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排序方式: 共有508条查询结果,搜索用时 31 毫秒
31.
We have observed phase defects in quasi-2D Bose-Einstein condensates close to the condensation temperature. Either a single or several equally spaced condensates are produced by selectively evaporating the sites of a 1D optical lattice. When several clouds are released from the lattice and allowed to overlap, dislocation lines in the interference patterns reveal nontrivial phase defects. 相似文献
32.
Using a density functional approach, we study the structural and magnetic properties of the pyrox-ene compound NaTiSi2O6. While all previous workers are taking that NaTiSi2O6 is a quasi-one-dimensional S=1/2 system, our theoretical results indicate that this is a Haldane S=1 chain compound below the phase transition at 210 K. A good agreement is obtained between the calculated and the measured Ti-Ti distances in the dimerized low temperature phase. We present a simple explanation of the flow of the unusual phase transition which is taking place in this compound. 相似文献
33.
Radosav?Dordevi? Miodrag? Ra?kovi? Zoran?Ognjanovi?Email author 《Archive for Mathematical Logic》2004,43(4):557-563
A propositional logic is defined which in addition to propositional language contains a list of probabilistic operators of the form Ps (with the intended meaning the probability is at least s). The axioms and rules syntactically determine that ranges of probabilities in the corresponding models are always finite. The completeness theorem is proved. It is shown that completeness cannot be generalized to arbitrary theories.This research was supported by Ministarstvo za nauku, tehnologije i razvoj Republike Srbije, through Matematiki institut, under grant 1379Mathematics Subject Classification (2000): 03C70, 03B48 相似文献
34.
35.
Zoran S. Marković Jasmina M. Dimitrić Marković Ćemal B. Doličanin 《Theoretical chemistry accounts》2010,127(1-2):69-80
The extensive theoretical study of the interaction of one of the most abundant and reactive flavonols, quercetin, with hydroperoxy radical (HOO·), using the M052X/6-31 + Gd, p level of theory, was performed. Results indicating that quercetin is not a planar molecule are in accord with the X-ray analysis. The applied method successfully reproduces the bond dissociation enthalpy, and reveals that the reaction of quercetin with the hydroperoxy radical is governed by a hydrogen atom transfer mechanism. It is confirmed that the 3′OH and 4′OH are the most reactive sites, and that the reaction in the 3′OH position is faster than that in the 4′OH position. 相似文献
36.
37.
Dean P Lim YL Valavanis A Kliese R Nikolić M Khanna SP Lachab M Indjin D Ikonić Z Harrison P Rakić AD Linfield EH Davies AG 《Optics letters》2011,36(13):2587-2589
We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect of self-mixing in the THz QCL, and, specifically, by monitoring perturbations to the voltage across the QCL, induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures. 相似文献
38.
We use the dielectric-response formalism to evaluate the induced density of charge carriers in supported graphene due to an external moving charged particle in terms of its velocity and distance from graphene for several equilibrium charge carrier densities due to graphene doping. We show that, when the particle speed exceeds a threshold value, an oscillatory wake effect develops in the induced charge density trailing the particle. Strong effects are observed in the wake pattern due to finite size of the graphene–substrate gap, as well as due to strong coupling effects, and plasmon damping of graphene?s π electrons. 相似文献
39.
Slobodan M. Vuković Zoran Jakšić Ilya V. Shadrivov Yuri S. Kivshar 《Applied Physics A: Materials Science & Processing》2011,103(3):615-617
We study the properties of electromagnetic waves propagating along the waveguides with a periodic core created by alternating
metal and dielectric layers, the so-called quasi-one-dimensional plasmonic crystal waveguides. Such waveguides can be symmetric
or asymmetric, depending on the cladding or substrate material properties, as well as on the termination of the periodic structure.
We analyze the dispersion characteristics as well as the profiles of the guided modes for several types of waveguide structure. 相似文献
40.
Zoran Petrić 《Journal of Algebraic Combinatorics》2014,39(1):99-125
A family of polytopes introduced by E.M. Feichtner, A. Postnikov, and B. Sturmfels, which were named nestohedra, consists in each dimension of an interval of polytopes starting with a simplex and ending with a permutohedron. This paper investigates a problem of changing and extending the boundaries of these intervals. An iterative application of Feichtner–Kozlov procedure of forming complexes of nested sets is a solution of this problem. By using a simple algebraic presentation of members of nested sets it is possible to avoid the problem of increasing the complexity of the structure of nested curly braces in elements of the produced simplicial complexes. 相似文献