Aircrafts damages caused by lightning strikes have been known since the early days of aviation.However,the physical effects on the aircraft structure are still being investigated.This work seeks to evaluate the lightn...Aircrafts damages caused by lightning strikes have been known since the early days of aviation.However,the physical effects on the aircraft structure are still being investigated.This work seeks to evaluate the lightning strike effects in the aluminum alloy 7075-T6.Samples were submitted to lightning strike simulation in laboratory and the damages evaluated through characterization techniques.Ultrasound and profilometry tests have shown material loss to 0.272 mm depth in the damaged region.In addition,it was detected the material accumulation occurrence in the damage vicinity of the region.Below the damage,it was found a region where metallurgical changes were identified.The tensile and microhardness tests results have shown reduction in the percentage elongation and hardness increasing in the material affected by lightning.These results are corroborated by the X-Ray Diffraction(XRD)and Rietveld Method(red line)that indicated an increasing in dislocation density and micro-deformation in the material matrix.Optical microscopy results have shown the presence of microcracks on the normal and cross-section surface of the samples damaged.The Energy Dispersive X-Ray Spectroscopy(EDXS)and Electron Backscattered Diffraction Test(EBSD)found coarse intermetallic phases and precipitates compounds with dimensions greater than 1 lm in length.They were responsible for nucleation of the microcracks that propagate along the material grain boundaries.展开更多
This article presents a mathematical model for simulating the mechanical behaviour of lightning strikes and analysing the resulting damage to the soil.This article focuses on the electro-thermal effect and seepage cau...This article presents a mathematical model for simulating the mechanical behaviour of lightning strikes and analysing the resulting damage to the soil.This article focuses on the electro-thermal effect and seepage caused by lightning strikes in particular.Then,a numerical model based on the conservation laws of momentum,mass and energy is developed for soil subjected to lightning strikes.Comparisons to field observations and theoretical calculations are used to demonstrate the efficacy and accuracy of numerical simulations.The findings demonstrate that lightning strikes can cause soils to experience both seepage force and heat stress.Under the calculative condition of this article:by increasing the intrinsic permeability of the soil,k_(p)(≥10^(-10)m^(2)),the seepage force can be effectively reduced,hence reducing the risk of lightning strikes;improving the electrical conductivity of the soil β(≥10^(-1) S/m^(2))and lowering its thermal expansion coefficient(≤10^(-6)K^(-1))can greatly reduce the damage caused by lightning strikes to the soil.The preceding investigations demonstrate that the suggested model is capable of evaluating mechanical damage caused by lightning in the soil,and the findings contribute to a better understanding of soil mechanical response to lightning strikes.展开更多
Suffering from rampant piracy, China's film, music and software industries look to special measures to counter attack Watching out for pirates has taken on an entirely new meaning for Fang Yunyun. No, she's no...Suffering from rampant piracy, China's film, music and software industries look to special measures to counter attack Watching out for pirates has taken on an entirely new meaning for Fang Yunyun. No, she's not looking through a telescope for a ship loaded with mean-looking sailors brandishing swords. Fang is an executive at an audio-video company in Beijing, and her anti-piracy watch means being on the展开更多
The severity of lightning strikes on offshore wind turbines built along coastal and nearshore regions can pose safety concerns that are often overlooked.In this research study the behavior of electrical discharges for...The severity of lightning strikes on offshore wind turbines built along coastal and nearshore regions can pose safety concerns that are often overlooked.In this research study the behavior of electrical discharges for wind turbines that might be located in the nearshore regions along the East Coast of China and Sea of Japan were characterized using a physics-based model that accounted for a total of eleven different geometrical and lightning parameters.Utilizing the electrical potential field predicted using this model it was then possible to estimate the frequency of lightning strikes and the distribution of electrical loads utilizing established semi-empirical relationships and available data.The total number of annual lightning strikes on an offshore wind turbine was found to vary with hub elevation,extent of cloud cover,season and geographical location.The annual lightning strike rate on a wind turbine along the nearshore region on the Sea of Japan during the winter season was shown to be moderately larger compared to the lightning strike frequency on a turbine structure on the East Coast of China.Short duration electrical discharges,represented using marginal probability functions,were found to vary with season and geographical location,exhibiting trends consistent with the distribution of the electrical peak current.It was demonstrated that electrical discharges of moderately long duration typically occur in the winter months on the East Coast of China and the summer season along the Sea of Japan.In contrast,severe electrical discharges are typical of summer thunderstorms on the East Coast of China and winter frontal storm systems along the West Coast of Japan.The electrical charge and specific energy dissipated during lightning discharges on an offshore wind turbine was found to vary stochastically,with severe electrical discharges corresponding to large electrical currents of long duration.展开更多
