In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tid...In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.展开更多
The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are tw...The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are two major problems existing in current-source multilevel inverters, one is the complex PWM control method (2-logic to 3-logic conversion), and the other is the problem of current-unbalance between different levels. A simple current-balance control method via DC current feedback is applied in each single-phase 5-level CSI cell to implement the current-balance control between different levels. And to reduce the output current harmonics, POD PWM control technique was used. Simulation and experimental results showed that this new three-phase 5-level CSI topology operates correctly.展开更多
这研究集中于 Hangzhou 海湾近海的沉积环境变化，华东，自从晚第四级。AMS < 啜 class= “ a-plus-plus ” > 14 </sup > 从核心 CJK10，岩性学，有孔虫类的分发，重矿物质，和 S 和 Cl 元素的 C 年龄在 23.211.0 cal ka ...这研究集中于 Hangzhou 海湾近海的沉积环境变化，华东，自从晚第四级。AMS < 啜 class= “ a-plus-plus ” > 14 </sup > 从核心 CJK10，岩性学，有孔虫类的分发，重矿物质，和 S 和 Cl 元素的 C 年龄在 23.211.0 cal ka BP 期间显示出河的平台环境；一对潮汐公寓的环境沿岸在 11.010.2 cal ka BP 期间；并且有相对低的沉积的浅海洋的环境自从 4.3 cal ka BP，评估 0.10.22 cm/a。高 depositional 从 10.9 ～ 10.2 cal ka BP 评估 1.6 cm/a 源于快速的海水平上升从 44 创造的足够的住所空间 m 到 33 m 从本地河边的高沉积交货，并且由潮汐公寓的植被的沉积的有效套住。海水平上升的率是可变的；自从 10.6 cal ka BP 1.2 cm/a 相对从 10.9 ～ 10.6 cal ka BP 2.1 cm/a 高、更低。Changjiang 沿著岸水流穿过 Hangzhou 海湾比 9.4 cal ka BP 晚在华东海的内部架上形成泥楔。CJK10 地点从近似 9.4-9.2 cal ka BP 是潮主导的架环境和富有经验的侵蚀到 4.3 cal ka BP。depositional 中断被 Changjiang 沿著岸水流引起，它在 9.4-7.5 cal ka BP 期间是相对弱的并且在 7.5-4 cal ka BP 期间在力量增加了。从 4.3 cal ka BP，来自 Changjiang 河的大量沉积部分在 Hangzhou 海湾的大陆人架上被扔，一些搬运了向南方。因此，这研究澄清导出 Changjiang 的沉积疏开和免职的历史，尽管在自从 4.3 cal ka BP 当前的 Changjiang 沿著岸的变化的一个详细记录是困难的因为证据的缺乏，获得。展开更多
The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination o...The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.展开更多
Sub-tidal barotropic current variations coupled with residual sea level fluctuation in the Bohai and Yellow Seas during wintertime are addressed in this study.The temporal evolution and spatial distribution of current...Sub-tidal barotropic current variations coupled with residual sea level fluctuation in the Bohai and Yellow Seas during wintertime are addressed in this study.The temporal evolution and spatial distribution of current fluctuation are investigated using moored acoustic Doppler current profiler data in a three-dimensional numerical model.It is found that a southward current followed by a northward current occurred in the northern Yellow Sea during the fluctuation,concurrent with a significant outflow followed by inflow through the Bohai Strait.The process is consistent from surface to bottom and is coupled with remarkable residual sea level fluctuation.This quasi three-day fluctuation with amplitude 0.2-0.3 m/s leads to 1 m/1.2 m drawdown in the northern Yellow and Bohai Seas,respectively,strongly influencing water exchange between those seas.Because this a prominent feature in the seas,it is necessary to evaluate its effect on fluctuation during winter in future studies,in particular,the northward current during the recovery phase of sea level in the Bohai and Yellow Seas regarding seasonal variation.展开更多
The State Council decided to raise the retail electricity price by 0.25 Yuan/kWh from July, 2008. This will, to some extent, relieve the conflicts between power supply and demand, and decrease the economic losses in
The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To ...The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.展开更多
A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power ca...A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current Ic ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.展开更多
基金The National Key Fundamental Research and Development Program ("973" Program) of China under contract No. 2010CB429001
文摘In order to determine the design tide levels in the areas without measured tide level data, especially in the areas where it is difficult to measure tidal levels, a calculation method based on a numerical model of tidal current is proposed. The essentials of the method are described, and its application is illustrated with an example. The results of the application show that the design tide levels calculated by the method are close to those determined by long-time measured tide level data, and its calculation precision is high, so it is feasible to use the method to determine the design tide levels in the areas.
