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    Active brownian particles and run-and-tumble particles separate inside a maze

    , Article Scientific Reports ; Volume 6 , 2016 ; 20452322 (ISSN) Khatami, M ; Wolff, K ; Pohl, O ; Ejtehadi, M. R ; Stark, H ; Sharif University of Technology
    Nature Publishing Group  2016
    A diverse range of natural and artificial self-propelled particles are known and are used nowadays. Among them, active Brownian particles (ABPs) and run-and-tumble particles (RTPs) are two important classes. We numerically study non-interacting ABPs and RTPs strongly confined to different maze geometries in two dimensions. We demonstrate that by means of geometrical confinement alone, ABPs are separable from RTPs. By investigating Matryoshka-like mazes with nested shells, we show that a circular maze has the best filtration efficiency. Results on the mean first-passage time reveal that ABPs escape faster from the center of the maze, while RTPs reach the center from the rim more easily.... 

    Dynkin game with asymmetric information

    , Article Bulletin of the Iranian Mathematical Society ; Volume 45, Issue 1 , 2019 , Pages 283-301 ; 10186301 (ISSN) Esmaeeli, N ; Imkeller, P ; Nzengang, V ; Sharif University of Technology
    Springer International Publishing  2019
    We consider a Dynkin game where the seller possesses additional information compared to the buyer. The additional information is described by a random variable taking finitely many values. We show that the game possesses a value and we provide a necessary and sufficient condition for the existence of a Nash equilibrium. Results are illustrated with an explicit example. © 2018, Iranian Mathematical Society  

    PVDF/PAN blend membrane: preparation, characterization and fouling analysis

    , Article Journal of Polymers and the Environment ; 2016 , Pages 1-11 ; 15662543 (ISSN) Anvari, A ; Azimi Yancheshme, A ; Rekaabdar, F ; Hemmati, M ; Tavakolmoghadam, M ; Safekordi, A ; Sharif University of Technology
    Springer New York LLC  2016
    Ultrafiltration membranes were prepared from blend of the poly(vinylidene fluoride) (PVDF) with polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effect of blending ratio on the morphology and antifouling behavior of the prepared membranes was investigated. The performance of the membranes was evaluated by using cross flow filtration of pure water and buffered bovine serum albumin (BSA) solution as feed. Contact angle measurements indicated that the hydrophilicities of the PVDF/PAN membranes increased by increasing PAN concentration in the casting... 

    PVDF/PAN blend membrane: preparation, characterization and fouling analysis

    , Article Journal of Polymers and the Environment ; Volume 25, Issue 4 , 2017 , Pages 1348-1358 ; 15662543 (ISSN) Anvari, A ; Yancheshme, A. A ; Rekaabdar, F ; Hemmati, M ; Tavakolmoghadam, M ; Safekordi, A ; Sharif University of Technology
    Ultrafiltration membranes were prepared from blend of the poly(vinylidene fluoride) (PVDF) with polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. N,N-dimethylacetamide (DMAc) and water were used as solvent and coagulant (non-solvent), respectively. The effect of blending ratio on the morphology and antifouling behavior of the prepared membranes was investigated. The performance of the membranes was evaluated by using cross flow filtration of pure water and buffered bovine serum albumin (BSA) solution as feed. Contact angle measurements indicated that the hydrophilicities of the PVDF/PAN membranes increased by increasing PAN concentration in the casting... 

    Experimental Study on Fluid Loss and its Effect on Permeability

    , M.Sc. Thesis Sharif University of Technology Zamani, Hossein (Author) ; shad, Saeed (Supervisor)

    In order to prevent a blow out, cooling the bit, displacement of drilling particle, etc., it is necessary to use a suitable fluid called drilling mud. The construction of drilling mud, especially the oil base, has a high cost and covers more than 20% of drilling costs, so maintaining and proper use of it is important, as well as drilling the reservoir layer due to the higher permeability of this layer than Other layers allow the drilling mud to influx into the formation, which in addition to the cost of fluid loss, damage to the reservoir, reduce its permeability and many problems during production. Therefore, in order to investigate the phenomenon of fluid loss, measure its size and... 

