Mutual relationships in neighborhood socioeconomic change     

Elizabeth C. Delmelle  Jean-Claude Thill 《Urban geography》2013,34(8):1215-1237

In this article, we investigate the factors that lead to changes in the socioeconomic complexion of urban neighborhoods along four critical dimensions: crime, youth social distress, home ownership, and economic conditions. We argue that the dynamics of these dimensions are better apprehended simultaneously considering their potential mutual relationships and we propose a cross-lagged panel model approach within a structural equation modeling framework. Neighborhoods in Charlotte, North Carolina, are used as a case study, and change is modeled at several time lags throughout the 2000–2010 decade. Findings indicate that the model performs well and that it offers a very promising avenue for modeling the socioeconomic changes of neighborhoods that accounts for complex longitudinal effects as well as spatial dependencies. Specifically, it shows that lower human capital manifested by a decline in youth indicators is significant in explaining subsequent increases in crime and declines in economic indicators. Also, the predominance of housing stock constructed in the 1950s and 1960s is a significant trigger of declines across all neighborhood indicators. Finally, spatial spillover effects between neighborhoods are found to be short-lived and dissipate after a few years.  相似文献   

Developing environmental standards for abstractions from UK rivers to implement the EU Water Framework Directive / Développement de standards environnementaux sur les prélèvements d'eau en rivière au Royaume Uni pour la mise en œuvre de la directive cadre sur l'eau de l'Union Européenne     

《水文科学杂志》2013,58(6):1105-1120

Abstract

Under the European Union Water Framework Directive, Member States must put in place a river basin planning framework to determine what measures are necessary to maintain and improve the ecological status for all surface water bodies. The governmental organisations legally responsible for implementing the Directive in the UK have recognised that an appropriate river flow regime is fundamental to maintain a healthy river and, as a result, they need to regulate abstractions and effluent discharges and ensure sufficient water is released from impoundments. This paper reports on the process of producing environmental standards that define the maximum abstraction allowable from UK rivers, to leave sufficient flow to maintain a healthy river ecosystem. As there are currently insufficient data available to determine the relationships between river flow and ecological status empirically, expert knowledge was captured through a series of workshops at which leading UK freshwater scientists defined maximum levels of river flow regime alteration that would achieve ecological objectives for different river water body types. For the least ecologically sensitive rivers, maximum abstractions in the range 15–35% of the natural flow were proposed, depending on the flow magnitude and time of year. For the most sensitive rivers, the maximum abstraction proposed was in the range 7.5–25%. The knowledge was used by the responsible UK authorities to develop environmental standards. The authorities subsequently used the environmental standards to determine regulatory standards that could be implemented within practical constraints and current licensing policies.  相似文献   

预制钢筋混凝土剪力墙结构抗震性能研究进展（Ⅱ）：结构性能研究   总被引：2，自引：0，他引：2  

李爱群  王维  贾洪  潘志宏  吴晓莉 《地震学刊》2013,(6):736-742

阐述了预制钢筋混凝土剪力墙结构抗震性能研究的重要性和预制钢筋混凝土剪力墙结构抗震性能研究的最新进展。综述了国内外预制钢筋混凝土剪力墙结构设计规范以及设计方法的研究进展。指出常规预制装配式钢筋混凝土剪力墙结构的抗震性能较差,在地震作用下,主要靠结构构件连接处的损伤和结构构件损坏来消耗能量;无粘结后张拉预应力预制混凝土剪力墙结构,在地震作用下具有自恢复中心能力和良好的抗震能力,但该结构体系的耗能能力不足。认为在预制钢筋混凝土剪力墙结构中设置耗能减震元件,或将预制钢筋混凝土剪力墙结构设计成隔震结构,将有效提高预制钢筋混凝土剪力墙结构的抗震性能。该类预制装配式剪力墙结构的抗震性能有待于进一步研究。  相似文献   

中国与OECD在非援助国别分配的空间关系研究     

邵静  王茂军 《地理科学进展》2020,39(5):766-778

中国在非援助规模持续扩大,在打破原有援助格局的同时,其援助行为日益受到国际社会的关注,但现有研究较少关注中国和经济合作与发展组织(Organization for Economic Co-operation and Development,OECD)之间的空间关系。论文利用2000—2012年中国对非援助(Aid)与OECD对非援助(ODA)在非洲44个国家的数据,对比分析了二者的时间推移及国别分配特征,构建Aid和ODA静态面板模型,定量识别了二者的空间趋同关系。主要结论如下：① 援助金额大幅增加,时序相关性明显,受援国规模位序升降趋同,时间推移上呈同步性;② 地理匹配度高,重点援助国高度雷同,空间分布上呈同质性;③ Aid与ODA间存在稳健、显著的正向关系,响应方式具有一致性,但Aid对ODA响应程度更为敏感、强烈;④ 人均GDP和营养不良发生率是影响援助的2个强有力的因素,影响机制具有相似性。  相似文献   

