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Time series analysis of categorical data using auto-mutual information

JOURNAL OF STATISTICAL PLANNING AND INFERENCE 2009年第9期139卷 3076-3087页

作者： Biswas, Atanu Guha, Apratim Indian Stat Inst Appl Stat Unit Kolkata 700108 India Univ Birmingham Sch Math Birmingham B15 2TT W Midlands England Natl Univ Singapore Dept Stat & Appl Probabil Singapore 117548 Singapore

Despite its importance, there has been little attention in the modeling of time series data of categorical nature in the recent past. In this paper, we present a framework based on the Pegram's [An autoregressive model for multilag Markov chains. Journal of Applied Probabability 17, 350-362] operator that was originally proposed only to construct discrete AR(p) processes. We extend the Pegram's operator to accommodate categorical processes with ARMA representations. We observe that the concept of correlation is not always suitable for categorical data. As a sensible alternative, we use the concept of mutual information, and introduce auto-mutual information to define the time series process of categorical data. Some model selection and inferential aspects are also discussed. We implement the developed methodologies to analyze a time series data set on infant sleep status. (C) 2008 Elsevier B.V. All rights reserved,

关键词： auto-correlation function Maximum likelihood estimates Mixture distribution Mutual information Partial auto-correlation function Thinning operator

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Restricted diffusion of DNA segments within the isolated Escherichia coli nucleoid

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JOURNAL OF STRUCTURAL BIOLOGY 2005年第2期150卷 226-232页

作者： Cunha, S Woldringh, CL Odijk, T Delft Univ Technol Kluyver Inst Biotechnol Sect Theory Complex Fluids NL-2628 BC Delft Netherlands Univ Amsterdam Swammerdam Inst Life BioCtr Amsterdam NL-1098 SM Amsterdam Netherlands

To study the dynamics and organization of the DNA within isolated Escherichia coli nucleoids, we track the movement of a specific DNA region. Labeling of such a region is achieved using the Lac-O/Lac-I system. The Lac repressor-GFP fusion protein binds to the DNA section where tandem repeats of the Lac operator are inserted, which allows us to monitor the motion of the DNA. The movement of such a GFP spot is followed at 48 ms temporal resolution during 12 s. The spots are found to diffuse within a confined space, so that the nucleoid appears to behave like a viscoelastic network. The distribution of the '' particle '' position in time can be fitted to a Gaussian function indicating that the motion of the particle is Brownian. Ail average self-diffusion constant D-s = 0.12 mu m(2) s(-1) is derived via the time auto-correlation functions of the displacement and is compatible with the collective diffusion coefficient measured previously by dynamic light scattering. Restriction of a DNA sequence to a small region of the nucleoid is tentatively related to the existence of so-called supercoiling domains. (c) 2005 Elsevier Inc. All rights reserved.

关键词： isolated nucleoids E. coli oriC-GFP particles auto-correlation function Brownian motion restricted diffusion

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Space-Time Dynamics of Gazeau-Klauder Coherent States in Power-Law Potentials

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INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS 2010年第10期49卷 2540-2557页

作者： Iqbal, Shahid Riviere, Paula Saif, Farhan Quaid I Azam Univ Dept Elect Islamabad 45320 Pakistan Max Planck Inst Phys Komplexer Syst D-01187 Dresden Germany

Gazeau-Klauder coherent states are developed for power-law potentials and their evolution in space and time is analyzed. We show that these states follow classical dynamics as long as the underlying energy spectrum is linear, otherwise they follow a classical-like evolution upto a few classical periods and disperse thereafter, despite its special construction. auto-correlation function and probability density as a function of space and time explain the spatio-temporal behavior of these states.

关键词： Gazeau-Klauder coherent states Generalized coherent states Space-time dynamics Temporal stability Quantum revivals Quantum carpets Power-law potentials Loosely binding potentials Tightly binding potentials auto-correlation function Probability density function

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An Enhanced Doppler Spread Estimation Method for OFDM Systems

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IEICE TRANSACTIONS ON COMMUNICATIONS 2012年第12期E95B卷 3911-3914页

作者： Sheng, Bin Zhu, Pengcheng You, Xiaohu Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Jiangsu Peoples R China

In OFDM systems, the correlation of cyclic prefix (CP) with its corresponding part at the end of the symbol can be used to estimate the maximum Doppler spread. However, the estimation accuracy of this CP based method is seriously affected by the inter-symbol interference (ISI) generated in the multipath channel. In this letter, we propose an enhanced CP based method which is immune to the ISI and can hence obtain an unbiased estimate of the auto-correlation function in multipath channels.

