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1.
Hydrothermal vent incidence was once thought to be proportional to the spreading rate of the mid-ocean ridges (MORs). However, more and more studies have shown that the ultraslow-spreading ridges (e.g., Southwest Indian Ridge (SWIR)) have a relatively higher incidence of hydrothermal venting fields. The Qiaoyue Seamount (52.1°E) is located at the southern side of segment #25 of the SWIR, to the west of the Gallieni transform fault. The Chinese Dayang cruises conducted eight preliminary deep-towed surveys of hydrothermal activity in the area during 2009 and 2018. Here, through comprehensive analyses of the video and photos obtained by the deep-towed platforms, rock samples, and water column turbidity anomalies, a high-temperature, ultramafic-hosted hydrothermal system is predicted on the northern flank of the Qiaoyue Seamount. We propose that this hydrothermal system is most likely to be driven by gabboric intrusions. Efficient hydrothermal circulation channels appear against a backdrop of high rock permeability related to the detachment fault.  相似文献   
2.
Huang  Heng  Chen  Xu-jun  Liu  Jun-yi  Miao  Yu-ji  Ji  Song 《中国海洋工程》2021,35(5):687-699
China Ocean Engineering - Based on the elastic foundation beam theory and the multi-floating-module hydrodynamic theory, a novel method is proposed to estimate the dynamic responses of VLFS (Very...  相似文献   
3.
在西大别造山带的区调工作中,新识别出一系列中元古代末-新元古代的岩石-构造单元,它们沿着吕王-高桥-永佳河一线展布,并构成一条NNW-SEE向展布的构造混杂岩带.该混杂岩带主要由超镁铁质-镁铁质岩、硅泥质岩、石英质岩、大理岩、含碳陆源碎屑岩、双峰式火山岩以及卷入其中的榴辉岩等多种变质岩块(片)共同组成,并赋存于一套遭受了强烈剪切变形的泥质片岩之中.混杂岩带内各岩块(片)的原岩年龄跨度较大(>4亿年),分别集中在1 200~1 100 Ma和800~700 Ma之间.锆石记录的变质年龄和云母的冷却年龄则主要集中在240~200 Ma之间.结合接触关系、岩性组合、年代学及地球化学数据的综合研究认为,混杂岩带的物质来源既包括中元古代末-新元古代早期的弧-弧后盆地系统的沉积岩-火山岩-侵入岩;也包括叠置其上的新元古代中-晚期大陆裂解期的沉积岩-火成岩.这些不同时代、不同性质岩石在三叠纪不同程度地卷入了华南陆块北缘向华北陆块之下的俯冲,而后快速折返,最终沿着区域上折返断裂(桃花-七角山断裂)就位于西大别造山带之中,形成一条包含高压-超高压变质岩的三叠纪构造混杂岩带.混杂岩带内新厘定的中元古代末弧-弧后岩浆-沉积事件,可与大洪山-黄陵庙湾同时期的地质事件对比,它们共同揭示扬子北缘曾经存在一条中元古代末-新元古代早期的俯冲岩浆带.   相似文献   
4.
利用机器学习和人工智能技术研发了广西大风短临预报预警系统,该系统的产品与同期广西各地气象局发布的大风预警信号(以下简称“人工预警”)进行比较分析。结果表明:(1)按业务评分规定,大风预警系统在漏报率和命中率方面更优,人工预警在TS评分和空报率方面更优;(2)有效提前预警情况下,大风预警系统在大风蓝色、黄色预警和不分级预警中TS评分较高。基于对大风预警系统和人工预警的数量、TS评分和预警提前量的差异分析,广西大风短临预报预警系统的产品性能达到同期人工预警水平。  相似文献   
5.
现如今,新冠肺炎(COVID-19)严重威胁着世界各国人民的生命健康.许多流行病学模型已经被用于为政策制定者和世界卫生组织提供决策参考.为了更加深刻的理解疫情趋势的变化特征,许多参数优化算法被用于反演模型参数.本文提议使用结合了高斯-牛顿法和梯度下降法的Levenberg-Marquardt(LMA)算法来优化模型参数.使用四个病例数相对较多的国家来验证这一算法的优势:相较于传统流行病学模型模拟曲线过早过快的到达峰值,应用 LMA 的 Statistical-SIR(Statistical-Susceptible-Infected-Recovered)模型可以更好地拟合实际疫情曲线.  相似文献   
6.
Soil resources in parts of Tanzania are rapidly being depleted by increased rates of soil erosion and downstream sediment transport, threatening ecosystem health, water and livelihood security in the region. However, incomplete understanding to what effect the dynamics of soil erosion and sediment transport are responding to land-use changes and climatic variability are hindering the actions needed to future-proof Tanzanian land-use practices. Complementary environmental diagnostic tools were applied to reconstruct the rates and sources of sedimentation over time in three Tanzanian river systems that have experienced changing land use and climatic conditions. Detailed historical analysis of sediment deposits revealed drastic changes in sediment yield and source contributions. Quantitative sedimentation reconstruction using radionuclide dating showed a 20-fold increase in sediment yield over the past 120 years. The observed dramatic increase in sediment yield is most likely driven by increasing land-use pressures. Deforestation, cropland expansion and increasing grazing pressures resulted into accelerating rates of sheet erosion. A regime shift after years of progressive soil degradation and convergence of surface flows resulted into a highly incised landscape, where high amounts of eroded soil from throughout the catchment are rapidly transported downstream by strongly connected ephemeral drainage networks. By integrating complementary spatial and temporal evidence bases, this study demonstrated links between land-use change, increased soil erosion and downstream sedimentation. Such evidence can guide stakeholders and policy makers in the design of targeted management interventions to safeguard future soil health and water quality.  相似文献   
7.
