Buried pipelines are an essential component of the urban infrastructure of modern cities.Traditional buried pipes are mainly made of metal materials.With the development of material science and technology in recent ye...Buried pipelines are an essential component of the urban infrastructure of modern cities.Traditional buried pipes are mainly made of metal materials.With the development of material science and technology in recent years,non-metallic pipes,such as plastic pipes,ceramic pipes,and concrete pipes,are increasingly taking the place of pipes made from metal in various pipeline networks such as water supply,drainage,heat,industry,oil,and gas.The location technologies for the location of the buried metal pipeline have become mature,but detection and location technologies for the non-metallic pipelines are still developing.In this paper,current trends and future perspectives of detection and location of buried non-metallic pipelines are summarized.Initially,this paper reviews and analyzes electromagnetic induction technologies,electromagnetic wave technologies,and other physics-based technologies.It then focuses on acoustic detection and location technologies,and finally introduces emerging technologies.Then the technical characteristics of each detection and location method have been compared,with their strengths and weaknesses identified.The current trends and future perspectives of each buried non-metallic pipeline detection and location technology have also been defined.Finally,some suggestions for the future development of buried non-metallic pipeline detection and location technologies are provided.展开更多
The spread of the worm causes great harm to the computer network. It has recently become the focus of the network security research. This paper presents a local-worm detection algorithm by analyzing the characteristic...The spread of the worm causes great harm to the computer network. It has recently become the focus of the network security research. This paper presents a local-worm detection algorithm by analyzing the characteristics of traffic generated by the TCP-based worm. Moreover, we adjust the worm location algorithm, aiming at the differences between the high-speed and the low-speed worm scanning methods. This adjustment can make the location algorithm detect and locate the worm based on different scanning rate. Finally, we verified the validity and efficiency of the proposed algorithm by simulating it under NS-2.展开更多
The aftershocks of the 1975 M_(S)7.3 Haicheng and 1999 M_(S)5.4 Xiuyan earthquakes have persisted for a long time.The ChinArray-III dense stations,deployed in eastern North China from 2018 to 2020,increased seismic mo...The aftershocks of the 1975 M_(S)7.3 Haicheng and 1999 M_(S)5.4 Xiuyan earthquakes have persisted for a long time.The ChinArray-III dense stations,deployed in eastern North China from 2018 to 2020,increased seismic monitoring capability in the Haicheng-Xiuyan region,which can facilitate the construction of high-precision earthquake catalogs to better clarify the fault structures and seismogenic mechanisms of the two earthquakes.In this study,we selected 15 permanent stations and 37 ChinArray-III stations within 150 km of the epicenter of the Haicheng Earthquake.Next,we used deep learning methods to pick P-and S-wave phases from continuous waveforms recorded at these stations from January 2018 to July 2020.Based on these picks,we constructed an automatic earthquake catalog of the Haicheng-Xiuyan region.Compared with the routine manual catalog by China Earthquake Networks Center(CENC),our catalog contains 9.7 times more seismic events,including 98.3%of the seismic events in the CENC catalog,and has a lower magnitude of completeness(M_(c)=1.1 vs M_(c)=1.8 for the CENC catalog).The relocated events indicate that the strike of the Haichenghe-Dayanghe fault varies considerably from northwest to southeast,indicating that the fault bends slightly around the hypocenter of the 1975 M_(S)7.3 Haicheng earthquake which may act as a channel for fluid migration.The weak seismicity in the area between Haicheng and Xiuyan indicates that the fault section may be locked.Furthermore,the 1999 M_(S)5.4 Xiuyan earthquake and its aftershock sequence occurred on the Kangjialing fault and its ENE-trending conjugate fault,and the intersection of the two faults coincides with the source areas of the 1999 M_(S)5.4 and 2000 M_(S)5.1 Xiuyan earthquakes.Therefore,the Xiuyan earthquake sequence may be controlled by the Kangjialing fault and its conjugate fault.This study shows that the automatic earthquake catalog,obtained by deep learning methods and dense seismic array,can provide valuable information for fault structures and the seismogenic mechanisms of moderate-to-strong earthquakes.展开更多
