Search for: change-detection
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    A novel concept drift detection method in data streams using ensemble classifiers

    , Article Intelligent Data Analysis ; Volume 20, Issue 6 , 2016 , Pages 1329-1350 ; 1088467X (ISSN) Dehghan, M ; Beigy, H ; Zaremoodi, P ; Sharif University of Technology
    IOS Press  2016
    Concept drift, change in the underlying distribution that data points come from, is an inevitable phenomenon in data streams. Due to increase in the number of data streams' applications such as network intrusion detection, weather forecasting, and detection of unconventional behavior in financial transactions; numerous researches have recently been conducted in the area of concept drift detection. An ideal method for concept drift detection should be able to rapidly and correctly identify changes in the underlying distribution of data points and adapt its model as quickly as possible while the memory and processing time is limited. In this paper, we propose a novel explicit method based on... 

    Texture Change Detection in Hyperspectral Images

    , Ph.D. Dissertation Sharif University of Technology Dianat, Rouhollah (Author) ; Kasaei, Shohreh (Supervisor)
    In this thesis, change detection in hyperspectral images is investigated. In this process, two hyperspectral images captured from the same scene but in different time instances are given and we intend to detect the occurred changes in the scene. A specific change detection algorithm contains four different steps; namely, preprocessing, selection of the criterion, postprocessing, and decision making. Dimension reduction as a critical process is also deeply investigated to be performed before classification (for decision making purposes.) Two new methods are proposed in the thesis. The proposed MCRD method is designed for dimension reduction and the MPR method is related to the change... 

    Aberrant frequency related change-detection activity in chronic tinnitus

    , Article Frontiers in Neuroscience ; Volume 14 , 2020 Asadpour, A ; Jahed, M ; Mahmoudian, S ; Sharif University of Technology
    Frontiers Media S.A  2020
    Tinnitus is the perception of sound without the occurrence of an acoustic event. The deficit in auditory sensory or echoic memory may be the cause of the perception of tinnitus. This study considered the mismatch negativity (MMN) to investigate the potential difference between and within groups of persons with normal hearing (NH) and tinnitus. Using an auditory multi-feature paradigm to elicit the MMN, this study considered the MMN peak amplitude at two central frequencies for two MMN subcomponents. These central frequencies were 1 and 5 kHz, which the latter was closer to the perceived tinnitus frequency in the group with tinnitus. The deviants were higher frequency, lower frequency, higher... 

    Fast registration of remotely sensed images for earthquake damage estimation

    , Article Eurasip Journal on Applied Signal Processing ; Volume 2006 , 2006 ; 11108657 (ISSN) Abadpour, A ; Kasaei, S ; Amiri, S. M ; Sharif University of Technology
    Analysis of the multispectral remotely sensed images of the areas destroyed by an earthquake is proved to be a helpful tool for destruction assessments. The performance of such methods is highly dependant on the preprocess that registers the two shots before and after an event. In this paper, we propose a new fast and reliable change detection method for remotely sensed images and analyze its performance. The experimental results show the efficiency of the proposed algorithm. Copyright © 2006 Hindawi Publishing Corporation. All right reserved  

    A hybrid approach for refreshing web page repositories

    , Article 10th International Conference on Database Systems for Advanced Applications, DASFAA 2005, Beijing, 17 April 2005 through 20 April 2005 ; Volume 3453 , 2005 , Pages 588-593 ; 03029743 (ISSN) Ghodsi, M ; Hassanzadeh, O ; Kamali, Sh ; Monemizadeh, M ; Sharif University of Technology
    Springer Verlag  2005
    Web pages change frequently and thus crawlers have to down-load them often. Various policies have been proposed for refreshing local copies of web pages. In this paper, we introduce a new sampling method that excels over other change detection methods in experiment. Change Frequency (CF) is a method that predicts the change frequency of the pages and, in the long run, achieves an optimal efficiency in comparison with the sampling method. Here, we propose a new hybrid method that is a combination of our new sampling approach and CF and show how our hybrid method improves the efficiency of change detection. © Springer-Verlag Berlin Heidelberg 2005  

    Remotely sensed change detection using multiresolution analysis and motion estimation

