Cycling hardening and serration yielding of Fe-Ni-Cr alloy at high temperature under out-phase TMF

Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling (ISC) and out-phase TMF was studied on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC depend on the temperature and the total strain range, stronger hardening with serrated yielding at higher strain range under ISC at 600 °C, but no hardening and serrated yielding occurred under ISC at 800 °C. Stronger hardening with stress serration occurred at the thermal path going to the lowest temperature, no stress serration occurred at the highest temperature under the out-phase. The hardening also depends on the total strain range, higher total strain range with lower cycling temperature resulted in a stronger hardening and remarkable serration yielding behavior. Weaker hardening without serrated yielding occurred at near 800 °C may due to an obvious cycling stress drop under out-phase TMF. Change in the shape of the hysteresis loops also expresses the degree of the damage of the tested alloy under out-phase and ISC.     

片上网络中有保障服务的性能评估

本文针对如何评测片上网络中的有保障服务(Guaranteed-Services,GS)对尽力而为(Best-Effort,BE)流量的传输性能的影响进行了研究,提出了评测重点及相关性能指标,给出了构建网络流量的方法,采用了一种分层逐级抽象的方法搭建了支持任意拓扑结构、任意规模、多种网络协议的性能评估平台,实现了对片上网络中GS服务的性能评估.评测实例的结果表明该平台达到了评价片上网络中GS服务的服务质量和分析GS服务对网络整体性能的影响的目的,有效的帮助设计者在保障局部服务质量的同时提高网络性能,为设计优化提供了依据.     

Optimizing storage performance in public cloud platforms

Cloud computing is an elastic computing model where users can lease computing and storage resources on demand from a remote infrastructure.It is gaining popularity due to its low cost,high reliability,...     

聚丙烯工程化研究

采用纳米填充、交联和转晶的复合技术对聚丙烯进行了改性，优选了纳米碳酸钙为填料。当β成核剂用量为0．5％、助交联剂为3％时，复合材料的综合性能达到最好，接近普通工程塑料的各项力学性能。红外光谱分析和熔体质量流动速率的测定表明，复合材料体系产生了微交联；DSC分析发现，PP材料的聚集态结构中含有β球晶。     

钢框架-钢板剪力墙结构修复后的使用性能指标

为便于钢框架-钢板剪力墙结构震后快速修复,统计既有实验结果,提出修复后使用的三级性能指标,基于等效拉杆理论,研究结构在侧向载荷作用下塑性铰的出现顺序、层间位移角和结构应力发展等情况,并建立有限元模型对指标进行验证.结果 表明:在一级修复性能指标(位移角1/220)下,结构板墙轻微受损,对应的修复方法为对板墙进行轻微修复;在二级修复性能指标(位移角1/110)下,结构板墙几乎全面进入塑性状态,需要考虑换板或增加加劲肋修复;在三级修复性能指标(位移角1/85)下,结构板墙已经全部进入屈服状态,而且框架梁端也出现塑性铰,此时不仅需要对板墙进行修复,还要考虑对框架进行修复.     

金属材料屈服强度的应变率效应和热激活理论

对４种金属材料进行了应变率为１０＾－４－１０＾３ｓ＾－１的拉伸试验，结果表明，屈服中度随应变率的升高分两阶段线性升高，提出了位错线热振动对加载频率的响应的热激活作用机理，依据该机理计算所得Ⅰ，Ⅱ区临界应变εｃ与实测值相符，并在此基础上将应变率对掘强度影响的机制图重新划分为：Ｉ区，富热激活区；Ⅱ区，贫热激活区。     

The impact of global dispersion on coordination,team performance and software quality – A systematic literature review

ContextGlobal software development (GSD) contains different context setting dimensions, which are essential for effective teamwork and success of projects. Although considerable research effort has been made in this area, as yet, no agreement has been reached about the impact of these dispersion dimensions on team coordination and project outcomes.ObjectiveThis paper summarizes empirical evidence on the impact of global dispersion dimensions on coordination, team performance and project outcomes.MethodWe performed a systematic literature review of 46 publications from 25 journals and 19 conference and workshop proceedings, which were published between 2001 and 2013. Thematic analysis was used to identify global dimensions and their measures. Vote counting was used to decide on the impact trends of dispersion dimensions on team performance and software quality.ResultsGlobal dispersion dimensions are consistently conceptualized, but quantified in many different ways. Different dispersion dimensions are associated with a distinct set of coordination challenges. Overall, geographical dispersion tends to have a negative impact on team performance and software quality. Temporal dispersion tends to have a negative impact on software quality, but its impact on team performance is inconsistent and can be explained by type of performance.ConclusionFor researchers, we reveal several opportunities for future research, such as coordination challenges in inter-organizational software projects, impact of processes and practices mismatches on project outcomes, evolution of coordination needs and mechanism over time and impact of dispersion dimensions on open source project outcomes. For practitioners, they should consider the tradeoff between cost and benefits while dispersing tasks, alignment impact of dispersion dimensions with individual and organizational objectives, coordination mechanisms as situational approaches and collocation of development activities of high quality demand components in GSD projects.     

云环境下性能测试研究与应用

性能测试是一种昂贵且耗时的测试活动,是评估系统性能至关重要的手段。在传统测试环境下进行性能测试存在冗余测试次数增多、性能瓶颈定位困难等问题,人们开始思考和研究如何利用当前流行的云计算技术来提高性能测试的效率。在本文中,研究了云环境下性能测试技术的最新研究成果,设计并实现了基于CloudStack云平台的自动化性能测试原型系统。实验结果表明,在云环境下的性能测试,能显著简化用户的测试工作,并具有与传统测试环境下相一致的性能测试结果。     

Using task migration to improve non-contiguous processor allocation in NoC-based CMPs

In this paper, a processor allocation mechanism for NoC-based chip multiprocessors is presented. Processor allocation is a well-known problem in parallel computer systems and aims to allocate the processing nodes of a multiprocessor to different tasks of an input application at run time. The proposed mechanism targets optimizing the on-chip communication power/latency and relies on two procedures: processor allocation and task migration. Allocation is done by a fast heuristic algorithm to allocate the free processors to the tasks of an incoming application when a new application begins execution. The task-migration algorithm is activated when some application completes execution and frees up the allocated resources. Task migration uses the recently deallocated processors and tries to rearrange the current tasks in order to find a better mapping for them. The proposed method can also capture the dynamic traffic pattern of the network and perform task migration based on the current communication demands of the tasks. Consequently, task migration adapts the task mapping to the current network status. We adopt a non-contiguous processor allocation strategy in which the tasks of the input application are allowed to be mapped onto disjoint regions (groups of processors) of the network. We then use virtual point-to-point circuits, a state-of-the-art fast on-chip connection designed for network-on-chips, to virtually connect the disjoint regions and make the communication latency/power closer to the values offered by contiguous allocation schemes. The experimental results show considerable improvement over existing allocation mechanisms.