特高压(ultra high voltage,UHV)换流站阀厅的金属屋面系统在风荷载作用下易发生屋面表层风揭事故。为深入探讨该类建筑屋面的风压极值特性,基于风洞试验分别探讨了大气边界层(atmospheric-boundary-layer,ABL)风、壁面射流、均匀湍流...特高压(ultra high voltage,UHV)换流站阀厅的金属屋面系统在风荷载作用下易发生屋面表层风揭事故。为深入探讨该类建筑屋面的风压极值特性,基于风洞试验分别探讨了大气边界层(atmospheric-boundary-layer,ABL)风、壁面射流、均匀湍流三种风场作用下的屋面风压特性,比较了平均风剖面、风速、风向、湍流强度等因素对屋面风压的影响。结果表明:阀厅屋盖迎风前缘负风压最大,且控制风向角在45°左右;壁面射流风场下平均风压系数与脉动风压系数均超过大气边界层风场的结果;风速对阀厅屋盖的负风压系数均值和极值影响较小,而湍流度对风压系数的极值影响较大;大气边界风场时,JGJ/T 481—2019《屋盖结构风荷载标准》的最不利风压系数建议值偏于安全;而在壁面射流风场下,阀厅屋盖全风向最不利风压系数在所有区域都大于JGJ/T 481—2019的建议值,设计中应加以重视。展开更多
Skyrmions are very promising for applications in spintronics and magnetic memory.It is desired to manipulate and operate a single skyrmion.Here we report on the thermal effect on the motion of current-driven magnetic ...Skyrmions are very promising for applications in spintronics and magnetic memory.It is desired to manipulate and operate a single skyrmion.Here we report on the thermal effect on the motion of current-driven magnetic Skyrmions in magnetic metal.The results show that the magnon current induced by the thermal gradient acts on Skyrmions via magnonic spin-transfer torque,an effect of the transverse and longitudinal Skyrmions drift velocities,thus leading to the effective manipulation of the Hall angle through the ratio of thermal gradient to electric current density,which can be used as a Skyrmion valve.展开更多
为提升特高压换流站消防系统灭火效能,针对目前以水喷雾灭火系统为主的消防设施应对换流变火灾蔓延等恶劣情况存在的不足,提出一种将消防炮增设于阀厅挑檐上的固定式压缩空气泡沫消防系统(compressed air foam fire-fighting system,CA...为提升特高压换流站消防系统灭火效能,针对目前以水喷雾灭火系统为主的消防设施应对换流变火灾蔓延等恶劣情况存在的不足,提出一种将消防炮增设于阀厅挑檐上的固定式压缩空气泡沫消防系统(compressed air foam fire-fighting system,CAFS)。该系统在不占用现有设备空间和检修通道的情况下,利用其灭火能力强、响应速度快、灭火效率高等特点,成倍提升变电站内换流变集中区域的消防能力,保证了最不利情况下换流变火灾消防工作需求。展开更多
Mussels close their shell as a protective strategy and the quantification of this behavioral marker may represent an alarm signal when they are exposed to environmental stressors.In the present study,we investigated t...Mussels close their shell as a protective strategy and the quantification of this behavioral marker may represent an alarm signal when they are exposed to environmental stressors.In the present study,we investigated the ability of the Mediterranean mussel Mytilus galloprovincialis to recover and then the resilience or inertia of valve activity after a pulsing exposition to diverse levels of salinity(5,10,20,and 35 PSU as reference value).The trial simulated an event of drastic and sudden reduction of seawater salinity thus mimicking an event of flash flood from intense rain.Valve gaping and movements were measured in continuous cycle for 10 days using a customized magnetoelectric device which uses Hall sensors.Results showed that under normal conditions of salinity(35 PSU),the general pattern of valve movements was a continuously open state with sporadic spikes indicating a closing motion.At salinity of 5,PSU mussels reacted by closing their valves,leading to a 77%mortality on the 4th day.At salinity of 10,PSU animals were observed with closed valves for the entire duration of the exposure and no mortality occurred,they showed a significant reduction in the valve activity once the reference value of salinity was reestablished.In contrast,salinity of 20 PSU did not trigger a significant behavioral response.Interestingly,there no define rhythms of valve movements were recorded during salinity challenges.展开更多
The electromagnetic interference(EMI)from the valve hall as an important consideration in the design of high voltage direct current(HVDC)converter stations is analyzed by electromagnetic field numerical method and mea...The electromagnetic interference(EMI)from the valve hall as an important consideration in the design of high voltage direct current(HVDC)converter stations is analyzed by electromagnetic field numerical method and measurements.By using moment method,the EMI filed strength level as well as radio interference level(RIL)of the valve hall during the normal operation are computed after an antenna model is built for the valve tower.According to the character of EMI obtained,the practical shielding measures for valve hall are discussed to satisfy the relative standards.The test results for the500 kV converter station show that both the numerical method and shielding technique used in this paper are practical.展开更多
