Extracting invariant characteristics of sketch maps: Towards place query‐by‐sketch     

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   

A hierarchical indexing strategy for optimizing Apache Spark with HDFS to efficiently query big geospatial raster data     

Fei Hu  Yongyao Jiang  Yun Li  Weiwei Song  Daniel Q. Duffy 《International Journal of Digital Earth》2020,13(3):410-428

ABSTRACT

Earth observations and model simulations are generating big multidimensional array-based raster data. However, it is difficult to efficiently query these big raster data due to the inconsistency among the geospatial raster data model, distributed physical data storage model, and the data pipeline in distributed computing frameworks. To efficiently process big geospatial data, this paper proposes a three-layer hierarchical indexing strategy to optimize Apache Spark with Hadoop Distributed File System (HDFS) from the following aspects: (1) improve I/O efficiency by adopting the chunking data structure; (2) keep the workload balance and high data locality by building the global index (k-d tree); (3) enable Spark and HDFS to natively support geospatial raster data formats (e.g., HDF4, NetCDF4, GeoTiff) by building the local index (hash table); (4) index the in-memory data to further improve geospatial data queries; (5) develop a data repartition strategy to tune the query parallelism while keeping high data locality. The above strategies are implemented by developing the customized RDDs, and evaluated by comparing the performance with that of Spark SQL and SciSpark. The proposed indexing strategy can be applied to other distributed frameworks or cloud-based computing systems to natively support big geospatial data query with high efficiency.  相似文献   

水岩作用下泥质板岩软化非线性机制研究     

黄智刚  左清军  吴立  陈福榜  胡圣松  朱盛 《岩土力学》2020,41(9):2931-2942

水岩作用下泥质板岩表现出明显的软化特征。通过单轴压缩试验分析了泥质板岩软化过程中单轴压缩强度、弹性模量和泊松比与吸水时间之间的关系；借助核磁共振试验研究了水岩作用下泥质板岩软化过程中孔隙的产生、扩展和贯通规律，分析了泥质板岩软化过程中孔隙度与吸水时间之间的关系；采用电镜扫描试验分析了水岩作用下泥质板岩软化过程中微观结构的演变规律，基于分形理论研究了不同浸泡时间下泥质板岩分形维数的变化规律；运用非线性动力学理论，选取微观结构孔隙形状分维值、孔隙度、单轴抗压强度、弹性模量作为描述泥质板岩与水溶液相互作用系统的变量，建立了水岩作用下泥质板岩的软化模型，结合试验数据验证了模型的适用性。结果表明：泥质板岩单轴抗压强度、弹性模量随吸水时间增大而减小，呈负线性相关，而泊松比与吸水时间之间的关系不明显；在浸泡初期，水岩作用强烈，泥质板岩内部微孔隙会发生扩展贯通进而形成更大尺寸的孔隙，孔隙度在浸泡初期增长较快；随着浸泡时间的延长，水岩作用减弱，孔隙度增长速率趋缓；随着吸水时间的推移，泥质板岩内部孔隙相互连通，进而形成复杂网状结构的大孔，泥质板岩分形维数呈对数增长，最终趋于稳定；采用非线性模型计算的结果与试验数据较接近，说明泥质板岩的软化过程具有明显的非线性动力学特征，利用非线性动力学模型可以较好地表征水岩作用下泥质板岩的软化规律。研究成果可为软岩?水相互作用理论研究提供参考。  相似文献   

星基增强系统L1频段信息服务性能分析     

赵镇  陈刚  胡志刚 《中国地震》2020,36(4):912-923

在北斗全球导航服务进程中，北斗星基增强服务的建设是我国卫星导航事业自身建设和不断完善发展的内在需求，更是我国卫星导航系统标准化建设的必然要求。本文基于星基增强信息定位原理，研究并实现星基增强系统的标准定位算法，采用IGS站点数据及增强信息电文，对WAAS与EGNOS系统服务性能进行分析评估，在“陆态网络”数据处理中，加入SBAS信息也可对相关误差进行改正。结果表明，加入播发的差分改正信息定位精度相对于伪距单点定位显著提高，平面方向统计均方根残差优于1m，高程方向优于1.2m；研究发现受地面参考站分布区域以及电离层、观测星座的影响，WAAS和EGNOS在定位服务性能覆盖范围内均表现出一定的区域性。从总体分析来看，不同系统空间段GEO卫星播发SBAS消息特性不一，均满足单频定位需求，EGNOS稳定性低于WAAS系统，播发消息时有中断现象，在实时单频定位性能方面，WAAS的服务性能较EGNOS得到更优的解算结果。  相似文献   

