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41.
余淑均 《武汉化工学院学报》2007,29(5):40-42
在分析不同国际组织、机构对环境友好技术概念的不同界定方法及其特点的基础上,以系统性、层次性和可操作性为原则,以环境亲和程度为标准,从基础绿色技术、创新绿色技术和生态绿色技术三个层次对绿色技术的涵义和类别进行了界定。 相似文献
42.
The deactivation characteristics of Pd/SiO2 in the selective hydrogenation of acetylene were correlated with changes in the amount of the C4 species produced. The amounts of butenes produced changed in parallel with the catalyst activity, indicating that the rate limiting step for butene production was the same as that for acetylene hydrogenation. On the other hand, the amount of 1,3-butadiene produced changed, showing a maximum with catalyst deactivation because 1,3-butadiene is an intermediate in the sequential reaction process which involves both the production and consumption of 1,3-butadiene. This was verified by a simultaneous TG/reaction experiment showing that 1,3-butadiene was a precursor of green oil. The catalyst showed a self-regenerative behavior in its activity and the amounts of C4 species produced during the early stage of deactivation because two opposite factors, which contributed to either the lowering or the promotion of activity, were involved in the process. A specific type of polymer species, produced during the initial period of deactivation, is proposed to be responsible for the promotion of catalyst activity. 相似文献
43.
Preparation of nanocrystalline ZSM-5 has been proven possible with carbon matrix by using confined space synthesis. In combination with the hydrothermal method, by the use of a mesoporous carbon nanotube as the inert support material, ZSM-5 with SiO2/Al2O3 ratios of 100 was successfully synthesized with an average crystal size of 27 nm. Their structures were preliminarily characterized by x-ray power diffraction (XRPD) and infrared spectroscopy (IR), and scanning electron microscopy (SEM), respectively. At the same time, we put forward the mechanism about the confined space synthesis in terms of the results. 相似文献
44.
Shift in thinking to address the 21st century hunger gap 总被引:1,自引:1,他引:0
Malin Falkenmark 《Water Resources Management》2007,21(1):3-18
The present water policy debate is dominated by the 30 yr old mission to secure water supply and sanitation to all people.
The water needed to produce a nutritionally acceptable diet for one person is however 70 times as large as the amount needed
for domestic water supply. The food security dilemma is largest in arid climate regions, a situation constituting a formidable
challenge. It is suggested that an additional 5 600 km3/yr of consumptive water use will be needed to produce an adequate amount of food by 2050 – i.e almost a doubling of today’s
consumptive use of 6800 km3/yr. Past misinterpretations and conceptual deficiencies show the importance of a shift in thinking. Combining the scale of
the challenge and the time scale of the efforts to feed humanity and eradicate hunger leads to an impression of great urgency.
This urgency strengthens the call for international research both for supporting agricultural upgrading, and for much better
handling of issues of environmental sustainability. What stands out is the need of a new generation of water professionals,
able to handle complexity and able to incorporate water implications of land use and of ecosystem health in integrated water
resources management. It will for those reasons be essential and urgent to upgrade the educational system to producing this
new generation. 相似文献
45.
46.
应用数学理论知识和CAD技术对施工图进行建模,从而获得准确的放样参数指导施工,并结合工程实例对计算机辅助施工放样过程进行了具体的介绍。 相似文献
47.
阐述了时空效应规律在软土深基坑工程中的运用情况,实践证明,运用时空效应规律,能可靠而合理地利用土体自身在基坑开挖过程中控制土体位移的潜力而达到保护环境的目的。 相似文献
48.
In this paper, some biparametric models for an elastic foundation are proposed. It is assumed that the foundation has the shape of the wedge. The modeling procedure starts from the linear elasticity equations into which we introduce some simplifying assumptions based on the conceptions of decay functions. The simplified models are described by the ordinary differential equations. Stationary and nonstationary Green’s functions for the foundation considered are obtained by applying the Hankel and Laplace transform methods. An example of the interaction between the rigid plate and the elastic wedge foundation is studied. 相似文献
49.
减少GPS接收机多径干扰的办法是采用特殊天线和在接收机中采取一定的措施。文中针对窄相关技术展开分析。重点分析影响接收机多径误差的因素及窄相关的性能,并给出仿真及分析结果。 相似文献
50.
星间激光通信技术进展与趋势 总被引:3,自引:3,他引:0
较详细地评述了目前国外卫星间光通信技术研究的现状.根据关键单元技术的进展情况,总结了未来星间光通信系统的发展趋势。 相似文献