文摘特高压(ultra high voltage,UHV)换流站阀厅的金属屋面系统在风荷载作用下易发生屋面表层风揭事故。为深入探讨该类建筑屋面的风压极值特性,基于风洞试验分别探讨了大气边界层(atmospheric-boundary-layer,ABL)风、壁面射流、均匀湍流三种风场作用下的屋面风压特性,比较了平均风剖面、风速、风向、湍流强度等因素对屋面风压的影响。结果表明:阀厅屋盖迎风前缘负风压最大,且控制风向角在45°左右;壁面射流风场下平均风压系数与脉动风压系数均超过大气边界层风场的结果;风速对阀厅屋盖的负风压系数均值和极值影响较小,而湍流度对风压系数的极值影响较大;大气边界风场时,JGJ/T 481—2019《屋盖结构风荷载标准》的最不利风压系数建议值偏于安全;而在壁面射流风场下,阀厅屋盖全风向最不利风压系数在所有区域都大于JGJ/T 481—2019的建议值,设计中应加以重视。
基金Project supported by the National Natural Science Foundation of China(Grant No.51331006)the Fund from the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)
文摘Skyrmions are very promising for applications in spintronics and magnetic memory.It is desired to manipulate and operate a single skyrmion.Here we report on the thermal effect on the motion of current-driven magnetic Skyrmions in magnetic metal.The results show that the magnon current induced by the thermal gradient acts on Skyrmions via magnonic spin-transfer torque,an effect of the transverse and longitudinal Skyrmions drift velocities,thus leading to the effective manipulation of the Hall angle through the ratio of thermal gradient to electric current density,which can be used as a Skyrmion valve.
文摘为提升特高压换流站消防系统灭火效能,针对目前以水喷雾灭火系统为主的消防设施应对换流变火灾蔓延等恶劣情况存在的不足,提出一种将消防炮增设于阀厅挑檐上的固定式压缩空气泡沫消防系统(compressed air foam fire-fighting system,CAFS)。该系统在不占用现有设备空间和检修通道的情况下,利用其灭火能力强、响应速度快、灭火效率高等特点,成倍提升变电站内换流变集中区域的消防能力,保证了最不利情况下换流变火灾消防工作需求。
基金This study is part of the project“Effects of climate environmental shifts on species,communities and ecosystems,”funded by the Fondazione di Sardegna(2018).
文摘Mussels close their shell as a protective strategy and the quantification of this behavioral marker may represent an alarm signal when they are exposed to environmental stressors.In the present study,we investigated the ability of the Mediterranean mussel Mytilus galloprovincialis to recover and then the resilience or inertia of valve activity after a pulsing exposition to diverse levels of salinity(5,10,20,and 35 PSU as reference value).The trial simulated an event of drastic and sudden reduction of seawater salinity thus mimicking an event of flash flood from intense rain.Valve gaping and movements were measured in continuous cycle for 10 days using a customized magnetoelectric device which uses Hall sensors.Results showed that under normal conditions of salinity(35 PSU),the general pattern of valve movements was a continuously open state with sporadic spikes indicating a closing motion.At salinity of 5,PSU mussels reacted by closing their valves,leading to a 77%mortality on the 4th day.At salinity of 10,PSU animals were observed with closed valves for the entire duration of the exposure and no mortality occurred,they showed a significant reduction in the valve activity once the reference value of salinity was reestablished.In contrast,salinity of 20 PSU did not trigger a significant behavioral response.Interestingly,there no define rhythms of valve movements were recorded during salinity challenges.
文摘The electromagnetic interference(EMI)from the valve hall as an important consideration in the design of high voltage direct current(HVDC)converter stations is analyzed by electromagnetic field numerical method and measurements.By using moment method,the EMI filed strength level as well as radio interference level(RIL)of the valve hall during the normal operation are computed after an antenna model is built for the valve tower.According to the character of EMI obtained,the practical shielding measures for valve hall are discussed to satisfy the relative standards.The test results for the500 kV converter station show that both the numerical method and shielding technique used in this paper are practical.
