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A novel revolving piston minipump
, Article Sensors and Actuators, B: Chemical ; Volume 218 , October , 2015 , Pages 237-244 ; 09254005 (ISSN) ; Shafii, M. B ; Moosavi, A ; Amiri Hezave, H ; Sharif University of Technology
Elsevier
2015
Abstract
In this study, a novel prototype high-efficiency miniature pump that uses magnetic properties of a ferrofluid in both pumping and valving mechanisms is presented. The minichannel consisting of a cylindrical pumping chamber, a check valve, an inlet and an outlet, comprises six bonded layers of PMMA. A cylindrical permanent magnet that is placed inside the chamber and is externally actuated by a motorized off-center permanent magnet, functions as a revolving piston which sweeps the perimeter of the cylinder. Ferrofluid is used to cover the gaps between the magnetic piston and the channel walls, also serves as a separating plug between the inlet and the outlet of the chamber preventing...
Removal of airborne hexavalent chromium mist using chitosan gel beads as a new control approach
, Article International Journal of Environmental Science and Technology ; Volume 3, Issue 3 , 2006 , Pages 305-313 ; 17351472 (ISSN) ; Golbabaei, F ; Hamedi, J ; Nourijelyani, K ; Shahtaheri, S. J ; Moosavi, S. R ; Sharif University of Technology
CEERS
2006
Abstract
Airborne hexavalent chromium is a known human respiratory carcinogen and allergen. Many workers are exposed to hexavalent chromium in various processes which chromium electroplating plants are the most common. In this study, the feasibility of a new control approach to remove this pollutant using chitosan beads as a biosorbent was investigated. Hexavalent chromium sorption was studied relative to pH, pollution concentration, sorbent concentration, temperature, and air velocity using one factor at a time approach and Taguchi experimental design. Polluted air with different chromium mist concentrations (10-5000 μg/m3) was contacted to chitosan beads (3.3-20 g/L), floating in distilled water...
Synthesis, chemical and thermal characterization of poly(cis-2-butenylene oxalate) [electronic resource]
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 46, Issue 3-4, 2000 ; Zohuriaan-Mehr, M. J ; Rezai, N ; Sharif University of Technology
Abstract
A non-terminated, low molecular weight, highly crystalline, linear aliphatic polyester was successfully synthesized via ester-interchange polycondensation of cis-2-butene-1,4-diol and diethyl oxalate by using of lead (II) oxide as the catalyst. No decarboxylation occurred during the optimized polymerization. Structural and Chemical identification was performed by elemental analysis, FTIR, 'H-NMR, and Mass spectroscopy. Some macrocyle species were detected in the product, according to GPC. Fragmentation patterns were suggested for the main m/e's of the mass spectrum. Thermal characterization was performed by DSC and TGA. It was found that the overall thermal stability of the polyester is...
Fabrication of durable superhydrophobic surfaces using PDMS and beeswax for drag reduction of internal turbulent flow
, Article Applied Surface Science ; Volume 513 , 2020 ; Liravi, M ; Moosavi, A ; Nouri Borujerdi, A ; Najafkhani, H ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Nowadays, one of the biggest concerns in the world is increasing the CO2 emissions and global warming due to the over-consumption of fossil fuels. In addition, under the intense market competition, the demand for more efficient systems with higher performance and lower energy consumption has escalated. Since the drag force contributes to a considerable percentage of the energy loss and reducing the performance, a large number of studies have been conducted to improve the surface characteristics and, subsequently, declining the drag force. Making the surface superhydrophobic is one of the most effective ways for this purpose. In this work, two different superhydrophobic surfaces using SiO2...
The effect of nanopores geometry on desalination of single-layer graphene-based membranes: A molecular dynamics study
, Article Journal of Molecular Liquids ; Volume 339 , 2021 ; 01677322 (ISSN) ; Chogani, A ; Shariat, M ; Moosavi, A ; Kariminasab, H ; Sharif University of Technology
Elsevier B.V
2021
Abstract
The water desalination process using nanoporous single-layer graphene membranes is simulated through classical molecular dynamics. The effect of nanopores shapes on the capacity of the membrane for filtration of water is investigated. According to the results, the geometry of the nanopores considerably affects the performance of the membrane and can completely change the water flow rate and salt rejection. The results reveal that the effective area of the nanopores plays a critical role and for a better understanding of the impact of this parameter, aspect ratio and the equal diameter of noncircular pores based on different methods such as equal area, equal perimeter, and hydraulic diameter...
