Loading...
Search for: correlation-coefficients
0.006 seconds

    Prediction of natural gas flow through chokes using support vector machine algorithm

    , Article Journal of Natural Gas Science and Engineering ; Vol. 18, issue , 2014 , pp. 155-163 ; ISSN: 18755100 Nejatian, I ; Kanani, M ; Arabloo, M ; Bahadori, A ; Zendehboudi, S ; Sharif University of Technology
    Abstract
    In oil and gas fields, it is a common practice to flow liquid and gas mixtures through choke valves. In general, different types of primary valves are employed to control pressure and flow rate when the producing well directs the natural gas to the processing equipment. In this case, the valve normally is affected by elevated levels of flow (or velocity) as well as solid materials suspended in the gas phase (e.g., fine sand and other debris). Both surface and subsurface chokes may be installed to regulate flow rates and to protect the porous medium and surface facilities from unusual pressure instabilities.In this study a reliable, novel, computer based predictive model using Least-Squares... 

    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) Mousavi, S. M ; 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... 

    Advantage of applying OSC to 1H NMR-based metabonomic data of celiac disease

    , Article International Journal of Endocrinology and Metabolism ; Volume 10, Issue 3 , 2012 , Pages 548-552 ; 1726913X (ISSN) Rezaei Tavirani, M ; Fathi, F ; Darvizeh, F ; Zali, M. R ; Nejad, M. R ; Rostami, K ; Tafazzoli, M ; oskouie, A. A ; Mortazavi Tabatabaei, S. A ; Sharif University of Technology
    2012
    Abstract
    Background: Celiac disease (CD) is a disorder associated with body reaction to gluten. After the gluten intake, an immune reaction against the protein occurs and damages villi of small intestine in celiac patients gradually. Objectives: The OSC, a filtering method for minimization of inter- and intra-spectrom-eter variations that influence on data acquisition, was applied to biofluid NMR data of CD patients. Patients and Methods: In this study, metabolites of total 56 serum samples from 12 CD patients, 15 CD patients taking gluten-free diet (GFD), and 29 healthy cases were analyzed using nuclear magnetic resonance (NMR) and associated theoretical analysis. Employ-ing ProMetab (version... 

    The estimation of formation permeability in a carbonate reservoir using an artificial neural network

    , Article Petroleum Science and Technology ; Volume 30, Issue 10 , 2012 , Pages 1021-1030 ; 10916466 (ISSN) Yeganeh, M ; Masihi, M ; Fatholahi, S ; Sharif University of Technology
    2012
    Abstract
    Reservoir permeability is an important parameter that its reliable prediction is necessary for reservoir performance assessment and management. Although many empirical formulas are derived regarding permeability and porosity in sandstone reservoirs, these correlations cannot be accurately depicted in carbonate reservoir for the wells that are not cored and for which there are no welltest data. Therefore, having a framework for estimation of these parameters in reservoirs with neither coring samples nor welltest data is crucial. Rock properties are characterized by using different well logs. However, there is no specific petrophysical log for estimating rock permeability; thus, new methods... 

    A well-dispersed Pt/Ni/TiO 2 nanotubes modified electrode as an amperometric non-enzymatic glucose biosensor

    , Article Sensor Letters ; Volume 9, Issue 5 , October , 2011 , Pages 1598-1605 ; 1546198X (ISSN) Mahshid, S. S ; Luo, S ; Yang, L ; Mahshid, S ; Dolati, A ; Ghorbani, M ; Cai, Q ; Sharif University of Technology
    2011
    Abstract
    In this study a novel Pt/Ni nanostructure consisting of nano-bushes and nanocubes was fabricated onto TiO 2 nanotubes. The scanning electron microscopy images showed that a large amount of well-dispersed nano-architectures had uniformly covered all over the surface which made an electrode with high surface area. It was obviously seen that the nanocube structures mainly consists of Ni had been grown on top of each other while the Pt colonies represented bush-like structures. As a non-enzymatic glucose biosensor, the Pt/Ni TiO 2 nanotubes modified electrode exhibited an excellent performance. The proposed biosensor had two linear ranges for detection of glucose from 0 to 0.12 mM (correlation... 

