Dynamics and local boundary properties of the dawn-side magnetopause under conditions observed by Equator-S

Magnetic field measurements, taken by the magnetometer experiment (MAM) on board the German Equator-S spacecraft, have been used to identify and categorise 131 crossings of the dawn-side magnetopause at low latitude, providing unusual, long duration coverage of the adjacent magnetospheric regions and near magnetosheath. The crossings occurred on 31 orbits, providing unbiased coverage over the full range of local magnetic shear from 06:00 to 10:40 LT. Apogee extent places the spacecraft in conditions associated with intermediate, rather than low, solar wind dynamic pressure, as it processes into the flank region. The apogee of the spacecraft remains close to the magnetopause for mean solar wind pressure. The occurrence of the magnetopause encounters are summarised and are found to compare well with predicted boundary location, where solar wind conditions are known. Most scale with solar wind pressure. Magnetopause shape is also documented and we find that the magnetopause orientation is consistently sunward of a model boundary and is not accounted for by IMF or local magnetic shear conditions. A number of well-established crossings, particularly those at high magnetic shear, or exhibiting unusually high-pressure states, were observed and have been analysed for their boundary characteristics and some details of their boundary and near magnetosheath properties are discussed. Of particular note are the occurrence of mirror-like signatures in the adjacent magnetosheath during a significant fraction of the encounters and a high number of multiple crossings over a long time period. The latter is facilitated by the spacecraft orbit which is designed to remain in the near magnetosheath for average solar wind pressure. For most encounters, a well-ordered, tangential (draped) magnetosheath field is observed and there is little evidence of large deviations in local boundary orientations. Two passes corresponding to close conjunctions of the Geotail spacecraft are analysed to confirm boundary orientation and motion. These further show evidence of an anti-sunward moving depression on the magnetopause (which is much smaller at Equator-S). The Tsyganenko model field is used routinely to assist in categorising the crossings and some comparison of models is carried out. We note that typically the T87 model fits the data better than the T89 model during conditions of low to intermediate K_p index near the magnetopause and also near the dawn-side tail current sheet in the dawnside region.     

浮式两级缓冲防撞系统及浮体结构构型研究

以浮式两级缓冲防撞系统为研究对象,介绍其工作原理,利用动力学分析软件LS-DYNA构建了碰撞模型并进行了仿真计算,依据仿真结果完成了以阻尼索组与浮体结构构型为主要内容的防撞系统设计。研究确定了阻尼索组的布置位置、材料及数量,为浮体内部结构构型设计了7种比选方案,分别对5 000 t船舶撞击浮体前梁和侧梁的动态过程进行了仿真分析,对比了不同方案及不同板梁厚度下的接触力。研究结果表明:浮体内部构造若选用板梁厚度12 mm的方案6设计,则碰撞发生时浮体前梁和侧梁分别可以稳定地提供10.4 MN和7.9 MN的均值力,以及11.5 MN和8.9 MN的峰值力,设计浮体能够满足整体刚度要求,防撞系统符合双保护原则。防撞系统及浮体结构构型设计为下一步全面开展船舶撞击防撞系统后的动力学响应分析奠定了基础。     

基于流场强度评价的点坝砂体特高含水期水平井挖潜技术

针对高含水期油藏点坝砂体剩余油挖潜困难等问题,通过室内实验明确中高渗储层高倍水驱物性变化规律,确定时变数值模拟方法,基于渗流场强度的评价将油藏划分为三类渗流特征分区,通过点坝砂体内部构型的建模方法确定特高含水期水平井的部署位置.研究表明:基于流场强度分布的水平井部署方法能够突出反映高含水期点坝砂体内部流体流动的非均质性...     

