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741.
A water mass in the sea area under investigation is defined as a fuzzy subset in the discourse universe. Possible forms of membership function of water masses in the mixing modified process are discussed with the mixing theory for conservative concentration of sea water. It may provide bases for making membership functions. Results in this paper may be extended and applied to shallow water. Examples and discussion are given in this paper.  相似文献   
742.
自适应遗传算法解决集装箱装载问题的方法探讨   总被引:8,自引:0,他引:8  
集装箱装箱问题是1个有很强应用背景的组合优化问题,约束条件多,求解极为困难。本文探讨了自适应遗传算法在复杂集装箱装载问题中的应用,算法中采用跨世纪精英选择策略保持了群体的多样性,并给出了有效的解码算法。实例仿真结果显示出很好的效果,同等条件下求解结果比使用启发式算法高出近10个百分点,表明该算法是行之有效的。  相似文献   
743.
声相关海流剖面(ACCP)测量的流速估值方法   总被引:3,自引:0,他引:3  
声相关海流剖面(ACCP)测量技术对水体回波信号进行空间相关处理来估计流速值,与声学多普勒海流剖面仪(ADCP)相比ACCP的工作频工,更适合深海测流应用,ACCP测量系统对回波信号进行时空相关处理,根据相关函数的位置来估计被测水团的流速值,ACCP从信号中提取流速值要运用参数估计技术,本文介绍了采用极大似然法和最小二乘法进行流速参数的处理方法,给出一些典型流速情形的数值计算结果。  相似文献   
744.
该文引入 1墨水点 2方向交替式下推自动机 ,它是 1个具有额外能力的 2方向交替式下推自动机 ,能够用 1个墨水点在输入带上标记出最多 1个单元格。对具有 1个墨水点的和没有墨水点的亚对数空间限定交替式下推自动机之间的关系进行研究。实例证明了具有 1个墨水点的亚对数空间限定交替式下推自动机的语言受理能力强于没有墨水点的亚对数空间限定交替式下推自动机  相似文献   
745.
陈初才 《地理研究》1989,8(3):42-50
我国方志是反映各种区域时空实体的文化载体。方志的演化可分先秦至西汉。东汉至南宋和南宋以后三个时期。与西方方志比较中国方志具有重区内、轻区间;重人文,轻自然和含“天—地—人”的原始系统论等特点。新方志可有资料性、知识性和研究性三种类型。创新方志应该从“方志乃一方全史”说中解脱出来,加强区域研究。  相似文献   
746.
Spatial access to healthy foods has drawn growing attention regarding the relationship with people's health conditions and demographic and socioeconomic characteristics. Individuals' differences and the impact of travel behaviors on food accessibility, however, are rarely studied. This study incorporates mobility, time, and transportation mode components to measure each individual's access to healthy foods. We employed three activity space measures to estimate food accessibility: route network buffer, time-weighted standard deviational ellipse (SDE), and mode-weighted SDE. Food accessibility in three activity spaces shows similar variabilities. Geographic size and spatial access to healthy foods differ significantly by income and employment for all three activity space measures. People with higher incomes and those who are currently employed are likely to have larger activity spaces and higher food accessibility. As age increases, people tend to increase their size of activity spaces (in both SDE measures) and food accessibility significantly. Females are likely to have smaller activity spaces and less accessibility to healthy foods (only in the time-weighted SDE measure). Geographic size and spatial access do not differ significantly by education and number of vehicles per household. Although three activity spaces are highly correlated in both geographic size and spatial access, differences still exist among them.  相似文献   
747.
By virtue of a pair of scalar potentials for the displacement of the solid skeleton and the pore fluid pressure field of a saturated poroelastic medium, an alternative solution method to the Helmholtz decomposition is developed for the wave propagation problems in the framework of Biot's theory. As an application, a comprehensive solution for three‐dimensional response of an isotropic poroelastic half‐space with a partially permeable hydraulic free surface under an arbitrarily distributed time‐harmonic internal force field and fluid sources is developed. The Green's functions for the poroelastic fields, corresponding to point, ring, and disk loads, are reduced to semi‐infinite complex‐valued integrals that can be evaluated numerically by an appropriate quadrature scheme. Analytical and numerical comparisons are made with existing elastic and poroelastic solutions to illustrate the quality and features of the solution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
748.
在Hausdorff局部凸线性拓扑空间中得到了Kannan型非扩张集值映射不动点定理,附带给出单值映射族具有公共不动点的结果。  相似文献   
749.
全球强震的分布及其与地球自转速率变化的关系   总被引:4,自引:0,他引:4  
结合文[1]作者给出的全球地震目录,重点考察1832~1994年间全球强震(Ms≥7.5)的分布特征,并初步探讨了全球强震与地球自转速率变化的可能关联。结果表明,1832年以来的全球强震分布与现代的地震观测结果比较一致,这些强震主要集中在环太平洋和地中海—喜马拉雅两大地震带,地球自转速率变化与全球强震的频次存在较为密切的联系。  相似文献   
750.
Cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so. A model that incorporates the effects of vegetation and its interactions with geomorphic landscape development – the Discrete Ecogeomorphic Aeolian Landscapes (DECAL) model – can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments. A key challenge in this research area is the analysis and comparison of both simulated and real‐world vegetated dune landscapes using objective and quantifiable principles. This study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes, using a suite of mathematically defined landscape metrics, to provide a rigorous and statistical evaluation of vegetated dune field evolution. Within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real‐world landscapes. Based on a simplified scenario of parabolic dunes developing out of blow‐outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types (pioneer grass and successional woody shrub) by establishing a typological phase‐diagram of different landscape classes. The set of simulation outcomes furthermore defines a higher‐dimensional phase‐space, whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics, or state variables, contribute to the data distribution. Principal component analysis can reduce this to a visual three‐dimensional (3D) phase‐space where landscape evolution can be plotted as time‐trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario. The use of landscape state variables and the construction of a 3D phase‐space presented here may provide a general template for quantifying many other eco‐geomorphic systems on the Earth's surface. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
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