As a vessel navigates at high speeds in waves,considerable pitching motion can result in the discomfort of passengers.In this study is proposed a ride control system consisting of dual T-foils to generate a larger rig...As a vessel navigates at high speeds in waves,considerable pitching motion can result in the discomfort of passengers.In this study is proposed a ride control system consisting of dual T-foils to generate a larger righting moment than a common single T-foil system.One T-foil is mounted at the bow,and the other at the stern.Accordingly,different control strategies for dual T-foils were proposed To verify the stratigies,a model experiment was conducted in the Towing Tank,Dalian Unievrsity of Technology.The optimal control signal was determined by comparing the pitch responses,heave responses,bow accelerations,and stern accelerations of a vessel in regular waves.In addition,the control strategy for the best motion-reduction effect was investigated.The optimized dual T-foil system provides a 34%reduction in pitch motion.展开更多
An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to d...An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover,the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode.Throughout the whole of these three periods(eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB(depending on the relative location of eddy center to the source).展开更多
In this paper,an effective target locating approach based on the fingerprint fusion posi-tioning(FFP)method is proposed which integrates the time-difference of arrival(TDOA)and the received signal strength according t...In this paper,an effective target locating approach based on the fingerprint fusion posi-tioning(FFP)method is proposed which integrates the time-difference of arrival(TDOA)and the received signal strength according to the statistical variance of target position in the stationary 3D scenarios.The FFP method fuses the pedestrian dead reckoning(PDR)estimation to solve the moving target localization problem.We also introduce auxiliary parameters to estimate the target motion state.Subsequently,we can locate the static pedestrians and track the the moving target.For the case study,eight access stationary points are placed on a bookshelf and hypermarket;one target node is moving inside hypermarkets in 2D and 3D scenarios or stationary on the bookshelf.We compare the performance of our proposed method with existing localization algorithms such as k-nearest neighbor,weighted k-nearest neighbor,pure TDOA and fingerprinting combining Bayesian frameworks including the extended Kalman filter,unscented Kalman filter and particle fil-ter(PF).The proposed approach outperforms obviously the counterpart methodologies in terms of the root mean square error and the cumulative distribution function of localization errors,espe-cially in the 3D scenarios.Simulation results corroborate the effectiveness of our proposed approach.展开更多
Secret image sharing(SIS)is a significant research topic of image information hiding,which divides the image into multiple shares and dis-tributes them to multiple parties for management and preservation.In order to r...Secret image sharing(SIS)is a significant research topic of image information hiding,which divides the image into multiple shares and dis-tributes them to multiple parties for management and preservation.In order to reconstruct the original image,a subset with predetermined number of shares is needed.And just because it is not necessary to use all of the shares to make a reconstruction,SIS creates a high fault tolerance which breaks the limitations of traditional image protection methods,but at the same time,it causes a reduce of safety.Recently,new technologies,such as deep learning and blockchain,have been applied into SIS to improve its efficiency and security.This paper gives an overall review of SIS,discusses four important approaches for SIS,and makes a comparison analysis among them from the perspectives of pixel expansion,tamper resistance,etc.At the end,this paper indicates the possible research directions of SIS in the future.展开更多
Using the daily precipitation data from the global precipitation measurement(GPM)satellite and meteorological stations from 2001 to 2020,the present study has analyzed the seasonal and interannual spatial-temporal var...Using the daily precipitation data from the global precipitation measurement(GPM)satellite and meteorological stations from 2001 to 2020,the present study has analyzed the seasonal and interannual spatial-temporal variations of the precipitation over the Three-River Headwaters region.The rainfall of the Three-River Headwaters region is verified to have obvious spatial-temporal variations and is mainly concentrated in summer.Then,the empirical orthogonal function(EOF)method is performed and reveals that the summer precipitation in the Three-River Headwaters region mainly shows three patterns,e.g.,the“north−south dipole pattern,”“northeast−southwest diploe pattern,”and“east−west dipole pattern,”among which the northeast−southwest diploe pattern has a strong correlation with the mid-latitude westerlies and summer monsoon.Further analysis reveals that the northeast-southwest diploe pattern of summer precipitation is significantly