钢制扬克平盖烘缸的结构优化

为了实现扬克烘缸的轻量化设计,针对规格为φ3 680 mm x3 120 mm的钢制扬克平盖烘缸进行有限元应力分 析,得出对烘缸应力强度产生显著影响的结构参数,在此基础上,分别用零阶和一阶2种优化方法对烘缸结构进行优化 设计,优化结果表明优化效果明显,达到了减轻质量、节约成本的目的。同时为钢制平盖烘缸结构优化设计提供参考。     

土地利用/土地覆盖变化对生态环境的影响

综合介绍了土地利用/土地覆盖变化对大气环境、水环境、土壤环境、生态系统以及生态安全的影响。     

The Impact of Climate Variability on Flood Risk in Poland

This article examines the role of climatic and hydrological variability in assessing the cumulative risk of flood events in Poland over a T-year period. In a broad sense flood-risk estimation combines a frequency analysis of extreme hydrological phenomena with an evaluation of flood-induced damages. The damage from floods depends on the critical values of the river discharges. The probabilistic flood analysis usually includes an estimation of the expected annual probability of the critical discharge Qcr being exceeded and the equivalent long-term risk of it being exceeded over the next T years. If, however, the process is nonstationary, the T-year risk of flood damage may depend importantly on the variation of hydrological processes. As a possible explanation for the variations observed in snowmelt-induced floods in Polish rivers, this article investigates the possible impact of the North Atlantic Oscillation (NAO) on surface air temperature T and precipitation P. The spatial distribution of the correlation coefficients between NAO and T, as well as NAO and P, show very significant differences in the NAO impact on meteorological variables in various parts of Europe. To assess the implications of NAO variations on spring flood discharges, a simple model of Snow Cover Water Equivalent (SCWE) was applied to selected Polish river catchments. The conclusion of this analysis is that the yearly maximum of SCWE values significantly decreases with increasing NAO. This leads to a temporal redistribution of winter and spring runoff. The question of spring flood characteristics being stationary or nonstationary may therefore be linked with stochastic properties of the NAO index time series.     

完全环和半完全环

本文定义了相对投射复盖,用它刻划了完全环和半完全环,并讨论了半完全环中生成子的等价条件.     

Proximate Population Factors and Deforestation in Tropical Agricultural Frontiers

Forest conversion for agriculture expansion is the most salient signature of human occupation of the earth's land surface. Although population growth and deforestation are significantly associated at the global and regional scales, evidence for population links to deforestation at micro-scales—where people are actually clearing forests—is scant. Much of the planet's forest elimination is proceeding along tropical agricultural frontiers. This article examines the evolution of thought on population–environment theories relevant to deforestation in tropical agricultural frontiers. Four primary ways by which population dynamics interact with frontier forest conversion are examined: population density, fertility, and household demographic composition, and in-migration.     

过去2000年中国环境变化综合研究的回顾

过去2 000年中国环境变化综合研究的目标有三个：其一,跟踪国际IGBP研究前沿;其二,中国作为东亚的重要地区,加上中华文明传承的大量文献记录,可以成为这个研究领域中中国对全球环境变化研究的独特贡献;其三,为全球变暖背景下国家的重大战略决策提供我们自己的科学参考。当然,中国环境变化综合研究的框架很大,但其中最主要的是气候变化中的温度问题以及土地利用和土地覆盖的变化问题等。     

滨水城市空间规划与雨洪管理研究初探：以荷兰城市阿尔梅勒为例

在全球气候变化的背景下,随着城市化进程的加快,许多城市面临了雨洪灾害的风险。而合理的城市空间规划对于雨洪管理是可以产生积极作用的。文章介绍了荷兰城市阿尔梅勒的地表水系与城市空间的特点,利用ARCGIS软件工具对它的地表水系形态与地表类型分布进行了统计分析。通过案例研究,对城市空间规划设计与雨洪管理之间的关系进行了探讨,提出了有利于减小城市雨洪风险的用地与水系规划的建议。     

多模态视角下《简·爱》中译本封面解析

任何文本的发展都脱离不了特定的社会文化语境。作为一部文学名著,《简·爱》在其传播的过程中受到多种因素制约,其封面便可集中反映这一点。因此,在视觉语法的基础上,从互动意义角度,对不同年代出版的具有代表性的《简·爱》中译本封面进行解读,有助于探讨《简·爱》在中国传播与接受的变迁过程。     

A {{10}}-Approximation Algorithm for a Generalization of the Weighted Edge-Dominating Set Problem

We study the approximability of the weighted edge-dominating set problem. Although even the unweighted case is NP-Complete, in this case a solution of size at most twice the minimum can be efficiently computed due to its close relationship with minimum maximal matching; however, in the weighted case such a nice relationship is not known to exist. In this paper, after showing that weighted edge domination is as hard to approximate as the well studied weighted vertex cover problem, we consider a natural strategy, reducing edge-dominating set to edge cover. Our main result is a simple -approximation algorithm for the weighted edge-dominating set problem, improving the existing ratio, due to a simple reduction to weighted vertex cover, of 2r _WVC, where r _WVC is the approximation guarantee of any polynomial-time weighted vertex cover algorithm. The best value of r _WVC currently stands at . Furthermore we establish that the factor of is tight in the sense that it coincides with the integrality gap incurred by a natural linear programming relaxation of the problem.     

荀子人性论及其政治观述评

荀子是我国古代杰出的思想家,先秦思想的集大成者。他独出特行的“性恶论”认为,人性好利恶害,人们并因此引发争夺、导致战乱。然而,人的先天恶性可以通过“化性起伪”即后天的礼义教化、法规约束使之弃恶从善。荀子在“性恶论”基础上建构了以“隆礼”“重法”为核心的政治学说,富有创见地提出了“王霸兼用”、“礼法并施”的治国理念。荀子鉴古察今的政治智慧至今仍能给予世人启迪与裨益。