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A modified thermodynamic modeling of wax precipitation in crude oil based on PC-SAFT model
, Article Fluid Phase Equilibria ; Volume 429 , 2016 , Pages 313-324 ; 03783812 (ISSN) ; Ghotbi, C ; Jafari Behbahani, T ; Sharif University of Technology
Elsevier
2016
Abstract
Wax precipitation may occur in production or transportation of crude oil form field which is a serious problem in petroleum industry. Flow assurance issues concerning wax precipitation make it necessary to develop a precise thermodynamic model to predict the wax appearance temperature and amount of precipitation at different conditions. In this work a new procedure has been proposed to characterize crude oil based on the SARA test considering the wax and asphaltene as single pseudo components. Two scenarios have been investigated for the survey of the crude oil characterization, with and without asphaltene pseudo component. Also, in this work, the Perturbed Chain form of the Statistical...
A new investigation of wax precipitation in iranian crude oils: Experimental method based on FTIR spectroscopy and theoretical predictions using PC-SAFT model
, Article Journal of Molecular Liquids ; Volume 249 , 2018 , Pages 970-979 ; 01677322 (ISSN) ; Ghotbi, C ; Jafari Behbahani, T ; Sharifi, Kh ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Temperature dependency of infrared band intensity for methylene rocking vibration could be used as indication for creation of solid crystals while decreasing temperature. In this work, different experiments were conducted to measure wax appearance temperature, WAT, such as cross polarized microscopy, rheometry and FTIR spectroscopy. Three Iranian crude oils were characterized based on the SARA test and PC-SAFT model was developed to predict WAT. The obtained results by FTIR spectroscopy and PC-SAFT model were in quite agreement. FTIR spectroscopy determined higher WAT values which may be due to its higher sensitivity to smaller wax crystals. Also, the effect of a polymeric crystal modifier...
Evaluation of PC-SAFT model and support vector regression (SVR) approach in prediction of asphaltene precipitation using the titration data
, Article Fluid Phase Equilibria ; Volume 456 , 2018 , Pages 171-183 ; 03783812 (ISSN) ; Ghotbi, C ; Jafari Behbahani, T ; Sharifi, K ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Asphaltene deposition in porous media, wellbore and surface facilities has been a severe problem in petroleum industry which causes considerable remediation costs annually. Asphaltenes are heavy and polydisperse fractions of crude oil which are insoluble in n-alkanes such as n-heptane. In this work, three Iranian crude oils were prepared for titration experiments with n-pentane, n-heptane and n-dodecane at different solvent ratios and constant temperature. The experimental data were correlated by perturbed chain form of statistical associating fluid theory (PC-SAFT). The association of asphaltene molecules has been considered in this model with adjusting the uncertain parameters (such as...
Artificial intelligence vs. Classical approaches: A new look at the prediction of flux decline in wastewater treatment
, Article Desalination and Water Treatment ; Volume 51, Issue 40-42 , 2013 , Pages 7476-7489 ; 19443994 (ISSN) ; Dehghani, A ; Rekabdar, F ; Hemmati, M ; Goodarznia, I ; Sharif University of Technology
Taylor and Francis Inc
2013
Abstract
This study compares the performance of three different approaches to modeling namely the classical pore-blocking models, artificial neural networks (ANN) and the novel genetic programming (GP) approach. Among the available models proposed by Hermia, standard pore-blocking and cake filtration models were opted because of their better fitness with experimental measurements. A feedforward backpropagation network using Bayesian Regulation as well as Levenberg-Marquardt training methods was developed based on the experimental results. Network inputs include the controlling parameters of permeate flux namely: temperature, transmembrane pressure, crossflow velocity, pH, and filtration time. The...
Optimal operating conditions of micro- and ultra-filtration systems for produced-water purification: Taguchi method and economic investigation
, Article Desalination and Water Treatment ; Volume 57, Issue 42 , 2016 , Pages 19642-19654 ; 19443994 (ISSN) ; Mashhadi Meighani, H ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
In this study, treatment of two real produced waters was studied using microfiltration (MF) and ultrafiltration. In the first step, the effects of operating parameters including temperature, transmembrane pressure (TMP), cross-flow velocity (CFV), and back pulse time (BPT) (in the MF system) at three levels on the amount of permeate flux were investigated using ceramic and polymeric membranes. To design the experiments and optimize the experimental results, the L9 (34) and L9 (33) orthogonal arrays of the Taguchi method and a response category of the-larger-the-better were applied. Analysis of variance was used to determine the most important parameters affecting the permeate flux. The...