related to the tripolar sea surface temperature(SST)anomalies(SSTAs)of the North Atlantic Ocean in the preceding winter and the tropical Indian Ocean SSTAs in the simultaneous summer.In the preceding winter,a wave-like pattern zonally propagating along the mid-latitude westerlies is triggered downstream by the North Atlantic tripolar SSTAs.One of the cyclones generated by the wave-like pattern coincidentally locates in Northeastern China and forms a deep northeastern low system in summer.Moreover,the warming of the tropical Indian Ocean SSTAs in summer weakens the Walker circulation,which leads to the strengthening and westward extension of the Western Pacific subtropical high(WPSH).Northerly anomalies from the deep northeastern cyclonic anomalies and southwesterly anomalies from the enhancing WPSH exactly met at the eastern Three-River Headwaters region.Hence,more water vapor and ascending motion anomalies likely appear over the east part of the Three-River Headwaters region.Opposite anomalies cover the south-western Three-River Headwaters region and its surroundings.Then,the northeast-southwest reverse diploe pattern of the summer rainfall in the Three-River Headwaters region is directly produced.展开更多
The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is p...The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is proposed.After obtaining the response of the entire system,the transducer is excited with wide-band,short-duration signals.Then,the received signals are processed with inverse filters and the ＂blurred＂ reflective signals of standard reflector and test sample are recovered respectively,finally,the reflection coefficient and absorption coefficient are calculated.Simulation work is implemented to verify the advantage of postprocessing inverse filter over pre-processing inverse filter in terms of low frequency measurement.To verify the proposed method,two different wide-band pulses in the separate frequency ranges are adopted to measure the same rubber material.The experimental results indicate that the wide-band pulse method and CW（Continuous Wave） pulse method have good agreement in both low frequency range and high frequency range.Wide-band pulse method is of high efficiency,and the low frequency reaches 350 Hz,which is able to extend the low frequency range.展开更多
基金supported by Shenzhen 2022 Key Project for Technological Research(Grant Number JSGG20220831110803006)key technology research and demonstration project of 10 MW deep-sea floating offshore wind turbine(DTGD-2023-10174)key technology research task of floating offshore combined wind and wave power generation and MIIT program for Floating VAWT.
文摘As a vessel navigates at high speeds in waves,considerable pitching motion can result in the discomfort of passengers.In this study is proposed a ride control system consisting of dual T-foils to generate a larger righting moment than a common single T-foil system.One T-foil is mounted at the bow,and the other at the stern.Accordingly,different control strategies for dual T-foils were proposed To verify the stratigies,a model experiment was conducted in the Towing Tank,Dalian Unievrsity of Technology.The optimal control signal was determined by comparing the pitch responses,heave responses,bow accelerations,and stern accelerations of a vessel in regular waves.In addition,the control strategy for the best motion-reduction effect was investigated.The optimized dual T-foil system provides a 34%reduction in pitch motion.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11434012 and 41561144006)
文摘An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover,the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode.Throughout the whole of these three periods(eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB(depending on the relative location of eddy center to the source).
基金partially supported by the National Natural Science Foun-dation of China(No.62071389).
文摘In this paper,an effective target locating approach based on the fingerprint fusion posi-tioning(FFP)method is proposed which integrates the time-difference of arrival(TDOA)and the received signal strength according to the statistical variance of target position in the stationary 3D scenarios.The FFP method fuses the pedestrian dead reckoning(PDR)estimation to solve the moving target localization problem.We also introduce auxiliary parameters to estimate the target motion state.Subsequently,we can locate the static pedestrians and track the the moving target.For the case study,eight access stationary points are placed on a bookshelf and hypermarket;one target node is moving inside hypermarkets in 2D and 3D scenarios or stationary on the bookshelf.We compare the performance of our proposed method with existing localization algorithms such as k-nearest neighbor,weighted k-nearest neighbor,pure TDOA and fingerprinting combining Bayesian frameworks including the extended Kalman filter,unscented Kalman filter and particle fil-ter(PF).The proposed approach outperforms obviously the counterpart methodologies in terms of the root mean square error and the cumulative distribution function of localization errors,espe-cially in the 3D scenarios.Simulation results corroborate the effectiveness of our proposed approach.
