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排序方式: 共有116条查询结果,搜索用时 46 毫秒
61.
Maor E Ivorra A Leor J Rubinsky B 《IEEE transactions on bio-medical engineering》2008,55(9):2268-2274
62.
Mentovich ED Rosenberg-Shraga N Kalifa I Tsukernik A Hendler N Gozin M Richter S 《Journal of nanoscience and nanotechnology》2010,10(12):8260-8264
High-yield fabrication and characterization of a ferrocene-based molecular device is reported. This device, fabricated with the use of modified nanocavity architecture shows very high yield, thus providing a template for exploring the transport properties of molecular junctions. The ferrocene-based devices show multiple negative differential peaks with high reproducibility and temperature stability. We use the multiple arrays to investigate the top-contact effect on the NDR signal at different locations in the wafer. 相似文献
63.
Elad M. Bruckstein A.M. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2002,48(9):2558-2567
An elementary proof of a basic uncertainty principle concerning pairs of representations of R/sup N/ vectors in different orthonormal bases is provided. The result, slightly stronger than stated before, has a direct impact on the uniqueness property of the sparse representation of such vectors using pairs of orthonormal bases as overcomplete dictionaries. The main contribution in this paper is the improvement of an important result due to Donoho and Huo (2001) concerning the replacement of the l/sub 0/ optimization problem by a linear programming (LP) minimization when searching for the unique sparse representation. 相似文献
64.
A New Nonparametric Pairwise Clustering Algorithm Based on Iterative Estimation of Distance Profiles
Dubnov Shlomo El-Yaniv Ran Gdalyahu Yoram Schneidman Elad Tishby Naftali Yona Golan 《Machine Learning》2002,47(1):35-61
We present a novel pairwise clustering method. Given a proximity matrix of pairwise relations (i.e. pairwise similarity or dissimilarity estimates) between data points, our algorithm extracts the two most prominent clusters in the data set. The algorithm, which is completely nonparametric, iteratively employs a two-step transformation on the proximity matrix. The first step of the transformation represents each point by its relation to all other data points, and the second step re-estimates the pairwise distances using a statistically motivated proximity measure on these representations. Using this transformation, the algorithm iteratively partitions the data points, until it finally converges to two clusters. Although the algorithm is simple and intuitive, it generates a complex dynamics of the proximity matrices. Based on this bipartition procedure we devise a hierarchical clustering algorithm, which employs the basic bipartition algorithm in a straightforward divisive manner. The hierarchical clustering algorithm copes with the model validation problem using a general cross-validation approach, which may be combined with various hierarchical clustering methods.We further present an experimental study of this algorithm. We examine some of the algorithm's properties and performance on some synthetic and standard data sets. The experiments demonstrate the robustness of the algorithm and indicate that it generates a good clustering partition even when the data is noisy or corrupted. 相似文献
65.
An improved P300-based brain-computer interface. 总被引:7,自引:0,他引:7
Hilit Serby Elad Yom-Tov Gideon F Inbar 《IEEE transactions on neural systems and rehabilitation engineering》2005,13(1):89-98
A brain-computer interface (BCI) is a system for direct communication between brain and computer. The BCI developed in this work is based on a BCI described by Farwell and Donchin in 1988, which allows a subject to communicate one of 36 symbols presented on a 6 x 6 matrix. The system exploits the P300 component of event-related brain potentials (ERP) as a medium for communication. The processing methods distinguish this work from Donchin's work. In this work, independent component analysis (ICA) was used to separate the P300 source from the background noise. A matched filter was used together with averaging and threshold techniques for detecting the existence of P300s. The processing method was evaluated offline on data recorded from six healthy subjects. The method achieved a communication rate of 5.45 symbols/min with an accuracy of 92.1% compared to 4.8 symbols/min with an accuracy of 90% in Donchin's work. The online interface was tested with the same six subjects. The average communication rate achieved was 4.5 symbols/min with an accuracy of 79.5 % as apposed to the 4.8 symbols/min with an accuracy of 56 % in Donchin's work. The presented BCI achieves excellent performance compared to other existing BCIs, and allows a reasonable communication rate, while maintaining a low error rate. 相似文献
66.
