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current-limiting characteristics of saturated iron-core fault current limiters in VSC-HVDC systems based on electromagnetic energy conversion mechanism

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Journal of Modern Power Systems and Clean Energy 2019年第2期7卷 412-421页

作者： Botong LI Hanqing CUI Fangjie JING Bin LI Yichao LIU Key Laboratory of Smart Grid of Ministry of Education Tianjin University

A common method to examine the current-limiting performance of saturated iron-core fault current limiter(SI-FCL) in high-voltage direct-current transmission based on voltage source converter(VSC-HVDC) systems is to solve differential equations based on the system fault transient characteristics and the equivalent inductance calculation equation. This method analyzes the fault current of the VSC-HVDC system in the time domain. However, it is computationally complex and cannot directly reflect the relationship between parameters and the currentlimiting effect of the *** this paper,the relationship between the magnetic flux density and magnetic field energy of the SI-FCL is analyzed. The energy exchange between the DC capacitor and the SI-FCL in the DC short circuit fault process is analyzed. From the perspective of electromagnetic energy conversion, the criterion for determining the current-limiting ability of the SI-FCL in the transient process is given based on the parameters of the SI-FCL and VSC-HVDC system. On this basis, the characteristics of the DC side fault current and the capacitor voltage when the SI-FCL has current-limiting ability are *** on the parameters of the SI-FCL and VSC-HVDC system, a method for calculating the fault current peak value and capacitor voltage drop time is given. Finally, the accuracy of the analysis of the SI-FCL in the VSC-HVDC system based on the electromagnetic energy conversion mechanism is demonstrated through a case study and simulation results of the VSC-HVDC system with different SI-FCLs.

关键词： Electromagnetic energy Saturated iron-core fault current limiter(SI-FCL) High-voltage direct-current transmission based on voltage source converter(VSCHVDC) system Fault analysis

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current diffusion and efficiency droop in vertical light emitting diodes

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Chinese Physics B 2019年第1期28卷 561-569页

作者： R Q Wan T Li Z Q Liu X Y Yi J X Wang J H Li W H Zhu J M Li L C Wang State Key Laboratory of High Performance Complex Manufacturing College of Mechanical and Electrical EngineeringCentral South University Semiconductor Lighting Technology Research and Development Center Institute of SemiconductorsChinese Academy of Sciences College of Materials Science and Opto-Electronic Technology University of Chinese Academy of Sciences

current diffusion is an old issue, nevertheless, the relationship between the current diffusion and the efficiency of light emitting diodes(LEDs) needs to be further quantitatively clarified. By incorporating current crowding effect(CCE) into the conventional ABC model, we have theoretically and directly correlated the current diffusion and the internal quantum efficiency(IQE), light extraction efficiency(LEE), and external quantum efficiency(EQE) droop of the lateral ***, questions still exist for the vertical LEDs(V-LEDs). Here firstly the current diffusion length L_s(I) and L_s(II) have been clarified. Based on this, the influence of CCE on the EQE, IQE, and LEE of V-LEDs were investigated. Specifically to our V-LEDs with moderate series resistivity, L_s(III) was developed by combining L_s(I) and L_s(II), and the CCE effect on the performance of V-LEDs was investigated. The wall-plug efficiency(WPE) of V-LEDs ware investigated finally. Our works provide a deep understanding of the current diffusion status and the correlated efficiency droop in V-LEDs, thus would benefit the V-LEDs' chip design and further efficiency improvement.

关键词： efficiency droop vertical light emitting diodes current crowding effect current blocking layer

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current–Voltage Characteristics of the Aziridine-Based Nano-Molecular Wires: a Light-Driven Molecular Switch

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Chinese Physics Letters 2018年第4期35卷 118-122页

作者： Ayoub Kanaani Mohammad Vakili Davood Ajloo Mehdi Nekoei School of Chemistry Damghan University Department of Chemistry Faculty of Science Ferdowsi University of Mashhad Department of Chemistry Shahrood Branch Islamic Azad University

Using nonequilibrium Green＇s function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-（4-nitrophenyl）-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials Y（111）（Y =Au, Ag and Pt） on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state（low resistance switches to high resistance）. Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.

