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IEEE Nuclear Science Symposium/Medical Imaging Conference (NSS/MIC)/18th International Workshop on Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors

作者： Wang, Weiyi He, Zhong Univ Michigan Dept Nucl Engn & Radiol Sci Ann Arbor MI 48109 USA

ISBN: (纸本)9781467301206

In previous research, our group developed a gamma-ray image reconstruction method using Compton events from a 3-D position-sensitive CdZnTe detector, which is capable of deconvolving the source image at any specific energy, as well as the incident spectrum at any specific direction. T his gamma-ray energy-imaging integrated deconvolution method takes place in integrated spatial and energy space using the maximum-likelihood expectation maximization (MLEM) algorithm. By including Compton scattering events in the system model, the MLEM solution estimates the incident gamma-ray spectrum in the source direction free of the Compton continuum for source energies lower than 1.02 MeV. In order to correctly reconstruct images for higher energy events, pair-production effect needs to be included in the system model. Since it is impossible to pre-calculate the system response function due to the huge number of possible recorded events, analytic formulas are derived to allow the calculation of the system response function during the reconstruction. After including pair-production events in the system response function, the deconvolved spectrum reflects the incident spectrum and is free of single and double escape peaks.

关键词： 3D position sensitive detector Acceleration Compton effect Compton scattering MLEM algorithm deconvolution energy imaging integrated deconvolution algorithm expectation-maximisation algorithm gamma-ray applications gamma-ray image reconstruction gamma-rays image reconstruction maximum likelihood expectation maximization pair production event position sensitive particle detectors system response function

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Statistical Trilateration with Skew-t Errors

Statistical Trilateration with Skew-t Errors

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International Conference on Location and GNSS (ICL-GNSS)

作者： Muller, Philipp Piche, Robert Tampere Univ Technol Dept Automat Sci & Engn ASE POB 692 FI-33101 Tampere Finland

ISBN: (纸本)9781479998586

In the problem of determining a target's location using radio signal time-of-flight to reference nodes with known locations, measurement errors can be skewed because of multipath effects. In this paper, range errors are modelled using the skew-t distribution. An expectation-maximisation (EM) algorithm for computing the unknown location is presented, and its accuracy is compared with a descending Gauss-Newton algorithm by simulations. The EM algorithm improves the positioning accuracy significantly. Furthermore, it is shown how to fit the parameters of a skew-t distribution to training data using a Gibbs sampler.

关键词： Student's t-distribution expectation-maximisation algorithm trilateration multipath effect range errors reference node Signal timing RADIO SIGNALS positioning accuracy

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Decision support systems in Wireless Capsule Endoscopy: Revisited

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INTELLIGENT DECISION TECHNOLOGIES-NETHERLANDS 2007年第1-2期1卷 17-31页

作者： Kodogiannis, Vassilis S. Univ Westminster Ctr Syst Anal Sch Comp Sci London HA1 3TP England

Decision Support Systems have been utilised since 1960, providing physicians with fast and accurate means towards more accurate diagnoses, increased tolerance when handling missing or incomplete data. In this paper, an intelligent diagnostic system has been developed for the analysis of Wireless Capsule Endoscopic Images. Wireless Capsule Endoscopy (WCE) constitutes a recent technology in which a capsule with micro-camera attached to it, is swallowed by the patient. Two issues are being addressed, including the extraction of texture features from the texture spectra in the chromatic and achromatic domains from each colour component histogram of WCE images and the concept of a fusion of multiple classifiers. The implementation of an advanced neural network, based on a modified expectation maximisation scheme that incorporates a dynamic structure methodology has been also adopted in this paper. The high detection accuracy of the proposed system provides thus an indication that such intelligent schemes could be used as a supplementary diagnostic tool in WCE.

关键词： Medical imaging computer aided diagnosis endoscopy neural networks expectation-maximisation algorithm fuzzy integral

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Unsupervised Online Learning Trajectory Analysis Based On Weighted Directed Graph

Unsupervised Online Learning Trajectory Analysis Based On We...

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21st International Conference on Pattern Recognition (ICPR)

作者： Shen, Yuan Miao, Zhenjiang Zhang, Jian Beijing Jiaotong Univ Inst Informat Sci Beijing Peoples R China Univ Technol Sydney Fac Engn & Informat Technol Sydney NSW Australia

ISBN: (纸本)9784990644109;9781467322164

In this paper, we propose a novel unsupervised online learning trajectory analysis method based on weighted directed graph. Each trajectory can be represented as a sequence of key points. In the training stage, unsupervised expectation-maximization algorithm (EM) is applied for training data to cluster key points. Each class is a Gaussian distribution. It is considered as a node of the graph. According to the classification of key points, we can build a weighted directed graph to represent the trajectory network in the scene. Each path is a category of trajectories. In the test stage, we adopt online EM algorithm to classify trajectories and update the graph. In the experiments, we test our approach and obtain a good performance compared with state-of-the-art approaches.

