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Random changepoint segmented regression with smooth transition

STATISTICAL METHODS IN MEDICAL RESEARCH 2021年第3期30卷 643-654页

作者： Singer, Julio M. Rocha, Francisco M. M. Pedroso-de-Lima, Antonio Carlos Silva, Giovani L. Coatti, Giuliana C. Zatz, Mayana Univ Sao Paulo Dept Estat Rua Matao 1010 BR-05508090 Sao Paulo SP Brazil Univ Fed Sao Paulo Dept Multidisciplinar Escola Paulista Polit Econ & Negocios Sao Paulo SP Brazil Univ Lisbon Dept Matemat IST Lisbon Portugal Univ Lisbon CEAUL Lisbon Portugal Univ Sao Paulo Inst Biociencias Sao Paulo Brazil

We consider random changepoint segmented regression models to analyse data from a study conducted to verify whether treatment with stem cells may delay the onset of a symptom of amyotrophic lateral sclerosis in genetically modified mice. The proposed models capture the biological aspects of the data, accommodating a smooth transition between the periods with and without symptoms. An additional changepoint is considered to avoid negative predicted responses. Given the nonlinear nature of the model, we propose an algorithm to estimate the fixed parameters and to predict the random effects by fitting linear mixed models iteratively via standard software. We compare the variances obtained in the final step with bootstrapped and robust ones.

关键词： Amyotrophic lateral sclerosis fitting algorithm mixed models random effects

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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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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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Research on key technologies of non-contact measurement system of optical aspheric surface - art. no. 672359

Research on key technologies of non-contact measurement syst...

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3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies

作者： Liu Gujin Guo Yinbiao Liu Jianchun Xiamen Univ Dept Mech Electro Engn Xiamen 361005 Peoples R China

ISBN: (纸本)9780819468802

According to the requirement of high precision measurement of optical aspheric surface, 4D measurement platform is under development. Open motion control system is adapted and multi-axes motion control card is mounted in IPC. Repeatability accuracy and positioning accuracy of the full travel of the driving unit of the platform can reach to 0.3 mu m and 1 mu m respectively. Laser sensor is droven by the ultrasonic LM (USLM) to the position needed to be tested. The fine positioning of the unit is achieved by USLM with its DC drive mode, which can perform nanometer steps proportional to the input voltages. The positioning error of the driving unit can not be prevented. In this paper, the mathematic model of error compensation of the USLM driving unit is found and software compensation is introduced. Results of compensation show that the position accuracy of this driving unit is greatly improved and can fulfill the task of optical aspheric mirror surface measurement.

关键词： aspheric mirror ultrasonic LM positioning accuracy measurement fitting algorithm

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Measurement of Tank Cooling Airflow Based on Array Sensors

Measurement of Tank Cooling Airflow Based on Array Sensors

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International Conference on Fluid Mechanics and Industrial Applications (FMIA)

作者： Zhou, Hui Han, Yan Wang, Jianguo Zhang, Pizhuang North Univ China Sch Informat & Commun Engn Taiyuan 030051 Shanxi Peoples R China North Automat Control Technol Inst Taiyuan 030006 Shanxi Peoples R China

Researching on the cooling airflow characters of tank will be helpful for optimizing the design of cooling system, and will be of great importance to improve the performance of armoured vehicles. According to the test requirements of tank under the actual working conditions, we studied and designed the proposed cooling airflow measurement system. The most important thing was that we finished the assembly of array sensors without any damage to tank. In addition, according to national standard we set the quantity and locations of the sensors, which was on the premise of avoiding the influence to airway. In this paper, there was description of cooling airflow signal processing;and there was analysis of air pressure distribution which was presented simultaneously by three-dimensional surface graph and plane graph at the exhaust port of tank engine compartment according to fitting algorithm.

关键词： Tank Cooling Airflow Array Sensors Assembly Signal Processing fitting algorithm Air Pressure Distribution

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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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Non-contacting measurement system design of ultra-precision aspheric surface

Non-contacting measurement system design of ultra-precision ...

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2nd International Symposium on Advanced Optical Manufacturing and Testing Technologies

作者： Liu, JC Guo, YB Huang, J Liu, GJ Xiamen Univ Dept Mech & Elect Engn Xiamen 361005 Peoples R China

ISBN: (纸本)081946189X

Aiming at various influential factors during the ultra-precision aspheric surface testing, this paper introduces an aspheric measurement technique based on the high accuracy and non-contacting measuring equipment of laser. To form the platform of four-dimension control system, the measuring instrument of laser is used to realize on-line testing process error of aspheric mirror, and the results of measurement provide error data for compensation processing. To build testing and controlling mathematical model and to design the measurement of ultra-precision aspheric workpiece, the method of compensation based on analyzing the reason of non-contacting error comes into being and the finest way of processing data is given. With full automatic measuring and data processing of the system, error analyzing, displaying could be realized, and data could be provided for compensation processing to processing system.

关键词： aspheric mirror accuracy measurement laser sensor 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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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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A Joint Signal Detection and Channel Estimation Method in Multi-user MIMO Relay Systems 2020

A Joint Signal Detection and Channel Estimation Method in Mu...

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4th International Conference on High Performance Compilation, Computing and Communications (HP3C)

作者： Pan, Xinhong Luo, Xin Zhang, Zhihai Lin, Heyun Dong, Jingyi Guangxi Power Grid Dispatching Control Ctr Nanning Peoples R China Commun Univ China Sch Informat & Commun Engn Beijing Peoples R China

ISBN: (纸本)9781450376914

For multi-user multiple-input multiple-output (MIMO) Relay System, this paper develops a joint signal detection and channel estimation method based on Tucker-2 model. First, the proposed method encodes the transmitted information symbols at the source and transmits them to the relay. Then, the relay amplifies the received signals and broadcasts them to all users. Last, the Tucker-2 model is constructed and the iterative fitting algorithm is designed at the user end to realize the joint estimation of signals and channels. Theoretical analysis and simulation results show that the proposed method can effectively detect the information symbols and estimate the channel matrix when channel state information (CSI) is unknown and pilot signal is not used. In addition, compared with the existing algorithms, the proposed method has higher estimation performance and more relaxed application conditions.

关键词： Multi-user MIMO Relay tucker-2 fitting algorithm CSI

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