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correlation-coefficients
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On the positive definiteness of polarity coincidence correlation coefficient matrix
, Article IEEE Signal Processing Letters ; Volume 15 , January , 2008 , Pages 73-76 ; 10709908 (ISSN) ; Nayebi, M. M ; Aref, M. R ; Sharif University of Technology
2008
Abstract
Polarity coincidence correlator (PCC), when used to estimate the covariance matrix on an element-by-element basis, may not yield a positive semi-definite (PSD) estimate. Devlin et al. (Devlin, 1975) claimed that element-wise PCC is not guaranteed to be PSD in dimensions p > 3 for real signals. However, no justification or proof was available on this issue. In this letter, it is proved that for real signals with p ≤ 3 and for complex signals with p ≤ 2, a PSD estimate is guaranteed. Counterexamples are presented for higher dimensions which yield invalid covariance estimates. © 2007 IEEE
Multivariate variability monitoring using EWMA control charts based on squared deviation of observations from target
, Article Quality and Reliability Engineering International ; Volume 27, Issue 8 , 2011 , Pages 1069-1086 ; 07488017 (ISSN) ; Niaki, S. T. A ; Sharif University of Technology
Abstract
Recent research works have shown that control statistics based on squared deviation of observations from target have the ability to monitor variability in both univariate and multivariate processes. In the current research, the properties of the control statistic S t that has been proposed by Huwang et al. (J. Quality Technology 2007; 39:258-278) are first reviewed and three new S t-based multivariate schemes are then presented. Extensive simulation experiments are performed to compare the performances of the proposed schemes with those of the multivariate exponentially weighted mean squared deviation (MEWMS) and the L 1-norm distance of the MEWMS deviation from its expected value (MEWMSL 1)...
Multiple partial discharge sources separation using a method based on laplacian score and correlation coefficient techniques
, Article Electric Power Systems Research ; Volume 210 , 2022 ; 03787796 (ISSN) ; Vakilian, M ; Firuzi, K ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Partial discharge (PD) activity can be destructive to the transformer insulation, and ultimately may result in total breakdown of the insulation. Partial discharge sources identification in a power transformer enables the operator to evaluate the transformer insulation condition during its lifetime. In order to identify the PD source; in the case of presence of multiple sources; the first step is to capture the PD signals and to extract their specific features. In this contribution, the frequency domain analysis, the time domain analysis and the wavelet transform are employed for feature extraction purpose. In practice, there might be plenty of features, and in each scenario, only some of...
Methylene blue removal using modified celery (Apium graveolens) as a low-cost biosorbent in batch mode: Kinetic, equilibrium, and thermodynamic studies
, Article Journal of Molecular Structure ; Volume 1173 , 2018 , Pages 541-551 ; 00222860 (ISSN) ; Bastani, D ; Shayesteh, H ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Celery residue modified with H2SO4 was utilized as a low-cost adsorbent for elimination of methylene blue cationic dye from aqueous solution in batch adsorption process. The adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). The efficacy of dye removal of the modified celery residue (MCR) was verifying by changing adsorbent dose, contact time, pH, initial dye concentration, and temperature. The isotherm models analysis shows that the experimental data can be better demonstrated by Freundlich isotherm model. In order to evaluate the best fit isotherm, three error analysis methods (χ2, ARE and MPSD) as well as correlation...
Membrane interactions control residue fluctuations of outer membrane porins
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 81, Issue 5 , May , 2010 ; 15393755 (ISSN) ; Mobasheri, H ; Ejtehadi, M. R ; Sharif University of Technology
2010
Abstract
Bacterial outer membrane porins (Omp) that have robust β -barrel structures, show potential applications for nanomedicine devices in synthetic membranes and single molecule detection biosensors. Here, we explore the conformational dynamics of a set of 22 outer membrane porins, classified into five major groups: general porins, specific porins, transport Omps, poreless Omps and composed pores. Normal mode analysis, based on mechanical vibration theory and elastic network model, is performed to study the fluctuations of residues of aforementioned porins around their equilibrium positions. We find that a simple modification in this model considering weak interaction between protein and...
