Evidence of hyperpycnal flows at the head of the meandering Kaoping Canyon off SW Taiwan

Using seismic and Chirp sonar profiles, this paper tests the hypothesis that hyperpycnal flows are the main factor controlling the formation and maintenance of the meandering Kaoping submarine canyon off SW Taiwan. Cross-section geometries, and erosional as well as depositional features vary along the canyon course. In the proximal, sinuous part of the canyon, down-cutting into the shelf strata has created a relief of 340 m. The cause of this intense erosion of the seafloor is suggested to be the frequent development of hyperpycnal flows. A seismic section across a meander in the distal part of the canyon shows levees formed by overspilled sediments at the outer bend, and a terrace characterized by relatively flat stratified facies at the inner bend. The geological setting and climatic conditions in SW Taiwan (e.g. earthquakes, typhoons, floods), as well as major river–canyon connections (for example, direct input of highly concentrated suspended sediment) would all promote hyperpycnal flow generation. This causes axial incision, canyon wall slumping, and the formation of levees by spill-over deposition in the upper reach of the Kaoping Canyon.     

Sediment resuspension events induced by the wake wash of deep-draft vessels

Hydrodynamics and sediment resuspension events, induced at the shoreline by a deep-draft vessel passing nearby, are described. Measurements (pressure, currents and turbidity) were obtained at 4 Hz, on a lower beach ~50 m from a channel where large car ferries operate in Wootton Creek, Isle of Wight. The study focuses on a representative 8-min 32-s-long record, during which two large vessels passed the channel section. At the shore, the passage of each vessel induced a long-period water-level drawdown, followed by a water-level oscillation (seiche) of similar period, and the short-period waves of the wake. Both drawdowns were the main constituents of the prevailing wave pattern. The second drawdown was the largest in amplitude, in response to a higher speed of the ferry, and the influence of the seiche which had been activated during the preceding event. Two successive peaks of turbidity were observed shortly after this drawdown. Analyses of current velocity and direction indicate that the sediments resuspended originated from the shallower upper beach. Anthropogenically induced erosion of the foreshore is predicted at Wootton Creek.     

耐压柱壳参数化设计与灵敏度分析

为提高耐压柱壳设计效率,设计了耐压柱壳参数化分析流程。研究了有限元分析所涉及的材料属性、载荷施加、边界条件设置等内容,确定了采用弧长法分析耐压柱壳稳定性。利用Python语言对于ABAQUS软件进行了二次开发,利用Isight软件实现了ABAQUS的集成,实现了耐压柱壳有限元分析模型的网格自动划分、自动分析计算等。选择样本点进行参数化分析,利用响应面模型对于样本点进行了拟合,得到了具有较高拟合精度、满足工程需要的近似模型,进行了设计变量的灵敏度分析。研究结果表明:参数化分析流程可实现耐压柱壳的自动分析、近似模型及灵敏度分析,可降低耐压柱壳分析难度,均可提高耐压柱壳设计效率。     

Assessing conservation practices in Amalacaxco Gorge (Izta-Popo National Park,Central Mexico) using fallout ~(137)Cs and Optically Stimulated Luminescence (OSL)

This study aims to assess conservation practices in Izta-Popo National Park(Central Mexico) by evaluating the mechanisms of sediment transfer. We applied a methodology based on fallout ~(137)Cs and optically stimulated luminescence(OSL) analysis. This was tested in the upper catchment of Amalacaxco Gorge, selected for being one of the sectors of the park in which man-made actions have been implemented in last decades to favor forest growth in the alpine grassland and to reduce the effect of water runoff. We quantified the ~(137)Cs activity using gamma and beta spectrometry of fine sediment grains extracted from the surface of parcels of 0.4 m2 in areas of natural forest, natural alpine grassland, alpine grassland with conservation practices, ravines and trails. In general, ~(137)Cs values increases as local slope decreases as it was expected. The natural forest is the most stable area in terms of soil erosion and sediment accumulation and, mean ~(137)Cs activity was taken as reference to assess cumulative zones, with higher ~(137)Cs values and erosive, with lower. We found that trails are accumulative surfaces but in other areas, erosion predominates. Man-made ditches, trenches and afforestation in the alpine grassland have higher ~(137)Cs values than thenatural grassland, which indicates that conservation practices are limiting the sediment transfer from hillslopes to channels, however, soil retention is less than in the natural grassland. Additionally, we evaluated the luminescence(OSL) values obtained from samples extracted from the sediment transported in ravines that are cutting into different sectors of the study area to assess the grade of resetting of fluvial materials. These luminescence results indicated that the sediment transported in ravines that are cutting into the natural forest and alpine grassland is bleached more efficiently than the sediment transported in the alpine grassland with conservation practices. Results of fallout ~(137)Cs and luminescence strongly suggest that man-made actions in this part of the Izta-Popo National Park are dramatically modifying the natural mechanisms of sediment transfer and favoring soil erosion. We conclude that made ditches, trenches and afforestation are not an effective conservation practice in Amalacaxco Gorge because they are promoting soil erosion instead of reducing it.     

