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991.
Kenneth S. Alexander 《Journal of statistical physics》2001,104(1-2):59-87
We establish upper bounds for the spectral gap of the stochastic Ising model at low temperature in an N×N box, with boundary conditions which are plus except for small regions at the corners which are either free or minus. The spectral gap decreases exponentially in the size of the corner regions, when these regions are of size at least of order logN. This means that removing as few as O(logN) plus spins from the corners produces a spectral gap far smaller than the order N
–2 gap believed to hold under the all-plus boundary condition. Our results are valid at all subcritical temperatures. 相似文献
992.
We establish upper bounds for the spectral gap of the stochastic Ising model at low temperatures in an l×l box with boundary conditions which are not purely plus or minus; specifically, we assume the magnitude of the sum of the boundary spins over each interval of length l in the boundary is bounded by l, where <1. We show that for any such boundary condition, when the temperature is sufficiently low (depending on ), the spectral gap decreases exponentially in l. 相似文献
993.
Lifetimes of high spin states up to {
}=22+ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in 72, 74Se. The Q
t values derived from these measurements indicate that prolate shape stabilizes for 72Se, while a triaxial shape develops for 74Se at higher spins. Comparison of the observed trend in Q
t with spin for 72, 74Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency. 相似文献
994.
U. Deva Priyakumar 《Tetrahedron letters》2004,45(7):1515-1517
Ab initio and density functional theory calculations indicate that a benzene dication isomer (1: C6H62=) with three contiguous planar tetracoordinate carbons is at a minimum on the potential energy surface. The remarkable preference for the planar structure for 1 is traced to the aromatic stabilization present in the three membered ring formed by the three planar tetracoordinate carbon atoms. 相似文献
995.
Remote functionalized zwitterionic diaminodicyanoquinodimethanes are found to exhibit a dramatic enhancement of light emission in the solid state and when doped in polymer films, as compared to the solution state. Crystal structure analysis of prototypical molecules reveals the role of the remote functionality in the solid state molecular organization. Semiempirical quantum chemical computations provide a viable model to explain the interesting phenomenon of fluorescence enhancement as arising from the inhibition of geometry relaxation of the vertical excited state to a nonemitting state. The reversible switching of a doped polymer film fluorescence triggered by solvent vapors is demonstrated. 相似文献
996.
We consider multistage stochastic optimization models containing nonconvex constraints, e.g., due to logical or integrality requirements. We study three variants of Lagrangian relaxations and of the corresponding decomposition schemes, namely, scenario, nodal and geographical decomposition. Based on convex equivalents for the Lagrangian duals, we compare the duality gaps for these decomposition schemes. The first main result states that scenario decomposition provides a smaller or equal duality gap than nodal decomposition. The second group of results concerns large stochastic optimization models with loosely coupled components. The results provide conditions implying relations between the duality gaps of geographical decomposition and the duality gaps for scenario and nodal decomposition, respectively.Mathematics Subject Classification (1991): 90C15Acknowledgments. This work was supported by the Priority Programme Online Optimization of Large Scale Systems of the Deutsche Forschungsgemeinschaft. The authors wish to thank Andrzej Ruszczyski (Rutgers University) for helpful discussions. 相似文献
997.
In this paper, we consider general convex programming problems and give a sufficient condition for the equality of the infimum of the original problem and the supremum of its ordinary dual. This condition may be seen as a continuity assumption on the constraint sets (i.e. on the sublevel sets of the constraint function) under linear perturbation. It allows us to generalize as well as treat previous results in a unified framework. Our main result is in fact based on a quite general constraint qualification result for quasiconvex programs involving a convex objective function proven in the setting of a real normed vector space.Mathematics Subject Classification (2000):90C25, 90C26, 90C30, 90C31 相似文献
998.
GK Johri Akhilesh Tiwari Saumya Saxena Rajesh Sharma Kuldeep Srivastava Manoj Johri 《Pramana》2002,58(3):563-567
Calculations for the relative width (Δω/ω0) as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric
microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is
useful for the understanding of photonic crystals and occurrence of the photonic band gap. 相似文献
999.
Raffaele Luigi De La Rue Richard M. Krauss Thomas F. 《Optical and Quantum Electronics》2002,34(1-3):101-111
We present very compact, as short as 20 m long, low-threshold in-plane semiconductor lasers operating at a wavelength of 980 nm, in which microstructured mirrors have been formed at both cavity ends by deep reactive ion etching (RIE). The back mirror consists of a seven-period third order Bragg reflector with a measured reflectivity of 95%. The front mirror has a similar configuration, but consists of three periods with a lower reflectivity (80%) in order to allow output coupling. Lasing has been achieved from 20 m long and 8 m wide devices exhibiting a current threshold of 7 mA. These are among the shortest in-plane Fabry–Perot electrically pumped lasers demonstrated to date. Design issues are discussed, along with experimental data from which values for the reflectivity of the mirrors are derived. State-of-the-art electron beam lithography (EBL) and high-aspect-ratio RIE have been used for device fabrication, while additional strategies are proposed for the further improvement of the device performance. 相似文献
1000.
In order to evaluate the efficiency of application of an analyzed substance in electrode light sources for spectral analysis, it is suggested to use the ratio between the intensity of the concentrationsensitive spectral line of a chemical element and the product of the mass of the substance brought from the sample during exposure and the energy of a single pulse of a light source. It is established that annealing and sparking may favor stable selective entry of a substance into a plasma. 相似文献