关键词： TRAJECTORY ANALYSIS trajectory directed graphs expectation-maximisation algorithm Line graph e-learning Gaussian distribution Mentoring

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ROBUST RETINAL IMAGE REGISTRATION USING expectation maximisation WITH MUTUAL INFORMATION

ROBUST RETINAL IMAGE REGISTRATION USING EXPECTATION MAXIMISA...

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IEEE International Conference on Acoustics, Speech and Signal Processing

作者： Parminder Singh Reel Laurence S. Dooley K. C. P. Wong Anko Borner Department of Communication and Systems The Open University Milton Keynes United Kingdom

ISBN: (纸本)9781479903573

Retinal images (RI) are widely used to diagnose a variety of eye conditions and diseases such as myopia and diabetic retinopathy. They are inherently characterised by having nonuniform illumination and low-contrast homogeneous regions which represent a unique set of challenges for retinal image registration (RIR). This paper investigates using the expectation maximization for principal component analysis based mutual information (EMPCA-MI) algorithm in RIR. It combines spatial features with mutual information to efficiently achieve improved registration performance. Experimental results for mono-modal RI datasets verify that EMPCA-MI together with Powell-Brent optimization affords superior robustness in comparison with existing RIR methods, including the geometrical features method.

关键词： Image registration principal component analysis mutual information expectation-maximization algorithms retinopathy image registration expectation-maximisation algorithm principal components analysis Retinopathy

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Measurements and Analysis of a 4x4 Vehicle-to-Ground MIMO Channel Using SAGE

Measurements and Analysis of a 4x4 Vehicle-to-Ground MIMO Ch...

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International Symposium on Wireless Personal Multimedia Communications (WPMC)

作者： Yang Jiaqi Wu Muqing Zhao Ruojun Wang Qian Beijing Univ Posts & Telecommun Beijing Key Lab Network Syst Architecture & Conve Beijing 100876 Peoples R China

ISBN: (纸本)9789860334074

The widely used broadband wireless technology enables a novel application of providing high-quality communications between vehicles and traffic control centers, which is collectively referred to as vehicle-to-ground communications. Channel modeling is in rapidly increasing demand to design and optimize the vehicle-to-ground communication systems. And practical channel models are only available when accurate estimations of the channel parameters are feasible. By adopting quadrature encoding and spectrum spreading, a novel and low-cost measurement method is proposed in this paper. The method can be implemented to achieve channel matrix accurately and furthermore determinate the parameters of a MIMO channel by using the space-alternating generalized expectation-maximization (SAGE) algorithm. Then the method was carried out in a measurement of a vehicle-mounted 4x4 MIMO system. Both large-scale and small-scale fading are investigated and analyzed. A path loss (PL) model and characteristics of channel parameters including PDP, K-factor, angle of arrival (AOA), angle of departure (AOD) and spatial correlation matrixes for V2G channel modeling are given based on the estimations. These results offer a valuable reference for future studies.

关键词： MIMO communication expectation-maximisation algorithm fading channels matrix algebra mobile radio wireless channels PDP characteristics SAGE algorithm V2G channel modeling angle of arrival angle of departure broadband wireless technology channel matrix channel parameters low-cost measurement method path loss model quadrature encoding small-scale fading space-alternating generalized expectation-maximization algorithm spatial correlation matrices traffic control centers vehicle-to-ground MIMO channel Correlation Delays MIMO Receiving antennas Transmitting antennas Vectors Wireless communication angles of departure SAGE algorithm expectation-maximisation algorithm channel matrix multiple input multiple output systems Angle of arrival Receiving antennas transmitting antennas MIMO communication wireless channels Mobile radios matrix algebra CARRIER SYSTEM Fading channels Wireless Technology

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Maximum-likelihood spatial spectrum estimation in dynamic environments with a short maneuverable array

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JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013年第1期133卷 311-322页

作者： Odom, Jonathan L. Krolik, Jeffrey L. Rogers, Jeffrey S. Duke Univ Dept Elect & Comp Engn Durham NC 27708 USA USN Res Lab Acoust Div Washington DC 20375 USA

This work concerns the development of field directionality mapping algorithms for short acoustic arrays on mobile maneuverable platforms that avoid the left/right ambiguities and endfire resolution degradation common to longer non-maneuverable line arrays. In this paper, it is shown that short maneuverable arrays can achieve a high fraction of usable bearing space for target detection in interference-dominated scenarios, despite their lower array gain against diffuse background noise. Two narrowband techniques are presented which use the expectation-maximization maximum likelihood algorithm under different models of the time-varying field directionality. The first, derivative based maximum likelihood, uses a deterministic model while the second, recursive Bayes maximum likelihood, uses a stochastic model for the time-varying spatial spectrum. In addition, a broadband extension is introduced that incorporates temporal spectral knowledge to suppress ambiguities when the average sensor array spacing is greater than a half-wavelength. Dynamic multi-source simulations demonstrate the ability of a short, maneuvering array to reduce array ambiguities and spatial grating lobes in an interference dominated environment. Monte Carlo evaluation of receiver operating characteristics is used to evaluate the improvement in source detection achieved by the proposed methods versus conventional broadband beamforming. (C) 2013 Acoustical Society of America. [http://dx. ***/10.1121/1.4770233]

