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An algorithm for fitting Heavy-Tailed Distributions via Generalized Hyperexponentials

INFORMS JOURNAL ON COMPUTING 2012年第1期24卷 42-52页

作者： Yu, Kaiqi Huang, Mei-Ling Brill, Percy H. Univ Windsor Dept Management Sci Windsor ON N9B 3P4 Canada Univ Windsor Dept Math & Stat Windsor ON N9B 3P4 Canada Brock Univ Dept Math St Catharines ON LS2 3A1 Canada

In this paper, we propose an algorithm to fit heavy-tailed (HT) distribution functions by generalized hyperexponential (GH) distribution functions. A discussion of the steps, usage, and accuracy of the GH algorithm is given. Several examples in this paper show that the proposed method can be applied to fit HT distributions with a completely monotone probability density function (pdf) very well, like the Pareto distribution and the Weibull distribution with the shape parameter less than one, as well as HT distributions whose pdf is not completely monotone, like the lognormal distribution. In addition, we provide an example that shows that the proposed method can be applied to density estimation of real data presenting a heavy tail.

关键词： fitting algorithm heavy-tailed distribution generalized hyperexponential distribution hyperexponential distribution

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MultiSig: a new high-precision approach to the analysis of complex biomolecular systems

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EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS 2013年第10期42卷 777-786页

作者： Gillis, Richard B. Adams, Gary G. Heinze, Thomas Nikolajski, Melanie Harding, Stephen E. Rowe, Arthur J. Univ Nottingham Sch Biosci Natl Ctr Macromol Hydrodynam Loughborough LE12 5RD Leics England Univ Jena Ctr Excellence Polysaccharide Res Inst Organ Chem & Macromol Chem D-07743 Jena Germany

MultiSig is a newly developed mode of analysis of sedimentation equilibrium (SE) experiments in the analytical ultracentrifuge, having the capability of taking advantage of the remarkable precision (similar to 0.1 % of signal) of the principal optical (fringe) system employed, thus supplanting existing methods of analysis through reducing the 'noise' level of certain important parameter estimates by up to orders of magnitude. Long-known limitations of the SE method, arising from lack of knowledge of the true fringe number in fringe optics and from the use of unstable numerical algorithms such as numerical differentiation, have been transcended. An approach to data analysis, akin to 'spatial filtering', has been developed, and shown by both simulation and practical application to be a powerful aid to the precision with which near-monodisperse systems can be analysed, potentially yielding information on protein-solvent interaction. For oligo- and poly-disperse systems the information returned includes precise average mass distributions over both cell radial and concentration ranges and mass-frequency histograms at fixed radial positions. The application of MultiSig analysis to various complex heterogenous systems and potentially multiply-interacting carbohydrate oligomers is described.

关键词： Sedimentation equilibrium fitting algorithm Rayleigh interference optics Molecular weight histograms Point average molecular weights Spatial filtering

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Center wavelength detection algorithm of FBG based on neural network

Center wavelength detection algorithm of FBG based on neural...

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3rd International Conference on Frontiers of Manufacturing Science and Measuring Technology (ICFMM 2013)

作者： Yin, Chengqun Lu, Dan He, Yujun North China Elect Power Univ Dept Elect & Commun Engn Baoding Hebei Peoples R China

ISBN: (纸本)9783037858462

In order to find a more accurate center wavelength detection fitting algorithm for fiber Bragg grating (FBG) reflection spectrum, Based on the theory of neural network, we designed different neural network to study and fit the spectral data which has been acquired from *** this paper,we have studied BP,RBFand wavelet neural network structure,comparing the network training time and the result of fitting curves,wavelet neural network is proved to be the best fitting algorithm.

关键词： FBG neural network fitting algorithm

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Spectral calibration for convex grating imaging spectrometer

Spectral calibration for convex grating imaging spectrometer

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International Conference on Optical Instruments and Technology (OIT) - Optoelectronic Imaging and Processing Technology

作者： Zhou, Jiankang Chen, Xinhua Ji, Yiqun Chen, Yuheng Shen, Weimin Soochow Univ Key Lab Adv Opt Mfg Technol Jiangsu Prov Inst Modern Opt Technol Suzhou 215006 Jiangsu Peoples R China Soochow Univ Key Lab Modern Opt Technol Educ Minist China Suzhou 215006 Jiangsu Peoples R China

