基于物流企业数据的2007-2017年中国城市网络空间特征及演化     

宗会明  吕瑞辉 《地理科学》2020,40(5):760-767

采用2007、2012和2017年中国百强物流企业网络数据,运用世界城市网络研究的链锁网络模型方法,分析中国城市网络的等级结构、空间分异、空间联系及其演变特征。研究表明：基于物流企业数据的中国城市网络具有明显的层级特征,并呈现“两主多中心”的区域空间结构,网络联系的离散水平逐渐降低,其稳定性和均衡性有所增加,等级结构趋于合理;各节点城市组织能力空间分异明显,京津冀、长三角、珠三角的组织能力和介中心性始终处于较高水平,城市间物流联系逐渐增强,并有协同发展的趋势;城市网络联系中,长江沿线城市物流网络联系地位上升,上海为中心的T字型空间结构替代以北京为中心的核心网络结构,在全国尺度形成以胡焕庸线为界线,物流联系网络呈中东部密集、西部相对稀疏的空间格局,其演变过程呈现由等级网络联系特征向等级性与空间近邻性网络联系特征转变趋势。  相似文献   

地震台阵监测能力综述     

郝春月  郑重 《地震地磁观测与研究》2020,41(6):3-14

根据各大网站地震目录和前人研究成果，分析全球地震台网与地震台阵、我国区域台网与地震台阵的监测能力，阐述了地震台阵与密集台网/台阵的区别。研究表明，对同一地区所检测的地震数，地震台阵是地震台网的3-10倍，而震级下限可降低1.2-2级。一般情况下，以微弱信号检测为目的的地震台阵监测能力均优于以结构研究为目的的密集台网/台阵，2种台阵是目的、性质、孔径、形状、台间距、技术手段、研究方法均不同的监测系统。  相似文献   

全球海潮模型最新进展及在中国沿海精度评估     

范长新 《大地测量与地球动力学》2019,39(5):476-481

介绍TPXO、FES、Chinatide、MIKE Global Tide、Utide等典型海潮模型，总结归纳其同化潮汐数据来源和最新的海洋地形数据，利用我国沿岸长期验潮站以外的26个中短期潮位观测站评估TPXO等海潮模型预报精度。结果表明，全球海潮模型对我国沿海M2分潮的预报精度普遍较低，且主导了几种海潮模型在中国海域的整体预报精度；相比MIKE Global Tide和TPXO7.2,TPXO8、TPXO_Yellow Sea 2010和TPXO_China&Ind模型在我国沿海的预报精度更高。  相似文献   

基于全球分布的地震观测数据估计0S0模态的特征频率及品质因子     

周丰森  王迪晋  旦增 《大地测量与地球动力学》2019,39(10):1013-1016

选取2011-03-11日本MW9.3地震后全球地震台站记录的约220 h波形数据，基于一定的判断准则，筛选出质量较高的448个垂向观测数据，采用频域AR方法对0S0模态的特征频率和品质因子进行估值，并以信噪比为权重进行加权平均，得到特征频率f=0.814 658 4±5.3×10-7，品质因子Q=5 586±12。该结果与已有研究成果相比精度更高，有助于约束现有地球介质密度和衰减模型，使其更接近真实地球。  相似文献   

云南武定县朱家坝尾矿库渗漏原因浅析     

周南  李卿  喻涌麒 《云南地质》2020,(1):118-124

位于云南省楚雄州武定县朱家坝新建尾矿库,在使用过程中,该尾矿库下游一泉水点出现尾矿粉渗漏污染,通过地质勘查,发现该尾矿库下伏昆阳群绿汁江组(Pt2lz)的白云岩基底,存在一隐伏断层,渗漏污染原因与该断层及其形成的岩溶裂隙有直接的关系。  相似文献   

