Accurate prediction of droplet impingement on wind turbine blade is one of the most important premises of anti-icing and de-icing system design.In a super-cooled large droplets(SLD)conditions,droplet no longer maintai...Accurate prediction of droplet impingement on wind turbine blade is one of the most important premises of anti-icing and de-icing system design.In a super-cooled large droplets(SLD)conditions,droplet no longer maintains a sphere shape,and it may deform,break up,and splash when moving or impinging on the surface.Semi-empirical models of droplet dynamic behaviours are embedded into the Eulerian droplet model to improve the accuracy of the numerical simulation of droplet impingement limits and local collection efficiency.Eulerian droplet model(Model 1)for small droplets and improved Eulerian droplet model(Model 2)for large droplet are both validated by comparing to the wind tunnel experiment results.Using the proposed methods,droplet impingement limitation and local collection efficiency on the S809 airfoil are calculated in various conditions.A detailed derivation of Model 1and Model 2is presented along with a comparison of numerical trajectories,drag coefficient and collection efficiency distributions.The results show that droplet dynamic behaviours,including splashing,break-up and deforming,must be considered to accurately simulate the impingement behaviour in the SLD conditions.And with the increase of the droplet diameters,the effects of the droplet dynamic behaviors on the impingement characteristics are more obvious.展开更多
目的建立烟酰胺凝胶的制备工艺及含量测定方法。方法采用正交实验,以卡波姆、中和剂、保湿剂为考察因素,以凝胶剂的外观性状为考察指标,筛选凝胶剂最优处方基质;以卡波姆-940、丙二醇、聚山梨酯-80等制备烟酰胺凝胶剂,采用紫外—可见光...目的建立烟酰胺凝胶的制备工艺及含量测定方法。方法采用正交实验,以卡波姆、中和剂、保湿剂为考察因素,以凝胶剂的外观性状为考察指标,筛选凝胶剂最优处方基质;以卡波姆-940、丙二醇、聚山梨酯-80等制备烟酰胺凝胶剂,采用紫外—可见光分光度法测定含量。结果烟酰胺在2.0~12.0 g/mL浓度范围内线性关系良好(r=0.9992),加样平均回收率为99.65%,相对标准偏差(relative standard deviation,RSD)值为0.42%。结论此次研究成功建立了适合批量生产烟酰胺凝胶的制备工艺及便捷可靠的含量测定方法。展开更多
Different ocean features usually appear in synthetic aperture radar(SAR)images simultaneously.This makes the image complicated and hard to understand.Because of lower signal-to-noise rate,it is much more difficult to ...Different ocean features usually appear in synthetic aperture radar(SAR)images simultaneously.This makes the image complicated and hard to understand.Because of lower signal-to-noise rate,it is much more difficult to separate different ocean features than to separate different land features.A completely novel method is presented to separate ocean features from multifrequency polarimetric SAR imagery.AIRSAR data from Jet Propulsion Laboratory(JPL),National Aeronautics and Space Administration(NASA)are used in the case studies and good results are achieved.展开更多
An impact angle constrained fuzzy adaptive fault tolerant integrated guidance and control method for Ski-to-Turn(STT)missiles subject to unsteady aerodynamics and multiple disturbances is proposed.Unsteady aerodynamic...An impact angle constrained fuzzy adaptive fault tolerant integrated guidance and control method for Ski-to-Turn(STT)missiles subject to unsteady aerodynamics and multiple disturbances is proposed.Unsteady aerodynamics appears when flight vehicles are in a transonic state or confronted with unstable airflow.Meanwhile,actuator failures and multisource model uncertainties are introduced.However,the boundaries of these multisource uncertainties are assumed unknown.The target is assumed to execute high maneuver movement which is unknown to the missile.Furthermore,impact angle constraint puts forward higher requirements for the interception accuracy of the integrated guidance and control(IGC)method.The impact angle constraint and the precise interception are established as the object of the IGC method.Then,the boundaries of the lumped disturbances are estimated,and several fuzzy logic systems are introduced to compensate the unknown nonlinearities and uncertainties.Next,a series of adaptive laws are developed so that the undesirable effects arising from unsteady aerodynamics,actuator failures and unknown uncertainties could be suppressed.Consequently,an impact angle constrained fuzzy adaptive fault tolerant IGC method with three loops is constructed and a perfect hit-to-kill interception with specified impact angle can be implemented.Eventually,the numerical simulations are conducted to verify the effectiveness and superiority of the proposed method.展开更多
