Temperature and salinity data,obtained by two snapshot surveys during 19-20 May 2019 and 12-25 September 2019 across the East China Sea(ECS)shelf,revealed that the Kuroshio intrusion to the north of 28°N comprise...Temperature and salinity data,obtained by two snapshot surveys during 19-20 May 2019 and 12-25 September 2019 across the East China Sea(ECS)shelf,revealed that the Kuroshio intrusion to the north of 28°N comprised the Nearshore Kuroshio Branch Current(NKBC)and the Off shore Kuroshio Branch Current(OKBC)at the bottom of the ECS during spring 2019,and that the NKBC was weak during autumn 2019.The Regional Ocean Model System was used to reproduce the distribution of water masses and the current structure over the continental shelf of the ECS during 2019.Analyses of the momentum balances indicated that the cross-shore range and the intensity of the NKBC were determined by the combination of the geostrophic fl ow and bottom Ekman current.In comparison with that in May 2019,a weakened shoreward bottom Ekman current and an increased off shoreward geostrophic fl ow caused the disappearance of cross-shore range of the NKBC in September 2019.Meanwhile,a diminished northeastward alongshore geostrophic fl ow in September 2019 also weakened the intensity of the NKBC.Sensitivity experiments indicated that a strong southwestward wind can push the western(eastern)boundary of the NKBC further off shoreward(shoreward)by increasing(decreasing)the off shore geostrophic fl ow(bottom Ekman current).A weak Taiwan Warm Current(TWC)can move the eastern boundary of the NKBC shoreward by decreasing the onshore bottom Ekman current.A weak Kuroshio Current(KC)can move the eastern boundary of the NKBC shoreward by increasing the off shoreward geostrophic fl ow.Furthermore,a strong(weak)southwestward wind,weak(strong)TWC,and strong(weak)KC can diminish(enhance)the intensity of the NKBC.Of the three factors,the wind plays the major role in infl uencing the NKBC.展开更多
In the actual use of a parallel battery pack in electric vehicles(EVs),current distribution in each branch will be different due to inconsistence characteristics of each battery cell.If the branch current is approxima...In the actual use of a parallel battery pack in electric vehicles(EVs),current distribution in each branch will be different due to inconsistence characteristics of each battery cell.If the branch current is approximately calculated by the total current of the battery pack divided by the number of the parallel branches,there will be a large error between the calculated branch current and the real branch current.Adding current sensors to measure each branch current is not practical because of the high cost.Accurate estimation of branch currents can give a safety warning in time when the parallel batteries of EVs are seriously inconsistent.This paper puts forward a method to estimate and correct branch currents based on dual back propagation(BP)neural networks.In the proposed method,one BP neural network is used to estimate branch currents,the other BP neural network is used to reduce the estimation error cause by current pulse excitations.Furthermore,this paper makes discussions on the selection of the best inputs for the dual BP neural networks and the adaptability of the method for different battery capacity and resistence differences.The effectiveness of the proposed method is verified by multiple dynamic conditions of two cells connected in parallel.展开更多
Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or...Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.展开更多
基于前置放大器对于高稳定性基准电流源的需求,设计了一种结构简单、对温度不敏感、有较高电压稳定性的三支路基准源电路。利用与绝对温度成比例(Proportional to Absolute Temperature,PTAT)和与绝对温度互补变化(Complementary to Abs...基于前置放大器对于高稳定性基准电流源的需求,设计了一种结构简单、对温度不敏感、有较高电压稳定性的三支路基准源电路。利用与绝对温度成比例(Proportional to Absolute Temperature,PTAT)和与绝对温度互补变化(Complementary to Absolute Temperature,CTAT)的电流产生一个对温度不敏感的电流。同时,利用第三支路产生的电压增益形成的负反馈回路来提高电路的稳定性,减少电源电压波动对输出电流产生的影响。对电流源集成电路拓扑结构进行前仿和后仿,结果表明:当电源电压供电5 V时,在-25~145℃,温度系数较低;在0~15.8 kHz范围内,电源抑制比(Power Supply Rejection Ratio,PSRR)为-80 dB左右;整体静态电流仅为20μA。该拓扑结构在设计低温漂高电源抑制比方面具有非常好的效果,并且可以很好的为前置放大器提供稳定的工作电流。展开更多
柔性光学电流互感器(flexible optical current transformer,FOCT)在水电领域的推广应用,为奇数多分支发电机主保护定量化改造奠定了基础。经内部故障的全面分析计算,某每相7分支的大型发电机主保护定量化设计结果推荐采用“3-1-3”分...柔性光学电流互感器(flexible optical current transformer,FOCT)在水电领域的推广应用,为奇数多分支发电机主保护定量化改造奠定了基础。经内部故障的全面分析计算,某每相7分支的大型发电机主保护定量化设计结果推荐采用“3-1-3”分支分组方式,相应的主保护配置方案保护死区虽小(0.5%)但对相间短路存在保护死区——发生在每相未装设分支电流互感器(TA)的第4分支之间,利用柔性光学TA绕制灵活的特点,通过增设每相第4分支的光学TA及对应的不完全纵差保护即可消除上述相间短路保护死区。上述主保护定量化改造思路将为后续奇数多分支大型发电机的技术改造提供借鉴。展开更多
