An orange reddish phosphor Sr BPO_(5):Sm^(3+)was synthesized by the traditional solid-state method.The phosphor component was characterized by the X-ray powder diffraction(XRD).The photoluminescence excitation(PLE)and...An orange reddish phosphor Sr BPO_(5):Sm^(3+)was synthesized by the traditional solid-state method.The phosphor component was characterized by the X-ray powder diffraction(XRD).The photoluminescence excitation(PLE)and emission spectra(PL)were investigated.The influence of the concentration of Sm^(3+)ions on luminescence properties of samples and concentration quenching mechanism were investigated.The results show that the as-prepared phosphor can be excited by 342 nm,358 nm,370 nm and 399 nm UV light and the strongest one at 399 nm.On being excited by 399 nm,the sample emits yellow,orange and red emission at different wavelength.The optimal activator molar fraction in this phosphor is 0.016 and the only sintering temperature is 1000℃.It is meant for enhancing the emission intensity of Sr BPO_(5):Sm^(3+)phosphor if appropriate Li^(+)ions are added as charge compensator.The thermal stability was evaluated by emission spectra of phosphor at different measuring temperatures.This research studied the influence of reaction temperature and charge compensator on the luminescence characteristics.The chromaticity coordinates of Sr BPO_(5):Sm^(3+),R+phosphor was explored.The results indicate that Sr BPO_(5):Sm^(3+),Li^(+)is a potential orange-reddish phosphor in near UV based white LEDs.展开更多
Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the constructi...Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.展开更多
The advantages of the all-fiber optical current transformer include but are not limited to being small in size,having no magnetic saturation,exhibiting high measurement accuracy,and boasting strong electromagnetic int...The advantages of the all-fiber optical current transformer include but are not limited to being small in size,having no magnetic saturation,exhibiting high measurement accuracy,and boasting strong electromagnetic interference resistance.However,the high cost of the all-fiber optical transformer limits its promotion and application in engineering.This paper proposes a design scheme of an independent double acquisition loop for the all-fiber optical current transformer based on the single optical path.Firstly,based on the closed-loop control mode and open-loop control mode,the twochannel sampling signal demand for relay protection,and the independent dual-acquisition loop design scheme of the all-fiber optical current transformer are proposed.Secondly,the reliability and economic feasibility of the scheme are demonstrated by an analysis of system failure and cost.The results show that the scheme can actualize the acquisition function of two independent all-fiber optical current transformer products on a single all-fiber current transformer in an integrated manner,which greatly reduces the cost of the all-fiber optical current transformer in engineering applications.展开更多
基金supported by the Scientific Research Fund of Beijing Jiaotong University(KSRC12006536)the National Natural Science Foundation of China(61674011,61735004)~~
基金National Natural Science Foundation of China(61205180)Natural Science Foundation of Hebei Province,China(A2012201013)Distinguished Young Scholars of Hebei University(2012JQ01)
文摘An orange reddish phosphor Sr BPO_(5):Sm^(3+)was synthesized by the traditional solid-state method.The phosphor component was characterized by the X-ray powder diffraction(XRD).The photoluminescence excitation(PLE)and emission spectra(PL)were investigated.The influence of the concentration of Sm^(3+)ions on luminescence properties of samples and concentration quenching mechanism were investigated.The results show that the as-prepared phosphor can be excited by 342 nm,358 nm,370 nm and 399 nm UV light and the strongest one at 399 nm.On being excited by 399 nm,the sample emits yellow,orange and red emission at different wavelength.The optimal activator molar fraction in this phosphor is 0.016 and the only sintering temperature is 1000℃.It is meant for enhancing the emission intensity of Sr BPO_(5):Sm^(3+)phosphor if appropriate Li^(+)ions are added as charge compensator.The thermal stability was evaluated by emission spectra of phosphor at different measuring temperatures.This research studied the influence of reaction temperature and charge compensator on the luminescence characteristics.The chromaticity coordinates of Sr BPO_(5):Sm^(3+),R+phosphor was explored.The results indicate that Sr BPO_(5):Sm^(3+),Li^(+)is a potential orange-reddish phosphor in near UV based white LEDs.
基金supported by National Key Research and Development Program of China(2016YFB0900100)
文摘Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.
基金supported by the National Natural Science Foundation of China (No. U1866203)
文摘The advantages of the all-fiber optical current transformer include but are not limited to being small in size,having no magnetic saturation,exhibiting high measurement accuracy,and boasting strong electromagnetic interference resistance.However,the high cost of the all-fiber optical transformer limits its promotion and application in engineering.This paper proposes a design scheme of an independent double acquisition loop for the all-fiber optical current transformer based on the single optical path.Firstly,based on the closed-loop control mode and open-loop control mode,the twochannel sampling signal demand for relay protection,and the independent dual-acquisition loop design scheme of the all-fiber optical current transformer are proposed.Secondly,the reliability and economic feasibility of the scheme are demonstrated by an analysis of system failure and cost.The results show that the scheme can actualize the acquisition function of two independent all-fiber optical current transformer products on a single all-fiber current transformer in an integrated manner,which greatly reduces the cost of the all-fiber optical current transformer in engineering applications.