Optimal operating conditions of micro- and ultra-filtration systems for produced-water purification: Taguchi method and economic investigation
, Article Desalination and Water Treatment ; Volume 57, Issue 42 , Oct , 2015 , Page 19642-19654 ; 19443994 (ISSN) ; Mashhadi Meighani, H ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
In this study, treatment of two real produced waters was studied using microfiltration (MF) and ultrafiltration. In the first step, the effects of operating parameters including temperature, transmembrane pressure (TMP), cross-flow velocity (CFV), and back pulse time (BPT) (in the MF system) at three levels on the amount of permeate flux were investigated using ceramic and polymeric membranes. To design the experiments and optimize the experimental results, the L9 (34) and L9 (33) orthogonal arrays of the Taguchi method and a response category of the-larger-the-better were applied. Analysis of variance was used to determine the most important parameters affecting the permeate flux. The...
Theoretical and Experimental Investigation of WAX Precipitation in Crude Oil Transportation Pipelines
, Ph.D. Dissertation Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Jafari Behbahani, Taraneh (Supervisor) ; Sharifi, Khashayar (Co-Supervisor)
Abstract
Wax precipitation may occur in production or transportation of crude oil form field which is a serious problem in petroleum industry. Flow assurance issues concerning wax precipitation make it necessary to develop a precise thermodynamic model to predict the wax appearance temperature and amount of precipitation at different conditions. In this work a new procedure has been proposed to characterize crude oil based on the SARA test considering the wax and asphaltene as single pseudo components. Two scenarios have been investigated for the survey of the crude oil characterization, with and without asphaltene pseudo component. Also, in this work, the Perturbed ...
Performance of three-level spectrally encoded spreadtime CDMA in the presence of multiple interferences [electronic resource]
, Article IET Communications ; July 2011, Volume 5, Issue 10, P. 1328-1335 ; Mashhadi, Saeed ; Salehi, J. A ; Sharif University of Technology
Abstract
In this study the authors present an in-depth study, analysis and discussion on maximum likelihood (ML)-based receiver for a typical spectrally encoded spread-time CDMA in the presence of multiple narrowband interference (NBI) signals in an additive white Gaussian noise channel. Furthermore, the authors demonstrate that by combining useful properties of ML-based receiver and three-level codes, that is, codes with values of -1, 0, +1, the authors can introduce a new strategy in which superior performance with respect to previous receiver structure based on two-level codes, that is, codes with values of -1, +1, can be attained. With the help of an example, the authors drive, first, the...
Novel probabilistic bounds on power level profile of spectrally-encoded spread-time CDMA signals [electronic resource]
, Article IEEE Transactions on Wireless Communications ; Vol. 8, No. 5, PP. 2296-2301, May 2009 ; Sharif University Of Technology
Abstract
In this letter we introduce an effective tool to demonstrate signal power behavior of a typical spectrally encoded spread-time (SE/ST) CDMA system using probabilistic approach. By defining power level profile (PLP), as the probability of stretching instantaneous power from a pre-specified threshold, we can find novel upper bounds on the signal power profile. We discuss various properties owing to PLP and elaborate on the main parameters affecting the PLP value. We present three theorems, propose some simple upper bounds on the PLP, and give an insight on the main contributions of the results. We introduce a fundamental parameter, namely ß, as a key design parameter which relates the most...
The first chicago valuation method
, Article Contributions to Finance and Accounting ; Volume Part F1460 , 2023 , Pages 159-181 ; 27306038 (ISSN) ; Sharif University of Technology
Springer Nature
2023
Abstract
The First Chicago valuation method can be seen as a variation of the discounted cash flow (DCF) methodology. It provides a differentiated approach to analyzing companies at different stages in their lifecycle, further helping you to grasp the uncertainty involved. A further benefit of this approach is that it generates a variety of payoff scenarios for the company. Traditionally, three scenarios are constructed—the best, the base, and the worst case—and each scenario is assigned a probability. The valuation result is derived from a probability-weighted average of all three scenarios, so it includes both possible gains as well as potential losses in order to provide a precise valuation. This...
