拉格兰德二级电站严重汽蚀问题的解决

格拉兰德二级电站由多米宁工程公司供货的第一台机组,投入运行后3000小时就发现了严重的汽蚀问题。经几次对原型机组进行修正无效,为了尽快解决问题,进行了一系列模型试验。通过花费了几个月时间作的这些试验,得到了非常满意的简单易行的解决办法。     

高等教育多元投入模式

高等教育经费短缺已经成为一个世界性问题,拓宽经费渠道,提高投资的效率和效益,是各国高等教育投入模式改革的普遍趋势。国家和社会“不应把高校看成一种预算上的负担,而应看成加强经济竞争力、发展文化和加强民族的社会凝聚力的长期投资”。因此,充分认清高等教育的经济属性,明确对其投入的合理模式,改革现有投入模式的弊端,具有非常重要的战略意义。     

闸下出流量估算

垂直闸门的闸下出流,只要闸门开度a比上、下游水位H_0、H_1小的情况下,可假定其出流量与通过矩形孔口的出流量相同。     

走向明天的辉煌

茄子河,一个别致的名字。它镶嵌在七台河市东部地区的版图上。它的周围分别与宝清、密山、鸡东、北兴农场接壤。总人口12.6万,面积1558.4平方公里。区内地下资源丰富,不仅有可开采的黄金、煤炭,还有石灰石、花岗岩、腐植酸、矿泉水等。森林资源更是     

Households,history and black urbanisation: response to Graaff

A critique of a recent article by J. F. de V. Graaff concerning urbanization of blacks in South Africa is presented. A reply by Graaff (pp. 402-4) is included.     

The environment for development

This overview of the World Bank 1992 World Development Report reveals some of the means to close the gap between policy and practice in linking environmental and development policy. The nature of the problem is defined and win-win policies which show mutual support for environment and development concerns are differentiated from negative links. Sound environmental management can be achieved with improved information, enhancing institutional arrangements, and involving local people. The rapid implementation of policies and programs will involve both political and financial costs and a shift in policies and priorities. The challenges ahead are tremendous and include overcoming poverty and turning population growth and environmental pollution around. World consumption of energy and manufactured goods is expected to triple; without curbs on emissions, mortality increases, water shortages, and forest and natural habitat loss will ensue. It is not entirely true that economic activity hurts the environment when positive forces of substitution, technological innovation, and structural change outweigh the negative consequences. Environmental consequences change with income levels. Some problems decline with income increases. Some problems deteriorate temporarily and then improve as incomes rise, i.e., air and water pollution and some types of deforestation and habitat dislocation. Some problems continue to grow with income increases, such as carbon and nitrogen oxide emissions. Win-win policies are ones that foster and end to excessive resource use, clarify property rights and stop open access to land, accelerate education and family planning programs, accelerate agricultural extension and research, and invest in sanitation and water supply. These policies will not sacrifice economic growth. Tradeoffs must be identified and costs and benefits of alternative policies assessed; priorities and standards must be established in consort with costs and benefits. Behavior change can be achieved with properly designed practical and cost-effective policies.     

Combining health education, risk-rated insurance and employee rebates into an integrated health care cost management strategy

Health education, risk rating and employee rebates can be combined into a comprehensive health promotion program within a benefits plan, reflecting health promotion in its truest sense.     

The Harris-Todaro model and economies of scale

The authors attempt to reanalyze the Harris-Todaro migration model in the presence of economies of scale in the manufacturing sector, focusing on economies of scale that are external to a given firm but internal to the industry.