Loading...
Search for:
ph
0.011 seconds
Total 374 records
Control of pH processes using fuzzy modeling of titration curve
, Article Fuzzy Sets and Systems ; Volume 157, Issue 22 , 2006 , Pages 2983-3006 ; 01650114 (ISSN) ; Shahrokhi, M ; Sharif University of Technology
2006
Abstract
Model-based pH control is a difficult problem due to its inherent nonlinearity and time-varying characteristics. This is specially the case when the pH regulation of streams consisting hundreds of constituents with varying concentrations is desired. The pH process can be modeled by using conservation laws and neutrality condition. An alternative to this mechanistic modeling is using nonlinear empirical modeling such as fuzzy modeling. This paper proposes a new approach of fuzzy modeling of titration curves, which can be used for control purposes. The Takagi-Sugeno model was used for the modeling of titration curve. Two control algorithms, which are designed based on the titration curve,...
Removal of heavy metals from aqueous solution using platinum nanopartcles/Zeolite-4A
, Article Journal of Environmental Health Science and Engineering ; Vol. 12, issue. 1 , 2014 ; ISSN: 2052336X ; Sadjadi, S ; Ahmadi, S. J ; Outokesh, M ; Sharif University of Technology
Abstract
The effects of varying operating conditions on metals removal from aqueous solution using a novel platinum nanopartcles/Zeolite-4A adsorbent are reported in this paper. Characterization of the adsorbent showed successful production of platinum nanopartcles on Zeolite-4A using 3 Wt% platinum. The effects of operation conditions on metals removal using this adsorbent were investigated. The optimal metals adsorption was observed at pH 7, 0.1 g/10 mL dosage and 30 min contact time. Sorption data have been interpreted in terms of Langmuir and Freundlich isotherms
Dye-sensitized solar cells based on TiO2 particulate gels: Impact of gel formation mechanism on photovoltaic performance
, Article Journal of Photochemistry and Photobiology A: Chemistry ; Volume 338 , 2017 , Pages 104-114 ; 10106030 (ISSN) ; Mohammadi, M. R ; Sharif University of Technology
Elsevier B.V
2017
Abstract
In this work the influence of different particulate gels on morphology and photoelectric performance of TiO2 dye-sensitized solar cells (DSCs) is studied. Two coagulant and flocculant agents are used to convert a TiO2 particulate sol into the gels using double layer compression and charge neutralization mechanisms. One more TiO2 particulate gel is also prepared by changing the pH of the sol using acid: alkoxide molar ratio higher than the critical ratio to obtain an unstable sol. Based on X-ray diffraction (XRD) analysis, the films contain primary nanoparticles with average crystallite size of 13–15 nm. Field emission scanning electron microscopy (FE-SEM) images show uniform, nanostructured...
Real-time output feedback neurolinearization
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 28, Issue 2 , 2009 , Pages 121-130 ; 10219986 (ISSN) ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
2009
Abstract
An adaptive input-output linearization method for general nonlinear systems is developed without using states of the system. Another key feature of this structure is the fact that, it does not need model of the system. In this scheme, neurolinearizer has few weights, so it is practical in adaptive situations. Online training of neurolinearizer is compared to model predictive recurrent training. Relationships between this controller and neural network based model reference adaptive controller are established. A CSTR reactor and pH control in a neutralization process illustrate performance of this method. Simulation studies show a superior performance with respect to a PI controller
Persistent homology analysis of multiqubit entanglement
, Article Quantum Information and Computation ; Volume 20, Issue 5-6 , July , 2020 , Pages 375-399 ; Di Pierro, A ; Memarzadeh, L ; Mancini, S ; Sharif University of Technology
Rinton Press Inc
2020
Abstract
We introduce a homology-based technique for the classification of multiqubit state vectors with genuine entanglement. In our approach, we associate state vectors to data sets by introducing a metric-like measure in terms of bipartite entanglement, and investigate the persistence of homologies at different scales. This leads to a novel classification of multiqubit entanglement. The relative occurrence frequency of various classes of entangled states is also shown. © Rinton Press
Comparison of furfural degradation by different photooxidation methods
, Article Chemical Engineering Journal ; Volume 139, Issue 3 , 2008 , Pages 482-488 ; 13858947 (ISSN) ; Hosseini, S. N ; Sharif University of Technology
2008
Abstract
In this paper, the degradation of C5H4O2 "Furfural" in aqueous solution by photooxidation technology using UV, UV/H2O2, UV/H2O2/O2, UV/H2O2/Fe2+, UV/O2/Fe2+, O3, UV/O3 process and also oxidation by sodium hypochlorite was investigated in a lab-scale batch photo-reactor. To evaluate the performance of different processes, the efficiency of furfural degradation was studied by measuring the total organic carbon (TOC) throughout the experimentation. Results show that compare to other reactions studied in this research, the UV/H2O2 is a simple and effective process for furfural degradation and presence of Fe2+ ions (UV/H2O2/Fe2+) enhanced removal of furfural in solution. The influence of...