Founded in 1902 as the Transvaal Miners＇ Association, the South African Mine Workers＇ Union （MWU）, as it was renamed in 1913, rose to prominence as a militant union for white miners, especially during the turbulen...Founded in 1902 as the Transvaal Miners＇ Association, the South African Mine Workers＇ Union （MWU）, as it was renamed in 1913, rose to prominence as a militant union for white miners, especially during the turbulent years of industrial strife and bloody strike action in the first two decades of the 20th century. Since the election victory of the Pact government in 1924 a program of pro-white protectionist legislation was introduced. As South Africa＇s most prominent white trade union of the 20th century, the MWU therefore became renowned for defending job reservation in the mining industry. After 1948, it enjoyed the National Party government＇s support in this regard. However, skilled labor shortages and changing labor conditions in the 1970s forced the government to introduce labor reform. Job reservation was scrapped and black unions were officially recognized. These initiatives put the MWU on a confrontational path with the government and the union aligned itself with right-wing political resistance and protest. But, the altered political and economic South African realities after 1994 forced the MWU to rethink its strategies. By 2002, it had reinvented and transformed itself into Solidarity, adequately equipped for addressing the labor challenges and demands of a post-apartheid South Africa. This article, based on the author＇s research of the South African labor movement in the early 20th century, traces the historical development of the union and its influence on South African political and labor history.展开更多
IN 1987, the Fourth International Music Festival was held in Belgrade. When the Chinese song "The Green Leaves’s Love for the Root" was reverberating through the hall, the whole audience held their breath, ...IN 1987, the Fourth International Music Festival was held in Belgrade. When the Chinese song "The Green Leaves’s Love for the Root" was reverberating through the hall, the whole audience held their breath, listening attentively. This song not only moved all the people present but its approach of mode and the smooth and lyric melody left a deep impression on the adjudicators. As a result, this song won the third prize, the highest award any Chinese pop song had ever won at any international contest before 1987. The composer of this song is Gu Jianfen. Since the early 1980s, Gu Jianfen’s compositions have won her various awards in Chinese song contests. In 1985, five of her compositions won "Prize for Songs Favored展开更多
Non-alcoholic fatty liver disease(NAFLD)is a liver disease characterized by ectopic liver steatosis and steatosis.It is the most common chronic liver disease in China,and its incidence has gradually increased worldwid...Non-alcoholic fatty liver disease(NAFLD)is a liver disease characterized by ectopic liver steatosis and steatosis.It is the most common chronic liver disease in China,and its incidence has gradually increased worldwide,accompanied by the prevalence of obesity.In addition,NAFLD is associated with an increase in overall mortality,particularly in cardiovascular disease.So far,the mechanism of NAFLD is not very clear.This article aims to discuss the recent progress of various researches on NAFLD mechanism.展开更多
文摘Aircrafts damages caused by lightning strikes have been known since the early days of aviation.However,the physical effects on the aircraft structure are still being investigated.This work seeks to evaluate the lightning strike effects in the aluminum alloy 7075-T6.Samples were submitted to lightning strike simulation in laboratory and the damages evaluated through characterization techniques.Ultrasound and profilometry tests have shown material loss to 0.272 mm depth in the damaged region.In addition,it was detected the material accumulation occurrence in the damage vicinity of the region.Below the damage,it was found a region where metallurgical changes were identified.The tensile and microhardness tests results have shown reduction in the percentage elongation and hardness increasing in the material affected by lightning.These results are corroborated by the X-Ray Diffraction(XRD)and Rietveld Method(red line)that indicated an increasing in dislocation density and micro-deformation in the material matrix.Optical microscopy results have shown the presence of microcracks on the normal and cross-section surface of the samples damaged.The Energy Dispersive X-Ray Spectroscopy(EDXS)and Electron Backscattered Diffraction Test(EBSD)found coarse intermetallic phases and precipitates compounds with dimensions greater than 1 lm in length.They were responsible for nucleation of the microcracks that propagate along the material grain boundaries.