Kinetic studies of Bisphenol A in aqueous solutions by enzymatic treatment
, Article International Journal of Environmental Science and Technology ; Volume 16, Issue 2 , Febraury , 2018 , Pages 821–832 ; 17351472 (ISSN) ; Borghei, S. M ; Yaghmaei, S ; Sharif University of Technology
Center for Environmental and Energy Research and Studies
2018
Abstract
Bisphenol A (BPA), which is a major component in the production of various consumer products, is one of the most significant endocrine-disrupting chemicals. In this research, the biocatalytic elimination of Bisphenol A using laccase produced by Phanerochaete chrysosporium was examined and optimized. The response surface methodology was used to study the effect of independent variables such as pH, temperature, initial laccase activity, initial Bisphenol A concentration, and the interactive effects of each variable on the removal of Bisphenol A and residual enzyme activity. Based on response surface plots, the maximum Bisphenol A removal (93%) was detected at a pH value of 8, temperature 40...
Kinetic studies of Bisphenol A in aqueous solutions by enzymatic treatment
, Article International Journal of Environmental Science and Technology ; Volume 16, Issue 2 , 2019 , Pages 821-832 ; 17351472 (ISSN) ; Borghei, S. M ; Yaghmaei, S ; Sharif University of Technology
Center for Environmental and Energy Research and Studies
2019
Abstract
Bisphenol A (BPA), which is a major component in the production of various consumer products, is one of the most significant endocrine-disrupting chemicals. In this research, the biocatalytic elimination of Bisphenol A using laccase produced by Phanerochaete chrysosporium was examined and optimized. The response surface methodology was used to study the effect of independent variables such as pH, temperature, initial laccase activity, initial Bisphenol A concentration, and the interactive effects of each variable on the removal of Bisphenol A and residual enzyme activity. Based on response surface plots, the maximum Bisphenol A removal (93%) was detected at a pH value of 8, temperature...
Kinetics of organic removal in fixed-bed aerobic biological reactor
, Article Bioresource Technology ; Volume 99, Issue 5 , 2008 , Pages 1118-1124 ; 09608524 (ISSN) ; Sharbatmaleki, M ; Pourrezaie, P ; Borghei, G ; Sharif University of Technology
2008
Abstract
The process kinetics of a lab-scale upflow aerobic immobilized biomass (UAIB) reactor using simulated sugar-manufacturing wastewater as feed was investigated. The experimental unit consisted of a 22 l reactor filled with high porosity pumice stone. The UAIB reactor was tested under different organic loads and different hydraulic retention times (HRT) and the substrate loading removal rate was compared with prediction of Stover-Kincannon model, second-order model and the first order substrate removal model. After obtaining steady-state conditions, organic loading rate was increased from 750 to 4500 g COD/m3 day to resemble wastewater from sugar production lines, and hydraulic retention time...
Is there a reliable and invariant set of muscle synergy during isometric biaxial trunk exertion in the sagittal and transverse planes by healthy subjects?
, Article Journal of Biomechanics ; Volume 48, Issue 12 , Sep , 2015 , Pages 3234-3241 ; 00219290 (ISSN) ; Mousavi, S. J ; Hadizadeh, M ; Narimani, R ; Khalaf, K ; Campbell Kyureghyan, N ; Parnianpour, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
It has been suggested that the central nervous system simplifies muscle control through basic units, called synergies. In this study, we have developed a novel target-matching protocol and used non-negative matrix factorization (NMF) technique to extract trunk muscle synergies and corresponding torque synergies. Isometric torque data at the L5/S1 level and electromyographic patterns of twelve abdominal and back muscles from twelve healthy participants (five females) were simultaneously recorded. Each participant performed a total number of 24 isometric target-matching tasks using 12 different angular directions and 2 levels of uniaxial and biaxial exertions. Within- and between-subject...
Introducing a response-based duration metric and its correlation with structural damages
, Article Bulletin of Earthquake Engineering ; Volume 17, Issue 11 , 2019 , Pages 5987-6008 ; 1570761X (ISSN) ; Harati, M ; Ashoori Barmchi, M ; Estekanchi, H. E ; Sharif University of Technology
Springer Netherlands
2019
Abstract
This study proposes a response-based parameter for strong motion duration which is computed for structures and is the total time they are nonlinear during an earthquake. Correlation between structural response and duration for structures, subjected to a set of spectrum matched ground motions, is employed to examine the efficiency of the proposed method. The spectral matching procedure ensures that the influence of amplitude and frequency content of motions on structural response variability is significantly removed. Four concrete building type systems are studied and correlation coefficients of structural response with the proposed duration definition are examined. Comparison of the proposed...