关键词： current Voltage Characteristics of the Aziridine-Based Nano-Molecular Wires a Light-Driven Molecular Switch

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current Model Analysis of South China Sea Based on Empirical Orthogonal Function(EOF) Decomposition and Prototype Monitoring Data

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Journal of Ocean University of China 2019年第2期18卷 305-316页

作者： WU Wenhua LIU Ming YU Siyuan WANG Yanlin Department of Engineering Mechanics Faculty of Vehicle and Mechanics Dalian University of Technology State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology School of Ocean Science and Technology Dalian University of Technology

Environmental load is the primary factor in the design of offshore engineering structures and ocean current is the principal environmental load that causes underwater structural failure. In computational analysis, the calculation of current load is mainly based on the current profile. The current profile model, which is based on a structural failure criterion, is conducive to decreasing the uncertainty of the current load. In this study, we used prototype monitoring data and the empirical orthogonal function(EOF) method to investigate the current profile in the South China Sea and its correlation with the design of underwater structural strength and the dynamic design of fatigue. The underwater structural strength design takes into account the size of the structure and the service water depth. We propose profiles for the overall and local designs using the inverse first-order reliability method(IFORM). We extracted the characteristic profile current(CPC) of the monitored sea area to solve dynamic design problems such as vortex-induced vibration(VIV). We used random sampling to verify the feasibility of using the EOF method to calculate the CPC from the current data and identified the main problems associated with using the CPC, which deserve close attention in VIV design. Our research conclusions provide direct references for determining current load in this sea area. This analysis method can also be used in the analysis of other sea areas or field variables.

关键词： current profile model failure criteria prototype monitoring inverse first-order reliability method(IFORM) Characteristic profile current(CPC)

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current Trend in Synthesis,Post-Synthetic Modifications and Biological Applications of Nanometal-Organic Frameworks(NMOFs)

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Chinese Journal of Chemistry 2019年第4期37卷 378-404页

作者： Ebenezer Baa Gary M.Watkins Rui.W.Krause Derek.N.Tantohb Department of Chemistry Rhodes UniversityPO Box 94Grahamstown6140South Africa Department of Applied Chemistry University of JohannesburgPO Box 524Auckland Park2006South Africa

Since the early reports of MOFs and their interesting properties,research involving these materials has grown wide in scope and *** synthetic approaches have ensued in view of obtaining materials with optimised properties,the extensive scope of application spanning from energy,gas sorption,catalysis biological applications has meant exponentially evolved over the *** far-reaching synthetic and PSM approaches and porosity control possibilities have continued to serve as a motivation for research on these *** respect to the biological applications,MOFs have shown promise as good candidates in applicati ons involving drug delivery,BioMOFs,sensing,imaging amongst *** being a while away from successful entry into the market,observed results in sensing,drug delivery,and imaging put these materials on the spot light as candidates poised to usher in a revolution in *** this regard,this review article focuses current approaches in synthesis,post functionalization and biological applications of these materials with particular attention on drug delivery,imaging,sensing and BioMOFs.

关键词： current Trend Post-Synthetic Modifications Nanometal-Organic Frameworks(NMOFs)

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Development of gas tungsten arc welding using current pulsing technique to preclude chromium carbide precipitation in aerospace-grade alloy 80A

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International Journal of Minerals,Metallurgy and Materials 2019年第2期26卷 210-221页

作者： P.Subramani M.Manikandan School of Mechanical Engineering Vellore Institute of Technology

Weldments were produced using gas tungsten arc welding(GTAW) and pulsed current gas tungsten arc welding(PCGTAW) techniques with ERNiCr-3 filler wire. Macro examination revealed that the resultant weldments were free from defects. A refined microstructure was observed in the weldment fabricated through PCGTAW. Scanning electron microscopy(SEM) analysis revealed secondary phases in the grain boundaries. Energy-dispersive X-ray spectroscopy(EDS) analysis revealed that microsegregation of Cr carbide precipitates was completely eradicated through PCGTAW. The microsegregation of Nb precipitates was observed in the GTA and PCGTA weldments. X-ray diffraction(XRD) analysis revealed the existence of M_(23)C?_6 Cr-rich carbide and Ni_8Nb phases in the GTA weldments. By contrast, in the PCGTA weldments, the Ni_8Nb phase was observed. The Cr_2Ti phase was observed in both the GTA and the PCGTA weldments. Tensile tests showed that the strength and ductility of the PCGTA weldments were slightly higher than those of the GTA weldments.

关键词： Ni-based superalloy welding pulse current microsegregation chromium carbide

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Optimization of ambipolar current and analog/RF performance for T-shaped tunnel field-effect transistor with gate dielectric spacer

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Chinese Physics B 2019年第1期28卷 656-662页

作者： Ru Han Hai-Chao Zhang Dang-Hui Wang Cui Li School of Computer Science and Engineering Northwestern Polytechnical University

A new T-shaped tunnel field-effect transistor(TTFET) with gate dielectric spacer(GDS) structure is proposed in this paper. To further studied the effects of GDS structure on the TTFET, detailed device characteristics such as current-voltage relationships, energy band diagrams, band-to-band tunneling(BTBT) rate and the magnitude of the electric field are investigated by using TCAD simulation. It is found that compared with conventional TTFET and TTFET with gate-drain overlap(GDO) structure, GDS-TTFET not only has the minimum ambipolar current but also can suppress the ambipolar current under a more extensive bias range. Furthermore, the analog/RF performances of GDS-TTFET are also investigated in terms of transconductance, gate-source capacitance, gate-drain capacitance, cutoff frequency, and gain bandwidth production. By inserting a low-κ spacer layer between the gate electrode and the gate dielectric, the GDS structure can effectively reduce parasitic capacitances between the gate and the source/drain, which leads to better performance in term of cutoff frequency and gain bandwidth production. Finally, the thickness of the gate dielectric spacer is optimized for better ambipolar current suppression and improved analog/RF performance.

