非平衡进程到达模式下MPI广播的性能优化方法

为了提高非平衡进程到达(unbalanced process arrival,简称UPA)模式下MPI广播的性能,对UPA模式下的广播问题进行了理论分析,证明了在多核集群环境中通过节点内多个MPI进程的竞争可以有效减少UPA对MPI广播性能的影响,并在此基础上提出了一种新的优化方法,即竞争式流水化方法(competitive and pipelined method,简称CP).CP方法通过一种节点内进程竞争机制在广播过程中尽早启动节点间通信,经该方法优化的广播算法利用共享内存在节点内通信,利用由竞争机制产生的引导进程执行原算法在节点间通信.并且,该方法使节点间通信和节点内通信以流水方式重叠执行,能够有效利用集群系统各节点的多核优势,减少了MPI广播受UPA的影响,提高了性能.为了验证CP方法的有效性,基于此方法优化了3种典型的MPI广播算法,分别适用于不同消息长度的广播.在真实系统中,通过微基准测试和两个实际的应用程序对CP广播进行了性能评价,结果表明,该方法能够有效地提高传统广播算法在UPA模式下的性能.在应用程序的负载测试实验结果中,CP广播的性能较流水化广播的性能提高约16%,较MVAPICH21.2中广播的性能提高18%～24%.     

在线用户打分行为长记忆效应与信任关系研究

对在线打分行为的动态研究能够帮助深入理解社交网络用户集群行为和信任关系的演化机制,当前许多在线系统用户能够通过对物品进行打分传达自己的观点。通过去趋势波动分析法研究了用户打分行为在信任关系建立前后的长记忆效应,并通过随机化打分时间和信任时间建立零模型,最后进行用户打分行为异质性分析。采用Epinions数据集进行实证研究,结果表明用户打分的长记忆效应在信任关系建立前出现下降趋势（8.06%）,并于之后逐步回升（8.43%）,而在两个零模型中赫斯特指数分别稳定在0.5和0.6左右,且用户长记忆效应变动与用户度呈正相关,Pearson相关系数分别为0.9358和0.9278。该工作有助于深入理解用户集群行为和信任关系的动态演化机制。     

Combining social media affordances for organising collective action

Social media provide new opportunities for supporting the dynamics of collective action (CA), allowing for the mobilisation of people into debates and involving them in new forms of collective decision making. Although current studies focus on opportunities offered by social media for collective action, there is still a need to deepen the understanding of how social media support the organisation of CA and to study the effects of individual actions performed on social media in complex organisational settings. We here explore how social media are used to manage CA by the Italian political movement Movimento Cinque Stelle, using the concept of affordances as the conceptual framing. Based on the qualitative case analyses, our study contributes to the knowledge base by identifying a typology of nine affordances supporting CA and exploring how the combined actualisations of some affordances of the typology create antecedents of the fundamental processes of CA. On the basis of the study analysis, we suggest a model to describe how social media support CA through affordances, their combinations, and the creation of antecedents and then formulate implications for research and practice.     

A stochastic performance model for pipelined Krylov methods

Pipelined Krylov methods seek to ameliorate the latency due to inner products necessary for projection by overlapping it with the computation associated with sparse matrix‐vector multiplication. We clarify a folk theorem that this can only result in a speedup of 2× over the naive implementation. Examining many repeated runs, we show that stochastic noise also contributes to the latency, and we model this using an analytical probability distribution. Our analysis shows that speedups greater than 2× are possible with these algorithms. Copyright © 2016 John Wiley & Sons, Ltd.     

基于机器人群的主动传感器网络自组织的运动规划

主动传感器网络的自组织通常要求移动节点群(机器人群)通过障碍物环境移动到指定地点后, 重新调整并按预定布局组网. 在网络的自组织过程中要保证每个移动节点(机器人)与整个网络之间的连通性. 在对移动机器人的保持连通性进行优化的基础上, 提出了单步位置预测与群体势场相结合的分布式运动规划方法进行主动传感器网络的部署和重置, 证明了机器人运动控制的稳定性和网络的连通性保持, 进行了有和无障碍物环境下超过40个机器人的仿真, 结果表明该方法适用于大规模的主动传感器网络重置, 并对不同规模的网络具有可扩展性.     

Global Village Media: Coming Together in the Early 1970s at Whiz Bang Quick City

Felicity D Scott , Associate Professor of Architecture at Columbia University Graduate School of Architecture, Planning and Preservation (GSAPP), describes here the instant city events of the early 1970s. These foreshadowed current global village media practices in what now seems a quaintly material manner: communication between sites involved the physical mailing of videotapes and ‘wire photos’ through the postal service. The sites themselves – in the US and elsewhere – were transformed into ‘instant cities’ through the erection of physical geodesic domes, teepees and inflatables in seas of mud. The true antecedents of today's instant networking, these pioneers embraced the newest technology available at the time and the most innovative forms of temporary architecture.     

The Visceral City and the Theatre of Fear

Over the last decade in India, intensive urbanisation, with the aid of the mass media, has unleashed a new culture of fear. Widespread access to TV, text messaging and the Internet have heightened and played upon individuals' anxieties. Ravi Sundaram describes how in Delhi, in particular, the media provided the catalyst for ‘mass hysteria’ and ‘psychosis’ during the summer of 2002. Copyright © 2007 John Wiley & Sons, Ltd.     

从选铜尾矿中综合回收铜铋钨试验研究

在工艺矿物学研究的基础上,针对以嵌布粒度微细、品位极低的黄铜矿、自然铋和白钨矿为主要有用矿物的尾矿进行了选矿试验研究。在使用高选择性药剂条件和最优的药剂制度下,采用全浮选工艺流程实现了选铜尾矿中铜、铋和钨的综合回收,最终获得了含铜16.13%、回收率35.82%的铜精矿,含铋21.35%、回收率40.75%的铋精矿,含钨66.92%、回收率53.89%的白钨精矿的技术指标。     

Evolving Patterns: Correlated Systems of Interaction

Over the last four decades, the onset of computation has enabled architects and designers to employ generative patterns in their exploration of emergent social, material and spatial systems. Theodore Spyropoulos provides an overview of the field and discusses how it has been developed by the Design Research Lab (DRL) at the Architectural Association into an ‘Adaptive Ecologies’ agenda. In the context of parametric urbanism, the DRL has explored models of living through behavioural patterns found in nature, examining the role of the singular and the collective. Copyright © 2009 John Wiley & Sons, Ltd.     

Spaces of Freedom

The predicaments of the current global climate bring a new poignancy and focus to architecture. Emiliano Gandolfi , the curator of the much lauded ‘Experimental Architecture’ exhibition in the Padiglione Italia at the 2008 Venice Biennale, outlines how an emerging group of designers are redefining architecture as they seek to provide solutions that identify people's needs and address the exigencies of global warning, the environmental crisis and migration. Copyright © 2009 John Wiley & Sons, Ltd.