Interaction of lake-groundwater levels using cross-correlation analysis: A case study of Lake Urmia Basin, Iran
, Article Science of the Total Environment ; 2020 , Volume 729 ; Ataie Ashtiani, B ; Hosseini, S. M ; Simmons, C. T ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Lake Urmia (LU) is the second largest hypersaline lake in the world. Lake Urmia's water level has dropped drastically from 1277.85 m to 1270.08 m a.s.l (equal to 7.77 m) during the last 20 years, equivalent to a loss of 70% of the lake area. The likelihood of lake-groundwater connection on the basin-scale is uncertain and understudied because of lack of basic data and precise information required for physically-based modeling. In this study, cross-correlation analysis is applied on a various time-frames of water level of the lake and groundwater levels (2001–2018) recorded in 797 observation wells across 17 adjacent aquifers. This provides insightful information on the lake-groundwater...
In situ solid-phase microextraction and post on-fiber derivatization combined with gas chromatography-mass spectrometry for determination of phenol in occupational air
, Article Analytica Chimica Acta ; Volume 742 , 2012 , Pages 17-21 ; 00032670 (ISSN) ; Baghernejad, M ; Bagheri, H ; Sharif University of Technology
Elsevier
2012
Abstract
A method based on solid-phase microextraction (SPME) followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) for determination of phenol in air was developed. Three different types of SPME fibers, polar and non-polar poly(dimethylsiloxane) (PDMS) and polyethylene glycol (PEG) were synthesized using sol-gel technology and their feasibility to the sampling of phenol were investigated. Different derivatization reagents for post on-fiber derivatization of phenol were studied. Important parameters influencing the extraction and derivatization process such as type of fiber coating, type and volume of derivatizing reagent, derivatization time and temperature,...
Improving data protection in BSS based secure communication: mixing matrix design
, Article Wireless Networks ; Volume 27, Issue 7 , 2021 , Pages 4747-4758 ; 10220038 (ISSN) ; Shamsollahi, M. B ; Nouri, A ; Sharif University of Technology
Springer
2021
Abstract
Abstract: In this paper, a secure and efficient Blind Source Separation (BSS) based cryptosystem is presented. The use of BSS in audio and image cryptography in wireless networks has attracted more attention. A BSS based cryptosystem consists of three main parts: secret data, secret keys, and mixing matrix. In this paper, we propose a new design to create a proper mixing matrix in BSS based cryptosystem. We offer a mathematical criterion to select mixing matrix elements before encryption. The proposed criterion gives a simple way to attach the secret sources to keys, which makes source separation very hard for the adversary. Versus, we show that using the random mixing matrix can lead to...
Immersed solvent microextraction and gas chromatography-mass spectrometric detection of s-triazine herbicides in aquatic media
, Article Analytica Chimica Acta ; Volume 537, Issue 1-2 , 2005 , Pages 81-87 ; 00032670 (ISSN) ; Khalilian, F ; Sharif University of Technology
Elsevier
2005
Abstract
An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of s-triazine herbicides from aquatic media. A microdrop of butyl acetate was applied as the extraction solvent. After extraction, the microdrop was introduced directly into a gas chromatography-mass spectrometry (GC-MS) injection port. Some important extraction parameters such as type of solvent, extraction time, stirring rate, and temperature were investigated and optimized. The highest possible microdrop volume of 3 μl, a sampling temperature of 60°C, and use of butyl acetate are major parameters to obtain high enrichment factors. The enrichment factor and linearity was studied by...
Formulation of soil angle of shearing resistance using a hybrid GP and OLS method
, Article Engineering with Computers ; Volume 29, Issue 1 , September , 2013 , Pages 37-53 ; 01770667 (ISSN) ; Alavi, A.H ; Mollahasani, A ; Gandomi, A. H ; Arab Esmaeili, M ; Sharif University of Technology
2013
Abstract
In the present study, a prediction model was derived for the effective angle of shearing resistance (φ′) of soils using a novel hybrid method coupling genetic programming (GP) and orthogonal least squares algorithm (OLS). The proposed nonlinear model relates φ′ to the basic soil physical properties. A comprehensive experimental database of consolidated-drained triaxial tests was used to develop the model. Traditional GP and least square regression analyses were performed to benchmark the GP/OLS model against classical approaches. Validity of the model was verified using a part of laboratory data that were not involved in the calibration process. The statistical measures of correlation...
