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Drug nano-particles formation by supercritical rapid expansion method; operational condition effects investigation
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 1 , 2011 , Pages 7-15 ; 10219986 (ISSN) ; Akbarnejad, M. M ; Vaziri Yazdi, A ; Arjomand, M ; Safekordi, A. A ; Sharif University of Technology
2011
Abstract
Dissolution pressure and nozzle temperature effects on particle size and distribution were investigated for RESS (Rapid Expansion of Supercritical Solution) process. Supercritical CO2 was used as solvent and Ibuprofen was applied as the model component in all runs. The resulting Ibuprofen nano-particles (about 50 nm in optimized runs) were analyzed by SEM and laser diffraction particle size analyzer systems. Results show that in low supercritical pressure ranges, depending on the solvent and solid component properties (Lower than 105 bar for Ibuprofen-CO2 system), nozzle temperature should be as low as possible (80-90 °C for Ibuprofen-CO2 system). In the other hand in high supercritical...
A study of a polymeric membrane performance in an ultrafiltration system to use in industrial application
, Article Desalination and Water Treatment ; Volume 53, Issue 2 , Sep , 2015 , Pages 340-351 ; 19443994 (ISSN) ; Rajaei, F ; Shahmoradi, M ; Kahkesh, A ; Sharif University of Technology
Taylor and Francis Inc
2015
Abstract
The performance of a polymeric membrane in an ultrafiltration system under the chosen optimum conditions was studied. To achieve this, four real produced waters were dealt with. To find the optimum conditions, Taguchi method was applied. Results showed that PAN350 membrane is a potential candidate for industrial applications for three feeds which contained oil and total organic carbon (TOC) less than 1,500 and 300 ppm, respectively. The values of oil/grease, total suspended solids, and turbidity rejections were approximately 100%. Although TOC could not be entirely removed, the removal values for TOC were acceptable in this study. For the fourth feed due to the values of oil and TOC which...
Deformation, Yield and fracture of elastomer-modified polypropylene
, Article Journal of Applied Polymer Science ; Volume 90, Issue 14 , 2003 , Pages 3767-3779 ; 00218995 (ISSN) ; Bagheri, R ; Seyed Reihani, S. M ; Lazzeri, A ; Sharif University of Technology
2003
Abstract
In recent decades, great attention has been devoted to the toughening of isotactic poly(propylene) (PP) with elastomers such as ethylene-propylene rubber (EPR). The most important reasons for this interest are the moderate cost and favorable properties of PP. This article is focused on the role of EPR in the deformation and fracture mechanism of PP/EPR blends with different volume fractions of elastomer phase. Differential scanning calorimetry (DSC), tensile tests, and microscopy techniques were used in this study. The fracture mechanism of isotactic PP toughened by EPR (PP/EPR) has also been studied by three point bending (3-PB) and four point bending (4-PB) tests. Rubber particle...
Dependency of percolation critical exponents on the exponent of power law size distribution
, Article Physica A: Statistical Mechanics and its Applications ; Volume 392, Issue 24 , 2013 , Pages 6189-6197 ; ISSN: 03784371 ; Masihi, M ; King, P. R ; Sharif University of Technology
2013
Abstract
The standard percolation theory uses objects of the same size. Moreover, it has long been observed that the percolation properties of the systems with a finite distribution of sizes are controlled by an effective size and consequently, the universality of the percolation theory is still valid. In this study, the effect of power law size distribution on the critical exponents of the percolation theory of the two dimensional models is investigated. Two different object shapes i.e., stick-shaped and square are considered. These two shapes are the representative of the fractures in fracture reservoirs and the sandbodies in clastic reservoirs. The finite size scaling arguments are used for the...
Application of Rosin-Rammler model for analysis of CSD in sugar crystallization
, Article Crystal Research and Technology ; Volume 50, Issue 11 , 2015 , Pages 873-878 ; 02321300 (ISSN) ; Alamolhoda, A. A ; Matloubi Moghaddam, F ; Nayeri, S ; Sharif University of Technology
Wiley-VCH Verlag
2015
Abstract
Crystal-size distribution (CSD) is one of the most important parameters in sugar production. The objective is to grow crystals of uniform sizes or narrow CSD. CSD appears to be determined by the growth-rate history of the crystals and the relative supersaturation (SS) of the solution from which crystals growth takes place. Three methods for preparation of nucleation seeds were described and used for industrial crystallization of raw and white sugars; these are wet milling filtered sugar (ML), agitating saturated solution (AS) and powdered sugars (PD). Rosin-Rammler (RR) and mathematical models were adopted to investigate CSD and the uniformity of the produced crystals. Higher uniformity...
