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Measuring Near-Field Radiative Heat Transfer in a Graphene-SiC Heterostructure

Physical Review Applied 2023年第2期19卷 024019-024019页

作者： Naeem Iqbal Sen Zhang Shuai Wang Zezheng Fang Yaoyuan Hu Yongdi Dang Minjie Zhang Yi Jin Jianbin Xu Binfeng Ju Yungui Ma State Key Lab of Modern Optical Instrumentation Centre for Optical and Electromagnetic Research College of Optical Science and Engineering International Research Center for Advanced Photonics Zhejiang University Hangzhou China The State Key Lab of Fluid Power Transmission and Control School of Mechanical Engineering Zhejiang University Hangzhou China Zhejiang Province Key Laboratory of Quantum Technology and Device Department of Physics Zhejiang University Hangzhou China Department of Electrical and Electronic Engineering The University of Hong Kong Pokfulam Road Hong Kong China

Near-field radiative heat transfer between closely placed objects may exceed the far-field black-body radiation limit by orders of magnitude, especially between polaritonic materials. Great efforts have been made to experimentally measure this fundamental effect in various systems. In this work, we manage to experimentally characterize the near-field thermal emission between less explored plasmon-phonon hybrid material systems made of a graphene-SiC heterostructure. The experiment is carried out using a custom-designed all-optical measurement setup. A heat flux enhancement factor of 26 over the black-body radiation limit is obtained at a 150-nm vacuum gap. Three fundamental modes, i.e., surface plasmon and phonon polaritons with frustrated modes, are identified to contribute the near-field heat flux in this hybrid system. The measured results are well reproduced from the analytical calculations, indicating the robustness of the measurement. Deeper experimental explorations for near-field heat transfer between more complicated material systems could be encouraged in the future.

关键词： Energy harvesting devices Heat transfer Near-field optics Surface plasmon polariton Graphene Van der Waals systems Optical techniques

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Reduced-Order Model-Based Low-Frequency Mode Damping Analysis for Grid-Integrated Wind Farm Via Vsc-Hvdc System

SSRN

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SSRN 2023年

作者： Li, Qiutong Wang, Yukun Mu, Qing Sun, Haishun Li, Yutong Xiong, Xinyao State Key Lab of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan430074 China Central China Branch State Grid Corporation of China Wuhan430070 China China Electric Power Research Institute Beijing100192 China

The offshore subsystem of grid-integrated wind farm via VSC-HVDC (Voltage Source Converter-High Voltage Direct Current) consists of direct-drive type wind turbine generators (WTGs) and sending end converter (SEC) of VSC-HVDC. The SEC regulates AC voltage using voltage/frequency (V/F) control, while the grid-side converters (GSC) of WTGs synchronize to the AC voltage by a phase-locked loop (PLL). Eigenvalue analysis reveals that there exists a pair of low-frequency modes within the offshore subsystem which might be unstable at high level power output of WTGs. Participation factors and eigenvalue sensitivity analysis demonstrate that the low-frequency mode is closely related to the V/F control of SEC and PLL of GSC. According to this knowledge, a reduced-order s-domain model is derived from the full-order state-space model of the offshore subsystem with PLL dynamics of WTGs reserved. The damping of PLL dynamics is then investigated and divided into two parts, i.e., the intrinsic damping of PLL control and additional damping introduced by V/F control of the SEC. Consequently, a damping calculation method is developed. It is found that the damping calculation based on the reduced-order model represents the stability of the low-frequency mode exactly, implying that this reduced-order model reserved the mode dynamics mentioned above. The impact of different PLL and V/F control parameters on the damping characteristics is further studied. Time-domain simulations validate the effectiveness of the proposed damping analysis method, which could be helpful for control design to avoid the risk of low-frequency oscillation in the offshore system of grid-integrated wind farms via VSC-HVDC. © 2023, The Authors. All rights reserved.

