采空区场流安全理论及其研究的新进展

提出采空区场流安全理论的概念,并对采空区场流流态、瓦斯涌出和自燃“三带”理论及自燃温度等数值模拟计算的发展历程进行概要总结;分析了当前采空区场流安全理论研究的最新进展和发展趋势。指出目前的现代通风安全理论研究正处在前所未有的历史变革时期,即从网络流通风安全理论到场流安全理论的过渡与统一。采空区问题(瓦斯涌出和自燃)应综合考虑特定开采条件下的采场漏风与供氧系统的背景环境。其理论研究的主流方向应是基于场流方法的灾害与各因素影响关系的分析,重点是灾害机理和多灾害间耦合等一般规律;技术手段是多孔介质渗流力学、多相气体扩散、综合传热理论和有限元数值模拟方法,关键是模型求解的收敛稳定性和流场分布解问题。     

Why dual leaders will drive innovation: Resolving the exploration and exploitation dilemma with a conservation of resources solution

Using conservation of resources theory, we challenge traditional unity of command models of leadership and propose that a dual‐leadership framework can serve as a potential solution to the inherent challenges of innovation. Leading for innovation demands are depicted as uniquely disparate from other forms of leadership, resulting in several types of conflict and resource depletion for individual leaders. We contend that this exploration–exploitation role conflict and the resulting need to manage incongruent role identities produce stress, strain, and resource depletion that in turn hamper innovative goal achievement for both a single leader directly and via subordinates more indirectly. We propose, however, that as an extension of the resource investment tenet of the conservation of resources theory, a dual‐leadership approach may alleviate many of these challenges for innovation. Specifically, the addition of a second leader can add resources to innovation and in turn decrease the role conflict inherent in managing the generation and implementation of creative ideas. Limitations and areas for future research are offered.     

基于安全度的机场围界安全评估方法

针对机场围界存在虚警率高、信息分散和难以从全局角度管理等问题,提出基于安全度的机场围界安全评估方法。基于分散环境集中监控思想,利用改进DS证据理论将前端探测设备获取的信息进行融合,再利用模糊集理论获得区段安全度,进而求得防区安全度和全局安全度。基于C#和Map Xtreme开发机场围界监控平台,结果表明,基于安全度的评估方法能够准确反映机场围界安全运行状况。     

Chemical characteristics and sources of water-soluble organic aerosol in southwest suburb of Beijing

PM_2.5 filter sampling and components measurement were conducted in autumn and winter from 2014 to 2015 at a suburban site (referred herein as “LLH site”) located in the southwest of Beijing. The offline aerosol mass spectrometry (offline-AMS) analysis and positive matrix factorization (PMF) were applied for measurement and source apportionment of water-soluble organic aerosol (WSOA). Organic aerosol (OA) always dominated PM_2.5 during the sampling period, especially in winter. WSOA pollution was serious during the polluted period both in autumn (31.1 µg/m³) and winter (31.9 µg/m³), while WSOA accounted for 54.4% of OA during the polluted period in autumn, much more than that (21.3%) in winter. The oxidation degree of WSOA at LLH site was at a high level (oxygen-to-carbon ratio, O/C=0.91) and secondary organic aerosol (SOA) contributed more mass ratio of WSOA than primary organic aerosol (POA) during the whole observation period. In winter, coal combustion OA (CCOA) was a stable source of OA and on average accounted for 25.1% of WSOA. In autumn, biomass burning OA (BBOA) from household combustion contributed 38.3% of WSOA during polluted period. In addition to oxygenated OA (OOA), aqueous-oxygenated OA (aq-OOA) was identified as an important factor of SOA. During heavy pollution period, the mass proportion of aq-OOA to WSOA increased significantly, implying the significant SOA formation through aqueous-phase process. The result of this study highlights the concentration on controlling the residential coal and biomass burning, as well as the research needs on aqueous chemistry in OA formation.     

苯为前驱物形成二噁英的反应机理

苯作为垃圾中普遍存在的成分是形成多氯二苯并对二噁英/呋喃（PCDD/Fs）的重要前驱物之一.应用密度泛函理论（DFT）在B3LYP/6-311+G （d,p）水平上研究了苯生成PCDD/Fs的两阶段气相反应机理,获得相关基元反应的势垒与反应热.采用隧道效应校正的变分过渡态理论（VTST）对300~1300K的各基元反应进行速率常数计算.结果表明：苯的氯化过程在合成PCDD/Fs各基元反应中势垒最高,是整个过程的控速步骤;氯酚更有可能被HO·进攻氯苯发生亲核反应后经分子内脱氢形成;邻位Cl能提高芳香烃H的抽取势垒,降低分子反应活性;苯氧自由基经碳碳或碳氧耦合二聚化过程形成不同PCDD/Fs存在竞争机制.相关计算结果可以用于在总二噁英产量基础上评估由苯产生的PCDD/Fs贡献率.     

