大功率人工源极低频电磁波(Control Source of Extremely Low Frequency method,CSELF)技术中,辐射天线由布设在高大地电阻率区的接地长导线源构成,通过接地点向大地注入数百安培的强电流.目前有关强电流在大地中的流动特性和分布规律,...大功率人工源极低频电磁波(Control Source of Extremely Low Frequency method,CSELF)技术中,辐射天线由布设在高大地电阻率区的接地长导线源构成,通过接地点向大地注入数百安培的强电流.目前有关强电流在大地中的流动特性和分布规律,尚未完全弄清楚.本文提出一个新思路,将CSELF发射天线分解为两部分:交变的接地长导线源和接地处的交流点电流源,二者响应的叠加构成总场.本文重点讨论了均匀空间下交流点电流源的求解,对比研究了交流点电流源响应、直流点电流源响应之间的差异.结果表明,在小范围内(场源距几十、几百米以内),均匀空间下交流点电流源场和直流源场差别较小,可相互近似,但在大范围内,交流点电流场比直流场的衰减要快得多.由于CSELF辐射天线跨度上百公里,场源距很大,其电流分布规律遵循交变场规则,不能近似为直流场.展开更多
Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width mo...Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.展开更多
We investigate alternating response of the spin current in a quantum dot system coupled to a normal metal electrode, to which an alternating driving voltage and a pumping rotating magnetic field are applied. The expre...We investigate alternating response of the spin current in a quantum dot system coupled to a normal metal electrode, to which an alternating driving voltage and a pumping rotating magnetic field are applied. The expression of the time-averaged spin current and its differential is obtained based on a non-equilibrium Green＇s function method. We find that for a given rotating frequency, the spin current increases rapidly and appears to have small steps when the driven frequency increases. As the driven frequency is further increasing, the spin current can be significantly enhanced and approaches a stable value. The photon-assisted processes bring about interesting features of spin current. The influence of the gate voltage and temperature on the spin current is examined in detail.展开更多
Idioms, composed of various linguistic characteristics, are frequently used by both Chinese and foreign people, making them perfect material to analyze different topics of intercultural communication. Through translat...Idioms, composed of various linguistic characteristics, are frequently used by both Chinese and foreign people, making them perfect material to analyze different topics of intercultural communication. Through translations of idioms, we can easily find the integration and differences between English and Chinese idioms. In the process of translating, translators have to be acutely aware of not only the language differences, but also the associations and differences between the cultural background of two languages. By studying bilingual material after the translation is completed, re-comprehension of different cultures and their features can be acquired and it can feed back to our translation missions and foreign exchange activities. This paper aims to analyze the differences and integration of intercultural communication through examples of several idioms translation to illustrate the importance of intercultural communication view in translating and give translators a new prospective for translation strategies.展开更多
Sensor networks tend to support different traffic patterns since more and more emerging applications have diverse needs. We present MGRP, a Multi-Gradient Routing Protocol for wireless sensor networks, which is fully ...Sensor networks tend to support different traffic patterns since more and more emerging applications have diverse needs. We present MGRP, a Multi-Gradient Routing Protocol for wireless sensor networks, which is fully distributed and efficiently supports endto-end, one-to-many and many-to-one traffic patterns by effectively construct and maintain a gradient vector for each node. We further combine neighbor link estimation with routing information to reduce packet exchange on network dynamics and node failures. We have implemented MGRP on Tiny OS and evaluated its performance on real-world testbeds. The result shows MGRP achieves lower end-to-end packet delay in different traffic patterns compared to the state of the art routing protocols while still remains high packet delivery ratio.展开更多
This paper proposes a multi-layer multi-agent model for the performance evaluation of powersystems,which is different from the existing multi-agent ones.To describe the impact of the structureof the networked power sy...This paper proposes a multi-layer multi-agent model for the performance evaluation of powersystems,which is different from the existing multi-agent ones.To describe the impact of the structureof the networked power system,the proposed model consists of three kinds of agents that form threelayers:control agents such as the generators and associated controllers,information agents to exchangethe information based on the wide area measurement system (WAMS) or transmit control signals tothe power system stabilizers (PSSs),and network-node agents such as the generation nodes and loadnodes connected with transmission lines.An optimal index is presented to evaluate the performance ofdamping controllers to the system's inter-area oscillation with respect to the information-layer topology.Then,the authors show that the inter-area information exchange is more powerful than the exchangewithin a given area to control the inter-area low frequency oscillation based on simulation analysis.展开更多
文摘大功率人工源极低频电磁波(Control Source of Extremely Low Frequency method,CSELF)技术中,辐射天线由布设在高大地电阻率区的接地长导线源构成,通过接地点向大地注入数百安培的强电流.目前有关强电流在大地中的流动特性和分布规律,尚未完全弄清楚.本文提出一个新思路,将CSELF发射天线分解为两部分:交变的接地长导线源和接地处的交流点电流源,二者响应的叠加构成总场.本文重点讨论了均匀空间下交流点电流源的求解,对比研究了交流点电流源响应、直流点电流源响应之间的差异.结果表明,在小范围内(场源距几十、几百米以内),均匀空间下交流点电流源场和直流源场差别较小,可相互近似,但在大范围内,交流点电流场比直流场的衰减要快得多.由于CSELF辐射天线跨度上百公里,场源距很大,其电流分布规律遵循交变场规则,不能近似为直流场.
