The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave ch...The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave channels is the most suitable protection scheme for long distance EHV transmission lines and is widely used in power systems.The key element of such protection is a directional relay used to discriminate the fault direction.In order to overcome the disadvantages of conventional directional relays,the authors of this paper put forward the directional comparison carrier protection based on the artificial neural network(ANN).The protection is extensively tested using electromagnetic transient program (EMTP) under various electric power system operating and fault conditions.It is proved that the directional comparison carrier protection based on ANN,which can recognize various fault patterns of the protected transmission line(such as fault direction,fault phases etc.)correctly in any kind of operating and fault conditions and the whole process,is satisfactory for EHV transmission line protection.展开更多
As the take-off of China’s macro economy,as well as the rapid development of infrastructure construction,real estate industry,and highway logistics transportation industry,the demand for heavy vehicles is increasing ...As the take-off of China’s macro economy,as well as the rapid development of infrastructure construction,real estate industry,and highway logistics transportation industry,the demand for heavy vehicles is increasing rapidly,the competition is becoming increasingly fierce,and the digital transformation of the production line is imminent.As one of themost important components of heavy vehicles,the transmission front andmiddle case assembly lines have a high degree of automation,which can be used as a pilot for the digital transformation of production.To ensure the visualization of digital twins(DT),consistent control logic,and real-time data interaction,this paper proposes an experimental digital twin modeling method for the transmission front and middle case assembly line.Firstly,theDT-based systemarchitecture is designed,and theDT model is created by constructing the visualization model,logic model,and data model of the assembly line.Then,a simulation experiment is carried out in a virtual space to analyze the existing problems in the current assembly line.Eventually,some improvement strategies are proposed and the effectiveness is verified by a new simulation experiment.展开更多
Blockage and imperfect beam alignment are two principal difficulties in high-frequency bands directional transmissions.In this paper,the coverage performance of downlink directional transmissions in ultra-dense networ...Blockage and imperfect beam alignment are two principal difficulties in high-frequency bands directional transmissions.In this paper,the coverage performance of downlink directional transmissions in ultra-dense networks is analyzed,with the consideration of beam alignment error and link blockage through stochastic geometry.Numerical experiments demonstrate that narrower beam leads to higher coverage probability with perfect beam alignment,but it is not the case with imperfect beam alignment.Therefore,the optimal beamwidth that maximize the coverage probability is characterized and a closed-form approximation of the optimal beamwidth is derived under imperfect beam alignment,accordingly.Furthermore,the optimal beamwidth is a monotonically increasing function of the standard deviation of the beam alignment error,and a monotonically decreasing function of the beamwidth of correspondent communication end,indicating that the beamwidth of the communication pairs ought to be jointly designed.展开更多
In this paper, we propose directdetection optical orthogonal frequency division multiplexing superchannel （DDOOFDMS） and optical multiband receiving method （OMBR） to support a greater than 200 Gb/s data rate and l...In this paper, we propose directdetection optical orthogonal frequency division multiplexing superchannel （DDOOFDMS） and optical multiband receiving method （OMBR） to support a greater than 200 Gb/s data rate and longer distance for direct-detection systems. For the new OMBR, we discuss the optimum carriertosideband power ratio （CSPR） in the cases of backtoback and post transmission. We derive the analytical form for CSPR and theoretically verify it. A low overhead training method for estimating I/Q imbalance is also introduced in order to improve performance and maintain high system throughput. The experiment results show that these proposals enable an unprecedented data rate of 214 Gb/s （190 Gb/s without overhead） per wavelength over an unprecedented distance of 720 km SSMF in greater than 100 Gb/s DDOFDM systems.展开更多
By using function one direction S-rough sets （function one direction singular rough sets）, the concept of one direction rough law is proposed, where one direction rough law is the law pair { w（x）-, w（x） - } comp...By using function one direction S-rough sets （function one direction singular rough sets）, the concept of one direction rough law is proposed, where one direction rough law is the law pair { w（x）-, w（x） - } composed by w（x）- and w（x）-, ffthe attribute set {a_ , a-} of function one direction S-rough sets changes, then one direction rough law { w（x）_, w（x）- } will change, too. By employing ellipse curves, the concept of one direction rough law security is presented, the security theorem of one direction rough law is proposed and the applications are given. One direction rough law security, which is generated by the intersection and penetration between function one direction S-rough sets and ellipse curves, is a new applied research direction of function S-rough sets.展开更多