波纹钢管铅阻尼器耗能性能分析研究          下载免费PDF全文

周云  吴胜 《世界地震工程》2020,(4):103-111

提出一种波纹钢管铅阻尼器，介绍了其构造、工作机理、布置形式及特点，采用ABAQUS软件，建立钢管阻尼器、波纹钢管阻尼器和波纹钢管铅阻尼器有限元模型，对其应力分布，传力路径和滞回性能进行模拟分析。结果表明:波纹钢管铅阻尼器耗能减震机理明确，工作性能和耗能性能稳定，滞回曲线饱满以及耗能能力强，具有良好的变形和延性，极限变形大；波纹钢管铅阻尼器通过在波纹钢管内设置铅芯使初始刚度、承载能力和耗能能力得到大幅度提高，既有效保持了波纹钢管的变形能力，又避免波纹钢管发生局部屈曲，使波纹钢管耗能能力得到充分发挥。波纹钢管铅阻尼器在1mm小位移下就可以进入耗能，而且很快进入稳定耗能状态，等效阻尼比稳定在0.3~0.4之间。  相似文献   

Season Effects on Subsurface Constructed Wetlands Performance: Role of Radial Oxygen Loss of Phragmites australis     

Qian Wang  Zhenfeng Cao  Yanbiao Hu  Qiang Kong  Fei Xu  Yuanda Du  Congcong Zhao 《洁净——土壤、空气、水》2019,47(8)

  相似文献   

Mechanical behavior of porous solid considering mesoscopic elastic buckling     

Hao-Yue Zhang  Xiao-Xong Hu  Gao-Feng Zhao 《国际地质力学数值与分析法杂志》2020,44(7):962-982

In this work, the elastic buckling of porous solids was investigated using a lattice spring model (LSM). The capability of the LSM to solve elastic buckling problems was comprehensively verified by comparing well-established numerical and analytical solutions. Following this, the buckling of a porous solid was studied, in which two porous structures were considered, ie, the random porous model and the Voronoi porous model. The results reveal that both the porosity and the shape of the pores influence the elastic buckling bearing capacity of the porous solid. Finally, the mechanical responses of a porous solid with an extra high porosity (0.85) were numerically investigated. Our numerical results demonstrated that the nonlinear elastic response of the porous solid might come from its mesoscale elastic buckling. This work shows the ability and promise of using the LSM as a fundamental numerical tool for the deep investigation of the buckling mechanical behavior of porous solids.  相似文献   

Effects of Solid Organic Wastes on Soil Particulate Organic Carbon Structure Under Different Water Conditions     

Xiaojing Qu  Jinggui Wu  Jinghong Zhao  Jianming Li  Juan Hu  Opoku‐Kwanowaa Yaa 《洁净——土壤、空气、水》2019,47(8)

  相似文献   

Analytical solution of seismic response of base-isolated structure with supplemental inerter     

Kun Ye  Shuai Shu  Liang Hu  Hongping Zhu 《地震工程与结构动力学》2019,48(9):1083-1090

Closed-form solutions are derived for the modal characteristics and seismic response of a base-isolated structure equipped with additional inerters. By simplifying the structure-isolator-inerter system in terms of the two-degree-of-freedom (2DOF) model, the modal frequencies, mode shapes, damping ratios, and participation factors of the system are derived. Consequently, analytical seismic response solutions are formulated by the modal superposition method. Utilizing these analytical solutions, an extensive parametric study has been carried out to investigate the effect of supplement inerters on both the modal characteristics and seismic response of the structure-isolator-inerter system. There is a critical inertance leading to the zero second modal participation factor (ie, the disappearance of the second modal response). The associated critical inertance ratio is derived in closed form as well. Moreover, it is observed that the reduction of deformation of isolators by increasing the inertance may be offset by the increase in relative displacements of the superstructure. To circumvent this adverse effect, an optimal range of inertance is identified whereby both the deformation of isolators and the relative displacement of the superstructure are mitigated concurrently.  相似文献   

北部湾典型海岛生态系统服务价值空间异质性对比研究     

田义超  黄远林  张强  陶进  张亚丽  黄鹄  梁铭忠  周国清 《海洋科学》2019,43(2):60-68

基于北部湾海域典型海岛高分1号数据,借助于CART决策树方法,获取了广西北部湾两个典型海岛的景观格局数据,并采用生态系统服务价值计量模型、空间自相关模型及地统计学中的变异函数模型对其生态系统服务价值进行了空间异质性分析。结果表明:团和岛单位面积生态系统服务价值是七星岛的1.08倍,但其变异系数低于七星岛;七星岛由于其地质背景为泥沙岛,景观格局受到人类活动以及自然环境的强烈干扰,趋向于复杂化和破碎化;而团和岛由于所处的外部环境以及自身的地质特征,景观格局呈现出整体斑块化分布状态;团和岛的景观格局主要受到结构性因素的控制,而七星岛则以随机性因素控制为主,选用变程和Moran’s指数来表征其复杂化和破碎化,来决定其优先开发时序,可对前者进行适当开发,而对后者适当进行生态保护;对受到结构性因素影响的岛屿在进行开发时,时序的识别选用变程和Moran’s指数来表征,若变程和Moran’s指数越小,说明海岛整体的景观分布格局趋向于复杂化和破碎化,反之生态系统较好,可进行优先开发。同时本文构建了北部湾海岛生态系统异质性评估与自然资源管理框架,并提出了海岛管理的建议与对策。  相似文献