Numerical simulation of collision between two droplets in the T-shaped microchannel with lattice Boltzmann method
, Article AIP Advances ; Volume 6, Issue 11 , 2016 ; 21583226 (ISSN) ; Ebrahimi, S ; Moosavi, A ; Shafii, M. B ; Kowsary, F ; Sharif University of Technology
American Institute of Physics Inc
2016
Abstract
In this study, the Lattice Boltzmann Method (LBM) is used to investigate the deformation of two droplets within microfluidic T-junctions (MFTD). In order to increase the accuracy the two immiscible fluids are modeled using the He-Chen-Zhang model. First, this model is applied to ensure that the surface tension effect existing between the droplets and the continuous fluid is properly implemented in the model. Then the collision and merging of the two droplets within the intersection of a T-shaped microchannel is investigated. For generating droplet formation the effects of relevant dimensionless parameters such as the Reynolds, the Weber numbers as well as a collision parameter affecting the...
Simulation of a falling droplet in a vertical channel with rectangular obstacles
, Article European Journal of Mechanics, B/Fluids ; Volume 68 , March-April , 2018 , Pages 108-117 ; 09977546 (ISSN) ; Ebrahimi, S ; Moosavi, A ; Shafii, M. B ; Kowsary, F ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Droplet microfluidic systems have attracted a large amount of research due to their numerous applications in biomedical micro-devices and drug discovery/delivery platforms. One of the most important problems in such systems is to investigate deformation, coalescence, and breakup of droplets within the channel. The present study demonstrates numerical simulation of a falling droplet subject to gravitational force in a channel with embedded rectangular obstacles. The lattice Boltzmann method incorporated using He–Chen–Zhang method for two phase flow is employed. Two rectangular obstacles with inverse aspect ratios are introduced to investigate the mechanism of breakup and deformation of the...
Shear-thinning droplet formation inside a microfluidic T-junction under an electric field
, Article Acta Mechanica ; Volume 232, Issue 7 , 2021 , Pages 2535-2554 ; 00015970 (ISSN) ; Honarmand, M ; Dizani, M ; Moosavi, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
Springer
2021
Abstract
Researchers usually simplify their simulations by considering the Newtonian fluid assumption in microfluidic devices. However, it is essential to study the behavior of real non-Newtonian fluids in such systems. Moreover, using the external electric or magnetic fields in these systems can be very beneficial for manipulating the droplet size. This study considers the simulation of the process of non-Newtonian droplets’ formation under the influence of an external electric field. The novelty of this study is the use of a shear-thinning fluid as the droplet phase in this process, which has been less studied despite its numerous applications. The effects of an external electric field on this...
Semi-Solid Forming of AZ91 Magnesium Alloy by using Electromagnetic Stirring
, M.Sc. Thesis Sharif University of Technology ; Aashuri, Hossein (Supervisor)
Abstract
In the last decade, magnesium alloy has been developed owing to it’s low density, high specific strength, good castability and damping property. AZ91 alloy is proved to be the most common and most important magnesium casting alloy. It is shown that, rheocasting process is a proper way which increases the mechanical properties of the products. Since 28 years, so many new methods for preparing Semi-Solid alloy slurry and rheoforming process have been suggested. Electromagnetic Stirring ( EMS ) method was used for making globular structures. In this research, the semi-solid slurry of AZ91 magnesium alloy was prepared by electromagnetic stirrer under different conditions of stirring current and...
Geochemical Simulation of Acidizing Sandstone Core Samples
, M.Sc. Thesis Sharif University of Technology ; Bazargan, Mohammad (Supervisor)
Abstract
Acidizing is one of the widely used practices of formation damage remediation. The success of this rather expensive job depends on the precise design and operation. Though, improper execution of an acid job, not only does not improve the formation damage but also can contribute to even more damage itself. For this purpose, it is critically important to thoroughly design an acidizing job conducting extensive lab experiments and utilizing numerical tools before operation in order for a successful acidizing. Unlike, carbonate acidizing, the chemistry of sandstone acidizing is very complex and challenging because of the wide variety of minerals and aqueous species present in the system. Hence, a...
