A series of tunable phosphors NaAlSiO_4：Ce^（3＋）,Sm^（3＋） were synthesized using a conventional high-temperature, solid-state method. Crystal structure, photoluminescence excitation, and emission spectra with flu...A series of tunable phosphors NaAlSiO_4：Ce^（3＋）,Sm^（3＋） were synthesized using a conventional high-temperature, solid-state method. Crystal structure, photoluminescence excitation, and emission spectra with fluorescence decay curves were investigated. Under UV excitation（325 nm）, NaAlSiO_4：Ce^（3＋）,Sm^（3＋） showed strong blue emission located at 444 nm and orange-reddish emission centered at 563, 601, 648 and 712 nm, stemming from the characteristic emission for 4f-5d transition of Ce^（3＋） and ~4G_（5/2）→~6H_J（J=5/2, 7/2, 9/2, 11/2） transition of Sm^（3＋）, respectively. In addition, we studied the detailed energy transfer process between Ce^（3＋） and Sm^（3＋） and found that it belonged to dipole-dipole resonance energy transfer. Furthermore, we noted that the white light emitting from the Ce^（3＋）, Sm^（3＋） co-doped phosphors with the color coordinate（x=0.313, y=0.283） could be observed under 325 nm excitation, which was close to the ideal white light（x=0.33, y=0.33）. The results indicated that this phosphor has a potential application as a single-phased alumino-silicate phosphor for ultraviolet white light-emitting diodes（UV-WLEDs）.展开更多
A two colour phosphor Ba2Mg（BO3）2：Ce^3＋,Eu^2＋,Na^＋ was synthesized using solid-state reaction method. Luminescence of Ba2Mg（BO3）2：Ce^3＋,Eu^2＋,Na^＋ showed 416 and 618 nm emission bands attributed to Ce^3＋ ...A two colour phosphor Ba2Mg（BO3）2：Ce^3＋,Eu^2＋,Na^＋ was synthesized using solid-state reaction method. Luminescence of Ba2Mg（BO3）2：Ce^3＋,Eu^2＋,Na^＋ showed 416 and 618 nm emission bands attributed to Ce^3＋ and Eu^2＋ emission, respectively. Energy transfer occurred from Ce^3＋ to Eu^2＋ through a significant overlap of Eu^2＋ excitation spectrum with Ce^3＋ emission spectum in Ba2Mg（BO3）2. They also showed that under the excitation of UV radiation, bluish or yellowish white light was generated by coupling a broad blue emission band and a red emission band. By combining with green phosphor, Ba2Mg（BO3）：Ce^3＋,Eu^2＋,Na^＋ phosphor showed potential application for white light-emitting diodes （LEDs）.展开更多
The establishment of an approach to design tunable yellow emission through singly doped single-phased phosphors to obtain white LED-based InGaN chip was reported. BaY2–xS4：xHo3＋ phosphors were prepared by the high ...The establishment of an approach to design tunable yellow emission through singly doped single-phased phosphors to obtain white LED-based InGaN chip was reported. BaY2–xS4：xHo3＋ phosphors were prepared by the high temperature solid state reaction and characterized by X-ray diffraction and photoluminescence spectra. Under the excitation of 465 nm,the emission spectra of these phosphors exhibited three sharp emission lines peaked at about 492,543 and 661 nm of Ho3＋ corresponding to 5F3,5F4 （5S2） and 5F5→5I8 transitions,respectively,with comparable intensities,resulting in a yellow light emission. The luminescence mechanism for Ho3＋ in BaY2S4 was explained.展开更多
Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck lim- iting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics...Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck lim- iting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics with strong magnetoelectric coupling effect. Here, those progresses of the mechanism for coexistence of ferroelectric and magnetic order, experimental and theoretical studies on single-phased magnetic ferroelectrics, and the relationship between magnetic structure and crystal symmetry are summarized. With examples of BiFeO3, BiMnO3 and Bi2FeCrO6, the difficulties encountered in this field are analyzed. At last, some prospects to develop high-temperature single-phased ferromagnetic-ferro- electric multiferroics are also presented.展开更多