海峡西岸城市群旅游经济网络演化的动力机制与因果组合配置

以海峡西岸城市群为例,通过修正引力模型构建旅游经济网络,依托“增长极”理论,运用QAP和地理探测器分析方法,探讨旅游经济网络驱动因素,并运用fsQCA方法探讨其因果组合配置策略。结果如下：(1)海峡西岸城市群旅游经济网络空间结构呈东部沿海地区网络相对密集、中西部网络稀疏特征。(2)地区经济水平、对外开放程度是其核心驱动因素;各影响因子对促进旅游经济空间发展的影响强度均较高。(3)地理探测器分析结果显示,各影响因素在旅游经济网络系统中处相对优势地位,旅游经济空间发展核心驱动因素明显,其中,以地区GDP、对外开放程度最为突出,这也体现为旅游需求不断提升以及旅游供给向高质量方向发展的趋势。研究最终识别出两种因果组合配置方案。本研究有助于实现区域旅游经济空间发展优化及管理。     

基于Oracle 9i和ArcSDE的城市基础地理数据库配置研究

在城市地理信息系统中,数据库是其核心组成部分,而数据库的配置是否合理则又直接影响到数据库建成后的性能及应用。本文以赣州市基础地理数据库为例探讨基于Oracle 9i和ArcSDE的城市基础地理数据库配置问题。     

Coaxial coil towed EMI sensor array for UXO detection and characterization

A new broadband electromagnetic induction (EMI) array sensor, GEM-5, for detecting and characterizing Unexploded Ordnance (UXO) has been developed in order to provide high production rates for EMI surveys. The sensor consists of a single rectangular loop transmitter around a linear array of seven pairs of coaxial receiver coils, with each coil in a pair located at the same vertical distance above and below the loop transmitter. The coil pairs are wired in an inverted series so that the signal consists of the difference between the voltage induced in the upper and lower coils. This particular configuration provides a high degree of primary field cancellation, dense spatial sampling rate due to simultaneous and continuous operation of all sensors, suppression of motion-induced and environmental noise, and strong source fields at typical UXO burial depths providing deep detection range. Our prototype tests indicate that the array yields a lower static and motion-induced noise over the critical low frequencies than that of existing sensors, and in particular, the signal-to-noise ratio at 90 Hz is 32 dB higher. Environmental noise can be largely removed from the difference measurements. The field test results from UXO test sites show that the prototype sensor has smoother background and appears to detect more seeded targets than the GEM-3 concentric sensor, however some of that gain can be attributed to higher power transmitter electronics.     

华南弧形海岸岸线形态与地貌发育模式

Coastline configuration indexes of 34 typical arc-shaped coasts in South China are investigated by the method of principal component analysis, and meanwhile deposition and geomorphologic features of arc-shaped coast are also analyzed. The results show: (1) The configuration of arc-shaped coast in South China is of the characteristic of variability and complexity. (2) The wave power and the openings of the bay are the decisive factors to result in the changes of the configuration of the arc-shaped coast in South China, however, incidence direction of the wave has no effect on configuration development of the coast. (3) Commonly, geomorphologic modes of the arc-shaped coast system in South China consist of barriers, lagoons and tidal-inlets, and can be divided into four types:the openings of the bay leaning to the east, the openings of the bay leaning to the south, the openings of the bay leaning to the west and the openings of the bay leaning to the north.     

黄河流域地表水耗损分析

在总结分析黄河流域1956~2000年地表水耗损量逐年过程变化特点的基础上,根据黄河流域大型灌区如上游宁夏引黄灌区、中游关中灌区、下游引黄灌区地表水耗损量结构现状,研究了黄河流域用水量结构调整的思路并论证了其实施可行性,分析了黄河流域地表水供、用、耗、排关系,这对于水资源供需平衡分析、水资源优化配置、维持河流健康生命等方面具有实际意义。     

虚拟地理环境中地图注记的配置研究

在虚拟地理环境的表示中注记配置是一个重要方面,注记配置的好坏直接影响着虚拟地理环境的表达.为此,本文从虚拟地理环境的特点出发,分析了三维环境中注记配置研究存在的不足,主要探讨了注记配置应解决的关键问题、配置规则以及配置参数的质量评价原则.     

ArcEngine插件式GIS二次开发框架的设计与实现

本文针对GIS实际二次开发模式中存在的一些问题,提出了一种更易于开发应用程序的框架模式,框架基于ArcEngine与NET平台进行开发,采用插件武开发技术,按照ArcObjects框架接口规范,在ArcEngine下实现、重写框架类并进行封装而成,通过动态配置管理方式动态地生成菜单、停靠窗体和工具栏等,可以方便地定制应...