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Overview of KSTAR research progress and future plans toward ITER and K-DEMO
Park, H.K.,Choi, M.J.,Hong, S.H.,In, Y.,Jeon, Y.M.,Ko, J.S.,Ko, W.H.,Kwak, J.G.,Kwon, J.M.,Lee, J.,Lee, J.H.,Lee, W.,Nam, Y.B.,Oh, Y.K.,Park, B.H.,Park, J.K.,Park, Y.S.,Wang, S.J.,Yoo, M.,Yoon, S.W.,B IOP 2019 Nuclear fusion Vol.59 No.11
<P>A decade-long operation of the Korean Superconducting Tokamak Advanced Research (KSTAR) has contributed significantly to the operation of superconducting tokamak devices and the advancement of tokamak physics which will be beneficial for the ITER and K-DEMO programs. Even with limited heating capability, various conventional as well as new operating regimes have been explored and have achieved improved performance. As examples, a long pulse high-confinement mode operation with and without an edge-localized mode (ELM) crash was well over 70 and 30 s, respectively. The unique capabilities of KSTAR allowed it to improve the capability of controlling harmful instabilities, and they have been instrumental in uncovering much new physics. The highlights are that the L/H transition threshold power is sensitive to the resonant magnetic perturbation (RMP) and insensitive to non-resonant magnetic perturbation. Co-<I>I</I> <SUB>p</SUB> offset rotation dominated by an electron channel predicted by general neoclassical toroidal viscosity theory was confirmed. Improved heat dispersal in a divertor system using three rows of rotating RMP was demonstrated and predictive control of the ELM-crash with <I>a priori</I> modeling was successfully tested. In magnetohydrodynamic physics, validation of the full reconnection model (i.e. <I>q</I> <SUB>0</SUB> > 1 right after the sawtooth crash) and self-consistent validation of the anisotropic distribution of turbulence amplitude and flow in the presence of the 2/1 island with theoretical models were achieved. The turbulence amplitude induced by RMP was linearly increased with the slow RMP coil current ramp-up time (i.e. the magnetic diffusion time scale). The <I>D</I> <SUB> <I>α</I> </SUB> spikes (i.e. ELM-crash amplitude) was linearly decreased with the turbulence amplitude and not correlated with the perpendicular electron flow. In the turbulence area, a non-diffusive ‘avalanche’ transport event and the role of a quiescent coherent mode in confinement were studied. To accommodate the anticipation of a higher performance of the KSTAR plasmas with the increased heating powers, a new divertor/internal interface with a full active cooling system will be implemented after a full test of the new heating (neutral beam injection II and electron cyclotron heating) and current drive (CD) (Helicon and lower hybrid CD) systems. An upgrade plan for the internal hardware, heating systems and efficient CD system may allow for a long pulse operation of higher performance plasmas at <I>β</I> <SUB>N</SUB> > 3.0 with <I>f</I> <SUB>bs</SUB> ~ 0.5 and <I>T</I> <SUB>i</SUB> > 10 keV.</P>
Effect of Temperature on Mechanical Anisotropy of Zircaloy-4 Sheet
Wang, Y .,Murty, K . L . 대한금속재료학회(대한금속학회) 1998 METALS AND MATERIALS International Vol.4 No.4
The effect of test temperature on the mechanical anisotropy parameters of Zircaloy-4 sheet was investigated using grilled tensile samples. The anisotropy parameters R and P were determined from tensile tests along the rolling (RD) and transverse (TD) directions respectively. Tests were carried out at a cross-head speed of 2.54 × 10^(-3) mm/s for various temperatures in the. range of ambient to 828 K. It was observed that the R parameter was essentially constant with a value of around 1.5. P parameter was constant in the range of ambient to 600 K with a value of around 2.8 while it decreased at higher temperatures to a value of around 1.
Wang, Y.P.,Xu, Q.,Huang, D.P.,Zhao, K.,Chen, M.,Kim, B.H. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.15
<P>The electrical conducting, thermal expansion and electrochemical properties of La1.8Sr0.2NiO4+delta were investigated in view of cathode utilization for intermediate temperature solid oxide fuel cells. La1.8Sr0.2NiO4+delta exhibited electrical conductivities of 96 -114 S cm(-1) at 600-800 degrees C and a thermal expansion coefficient of 12.6 x 10(-6) K-1 between 50 and 1000 degrees C. Based on a three-electrode half cell, the electrode properties of La1.8Sr0.2NiO4+delta were diagnosed using electrochemical impedance spectroscopy and chronopotentiometry techniques. Moreover, the, performance of an anode-supported single cell with La1.8Sr0.2NiO4+delta cathode was examined. Compared with La2NiO4+delta, La1.8Sr0.2NiO4+delta manifested improved electrode properties under cathodic polarization conditions while showing an analogous catalytic activity under open-circuit conditions. At 800 degrees C in air, La1.8Sr0.2NiO4+delta electrode displayed a polarization resistance of 0.41 0 cm(2) and a cathodic overpotential of 90 mV at 200 mA cm(-2). The anode-supported single cell with La1.8Sr0.2NiO4+delta cathode achieved a maximum power density of 520 mW cm(-2) at 800 degrees C in hydrogen fuel. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>
Wang, L.,Song, T.K.,Lee, S.C.,Cho, J.H.,Sung, Y.S.,Kim, M.H.,Choi, K.S. Elsevier 2010 CURRENT APPLIED PHYSICS Vol.10 No.4
Lead-free 0.79(Bi<SUB>0.5</SUB>Na<SUB>0.5</SUB>)TiO<SUB>3</SUB>-0.14[Bi<SUB>0.5</SUB>(K<SUB>0.5-x</SUB>Li<SUB>x</SUB>)]TiO<SUB>3</SUB>-0.07BaTiO<SUB>3</SUB> (BNBK79+xLi, x=0.0, 0.1, 0.2, 0.25, 0.3, and 0.4) ceramics were prepared by conventional solid state reaction process. The crystalline structures and surface morphologies are investigated by X-ray diffraction method and scanning electron microscopy. Dielectric and piezoelectric properties were measured. With increasing of lithium substitution, the Curie temperatures of BNBK79+xLi ceramics increase, but the maximum value of the dielectric constant decreases. And a relatively large remnant polarization of 17.6μC/cm<SUP>2</SUP> and 157pC/N of d<SUB>33</SUB> has been obtained when x=0.3.
