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Wang J.J.,Deng Q.J.,He Y.Y.,Feng Y.N.,Kang M.P.,Duan X.L.,Yang Y.L. 한국물리학회 2022 Current Applied Physics Vol.39 No.-
CCTO (Calcium copper titanate) powder as inorganic filler was synthesized by the Sol-gel method firstly. CCTO/ PVDF (Polyvinylidene fluoride) composite was fabricated by solution mixing based on high temperature resistance of PVDF and insulated property of CCTO. The composite of CCTO/PVDF were characterized by X-ray diffraction, Fourier Transform infrared spectroscopy, Scanning Electron Microscope and impedance analysis. The results showed that the addition of CCTO and increasing in its content did not affect the phase- and microstructure of the composites,but the increase of CCTO content can induce the generation of C–F new bonds. PVDF/CCTO composites were enhanced in performance of thermal and frequency-depended stability with increasing in the fraction of CCTO. The dielectric constant of CCTO/PVDF composite materials with 50% CCTO achieved to a maximum value of 50 almost, which is 5 times higher the pure PVDF. The conductivity felled into 10-8 to 10-1 S m-1 during the frequency of 102–108 Hz. The composite material would be expected to be applied in the field of integrated circuit.
Improvement of lower hybrid current drive systems for high-power and long-pulse operation on EAST
Wang M.,Liu L.,Zhao L.M.,Li M.H.,Ma W.D.,Hu H.C.,Wu Z.G.,Feng J.Q.,Yang Y.,Zhu L.,Chen M.,Zhou T.A.,Jia H.,Zhang J.,Cao L.,Zhang L.,Liang R.R.,Ding B.J.,Zhang X.J.,Shan J.F.,Liu F.K.,Ekedahl A.,Gonich 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11
Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m2 . Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 C, much below the permissible value of tungsten material (~1200 C). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-activemultijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5 toroidally from the 4.6 GHz LH system and is not magnetically connected
Feng, M.L.,Dhanasekar, M.,Xiao, Q.Z. Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.13 No.5
Recently we formulated a 2D hybrid stress element from the 3D Hellinger-Reissner principle for the analysis of thick bodies that are symmetric to the thickness direction. Polynomials have typically been used for all the displacement and stress fields. Although the element predicted the dominant stress and all displacement fields accurately, its prediction of the out-of-plane shear stresses was affected by the very high order terms used in the polynomials. This paper describes an improved formulation of the 2D element using Fourier series expansion for the out-of-plane displacement and stress fields. Numerical results illustrate that its predictions have markedly improved.
Bahramy, M. ,S.,Clark, O. ,J.,Yang, B.-J.,Feng, J.,Bawden, L.,Riley, J. ,M.,Marković,, I.,Mazzola, F.,Sunko, V.,Biswas, D.,Cooil, S. ,P.,Jorge, M.,Wells, J. ,W.,Leandersson, M Nature Publishing Group, a division of Macmillan P 2018 NATURE MATERIALS Vol.17 No.1
Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied bulk properties, while their single-layer variants have become one of the most prominent examples of two-dimensional materials beyond graphene. Their disparate ground states largely depend on transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date. Here, we focus on the chalcogen-derived states. From density-functional theory calculations together with spin- and angle-resolved photoemission, we find that these generically host a co-existence of type-I and type-II three-dimensional bulk Dirac fermions as well as ladders of topological surface states and surface resonances. We demonstrate how these naturally arise within a single p-orbital manifold as a general consequence of a trigonal crystal field, and as such can be expected across a large number of compounds. Already, we demonstrate their existence in six separate TMDs, opening routes to tune, and ultimately exploit, their topological physics.
Two-dimensional ZrSe2/ZrS2 heterobilayer tuned by electric field for optoelectronic devices
Zhang L. M.,Zhang W. B.,Qiao S.,Yang Y.,Shang J. M.,Feng S. Q. 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.7
Constructing two-dimensional heterostructures can obtain more desirable device performance. In this work, we discuss the electronic properties and optical absorption of ZrSe2/ ZrS2 van der Waals (vdW) heterobilayer by density function theory. ZrSe2/ ZrS2 heterobilayer presents an intrinsic type-II band alignment, and the electrons and holes can be separated in different layers of ZrSe2/ ZrS2 heterobilayer, which can improves its carrier lifetime in photovoltaic devices. The electric field can effectively adjust the electronic properties of heterostructures. By applying a certain electric field, the band alignment can realize the transition from type-II to type-I, which is very beneficial to optical emission devices. To understand the inherent physical mechanism of electric field modulation, we analyze the variation trends of the band gap and band offset with external field in detail. In addition, ZrSe2/ ZrS2 heterostructure presents much stronger light absorption than isolated monolayers. Our results suggest that ZrSe2/ ZrS2 heterostructure can provide more potential application in optoelectronic devices.
Y.L.Feng,M.Ishitobi,A.Okuno,M.Nakaoka,H.W.Lee 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10
This paper presents a novel prototype of ZCS-PFM high frequency series resonant inverter using IGBT power module for electromagnetic induction eddy current-heated roller in copy and printing machines. The operating principle and unique features of this voltage source half bridge inverter with (wo additional soft commutation inductor snubber are presented including the transformer modeling of induction heated rolling drum. This soft switching inverter can achieve stable zero current soft commutation under a discontinuous and continuous resonant load current for a widely specified power regulation processing. The experimental results and computer-aided analysis of this inverter are discussed from a practical point of view.<br/>
R&D Status of High-current Accelerators at IFP
J. J. Deng,J. S. Shi,W. P. Xie,L. W. Zhang,K. Z. Zhang,S. P. Feng,J. Li,M. Wang,Y. He,L. S. Xia,Z. Y. Dai,H. T. Li,L. Wen,S. F. Chen,X. Li,Q. G. Lai,M. H. Xia,Y. C. Guan,S. Y. Song,L. Chen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.61
High-current accelerators have many important applications in Z-pinches, high-power microwaves, and free electron lasers, imploding liners and radiography and so on. Research activities on Zpinches, imploding liners, radiography at the Institute of Fluid Physics (IFP) are introduced. Several main high-current accelerators developed and being developed at IFP are described, such as the Linear Induction Accelerator X-Ray Facility Upgrade (LIAXFU, 12 MeV, 2.5 kA, 90 ns), the Dragon-I linear induction accelerator (20 MeV, 2.5 kA, 60 ns), and the Primary Test Stand for Z-pinch (PTS, 10 MA, 120 ns). The design of Dragon-II linear induction accelerator (20 MeV, 2.5 kA, 3 × 60 ns) to be built will be presented briefly.
Recent Developing of Research on the Safety of Rock Slope in China
M.C. He,J.L. Feng 한국암반공학회 2007 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-
Recent developing of research on the safety of rock slope in China is discussed in the paper. Firstly, complex rock slope at Fushun open coal pit has been modeled and curious deformation phenomenon appeared with it has also been explained. Secondly, optimal excavated scheme with relatively steep slope angle 47˚ instead of 30˚ has been successfully implemented at the west wall of Antaibao coalmine. Mohr-Coulomb failure criterion was used in all present simulations. Engineering protect measures and treatments were provided and sufficiently implemented under mining operation to improve slope stability and safety, based on the numerical simulation of optimal excavated sequence and in-situ monitoring data. Finally, a remote intelligent monitoring system is developed, including the warning modes proposed. Their typical applications are also presented.