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    The wet precipitation process of hydroxyapatite

    , Article Materials Letters ; Volume 57, Issue 24-25 , 2003 , Pages 4064-4069 ; 0167577X (ISSN) Saeri, M. R ; Afshar, A ; Ghorbani, M ; Ehsani, N ; Sorrell, C. C ; Sharif University of Technology
    Stoichiometric hydroxyapatite (HA) powder was synthesized by wet method using orthophosphoric acid and calcium hydroxide, as raw materials. In this regard, the time-depending changes of the precipitated particles and effects of heating on them were investigated. The as-precipitated and heated powder samples were examined using field emission electron microscopy (FESEM), XRD and Raman spectroscopy methods. The results revealed that the morphology and size of the precipitated particles change in each stage of the process. After drying, these nanoparticles tend to form small agglomerates. © 2003 Elsevier Science B.V. All rights reserved  

    Wet spinning of low gel content SBR/PMMA core/shell particles dispersed in a good solvent for the shell

    , Article Polymer ; Volume 44, Issue 14 , 2003 , Pages 4011-4019 ; 00323861 (ISSN) Moghbeli, M. R ; Mohammadi, N ; Bagheri, R ; Ghaffarian, S. R ; Sharif University of Technology
    Elsevier BV  2003
    A low gel content poly (styrene-ran-butadiene)/poly (methyl methacrylate) (SBR/PMMA) core/shell particles dispersed in a good solvent for the shell was wet spun into a coagulation bath at room temperature. The SEM micrographs of as spun fibers showed various surface topographies and fiber diameters, ranging from 4.2 up to 20 μm depend upon the draw ratio. The osmium tetroxide stained cross-section of fibers observed by transmission electron microscope (TEM), indicated a heterogeneous morphology consisting of dark cores and fairly light shells, which is a result of self-stratification to an overall core/shell morphology in fiber cross-section. The inner core consisted of higher concentration... 

    A generalized multi-layer information hiding scheme using wet paper coding

    , Article 2014 11th International ISC Conference on Information Security and Cryptology, ISCISC 2014 ; 2014 , p. 210-213 Bidokhti, A ; Ghaemmaghami, S ; Sharif University of Technology
    Multi-layer schemes have been proposed for steganography. Also some authors have combined these methods with the idea of wet paper codes and gained higher embedding efficiency. This paper proposes a generalized multi-layer method for wet paper embedding. First, the cover bits are divided into blocks and, by combining these bits in groups of 3, a pyramid is formed. Next, the secret message is embedded through a layer-by-layer procedure. The proposed method has higher embedding efficiency in some cases and provides more flexibility for choosing the embedding payload, especially in lower payload conditions  

    A physicochemical evaluation of modified HZSM-5 catalyst utilized for production of dimethyl ether from methanol

    , Article Petroleum Science and Technology ; Vol. 32, issue. 8 , Feb , 2014 , pp. 904-911 ; ISSN: 10916466 Pedram, M. Z ; Kazemeini, M ; Fattahi, M ; Amjadian, A ; Sharif University of Technology
    A number of HZSM-5 catalysts modified with 5 wt% Mg, Na, Zr, and Al as well as others modified with 5-60 wt% Zn prepared by wet impregnation. These materials were characterized by the NH3-TPD, XRF, and XRD analyses and tested in a slurry reactor to determine their activities in dehydration of methanol solution in kerosene. Reactions were carried out at 230°C and 19 bar for 4 h of residence time in the reactor. Results showed that in the first series, the catalyst modified with Zr and in the second series, the one modified with 10 wt% Zn led to the highest methanol conversion. It was deduced that elimination of strong acid sites and partial replacement of active cations in the HZSM-5 zeolite... 

    Wettability alteration of reservoir rocks to gas wetting condition: a comparative study

    , Article Canadian Journal of Chemical Engineering ; Volume 96, Issue 4 , April , 2018 , Pages 997-1004 ; 00084034 (ISSN) Erfani Gahrooei, H. R ; Ghazanfari, M. H ; Karimi Malekabadi, F ; Sharif University of Technology
    Wiley-Liss Inc  2018
    Productivity of gas condensate reservoirs reduces significantly due to the near wellbore condensate/water blockage phenomenon. A novel, permanent solution to alleviate this problem is near wellbore wettability alteration of reservoir rocks to preferentially gas wetting conditions; industrial chemical materials are good candidates for this purpose, because of their eco-friendly characteristics, economical price, and mass production. In this paper, a comparative study is conducted on two industrial fluorinated chemicals, MariSeal 800 and SurfaPore M. Static and dynamic contact angle measurements, spontaneous imbibition, and core flooding tests were conducted to investigate the effect of... 

