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    Carbon-based nanocomposites: Distinguishing between deep-bed filtration and external filter cake by coupling core-scale mud-flow tests with computed tomography imaging

    , Article Journal of Natural Gas Science and Engineering ; Volume 105 , 2022 ; 18755100 (ISSN) Heydarzadeh Darzi, H ; Fouji, M ; Ghorbani Heidarabad, R ; Aghaei, H ; Hajiabadi, S. H ; Bedrikovetsky, P ; Mahani, H ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    Although Multi-Walled Carbon NanoTubes (MWCNTs) are found to influence the rheological behavior of drilling fluids, there are yet some controversies regarding their performance towards reducing formation damage induced by the invasion of water-based drilling fluids (WBFs). To address this important question, we synthesized novel nanocomposite materials via modifying the MWCNT via varying the proportion of carboxylated MWCNTs to PolyVinyl Alcohol (PVA). These nanocomposites were then used to make nano-based drilling-fluids (NDFs). The performance of the NDFs was evaluated by a set of rheological behavior tests, filtration experiments, and core-scale mud flow tests. To distinguish between the... 

    A soil-brine retention model for wetting processes considering the hysteresis effects

    , Article Transportation Geotechnics ; Volume 41 , 2023 ; 22143912 (ISSN) Golaghaei Darzi, A ; Sadeghi, H ; Zhou, C ; Sharif University of Technology
    Elsevier Ltd  2023
    Abstract
    Wetting hydrological processes are relevant to a considerable number of natural hazards, including landslides, dam breaks, surface runoff after floods, etc. The notable difference between wetting and drying soil–water retention curves (SWRC) has been attributed to the hysteresis phenomenon. Although recent studies confirm enhanced impurity levels of permeating fluid, most modeling approaches simply consider water retention along the drying path and neglect the impurity of pore water. Therefore, the main objective of this paper is to introduce a new water retention model along the wetting path by taking the osmotic potential into account, reflecting the influence of dissolved salts. The new... 

    A fully linear 5.2 GHz - 5.8 GHz digitally controlled oscillator in 65-nm CMOS technology

    , Article Microelectronics Journal ; Volume 90 , 2019 , Pages 48-57 ; 00262692 (ISSN) Heydarzadeh, S ; Torkzadeh, P ; Sadughi, S ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    A low-power fully linear integrated CMOS LC-based Digitally Controlled Oscillator is presented. The DCO operates in 5.2 GHz to 5.8 GHz range for using in IEEE 802.11a wireless applications. The system has been designed using 65 nm CMOS technology and 1.2 V supply voltage. By applying a proposed filter in DCO architecture −133.41 dBc/Hz phase noise at 1 MHz offset frequency from the fundamental carrier is achieved. The code generator and digital to analog converter designed to provide the high precision voltage required for fine-tuning. The output frequency swept through 10 control bits with 100 KHz resolution. The measured RMS jitter (∑ [1 KHz – 2 GHz]) from 5.8 GHz carrier is 1.65 fs. The... 

    Numerical Simulation of One-Dimensional Compressible Flow with Real Gas Effects by Solving Boltzmann Equation Using High-Order Accurate Finitedifference Method

    , M.Sc. Thesis Sharif University of Technology Heydarzadeh, Amir Hossein (Author) ; Hejranfar, Kazem (Supervisor)
    Abstract
    In this study, the Shokov-BGK model of the Boltzmann equation is reformulated and generalized to consider the real gas effects. At first, the formulation is performed to consider an arbitrary specific heats ratio and the correct Prandtl number for polyatomic gases. Here, the resulting equations of the present formulation are numerically solved by applying the high-order finite-difference weighted essentially non-oscillatory (WENO) scheme. The present solution method is tested by computing the one-dimension Reiman problem with different specific heats ratios for a wide range of the Knudsen numbers. The results are compared with the available gas-kinetic results which show good agreement. It... 

    Incorporation of strong motion duration in incremental-based seismic assessments

    , Article Engineering Structures ; Volume 223, Issue 15 , November , 2020 Mashayekhi, M ; Harati, M ; Darzi, A ; Estekanchi, H. E ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    This study proposes a new approach to incorporate motion duration in incremental dynamic assessments. In the proposed methodology, at each intensity level, a simulation-based approach which is verified with actual data is employed to determine the median duration and the median acceleration spectra of ground motions expected to occur at the site. Afterward, at each intensity level, artificial or spectrally matched motions are produced based on the median acceleration spectra and the median duration, indicating that different intensity levels are directly covered by the generated artificial or adjusted motions rather than just scaling up and down a set of recorded ground motions. In the... 

