Search for: correlation-coefficients
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    Fast correlation attacks on the summation generator

    , Article Journal of Cryptology ; Volume 13, Issue 2 , 2000 , Pages 245-262 ; 09332790 (ISSN) Golić, J. D ; Salmasizadeh, M ; Dawson, E ; Sharif University of Technology
    Springer New York  2000
    Abstract. The linear sequential circuit approximation method for combiners with memory is used to find mutually correlated linear transforms of the input and output sequences in the well-known summation generator with any number of inputs. It is shown that the determined correlation coefficient is large enough for applying a fast correlation attack to the output sequence to reconstruct the initial states of the input linear feedback shift registers. The proposed attack is based on iterative probabilistic decoding and appropriately generated low-weight parity-checks. The required output sequence length and the computational complexity are both derived. Successful experimental results for the... 

    Solvent effects on kinetics of the reaction between 2-chloro-3,5- dinitropyridine and aniline in aqueous and alcoholic solutions of [bmim]BF 4

    , Article International Journal of Chemical Kinetics ; Volume 39, Issue 12 , December , 2007 , Pages 681-687 ; 05388066 (ISSN) Harifi Mood, A ; Habibi Yangjeh, A ; Gholami, M. R ; Sharif University of Technology
    Rate constants, kA. for the aromatic nucleophilic substitution reaction of 2-chloro-3,5-dinitropyridine with aniline were determined in different compositions of 1-(1-butyl)-3-methylimidazolium terafluoroborate ([bmim]BF4) mixed with water, methanol, and ethanol at 25°C. The obtained rate constants of the reaction in pure solvents are in the following order: water > methanol > ethanol > [bmim]BF4. In these solutions, rate constants of the reaction decrease with the mole fraction of the ionic liquid. Single-parameter correlations of log kA versus normalized polarity parameter (ETN), hydrogen bond acceptor basicity (β), hydrogen bond donor acidity (α), and dipolarity/polarizability (π*) do not... 

    Comparison of River Daily Runoff Simulation Results using Time Series and IHACRES Rainfall-runoff Model

    , M.Sc. Thesis Sharif University of Technology Rahsepar Tolouei, Talaye (Author) ; Shamsaei, Abolfazl (Supervisor)
    Hydrologic models are the best tools to reduce hydrological uncertainties in rivers runoff estimation. Considering structure of model and calibration of parameters, there are several approaches to extend. In this study, we try to simulate daily river runoff by using two different approaches and then compare the results of them with each other. In first approach, IHACRES model is used to simulate rainfall- runoff, which is a conceptual model based on rainfall, runoff and evapotranspiration or temperature data. This model uses conceptual part to estimate effective rainfall and also it uses a transformation function to transform effective rainfall to output flow. This model works in daily time... 

    Simple and efficient method to measure vessel tortuosity

    , Article Proceedings of the 3rd International Conference on Computer and Knowledge Engineering, ICCKE 2013, Mashhad: Iran ; 2013 , Pages 219-222 ; 9781479920921 (ISBN) Pourreza, H. R ; Pourreza, M ; Banaee, T ; Sharif University of Technology
    Retinal vessels tortuosity is one of the important signs of cardiovascular diseases such as diabetic retinopathy and hypertension. In this paper we present a simple and efficient algorithm to measure the grade of tortuosity in retinal images. This algorithm consists of four main steps,vessel detection, extracting vascular skeleton via thinning, detection of vessel crossovers and bifurcations and finally calculating local and global tortuosity. The last stage is based on a circular mask that is put on every skeleton point of retinal vessels. While the skeleton of vessel splits the circle in each position, the local tortuosity is considered to be the bigger to smaller area ratio. The proposed... 

    Preconcentration and determination of carbaryl and carbofuran in water samples using ionic liquids and in situ solvent formation microextraction

    , Article Analytical Methods ; Volume 5, Issue 9 , 2013 , Pages 2406-2412 ; 17599660 (ISSN) Tehrani, M. S ; Givianrad, M. H ; Akhoundi, L ; Akhoundi, M ; Sharif University of Technology
    In the present work, a novel microextraction method named in situ solvent formation microextraction (ISFME) using ionic liquids (ILs) for preconcentration of carbaryl and carbofuran in water samples is introduced. In this method, a small amount of sodium hexafluorophosphate (NaPF6), as an ion pairing agent, was added to a sample solution containing a small quantity of 1-hexyl-3-methylimidazolium tetrafluoroborate [Hmim][BF4] as a hydrophobic ionic liquid. A cloudy solution formed as a result of formation of fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF 6]. After centrifugation, the fine droplets of the extractant phase settled to the bottom of the conical-bottom... 