基金supported in part by the National Natural Science Foundation of China under Grant 61972205,Grant U1936218in part by the Guangdong Natural Science Funds for Distinguished Young Scholar+2 种基金in part by CSSC Systems Engineering Research Institute(Grant No.193-A11-107-01-33)in part by Science and Technology Planning Project of Changsha(No.kq2004004)in part by the Collaborative Innovation Center of Atmospheric Environment and Equipment Technology(CICAEET)fund,China.
文摘Secret image sharing(SIS)is a significant research topic of image information hiding,which divides the image into multiple shares and dis-tributes them to multiple parties for management and preservation.In order to reconstruct the original image,a subset with predetermined number of shares is needed.And just because it is not necessary to use all of the shares to make a reconstruction,SIS creates a high fault tolerance which breaks the limitations of traditional image protection methods,but at the same time,it causes a reduce of safety.Recently,new technologies,such as deep learning and blockchain,have been applied into SIS to improve its efficiency and security.This paper gives an overall review of SIS,discusses four important approaches for SIS,and makes a comparison analysis among them from the perspectives of pixel expansion,tamper resistance,etc.At the end,this paper indicates the possible research directions of SIS in the future.
基金Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0105)National Natural Science Foundation of China(91937000)。
文摘Using the daily precipitation data from the global precipitation measurement(GPM)satellite and meteorological stations from 2001 to 2020,the present study has analyzed the seasonal and interannual spatial-temporal variations of the precipitation over the Three-River Headwaters region.The rainfall of the Three-River Headwaters region is verified to have obvious spatial-temporal variations and is mainly concentrated in summer.Then,the empirical orthogonal function(EOF)method is performed and reveals that the summer precipitation in the Three-River Headwaters region mainly shows three patterns,e.g.,the“north−south dipole pattern,”“northeast−southwest diploe pattern,”and“east−west dipole pattern,”among which the northeast−southwest diploe pattern has a strong correlation with the mid-latitude westerlies and summer monsoon.Further analysis reveals that the northeast-southwest diploe pattern of summer precipitation is significantly related to the tripolar sea surface temperature(SST)anomalies(SSTAs)of the North Atlantic Ocean in the preceding winter and the tropical Indian Ocean SSTAs in the simultaneous summer.In the preceding winter,a wave-like pattern zonally propagating along the mid-latitude westerlies is triggered downstream by the North Atlantic tripolar SSTAs.One of the cyclones generated by the wave-like pattern coincidentally locates in Northeastern China and forms a deep northeastern low system in summer.Moreover,the warming of the tropical Indian Ocean SSTAs in summer weakens the Walker circulation,which leads to the strengthening and westward extension of the Western Pacific subtropical high(WPSH).Northerly anomalies from the deep northeastern cyclonic anomalies and southwesterly anomalies from the enhancing WPSH exactly met at the eastern Three-River Headwaters region.Hence,more water vapor and ascending motion anomalies likely appear over the east part of the Three-River Headwaters region.Opposite anomalies cover the south-western Three-River Headwaters region and its surroundings.Then,the northeast-southwest reverse diploe pattern of the summer rainfall in the Three-River Headwaters region is directly produced.
基金supported by the National Natural Science Foundation of China(11474230)the National Key Research and Development Program of China(2016YFF0200900)the Science and Technology Research and Development Program of Shaanxi Province(2016GY-111)
文摘The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is proposed.After obtaining the response of the entire system,the transducer is excited with wide-band,short-duration signals.Then,the received signals are processed with inverse filters and the ＂blurred＂ reflective signals of standard reflector and test sample are recovered respectively,finally,the reflection coefficient and absorption coefficient are calculated.Simulation work is implemented to verify the advantage of postprocessing inverse filter over pre-processing inverse filter in terms of low frequency measurement.To verify the proposed method,two different wide-band pulses in the separate frequency ranges are adopted to measure the same rubber material.The experimental results indicate that the wide-band pulse method and CW（Continuous Wave） pulse method have good agreement in both low frequency range and high frequency range.Wide-band pulse method is of high efficiency,and the low frequency reaches 350 Hz,which is able to extend the low frequency range.