The spectrum allocation for links in multi-hop cognitive radio networks is addressed.The links rent the vacant licensed bands offered by primary users for implementing directional transmission.To minimize the individu...The spectrum allocation for links in multi-hop cognitive radio networks is addressed.The links rent the vacant licensed bands offered by primary users for implementing directional transmission.To minimize the individual cost,the links share the licensed band and rental fee.An interference model for the directional transmission in cognitive radio networks is proposed to formulate the cooperative and dynamic behavior of the links using the theory of hedonic game,called spectrum allocation game.The game is proved to converge to the core stable state indicating that all links satisfy with their current conditions and do not deviate from their coalitions.Numerical results show that the game improves spectral efficiency and contributes to reducing the individual cost of the links.展开更多
The demands for massive renewable energy integration, passive network power supply, and global energy interconnection have all gradually increased, posing new challenges for high voltage direct current(HVDC) power tra...The demands for massive renewable energy integration, passive network power supply, and global energy interconnection have all gradually increased, posing new challenges for high voltage direct current(HVDC) power transmission systems, including more complex topology and increased diversity of bipolar HVDC transmission. This study proposes that these two factors have led to new requirements for HVDC control strategies. Moreover, due to the diverse applications of HVDC transmission technology, each station in the system has different requirements. Furthermore, the topology of the AC-DC converter is being continuously developed, revealing a trend towards hybrid converter stations.展开更多
In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It main...In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It mainly analyzed two ways of the long-distance transmission: UHV AC transmission and UHV DC transmission. The fractional frequency transmission technology and half wavelength AC transmission technology of AC transmission are introduced. Some key technologies of long-distance transmission are described. It has a guess for long-distance transmission future direction.展开更多
With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net w...With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.展开更多
The traditional cryptographic security techniques are not sufficient for secure routing of message from source to destination in Wireless Sensor Networks (WSNs), because it requires sophisticated software, hardware, l...The traditional cryptographic security techniques are not sufficient for secure routing of message from source to destination in Wireless Sensor Networks (WSNs), because it requires sophisticated software, hardware, large memory, high processing speed and communication bandwidth. It is not economic and feasible because, depending on the application, WSN nodes are high-volume in number (hence, limited resources at each node), deployment area may be hazardous, unattended and/or hostile and sometimes dangerous. As WSNs are characterized by severely constrained resources and requirement to operate in an ad-hoc manner, security functionality implementation to protect nodes from adversary forces and secure routing of message from source node to base station has become a challenging task. In this paper, we present a direct trust dependent link state routing using route trusts which protects WSNs against routing attacks by eliminating the un-trusted nodes before making routes and finding best trustworthy route among them. We compare our work with the most prevalent routing protocols and show its benefits over them.展开更多
Phase modulation is a crucial step when the frequency-based wavefront optimization technique is exploited to measure the optical transmission matrix(TM) of a scattering medium. We report a simple but powerful method, ...Phase modulation is a crucial step when the frequency-based wavefront optimization technique is exploited to measure the optical transmission matrix(TM) of a scattering medium. We report a simple but powerful method, direct digital frequency synthesis(DDS) technology to modulate the phase front of the laser and measure the TM. By judiciously modulating the phase front of a He–Ne laser beam, we experimentally generate a high quality focus at any targeted location through a 2 mm thick 120 grit ground glass diffuser, which is commercially used in laser display and laser holographic display for improving brightness uniformity and reducing speckle. The signal to noise ratio(SNR) of the clear round focus is 50 and the size is about 44 μm. Our study will open up new avenues for enhancing light energy delivery to the optical engine in laser TV to lower the power consumption, phase compensation to reduce the speckle noise, and controlling the lasing threshold in random lasers.展开更多
文摘The increasing scale and complexity of power systems require high performance and high reliability of power system protection.Protective relaying based on directional comparison with power line carrier or microwave channels is the most suitable protection scheme for long distance EHV transmission lines and is widely used in power systems.The key element of such protection is a directional relay used to discriminate the fault direction.In order to overcome the disadvantages of conventional directional relays,the authors of this paper put forward the directional comparison carrier protection based on the artificial neural network(ANN).The protection is extensively tested using electromagnetic transient program (EMTP) under various electric power system operating and fault conditions.It is proved that the directional comparison carrier protection based on ANN,which can recognize various fault patterns of the protected transmission line(such as fault direction,fault phases etc.)correctly in any kind of operating and fault conditions and the whole process,is satisfactory for EHV transmission line protection.