关键词： cyclic prefix auto-correlation function OFDM

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Yarn strength dependence on test length

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FIBRES & TEXTILES IN EASTERN EUROPE 2002年第3期10卷 32-34页

作者： Lizák, P Univ Trencin Fac Ind Technol Dept Text Technol Ruzomberok 03401 Slovakia

Standard measurement of yarn strength is executed on a gauge length of 500 mm. Clamped yarn breaks in its weakest place. It is therefore important to measure the strength of 50-mm short links and to break them one after another lengthwise along the yarn. This allows us to observe how the strength changes along the yarn and to evaluate the auto-correlation functions of the strength of short yarn links. Some similar cotton yarns were analysed and compared by applying this methodology.

关键词： yarn strength yarn metrology cotton strength test length weakest link auto-correlation function

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Post-combustion artificial neural network modeling of nickel-producing multiple hearth furnace

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INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING 2020年第7期18卷 p1-14页

作者： Montero Gongora, Deynier Van Caneghem, Jo Haeseldonckx, Dries Gongora Leyva, Ever Ramirez Mendoza, Mercedes Dutta, Abhishek Univ Moa Holguin Cuba Katholieke Univ Leuven Campus Groep TAndreas Vesaliusstr 13 B-3000 Leuven Belgium Univ Oriente Santiago De Cuba Cuba

In a nickel-producing multiple hearth furnace, there is a problem associated to the automatic operation of the temperature control loops in two of the hearths, since the same flow of air is split into two branches. A neural model of the post-combustion sub-process is built and served to increase the process efficiency of the industrial furnace. Data was taken for a three-months operating time period to identify the main variables characterizing the process and a model of multilayer perceptron type is built. For the validation of this model, process data from a four-months operating time period in 2018 was used and prediction errors based on a measure of closeness in terms of a mean square error criterion measured through its weights for the temperature of two of the hearths (four and six) versus the air flow to these hearths. Based on a rigorous testing and analysis of the process, the model is capable of predicting the temperature of hearth four and six with errors of 0.6 and 0.3 degrees C, respectively. In addition, the emissions by high concentration of carbon monoxide in the exhaust gases are reduced, thus contributing to the health of the ecosystem.

关键词： artificial neural network auto-correlation function dynamic characteristics multi-hearth furnace post-combustion

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A new way to analyze resuscitation quality by reviewing automatic external defibrillator data

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RESUSCITATION 2012年第2期83卷 171-176页

作者： Lin, Lian-Yu Lo, Men-Tzung Chiang, Wen-Chu Lin, Chen Ko, Patrick Chow-In Hsiung, Kuang-Hua Lin, Jiunn-Lee Chen, Wen-Jone Ma, Matthew Huei-Ming Natl Taiwan Univ Hosp Dept Emergency Med Taipei Taiwan Natl Taiwan Univ Hosp Dept Internal Med Taipei 100 Taiwan Natl Cent Univ Ctr Dynam Biomarkers & Translat Med Res Ctr Adapt Data Anal Tao Yuan Taiwan Natl Cent Univ Inst Syst Biol & Bioinformat Tao Yuan Taiwan Taipei City Fire Dept Taipei Taiwan

Aims: High quality cardiopulmonary resuscitation (CPR) plays an important role in survival of out-of-hospital cardiac arrests (OHCAs). We have developed an algorithm to automatically identify the quality of chest compressions from data retrieved from automatic external defibrillators (AEDs). Methods: Electrocardiographic (ECG) signals retrieved from AEDs were analyzed by a newly developed algorithm to identify fluctuations in CPR. The algorithm contained three steps. First, it decomposed the AED signals into several intrinsic mode fluctuations (IMFs) by empirical mode decomposition (EMD). Second, it identified the dominant IMFs that carried the chest compression signals and weighted the IMFs to both enhance the chest compression oscillations and filter the noise. Third, it calculated the autocorrelation function (ACF) of the reconstructed signals and tested their periodicity. Using this algorithm, several CPR quality indicators were automatically calculated minute-by-minute and compared with those derived by audio and visual review of AED data by experienced physicians. Results: A total of 77 (29 women, 48 men) OHCA patients were enrolled, and 351 one-min segments were analyzed. The results showed that the CPR quality parameters calculated from the algorithm were highly correlated with those from the manual review (all P<0.001). The limits of agreement by Bland-Altman analysis were acceptable for chest compression number, total flow time, and no flow time, but not for CPR rate. We also demonstrated that only 41.8 +/- 29.8% of time was spent in chest compressions and only 7.5 +/- 16.8% was spent in adequate chest compressions. Conclusion: Our results demonstrated that several indicators of CPR quality can be precisely and automatically determined by analyzing the ECG signals from AEDs using EMD and autocorrelograms. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

关键词： Cardiopulmonary resuscitation automated external defibrillator Empirical mode decomposition auto-correlation function Out-of-hospital cardiac arrest