Optimum code structures for positive optical CDMA using normalized divergence maximization criterion [electronic resource]
, Article IEEE Transactions on Communications ; Vol. 56, No. 9, PP. 1414-1421, September 2008 ; Salehi, J. A ; Sharif Unversity Of Technology
Abstract
In this letter we consider optimum code structure for positive optical code division multiple-access (optical CDMA) systems. Positive systems are a class of systems that operate with positive real numbers only. We consider the effect of multipleaccess interference in our model and show that code design for both On-Off Keying (OOK) and Binary PPM optical CDMA systems results in the same solutions. Furthermore, we show that a class of codes known as optical orthogonal codes (OOCs) are the best possible positive codes. In obtaining the results we define normalized divergence based on signal-to-multipleaccess interference ratio (SIR) for a multiple-access system in a useful manner and use it as...
UWB spectrally encoded spread-time CDMA in the presence of multiple gaussian interference: RAKE receiver and three-level codes [electronic resource]
, Article IEEE Transactions on Communications ; Volume 56, Issue 12, 2008, Pages 2178-2189 ; Salehi, J. A ; Sharif University Of Technology
Abstract
In this paper we study and analyze the performance of the RAKE receiver for a typical Ultrawideband (UWB) Spectrally-Encoded Spread-Time (ST) CDMA in the presence of multiple Gaussian Interference (GI) signals. We demonstrate that by combining useful properties of three-level codes, i.e., codes with values of - 1, 0, +1, and RAKE receiver, we can introduce a new strategy in which it can result in superior performance when compared to previous results. In particular, following a discussion on three-level codes we can show that RAKE receiver with optimum multiplicative weights achieves a better performance when compared with simple two-level codes. With the help of an example we show various...
Code- division multiple- access techniques in optical fiber networks, part III: optical and gate receiver structure using generalized optical orthogonal codes
, Article IEEE Transactions on Communication ; 2006, Vol.54, No.8, PP. 1457-1468 ; Salehi, J. A ; Sharif University Of Technology
Abstract
In this paper, we present a deep insight into the behavior of optical code-division multiple-access (OCDMA) systems based on an incoherent, intensity encoding/decoding technique using a well-known class of codes, namely, optical orthogonal codes (OOCs). As opposed to parts I and II of this paper, where OOCs with cross-correlation lambda=1 were considered, we consider generalized OOCs with 1leslambdalesw, where w is the weight of the corresponding codes. To enhance the performance of such systems, we propose the use of an optical and logic gate receiver, which, in an ideal case, e.g., in the absence of any noise source, except the optical multiple-access interference, is optimum. Using some...
Novel probabilistic bounds on power level profile of spectrally-encoded spread-time CDMA signals
, Article IEEE Transactions on Wireless Communications ; Volume 8, Issue 5 , 2009 , Pages 2296-2301 ; 15361276 (ISSN) ; Salehi, J ; Sharif University of Technology
2009
Abstract
In this letter we introduce an effective tool to demonstrate signal power behavior of a typical spectrallyencoded spread-time (SE/ST) CDMA system using probabilistic approach. By denning power level profile (PLP), as the probability of stretching instantaneous power from a pre-specified threshold, we can find novel upper bounds on the signal power profile. We discuss various properties owing to PLP and elaborate on the main parameters affecting the PLP value. We present three theorems, propose some simple upper bounds on the PLP, and give an insight on the main contributions of the results. We introduce a fundamental parameter, namely β, as a key design parameter which relates the most...