    Numerical investigation of saturated-unsaturated flow and stability analysis of tailings dams considering the influence of saline solutions

    , Article E3S Web of Conferences ; Volume 382 , 2023 ; 25550403 (ISSN) Anbarestani, M ; Sadeghi, H ; Darzi, A. G ; Bardanis M ; Sharif University of Technology
    EDP Sciences  2023
    Abstract
    A tailings dam is normally constructed through self-consolidation with minimum compaction effort. Accordingly, special attention to the ultimate limit design in assessing the tailings dam instability condition is of primary importance. Furthermore, the existence of pore fluid chemical contaminants with high concentrations makes soil hydraulic and shear resistance properties subject to considerable changes.Therefore, this study aims to investigate the stability of a tailing dam using saturated-unsaturated flow analysis under 0.2 and 0.6 M sodium chloride solutions and pure water as a benchmark. To make the analyses as realistic as possible, recently developed solute-dependent hydraulic... 

    Thermo-hydraulic analysis of desiccation cracked soil strata considering ground temperature and moisture dynamics under the influence of soil-atmosphere interactions

    , Article Geomechanics for Energy and the Environment ; Volume 38 , 2024 ; 23523808 (ISSN) Jabbarzadeh, M ; Sadeghi, H ; Tourchi, S ; Golaghaei Darzi, A ; Sharif University of Technology
    2024
    Abstract
    Global warming and climate change significantly affect ground temperature and flow patterns. Moreover, areas prone to cracking experience intensified temperature and moisture variations. Therefore, the aim of this study is to investigate ground temperature and moisture dynamics considering soil-atmosphere interaction through a coupled thermo-hydraulic analysis. Heat transfer, advective, and non-advective fluxes were simulated using CODE_BRIGHT finite element program to study water flow and energy transfer within the soil. Statistical analyses were conducted using an existing dataset to match the crack geometry with previous studies and find the best distribution for the width-to-depth ratio... 

    27Al and 31P NMR investigations of soluble aluminophosphate species in alcohol-water mixtures

    , Article Journal of Solution Chemistry ; Volume 41, Issue 5 , 2012 , Pages 888-897 ; 00959782 (ISSN) Samadi Maybodi, A ; Nejad Darzi, S. K. H ; Tafazzoli, M ; Sharif University of Technology
    2012
    Abstract
    In this work, phosphorus-31 and aluminum-27 nuclear magnetic resonance techniques were used to characterize the distribution of soluble aluminophosphate species in methanol + water and ethanol + water mixtures. The assignment of the peaks to alu-minate species was attempted, clarifying earlier work and producing information on the different aluminophosphate complexes. Nine peaks were observed at -0.41, -6.4, -7.5, -7.9, -13.1, -13.9, -16.6, -18.1 and -20.6 ppm. Four new peaks appeared in the 31P NMR spectra of the alcoholic aluminophosphate solutions and their intensities changed with changes of the alcohol:water volume ratio. These new peaks were observed in the presence of methanol or... 

    Field reconnaissance and InSAR investigation of subsidence-induced damage to electricity dispatch centers - a case study in Tehran

    , Article Smart Geotechnics for Smart Societies ; 2023 , Pages 1200-1203 ; 978-100099253-3 (ISBN); 978-100329912-7 (ISBN) Ghorbani, Z ; Golaghaei Darzi, A ; Sadeghi, H ; Garakani, A. A ; Sharif University of Technology
    CRC Press  2023
    Abstract
    Land subsidence, as a gradual settling of the ground surface, has become a threatening hazard to many infrastructures and lifelines. Among them, electricity dispatch centers (EDC) are considered the heart of a typical power transmission system, closely related to both domestic and industrial aspects of society. Therefore, this study aims to systematically explore early warnings and damages imposed on EDCs in Tehran. A combination of field reconnaissance and InSAR time series analyses are adopted to correlate subsidence-induced damages with several triggering mechanisms, such as the dynamic effects of subways and extra groundwater exploitation. Accordingly, spatially- and... 

    Quantitative Evaluation of Seismic Vulnerability of Reinforced Concrete Bridges Pier's Using the Theory of Distributed Plasticity, Plastic Hinges and C/D Methods and Compare their

    , M.Sc. Thesis Sharif University of Technology Darzi, Nima (Author) ; Vafaei, Abolhassan (Supervisor)
    Abstract
    Performance based design was first introduced in order to evaluate seismic vulnerability of structures in retrofitting topic and was rapidly implemented in new design codes. The main cause conducting widely developing of performance based design methods, has been accurate estimation of seismic demand parameters. Since seismic structural members displacement during earthquake has a direct effect on the amount of sustained damages, displacement index has always been a key concept in performance based design. The main goal followed by this research is comparing the results obtained from the standard pushover method (with two theorems of distributed plasticity and plastic hinges) and the... 