The upper ocean currents in the Pacific Ocean are calculated by using an ocean model with higher horizontal resolution. The large current systems in the Pacific Ocean, such as Kuroshio, Oyashio, NEC, SEC, NECC,Califom...The upper ocean currents in the Pacific Ocean are calculated by using an ocean model with higher horizontal resolution. The large current systems in the Pacific Ocean, such as Kuroshio, Oyashio, NEC, SEC, NECC,Califomia Current and East Australia Current, are well simulated. This paper only gives the numerical simulation results of the upper ocean currents of the representative months in four seasons in the South China Sea (SCS). It showsthat the SCS branch of Kuroshio is the most important current in the northem SCS and it is not only the water resourceof the SCS warm current but also a significant part of the overall SCS circulation. There is a relatively strong northeastward flow entering the SCS through the Taiwan Strait throughout the year except for specific months. Some of thenumerical results have been confirmed by the observational evidences.展开更多
Based on the data of temperature and salinity of the 137°E section in the winters and summers from 1967 to 1995, the geo-strophic current of the section is calculated and analyzed, and the drifting tracks of the ...Based on the data of temperature and salinity of the 137°E section in the winters and summers from 1967 to 1995, the geo-strophic current of the section is calculated and analyzed, and the drifting tracks of the satellite tracking drift buoy distributed on the 144°E section are also analyzed. In light of the surface dynamic height distribution in the CSK atlas, this paper compares some features of the Subtropical Countercurrent, the North Equatorial Current and the North Equatorial Countercurrent. The main results are as follows:1. The Subtropical Countercurrent, the North Equatorial Current and the North Equatorial Countercurrent are not simple single currents, but have two branches or more. One of the common features of the three currents mentioned above is "multi-branching" of the current.2. The zonal distribution of the flow velocity structure, the alternate and intermittent occurrence of the eastward and westward flows, with a shallower flow layer and belonging to the surface flow or subsurface展开更多
基金Supported by the National Natural Science Foundation of China(Nos.41630967,41776020)。
文摘Temperature and salinity data,obtained by two snapshot surveys during 19-20 May 2019 and 12-25 September 2019 across the East China Sea(ECS)shelf,revealed that the Kuroshio intrusion to the north of 28°N comprised the Nearshore Kuroshio Branch Current(NKBC)and the Off shore Kuroshio Branch Current(OKBC)at the bottom of the ECS during spring 2019,and that the NKBC was weak during autumn 2019.The Regional Ocean Model System was used to reproduce the distribution of water masses and the current structure over the continental shelf of the ECS during 2019.Analyses of the momentum balances indicated that the cross-shore range and the intensity of the NKBC were determined by the combination of the geostrophic fl ow and bottom Ekman current.In comparison with that in May 2019,a weakened shoreward bottom Ekman current and an increased off shoreward geostrophic fl ow caused the disappearance of cross-shore range of the NKBC in September 2019.Meanwhile,a diminished northeastward alongshore geostrophic fl ow in September 2019 also weakened the intensity of the NKBC.Sensitivity experiments indicated that a strong southwestward wind can push the western(eastern)boundary of the NKBC further off shoreward(shoreward)by increasing(decreasing)the off shore geostrophic fl ow(bottom Ekman current).A weak Taiwan Warm Current(TWC)can move the eastern boundary of the NKBC shoreward by decreasing the onshore bottom Ekman current.A weak Kuroshio Current(KC)can move the eastern boundary of the NKBC shoreward by increasing the off shoreward geostrophic fl ow.Furthermore,a strong(weak)southwestward wind,weak(strong)TWC,and strong(weak)KC can diminish(enhance)the intensity of the NKBC.Of the three factors,the wind plays the major role in infl uencing the NKBC.