    Simultaneous measurements of the resistance and capacitance using a cylindrical sensor system

    , Article Modern Physics Letters B ; Volume 22, Issue 8 , 2008 , Pages 595-610 ; 02179849 (ISSN) Golnabi, H ; Azimi, P ; Sharif University of Technology
    In this article, the design and operation of a cylindrical capacitive sensor based on the dielectric reactance capacitance and conductance changes of the gap medium is reported. The proposed system was used to determine characteristics of different water liquids as a result of the capacitance and resistance variations. The air gap capacitance (dry signal) is measured and then by filling the gap with a liquid, the capacitance (wet signal) is monitored for different liquids. A reported sensor is used for the distilled, tap, boiled, and salt water measurements and the capacitance and resistance results are compared. A big difference of about 38.5 μF in the measured capacitance values for the... 

    Some important factors in the wet precipitation process of hydroxyapatite

    , Article Materials and Design ; Volume 24, Issue 3 , 2003 , Pages 197-202 ; 02641275 (ISSN) Afshar, A ; Ghorbani, M ; Ehsani, N ; Saeri, M. R ; Sorrell, C. C ; Sharif University of Technology
    Elsevier Ltd  2003
    The precipitation process considered here, involved the addition of orthophosphoric acid solution to a calcium hydroxide solution. Several parameters such as the effects of atmosphere controlling, pH, adding extra acid solution, the amount of stirring speed, and post-chemical treatment were studied. In order to study the thermal stability of synthesised powders, they were sintered for 2 h at 1200 °C and the as-precipitated and sintered powder samples were examined using SEM, XRD, FTIR and ICP methods. The results clearly revealed that the final precipitated powder is hydroxyapatite (HA) with good purity, stoichiometry and successful thermal stability. SEM high magnification micrographs... 

    Investigation of the effect of water based nano-particles addition on hysteresis of oil and-water relative permeability curves

    , Article Society of Petroleum Engineers - SPE International Oilfield Nanotechnology Conference 2012 ; June , 2012 , p. 267-277 Parvazdavani, M ; Masihi, M ; Ghazanfari, M. H ; Sherafati, M ; Mashayekhi, L ; Sharif University of Technology
    It has been shown that one kind of poly silicon particles with sizes ranging from 10-500 nm, can be used in oilfields to enhance the oil recovery of water injection by 15-20%. The contributing mechanism might be reducing the interfacial tension which appears through improving relative permeability of the oil-phase. However, fundamental understanding of how hysteretic behavior of relative permeability curves affected by nanosilica particles remains a topic of debate in the literature. In this study, water as well as water dispersed nanosilica particles floods was performed on sandstone rock sample saturated by light crude oil supplied from one of Iranian oil reservoir, and the relative... 

    Extended gibbs free energy and laplace pressure of ordered hexagonal close-packed spherical particles: A wettability study

    , Article Langmuir ; Volume 37, Issue 28 , 2021 , Pages 8382-8392 ; 07437463 (ISSN) Bayat, A ; Ebrahimi, M ; Rahemi Ardekani, S ; Saievar Iranizad, E ; Zaker Moshfegh, A ; Sharif University of Technology
    American Chemical Society  2021
    The wetting property of spherical particles in a hexagonal close-packed (HCP) ordering from extended Gibbs free energy (GFE) and Laplace pressure view points is studied. A formalism is proposed to predict the contact angle (θ) of a droplet on the HCP films and penetration angle (α) of the liquid on the spherical particles. Then, the extended Laplace pressure for the layered HCP ordering is calculated and a correlation between the wetting angle, sign of pressure, and pressure gradient is achieved. Our results show that the sign and the slope of pressure are important criteria for determining the wettability state and it is found that the contact angle is independent of the particle radius, as... 

    Effect of brine salinity and hydrolyzed polyacrylamide concentration on the Oil/Brine and Brine/Rock Interactions: Implications on enhanced oil recovery by hybrid low salinity polymer flooding in sandstones

    , Article Fuel ; Volume 324 , 2022 ; 00162361 (ISSN) Amiri, M ; Fatemi, M ; Biniaz Delijani, E ; Sharif University of Technology
    Elsevier Ltd  2022
    The main idea behind the application of Low salinity polymer flooding (LSPF) enhanced oil recovery (EOR) method is that diluted brine improves the oil recovery by wettability alteration from oil-wet (OW) towards water-wet (WW) condition, while polymer enhances the mobility of the displacing phase. However the possible effect of polymer on the fluid/fluid and fluid/rock interactions are not investigated systematically in the literature. The main objective of the present reserach is to examine the possible effect of hybrid application of low-salinity and polymer on the brine/rock and brine/oil interfaces properties. Formation water (FW) and sea water (SW) and its two different dilutions, i.e.... 