ISBN: (纸本)9780819499639

Spectral calibration of imaging spectrometer plays an important role for acquiring target accurate spectrum. There are two spectral calibration types in essence, the wavelength scanning and characteristic line sampling. Only the calibrated pixel is used for the wavelength scanning methods and he spectral response function (SRF) is constructed by the calibrated pixel itself. The different wavelength can be generated by the monochromator. The SRF is constructed by adjacent pixels of the calibrated one for the characteristic line sampling methods. And the pixels are illuminated by the narrow spectrum line and the center wavelength of the spectral line is exactly known. The calibration result comes from scanning method is precise, but it takes much time and data to deal with. The wavelength scanning method cannot be used in field or space environment. The characteristic line sampling method is simple, but the calibration precision is not easy to confirm. The standard spectroscopic lamp is used to calibrate our manufactured convex grating imaging spectrometer which has Offner concentric structure and can supply high resolution and uniform spectral signal. Gaussian fitting algorithm is used to determine the center position and the Full-Width-Half-Maximum (FWHM) of the characteristic spectrum line. The central wavelengths and FWHMs of spectral pixels are calibrated by cubic polynomial fitting. By setting a fitting error thresh hold and abandoning the maximum deviation point, an optimization calculation is achieved. The integrated calibration experiment equipment for spectral calibration is developed to enhance calibration efficiency. The spectral calibration result comes from spectral lamp method are verified by monochromator wavelength scanning calibration technique. The result shows that spectral calibration uncertainty of FWHM and center wavelength are both less than 0.08nm, or 5.2% of spectral FWHM.

关键词： imaging spectrometer spectral calibration spectroscopic lamp spectral response function fitting algorithm

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Shape Model fitting using Non-Isotropic GMM

Shape Model fitting using Non-Isotropic GMM

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IET Irish Signals and Systems Conference

作者： Claudia Arellano Rozenn Dahyot School of Computer Science and Statistics Trinity College Dublin

ISBN: (纸本)9781629935867

We present a Mean Shift algorithm for fitting shape models. This algorithm maximises a posterior density function where the likelihood is defined as the Euclidean distance between two Gaussian mixture density functions, one modelling the observations while the other corresponds to the shape model. We explore the role of the covariance matrix in the Gaussian kernel for encoding the shape of the model in the density function. Results show that using non-isotropic covariance matrices improve the efficiency of the algorithm and allow to reduce the number of kernels to use in the mixture without compromising the robustness of the algorithm.

关键词： Morphable Models fitting algorithm Gaussian Mixture Models Mean Shift

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A neural mass model of interconnected regions simulates rhythm propagation observed via TMS-EEG

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NEUROIMAGE 2011年第3期57卷 1045-1058页

作者： Cona, F. Zavaglia, M. Massimini, M. Rosanova, M. Ursino, M. Univ Bologna Dept Elect Comp Sci & Syst I-47521 Cesena Italy Univ Milan Dept Clin Sci Luigi Sacco I-20157 Milan Italy

Knowledge of cortical rhythms represents an important aspect of modern neuroscience, to understand how the brain realizes its functions. Recent data suggest that different regions in the brain may exhibit distinct electroencephalogram (EEG) rhythms when perturbed by Transcranial Magnetic Stimulation (TMS) and that these rhythms can change due to the connectivity among regions. In this context, in silico simulations may help the validation of these hypotheses that would be difficult to be verified in vivo. Neural mass models can be very useful to simulate specific aspects of electrical brain activity and, above all, to analyze and identify the overall frequency content of EEG in a cortical region of interest (ROI). In this work we implemented a model of connectivity among cortical regions to fit the impulse responses in three ROIs recorded during a series of TMS/EEG experiments performed in five subjects and using three different impulse intensities. in particular we investigated Brodmann Area (BA) 19 (occipital lobe), BA 7 (parietal lobe) and BA 6 (frontal lobe). Results show that the model can reproduce the natural rhythms of the three regions quite well, acting on a few internal parameters. Moreover, the model can explain most rhythm changes induced by stimulation of another region, and inter-subject variability, by estimating just a few long-range connectivity parameters among ROIs. (C) 2011 Elsevier Inc. All rights reserved.

关键词： TMS Neural mass model EEG rhythms Connectivity fitting algorithm

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Trace data characterization and fitting for Markov modeling

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PERFORMANCE EVALUATION 2010年第2期67卷 61-79页

作者： Casale, Giuliano Zhang, Eddy Z. Smirni, Evgenia SAP Res CEC Belfast Newtownabbey North Ireland Coll William & Mary Dept Comp Sci Williamsburg VA 23185 USA

