At present, lightning is one of the 10 natural disasters, and it is also the top environmental factor of power interruption. It often causes huge losses to the electric system. The Wuhan High Voltage Institute of the ...At present, lightning is one of the 10 natural disasters, and it is also the top environmental factor of power interruption. It often causes huge losses to the electric system. The Wuhan High Voltage Institute of the State Grid Corporation of China and Huazhong University of Science and Technology have been researching and developing lightning location systems （LLSs） since the late 1980s. In the mid-1990s, a lightning detection network was created in 29 provinces and cities in China. It is primarily applied to rapidly find lightning accidents, which greatly reduces power interruption. Also, it ensures high efficiency and safe operation of the electricity system. Remarkable benefit is achieved. China＇s LLS went through an ＂orientation positioning - time difference positioning - integrated positioning＂ development process. The positioning precision, detection efficiency, degree of automation, practicability and applied range are improved. Also, a lightning information system plan of the national network has been implemented, which services the whole society.展开更多
Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind p...Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.展开更多
A set of water powered excavation test system was developed for the comprehensive performance testing and evaluation of water powered percussive rock drill indoors. The whole system contains hydraulic power section, e...A set of water powered excavation test system was developed for the comprehensive performance testing and evaluation of water powered percussive rock drill indoors. The whole system contains hydraulic power section, electronic control system, test and data acquisition system, and assistant devices, such as guideway and drilling bench. Parameters of the water powered percussive rock drill can be obtained by analyzing testing data, which contain impact energy, front and back cavity pressure, pressure and flow in each working part, drilling velocity, frequency and energy efficiency etc. The system is applied to test the self-designed water powered percussive rock drill SYYG65. The parameters of water powered percussive rock drill with impact pressure of about 8.9 MPa are 58.93 J for impact energy, and 8.97% for energy efficiency, which prove the effectiveness of system.展开更多
To investigate the mechanism of brain protection of woodpecker,we built a finite element model of a whole woodpecker using computed topography scanning technique and geometry modeling.Dynamic analyses reveal:(i)99.7%o...To investigate the mechanism of brain protection of woodpecker,we built a finite element model of a whole woodpecker using computed topography scanning technique and geometry modeling.Dynamic analyses reveal:(i)99.7%of the impact energy is converted into strain energy in the bulk of body and 0.3%is converted into strain energy in the head after three successive peckings,indicating the majority of the impact energy is stored in the bulk of body;(ii)the strain energy in brain is mainly converted into the dissipated energy,alleviating the mechanical injury to brain;(iii)the deformation and the effective energy dissipation of the beaks facilitate the decrease of the stress and impact energy transferred to the brain;(iv)the skull and dura mater not only provide the physical protection for the brain,but also diminish the strain energy in the brain by energy dissipation;(v)the binding of skull with the hyoid bone enhances the anti-shock ability of head.The whole body of the woodpecker gets involved in the energy conversion and forms an efficient anti-shock protection system for brain.展开更多
文摘At present, lightning is one of the 10 natural disasters, and it is also the top environmental factor of power interruption. It often causes huge losses to the electric system. The Wuhan High Voltage Institute of the State Grid Corporation of China and Huazhong University of Science and Technology have been researching and developing lightning location systems （LLSs） since the late 1980s. In the mid-1990s, a lightning detection network was created in 29 provinces and cities in China. It is primarily applied to rapidly find lightning accidents, which greatly reduces power interruption. Also, it ensures high efficiency and safe operation of the electricity system. Remarkable benefit is achieved. China＇s LLS went through an ＂orientation positioning - time difference positioning - integrated positioning＂ development process. The positioning precision, detection efficiency, degree of automation, practicability and applied range are improved. Also, a lightning information system plan of the national network has been implemented, which services the whole society.
文摘Generally, lightning damage has mainly been to home appliances and telephones, towers and power transmission and generation equipment mal functions and damage due to strikes on power lines. With the adoption of wind power generation equipment, however, lightning damage is also increasing in this area. Through his dimensional characteristics, the wind power system is more exposed in the nature compared to all others systems. Lightning damage is the single largest cause of unplanned downtime in wind turbines, and that downtime is responsible for the loss of countless megawatts of power generation. The wind turbines are important structures, since they can easily attract the wrath of storms hits heights close, they can also capture the most distant. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. We present our contribution in this paper to study lightning strokes and their effects on the wind turbines with the aim to enrich the work and to suggest more effective means of protection against lightning.
基金Project(2006AA06Z134) supported by the National High Technology Research and Development Program of ChinaProjects(50934006, 50904079) supported by the National Natural Science Foundation of China
文摘A set of water powered excavation test system was developed for the comprehensive performance testing and evaluation of water powered percussive rock drill indoors. The whole system contains hydraulic power section, electronic control system, test and data acquisition system, and assistant devices, such as guideway and drilling bench. Parameters of the water powered percussive rock drill can be obtained by analyzing testing data, which contain impact energy, front and back cavity pressure, pressure and flow in each working part, drilling velocity, frequency and energy efficiency etc. The system is applied to test the self-designed water powered percussive rock drill SYYG65. The parameters of water powered percussive rock drill with impact pressure of about 8.9 MPa are 58.93 J for impact energy, and 8.97% for energy efficiency, which prove the effectiveness of system.
基金supported by the National Natural Science Foundation of China(Grant No.11272080)the Doctoral Education Foundation of China Education Ministry(Grant No.20110041110021)the Fundamental Research Funds for the Central Universities of China(Grant No.DUT14LK36)
文摘To investigate the mechanism of brain protection of woodpecker,we built a finite element model of a whole woodpecker using computed topography scanning technique and geometry modeling.Dynamic analyses reveal:(i)99.7%of the impact energy is converted into strain energy in the bulk of body and 0.3%is converted into strain energy in the head after three successive peckings,indicating the majority of the impact energy is stored in the bulk of body;(ii)the strain energy in brain is mainly converted into the dissipated energy,alleviating the mechanical injury to brain;(iii)the deformation and the effective energy dissipation of the beaks facilitate the decrease of the stress and impact energy transferred to the brain;(iv)the skull and dura mater not only provide the physical protection for the brain,but also diminish the strain energy in the brain by energy dissipation;(v)the binding of skull with the hyoid bone enhances the anti-shock ability of head.The whole body of the woodpecker gets involved in the energy conversion and forms an efficient anti-shock protection system for brain.
