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Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences
Hubei University
Institute of 0ceanology, Chinese Academy of Sciences
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摘要:After experiencing 8-day combined tidal current, circulation and wave actions, scour depth surrounding cylinder object freely resting on sandy seabed in the East China Sea (ECS) in January is numerically predicted using the DRAMBUIE model designed for scour burial, which has been widely used and verified by in-situ experiments. During the period of numerical integration, the value of time t is generally variable at every time step via the special time-stepped approach developed by this paper to eliminate the time error. The tidal current velocity, wave orbital velocity and the depth-averaged circulation in the ECS have been obtained by numerical simulations with Estuarine Coastal and Ocean Model (ECOM), Simulating Waves Nearshore (SWAN) model and Regional Ocean Modeling System (ROMS) model respectively. The control experiment and several idealized test cases on influential factors in scour depth reveal that the dominant hydrodynamic factor is tidal current in the ECS under normal weather conditions, and the impacts of shelf circulation and wave motion on local scour almost can be ignored with an exception of the Kuroshio area where the high-speed mainstream of Kuroshio flows. It is also indicated that in sandy sediments, the distribution of scour depth nearly follows the pattern of tidal currents, while the secondary influencing factor on scour depth appears to be grain size of sandy sediment in the ECS. Numerical tests on sediment grain size further testify that much finer sand is more easily scoured, and an increasing trend for scour depth with reduction of grain size is displayed due to imposed resistance of larger sized particles. Three aspects explored by this paper, including the empirical equations in the Defense Research Agency Mine Burial Environment (DRAMBUIE) model, the accuracy of inputs and infill process can severely affect the prediction of scour depth surrounding cylinder objects freely resting on sandy seabed in the ECS....
摘要:In order to implement 3D scanning of those complicated parts such as blades in the aviation field,a non-contact optical measuring system is established in the paper,which integrates a laser displacement sensor,a probe head,the frame of a coordinate measuring machine (CMM),etc.As the output of the laser sensor directly obtained possesses the 1D length of the laser beam,it needs to determine the unit direction vector of the laser beam denoted as (l,m,n) by calibration so as to convert the 1D values into 3D coordinates of target points.Therefore,an extrinsic calibration method based on a standard sphere is proposed to accomplish this task in the paper.During the calibration procedure,the laser sensor moves along with the motion of the CMM and gathers the required data on the spherical surface.Then,both the output of the laser sensor and the grating readings of the CMM are substituted into the constraint equation of the spherical surface,in which an over-determined nonlinear equation group containing unknown parameters is established.For the purpose of solving the equation group,a method based on non-linear least squares optimization is put forward.Finally,the system after calibration is utilized to measure the diameter of a metallic sphere 10 times from different orientations to verify the calibration accuracy.In the experiment,the errors between the measured results and the true values are all smaller than 0.03 mm,which manifests the validity and practicality of the extrinsic calibration method presented in the paper....
摘要:Four kinds of Mg alloys reinforced with carbon fibres were fabricated by a gas pressure infiltration technique.The fibres were pre-coated a SiO2 layer prior to fabrication.Different microstructures and interactions in the fibre-matrix interface of these composites were observed by transmission electron microscopy (TEM).The results showed that the interracial interaction strongly depended on the content of Al in the Mg-based matrices.The microstructure of the interface could then be controlled by adjusting the Al content of the Mg-based matrix.In addition,fibres extracted from different Mg-based matrix all had some degradation owing to the interracial reaction and the fibre-matrix interdiffusion....