文摘Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.
基金Project supported by the National Natural Science Foundation of China(Grant No.60671042)the Key Project of Shanghai Municipal Commission of Science and Technology(Grant No.06JC14032)
文摘We investigate alternating response of the spin current in a quantum dot system coupled to a normal metal electrode, to which an alternating driving voltage and a pumping rotating magnetic field are applied. The expression of the time-averaged spin current and its differential is obtained based on a non-equilibrium Green＇s function method. We find that for a given rotating frequency, the spin current increases rapidly and appears to have small steps when the driven frequency increases. As the driven frequency is further increasing, the spin current can be significantly enhanced and approaches a stable value. The photon-assisted processes bring about interesting features of spin current. The influence of the gate voltage and temperature on the spin current is examined in detail.
文摘Idioms, composed of various linguistic characteristics, are frequently used by both Chinese and foreign people, making them perfect material to analyze different topics of intercultural communication. Through translations of idioms, we can easily find the integration and differences between English and Chinese idioms. In the process of translating, translators have to be acutely aware of not only the language differences, but also the associations and differences between the cultural background of two languages. By studying bilingual material after the translation is completed, re-comprehension of different cultures and their features can be acquired and it can feed back to our translation missions and foreign exchange activities. This paper aims to analyze the differences and integration of intercultural communication through examples of several idioms translation to illustrate the importance of intercultural communication view in translating and give translators a new prospective for translation strategies.
基金supported by National Key Technologies Research and Development Program of China under Grant No.2014BAH14F01National Science and Technology Major Project of China under Grant No.2012ZX03005007+1 种基金National NSF of China Grant No.61402372Fundamental Research Funds for the Central Universities Grant No.3102014JSJ0003
文摘Sensor networks tend to support different traffic patterns since more and more emerging applications have diverse needs. We present MGRP, a Multi-Gradient Routing Protocol for wireless sensor networks, which is fully distributed and efficiently supports endto-end, one-to-many and many-to-one traffic patterns by effectively construct and maintain a gradient vector for each node. We further combine neighbor link estimation with routing information to reduce packet exchange on network dynamics and node failures. We have implemented MGRP on Tiny OS and evaluated its performance on real-world testbeds. The result shows MGRP achieves lower end-to-end packet delay in different traffic patterns compared to the state of the art routing protocols while still remains high packet delivery ratio.
基金supported in part by the National Natural Science Foundation of China under Grants Nos. 50707035, 50595411, 60425307, 60221301 and 50607005, in part by the 111 project (B08013)Program for Changjiang Scholars and Innovative Research Team in University (IRT0515)in part by the Program for New Century Excellent Talents in University (NCET-05-0216)
文摘This paper proposes a multi-layer multi-agent model for the performance evaluation of powersystems,which is different from the existing multi-agent ones.To describe the impact of the structureof the networked power system,the proposed model consists of three kinds of agents that form threelayers:control agents such as the generators and associated controllers,information agents to exchangethe information based on the wide area measurement system (WAMS) or transmit control signals tothe power system stabilizers (PSSs),and network-node agents such as the generation nodes and loadnodes connected with transmission lines.An optimal index is presented to evaluate the performance ofdamping controllers to the system's inter-area oscillation with respect to the information-layer topology.Then,the authors show that the inter-area information exchange is more powerful than the exchangewithin a given area to control the inter-area low frequency oscillation based on simulation analysis.