With the rapid development of modern distribution network and the access of distributed generation,the network structure is becoming increasingly complex.Frequent single-phase break faults have seriously affected equi...With the rapid development of modern distribution network and the access of distributed generation,the network structure is becoming increasingly complex.Frequent single-phase break faults have seriously affected equipment and personal safety and stable operation of the power system.However,with the development and application of the composite neutral grounding modes,the protection of single-phase break fault is facing new challenges.This paper proposes a protection method of single-phase break fault for distribution network considering the influence of neutral grounding modes.The characteristics of neutral voltage and sequence current are analyzed under normal operation and single-phase break fault with different grounding modes.Following this,the protection criterion based on neutral voltage and sequence current variation is constructed.The protection method of singlephase break fault for distribution network is proposed,which is applicable for various neutral grounding modes.Theoretical analysis and simulation results show that the protection method is less affected by system asymmetry,fault location and load distribution.The method has higher sensitivity,reliability and adaptability.展开更多
以电力电子变压器(power electronic transformer,PET)牵引传动系统前端的单相级联H桥整流器(cascadedH-bridge rectifiers,CHBR)为研究对象,首先推导了其离散数学模型,并分析了传统有限集模型预测电流控制(finite-control-set model pr...以电力电子变压器(power electronic transformer,PET)牵引传动系统前端的单相级联H桥整流器(cascadedH-bridge rectifiers,CHBR)为研究对象,首先推导了其离散数学模型,并分析了传统有限集模型预测电流控制(finite-control-set model predictive current control,FCS-MPCC)算法原理;然后,为了减小FCS-MPCC算法实现时所带来的巨大计算量,进一步提高系统稳态性能,提出一种基于两矢量的简化模型预测控制算法(simplified model predictive currentcontrol,SMPCC)。所提算法对控制集的选取进行简化,减少备选电压矢量数目,且摒弃传统的在线寻优方法,通过简化计算判断最优扇区,在显著减少数字运算量的同时实现开关频率固定与电容电压平衡控制。最后,将所提算法与2种传统FCS-MPCC算法进行半实物对比验证,实验结果证明了所提算法的合理性和有效性。展开更多
基金supported by the National Natural Science Foundation of China(11464045)Autonomous Region Postgraduate Research Innovation Fund Project(XJGRI2016093)+1 种基金the subject of Xinjiang Normal University Key Laboratory(KWFG1605)the Introduction Program of High-Level Talents of Xinjiang Province
文摘A series of tunable phosphors NaAlSiO_4：Ce^（3＋）,Sm^（3＋） were synthesized using a conventional high-temperature, solid-state method. Crystal structure, photoluminescence excitation, and emission spectra with fluorescence decay curves were investigated. Under UV excitation（325 nm）, NaAlSiO_4：Ce^（3＋）,Sm^（3＋） showed strong blue emission located at 444 nm and orange-reddish emission centered at 563, 601, 648 and 712 nm, stemming from the characteristic emission for 4f-5d transition of Ce^（3＋） and ~4G_（5/2）→~6H_J（J=5/2, 7/2, 9/2, 11/2） transition of Sm^（3＋）, respectively. In addition, we studied the detailed energy transfer process between Ce^（3＋） and Sm^（3＋） and found that it belonged to dipole-dipole resonance energy transfer. Furthermore, we noted that the white light emitting from the Ce^（3＋）, Sm^（3＋） co-doped phosphors with the color coordinate（x=0.313, y=0.283） could be observed under 325 nm excitation, which was close to the ideal white light（x=0.33, y=0.33）. The results indicated that this phosphor has a potential application as a single-phased alumino-silicate phosphor for ultraviolet white light-emitting diodes（UV-WLEDs）.
基金supported by National Natural Science Foundation of China (10804099,11274299)the Natural Science Foundation of Zhejiang Province(Y4110536)the Key Science and Technology Innovation Team of Zhejiang Province (2009R50002)
文摘A two colour phosphor Ba2Mg（BO3）2：Ce^3＋,Eu^2＋,Na^＋ was synthesized using solid-state reaction method. Luminescence of Ba2Mg（BO3）2：Ce^3＋,Eu^2＋,Na^＋ showed 416 and 618 nm emission bands attributed to Ce^3＋ and Eu^2＋ emission, respectively. Energy transfer occurred from Ce^3＋ to Eu^2＋ through a significant overlap of Eu^2＋ excitation spectrum with Ce^3＋ emission spectum in Ba2Mg（BO3）2. They also showed that under the excitation of UV radiation, bluish or yellowish white light was generated by coupling a broad blue emission band and a red emission band. By combining with green phosphor, Ba2Mg（BO3）：Ce^3＋,Eu^2＋,Na^＋ phosphor showed potential application for white light-emitting diodes （LEDs）.
