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何忠蛟 《中国光学快报(英文版)》2010,(3):259-261
<正>A novel band-rejection filter based on a Bragg fiber with a defect layer is proposed.A defect layer is introduced in the periodic high/low index layers in the cladding of the Bragg fiber,which results in large confinement loss for some resonant wavelengths inside the band gap range of the Bragg fiber.A segment of the Bragg fiber with a defect layer can be used as a band-rejection filter,whose characteristics are mainly determined by the structure of the Bragg fiber.The simulation results show that the bandwidth of such a band-rejection filter is dependent on the number of the periodic high/low index layers in both sides of the defect layer in the cladding of the Bragg fiber. 相似文献
986.
状态概率的E-Bayes估计与多层Bayes估计 总被引:1,自引:0,他引:1
在文献[1]中提出了参数估计的一种方法--E-Bayes估计并给出了状态概率的E-Bayes估计的定义、E-Bayes估计公式、预测模型及其在证券投资中应用,本文在此基础上将给出状态概率的多层Bayes估计、状态概率的E-Bayes估计的性质--E-Bayes估计,多层Bayes估计的关系.最后,给出模拟算例. 相似文献
987.
A hybrid inversion scheme of geoacoustic parameters, which combines dispersion characteristics of normal modes with transmission loss, has been proposed based on the facts that different parameters have different effects on sound field. First, considering the dispersion characteristics of normal modes were sensitive to the density and the sound speed of seabottom, and not sensitive to the seabottom attenuation coefficient, the group time delays of different modes and different frequencies were acquired through adaptive optimal kernel time-frequency representation, then the group time delays were taken as the cost function, and using a global optimal algorithm, the seabottom density and the profile of seabottom sound speed were deduced. Successively, the validity of inversion results was evaluated by the a posteriori probability. Last, the attenuation coefficient of sediment is inverted using the transmission loss data recorded from the ship radiation noise. The validity of the total inversion results has been evaluated by making use of the matched field processing source localization. 相似文献
988.
We perform a first-principles calculation based on density functional theory to investigate the interface between single layer graphene and metal oxides. Our study reveals that the monolayer graphene becomes semiconducting by single crystal SiO2 and Al2O3 contact, with energy gaps to - 0.9 and - 1.8 eV, respectively. We find the gap originates from the breakage of π bond integrity, whose extent is related to the interface atom configuration. We believe that our results highlight a promising direction for the feasibility to apply large scale graphene layers as building blocks in future electronics devices. 相似文献
989.
By using a semi-empirical Lennard-Jones embedded-atom-method potential, we study the influence of many-body forces and atomic size mismatch on the wetting behavior of nano droplets on a solid surface. With molecular dynamics simulations, we find that the contact angle decreases with increasing many-body forces. The increase of atomic size mismatch between solid and liquid results in the decrease of contact angles. Our calculation also shows that the interface structure is strongly affected by the interaction between liquid and solid as well as the atomic size mismatch. For weak solid-liquid interaction, the interface layer of the droplet nearest to the solid exhibits a typical simple liquid structure regardless of the size mismatch. For strong solid-liquid interaction, evident ordering in the interface layer is observed for well matched cases. 相似文献
990.
Numerical Study on Open-Circuit Voltage of Single Layer Organic Solar Cells with Schottky Contacts: Effects of Molecular Energy Levels, Temperature and Thickness
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We numerically investigate the effects of the exciton generation rate G, temperature T, the active layer thickness d and the position of LUMO level EL related to the cathode work function Wc at a given energy gap on the opencircuit voltage Voc of single layer organic solar cells with Schottky contact. It is demonstrated that open-circuit voltage increases concomitantly with the decreasing cathode work function Wc for given anode work functions and exciton generation rates. In the case of given cathode and anode work functions, the open-circuit voltage first increases with the exciton generation rate and then reaches a saturation value, which equals to the builtin voltage. Additionally, it is worth noting that a significant improvement to Voc could be made by selecting an organic material which has a relative high LUMO level (low |EL| value). However, Voc decreases as the temperature increases, and the decreasing rate reduces with the enhancement of exeiton generation rate. Our study also shows that it is of no benefit to improve the open-circuit voltage by increasing the device thickness because of an enhanced charge recombination in thicker devices. 相似文献