基金Project (No. 50477033) supported by the National Natural Science Foundation of China
文摘The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are two major problems existing in current-source multilevel inverters, one is the complex PWM control method (2-logic to 3-logic conversion), and the other is the problem of current-unbalance between different levels. A simple current-balance control method via DC current feedback is applied in each single-phase 5-level CSI cell to implement the current-balance control between different levels. And to reduce the output current harmonics, POD PWM control technique was used. Simulation and experimental results showed that this new three-phase 5-level CSI topology operates correctly.
基金Supported by the National Special Research Fund for Non-Profit Marine Sector(No.200805063)the Continental Shelf Drilling Program(No.GZH201100202)the State Key Laboratory of Marine Geology and Environment,Institute of Oceanology Program(No.MGE2012KG09)
文摘这研究集中于 Hangzhou 海湾近海的沉积环境变化，华东，自从晚第四级。AMS < 啜 class= “ a-plus-plus ” > 14 </sup > 从核心 CJK10，岩性学，有孔虫类的分发，重矿物质，和 S 和 Cl 元素的 C 年龄在 23.211.0 cal ka BP 期间显示出河的平台环境；一对潮汐公寓的环境沿岸在 11.010.2 cal ka BP 期间；并且有相对低的沉积的浅海洋的环境自从 4.3 cal ka BP，评估 0.10.22 cm/a。高 depositional 从 10.9 ～ 10.2 cal ka BP 评估 1.6 cm/a 源于快速的海水平上升从 44 创造的足够的住所空间 m 到 33 m 从本地河边的高沉积交货，并且由潮汐公寓的植被的沉积的有效套住。海水平上升的率是可变的；自从 10.6 cal ka BP 1.2 cm/a 相对从 10.9 ～ 10.6 cal ka BP 2.1 cm/a 高、更低。Changjiang 沿著岸水流穿过 Hangzhou 海湾比 9.4 cal ka BP 晚在华东海的内部架上形成泥楔。CJK10 地点从近似 9.4-9.2 cal ka BP 是潮主导的架环境和富有经验的侵蚀到 4.3 cal ka BP。depositional 中断被 Changjiang 沿著岸水流引起，它在 9.4-7.5 cal ka BP 期间是相对弱的并且在 7.5-4 cal ka BP 期间在力量增加了。从 4.3 cal ka BP，来自 Changjiang 河的大量沉积部分在 Hangzhou 海湾的大陆人架上被扔，一些搬运了向南方。因此，这研究澄清导出 Changjiang 的沉积疏开和免职的历史，尽管在自从 4.3 cal ka BP 当前的 Changjiang 沿著岸的变化的一个详细记录是困难的因为证据的缺乏，获得。
文摘The ?method is used in this paper to calculate the leakage magnetic field of SSZ11-50000/110 Power transformer, and by which the structures’ influences to the main leakage flux are analyzed. Through the combination of the product and TEAM Problem 21B, the surface impedance method shows its great advantage in the calculation of eddy current loss.
基金Supported by the National Natural Science Foundation of China(Nos.41430963,41276013)
文摘Sub-tidal barotropic current variations coupled with residual sea level fluctuation in the Bohai and Yellow Seas during wintertime are addressed in this study.The temporal evolution and spatial distribution of current fluctuation are investigated using moored acoustic Doppler current profiler data in a three-dimensional numerical model.It is found that a southward current followed by a northward current occurred in the northern Yellow Sea during the fluctuation,concurrent with a significant outflow followed by inflow through the Bohai Strait.The process is consistent from surface to bottom and is coupled with remarkable residual sea level fluctuation.This quasi three-day fluctuation with amplitude 0.2-0.3 m/s leads to 1 m/1.2 m drawdown in the northern Yellow and Bohai Seas,respectively,strongly influencing water exchange between those seas.Because this a prominent feature in the seas,it is necessary to evaluate its effect on fluctuation during winter in future studies,in particular,the northward current during the recovery phase of sea level in the Bohai and Yellow Seas regarding seasonal variation.
文摘The State Council decided to raise the retail electricity price by 0.25 Yuan/kWh from July, 2008. This will, to some extent, relieve the conflicts between power supply and demand, and decrease the economic losses in
基金supported by the Science and Technology Project of State Grid Corporation of China (No.5200202155587A-0-5-GC)。
文摘The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.
基金supported by National Key R&D Project under Grant(2018YFB0904400).
文摘A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current Ic ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.