    Developing a Model for Vehicle-kilometer Traveled Estimation in Urban Network: Case Study of Shiraz

    , M.Sc. Thesis Sharif University of Technology Darzi, Aref (Author) ; Kermanshah, Mohammad (Supervisor)
    Abstract
    One of the most important criteria in travel analysis is the vehicle kilometer traveled (VKT). The distance which personal cars, vans or other automobiles travel is measured through this criterion. In addition, the VKT is used in transportation planning, accident analysis, transportation budgets assignment, and estimation of automobile pollutions. In this work we process origin-destination data gathered in Shiraz, Iran to estimate the VKT. To this end, we incorporate the linear regression and geographically weighted regression (GWR) methods. Through this research, data from origin-destination statistics of Shiraz, gathered by the transportation institute of Sharif University of Technology in... 

    Investigation of the Relationship between Microstructure and Mechanical Properties of High Density Polyethylene Film (HDPE) with Bimodal Weight Distribution

    , M.Sc. Thesis Sharif University of Technology Darzi Bourkhani, Rasool (Author) ; Pircheraghi, Gholamreza (Supervisor)
    Abstract
    Polymeric film for packaging applications are commonly made from a variety of polyethylenes using a blown film process. Nowadays high density polyethylene with bimodal molecular weight distributions are used to improve the performance and the final properties. In the present study samples with different bimodal molecular weight distribution in a similar film preparation are developed. The EX5 sample from the Jam Petrochemical showed microstructure with heavily oriented stack of lamellae in the machine direction. In contrast, the 7000F sample from the Mehr Petrochemical presented a microstructure with a lower degree of lamellae, containing lamella twist and more link between the crystalline... 

    The Study of Currents Caused by the Sunlight in Coastal Areas with Submerged and Emergent Vegetation

    , M.Sc. Thesis Sharif University of Technology Mousazadeh Darzi, Fatereh (Author) ; Jamali, Mirmosadegh (Supervisor)
    Abstract
    Aqueous environment with vegetation in coastal areas plays important role in ecologic systems. The plants in aqueous environment caused to vertical and lateral changes of flow velocity profile. When sunlight penetrates the water, it will turns into heat energy. The plants caused to blocking the light path, to make a difference in temperature and thus the density differences on the horizon. This density gradient will lead to the gravity flow. Due to the observations, in coastal wetlands, beside the plants the emerged from the water, there are some completely submerged plants that their root in the soil and shallow layer of fluid covered on them. This study to approaching the conditions, is... 

    Development of a New Analytical Model based on Soil-water Retention Curve Microstructure Considering the Effects of Osmotic Potential

    , M.Sc. Thesis Sharif University of Technology Golaghaei Darzi, Ali (Author) ; Sadeghi, Hamed (Supervisor)
    Abstract
    The soil-water retention curves (SWRC) is an unsaturated soil mechanics hydro chemical state surface, which expresses the relationship between the soil suction and water content. The soil-water retention curve could describe the water adsorption and desorption process that happened in soils. The difference between the desorption or drying retention curve and the adsorption or wetting retention curves in a specific soil specimen indicates the hydraulic hysteresis phenomenon. Generally, the amount of water remaining in the drying process is greater than the amount of water adsorbed in the wetting process at a certain amount of suction. Suction due to the combined effects of capillary and... 

    Prediction of stress-dependent soil water retention using machine learning

    , Article Geotechnical and Geological Engineering ; Volume 42, Issue 5 , 2024 , Pages 3939-3966 ; 09603182 (ISSN) Fazel Mojtahedi, S. F ; Akbarpour, A ; Darzi, A. G ; Sadeghi, H ; van Genuchten, M. T ; Sharif University of Technology
    2024
    Abstract
    The soil water retention curve (SWRC) provides information for a wide range of geoenvironmental problems, such as analyses of transient two-phase flow, the bearing capacity and shear strength of unsaturated soils. Many past studies have shown experimentally the effects of stress on the SWRC. Unfortunately, direct stress-dependent water retention measurements are relatively time-consuming and generally require special equipment and a certain level of expertise. This study primarily aimed to develop a novel predictive framework within the context of soft computing to capture the dependency of the SWRC on several variables, with an emphasis on stress and soil type. To achieve this, the three... 

