共查询到20条相似文献,搜索用时 8 毫秒
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SUMMARY In many developing countries, the determination of a ranking of investments designed to improve and extend the road system is a commonplace prerequisite of planning for the transport sector as a whole and the road sub-sector within it. A major objective of determining investment priorities is to secure the greatest efficiency in the use of resources allocated to the sector and, for this reason, any system of assigning priorities must rely upon conventional investment appraisal techniques producing quantifiable measures of worth. Exercises of this kind, in which road investments are identified and ranked, are usually undertaken to produce a road sector investment plan. The implementation of such plans is, however, often compromised because of perceived deficiencies with a methodology which places undue reliance on investment appraisal and fails to properly address the issue of public interest and sustainability. This paper attempts to produce a pragmatic set of ground rules which, while mindful of the need to promote economic efficiency, allow for other factors to be embraced in a more holistic methodology. 相似文献
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E. Yoshioka 《Marine Biology》1987,96(3):371-374
Annual reproductive cycle of the chiton Acanthopleura japonica (Lischke) was studied by observing both gonad index and histological features from October 1980 to October 1981. No significant changes in each factor were observed from October to April. Increased values of gonad index and spermatogenesis or vitellogenesis in gondas were observed from May to September. In the same time, gonad index decreased and sperms or oocytes in gonalds disappeared in the days around spring tide, and they were recovered around neap tide. Suggested spawning around spring tide from May to September is also supported by the occurrence of released eggs in the days around the new and full moons. 相似文献
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Ffion C. W. Davies 《Environmental geochemistry and health》1991,13(1):35-38
Minamata disease first became evident in Japan in 1956 and was caused by methyl mercury exposure. Over 20,000 people are now thought to have been affected. This article compares the situation immediately following the initial discovery with that now prevalent.The author, then a final year medical student, spent her elective period (a nine week study period) in the area in the summer of 1989. This paper is based on that experience and is published in order to provide an update on a classic pollution episode which was widely publicised in the years immediately after its discovery but about which less has been heard in recent years. 相似文献