Loading...
Search for:
surface-property
0.009 seconds
Total 335 records
Production of biodiesel from waste frying oil using whole cell biocatalysts: Optimization of effective factors
, Article Waste and Biomass Valorization ; Vol. 5, issue. 6 , 2014 , pp. 947-954 ; ISSN: 18772641 ; Kariminia, H. R ; Yaghmaei, S ; Sharif University of Technology
Abstract
Using whole cell as a catalyst of enzymatic transesterification is a method to produce biodiesel with fewer drawbacks and at a lower cost. In the present study, biodiesel was produced by the reaction of waste frying oil with methanol in the presence of Rhizopus oryzae PTCC 5174 in both immobilized and free forms. Effect of four influencing factors including temperature, methanol to oil molar ratio, amount of biomass, and shaking speed was investigated. Response surface methodology was used to find the optimum conditions of the transesterification reaction. Each factor was set at three levels and the yield of the biodiesel was considered as the response. A quadratic equation was well-fitted...
Electrochemical determination of atorvastatin on nano-scaled polypyrrole film
, Article Bioelectrochemistry ; Vol. 98 , 2014 , pp. 1-10 ; ISSN: 15675394 ; Shahrokhian, S ; Sharif University of Technology
Abstract
Pyrrole was electro-polymerized on the surface of the glassy carbon electrode (GCE) coated with a thin film of carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG) or graphite nanopowder (GNP). Morphology, thickness, stability and loading of the polypyrrole (PPY) film were significantly affected by the structure and morphology of the sub-layer of carbon nanomaterials. Electrochemical oxidation of atorvastatin (ATOR) was investigated. Under the optimized conditions, a significant increase in the peak current (compared to other modified electrodes and bare GCE) and a negative shift in the peak potential (compared to bare GCE) were...
Effects of electrophoretic deposition parameters on the photocatalytic activity of TiO2 films: Optimization by response surface methodology
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Vol. 452, Issue. 1 , 2014 , pp. 1-8 ; ISSN: 09277757 ; Vossoughi, M ; Feilizadeh, M ; Rashtchian, D ; Moradi, S ; Alemzadeh, I ; Sharif University of Technology
Abstract
In this work, the electrophoretic deposition method was utilized to immobilize TiO2 particles on stainless steel substrates. In addition, for the first time, statistics-based experimental design using response surface methodology was employed to investigate the effect of four key coating parameters (i.e. applied voltage, calcination temperature, photocatalyst weight percentage, and deposition time) on the photocatalytic degradation. Analysis of variance revealed that the proposed model was adequate. X-ray diffraction and scanning electron microscope were used to evaluate the effects of the parameters on degradation efficiency. The optimum applied voltage, calcination temperature, catalyst...
Effect of resins on asphaltene deposition and the changes of surface properties at different pressures: A microstructure study
, Article Energy and Fuels ; Vol. 28, issue. 4 , April , 2014 , pp. 2415-2421 ; ISSN: 08870624 ; Zolghadr, A ; Ayatollahi, S ; Sharif University of Technology
Abstract
Asphaltene deposition has hindered oil production from asphaltenic oil reservoirs through deposition in reservoir rock and surface facilities. This paper investigates the effect of resin on asphaltene deposition at different pressures. To investigate the asphaltene deposition in the presence of resins at reservoir temperature and different pressures, a pressure, volume, and temperature (PVT) visual cell was designed. A high-resolution microscope and image processing software were used to detect and determine the amount of deposited asphaltene as well as its size distribution at different conditions. Two types of Iranian crude oils with different potential of deposition (low and high) were...
