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921.
混沌理论:人类认识自然灾害的工具之一 总被引:8,自引:1,他引:7
自然灾害实际上是“人-自然系统”呈现为一种无序的状态.在人类面临的众多的自然灾害中,有一些特殊类型的自然灾害具有“混沌性态”的无序性.当(1)人-自然系统内出现混沌无序并超过某一临界值时,或(2)人-自然系统的某一纯粹的自然子系统出现混沌无序性且继而引发了整个人-自然系统的无序性时,危及人类生存,便产生了自然灾害。在人-自然系统中,导致混沌性自然灾害的条件至少有四种:(1)三个或三个以上作用源加上非线性关系;(2)某些变量的周期性解变得不稳定;(3)控制参量超过临界值导致周期倍增;(4)周期性扰动作用于非线性项.在此基础上,本文进一步提出了防灾或减灾的如下四条原则措施:在人—自然系统中,(1)减弱某些非线性机制;(2)隔离某些相互作用的要素及其子环路;(3)控制某些关键性参量的变化,(4)提高(或降低)某些重要变量的临界值. 相似文献
922.
923.
研究了Al-Si/Al-Mn/Al-Si三层复合板热轧复合工艺,借助金相显微镜、扫描电镜、能谱仪分析了复合工艺参数对轧后结合强度和剥离面形貌的影响,得到了优化热轧复合工艺,并对热轧复合板界面结合机制进行了探讨. 相似文献
924.
Hosny K. Khordagui 《Environmental management》1992,16(3):309-316
It is estimated that some 17 metric tons of residual oxidants (chlorine) are discharged into the enclosed coastal seawater
of Kuwait on a daily basis from power-desalination plants alone. Alarmed by the unlimited number of reported cases of damage
to marine aquatic systems due to chlorine discharge around the world, several alternatives were proposed to control such a
massive discharge of residual oxidant into seawaters. Most of the proposed alternatives lacked the basic criteria necessary
for their evaluation, justification, and then selection.
The objective of this article is to provide a conceptual approach that can be used to select a control measure for residual
oxidant discharge in Kuwait coastal seawaters. This approach is based on state-of-the-art knowledge and the unique operational
and environmental factors involved. A matrix system was designed whereby the cost of residual chlorine control alternative,
its effectiveness, and environmental and public health impact, performance, and reliability in Kuwait can be compared and
evaluated. The selection approach considered currently operating power plants in terms of their engineering design and material
(cast iron or steel condensers), current operational conditions, operator's perception, acceptability, and projected problems
associated with the environmental management of proposed modifications.
The proposed approach revealed that in Kuwait, conventinal chlorination was marginally superseded only by chlorination/dechlorination
using SO2 and operation alteration using process optimization. The overall cost-effective assessment matrix classified other alternatives
as worse than chlorination by various degrees.
Ozone and UV were found to be the worst and the least desirable alternatives for biofouling control of seawater in Kuwait.
In light of the available information on the consequences of the Gulf War on the marine environment, and the potential formation
of additional halogenated organic compounds through the reaction of residual chlorine with the released petroleum hydrocarbons,
it is essential to control residual chlorine discharged into the nearshore environment of Kuwait. 相似文献
925.
农药的环境问题及发展动向 总被引:2,自引:0,他引:2
本文综述了农药对环境的污染,以及昆虫对农药产生的抗性。报道了农药最近的研究动向。 相似文献
926.
目的研究在舰载垂直发射装置舱口盖系统中设计平面四杆机构的方案的可行性与可靠性。方法提出舱口盖开盖系统设计方案,建立平面四杆机构开盖模型,进行理论分析与计算,建立ADAMS动力学仿真模型,对曲柄摇杆机构进行仿真分析,并与理论计算值进行对比。进行30~90kg负载试验,计算舱口盖开盖的角度和时间。结果舱口盖开盖解锁机构各构件的长度及电机的开盖扭矩应不小于569 N·m,转速应小于10 r/min。电机的开盖扭矩值应不小于509 N·m,复核复算结果基本一致。舱口盖开盖的角度应大于93°,开盖时间为2.8 s,满足要求。结论验证了方案的可行性,为其他垂直发射装置的舱口盖设计提供了工程经验。 相似文献
927.
针对某染料厂蒽醌染料生产过程中排放的废水,具有COD、色度、酸度均较高的特点,采用铁床/二氧化氯组合工艺处理,废水水质得到了较好的处理,达到了当地污水处理厂的接管标准。 相似文献
928.
929.
930.
Electrochemical reduction characteristics and mechanism of nitrobenzene compounds in the catalyzed Fe-Cu process 总被引:2,自引:0,他引:2
The reduction of the nitrobenzene compounds (NBCs) by the catalyzed Fe-Cu process and the relationship between the electrochemical reduction characteristics of NBCs at copper electrode and reduction rate were studied in alkaline medium(pH=11). The catalyzed Fe-Cu process was found more effective on degradation of NBCs compared to Master Builder's iron. The reduction rate by the catalyzed Fe-Cu process decreased in the following order: nitrobenzene 〉4-chloro-nitrobenzene ≥m-dinitrobenzene :〉 4-nitrophenol ≥2,4-dinitrotoluene 〉2-nitrophenol. The reduction rate by Master Builder's iron decreased in the following order: m-dinitrobenzene ≥4-chloro-nitrobenzene 〉4-nitrophenol 〉2,4-dinitrotoluene ≈nitrobenzene 〉2-nitrophenol. NBCs were reduced directly on the surface of copper rather than by the hydrogen produced at cathode in the catalyzed Fe-Cu process. The reduction was realized by the hydrogen produced at cathode and Fe(OH)2 in Master Builder's iron, It is an essential difference in reaction mechanisms between these two technologies. For this reason, the reduction by the catalyzed Fe-Cu depended greatly on NBC's electron withdrawing ability. 相似文献