    Prediction of standard enthalpy of combustion of pure compounds using a very accurate group-contribution-based method

    , Article Energy and Fuels ; Volume 25, Issue 6 , April , 2011 , Pages 2651-2654 ; 08870624 (ISSN) Gharagheizi, F ; Mirkhani, S. A ; Tofangchi Mahyari, A. R ; Sharif University of Technology
    The artificial neural network-group contribution (ANN-GC) method is applied to estimate the standard enthalpy of combustion of pure chemical compounds. A total of 4590 pure compounds from various chemical families are investigated to propose a comprehensive and predictive model. The obtained results show the squared correlation coefficient (R 2) of 0.999 99, root mean square error of 12.57 kJ/mol, and average absolute deviation lower than 0.16% for the estimated properties from existing experimental values  

    Application of artificial neural network for estimation of formation permeability in an iranian reservoir

    , Article 1st International Petroleum Conference and Exhibition, Shiraz, 4 May 2009 through 6 May 2009 ; 2009 Yeganeh, M ; Masihi, M ; Fatholahi, S ; Sharif University of Technology
    European Association of Geoscientists and Engineers, EAGE  2009
    The permeability is one of the most important reservoir parameters and its accurate prediction is necessary for reservoir management and enhancement. Although many empirical formulas are derived regarding permeability and porosity in sandstone reservoirs [1], these correlations cannot be modified accurately in carbonate reservoir for the wells which are not cored and there is no welltest data. Therefore estimation of these parameters is a challenge in reservoirs with no coring sample and welltest data. One of the most powerful tools to estimate permeability from well logs is Artificial Neural Network (ANN) whose advantages and disadvantages have been discussed by several authors [2]. In this... 

    Reliability of center of pressure measures of postural stability in patients with unilateral anterior cruciate ligament injury

    , Article Journal of Applied Sciences ; Volume 8, Issue 17 , 2008 , Pages 3019-3025 ; 18125654 (ISSN) Hadian, M. R ; Negahban, H ; Talebian, S ; Salavati, M ; Jafari, A. H ; Sanjari, M. A ; Mazaheri, M ; Parnianpour, M ; Sharif University of Technology
    The aim of this study was to estimate the test-retest reliability of some commonly used center of pressure measures in postural control investigations of sport injuries under the diverse stressful postural conditions. Twelve patients with anterior cruciate ligament injury were evaluated on two separate sessions. The center of pressure was recorded from force platform and the following measures were calculated (1) standard deviation of amplitude (2) mean velocity (3) standard deviation of velocity (4) phase plane parameters and (5) area (95% confidence ellipse). Relative and absolute reliability was assessed using intra-class correlation coefficient and coefficient of variation, respectively.... 

    Improving data protection in BSS based secure communication: mixing matrix design

    , Article Wireless Networks ; Volume 27, Issue 7 , 2021 , Pages 4747-4758 ; 10220038 (ISSN) Aslani, M. R ; Shamsollahi, M. B ; Nouri, A ; Sharif University of Technology
    Springer  2021
    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) Bagheri, H ; Khalilian, F ; Sharif University of Technology
    Elsevier  2005
    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... 

    Prediction of Lumbar Muscle Forces Due to Applied Externally Moment and Analaysing Coactivation Between Lumbar Muscles

    , M.Sc. Thesis Sharif University of Technology Khodadad Kani, Hadi (Author) ; Parnianpour, Mohammad (Supervisor) ; Shams Al-Allahi, Mohammad Bagher (Co-Advisor)
    The role of the lumbar muscles in maintaining posture and balancing externally applied loads has been studied for many years.preliminary studies used electromyograpy (EMG) to establish a relationship between trunk posture and muscle ativity.so developing a better undrestanding of the functional role of those muscles. Determination of lumbar muscle forces, will have an important role in reducing low back pain I future.For this reason,reaserchers have done many studies for understanding the resistence and function on the musulosketal system bye using of various protocls and have utilized of various biomechanical models for determining the effects of applied externally loads on lumbar... 