Magnetic pH-responsive nanocarrier with long spacer length and high colloidal stability for controlled delivery of doxorubicin
, Article Colloids and Surfaces B: Biointerfaces ; Vol. 116 , April , 2014 , pp. 49-54 ; ISSN: 09277765 ; Hosseini, S. H ; Alizadeh, M ; Bennett, C ; Sharif University of Technology
Abstract
A novel magnetic nanocarrier with long spacer length and high colloidal stability has been prepared for effective delivery of doxorubicin (DOX). First, poly(amidoamine) (PAMAM) dendrimer was grown up onto the surface of superparamagnetic iron oxide nanoparticles to increase the loading amount of amine groups. Then, terminal amine groups were functionalized by polyethylene glycol dimethylester to increase the spacer length. Then anticancer drug DOX was covalently attached onto the system by hydrazone bond to forms a pH-sensitive nanocarrier. This system is designed to combine the advantage of magnetic targeting, high drug loading capacity, and controlled release
A chitosan-polypyrrole magnetic nanocomposite as μ-sorbent for isolation of naproxen
, Article Analytica Chimica Acta ; Vol. 816 , 2014 , Pages 1-7 ; ISSN: 00032670 ; Roostaie, A ; Baktash, M. Y ; Sharif University of Technology
Abstract
An extracting medium based on chitosan-polypyrrole (CS-PPy) magnetic nanocomposite was synthesized by chemical polymerization of pyrrole at the presence of chitosan magnetic nanoparticles (CS-MNPs) for micro-solid phase extraction. In this work, magnetic nanoparticles, the modified CS-MNPs and different types of CS-PPy magnetic nanocomposites were synthesized. Extraction efficiency of the CS-PPy magnetic nanocomposite was compared with the CS-MNPs and Fe3O4 nanoparticles for the determination of naproxen in aqueous samples, via quantification by spectrofluorimetry. The scanning electron microscopy images obtained from all the prepared nanocomposites revealed that the CS-PPy magnetic...
Optimization of biodiesel production by alkali-catalyzed transesterification of used frying oil
, Article Process Safety and Environmental Protection ; Vol. 92, issue. 2 , 2014 , pp. 179-185 ; ISSN: 09575820 ; Kariminia, H. R ; Moslehabadi, P. M ; Sharif University of Technology
Abstract
Biodiesel as an alternative fuel for fossil diesel has many benefits such as reducing regulated air pollutants emissions, reducing greenhouse gases emissions, being renewable, biodegradable and non-toxic. In this study, used frying oil was applied as a low cost feedstock for biodiesel production by alkali-catalyzed transesterification. The design of experiments was performed using a double 5-level-4-factor central composite design coupled with response surface methodology in order to study the effect of factors on the yield of biodiesel and optimizing the reaction conditions. The factors studied were: reaction temperature, molar ratio of methanol to oil, catalyst concentration, reaction time...
Influence of glycerol and clay contents on biodegradability of corn starch nanocomposites
, Article International Journal of Engineering, Transactions B: Applications ; Vol. 27, issue. 2 , 2014 , pp. 203-214 ; ISSN: 10252495 ; Alemzadeh, I ; Vossoughi, M ; Sharif University of Technology
Abstract
In this study, biodegradation of corn starch/glycerol/Na-MMT nanocomposites by soil burial tests were carried out for up to 6 months. Films were prepared by casting method according to central composite design and response surface methodology was applied for analysis of the results. The effects of formulation on the water solubility, contact angle and tensile strength of starch films were investigated. Increasing in Na-MMT content decreased biodegradability; while presence of glycerol, increased it. The effect of nanoparticles content might have been attributed to interactions between starch and Na-MMT that further prevented enzymatic attack on the biopolymer. In addition, the films with...
Marangoni instabilities for convective mobile interfaces during drop exchange: Experimental study and CFD simulation
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Vol. 441, issue , 2014 , pp. 846-854 ; ISSN: 09277757 ; Karbaschi, M ; Bastani, D ; Ferri, J. K ; Kovalchuk, V. I ; Kovalchuk, N. M ; Javadi, K ; Miller, R ; Sharif University of Technology
Abstract
The inflow pattern of liquid into a droplet is studied experimentally using a surface active dye and compared with results of CFD simulations. The results show visual agreement between experiments and simulations. The CFD simulations show also good agreement with the surface tension measured by drop profile analysis tensiometry (PAT). The inflow of the surfactant induces a Marangoni instability caused by the local arrival of the surfactant at the drop surface. The onset of this Marangoni instability observed experimentally has a delay of about 10. s when compared with the simulation results. Different scenarios are discussed, including a boundary layer barrier, a kinetic-controlled...
Optimization of uhmwpe/graphene nanocomposite processing using ziegler-natta catalytic system viaresponse surface methodology
, Article Polymer - Plastics Technology and Engineering ; Vol. 53, Issue. 9 , June , 2014 , pp. 969-974 ; ISSN: 03602559 ; Ramazani, S. A. A ; Sharif University of Technology
Abstract
Optimization of operational conditions for the preparation of Ultrahigh-molecular-weight polyethylene (UHMWPE)/Graphene nanocomposites with Ziegler-Natta catalyst was carried out via response surface methodology (RSM). This study deals with the optimization of process variables to optimize the productivity and molecular weight. A three-factor, three-level Box-Behnken design with temperature (X1), monomer pressure (X2), and [Al]/[Ti] molar ratio (X3) as the independent variables were selected for the study. The dependent variables were productivity and molecular weights of the final nanocomposites. It was developed by using the three parameters at three levels including 50, 60, and 70°C for...
