Hydrological cycle and water balance estimates for the megadune–lake region of the Badain Jaran Desert,China          下载免费PDF全文

Yan‐Dong Ma  Jing‐Bo Zhao  Xiao‐Qing Luo  Tian‐Jie Shao  Zhi‐Bao Dong  Qi Zhou 《水文研究》2017,31(18):3255-3268

The hydrology and water balance of megadunes and lakes have been investigated in the Badain Jaran Desert of China. Field observations and analyses of sand layer water content, field capacity, secondary salt content, and grain size reveal 3 types of important natural phenomenon: (a) vegetation bands on the leeward slope of the megadunes reflect the hydrological regime within the sandy vadose zone; (b) seepage, wet sand deposits, and secondary salt deposits indicate the pattern of water movement within the sandy vadose zone; (c) zones of groundwater seeps and descending springs around the lakes reflect the influence of the local topography on the hydrological regime of the megadunes. The seepage exposed on the sloping surface of the megadunes and gravity water contained within the sand layer confirm the occurrence of preferential flow within the vadose zone of the megadunes. Alternating layers of coarse and fine sand create the conditions for the formation of preferential flows. The preferential flows promote movement of water within the sand layer water that leads to deep penetration of water within the megadunes and ultimately to the recharging of groundwater and lake water. Our results indicate that a positive water balance promotes recharge of the megadunes, which depends on the high permeability of the megadune material, the shallow depth of the surface sand layer affected by evaporation, the occurrence of rainfall events exceeding 15 mm, and the sparse vegetation cover. Water balance estimates indicate that the annual water storage of the megadunes is about 7.5 mm, accounting for only 8% of annual precipitation; however, the shallow groundwater per unit area under the megadunes receives only 3.6% of annual precipitation, but it is still able to maintain a dynamic balance of the lake water. From a water budget perspective, the annual water storage in the megadunes is sufficient to serve as a recharge source for lake water, thereby enabling the long‐term persistence of the lakes. Overall, our findings demonstrate that precipitation is a significant component of the hydrological cycle in arid deserts.  相似文献   

Slope stability analysis using evolutionary optimization techniques          下载免费PDF全文

A.H. Gandomi  A.R. Kashani  M. Mousavi  M. Jalalvandi 《国际地质力学数值与分析法杂志》2017,41(2):251-264

Slope stability optimization, in the presence of a band of a weak layer between two strong layers, is accounted for in complicated geotechnical problems. Classical optimization algorithms are not suitable for solving such problems as they need a proper preliminary solution to converge to a valid result. Therefore, it is necessary to find a proper algorithm which is capable of finding the best global solution. Recently a lot of metaheuristic algorithms have been proposed which are able to evade local minima effectively. In this study four evolutionary algorithms, including well‐known and recent ones, such as genetic algorithm, differential evolution, evolutionary strategy and biogeography‐based optimization (BBO), are applied in slope stability analysis and their efficiencies are explored by three benchmark case studies. Result show BBO is the most efficient among these evolutionary algorithms and other proposed algorithms applied to this problem. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Transition in place: Dynamics,possibilities, and constraints     

《Geoforum》2016

The Transition Movement is a translocal phenomenon circulated through transnational grassroots networks. This study explores the geographies of the Transition Movement with a theoretical framework that perceives it as both a social movement and a grassroots innovation. Participant-observation of Transition Salt Lake (TSL), located in the suburban metropolis of Salt Lake City, Utah, was conducted, as the United States remains a largely understudied country in regards to this particular movement. In this pursuit, we asked: (i) how and what this transition initiative draws from geographically extensive and intensive relations, (ii) how it combines place-specific elements and generalized models (embeddedness), and (iii) how this impacts the success of the transition initiative and how these impacts (positive or negative) are generated. Place, space, and scale played a large role in defining the nature, dynamics, possibilities, and constraints of this transition initiative. Specifically, geographically intensive and extensive relations were critical for the mobilization of complementary resources. The Transition model was found to be flexible, allowing for the initiative to adopt those elements that worked in place and to focus on locally relevant topics. TSL faced many challenges identified by previous researchers regarding finances, participation, diversity, and intragroup competition. While networking with other similar groups, TSL demonstrated that fertile environments of activism are incubatory pools for grassroots innovations and social movements, and a trade-off was found with competition for resources between local groups.  相似文献   