无人机在露天矿山监测中的应用   总被引：3，自引：0，他引：3  

白洋  康会涛  张文超  贾玉娜  郑浩 《测绘通报》2020,(9):85-88

在露天矿山开采过程中，对矿山进行实时动态监测很有必要，它不仅能够实时掌握开采进度和开采方案实施的准确性，还有利于数字矿山建设。本文以河北省保定市涞源县某露天矿区为例，利用Pix4Dmapper软件对无人机航拍影像进行数据采集与处理，获取矿区的三维点云数据、数字正射影像和数字地表模型，并利用ArcGIS和Global Mapper软件对生产成果进行矿山开发占地分析，实现露天矿山三维可视化。本文为准确掌握矿山环境治理执行情况，把握矿山开发整体情况给予了有力的参考和借鉴作用。  相似文献   

基于MCR模型和DO指数的九江滨水城市生态安全网络构建   总被引：1，自引：1，他引：0  

戴璐  刘耀彬  黄开忠 《地理学报》2020,75(11):2459-2474

兼顾生态保护和经济增长的生态安全网络对引导滨水城市走可持续发展道路具有重要指导意义。本文以九江市为例,采用景观生态数据集和产业信息数据集,结合最小累积阻力模型（MCR）和连续空间的产业集聚测度指数（DO）构建了综合评价方法,分别对景观生态格局和经济生产空间进行分析,诊断二者的空间冲突确定战略节点并构建生态安全网络。结果表明：① 研究区包含重要生态源地29个,总面积为7323 km²;生态安全阻力高值区面积占39.69%,位于城市中部和东部连片区域,低值区则处于外围,且连通过渡区域较少,呈现空间上两极分化的“中心—外围”景观生态格局;② 经济生产空间临近水资源分布,呈现为小尺度集聚、大尺度分散的空间格局;主要产业集聚区的平均长度和数量均显示出重度污染行业>轻度污染行业>中度污染行业的空间关系;③ 识别出景观生态廊道总长685.57 km,选取了25个生态—经济战略节点,规划了18条总长424.53 km的重要绿带和26条总长662.46 km的一般绿带,共同构成了“蜂巢状”九江市生态安全网络格局。本文采用自然和经济条件相结合的综合分析视角,为生态安全格局的构建提供了多样化的实现途径。  相似文献   

Dynamic loading tests and seismic response analysis of a stud-type damper composed of multiple friction units with disc springs     

Takeshi Sano  Kazutaka Shirai  Yasumasa Suzui  Yoshikazu Utsumi 《地震工程与结构动力学》2020,49(13):1259-1280

This paper presents an experimental study on the performance of a shear-sliding stud-type damper composed of multiple friction units with high-tension bolts and disc springs. A numerical evaluation of the response reduction effects achieved by the stud-type damper is also presented. In dynamic loading tests, the behavior of stud-type multiunit friction damper specimens was investigated. Three different full-scale damper specimens, which were composed of five, six, or seven friction units with two or four sliding surfaces, were incorporated into loading devices for testing. The stud-type friction dampers demonstrated stable rigid-plastic hysteresis loops without any remarkable decrease in the sliding force even when subjected to repetitive loading, in addition to showing no unstable behavior such as lateral buckling. The damper produced a total sliding force approximately proportional to the number of sliding surfaces and friction units. The total sliding force of the stud-type damper can thus be estimated by summing the contributions of each friction unit. In an earthquake response simulation, the control effects achieved by stud-type dampers incorporated into an analytical high-rise building model under various input waves, including long-period, long-duration and pulse-like ground motions, were evaluated. A satisfactory response reduction was obtained by installing the developed stud-type dampers into the main frame without negatively impacting usability and convenience in terms of building planning.  相似文献   

Debris-flow-dominated sediment transport through a channel network after wildfire     

Petter Nyman  Walter A.C. Box  Justin C. Stout  Gary J. Sheridan  Saskia D. Keesstra  Patrick N.J. Lane  Christoph Langhans 《地球表面变化过程与地形》2020,45(5):1155-1167