Monitoring the evolution of foreshocks can be a valuable way to analyze the nucleation process.Foreshocks accompanying moderate mainshocks have been recorded in the west of Yunnan Province,China.We obtain the earthqua...Monitoring the evolution of foreshocks can be a valuable way to analyze the nucleation process.Foreshocks accompanying moderate mainshocks have been recorded in the west of Yunnan Province,China.We obtain the earthquake catalog and source parameters of the 2016 Yunlong foreshocks,and discuss the implications for the nucleation processes of the earthquake in western Yunnan,China.By using the matched filter detection,we identify 343 foreshocks with a magnitude of -0.8-4.5,starting with a magnitude 1.0 foreshock approximately 3 months before the 2016 M_(S)5.1 Yunlong mainshock.The spatial distribution of foreshocks doesn’t show localization or directional migration towards the mainshock.Coulomb stress analysis suggests a positive stress perturbation at the mainshock nucleate area.These observations indicate a cascade-triggering mechanism of the 2016 Yunlong earthquakes.We further collect published catalogs of 2021 Yangbi and 2017 Yangbi foreshocks in the adjacent area,and analyze the temporal changes in b values.The temporal changes in b values reveal precursory drops before the mainshocks.展开更多
High voltage direct current (HVDC) transmission is an economical option for transmitting a large amount of power over long distances. Initially, HVDC was developed using thyristor-based current source converters (CSC)...High voltage direct current (HVDC) transmission is an economical option for transmitting a large amount of power over long distances. Initially, HVDC was developed using thyristor-based current source converters (CSC). With the development of semiconductor devices, a voltage source converter (VSC)-based HVDC system was introduced, and has been widely applied to integrate large-scale renewables and network interconnection. However, the VSC-based HVDC system is vulnerable to DC faults and its protection becomes ever more important with the fast growth in number of installations. In this paper, detailed characteristics of DC faults in the VSC-HVDC system are presented. The DC fault current has a large peak and steady values within a few milliseconds and thus high-speed fault detection and isolation methods are required in an HVDC grid. Therefore, development of the protection scheme for a multi-terminal VSC-based HVDC system is challenging. Various methods have been developed and this paper presents a comprehensive review of the different techniques for DC fault detection, location and isolation in both CSC and VSC-based HVDC transmission systems in two-terminal and multi-terminal network configurations.展开更多
基金Supported by Downhole Intelligent Measurement and Control Science and Technology Innovation Team of Southwest Petroleum University(Grant No.2018CXTD04)National Natural Science Foundation of China(Grant Nos.61701085,51974273)+1 种基金Chengdu Municipal international science and technology cooperation project of China(Grant Nos.2020-GH02-00016-HZ)2020 National Mountain Highway Engineering Technology Research Center Open Fund Project(Grant No.GSGZJ-2020-01).
文摘Buried pipelines are an essential component of the urban infrastructure of modern cities.Traditional buried pipes are mainly made of metal materials.With the development of material science and technology in recent years,non-metallic pipes,such as plastic pipes,ceramic pipes,and concrete pipes,are increasingly taking the place of pipes made from metal in various pipeline networks such as water supply,drainage,heat,industry,oil,and gas.The location technologies for the location of the buried metal pipeline have become mature,but detection and location technologies for the non-metallic pipelines are still developing.In this paper,current trends and future perspectives of detection and location of buried non-metallic pipelines are summarized.Initially,this paper reviews and analyzes electromagnetic induction technologies,electromagnetic wave technologies,and other physics-based technologies.It then focuses on acoustic detection and location technologies,and finally introduces emerging technologies.Then the technical characteristics of each detection and location method have been compared,with their strengths and weaknesses identified.The current trends and future perspectives of each buried non-metallic pipeline detection and location technology have also been defined.Finally,some suggestions for the future development of buried non-metallic pipeline detection and location technologies are provided.
基金the National Natural Science Foundation of China (Grant No. 60403028)
文摘The spread of the worm causes great harm to the computer network. It has recently become the focus of the network security research. This paper presents a local-worm detection algorithm by analyzing the characteristics of traffic generated by the TCP-based worm. Moreover, we adjust the worm location algorithm, aiming at the differences between the high-speed and the low-speed worm scanning methods. This adjustment can make the location algorithm detect and locate the worm based on different scanning rate. Finally, we verified the validity and efficiency of the proposed algorithm by simulating it under NS-2.
基金supported by the National Natural Science Foundation of China(No.U2239206)Selfinitiated Project of the Institute of Geophysics of the China Earthquake Administration(JY2022Z48)+1 种基金the Dedicated Fundamental Research Funds of the Institute of Geophysics of the China Earthquake Administration(No.DQJB23X16)the Science and Technology Support Project of Guizhou Province(QKHZC[2022]General 238).