A theoretical note on mode-I crack branching and kinking
Xie, Y.J.,Hu, X.Z.,Wang, X.H.,Chen, J.,Lee, K.Y. Pergamon Press ; Elsevier Science Ltd 2011 Engineering fracture mechanics Vol.78 No.6
An energy-based fracture mode has been derived for the mode-I crack branching and kinking. The classic J<SUB>i</SUB>-integral has been further explored by a new partial integral path and the analytical solution of the energy release rate for crack branching and kinking from a mode-I crack tip has been established. The crack branching/kinking angle has also been analytically derived. It shows that the Griffith's theorem and conservation law can be applied to both mode-I crack extension and mode-I crack branching and kinking. The branching mechanism for quasi-static mode-I crack has been theoretically investigated. The branching toughness and the K-based criterion for crack branching have been defined. The crack branching phenomena predicted by the present model are in well agreement with the experimental observations reported in the literatures.
Kang, J.S.,Park, J.M.,Jung, L.,Kim, S.K.,Wang, J.,Lee, C.Y.,Na, D. H.,Im, K.,Na, Y.-S.,Hwang, Y.S. IOP 2017 Nuclear fusion. Fusion nucléaire. &n.Illiga Vol.57 No.12
<P>An optimum plasma pressure/current density profile and corresponding heating/current drive (H/CD) determination scheme is newly developed by integrating equilibrium, stability, confinement, and H/CD, self-consistently subject to maximize the fusion gain for Korean fusion demonstration reactor (K-DEMO) steady-state operation scenarios. The integrated plasma modeling package, FASTRAN/IPS, is adopted for the integrated numerical apparatus. The target pressure profile with a pedestal structure is investigated by varying its peaking, pedestal height and width as a first step. Formation of stable equilibria is evaluated by solving the Grad–Shafranov equation and checking linear MHD stability. For the case of potentially stable equilibrium, required external heating distribution is calculated by considering both power balance and external current drive alignment to reproduce the pressure profile of the stable equilibrium. Electron/ion temperature and poloidal flux evolutions are solved with the derived heating configuration to find a steady-state scenario and achieve self-consistent plasma profiles. A self-consistent target steady-state pressure and current profile parameters are proposed through designed systematic algorithm with fusion power <I>P</I> <SUB>F</SUB> = 2070 MW, fusion gain <I>Q</I> = 19.7, and normalized beta <I>β</I> <SUB>N</SUB> = 2.8 at toroidal field <I>B</I> <SUB>T</SUB> = 7.4 T and plasma current <I>I</I> <SUB>P</SUB> = 15.5 MA. Feasibility of fusion power <I>P</I> <SUB>F</SUB> = 3000 MW operation is also explored with enhanced density and temperature limit assumption.</P>
Lu, F.,Lim, C.S.,Nam, D.H.,Kim, K.,Lin, K.,Kim, T.S.,Lee, H.W.,Chen, J.H.,Wang, Y.,Sattabongkot, J.,Han, E.T. Verlag für Recht und Gesellschaft ; Elsevier 2011 Acta Tropica Vol.117 No.2
Treatment failure of chloroquine for Plasmodium vivax infection has increased in endemic countries. However, the molecular mechanisms for resistance and in vitro susceptibility of P. vivax to chloroquine remain elusive. We investigated the prevalence of mutations in the pvmdr1 and pvcrt-o genes, and the copy number of the pvmdr1 gene in isolates from the Republic of Korea (ROK), Thailand, the Union of Myanmar (Myanmar), and Papua New Guinea (PNG). We also measured in vitro susceptibility of Korean isolates to antimalarial drugs. The pvmdr1 analysis showed that mutations at amino acid position Y976F of pvmdr1 were found in isolates from Thailand (17.9%), Myanmar (13.3%), and PNG (100%), but none from the ROK, and mutation at position F1076L was present in isolates from the ROK (100%), Thailand (60.7%), and Myanmar (46.7%). One copy of the pvmdr1 gene was observed in most isolates and double copy numbers of the gene were observed in two Thai isolates. In the exons of the pvcrt-o gene that were sequenced, a K10 insertion was present in isolates from Thailand (56.0%) and Myanmar (46.2%), and the wild type was found in all Korean isolates. The results suggest that gene polymorphisms and copy number variation was observed in isolates of P. vivax from Southeast Asian countries. In Korean isolates polymorphism as limited to the F1076L variant, and no isolates with high level of resistance were found by in vitro susceptibility determinations. Moreover, our results provide a baseline for future prospective drug studies in malaria-endemic areas.