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11.
 The Cenozoic shelf margin of the Amazon Mouth Basin is characterized by a thick prograding prism of siliciclastic sediments. This prism, composed mainly of Upper Miocene and younger sediments, overlies a Lower Tertiary carbonate shelf. Two tectonic–sedimentary models for the area were developed with the aid of new deep-reflection seismic data. Gravitational tectonics dominate the regional geological framework. Tensional stresses are created near the shelf margin, and compressional features dominate at the base of the slope. The morphology of this compressional zone is closely associated with the St. Paul Fracture Zone and the boundary between continental and oceanic crusts. Received: 20 August 1996 / Revision received: 11 June 1998  相似文献   
12.
文中详细研究了当前世界上最典型的海底观测网的建设发展规模、形式、设备类型以及我国海底观测网的发展现状,并对国内外海底观测网的发展趋势进行总结。对日本、加拿大、美国及欧洲的海底观测网进行了设备级研究,对我国台湾地区、东海、南海的海底观测网现状进行了研究,并讨论了国外先进观测网对我国的海底观测网建设的借鉴意义。文中总结出海底观测网发展的整体趋势为:单节点网络加速验证新型设备及传感器的水下能力;区域尺度网络用于加速多学科发展并提升灾害预警能力;而浮标平台网络作为补充,铺设在远海区域以降低阶段建设成本。  相似文献   
13.
深水半潜式平台系泊锚链的倾角变化是评价平台系泊状态与锚链受力的重要指标,是半潜式平台重要的监测内容。目前,深水锚链的测量主要是采用自容式的传感器,针对其水下长时间测量的应用特点,要求它的设计必须具有低功耗、高可靠性、大存储量、体积小、防水耐压等指标。根据我国南海流花平台的锚链监测需要,设计与制作了专用的水下自容式倾角传感器,并在实际应用中进行了检验。  相似文献   
14.
Inlet stabilization is a common practice in Brazil, as it is worldwide. In this paper we present results of the analysis of the stabilization practices of the Camacho Inlet, located in Santa Catarina State, southern Brazil. This inlet is maintained intermittently, in accordance with a regime designed to benefit both local fishermen and rice farmers. Fishermen require this inlet to be open as a navigation channel during the fishing season; rice farmers needs it closed during the irrigation period to allow the pumping of fresh water from the Congonhas River which drains into the Camacho’s backbarrier lagoon. An additional complication arises from the tendency of this inlet to close naturally due to infilling by dune migration. Aerial images spanning a 65 year time period (1938-2003) were analyzed, demonstrating the variability in the inlet’s width between 0 (closed) and 360 m. The analysis of inlet stability and user needs indicate that an appropriate solution is the implementation of an annual inlet dredging program in the austral autumn. This would allow for the inlet to remain open from May to September and then close naturally for the rest of the year, providing for a backbarrier fresh water reservoir during the irrigation period.  相似文献   
15.
详细介绍了地下水水源保护区范围的计算方法:Krijgsman-Lobo-Ferreira(KLF)法,分别推导出了正水流梯度方向、负水流梯度方向和垂直于地下水流方向保护区范围的计算公式,并就方法的适用性及参数取值等问题进行了探讨.在徐州张集地区应用的结果表明,KLF法提供了一种计算地下水保护区范围的便捷、科学、有效的方法,计算结果对于确定地下水源保护区范围及有效保护地下水源具有实际意义.  相似文献   
16.
In this study the clam, Tapes philippinarum, a filter-feeding bivalve living in soft bottoms, was used to investigate the water/sediment pollution in Venice Lagoon (Venice, Italy), a heavily urbanised and industrialised area. To this end, clams collected from indigenous populations in a clean farming area (Val Dogà) were transplanted into a relatively low contaminated site (Palude della Rosa) and in a heavily polluted area (Porto Marghera), for 5 weeks. A range of possible induced stress indices were measured, on the basis of potential toxicity mechanisms, including specific enzymatic activities [Bap hydroxylase and NADPH cytochrome c reductase, superoxide dismutase, catalase, glutathione peroxidase and propionaldehyde dehydrogenase (PDH)] and general cellular responses (lysosomal latency). Moreover, chemical analyses (polychlorinated biphenyls, polycyclic aromatic hydrocarbon, DDTs) were carried out on sediments and animal tissues at the beginning and end of the transplantation experiments. The chemical results show an active bio-accumulation activity from sediment in clams translocated to the most polluted area. Correspondingly, biological data indicate marked effects on PDH activity and latency in T. philippinarum from the same site. In contrast, no similar pattern has been observed in the other considered indices, possibly due to antagonistic effects of the complex contaminant mixture present in the environment.  相似文献   
17.