History of faulting in the Northern Hastings Block,southern New England Orogen     

J. Yan  R. Offler 《Australian Journal of Earth Sciences》2016,63(7):821-841

Brittle failure is common in the Devonian to Permian rocks in the Northern Hastings Block (NHB) and is manifested by faults of different orientation and kinematic histories, but the timing of fault movement is not well defined. In this study, faults in the NHB were analysed with the map pattern of cross-cutting faults used to estimate the relative time of movement and relationship to other faults. We defined five episodes of faulting or fault reactivation that affected the NHB. The Yarras Fault System on the southwestern side of the NHB and the Parrabel Fault and related faults on the eastern side of the NHB are the two major fault systems responsible for transporting and rotating the NHB in the late Carboniferous. Faults on the eastern, northeastern and northern part of Parrabel Dome started and stopped moving after emplacement of the Hastings Block and before the intrusion of the Werrikimbe Triassic granitoids. We suggested that the movement on the major bounding faults is related to the accommodation of the NHB to the folding and cleavage development in the adjoining Nambucca Block, and is associated with the earliest part of the Hunter–Bowen Orogeny. Limited dextral movement on the extensions of the Taylors Arm Fault System caused minor displacements in the northeastern part of the NHB during the Late Triassic. Some small faults cut the Triassic granitoids or Triassic Lorne Basin sediments indicating tectonic activity continued post-Triassic.  相似文献   

分数阶混合随机泛函微分方程的能控性     

杨加顺  胡军浩 《南京气象学院学报》2016,8(2):186-192

主要研究了分数阶混合随机泛函微分方程的能控性.在无限维空间下,假设所考虑方程线性部分生成半群不是紧的,使用非紧性测度技术和Mönch不动点定理,给出了方程能控性充分条件,并通过一个例子说明了结论的有效性.  相似文献   

地壳运动驱动力的探讨——核能与地球演化   总被引：1，自引：0，他引：1  

马学昌 《地质学报》2016,90(1):24-36

本文综合核物理、天文和地质学的最新研究成果,推导出在45亿年前太阳系的全部原始类地行星及其某些卫星(包括地球及月球)上,发生过大规模的、持续的铀、钚链式核裂变,释出了巨大的热能,熔化了整个原始星球。新星球的物质发生了重力分异作用、形成了按密度划分的圈层结构。地球中心是内地核,在高压下压成了固态。铀、钚下沉到内地核顶部停留,继续发生链式核裂变,但改变不了内地核的固态性质。从此处产生的核裂变能,主要以热对流的形式外导。直到前45亿年以后,铀的链式核裂变停止了,只剩下钚的链式核裂变,生成的热能减少了,地球开始冷凝。当熔浆表面温度下降到700~800℃时,较轻的花岗岩质岩浆首先凝固成薄层。它很脆弱、经不起大风浪和潮汐力的冲击,破碎成小块,随着下面对流的玄武岩质熔浆汇集起来,形成大片飘浮物,后来就成为大陸;小片的便成为岛屿。温度逐渐下降,地幔冷凝成固体。温度下降至100℃以下,大气中的水蒸气冷凝成水,下落汇集在地表低凹处,便有了海洋和湖泊。所以海洋底主要分布着玄武岩。从内地核顶部不断产生的核能以"地幔柱"的形式穿过固体地幔,上升至地壳。受坚硬地壳的隔挡、便集中在地壳下构成软流层。当地壳岩石受热软化和可以流动之后,便开始向压力小的方向流动。又受日、月引力和地球自身自转力的作用,软流层的动能又有了增强。这种巨大的能量支配了地壳的升降、褶曲、断裂、变质、岩浆、火山和地震等活动。地球是天体之一,无时不受自然界各种作用力的影响,但支配它演化的主要作用力是核能。本文还简述了核能、核素与太阳系星体演化的关系。  相似文献   

城区地表形变差分TomoSAR监测方法     

王爱春  向茂生  汪丙南 《测绘学报》2016,45(12):1413-1422

压缩感知技术(CS)的差分TomoSAR技术解决了中高分辨率SAR数据在城区出现的叠掩问题,实现了城区地表形变信息的重构,但是该方法仅利用了目标的稀疏特性并没有考虑目标的结构特性,对具有这两种特性的目标进行重构时其性能较差。针对这一问题,本文采用联合Khatri-Rao子空间和块压缩感知(KRS-BCS),提出了一种差分SAR层析成像方法。该方法依据目标的结构特性和重构观测矩阵具有的Khatri-Rao积性质,将稀疏结构目标的差分TomoSAR问题转化为Khatri-Rao子空间下的BCS问题,然后对目标进行块稀疏的l1/l2范数最优化求解,最后通过理论分析和仿真试验对分辨能力和重构估计性能进行了定性和定量评价,仿真结果表明本文所采用的KRS-BCS方法不仅保持了高分辨率的优点,而且有效地降低了虚假目标出现的概率,大幅度提高了散射点准确重构概率,切实可行地解决了CS方法的不足。应用实例研究中,利用34景Envisat卫星ASAR时间序列影像对日本千叶县茂原市城区进行地表形变监测,并以一等水准点和实时测量的GPS站点观测数据作为参考形变结果进行验证,试验结果表明采用KRS-BCS方法反演的结果与参考形变结果保持了良好的一致性且形变速率整体偏差也较小,实现了较高精度的城区地表形变估计。  相似文献   