    Effects of structural configuration on vibration control of smart laminated beams under random excitations

    , Article Journal of Mechanical Science and Technology ; Volume 24, Issue 5 , 2010 , Pages 1119-1125 ; 1738494X (ISSN) Zabihollah, A ; Sharif University of Technology
    Abstract
    The influence of structural configuration on vibration responses of smart laminated beams under random loading is studied. The effect of laminate configurations and locations of sensors/actuators in the smart system is also investigated. The layer-wise approximation for displacement and electric potential is utilized to construct the finite element model. The closed-loop control response is determined through an optimal control algorithm based on the Linear Quadratic Regulator (LQR). The correlation coefficient between the input random force and the applied actuating voltage for various configurations is also computed. It is revealed that for softer configurations, the correlation... 

    Prediction of limiting activity coefficients for binary vapor-liquid equilibrium using neural networks

    , Article Fluid Phase Equilibria ; Volume 433 , 2017 , Pages 174-183 ; 03783812 (ISSN) Ahmadian Behrooz, H ; Bozorgmahry Boozarjomehry, R ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    The activity coefficient at infinite dilution is a representative of the limiting non-ideality of a solute in a mixture. Various methods for the prediction of infinite dilution activity coefficients (IDACs) have been developed. Artificial neural networks are powerful mapping tools for nonlinear function approximations. Accordingly, an artificial neural network model is proposed for the prediction of the IDACs of binary systems where the properties of the individual components are used as inputs to the network. The input parameters of the neural network are the mixture temperature, critical temperature, critical pressure, critical volume, molecular weight, dipole moment and the acentric... 

    Vulnerability assessment of urban groundwater resources to nitrate: the case study of Mashhad, Iran

    , Article Environmental Earth Sciences ; Volume 76, Issue 1 , 2017 ; 18666280 (ISSN) Asadi, P ; Ataie Ashtiani, B ; Beheshti, A ; Sharif University of Technology
    Springer Verlag  2017
    Abstract
    Groundwater vulnerability assessment of urban areas is a challenging task in the fast trend of urbanization around the globe. This study introduces a new approach for modifying well-known parameters of common vulnerability indexes to adjust them for urban areas. The approach is independent of a specific weighting system. The aquifer of Mashhad city, contaminated by domestic wastewater, is selected as a case in this study. In order to evaluate the aquifer vulnerability due to anthropogenic activities, at first, parameters of depth to groundwater, recharge, land use, and soil are modified based on their basic concepts and their influences on contamination attenuation. Then, the modified... 

    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) Mohebali, S ; 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... 

    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) Attari, S ; 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) Tashayo, B ; 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... 

    ECG-derived respiration estimation from single-lead ECG using gaussian process and phase space reconstruction methods

    , Article Biomedical Signal Processing and Control ; Volume 45 , 2018 , Pages 80-90 ; 17468094 (ISSN) Janbakhshi, P ; Shamsollahi, M. B ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    Respiratory activity influences electrocardiographic measurements (ECG) in various ways. Therefore, extraction of respiratory information from ECG, namely ECG-derived respiratory (EDR), can be used as a promising noninvasive method to monitor respiration activity. In this paper, an automatic EDR extraction system using single-lead ECG is proposed. Respiration effects on ECG are categorized into two different models: additive and multiplicative based models. After selection of a proper model for each subject using a proposed criterion, gaussian process (GP) and phase space reconstruction area (PSRArea) are introduced as new methods of EDR extraction for additive and multiplicative models,... 

    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) Mashayekhi, M ; 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... 

    Feasibility of imperialist competitive algorithm to predict the surface settlement induced by tunneling

    , Article Engineering with Computers ; Volume 35, Issue 3 , 2019 , Pages 917-923 ; 01770667 (ISSN) Tashayo, B ; Behzadafshar, K ; Soltani Tehrani, M ; Afkhami Banayem, H ; Hashemi, M. H ; Taghavi Nezhad, S. S ; Sharif University of Technology
    Springer London  2019
    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... 

    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) Ghobadi Nejad, Z ; 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... 

    fMRI functional connectivity analysis via kernel graph in Alzheimer’s disease

    , Article Signal, Image and Video Processing ; 2020 Ahmadi, H ; 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... 

