3维地形的金字塔上下采样局部实时简化算法

在大型三维地理信息系统中,往往需要在预加载整体地形数据的基础上,对局部地形数据重新构建三角网,用于物理模拟等应用。针对这一问题,本文提出了一种三维地形的金字塔“上下采样”局部实时简化算法,实现对局部三角网地形实时高效的简化。该算法基于图像金字塔思想,通过对原始地形的三角格网执行“下采样”和“上采样”,结合“预测残差”对“下采样”的地形做局部简化,简化后的三角网十分逼近原始的高精度三角网。本文将该算法用于GeoBeans 3D平台的汽车驾驶模拟系统中。该算法生成的地形简化且稳定,随着汽车活动范围的变化,按需销毁及重构更新地形。实验证明,当预测残差阈值取0.1时,三角形个数能简化到原始数量的2/3;阈值取0.2时,三角形个数可以简化到原始个数的1/4左右。由此可见,在视觉精度允许的范围之内,该算法对地形的简化效果较好,且耗时少,满足了三维系统及车辆驾驶模拟的实时性。     

Regional land-use allocation using a coupled MAS and GA model: from local simulation to global optimization,a case study in Caidian District,Wuhan, China

China is facing the pressures of both rapid economic development and environmental protection, and land-use allocation optimization is an important way to manage the conflicts between these pressures and to achieve sustainable development. Optimization of land-use allocation is a nonlinear multiobjective spatial optimization problem, and a purely local simulation model or global optimization model is insufficient to solve it. It is essential to bridge the gap between the two models through the combination of top-down and bottom-up approaches. This study integrates a multiagent system (MAS) that simulates the behaviors of land-use stakeholders with regard to their choices of specific locations, with a genetic algorithm (GA) that simultaneously evaluates and optimizes land-use configurations to meet various regional development objectives. The model is expected to achieve the optimization of land use in terms of the composition and spatial configuration. Caidian District, Wuhan, China, was chosen as the study area to test the model in this paper. The results show that the performance of the coupled model is superior to a pure GA model or MAS model. The optimal configuration improves on the economic output, spatial compactness, and carbon storage of the current configuration and promotes sustainable regional land-use development from the local scale to the regional scale.     

Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant characteristics.Two practical pile inclinations of 5° and 10° in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are considered.Results obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of piles.Horizontal impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination increases.Distinct values of horizontal impedance functions are obtained for the ’positive’ and ’negative’ cycles of harmonic loadings,leading to asymmetric force-displacement relationships for the inclined piles.Validation of these experimental results is carried out through three-dimensional nonlinear finite element analyses,and the results from the numerical models are in good agreement with the experimental data.Sensitivity analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.     

地磁场时空差异对磁测精度影响

通过对辽宁地区流动地磁的观测资料进行对比分析,研究探讨了影响磁测精度的各测点与通化台之间的通化距离、经度方向距离等因素对磁测精度的影响情况。为提高流动地磁观测的磁测精度提供了参考。     

LOCAL LABOR MARKETS: THEORIES AND POLICIES IN THE U.S. DURING THE 1970s∗

Local labor market policies of the federal government are critically evaluated with respect to their target efficiency and underlying theoretical assumptions. Policies of the Economic Development Administration are considered to be target inefficient compared to those of the Comprehensive Employment Training Act. Experimental mobility policies of the Department of Labor appear to be have questionable impact locally as opposed to nationally. Some local hybrid programs offer improved place and people targeting.     

Urbanizing the periphery: infrastructure funding and local growth coalition in China’s peasant relocation programs

The Chinese State has addressed the dilemma between urban growth and farmland loss by launching mass peasant relocation programs. By moving peasants into high-rises and reclaiming their living space, arable lands are created to counterbalance the farmland loss. However, the current infrastructure funding model, which relies on local government’s bank loans, falls short of supporting the relocation programs. This paper explores this latest phase of urbanization in China by examining relocation programs in two counties in Chengdu, Sichuan and Shangqiu, Henan – before and after the transition to private investment. The paper reveals that private investors are becoming the main funders of relocation programs, and that the transition to private investment in relocation programs resulted in power reshuffle within the local growth coalition, compromises by the local government and consequently the exacerbation of peasant conditions. The paper concludes by reflecting on the social consequences of the transition, specifically benefit encroachment and risk transfer.     

Models of local governing coalitions: city politics and policy effects in Spanish municipalities

Local governance involves coalitions between public and private actors on policy issues. Actors participating in these coalitions may vary according to the issue in question, even within the same city. Based on a survey carried out among actors from different sectors of the local political community in four Spanish cities, governance networks are analyzed across five different issues: public housing, cultural tourism, urban regeneration, social policy, and citizen participation. Using network analysis and indexes in a comparative examination of 20 policy networks, we show that variations across networks are explained by policy issue content and supra-municipal regulations, regardless of the cities’ political characteristics.     

商业化大潮中丽江古城的文化特质分析

丽江旅游开发30年呈现表象的商业化与内在的文化自觉两条线索.基于访谈样本,认为丽江古城独特的地方智慧是吸引游客的主要原因,这使其呈现世界休闲古都的文化意象.最后进行两点学术讨论：（1）丽江古城遗产保护,应该兼顾物质文化遗产和非物质文化遗产.（2）丽江古城作为茶马古道的重镇,其未来的发展不应该摒弃纳西族文化、马帮文化、人-水-城-大环境四合一的中庸文化等特质,高品质的深度旅游和文化传承才是符合世界遗产旅游的潮流和可持续的.     

华南一次飑线升尺度增长过程的机制分析

利用中国自动站与CMORPH降水产品融合的逐时降水量0.1°×0.1°网格数据集、1°×1°NCEP再分析气象资料、常规观测资料和高分辨率的WRF数值模拟资料对2016年4月13日前后发生在华南的一次飑线升尺度增长过程进行了动力和热力环境条件分析。飑线形成前,对流层高层有急流,华南位于急流入口区右侧,有利于高空辐散。高空有弱槽存在,并且温度槽落后于高度槽,有利于槽发展。近地面上有低压系统控制,并且有风场的辐合,加强了抬升运动。模拟的结果表明:WRF模式成功模拟了此次飑线升尺度过程,飑线的降水量和落区较为接近实况。与以往的飑线过程相比,此次飑线过程中,升尺度阶段有效位能较初始对流阶段要高,但是整个华南地区对流有效位能始终处于中低水平。除了天气尺度系统的影响,多种中尺条件的配合对这次飑线升尺度发展很有利。低层的垂直风切变、低位涡和较高温度递减率是触发条件,提供了一定的不稳定条件和抬升条件。低层风场转向加强,垂直风切变的方向改变,充足的水汽供应和后部入流的加深加剧了不稳定和垂直抬升运动,是促进β中尺度飑线升尺度的重要条件。冷池在升尺度阶段不明显,但冷池对维持成熟阶段的α中尺度飑线结构很重要。