Minimizing effects of scale distortion for spatially grouped census data using rough sets     

Gift Dumedah  Nadine Schuurman  Wanhong Yang 《Journal of Geographical Systems》2008,10(1):47-69

  相似文献   

我国乡村旅游发展的问题及对策初探     

孙婷  覃建雄 《四川地质学报》2008,28(3):230-232

本文对乡村旅游的市场特点,发展趋势和存在的问题进行了分析,提出了解决问题的对策。指出乡村旅游和文化旅游紧密结合是乡村旅游可持续发展的基本要求。提出依托优美的乡村自然环境、挖掘浓郁的地方特色（包括乡土文化和民族文化）、展现真实的乡村生活,是发展乡村旅游的基本条件,也是发展乡村旅游、开发乡村旅游产品的基本要求。  相似文献   

Extended Probability Perturbation Method for Calibrating Stochastic Reservoir Models   总被引：1，自引：0，他引：1  

Lin Y. Hu 《Mathematical Geosciences》2008,40(8):875-885

Calibrating a stochastic reservoir model on large, fine-grid to hydrodynamic data requires consistent methods to modify the petrophysical properties of the model. Several methods have been developed to address this problem. Recent methods include the Gradual Deformation Method (GDM) and the Probability Perturbation Method (PPM). The GDM has been applied to pixel-based models of continuous and categorical variables, as well as object-based models. Initially, the PPM has been applied to pixel-based models of categorical variables generated by sequential simulation. In addition, the PPM relies on an analytical formula (known as the tau-model) to approximate conditional probabilities. In this paper, an extension of the PPM to any type of probability distributions (discrete, continuous, or mixed) is presented. This extension is still constrained by the approximation using the tau-model. However, when applying the method to white noises, this approximation is no longer necessary. The result is an entirely new and rigorous method for perturbing any type of stochastic models, a modified PPM employed in similar manner to the GDM.  相似文献   

基于Neumann级数的有偏估计方法     

杨秋伟  白志超  李翠红 《大地测量与地球动力学》2020,40(5):512-516

针对病态最小二乘问题,提出基于Neumann级数的有偏估计方法。由该方法建立的有偏估计公式,包含现有的最小二乘估计、岭估计和广义岭估计公式,建立有偏估计和无偏估计的本质联系,并可以据此引申出一系列新的有偏估计形式。在这一系列的有偏估计中,存在着比岭估计或广义岭估计更接近于真值的解。以一个病态方程组为例对该方法进行验证表明,当观测向量中含有误差时,由最小二乘估计所得结果和真值误差较大,而各级有偏估计的结果和真值更加接近,且二级和三级有偏估计结果比相应的岭估计更接近于真值。  相似文献   

A numerical investigation of the one-dimensional newtonian three-body problem II. Positive energies     

Seppo Mikkola  Jarmo Hietarinta 《Celestial Mechanics and Dynamical Astronomy》1989,47(4):321-331

Numerical orbit integrations have been conducted to characterize the types of trajectories in the one-dimensional Newtonian three-body problem with equal masses and positive energy. At positive energies the basic types of motions are binary + single particle and ionization, and when time goes from – to + all possible transitions between these states can take place. Properties of individual orbits have been summarized in the form of graphical maps in a two-dimensional grid of initial values. The basic motion types exist at all positive energies, but the binary + single particle configuration is obtained only in a narrow region of initial values if the total energy is large. At very large energies the equations of motion can be solved approximately, and this asymptotic result, exact in the limit of infinite energy, is presented.  相似文献   