摘要:This study explored different methodologies using a C-band RADARSAT-2 quad-polarized Synthetic Aperture Radar (SAR) image located over China's Yellow Sea to investigate polarization decomposition parameters for identifying mixed floating pollutants from a complex ocean background.It was found that solitary polarization decomposition did not meet the demand for detecting and classifying multiple floating pollutants,even after applying a polarized SAR image.Furthermore,considering that Yamaguchi decomposition is sensitive to vegetation and the algal variety Enteromorpha prolifera,while H/A/alpha decomposition is sensitive to oil spills,a combination of parameters which was deduced from these two decompositions was proposed for marine environmental monitoring of mixed floating sea surface pollutants.A combination of volume scattering,surface scattering,and scattering entropy was the best indicator for classifying mixed floating pollutants from a complex ocean background.The Kappa coefficients for Enteromorpha prolifera and oil spills were 0.7514 and 0.8470,respectively,evidence that the composite polarized parameters based on quad-polarized SAR imagery proposed in this research is an effective monitoring method for complex marine pollution....
摘要:在实验室条件下对熔融态钒渣直接氧化钙化提钒新工艺进行研究。在反应过程中利用纯氧氧化,CaO作为添加剂,硫酸浸出熟料。采用XRD、XPS、SEM 及 EDS等手段对钒渣熟料进行分析,考察不同CaO/V2O5质量比与硫酸浓度对熟料中钒浸出的影响,并与现行焙烧工艺在能耗方面进行对比。结果表明:钒渣熟料中形成了钒的富集相,钒渣的氧化钙化产物主要为CaV2O5和Ca2V2O7,并对钒酸钙的形成机理进行了阐释;XRD和XPS分析得出熔渣中钒的氧化反应在供氧充足的情况下存在一定限制,CaO的增加能促进五价钒在熔渣中的稳定;在优化的实验条件下(CaO/V2O5质量比0.6,粒度120~150μm,浸出时间2 h,浸出温度90°C,液固比5:1 mL/g, H2SO4浓度20%,搅拌强度500 r/min),钒的浸出率能达到90%;能耗计算得到每处理1000 kg钒渣,利用新工艺可以节约能量1.85×106 kJ。实验与计算结果验证新工艺是一种节能减排的提钒手段。...
摘要:通过光学显微镜、扫描电镜、电子探针和拉伸测试研究添加镧铈稀土后Al?18Si?4Cu?0.5Mg合金的组织演变和力学性能.光学显微镜和扫描电镜结果表明,添加镧铈稀土后初晶硅颗粒由粗大块状和不规则多边形状明显细化为细片状,共晶硅由粗长针状细化为短棒状和珊瑚状.添加0.3%镧铈稀土时,合金具有最小初晶硅尺寸和最佳力学性能.此时,初晶硅平均尺寸由61μm细化至28μm,抗拉强度由222 MPa增大到242 MPa,伸长率由3.2%提高至6.3%.此外,还通过扫描电镜和电子探针探究合金的变质机制和断裂模式....
摘要:本文采用顶部籽晶熔融织构法(TSMTG)研究了Gd2Ba4CuNbO (GdNb2411)的掺杂量及其初始粉体粒度对单畴GdBCO超导块材磁悬浮力的影响.制备单畴GdBCO超导块材的初始成份为GdBa2Cu3O-δ∶Gd2BaC-uO5∶ GdNb2411=1∶ (0.4-x)∶x,x=0、0.02、0.06、0.1、0.14;GdNb2411粒子的初始粒度(d)范围分别在0≤d≤40m、40<d≤61m、61<d≤120m、120<d≤180m.结果表明:(1) GdBCO超导块材的生长形貌与其掺杂量x密切相关,当x≤0.06时,样品具有单畴形貌,且表面光滑平整;当x>0.06mol时,样品仍具有单畴形貌,但其表面出现皱褶现象;(2)随着x的增加,样品的磁悬浮力先增大后减小,当x=0.06mol时达到最大25N.(3)掺入样品的GdNb2411粉体粒度越小,最终在样品中生成的GdNb2411粒子的粒径也越小.(4)当固定x=0.06时发现,随着掺杂GdNb2411粉体粒度的减小,单畴GdBCO超导块材的磁悬浮力逐渐增大,当粒度d≤40mm时,样品中的Gd-Nb2411粒度约在100nm~250nm之间,相应样品的磁悬浮力最大,约25N.这些结果对进一步提高GdBCO超导块材的质量具有一定的指导意义....
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