虚拟专用网技术在远程数据传输中的应用

野外地质调查工作者作为远程用户需要与其所在的地质调查研究机构进行数据的安全传输.应用虚拟专用网络技术可以在使用公用网络进行数据传输时保证其安全.本文讨论了虚拟专用网的分类、关键技术,通过分析某地质研究所的网络拓扑,给出了一个虚拟专用网的解决方案,对其中的基于Windows Server 2003的虚拟专用网服务器进行了详细配置.     

Economy,culture and environment: perspectives on the Australian food industry

Intersections between economy, culture and environment pose exciting future challenges for human geography. Part of Griffith Taylor's pioneering role as a geographer was to investigate relationships between these three aspects of human life, although his agenda was that of environmental determinism. This paper considers these intersections as they relate to contemporary geographical studies of restructuring, in particular the emergence of a genuinely global economic system since about 1980. Recent developments in cultural geography argue that geographical analysis of restructuring has been dominated by an economic determinism which has buried other stories which could be told about industrial change. The paper sketches lines of possible dialogue between economic geography and cultural studies, illustrating the argument with examples from restructuring in the Australian food industry. In opening such a dialogue, economic geography would be better placed to return to interactions between economy, culture and environment. In his day, Taylor was not afraid to upset the conventional wisdom about these relationships and this may be one of his most enduring legacies.     

新形势下测绘保密工作的思考

在《中华人民共和国测绘成果管理规定》及其相关的管理规定中 ,对基础测绘成果保密等级的划分、调整和解密都作了详细的规定。但是在新形势下 ,现行保密法规的对象发生了变化 ,传统的保密管理方式已不适用 ,因此 ,应在保守国家核心机密的前提下 ,重新审定各种地理信息产品的密级 ,最大限度地扩大流通服务范围 ,使地理信息能更多更好地为国民经济建设服务     

发达国家资源安全供应模式及其借鉴意义

资源安全供应是保障国民经济持续健康发展的必要条件。阐述了发达国家资源安全供应的3个模式：比较优势模式、贸易一投资模式和系统论模式。通过实例，就模式的作用机理进行了简要分析。结合我国的实际情况，借鉴发达国家资源安全供应的经验，就我国资源的安全供应提出了4个方面的建议。     

湖南土地资源可持续利用的生态安全评价

生态安全是土地可持续利用的基础，土地生态安全评价是土地可持续利用研究的前沿课题。以湖南省14个地州市为样本，从1999年社会经济和土地生态环境压力、土地生态环境质量、土地生态环境保护和整治能力等方面的运行数据中选取人口密度、城镇化水平、人均耕地等24个指标，采用均方差客观赋权，从各指标的统计特征值及全国的平均值出发，确定本省的生态安全评价阈值S，计算各地市多指标加权综合评价值，试图对本省土地生态安全进行客观综合评价。     

防震减灾技术系统网络应用中的网络安全

扼要介绍计算机网络安全结构及Internet网络应用中的数据服务。国家防震减灾技术系统网络中心计算机网络的组成及安全。介绍了Internet提供的服务；网络中心与Internet的2个出口以及它提供的DNS、FTP、E－MAIL、WWW等服务。重点介绍网络中心的防火墙安全及防火墙的过滤作用。     

中国食物安全基础的定量评估

食物安全水平受粮食生产和供给能力、食物结构的多样化以及居民的收入水平或获取维持生命所需食物的能力等因素共同作用和影响。本文从食物安全的内涵出发,依据评价指标选取原则,选定了与食物安全密切相关的评价指标,包括粮食自给率、食物消费水平及居民消费水平等,构建了食物安全可持续性综合指数模型,计算了1950～1998年我国食物安全可持续性综合指数,对我国食物安全可持续状况进行了单因子和多因子综合评价。结果表明:在50年代我国处于食物基本安全状态,60～70年代处于食物不安全状态,80年代初期及至90年代已进入食物安全阶段。从60年代开始食物安全水平逐年提高,80年代以来进入持续良性发展阶段。     

Diel changes in the feeding behaviour of Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in Ellidavatn, a small lake in southwest Iceland

In the lake Ellidavatn, southwest Iceland, the diel activity of Arctic char and brown trout was studied in autumn (September) and spring (April) by removing the fish from gillnets every 3 hours for three days. Additional fish samples, evening and morning, were taken at other times of the year. The catch per unit effort was about 10 times higher during the nighttime than daytime for both char and trout. The median weight of char was lowest near the middle of night (80 g) and highest near the middle of day (140 g). The median weight of trout was also lowest near the middle of night (110 g) and highest near the middle of day (330 g). The main diet of char consisted of the cladoceran Eurycercus lamellatus in September and chironomid larvae in April and the main diet of trout was always sticklebacks. In autumn and spring, the feeding was nocturnal in the char but crepuscular in the trout. The median stomach content of char was highest at dawn (0.52% of body weight) and lowest at dusk (0.14% of body weight). It is proposed that nocturnal char shift through the bottom substrate in search for prey. The median stomach content of trout was highest at 09.00–18.00 and 24.00–03.00 hours (0.13–0.18% of body weight) and lowest at 03.00–06.00 and 18.00–21.00 hours (0.02–0.07% of body weight). Different feeding times may help to secure mutual coexistence of char and trout in a small lake. In autumn and spring, the average daily consumption of char was about 0.8% of body weight, less than half their maximum food intake.     

南极中山站附近麦氏贼鸥食性研究

对东南极中山站附近麦氏贼鸥巢区和无巢贼鸥群栖地的贼鸥回吐渣团及其他食物残物进行收集、分析和鉴定 ,结果表明 ,本区麦氏贼鸥主要捕食雪　 ,其残物在食物项中的平均出现率为 6 7～ 80 %;同时贼鸥从本区几个考察站觅取人类遗弃的垃圾食物作为其重要的食物补充 ,垃圾食物的平均出现率为 6 .8～ 1 1 .6 %。不同巢区贼鸥对雪　的捕杀量和垃圾的需求差异较大 ,其主要与营巢地域的雪　分布密度以及摄食区的占有与否有关。