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  

丁香乾  韩运实  张晓丽 《中国海洋大学学报(自然科学版)》2004,34(5):844-848

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   

浙江乐清湾海岸带功能区划分与海洋产业发展   总被引：7，自引：0，他引：7  

李春平  张灵杰  董丽晶 《海洋通报》2003,22(5):38-43

乐清湾为浙江省重点海湾之，资源的多宜性与不同行业开发利用的矛盾冲突是当前海湾可持续发展面I临的主要障碍。本文从乐清湾海岸带地区的自然环境与社会经济条件出发，探讨了开展海岸带功能区划的必要性，提出了区划的基本方案。在分析乐清湾海岸带地区海洋产业发展现状与问题的基础上，运用层次分析法研究了该湾近期海洋产业的发展方向与主导产业。最后，讨论了实现海洋产业协调发展的若干对策与建议。  相似文献   

Limiting similarity, niche filtering and functional diversity in coastal lagoon fish communities     

David Mouillot  Olivier Dumay  Jean Antoine Tomasini 《Estuarine, Coastal and Shelf Science》2007,71(3-4):443-456

The fundamental idea behind the study of biodiversity patterns is the presumed connection between the shape of species assemblages and the functional ways in which they are organized, this functional organization referring to how species are related to one another, as competitors or members of a web of interactions and to how species are facing similar environmental constraints. Amongst the different facets of biodiversity, functional diversity is certainly a key for ecosystem processes in coastal areas. However, surprisingly, patterns of functional diversity have received little attention until now. After presenting a common framework linking functional diversity patterns to species coexistence theories, the aim of our study was twofold: (1) to seek assembly rules in brackish lagoon fish communities drove by functional traits. To this aim we used null models to examine the influence of two opposing forces acting on community structure: interspecific competition that might prevent the coexistence of the most similar species, and environmental filters that might result in the most similar species to coexist. (2) To seek relationships between fish functional diversity and environmental gradients, if any. Fish sampling was carried out in two coastal lagoons where stations differ considerably in terms of physicochemical parameters. Using morphological functional traits, functional diversity of fish communities was estimated using two recently published indices as well as a new proposed index. Firstly our study was not able to demonstrate a limitation of similarity in coexisting lagoon fishes due to interspecific competition. Conversely our results support the niche filtering hypothesis preventing species too dissimilar from one another to co-occur at the same station. Secondly, salinity was positively related to the functional diversity of fishes in both lagoons suggesting that within species assemblages near the channel species are less redundant than at stations far from the channel where species tend to be functionally similar (benthic and eating zooplankton).  相似文献   

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  

郭纪捷  荀俊姑  徐正高 《海洋技术学报》2001,20(1):93-96

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   

有无1墨水点亚对数空间限定交替式下推自动机之间的关系     

徐建良  孙剑  陈勇  孟庆春 《中国海洋大学学报(自然科学版)》2003,33(3):449-456

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   

N阶中立型泛函微分方程新的振动准则     

夏青 《中国海洋大学学报(自然科学版)》2001,31(3):448-454

作者对一类N阶中立型泛函微分方程给出了新的区间振动准则。文中的结果推广和改进了由Lalli等人得到的广义Kamenev型准则及其它已知结果。  相似文献   

方志和区域研究     

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   

Measuring Individuals' Spatial Access to Healthy Foods by Incorporating Mobility,Time, and Mode: Activity Space Measures     

Jingjing Li  Changjoo Kim 《The Professional geographer》2018,70(2):198-208

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   

Generation of a realistic 3D sand assembly using X‐ray micro‐computed tomography and spherical harmonic‐based principal component analysis          下载免费PDF全文

B. Zhou  J. Wang 《国际地质力学数值与分析法杂志》2017,41(1):93-109

Three‐dimensional particle morphology is a significant problem in the discrete element modeling of granular sand. The major technical challenge is generating a realistic 3D sand assembly that is composed of a large number of random‐shaped particles containing essential morphological features of natural sands. Based on X‐ray micro‐computed tomography data collected from a series of image processing techniques, we used the spherical harmonics (SH) analysis to represent and reconstruct the multi‐scale features of real 3D particle morphologies. The SH analysis was extended to some highly complex particles with sharp corners and surface cavities. We then proposed a statistical approach for the generation of realistic particle assembly of a given type of sand based on the principle component analysis (PCA). The PCA aims to identify the major pattern of the coefficient matrix, which is made up of the SH coefficients of all the particles involved in the analysis. This approach takes into account the particle size effect on the variation of particle morphology, which is observed from the available results of micro‐computed tomography and QICPIC analyses of sand particle morphology. Using the aforementioned approach, two virtual sand samples were generated, whose statistics of morphological parameters were compared with those measured from real sand particles. The comparison shows that the proposed approach is capable of generating a realistic sand assembly that retains the major morphological features of the mother sand. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Linear theory of rotating fluids using spherical harmonics part I: Steady flows     

Michel Rieutord 《地球物理与天体物理流体动力学》2013,107(3):163-182

Abstract

It is shown that a systematic development of physical quantities using spherical harmonics provides analytical solutions to a whole class of linear problems of rotating fluids.

These solutions are regular throughout the whole domain of the fluid and are not much affected by the equatorial singularity of steady boundary layers in spherical geometries.

A comparison between this method and the one based on boundary layer theory is carried out in the case of the steady spin-up of a fluid inside a sphere.  相似文献