闾阳-康平-梨树深地震测深剖面野外资料数字化的设计与实现     

白云  姜德录  吴小兵  翟文杰  李爱民 《东北地震研究》2002,18(2):51-56

通过分析闾阳－康平－梨树深地震测深剖面的观测设计、观测结果以及仪器系统特点，根据项目研究目的及要求，对该剖面的模拟记录进行了数字化设计与实现，以满足用新方法对资料的进一步处理运算，并为资料的交流和永久保存打下了良好基础。  相似文献   

草滩沟群、丹凤岩群火山岩对比及其构造环境分析   总被引：2，自引：0，他引：2  

王德耀 《西北地质》2002,35(3):59-66

通过北泰岭造山带西段凤县地区1：5万辛家庄、红花铺幅区调填图及前人成果，对位于秦岭岩群南北两侧的丹凤岩群和草滩沟群火山岩的岩石类型、岩石化学及地球化学特征进行对比，认为二者均属亚碱性岩系之钙性－钙碱性系列；前者为中－基性岩组合，显示了岛弧外侧－边缘海型的构造背景特征；后者为中－酸性岩组合，具弧后盆地拉张裂谷活动背景特征。为探讨北秦岭造山带的地质发展史提供了新的资料。  相似文献   

322矿田铀矿床原地破碎浸出经济评估   总被引：1，自引：3，他引：1  

李德平  顾连兴  周青生  李顺初 《铀矿地质》2002,18(4):242-249,201

本文从原地破碎浸出法采矿工艺流程出发，对322铀矿田碎裂蚀变化岗岩型铀矿床（点）的各项成本要素进行了研究，建立了原地破碎浸出经济模型，引入了铀浸出率和回收率高速系数。利用原地爆破筑堆试验及一系列铀矿柱浸工艺试验获得的原地破碎浸出经济分析参数及经济评价模型对322矿田铀矿床原地破碎浸出进行了经济评估。  相似文献   

土地利用方式对岩溶山地土壤种子库的影响   总被引：11，自引：0，他引：11  

李阳兵  魏朝富  李先源  谢德体 《山地学报》2002,20(3):319-324

本文从种类组成、种子数量、生态优势度、物种多样性、种子分布规律和物种相似性等方面比较了重庆市岩溶低山10种不同土地利用系统的土壤种子库特点，10种土地利用类型包括耕地、弃耕地、果园、灌草坡、人工林和次生林。结果表明，研究区种子以草本为主，随土利用强度增加，种子类和数量减少，与地面农田杂草相似性增加，土壤种子库出质和量方面的锐减。从土壤种子角度说明研究区生态退化严重。  相似文献   

Orbital forcing signal in sediments of two Amazonianlakes     

M.B. Bush  M.C. Miller  P.E. De Oliveira  P.A. Colinvaux 《Journal of Paleolimnology》2002,27(3):341-352

Paleolimnological data from two ancient lakes at 0° latitudein Amazonia indicate that past lake level changes reflect precessional (19,000to 22,000 years) variations in insolation over the last 170,000 years. Waterlevel in Lakes Pata and Verde, Brazil, is determined by the ratio ofprecipitation:leakage. Times of low lake level are indicated in sediments byoxidized clays, evidence of algal blooms and high K⁺ concentrations.Peak K⁺ values are attributed to biogenic concentration when thelake was reduced to a shallow, productive pool. Low lake phases correlate withmaximum insolation during the dry season (June–July–August). Thusthe last glacial maximum 18,000 to 22,000 yr BP was a wet time in northernAmazonia, and the driest period of the last 170,000 years was from 35,000 to27,000 yr BP. These results from near the equator do not imply thatprecipitation changed synchronously across Amazonia, because geographiclocations throughout the vast watershed were undoubtedly influenced by localmoisture sources.  相似文献   

长江经济带生态用地变化类型识别及驱动因素分析   总被引：1，自引：1，他引：0  

周婷  戚佳玲  徐之寒  周德 《资源与生态学报(英文版)》2021,12(2):175-191

生态用地能够为人们提供生态产品和生态服务,对于维持生态系统健康与安全有着不可替代的作用。在我国城镇化进程快速推进的过程中,生态用地被大量侵占、受损严重,许多土地生态功能丧失。本研究基于1995-2015年的土地利用数据,探究长江经济带生态用地变化时空演变规律,并使用地理探测器和地理加权回归模型对于生态用地变化的驱动机制分别开展全局效应与局部效应分析。本研究将生态用地变化划分为5个类型:严重受损、轻微受损、保持不变、轻微恢复、明显恢复。研究结果表明:1995年至2015年,长江经济带生态用地面积呈现先增加后减少的趋势,但是总体的趋势是减少的,受损面积大于恢复面积。其中,减少的面积主要来自于林地和耕地。在这20年间,从生态用地变化类型来看,保持不变类型的面积最大,其次是轻微受损和轻微恢复类型。生态用地变化是多种因素相互作用的结果,而任何两个驱动因子共同作用的解释力都大于单一的驱动因素。此外,根据地理位置的不同,不同驱动因子对于生态用地变化的影响也不同。本文研究结果有助于土地管理者和政策制定者更好地制定区域和地方的相关土地利用政策。相关经验教训也可以推广到其他地区,以更好地管理生态用地,实现可持续发展。  相似文献   