基金supported by China National Heavy Duty Truck Group Co.,Ltd.(Grant No.YF03221048P)the Shanghai Municipal Bureau of Market Supervision and Administration(Grant No.2022-35)New Young TeachersResearch Start-Up Foundation of Shanghai Jiao Tong University(Grant No.22X010503668).
文摘As the take-off of China’s macro economy,as well as the rapid development of infrastructure construction,real estate industry,and highway logistics transportation industry,the demand for heavy vehicles is increasing rapidly,the competition is becoming increasingly fierce,and the digital transformation of the production line is imminent.As one of themost important components of heavy vehicles,the transmission front andmiddle case assembly lines have a high degree of automation,which can be used as a pilot for the digital transformation of production.To ensure the visualization of digital twins(DT),consistent control logic,and real-time data interaction,this paper proposes an experimental digital twin modeling method for the transmission front and middle case assembly line.Firstly,theDT-based systemarchitecture is designed,and theDT model is created by constructing the visualization model,logic model,and data model of the assembly line.Then,a simulation experiment is carried out in a virtual space to analyze the existing problems in the current assembly line.Eventually,some improvement strategies are proposed and the effectiveness is verified by a new simulation experiment.
基金This work is sponsored in part by the National Key R&D Program of China No.2020YFB1806605by the Nature Science Foundation of China(No.62022049,No.61871254,No.62111530197)by Open Research Fund Program of Beijing National Research Center for Information Science and Technology,and Hitachi Ltd.
文摘Blockage and imperfect beam alignment are two principal difficulties in high-frequency bands directional transmissions.In this paper,the coverage performance of downlink directional transmissions in ultra-dense networks is analyzed,with the consideration of beam alignment error and link blockage through stochastic geometry.Numerical experiments demonstrate that narrower beam leads to higher coverage probability with perfect beam alignment,but it is not the case with imperfect beam alignment.Therefore,the optimal beamwidth that maximize the coverage probability is characterized and a closed-form approximation of the optimal beamwidth is derived under imperfect beam alignment,accordingly.Furthermore,the optimal beamwidth is a monotonically increasing function of the standard deviation of the beam alignment error,and a monotonically decreasing function of the beamwidth of correspondent communication end,indicating that the beamwidth of the communication pairs ought to be jointly designed.
文摘In this paper, we propose directdetection optical orthogonal frequency division multiplexing superchannel （DDOOFDMS） and optical multiband receiving method （OMBR） to support a greater than 200 Gb/s data rate and longer distance for direct-detection systems. For the new OMBR, we discuss the optimum carriertosideband power ratio （CSPR） in the cases of backtoback and post transmission. We derive the analytical form for CSPR and theoretically verify it. A low overhead training method for estimating I/Q imbalance is also introduced in order to improve performance and maintain high system throughput. The experiment results show that these proposals enable an unprecedented data rate of 214 Gb/s （190 Gb/s without overhead） per wavelength over an unprecedented distance of 720 km SSMF in greater than 100 Gb/s DDOFDM systems.
