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排序方式: 共有164条查询结果,搜索用时 15 毫秒
91.
W. A. HERREBOUT B. J. VAN DER VEKEN A. MEDINA A. CALVO HERNÁNDEZ M. O. BULANIN 《Molecular physics》2013,111(7):1115-1124
New experimental results are reported on the relative absorption intensity distribution in the FIR spectra of HCl dissolved in liquefied Ar, Kr, and Xe at several temperatures along the liquid—vapour coexistence curve. These are treated further by applying a previously developed quantum-statistical spectral theory, which accounts for the line mixing and memory effects. Theoretical spectra are given in terms of the anisotropic potential time autocorrelation functions obtained from classical MD simulations using several empirical analytical potentials with density-adjusted well depths. Globally fair agreement between the theoretical and experimental spectra is demonstrated, except in the high frequency wings, where the theory underestimates the observed intensities. The choice of a particular radial form for the anisotropic HCl/RG potentials is found to be not critical for reproducing the experimental absorption profiles. 相似文献
92.
HUNG THANH LE PHAM CAM NAM VAN LUONG DAO TAMÁS VESZPRÉMI MINH THO NGUYEN 《Molecular physics》2013,111(15):2347-2355
Quantum chemical calculations using molecular orbital (HF, CASSCF) and density functional theory (B3LYP) methods, in conjunction with the 6–311 + + G(d,p) basis set, have been applied to investigate the molecular and electronic structure of two diamino-meta-quinonoid molecules 1a and 2a, each containing a six-membered ring coupled with two exocyclic C = O bonds situated in a meta position, along with two amino substituents (NH2 and NH-CH3). It is confirmed that these substituted meta-quinone systems exhibit a zwitterionic structure in which the positively charged N-C-C(H)-C-N subunit, containing the two amino-groups, forms two chemical bonds with the negatively charged O-C-C(H)-C-O subunit. The negative charge amounts to about half of an electron. The charge separation has been approached in terms of geometries, vibrational frequencies, and electronic distribution. The ionization energy for molecule 1a is about 7.8±0.3eV. The quinonoid systems are essentially non-aromatic characterized by the NICS(+1) values of around 1.2 ppm. 相似文献
93.
94.
Analytical chemistry does play a key role in the chemical characterization of the environment and it appears that X-ray spectrometry,
in its many forms, is one of the most relevant analytical techniques in preventive conservation, as it is in cultural heritage
research in general. X-ray spectrometry has indeed been the method of choice for the characterization of the inorganic composition
of atmospheric aerosols, for a long time. 相似文献
95.
Elementary properties of the Koornwinder--Macdonald multivariable Askey--Wilson polynomials are discussed. Studied are the orthogonality, the difference equations, the recurrence relations, and the orthonormalization constants for these polynomials. Essential in our approach are certain commuting difference operators simultaneously diagonalized by the polynomials. 相似文献
96.
97.
ASSESSING UNCERTAINTY IN A MULTISPECIES AGE‐STRUCTURED ASSESSMENT FRAMEWORK: THE EFFECTS OF DATA LIMITATIONS AND MODEL ASSUMPTIONS
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KRAY F. VAN KIRK TERRANCE J. QUINN II JEREMY S. COLLIE Z. T. A'MAR 《Natural Resource Modeling》2015,28(2):184-205
Performance of a multispecies age‐structured assessment (MSASA) model in the Gulf of Alaska (GOA) relative to changes in data and model assumptions was examined through simulation exercises. Species included arrowtooth flounder (Atheresthes stomias), Pacific cod (Gadus macrocephalus), walleye pollock (Theragra chalcogramma), Pacific halibut (Hippoglossus stenolepis), and Steller sea lion (Eumetopias jubatus). Age‐specific predation mortality was estimated as a flexible function of predator and prey abundances and fitted to diet data. Simulated data sets were constructed by applying random error to estimates of catch, survey, and diet data from an operating model, whose structure was identical to that of the estimating model. Simulations explored the effects of data variability, mismatched assumptions regarding model structure, and lack of diet data on model performance. Model misspecification and uninformative diet data had the greatest influence on model performance. Given the current emphasis on the development of ecosystem‐based models and management, prioritizing the rigorous sampling of diet data would best facilitate the development of predation models useful to management agencies. 相似文献
98.
A regular perturbation technique is employed to approximate the solution for fluid infiltration from a circular opening into an unsaturated medium. Introducing two empirical constitutive relations
and
relating the permeability k and water content with pore fluid pressure p, a nonlinear diffusion equation in terms of pore pressure is established. After rearranging the nonlinear diffusion equation, a parameter perturbation on
is performed and an approximate solution with an error of
is obtained, which correlate to a condition in which = . This approximate solution is verified by a finite difference solution and compared also with a linear solution in which the diffusivity is constant. It is shown that the perturbation solution with terms up to and including first-order can give a reasonably accurate solution for the parameter range for p
0 selected in this paper. The solution procedure provided in this paper also avoids the numerical problem normally encountered for a small time solution. The solution may also be used to overcome difficulties arising in solution procedure by the similarity transformation (Boltzmann), commonly conducted on diffusion equation, which cannot be applied for a finite wellbore problem. 相似文献
99.
100.
XIE Hai-ming YAN Xue-dong YU Hai-ying ZHANG Ling-yun YANG Gui-ling XU Yang WANG Rong-shun **. Department of Chemistry Northeast Normal University Changchun P. R. China . Department of Chemistry Inner Mongolia University for Nationalities Tongliao P. R. China 《高等学校化学研究》2006,22(5):639-642
IntroductionLithium ion batteries have attracted a great interestbecause of their commercial applications in portable de-vices[1,2].Great efforts have been made to improve theenergy density of new anode materials.For example,Sn-based compounds,such as SnO… 相似文献