Loading...
Search for:
optimum
0.008 seconds
Total 421 records
Finding aggregation tree with genetic algorithm for network correlated data gathering
, Article 2nd International Conference on Sensor Technologies and Applications, SENSORCOMM 2008, Cap Esterel, 25 August 2008 through 31 August 2008 ; 2008 , Pages 429-434 ; 9780769533308 (ISBN) ; Tahaee, S. A ; Jahangir, A. H ; Sharif University of Technology
2008
Abstract
The critical issue in designing correlated data networks like Wireless Sensor Networks is to minimize the total cost of data transmission in the network, and decrease the amount of data flow. The problem of finding optimal aggregation tree for correlated data gathering in single sink network is considered as an NP-Complete problem and hence heuristic methods are usually applied to solve it[1]. In this paper, we apply genetic algorithm (GA) to solve the problem. In our method, we improve the performance of genetic search by selecting proper initial population. This initial population is determined in two ways, by using Prime's algorithm, and shortest path tree. The main issue is to regard...
Fabrication of a sensitive colorimetric nanosensor for determination of cysteine in human serum and urine samples based on magnetic-sulfur, nitrogen graphene quantum dots as a selective platform and Au nanoparticles
, Article Talanta ; Volume 226 , 2021 ; 00399140 (ISSN) ; Dadfarnia, S ; Haji Shabani, A. M ; Kazemi, E ; Pedrini, A ; Verucchi, R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
A novel colorimetric nanosensor is reported for the selective and sensitive determination of cysteine using magnetic-sulfur, nitrogen graphene quantum dots (Fe3O4/S, N-GQDs), and gold nanoparticles (Au NPs). Thus, S, N-GQDs was firstly immobilized on Fe3O4 nanoparticles through its magnetization in the presence of Fe3+ in the alkali solution. The prepared Fe3O4/S, N-GQDs were dispersed in cysteine solution resulting in its quick adsorption on the surface of the Fe3O4/S, N-GQDs through hydrogen bonding interaction. Then, Au NPs solution was added to this mixture that after a short time, the color of Au NPs changed from red to blue, the intensity of surface plasmon resonance peak of Au NPs at...
Fabrication of a sensitive colorimetric nanosensor for determination of cysteine in human serum and urine samples based on magnetic-sulfur, nitrogen graphene quantum dots as a selective platform and Au nanoparticles
, Article Talanta ; Volume 226 , 2021 ; 00399140 (ISSN) ; Dadfarnia, S ; Haji Shabani, A. M ; Kazemi, E ; Pedrini, A ; Verucchi, R ; Sharif University of Technology
Elsevier B.V
2021
Abstract
A novel colorimetric nanosensor is reported for the selective and sensitive determination of cysteine using magnetic-sulfur, nitrogen graphene quantum dots (Fe3O4/S, N-GQDs), and gold nanoparticles (Au NPs). Thus, S, N-GQDs was firstly immobilized on Fe3O4 nanoparticles through its magnetization in the presence of Fe3+ in the alkali solution. The prepared Fe3O4/S, N-GQDs were dispersed in cysteine solution resulting in its quick adsorption on the surface of the Fe3O4/S, N-GQDs through hydrogen bonding interaction. Then, Au NPs solution was added to this mixture that after a short time, the color of Au NPs changed from red to blue, the intensity of surface plasmon resonance peak of Au NPs at...
Design and optimization of a large-scale permanent magnet synchronous generator
, Article Scientia Iranica ; Volume 29, Issue 1 D , 2022 , Pages 217-229 ; 10263098 (ISSN) ; Rezazadeh, G ; Alipour Sarabi, R ; Tahami, F ; Sharif University of Technology
Sharif University of Technology
2022
Abstract
Direct-drive permanent magnet synchronous generators enjoy numerous advantages including improved reliability, low maintenance, long life, and developed performance characteristics. In recent years, many researchers have worked on these generators to enhance their performance, especially for the wind turbine application. The focus of this paper is on the development of a step-by-step method for the design of a permanent magnet synchronous generator. Then, the winding function method is used to model the generator and calculate its output characteristics analytically. The analytical results of the designed generator are validated using Finite Element Analysis (FEA) and it is demonstrated that...
An experimental investigation of foam for gas mobility control in a low-temperature fractured carbonate reservoir
, Article Petroleum Science and Technology ; Volume 30, Issue 10 , 2012 , Pages 976-985 ; 10916466 (ISSN) ; Kharrat, R ; Motealleh, M ; Khanamiri, H. H ; Nematzadeh, M ; Ghazanfari, M. H ; Sharif University of Technology
2012
Abstract
This work concerns the experimental investigation of surfactant alternating CO 2 injection in carbonate rocks. The core samples provided from a low-temperature fractured light oil reservoir, located in southwest Iran. The experiments were designed to observe the effect of CO 2-foam injection on gas mobility and oil recovery at different surfactant concentrations. The core samples were initially saturated with synthetic/field brine, 5,000 ppm, and then flooded with live oil to reach connate water saturation at reservoir condition, 115F and 1,700 psia. The commercial surfactant used was sodium lauryl sulfate as an anionic surfactant. The results of this work, along with field-scale simulation...