Humanitarianism and Local Service Institutions in Angola

The role of local service institutions is not a major focus of current discourse on humanitarianism and complex emergencies. These institutions, in the few places where they are mentioned, are usually presented as either the seed of civil society and future democracy, or as pawns and components of the predatory economic, political and military élites. Few would deny that examples can be found which conform to both of these stereotypes. This simplistic representation of local institutions ignores the perspectives of the actors themselves — the nurses, extension agents, school teachers and others who actually staff most NGO-supported projects. The debate has focused on what ‘we’ should do; the moral dilemmas of aid agencies and their expatriate staff, inevitably leading to the question of whether or not humanitarian workers should stay or leave situations in which aid may be causing more harm than good. Without denying the fundamental importance of these issues, it is important to consider also how the discourse has unfortunately moved away from those humanitarian workers who have no such choice, since they live there. Current concerns about keeping humanitarian aid from feeding local political and military struggles may inadvertently and paradoxically serve to constrain room for man?uvre in the field, particularly among those individuals with the greatest tacit understanding of the predatory environment. There is a need to understand how actors in local service institutions make sense of their own situations, including the factors which frame their moral dilemmas and their day-to-day choices. By analysing the organisational processes within local service institutions, this study is intended to provoke consideration of how these individuals and their institutions may be effectively supported in complex emergencies through a focus on how they themselves deal with danger and complexity. It is suggested that there is a value in considering the lessons learnt in recent years about how service organisations in the North function in turbulent environments. This experience points to the importance of allowing workers the discretion to develop a relationship with their clients, and in so doing make sense of a confusing and ambivalent environment.     

The Northridge Earthquake: Community-based Approaches to Unmet Recovery Needs

The 1994 Northridge, California earthquake has proven to be one of the most costly disasters in United States history. Federal and state assistance programmes received some 681,000 applications from victims for various forms of relief. In spite of the flow of US$11 billion in federal assistance into Los Angeles and Ventura counties, many victims have failed to obtain adequate relief. These unmet needs relate to the vulnerability of particular class and ethnic groups. In response to unmet needs, a number of non-governmental organisations (NGOs) have become involved in the recovery process. This paper, based on evidence collected from hundreds of in-depth interviews with the people involved, examines the activities of several community-based organisations (CBOs) and other NGOs as they have attempted to assist vulnerable people with unmet post-disaster needs. We discuss two small ethnically diverse communities in Ventura County, on the periphery of the Los Angeles metropolitan region. The earthquake and resultant disaster declaration provided an opportunity for local government and NGOs to acquire federal resources not normally available for economic development. At the same time the earthquake created political openings in which longer-term issues of community development could be addressed by various local stakeholders. A key issue in recovery has been the availability of affordable housing for those on low incomes, particularly Latinos, the elderly and farm workers. We discuss the successes and limitations of CBOs and NGOs as mechanisms for dealing with vulnerable populations, unmet needs and recovery issues in the two communities.     

分形理论在松嫩平原西部生态环境胁迫研究中的应用

以松嫩平原西部为例,在构建生态环境胁迫评价指标体系的基础上,运用分形理论对生态环境胁迫进行量化研究.结果表明,1989-2004年15 a间,除松原市和扶余县以外,其他县市生态环境胁迫系数都呈增大趋势,特别是大安市、长岭县、乾安县等地胁迫系数较大.采用相对指标法,运用GIS-EIS集成技术,对松嫩平原西部生态环境胁迫度进行分级.最后,分析了影响生态环境胁迫变化的驱动因子,并提出减缓生态环境胁迫的措施.     

Extra-pair paternity,sperm competition and the evolution of testis size in birds

Sperm competition should select for increased sperm production if the probability of fertilization by a specific male is proportional to the relative number of sperm inseminated. A review of the literature generally supports the predicted positive association between sperm production or allocation and various measures of the presumed intensity of sperm competition. However, it is not clear how increased sperm competition is related to extra-pair paternity, and it remains unknown whether certainty of paternity should be associated with relative testis size. Based on a large sample of bird species with information on extra-pair paternity gathered from the literature, we demonstrate that testis mass is related positively to the level of extra-pair paternity, after controlling for body size and phylogeny. Although large testes may be necessary to avoid sperm depletion in species in which males frequently engage in multi-pair copulations, we argue that selection has favoured increased testis mass in situations of more intense sperm competition in order to retaliate against copulations by rival males. The fact the males are not always successful in retaliating against rival ejaculates further suggests that females may largely control the allocation of paternity in birds and that increased sperm production by males may simply be a male strategy to make the best of a bad situation.