检索结果-内蒙古大学图书馆

Asia-Pacific Conference on Environmental Electromagnetics

作者： Fan Li Tie-Hua Jiang San-Qing Zhang Yong Tao Beijing Institute of Aerospace Systems Engineering Beijing China

This paper has proposed and illustrated two fast methods of computing antenna factor (AF) of a compact wideband antenna (CWA), which is designed to measure the electromagnetic environment inside spacecraft cabin. The ... 详细信息

ISBN: (纸本)9781467394468

关键词： Antenna Factor computation methods

来源：评论

学校读者我要写书评

暂无评论

Space-frequency analysis with parallel computing in a phase-sensitive optical time-domain reflectometer distributed sensor

引用

APPLIED OPTICS 2014年第28期53卷 6586-6590页

作者： Hui, Xiaonan Ye, Taihang Zheng, Shilie Zhou, Jinhai Chi, Hao Jin, Xiaofeng Zhang, Xianmin Zhejiang Univ Dept Informat Sci & Elect Engn Hangzhou 310027 Zhejiang Peoples R China Zhejiang Univ Cyrus Tang Ctr Sensor Mat & Applicat Hangzhou 310027 Zhejiang Peoples R China

For a phase-sensitive optical time-domain reflectometer (phi-OTDR) distributed sensor system, space-frequency analysis can reduce the false alarm by analyzing the frequency distribution compared with the traditional difference value method. We propose a graphics processing unit (GPU)-based parallel computing method to perform multichannel fast Fourier transform (FFT) and realize the real-time space-frequency analysis. The experiment results show that the time taken by the multichannel FFT decreased considerably based on this GPU parallel computing. The method can be completed with a sensing fiber up to 16 km long and an entry-level GPU. Meanwhile, the GPU can reduce the computing load of the central processing unit from 70% down to less than 20%. We carried out an experiment on a two-point space-frequency analysis, and the results clearly and simultaneously show the vibration point locations and frequency components. The sensor system outputs the real-time space-frequency spectra continuously with a spatial resolution of 16.3 m and frequency resolution of 2.25 Hz. (C) 2014 Optical Society of America

关键词： computation methods Discrete Fourier transforms Erbium doped fiber amplifiers Fast Fourier transforms Spatial resolution Spectroscopy

来源：评论

学校读者我要写书评

暂无评论

Simulation method for resonant light scattering of exciton confined to arbitrary geometry

引用

OPTICS EXPRESS 2014年第8期22卷 9450-9464页

作者： Uemoto, Mitsuharu Ajiki, Hiroshi Osaka Univ Grad Sch Engn Sci Dept Mat Engn Sci Osaka 5608531 Japan Osaka Univ Photon Pioneers Ctr Suita Osaka 5650871 Japan

We develop an electromagnetic (EM) simulation method based on a finite-element method (FEM) for an exciton confined to a semiconductor nanostructure. The EM field inside the semiconductor excites two transverse exciton polariton and a single longitudinal exciton at a given frequency. Established EM simulation methods cannot be applied directly to semiconductor nanostructures because of this multimode excitation;however, the present method overcomes this difficulty by introducing an additional boundary condition. To avoid spurious solutions and enhance the precision, we propose a hybrid edge-nodal element formulation in which edge and nodal elements are employed to represent the transverse and longitudinal polarizations, respectively. We apply the developed method to the EM-field scattering and distributions of exciton polarizations of spherical and hexagonal-disk quantum dots. (C) 2014 Optical Society of America

关键词： computation methods Light scattering Mie theory Photonic crystal cavities Physical vapor deposition Quantum dots

来源：评论

学校读者我要写书评

暂无评论

Photorealistic ray tracing to visualize automobile side mirror reflective scenes

引用

OPTICS EXPRESS 2014年第21期22卷 25729-25738页

作者： Lee, Hocheol Kim, Kyuman Lee, Gang Lee, Sungkoo Kim, Jingu Hanbat Natl Univ Dept Mech Engn Taejon 305719 South Korea Bullsone Co Ltd R&D Inst Inchon 406840 South Korea