上海都市区边界划分——基于手机信令数据的探索   总被引：5，自引：0，他引：5  

王德  顾家焕  晏龙旭 《地理学报》2018,73(10):1896-1909

都市区是中心城市及其主要影响范围,在区域经济发展中有重要的引领作用。国外都市区范围根据中心城市与外围地区的通勤联系划分,本质上是与中心城市具有密切经济联系的统一劳动市场区。国内由于统计数据的缺乏,通过通勤联系划分都市区的相关研究难以开展,且划分结果在内涵上与国外都市区差异较大。移动电话是目前普及率最高的移动通讯终端设备,其包含的地理位置标签可反映用户的职住地信息。利用上海移动2014年上半年某两周2G手机信令数据,识别用户的居住地和工作地,参照国外标准,根据中心与外围地区的通勤联系划分上海市都市区。在通勤联系的基础上,尝试采用消费联系作为都市区划分的辅助标准,并对划分结果进行了调整。结果表明：① 基于通勤联系的上海都市区主要包括中心城周边地区、松江新城及外围大型工业区,基于消费联系调整的上海都市区包括中心城周边地区、松江、嘉定、青浦等新城及浦东惠南地区、长兴岛,整体上呈现东西略长、南北略窄的形态;② 通勤联系和消费联系可以相互结合划分中国的都市区边界,通勤联系作为主要指标,消费联系作为辅助指标;③ 上海与国外城市都市区差异较大,国外都市区范围扩展极广,上海都市区范围未超过行政边界,局限在在中心城周围相对较小的范围内。  相似文献   

Superthermal plasma nodules and their relation to solar flares     

L. D. De Feiter  C. De Jager 《Solar physics》1973,28(1):183-186

We define superthermal plasma nodules as bright points (diameter 20), visible on high resolution X-ray heliograms. Flares appear to show a strong tendency to occur at the places of these nodules. There are indications that (part of) the hot plasma produced by consecutive flares is accumulated and confined in the superthermal plasma nodules, and that with increasing energy content of a nodule the probability for a drastic change of its magnetic structure increases, thus reducing the possibility for more flares to occur.  相似文献   

Probabilistic neural networks for seismic damage mechanisms prediction     

A. De Stefano  D. Sabia  L. Sabia 《地震工程与结构动力学》1999,28(8):807-821

The procedure commonly employed to assess the seismic vulnerability of buildings uses simplified qualitative and quantitative observations obtained from the measured data entered into report forms. In Italy, the data sheets adopted by the National Defence Group against Earthquakes (Gruppo Nazionale per la Difesa dai Terremoti—GNDT) play a unifying and reference role. This paper proposes a method for the processing of the data contained in such report forms which is based on probabilistic neural networks producing a Bayesian classification. The final goal is to exploit the fundamental learning and generalization capabilities of neural networks to obtain an estimate of the vulnerability of structural systems. In particular, the aim is to be able to predict the damage mechanisms which may be triggered in the macro-elements of public worship buildings. Copyright © 1999 John Wiley & Sons Ltd.  相似文献   

Face stability of shallow circular tunnels driven under the water table: a numerical analysis     

P. De Buhan  A. Cuvillier  L. Dormieux  S. Maghous 《国际地质力学数值与分析法杂志》1999,23(1):79-95

The stability analysis of a tunnel excavated in a water-saturated frictional soil is investigated in the light of a failure design approach. The soil strength properties being classically formulated in terms of effective stresses, it is first shown how the effect of seepage flow generated by the excavation process, may be accounted for in such an analysis by means of driving body forces derived from the gradient of an excess pore pressures distribution. The latter is obtained as the solution of a hydraulic boundary value problem, in which both water table evolution and soil deformability can be neglected. A variational formulation of this hydraulic problem in terms of filtration velocities is then presented, leading through appropriate numerical treatment, to a search for the minimum without constraints of a quadratic functional (hybrid formulation), which is formulated by a finite element method. Some numerical examples are given, which provide ample evidence of the crucial role played by seepage forces in the tunnel face stability, since the factor of stability may be divided by as much as three. The influence of such parameters as the tunnel relative depth or soil anisotropic permeability is finally discussed, thus offering a first illustration of the various capabilities of this numerical tool. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献