fMRI functional connectivity analysis via kernel graph in Alzheimer’s disease
, Article Signal, Image and Video Processing ; 2020 ; Fatemizadeh, E ; Motie-Nasrabadi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2020
Abstract
Functional magnetic resonance imaging (fMRI) is an imaging tool that is used to analyze the brain’s functions. Brain functional connectivity analysis based on fMRI signals often calculated correlations among time series in different areas of the brain. For FC analysis most prior research works generate the brain graphs based on linear correlations, however, the nonlinear behavior of the brain can lower the accuracy of such graphs. Usually, the Pearson correlation coefficient is used which has limitations in revealing nonlinear relationships. One of the proper methods for nonlinear analysis is the Kernel trick. This method maps the data into a high dimensional space and calculates the linear...
fMRI functional connectivity analysis via kernel graph in Alzheimer’s disease
, Article Signal, Image and Video Processing ; Volume 15, Issue 4 , 2021 , Pages 715-723 ; 18631703 (ISSN) ; Fatemizadeh, E ; Motie Nasrabadi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Functional magnetic resonance imaging (fMRI) is an imaging tool that is used to analyze the brain’s functions. Brain functional connectivity analysis based on fMRI signals often calculated correlations among time series in different areas of the brain. For FC analysis most prior research works generate the brain graphs based on linear correlations, however, the nonlinear behavior of the brain can lower the accuracy of such graphs. Usually, the Pearson correlation coefficient is used which has limitations in revealing nonlinear relationships. One of the proper methods for nonlinear analysis is the Kernel trick. This method maps the data into a high dimensional space and calculates the linear...
fMRI functional connectivity analysis via kernel graph in Alzheimer’s disease
, Article Signal, Image and Video Processing ; Volume 15, Issue 4 , 2021 , Pages 715-723 ; 18631703 (ISSN) ; Fatemizadeh, E ; Motie-Nasrabadi, A ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Functional magnetic resonance imaging (fMRI) is an imaging tool that is used to analyze the brain’s functions. Brain functional connectivity analysis based on fMRI signals often calculated correlations among time series in different areas of the brain. For FC analysis most prior research works generate the brain graphs based on linear correlations, however, the nonlinear behavior of the brain can lower the accuracy of such graphs. Usually, the Pearson correlation coefficient is used which has limitations in revealing nonlinear relationships. One of the proper methods for nonlinear analysis is the Kernel trick. This method maps the data into a high dimensional space and calculates the linear...
Finite state machine based countermeasure for cryptographic algorithms
, Article 2017 14th International ISC (Iranian Society of Cryptology) Conference on Information Security and Cryptology, ISCISC 2017, 6 September 2017 through 7 September 2017 ; 2018 , Pages 58-63 ; 9781538665602 (ISBN) ; Rezaei Shahmirzadi, A ; Salmasizadeh, M ; Gholampour, I ; Sharif University of Technology
Abstract
In this work, we present a novel FPGA-based implementation of the AES algorithm which has a two-layered resistance against power analysis attacks. Our countermeasure is based on the concept of finite state machine equipped with a random number generator. Beyond masking the intermediate variables as the first layer of defense, we randomize the sequences of operations and add dummy computations as the second layer of defense. Therefore, the first order attack is prevented and the number of power traces needed for a successful second order attack is vastly increased and the correlation coefficient is decreased, as expected. © 2017 IEEE
Feasibility of imperialist competitive algorithm to predict the surface settlement induced by tunneling
, Article Engineering with Computers ; 2018 ; 01770667 (ISSN) ; Behzadafshar, K ; Soltani Tehrani, M ; Afkhami Banayem, H ; Hashemi, M. H ; Taghavi Nezhad, S. S ; Sharif University of Technology
Springer London
2018
Abstract
Surface settlement is considered as an adverse effect induced by tunneling in the civil projects. This paper proposes the use of the imperialist competitive algorithm (ICA) for predicting the maximum surface settlement (MMS) resulting from the tunneling. For this work, three forms of equations, i.e., linear, quadratic and power are developed and their weights are then optimized/updated with the ICA. The requirement datasets were collected from the line No. 2 of Karaj urban railway, in Iran. In the ICA models, vertical to horizontal stress ratio, cohesion and Young’s modulus, as the effective parameters on the MSS, are adopted as the inputs. The statistical performance parameters such as root...