    Prediction of the pressure drop for CuO/(Ethylene glycol-water) nanofluid flows in the car radiator by means of Artificial Neural Networks analysis integrated with genetic algorithm

    , Article Physica A: Statistical Mechanics and its Applications ; Volume 546 , 2020 Ahmadi, M. H ; Ghazvini, M ; Maddah, H ; Kahani, M ; Pourfarhang, S ; Pourfarhang, A ; Zeinali Herisg, S ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    In this investigation, neural networks were used to predict pressure drop of CuO-based nanofluid in a car radiator. For this purpose, the neural network with the multilayer perceptron structure was used to formulate a model for estimating the pressure drop In this way, different concentrations of copper oxide-based nanofluid were prepared. The base fluid was the mixture of ethylene glycol and pure water (60:40 wt%) which usually used as the cooling fluid in automotive industries. The prepared nanofluid samples were used in a car radiator and the pressure drop of nanofluid flows in the system at different Reynolds were measured. The main purpose of this study was developing the optimized... 

    Qquantitative structure - retention relationship study of a variety of compounds in reversed-phase liquid chromatography: A PLS-MLR-STANN approach

    , Article QSAR and Combinatorial Science ; Volume 27, Issue 2 , 2008 , Pages 137-146 ; 1611020X (ISSN) Jalali Heravi, M ; Garkani Nejad, Z ; Kyani, A ; Sharif University of Technology
    2008
    Abstract
    A quantitative structure-retention relationships model has been developed to study the retention behavior of 87 aliphatic and aromatic compounds in Reversed-Phase Liquid Chromatography (RPLC) on five bonded-phase columns differing in silanol group acidity. Six numerical descriptors of Molecular Mass (M), partial charge of the most negative atom (NPCH), partial charge of the most positive hydrogen (PCHH), van der Waals volume (VOLUME), Dipole Moment (DIMO), and Highest Occupied Molecular Orbital (HOMO) have been calculated for each compound. A separate Multiple Linear Regression (MLR) model has been developed using the six descriptors for each column. Partial Least Square (PLS) combined with... 

    Translation and validation study of the Iranian versions of the neck disability index and the neck pain and disability scale

    , Article Spine ; Volume 32, Issue 26 , 2007 , Pages E825-E831 ; 03622436 (ISSN) Mousavi, J ; Parnianpour, M ; Montazeri, A ; Mehdian, H ; Karimi, A ; Abedi, M ; Askary Ashtiani, A ; Mobini, B ; Hadian, M. R ; Sharif University of Technology
    2007
    Abstract
    STUDY DESIGN. Cultural translation and psychometric testing. OBJECTIVE. To translate and validate the Iranian versions of the Neck Disability Index (NDI-IR) and the Neck Pain and Disability Scale (NPDS-IR). SUMMARY OF BACKGROUND DATA. The widely used the NDI and the NPDS scales have not been translated and validated for Persian-speaking patients with neck pain. This was to provide a validated instrument to measure functional status in patients with neck pain in Iran. METHODS. The translation and cultural adaptation of the original questionnaires were carried out in accordance with the published guidelines. One hundred and eighty-five patients with neck pain were participated in the study.... 

    The Oswestry Disability Index, the Roland-Morris Disability Questionnaire, and the Quebec Back Pain Disability Scale: Translation and validation studies of the Iranian versions

    , Article Spine ; Volume 31, Issue 14 , 2006 , Pages E454-E459 ; 03622436 (ISSN) Mousavi, S.J ; Parnianpour, M ; Mehdian, H ; Montazeri, A ; Mobini, B ; Sharif University of Technology
    2006
    Abstract
    STUDY DESIGN. Cross-cultural translation and psychometric testing were performed. OBJECTIVES. To cross-culturally translate the Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RDQ), and Quebec Back Pain Disability Scale (QDS) into Persian, and then investigate the psychometric properties of the Persian versions produced. SUMMARY OF BACKGROUND DATA. To the authors' knowledge, there is no validated instrument to measure functional status in Persian-speaking patients with low back pain (LBP) in Iran. To our knowledge, the widely used back-specific measures, the ODI, RDQ, and QDS, have not been translated and validated for Persian-speaking patients with LBP. METHODS. The...