We describe an interactive visualization procedure for determining the optimal surface of a special automobile side mirror, thereby removing the blind spot, without the need for feedback from the error-prone manufacturing process. If the horizontally progressive curvature distributions are set to the semi-mathematical expression for a free-form surface, the surface point set can then be derived through numerical integration. This is then converted to a NURBS surface while retaining the surface curvature. Then, reflective scenes from the driving environment can be virtually realized using photorealistic ray tracing, in order to evaluate how these reflected images would appear to drivers. (C) 2014 Optical Society of America

关键词： computation methods Freeform surfaces Image metrics Image processing Optical aberrations Ray tracing

来源：评论

学校读者我要写书评

暂无评论

Illuminant direction estimation for a single image based on local region complexity analysis and average gray value

引用

APPLIED OPTICS 2014年第2期53卷 226-236页

作者： Yi, Jizheng Mao, Xia Chen, Lijiang Xue, Yuli Compare, Angelo Beihang Univ Sch Elect & Informat Engn Beijing 100191 Peoples R China Univ Bergamo Dept Human Sci I-24129 Bergamo Italy

Illuminant direction estimation is an important research issue in the field of image processing. Due to low cost for getting texture information from a single image, it is worthwhile to estimate illuminant direction by employing scenario texture information. This paper proposes a novel computation method to estimate illuminant direction on both color outdoor images and the extended Yale face database B. In our paper, the luminance component is separated from the resized YCbCr image and its edges are detected with the Canny edge detector. Then, we divide the binary edge image into 16 local regions and calculate the edge level percentage in each of them. Afterward, we use the edge level percentage to analyze the complexity of each local region included in the luminance component. Finally, according to the error function between the measured intensity and the calculated intensity, and the constraint function for an infinite light source model, we calculate the illuminant directions of the luminance component's three local regions, which meet the requirements of lower complexity and larger average gray value, and synthesize them as the final illuminant direction. Unlike previous works, the proposed method requires neither all of the information of the image nor the texture that is included in the training set. Experimental results show that the proposed method works better at the correct rate and execution time than the existing ones. (C) 2014 Optical Society of America

关键词： computation methods Edge detection Image processing Image recognition algorithms Light properties Light sources

来源：评论

学校读者我要写书评

暂无评论

Robust topology optimization of three-dimensional photonic-crystal band-gap structures

引用

OPTICS EXPRESS 2014年第19期22卷 22632-22648页

作者： Men, H. Lee, K. Y. K. Freund, R. M. Peraire, J. Johnson, S. G. MIT Dept Aeronaut & Astronaut Cambridge MA 02139 USA MIT Dept Math Cambridge MA 02139 USA MIT Alfred P Sloan Sch Management Cambridge MA 02142 USA

We perform full 3D topology optimization (in which "every voxel" of the unit cell is a degree of freedom) of photonic-crystal structures in order to find optimal omnidirectional band gaps for various symmetry groups, including fcc (including diamond), bcc, and simple-cubic lattices. Even without imposing the constraints of any fabrication process, the resulting optimal gaps are only slightly larger than previous hand designs, suggesting that current photonic crystals are nearly optimal in this respect. However, optimization can discover new structures, e. g. a new fcc structure with the same symmetry but slightly larger gap than the well known inverse opal, which may offer new degrees of freedom to future fabrication technologies. Furthermore, our band-gap optimization is an illustration of a computational approach to 3D dispersion engineering which is applicable to many other problems in optics, based on a novel semidefinite-program formulation for nonconvex eigenvalue optimization combined with other techniques such as a simple approach to impose symmetry constraints. We also demonstrate a technique for robust topology optimization, in which some uncertainty is included in each voxel and we optimize the worst-case gap, and we show that the resulting band gaps have increased robustness to systematic fabrication errors. (C) 2014 Optical Society of America

关键词： computation methods Inverse problems Negative refraction Nonlinear optics Phase matching Photonic crystals

来源：评论

学校读者我要写书评

暂无评论

Double freeform surfaces design for laser beam shaping with Monge-Ampere equation method

引用

OPTICS COMMUNICATIONS 2014年 331卷 297-305页

作者： Zhang, Yaqin Wu, Rengmao Liu, Peng Zheng, Zhenrong Li, Haifeng Liu, Xu Zhejiang Univ Dept Opt Engn State Key Lab Modern Opt Instrumentat Hangzhou 310027 Zhejiang Peoples R China Univ Politecn Madrid Cedint Madrid 28223 Spain