基金Natural Science Foundation of Fujian Province of China( No.2009J01293)Open Project of Brain-like Key Laboratory Research of Fujian Province of China (No. BLISSOS20101015)
文摘By using function one direction S-rough sets （function one direction singular rough sets）, the concept of one direction rough law is proposed, where one direction rough law is the law pair { w（x）-, w（x） - } composed by w（x）- and w（x）-, ffthe attribute set {a_ , a-} of function one direction S-rough sets changes, then one direction rough law { w（x）_, w（x）- } will change, too. By employing ellipse curves, the concept of one direction rough law security is presented, the security theorem of one direction rough law is proposed and the applications are given. One direction rough law security, which is generated by the intersection and penetration between function one direction S-rough sets and ellipse curves, is a new applied research direction of function S-rough sets.
基金Supported by the National High Technology Research and Development Programme of China(No.2011AA010503)the National Natural Science Foundations of China(No.60903192)
文摘The spectrum allocation for links in multi-hop cognitive radio networks is addressed.The links rent the vacant licensed bands offered by primary users for implementing directional transmission.To minimize the individual cost,the links share the licensed band and rental fee.An interference model for the directional transmission in cognitive radio networks is proposed to formulate the cooperative and dynamic behavior of the links using the theory of hedonic game,called spectrum allocation game.The game is proved to converge to the core stable state indicating that all links satisfy with their current conditions and do not deviate from their coalitions.Numerical results show that the game improves spectral efficiency and contributes to reducing the individual cost of the links.
基金supported by the State Grid Science & Technology Project (GEIGC-E-[2018]026)
文摘The demands for massive renewable energy integration, passive network power supply, and global energy interconnection have all gradually increased, posing new challenges for high voltage direct current(HVDC) power transmission systems, including more complex topology and increased diversity of bipolar HVDC transmission. This study proposes that these two factors have led to new requirements for HVDC control strategies. Moreover, due to the diverse applications of HVDC transmission technology, each station in the system has different requirements. Furthermore, the topology of the AC-DC converter is being continuously developed, revealing a trend towards hybrid converter stations.
文摘In view of the imbalanced distribution of power load and resources, including the status of “electric shortage” in some cities in our country, the article discusses the long-distance transmission technology. It mainly analyzed two ways of the long-distance transmission: UHV AC transmission and UHV DC transmission. The fractional frequency transmission technology and half wavelength AC transmission technology of AC transmission are introduced. Some key technologies of long-distance transmission are described. It has a guess for long-distance transmission future direction.
基金Sponsored by the Ph.D. Programs Foundation of Ministry of Education of China(Grant No.20070286047)the Scientific Innovation Foundation forYoungster of CSEE
文摘With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.
文摘The traditional cryptographic security techniques are not sufficient for secure routing of message from source to destination in Wireless Sensor Networks (WSNs), because it requires sophisticated software, hardware, large memory, high processing speed and communication bandwidth. It is not economic and feasible because, depending on the application, WSN nodes are high-volume in number (hence, limited resources at each node), deployment area may be hazardous, unattended and/or hostile and sometimes dangerous. As WSNs are characterized by severely constrained resources and requirement to operate in an ad-hoc manner, security functionality implementation to protect nodes from adversary forces and secure routing of message from source node to base station has become a challenging task. In this paper, we present a direct trust dependent link state routing using route trusts which protects WSNs against routing attacks by eliminating the un-trusted nodes before making routes and finding best trustworthy route among them. We compare our work with the most prevalent routing protocols and show its benefits over them.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2016YFB0401902 and 2016YFB0402001)Key-Area Research and Development Program of Guang Dong Province,China(Grant No.2019B010926001)。
文摘Phase modulation is a crucial step when the frequency-based wavefront optimization technique is exploited to measure the optical transmission matrix(TM) of a scattering medium. We report a simple but powerful method, direct digital frequency synthesis(DDS) technology to modulate the phase front of the laser and measure the TM. By judiciously modulating the phase front of a He–Ne laser beam, we experimentally generate a high quality focus at any targeted location through a 2 mm thick 120 grit ground glass diffuser, which is commercially used in laser display and laser holographic display for improving brightness uniformity and reducing speckle. The signal to noise ratio(SNR) of the clear round focus is 50 and the size is about 44 μm. Our study will open up new avenues for enhancing light energy delivery to the optical engine in laser TV to lower the power consumption, phase compensation to reduce the speckle noise, and controlling the lasing threshold in random lasers.