关键词： tunneling field effect transistor T-shaped tunnel field-effect transistor gate dielectric spacer ambipolar current analog/RF performance

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current measurements and spectral analyses in the upper 450 m and deep layers of the northeastern South China Sea

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Science China Earth Sciences 2002年第11期45卷 1008-1026页

作者：袁耀初赵进平王惠群楼如云陈洪王康墡

On the basis of the current measurements from the moored Long Ranger ADCP in the upper 450 m layer and the deep current measurements at 2000 and 2300 m from the moored current meters with the time series data of about 7 months at the mooring station in the northeastern South China Sea, the spectral analyses and calculation have been made. The major results are as follows: (i) From the progressive vector diagrams of the observed daily currents at the water levels from 50 m to 400 m, its temporal variation of velocity rotated counterclockwise in most of the observing time. This agrees basically with the result from the qualitative analysis of the sea surface height data, which was obtained from TOPEX/ERS-2 altimeter data by CCAR. The daily and monthly average velocities are both the largest in November, next in October and minimum in August. (ii) At the 2000 and 2300 m levels, the daily and monthly average velocities are both the largest in January, next in September and minimum in August. From the seasonal change of currents, the current velocity is the strongest in winter (January-March), next in autumn, and weak in summer. (iii) There exists the variation of tidal current with the change of depth. In the upper layer, the height of diurnal peak is higher than that of semidiurnal peak. However, the semidiurnal peak is higher than the diurnal peak at the levels from 200 m to 400 m. In the layers above 450 m the clockwise component is dominant in their fluctuations. In the layers below 1500 m the diurnal peak is again higher than the semidiurnal peak. (iv) There is the prominent periodic fluctuation of more than two months in the layer from 50 m to 2300 m. The period of this prominent peak is 75 d and its fluctuation is counterclockwise in the upper 450 m layers, and is 68 d and 69 d at the depths of 2000 and 2300 m, respectively, and the counterclockwise component is dominant in their fluctuations. (v) There are the variations of periods fluctuating with the change of

关键词： northeastern South China Sea, current measurement in the upper 450 m layer, current measurement in the deep layer, spectral analysis, fluctuation of long period.

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Reaction Selectivity Improvement for Reduction of Nitrobenzene in a Packed-Bed Electrode Reactor under Periodic-current Control

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Chinese Journal of Chemical Engineering 1998年第4期6卷 44-51页

作者：丁平杨晓勤袁渭康华东理工大学化学反应研究中心上海

Rectangular wave current control of the electrochemical reduction of nitrobenzene im-proves the selectivity for p-aminophenol(PAP) compared to direct current(d.c.) control at thesame average current density in a flow-by packed-bed *** increase in PAP selectivitycan be obtained at about a frequency of 50Hz and a duty cycle of 0.2.A mathematical model isset up to incorporate the effects of mass transfer,hydrogen evolution and double layer charging,and is solved using the Duhamel’s superposition principle and the modified Crank-Nicolson methodwith the upwind *** conventional *** cases are also calculated for *** can be applied to predict the reaction results under periodic current and ***,but both display the same trends compared to experimental data.

关键词： nitrobenzene electroreduction packed-bed electrode reactor periodic current control

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current status and future directions of the Tibetan Plateau ecosystem research

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Science Bulletin 2019年第7期64卷 428-430页

作者： Yangjian Zhang Yixuan Zhu Junxiang Li Yao Chen Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of Sciences College of Resources and Environment University of Chinese Academy of Sciences

The Tibetan Plateau (TP) encompasses Xizang and Qinghai and parts of northern Yunnan and Sichuan provinces, with a total area of circa 2.6 millions km2. The 2013 satellite data showed that grasslands, forests, wetlands, agricultural lands, and deserts account for 60%, 7.7%, 1.4%, 0.3%, and 30%, respectively, of total TP land (1)Due to its existence in dry, high altitude and cold environments, the TP ecosystem is extremely vulnerable to global climate change and studies on the TP ecosystem can be utilized as a pre-warning for other ecosystems.

关键词： current status and future directions of the Tibetan Plateau ecosystem research TP

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