In this work, a direct green solid-phase reduction method for the fabrication of large yield of ordered phase Fe-Pt alloy nanoparticles was reported, in which inorganic salts were used as metal precursors and H_2-cont...In this work, a direct green solid-phase reduction method for the fabrication of large yield of ordered phase Fe-Pt alloy nanoparticles was reported, in which inorganic salts were used as metal precursors and H_2-containing atmosphere was used as reducer. Utilizing this method, the composition and chemical ordered phase, such as L1_2-Fe_3 Pt, L1_2-FePt_3, and L1_0-FePt phases can be easily achieved by one step reaction. The synthesized nanoparticles have clean surface because no organic precursors, no organic solutions or organic surfactants/ligands were used. Their magnetic performance and the formation mechanism of Fe-Pt alloy nanoparticles were also investigated. This strategy can be applied to synthesize many other types of alloy nanoparticles with desired composition and necessary crystal structure, which can be used for a variety of practical applications, such as in magnetism and catalyst research fields.展开更多
Energy storage systems with multilevel converters play an important role in modern electric power systems with large-scale renewable energy integration.This paper proposes a reverse-blocking modular multilevel convert...Energy storage systems with multilevel converters play an important role in modern electric power systems with large-scale renewable energy integration.This paper proposes a reverse-blocking modular multilevel converter for a battery energy storage system(RB-MMCBESS). Besides integrating distributed low-voltage batteries to medium or high voltage grids, with the inherited advantages of traditional MMCs, the RB-MMC-BESS also provides improved DC fault handling capability. This paper analyzes such a new converter configuration and its operating principles. Control algorithms are developed for AC side power control and the balancing of battery state of charge. The blocking mechanism to manage a DC pole-topole fault analyzed in depth. Comprehensive simulation results validate both the feasibility of the RB-MMC-BESS topology and the effectiveness of the control and fault handling strategies.展开更多
The corrosion behavior and electrochemical impedance spectroscopy (EIS) features of 8090 Al-Li alloys in EXCO solution were investigated, and the EIS was simulated using an equivalent circuit. At the beginning of imme...The corrosion behavior and electrochemical impedance spectroscopy (EIS) features of 8090 Al-Li alloys in EXCO solution were investigated, and the EIS was simulated using an equivalent circuit. At the beginning of immersion in EXCO solution, the EIS is comprised by a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency, and the inductive component decreases and disappears with im- mersion time. Once exfoliation or severe pitting corrosion is produced, two capacitive arcs appear in the EIS. These two capacitive arcs are originated from the two parts of the corroded alloy surface, the original flat alloy surface and the new inter-face exposed to the aggressive EXCO solution due to the exfoliation or pitting corrosion. Some corrosion development features of 8090 Al-Li alloys in EXCO solution can be obtained through simulated EIS information.展开更多
In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking su...In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking submodules(QRBSMs)and current limit modules(CLMs)are employed to improve the DC fault handling capability for HVDC applications.This paper analyzes such a new converter configuration and operation principles.Then the DC pole-to-pole short circuit fault is taken into consideration for further study,as well as the fault current blocking mechanism and quantitative relationship between system electrical stress and key parameters.To validate the feasibility of the proposed topology and fault protection theory,extensive simulation results are demonstrated.It is concluded that the QRB-MMC can effectively block the fault current under DC fault condition.In addition,CLMs play an important role in further accelerating fault current attenuation.Moreover,QRB-MMC employs the original control and modulation strategies under normal operation conditions;thus,it further reduces the complexity of industry design.展开更多
The common-mode current is an important indicator with transformerless photovoltaic inverters.However,up to now,there is not an accurate method to predict common-mode current in the inverter design process,resulting f...The common-mode current is an important indicator with transformerless photovoltaic inverters.However,up to now,there is not an accurate method to predict common-mode current in the inverter design process,resulting from inappropriate device selection or exceeded the expected common-mode current.In order to solve this problem,this paper proposes an accurate common-mode current prediction method based on graph theory for transformerless photovoltaic inverters.In this paper,the mathematic model of the common-mode current is derived using graph theory analysis method in the full-bridge topology,and it is used to predict common-mode current.The validity and correctness of the proposed prediction method are validated by simulation and experiment.The oscillation frequency and amplitude can be predicted by the proposed common-mode prediction method,whereas the traditional common-mode analysis method cannot.This paper provides a novel way to predict and analyze common-mode current in the transformerless photovoltaic inverters.展开更多