关键词： Offshore wind farms

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First-Principles Study on the Cu-Cr Interfaces in Vacuum Circuit Breaker Contacts

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SSRN 2023年

作者： Gui, Xianxian Wu, Chuanqi Yuan, Zhao Liu, Liming Wang, Cao Chen, Lixue Liu, Xueliang Ye, Jingjing Liu, Shan State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Hubei Wuhan430074 China Key Lab Pulsed Power Technol Minist Educ School of Electrical and Electronic Engineering Hubei Wuhan430074 China State Grid Hubei Electric Power Research Institute Hubei Wuhan430077 China

Based on the experimental phenomenon that the breakdown position of the CuCr contact head in a vacuum circuit breaker may be the Cu-Cr phase boundary, the Cu-Cr interfacial binding models have been developed. The work function, density of states, work of interfacial separation, interfacial energy, charge transfer, band energy, and charge density distribution of Cu, Cr and Cu-Cr phase boundaries are calculated from the first principles. The internal properties of CuCr contact breakdown have been analyzed from the microscopic atomistic point of view. The CuCr interface junction was found to have a smaller work function than pure copper and pure chromium. The reduced work function is prone to field emission, thus increasing the possibility of electrical breakdown. Three interfacial binding models Cu(110)/Cr(110), Cu(111)/Cr(111) and Cu(110)/Cr(100) are established in this paper. By comparing the separation work and interfacial energy, it is found that Cu(111)/Cr(111) is relatively stable. In this paper, we provide a theoretical basis for increasing the voltage strength of vacuum circuit breakers. © 2023, The Authors. All rights reserved.

关键词： Timing circuits

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Track-before-detect of weak ballistic target using elliptical hough transform

Track-before-detect of weak ballistic target using elliptica...

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IET International Radar Conference 2013

作者： Rao, Bin Zong, Zhi-Wei Nie, Yuanping State Key Lab. of Complex Electromagnetic Environ. Effects on Electron. and Info. Syst. Changsha 410073 China College of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China

ISBN: (纸本)9781849196031

A track-before-detect (TBD) algorithm based on elliptical Hough transform (EHT) is presented for jointly detecting and tracking weak ballistic targets during its exoatmospheric flight. The new method makes use of the fact that the ballistic target follows the elliptical orbit when restricted to two-body problem. The relationship between raw radar measurements in the data space and the elliptical parameters in the parameter space is established with coordinate transformations. The EHT detection algorithm is designed and the orbit planarity is also considered to reduce the noise accumulation effect. The detection performances related to primary and second thresholds and signal-to-noise ratio (SNR) are analyzed and verified through simulations. The advantage of the new method lies in it can not only detect and track weak ballistic targets but also can predict the impact point by using availab.e parameters.

关键词： Hough transforms

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Electrochemical Mechanism of Blood-Compatibility of TiO2-x Film for Surface Modification of Cardiovascular Bio-medical Devices

Electrochemical Mechanism of Blood-Compatibility of TiO2-x F...

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The 60th Annual Meeting of The International Society of Electrochemistry(第60届国际电化学会议)

作者： G.J.Wan N.Huang J.Zh.Zhou P.Yang Y.X.Leng H.Sun X.Wu Zh.H.Lin State Key Lab. of Physical Chemistry of the Solid Surface College of Chem. & Chem. Engin.Xiamen UniversityXiamen 361005China Key Lab. of Advanced Technology for Materials of Education Ministry of ChinaCollege of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu610031China State Key Lab. of Physical Chemistry of the Solid SurfaceCollege of Chem. & Chem. Engin.Xiamen UniversityXiamen 361005China Key Lab. of Advanced Technology for Materials of Education Ministry of China College of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu610031China

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Experimental research on the characteristics of steam-water counter-current flow in the Pressurizer Surge Line assembly

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Experimental Thermal and Fluid Science 2018年 96卷 180-191页

