摘要：
We theoretically investigate the Autler-Townes (AT) splitting in the photoelectron spectra of threelevel ladder K2 molecule driven by a pump-probe pulse via employing the time-dependent wave packet approach. The effect of the pump/probe laser intensity and wavelength on AT splitting is detailed studied. The magnitude of AT splitting increases with increasing the pump laser intensity, but does not vary with probe intensity. The double splitting with asymmetric profiles arises due to the nonresonant excitation. The double structure is transformed into one peak progressively as the pump is detuned from the resonance wavelength, which can be explained in terms of the asymmetric excitation/population of dressed states. The splitting between AT doublet changes with pump wavelength, but does not change with probe wavelength. The double peaks shift to lower energy with the different shift with increasing pump wavelength, but with the same shift with probe wavelength.
摘要：
Finite-difference time-domain (FDTD) method is employed to study the optical properties of a novel kind of periodic subwavelength hole arrays composed of Tai-chi-shaped holes in silver film, and the optical transmission properties of femtosecond optical pulse excitation is numerically calculated. We find that this Tai-chi-shaped device has better optical band-pass filtering properties, such as narrower pass band and higher transmissivity in visible wavelengths range, than other devices under consideration. Based on the generation of surface plasmons resonance mode in the dielectric-metal interface, the center wavelength of transmission can be tuned by changing the array periodicities. We observe that the tune ability mainly depends on the space period along the direction parallel to that of the incident pulse polarization. It is also found that both the strength and the wavelength of the transmission peaks of rectangularly distributed metal hole arrays are determined by the polarization of incident light. Additionally, we demonstrate the typical band-pass filtering properties of this Tai-Chi-shaped holes structure. The full-width at half-maximum (FWHM) of the narrow pass band is about 20 nm in visible wavelengths range. (C) 2014 Elsevier B.V. All rights reserved.
期刊：
Digital Signal Processing,2015年40(1):31-39 ISSN：1051-2004
通讯作者：
Ling, Bingo Wing-Kuen
作者机构：
[Ling, Bingo Wing-Kuen; Zhang, Xiao-Zhi] Guangdong Univ Technol, Fac Informat Engn, Guangzhou 510006, Guangdong, Peoples R China.;[Zhang, Xiao-Zhi] Univ South China, Engn Training Ctr, Fac Elect Engn, Hengyang 421001, Peoples R China.;[Subramaniam, Suba R.; Georgakis, Apostolos] Kings Coll London, Div Engn, Dept Elect Engn, London WC2R 2LS, England.
通讯机构：
[Ling, Bingo Wing-Kuen] G;Guangdong Univ Technol, Fac Informat Engn, Guangzhou 510006, Guangdong, Peoples R China.
关键词：
Rotated axis of time frequency plane;Fractional Fourier transform;Two sets of mask coefficients;Nonconvex global optimization;Modified filled function method
摘要：
The benefits of applying two mask operations in two different rotated axes of the time frequency (TF) plane are well known especially for signal restoration applications. Compared to just applying a single mask operation in a single rotated axis of the TF plane, it has been shown that applying two mask operations in two different rotated axes of the TF plane carefully can improve the restoration performances. However, there is no systematic approach for the globally optimal joint design of these two sets of mask coefficients in two different predefined rotated axes of the TF plane. In this paper, this optimal joint design problem is formulated as a nonconvex optimization problem. Then, a modified filled function method is employed for finding the globally optimal solution of the optimization problem. Computer numerical simulation results show that the obtained restoration system outperforms existing ones. (C) 2015 Elsevier Inc. All rights reserved.
关键词：
Sensor scheduling;wireless sensor networks;multi-modal confident information coverage;set cover
摘要：
Network lifetime maximization with guaranteed coverage is an important issue in wireless sensor networks. Based on our recently proposed confident information coverage (CIC) model, this paper studies the multi-modal confident information coverage (M2CIC) problem. Assuming that each node is equipped with different types of sensors, the objective is to schedule the multi-modal sensors' activity, such that the confident information coverage for each sensing modality can be guaranteed while the network lifetime can be maximized. We model the M2CIC problem as a multi-modal set cover problem (M2SC) and prove its NP-completeness. For solving the M2SC problem, we design two energy-efficient heuristics including a centralized one and a distributed one. In the proposed algorithms, different modal sensors are organized into a family of set covers, each of which can provide confident information coverage for all the monitored physical phenomena. Simulation results show that both the proposed algorithms can efficiently prolong the network lifetime and outperform two classical peer algorithms in terms of the extended network lifetime.
摘要：
We demonstrate an efficient scheme for controlling the tunneling ionization of a H2+ molecular ion. Our scheme is based on the idea that the tunneling ionization rate is highly dependent on the instantaneous magnitude of the electric field. By manipulating the relative phase of the synthesized 5-fs, 790–395-nm laser field, the fragments yielded by the tunneling ionization show a large asymmetry relative to the laser polarization. We find that the time-dependent ionization rate is sharply peaked near the antinodes of the synthesized field. Most importantly, the critical internuclear distances at which the tunneling ionization rate is enhanced depend on the field strength of the antinodes. It is well explained by tracing the laser-driven motion of the electron in the field-dressed double well potential.
摘要：
Image fusion techniques aim at transferring useful information from the input source images to the fused image. The common assumption for most fusion approaches is that the useful information is defined by local features such as contrast, variance, and gradient. However, there is no consideration of global visual attention of the whole source images which indicates the "interesting" information of the source images. In this paper, we firstly review the patch-based image fusion methods which attract the attention and interest of many researchers. Then, a visual attention guided patch-based image fusion method is proposed. The visual attention maps of the source images are calculated from the sparse represent coefficients of the source images. Then, the sparse coefficients are fused with the guidance of visual attention maps in order to emphasize the global "interesting" objects in the source images. Finally, the fused image is reconstructed from the fused sparse coefficients. The new fusion strategy ensures that the objects being "interesting" for our visual system are preserved in the fused image. The proposed approach is tested on infrared and visual, medical, and multi-focus images. The results compared with those of traditional methods show obvious improvement in objective and subjective quality measurements. (C) 2014 Elsevier GmbH. All rights reserved.
摘要：
Coverage is an important performance metric in sensor networks. The traditional disk coverage model uses a very simple geometric relation between a sensor and its surrounding space points to capture the sensor's sensing capability and quality, which are not enough for many practical applications. In this article, motivated from the application of precision agriculture, we propose a new confident information coverage model for field reconstruction, where the objective is to obtain reconstruction maps of some physical phenomena's attribute with a given reconstruction quality for the whole sensor field, including points been sampled and not sampled. The proposed model is downward compatible with the disk coverage model, while it can greatly reduce sensor density for area coverage. Simulation results show that for the same reconstruction quality, the required sensor density based on the proposed new model is much less than that based on the disk model in both the deterministic and random sensor deployment. In practice, the proposed model helps to determine the number of sensors to be deployed for a given farmland and their locations in the deterministic deployment. The proposed model can also help to guide network operations for energy efficient data collection with guaranteed reconstruction quality.