基金supported by the National Basic Research Program of China(″973″Program)(No.2014CB046200)the National Natural Science Foundation of China(Nos.11402114,51506089)+1 种基金the Fundamental Research Funds for Central UniversitiesNanjing University of Aeronautics,and Astronautics Basic Scientific Research Projects for Youth Science(No.NS2014014)
文摘Accurate prediction of droplet impingement on wind turbine blade is one of the most important premises of anti-icing and de-icing system design.In a super-cooled large droplets(SLD)conditions,droplet no longer maintains a sphere shape,and it may deform,break up,and splash when moving or impinging on the surface.Semi-empirical models of droplet dynamic behaviours are embedded into the Eulerian droplet model to improve the accuracy of the numerical simulation of droplet impingement limits and local collection efficiency.Eulerian droplet model(Model 1)for small droplets and improved Eulerian droplet model(Model 2)for large droplet are both validated by comparing to the wind tunnel experiment results.Using the proposed methods,droplet impingement limitation and local collection efficiency on the S809 airfoil are calculated in various conditions.A detailed derivation of Model 1and Model 2is presented along with a comparison of numerical trajectories,drag coefficient and collection efficiency distributions.The results show that droplet dynamic behaviours,including splashing,break-up and deforming,must be considered to accurately simulate the impingement behaviour in the SLD conditions.And with the increase of the droplet diameters,the effects of the droplet dynamic behaviors on the impingement characteristics are more obvious.
文摘目的建立烟酰胺凝胶的制备工艺及含量测定方法。方法采用正交实验,以卡波姆、中和剂、保湿剂为考察因素,以凝胶剂的外观性状为考察指标,筛选凝胶剂最优处方基质;以卡波姆-940、丙二醇、聚山梨酯-80等制备烟酰胺凝胶剂,采用紫外—可见光分光度法测定含量。结果烟酰胺在2.0~12.0 g/mL浓度范围内线性关系良好(r=0.9992),加样平均回收率为99.65%,相对标准偏差(relative standard deviation,RSD)值为0.42%。结论此次研究成功建立了适合批量生产烟酰胺凝胶的制备工艺及便捷可靠的含量测定方法。
基金National Natural Science Foundation of China under contract Nos 40206023 and 40776099.
文摘Different ocean features usually appear in synthetic aperture radar(SAR)images simultaneously.This makes the image complicated and hard to understand.Because of lower signal-to-noise rate,it is much more difficult to separate different ocean features than to separate different land features.A completely novel method is presented to separate ocean features from multifrequency polarimetric SAR imagery.AIRSAR data from Jet Propulsion Laboratory(JPL),National Aeronautics and Space Administration(NASA)are used in the case studies and good results are achieved.
基金supported by the National Natural Science Foundation of China(62003264).
文摘An impact angle constrained fuzzy adaptive fault tolerant integrated guidance and control method for Ski-to-Turn(STT)missiles subject to unsteady aerodynamics and multiple disturbances is proposed.Unsteady aerodynamics appears when flight vehicles are in a transonic state or confronted with unstable airflow.Meanwhile,actuator failures and multisource model uncertainties are introduced.However,the boundaries of these multisource uncertainties are assumed unknown.The target is assumed to execute high maneuver movement which is unknown to the missile.Furthermore,impact angle constraint puts forward higher requirements for the interception accuracy of the integrated guidance and control(IGC)method.The impact angle constraint and the precise interception are established as the object of the IGC method.Then,the boundaries of the lumped disturbances are estimated,and several fuzzy logic systems are introduced to compensate the unknown nonlinearities and uncertainties.Next,a series of adaptive laws are developed so that the undesirable effects arising from unsteady aerodynamics,actuator failures and unknown uncertainties could be suppressed.Consequently,an impact angle constrained fuzzy adaptive fault tolerant IGC method with three loops is constructed and a perfect hit-to-kill interception with specified impact angle can be implemented.Eventually,the numerical simulations are conducted to verify the effectiveness and superiority of the proposed method.