Modification of carbohydrate polymers via grafting in air: 2. Ceric-initiated graft copolymerization of acrylonitrile onto natural and modified polysaccharides
, Article Starch/Staerke ; Volume 54, Issue 10 , 2002 , Pages 482-488 ; 00389056 (ISSN) ; Zohuriaan Mehr, M. J ; Sharif University of Technology
2002
Abstract
Acrylonitrile (AN) was grafted onto various natural and modified polysaccharides (i.e., gum arabic, gum tragacanth, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) by using ceric-carbohydrate redox initiating system. After overcoming practical problems, mainly from the high viscosity of the aqueous solutions of the different substrates, the graft copolymerization reactions were run either in air or in N2 atmosphere under similar conditions. Grafting was confirmed using chemical and spectral (FTIR) proofs. The reactions were kinetically investigated using semi-empirical expressions and time-temperature profiles. An anomalous...
Modification of carbohydrate polymers via grafting in air. 1. Ceric-induced synthesis of starch-g-polyacrylonitrile in presence and absence of oxygen
, Article Starch/Staerke ; Volume 54, Issue 3-4 , 2002 , Pages 140-147 ; 00389056 (ISSN) ; Zohuriaan Mehr, M. J ; Sharif University of Technology
2002
Abstract
Monomer grafting, a unique technique for polysaccharide modification, is always performed under inert (e.g., N2) atmosphere. This work is the first report related to evaluating the possibility and efficiency of the grafting of acrylonitrile (AN) onto starch in presence of oxygen. Thus, corn starch (in both granular and gelatinized states) as well as soluble starch were grafted by AN using a ceric-carbohydrate redox initiating system. Graft copolymerizations were performed under nitrogen, air, and oxygen atmospheres at similar conditions. Grafting occurrence was verified using chemical and spectral proofs. The polymerization mechanism and kinetics were investigated by recording the...
New polysaccharide-g-polyacrylonitrile copolymers: Synthesis and thermal characterization
, Article Polymers for Advanced Technologies ; Volume 14, Issue 7 , 2003 , Pages 508-516 ; 10427147 (ISSN) ; Pourjavadi, A ; Sharif University of Technology
2003
Abstract
Various natural and modified polysaccharides (i.e. arabic gum, tragacanth gum, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) were modified using cericinitiated graft polymerization of acrylonitrile under inert atmosphere. Grafting was confirmed using spectral (FT-IR) proofs. The grafting parameters were determined by conventional methods. Thermal characteristics of the homopolymer-free copolymers were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. The major thermal transitions as well as the activation energy of the major decomposition stages were...
Superabsorbent hydrogels from starch-g-PAN: Effect of some reaction variables on swelling behavior
, Article Journal of Polymer Materials ; Volume 20, Issue 1 , 2003 , Pages 113-120 ; 09700838 (ISSN) ; Pourjavadi, A ; Sharif University of Technology
2003
Abstract
Two series of alkali hydrolyzed starch-g-polyacrylonitrile (H-SPAN) superabsorbents were prepared from granular and gelatinized corn starches. The grafting parameters of SPAN copolymers were determined and the polymers were analyzed by FTIR spectroscopy. A combination of three influencing factors (i.e. thermal pre-treatment of the initial starch, presence or absence of oxygen in the stage of ceric-initiated PAN grafting, and neutralization after alkali treatment) on swelling characteristics of the final hydrogel was evaluated in a practical viewpoint. The superabsorbents were discriminated according to their swelling behavior in water and different aqueous salt solutions. The swelling...
Numerical Investigation of Fire Spread in Natural Habitats Using Physical Models in Small-Scale
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor)
Abstract
Wildfire in natural habitats is a common natural disaster that can have natural or human origins. With the increasing global temperature and consecutive droughts, the number and intensity of these fires are increasing. In our country, due to a lack of natural resources and recent droughts, the importance of preventive measures in starting and effectively extinguishing fires is increasingly felt. Nowadays, with the increase in computational power, numerical methods have come as the aid of physical models to predict the spread of fire and have become a worthy replacement for experimental tests due to the destructive nature of fire. In this research, we have investigated the effect of main...
