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101.
We combine different split ring resonator (SRR) unit cells along three axes respectively and study the electromagnetic behaviors of combinations numerically, with the purpose of broadening the frequency band of negative permeability. When combining SRRs in z-direction, the wave propagation direction, it is found that the bandwidth of negative permeability is broadened by 0.22 GHz. The same bandwidth expansion effects, however, are not observed along the other two axes. In addition, it is feasible to obtain two isolated frequency bands with negative permeability by combining SRRs along three axes. 相似文献
103.
104.
Exotic electronic excitations beyond normal selection rules would open novel possibilities for photoenergy conversion. The large intensity gradient of electromagnetic fields resulting from the confinement of localized surface plasmons at the molecular scale could exceed the limit of light–matter interactions via modification of electronic excitation selection rules. We discuss the possible application of surface-enhanced Raman scattering as a probe for exotic electronic excitations by reviewing studies on small numbers of molecules at the surface of plasmonic metal nanostructures. Future innovative photo-functionalization is also discussed by considering the excited states produced by the exotic electronic excitations. 相似文献
105.
We study existence and stability of stationary solutions of a system of semilinear parabolic partial differential equations that occurs in population genetics. It describes the evolution of gamete frequencies in a geographically structured population of migrating individuals in a bounded habitat. Fitness of individuals is determined additively by two recombining, diallelic genetic loci that are subject to spatially varying selection. Migration is modeled by diffusion. Of most interest are spatially non-constant stationary solutions, so-called clines. In a two-locus cline all four gametes are present in the population, i.e., it is an internal stationary solution. We provide conditions for existence and linear stability of a two-locus cline if recombination is either sufficiently weak or sufficiently strong relative to selection and diffusion. For strong recombination, we also prove uniqueness and global asymptotic stability. For arbitrary recombination, we determine the stability properties of the monomorphic equilibria, which represent fixation of a single gamete. 相似文献
106.
We propose a type-dependent branching model with mutation and competition for modelling phylogenies of a virus population. The competition kernel depends on the total mass, the types of the virus particles, and the genetic information available through the number of nucleotide substitutions separating the virus particles. We consider evolving phylogenies in the huge population, short reproduction time and frequent mutation regime, show tightness in the space of marked metric measure spaces and characterize the limit through a martingale problem. Due to heterogeneity in the branching rates, the phylogenies are not ultra-metric. We therefore develop new techniques for verifying compact containment. 相似文献
107.
随着中央关于“职业院校制造业和现代服务业技能型紧缺性人才培养培训工程”的政策出台,以及“2004年全国首届数控技能大赛”的成功举办,使得职业学校的数控专业建设逐步发展并完善起来,各种形式的数控技能竞赛也如火如荼地开展起来。本文从参加数控技能比赛学生的选拔和培训两个方面做了简单的介绍. 相似文献
108.
Xinjie Lv Zhan Sui Zhida Gao Mingzhong Li Qinghua Deng Shi-ning Zhu 《Optics & Laser Technology》2008,40(1):21-29
We report a theoretical analysis and numerical simulation of bandwidth and stability enhancement in optical parametric amplification (OPA) when using chirped periodically poled KTiOPO4. Calculation results show that the bandwidth and stability are enhanced significantly by the use of a chirped grating. Temperature-gradient and fanned gratings are introduced and chirp factors of them are deduced and calculated. The use of a fanned grating flattens the Quasi-phase-matching response and improves the efficiency. Finally, we propose a method to reduce the instability induced by an unstable pump. 相似文献
110.
Young Kyung Lee Byeong U. Park 《Annals of the Institute of Statistical Mathematics》2006,58(2):327-340
Motivated from the bandwidth selection problem in local likelihood density estimation and from the problem of assessing a
final model chosen by a certain model selection procedure, we consider estimation of the Kullback–Leibler divergence. It is
known that the best bandwidth choice for the local likelihood density estimator depends on the distance between the true density
and the ‘vehicle’ parametric model. Also, the Kullback–Leibler divergence may be a useful measure based on which one judges
how far the true density is away from a parametric family. We propose two estimators of the Kullback-Leibler divergence. We
derive their asymptotic distributions and compare finite sample properties.
Research of Young Kyung Lee was supported by the Brain Korea 21 Projects in 2004. Byeong U. Park’s research was supported
by KOSEF through Statistical Research Center for Complex Systems at Seoul National University. 相似文献