    Simulation of Clogging in Porous Media by Pore Network Model

    , M.Sc. Thesis Sharif University of Technology Razavy, Sina (Author) ; Jamshidi, Saeed (Supervisor) ; Raoof, Amir (Co-Supervisor)
    Clogging of the pores of the porous medium occurs in different processes such as geothermal injection pumps, hydrocarbon wells, and underground water extraction wells. We need a model that can simulate these blockages in order to predict how fundamental variables of the porous medium change under different flow regimes and different particle sizes in the fluid (for example, the relationship between porosity and permeability changes). The aim is to simulate clogging in a porous medium using a pore network model. Simulations should model pore clogging and show how the permeability of the sample changes due to pore clogging. In the pore network, there are often thousands (or millions) of pores... 

    Experimental Study of Geotextile's Drainage and Filtration Properties in Dams under Different Hydraulic Gradients and Boundary Conditions

    , M.Sc. Thesis Sharif University of Technology Zahmatkesh, Zahra (Author) ; Pak, Ali (Supervisor)
    Geotextiles are one of the most widely used materials in filtration and drainage applications. Since geotextiles are exposed to different stresses and hydraulic gradients, thier hydraulic behavior in real situations is of great importance. In this study, filtration and drainage of several nonwoven needle-punched geotextiles with different properties and unit masses per area of 200g/m2, 400g/m2, 500g/m2 and 800g/m2 under various confined stresses and hydraulic gradients are investigated. To get to these aims, permittivity and transmissivity apparatuses were designed and built in the course of this investigation. Then samples which were emerged for at least 24 hours were tested under different... 

    Humic acid removal from water using a novel fabricated antifouling carbon nanotube bucky - paper membrane and effect of operating parameters

    , Article Global Nest Journal ; Volume 19, Issue 2 , 2017 , Pages 217-224 ; 17907632 (ISSN) Jafari, A ; Nasseri, S ; Nabizadeh, R ; Mousavi, S. A ; Rezaee, R ; Mahvi, A. H ; Sharif University of Technology
    Global NEST  2017
    In present work, a novel supported bucky paper (BP) membrane was fabricated and evaluated for humic acid (HA) removal from water. For better understanding the effect of operating variables, response surface methodology (RSM) was also applied. Three independent parameters namely TOC concentration (5, 10 and 15 mg l-1), operating time (10, 20 and 30 min) and transmembrane pressure (TMP) (1, 2 and 3 bar) were selected for TOC removal (%) and permeate flux analysis. The results revealed that the membrane could effectively remove HA primarily through electrostatic repulsion and then adsorption mechanisms. The study also showed that about 65% and 35% of the removed HA were through repulsion and... 

    American options with asymmetric information and reflected BSDE

    , Article Bernoulli ; Volume 24, Issue 2 , May , 2018 , Pages 1394-1426 ; 13507265 (ISSN) Esmaeeli, N ; Imkeller, P ; Sharif University of Technology
    International Statistical Institute  2018
    We consider an American contingent claim on a financial market where the buyer has additional information. Both agents (seller and buyer) observe the same prices, while the information available to them may differ due to some extra exogenous knowledge the buyer has. The buyer's information flow is modeled by an initial enlargement of the reference filtration. It seems natural to investigate the value of the American contingent claim with asymmetric information. We provide a representation for the cost of the additional information relying on some results on reflected backward stochastic differential equations (RBSDE). This is done by using an interpretation of prices of American contingent... 

    New insight into the filtration control of drilling fluids using a graphene-based nanocomposite under static and dynamic conditions

    , Article ACS Sustainable Chemistry and Engineering ; Volume 9, Issue 38 , 2021 , Pages 12844-12857 ; 21680485 (ISSN) Movahedi, H ; Jamshidi, S ; Hajipour, M ; Sharif University of Technology
    American Chemical Society  2021
    During oil and gas well drilling, the filtration control of bentonite water-based drilling fluids (BT-WBDFs), as an environmentally friendly fluid, is crucial to avoid formation damage and swelling shale problems. One of the most critical problems is undesirable changes in the rheology and filtration properties of the BT-WBDFs because of salt contamination. Herein, the potential of using both graphene oxide (GO) nanosheets and a graphene oxide-polyacrylamide (GO-PAM) nanocomposite is evaluated for controlling the filtration properties, especially in a salty medium. First, GO nanosheets were functionalized, and then the GO-PAM nanocomposite was synthesized using the solution polymerization... 