Detection and Performance Analysis of Spread Time CDMA Systems in the Presence of Multitone Jammers
, M.Sc. Thesis Sharif University of Technology ; Mashhadi, Saeed (Supervisor)
Abstract
In this thesis, we study and analyze the performance of matched and partially-matched re-ceivers for a typical Ultra Wide-band Spectrally-Encoded Spread-Time (SE/ST) CDMA in the presence of multiple tone jammers and a coexisting OFDM system. We investigate a scenario in which there is not any information about the jammer and OFDM subcarrier frequencies in the transmitter side and we try to cancel jammers and interferences at the receiver. For this case, we demonstrate that by using a partially-matched filter at the receiver in an environment with multiple tone jammers and some coexisting systems the performance of the SE/ST system can be improved. We also assume K asynchronous users and...
Joint Pilot Power & Pattern Design for Compressive OFDM Channel Estimation
, M.Sc. Thesis Sharif University of Technology ; Mashhadi, Saeed (Supervisor)
Abstract
Increasing need to high rates of transmission through radio channels is a challenging problem in wireless communications. Simple implementation and high spectral efficiency of OFDM system turned it into a suitable choice to meet this need. Accurate estimation of the communication channel has a significant impact on performance of Orthogonal Frequency Division Multiplexing (OFDM) systems. Conventional methods of channel estimation are not able to exploit the inherent sparsity of the channel that is due to sparse distribution of scaterrers. On the other hand, Compressed Sensing (CS) is getting attention in variety of aspects such as communications, recently.CS-based channel estimation exploits...
Effect of Amplitude of Electric Field on the Rotation of Liquid Film
, M.Sc. Thesis Sharif University of Technology ; Amjadi, Ahmad (Supervisor)
Abstract
By direct and alternating electric field applied to thin film of liquid suspended in the air we can spin out and control it. Rotation pattern depends on the geometry of the electrodes and the applied magnetic field. This is called a rotating liquid film (Liquid Film Motor). To determine the cause of rotation, different models have been proposed. In this project we have tried to check the accuracy of any of the models. Using particle velocimetry using the photo, we calculate the velocity pattern. Then, using the Navier-Stokes equation calculate the acceleration and viscosity from the velocity. Then, for a special arrangement using a finite diffrent method, electric potential and the electric...
MIMO SAR Ground Moving Target Indication via Compressed Sensing
, M.Sc. Thesis Sharif University of Technology ; Mashhadi, Saeed (Supervisor)
Abstract
Synthetic Aperture Radar (SAR) is a coherent imaging technique capable of generating fine resolution images from long term standoff ranges, either day or night. The use of multiple antennas for SAR is referred to as multichannel SAR or Multiple-Input Multiple-Output(MIMO) SAR and offers the additional abilities to perform height estimation of the ground, improve the resolution and suppress undesired interferences. Ground moving target indication (GMTI) is the one that we explored in this research. Since the pattern of moving target in imaging zone is sparse, we can use compressed sensing for reducing computational complexity caused by additional channels. In our thesis, after modelling the...
Narrowband Interference Cancellation in Wireless Ultra Wideband Communication Systems via Three-Level Spread Time Codes
, Ph.D. Dissertation Sharif University of Technology ; Salehi, Javad (Supervisor)
Abstract
Achieving various data rates over a wide range of applications and in a multiple-access scenario should be done under certain power and bandwidth constraints. Emerging UWB communications has opened a novel perspective against different wireless network challenges, especially overwhelming data rates. In the research field, we begin our thesis with exposition of UWB, narrowband interference and spread time codes. We elaborate on the properties of spread time codes through frequency domain analysis of a reusable multiple-access scheme. Evaluating the variance of ISI, MAI and RUI, we demonstrate the spread time codes behave in an optimum manner, i.e., the most RUI resistibility, along with all...
Productivity Improvement in Mashhad Wheel Manufacturing Company
, M.Sc. Thesis Sharif University of Technology ; Mostofi (Supervisor)
Abstract
The present study, which is about practical methods of improving productivity in Mashhad ring factory, is presented in five chapters. In the foreword, the need for an attitude to improve productivity at the national level as well as in industry has been mentioned and has laid the groundwork for starting a discussion of productivity and practical solutions to improve it. In the first chapter, by defining productivity, considers the different perceptions of societies about productivity and finally deals with misconceptions about the concept of productivity. In the second chapter, based on committed articles from the American Society of Industrial Engineering, discusses the role of industrial...