江苏省耕地资源劳动力承载力研究

农业剩余劳动力的转移问题是中国目前重要的社会和经济问题,论文从农业耕地资源所能承栽的劳动力数量角度,对此问题进行探讨,利用最小劳均耕地面积、规模种植压力指数和耕地资源劳动力承栽力指数等概念对江苏省2005年实际需要的农林牧渔业劳动力数量、耕地的规模压力指数、农林牧渔业剩余劳动力进行了估算。     

中国耕地压力指数时空规律分析

耕地压力指数是指最小人均耕地面积与实际人均耕地面积之比。文章通过对改革开放以来我国耕地压力指数的测算，发现耕地压力指数在1981年～1996年间呈下降趋势，主要原因是由于期间最小人均耕地面积减少速度大于实际人均耕地面积的减少速度；1996年后耕地压力指数整体处于上升趋势，这主要是由于期间实际人均耕地面积急剧减少所致。通过对2004年各省份压力指数的测算，发现有21个省份的耕地压力指数大于1，其中上海的耕地压力指数达到了2.84；即便是在无明显压力的5个省份中，其压力指数也均在0.78以上，区域耕地压力非常明显。导致各省份耕地压力指数过大的主要原因有3个：一是由于耕地大量被占用，实际人均耕地面积偏小而导致的压力指数过大；二是因单产水平过低而导致最小人均耕地面积偏大，从而使压力指数偏大；三是粮食主产区由于要承担国家商品粮任务，使区域粮食自给率过高，导致最小人均耕地面积过大，从而使耕地压力指数偏大。通过控制耕地面积减少速度、提高农业科技水平可以有效缓解耕地压力状况。     

区域粮食安全性分析与预测 ——以陕西省关中地区为例

本文根据最小人均耕地面积和耕地压力指数理论,应用趋势预测分析和回归分析方法,建立研究区域粮食安全状况预测模型,进行预测分析研究.论文主要以陕西省关中地区为例进行分析与实践论证.结果为,1999年关中地区粮食处于安全状态,对于各个地区而言,西安和铜川的粮食状况不容乐观;而宝鸡、咸阳、渭南和杨陵区粮食状况相对安全.特别是杨陵区,在农业科技不断进步的作用下,耕地生产力水平提高,因此粮食状况最安全.到2015年如果人均粮食消费以小康水平记,关中地区耕地承受压力明显增加,甚至超过了耕地压力安全警戒线.关中地区各地耕地压力指数都比1999年的要大,特别是西安和铜川.另外,在粮食增长的同时,需加大灌溉用水,机械、化肥等物质生产资料的投入,必将导致粮食价格上涨,从而影响社会经济;而且,大量的化肥使用威胁生态系统安全.为防止关中出现粮食及相关问题,应限制耕地流失,加大农业科技投入,发展高效生态农业,促进农民产粮积极性.     

浙江省近期农作物播种面积的变化及其主导因素分析

利用1978年～2005年农产品成本收益资料和农业统计资料,研究了浙江省稻谷和棉花播种面积变化情况,及其与纯收益相关性和对劳动力投入的弹性。结果表明：近年来浙江省农作物播种面积下降迅速,除耕地面积减少原因外,农业劳动力投入下降造成的耕地复种指数降低是主要原因;从播种面积和纯收益的相关性分析看出,稻谷播种面积受纯收益影响较小,棉花播种面积变化一定程度上受到纯收益影响,但影响程度不大;而稻谷与棉花播种面积对劳动力投入的敏感性较大,且弹性系数呈显著增高趋势,棉花由于耗工量较大,对劳动力投入逐渐由缺乏弹性过渡到富有弹性。文章认为,目前促进我国农业生产的关键是推进土地适度规模经营,在加速机械替补劳动力投入不足的同时,提高农业的劳动回报率。     

西北地区水资源承载力分析预测与评价

水资源是干旱、半干旱地区社会经济发展和生态环境保护的关键制约因素，水资源承载力的分析计算和评价是干旱、半干旱地区寻求区域可持续发展道路的重要依据。该文探讨了水资源承载力状况的评价方法，建立了水资源承载力评价指标体系，对各评价指标的可承载极限临界值和理想值进行了界定，建立了水资源承载力模糊综合评判模型，并运用之对西北地区现状年及未来10a、20a、50a不同发展情景方案下的水资源承载状况进行了评价。模型预测结果表明，通过生态环境治理、节水技术进步和产业结构调整等综合措施，未来各年段西北地区水资源承载力状况将逐步改善，其中以采用A1+B2+C2发展情景方案将使水资源承载状况综合效果最佳，节约用水、降低水资源开发利用率，提高用水效率和控制人口增长则是提高西北地区水资源承载力水平的关键因素。     

集约化农区耕地资源多样性及其发展模式

保护耕地资源生态多样性与提高耕地集约利用效益,对集约化农区耕地资源可持续发展具有重要意义.本文应用生态足迹方法,以新疆生产建设兵团45团灌区为例,对集约化条件下耕地资源生态多样性及其利用模式进行了分析.结果表明:1995年～2005年灌区耕地人均生态足迹呈逐年增加趋势,且与生态承载力基本协调;灌区耕地生态足迹的多样性指数呈现逐年下降的趋势,发展能力有待提高;耕地资源发展能力与多样性指数、GDP足迹三者之间关系达到极显著或显著水平.因此,积极稳妥的搞好集约化农区农业结构调整,走农林牧复合型农业发展模式,是促进耕地资源生态多样性、提高耕地资源集约利用效益的有效手段,最终建立资源节约型和环境友好型的耕地利用保障体系.     