基金funded by the Natural Science Foundation of China(Grant No.42077435)。
文摘This article presents a mathematical model for simulating the mechanical behaviour of lightning strikes and analysing the resulting damage to the soil.This article focuses on the electro-thermal effect and seepage caused by lightning strikes in particular.Then,a numerical model based on the conservation laws of momentum,mass and energy is developed for soil subjected to lightning strikes.Comparisons to field observations and theoretical calculations are used to demonstrate the efficacy and accuracy of numerical simulations.The findings demonstrate that lightning strikes can cause soils to experience both seepage force and heat stress.Under the calculative condition of this article:by increasing the intrinsic permeability of the soil,k_(p)(≥10^(-10)m^(2)),the seepage force can be effectively reduced,hence reducing the risk of lightning strikes;improving the electrical conductivity of the soil β(≥10^(-1) S/m^(2))and lowering its thermal expansion coefficient(≤10^(-6)K^(-1))can greatly reduce the damage caused by lightning strikes to the soil.The preceding investigations demonstrate that the suggested model is capable of evaluating mechanical damage caused by lightning in the soil,and the findings contribute to a better understanding of soil mechanical response to lightning strikes.
文摘Suffering from rampant piracy, China's film, music and software industries look to special measures to counter attack Watching out for pirates has taken on an entirely new meaning for Fang Yunyun. No, she's not looking through a telescope for a ship loaded with mean-looking sailors brandishing swords. Fang is an executive at an audio-video company in Beijing, and her anti-piracy watch means being on the
文摘The severity of lightning strikes on offshore wind turbines built along coastal and nearshore regions can pose safety concerns that are often overlooked.In this research study the behavior of electrical discharges for wind turbines that might be located in the nearshore regions along the East Coast of China and Sea of Japan were characterized using a physics-based model that accounted for a total of eleven different geometrical and lightning parameters.Utilizing the electrical potential field predicted using this model it was then possible to estimate the frequency of lightning strikes and the distribution of electrical loads utilizing established semi-empirical relationships and available data.The total number of annual lightning strikes on an offshore wind turbine was found to vary with hub elevation,extent of cloud cover,season and geographical location.The annual lightning strike rate on a wind turbine along the nearshore region on the Sea of Japan during the winter season was shown to be moderately larger compared to the lightning strike frequency on a turbine structure on the East Coast of China.Short duration electrical discharges,represented using marginal probability functions,were found to vary with season and geographical location,exhibiting trends consistent with the distribution of the electrical peak current.It was demonstrated that electrical discharges of moderately long duration typically occur in the winter months on the East Coast of China and the summer season along the Sea of Japan.In contrast,severe electrical discharges are typical of summer thunderstorms on the East Coast of China and winter frontal storm systems along the West Coast of Japan.The electrical charge and specific energy dissipated during lightning discharges on an offshore wind turbine was found to vary stochastically,with severe electrical discharges corresponding to large electrical currents of long duration.
文摘Founded in 1902 as the Transvaal Miners＇ Association, the South African Mine Workers＇ Union （MWU）, as it was renamed in 1913, rose to prominence as a militant union for white miners, especially during the turbulent years of industrial strife and bloody strike action in the first two decades of the 20th century. Since the election victory of the Pact government in 1924 a program of pro-white protectionist legislation was introduced. As South Africa＇s most prominent white trade union of the 20th century, the MWU therefore became renowned for defending job reservation in the mining industry. After 1948, it enjoyed the National Party government＇s support in this regard. However, skilled labor shortages and changing labor conditions in the 1970s forced the government to introduce labor reform. Job reservation was scrapped and black unions were officially recognized. These initiatives put the MWU on a confrontational path with the government and the union aligned itself with right-wing political resistance and protest. But, the altered political and economic South African realities after 1994 forced the MWU to rethink its strategies. By 2002, it had reinvented and transformed itself into Solidarity, adequately equipped for addressing the labor challenges and demands of a post-apartheid South Africa. This article, based on the author＇s research of the South African labor movement in the early 20th century, traces the historical development of the union and its influence on South African political and labor history.
文摘IN 1987, the Fourth International Music Festival was held in Belgrade. When the Chinese song "The Green Leaves’s Love for the Root" was reverberating through the hall, the whole audience held their breath, listening attentively. This song not only moved all the people present but its approach of mode and the smooth and lyric melody left a deep impression on the adjudicators. As a result, this song won the third prize, the highest award any Chinese pop song had ever won at any international contest before 1987. The composer of this song is Gu Jianfen. Since the early 1980s, Gu Jianfen’s compositions have won her various awards in Chinese song contests. In 1985, five of her compositions won "Prize for Songs Favored
基金National natural science foundation of China(No.81774132)。
文摘Non-alcoholic fatty liver disease(NAFLD)is a liver disease characterized by ectopic liver steatosis and steatosis.It is the most common chronic liver disease in China,and its incidence has gradually increased worldwide,accompanied by the prevalence of obesity.In addition,NAFLD is associated with an increase in overall mortality,particularly in cardiovascular disease.So far,the mechanism of NAFLD is not very clear.This article aims to discuss the recent progress of various researches on NAFLD mechanism.
