Deep origin of Cenozoic volcanoes in Northeast China revealed by 3-D electrical structure

The three-dimensional(3-D)electrical structure of the upper-mantle was used to examine the deep origins of and relationship among the Cenozoic volcanoes located in Northeast China(NEC).High-quality,long-period magnetotelluric(LMT)full-impedance tensor data were collected in NEC and subjected to 3-D Gauss-Newton inversion in order to construct a resistivity model.The resulting model reveals the presence of multiple localized low-resistivity anomalies(LRAs)within the high resistivity lithosphere beneath NEC.These LRAs partially coincide with Cenozoic volcanoes on the surface.Three LRAs that form a larger,annular LRA were observed in the deep upper mantle beneath the Songliao Basin,whereas vein-like LRAs were found in the asthenosphere that connect the lithosphere and deep upper mantle.Petrophysical analyses suggest that the LRAs may have been caused by fluid-induced melting.Based on our electrical model,we propose that,following dehydration of the subducted Western Pacific slab into the mantle transition zone(MTZ)beneath NEC,the released water migrated upward and caused partial melting at the top of the MTZ beneath the Songliao Basin.Under the effect of buoyancy,the melted mantle formed a thermal upwelling that caused melting of asthenosphere before diapiring at the base of the dry lithosphere.The magma then penetrated structural boundaries(such as thinner,weaker,or activated suture zones)and finally reached the Earth's surface.This melting and upwelling of hot mantle materials may have resulted in large-scale volcanism in the region throughout the Cenozoic,including the eruption of Changbai Mountain and Halaha Volcanoes.Our results suggest that the Cenozoic NEC volcanoes may all share a similar mode of genesis,and probably originated from the annular LRA in the deep upper mantle.     

基于ArcGIS Engine的自主旅游信息系统的设计和实现

传统旅游信息系统注重旅游信息的查询以及决策和管理,很少有自主发布信息的、个性化的、注重自主享受旅游和回顾评价旅游过程的信息系统出现。为此,本文以C#语言为基础用Arc GIS Engine二次开发的方法,设计和实现了一个自主旅游信息系统原型,详细剖析了该系统的设计和实现流程,测试表明该系统能初步满足游客个性化旅游的要求,为宣传"智慧旅游"提供了新的方法和手段。     

Effects of non-submerged boulder on flow characteristics – A field investigation

The effect of fully submerged boulders on the flow structure in channels has been studied by some researchers. However, many natural streams have bed material with boulders that are not fully submerged under water. In many natural streams, boulders cover between 1% and 10% of the area of the stream reach. The effect of non-submerged boulders on the velocity profile and flow characteristics is very important for assessing riverbed deformation. The objectives of this paper are to find the pattern of velocity distribution around a non-submerged boulder and to compare it with the classical studies on flow resistance and Reynolds stress distribution in open channels. Also, by considering the variation in the Reynolds stress distribution at different locations around a non-submerged boulder, the effect of a non-submerged boulder on the estimation of shear velocity and resistance to flow has been investigated. Results indicates that inside the scour hole caused by a non-submerged boulder in a river velocity distributions are irregular. However, velocity distributions are regular outside the scour hole. The presence of the boulder causes a considerable deviation of the Reynolds shear stress from the classic distribution, showing a non-specific distribution with negative values. The classical methods for calculating shear velocity are not suitable because these methods do not give detailed velocity and Reynolds stress distributions in natural rivers with a lot of boulders. Thus, the effect of a non-submerged boulder on the estimation of the resistance to flow by considering the variations in velocity and Reynolds stress distributions at different locations around a non-submerged boulder is important and needs to be studied in a natural river instead of just in laboratory flumes. The negative values in Reynolds stress distribution around a boulder indicate that the classical methods are unable to predict resistance to flow, and also show strong turbulence inside the scour hole where the complex flow conditions present ambiguous Reynolds stress distributions. In the current study, to obtain a reasonable estimation of parameters in natural rivers, the classical method has been modified by considering velocity and Reynolds stress distributions through the boundary layer method.     

海上距离元胞自动机分析法

针对障碍存在情况下距离变换研究较少的问题,提出了一种基于元胞自动机的绕障欧氏距离变换方法。以南海为例,基于海陆分布数据和目标点数据,以最短绕障路径长度为元胞状态,设计了包含距离算子的元胞状态转换规则。通过元胞自动机模拟距离扩散计算过程,得到绕障距离变换结果,并分析了绕障效果和精度。结果表明:本文方法动态直观地展示了绕障距离变换过程,能够自动计算绕过障碍的最短距离;具有更新机制,能够根据邻域的变化修正状态值;为绕障距离变换问题提供了一种近似的解决途径,错误率低于3.96%,可应用于航线设计、海上救助等领域。     

利用星载SAR单轨多角度地距图像提取高程信息

针对传统基于多个轨道上获得的不同星载SAR图像提取场景区域高程信息的方法具有系统复杂度较大的问题,该文提出一种利用星载SAR单轨多角度地距图像之间像点偏移量进行高程提取的方法。像点偏移是由星载SAR观测航迹的弯曲带来的。根据距离-多普勒原理,不同角度的地距子孔径图像之间存在与高程相关的像点偏移。文中推导了星载几何下高程值和像点偏移量之间的关系式,并得出了高程值和像点偏移量是近似线性关系这一结论,最后通过仿真实验验证了该方法。结果表明,该方法提取成像场景区域的高程信息是可行的。     

