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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.
Variation of magnetic properties with different annealed temperatures in the Ni_3[Fe(CN)_6]_2ㆍXH_2O
M. Liu,X.F. Bian,Y.F. Xia,Z. Bao,H.S. Wu,M.X. Xu 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Molecular magnet nickel(II) hexacyanoferrate(III) powder Ni_3[Fe(CN)_6]_2ㆍXH_2O was prepared by coprecipitation method. The coprecipitated powder was annealed in vacuum at different temperatures of 140,and 160 ℃. Water molecules contained in Prussian blue analogues were removed by heating. The annealing of Ni^II ferricyanide induced an inner charge transfer from Ni^II towards Fe^III to form the mixed valence system Ni(II) Ni(III) ferri-ferro-cyanide. Variation of magnetic properties with different annealed temperatures was studied by elemental analysis, powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared, and Mössbauer and magnetization measurements. The differences in magnetic phase transition temperature, coercivity, remanence and effective magnetization are studied. Differences in magnetic properties may be attributed to a partial charge transfer from Ni^II to Fe^III.
Thermodynamic Analysis of Intergranular Additives in Sintered Nd-Fe-B Magnet
X. G. Cui,X. H. Wang,C. Y. Cui,G. C. Yin,C. D. Xia,X. N. Cheng,X. J. Xu 한국자기학회 2017 Journal of Magnetics Vol.22 No.2
To get deeper insight into the effect of intergranular additives in sintered Nd-Fe-B magnet and consequently improve the properties better, the interaction between additives (oxide, nitride, and carbide) and Nd-rich phase in the temperature range of 298.15-1400 K was analyzed thermodynamically. It can be found that the oxide additives became less stable than nitrides and carbides. Except for calcium oxide, almost all oxides could react with Nd from Nd-rich phase. To be different from oxide additives, the mechanism of nitrides and carbides was defined with various elements, either reaction with Nd from Nd-rich phase or not. The two different mechanisms would show different effects on the microstructure and hence properties of magnet. The thermodynamic analysis had a better agreement with the experimental information.
Y.Q. Ni,Y.W. Wang,Y.X. Xia 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.2
Modal identification of civil engineering structures based on ambient vibration measurement has been widely investigated in the past decades, and a variety of output-only operational modal identification methods have been proposed. However, vibration modes, even fundamental low-order modes, are not always identifiable for large-scale structures under ambient vibration excitation. The identifiability of vibration modes, deficiency in modal identification, and criteria to evaluate robustness of the identified modes when applying output-only modal identification techniques to ambient vibration responses were scarcely studied. In this study, the mode identifiability of the cable-stayed Ting Kau Bridge using ambient vibration measurements and the influence of the excitation intensity on the deficiency and robustness in modal identification are investigated with long-term monitoring data of acceleration responses acquired from the bridge under different excitation conditions. It is observed that a few low-order modes, including the second global mode, are not identifiable by common output-only modal identification algorithms under normal ambient excitations due to traffic and monsoon. The deficient modes can be activated and identified only when the excitation intensity attains a certain level (e.g., during strong typhoons). The reason why a few low-order modes fail to be reliably identified under weak ambient vibration excitations and the relation between the mode identifiability and the excitation intensity are addressed through comparing the frequency-domain responses under normal ambient vibration excitations and under typhoon excitations and analyzing the wind speeds corresponding to different response data samples used in modal identification. The threshold value of wind speed (generalized excitation intensity) that makes the deficient modes identifiable is determined.
Extrapolation of extreme traffic load effects on bridges based on long-term SHM data
Y.X. Xia,Y.Q. Ni 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.17 No.6
In the design and condition assessment of bridges, it is usually necessary to take into consideration the extreme conditions which are not expected to occur within a short time period and thus require an extrapolation from observations of limited duration. Long-term structural health monitoring (SHM) provides a rich database to evaluate the extreme conditions. This paper focuses on the extrapolation of extreme traffic load effects on bridges using long-term monitoring data of structural strain. The suspension Tsing Ma Bridge (TMB), which carries both highway and railway traffic and is instrumented with a long-term SHM system, is taken as a testbed for the present study. Two popular extreme value extrapolation methods: the block maxima approach and the peaks-over-threshold approach, are employed to extrapolate the extreme stresses induced by highway traffic and railway traffic, respectively. Characteristic values of the extreme stresses with a return period of 120 years (the design life of the bridge) obtained by the two methods are compared. It is found that the extrapolated extreme stresses are robust to the extrapolation technique. It may owe to the richness and good quality of the long-term strain data acquired. These characteristic extremes are also compared with the design values and found to be much smaller than the design values, indicating conservative design values of traffic loading and a safe traffic-loading condition of the bridge. The results of this study can be used as a reference for the design and condition assessment of similar bridges carrying heavy traffic, analogous to the TMB.
