最大熵原理在闪电时程方程中的应用分析

以最大熵原理为依据,首先通过对雷暴过程中闪电总量与闪电频次的关系分析,得到一分布函数。然后进一步讨论相对闪电量与相对历时时间之间的函数关系,建立闪电时程方程。最后选取江苏省闪电定位仪监测记录中2007—2009年20次雷暴日资料,进行分析计算,论证了最大熵原理在闪电时程中应用的可行性。     

舟山群岛东侧海域蟹类群落结构及其与环境因子的关系

根据2018年4月(春季)和10月(秋季)在舟山群岛东侧海域(29°10′25.54"～30°45′00"N,122°53′3.88"～124°48′28.31"E)开展的渔业资源底拖网调查所获得的蟹类数据,研究了该海域蟹类资源的种类组成、优势种、生物多样性等群落结构特征,同时分析了蟹类数量分布及其群落结构与温、盐等环...     

以实践为导向的旅游地返贫机制分析框架构建

防范返贫风险、实现可持续减贫是“后扶贫时代”原贫困旅游地巩固脱贫成效的重点工作。本文以实践为导向,以旅游减贫经典理论为骨架,整合多学科返贫研究成果,构建旅游地返贫机制分析框架。该框架建立了旅游返贫类型体系,指明了返贫风险可能的发生途径与机制。框架指出：扶贫机制不完善将导致机会、增权、保障3个关键因素不同程度的缺失,这些缺失将通过直接效应、间次效应或动态效应三种路径导致低资产返贫、低增长返贫、再结构返贫或暂时性返贫的产生。文章进而给出分析框架的实际应用步骤,以指导旅游减贫实践者检视返贫风险、判断可能的返贫类型结果、阻断返贫发生路径,为脱贫地区旅游可持续发展及返贫风险防范提供了指引。尽管以解决实践问题、提高实践效率、降低实践成本为导向,但该框架也能在理论上指引未来的旅游地返贫研究面向现实需求,探索是否有更优的返贫分类方法、是否有需要补充的返贫成因、是否有新的返贫路径等问题,有助于明确该领域的未来研究方向。     

Transformation of relational space in targeted poverty alleviation from the perspective of actor network: A case study of Hebian Village,Mengla County,Yunnan Province北大核心CSCD

精准扶贫中政府主导、企业和社会积极响应,共同助力贫困户脱贫,引致乡村关系空间在脱贫前后发生转化。论文使用参与式观察、半结构访谈和问卷调查等方法,从行动者网络视角重新审视云南省勐腊县河边村的精准扶贫,将关系空间转化划分为阶段内关系空间转化和阶段间关系空间转化,拓展了行动者网络理论对关系空间转化的解释,发现了河边村关系空间的阶段特征与转化路径:(1)精准扶贫中河边村的关系空间存在阶段性特征,包括脱贫攻坚阶段的前关系空间(标准空间较大)和巩固脱贫成果阶段的后关系空间(协商空间较大)。(2)阶段内关系空间转化是标准空间向协商空间转化的过程。以脱贫攻坚阶段为例,“两不愁、三保障”这一明确政策目标下的标准行为构建了较大的标准空间,有利于确立强制通行点,促进阶段内关系空间转化。(3)阶段间关系空间转化是前一阶段的协商空间转化为后一阶段的标准空间的过程,脱贫攻坚阶段的前协商空间就转化成了巩固脱贫成果阶段的后标准空间。这一关系空间转化的过程可结合新标准行为的应用和空间稳定性测度进行验证。(4)关系空间转化促成了村小组和村民转变为后关系空间中的关键行动者,他们在参与改善建成环境的过程中被动员起来,通过成立合作社的形式和其他行动者结成紧密网络联盟,未来会在巩固拓展脱贫攻坚成果、全面推进乡村振兴的过程中发挥关键作用。论文所构建的关系空间转化框架对分析和促进乡村地区的发展兼具理论价值与现实意义。     

Geographic approaches to resolving environmental problems in search of the path to sustainability: The case of polluting plant relocation in China

This paper applies a spatial perspective to environmental problems in search for the paths to sustainability, using polluting plant relocation in China as a case study. It examines how environmental improvement in one place may lead to environmental degradation in another place, how geographic concepts such as location, distance, spread and backwash effects, and land use models can help understand such phenomenon, and what the implications are for the environmental Kuznets curve (EKC) and development policies. Field research was conducted from 2006 to 2012 in Chinese cities of Beijing, Dalian, Shanghai, Guangzhou, Wuxi, Hangzhou, and Ningbo. It involved intensive site observations and in-depth interviews with government officials of environmental protection, economic development, and business recruitment, and grassroots environmentalists. The results indicate that environmental improvement in all these cities has led to environmental degradation in their suburbs and rural areas due to relocation of polluting plants. Environmental spread and backwash effects may help explain the severe intra-regional environmental and economic disparities and environmental injustice. The powerful and wealthy may achieve rapid economic growth and environmental recovery at the expenses of the powerless and poor, leading to environmental poverty and sustainability disparities.     