Marine populations in Europe are in decline due to the unsuccessful results of the Common Fisheries Policy. By combining data of scientific recommendations from ICES, TACs approved and reported landings with an age-structured model, the objectives of this paper are to investigate the level of compliance of the TAC regulation, and the level of enforcement and its economic impact on fishery resources. The results presented here suggest that while there does not exist a regular pattern between TAC proposal and TAC approved, there is a clear pattern between TAC approved and reported landings. As a consequence, there is a regular lack of enforcement at national fisheries authority level. The paper also presents results of the recovery plans for the Southern hake and the Atlantic cod fisheries as case studies to illustrate the level of enforcement based on collusion between national fisheries advisers and industry. The results from both cases studies analyzed here indicate that drastic solutions could generate positive results for the recovery of the stocks, but perhaps they are not always the best measure in fisheries management due to the high economic losses for fishermen and social effects on coastal communities in the short and medium term. Finally, this work demonstrates that if the recovery plans had been implemented, the net present profits for both fisheries would have increased over time.  相似文献   
18.
Despite the high number of species and ecological diversity of pandalid shrimps, there has been no previous attempt to resolve evolutionary relationships of several genera using molecular tools. Although mitochondrial DNA cytochrome oxidase I (COI) is widely used in barcoding studies to delimit species boundaries, additional insights into phylogenetic affinities can be obtained, especially when used in combination with data from additional genes. The knowledge of molecular diversity is essential to understand phylogenetic relationships and will help systematic clarifications. Based on partial fragments of the 16S and COI genes, we have focused specifically on addressing the systematic relationships of the economically and ecologically important shrimp genus Plesionika within a framework of five genera from within the Pandalidae. Our results showed that species within Plesionika are substantially divergent when compared with other genera, exhibiting the highest average nucleotide divergence, with 0.1123 and 0.0846 in COI and 16S genes, respectively. In addition, sequence divergence was found to vary greatly within the genus Plesionika (COI/16S): 0.0247/0.0016 between Plesionika antigai and Plesionika heterocarpus and 0.1616/0.098 between Plesionika heterocarpus and Plesionika edwardsii. We did not find amino acid sequence divergence between P. heterocarpus and P. antigai compared with P. heterocarpus and P. edwardsii (8.10%, K2P distance). Three species of Plesionika (P. antigai, P. heterocarpus and Plesionika scopifera) appear well separated from other Plesionika species in both maximum likelihood and Bayesian analyses. The present study confirms the utility of COI over 16S as a genetic marker to resolve relationships between different species of Plesionika from the Northeast Atlantic and Mediterranean Sea, in addition to species delimitation. The findings highlight the need to further review paraphyly within Plesionika in an attempt to recognize a concordance in the evolutionary history of Plesionika with major ecological and geological events.  相似文献   
19.
Sugarcane is an annual crop with a dynamic canopy that changes over time mainly because of genetic adaptation. There is uncertainty about the temporal trends of throughfall (TF) in this important commercial crop. In the present paper, we used troughs to measure TF in a third and fourth ratoon and subsequently in a fourth and fifth ratoon. Additional measurements were carried out in an adjacent riparian forest. There were no significant differences between cycles of sugarcane, growth phases and riparian forest. The TF results for ratoon crop and riparian forest in 2011/2012 were 76% and 79.5% of gross rainfall, respectively, while in 2012/2013, they were 79% and 78%, respectively. However, TF was remarkably lower in the riparian forest relative to ratoon from the second half of the culm formation and elongation phase (280 days after harvest) until harvest. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
20.
本文以天津市房地产开发(集团)河西友谊小区综合楼为研究对象,研究其在地震作用下高层建筑的可靠性,探索高层建筑结构系统的抗震可靠性分析方法,本文还对比一般框架梁柱结构与后张无粘结预应力板柱结构抗震可靠性的差异,研究层数变化时可靠性所受的影响,得到满意的结果。  相似文献   
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