Machine learning and network analysis of molecular dynamics trajectories reveal two chains of red/Ox-specific residue interactions in human protein disulfide isomerase
, Article Scientific Reports ; Volume 7, Issue 1 , 2017 ; 20452322 (ISSN) ; Karimi Jafari, M. H ; Sharifi Zarchi, A ; Chitsaz, H ; Salekdeh, G. H ; Moosavi Movahedi, A. A ; Sharif University of Technology
2017
Abstract
The human protein disulfide isomerase (hPDI), is an essential four-domain multifunctional enzyme. As a result of disulfide shuffling in its terminal domains, hPDI exists in two oxidation states with different conformational preferences which are important for substrate binding and functional activities. Here, we address the redox-dependent conformational dynamics of hPDI through molecular dynamics (MD) simulations. Collective domain motions are identified by the principal component analysis of MD trajectories and redox-dependent opening-closing structure variations are highlighted on projected free energy landscapes. Then, important structural features that exhibit considerable differences...
Modified CMC.2. Novel carboxymethylcellulose-based poly (amidoxime) chelating resin with high metal sorbtion capacities [electronic resource]
, Article Reactive and Functional Polymers ; Volume 61, Issue 1, August 2004, Pages 23–31 ; Pourjavadi, A ; Sadeghi, M ; Sharif University of Technology
Abstract
Carboxymethylcellulose sodium salt (CMC) was doubly modified to prepare a novel poly(acrylamidoxime) chelating resin. Acrylonitrile was firstly graft polymerized onto CMC using cerium ammonium nitrate as an initiator. The polyacrylonitrile (PAN) grafted CMC was then amidoximized via treatment with hydroxylamine to prepare the ion exchange resin. The sorption capacity of the resin towards bivalent metal ions was evaluated while varying the pH, the loading of the PAN and the initial metal ion concentration. The adsorption kinetics were investigated for the cupric ion. The chelating resin exhibited very high metal sorption capacity in comparison with either synthetic or polysaccharide-based...
Modified Chitosan. 3. Superabsorbency, Salt- and pH-Sensivity of Smart Ampholitic hydrogels from Chitosan-g-PAN [electronic resource]
, Article Polymers for Advanced Technologies ; Volume 15, Issue 4, pages 173–180, April 2004 ; Zohuriaan-Mehr, M. J ; Pourjavadi, M. J
Abstract
Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a...
Oil-soluble drag-reducing polymers [electronic resource]
, Article Journal of polymer materials ; December 1994, Volume 11, Number 4; Page(s) 239 To 247 ; Pourjavadi, A ; Nadali, M ; Sharif University of Technology
Abstract
This article reviews the oil-soluble polymeric drag-reducing agents (DRAs) with an outlook to their large-scale application in petroleum industry. A general discussion on mechanism of the DR phenomenon and mechanical degradation of the drag reducers in turbulent flow is offered with an emphasis on the molecular parameters. Furthermore, low charge density associating polymers, as a new class of oil-soluble flow improvers, are described
Partially aromatic polyamides based on tetraphenylthiophene diamine: Synthesis and characterization [electronic resource]
, Article Journal of Applied Polymer Science ; Volume 77, Issue 5, pages 1144–1153, 1 August 2000 ; Zamanlu, M. R ; Zohuriaan-Mehr, M. J ; Sharif University of Technology
Abstract
Tetraphenylthiophene diamine (TPTDA) was prepared through a modified three-step route to achieve an improved overall yield. TPTDA reacted with succinic, adipic, suberic, sebasic, and fumaric acids via the Yamazaki phosphorylation method to yield novel partially aromatic polyamides (TPT series). A counterpart polyamide series based on p-phenylene diamine (Ph series) was also synthesized under the same conditions. All of the polymers were characterized by means of spectrochemical (Fourier transform infrared spectroscopy, 1H-nuclear magnetic resonance (NMR), and 13C-NMR) and thermal (differential scanning calorimetry and thermogravimetric) methods of analysis. Solubility of TPT polyamides was...