An integrated approach for enhancing the quality of the product by combining robust design and customer requirements
, Article Quality and Reliability Engineering International ; Vol. 30, Issue. 8 , 2014 , pp. 1285-1292 ; ISSN: 07488017 ; Haji, M. J ; Eslamipoor, R ; Sharif University of Technology
Abstract
Enhancing the quality of the product has always been one considerable concern of production process management, and this subject gave way to implementing so many methods including robust design. In this paper, robust design utilizes response surface methodology (RSM) considering the mean and variance of the response variable regarding system design, parameter design, and tolerance design. In this paper, customer requirements and robust design are regarded simultaneously to achieve enriched quality. Subsequently, with a non-linear programming, a novel method for integrating RSM and quality function deployment has been proposed to achieve robustness in design. The customer requirements are...
Classification of normal and diseased liver shapes based on spherical harmonics coefficients
, Article Journal of Medical Systems ; Vol. 38, issue. 5 , April , 2014 ; ISSN: 01485598 ; Zoroofi, R. A ; Tehrani-Fard, A. A ; Akhlaghpoor, S ; Sato, Y ; Sharif University of Technology
Abstract
Liver-shape analysis and quantification is still an open research subject. Quantitative assessment of the liver is of clinical importance in various procedures such as diagnosis, treatment planning, and monitoring. Liver-shape classification is of clinical importance for corresponding intra-subject and inter-subject studies. In this research, we propose a novel technique for the liver-shape classification based on Spherical Harmonics (SH) coefficients. The proposed liver-shape classification algorithm consists of the following steps: (a) Preprocessing, including mesh generation and simplification, point-set matching, and surface to template alignment; (b) Liver-shape parameterization,...
A new approach to solve multi-response statistical optimization problems using neural network, genetic algorithm, and goal attainment methods
, Article International Journal of Advanced Manufacturing Technology ; Vol. 75, issue. 5-8 , November , 2014 , pp. 1149-1162 ; Niaki, S. T. A ; Atyabi, S. M ; Sharif University of Technology
Abstract
Adjusting control factors (independent variables) to achieve an optimal level of output (response variable) is usually required in many real-world manufacturing problems. Common optimization methods often begin with estimating the relationship between a response and independent variables. Among these techniques, response surface methodology (RSM), due to its simplicity, has recently attracted extensive attention. However, on the one hand, in some cases, the relationship between a response and independent variables is too complex to be estimated using polynomial regression models. On the other hand, solving the obtained optimization model is not easy by exact methods. This paper introduces a...
Pd-Au nanoparticle decorated carbon nanotube as a sensing layer on the surface of glassy carbon electrode for electrochemical determination of ceftazidime
, Article Materials Science and Engineering C ; Vol. 34, issue. 1 , 2014 , pp. 318-325 ; ISSN: 09284931 ; Salimian, R ; Rastgar, S ; Sharif University of Technology
Abstract
A simple electrodeposition method is employed to construct a thin film modifier of palladium-gold nanoparticles (Pd-AuNPs) decorated multi-walled carbon nanotube (MWCNT) on the surface of glassy carbon electrode (GCE). Morphology and property of Pd-AuNPs-MWCNT have been examined by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Electrochemical performance of Pd-AuNPs-MWCNT/GCE for detection of ceftazidime (CFZ) has been investigated by cyclic voltammetry (CV). This nanostructured film modified electrode effectively exhibited enhanced properties for detection of ceftazidime (CFZ). The effects of various experimental variables such as, the amount of casted MWCNT,...
Dynamics of liquid interfaces under various types of external perturbations
, Article Current Opinion in Colloid and Interface Science ; Vol. 19, issue. 4 , Aug , 2014 , p. 309-319 ; Karbaschi, M ; Javadi, A ; Mucic, N ; Kragel, J ; Kovalchuk, V. I ; Rubio, R. G ; Fainerman, V. B ; Miller, R ; Sharif University of Technology
Abstract
Dynamic interfacial parameters are the key properties of interfaces in many modern technologies and can be studied in various ways. For applications like foams and emulsions, the dynamics of adsorption and the dilational and shear rheology of liquid-fluid interfaces are investigated most frequently. This work gives an insight into recently developed new experimental approaches, such as fast capillary pressure tensiometry for growing and oscillating drops. These experiments are presented in comparison to more classical techniques like drop profile tensiometry and capillary wave damping. Progress in these experiments based on generated interfacial perturbations can be expected only by a close...
