Applying search theory to determine the feasibility of eradicating an invasive population in natural environments

The detectability of invasive organisms influences the feasibility of eradicating an infestation. Search theory offers a framework for defining and measuring detectability, taking account of searcher ability, biological factors and the search environment. In this paper, search theory concepts are incorporated into a population model, and the costs of search and control are calculated as functions of the amount of search effort (the decision variable). Simulations are performed on a set of weed scenarios in a natural environment, involving different combinations of plant longevity, seed longevity and plant fecundity. Results provide preliminary estimates of the cost and duration of eradication programs to assist in prioritising weeds for control. The analysis shows that the success of an eradication program depends critically on the detectability of the target plant, the effectiveness of the control method, the labour requirements for search and control, and the germination rate of the plant.     

中国城市化水平测定研究综述

城市化水平测度的方法主要有两种 :主要指标法和复合指标法 ,而人口比例指标则又是主要指标法中最常用的城市化测度指标。文章回顾了我国城镇人口统计口径的历次演变 ,阐明了其中存在的主要问题 ,综合论述并评价了国内学者对这些问题的解决办法 ;同时进一步讨论了对其它主要指标法和复合指标法的研究 ,分析了存在的缺陷。     

城市人口流动的灰色关联分析

以泰州市为例,收集了2002—2009年的多方面的数据,对人口的构成及其发展进行了分析;利用灰色关联分析对数据进行处理,通过关联度的计算,指出城乡收入差距是引起人口流动的主要原因,给出了相关建议,促进农村人口流动与就业的协调发展。     

山东省农业转移人口市民化成本测算及分担机制构建

农业转移人口市民化的综合成本主要包括政府财政负担的公共成本和个人承担的个人成本两部分。采用分类加总法测算得出山东省农业转移人口市民化的人均公共成本约为15.07万元,个人成本约为2.37万元/年,同时绝大多数农业转移人口还需要集中支付一笔可观的购房成本,人均约12.43万元。合理消化这一巨额成本,需要发挥政府的主导作用,同时鼓励企业、农业转移人口、社会积极参与,构建一个由政府、企业、农业转移人口、社会等共同参与的多元化成本及责任分担机制。     

人口老龄化背景下如何构建我国的农村养老保险制度

人口老龄化是我国未来面临的一个重大问题,它对我国,特别是对农村的养老保险制度提出了挑战.针对我国农村养老保险制度现存的问题,提出了构建合理有效的农村养老保险制度的若干建议.     

从酸刺村看宁夏南部山区人口发展问题

人口过快的增长是制约宁南山区经济发展的关键所在.科技扶贫是以人为本的扶贫,有利于经济发展和人口素质的提高.本文通过对宁南西吉县酸刺村的调查分析来论述宁夏南部山区的人口发展问题.     

城市人口研究的视点

从城市人口的一个重要视点——“居住地”和“工作地”的人口概念出发 ,对城市中发生的许多现象进行了解释。对“工作地”和“生活地”的城市人口的研究 ,把人口学研究和社会学、经济学、地理学等多学科的研究结合起来 ,能丰富和拓展人口研究的内容。还介绍了“居住地”和“工作地”的人口资料来源     

人类能最终战胜“人口魔鬼”吗？

界定了两种"人口魔鬼"的概念,并简单回顾了人类与"人口魔鬼"斗争的历程.在今后几十年或者稍长的时间里,世界人口总数不会无限增殖下去,人类有望战胜"过剩人口魔鬼".但在达到人口顶峰后,由于人口持续缩减,人类的未来不太乐观.     

Social Security and personal saving: 1971 and beyond

Feldstein (1996, 1974) reported that Social Security in the U.S.A. reduced personal saving (“saving”) in 1992 (1971) by $416 ($61) billion. I reestimate his life-cycle consumption specification using data from the latest NIPA revision, correct his calculations, and find that the implied reduction in 1992 (1971) saving is now $280 ($22) billion, 48% (16%) of actual net private saving, with a standard error of $114 ($14) billion. If structural breaks around WWII and the 1972 Social Security amendments (which raised real per capita SSW by 22%) are allowed, and the market value of Treasury debt included in the specification, the reduction in 1971 and 1992 saving attributable to Social Security is at most 0.55 times its standard error, and 12% of net private saving. I then reestimate the preferred specification of Coates and Humphreys (1999), allowing for these structural breaks and relaxing other restrictions. The implied effect of Social Security on saving is again statistically zero. First version received: September 2000/Final version received: September 2001 RID="*" ID="*"  I thank Les Oxley for pointing out that correcting for AR(1) residuals is not a categorical imperative but a cultural relative, in which case common factor restrictions are crucial.     

基于GIS的大连地被指数研究

根据<国家人口发展功能分区技术导则>要求,在大连市人口发展功能区规划中首要进行的工作就是大连市人居环境适应性评价,而影响人居环境适宜性的诸多自然因素中,最为根本且起主导作用的则主要为能综合反映区域自然条件的土地利用及土地覆盖特征.本文基于gis手段,利用mapinfo和idris软件,以大连市乡镇街道和公里网格为评价单...