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Subtractive and divisive adaptation in visual motion computations

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VISION RESEARCH 2007年第5期47卷 673-686页

作者： Langley, Keith Anderson, Stephen J. UCL Dept Psychol London W1N 8AA England Aston Univ Sch Life & Hlth Sci Birmingham B4 7ET W Midlands England

Models of visual motion processing that introduce priors for low speed through Bayesian computations are sometimes treated with scepticism by empirical researchers because of the convenient way in which parameters of the Bayesian priors have been chosen. Using the effects of motion adaptation on motion perception to illustrate, we show that the Bayesian prior, far from being convenient, may be estimated on-line and therefore represents a useful tool by which visual motion processes may be optimized in order to extract the motion signals commonly encountered in every day experience. The prescription for optimization, when combined with system constraints on the transmission of visual information, may lead to an exaggeration of perceptual bias through the process of adaptation. Our approach extends the Bayesian model of visual motion proposed by Weiss et al. [Weiss Y., Simoncelli, E., & Adelson, E. (2002). Motion illusions as optimal perception Nature Neuroscience, 5:598-604.], in suggesting that perceptual bias reflects a compromise taken by a rational system in the face of uncertain signals and system constraints. (c) 2007 Published by Elsevier Ltd.

关键词： Lalman filter leaky predictive coding auto-correlation function Bayes prior Garotte function

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Time-variance of 60 GHz vehicular infrastructure-to-infrastructure (I2I) channel

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VEHICULAR COMMUNICATIONS 2020年 26卷

作者： Rahman, Aniq Ur Ghosh, Anirban Chandra, Aniruddha Vychodil, Josef Blumenstein, Jiri Mikulasek, Tomas Prokes, Ales Indian Inst Sci Dept Elect Commun Engn Bangalore 560012 Karnataka India SRM Univ AP Dept Elect & Commun Engn Amaravati 522502 India Natl Inst Technol Dept Elect & Commun Engn Durgapur 713209 India Brno Univ Technol Dept Radio Elect Brno 61600 Czech Republic

In this paper, we study the time-variance of a roadside infrastructure to infrastructure (I2I) channel operating at 60 GHz millimetre wave (mmWave) band, where the time-variance is caused by moving vehicles acting as scatterers. At first, measurement data is obtained by placing the transmitter (TX) and the receiver (RX) at different heights to emulate a link between two nonidentical roadside units (RSUs), and time-domain channel sounding is performed by sending complementary Golay sequences from the TX to the RX. A linear piece-wise interpolation of the corresponding temporal auto-correlation function (ACF) is used to find the Doppler spread of the I2I channel, where our interpolation method compensates for a slower sampling rate. Next, a framework is presented for time-variant channel impulse response (CIR) simulation which focuses on moving scatterers only and validates the linear piece-wise ACF model. The framework is useful for time-variant vehicular I2I channel simulation and in speed estimation related vehicular applications. Finally, a double-slope curve-fitted analytical model for ACF is proposed as a generalisation to the linear piece-wise model. The proposed model and its Doppler spectrum are found to be in agreement with the analytical results for fixed-to-fixed (F2F) channels with moving scatterers and matches perfectly with the measured data. (c) 2020 Elsevier Inc. All rights reserved.

关键词： auto-correlation function Doppler spectrum 60 GHz millimetre wave Fixed-to-fixed channel Moving scatterers

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Transmission electron microscopy investigation of the formation of C54-TiSi₂ phase on stressed (001)Si

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MICRON 2002年第6期33卷 543-547页

作者： Cheng, SL Chang, SM Huang, HY Chen, LJ Tsai, CJ Natl Tsing Hua Univ Dept Mat Sci & Engn Hsinchu 300 Taiwan

The effects of stress on the formation of C54-TiSi2 phase in Ti/(001)Si samples have been investigated by high-resolution transmission electron microscopy in conjunction with auto-correlation function (ACF) analysis. The C54-TiSi2 phase transformation temperature in tensily stressed samples was found to be lowered by about 100 degreesC than that in compressively stressed samples. The thickness of amorphous interlayers (a-interlayers) between Ti metal thin films and Si substrates was found to be thicker and thinner in the tensily and compressively stressed Si samples, respectively. Furthermore. the thicker a-interlayer was found to consist of a higher density of crystallites from the ACF analysis. With a higher density of crystallites in the a-interlayer, the grain size of C49-TiSi2 was reduced since more nucleation sites are available for the formation of C49-TiSi2. The small grain size of C49-TiSi2 in turn enhances the formation of C54-TiSi2. As a result, the phase transformation of C49- to C54-TiSi2 is enhanced by the tensile stress present in silicon substrates. (C) 2002 Elsevier Science Ltd. All rights reserved.

关键词： stress silicide amorphous interlayer auto-correlation function

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