Exact dimer ground states for a continuous family of quantum spin chains and zigzag ladders
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 76, Issue 6 , 2007 ; 10980121 (ISSN) ; Karimipour, V ; Sadrolashrafi, A ; Sharif University of Technology
2007
Abstract
Using the matrix product formalism, we define a multiparameter family of spin models on one-dimensional chains, with nearest- and next-nearest-neighbor interactions for which exact analytical expressions can be found for its doubly degenerate ground states. The family of Hamiltonians depends on five continuous parameters and the Majumdar-Ghosh model is a particular point in this parameter space. The model can also be represented as a zigzag spin ladder in which there are extra three-particle couplings between spins on vertices of triangles. The doubly degenerate ground states of these models models have a very simple structure, they are the product of entangled (dimer) states on adjacent...
Water adsorption in the organic phase for the D2EHPA-kerosene/water and aqueous Zn2+, Co2+, Ni2+ sulphate systems
, Article Hydrometallurgy ; Volume 88, Issue 1-4 , 2007 , Pages 92-97 ; 0304386X (ISSN) ; Haghshenas, D. F ; Etemadi, S ; Keshavarz Alamdari, E ; Sadrnezhaad, Kh ; Sharif University of Technology
2007
Abstract
Water adsorption by bis-2-ethylhexyl phosphoric acid (D2EHPA) during the extraction of zinc, cobalt and nickel using a D2EHPA-kerosene/H2O mixture is investigated. Based on the experimental results, about 1 mol of water is adsorbed by 2 mol of D2EHPA (which exists in the form of a dimer), irrespective of the pH. Water adsorption decreases with presence of zinc, cobalt and nickel. The stoichiometric coefficients of D2EHPA in water adsorption reactions are determined with and without zinc, cobalt and nickel by applying the slope-analysis method. It is experimentally confirmed that 1.0, 1.8 and 1.2 mol of adsorbed water will be rejected from the organic phase when zinc, cobalt and nickel are...
Synthesis and properties of biodegradable hydrogels of κ-carrageenan grafted acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid as candidates for drug delivery systems
, Article Reactive and Functional Polymers ; Volume 67, Issue 7 , 2007 , Pages 644-654 ; 13815148 (ISSN) ; Barzegar, Sh ; Zeidabadi, F ; Sharif University of Technology
2007
Abstract
Novel types of highly swelling hydrogels were prepared by grafting crosslinked polyacrylic acid-co-poly-2-acrylamido-2-methylpropanesulfonic acid (PAA-co-PAMPS) chains onto κ-carrageenan through a free radical polymerization method. Here, we propose a mechanism for κ-carrageenan-g-PAA-co-PAMPS formation and confirm the hydrogel structure using FTIR spectroscopy. The effect of grafting variables (i.e. concentration of methylenebisacrylamide (MBA), acrylic acid/-2-acrylamido-2-methylpropanesulfonic acid (AA/AMPS) weight ratio, ammonium persulfate (APS), κ-carrageenan, neutralization percent and reaction temperature) were systematically optimized to achieve a hydrogel with a maximum swelling...
Dynamical tidal locking theory: A new source of the spin of dark matter halos
, Article Astrophysical Journal ; Volume 912, Issue 1 , 2021 ; 0004637X (ISSN) ; Abolhasani, A.A ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
We revisit the question of what mechanism is responsible for the spins of halos of dark matter. The answer to this question is of high importance for modeling galaxy intrinsic alignment, which can potentially contaminate current and future lensing data. In particular, we show that when the dark matter halos pass nearly each other in dense environments - namely halo assemblies - they swing and spin each other via exerting mutual tidal torques. We show that this has a significant contribution to the spin of dark matter halos comparable to that calculated by the so-called tidal torque theory. We use the results of the state-of-the-art simulation of Illutris to check the prediction of this...
Experimental study on enhanced oil recovery by low salinity water flooding on the fractured dolomite reservoir
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 40, Issue 5 , 2021 , Pages 1703-1719 ; 10219986 (ISSN) ; Gerami, S ; Safekordi, A. A ; Bahramian, A. R ; Ganjeh Ghazvini, M ; Sharif University of Technology
Iranian Institute of Research and Development in Chemical Industries
2021
Abstract
Enhanced Oil Recovery from carbonate reservoirs is a major challenge especially in naturally fractured formations where spontaneous imbibition is a main driving force. The Low Salinity Water Injection (LSWI) method has been suggested as one of the promising methods for enhanced oil recovery. However, the literature suggests that LSWI method, due to high dependence on rock mineralogy, injected and formation water salt concentration, and complexity of reactions is not a well-established technology in oil recovery from carbonate reservoirs. The underlying mechanism of LSWI is still not fully understood. Due to lack of LSWI study in free clay dolomite fractured reservoir, and to investigate of...