A hybrid approach to modeling territorial control in violent armed conflicts          下载免费PDF全文

Ran Tao  Daniel Strandow  Michael Findley  Jean‐Claude Thill  James Walsh 《Transactions in GIS》2016,20(3):413-425

Territorial control is central to the understanding of violent armed conflicts, yet reliable and valid measures of this concept do not exist. We argue that geospatial analysis provides an important perspective to measure the concept. In particular, measuring territorial control can be seen as an application of calculating service areas around points of control. The modeling challenge is acute for areas with limited road infrastructure, where no complete network is available to perform the analysis, and movements largely occur off road. We present a new geospatial approach that applies network analysis on a hybrid transportation network with both actual road data and hexagon‐fishnet‐based artificial road data representing on‐road and off‐road movements, respectively. Movement speed or restriction can be readily adjusted using various input data. Simulating off‐road movement with hexagon‐fishnet‐based artificial road data has a number of advantages including scalability to small or large study areas and flexibility to allow all‐directional travel. We apply this method to measuring territorial control of armed groups in Sub‐Saharan Africa where inferior transport infrastructure is the norm. Based on the Uppsala Conflict Data Program's (UCDP) Georeferenced Event Data (GED) as well as spatial data on terrain, population locations, and limited transportation networks, we enhance the delineation of the specific areas directly controlled by each warring party during civil wars within a given travel time.  相似文献   

Present-day Block Movement and Fault Activity on the Eastern Margin of the Tibetan Plateau     

TANG Wenqing  ZHANG Yongshuang  ZHANG Qingzhi  ZHOU Hongfu  PAN Zhongxi  LI Jun  YANG Cheng 《《地质学报》英文版》2016,90(2):456-466

The geology and tectonics in the eastern margin of Tibetan Plateau are complex. The main tectonic framework is composed of blocks and faults. Using discontinuous global positioning system survey data for 2008–2014, the velocity field for the Eurasia reference framework was obtained. Based on the velocity field, the present-day velocities of the blocks and boundary faults were estimated. The results reveal that the movement rates of the Chuan-Qing, South China, Chuan-Dian and Indo-China blocks are(17.02±0.60) mm/a,(8.77±1.51) mm/a,(13.85±1.31) mm/a and(6.84 ± 0.74) mm/a, respectively, and their movement directions are 99.5°, 120.3°, 142.9° and 153.3°, respectively. All blocks exhibit clockwise rotation. The displacement rates of the Xianshuihe, Longmenshan, Anninghe, Zemuhe, Xiaojiang and Red River faults are(7.30±1.25–8.30±1.26) mm/a,(10.07±0.97–11.79±0.89) mm/a,(0.96±0.74–2.98±1.73) mm/a,(2.03±0.49–3.20±0.73) mm/a,(3.45±0.40–6.02±0.50) mm/a and(6.23±0.56) mm/a, respectively. The Xianshuihe, Anninghe, Zemuhe and Xiaojiang faults show leftlateral strike-slip movement, while the Longmenshan and Red River faults show right-lateral strikeslip. These characteristics of the blocks and faults are related to the particular tectonic location and dynamic mechanism.  相似文献   

天山山脉中新生代差异隆升及其机制探讨     

孙岳  陈正乐  王永  韩凤彬  吴玉  孟令通  张昊 《大地构造与成矿学》2016,(2):335-343

为了揭示长约2500 km的天山山脉中新生代隆升特征,本文系统梳理分析了已发表的磷灰石裂变径迹数据和本次野外采样测得磷灰石裂变径迹数据约460个,岩性以花岗岩和砂岩为主。结果显示整个天山山脉隆升具有明显的时空差异性。白垩纪以前记录的径迹数据约占14%,白垩纪以来的数据约占86%,晚古生代末天山已有径迹年龄记录,到晚侏罗世天山部分地区发生隆升,整体隆升不明显,早白垩世以来整个天山普遍隆升,且存在多期隆升事件,但隆升剥蚀速率存在明显差异。南北方向上,自南向北径迹年龄有减小的趋势,揭示山脉隆升自南天山向北天山扩展;东西方向上,西天山隆升时限较东天山隆升早,但白垩纪以来东、西天山均有隆升记录。天山山脉差异性隆升是不同陆块对亚洲板块南缘碰撞增生作用的共同结果,其内部块体的结构特征和力学性质是差异隆升的基础和前提。  相似文献