Atmospheric modulation transfer function in the infrared 总被引:2,自引:0,他引:2
Buskila K Towito S Shmuel E Levi R Kopeika N Krapels K Driggers RG Vollmerhausen RH Halford CE 《Applied optics》2004,43(2):471-482
In high-resolution ultranarrow field-of-view thermal imagers, image quality over relatively long path lengths is typically limited by atmospheric degradation, especially atmospheric blur. We report our results and analyses of infrared images from two sites, Fort A. P. Hill and Aberdeen Proving Ground. The images are influenced by the various atmospheric phenomena: scattering, absorption, and turbulence. A series of experiments with high-resolution equipment in both the 3-5- and 8-13-microm regions at the two locations indicate that, as in the visible, image quality is limited much more by atmosphere than by the instrumentation for ranges even of the order of only a few kilometers. For paths close to the ground, turbulence is more dominant, whereas for paths involving higher average elevation, aerosol modulation transfer function (MTF) is dominant. As wavelength increases, turbulence MTF also increases, thus permitting aerosol MTF to become more dominant. A critical role in aerosol MTF in the thermal infrared is attributed to absorption, which noticeably decreases atmospheric transmission much more than in the visible, thereby reducing high-spatial-frequency aerosol MTF. These measurements indicate that atmospheric MTF should be a basic component in imaging system design and analysis even in the infrared, especially as higher-resolution hardware becomes available. 相似文献
67.
Carl Staelin Michael Elad Darryl Greig Oded Shmueli Marie Vans 《International Journal on Document Analysis and Recognition》2007,10(2):113-126
Biblio is an adaptive system that automatically extracts meta-data from semi-structured and structured scanned documents.
Instead of using hand-coded templates or other methods manually customized for each given document format, it uses example-based
machine learning to adapt to customer-defined document and meta-data types. We provide results from experiments on the recognition of document information in two document corpuses: a set of scanned journal articles and a set of scanned legal documents. The first set is semi-structured,
as the different journals use a variety of flexible layouts. The second set is largely free-form text based on poor quality
scans of FAX-quality legal documents. We demonstrate accuracy on the semi-structured document set roughly comparable to hand-coded
systems, and much worse performance on the legal documents. 相似文献
68.
Fast and robust multiframe super resolution 总被引:39,自引:0,他引:39
Farsiu S. Robinson M.D. Elad M. Milanfar P. 《IEEE transactions on image processing》2004,13(10):1327-1344
Super-resolution reconstruction produces one or a set of high-resolution images from a set of low-resolution images. In the last two decades, a variety of super-resolution methods have been proposed. These methods are usually very sensitive to their assumed model of data and noise, which limits their utility. This paper reviews some of these methods and addresses their short-comings. We propose an alternate approach using L1 norm minimization and robust regularization based on a bilateral prior to deal with different data and noise models. This computationally inexpensive method is robust to errors in motion and blur estimation and results in images with sharp edges. Simulation results confirm the effectiveness of our method and demonstrate its superiority to other super-resolution methods. 相似文献
69.
A Variational Framework for Retinex 总被引:25,自引:1,他引:25
Kimmel Ron Elad Michael Shaked Doron Keshet Renato Sobel Irwin 《International Journal of Computer Vision》2003,52(1):7-23
Retinex theory addresses the problem of separating the illumination from the reflectance in a given image and thereby compensating for non-uniform lighting. This is in general an ill-posed problem. In this paper we propose a variational model for the Retinex problem that unifies previous methods. Similar to previous algorithms, it assumes spatial smoothness of the illumination field. In addition, knowledge of the limited dynamic range of the reflectance is used as a constraint in the recovery process. A penalty term is also included, exploiting a-priori knowledge of the nature of the reflectance image. The proposed formulation adopts a Bayesian view point of the estimation problem, which leads to an algebraic regularization term, that contributes to better conditioning of the reconstruction problem.Based on the proposed variational model, we show that the illumination estimation problem can be formulated as a Quadratic Programming optimization problem. An efficient multi-resolution algorithm is proposed. It exploits the spatial correlation in the reflectance and illumination images. Applications of the algorithm to various color images yield promising results. 相似文献
70.
The π-phase monochalcogenides are a recently discovered new family of cubic semiconductors with band gaps in the infrared. Unusually, they consist of a low-symmetry, non-centrosymmetric 64 atom simple cubic unit cell and thus may be expected to present exceptional physical properties. Furthermore, they have been obtained only in nanometric form, which raises questions concerning their thermodynamic stability. In a series of studies over the last three years, the authors and others have attempted to unravel the nature and properties of this family of materials through ab-initio materials modelling. An integrated overview of these works is presented here. 相似文献