关键词： acoustic arrays acoustic noise acoustic receivers acoustic signal processing acoustic wave interference Bayes methods expectation-maximisation algorithm Monte Carlo methods object detection stochastic processes underwater sound

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Joint distribution of individual wave heights and periods in mixed sea states using finite mixture models

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COASTAL ENGINEERING 2020年 161卷 103773-103773页

作者： Huang, Weinan Dong, Sheng Ocean Univ China Coll Engn Qingdao 266100 Peoples R China

The bivariate distribution of zero-up-crossing wave heights and associated periods is important in the stochastic modelling of ocean waves and is of theoretical and practical interest among scientists and engineers. Recently, joint descriptions in mixed sea states have garnered attention. The present study proposes a mixture bivariate lognormal model to characterise the joint distribution in sea states with two-peaked spectra. A parametric distribution based on conditional modelling is compared with the presented model. To verify the fitted models, secondary waves, which can be formed when waves propagate over marine obstacles, were generated in laboratory conditions and simulated data were obtained by the Ochi-Hubble model. The joint distributions of wave heights and periods, as well as the marginal distributions of these two wave parameters in three types of combined sea states are studied and discussed. Results show that the conditional model is not suitable for fitting the bivariate distribution, which may be primarily owing to its inaccurate description of the wave period distribution. Joint probability density functions of wave heights and periods created using a finite mixture model provide improved performance and can describe the bimodal nature of the distribution relatively well.

关键词： Wave parameters Joint distribution Conditional model Mixture model expectation-maximisation algorithm Mixed sea state

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Time-varying spatial spectrum estimation with a maneuverable towed array

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JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2010年第6期128卷 3543-3553页

作者： Rogers, Jeffrey S. Krolik, Jeffrey L. Duke Univ Dept Elect & Comp Engn Durham NC 27708 USA

This paper addresses the problem of field directionality mapping (FDM) or spatial spectrum estimation in dynamic environments with a maneuverable towed acoustic array. Array processing algorithms for towed arrays are typically designed assuming the array is straight, and are thus degraded during tow-ship maneuvers. In this paper, maneuvering the array is treated as a feature allowing for left and right disambiguation as well as improved resolution toward endfire. The Cramer-Rao lower bound is used to motivate the improvement in source localization which can be theoretically achieved by exploiting array maneuverability. Two methods for estimating time-varying field directionality with a maneuvering array are presented: (1) Maximum likelihood (ML) estimation solved using the expectation maximization algorithm and (2) a non-negative least squares (NNLS) approach. The NNLS method is designed to compute the field directionality from beamformed power outputs, while the ML algorithm uses raw sensor data. A multi-source simulation is used to illustrate both the proposed algorithms' ability to suppress ambiguous towed array backlobes and resolve closely spaced interferers near endfire which pose challenges for conventional beamforming approaches especially during array maneuvers. Receiver operating characteristics are presented to evaluate the algorithms' detection performance versus signal-to-noise ratio. The results indicate that both FDM algorithms offer the potential to provide superior detection performance when compared to conventional beamforming with a maneuverable array. (C) 2010 Acoustical Society of America. [DOI: 10.1121/1.3505121]

关键词： array signal processing expectation-maximisation algorithm sonar arrays sonar signal processing

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Obtaining point spread function of penumbral encoding aperture with "expectation maximization" algorithm based on matched source-image pair experiment

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REVIEW OF SCIENTIFIC INSTRUMENTS 2010年第5期81卷 053502-053502页

作者： Wu, Y. L. Hu, H. S. Zhang, T. K. Li, Z. H. Chen, D. Xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Peoples R China China Acad Engn Phys Inst Nucl Phys & Chem Mianyang 621900 Peoples R China Nanjing Univ Aeronaut & Astronaut Coll Mat Sci & Technol Nanjing 210016 Peoples R China

A source penumbral image reconstruction method with linear mapping principle for geometrical optics is established. The ideal binary point spread function (PSF) can be obtained using a geometrical optics model. The system PSF with certain sharpness was obtained using a Monte Carlo (MC) model. Considering other factors besides the transportation of the x (gamma)-rays or particles (fusion neutrons) in the penumbral encoding aperture in MC model, such as the scattering background and the systematic error, the PSF from MC model "source-image pair matching" experiments with a large area standard oval shape source were processed. A method for correcting and calibrating the PSF by the expectation maximization adaptive algorithm was established and the optimized PSF with 22.30 mu m sharpness was achieved. This is more consistent with the real system PSF despite the increased noise level of the two-dimensional PSF and large irregularity in the PSF profile. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3427208]

关键词： expectation-maximisation algorithm geometrical optics image matching image reconstruction Monte Carlo methods optical transfer function

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