利用偏度平衡自动提取机载LiDAR点云城区道路

针对机载LiDAR点云提取城区道路自动化程度低以及提取道路网不完整的问题,提出一种基于偏度平衡算法自动提取城区道路的方法。首先,计算末次回波点云中邻近点的坡度,依据城市道路设计标准选择坡度阈值,分离非地面点并获得初始道路点云;然后,利用偏度平衡算法计算出最优强度阈值,滤除非道路点,再结合道路与停车场的空间位置关系,通过点距精化初始道路点云;最后,对道路区域进行细化和平滑,得到道路中心线。通过定量分析及对比实验,该方法能够自动地从LiDAR点云中提取出较为完整的道路网。     

地质要素在工程构筑选址中的影响特性分析

新的作战样式催生地质环境下工程构筑选址这一全新的命题。本文探究了地质要素对工程构筑选址的影响,将工程分成三大类,总结三类工程的地质影响要素;通过分析土体、岩体的物理化学和力学性质对工事的作用,总结陆域水体对岩体和建筑材料的物理化学作用,梳理主要的构造、地质灾害和资源类型对工程的影响,明确了六大类地质要素在工程构筑选址中的影响特性,为下一步确定各要素在工程构筑选址中的权重以及构建工程构筑选址信息模型奠定了基础。     

基于二阶局部纹理熵的边缘检测方法

针对传统的边缘检测方法将灰度变化较为平缓的区域误判为边缘的问题,提出了基于二阶局部纹理熵的边缘检测方法。利用了二阶局部纹理熵能表示局部区域灰度变化大小的性质,并采用灰度错位压缩法消除灰度值压缩造成的条纹现象。实验表明,本文提出的方法能有效地检测出各类边缘,解决了上述的误判问题;通过不同大小窗口的边缘检测效果比较,建议在采用基于二阶局部纹理熵的边缘检测方法时将窗口设置为3×3。     

“Contested policy mobility”: the creative transformation and temporary use of brownfields in Redtory,Guangzhou

This article argues that the changing distribution of power between coalitions of stakeholders challenges typical top-down dynamics of policy mobility, and causes contestations that in turn lead to the multi-scalar co-construction of policy- and place-making in China. When property-led redevelopment, commandeered by the coalition between government and investors, could no longer dominate the renewal of brownfield sites, a nationally endorsed mobile policy of creative transformation led China’s renewal of these areas into a new phase of “contested policy mobility”. Three kinds of contestations have been observed in Redtory, Guangzhou. First, in adopting the alternative mobile policy of using brownfields temporarily before permanent redevelopment, local governments were aiming to retain control of development rights throughout a nationally mandated urban economic “creative transformation” process. Second, emerging new interest groups from within the public sphere were able to resist subsequent redevelopment plans, thereby challenging the mobile policy’s top-down momentum. Finally, divisive interests within the coalition ultimately weakened their power when contesting the government and investors.     

Wave Reflection Coefficient Spectrum

1 .IntroductionWavereflectionfromstructuresisanimportantfactorforthedesignofthestructures .Therehavebeenmanyresearchesonwavereflectionwithregularwavesandmonochromaticirregularwaves .Miche( 1 951 )proposedanon dimensionalMichenumberMfornormallyincidentirregularwavesconsideringwavebreakingbecauseofthedeepeningofwavesteepnessontheslopeofbreakwaters .ThereflectioncoefficientisproportionaltoM ,i.e .,Kr ∝M =4g( 2π) 5/ 2tan5/ 2 α(Hsf2p) ( 1 )wheregisthegravitationalacceleration ,Hsthesignifican…     

近海海洋对热带风暴线性响应的底坡度和底摩擦效应

一个简单的二维线性模式用于考查近海海洋对过境热带风暴的动力响应过程中的底坡度和底摩擦效应。选择了自东向西和向西后转向的两个模式风暴路径。数值试验结果表明，海底坡度与风暴引起的水位波动、风暴中心后部的尾流以及路径右侧后方面的涡旋密切相关。而底摩察是阻尼风暴潮和风暴流持续增长的重要因子。结果还表明，近海对风暴的强响应偏向于风暴轨迹的右侧，这与Ｃｈａｎｇ和Ａｎｔｈｅｓ（１９７８）对深海响应的研究结论是一     

Probability distribution of surface slope for nonlinear random sea waves and calculation of whitecap coverage

Based on the nonlinear model of two-dimensional random sea waves, a statistical distribution of wave surface slope exact to the third order is derived by using the expansion of the characteristic function and direct calculations of each order moment. Based on the distribution of wave surface slope derived in this paper, a whitecap coverage is proposed by using the limit surface slope as a criterion of wave breaking. The whitecap coverage expressed by the model depends on three parameters which can be determined in principle by the linear wave spectrum and three kinds of wave-wave interaction.     

Numerical Analysis of Interaction Between Pile-Supported Pier and Bank Slope

Two- and three-dimensional finite element analysis programs for pile-soil interaction are compiled. Duncan-Chang's Model is used. The construction sequence of the pier is modeled. The pile-soil interface element is used. The influence of the combination type of piles on the deformation of bank slope and pile behaviour is analyzed. Different designs of a pile-supported pier are compared thoroughly. Calculation results show that the stresses and displacements of the pile are directly related to the distance from the bank slope and the direction of inclination. An inclined prop pile set in the rear platform would remarkably reduce the stresses of piles and the displacement of the pier.