An unexpected geography of opportunity in the wake of the foreclosure crisis: low-income renters in investor-purchased foreclosures in Phoenix,Arizona

During the recent United States foreclosure crisis, investors purchased and leased thousands of homes nationwide, opening up formerly owner-occupied neighborhoods to renters. Yet, little is known about how this process affected regional patterns of residential segregation and inequality. In this study, we combine property-level data on real estate transactions and subsidized housing vouchers from 2004 to 2014 to assess whether the conversion of foreclosures to rentals enabled low-income renters to live in more advantaged neighborhoods in Phoenix, Arizona. Renters with vouchers living in investor-purchased foreclosures were in lower-poverty neighborhoods compared with those not living in investor-purchased foreclosures. This suggests that foreclosure sales may have widened the geography of opportunity for low-income renters with subsidized housing.     

Do medical marijuana centers behave like locally undesirable land uses? Implications for the geography of health and environmental justice

As of 2013, medical marijuana is legal in 20 US States and the District of Columbia, but few studies have investigated the impact of the retail centers that sell the drug. We draw upon the social construction literature to frame our research and help us determine whether medical marijuana centers in Denver, Colorado, are considered locally undesirable land uses (LULUs). The geography of health and environmental justice frameworks lead us to hypothesize that marijuana centers are more likely to be opened in Hispanic, Black, and poor neighborhoods than in non-Hispanic White and affluent neighborhoods. We also hypothesize that marijuana centers will tend to increase the minority composition and poverty of the neighborhoods in which they are located. Contrary to expectations, we find no empirical support for these two hypotheses. Instead, results suggest that marijuana centers are likely to be situated in neighborhoods with higher crime rates and more retail employment. Thus, despite the view by many planners and law enforcement officials that these centers are problematic, they do not take on LULU characteristics in siting and demographic changes. This finding, while limited to Denver, has important implications for policymakers who are considering similar marijuana policies.     

Uneven development of the sustainable city: shifting capital in Portland,Oregon

Portland, Oregon, is renowned as a paradigmatic “sustainable city.” Yet, despite popular conceptions of the city as a progressive ecotopia and the accolades of planners seeking to emulate its innovations, Portland’s sustainability successes are inequitably distributed. Drawing on census data, popular media, newspaper archives, city planning documents, and secondary source histories, we attempt to elucidate the structural origins of Portland’s “uneven development,” exploring how and why the urban core of this paragon of sustainability has become more White and affluent while its outer eastside has become more diverse and poor. We explain how a “sustainability fix”—in this case, green investment in the city’s core—ultimately contributed to the demarcation of racialized poverty along 82nd Avenue, a major north–south arterial marking the boundary of East Portland. Our account of structural processes taking place at multiple scales contributes to a growing body of literature on eco-gentrification and displacement and inner-ring suburban change while empirically demonstrating how Portland’s advances in sustainability have come at the cost of East Portland’s devaluation. Our “30,000 foot” perspective reveals systemic patterns that might then guide more fine-grained analyses of particular political-socio-cultural processes, while providing cautionary insights into current efforts to extend the city’s sustainability initiatives using the same green development model.     

减轻山区资源环境承载压力与扶贫的途径探讨——安康市教育扶贫模式实证研究

秦巴山区生态良好,是中国的绿心,但经济极端贫困,且生态保护难度大,对外联系不便,外在形象与内在发展水平矛盾突出.选取秦巴山区腹地安康地区,通过分类问卷调查和座谈的方法进行调研,发现安康市通过教育扶贫,已产生了教育移民效应.高等教育和中等职业教育每年产生永久性移民在1万人左右(0.96万人),间接移民在3万人左右,起到了减轻当地资源承载压力的作用;农民工培训每年产生暂时性移民达63.2万人.安康市的实践经验对解决资源脆弱地区的脱贫致富和环境保护提供了范式.     

Urban Underclass: The Wayward Travels of a Chaotic Concept

This commentary critically engages with arguments made by Loïc Wacquant in his book Urban Outcasts on the nature of public discourse regarding concentrated urban poverty in the United States. In particular, it elaborates a critical reading of the international circulation of social-scientific analyses of urban poverty—in particular the concept of the "urban underclass"—which rose to prominence through research on Chicago neighborhoods. This concept has subsequently influenced scholarly and public policy approaches to characterizing and combating entrenched urban poverty and long-term unemployment in Europe, Asia, and elsewhere. I challenge the appropriateness of the concept as well as the direction of public policymaking that has downplayed, if not ignored, questions of job availability and job quality in urban areas.