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991.
Yoshio Tatamitani Akinori Sato Yoshiyuki Kawashima Nobukimi Ohashi James M. LoBue Eizi Hirota 《Journal of Molecular Spectroscopy》2009,257(1):11-19
The rotational spectra of three isotopomers of the Ar–dimethyl sulfide (DMS) complex – normal, 34S, and 13C species – were measured in the frequency region from 3.7 up to 24.1 GHz by Fourier transform microwave spectroscopy. The normal species yielded 43 a-type and 79 c-type transitions. No Ar tunneling splitting was observed, while many transitions were split by the internal rotation of the two methyl tops of the DMS unit. In cases where the K-type splitting was close to that due to methyl internal-rotation, several forbidden transitions were observed that followed b-type selection rules. All of the observed transition frequencies were analyzed simultaneously using a phenomenological Hamiltonian also used in previously published work describing the Ar–dimethyl ether (DME) and Ne–DME complexes. The rotational and centrifugal distortion constants and the potential barrier height to methyl-top internal rotation, V3, were determined. The rotational constants were consistent with an Ar–DMS center of mass (cm) distance of 3.796 (3) Å and a S–cm–Ar angle of 104.8 (2)°. The V3 potential barrier obtained, 736.17 (32) cm−1, was 97.8% of the DMS monomer barrier. By assuming a Lennard–Jones-type potential, the dissociation energy was estimated to be 2.4 kJ mol−1, which was close to the value for Ar–DME, 2.5 kJ mol−1. 相似文献
992.
Nicolae Aldea Rodica Turcu Alexandrina Nan Izabella Craciunescu Ovidiu Pana Xie Yaning Zhonghua Wu Doina Bica Ladislau Vekas Florica Matei 《Journal of nanoparticle research》2009,11(6):1429-1439
In this article, we focus on the structural peculiarities of nanosized Fe3O4 in the core-shell nanocomposites obtained by polymerization of conducting polypyrrole shell around Fe3O4 nanoparticles. The local structure of Fe atoms was determined from the Extended X-ray Absorption Fine Structure analysis
using our own package computer programs. An X-ray diffraction method that is capable to determine average particle size, microstrains,
as the particle size distribution of Fe3O4 nanoparticles is presented. The method is based on the Fourier analysis of a single X-ray diffraction profile using a new
fitting method based on the generalized Fermi function facilities. The crystallites size obtained by X-ray diffraction spectra
analysis was estimated between 3.2 and 10.3 nm. Significant changes in the first and the second Fe coordination shell in comparison
with standard bulk were observed. The global and local structure of the nanosized Fe3O4 are correlated with the synthesis conditions of the core-shell polypyrrole nanocomposites. 相似文献
993.
Sequences of experimental ground-state energies for both odd and even A are mapped onto concave patterns cured from convexities due to pairing and/or shell effects. The same patterns, completed by a list of excitation energies, give numerical estimates of the grand potential Ω(β,μ) for a mixture of nuclei at low or moderate temperatures T=β−1 and at many chemical potentials μ. The average nucleon number A(β,μ) then becomes a continuous variable, allowing extrapolations towards nuclear masses closer to the drip lines. We study the possible concavity of several thermodynamical functions, such as the free energy and the average energy, as functions of A. Concavity, which always occurs for the free energy and is usually present for the average energy, allows easy interpolations and extrapolations providing upper and lower bounds, respectively, to binding energies. Such bounds define an error bar for the prediction of binding energies. Finally we show how concavity and universality are related in the theory of the nuclear density functional. 相似文献
994.
Mathematical models with stage structures are proposed to describe the process of awareness, evaluation and decision-making. First, a system of ordinary differential equations is presented that incorporates the awareness stage and the decision-making stage. If the adoption rate is bilinear and imitations are dominant, we find a threshold above which innovation diffusion is successful. Further, if the adoption rate has a higher nonlinearity, it is shown that there exist bistable equilibria and a region such that an innovation diffusion is successful inside and is unsuccessful outside. Secondly, a model with a time delay is proposed that includes an evaluation stage of a product. It is proved that the system exhibits stability switches. The bifurcation direction of equilibria is also discussed. 相似文献
995.
