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排序方式: 共有316条查询结果,搜索用时 15 毫秒
91.
92.
J.W. Cipolla T.F. Morse 《Journal of Quantitative Spectroscopy & Radiative Transfer》1979,22(4):365-388
A resonance transition in a one-dimensional layer of gas contained between transparent parallel plates and optically excited by external radiation has been treated using kinetic theory. A perturbation method has been used to obtain the “first scattering” results for the velocity distribution and number density of excited atoms and the intensity of radiation at any point in the gas. Two special cases are discussed in detail: broad band excitation with inhomogeneous broadening and monochromatic excitation with homogeneous broadening. The effects of particle streaming and wall quenching are shown to produce boundary layer behavior in the excited level density which scales with the particle mean free path. In addition, line reversal of the radiation reemited from the gas is shown to occur and to be a direct result of particle streaming. Numerical and asymptotic results are presented which show these effects. These results should be pertinent to many laboratory and industrial devices in which the particle and photon mean free paths are comparable and to diagnostic techniques which use resonance fluorescence to infer excited level densities. 相似文献
93.
94.
Marston Morse 《Annali di Matematica Pura ed Applicata》1960,49(1):117-128
Summary Let M be a compact differentiable m-manifold of class Cm in En, n=2m+1. Let x=(x1, ..., xn) represent a point in En. The union of the direction c on the direction sphere Sn−1 in En such that the scalar product c · x defines a non-degenerate fonction on M is an open subset of Sn−1 whose complement θ has a Lebesgue measure zero on Sn−1. When M is non-compact θ can be everywhere dense on Sn−1, but still has Lebesgue measure zero.
To Giovanni Sansone on his 70th birth day. 相似文献
95.
The presence of ? 5% chemical impurities in Rhodamine 6G [Cl-] is shown to decrease the fluorescence quantum efficiency, increase the self-absorption cross-section, reduce lasing efficiency and shorten the usable lifetime of the lasing solution. 相似文献
96.
97.
Impulse backscattering measurements by a thick-walled finite cylindrical shell are examined in the time-frequency domain to identify and characterize individual ray contributions from generalized Lamb waves excited on the shell. Previous experiments and analysis in the frequency-aspect angle domain [S. F. Morse et al., J. Acoust. Soc. Am. 103, 785-794 (1998)] indicate that large backscattering enhancements occur in the midfrequency region for the shell tilted at large angles. Presently this experimental data is examined in the time-frequency domain for selected angles of incidence. Individual ray contributions are evident and their evolution over aspect angle is discussed. The most prominent contribution is due to the meridional ray of the a0 leaky Lamb wave. This feature distinctly highlights the truncation of the shell and is found over a range of aspect angles spanning 200 degrees for the frequencies examined. Also observed are periodic features corresponding to end-reflected helical waves of the a0-. These scattering features are significantly different from those reported for thin-walled finite cylinders at low frequencies. The present results may be useful for target identification and localization and as a comparison tool for high-frequency computational scattering models. 相似文献
98.
Bennett GW Bousquet B Brown HN Bunce G Carey RM Cushman P Danby GT Debevec PT Deile M Deng H Deninger W Dhawan SK Druzhinin VP Duong L Efstathiadis E Farley FJ Fedotovich GV Giron S Gray FE Grigoriev D Grosse-Perdekamp M Grossmann A Hare MF Hertzog DW Huang X Hughes VW Iwasaki M Jungmann K Kawall D Khazin BI Kindem J Krienen F Kronkvist I Lam A Larsen R Lee YY Logashenko I McNabb R Meng W Mi J Miller JP Morse WM Nikas D Onderwater CJ Orlov Y Ozben CS Paley JM Peng Q Polly CC Pretz J Prigl R 《Physical review letters》2002,89(10):101804
A higher precision measurement of the anomalous g value, a(mu)=(g-2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron, based on data collected in the year 2000. The result a(mu(+))=11 659 204(7)(5)x10(-10) (0.7 ppm) is in good agreement with previous measurements and has an error about one-half that of the combined previous data. The present world average experimental value is a(mu)(expt)=11 659 203(8)x10(-10) (0.7 ppm). 相似文献
99.
Marston D. E. Conder Tomaž Pisanski Arjana Žitnik 《Journal of Algebraic Combinatorics》2014,40(1):209-231
The class of generalized Petersen graphs was introduced by Coxeter in the 1950s. Frucht, Graver and Watkins determined the automorphism groups of generalized Petersen graphs in 1971, and much later, Nedela and ?koviera and (independently) Lovre?i?-Sara?in characterised those which are Cayley graphs. In this paper we extend the class of generalized Petersen graphs to a class of GI-graphs. For any positive integer n and any sequence j 0,j 1,…,j t?1 of integers mod n, the GI-graph GI(n;j 0,j 1,…,j t?1) is a (t+1)-valent graph on the vertex set \(\mathbb{Z}_{t} \times\mathbb{Z}_{n}\) , with edges of two kinds:
- an edge from (s,v) to (s′,v), for all distinct \(s,s' \in \mathbb{Z}_{t}\) and all \(v \in\mathbb{Z}_{n}\) ,
- edges from (s,v) to (s,v+j s ) and (s,v?j s ), for all \(s \in\mathbb{Z}_{t}\) and \(v \in\mathbb{Z}_{n}\) .
100.
Marston PL 《The Journal of the Acoustical Society of America》2011,130(3):1091-1094
A superposition of propagating Bessel beams was recently numerically demonstrated to approximate a Gaussian beam and was used to evaluate the scattering by a sphere centered on the focal point of the beam. An analytical beam synthesis used in optics by Agrawal and Pattanayak [J. Opt. Soc. Am. 69, 575-578 (1979)] is found here to be recovered as the weak focusing limit of the quasi-Gaussian beam when evanescent contributions are omitted from the analytical synthesis. The propagating-wave part of the analytical synthesis has similarities to, and differences from, the recent quasi-Gaussian approximation. 相似文献