Modeling and Simulation of Particle Size Distribution in Batch Crystallization Processes
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
In this research, it was tried to present a suitable environment for simulation of crystallization systems. Chapter one presented a survey on crystallization systems, its application, operating methods, and its phenomena. Chapter two presented mechanism and kinetic of phenomena that occur in crystallization systems, in detail, and mathematical models to modeling this systems are implied. In chapter three, that is the simulation result section, firstly, it focused on solution methods to solve population balance equation, that explains the particle size distribution, and its validation, secondly, the simulation results in a case study was compared with those obtained from finite volume method....
Finite element modelling simulation of radial forging of tubes without mandrel
, Article Materials and Design ; Volume 29, Issue 4 , 2008 , Pages 867-872 ; 02613069 (ISSN) ; Movahhedy, M. R ; Karimi Taheri, A ; Sharif University of Technology
Elsevier Ltd
2008
Abstract
Radial forging is an open forging process used for reducing the diameters of shafts, tubes, stepped shafts and axels, as well as for creating internal profiles for tubes such as rifling the gun barrels. The radial forging of tubes is usually performed over a mandrel to create an internal profile and/or size the internal diameter; but the process can also be used without a mandrel when workpiece geometry does not allow it or the internal surface quality is not critical. In some industrial applications, it may not be possible to use a mandrel inside the tubular workpiece, e.g., due to geometrical limitations of the workpiece. In this study, finite element modelling is applied to model the...
Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media
, Article Applied Physics A: Materials Science and Processing ; Volume 84, Issue 1-2 , 2006 , Pages 215-219 ; 09478396 (ISSN) ; Irajizad, A ; Mahdavi, S. M ; Sharif University of Technology
2006
Abstract
We studied the effects of the surrounding liquid environment on the size and optical properties of silver nanoparticles prepared by laser ablation by a pulsed Nd:YAG laser operated at 1.064 nm. The silver targets used were kept in acetone, water and ethanol. TEM observations and optical extinction were employed for characterization of particle size, shape and optical properties, respectively. Nano silver in acetone showed a narrow size distribution with a mean size of 5 nm and the colloidal solution was stable. In deionised water a rather narrow size distribution with a mean size of 13 nm was observed and nanoparticles were precipitated slowly after about two weeks. In ethanol, a broadening...
The influence of grain size and grain size distribution on sliding frictional contact in laterally graded materials
, Article Mechatronics and Applied Mechanics, Hong Kong, 27 December 2011 through 28 December 2011 ; Volume 157-158 , 2012 , Pages 964-969 ; 16609336 (ISSN); 9783037853801 (ISBN) ; Adibnazari, S ; Tashi, S ; 2011 International Conference; on Mechatronics and Applied Mechanics, ICMAM2011 ; Sharif University of Technology
2012
Abstract
The sliding frictional contact problem for a laterally graded half-plane has been considered. Two finite element (FE) models, in macro and micro scales have been developed to investigate the effective parameters in contact mechanics of laterally graded materials loaded by flat and triangular rigid stamps. In macro scale model, the laterally graded half-plane is discretized by piecewise homogeneous layers for which the material properties are specified at the centroids by Mori-Tanaka method. In micro scale model, functionally graded material (FGM) structure has been modeled as ideal solid quadrant particles which are spatially distributed in a homogeneous matrix. Boundary conditions and...
Coke deposition mechanism on the pores of a commercial Pt-Re/γ- Al2O3 naphtha reforming catalyst
, Article Fuel Processing Technology ; Volume 91, Issue 7 , 2010 , Pages 714-722 ; 03783820 (ISSN) ; Mohammadi, M ; Ghorbanpour, A ; Sharif University of Technology
2010
Abstract
Coke deposition mechanism on a commercial Pt-Re/γ-Al 2O3 naphtha reforming catalyst was studied. A used catalyst that was in industrial reforming operation for 28 months, as well as the fresh catalyst of the unit were characterized using XRD, XRF, and nitrogen adsorption/desorption analyses. Carbon and sulfur contents of the fresh and the used catalysts were determined using Leco combustion analyzer. The pore size distributions (PSD) of the fresh and the used reforming catalysts were determined using BJH and Comparison Plot methods. The Comparison Plot method produced the most reasonable PSDs for the catalysts. Through comparison of the PSDs of the fresh and the used catalysts, it was...