    , Article Remote Sensing for Environmental Monitoring, GIS Applications, and Geology IV, Maspalomas, 14 September 2004 through 16 September 2004 ; Volume 5574 , 2004 , Pages 194-204 ; 0277786X (ISSN) Lakdashti, A ; Kasaei, S ; SPIE ; Sharif University of Technology
    Detection of changes in remotely sensed geographic images is required for a variety of applications including natural disasters. Change detection is an important process utilized for updating the geographic information system (GIS) data, monitoring natural resources and urban developments. It provides quantitative analysis of the spatial distribution of the area of interest. Different types of change detection techniques include: Multi-date visual composite (multitemporal composite), image differencing, post-classification, etc. In this work, we propose a change detection algorithm based on multiresolution analysis and motion estimation. We use multispectral satellite imagery and apply the... 

    A New Method for Measuring very Low Variation in Physical Parameters based on the Sensitivity to Conditions of Chaotic Systems

    , M.Sc. Thesis Sharif University of Technology Seddighi Renani, Jamal (Author) ; Zohoor, Hasan (Supervisor)
    Since the beginning of human civilization, improving the methods of measuring and identifying changes in order to improve the level of comfort and safety of human civilization is inevitable. The intrinsic property of high sensitivity to system conditions in chaos phenomena has led some researchers to use this feature for purposes of identifying and measuring changes. The most important bugs of previous researches in this area are the complexity, lack of coherence and dependence on the nominal parameters. By analyzing the effect of the type and magnitude of the initial deviation in a system parameter on all the characteristics of the Duffing system response in the chaotic regime, was observed... 

    Change detection in remote sensing images using modified polynomial regression and spatial multivariate alteration detection

    , Article Journal of Applied Remote Sensing ; Volume 3, Issue 1 , 2009 ; 19313195 (ISSN) Dianat, R ; Kasaei, S ; Sharif University of Technology
    A new and efficient method for incorporating the spatiality into difference-based change detection (CD) algorithms is introduced in this paper. It uses the spatial derivatives of image pixels to extract spatial relations among them. Based on this methodology, the performances of two famous difference-based CD methods, conventional polynomial regression (CPR) and multivariate alteration detection (MAD), are improved and called modified polynomial regression (MPR) and spatial multivariate alteration detection (SMAD), respectively. Various quantitative and qualitative evaluations have shown the superiority of MPR over CPR and SMAD over MAD. Also, the superiority of SMAD over all mentioned CD... 

    New control charts for monitoring covariance matrix with individual observations

    , Article Quality and Reliability Engineering International ; Volume 25, Issue 7 , 2009 , Pages 821-838 ; 07488017 (ISSN) Ostadsharif Memar, A ; Akhavan Niaki, T ; Sharif University of Technology
    It has recently been shown that the performance of multivariate exponentially weighted mean square and multivariate exponentially weighted moving variance charts of Huwang et al. (J. Qual. Technol. 2007; 39:258-278) in monitoring the variability of a multivariate process for individual observations is better than existing schemes. Both of these control charts monitor a distinct matrix which is an estimator of the in-control covariance matrix. Instead of using the trace, in this paper, we propose a L1-norm and a L2-norm-based distance between diagonal elements of the estimators from their expected values to design new control charts in monitoring the covariance matrix of a multivariate... 

    Change Point Detection in Molecular Carrier Based Nano Networks

    , M.Sc. Thesis Sharif University of Technology Ghoroghchian, Nafiseh (Author) ; Nasiri Kenari, Masoumeh (Supervisor) ; Aminzadeh Gohari, Amin (Co-Advisor)
    Molecular communication (MC) is an emerging communication paradigm, whereas molecules are used as information carriers to establish communication among elements in nano-meter to meter scales. In this thesis, we investigate the problem of detecting and monitoring changes (abnormality) based on molecular communication, using quickest change point detection scheme. We assume the distributions and parameters of the system are known. To this end, we consider a network of multiple sensors, each sensing its surrounding and employing On-Off-keying modulation for data transmission toward a fusion center (FC). An abnormality initiates randomly in time and location, and further propagates in the... 