    An optimal wavelet filtering method for noise suppression of PD measured signal and its location in power transformer winding

    , Article 2005 IEEE International Conference on Dielectric Liquids, ICDL 2005, Coimbra, 26 June 2005 through 1 July 2005 ; 2005 , Pages 269-272 ; 0780389549 (ISBN); 9780780389540 (ISBN) Naderi, M. S ; Vakilian, M ; Blackburn, T. R ; Phung, B. T ; Nam O, H ; Naderi, M. S ; Sharif University of Technology
    In this paper a method for selecting optimal wavelet is introduced, which is implemented for evaluating electrical measured partial discharges on a 66 kV/25 MVA fully interleaved winding of a power transformer. Applying wavelet transform to a signal produces a wavelet detail coefficient distribution throughout the time-scale, which depends on the wavelet chosen. This method is based on the capability of the chosen wavelet for generating coefficients with maximal values. The basic idea of this method is described and applications to partial discharge studies are explored. The paper demonstrates that the wavelet based de-noising method proposed in the paper can be employed in extracting the PD... 

    Preparation of Heat Resistance Fluid Loss Controlling Drilling Fluids Using Pistachios Shell and Nano Graphene Oxide as Additives

    , M.Sc. Thesis Sharif University of Technology Davoodi, Shadfar (Author) ; Ramazani, Ahmad (Supervisor) ; Jamshidi, Saeed (Supervisor)
    Given that the mean of the cost of drilling operation related to the required martials and preparation of the drilling fluids, therefore, the design and construction drilling fluid which omit has to be a proper rheology is essential in drilling operations and oil industry. A desirable property of the drilling fluid is the minimum fluid loss volume which can be achieved by formation of a low permeability filter cake on the wellbore. Drilling fluid filtrating invasion into the formation can cause formation damage and reduction in the productivity of the well. In drilling fluids, a series of natural synthetic and polymers may be used as fluid (filtration) loss control additives. However, high... 

    Comparing the Performance of Centrifuge, Membrane Filter and Filter Press for Clarification of Lipase Enzyme

    , M.Sc. Thesis Sharif University of Technology Taher Aslani, Ahmad Reza (Author) ; Rousta Azad, Reza (Supervisor)
    Lipases (Triacyl Glycerol Acyl Hydrolase, EC. are multidimensional biocatalysts which have many applications in food industrials, dairy, fats and oils processing, detergents, synthesis of pure chemical and pharmaceutical materials, paper industrial and cosmetics. Generally, industrial enzymes are produced extracellularly, so their separation from a low-cost complex medium (usually used for production) is one of the cost stages in their production process. Filtration is the most economical method of separation in the production of enzymes, but due to the small size of colloidal particles and cell masses present in the fermentation environment, its use is subject to limitations. In... 

    Investigating the Effect of Drilling Fluid Properties and its Compositions on the Mud Loss Mechanism

    , M.Sc. Thesis Sharif University of Technology Kazemzadeh, Amir (Author) ; Shad, Saeed (Supervisor) ; Zahedi Far, Amir (Co-Supervisor)
    Currently, one of the most important problems in the field of drilling is the issue of drilling fluid loss in different formations. The problem of mud loss has been evident since the beginning of oil and gas well drilling operations, so that oil companies spend millions of dollars annually to solve the problem of mud loss. Problems such as pipe jamming, loss of rig production time, well blowout, loss of a large volume of drilling mud and damage to reservoir formations due to loss of drilling fluid are caused. Regarding the drilling variables, many factors cause the decrease or increase of the loss, the most important of which are the weight on the drill bit, drilling speed, the rate of... 

    Dispersion and deposition of nanoparticles in microchannels with arrays of obstacles

    , Article Microfluidics and Nanofluidics ; Volume 21, Issue 4 , 2017 ; 16134982 (ISSN) Banihashemi Tehrani, S. M ; Moosavi, A ; Sadrhosseini, H ; Sharif University of Technology
    Springer Verlag  2017
    Air pollutants are among the hazardous materials for human health. Therefore, many scientists are interested in removing particles from the carrier gas. In this study, flow of air and airborne particles through the virtual multi-fibrous filters that consist of different fiber cross-sectional shapes and arrangements is simulated where particle deposition and filtration performance are studied. Regular and irregular arrangements of fibers with the circular, elliptical, and equilateral triangular cross sections have been considered. Effects of important parameters such as solid volume fraction, internal structure, and filter thickness on particle collection efficiency and pressure drop are... 