    Heat transfer enhancement of ferrofluid flow within a wavy channel by applying a non-uniform magnetic field

    , Article Journal of Thermal Analysis and Calorimetry ; Volume 139, Issue 5 , 2020 , Pages 3331-3343 Mousavi, S. M ; Biglarian, M ; Rabienataj Darzi, A. A ; Farhadi, M ; Hassanzadeh Afrouzi, H ; Toghraie, D ; Sharif University of Technology
    Springer Netherlands  2020
    Abstract
    This paper presents the effects of a non-uniform magnetic field on the hydrodynamic and thermal behavior of ferrofluid flow in a wavy channel by 3D numerical simulation. The wavy surfaces at the top and bottom of the channel are heated by constant heat fluxes. Moreover, the sidewalls are adiabatic. In the wavy section, in the perpendicular direction of the main flow, the magnetic field that linearly varies along the direction of the main flow is applied. The mathematical model that is consistent with the principles of ferrohydrodynamics and magnetohydrodynamics is used for the problem formulation. The results indicate that the wavy wall enhances the heat transfer rate on the bottom of the... 

    Binary classification of imbalanced datasets: The case of CoIL challenge 2000

    , Article Expert Systems with Applications ; Volume 128 , 2019 , Pages 169-186 ; 09574174 (ISSN) Khalilpour Darzi, M. R ; Akhavan Niaki, S. T ; Khedmati, M ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    This paper presents some approaches based on data mining techniques to solve the prediction task of Computational Intelligence and Learning (CoIL) Challenge 2000. The prediction task of the contest is a direct mailing problem and the goal is to improve its response rate. The main issue in this competition is the incompatibility of the dataset in which the distribution of the classes of the target attribute is highly unbalanced. This in turn causes high error rate in identifying the minority class samples. Three different level methods including data-level, algorithm-level, and hybrid method are used to overcome this issue. The specificity, sensitivity, precision-recall, and ROC criteria are... 

    Correlation-augmented Naïve Bayes (CAN) Algorithm: A Novel Bayesian Method Adjusted for Direct Marketing

    , Article Applied Artificial Intelligence ; 2021 ; 08839514 (ISSN) Khalilpour Darzi, M. R ; Khedmati, M ; Akhavan Niaki, S. T ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    Direct marketing identifies customers who buy, more probable, a specific product to reduce the cost and increase the response rate of a marketing campaign. The advancement of technology in the current era makes the data collection process easy. Hence, a large number of customer data can be stored in companies where they can be employed to solve the direct marketing problem. In this paper, a novel Bayesian method titled correlation-augment naïve Bayes (CAN) is proposed to improve the conventional naïve Bayes (NB) classifier. The performance of the proposed method in terms of the response rate is evaluated and compared to several well-known Bayesian networks and other well-known classifiers... 

    The Real Effect of Banks’ Money Creation Ability in a New Keynesian Framework

    , M.Sc. Thesis Sharif University of Technology Darzi Larijani, Samyar (Author) ; Madanizadeh, Ali (Supervisor) ; Mahmoodzadeh, Amineh (Supervisor)
    Abstract
    In much of the financial economics literature, banks are modeled as financial intermediaries that transfer household deposits to loan applicants. In these models, deposits are obtained from the accumulation of real amounts (household savings). In addition to this, another approach describes banks not as intermediaries of loanable funds, but as money-creators who do not need to accumulate deposit resources to lend. In this study, by modeling the money-creation behavior of the banking network, we try to answer the question that if the bank can create credit and purchasing power for the firm based on its future income, how will the general variables of the economy, including consumption and... 

    Numerical modelling of soluble contamination transport in landfills based on empirical function of membrane efficiency

    , Article Lecture Notes in Civil Engineering ; Volume 370 LNCE , 2023 , Pages 183-198 ; 23662557 (ISSN); 978-981994040-0 (ISBN) Hedayati Azar, A ; Sadeghi, H ; Golaghaei Darzi, A ; AliPanahi, P ; Yukselen Aksoy Y ; Reddy K. R ; Agnihotri A. K ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2023
    Abstract
    Clayey soils are widely used as barriers to control leachate leakage in landfills. Chemico-osmosis is one of the important phenomena influencing soluble contamination transport through clay barriers acting as a membrane. The membrane ability to restrict contamination transport is referred to as membrane efficiency. Experimental reports have revealed that membrane efficiency is a function of soil void ratio and contamination concentration. However, the currently used empirical function expresses the membrane efficiency simply in terms of average concentration. Therefore, the merit of this study is to enhance the reliability of this function to take into account various concentrations and void...