作者： Jiangtao Yu Dalin Zhang Leitai Shi Zhiwei Wang Wenxi Tian G.H. Su S.Z. Qiu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University 28 Xianning West Road Xi’an 710049 China Shaanxi Key Lab. of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University 28 Xianning West Road Xi’an 710049 China

To investigate Counter-Current Flow (CCF) characteristics in the Pressurizer Surge Line (PZR SL) assembly of the large advanced passive nuclear reactors, steam-water CCF experiments are carried out on a stainless steel test section, which is a 1:4 scaled-down model of the AP1000 PZR SL assembly. The inner diameter of the test PZR SL pipe is 90 mm, which also belongs to the large-diameter pipes, as same as the prototype PZR SL pipe, in the field of Counter-Current Flow Limitation (CCFL) researches. The present steam-water CCFL experiments are conducted under normal pressure and saturated temperature, with the PZR simulator collapse water level ranging from 350 to 900 mm. CCFL becomes severer at higher steam flow rate, and the most limiting CCFL effect locates between the PZR simulator bottom head and the vertical part of PZR SL pipe. The onset of CCFL and zero liquid penetration (ZP) are two critical conditions in the CCF development process, dividing the process into three stages: Before-CCFL, Partial-CCFL, and CCFL-ZP. According to the local CCFL conditions, the development of the CCFL process is also divided into four-regions since onset of CCFL. The present steam-water CCF data are well normalized in terms of dimensionless Kutateladze (Ku) numbers, and a Ku-type empirical partial CCFL correlation is developed. The comparisons of the present CCF data and partial CCFL correlation with the CCF data and correlations of former experiment researches validate that the present empirical partial CCFL correlation is conservative to predict steam-water partial CCFL in the prototype PZR SL assembly of the large advanced passive nuclear reactors.

关键词： Steam-water counter-current flow Partial CCFL correlation Pressurizer surge line assembly advanced passive nuclear reactors ADS Automatic Depressurization System ADS1-3 First to Third Stages of ADS ADS4 Fourth Stage of ADS CCF Counter-Current Flow CCFL Counter-Current Flow Limitation CCFL-1 The 1st grade of CCFL region CCFL-2 The 2nd grade of CCFL region CCFL-3 The 3rd grade of CCFL region CCFL-L Local CCFL at the T-junction of HL pipe and PZR SL pipe CCFL-S Local CCFL along the PZR SL pipe CCFL-U Local CCFL at the location between the PZR simulator bottom head and vertical part of PZR SL pipe CCFL-ZP Zero liquid penetration region or stage CMT Core Makeup Tank COCF Co-Current Flow HL Hot Leg IRWST In-containment Refueling Water Storage Tank Ku Kutateladze PRHR Passive Containment Cooling System PWRs Pressurized Water Reactors PZR SL Pressurizer Surge Line RC Reactor Core RCS Reactor Coolant System RPV Reactor Pressure Vessel SBLOCAs Small-Break Loss-of-Coolant Accidents ZP zero liquid penetration

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Sacos-Plate: A New Thermal-Hydraulic Subchannel Analysis Code for Plate Type Fuel Assemblies

SSRN

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SSRN 2023年

作者： Sun, Ruiyu Wang, Jianjun Wang, Jinshun Chen, Ronghua Jiang, Xing Tian, Wenxi Qiu, Suizheng Su, Guanghui Gui, Minyang Harbin Engineering University China School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University China State Key Lab. of Multiphase Flow in Power Engineering Xi’an Jiaotong University China Shanghai Nuclear Engineering Research Design Institute Shanghai China

Over the past few decades, plate-type fuel elements have been widely used in advanced research reactors, small modular pressurized water reactors, production reactors, etc., with the advantages of compact structure arrangement, good heat transfer characteristics and high fuel consumption. Currently, a thermal-hydraulic subchannel analysis code, namely SACOS-PLATE code, was newly designed to satisfy the calculation of different types of plate fuel elements under various steady-state operating conditions. Based on the original SACOS code, this updated version modifies the flow distribution model, the plate heat conduction model, the heat distribution model as well as the flow heat transfer model, and then realizes the simulation of the special thermal-hydraulic phenomena of the fuel and the rectangular flow channel. In this present study, the RA-6 experimental data was used to validate the code, and the simulation calculation was performed on the JRR-3 research reactor, which proved the good computing capability of SACOS-PLATE code. © 2023, The Authors. All rights reserved.