    Estimation of Power Peaking Factor (PPF)Parameter in VVER Reactor Using Soft Computing, Case Study: Bushehr Nuclear Power Plant

    , M.Sc. Thesis Sharif University of Technology Sharifi, Saeed (Author) ; Ghofrani, Mohammad Bagher (Supervisor) ; Moshkbar Bakhshayesh, Khalil (Supervisor)
    operation of a nuclear power plant. Therefore, constant monitoring of the reactor core with reliable methods is important. To monitor the reactor heart, it is necessary to estimate and calculate some parameters, with high speed and accuracy, such as power distribution inside the heart, reactivity feedback coefficients, PPF, DNBR, etc. Analytical methods are often used to calculate these parameters, which in case of failure of the sensors, the calculations will be practically disrupted, and the method used in this research can solve these problems by losing a small amount of accuracy.In this study using real data of Bushehr nuclear power plant (BNPP) and by soft computing methods and... 

    Forecasting the Possibility of Agricultural Drought using Markov Chain Based on Satellite data and Standard Precipitation Index

    , M.Sc. Thesis Sharif University of Technology Kolahdouzan, Mohammad Ehsan (Author) ; Abrishamchi, Ahmad (Supervisor)
    In comparison with flood, drought is a phenomenon that happens gradually and causes significant changes in water resources, environmental and economic damages specially farming. Due to random features of involving factors in occurrence and intensity of drought, it is assumed as a random process. Drought forecast has an important role in water resources management and control. Data validation, in drought forecast, is a matter of utmost importance. In recent years, satellite data is a type of data that has been used. Markov chain has been used here because one of the features of this method is that occurrence of each variable in current stage is dependent on its previous stage. On the other... 

    Short Time Effect of Auxetic Shoe on Kinematics and Kinetics of Vertebral Column During Drop Vertical Jump

    , M.Sc. Thesis Sharif University of Technology Rahmani Dahaghani, Mostafa (Author) ; Nourani, Amir (Supervisor) ; Arjmand, Navid (Supervisor)
    Investigating the influence of shoes on variables of human biomechanics is of a high importance. The purpose of this study was to examine the effect of auxetic Nike Free RN shoe on kinematics and kinetics of human body. It was asked from 11 healthy male to perform drop vertical jump in three conditions: with auxetic Nike Free RN, with conventional shoe and barefoot. 3D Cartesian positions of the markers, which were stuck to the subjects’ bodies, were recoeded using Vicon camera system. Ground reaction force and its center of pressure of each foot captured using two force plates. Moreover, activation of rectus abdominis, longissimus, iliocostalis lomburom and multifidus were recorded using... 

    An electrospun magnetic nanocomposite for a facile micro-scaled analysis approach

    , Article Analytical Methods ; Vol. 6, issue. 15 , 2014 , Pages 5838-5846 ; ISSN: 17599660 Bagheri, H ; Roostaie, A ; Daliri, R ; Sharif University of Technology
    A magnetic polyurethane (PU) nanocomposite was synthesized by an electrospinning technique and applied for isolation and preconcentration of fluoxetine from aquatic and biological samples. The nanocomposite was electrospun using a PU polymer solution containing the dispersed magnetic nanoparticles. The magnetic properties of iron nanoparticles, along with the use of an electrospinning technique, led to the formation of a suitable sorbent toward isolation of fluoxetine. The magnetic PU nanofibers could be subsequently removed from the sample solution by applying a permanent magnet. The scanning electron microscopy (SEM) image of the magnetic PU nanofibers confirms that their diameters are in... 

