城镇防沙的理论框架与技术模式

城镇防沙是在国家需求推动下产生的新领域,在没有形成自身理论体系的情况下,只能以风沙物理学、治沙工程学、恢复生态学,以及沙漠化防治和可持续发展等相关理论与技术为基础,通过工程实践和理论研究逐步建立城镇防沙理论体系。初步总结出的城镇防沙理论体系包括风沙灾害成因与区域风沙流场特征、城镇周边土地利用空间格局优化、防沙工程体系优化配置、防沙工程效率评估与预测4个分支领域,14项主要研究内容和9个支撑学科;技术体系包括8个分支技术领域和一个总目标（即:城镇防沙技术优化模式）。除青藏高原外的城镇防沙技术模式具有圈层结构特征,第一圈层都是以市（镇）区为核心的绿化景观带。对于地处半湿润风沙区外缘的城镇,第二圈层为高效农牧业生产区,第三圈层为生态涵养圈,第四圈层为封禁保护圈。对于半湿润风沙区内部的城镇,第二圈层为农牧业生产与沙丘封禁区,第三圈层为封禁保护圈。对于半干旱风沙区城镇,第二圈层为沙丘（地）封禁与农牧业生产区,分为近郊设施农业圈、远郊沙丘（地）封禁与农牧户独立生产圈两个次级圈层,第三圈层为沙丘（地）封禁保护圈。对于干旱风沙区城镇,第二圈层为节水灌溉农业区,第三圈层为外围防护带,第四圈层为封禁保护带。对于地处青藏高原山间盆地的城镇,防沙工程一般采取近郊“防护林带+人工草地+灌溉系统”,外层为“沙障+防护林带+人工草地+灌溉系统”,再外层为“防护林带+草地改良+封禁保护”的布局模式。对于地处青藏高原河流宽谷的城镇,防沙工程技术模式在宏观上根据河道走向布局,局部充分考虑防沙治沙与河道整治、水土流失和地质灾害治理有机结合,细节上依据沙尘源地类型和分布地貌位置选择防沙技术。     

上海世博效应与湖北长江旅游城市群互动发展创新思考

2010年上海世博会即将开幕,从世博会角度下探讨城市群发展也成为研究的热点问题之一。本文在分析上海世博会的价值理念和四大效应的基础上,立足于湖北长江旅游城市群的发展,提出其互动发展的创新思考,对未来湖北长江旅游城市群发展具有借鉴意义。     

大城市有利于小城市的经济增长吗?——来自长三角城市群的证据

厘清大城市是否有利于小城市经济增长这一问题,对于贯彻大中小城市和小城镇协调发展的国家新型城镇化战略具有重要意义。以长三角108个小城市为例,在传统经济增长模型中加入到大城市的地理距离、行政边界、市场潜能等因素,估计不同等级的大城市对小城市经济增长的空间影响及其异质性。研究发现：临近大城市有助于促进小城市的经济增长,并未发现存在集聚阴影效应的直接证据;空间相互作用的方向更多体现为高等级城市对低等级城市的影响,来自副省级城市的增长溢出最为显著,同层级小城市之间的空间关联效应相对微弱;城市间存在一定程度的市场分割,行政边界的存在阻碍了空间溢出效应的发挥。最后从强化中心城市的辐射带动功能、促进不同规模城市空间溢出效应的全域性释放、破除行政区经济的束缚等方面提出了促进大中小城市和小城镇协调发展的政策启示。     

APPRAISAL OF GEOGRAPHIC RESEARCH AND TRAINING PROGRAMS IN THE SOVIET UNION

Global distributions are commonly described by maps and tables which emphasize the dispersion of a distribution. The Mean Spheroidal Center (M.S.C.) defines the average location of a world distribution. It is an objectively determined point within the sphere's surface. The M.S.C. calculations are demonstrated using the world's 25 largest cities in each of four time periods.     

LAW AND THE INTERPRETIVE TURN IN THE SOCIAL SCIENCES

Legal cases are increasingly used in the social sciences as the raw material for social analysis. While this is entirely laudable as a research strategy, the analytical methods used in the social sciences to study cases are too often simplistic and reductionist. Positivism is too often the preferred analytical mode. I argue that the legal texture of cases ought to be retained by social scientists, just as we ought to be more aware of the problematic nature of interpretation, an issue embedded within legal discourse. In contrast to those who contend that the interpretive turn in the social sciences is nihilistic and subjective, I suggest reasons for understanding the interpretive turn as an organized social practice dependent upon social standards of right and wrong. These issues are illustrated by reference to a recent court case involving a corporation that secretly and illegally relocated production so as to avoid its pension obligations.     

JUVENILE GUN CRIME AND SOCIAL STRESS: BALTIMORE, 1980–1990

Violence, particularly among minority youths, is a perennial social problem widely regarded as synonymous with the inner city. This analysis examines 2, 639 juvenile gun crimes reported to the police in an 11-year period, 1980-1990, in Baltimore, Maryland. Attention focuses on patterns of selected categories of gun crimes and their relationship to a generalized areal measure of social stress. Salient findings were temporal persistence of pattern; close spatial relationship between gun crimes and (predominantly African-American) census tracts at or above the 8th decile in terms of a social stress index; the territorial nature of gun crimes; and a “frontier” effect with respect to gun crimes with black offenders and white victims. Applications of this analysis to violence prevention are discussed.     

On The Potential of Local Political Projects: A Response To Lake,Martin, and Wilson

Gentrification in the form of "neighborhood revitalization" is increasingly touted as one way of decreasing the social exclusion of residents of poor inner-city neighborhoods and of increasing levels of social mix and social interaction between different classes and ethnic groups. Yet the gentrification literature also suggests that the process may lead to increased social conflict, displacement of poorer residents to lower quality housing elsewhere, and, ultimately, social polarization. Much of this hinges on whether gentrifying neighborhoods can remain socially mixed, and whether neighborhood compositional changes result in more or less of a polarized class and ethnic structure. However, the impact of revitalization and gentrification on levels of social mix, income polarization, or ethnic diversity within neighborhoods remains unclear and under-explored. This study addresses this gap by examining the relationship between the timing of gentrification, changes in the income structure, and shifts in immigrant concentration and ethnic diversity, using census tract data for each decade from 1971 to 2001 in Toronto, Montreal, and Vancouver. This research demonstrates that gentrification is followed by declining, rather than improving, levels of social mix, ethnic diversity, and immigrant concentration within affected neighborhoods. At the same time, gentrification is implicated in the growth of neighborhood income polarization and inequality.