基于GIS与模糊层次分析法的景观视觉资源综合评价

景观视觉评价是评判景观视觉资源价值的重要方式。本研究从景观视觉的综合定量评价角度出发,设计基于基本视觉元素与景观视觉敏感度的综合评价指标体系,提出一种基于GIS空间分析与模糊层次分析法的景观视觉综合评价方法,利用综合视觉指数分别从整体视角和单因子视角客观揭示景观视觉资源的分布特征及其影响因素。以泰山风景区为研究区的实验结果显示：单因子视角中,玉皇顶、天烛峰、碧霞祠等景点分别在视域范围、相对坡度敏感度、相对距离敏感度等侧面具有最高的评分。综合视角下,景观视觉指数最高的景点为玉皇顶（0.819）,最低的景点为桃花峪（0.180）。通过与基于用户打分的景点评价结果的对比,验证了本方法的可靠性与先进性,为定量化描述与评价景观视觉资源提供了一种新的研究思路和研究方法,也为景区综合发展规划及景点的开发保护提供了客观的参考依据和决策支持。     

Water Security-based Hydrological Regime Assessment Method for Lakes with Extreme Seasonal Water Level Fluctuations: A Case Study of Poyang Lake,China

Extreme seasonal water level fluctuations characterize natural floodplain lakes in monsoon regions, which are crucial for ensuring lake water security, including flood prevention water supply and health of aquatic ecosystem. In order to achieve this goal, we established a hydrological regime assessment method based on a set of hydrological indicators for lakes with heavy seasonal water level fluctuations. The results suggest that time-sensitive hydrological indicators and specific time scales for various water security aspects must be considered. We discovered that it is more practical and meaningful to combine the water level classification derived from statistical analyses with characteristic hydrological values linked to water security. The case study of Poyang Lake results show that there are no discernable trends of Poyang Lake water regime status over the last 35 years, and the two periods of poor status are in accordance with climate variation in the lake basin area. Scholars and policy makers should focus on both floods and droughts, which are the main water security problems for Poyang Lake. It is hoped that this multi-scale and multi-element hydrological regime assessment method will provide new guidelines and methods for other international scholars of river and lake water assessment.     

秦巴山区乡村交通环境脆弱性及影响因素——以陕西省洛南县为例

山区乡村长期处于地形地貌制约、自然灾害频发的风险胁迫之下,乡村交通系统网络化水平低、抗灾能力弱,交通环境脆弱性问题突出。以秦巴山区洛南县为例,基于人地关系脆弱性的暴露、敏感、应对能力3个维度构建了涵盖风险事件、地理特征、关键出行路径、路网结构、交通工具、家庭资本等要素的乡村交通环境脆弱性基本构成框架,并针对性建立了评估指标体系。依托ArcGIS和GeoDa软件解析了洛南县交通环境脆弱性的空间结构和空间自相关特征,运用地理加权回归模型探寻了自然、人口、社会、经济因素对交通风险应对能力的影响及空间差异。结果显示：交通环境脆弱性以县城及城郊为中心向外递增形成圈层结构,且垂直差异显著;暴露度、敏感性均与应对能力呈现显著的空间负相关性,脆弱性局部“热点”区域广泛分布于北部中山地带,且陷入了高暴露、高敏感、低应对能力的窘境。“冷点”区域多为城郊或邻近镇区的村庄,敏感性低,应对能力高;地形条件、产业分布、人口结构与受教育程度、家庭规模对交通风险应对能力有显著影响,影响性质及强度存在空间差异。     

我国反水雷支援舰能力建设探讨

随着我国海军的战略转型,我军反水雷作战任务发生了变化,除了传统的近岸/ 近海反水雷任务,还增加了海峡反水雷、交通线反水雷以及海外基地反水雷等任务。 反水雷支援舰综合作战能力强、信息化与自动化程度高,在作战时为反水雷兵力提供指控、控制、通信及补给等方面的支持,快速提升反水雷系统的信息化、无人化、模块化水平,使反水雷装备能够协同工作,实现反水雷作战效能的最大化,是提高海军现有反水雷作战能力的理想装备。     

基于水池试验的毛发缆减阻性能研究

为了研究毛发长度和毛发密度对毛发缆减阻性能的影响,设计并进行了水池试验。通过研究6种不同毛发长度、不同毛发密度拖缆的阻力系数随航速的变化,找到减阻效果最优的缆型,得到最佳缆型的减阻率。结果显示：在相同的迎流角下,圆缆的阻力系数在1~1.1左右,毛发缆的阻力系数随速度变化不明显;在毛发长度为9~11倍拖缆直径、毛发密度为60根/m时,毛发缆的减阻效果最优,减阻率可达20%。验证了毛发缆具有很好的减阻性能,为大深度拖曳系统的缆型设计提供了参考依据。