Effects of various aging treatments on mechanical properties and microstructure of alloy 2195 have been investigated. The experimental results showed that a promising combination of strength and ductility was achievab...Effects of various aging treatments on mechanical properties and microstructure of alloy 2195 have been investigated. The experimental results showed that a promising combination of strength and ductility was achievable under T8 temper. The lower aging temperature reduced subgrain-or grain-boundary T1 precipitation and favored uniform dispersion of T1 phases, resulting in better strength and ductility. Prior deformation improved aging strength with promising ductility. Pre-aging after prior deformation had little effect on the age-hardening behavior of alloy 2195.展开更多
The obstetric issues and management styles in China are different from that in Western countries.Chinese medical education,residency training,obstetric care structure,and management of common obstetric complications a...The obstetric issues and management styles in China are different from that in Western countries.Chinese medical education,residency training,obstetric care structure,and management of common obstetric complications are briefly reviewed and compared to the United States.Maternal-fetal medicine(MFM)is rapidly developing in China,but the development of MFM may not follow the same trajectory as in the West.Understanding the difference between China and the West may facilitate communication and foster mutual development.展开更多
High temperature superconductivity,up to 258K,was observed in the Y_(1)Ba_(2)Cu_(3)F_(2x)O_(7-x-δ)(0.2≤x≤1)bulk materials prepared by means of conventional ceramic-technique.X-ray diffraction analysis shows that th...High temperature superconductivity,up to 258K,was observed in the Y_(1)Ba_(2)Cu_(3)F_(2x)O_(7-x-δ)(0.2≤x≤1)bulk materials prepared by means of conventional ceramic-technique.X-ray diffraction analysis shows that these materials are multiphase.It is believed that to obtain a high Tc superconducting material with Tc near room temperature is possible,though the high Tc state of samples is now very unstable.展开更多
The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of...The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant Nos.51772220,51772219,51771095,51422106)Zhejiang Provincial Natural Science Foundation of China (No.D19E010001)the National Basic Research Program of China (Grant No.2014CB643702)
文摘In this work, a direct green solid-phase reduction method for the fabrication of large yield of ordered phase Fe-Pt alloy nanoparticles was reported, in which inorganic salts were used as metal precursors and H_2-containing atmosphere was used as reducer. Utilizing this method, the composition and chemical ordered phase, such as L1_2-Fe_3 Pt, L1_2-FePt_3, and L1_0-FePt phases can be easily achieved by one step reaction. The synthesized nanoparticles have clean surface because no organic precursors, no organic solutions or organic surfactants/ligands were used. Their magnetic performance and the formation mechanism of Fe-Pt alloy nanoparticles were also investigated. This strategy can be applied to synthesize many other types of alloy nanoparticles with desired composition and necessary crystal structure, which can be used for a variety of practical applications, such as in magnetism and catalyst research fields.
基金supported by the State Key Laboratory of Large Electric Drive System and Equipment Technology(No.SKLLDJ042016005)the National Key Research and Development Program of China(No.2016YFE0131700)the National Natural Science Foundation of China(No.51577010)
文摘Energy storage systems with multilevel converters play an important role in modern electric power systems with large-scale renewable energy integration.This paper proposes a reverse-blocking modular multilevel converter for a battery energy storage system(RB-MMCBESS). Besides integrating distributed low-voltage batteries to medium or high voltage grids, with the inherited advantages of traditional MMCs, the RB-MMC-BESS also provides improved DC fault handling capability. This paper analyzes such a new converter configuration and its operating principles. Control algorithms are developed for AC side power control and the balancing of battery state of charge. The blocking mechanism to manage a DC pole-topole fault analyzed in depth. Comprehensive simulation results validate both the feasibility of the RB-MMC-BESS topology and the effectiveness of the control and fault handling strategies.
