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51.
The new theory of sporadic E density oscillation with double atmospheric gravity wave (AGW) frequency in two-dimensional case taking into account ions ambipolar diffusion is presented. It is found that densities of multi-layered sporadic E, formed under the influence of atmospheric vortical perturbation (with vertical wavelength λz≠0) evolving in the horizontal shear flow (shear wave), can oscillate with up to double Brunt-Väisälä frequency under the action of short-period AGW, in which shear wave is transformed. The formation of multi-layered sporadic E (inside regions with vertical thickness about λz/2) and its density changes in every half AGW period close to ions convergence region occur by combined action of ion-neutral collision and Lorentz forcing and can cause additional accumulation of ions responsible for sporadic E density oscillation with double AGW frequency. 相似文献
52.
Z. Hadjou Bélaid S. Ben Mansour D. Boroguiaa A. Boubris L. Benhabib F. Z. Benkhaled 《Journal of Macromolecular Science: Physics》2020,59(11):686-696
AbstractThis work examines the development and characterization of tripropylene glycol di-acrylate/liquid crystal E7 (TPGDA/LC E7) PDLCs composite materials (polymer-dispersed-liquid-crystals). These systems were produced by UV irradiation photopolymerization (PIPS) of a mixture of the monomer tripropylene glycol di-acrylate (TPGDA) and the liquid crystal E7 (LC E7, a mixture of three cyano-biphenyl and one cyano-terphenyl LCs), in the presence of 2?wt% (of the acrylate/E7 mixture) of a photoinitiator. Electro-optical, thermal and optical characterization was used to understand the effect of the LC concentration on the electro-optical and thermo-physical properties of these materials. Polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) studies were performed to observe the system morphology and to determine the transition temperatures of these materials, both as a function of their composition. The findings showed a slight variation of the nematic-isotropic transition temperature, TNI, of the LC E7 and of the glass transition temperature, Tg, of the TPGDA polymeric matrix as a function of the mass percentage of the LC E7. A very good electro-optical response for the composition 30/70?wt % TPGDA/LC E7 was obtained. 相似文献
53.
The effect of magnetic field h on the magnetic properties of the one-dimensional spin-1 ferromagnetic Heisenberg model is studied by the double-time Green’s function method. The magnetization and susceptibility are obtained within the Callen approximation. The zero-field susceptibility is as a decreasing function of the temperature T. The magnetization m increases in the whole field region, but the susceptibility maximum χ(Tm) decreases. The position Tm of the susceptibility maximum is both solved analytically and fits well to be a power law Tm∼hγ at low fields and to be linear increasing at high fields. The height χ(Tm) decreases as a power law χ(Tm)∼h−β with h increasing. The exponents (γ,β) obtained in our results agree with the other theoretical results. Our results are roughly in agreement with the results obtained in the experiment of Ni(OH)(NO3)H2O. 相似文献
54.
Effects of doping on the surface energies of nanocrystals and evidence from studies at high pressure
Zn1−XMnXS (X=0.85% and 1.26%) nanoparticles have been synthesized using a specially designed equipment and we have studied the influence of doping Mn2+ on the surface energy of ZnS. The high pressure behaviors of ZnS nanocrystals with different dopant contents have been investigated using angle-dispersive synchrotron X-ray powder diffraction up to 45.1 GPa. Theoretical calculations show that doping with Mn2+ increases the surface energy of the nanocrystals. The theoretical result has been further corroborated by our experimental observation of an increase in the phase transition pressure of Mn2+ doped ZnS nanocrystals in diamond-anvil-cell studies. 相似文献
55.
Freudenthal duality, introduced in Borsten et al. (2009) [1] and defined as an anti-involution on the dyonic charge vector in d=4 space-time dimensions for those dualities admitting a quartic invariant, is proved to be a symmetry not only of the classical Bekenstein-Hawking entropy but also of the critical points of the black hole potential.Furthermore, Freudenthal duality is extended to any generalized special geometry, thus encompassing all N>2 supergravities, as well as N=2 generic special geometry, not necessarily having a coset space structure. 相似文献
56.
We study the statistical properties of wave transport in a disordered waveguide. We first derive the properties of a “building block” (BB) of length δL starting from a potential model consisting of thin potential slices. We then find a diffusion equation—in the space of transfer matrices that describe our system—which governs the evolution with the length L of the disordered waveguide of the transport properties of interest. The latter depend only on the mean free paths and on no other property of the slice distribution. The universality that arises demonstrates the existence of a generalized central-limit theorem. We have developed a numerical simulation in which the universal statistical properties of the BB found analytically are first implemented numerically, and then the various BBs are combined to construct the full waveguide. The reported results thus obtained are in good agreement with microscopic calculations, for both bulk and surface disorder. 相似文献
57.
Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable component ratio and adjusting proper technological parameters, we have prepared high-coercivity sintered NdFeB magnets with hard magnetic properties of jHc=25.6 kOe, Br=13.2 kG and (BH)max=39.9 MGOe. The temperature coefficient of coercivity of the magnets (between 20 and 150 °C) is –0.53%/°C. The magnetic properties at high temperature satisfy the needs of permanent magnet motors. 相似文献
58.
In this paper we prove a relative index theorem for pairs of generalized Dirac operators on orbifolds which are the same at infinity. This generalizes to orbifolds a celebrated theorem of Gromov and Lawson. 相似文献
59.
J. Ekman D. Rudolph C. Fahlander R.J. Charity W. Reviol D.G. Sarantites V. Tomov R.M. Clark M. Cromaz P. Fallon A.O. Macchiavelli M. Carpenter D. Seweryniak 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):13-17
Eighteen previously unknown γ-ray transitions were identified in the T
z = - 1/2 nucleus 51Fe following the fusion-evaporation reaction 32S(28Si,2α1n)51Fe. The level scheme reaches the fully aligned I
π = 27/2- terminating state of the five holes in the f
7/2 shell. The 17/2- state was found to be isomeric, and the lifetime was measured to be 2.87 ns. The mirror symmetry of 51Fe and 51Mn is discussed, and the level scheme of 51Fe is compared to shell-model calculations.
Received: 20 July 2000 / Accepted: 1 August 2000 相似文献
60.
Alexander O. Smirnov 《Letters in Mathematical Physics》2006,76(2-3):297-316
We find a new class of Fuchsian equations, with algebro-geometric solutions associated to a hyperelliptic curve. A method for calculating its arithmetic genus and branching points is suggested. Numerous examples are given. 相似文献