The problem of a particle impacting on a wall, a common phenomenon in particle-laden flows in the minerals and process industries, is investigated computationally using a spectral-element method with the grid adjusting to the movement of the particle towards the wall. Remeshing is required at regular intervals to avoid problems associated with mesh distortion and the constantly reducing maximum time-step associated with integration of the non-linear convective terms of the Navier–Stokes equations. Accurate interpolation between meshes is achieved using the same high-order interpolation employed by the spectral-element flow solver. This approach allows the full flow evolution to be followed from the initial approach, through impact and afterwards as the flow relaxes. The method is applied to the generic two-dimensional and three-dimensional bluff body geometries, the circular cylinder and the sphere. The principal case reported here is that of a particle colliding normally with a wall and sticking. For the circular cylinder, non-normal collisions are also considered. The impacts are studied for moderate Reynolds numbers up to approximately 1200. A cylindrical body impacting on a wall produces two vortices from its wake that convect away from the cylinder along the wall before stalling while lifting induced wall vorticity into the main flow. The situation for a sphere impact is similar, except in this case a vortex ring is formed from the wake vorticity. Again, secondary vorticity from the wall and particle plays a role. At higher Reynolds number, the secondary vorticity tends to form a semi-annular structure encircling the primary vortex core. At even higher Reynolds numbers, the secondary annular structure fragments into semi-discrete structures, which again encircle and orbit the primary core. Vorticity fields and passive tracer particles are used to characterize the interaction of the vortical structures. The evolution of the pressure and viscous drag coefficients during a collision are provided for a typical sphere impact. For a Reynolds number greater than approximately 1000 for a sphere and 400 for a cylinder, the primary vortex core produced by the impacting body undergoes a short-wavelength instability in the azimuthal/spanwise direction. Experimental visualisation using dye carried out in water is presented to validate the predictions. 相似文献
996.
§1.IntroductionConsidera11tensorfieldIonasmoothmanifoldM.Thenaturalgeneralizationofthecomplexstructureandparacomplexstructu... 相似文献
997.
Xiao-ping YANG 《Frontiers of Physics》2009,4(3):280
The fantastic variation of the physical properties of carbon nanotubes (CNTs) and their bundles under mechanical strain and hydrostatic pressure makes them promising materials for fabricating nanoscale electromechanical coupling devices or transducers. In this paper, we review the recent progress in this field, with much emphasis on our first-principles numerical studies on the structural and vibrational properties of the deformed CNTs under uniaxial and torsional strains, and hydrostatic pressure. The nonresonant Raman spectra of the deformed CNTs are also introduced, which are calculated by the first-principles calculations and the empirical bond polarizability model. 相似文献
998.
研究了半结晶聚合物交联聚乙烯的聚集态和陷阱等对真空沿面闪络特性的影响.交联聚乙烯(XLPE)在135℃下恒温10min后,分别经过-56℃,-25℃淬火处理,自然降温,或1℃/min,0.5℃/min慢速降温等热处理过程,测量了热处理后试样的电气性能、显微结构、陷阱分布和真空中的沿面闪络特性.实验结果表明,与未热处理试样相比,热处理试样的直流闪络电压最高提高了76%,脉冲闪络电压最高提高了19%.认为热处理改变了XLPE试样的聚集态和陷阱,从而提高了XLPE试样的真空沿面闪络性能,提出了可以通过控制半结晶聚合物的聚集态和缺陷结构提高其真空沿面闪络性能. 相似文献
999.
1000.
A new eight-dimensional Lie superalgebra and two corresponding hierarchies of evolution equations 下载免费PDF全文
A new eight-dimensional Lie superalgebra is constructed
and two isospectral problems with six potentials are designed.
Corresponding hierarchies of nonlinear evolution equations, as well
as super-AKNS and super-Levi, are derived. Their super-Hamiltonian
structures are established by making use of the supertrace identity,
and they are integrable in the sense of Liouville. 相似文献