CFD Simulation of hydrodynamic of a bubble column reactor operating in churn-turbulent regime and effect of gas inlet distribution on system characteristics
, Article International Journal of Chemical Reactor Engineering ; Volume 14, Issue 1 , 2016 , Pages 213-224 ; 15426580 (ISSN) ; Zarkesh, J ; Rashtchian, D ; Anvari, A ; Sharif University of Technology
Walter de Gruyter GmbH
Abstract
CFD simulation of cylindrical bubble column including air as dispersed phase and water as continuous phase operating in churn-turbulent flow regime with diameter of 0.49 m, height of 3.6 m and gas superficial velocity of 0.14 m/s have been conducted. All simulations have been carried out in a 2D axisymmetric, unsteady and Euler/Euler framework with the aid of commercial software FLUENT v. 14.5. Simulations were validated by our experimental results through residence time distribution (RTD) data. Effect of bubble size distribution at inlet on column hydrodynamic was investigated and results clearly showed that equilibrium bubble size distribution in most parts of column is independent of...
A numerical approach to study the post-yield softening in cellular solids: role of microstructural ordering and cell size distribution
, Article Acta Mechanica ; Volume 228, Issue 6 , 2017 , Pages 2005-2016 ; 00015970 (ISSN) ; Bagheri, R ; Altstadt, V ; Sharif University of Technology
Springer-Verlag Wien
2017
Abstract
Designing meta-materials and cellular solids with biomimetic structures has received increasing attention in the past few years partially due to advances in additive manufacturing techniques that have enabled the fabrication of advanced materials with arbitrarily complex microarchitectures and novel functionalities. To impact on this trend, it is essential to develop our understanding about the role of microstructure on mechanical responses of these structures. Although a large literature exists on the general subject, the role of microstructure on the post-yield instability is not yet adequately documented. This research introduces a numerical approach to study the post-yield instability in...
The effects of different jet velocities and axial misalignment on the liquid sheet of two colliding jets
, Article Chemical Engineering Science ; Volume 206 , 2019 , Pages 235-248 ; 00092509 (ISSN) ; Kebriaee, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This experimental study investigated the patterns and characteristics of the liquid sheet formed by two axial misaligned colliding jets and two colliding jets with different velocities. The tests were limited to the low Reynolds number region, 100
Observational comparative study in Kühni and ORC agitated columns for the mechanism and performance of molybdenum extraction under various hydrodynamic conditions
, Article International Journal of Heat and Mass Transfer ; Volume 185 , 2022 ; 00179310 (ISSN) ; Torkaman, R ; Torab-Mostaedi, M ; Asadollahzadeh, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The present work is expressed to interpret the hydrodynamic parameters of rotation extraction columns in the reactive and non-reactive systems. The solvent extraction technique has been utilized for optimizing the transportation of molybdenum ions to the organic phase in two agitated columns (ORC and Kühni columns). Dispersed phase volume fraction, average droplet diameter, slip velocity, size distribution, and ions permeability of the aqueous phase have been investigated in terms of changing the operational variables including the agitation rate, flow rate of the inlet dispersed and continuous phases, column geometry, and reaction conditions. By considering the reactive and non-reactive...
Chemical Investigation of Molasses and Reducing Sugar Wastes of Molasses in Hakim Farabi Sugar Factory
, M.Sc. Thesis Sharif University of Technology ; Alamolhoda, Ali Asghar (Supervisor) ; Matloubi Moghaddam, Firouz (Supervisor)
Abstract
Sugar extraction from cane sugar is based on crystallization. Sucrose crystallization is a mass transfer process. Sucrose molecule's migration from solution to crystal is driven by concentration difference between the mother liquor and the crystal surface; the coefficient of super saturation is the most important parameter for the process. It has large influence on product quantity and quality (crystal yield, crystal size and size distribution). In this project, first the efficiency of sucrose extraction studied by crystallization in HAKIM FARABI sugar factory. Crystal size distribution (CSD) is the more accurate measure for monitoring crystallization processes. CSD depending on the seeds...
