WebGIS性能分析与优化

随着WebGIS的发展,用户对数据浏览、查询和分析等要求也越来越高。提高服务性能、满足用户需求已成为WebGIS发展的当务之急。本文在对WebGIS体系结构分析的基础上,主要从时间方面对其性能展开分析,通过实例进行验证。其实验结果表明,采取相应优化措施,对提高WebGIS服务性能取得了比较明显的效果,同时也达到了预期目的。     

BDS-3新频点信号双频精密单点定位精度分析

北斗卫星导航系统(BeiDou navigation satellite System, BDS)已于2020年7月正式建成并开通, 北斗三号(BDS-3)在旧信号B1I和B3I的基础上, 增加了B1C、B2a新信号. 为了全面评估BDS-3的新信号B1C、B2a的定位性能, 试验了GPS (Global Positioning System)、BDS-3、BDS-2/BDS-3新旧信号的定位性能和BDS系统不同频点与GPS组合定位性能, 对BDS (B1I+B3I、B1C/B2a)+GPS (L1+L2)组合静态PPP (Precise Point Positioning)定位性能进行分析, 并与单卫星系统对比分析. 试验结果表明: BDS-3 (B1C/B2a)在East (E)、\lk North (N)、Up (U)方向的定位精度优于1.25cm、0.89cm、1.67cm, BDS-3新旧频点在E、N方向上定位精度与GPS L1/L2在同一水平上, U方向上新频点定位精度高于GPS L1/L2和BDS-3旧频点, 较旧频点定位精度提升了34.2%, 新频点收敛时间25.9min比旧频点提升了12.7%; 相较于BDS、GPS单系统, 组合系统BDS/GPS定位精度和收敛时间有了明显的提高, BDS-3 (B1C/B2a)+GPS在E、N方向上与BDS-3 (B1I/B3I)+GPS定位精度相当, 在U方向上定位精度前者较后者有了明显的提升, 提升了17.2%, 组合系统新频点收敛时间20.1min比旧频点提升了17.6%.     

基于新型探测资料对西安一次弱降水预报失误的原因分析

利用微波辐射计、激光测风雷达、多普勒雷达、相控阵雷达等新型探测资料、地面加密观测资料、ERA5再分析及多模式数值预报结果对2022年4月24日西安城区一次弱降水预报出现明显失误的原因进行分析,结果表明：(1)全球数值预报模式和中尺度数值预报模式对本次过程西安城区均报有明显降水,主要原因为模式对低层相对湿度预报明显偏大;(2)多种新型探测数据分析认为近地层湿度条件较差及中层的绝对水汽含量低,中层的干暖空气不利于成云致雨,垂直上升运动不强,且由于低层非常干燥,使水滴在下沉过程中蒸发,从而无法形成雨滴下落,这些原因共同造成西安城区无降水,低层相对湿度预报偏大是造成这次西安城区降水预报失误的主要原因之一;(3)造成西安城区近地层湿度条件差的原因是城市干热岛效应和低层干暖平流输送,且降水云团翻越秦岭后其湿空气绝热下沉至城区后出现增温降湿,使得城区形成较为深厚的干层,即使有雨滴在下落过程中也会造成更强的蒸发,这也是城区没有降水的重要原因之一;(4)预报员主观预报订正出现空报主要是源于对边界层水汽、抬升条件等关键降水要素缺乏订正能力,且对大城市的干热岛效应和秦岭山区地形影响研究不足。     

Characteristics and evolution of lacustrine turbidite of Chang-7 Member of Yanchang Formation in northern Shaanxi

Lacustrine turbidite of Chang-7 Member in the studied area consists of sihstone and fine sandstone with respect to grain size, which is feldspathic lithie sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-7t, which can be favorable reservoir in deep-water.     

复合型滑坡体系统的工程地质勘察及其稳定性分析

滑坡工程地质勘察及其稳定性分析是滑坡治理工程设计及施工的重要依据.国道316线福建境内K160+840~K161+020山体滑坡是由2个主滑动轴线所构成的复合滑坡体,它具有牵引和推移性质特征,发育2个主滑动面和2个次滑动面.详细论述了复合滑坡体工程地质勘察的内容及侧重点.该滑坡体自然状态下的稳定系数为1.025,处于临界稳定状态,但安全储备极低,必须及早进行工程治理.     

织金白岩村大旗山崩塌危岩带发育特征及稳定性评价

通过对织金县城关镇白岩村危岩(崩塌带)调查,结合危岩体发育特征及周边地质环境状况,对危岩体稳定性进行定性评价和定量评价,并提出防治措施。     

消除全空域效应:原理、装置与应用实例

如何消除"全空域效应"是电磁勘探中的难题,国内外学者试图从基础理论、数据处理、测线布设等方面入手来解决,但存在求解条件苛刻、计算繁杂、技术实现困难、成本高等问题.文中提出了用屏蔽装置直接消除全空域效应以逼近地面式测量的新思路,研制了相应的装置,给出了使用方法和应用实例,取得了良好的实践效果.     

地震波的计算机自动提取——智能跟踪与细化

本文通过对地震图特征的分析,提出了一个地震波的计算机自动提取方法.该方法由地震图扫描输入、灰度规一化、水平线消除、时标和起震点提取及智能跟踪与细化等步骤组成.在地震波的跟踪与细化过程中,充分利用了地震波的先验知识,以提高地震波自动提取的智能化水平.实验证明,该方法可取得较满意的结果.     

中国沙漠（地）生态系统水文调控功能及其服务价值评估

荒漠生态系统是整个生物圈中分布较广的一个系统,是陆地生态系统中一个重要的子系统。开展荒漠生态系统服务价值研究和评价,对荒漠生态系统重要性认识和管理具有重要的现实意义。本文基于中国沙漠（地）生态系统的生态水文过程、水平衡机理和水文调控功能等,对其在淡水提供、原盐生产、水源涵养和气候调节方面的物质流——水资源进行了核算,结合不同类型生态服务价值通量,初步评估了中国荒漠生态系统在水文调控方面的服务价值。结果表明:中国沙漠（地）生态系统水文调控方面的生态服务价值为每年5 510.05亿元,其中供给服务价值370.42亿元,调节服务价值5 139.63亿元,分别占总服务价值的6.72%和93.28%。     

Spatial-temporal patterns of China’s interprovincial migration, 1985-2010

Migration plays an increasing role in China's economy since mobility rose and economic restructuring has proceeded during the last three decades. Given the background of most studies focusing on migration in a particular period, there is a critical need to analyze the spatial-temporal patterns of migration. Using bicomponent trend mapping technique and interprovincial migration data during the periods 1985-1990, 1990-1995, 1995-2000, 2000-2005, and 2005-2010 we analyze net-, in-, out-migration intensity, and their changes over time in this study. Strong spatial variations in migration intensity were found in China's interprovincial migration, and substantial increase in migration intensity was also detected in eastern China during 1985-2010. Eight key destinations are mostly located within the three rapidly growing economic zones of eastern China (Pearl River Delta, Yangtze River Delta and Beijing-Tianjin-Hebei Metropolitan Region), and they are classified into three types: mature, emerging, and fluctuant origins, while most key origins are relatively undeveloped central and western provinces, which are exactly in accordance with China's economic development patterns. The results of bicomponent trend mapping indicate that, in a sense, the migration in the south was more active than the north over the last three decades. The result shows the new changing features of spatial-temporal patterns of China's interprovincial migration that Fan and Chen did not find out in their research. A series of social-economic changes including rural transformation, balanced regional development, and labor market changes should be paid more attention to explore China's future interprovincial migration.