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排序方式: 共有846条查询结果,搜索用时 390 毫秒
171.
甘肃肃南县奥陶系构造地体中变质火山岩主要指蓝片岩、绿片岩及熔岩、凝灰岩。岩石化学特征表明,区内这些岩石属同源演化系列,多数为中基性,岩类属大洋拉斑玄武岩系列。与美国舒克桑岩套蓝片岩、绿片岩对比,两者具有相似的岩浆分异趋势,但肃南岩浆初始分异程度较低,相当现代FAMOUS区洋中脊岩石成分范围。进一步可分为LREE亏损组和LREE中等富集组,LREE亏损组也能与舒克桑蓝片岩和绿片岩类比,原岩产出环境为N型洋中脊。从矿物化学特征看,肃南硬柱石、绿纤石蓝闪片岩可与美国Cazadero硬柱石蓝片岩带、绿纤石蓝片岩带 相似文献
172.
辽河盆地大民屯凹陷厚层暗色富有机质泥页岩的沉积特征研究和地球化学数据分析结果表明,大民屯古近系凹陷古近系沙河街组发育湖泊和扇三角洲沉积。在扇三角洲中的沼泽地带,发育富有机质的碳质泥岩。暗色泥岩主要产生于半深湖-深湖环境中,具有厚度大、连续性强、分布广的特点。泥岩中的干酪根类型主要以腐泥腐殖质型(II2)和腐殖型(III)为主,利于产气。有机质成熟度(Ro)平均为0.8%~1.3%,有机质处于低熟-成熟阶段。TOC平均为3%~8.46%,有机质丰度较高。脆性矿物总量达到29.0%~51.7%,有利于页岩气的开采。页岩气类型主要为热成因页岩气和生物化学成因页岩气。在页岩气成藏的地质因素分析基础上,综合研究认为,荣胜堡洼陷和三台子洼陷是沙河街组页岩气富集的有利区域。 相似文献
173.
现代海洋牧场建设之我见 总被引:2,自引:0,他引:2
现代海洋牧场建设是实现我国海洋渔业与近海生态系统和谐发展的重要途径之一,作为一种海洋经济新业态,海洋牧场既能养护渔业资源,又能修复生态环境。本文论述了现代海洋牧场建设的必要性,分析了我国海洋牧场建设中存在的建设技术缺乏标准化、承载力评估缺乏模型化、建设理念缺乏生态化、管理缺乏信息化等问题,探讨了现代海洋牧场相关理念及分类模式。针对现代海洋牧场建设存在的突出问题,提出了构建陆海统筹现代海洋牧场亟待解决的技术先导和"四化"突破(工程化、机械化、自动化和信息化)等对策和建议。 相似文献
174.
Sensitivity Analysis of Air Gap Motion with Respect to Wind Load and Mooring System for Semi-Submersible Platform Design 总被引:1,自引:1,他引:0
A design of semi-submersible platform is mainly based on the extreme response analysis due to the forces experienced by the components during lifetime. The external loads can induce the extreme air gap response and potential deck impact to the semi-submersible platform. It is important to predict air gap response of platforms accurately in order to check the strength of local structures which withstand the wave slamming due to negative air gap. The wind load cannot be simulated easily by model test in towing tank whereas it can be simulated accurately in wind tunnel test. Furthermore, full scale simulation of the mooring system in model test is still a tuff work especially the stiffness of the mooring system. Owing to the above mentioned problem, the model test results are not accurate enough for air gap evaluation. The aim of this paper is to present sensitivity analysis results of air gap motion with respect to the mooring system and wind load for the design of semi-submersible platform. Though the model test results are not suitable for the direct evaluation of air gap, they can be used as a good basis for tuning the radiation damping and viscous drag in numerical simulation. In the presented design example, a numerical model is tuned and validated by ANSYS AQWA based on the model test results with a simple 4 line symmetrical horizontal soft mooring system. According to the tuned numerical model, sensitivity analysis studies of air gap motion with respect to the mooring system and wind load are performed in time domain. Three mooring systems and five simulation cases about the presented platform are simulated based on the results of wind tunnel tests and sea-keeping tests. The sensitivity analysis results are valuable for the floating platform design. 相似文献
175.
176.
In this paper, the control performance is investigated of Circular Tuned Liquid Column Dampers (CTLCD) over torsional response of offshore platform structures excited by ground motions. Based on the equation of motion for the CTLCD-structure system, the optimal control parameters of CTLCD are given through some derivations on the supposition that the ground motion is a stochastic process. The influence of systematic parameters on the equivalent damping ratio of the structures is analyzed with purely torsional vibration and translational-torsional coupled vibration, respectively, The results show that the Circular Tuned Liquid Column Damper (CTLCD) is an effective torsional response control device. 相似文献
177.
178.
This paper preliminarily investigates the application of the orthogonal conditional nonlinear optimal perturbations(CNOPs)–based ensemble forecast technique in MM5(Fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model). The results show that the ensemble forecast members generated by the orthogonal CNOPs present large spreads but tend to be located on the two sides of real tropical cyclone(TC) tracks and have good agreements between ensemble spreads and ensemble-mean forecast errors for TC tracks. Subsequently, these members reflect more reasonable forecast uncertainties and enhance the orthogonal CNOPs–based ensemble-mean forecasts to obtain higher skill for TC tracks than the orthogonal SVs(singular vectors)–, BVs(bred vectors)– and RPs(random perturbations)–based ones. The results indicate that orthogonal CNOPs of smaller magnitudes should be adopted to construct the initial ensemble perturbations for short lead–time forecasts, but those of larger magnitudes should be used for longer lead–time forecasts due to the effects of nonlinearities. The performance of the orthogonal CNOPs–based ensemble-mean forecasts is case-dependent,which encourages evaluating statistically the forecast skill with more TC cases. Finally, the results show that the ensemble forecasts with only initial perturbations in this work do not increase the forecast skill of TC intensity, which may be related with both the coarse model horizontal resolution and the model error. 相似文献
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