    Estimating the step-change time of the location parameter in multistage processes using MLE

    , Article Quality and Reliability Engineering International ; Volume 28, Issue 8 , 2012 , Pages 843-855 ; 07488017 (ISSN) Davoodi, M ; Niaki, S. T. A ; Sharif University of Technology
    In this paper, maximum likelihood step-change point estimators of the location parameter, the out-of-control sample and the out-of-control stage are developed for auto-correlated multistage processes. To do this, the multistage process and the concept of change detection are first discussed. Then, a time-series model of the process is presented. Assuming step changes in the location parameter of the process, next, the likelihood functions of different samples before and after receiving out-of-control signal from an X-bar control chart were derived under different conditions. The maximum likelihood estimators were then obtained by maximizing the likelihood functions. Finally, the accuracy and... 

    Change detection in optical remote sensing images using difference-based methods and spatial information

    , Article IEEE Geoscience and Remote Sensing Letters ; Volume 7, Issue 1 , 2010 , Pages 215-219 ; 1545598X (ISSN) Dianat, R ; Kasaei, S ; Sharif University of Technology
    A new and general frameworkcalled modified polynomial regression (MPR)is introduced in this letter, which detects the changes that occurred in remote sensing images. It is an improvement of the conventional polynomial regression (CPR) method. Most change detection (CD) methods, including CPR, do not consider the spatial relations among image pixels. To improve CPR, our proposed framework incorporates the spatial information into the CD process by using linear spatial-oriented image operators. It is proved that MPR preserves the affine invariance property of CPR. A realization of MPR is proposed, which employs the image derivatives to account for spatiality. Experimental results show the... 

    Abnormality detection and monitoring in multi-sensor molecular communication

    , Article IEEE Transactions on Molecular, Biological, and Multi-Scale Communications ; Volume 5, Issue 2 , 2019 , Pages 68-83 ; 23327804 (ISSN) Ghoroghchian, N ; Mirmohseni, M ; Nasiri Kenari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    In this paper, we investigate the problem of detecting and monitoring changes (abnormality) in molecular communication (MC), using the quickest change detection (QCD) schemes. The objective is to watch an environment using a sensor network and make decisions on the time and location of changes based on the received signals from sensors in the fusion center (FC). Such assumptions call for considering spatial and temporal correlations among sensors' transmitting signals. We use the framework of Partially Observable Markov Decision Processes (POMDPs) based on non-homogeneous Markov models. The metric in detection (stopping-time) scenario is to minimize the delay of announcing an abnormality... 

    Contourlet-based multispectral image fusion

    , Article 7th IASTED International Conference on Visualization, Imaging, and Image Processing, VIIP 2007, Palma de Mallorca, 29 August 2007 through 31 August 2007 ; 2007 , Pages 11-14 ; 9780889866911 (ISBN) Barmas, S. M ; Kasaei, S ; Sharif University of Technology
    Fusion of high spectral but low spatial resolution multispectral and low spectral but high spatial resolution panchromatic satellite images is a very useful technique in various remote sensing applications, such as change detection. Recently, some studies showed that wavelet-based image fusion methods provide high quality spectral content of the fused image. However, most of wavelet-based methods have a spatial resolution of the fused result less than the Brovey, IHS, and PCA fusion methods. This is mainly because real wavelet transform cannot efficiently represent the singularity of linear/curved contents. In this paper, we introduce a new method based on the contourlet transform which... 

    The potential role of auditory prediction error in decompensated tinnitus: An auditory mismatch negativity study

    , Article Brain and Behavior ; Volume 9, Issue 4 , 2019 ; 21623279 (ISSN) Mohebbi, M ; Daneshi, A ; Asadpour, A ; Mohsen, S ; Farhadi, M ; Mahmoudian, S ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    Introduction: Some tinnitus subjects habituate to their tinnitus but some others do not and complain of its annoyance tremendously. Normal sensory memory and change detection processes are needed for detecting the tinnitus signal as a prediction error and habituation to tinnitus. The purpose of this study was to compare auditory mismatch negativity as the index of sensory memory and change detection among the studied groups to search for the factors involving in the perception of tinnitus and preventing habituation in decompensated tinnitus subjects. Methods: Electroencephalography was recorded from scalp electrodes in compensated tinnitus, decompensated tinnitus, and no tinnitus control...