Relationship between the fatigue cracking probability and the grain-boundary category

In this paper, the probability of fatigue cracking along different kinds of grain boundary (GB) and persistent slip bands (PSBs) is considered in the light of data obtained by cyclic deformation of copper bicrystals and columnar crystals. It is found that, in copper bicrystals, fatigue cracks always nucleate and propagate along large-angle GBs, irrespective of whether the GB is perpendicular, parallel or inclined to the stress axis. On the contrary, for columnar copper crystals containing small-angle GBs, PSB-matrix interfaces become the preferential sites for initiation of fatigue crack; fatigue cracking along the small-angle GBs was never observed. For a special [1-34]/[182^-7] copper bicrystal with a Sigma = 19b GB and a common primary slip plane, GB cracking also results in fatigue failure. Based on the results above, the interactions of dislocations carried by PSBs with GBs, including 'pile-up of dislocations', 'passing through of dislocations' and 'partial passing-through dislocations', are discussed. It is suggested that the probability of fatigue cracking in fatigued copper crystals increases in the order of small-angle GBs, PSBs and large-angle GBs.     

Enhancement of hardening and thermal resistance of Mg–Sn-based alloys by addition of Cu and Al

Mg–Sn-based alloys are considered as a promising precipitation-hardening system for applications at elevated temperatures, but the hardening effect is not satisfactory owing to sluggish nucleation and rapid coarsening of the major Mg₂Sn lath precipitates. In this study, Cu and Al are added to a Mg–6Sn–1Mn base alloy. The age-hardening response and the microstructures of these modified alloys have been investigated and are compared to that of the base alloy. The additional elements are found to bring several beneficial effects to the alloys for applications at elevated temperatures. Firstly, a eutectic structure consisting of strong intermetallic phases, i.e. Mg₂Cu in the Mg–6Sn–1Mn–2Cu alloy and Al_0.93Cu_1.07Mg in the Mg–6Sn–1Mn–2Cu–2Al alloy, remains stable along the grain boundaries after solution and ageing heat treatments. Secondly, the precipitate density has been increased significantly and the precipitate size has been refined remarkably during ageing at 200?°C. Moreover, the growth of the precipitates is inhibited remarkably during the over-ageing period. Therefore, the age-hardening response and over-ageing resistance are notably improved.     

青少年时间管理倾向量表的编制

时间管理倾向是个体在运用时间方式上所表现出来的心理和行为特征,具有多维度多层次的心理结构。参照有关文献并结合国内的广泛调查研究,编制出我国青少年时间管理倾向量表。通过对1027名大中学生的探索性因素分析和507名大中学生的验证性因素分析,结果表明时间管理倾向问卷由时间价值感(社会取向和个人取向的时间价值感)、时间监控观(设置目标、计划、优先级、时间分配和反馈性)和时间效能感(时间管理效能和时间管理行为效能)三个维度构成。该量表的因素结构清晰,信度和效度较好,可以作为评鉴青少年时间管理倾向的有效工具。     

大学生考期应激的特征及原因分析

旨在研究考期应激的表现特征,并探讨其产生的原因和影响因素。以问卷方法测量了261名在校大学生。结果发现47．89％的被试有不同程度的考期应激症状,其中以睡眠症状为最典型的特征。考期应激症状很少受性别、专业、年级、是否担任班干部和个性倾向等因素的影响,且具有较明显的时间特征。诱发考期应激的主要因素有：考生“对考试目的的认知”、“对考试内容的认知”及“生恬和学习环境”等。结论为,考期应激是一种大学生中较普遍且具有多重原因的应激现象。     

从面孔模块到马赛克──视觉特异性加工的脑机制

“脑功能的模块性”是视觉乃至整个认知神经科学的研究热点。特异性的面孔加工模块被当作是认知模块假说的最好证据。但综述跨学科的正反两方面实验证据表明,视觉加工存在特异性,并没有普遍的模块式的亚单元,而是“马赛克”镶嵌式的组构。     

类比迁移发生机制的研究

本研究包含两个实验,探讨类比迁移发生的机制。实验一主要探索类比迁移中的图式归纳是一种自动加工还是控制加工。实验二主要探索类比迁移中的图式归纳是保留性的还是排除性的。本实验结果表明,类比迁移中的图式归纳主要是控制加工,是一种保留性的归纳。     

年轻成年人昼夜体温“钟”的研究

年轻成年被试在现代人类觉醒期间“标准环境温度”(standard ambient tem-perature)(～20℃)和人体产生和散发热量保持最佳平衡状态的睡眠期间“热中性”(thermal neutrality)环境温度(～30℃)条件下。24-h昼夜测量体(口腔)和皮肤(中背,耳后,肘,手背,足背)温度。皮肤温度借助特制WMSX-01巡回检测温度仅远距离连续测温和自动打印。结果表明;(1)在“标准环境温度”(～20℃)和“热中性”环境温度[～30℃间可见四肢(特别足部)]皮肤温度呈现显著相位性倒转。(2)“非午睡组”和“午睡组”均可见在14:00左右呈现一个体温“钟”的“次要低谷”(Minor nadir),从而表示成年人的体温“钟”也可能具有“半24-h昼夜节律”(Circasemidian rhythm)的内源性特征。     

灵魂不朽与柏拉图的新神话——《理想国》卷十厄尔神话解读

本文通过对柏拉图<理想国>篇末厄尔神话的解读,试图回答柏拉图对诗的态度问题,并通过对该神话三个层面的解读,考察柏拉图如何构建他的新神话.本文认为对厄尔神话的理解必须放到<理想国>大的政治哲学背景下进行理解,文中提出柏拉图对传统诗人的批判同时也是在批判智者以及智者对城邦基础的攻击,柏拉图试图为城邦确立不同于传统习俗和智者"自然"意义的新的基础,而厄尔神话正是柏拉图在这一新基础上书写的新神话.     

家电销售人员胜任特征模型建构

本研究旨在探讨优秀家电销售人员应具备的胜任特征。首先通过对20名家电销售人员的行为事件访谈,初步构建了家电销售人员胜任特征模型;然后通过对20例顾客与家电销售人员的互动进行自然观察,进而对所建构的模型加以验证。研究表明,家电销售人员胜任特征模型共包括9项:成就导向、主动性、学习发展、影响力、洞察力、服务意识、可信赖、情绪稳定性以及产品知识。     

大学生在双趋冲突和趋避冲突中的折扣率差异

目的探讨大学生被试在双趋冲突和趋避冲突条件下的折扣率差异。方法让70名大学生完成两种条件下的延迟折扣任务（DDT）。结果趋避冲突条件下大学生被试的折扣率显著低于双趋冲突条件下的折扣率,在延迟奖赏为中幅度（50-60元）时折扣率最大。结论相对于双趋冲突,损益情况和延迟时间同时影响着被试在趋避冲突条件下的选择。