文摘The corrosion behavior and electrochemical impedance spectroscopy (EIS) features of 8090 Al-Li alloys in EXCO solution were investigated, and the EIS was simulated using an equivalent circuit. At the beginning of immersion in EXCO solution, the EIS is comprised by a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency, and the inductive component decreases and disappears with im- mersion time. Once exfoliation or severe pitting corrosion is produced, two capacitive arcs appear in the EIS. These two capacitive arcs are originated from the two parts of the corroded alloy surface, the original flat alloy surface and the new inter-face exposed to the aggressive EXCO solution due to the exfoliation or pitting corrosion. Some corrosion development features of 8090 Al-Li alloys in EXCO solution can be obtained through simulated EIS information.
基金supported in part by the State Key Laboratory of Large Electric Drive System and Equipment Technology(No.SKLLDJ042016005)in part by Open Fund of State Key Laboratory of Operation and Control of Renewable Energy&Storage Systemsin part by the National Key Research and Development Program of China(2016YFE0131700).
文摘In view of the DC fault current isolation deficiency for the conventional half-bridge sub-module(HBSM)based modular multilevel converter(MMC),this paper presents an improved MMC topology.Both quasi reverse blocking submodules(QRBSMs)and current limit modules(CLMs)are employed to improve the DC fault handling capability for HVDC applications.This paper analyzes such a new converter configuration and operation principles.Then the DC pole-to-pole short circuit fault is taken into consideration for further study,as well as the fault current blocking mechanism and quantitative relationship between system electrical stress and key parameters.To validate the feasibility of the proposed topology and fault protection theory,extensive simulation results are demonstrated.It is concluded that the QRB-MMC can effectively block the fault current under DC fault condition.In addition,CLMs play an important role in further accelerating fault current attenuation.Moreover,QRB-MMC employs the original control and modulation strategies under normal operation conditions;thus,it further reduces the complexity of industry design.
基金This work was supported by the National Natural Science Foundation of China under Grant 51577010the Fundamental Research Funds for the Central Universities under Grant 2017JBM054the Natural Science Foundation of Guangdong Province under Grant 1714060000016.
文摘The common-mode current is an important indicator with transformerless photovoltaic inverters.However,up to now,there is not an accurate method to predict common-mode current in the inverter design process,resulting from inappropriate device selection or exceeded the expected common-mode current.In order to solve this problem,this paper proposes an accurate common-mode current prediction method based on graph theory for transformerless photovoltaic inverters.In this paper,the mathematic model of the common-mode current is derived using graph theory analysis method in the full-bridge topology,and it is used to predict common-mode current.The validity and correctness of the proposed prediction method are validated by simulation and experiment.The oscillation frequency and amplitude can be predicted by the proposed common-mode prediction method,whereas the traditional common-mode analysis method cannot.This paper provides a novel way to predict and analyze common-mode current in the transformerless photovoltaic inverters.
文摘Effects of various aging treatments on mechanical properties and microstructure of alloy 2195 have been investigated. The experimental results showed that a promising combination of strength and ductility was achievable under T8 temper. The lower aging temperature reduced subgrain-or grain-boundary T1 precipitation and favored uniform dispersion of T1 phases, resulting in better strength and ductility. Prior deformation improved aging strength with promising ductility. Pre-aging after prior deformation had little effect on the age-hardening behavior of alloy 2195.
文摘The obstetric issues and management styles in China are different from that in Western countries.Chinese medical education,residency training,obstetric care structure,and management of common obstetric complications are briefly reviewed and compared to the United States.Maternal-fetal medicine(MFM)is rapidly developing in China,but the development of MFM may not follow the same trajectory as in the West.Understanding the difference between China and the West may facilitate communication and foster mutual development.
文摘High temperature superconductivity,up to 258K,was observed in the Y_(1)Ba_(2)Cu_(3)F_(2x)O_(7-x-δ)(0.2≤x≤1)bulk materials prepared by means of conventional ceramic-technique.X-ray diffraction analysis shows that these materials are multiphase.It is believed that to obtain a high Tc superconducting material with Tc near room temperature is possible,though the high Tc state of samples is now very unstable.
基金supported by the National Key R&D Program of China under Contract No.2022YFA1602200the International Partnership Program of the Chineses Academy of Sciences under Grant No.211134KYSB20200057the STCF Key Technology Research and Development Project.
文摘The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.