Adsorption properties of halloysite modified acrylamide/quince seeds-based hydrogel: Experimental and DFT investigation
, Article Journal of Polymers and the Environment ; Volume 30, Issue 11 , 2022 , Pages 4637-4650 ; 15662543 (ISSN) ; Mirzaee Valadi, F ; Akbarzadeh, E ; Gholami, M. R ; Sharif University of Technology
Springer
2022
Abstract
In this work Halloysite nanotubes were used to synthesis a series of modified acrylamide/Quince seeds-based hydrogels (Poly (AAm-co-QS)/Haln). The as-prepared Poly (AAm-co-QS)/Haln hydrogels displayed improved performance as adsorbent in elimination of methylene blue (MB) from aqueous solution. The structures of the prepared Poly (AAm-co-QS)/Haln hydrogels were identified by XRD, FT-IR, FE-SEM, BET, TGA and EDX. Effect of pH value on the swelling behavior and dye adsorption performance of as-prepared hydrogels was explored. The adsorption MB results suggested that the adsorption kinetics fitted the pseudo-second-order model. The adsorption experiments at various pH condition indicated that...
Effects of the temperature and the ph on the main protease of sars-cov-2: A molecular dynamics simulation study
, Article Biointerface Research in Applied Chemistry ; Volume 12, Issue 6 , 2022 , Pages 7239-7248 ; 20695837 (ISSN) ; Saadatabadi, A. R ; Sharif University of Technology
AMG Transcend Association
2022
Abstract
The novel coronavirus, recognized as COVID-19, is the cause of an infection outbreak in December 2019. The effect of temperature and pH changes on the main protease of SARS-CoV-2 were investigated using all-atom molecular dynamics simulation. The obtained results from the root mean square deviation (RMSD) and root mean square fluctuations (RMSF) analyses showed that at a constant temperature of 25℃ and pH=5, the conformational change of the main protease is more significant than that of pH=6 and 7. Also, by increasing temperature from 25℃ to 55℃ at constant pH=7, a remarkable change in protein structure was observed. The radial probability of water molecules around the main protease was...
PH-Sensitive stimulus-responsive nanocarriers for targeted delivery of therapeutic agents
, Article Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology ; Volume 8, Issue 5 , 2016 , Pages 696-716 ; 19395116 (ISSN) ; Eslami, M ; Sahandi Zangabad, P ; Mirab, F ; Farajisafiloo, N ; Shafaei, Z ; Ghosh, D ; Bozorgomid, M ; Dashkhaneh, F ; Hamblin, M. R ; Sharif University of Technology
Wiley-Blackwell
2016
Abstract
In recent years miscellaneous smart micro/nanosystems that respond to various exogenous/endogenous stimuli including temperature, magnetic/electric field, mechanical force, ultrasound/light irradiation, redox potentials, and biomolecule concentration have been developed for targeted delivery and release of encapsulated therapeutic agents such as drugs, genes, proteins, and metal ions specifically at their required site of action. Owing to physiological differences between malignant and normal cells, or between tumors and normal tissues, pH-sensitive nanosystems represent promising smart delivery vehicles for transport and delivery of anticancer agents. Furthermore, pH-sensitive systems...
Synthesis of Magnetic Nanocarriers Based on Coating of Fe3O4 with Modified Biodegradable Polysaccharides by pH Sensitive Agents for Targeted Release of Anticancer Drug Doxorubicin
, M.Sc. Thesis Sharif University of Technology ; Pourjavadi, Ali (Supervisor)
Abstract
One of the major problems in cancer treatment is the side effects of the drugs. Nowadays, scientists are developing smart nanocarriers which used for diagnosis and delivering drugs in order to circulate through blood vessels, pass the immune system, attach to cancer cells and kill them without any side effects. In the first research of this thesis, magnetic nanoparticles were coated by modified alginate and used as smart nanocarriers. Magnetic nanocarrier were sysnthesized based on hydrophobic coating of oleic acid and hydrazine oleate-modified alginate shell. The resulting carrier is pH-sensitive and the alginate shell removes in the low pH medium. DOX was placed between hydrophobic chains....
