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Measurements of synchrotron radiation emitted by 30-MeV runaway electrons in the TEXTOR-94 tokamak show that the runaway population decays after switching on neutral beam injection (NBI). The decay starts only with a significant delay, which decreases with increasing NBI heating power. This delay provides direct evidence of the energy dependence of runaway confinement, which is expected if magnetic modes govern the loss of runaways. Application of the theory by Mynick and Strachan [Phys. Fluids 24, 695 (1981)] yields estimates for the "mode width" (delta) of magnetic perturbations: delta<0.5 cm in Ohmic discharges, increasing to delta = 4.4 cm for 0. 6 MW NBI. 相似文献
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Deyonker NJ Peterson KA Steyl G Wilson AK Cundari TR 《The journal of physical chemistry. A》2007,111(44):11269-11277
The correlation consistent Composite Approach (ccCA), which has been shown to achieve chemical accuracy (+/-1 kcal mol-1) for a large benchmark set of main group and s-block metal compounds, is used to compute enthalpies of formation for a set of 17 3d transition metal species. The training set includes a variety of metals, ligands, and bonding types. Using the correlation consistent basis sets for the 3d transition metals, we find that gas-phase enthalpies of formation can be efficiently calculated for inorganic and organometallic molecules with ccCA. However, until the reliability of gas-phase transition metal thermochemistry is improved, both experimentally and theoretically, a large experimental training set where uncertainties are near +/-1 kcal mol-1 (akin to commonly used main group benchmarking sets) remains an ambitious goal. For now, an average deviation of +/-3 kcal mol-1 appears to be the initial goal of "chemical accuracy" for ab initio transition metal model chemistries. The ccCA is also compared to a more robust but relatively expensive composite approach primarily utilizing large basis set coupled cluster computations. For a smaller training set of eight molecules, ccCA has a mean absolute deviation (MAD) of 3.4 kcal mol-1 versus the large basis set coupled-cluster-based model chemistry, which has a MAD of 3.1 kcal mol-1. However, the agreement for transition metal complexes is more system dependent than observed in previous benchmark studies of composite methods and main group compounds. 相似文献
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Bose-Einstein condensation in a gas of sodium atoms 总被引:2,自引:0,他引:2
Davis KB Mewes M Andrews MR van Druten NJ Durfee DS Kurn DM Ketterle W 《Physical review letters》1995,75(22):3969-3973
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The conformational behavior of oxalyl chloride has been investigated using ab initio Hartree-Fock (HF) and second-order Moller-Plesset (MP2) perturbation theories, and the coupled-cluster singles and doubles method appended with a perturbative inclusion of connected triple excitations [CCSD(T)]. Correlation consistent polarized valence quadruple-zeta (cc-pVQZ) and quintuple-zeta (cc-pV5Z) basis sets were used in this research. At the cc-pVQZ and cc-pV5Z HF levels, there is no stationary point corresponding to a stable gauche conformer. On the other hand, at the cc-pVQZ and cc-pV5Z MP2 levels and with the cc-pVQZ CCSD(T) method, the gauche conformer of oxalyl chloride was found at O[Double Bond]C-C[Double Bond]O dihedral angles of 81.9 degrees , 79.4 degrees , and 83.4 degrees , respectively. At the cc-pV5Z MP2 level, the energy barrier from trans to gauche was predicted to be 0.74 kcal mol(-1) and that from gauche to trans to be 0.09 kcal mol(-1). Thus, the potential-energy surface along the O[Double Bond]C-C[Double Bond]O torsional mode is exceedingly flat. The existence of the gauche conformation is mainly due to the minimization of steric repulsion. 相似文献
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A new approach to on-line oxygen isotope analysis has been developed which utilises existing elemental analyser and mass spectrometry technology to produce a sample of carbon dioxide gas for oxygen isotople analysis. The method relies on on-line high temperature pyrolysis of the sample over a carbon source followed by a rapid, non-contributive partial catalytic oxidation over nickel powder at between 550 and 600 degrees C. Initial results demonstrate both good precision (better than 0.2 per thousand) and accuracy for both cellulose and silver nitrate samples. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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谢崇进 《中国光学快报(英文版)》2010,(9):844-851
Using numerical simulations, the nonlinear transmission performance of polarization-division-multiplexed quadrature-phase-shift-keying (PDM-QPSK) coherent systems is studied. It is found that inter-channel cross-polarization modulation (XPolM) induced nonlinear polarization scattering can significantly degrade the transmission performance of PDM-QPSK coherent systems and change the perspective of dispersion management in optical coherent transmission systems. Some techniques to mitigate nonlinear polarization scattering in dispersion-managed PDM coherent transmission systems are discussed, including the use of time-interleaved return-to-zero (RZ) PDM formats, the use of periodic-group-delay PGD dispersion compensators, and the judicious addition of some polarization-mode-dispersion (PMD) in the transmission link. It is shown that if nonlinear polarization scattering can be well mitigated, a polarization multiplexed optical coherent transmission system with dispersion management could perform better than that without it. 相似文献
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Tingye Li AT&T Middletown NJ USA Zisen Zhao Wuhan Research Institute of Post Telecommunications Fiberhome Wuhan ChinaJianjun Yu ZTE USA Inc. wood ave. south FL Iselin NJ USA ZTE Inc. Beijing China 《中国光学快报(英文版)》2010,(9):815-815
<正>Fiber optics underpins the communications infrastructure for the information society today. Cables consisting of hair-like fibers speed data around the globe in the form of rapid pulses of light. Modern telecom 相似文献