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目的研究电子元器件表面化学防护的方法。方法应用选择性涂覆设备进行研究并优化工艺条件,选择丙烯酸清漆和稀释剂的体积混合比例从1∶0.2到1∶1进行实验,在100 mm/s的喷涂速度下,喷涂印制板的过程在0.5 min内完成,喷涂的相对标准偏差不超过±0.005 mm。结果涂层厚度可控制在25~75μm的范围内,符合国际标准ICP-CC-830的要求,涂层具有较好的流平性,无气泡、针孔和絮状物,无雾化等。结论这种方法可以成功地应用于印制板上电子元器件表面的化学防护。该方法具有涂覆准确性高,有毒稀释剂消耗量低,涂覆效果好,经济环保等的特点。 相似文献
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The economic inputs and outputs for the Possum Point Biological Station in Belize during 1990–1992 are described to illustrate
some aspects of an ecotourism operation. Eight hundred fifty-four people in 59 groups visited Possum Point during the study
period to tour rain forests, estuaries, and coral reefs. The economic input to Possum Point from these groups increased from
$74,552 in 1990 to $166,268 in 1992. Outputs were for license fees, capital improvements, goods and services, labor, fossil
fuels, and development of a historic sugar mill site. An annual donation was also made to a scholarship fund for local Belizean
students. The net cash balance of income and outputs changed from negative (−$6678) in 1990 to positive (+$4811) in 1992,
suggesting development of the economic operation. Possum Point meets the economic criteria for ecotourism by feeding back
some tourist monies for community and environmental support, particularly donations for the sugar mill site and the scholarship
fund. Most of the outputs from Possum Point (about 80%) were retained in the local economy through employment and purchases,
which have a positive influence on the local community. We conclude that ecotourism operations, such as Possum Point, offer
important sustainable development opportunities for Belize. 相似文献
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江静 《防灾科技学院学报》2005,7(2):107-110
本文采用次态卡诺图法对时序逻辑电路的功能进行分析,力图改进传统异步时序电路的分析方法,在保证分析结果正确无误的前提下,简化了常规分析方法中繁琐的步骤,更具有实用性。以一个8421BCD码表示的十进制异步减法计数器为例,给出各触发器状态方程的表达式,并用状态表、状态图分析其逻辑功能。 相似文献
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The U.S. Chemical Safety and Hazard Investigation Board (CSB) investigated three fatal dust explosions that all occurred in 2003. These explosions caused the deaths of 14 people and injured hundreds more. Two of the facilities were damaged beyond repair, and several hundred employees lost their jobs.
CSB's investigations revealed that the explosions had common causes, despite their geographic and industrial diversity. Consequently, CSB commissioned a study of combustible dust fire and explosion hazards. This paper presents a summary of CSB's findings and recommendations developed during that study. 相似文献
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Wildlife resources the world over have long been subject to harvest and management. As wildlife uses have grown, so too have the need and desire to ensure their sustainability.
This new context of sustainability presents opportunities to merge ecological, economic and social elements to foster development. This paper presents the management and harvesting of wild kangaroos as an example of the potentially sustainable use of a natural resource. Some comparisons are drawn between the use of other wild living resources, deer in Europe and crayfish in Western Australia. However, sustainability of kangaroo species and the industry is not just a matter of market economics and ecology, it must also be socially sustainable. The public policy instrument of a statutory advisory board with a marketing function is proposed in order to integrate the cultural and social aspects of kangaroo management with the economic and ecological aspects. Through such integration, full sustainability of a wild resource then might be achieved. 相似文献
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