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Contact with nature is vital for the development of children and teenagers. In the past, informal urban green spaces (IGS) such as vacant lots appear to have been used for such purposes. We need to better understand how previous generations used IGS to make sure young people today can also enjoy its social, mental, emotional and physical health benefits. This study quantitatively compared adult residents' memories of IGS use in their childhood and teenage years in two geographically and culturally distinct cities: Brisbane, Australia, and Sapporo, Japan. The results showed most respondents (>70%) remembered using IGS in the past, and preferred it over other green space because it was easily accessible. Most (>70%) recalled experiencing no problems (e.g. danger of injury) when using IGS, a contrast to recently increasing parental concern for children's safety. Such factors may limit present IGS use and prevent it from fulfilling the important role it played for previous generations' recreation.  相似文献   
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Vandana Desai  Alex Loftus 《对极》2013,45(4):789-808
In this paper, we seek to revisit earlier work on the theory of rent, situating it in the current period of economic crisis and in relation to informal housing in the global South. More than ever, land is treated as a pure financial asset. Finance capital now exerts a profound influence over the production of space and exposes the built environment to the kinds of speculative binges that we have witnessed over the last decade. This is now as much a feature of living conditions in the poorest settlements of the global South as it is in the financial heartlands of the global North. We question key assumptions behind development interventions by arguing that infrastructural upgrading may decrease the security of tenure of residents of informal housing and call for a more nuanced approach that recognises the (post)colonial histories of urbanisation structuring access to land and housing.  相似文献   
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Board games have a wide and complex distribution in the ancient world. Two board games from antiquity that were transmitted across the borders of empires and city states and played for nearly two millennia show only minor changes in the appearance of the board. This lack of branching for antique board games can be explained by the abstract characteristics of the games and the dominance of certain cultures in antiquity. A historical analysis of their transmission process supports this hypothesis.  相似文献   
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Eighteen taxa of Middle Devonian (Givetian) gastropods, including two new genera and five new species, are présent in the Tungkangling and Yingtang Formations, Wuxuan and Xiangxhou counties, Guangxi Province, China. Pingtianispira tuberculata gen. et sp. nov., Wuxuanella nodusa gen. et sp. nov. and Wuxuanella luifengshanensis sp. nov., Crenulazone wuxuanensis sp. nov. and Murchisonia luifengshanensis sp. nov. are erected from this distinct fauna. The fauna is dominated by nodose and unusual murchisonioids and has strong European and other Old World realm affinities.  相似文献   
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Spatial interaction models commonly use discrete zones to represent locations. The computational requirements of the models normally arise with the square of the number of zones or worse. For computationally intensive models, such as land use–transport interaction models and activity‐based models for city regions, this dependency of zone size is a long‐standing problem that has not disappeared even with increasing computation speed in PCs—it still forces modelers to compromise on the spatial resolution and extent of model coverage as well as on the rigor and depth of model‐based analysis. This article introduces a new type of discrete zone system, with the objective of reducing the time for estimating and applying spatial interaction models while maintaining their accuracy. The premise of the new system is that the appropriate size of destination zones depends on the distance to their origin zone: at short distances, spatial accuracy is important and destination zones must be small; at longer distances, knowing the precise location becomes less important and zones can be larger. The new method defines a specific zone map for every origin zone; each origin zone becomes the focus of its own map, surrounded by small zones nearby and large zones farther away. We present the theoretical formulation of the new method and test it with a model of commuting in England. The results of the new method are equivalent to those of the conventional model, despite reducing the number of zone pairs by 96% and the computation time by 70%. Los modelos de interacción espacial suelen utilizar zonas discretas para representar áreas o puntos de interés. Los requisitos computacionales de estos modelos normalmente aumentan a razón del número de zonas elevadas al cuadrado o más. Para modelos computacionalmente intensivos como los modelos de interacción entre uso de suelo y transporte y los modelos basados en actividades para ciudades‐región, el impacto del tamaño de la zona es un problema persistente no superado aun. Esta limitación persiste a pesar de los grandes avances en la velocidad de procesamiento en computadoras, pues obliga a los modeladores a hacer concesiones entre la resolución espacial y la extensión que abarca el modelo, así como en el rigor y profundidad del análisis. En este artículo se presenta un nuevo tipo de sistema de zonas discretas que: a) tienen como objetivo reducir el tiempo de estimación de la aplicación de modelos de interacción espacial; y b) al mismo tiempo mantienen su nivel de precisión. La premisa que gobierna este nuevo sistema es que el tamaño apropiado de las zonas de destino depende de la distancia a su zona de origen: a distancias cortas, la precisión espacial es importante y las zonas de destino deben ser pequeño; a distancias mas largas, conocer la ubicación precisa es progresivamente menos importante y las zonas pueden ser mayores. El nuevo método define un mapa específico de zonas para cada zona de origen; cada zona de origen se convierte en el foco de su propio mapa, rodeada de zonas cercanas pequeñas y zonas grandes a mayor distancia. El estudio presenta la formulación teórica del nuevo método y su demostración vía un modelo de desplazamientos residencia‐trabajo en Inglaterra. Los resultados del nuevo método son equivalentes a las del modelo convencional, a pesar de reducir del número de pares de zonas en un 96% y el tiempo de cálculo en un 70%. 空间相互作用模型通常采用离散区域代表区位。模型的计算量往往与区域数量呈平方甚至更高阶增长。对于可计算的精细模型,如土地利用‐交通相互作用模型和基于行为的城市区域模型,区域尺度的依赖性是长期存在的问题,即使计算机的计算速度增加,该问题仍无法消除。因此,建模者需在模型空间分辨率和覆盖范围以及模型分析的严谨性和深度上做出权衡。本文介绍了一种新型的离散分区系统,目的在于减少空间相互作用模型估算和计算时间,同时维持其精度。新系统的前提是目标区域的适当尺度取决于与初始区域的距离:在短距离范围内,空间精确性是重要的,且目标区域必须是小的;在更远距离上,位置精度的重要性降低,目标区域可以变大。该方法为每个初始区域制定了具体的尺度地图。每个初始区域成为其自身地图的中心,被近邻的小区域和更远距离的大区域所包围。本文给出了新方法的理论公式,并以英格兰地区的通勤模型进行检验。结果显示,尽管区域对的数量减少了96%,计算时间缩短了70%,但新方法的计算结果等效于常规模型。  相似文献   
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