    Investigating the Role of Nanoparticles and Chemicals on Wettability Alteration of Carbonate Rocks to Gas-Weting Condition and Analysis of Hystertic Behavior

    , M.Sc. Thesis Sharif University of Technology Azadi Tabar, Mohammad (Author) ; Ghazanfari, Mohammad Hossein (Supervisor)
    The purpose of this study was to investigate the experimental and modeling of the drop formation process on calcite rock and calcite aged in nano fluid surfaces in order to analyze size dependent contact angle and wettability modification. To do this, the calcite surfaces were prepared by cutting to an approximately size of 3*3*0.4 cm and grinded and polished to achieve different roughnesses. The purity and roughness of the samples were determined by X-ray diffraction and atomic force microscopy, respectively. In order to conduct the dynamic and static contact angle measurements on the calcite surface in vapor saturated condition, a small laboratory device was designed. The advanced contact... 

    Experimental Investigation of Surface Properties and Wettability Using Super Gas Wetting Surface Modified Multi-Nano-Composites

    , M.Sc. Thesis Sharif University of Technology Shayesteh, Mohammad (Author) ; Ghazanfari, Mohammad Hossein (Supervisor) ; Fakhroueian, Zahra (Supervisor)
    Recently, the researchers try to identify the application of nanofluids for wettability alteration. Changing the wettability of reservoirs, which gas injects to them, to gas wet can lead to enhanced oil recovery. Although several studies have been conducted to introduce proper nanofluids for altering the wettability of reservoirs to gas wet, there is not enough study to investigate the application of nanocomposites for wettability alteration of carbonate reservoirs. In this study, 20 nanoparticles with different compositional structures were synthesized, and then various nanofluids were prepared for the experimental survey. Also, the potential of these nanofluids for wettability alteration... 

    Numerical Study on the Influence of Magnetic and Electric Fields on Filtration Performance of Wet Granular Beds

    , M.Sc. Thesis Sharif University of Technology Sabbaghian, Sina (Author) ; Moosavi, Ali (Supervisor) ; Sadrhosseini, Hani (Supervisor)
    The aim of this study is to develop an understanding of the role of the magnetic and electric forces on the filtration performance of wet granular beds. At first, the effect of wetting is considered by locating micro water film around the square channel for particles deposition in four different Reynolds Re=1 to Re=10 number, Typically 1000 particles in different sizes (100nm-10μm) were injected to microchannel when air and water formed completely on the surface of the block. The Drag force, Brownian force, Saffman`s lift force and the gravity force are affecting the particles. After that Dielectrophoretic and Magnetophoretic forces were included in the domain for investigating the role of... 

    Electrowetting induced droplet jumping over a bump

    , Article Extreme Mechanics Letters ; Volume 32 , 2019 ; 23524316 (ISSN) ; https://www.sciencedirect.com/science/article/pii/S2352431619300410 Merdasi, A ; Daeian, M. A ; Moosavi, A ; Shafii, M. B ; Sharif University of Technology
    Elsevier Ltd  2019
    We study electrowetting induced droplet jumping over a system consisting of a flat surface and a topographical bump mounted on the surface. Different bump shapes including triangular and elliptical configurations are considered and the results are compared with the results of the flat surface. The results indicate that droplet jumping is enhanced over the bumps and the droplet jumps to larger heights compared with the flat surface because of the lower viscous dissipation. The shape of the bump can considerably affect the droplet dynamics. Between the considered shapes the triangular bump provides a larger dynamic and the droplet on the surface with this bump can jump with larger velocity.... 

    Experimental investigation of the wetted surfaces of stepped planing hulls

    , Article Ocean Engineering ; Volume 187 , 2019 ; 00298018 (ISSN) Najafi, A ; Nowruzi, H ; Karami, M ; Javanmardi, H ; Sharif University of Technology
    Elsevier Ltd  2019
    In the current study, experimental tests are conducted to evaluate the hydrodynamic characteristics and the bottom wetted surfaces of the planing hulls equipped by one transverse step. For this purpose, total resistance, dynamic trim angle, dynamic sinkage, reattachment lengths of the separated flow and forebody and aftbody wetted areas are quantitatively measured at different geometrical parameters of the step and hull velocities. Moreover, the bottom wetted surfaces are qualitatively investigated by analyzing the underwater photographs. Our experimental results are also compared by archival data with good accordance. Based on our experimental observations, dynamic trim angle and dynamic... 