文摘The aftershocks of the 1975 M_(S)7.3 Haicheng and 1999 M_(S)5.4 Xiuyan earthquakes have persisted for a long time.The ChinArray-III dense stations,deployed in eastern North China from 2018 to 2020,increased seismic monitoring capability in the Haicheng-Xiuyan region,which can facilitate the construction of high-precision earthquake catalogs to better clarify the fault structures and seismogenic mechanisms of the two earthquakes.In this study,we selected 15 permanent stations and 37 ChinArray-III stations within 150 km of the epicenter of the Haicheng Earthquake.Next,we used deep learning methods to pick P-and S-wave phases from continuous waveforms recorded at these stations from January 2018 to July 2020.Based on these picks,we constructed an automatic earthquake catalog of the Haicheng-Xiuyan region.Compared with the routine manual catalog by China Earthquake Networks Center(CENC),our catalog contains 9.7 times more seismic events,including 98.3%of the seismic events in the CENC catalog,and has a lower magnitude of completeness(M_(c)=1.1 vs M_(c)=1.8 for the CENC catalog).The relocated events indicate that the strike of the Haichenghe-Dayanghe fault varies considerably from northwest to southeast,indicating that the fault bends slightly around the hypocenter of the 1975 M_(S)7.3 Haicheng earthquake which may act as a channel for fluid migration.The weak seismicity in the area between Haicheng and Xiuyan indicates that the fault section may be locked.Furthermore,the 1999 M_(S)5.4 Xiuyan earthquake and its aftershock sequence occurred on the Kangjialing fault and its ENE-trending conjugate fault,and the intersection of the two faults coincides with the source areas of the 1999 M_(S)5.4 and 2000 M_(S)5.1 Xiuyan earthquakes.Therefore,the Xiuyan earthquake sequence may be controlled by the Kangjialing fault and its conjugate fault.This study shows that the automatic earthquake catalog,obtained by deep learning methods and dense seismic array,can provide valuable information for fault structures and the seismogenic mechanisms of moderate-to-strong earthquakes.
基金supported by the Laoshan Laboratory project(LSKJ202204100)National Natural Science Foundation of China(Nos.U2344221,92158205,42406064)+2 种基金Hong Kong Research Grant Council Grants(14306122)the Taishan Scholar Foundation of Shandong Province(tstp20230638)Shandong Province Outstanding Youth Science Fund Project Overseas(2023HWYQ-099).
文摘Monitoring the evolution of foreshocks can be a valuable way to analyze the nucleation process.Foreshocks accompanying moderate mainshocks have been recorded in the west of Yunnan Province,China.We obtain the earthquake catalog and source parameters of the 2016 Yunlong foreshocks,and discuss the implications for the nucleation processes of the earthquake in western Yunnan,China.By using the matched filter detection,we identify 343 foreshocks with a magnitude of -0.8-4.5,starting with a magnitude 1.0 foreshock approximately 3 months before the 2016 M_(S)5.1 Yunlong mainshock.The spatial distribution of foreshocks doesn’t show localization or directional migration towards the mainshock.Coulomb stress analysis suggests a positive stress perturbation at the mainshock nucleate area.These observations indicate a cascade-triggering mechanism of the 2016 Yunlong earthquakes.We further collect published catalogs of 2021 Yangbi and 2017 Yangbi foreshocks in the adjacent area,and analyze the temporal changes in b values.The temporal changes in b values reveal precursory drops before the mainshocks.
文摘High voltage direct current (HVDC) transmission is an economical option for transmitting a large amount of power over long distances. Initially, HVDC was developed using thyristor-based current source converters (CSC). With the development of semiconductor devices, a voltage source converter (VSC)-based HVDC system was introduced, and has been widely applied to integrate large-scale renewables and network interconnection. However, the VSC-based HVDC system is vulnerable to DC faults and its protection becomes ever more important with the fast growth in number of installations. In this paper, detailed characteristics of DC faults in the VSC-HVDC system are presented. The DC fault current has a large peak and steady values within a few milliseconds and thus high-speed fault detection and isolation methods are required in an HVDC grid. Therefore, development of the protection scheme for a multi-terminal VSC-based HVDC system is challenging. Various methods have been developed and this paper presents a comprehensive review of the different techniques for DC fault detection, location and isolation in both CSC and VSC-based HVDC transmission systems in two-terminal and multi-terminal network configurations.