Ni, Y.Q.,Wang, Y.W.,Xia, Y.X. Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.2
Modal identification of civil engineering structures based on ambient vibration measurement has been widely investigated in the past decades, and a variety of output-only operational modal identification methods have been proposed. However, vibration modes, even fundamental low-order modes, are not always identifiable for large-scale structures under ambient vibration excitation. The identifiability of vibration modes, deficiency in modal identification, and criteria to evaluate robustness of the identified modes when applying output-only modal identification techniques to ambient vibration responses were scarcely studied. In this study, the mode identifiability of the cable-stayed Ting Kau Bridge using ambient vibration measurements and the influence of the excitation intensity on the deficiency and robustness in modal identification are investigated with long-term monitoring data of acceleration responses acquired from the bridge under different excitation conditions. It is observed that a few low-order modes, including the second global mode, are not identifiable by common output-only modal identification algorithms under normal ambient excitations due to traffic and monsoon. The deficient modes can be activated and identified only when the excitation intensity attains a certain level (e.g., during strong typhoons). The reason why a few low-order modes fail to be reliably identified under weak ambient vibration excitations and the relation between the mode identifiability and the excitation intensity are addressed through comparing the frequency-domain responses under normal ambient vibration excitations and under typhoon excitations and analyzing the wind speeds corresponding to different response data samples used in modal identification. The threshold value of wind speed (generalized excitation intensity) that makes the deficient modes identifiable is determined.
SYNTHESIS OF POLYBENZONITRILE WITH ULTRAFAST OPTICAL KERR EFFECT
Zhao, X.Y,Xu, Q,He, Y.K,Chen, H.Y,Wang, C.F,Ai, X.C,Xia, Z.J,Zou, Y.H 한국재료학회 1995 Fabrication and Characterization of Advanced Mater Vol.1 No.3
Plasma polymerization of benzonitrile was carried out with RF glow discharge system. The polymer was characterized by FT-IR, UV-VIS, and Elemental Analysis. the molecular weitht was determined by vapor pressure osmometer. for the first time the nonresonant optical Kerr effect(OKE) of plasma polymerized benzonitrile was measured, and a power law dependence of ${\gamma}_{1111}$ on average polymerization degree was discussed. An ultrafast response was also observed.
Development of the 3.7 GHz LHCD System on HL-2A
B. Lu,M. Huang,H. Zeng,X. Y. Bai,X. H. Mao,Z. H. Lu,J. Liang,Z. H. Kang,M. W. Wang,K. Feng,H. Wang,C. Wang,J. Q. Wang,S. Wei,T. Yao,Y. N. Bu,J. Feng,G. Y. Cheng,S. D. Song,D. H. Xia,J. Rao 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8
A 2 MW-3.7 GHz lower hybrid current drive (LHCD) system is under development for physicsexperiments on the HL-2A device. The RF Power is generated by four TH2103A klystron amplifiersand propagates in the TE10 mode through WR284 waveguides. The transmission lines with a lengthof 20 m to 30 m are pressurized with 2 bars of nitrogen to decrease the possibility of arcing. Thelauncher, based on the passive-active multi-junction (PAM) concept, has been developed and iscurrently being realized. It was designed for a power spectrum peaked at Nk = 2.75 with goodcoupling properties over a wide range of plasma parameters. The four klystrons are fed by ahigh-voltage power supply (HVPS) based on the pulse step modulation (PSM) concept with a fastswitch-off time of less than ten μs. This system is expected to be in operation within 1 years and willexplore many international thermonuclear experimental reactor (ITER) related LH experiments inthe following years.