    Data-driven approach for evaluation of formation damage during the injection process

    , Article Journal of Petroleum Exploration and Production Technology ; Volume 10, Issue 2 , 2020 , Pages 699-710 Shabani, A ; Jahangiri, H. R ; Shahrabadi, A ; Sharif University of Technology
    Springer  2020
    Waterflooding is among the most common oil recovery methods which is implemented in the most of oil-producing countries. The goal of a waterflooding operation is pushing the low-pressure remained oil of reservoir toward the producer wells to enhance the oil recovery factor. One of the important objects of a waterflooding operation management is understanding the quality of connection between the injectors and the producers of the reservoir. Capacitance resistance model (CRM) is a data-driven method which can estimate the production rate of each producer and the connectivity factor between each pair of wells, by history matching of the injection and production data. The estimated connectivity... 

    Blood Filteration Modeling in the Glomerular Capillary Network

    , M.Sc. Thesis Sharif University of Technology Banazadeh, Mohamad Hossein (Author) ; Saeedi, Mohammad Saeed (Supervisor) ; Firoozabadi, Bahar (Co-Advisor)
    The mathematical analysis of the kidney has always been considered due to its complex performance. It’s about two decades that mathematicians work on the mathematical modeling of this tissue. Since Glomerular filtration of blood in the kidney has been regarded by physiologists for many years, they can access only to the qualitative data. Mathematicians can solve this problem by numerical modeling. In this research, an engineering model is presented for the analysis of this capillary network by investigating in the different scientific fields such as, physiology, medicine, computer science and mathematics.First of all, the homogeneous model introduced by Deen, are studied. The rate of the... 

    Investigating on Filtration of Solid Particles in Culture Media after Fermentation

    , M.Sc. Thesis Sharif University of Technology Maleki, Maziar (Author) ; Roosta Azad, Reza (Supervisor)
    In biotechnology processes, in addition of culture media there is a solid phase which dispensed across the system.In most of bioprocesses, first operational unit for downstream treatment is the separation of this particles from fermentation liquor. In contrast with other categories like inorganic chemistry, solid particles in fermentation liquor (which the main part of it is biomass itself) have complicated physical & rheological properties. For example, all of biomass species are hydrophilic and sometimes form colloidal solutions.With this perspective, separation of solid phase from fermentation liquor is a hard challenge in this kind of processes.In this research, with regard of great... 

    Nanofiltration process on dye removal from simulated textile wastewater

    , Article International Journal of Environmental Science and Technology ; Volume 5, Issue 3 , 2008 , Pages 401-408 ; 17351472 (ISSN) Hassani, H ; Mirzayee, R ; Nasseri, S ; Borghei, M ; Gholami, M ; Torabifar, B ; Sharif University of Technology
    CEERS  2008
    Dyestuffs removal from industrial wastewater requires special advanced technologies, since dyes are usually difficult to remove by biological methods. In this study nanofiltration process was used for removal of different dyestuffs from solutions. The rate of dye removal by spiral wound nanofiltration membrane in film thin composite MWCO=90 Dalton, was evaluated for four classes of dyes acidic, disperse, reactive and direct in red and blue dyes medium. Dye absorbance was measured by spectrophotometric method (2120 Standard Method 1998). Effects of feed concentration, pressure and total dissolved solids concentration were also studied. Results showed that increasing dye concentration lead to... 

    A study of feasibility for water purification using vertical porous concrete filter

    , Article International Journal of Environmental Science and Technology ; Volume 4, Issue 4 , 2007 , Pages 505-512 ; 17351472 (ISSN) Taghizadeh, M. M ; Torabian, A ; Borghei, M ; Hassani, A. H ; Sharif University of Technology
    CEERS  2007
    There is a need to find cheaper and simpler techniques for rural water filtration system in developing countries. Using a filter made of blocks for the water treatment enables one to make vertical filters. It is expected that the amount of land utilized would decrease by more than 70 % if vertical filters were used. The operation and washing would be simpler than using horizontal sand filters as filters made of blocks would be used instead. The feasibility study focused on finding adequate materials, compositions and methods of making a block with enough resistance to water pressure, sufficient porosity for water transformation, and using inexpensive, readily available materials. A pilot...