气象装备保障效能评估技术

随着气象部门装备保障业务重要性的不断提高,开展装备保障评估方法的研究,对保障质量进行科学评价成为一个新的课题。就监控、维护和维修3个装备保障子业务分别建立了各自的评估体系,还利用监控、维护和维修业务的独立性,提出了根据业务单位职责的组成,使用监控率、故障率和维修率三者的加权平均值评估装备保障综合效能的方法,对建立装备保障业务的考核体系有一定的参考借鉴意义。     

Southwestward intrusion of korea strait bottom cold water observed in 2003 and 2004

Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in June and November 2004. The bottom cold water, which was lower than 10°C, appeared in the channel trough except in March 2003. It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed of the intrusion current were about 20 km and approximately 25 cm s^-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv≡10⁶ m³ s^-1) in August 2003 and 0.026 Sv in November 2004.     

苏、皖石炭系石灰岩的胶结作用

分析了苏、皖石炭系石灰岩的胶结作用。查明了胶结物的晶形、碳、氧同位素成分、发光特征及包体均一化温度。指出胶结作用主要发生在大气淡水补给较充分的含水层内,这与本区属海退成岩序列有关。     

Meiobenthos in estuary part of ha long bay (gulf of tonkin, south china sea, vietnam)

The distribution of the taxonomical composition and the density of meiobenthos depending on some factors of environment has been studied in bottom sediments of the northern estuary part of Ha Long Bay (Cua Luc estuary). The basic factor of influence on meiobenthic community structure was the granulometric composition of sediment. The greatest taxonomic diversity is noted in the silted sands, lowest — in the silty sediments. The density of meiobenthic community was higher in the silty sediments. Slightly expressed correlation between the density of nematodes and the percentage of silty particles in the sediments is detected (Spearman rank correlation coefficient was 0.49±0.21, p=0.035). The nematodes were dominant at all stations. In total, representatives of 66 species of nematodes belonging to 17 families and 52 genera were identified.     

Seasonal variation of eddy shedding from the Kuroshio intrusion in the Luzon Strait

Altimeter data and output from the HYbrid Coordinate Ocean Model global assimilation run are used to study the seasonal variation of eddy shedding from the Kuroshio intrusion in the Luzon Strait. The results suggest that most eddy shedding events occur from December through March, and no eddy shedding event occurs in June, September, or October. About a month before eddy shedding, the Kuroshio intrusion extends into the South China Sea and a closed anticyclonic eddy appears inside the Kuroshio loop which then detaches from the Kuroshio intrusion. Anticyclonic eddies detached from December through February move westward at a speed of about 0.1 m s⁻¹ after shedding, whereas eddies detached in other months either stay at the place of origin or move westward at a very slow speed (less than 0.06 m s⁻¹). The HYCOM outputs and QuikSCAT wind data clearly show that the seasonal variation of eddy shedding is influenced by the monsoon winds. A comparison between eddy volume and integrated Ekman transport indicates that, once the integrated Ekman transport exceeds 2 × 10¹² m³ (which roughly corresponds to the volume of an eddy), the Kuroshio intrusion expands and an eddy shedding event occurs within 1 month. We infer that the Ekman drift of the northeasterly monsoon pushes the Kuroshio intrusion into the SCS, creates a net westward transport into the Strait, and leads to an eddy detachment from the Kuroshio.