基金Project supported by the National Natural Science Foundation of China (20971042 and 50772035)the Science and Technology Office of Educa-tion Department of Hunan Province (10A070)the Science and Technology Bureau of Changsha City Government (K0902014-11)
文摘The establishment of an approach to design tunable yellow emission through singly doped single-phased phosphors to obtain white LED-based InGaN chip was reported. BaY2–xS4：xHo3＋ phosphors were prepared by the high temperature solid state reaction and characterized by X-ray diffraction and photoluminescence spectra. Under the excitation of 465 nm,the emission spectra of these phosphors exhibited three sharp emission lines peaked at about 492,543 and 661 nm of Ho3＋ corresponding to 5F3,5F4 （5S2） and 5F5→5I8 transitions,respectively,with comparable intensities,resulting in a yellow light emission. The luminescence mechanism for Ho3＋ in BaY2S4 was explained.
基金supported by the National Natural Science Foundation of China (Grant No. 10304021)National Basic Research Program of China (Grant No. 2007CB924900)+2 种基金Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD-200744)Shanghai Pujiang Program (Grant No. 07pj14087)Program for New Century Excellent Talents in University (NCET-07-0624)
文摘Magnetic ferroelectrics are one of the most important functional materials. The present bottleneck lim- iting applications of them is lacking of high-temperature single-phased ferromagnetic-ferroelectric multiferroics with strong magnetoelectric coupling effect. Here, those progresses of the mechanism for coexistence of ferroelectric and magnetic order, experimental and theoretical studies on single-phased magnetic ferroelectrics, and the relationship between magnetic structure and crystal symmetry are summarized. With examples of BiFeO3, BiMnO3 and Bi2FeCrO6, the difficulties encountered in this field are analyzed. At last, some prospects to develop high-temperature single-phased ferromagnetic-ferro- electric multiferroics are also presented.
基金supported by the National Natural Science Foundation of China(NO.51877018).
文摘With the rapid development of modern distribution network and the access of distributed generation,the network structure is becoming increasingly complex.Frequent single-phase break faults have seriously affected equipment and personal safety and stable operation of the power system.However,with the development and application of the composite neutral grounding modes,the protection of single-phase break fault is facing new challenges.This paper proposes a protection method of single-phase break fault for distribution network considering the influence of neutral grounding modes.The characteristics of neutral voltage and sequence current are analyzed under normal operation and single-phase break fault with different grounding modes.Following this,the protection criterion based on neutral voltage and sequence current variation is constructed.The protection method of singlephase break fault for distribution network is proposed,which is applicable for various neutral grounding modes.Theoretical analysis and simulation results show that the protection method is less affected by system asymmetry,fault location and load distribution.The method has higher sensitivity,reliability and adaptability.
文摘以电力电子变压器(power electronic transformer,PET)牵引传动系统前端的单相级联H桥整流器(cascadedH-bridge rectifiers,CHBR)为研究对象,首先推导了其离散数学模型,并分析了传统有限集模型预测电流控制(finite-control-set model predictive current control,FCS-MPCC)算法原理;然后,为了减小FCS-MPCC算法实现时所带来的巨大计算量,进一步提高系统稳态性能,提出一种基于两矢量的简化模型预测控制算法(simplified model predictive currentcontrol,SMPCC)。所提算法对控制集的选取进行简化,减少备选电压矢量数目,且摒弃传统的在线寻优方法,通过简化计算判断最优扇区,在显著减少数字运算量的同时实现开关频率固定与电容电压平衡控制。最后,将所提算法与2种传统FCS-MPCC算法进行半实物对比验证,实验结果证明了所提算法的合理性和有效性。
