CantabrianHypselodoris species has led to the characterization of eight sesquiterpenoids. Among these, six have been found previously in both sponges and nudibranchs, while two are new natural products.Hypselodoris species cooccurring in the same area contained comparable mixtures of sesquiterpenoids. However, two populations ofH. cantabrica from different sites of the Cantabrian sea showed different metabolic patterns. All sesquiterpenoids induce feeding deterrence inCarassius auratus and two are also toxic toGambusia affinis.     

一种基于高阶统计信息的信噪比估计改进算法

针对多进制正交幅度调制(Multiple quadrature amplitude modulation,MQAM)信号在低信噪比条件下估计精度不高的问题,提出了一种基于综合利用高阶统计信息的信噪比估计改进算法。根据所选高阶统计量最高阶数的不同,建立了3种信噪比与多种高阶统计量运算式之间的线性关系,利用全回归线性分析方法将3种线性关系转化为3种全回归模型,并求解模型系数。该算法充分利用了多种高阶统计量的有用信息,提高了信噪比估计精度。MQAM的仿真结果表明:在低信噪比条件下,该算法减小了信噪比估计误差,其估计性能明显优于传统的其他算法,且3种模型估计性能依次增加,可依据不同的信噪比要求对3种模型进行选取。     

基于呼叫中心的客户关系管理系统服务流程优化研究

针对钢铁企业物流公司客户关系管理现状,及其客户服务请求处理流程中的不足,提出了基于呼叫中心的钢铁企业最优化客服请求处理流程及其技术实现,给出了平台功能设计,探讨了平台实现的关键技术。该系统充分满足客户满意度以及服务请求处理的及时性,快速性,确切性,可操作性等方面要求。     

基于降雨-径流试验的高寒草甸产流机制研究

对黄河源区高寒草甸产流机制进行研究,为河源区生态环境保护、水资源科学规划管理提供基础水文理论认知。基于野外降雨-径流试验,通过回归分析构建考虑坡度和覆被因子的暴雨和中小雨产流计算模式,精度良好,能够反映暴雨和中小雨2种降雨模式下高寒草甸产流的一般特征。试验结果表明,因草甸土-植体系蓄容能力较强,高寒草甸区地表产流主要发生在暴雨模式下,中小雨模式下的地表产流量一般很小。模式应用表明,草甸发生退化后,暴雨和中小雨入渗均有减少,暴雨模式下退化草甸比高覆草甸入渗减少约12%,中小雨模式下减少约3%。     

预制桥面板 ＵＨＰＣ湿接缝的界面受力性能研究

为确定合理的界面间约束与接触关系,采用ＡＢＡＱＵＳ中3种不同的约束与接触关系基于现有试验试件进行模拟,将数值分析结果与试验结果与进行对比分析。研究表明:采用内聚力模型的有限元模型破坏形态与试验结果较为一致,绑定约束次之,而采用接触摩擦模型的有限元模拟结果与试验差别最大;以试验开裂荷载与极限荷载为分析对象,绑定约束与内聚力模型的数值分析结果与试验吻合较好,而接触摩擦模型的数值分析结果与试验差异较大;与绑定约束模型相比,内聚力模型能够较好地模拟试件界面的损伤。因此,当采用ＡＢＡＱＵＳ进行预制桥面板与ＵＨＰＣ湿接缝的界面受力的有限元分析时,宜采用内聚力模型或绑定约束模型,不宜采用接触摩擦模型。