Quasi-static tensile behavior of large-diameter thin-walled Ti–6Al–4V tubes at elevated temperature

As promising light-weight and high-performance structure components, large-diameter thin-walled(LDTW) Ti–6Al–4V titanium alloy(TC4) bent tubes are needed most urgently in many industries such as aviation and aerospace. Warm bending may be a feasible way for manufacturing these components. Understanding their temperature and strain rate dependent tensile behavior is the foundation for formability improvement and warm bending design. In this paper, uniaxial tensile tests were conducted at elevated temperatures ranging from 298 K to 873 K at tensile velocities of 2, 10, 15 mm/min. The main results show that the tensile behavior of LDTW TC4 tubes is different from that of TC4 sheets. The typical elongation of TC4 tubes at room temperature is 10%lower than that of TC4 sheets. The flow stress of TC4 tubes decreases greatly by about 50% with the temperature rising to 873 K. At temperatures of 573–673 K, the hardening exponent is at its highest value, which means the deformation mechanism changes from twining to more dislocation movement by slipping. The fracture elongation of TC4 tubes fluctuates with increasing temperature,which is associated with changes in the deformation mechanism and with the blue brittleness. The fractography of TC4 tubes at various temperatures, especially at 673 K, shows that second phases and impurities significantly influence fracture elongation. By considering the characteristics of the tensile behavior and by properly choosing the die material, the warm bending for TC4 tubes can be achieved at temperatures of 723–823 K.     

信贷消费下我国消费行为模型的研究

分析了消费行为影响因素以及这些因素的变化，给出了有无信贷两种情况下消费行为模型，并结合我国特点，对信贷消费的市场拉动效应及相应的信用政策进行了研究。认为，消费信贷的刺激，消费总支出增加，消费行为将产生消费的“贷款效应”；在信用政策上应该引导消费文化和消费观念、增加有效供给、稳定的收入和支出预期的信心等。     

改型尾缘对翼型流场影响的数值模拟

建立了NACA23012翼型后缘加装Gurney襟翼模型和高度为2%弦长的Gurney襟翼翼型的后缘表面曲率进行修改的模型,并利用FLUENT软件对其进行数值模拟,得到不同模型在不同风速,不同攻角下的空气动力学性能（Cl、Cd）以及翼型表面压力、速度、马赫数的分布等.计算结果表明：四种单纯的加装Gurney襟翼的模型中,高度为2%弦长的Gurney襟翼模型具有最高的升阻比.而与单纯加装Gurney襟翼的模型相比,修改下表面后缘曲率的模型的升阻比可提高14%左右.在0.5度攻角以下及负攻角时,与 NACA23012原型相比,各改型的升阻比都有所提高.     

Wave propagation analysis for a second strain gradient rod theory

In this work, an enriched model describing the longitudinal wave propagation is established based on Mindlin’s Second Strain Gradient (SSG) theory, which can describe the heterogeneity caused by the micro-structure interactions in the frame of continuum mechanics. The governing equation and associated boundary conditions are derived based on Hamilton's principle, then the dispersion relation of non-classical longitudinal wave together with the extra-waves appearing exclusively in SSG theory model are investigated. The investigations are based on the modal density, energy flow, and forced response of the rod. Wave transmission and reflection through planar interfaces based on the proposed model have been calculated. Finally, the results of the enriched model are well interpreted by comparing with the classical theory results, and some useful conclusions are derived on the SSG theory based model in the wave propagation characterization.     

国有企业改制中的政府行为分析——兼评河北省首例诉政府国企改制无效案

国企改制是一个复杂的社会问题,容易导致各种利益冲突。面对改制中的各种纷争政府应如何面对？在国企改制中政府应当做什么以及不应当做什么？本文结合国企改制中发生的一起案件,探究国企改制中政府行为存在的问题及应对措施,准确定位政府在国企改制中的角色,规范政府行为。     

Hf对Nb15W5Si2B合金室温和高温力学性能的影响

 为了寻求Nb-Si基合金高温强度和室温塑性之间的平衡,设计了以Nb基固溶体相Nb-SS占主导的Nb15W5Si2BxHf(x= 0,5,10,15,原子百分数）合金,研究了Hf元素对Nb15W5Si2B合金的组织、室温和高温压缩性能以及高温蠕变性能的影响。结果表明,Nb15W5Si2B合金由Nb-SS和Nb5Si3两相组成,Nb5Si3相呈网状分布;Hf的加入不改变相组成,但Nb5Si3相由网状分布逐步变成不连续小岛状分布,而且体积分数减少。Hf同时提高Nb15W5Si2B合金的高温静强度和室温塑性,但对Nb15W5Si2B高温压缩蠕变性能不利。最后讨论了Hf对Nb15W5Si2B合金强化与塑性化机理。     

基于信息化的融合及其效应分析——从产业和企业视角

基于信息化的背景分析产业融合理论,从产业层面和企业层面分析了产业融合的含义和各自的特点。从产业层面上,产业融合就是高新技术及其产业作用于传统产业,使得两种产业或多种产业融为一体的产业新范式。不同产业的经济活动之间出现了相似性;从企业层面上,产业融合是指某一产业中一个具有较大影响力的企业或者相当数量的企业,出现了内容相同的多元化经营。企业融合深化了企业的竞争与合作关系,并使得企业战略由规模经济转变为范围经济。我国应对产业融合一是非政府创造产业融合的支持环境,二是发展高新技术,三是制定适合产业融合的管制政策。     

对当代大学生婚前性行为的反思

婚前性行为是个极为敏感而又不得不面对的话题。本文通过调查了解大学生的性观念和性行为取向,为高校的性教育及大学生的健康成长提供参考与借鉴。     

空管中带班主任管理模式研究

通过对中国空中交通管制中带班主任管理模式研究，提出了适用于该管理模式的权变-行为混合管理模型。采用对比研究方法，分析了传统的权变管理模型、行为管理模型等当今流行管理学理论和模型，从而提出了权变-行为混合管理模型。通过一线带班主任的反馈，能够最大限度调动发挥全班组人员的主观能动性和积极性，合理地组织人力、物力，从而预防和消除人为差错，提高管制工作效率。     

基于聚类分析的长沙市民体育休闲行为意向分异研究

城市居民作为体育休闲市场的主体,对其行为意向展开研究,对于发现城市体育休闲市场一般特征、开拓相关体育休闲市场等具有重要意义。通过对长沙市民抽样调查得到基础数据,运用聚类法得出3类意向不同的细分市场,采用对应分析方法对各细分市场的体育休闲意向进行分析,得出不同类型的细分市场的体育休闲意向有显著差异的结论,因而获得了体育休闲市场营销的启示。