明代以前黑河流域耕地面积重建

受人类活动变迁影响,黑河流域作为我国西北地区重要产粮基地以及大规模绿洲农业开发最早地区之一,其境内的耕地规模自古至今变化十分频繁.由于文献记载的有限性和疏漏性,目前关于区域内明代以前的耕地面积历史变化情况的分析十分欠缺.本文选择文献较丰富的汉、唐和元代,依据历史文献资料和前人研究成果,以人口数据为基础,运用基于人均耕地面积和粮食产量两种途径重建了黑河流域明代以前耕地面积.前者按各时期屯田制度,结合人均垦地面积分别重建民户耕地和军屯占地情况,汇总两类耕地面积进行重建,后者利用人均粮食消耗、耕地单产情况估算人均耕地需求,再结合人口数据重建耕地总量.重建结果表明黑河流域明代以前耕地面积以西汉时期为最大,达(16.30～19.49)万hm2,其后总体呈下降趋势,东汉、唐代与元代的面积分别为(9.57～11.80)万hm2,(3.59 ～3.93)万hm2和3.19万hm2.对比表明两种重建结果基本一致,证实了重建结果具有可靠性并在一定程度上可以反映研究时期内耕地规模的变化趋势.     

基于水足迹视角的中国北方10省三大粮食作物种植结构优化

水资源短缺与水-土-粮系统不协调是制约中国粮食生产可持续发展的重要因素,种植结构优化作为农业结构型节水的重要举措,对保障中国水资源安全与粮食安全具有重要意义。本文聚焦中国北方10省,揭示水足迹视角下水资源压力与三大粮食作物种植结构的关系,探讨不同目标权重情景下三大粮食作物种植结构的优化趋势,并通过构建多目标种植结构优化模型,得出不同节水情景下北方10省三大粮食作物种植结构优化方案。研究表明：①中国北方10省中粮食种植规模较大的地区水资源压力指数普遍偏高,水资源约束呈趋紧态势;②当使用熵权法对经济收益、蓝水（灌溉水）消耗和绿水（雨水）利用目标客观赋权时,北方10省将增加高收益高耗水的水稻种植。随着蓝水消耗最小化目标的权重逐渐加大,水稻种植面积和蓝水耗水量会逐步减少;③在15%节水情景中,山东、山西、内蒙古、陕西、甘肃、青海应调增玉米种植面积而减少水稻和小麦的种植面积,宁夏和新疆应调增小麦种植面积而调减水稻和玉米的种植面积,河南应调增水稻和玉米的种植面积而减少小麦的种植面积;④在节水5%、10%和15%情景中,优化的种植结构能够使北方10省三大粮食作物生产的蓝水足迹总量较2019年分别减少38亿m³、51亿m³和64亿m³,平均单位蓝水足迹的现金收益提升4%、3%和2%。本文结果对保障中国粮食安全,实现农业可持续发展具有重要的政策启示。     

矿业城市耕地资源时空动态变化特征分析

采用六盘水市1990-2010年遥感解译获取的土地利用变化数据,研究六盘水市1990年以来耕地资源时空变化过程。结合土地利用动态度模型、耕地变化强度指数和耕地变化空间分异指数分析六盘水市各乡镇耕地变化的地域差异。结果表明:1990-2010年,六盘水市耕地面积呈现先小幅增加后大幅减少的趋势;六枝特区在2000-2010年间耕地面积年变化率明显高于其他地区,耕地面积减少较快;各乡镇耕地变化强度差异较大,其中钟山区的凤凰、荷城办事处,德坞、黄土坡办事处以及水城县的比德乡耕地变化强度指数均在50%以上,最小的仅为0.07%。     

20世纪60年代以来日本耕地面积变化及其启示

本文截取1961年以后日本经济发展相对平稳的时间段,研究耕地面积变化及其驱动机制,可以在一定程度上避免重大历史事件对统计数据的干扰,从而得出符合社会发展规律的结论。研究结果表明,1960年以来日本耕地面积和人均耕地面积一直呈下降趋势,到2003年分别为1961年的79%和60%,符合直线变化规律。单位农业劳动力占有的耕地面积从1961年的0.2060hm2/人上升至1.0870hm2/人,接近1961年的5倍,符合二次曲线变化规律。借助主成分分析和回归分析方法对耕地面积驱动力的研究结果表明,经济发展造成的工业用地和城市用地面积扩大是耕地面积减少的根本原因;农产品价格的变化也造成部分耕地退出耕作;随着经济技术水平的提高和防灾减灾能力的增强,因自然灾害造成的耕地损失逐渐减少。增加耕地面积的诸因素中,土地开垦始终处于主导地位,其次为土地整理和复垦。在我国未来的经济发展过程中,要摒弃城市化进程中后期耕地流失会相应减少的观念;警惕加入WTO之后,农产品市场开放可能对粮食安全和我国耕地面积的影响;同时还要坚持耕地保护政策的持久性。     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.     

Rough Justice: A Statistical Assessment of ICANN's Uniform Dispute Resolution Policy

Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP.     

Prevalence of soft neurological signs in Chinese people

Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Monoculture Rubber Plantations Have Negative Ef ects on Controlling Splash Erosion

<正>In Xishuangbanna,one of China’s most biodiverse regions,landscape has changed dramatically during the past three decades due to the conversion of tropical rainforest to rubber plantations.In steep areas,terraces are often constructed before planting rubber trees,which causes two important changes in the soil:the destabilization of soil in the bench terraces and the increased vulnerability of unvegetated riser faces to erosion.Few studies have documented the nature and intensity of erosion on bench terraces.Prof.LIU Wenjie and his colleagues from the Xishuangbanna Tropical Botanical Garden(XTBG)conducted a study in Menglun County(21°5′39″N,101°15′55″E),Xishuangbanna to evaluate the influence