As a combination of bio-mechanism and engineering technology, robot fish has become a multidisci- plinary research that mainly involves both hydrodynamics-based control and actuation technology. This paper presents a ...As a combination of bio-mechanism and engineering technology, robot fish has become a multidisci- plinary research that mainly involves both hydrodynamics-based control and actuation technology. This paper presents a simplified propulsive model for carangiform propulsion, which is a swimming mode suitable for high speed and high efficiency. The carangiform motion is modeled as an N-joint nscillating mechanism that is composed of two basic components： the streamlined fish body represented by a planar spline curve and its hmate caudal tail by an oscillating foil. The speed of fish＇s straight swimming is adjusted by modulating the joint＇s oscillating frequency, and its orientation is tuned by different joint＇s deflection. The results from actual experiment showed that the proposed simplified propulsive model could be a viable eandidate for application in aquatic： swimming vehicles.展开更多
This study investigates the changes in January diurnal temperature range(DTR) in China during 1961-2000.The observed DTR changes during 1981-2000 relative to 1961-80 are first analyzed based on the daily temperature d...This study investigates the changes in January diurnal temperature range(DTR) in China during 1961-2000.The observed DTR changes during 1981-2000 relative to 1961-80 are first analyzed based on the daily temperature data at 546 weather stations.These observed DTR changes are classified into six cases depending on the changes in daily maximum and minimum temperatures,and then the occurrence frequency and magnitude of DTR change in each case are presented.Three transient simulations are then performed to understand the impact of greenhouse gases(GHGs) and aerosol direct forcing on DTR change:one without anthropogenic radiative forcing,one with anthropogenic GHGs,and another one with the combined forcing of GHGs and five species of anthropogenic aerosols.The predicted daily DTR changes during the years 1981-2000 are also classified into six cases and are compared with the observations.Results show that the previously proposed reason for DTR reduction,a stronger nocturnal warming than a daytime warming,explains only 19.8%of the observed DTR reduction days.DTR reductions are found to generally occur in northeastern China,coinciding with significant regional warming.The simulation with GHG forcing alone reproduces this type of DTR reduction with an occurrence frequency of 32.9%,which is larger than the observed value.Aerosol direct forcing reduces DTR mainly by daytime cooling.Consideration of aerosol cooling improves the simulation of occurrence frequencies of different types of DTR changes as compared to the simulation with GHGs alone,but it cannot improve the prediction of the magnitude of DTR changes.展开更多
文摘As a combination of bio-mechanism and engineering technology, robot fish has become a multidisci- plinary research that mainly involves both hydrodynamics-based control and actuation technology. This paper presents a simplified propulsive model for carangiform propulsion, which is a swimming mode suitable for high speed and high efficiency. The carangiform motion is modeled as an N-joint nscillating mechanism that is composed of two basic components： the streamlined fish body represented by a planar spline curve and its hmate caudal tail by an oscillating foil. The speed of fish＇s straight swimming is adjusted by modulating the joint＇s oscillating frequency, and its orientation is tuned by different joint＇s deflection. The results from actual experiment showed that the proposed simplified propulsive model could be a viable eandidate for application in aquatic： swimming vehicles.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant Nos.KZCX2-YW-Q11-03 and KZCX2-YW-Q1-02)the National Natural Science Foundation of China(Grant No.40825016)the China Meteorological Administration for the Special Project of Meteorological Sector(Grant No.GYHY200906020)
文摘This study investigates the changes in January diurnal temperature range(DTR) in China during 1961-2000.The observed DTR changes during 1981-2000 relative to 1961-80 are first analyzed based on the daily temperature data at 546 weather stations.These observed DTR changes are classified into six cases depending on the changes in daily maximum and minimum temperatures,and then the occurrence frequency and magnitude of DTR change in each case are presented.Three transient simulations are then performed to understand the impact of greenhouse gases(GHGs) and aerosol direct forcing on DTR change:one without anthropogenic radiative forcing,one with anthropogenic GHGs,and another one with the combined forcing of GHGs and five species of anthropogenic aerosols.The predicted daily DTR changes during the years 1981-2000 are also classified into six cases and are compared with the observations.Results show that the previously proposed reason for DTR reduction,a stronger nocturnal warming than a daytime warming,explains only 19.8%of the observed DTR reduction days.DTR reductions are found to generally occur in northeastern China,coinciding with significant regional warming.The simulation with GHG forcing alone reproduces this type of DTR reduction with an occurrence frequency of 32.9%,which is larger than the observed value.Aerosol direct forcing reduces DTR mainly by daytime cooling.Consideration of aerosol cooling improves the simulation of occurrence frequencies of different types of DTR changes as compared to the simulation with GHGs alone,but it cannot improve the prediction of the magnitude of DTR changes.
