直流激发极化法中的视电阻率参数及二次场采样     

赵聚林  薛斌义  冯军  何海军 《物探与化探》2009,33(1):46-48

目前的直流激发极化法仪器,一次场采集于供电方波的末端时间,包含了被激发形成的二次场,在高极化率地质体上,仪器反映的视电阻率将削弱其低阻特性或放大高阻特性。以甘肃北山地区某铜铁矿测量为例,说明在野外工作中,做适当的数据处理,可降低这种影响。  相似文献   

附加约束条件的DLT用于非量测数码相机的检校     

杨化超  邓喀中  张书毕  周鸣  赵卿 《测绘工程》2005,14(4):30-32,42

从直接线性变换DLT的基本原理出发,分析了数码相机检校的DLT一般方法存在的缺陷,提出了附加约束条件的DLT相机检校方法的数学模型,并通过实验验证了其正确性和可行性.  相似文献   

An interactive global optimization algorithm for geological problems     

Paul Schiffelbein 《Mathematical Geology》1985,17(7):703-728

A number of problems in geology can be formulated so that they consist of optimizing a real-valued function (termed the objective function) on some interval or over some region. Many methods are available for solution if the function is unimodal within the domain of interest. Direct methods, involving only function evaluations, are particularly useful in geological problems where the objective function may be strongly nonlinear and constructed from sampled data. In practical problems, the objective function often is not unimodal. Standard optimization routines are not capable of distinguishing between local extrema or of locating the global extremum, which is the point of interest in most cases. The usual approach—trying several different starting points in the hope that the best local extremum found is the global extremum—is inefficient and unreliable. An ancillary algorithm has been developed which avoids these problems and which couples with a variety of local optimization routines. The algorithm first constructs a grid of objective function values over some feasible region. The region dimensions and grid spacings are based on specific problem considerations. First differences are then calculated for successive points along each grid line and monitored in sign only, which rapidly locates extrema. User interaction determines how many of these extrema will undergo further investigation, which is carried out by passing locations to a local optimization subroutine. The algorithm has proved successful on a number of problems. A geological example—determination of benthic mixing parameters in deep-sea sediments via minimization of stratigraphic offset between ¹⁸ O signals from two different species of planktonic foraminifera—is given. FORTRAN code is provided for the global optimization routine, a golden section search subroutine for one-dimensional objective functions, and a simplex subroutine for multidimensional problems.  相似文献   

Placement of sensors/actuators on civil structures using genetic algorithms     

Makola M. Abdullah  Andy Richardson  Jameel Hanif 《地震工程与结构动力学》2001,30(8):1167-1184

The optimal design and placement of controllers at discrete locations is an important problem that will have impact on the control of civil engineering structures. Though algorithms exist for the placement of sensor/actuator systems on continuous structures, the placement of controllers on discrete civil structures is a very difficult problem. Because of the nature of civil structures, it is not possible to place sensors and actuators at any location in the structure. This usually creates a non‐linear constrained mixed integer problem that can be very difficult to solve. Using genetic algorithms in conjunction with gradient‐based optimization techniques will allow for the simultaneous placement and design of an effective structural control system. The introduction of algorithms based on genetic search procedures should increase the rate of convergence and thus reduce the computational time for solving the difficult control problem. The newly proposed method of simultaneously placing sensors/actuators will be compared to a commonly used method of sensors/actuators placement where sensors/actuators are placed sequentially. The savings in terms of energy requirements and cost will be discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

电感耦合等离子体质谱直接测定冰芯样品中痕量铅   总被引：6，自引：0，他引：6  

李月芳姚檀栋  王宁练唐富荣 《岩矿测试》2001,20(1):11-14,19

利用电感耦合等离子体质谱仪对冰芯样品中超痕量Pb进行了直接测定。确定了测定溶液中浓度为ng/L级Pb的最佳仪器参数，载气流速、进样速度等与灵敏度之间的关系,浓度和扫描参数对分析精度的影响。仪器对Pb的质量浓度在20～100ng/L的分析精度(RSD，n=3)＜10%,标准加入回收率在85%～115%，检测下限为0.62ng/L，并给出了采自可可西里马兰冰川M3冰芯中Pb的分析结果。  相似文献   

The potential and prospect for global cities in China: in the context of the world system   总被引：2，自引：0，他引：2  

Shi YulongChris Hamnett 《Geoforum》2002,33(1):121-135

Over the last two decades, accompanying their rapid economic development, many `mega-cities' in China have devoted themselves to changing their relationships to the global economy and some have aimed at attaining global (world) city status as a key future development goal. This paper examines the relationship between global (world) city status and the emerging world economic system, and discusses the intense competition between `mega-cities' in the Asia-Pacific region that Chinese cities will face in the 21st century, especially after the Asia financial crisis. It also explores the potential and possibility of achieving global or world city status in China. The main arguments are that only Hong Kong, Shanghai and Beijing have the possibility to attain leading positions in the global urban system in the future. Post-1997, it has been very important for the Chinese government to find a way to coordinate the functions of Hong Kong and the other major cities which allows them to operate smoothly together under quite different political systems. Finally, the authors analyse the relationships between these three metropolises and suggests some possibilities for coordinating their roles in the global urban system.  相似文献   

港澳地区对中国内地直接投资的区位选择及其空间扩散   总被引：29，自引：3，他引：29  

贺灿飞  陈颖 《地理科学》1997,17(3):193-200

对港澳地区在中国内地直接投资的空间分布及其空间转移做了上分析，表明了港澳地区对中国内地的直接投资趋向于沿海地区和与这这有特殊社会文化联系的区位，同时更有向中西部和北部转移的趋势，决定港澳地区对中国内地投资空间模式和转移态势的因素是经济规模，经济增长速率，劳动力因素，经济开放度，与沿海的经济距离等。  相似文献   

城市相对湿度的直接模式输出修正预报的研制          下载免费PDF全文

夏建国  陈爱琴 《气象》1997,23(10):16-20

给出了一种非统计的直接模式输出（ＤＭＯ）的修正方法，它无需任何历史资料，仅以我国国家气象中心实时Ｔ１０６模式的离地２ｍ之相对湿度预报格点值为基础，经非线性插值，部分系统性误差订正及相对湿度的日较差正后制作全国２６４个城市的相对湿度预报。其中北京、上海、香港等１０个城市的相对湿度预报经预报员把关后，第天晚间由中央电视台播出。  相似文献   

Mortality in megafaunal benthic populations caused by trawl fisheries on the Dutch continental shelf in the North Sea in 1994   总被引：4，自引：6，他引：4  

Bergman  Magda J. N; van Santbrink  Jan W 《ICES Journal of Marine Science》2000,57(5):1321-1331

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Influence of mesh size and tooth spacing on the proportion of damaged organisms in the catches of the Portuguese clam dredge fishery     

Gaspar  Miguel B.; Leitao  Francisco; Santos  Miguel N.; Sobral  Manuel; Chicharo  Luis; Chicharo  Alexandra; Monteiro  Carlos C. 《ICES Journal of Marine Science》2002,59(6):1228-1236

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