Robust estimation of multi-response surfaces considering correlation structure
, Article Communications in Statistics - Theory and Methods ; Vol. 43, issue. 22 , Oct , 2014 , p. 4749-4765 ; Bashiri, M ; Niaki, S. T. A ; Sharif University of Technology
Abstract
Response surfaces express the behavior of responses and can be used for both single and multi-response problems. A common approach to estimate a response surface using experimental results is the ordinary least squares (OLS) method. Since OLS is very sensitive to outliers, some robust approaches have been discussed in the literature. Although there are many methods available in the literature for multiple response optimizations, there are a few studies in model building especially robust models. Assuming correlated responses, in this paper, a robust coefficient estimation method is proposed for multi response problem based on M-estimators. In order to illustrate the performance of the...
Bi-objective resource constrained project scheduling problem with makespan and net present value criteria: Two meta-heuristic algorithms
, Article International Journal of Advanced Manufacturing Technology ; Volume 69, Issue 1-4 , 2013 , Pages 617-626 ; 02683768 (ISSN) ; Najafi, A. A ; Niaki, S.T. A ; Sharif University of Technology
2013
Abstract
Traditionally, the model of a resource-constrained project-scheduling problem (RCPSP) contains a single objective function of either minimizing project makespan or maximizing project net present value (NPV). In order to be more realistic, in this paper, two multi-objective meta-heuristic algorithms of multi-population and two-phase sub-population genetic algorithms are proposed to find Pareto front solutions that minimize the project makespan and maximize the project NPV of a RCPSP, simultaneously. Based on standard test problems constructed by the RanGen project generator, a comprehensive computational experiment is performed, where response surface methodology is employed to tune the...
Particle dispersion dependency on the entrance position in bidirectional flow
, Article Particulate Science and Technology ; Volume 31, Issue 6 , 2013 , Pages 576-584 ; 02726351 (ISSN) ; Saidi, M. H ; Mozafari, A. A ; Soleimani, F ; Sharif University of Technology
2013
Abstract
This article presents a process of numerically predicting and experimentally verifying the dispersion quality and penetration level of fuel particles entering and moving in various directions relative to vortex engine walls. If the length scale of particles considered in this study is not comparable to the chamber length and, furthermore, the density is ignored, the effect of the particle on the flow field can be neglected and a one-way solution will be viable for the problem. The solutions in each case are carried out to estimate the particle trajectory and parameters affecting it. The governing equations are converted to a set of nonlinear, coupled, ordinary differential equations (ODEs)...
Nonlinear dynamical structure of sway path during standing in patients with multiple sclerosis and in healthy controls is affected by changes in sensory input and cognitive load
, Article Neuroscience Letters ; Volume 553 , 2013 , Pages 126-131 ; 03043940 (ISSN) ; Sanjari, M. A ; Mofateh, R ; Parnianpour, M ; Sharif University of Technology
2013
Abstract
Although several studies have applied traditional linear measures to evaluate postural control of patients with multiple sclerosis (MS), little is known about the nonlinear dynamics of this patient group. In this study, recurrence quantification analysis (RQA), a well documented nonlinear method, was used to compare the nonlinear dynamical structure of postural sway in two groups consisting of MS patients (. n=. 23) and healthy matched controls (. n=. 23). The study focuses on three levels of postural difficulty consisting of (1) standing on a rigid surface (force platform) with eyes open, (2) standing on a rigid surface with eyes closed, and (3) standing on a foam surface with eyes closed....
Tissue growth into three-dimensional composite scaffolds with controlled micro-features and nanotopographical surfaces
, Article Journal of Biomedical Materials Research - Part A ; Volume 101, Issue 10 , 2013 , Pages 2796-2807 ; 15493296 (ISSN) ; Simchi, A ; Dunlop, J. W. C ; Fratzl, P ; Bagheri, R ; Vossoughi, M ; Sharif University of Technology
2013
Abstract
Controlling topographic features at all length scales is of great importance for the interaction of cells with tissue regenerative materials. We utilized an indirect three-dimensional printing method to fabricate polymeric scaffolds with pre-defined and controlled external and internal architecture that had an interconnected structure with macro- (400-500 μm) and micro- (∼25 μm) porosity. Polycaprolactone (PCL) was used as model system to study the kinetics of tissue growth within porous scaffolds. The surface of the scaffolds was decorated with TiO2 and bioactive glass (BG) nanoparticles to the better match to nanoarchitecture of extracellular matrix (ECM). Micrometric BG particles were...