The principal-agent problem and climate change adaptation on public lands     

《Global Environmental Change》2016

Climate change presents clear risks to natural resources, which carry potential economic costs. The limited nature of physical, financial, human and natural resources means that governments, as managers of natural resources, must make careful decisions regarding trade-offs and the potential future value of investments in climate change adaptation. This paper presents cost-benefit analysis of scenarios to characterise economic benefits of adaptation from the perspective of a public institution (the provincial government) and private agents (forest licensees). The example provided is the context of assisted migration strategies for regenerating forests that are currently being implemented in British Columbia to reduce future impacts of climate change on forests. The analysis revealed positive net present value of public investment in assisted migration across all scenarios under a range of conditions; however, private sector agents face disincentives to adopt these strategies. Uncertainty about how the costs, benefits and risks associated with climate change impacts will be distributed among public institutions and private actors influences incentives to adapt to climate change (the “principal-agent problem”) and further complicates adaptation. Absent development of risk-sharing mechanisms or re-alignment of incentives, uptake of assisted migration strategies by private agents is likely to be limited, creating longer-term risks for public institutions. Analyzing incentives and disincentives facing principals and agents using a well-known tool (cost-benefit analysis) can help decision-makers to identify and address underlying barriers to climate change adaptation in the context of public lands management.  相似文献   

一类二阶时滞微分方程的边值问题     

夏青 《中国海洋大学学报(自然科学版)》2005,35(4):587-590

考虑一类二阶时滞微分方程的无穷边值问题,从分析这类方程的解对初值的依赖性得到了保证这类边值问题存在唯一解的充分条件。  相似文献   

统计-动力相结合的相似误差订正法   总被引：28，自引：6，他引：22  

任宏利  丑纪范 《气象学报》2005,63(6):988-993

根据大气相似性原理,提出了利用历史资料的相似信息估计模式误差的反问题,并发展了一种相似误差订正(ACE)方法。该方法将统计和动力两种方法有机结合,在不改变现有数值预报模式的前提下,既充分利用了动力学发展的成就,又能够有效提取大量历史资料中的相似信息,达到减小模式误差、改进当前预报的目的。而且,ACE方法能够针对当前预报的特殊性来区分所利用过去资料的特殊性,提取历史相似信息间接求解反问题。定性分析表明,ACE方法与以往相似-动力模式原理是等价的,但无需重新建立复杂的相似离差预报模式,更具可行性和业务应用前景。在理想化的极限情形下,当数值模式或历史相似完全准确时,ACE方法的预报结果将分别蜕变为动力或统计学方法的预报结果。  相似文献   

Influence functions for stress and displacement discontinuity elements in an anisotropic medium     

M. A. Kayupov  S. Sakurai  M. Kuriyagawa 《国际地质力学数值与分析法杂志》1997,21(9):635-652

Influence functions, that permit us to determine stresses and displacements at an arbitrary point in an infinite, homogeneous, linear elastic, anisotropic medium due to different three-dimensional (3-D) stress or displacement discontinuities distributed on infinite, flat, band-type elements, are presented. Any straight-line segment on the band, which is perpendicular to its infinite side, has the same distribution of the discontinuities. Along with the functions, their Taylor series approximations are also provided. The last can be useful to analyse stresses and displacements at points distant from the elements. The functions allow us to avoid procedures of numerical integration in the Indirect Boundary Element Method and/or the Displacement Discontinuity Method computer codes that are able to solve complete plane-strain problems with 3-D boundary conditions for an elastic, anisotropic medium. © 1997 by John Wiley & Sons, Ltd.  相似文献   

中国主要城市环境地质调查评价   总被引：2，自引：0，他引：2  

文冬光  刘长礼 《城市地质》2006,1(2)

中国正处在快速城镇化发展时期,强烈的人类工程活动已经成为一种十分重要的作用力,对城市地质环境产生显著影响。在特殊的城市地质环境背景下,引发了不同程度的环境地质问题和地质灾害,诸如地下水资源衰减．地下水污染、地面沉降、地面塌陷、崩塌、滑坡、泥石流等,严重制约城市经济和社会的可持续发展。本文初步总结了目前中国主要城市存在的环境地质问题和地质灾害,以及近年来开展的全国主要城市环境地质调查评价的进展和未来工作部署。  相似文献