Process optimization for mineral carbonation in aqueous phase
, Article International Journal of Mineral Processing ; Vol. 130 , July , 2014 , pp. 20-27 ; ISSN: 03017516 ; Shayegan, J ; Bu, J ; Yeo, T. Y ; Sharratt, P ; Sharif University of Technology
Abstract
Carbon dioxide sequestration by a pH-swing carbonation process was considered in this work. A multi-step aqueous process is described for the fractional precipitation of magnesium carbonate and other minerals in an aqueous system at room temperature and atmospheric pressure. With the aim to achieve higher purity and deliver more valuable mineral products, the process was split into four steps. The first step consists of Mg leaching from the magnesium silicate in a stirred vessel using 1 M HCl at 80 °C, followed by a three step precipitation in reactors in sequence to remove Fe(OH)3, then Fe(OH)2 and other divalent ions, and finally MgCO3 nucleation and growth. Hydrated magnesium carbonate...
Comparison between backstepping and input-output linearization techniques for pH process control
, Article Journal of Process Control ; Volume 22, Issue 1 , 2012 , Pages 263-271 ; 09591524 (ISSN) ; Shahrokhi, M ; Mehrabani, A ; Sharif University of Technology
Abstract
In this work performances of adaptive backstepping controller (BSC) and globally linearizing controller (GLC) are compared for pH control. First, based on the system full order model a GLC has been designed and it has been shown that this controller is identical to BSC proposed in the literature. Next in order to avoid state estimator design, BSC and GLC are designed based on pH reduced order model and their identities have been established. Through computer simulations, it has been shown that the performance of non-adaptive GLC designed based on reduced order model is better than that of adaptive BSC designed based on pH full order model which requires state measurement for implementation....
Coupling behavior of the pH/temperature sensitive hydrogels for the inhomogeneous and homogeneous swelling
, Article Smart Materials and Structures ; Volume 25, Issue 8 , 2016 ; 09641726 (ISSN) ; Baghani, M ; Naghdabadi, R ; Sohrabpour, S ; Sharif University of Technology
Institute of Physics Publishing
2016
Abstract
In this work, a model is developed to continuously predict homogeneous and inhomogeneous swelling behavior of pH/temperature sensitive PNIPAM hydrogels. Employing the model, homogeneous swelling of the pH/temperature sensitive hydrogel is investigated for free and biaxial constrained swelling cases. Comparing the model results with the experimental data available in the literature, the validity of the model is confirmed. The model is then employed to investigate inhomogeneous swelling of a spherical shell on a hard core both analytically and numerically for pH or temperature variations. In this regard, numerical tools are developed via preparing a user defined subroutine in ABAQUS software....
Electrophoretic deposition of chitosan
, Article Materials Letters ; Volume 63, Issue 26 , 2009 , Pages 2253-2256 ; 0167577X (ISSN) ; Pishbin, F ; Boccaccini, A. R ; Sharif University of Technology
2009
Abstract
The electrophoretic deposition (EPD) of chitosan on metallic substrates was investigated. The electrophoretic mobility of the natural biopolymer in aqueous solution as a function of pH was studied. Because the protonation/deporotonation of chitosan is pH-dependent, the electrophoretic mobility and deposition rate is shown to increase with increasing pH from 2.9 to 4.1. The film growth rate is estimated to vary in the range 0.02-0.08 μm/s depending on the pH value. At high growth rates (> 0.05 μm/s), a porous film is obtained due to hydrogen entrapment. The EPD method developed here is applicable for the surface modification of metal implants by chitosan to develop novel bioactive coatings. ©...
PH-Responsive chitosan-adorned niosome nanocarriers for co-delivery of drugs for breast cancer therapy
, Article ACS Applied Nano Materials ; Volume 5, Issue 7 , 2022 , Pages 8811-8825 ; 25740970 (ISSN) ; Rezaei, N ; Jamshidifar, E ; Moradi Falah Langeroodi, S ; Abdihaji, M ; Mansouri, A ; Hosseini, M ; Ahmadkhani, N ; Rahmati, Z ; Heydari, M ; Vosough, M ; Akbarzadeh, I ; Mostafavi, E ; Sharif University of Technology
American Chemical Society
2022
Abstract
Breast cancer incidence has increased in recent decades. In the present study, an optimum formulation of chitosan (CS)-adorned niosome-based nanocarriers for co-delivery of doxorubicin (DOX) and vincristine (VIN) was developed for the treatment of breast cancer to reduce drug doses and overcome multidrug resistance. The three-level Box-Behnken method was utilized to optimize the particles in terms of size, polydispersity index (PDI), entrapment efficacy (EE (%)), and percent of drug release (%). The release rate of two drugs from CS-adorned nanoparticles (DOX+VIN/Nio/CS) in acidic and physiological pH is less than uncoated niosome (DOX+VIN/Nio). In addition, acidic pH increases the release...