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排序方式: 共有350条查询结果,搜索用时 15 毫秒
261.
Chien‐Pin Chou Aditya Wibawa Sakti Yoshifumi Nishimura Hiromi Nakai 《Chemical record (New York, N.Y.)》2019,19(4):746-757
The density‐functional tight‐binding (DFTB) method is one of the useful quantum chemical methods, which provides a good balance between accuracy and computational efficiency. In this account, we reviewed the basis of the DFTB method, the linear‐scaling divide‐and‐conquer (DC) technique, as well as the parameterization process. We also provide some refinement, modifications, and extension of the existing parameters that can be applicable for lithium‐ion battery systems. The diffusion constants of common electrolyte molecules and LiTFSA salt in solution have been estimated using DC‐DFTB molecular dynamics simulation with our new parameters. The resulting diffusion constants have good agreement to the experimental diffusion constants. 相似文献
262.
Shiraiwa S Ide S Itoh S Mitarai O Naito O Ozeki T Sakamoto Y Suzuki T Takase Y Tanaka S Taniguchi T Aramasu M Fujita T Fukuda T Gao X Gryaznevich M Hanada K Jotaki E Kamada Y Maekawa T Miura Y Nakamura K Nishi T Tanaka H Ushigusa K;JT- Team 《Physical review letters》2004,92(3):035001
A new operational scenario of advanced tokamak formation was demonstrated in the JT-60U tokamak. This was accomplished by electron cyclotron and lower hybrid waves, neutral beam injection, and the loop voltage supplied by the vertical field and shaping coils. The Ohmic heating (OH) solenoid was not used but a small inboard coil (part of the shaping coil), providing less than 20% of total poloidal flux, was used. The plasma thus obtained had both internal and edge transport barriers, with an energy confinement time of 1.6 times H-mode scaling, a poloidal beta of 3.6, and a normalized beta of 1.6, and a large bootstrap current fraction (>90%). This result opens up a possibility to reduce, and eventually eliminate, the OH solenoid from a tokamak reactor, which will greatly improve its economic competitiveness. 相似文献
263.
Kirk A Wilson HR Counsell GF Akers R Arends E Cowley SC Dowling J Lloyd B Price M Walsh M;MAST Team 《Physical review letters》2004,92(24):245002
This Letter provides information on the spatial and temporal structure of periodic eruptions observed in magnetically confined laboratory fusion plasmas, called edge-localized modes (ELMs), and highlights similarities with solar eruptions. Taken together, the observations presented in this Letter provide strong evidence for ELMs being associated with a filamentlike structure. These filaments are extended along a field line, are generated on a 100 micros time scale, erupt from the outboard side, and connect back into the plasma. Such structures are predicted by a theoretical model based on the "ballooning" instability, developed for both solar and tokamak applications. 相似文献
264.
Greenfield CM Burrell KH DeBoo JC Doyle EJ Stallard BW Synakowski EJ Fenzi C Gohil P Groebner RJ Lao LL Makowski MA McKee GR Moyer RA Rettig CL Rhodes TL Pinsker RI Staebler GM West WP;DIII-D Team 《Physical review letters》2001,86(20):4544-4547
A new sustained high-performance regime, combining discrete edge and core transport barriers, has been discovered in the DIII-D tokamak. Edge localized modes (ELMs) are replaced by a steady oscillation that increases edge particle transport, thereby allowing particle control with no ELM-induced pulsed divertor heat load. The core barrier resembles those usually seen with a low (L) mode edge, without the degradation often associated with ELMs. The barriers are separated by a narrow region of high transport associated with a zero crossing in the E x B shearing rate. 相似文献
265.