We propose a trace fitting algorithm for Markovian Arrival Processes (MAPs) that can capture statistics of any order of interarrival times between measured events. By studying real traffic and workload traces often used in performance evaluation studies, we show that matching higher order statistical properties, in addition to first and second order descriptors, results in increased queueing prediction accuracy with respect to algorithms that only match the mean, the coefficient of variation, and the autocorrelations of the trace. This result supports the approach of modeling traces by the interarrival time process instead of the counting process that is more frequently used in the literature. We proceed by first characterizing the general properties of MAPs using a spectral approach. Based on this result, we show how different MAPs can be combined together using Kronecker products to define a larger MAP with predefined properties of interarrival times. We then devise an algorithm that is based on this Kronecker composition and can accurately fit data traces. This MAP fitting algorithm uses nonlinear optimization that can be customized to fit an arbitrary number of moments and to meet the desired cost-accuracy tradeoff. Numerical results of the fitting algorithm on real data, such as the Bellcore Aug89 trace and a Seagate disk drive trace, indicate that the proposed fitting technique achieves increased prediction accuracy with respect to other state-of-the-art fitting methods. (C) 2009 Elsevier B.V. All rights reserved.

关键词： Markovian arrival process fitting algorithm Time series modeling Temporal dependence Correlations

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A new approach to characterising aspheric surfaces

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PRECISION ENGINEERING-JOURNAL OF THE INTERNATIONAL SOCIETIES FOR PRECISION ENGINEERING AND NANOTECHNOLOGY 2010年第1期34卷 171-179页

作者： Sun, W. McBride, J. W. Hill, M. Univ Southampton Sch Engn Sci Highfield SO17 1BJ Hants England

In this paper, a new approach to fitting aspheric surfaces in three-dimensional space is proposed, based on the nonlinear least-squares algorithm. For the conditions tested, there are good indications that this method provides better results than conventional solutions as all the surface parameters can be estimated simultaneously based on the design equation, thus allowing the result to be directly compared to design parameters. Conventionally, aspheric surfaces can be fitted with simplified surface models, such as a second order surface or polynomial model. Using this approach the estimated parameters cannot be compared with the design values, breaking the link between the designed and measured surface. The new method is developed here and tested on computer simulated aspheric surfaces. Both ideal surfaces and surfaces with random irregularities are considered. Issues regarding the application of the fitting method to real measured surfaces are discussed. (C) 2009 Elsevier Inc. All rights reserved.

关键词： Aspheric surfaces fitting algorithm Nonlinear least-squares

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Research On Course Radius Measurement For Vertical Petroleum Tank Volume Metrology Based On 3D Laser Scan Principle

Research On Course Radius Measurement For Vertical Petroleum...

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International Conference on Advanced Measurement and Test (AMT 2010)

作者： Wang Jin Tao Liu Zi Yong Zhang Long Guo Li Gong Bao Xue Song Tong Lin Natl Inst Metrol Div Mech & Acoust Beijing 100013 Peoples R China

ISBN: (纸本)0878492712

One course radius measurement method for vertical petroleum tank volume metrology based on 3D laser scan principle was researched. Method of distance measurement by laser phase-shift technology and angular measurement by optical grating was applied to acquire coordinates of points in each course under the control of servo system. The permitted error of measured point location is 2mm. fitting algorithms base on direct iterative method (DIM) and least square method (LSM) were used to process measured data and deduce equivalent radius of each course. In comparison experiment, one 1000m(3) vertical tank was used as test object. Compared to strapping method (international mandatory standard), the maximal deviation radius value of method discussed is 2.8mm. The maximal difference of radius value calculated by DIM and LSM is 0.1mm. The experimental results verified the method discussed in this paper.

关键词： course radius measurement vertical tank volume metrology fitting algorithm comparison experiment

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Development of fitting Program for Fully Implantable Middle Ear Hearing Device

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11th International Congress of the IUPESM/World Congress on Medical Physics and Biomedical Engineering

作者： Lee, Seung Hyun Lim, Hyung Gyu Jung, Eui Sung Kim, Min Woo An, Jinung Cho, Jin Ho Daegu Gyeongbuk Inst Sci & Technol Brain Robot Interact Lab Taegu South Korea Kyungpook Natl Univ Grad Sch Elect Engn & Comp Sci Taegu South Korea

ISBN: (纸本)9783642038907

A fully implantable middle ear hearing device (F-IMEHD) has been investigated in Korea. Generally, F-IMEHD is implanted under the skin at human temporal bone and it uses implantable microphone and vibrating transducer. Therefore, F-IMEHD must require a different fitting process from conventional hearing aids. In this paper, a fitting program for the F-IMEHD has been developed using LabVIEW. We calculate proper fitting parameters based on FIG6 fitting rule. And also, it takes account of frequency characteristics of F-IMEHD's components. Through experimental results, it can be confirmed that the proposed fitting program is suitable to F-IMEHD.

关键词： F-IMEHD hearing fitting fitting algorithm

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