This paper presents a method for designing double freeform surfaces to simultaneously control the intensity distribution and phase profile of the laser beam. Based on Snell's law, the conservation law of energy and the constraint imposed on the optical path length between the input and output wavefronts, the double surfaces design is converted into an elliptic Monge-Ampere (MA) equation with a nonlinear boundary problem. A generalized approach is introduced to find the numerical solution of the design model. Two different layouts of the beam shaping system are introduced and detailed comparisons are also made between the two layouts. Design examples are given and the results indicate that good matching is achieved by the MA method with more than 98% of the energy efficiency. The MA method proposed in this paper provides a reasonably good means for laser beam shaping. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Nonimaging optics Aspherics computation methods Laser beam shaping

来源：评论

学校读者我要写书评

暂无评论

Application of T-matrix method in solving mixed boundary separable obstacle problem

引用

OPTICS EXPRESS 2014年第13期22卷 16273-16281页

作者： Ye, Xiuzhu Song, Rencheng Chen, Xudong Beihang Univ Dept Elect & Comp Engn Beijing 100191 Peoples R China Natl Univ Singapore Dept Elect & Comp Engn Singapore 117576 Singapore

The practical problem of imaging scatterers enclosed by separable obstacles with mixed boundary is addressed. Both the unknown scatterers and the known obstacle media can be mixture of dielectric and perfect electric conducting (PEC) materials. The scattering phenomenon of such problem is well modeled by T-matrix method. By usage of separable prior information, the obstacle media are treated as known scatterers rather than part of the background. The number of unknowns is thus reduced greatly. After recovering the profiles of scatterers by T-matrix method, a criterion is further provided to classify the PEC and dielectric scatterers. Various numerical examples are presented to show the effectiveness and good performance of the method. (C)2014 Optical Society of America

关键词： computation methods Image storage Inverse problems Medical imaging Optical fibers Remote sensing

来源：评论

学校读者我要写书评

暂无评论

Phase-space measurement for depth-resolved memory-effect imaging

引用

OPTICS EXPRESS 2014年第25期22卷 31426-31433页

作者： Takasaki, Kevin T. Fleischer, Jason W. Princeton Univ Dept Elect Engn Princeton NJ 08544 USA

Random scattering of light by a turbid layer prevents conventional imaging of objects hidden behind it. Angular correlations in the scattered light, created by the so-called optical memory effect, have been shown to enable computational image retrieval of hidden sources. However, basic memory-effect imaging contains no spatial (x) information, as only angular (k-space) measurements are made. Here, we use windowed Fourier transforms to record scattered-light images in the full {x,k} phase space. The result is the ability to discriminate size and depth of individual sources that are hidden behind a thin scattering layer. (C) 2014 Optical Society of America

关键词： computation methods Image quality Light scattering Optical memory Phase conjugation Scattering media

来源：评论

学校读者我要写书评

暂无评论

Enhanced field-of-view integral imaging display using multi-Kohler illumination

引用

OPTICS EXPRESS 2014年第26期22卷 31853-31863页

作者： Tolosa, Angel Martinez-Cuenca, Raul Navarro, Hector Saavedra, Genaro Martinez-Corral, Manuel Javidi, Bahram Pons, Amparo Technol Inst Opt Color & Imaging AIDO E-46117 Paterna Spain Univ Jaume 1 Dept Mech Engn & Construct E-12071 Castellon de La Plana Spain Univ Valencia Dept Opt E-46100 Burjassot Spain Univ Connecticut Dept Elect & Comp Engn Storrs CT 06269 USA

A common drawback in 3D integral imaging displays is the appearance of pseudoimages beyond the viewing angle. These pseudoimages appear when the light rays coming from each elemental image are not passing through the corresponding microlens, and a set of barriers must be used to avoid this flipping effect. We present a pure optical arrangement based on Kohler illumination to generate these barriers thus avoiding the pseudoimages. The proposed system does not use additional lenses to project the elemental images, so no optical aberrations are introduced. As an added benefit, Kohler illumination provides a higher contrast 3D display. (C) 2014 Optical Society of America

关键词： computation methods Gradient index lenses Integral photography Optical aberrations Three dimensional imaging Viewing angles

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：