关键词： Plates (structural components)

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Nuclear Thermal Coupling Optimization of Baffled Ntp Reactor

SSRN

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SSRN 2022年

作者： Duan, Zimian Zhang, Jing Han, Zichao Wang, Mingjun Wu, Yingwei He, Yanan Tian, Wenxi Qiu, Siuzheng Su, Guanghui Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Xi’an710049 China Department of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Nuclear thermal propulsion (NTP) technology has characteristics of high power and high specific impulse. In particular, CERMET fuel reactor has received a lot of research due to its simple form and structure. A general CERMET fuel reactor model is established by using three-dimensional Monte Carlo neutron dynamics program and commercial CFD program Fluent. After nuclear thermal coupling optimization, three partition schemes of baffled reactor were proposed to reduce the temperature difference between the wall and the coolant and lower the relative spike factor in the inner region. A feasible design of redundant control system was then proposed, with a cold clean excess reactivity greater than $3.44 and a minimum dry shutdown reactivity lower than -$5.95, where there was a high control accuracy of 6.7 pcm/mm. The reactor realized safety of the core temperature lower than 3000K under the conditions of total exit temperature of 2650K and thrust of 25000lb. © 2022, The Authors. All rights reserved.

关键词： Cermets

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Optimal operating conditions and modulation format for 160 Gb/s signals in a fiber parametric amplifier used as a slow-light delay line element

Optimal operating conditions and modulation format for 160 G...

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OFC/NFOEC 2007 - Optical Fiber Communication and the National Fiber Optic Engineers Conference 2007

作者： Liu, Fangfei Su, Yikai Voss, Paul L. State Key Lab. of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University 800 DongChuan Rd Shanghai 200240 China School of Electrical and Computer Engineering Georgia Institute of Technology 777 Atlantic Drive Atlanta GA 30332-0250 United States Georgia Tech Lorraine GT-CNRS UMI 2958 2-3 rue Marconi Metz F-57070 France

We study optimal operating conditions for 160-Gb/s signals traversing a slow-light delay line based on parametric amplification. Six phase modulated formats are investigated, including CSRZ, PAP-CSRZ, GAP-CSRZ, RZ duo... 详细信息

ISBN: (纸本)1557528314

关键词： Fiber amplifiers

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Effects of Electrospun Carbon Nanofibers Interlayers on High Performance Lithium Sulfur Batteries

Effects of Electrospun Carbon Nanofibers Interlayers on High...

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2017年锂硫电池前沿学术研讨会

作者： Tianji Gao TrungHieu Le Ying Yang Zhihao Yu Zhenghong Huang Feiyu Kang State Key Lab. of Power System Tsinghua University Department of Chemical and Environmental Engineering China University of Mining and Technology Department of Electrical Engineering Tsinghua University Laboratory of Advanced Materials Department of Materials Science and EngineeringTsinghua University

Two different interlayers were introduced in the lithium-sulfur batteries to improve the cycling stability with sulfur loading as high as 80%of total mass of *** was recommended as a nitrogen-rich(N-rich)amine component to synthesize a modified polyacrylic acid(MPAA).The electrospun MPAA was carbonized into N-rich carbon nanofibers which was used as cathode interlayer,whilst,

关键词： Effects of Electrospun Carbon Nanofibers Interlayers on High Performance Lithium Sulfur Batteries

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