Wildfire increases the potential connectivity of runoff and sediment throughout watersheds due to greater bare soil, runoff and erosion as compared to pre-fire conditions. This research examines the connectivity of post-fire runoff and sediment from hillslopes (< 1.5 ha; n = 31) and catchments (< 1000 ha; n = 10) within two watersheds (< 1500 ha) burned by the 2012 High Park Fire in northcentral Colorado, USA. Our objectives were to: (1) identify sources and quantify magnitudes of post-fire runoff and erosion at nested hillslopes and watersheds for two rain storms with varied duration, intensity and antecedent precipitation; and (2) assess the factors affecting the magnitude and connectivity of runoff and sediment across spatial scales for these two rain storms. The two summer storms that are the focus of this research occurred during the third summer after burning. The first storm had low intensity rainfall over 11 hours (return interval <1–2 years), whereas the second event had high intensity rainfall over 1 hour (return interval <1–10 years). The lower intensity storm was preceded by high antecedent rainfall and led to low hillslope sediment yields and channel incision at most locations, whereas the high intensity storm led to infiltration-excess overland flow, high sediment yields, in-stream sediment deposition and channel substrate fining. For both storms, hillslope-to-stream sediment delivery ratios and area-normalised cross-sectional channel change increased with the percent of catchment that burned at high severity. For the high intensity storm, hillslope-to-stream sediment delivery ratios decreased with unconfined channel length (%). The findings quantify post-fire connectivity and sediment delivery from hillslopes and streams, and highlight how different types of storms can cause varying magnitues and spatial patterns of sediment transport and deposition from hillslopes through stream channel networks.  相似文献   
8.
A suction caisson can be extracted by applying reverse pumping water,which cannot be regarded as the reverse process of installation because of the dramatically different soil?structure interaction behavior.Model tests were first carried out in this study to investigate the extraction behavior of the modified suction caisson(MSC)and the regular suction caisson(RSC)in sand by reverse pumping water.The effects of the installation ways(suction-assisted or jacking installation)and the reverse pumping rate on the variations of the over-pressure resulting form reverse pumping water were investigated.It was found that neither the RSC nor the MSC can be fully extracted from sand.When the maximum extraction displacement is obtained,the hydraulic gradient of the sand in the suction caisson reaches the critical value,leading to seepage failure.In addition,the maximum extraction displacement decreases with the increasing reverse pumping rate.Under the same reverse pumping rate,the final extraction displacements for the RSC and MSC installed by suction are lower than those for the RSC and MSC installed by jacking.The final extraction displacement of MSC is almost equal to that of the RSC with the same internal compartment length.Based on the force equilibrium,a method of estimating the maximum extraction displacement is proposed.It has been proved that the proposed method can rationally predict the maximum extraction displacement and the corresponding over-pressure.  相似文献   
9.
为了比较不同陆面扰动方法对短时集合预报的影响,本研究设计了陆面模式扰动实验(LSMPE),初始土壤湿度扰动实验(ISMPE),陆面-大气耦合系数扰动实验(LCCPE)以及大气扰动对照实验(GEFSPE).结果表明,在三组陆面扰动实验中,LSMPE能代表最大的不确定性且误差最小;ISMPE的离散度要比LCCPE稍大,但是耦合系数的减弱能有效降低区域平均降水量.然而,所有陆面扰动实验产生的离散度均小于GEFSPE,这表明未来有必要将陆而扰动与大气扰动相结合,以使得模式能代表更多的不确定性.  相似文献   
10.
Based on the latest oceanic surface drifter dataset from the global drifter program during 2000–2019, this study investigated the global variation of relative frequency shift(RFS), near-inertial energy(NIE) and inverse excess bandwidth(IEB) of near-inertial motions, and analyzed their relations with oceanic mesoscale dynamics, relative vorticity and strain. Compared with previous works, we have some new findings in this study:(1) the RFS was high with negative values in some regions in which we found a significant blue shift of the RFS in the equatorward of 30°N(S) and from 50°N to 60°N in the Pacific, and a red shift in the western boundary currents and their extension regions, the North Atlantic and the Antarctic Circumpolar Current regions;(2) more peak values of the NIE were found in global regions like the South Indian Ocean, the Luzon Strait and some areas of the South Ocean;(3) the global distribution of the IEB were characterized by clear zonal bands and affected by vorticity and wind field;(4)the RFS was elevated as the absolute value of the gradient of vorticity increased, the IEB did not depend on the gradient of vorticity, and the eddy kinetic energy(EKE) weakened with the decrease of the absolute value of RFS;(5) the NIE decreased with increasing absolute value of the relative vorticity and the gradient of vorticity, but it increased with increasing strain and EKE when EKE was larger than 0.003 2 m~2/s~2.  相似文献   
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