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181.
Shengming Hu Zhijian Chen Chenghui Wan Chun Tang Wen Xiong 《Marine Georesources & Geotechnology》2020,38(4):385-392
AbstractCompared with traditional methods, the three-dimensional laser-scanning (3D-LS) technique can efficiently acquire many high-quality geometric properties of rock discontinuities. In practice, engineers usually prefer to simplify the processing by using single-station point data and roughly orienting owing to the complexity of registration/georeferencing multi-station point data. However, prior published studies have paid little attention to the accuracy and reliability when determining discontinuity orientations using 3D-LS. We propose a reliable and accurate method with robust on-site applicability. As part of an ongoing effort, we are evaluating the precision of the commonly used coarse registration method and the fine registration method, and promoted the optimized coarse- and fine-registration methods and evaluated their precision. It is found that: (1) the common and the optimized registration method can meet our project’s engineering requirements, and the optimized registration method improved accuracy in the dip direction by approximately 1°; (2) fine registration using an iterative closest point (ICP) algorithm can correct both dip direction and dip angle; and (3) the orientation is of high precision with commonly used coarse and fine registration, whereas the optimization effect to correct the orientation is slightly limited. 相似文献
182.
模拟实验作为地理实践力的主要组成要素之一,在培养高中生求知探索品质、活用所学地理知识、锻炼动手能力等方面具有独特作用。本文结合新课标、校情、学情,划分了地理模拟实验的实践力表现水平层次,以人教版高中《地理》必修1中的热力环流、洋流、火山这三个有代表性的知识点为题材,进行校本化的模拟实验、水平划分和量化测评,实现地理实践力素养培养和评价的落地。 相似文献
183.
Ming Tang Zoe Falomir Christian Freksa Yehua Sheng Haiyang Lyu 《Transactions in GIS》2020,24(4):903-943
In geography, invariant aspects of sketches are essential to study because they reflect the human perception of real‐world places. A person's perception of a place can be expressed in sketches. In this article, we quantitatively and qualitatively analyzed the characteristics of single objects and characteristics among objects in sketches and the real world to find reliable invariants that can be used to establish references/correspondences between sketch and world in a matching process. These characteristics include category, shape, name, and relative size of each object. Moreover, quantity and spatial relationships—such as topological, ordering, and location relationships—among all objects are also analyzed to assess consistency between sketched and actual places. The approach presented in this study extracts the reliable invariants for query‐by‐sketch and prioritizes their relevance for a sketch‐map matching process. 相似文献
184.
运用流体力学软件FloEFD对沽源单个建筑物周围的风场进行数值模拟。通过不断改变模型中计算参数的设置进行一系列模拟试验,对比模拟试验结果,并与观测资料进行比较,分析不同计算参数对模拟结果的影响,并获得适用于该模型的最佳参数。主要研究的计算参数包括计算域高度,初始网格等级,局部初始网格等级和不同平均风速剖面形式。结果表明:计算域高度从3倍建筑物高度开始,空腔区的长度、漩涡中心位置以及再发展区的边界位置基本保持稳定。随着初始网格等级的增加,空腔区的长度、再发展区的边界位置及计算时间逐渐增大。局部初始网格等级对模拟结果影响不显著。以两种不同平均风速剖面形式进行模拟,迎风漩涡长度不同,背风面影响不大。与观测资料比较显示,最优参数组合为:计算域高度为3倍建筑物高度,初始网格等级为4、局部初始网格等级为4、平均风速剖面形式为指数律。 相似文献
185.
高速水下航行体头肩部和表面突起等位置很容易产生空泡,不失一般性,将表面突起结构简化为一定高度的台阶.针对简化的航行体模型,基于数值模拟方法研究了头肩部空泡与台阶处空泡、头肩部空泡与尾空泡2种类型的双空泡相互作用问题.不同的来流攻角下,头肩部空泡与台阶处空泡的作用过程存在区别,可以分为大攻角和小攻角2种类型.当尾空泡内有... 相似文献
186.
187.
藏、汉对比视角下的城市空间环境认知研究——以中国西藏日喀则市为例 总被引:2,自引:0,他引:2
以分布式认知理论为基础,采用质性研究法、数量分析法以及GIS空间分析技术,探讨日喀则市藏族、汉族居民对城市空间环境认知的异同性。研究表明,藏族对城市空间环境的认知得分高于汉族对城市空间环境的认知得分。藏族、汉族对城市空间环境的认知水平可分为高、中、低3类。认知空间呈现圈层结构与混合结构模式,可分为藏汉一致性、藏族独立以及汉族独立3种认知空间类型。影响居民对城市空间环境的认知因素有共性因素和差异性因素。景观走廊质量、宜居性、基础设施两项是藏族居民关注的主要影响因素,汉族居民更关注公共服务设施的服务能力以及对当地文化的融入感。 相似文献
188.
Due to the specific dynamics, the probes located at the halo orbits or Lissajous orbits around the Earth-Moon collinear libration point L1 or L2 are always studied in the synodic system to understand their trajectories. In fact, they are also orbiting the Earth in a distant Keplerian ellipse. Because of their intrinsic orbital instability, in the orbit prediction the initial errors propagate more prominently than those of the normal orbiting satellites, this requires special attention in the orbit design, maneuver, and control. Despite of all this, they are similar to the normal orbiting satellites in orbit determination and hardly require other special attentions. In this paper, the quantitative results of error propagation under the unstable dynamics, together with the theoretical analysis are presented. The results of precise orbit determination and short-arc orbit predictions are also shown, and compared with the results from the Beijing Aerospace Control Center. 相似文献
189.
The community dynamics and potential carbon ?xation of intertidal macroalgae were investigated monthly from April 2014 to April 2015 in the northwest coast of Yellow Sea. Seasonal variations in biomass and carbon ?xation were presented and showed close relationship with community structure.The carbon ?xation rate ranged from 0.48±0.13 mg C/(g FW ·d) to 4.35±0.12 mg C/(g FW ·d). Sargassum thunbergii, Chondrus ocellatus and Ulva intestinalis were three most in?uential species which contributed27%, 21.9% and 18.5% variation of carbon ?xation rate, respectively. Standing carbon stocks ranged from7.52 g C/m~2 to 41.31 g C/m~2, and estimated carbon stocks varied from 11.77 g C/m 2 to 96.49 g C/m~2. The larger dif ference between estimated and standing carbon stocks implied that more ?xed carbon was exported from the community in summer and autumn than in winter. This study suggested that intertidal macroalgal community could provide a potential function in carbon ?xation of coastal ecosystem. 相似文献
190.