新型干树式半潜平台浮体结构设计研究     

李建勋  凌进  王仁军  郁芳  刘木南  唐修俊  王中念 《海洋工程》2019,37(1):12-19

为适应中国南海深水区域的油气田开发,研发出了一种具有渐变式立柱的深吃水干树式半潜钻井/生产平台(TCDDSemi)。平台的浮体采用了深吃水、变截面长立柱构型,即向底部逐渐扩大的渐变截面形式。结合干树式深吃水半潜平台的研发过程,通过采用压缩空气压载系统、全注水下浮体、压缩空气水密检测以及水密面板的三级正交加强筋设计等新兴技术,极大地提高了钢材的利用效率,达到了节省材料、减轻浮体自重的目的。对浮体的有限元(FEM)整体分析结果表明,浮体结构设计满足各工况强度要求。  相似文献   

“产业化节能建筑”住宅房屋结构的试验研究   总被引：1，自引：1，他引：0  

冼巧玲  李远辉  黄振熙  严忠 《地震工程与工程振动》2010,30(4)

"产业化节能建筑"住宅房屋以钢框架为主体结构,并采用钢筋混凝土轻质叠合楼板和整体预制复合外墙板。为研究这种房屋结构的抗震性能,进行了两层足尺结构模型的模拟地震振动台试验和有限元分析。对无墙板、X向外挂墙板和Y向外挂墙板三种不同结构状态,以及Y向外挂墙板时采用三种不同螺栓拧紧力矩的工况,分别输入三条实际地震动,按8度区调整其峰值加速度,测定模型结构的地震反应。对五种不同状况的模型结构进行有限元时程分析,研究结构的抗震性能以及外挂墙板对框架结构抗震性能的影响。试验和分析结果均表明,该房屋结构总体上具有较好的抗震性能,钢筋混凝土轻质叠合楼板和整体预制复合外墙板能够经受8度大震考验,墙板的不同螺栓拧紧力矩对结构的地震反应影响不大,轻质叠合楼板与梁柱的连接部位需要进一步加强。  相似文献   

USE OF SURFACE GUIDE PANELS AS PIER SCOUR COUNTERMEASURES     

Chin-Kun HUANG  Chii-Jau TANG 《国际泥沙研究》2005,20(2):117-128

1 INTRODUCTION Protection of bridge piers against local scour is of major importance to bridge maintenance. The safety of bridges is seriously threatened by the river flood during typhoons or thunderstorms. In Taiwan typhoon’s floods are often so strong in possession of high energy to transport a large amount of bed sediment in river. The average velocity in a flood river can go typically over 3 m/s even up to 5 m/s, several times of the regular flow speed. The peak discharge of flood i…  相似文献   

产业结构对区域碳排放的影响——基于多国数据的实证分析   总被引：1，自引：0，他引：1  

原嫄  席强敏  孙铁山  李国平 《地理研究》2016,35(1):82-94

人类行为所引起的全球气候变暖趋势已经无可争议,所带来的影响可能对全球发展方向和生产方式产生重大的作用。在建立产业结构对区域碳排放的影响模型基础上,在全球尺度下进行计量分析,主要结论：第一,理论模型证明区域碳排放随经济发展推进具有先上升后下降的不可抗的基本客观规律,故减排应从降低峰值高度、促进峰值提前等方向入手;第二,实证结果说明第二产业份额对碳排放的影响强度为恒正值,而服务业的影响强度逐步降低,促使第二产业向服务业的份额流动最终将带来整体影响强度的下降;第三,产业结构调整所引起的碳排放变动强度具有明显差异,产业升级对于中高等发展水平国家的减排效率明显高于极高发展水平国家,且中等发展水平国家将在更早的发展阶段迎来碳排放高峰。  相似文献   

中国区域创新的时空动态分析   总被引：7，自引：1，他引：6  

程叶青  王哲野  马靖 《地理学报》2014,69(12):1779-1789

基于探索性空间数据分析和验证性空间面板模型,本文探讨了2000年以来中国区域创新的时空动态。结果表明：① 自创新战略实施以来,中国各省区创新产出的年均增长率几乎都经历了一个剧烈的加速过程,说明区域创新能力的总体提升,但是,东部沿海地区仍然在创新产出中居于压倒性地位,导致“沿海—内陆”分化加剧和区域鸿沟的进一步突出,省区创新可能会陷入“强者愈强,弱者愈弱”的“马太效应”;② 中国区域创新产出与创新投入的空间集聚随时间推移不断强化,通过识别不同时期各变量“热点”,表明创新产出“热点”地区与创新投入“热点”具有高度的时空耦合特征;③ 人均GDP、研发投入、研发人员及在校大学生数对省区创新产出有显著的直接影响。省区间创新活动存在明显的空间溢出效应,其知识溢出的地理区域跨越了省区边界。空间依赖性的存在导致省区间创新活动具有反馈效应,相邻省区的知识溢出对该省区的创新活动具有实质性影响。  相似文献   

Reconstructing boundaries and reason in the climate debate     

Frans Berkhout   《Global Environmental Change》2010,20(4):565-569

  相似文献