美国国家公园系统保护区规模的变化特征及其原因分析

美国国家公园系统的保护区其规模具有随保护区类型、建设时间和地区分布的不同而变化的特征。自然保护思想和保护区建设中土地的可获得性是形成上述特征的主要因素。其中自然保护思想对保护区规模大小有指导作用，而土地的可获得性则直接影响保护区面积。     

国内地质学领域研究热点文献计量学分析

本文选取中国知网数据库（CNKI）中的中文期刊全文数据库作为数据来源,对地质学领域的10种中文核心期刊相关科技论文开展文献计量分析,着重分析了近五年来所刊载科技论文的发表量、基金资助、学科分布和关键词等特征及变化趋势。了解了近年来我国地质学领域研究的基本信息和研究热点,分析结果可以为今后进一步把握学科领域发展方向提供参考。     

广州长者饭堂供需匹配的类型、差异及调整思路

以广州市长者饭堂为研究对象,采用百度地图API、居民点POI、广州市为老综合服务平台等多源数据,综合考虑可达性和运营可行性,并对两步移动搜索法进行改进,通过转换测度结果和过程变量,刻画长者饭堂的供需匹配情景。研究发现：1）广州长者饭堂在“行政单元全覆盖”推广下供需空间匹配度六成合格,形成平衡型、剩余型和短缺型的数量“631”结构;2）供给和需求的主体优势、空间分布错位,需求获取优势高于供给,空间呈现“内低外高—单中心圈层”供给结构与“南强北弱—多核网状”需求结构;3）出行优势中心两级分化,成为剩余型和短缺型的主要聚集地。主核心片内出现“老城中心洼地”和“黄埔高地”,外围行政区出现多个剩余小高地或短缺谷地。最后,为精准干预长者饭堂网点布局,提出存量提升、配对整合、存量精简等适宜不同空间关联条件的不匹配型优化思路,优先考虑强空间关联的剩余型和短缺型街道配对整合;以及直接提升、主动提升、被动提升的匹配型提升思路,实现广州长者饭堂全覆盖全匹配目标。     

Long-term Circulation and Eutrophication Model for Tolo Harbour,Hong Kong

Since the early 1980s excessive discharges of organic waste into Tolo Harbour have created serious problems through nutrient enrichment. A number of eutrophication related problems have been reported which incurred financial losses of billions of dollars and serious ecological imbalance. This work addresses the development, verification and application of a water quality model to synthesize the available large database of water quality and to study water quality management issues of Tolo Harbour. Since detrimental water quality problems usually occur during summer when there is stratification and the water temperature is high, the tidally-averaged hydrodynamics and the relative contribution of gravitational circulation and tidal exchanges in Tolo Harbour have been studied. Gravitational circulation is found to be the dominant mixing process for most of the year, accounting for 70 percent of the mixing. A simple and tractable predictive two-layer mass transport and diagenetic dynamic eutrophication model has been developed. The model computes daily variation of key water quality variables in the water column: algal biomass, dissolved oxygen, organic-nitrogen, ammonium-nitrogen, nitrate-nitrogen, and carboneous oxygen demand. In addition, to study the response and impact of the seabed to the overall eutrophication process a sediment sub-model is developed. The diagenetic sediment sub-model computes explicitly the amount of nutrient recycled and the sediment oxygen demand exerted on the water column. The calibrated model has been validated against a 20 year water quality data base under a wide range of hydro-meteorological and environmental conditions. Both spatial and seasonal variation of observed water quality variables are reproduced. The verified model shows that a significant reduction of total nitrogen loading would be required to meet the water quality objectives, with a recovery time of three months for water column and more than two years for sediment.     

Forest conversion, conservation and forestry in Cross River State, Nigeria

This paper presents new data on the rate and patterns of loss of tropical moist forest cover to agriculture in Cross River State, Nigeria. Data from sequential aerial photographs and field surveys are used to derive an estimate of forest loss of 0.6 per cent per year. This rate is relatively modest, yet current conservation and forestry policy in the area is based on assumptions of rapid conversion of forest. The implications of these findings for debates about conservation and policy are discussed.     

地球空间信息学与数字地球

叙述了地球空间信息学和数字地球的基本概念。讨论了地球空间信息学的形成、理论基础和技术体系,以及数字地球的关键技术和应用。分析了两者的相互关系,提出空间数据基础设施是数字地球的基本建设,发展数字地球为传统测绘行业带来了一个极好的发展机遇和一系列的挑战。     

美国国家科学基金会(NSF)地学学部(GEO)基金资助战略分析

美国国家科学基金会（NSF）是国际上具有重要影响的资助基础科学研究的政府基金机构，对促进美国基础科学研究的发展和保持世界领先地位做出了重要贡献。其对基础研究的资助政策、方向遴选、评审程序、经费分配、管理机制等，形成了一套行之有效的模式，对其它国家的基础研究政府资助机构具有借鉴和示范意义。在分析美国NSF近3年经费状况及其领域分配情况、近5年项目受理与批准情况、近12年项目评议情况的基础上，重点分析了地学学部（GEO）的近期重点资助领域、近3年按照NSF的整体优先领域和战略产出目标的经费分配情况、近10年按科学处的经费分配情况及变化趋势、各科学处2004—2006财政年度经费状况与重点资助领域、近10年项目的资助率与资助强度变化情况等。NSF地学学部是美国政府资助以大学为主的地学基础研究的主要渠道，其经费约占美国政府资助地学基础研究经费的62%。对NSF的基金项目资助战略，特别是对其地学学部项目的资助情况予以全面分析，对我国相关部门的管理工作有重要参考价值和借鉴意义。     

应用ATC-40能力谱法评估结构目标位移

基于性能的抗震设计思想已得到国际上的普遍认可,其发展的一种趋势是建立简单的非线性方法确定结构非线性行为。非线性静力方法作为计算结构非线性行为的一种方法在工程界已得到普遍应用,其中ATC-40使用的能力谱法及改进的能力谱法是简化的非线性静力分析的主要方法。本文通过实例详细介绍并对比研究了这两种方法,发现ATC-40能力谱法低估了结构变形,改进的能力谱法(用非弹性设计谱建立需求谱)提供了相对较为准确的值。     

Ground-Motion Prediction Equations (GMPEs) for inelastic displacement and ductility demands of constant-strength SDOF systems

The objective of this paper is to present ground-motion prediction equations for ductility demand and inelastic spectral displacement of constant-strength perfectly elasto-plastic single-degree-of-freedom (SDOF) oscillators. Empirical equations have been developed to compute the ductility demand as a function of two earthquake parameters; moment magnitude, and source-to-site distance; one site parameter, the ground type; and three oscillator parameters, an undamped natural period, critical damping ratio, and the mass-normalized yield strength. In addition, a comparative study of the proposed model with selected previous studies and recommendations of Eurocode 8 is presented. Proposed equations can easily be incorporated in existing probabilistic seismic hazard analysis (PSHA) software packages with the introduction of an additional parameter. This leads to hazard curves for inelastic spectral displacement, which can provide better estimates of target displacement for nonlinear static procedures and an efficient intensity measure for probabilistic seismic demand analysis (PSDA). Proposed equations will be useful in performance evaluation of existing structures.     

有线光纤电视综述

有线电视ＣＡＴＶ正在迅速深入千家万户。有线光纤电视网将是２１世纪地面的主要广播形式。“信息高速公路”是将电脑、电话、电视结合在一起的通信网络。有线光纤电视网是“信息高速公路”的重要组成部分之一