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941.
Subsea Xmas tree is a vital equipment for offshore oil and gas development. Aiming at the fault mode of subsea Christmas tree system under production conditions, the fault tree of subsea tree system was established, which was transformed into Dynamic Bayesian network, and the reliability and availability of subsea tree system with different repair states are quantitatively analyzed. In this paper, the DBNs are partially verified by the method based on three axes. The results show that the reliability of subsea vertical tree system is slightly higher than that of subsea horizontal tree system. After repair and maintenance, the performance of subsea tree system has been significantly improved, and the improvement of the system performance by preventive maintenance is more obvious. Compared with the perfect repair, the performance of the system with imperfect repair is not significantly reduced. Compared with perfect repair & preventive maintenance, the performance of the system with imperfect repair & preventive maintenance is slightly reduced. In addition, the influence of failure rates and degradation probability on reliability and availability is analyzed. By comparing the influence of failure rates on the system performance of non-maintenance and maintenance, it is found that the change of failure rates has the greatest influence on the reliability and the least influence on the availability of perfect repair & preventive maintenance. By comparing the performance of each component in the subsea tree system, it is found that the failure rates has the most obvious influence on the chock module, and gate valve and tree cap have the most significant influence on the reliability of the system. In order to improve the reliability of subsea tree system, it is necessary to improve the reliability of chock module, gate valve and tree cap. 相似文献
942.
水电工程在发挥巨大效益的同时,也不同程度地破坏了原有生态环境的平衡.以水电工程开发与生态环境的关系为切入点,分析了水电工程开发对生态环境的正面影响和负面影响,并提出了几点生态环境的保护对策及措施,通过人力与自然力的共同作用达到改善生态环境的目的,实现水电工程开发经济效益、社会效益、生态环境效益的共同提高. 相似文献
943.
三峡水库泄水期香溪河库湾营养盐动态及干流逆向影响 总被引:10,自引:0,他引:10
为了研究水库干流对支流库湾营养盐动态的影响,于2009年春季三峡水库汛前泄水期,通过监测分析了库湾水流特点及叶绿素a、总氮、总磷和溶解性硅酸盐的时空动态。研究发现:三峡水库汛前泄水期,库湾水体表现为分层异向流动,干流水体以异重流形式倒灌入库湾;特定的水流特性为泄水期库湾营养物质运移提供了水动力基础,水库干流对库湾营养盐的补给及水华暴发范围有明显逆向作用;受干流影响,氮和硅自河口至回水末端呈递减趋势,磷主要受上游来水影响,空间分布趋势与氮、硅相反;叶绿素a浓度峰值向上游移动,水华范围向上游收缩,河口处叶绿素a浓度的时间均值明显低于回水末端,表明三峡水库泄水期香溪河库湾下游水体水华受到干流逆向影响的抑制。 相似文献
944.
In this paper, a simple model for analysing variability in radon concentrations in homes is tested. The approach used here involves two error components, representing additive and multiplicative errors, together with variation between-houses. We use a Bayesian approach for our analysis and apply this model to two datasets of repeat radon measurements in homes; one based on 3-month long measurements for which the original measurements were close to the current UK Radon Action Level (200 Bq m−3), and the other based on 6-month measurement data (from regional and national surveys), for which the original measurements cover a wide range of radon concentrations, down to very low levels. The model with two error components provides a better fit to these datasets than does a model based on solely multiplicative errors. 相似文献
945.
结合近年来国内外学者关于好氧污泥颗粒化的研究成果,对影响好氧污泥颗粒化的影响因素进行了较为深入系统的分析,提出了适宜的运行控制条件及所需注意的问题。 相似文献
946.
A process-convolution approach to modelling temperatures in the North Atlantic Ocean 总被引:3,自引:0,他引:3
David Higdon 《Environmental and Ecological Statistics》1998,5(2):173-190
This paper develops a process-convolution approach for space-time modelling. With this approach, a dependent process is constructed by convolving a simple, perhaps independent, process. Since the convolution kernel may evolve over space and time, this approach lends itself to specifying models with non-stationary dependence structure. The model is motivated by an application from oceanography: estimation of the mean temperature field in the North Atlantic Ocean as a function of spatial location and time. The large amount of this data poses some difficulties; hence computational considerations weigh heavily in some modelling aspects. A Bayesian approach is taken here which relies on Markov chain Monte Carlo for exploring the posterior distribution. 相似文献
947.
废水处理新技术中的超临界水氧化法 总被引:20,自引:1,他引:19
超临界水氧化法是一种有效处理有机废水的方法,本文在总结超临界水的特点和优点的基础上,着重介绍了超临界水氧化的基本原理,工艺流程及应用状况,探讨该项技术的前景与发展趋势。、 相似文献
948.
949.
950.
污水处理设施作为废水排放的处理终端,在区域水环境治理的过程中发挥关键作用。本文以长江经济带沿线1117座污水处理设施为样本,以单位污水处理能耗作为污水处理设施的投入变量,BOD5等污染物的削减率作为产出变量,在考虑各类污染物对环境造成的异质性影响下利用WSBM模型对污水处理设施的减排效率进行测度,并运用CLAD模型对影响污水处理设施减排效率的外部因素进行研究。结果表明:长江经济带污水处理设施综合减排效率较低且差异较大,设施单位污水处理能耗冗余率较高以及对总磷污染物减排效果不理想是制约其减排效率提高的重要因素;长江经济带污水处理设施的减排纯技术效率总体呈现"东高西低",以上海、湖南、云南三省份形成"三极"的空间分布特征,而设施减排规模效率则呈现出"中部高、东西低"的空间分布格局;设施减排效率外部影响因素的驱动效应差异明显,并据此提出了排水管网合理规划、推进新型城镇化建设等对策建议。 相似文献