基金Natural Science Program of Shandong Province(Grant No.ZR2020ME209)National Natural Science Foundation of China(Grant No.52177210)China Postdoctoral Science Foundation(Grant No.2021M690740).
文摘In the actual use of a parallel battery pack in electric vehicles(EVs),current distribution in each branch will be different due to inconsistence characteristics of each battery cell.If the branch current is approximately calculated by the total current of the battery pack divided by the number of the parallel branches,there will be a large error between the calculated branch current and the real branch current.Adding current sensors to measure each branch current is not practical because of the high cost.Accurate estimation of branch currents can give a safety warning in time when the parallel batteries of EVs are seriously inconsistent.This paper puts forward a method to estimate and correct branch currents based on dual back propagation(BP)neural networks.In the proposed method,one BP neural network is used to estimate branch currents,the other BP neural network is used to reduce the estimation error cause by current pulse excitations.Furthermore,this paper makes discussions on the selection of the best inputs for the dual BP neural networks and the adaptability of the method for different battery capacity and resistence differences.The effectiveness of the proposed method is verified by multiple dynamic conditions of two cells connected in parallel.
基金This project is supported by Provincial Science Foundation of Education Office of Hebei(No.Z2004455)Youth Research Fundation of State Power of China(No.SPQKJ02-10).
文摘Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.
文摘柔性光学电流互感器(flexible optical current transformer,FOCT)在水电领域的推广应用,为奇数多分支发电机主保护定量化改造奠定了基础。经内部故障的全面分析计算,某每相7分支的大型发电机主保护定量化设计结果推荐采用“3-1-3”分支分组方式,相应的主保护配置方案保护死区虽小(0.5%)但对相间短路存在保护死区——发生在每相未装设分支电流互感器(TA)的第4分支之间,利用柔性光学TA绕制灵活的特点,通过增设每相第4分支的光学TA及对应的不完全纵差保护即可消除上述相间短路保护死区。上述主保护定量化改造思路将为后续奇数多分支大型发电机的技术改造提供借鉴。
文摘The upper ocean currents in the Pacific Ocean are calculated by using an ocean model with higher horizontal resolution. The large current systems in the Pacific Ocean, such as Kuroshio, Oyashio, NEC, SEC, NECC,Califomia Current and East Australia Current, are well simulated. This paper only gives the numerical simulation results of the upper ocean currents of the representative months in four seasons in the South China Sea (SCS). It showsthat the SCS branch of Kuroshio is the most important current in the northem SCS and it is not only the water resourceof the SCS warm current but also a significant part of the overall SCS circulation. There is a relatively strong northeastward flow entering the SCS through the Taiwan Strait throughout the year except for specific months. Some of thenumerical results have been confirmed by the observational evidences.
文摘Based on the data of temperature and salinity of the 137°E section in the winters and summers from 1967 to 1995, the geo-strophic current of the section is calculated and analyzed, and the drifting tracks of the satellite tracking drift buoy distributed on the 144°E section are also analyzed. In light of the surface dynamic height distribution in the CSK atlas, this paper compares some features of the Subtropical Countercurrent, the North Equatorial Current and the North Equatorial Countercurrent. The main results are as follows:1. The Subtropical Countercurrent, the North Equatorial Current and the North Equatorial Countercurrent are not simple single currents, but have two branches or more. One of the common features of the three currents mentioned above is "multi-branching" of the current.2. The zonal distribution of the flow velocity structure, the alternate and intermittent occurrence of the eastward and westward flows, with a shallower flow layer and belonging to the surface flow or subsurface