Hobirk J Wolf RC Gruber O Gude A Günter S Kurzan B Maraschek M McCarthy PJ Meister H Peeters AG Pereverzev GV Stober J Treutterer W;ASDEX Upgrade Team 《Physical review letters》2001,87(8):085002
In the ASDEX Upgrade tokamak, high poloidal beta up to beta(pol) = 3 at the Greenwald density with H-mode confinement has been reached. Because of the high beta, the plasma current is driven almost fully noninductively, consisting of 51% bootstrap and 43% neutral beam driven current. To reach these conditions the discharge is operated at low plasma current ( I(P) = 400 kA) and high neutral beam heating power ( P(NBI) = 10 MW). The discharge combines an edge (H mode) and internal transport barrier at high densities without confinement-limiting MHD activities. The extrapolation to higher plasma currents may offer a promising way for an advanced scenario based fusion reactor. 相似文献
266.
Ryter F Leuterer F Pereverzev G Fahrbach HU Stober J Suttrop W;ASDEX Upgrade Team 《Physical review letters》2001,86(11):2325-2328
Energy transport by the electrons in a tokamak is examined in steady-state and power modulation experiments using electron cyclotron heating. The results are consistent with the assumption that temperature profiles are limited by a critical gradient length, leading to "stiff" profiles. The modulation experiments show that the stiffness factor increases with temperature. They strongly suggest that turbulence driven by the electron temperature gradient may be a dominant mechanism of electron transport. Although possibly not universal, these results are valid under various plasma conditions. 相似文献
267.
Leonid G. Eliseev Alexander V. Melnikov Ludmila I. Krupnik HIBP Team 《Czechoslovak Journal of Physics》2000,50(12):1413-1420
Heavy Ion Beam Probe diagnostics was used to study plasma potential and density in the regimes with improvement in confinement
on the T-10 tokamak. Time-spatial potential distribution was analyzed during the formation of transport barriers. The time
evolution of the potential profile shows simultaneous formation of the internal negative potential well and external layer
with strong Er, during the simultaneous formation of the internal and external transport barriers. The time history of the
plasma potential in the inner region (0.6<ρ<1) shows its clear correlation with theD
α intensity.
Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000.
This work was supported by Russian Basic Research Foundation, Grant No. 99-02-18457. 相似文献
268.
The local measurement of the island width w, around the resonant surface, allowed a direct test of the extended Rutherford model [P. H. Rutherford, PPPL Report-2277 (1985)], describing the evolution of radiation-induced tearing modes prior to disruptions of tokamak plasmas. It is found that this model accounts very well for the observed exponential growth and supports radiation losses as being the main driving mechanism. The model implies that the effective perpendicular electron heat conductivity in the island is smaller than the global one. Comparison of the local measurements of w with the magnetic perturbed field B showed that w proportional to B1/2 was valid for widths up to 18% of the minor radius. 相似文献
269.
Jianjun Gao Choi Look Law Hong Wang Sheel Aditya 《International Journal of Infrared and Millimeter Waves》2002,23(3):345-364
Pseudomorphic high electron mobility transistors (PHEMTs) are very important in millimeterwave application. A simple and accurate method for extracting small-signal equivalent curcuit for Double Heterojunction -doped PHEMT valid up to 40GHz is presented. First, the parasitic parameters of the equivalent circuit are determined using pinch off PHEMT except for PAD capacitances. The initial intrinsic elements are then determined by conventional analytical method. Advanced Design System is then used to optimize the whole model parameters with very small dispersion of initial values. Good agreement is obtained between simulation results and measured results for a 0.25um DH PHEMT. 相似文献
270.
Park HK Donné AJ Luhmann NC Classen IG Domier CW Mazzucato E Munsat T van de Pol MJ Xia Z;TEXTOR Team 《Physical review letters》2006,96(19):195004
High temporal and spatial resolution two-dimensional (2D) images of electron temperature fluctuations were employed to study the sawtooth oscillation in the Toroidal Experiment for Technically Oriented Research tokamak plasmas. The 2D images are directly compared with the expected 2D patterns of the plasma pressure (or electron temperature) from various theoretical models. The observed experimental 2D images are only partially in agreement with the expected patterns from each model: The image of the initial reconnection process is similar to that of the ballooning mode model. The intermediate and final stages of the reconnection process resemble those of the full reconnection model. The time evolution of the images of the hot spot or island is partially consistent to those from the full reconnection model but is not consistent with those from the quasi-interchange model. 相似文献