    Voltammetric monitoring of Cd (II) by nano-TiO2 modified carbon paste electrode sensitized using 1,2-bis-[o-aminophenyl thio] ethane as a new ion receptor

    , Article Sensors and Actuators, B: Chemical ; Vol. 192 , 2014 , pp. 648-657 ; ISSN: 09254005 Ramezani, S ; Ghobadi, M ; Bideh, B. N ; Sharif University of Technology
    The objective of the work ahead is presentation of a new carbon paste electrode (CPE) modified by TiO2 nanoparticles (TiO2NPs) and 1,2-bis-[o-aminophenyl thio] ethane (APTE) ligand as a selective cation receptor for determination of the Cd (II) ions using differential pulse anodic stripping voltammetry (DPASV). The electrode shows an excellent tendency to Cd (II) ions in presence of some interfering species. Under the optimum conditions, a linear calibration curve was obtained in the concentration range of 2.9 nM to 4.6 μM with a correlation coefficient of 0.9969 in the anodic potential of 0.54 (V vs. Ag/AgCl). The metal detection limit was 2.0 nM after 10 min preconcentration (S/N = 3). The... 

    State-of-the-art least square support vector machine application for accurate determination of natural gas viscosity

    , Article Industrial and Engineering Chemistry Research ; Vol. 53, issue. 2 , 2014 , pp. 945-958 ; ISSN: 08885885 Fayazi, A ; Arabloo, M ; Shokrollahi, A ; Zargari, M. H ; Ghazanfari, M. H ; Sharif University of Technology
    Estimation of the viscosity of naturally occurring petroleum gases is essential to provide more accurate analysis of gas reservoir engineering problems. In this study, a new soft computing approach, namely, least square support vector machine (LSSVM) modeling, optimized with a coupled simulated annealing technique was applied for estimation of the natural gas viscosities at different temperature and pressure conditions. This model was developed based on 2485 viscosity data sets of 22 gas mixtures. The model predictions showed an average absolute relative error of 0.26% and a correlation coefficient of 0.99. The results of the proposed model were also compared with the well-known predictive... 

    Sparse-induced similarity measure: Mono-modal image registration via sparse-induced similarity measure

    , Article IET Image Processing ; Volume 8, Issue 12 , 1 December , 2014 , Pages 728-741 ; ISSN: 17519659 Ghaffari, A ; Fatemizadeh, E ; Sharif University of Technology
    Similarity measure is an important key in image registration. Most traditional intensity-based similarity measures (e.g. sum-of-squared-differences, correlation coefficient, mutual information and correlation ratio) assume a stationary image and pixel-by-pixel independence. These similarity measures ignore the correlation among pixel intensities; hence, a perfect image registration cannot be achieved especially in the presence of spatially varying intensity distortions and outlier objects that appear in one image but not in the other. It is supposed here that non-stationary intensity distortion (such as bias field) has a sparse representation in the transformation domain. Based on this... 

    Assessment of competitive dye removal using a reliable method

    , Article Journal of Environmental Chemical Engineering ; Vol. 2, issue. 3 , September , 2014 , p. 1672-1683 Abdi, J ; Bastani, D ; Abdi, J ; Mahmoodi, N. M ; Shokrollahi, A ; Mohammadi, A. H ; Sharif University of Technology
    In this study, a reliable and predictive model namely, least-squares support vector machine (LS-SVM) was developed to predict dye removal efficiency. Four LS-SVM models have been developed and tested using more than 630 series of experimental data which were obtained from our previous paper. These data consist of adsorbate type, adsorbent dosage, initial dye concentration, salt, absorbance time and dye removal efficiency. Direct Red 31 (DR31), Direct Green 6 (DG6) and Acid Blue (AB92) were used as a model dyes. The results show that the developed model is more accurate and reliable with the average absolute relative deviation of 0.678%, 0.877%, 0.581% and 0.978% for single systems and... 

    Toward an intelligent approach for determination of saturation pressure of crude oil

    , Article Fuel Processing Technology ; Volume 115 , 2013 , Pages 201-214 ; 03783820 (ISSN) Farasat, A ; Shokrollahi, A ; Arabloo, M ; Gharagheizi, F ; Mohammadi, A. H ; Sharif University of Technology
    Bubble point pressure is a crucial PVT parameter of reservoir fluids, which has a significant effect on oil field development strategies, reservoir evaluation and production calculations. This communication presents a new mathematical model to calculate the saturation pressures of crude oils as a function of temperature, hydrocarbon and non-hydrocarbon reservoir fluid compositions, and characteristics of the heptane-plus fraction. The model was developed and tested using a total set of 130 experimentally measured compositions and saturation pressures of crude oil samples from different geographical locations covering wide ranges of crude oil properties and reservoir temperatures. In-depth...