Modeling, Simulation and Control of Batch Suspension Polymerization Reactor
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
Most of Final properties of polymers such as morphological characteristics are related to molecular weight distribution (MWD) and particle size distribution (PSD). It is possible to obtain the desired properties by controlling of these indices. In this work, modeling, simulation, and control of final properties of styrene have been considered. First, kinetic of reaction has been investigated which is a free radical type. Molecular weight distribution has been calculated by using moment method. Next, population balance equation (PBE) has been used to model PSD. For this system, mass, energy, and moment conservation equations are a set of stiff ordinary differential equations (ODEs). PBE is a...
Synthesis of metal nanoparticles using laser ablation technique
, Article Emerging Applications of Nanoparticles and Architectural Nanostructures: Current Prospects and Future Trends ; March , 2018 , Pages 575-596 ; 9780128135167 (ISBN); 9780323512541 (ISBN) ; Vahdatkhah, P ; Sharif University of Technology
Elsevier Inc
2018
Abstract
Pulse laser ablation (PLA) technique has been demonstrated to be a simple, compatible, promising, versatile, relatively low-cost, pure, and green approach with the absence of toxic chemicals and reagents for fabrication of metal nanoparticles. Purity is an especially important attribute of metal nanoparticles (NPs) in biological and medical technologies. For such applications, it is crucial to prepare metal NPs with the desired shape and size distribution. This chapter discusses the advantages of the PLA technique as compared with other techniques for metal NPs, explains the various mechanisms involved in the generation of metal NPs, outlines the effects of laser parameters, such as...
The effect of brine salinity on water-in-oil emulsion stability through droplet size distribution analysis: A case study
, Article Journal of Dispersion Science and Technology ; 2017 , Pages 1-13 ; 01932691 (ISSN) ; Ayatollahi, S ; Sharif University of Technology
Abstract
Water-in-oil emulsion usually forms during waterflooding in some heavy oil reservoirs. The composition and salinity of the injected water critically affect the w/o emulsion droplet size distribution, which control the emulsion stability and emulsion flow in porous media. The aim of the present work is to assess the effect of different sea water salinities on w/o emulsion stability through microscopic imaging. Therefore, w/o emulsions were prepared with different sea water samples, which were synthesized to resemble Persian Gulf, Mediterranean, Red Sea, and North Sea water samples. The results showed that log-normal distribution function predicts very well the experimental data to track the...
Application of population balance equation in modeling of asphaltene particle size distribution and characterization of aggregation mechanisms under miscible gas Injection
, Article Journal of Molecular Liquids ; Volume 232 , 2017 , Pages 207-213 ; 01677322 (ISSN) ; Hamed Mahvelati, E ; Ameli, F ; Dabir, B ; Rashtchian, D ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Particle size distribution (PSD) is an important factor that determines how asphaltene instability can damage porous media during natural depletion and enhanced oil recovery processes. In this work, aggregate size distribution under natural depletion and miscible nitrogen injection processes are determined via image analysis techniques and the results are modelled by population balance equation. Unimodal distribution curves in natural depletion show the dominance of particle-particle aggregation mechanism and the clustering is detected only around crude oil bubble point pressure. It is also observed that miscible nitrogen injection considerably increases the number and size of asphaltene...
Numerical investigation of gas bubble behavior in tapered fluidized beds
, Article Particuology ; 2017 ; 16742001 (ISSN) ; Askaripour, H ; Molaei Dehkordi, A ; Sharif University of Technology
Abstract
In this article, the behavior of gas bubbles in tapered fluidized beds is investigated with the use of a two-fluid model incorporating kinetic theory of granular flow. The effects of various parameters such as apex angle, particle size, and particle density on the size distribution and the rise velocity of gas bubbles were examined. In addition, the simulation results for the bubble fraction and axial velocity of gas bubbles were compared with experimental data reported in the literature and good agreement was observed. As the apex angle was increased, the fraction of gas bubbles with large sizes increased and the fraction of bubbles with small sizes decreased. As the particle size...