    Calibrating priestley-taylor model to estimate open water evaporation under regional advection using volume balance method-case study: chahnimeh reservoir, Iran

    , Article Journal of Applied Sciences ; Volume 8, Issue 22 , 2008 , Pages 4097-4104 ; 18125654 (ISSN) Daneshkar Arasteh, P ; Tajrishy, M ; Sharif University of Technology
    The objective of this study is to calibrate Priestley-Taylor (PT) model for estimating open water evaporation from an arid region reservoir called Chahnimeh. Chahnimeh Reservoir which is situated in the Sistan area in the southeast of Iran is being affected by regional energy advection during May to October. Therefore, common models of open water evaporation estimation such as PT require calibration. PT method was calibrated for Chahnimeh Reservoir using a volume balance method. Results showed that PT coefficient, αPT, as a constant over the year varies between 2.47±0.09 and 1.20±0.03 for two different hydrologic conditions of dry and wet. It means that there is also an intra-annular... 

    Electrowetting induced droplet generation in T-junctions

    , Article Journal of Heat Transfer ; Volume 143, Issue 5 , 2021 ; 00221481 (ISSN) Merdasi, A ; Moosavi, A ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2021
    In this study, droplet generation in a T-junction fluidic channel device was studied by using electrowetting actuation with the consideration of different droplet forming regimes. For this purpose, the finite element method (FEM) was used to solve the unsteady Naiver-Stokes equation. In addition, the level set method was applied to capture the interface between two phases. It was shown that there was a good agreement between obtained data and other work during the process of droplet generation in the absence of electrowetting actuation which results in the decrease in the size of the droplet with increasing the velocity ratios. In the shearing regime, the effectiveness of electrowetting on... 

    Investigations on the Effect of Biosurfactants on the Wettability of Carbonate Rocks via Interactions with Rock and Fluid in Ex-Sito MEOR

    , Ph.D. Dissertation Sharif University of Technology Adelzadeh, Mohammad Reza (Author) ; Roosta Azad, Reza (Supervisor) ; Kamali, Mohammad Reza (Supervisor) ; Shadizadeh, Reza (Co-Advisor)
    The effects of biosurfactants on sandstone rocks are known in the literature. However, there are few examples of experimental works in Iranian carbonate reservoirs dealing with the effects of biosurfactants under reservoir conditions. This thesis discusses the effect of an efficient biosurfactant produced from Pseudomonas aeroginosa MRo1, a bacterial strain isolated from oil excavation areas in southern Iran, on the recovery of residual oil trapped within carbonate rocks was investigated. The MRO1 could reduce surface tension from 72 to 28 dyne/cm. It also could reduce Interfacial tension from 18.382 to 5.646 dyne/cm.
    In a core holder set-up bearing four limestone- and... 

    Index for characterizing wettability of reservoir rocks based on spontaneous imbibition recovery data

    , Article Energy and Fuels ; Vol. 27, issue. 12 , November , 2013 , p. 7360-7368 ; ISSN: 08870624 Mirzaei-Paiaman, A ; Masihi, M ; Standnes, D. C ; Sharif University of Technology
    An index for characterizing wettability of reservoir rocks is presented using slope analysis of spontaneous imbibition recovery data. The slope analysis is performed using the known exact analytical solution to infinite acting period of counter-current spontaneous imbibition. The proposed theoretically based wettability index offers some advantages over existing methods: (1) it is a better measure of the spontaneous imbibition potential of rock (because the magnitude is directly proportional to the imbibition rate); (2) there is no need for forced displacement data; (3) there is no need for waiting until the spontaneous imbibition process ceases completely; and (4) the data needed to run the... 

    Steganographic schemes with multiple q-ary changes per block of pixels

    , Article Signal Processing ; Vol. 108, issue , 2014 , pp. 206-219 Gholampour, I ; Khosravi, K ; Sharif University of Technology
    A family of matrix embedding steganographic schemes for digital images is investigated. The target schemes are applied to blocks of n pixels in a cover image. In every block, at most m pixels are allowed to change with q-ary steps. We have derived some upper bounds on the embedding efficiency of these schemes for different values on m. It is also shown that these upper bounds approach the general upper bound on the embedding efficiency of q-ary steganography. For the case of q=3, we have shown that there is no feasible optimum member of the family for m=2, although for m=1, a well-known example exists. Instead, for m=2, a new close-to-bound scheme in the family is presented which exploits...