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931.
932.
Bingyou Jiang Baiquan Lin Chuanjie Zhu Cheng Zhai Qian Liu 《Journal of Loss Prevention in the Process Industries》2013,26(4):782-791
A completely adiabatic pipe that is similar to a coal-mine coal or rock roadway was simulated using the computational software AutoReaGas. A partially adiabatic pipe was established using an experimental steel pipe with heat-insulating material installed in the inner wall, and a non-adiabatic pipe was also established using the experimental steel pipe without the heat-insulating material. Premixed methane/air deflagrations were studied in the three types of pipe to reveal the influence of the condition of the pipe wall on gas explosions. The results showed that in the completely adiabatic pipe, the maximum explosion overpressure was dynamic and decreased and increased with increasing distance; however, the flame-propagation speed increased gradually. In the partially adiabatic pipe and the non-adiabatic pipe, the maximum explosion overpressure and flame-propagation speed increased initially and then gradually decreased with increasing distance. The majority of explosion overpressure and flame-propagation speed values at each gauge in the completely adiabatic pipe were larger than those of the partially adiabatic pipe. Both measurements at each gauge in the partially adiabatic pipe were much greater than those of the non-adiabatic pipe. The condition of the pipe wall has a large influence on the maximum explosion overpressure and the flame-propagation speed. In future explosion experiments, heat insulating materials should be installed in the inner wall of steel pipes to obtain data for application to the prevention and control of gas explosions in underground coal mines. 相似文献
933.
青海省自然环境、人口容量探讨 总被引:1,自引:0,他引:1
本文通过对青海省自然地理环境及不同类型土地资源生产潜力分析基础上,按不同的生活水平指标,对青海省人口容量进行了初步定量探讨,并就提高人口容量提出了措施与对策。 相似文献
934.
本文论述了低丘红壤地区种植制度优化设计的原则和方法,指出引种玉米和制定最佳的作物生产群体是该地区种植制度优化设计的重要方面。 相似文献
935.
For decades, industry has been the main source of pollution in China. Determined to make changes, the mainland Chinese authorities have decided to promote mechanisms that incorporate environmental concerns into the internal management of enterprises. This is manifested in the rapid adoption of the ISO14000 standards, including a significant increase in ISO14001 registrations in China. Thus, this study examined the environmental policy statements of 106 certified facilities in mainland China against a strict interpretation of the mandatory requirements of the ISO 14001:1996 standard and the nonmandatory ISO14004 requirements in order to shed some light on the implementation of environmental management systems in an emerging economic giant. It was decided to analyze the environmental policy statement because such a statement is a core element in the ISO system of environmental management of each facility and there are relatively clear and specific requirements on what an environmental policy statement shall include. An analysis of the contents of the environmental policy statements shows that conformance to the relevant requirements of both the mandatory ISO14001 standard and the nonmandatory ISO14004 standard is far from impressive and that the facilities in our sample seldom went beyond the minimum requirements. By using ISO14001 and ISO14004 conformance scores as the dependent variables, we found that conformity to ISO14001 and overall conformance to ISO14000 series can be explained to some extent by the degree of top management commitment, the experience with informal environmental management systems, and the form of ownership of the facilities. 相似文献
936.
937.
在后混合磨料射流或准直管磨料射流中,为使水射流的动量能够充分传递给磨料,往往需要用准直管同轴套住水射流,以避免因流的侵入。准直管水射流流动特性是影响准直管磨料射流混合和加速磨料效果的主要因素,利用可视化实验和动量守恒原理对准直管水射流的流动特性进行了研究,其结果表明:准直管水射流流动特性状态随压力变化而变化;高压准直管水射流具有扩散流动段、平行流动段和回气流动段;高压准直管水射流的打击力具有沿程损失和出口损失。此外,还推导出了高压准直管水射流打击力的计算公式。 相似文献
938.
A single microwave extraction procedure was conducted to investigate the bioavailability of rare earth elements (REEs) by using different extractants of 0.05 M EDTA, 0.10 M CH3COOH, 0.10 M HCl, and 0.05 M CaCl2. The experimental conditions of heating time and microwave power were optimized. A microwave power of 60% and extraction time of 30 min were adopted. Compared to the conventional single extraction schemes reported in the literature, the recommended technique shortened the operational time, simplified the experimental task, improved the precision, and obtained consistent results with those obtained by using the conventional methods. In addition, the suggested microwave extraction method has been successfully used to evaluate the bioavailability of REEs in soils. Soil samples collected from 15 sites in China were extracted by four different extractants with microwave ancillary. Extractable REEs from soils were well correlated with REEs contents in shoots of wheat (Troticum aestivum L.) under the greenhouse conditions. The correlation coefficients were 0.6514-0.8996, 0.4522-0.7783, 0.6506-0.8671, 0.4869-0.7014 between the extractable REEs in soils and their concentrations in wheat shoots for the extractants of CaCl2, EDTA, CH3COOH and HCl, respectively. 相似文献
939.
通过介绍发生在台站附近一次"宏观异常"落实事件,结合当前防震减灾工作的重点,就今后地震台站所面临的新形势,如何贯彻防震减灾总体发展战略和部署,发挥地震监测一线的重要作用作一探讨.本文提出了台站要转变思想,拓展职能,不断增强其基层窗口作用,向现代化、多功能、综合型的模式发展的新思路. 相似文献
940.