Field studies that investigate sediment transport between debris-flow-producing headwaters and rivers are uncommon, particularly in forested settings, where debris flows are infrequent and opportunities for collecting data are limited. This study quantifies the volume and composition of sediment deposited in the arterial channel network of a 14-km² catchment (Washington Creek) that connects small, burned and debris-flow-producing headwaters (<1 km²) with the Ovens River in SE Australia. We construct a sediment budget by combining new data on deposition with a sediment delivery model for post-fire debris flows. Data on deposits were plotted alongside the slope–area curve to examine links between processes, catchment morphometry and geomorphic process domains. The results show that large deposits are concentrated in the proximity of three major channel junctions, which correspond to breaks in channel slope. Hyperconcentrated flows are more prominent towards the catchment outlet, where the slope–area curve indicates a transition from debris flow to fluvial domains. This shift corresponds to a change in efficiency of the flow, determined from the ratio of median grain size to channel slope. Our sediment budget suggests a total sediment efflux from Washington Creek catchment of 61 × 10³ m³. There are similar contributions from hillslopes (43 ± 14 × 10³ m³), first to third stream order channel (35 ± 12 × 10³ m³) and the arterial fourth to fifth stream order channel (31 ± 17 × 10³ m³) to the total volume of erosion. Deposition (39 ± 17 × 10³ m³) within the arterial channel was higher than erosion (31 ± 17 × 10³ m³), which means a net sediment gain of about 8 × 10³ m³ in the arterial channel. The ratio of total deposition to total erosion was 0.44. For fines <63 μm, this ratio was much smaller (0.11), which means that fines are preferentially exported. This has important implications for suspended sediment and water quality in downstream rivers. © 2019 John Wiley & Sons, Ltd.  相似文献   

Surficial fractures in the Navajo sandstone,south-western USA: the roles of thermal cycles,rainstorms, granular disintegration,and iterative cracking     

David B. Loope  Garrison R. Loope  Caroline M. Burberry  Clinton M. Rowe  Gerald C. Bryant 《地球表面变化过程与地形》2020,45(9):2063-2077

Deep (> 5 m) sheeting fractures in the Navajo sandstone are evident at numerous sites in southern Utah and derive from tectonic stresses. Strong diurnal thermal cycles are, however, the likely triggers for shallow (< 0.3 m) sheeting fractures. Data from subsurface thermal sensors reveal that large temperature differences between sensors at 2 and 15 cm depth on clear summer afternoons are as great as those that trigger sheeting fractures in exposed California granite. Extensive polygonal patterns in the Navajo sandstone are composed of surface-perpendicular fractures and were produced by contractile stresses. Numerous studies have shown that porewater diminishes the tensile strength of sandstone. Based on our thermal records, we propose that cooling during monsoonal rainstorms triggers polygonal fracturing of temporarily weakened rock. On steep outcrops, polygonal patterns are rectilinear and orthogonal, with T-vertices. Lower-angle slopes host hexagonal patterns (defined by the dominance of Y-vertices). Intermediate patterns with rectangles and hexagons of similar scale are common. We posit that outcropping fractures are advancing downward by iterative steps, and that hexagons on sandstone surfaces (like prismatic columns of basalt) have evolved from ancestral orthogonal polygons of similar scale. In lava flows, fractures elongate intermittently as they follow a steep thermal gradient (the source of stress) as it rapidly moves through the rock mass. In our model, a steep, surficial thermal gradient descends through unfractured sandstone, but at the slow pace of granular disintegration. Through time, as the friable rock on stable slopes erodes, iterative cracking advances into new space. Hexagonal patterns form as new fractures, imperfectly guided by the older ones, propagate in new directions, and vertices drift into a configuration that minimizes the ratio of fracture length to polygon area. © 2020 John Wiley & Sons, Ltd.  相似文献