Enhanced photoelectrochemical activity of Ce doped ZnO nanocomposite thin films under visible light
, Article Journal of Electroanalytical Chemistry ; Volume 661, Issue 1 , 2011 , Pages 106-112 ; 15726657 (ISSN) ; Amiri, M ; Azimirad, R ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
Ce-doped ZnO and pure ZnO nanocomposite thin films with different Ce/Zn ratios (0, 2, 5, 10, 15, 20, and 30 at.%) have been prepared by sol-gel method at optimum annealing temperature of 500 °C. The synthesized samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometry. According to our XPS data analysis, there are three major metal ions namely Ce3+, Ce4+ and Zn 2+ that coexist on the surface. The XRD measurements indicate that the ZnO thin films have a hexagonal wurtzite structure, and CeO2 crystallites formed in the Ce-doped ZnO nanocomposite thin films. Photoelectrochemical property of the samples was studied by three...
Template-based growth of titanium dioxide nanorods by a particulate sol-electrophoretic deposition process
, Article Particuology ; Volume 9, Issue 2 , 2011 , Pages 161-169 ; 16742001 (ISSN) ; Ordikhani, F ; Fray, D. J ; Khomamizadeh, F ; Sharif University of Technology
Abstract
TiO2 nanorods have been successfully grown into a track-etched polycarbonate (PC) membrane by a particulate sol-electrophoretic deposition from an aqueous medium. The prepared sols had a narrow particle size distribution around 17 nm and excellent stability against aging, with zeta potentials in the range of 47-50 mV at pH 2. It was found that TiO2 nanorods were grown from dilute aqueous sol with a low, 0.1-M concentration. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversion of titanium isopropoxide was obtained by hydrolysis, resulting in the formation of TiO2 particles. X-ray diffraction (XRD) results revealed that TiO2 nanorods dried at 100 °C were a...
Cost and entropy generation minimization of a cross-flow plate fin heat exchanger using multi-objective genetic algorithm
, Article Journal of Heat Transfer ; Volume 133, Issue 2 , Nov , 2011 ; 00221481 (ISSN) ; Hajabdollahi, H ; Dincer, I ; Sharif University of Technology
2011
Abstract
In the present work, a thermal modeling is conducted for optimal design of compact heat exchangers in order to minimize cost and entropy generation. In this regard, an εNTU method is applied for estimation of the heat exchanger pressure drop, as well as effectiveness. Fin pitch, fin height, fin offset length, cold stream flow length, no-flow length, and hot stream flow length are considered as six decision variables. Fast and elitist nondominated sorting genetic algorithm (i.e., nondominated sorting genetic algorithm II) is applied to minimize the entropy generation units and the total annual cost (sum of initial investment and operating and maintenance costs) simultaneously. The results for...
Design Optimization of a Ladder Secondary Single-Sided Linear Induction Motor for Improved Performance
, Article IEEE Transactions on Energy Conversion ; Volume 30, Issue 4 , 2015 , Pages 1595-1603 ; 08858969 (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Abstract
In this paper, design and optimization of a ladder-type single-sided linear induction motor (Ladder SLIM) for machine tool applications is investigated. High-speed linear induction machines suffer from the end-effect phenomenon, which can reduce the thrust and result in declined output characteristics. Although it is common to consider this phenomenon in high-speed applications, it is essential to take it into account in the design and analysis of low-speed low-air-gap linear machines. In addition, Ladder SLIMs have significant flux density ripples, and using skewed bars for secondary of the machine is a common solution for it. Therefore, providing required equations, an algorithm for...
Synthesis of dimethyl ether over modified H-mordenite zeolites and bifunctional catalysts composed of Cu/ZnO/ZrO2 and modified H-mordenite zeolite in slurry phase
, Article Catalysis Letters ; Volume 129, Issue 1-2 , 2009 , Pages 111-118 ; 1011372X (ISSN) ; Kazemeini, M ; Aghaziarati, M ; Sharif University of Technology
2009
Abstract
Synthesis of dimethyl ether (DME) via methanol dehydration were investigated over various catalysts, and via direct CO hydrogenation over hybrid catalysts composed of Al-modified H-Mordenite zeolite and Cu/ZnO/ZrO 2. H-Mordenite zeolite exhibited the highest activity in dehydration of methanol. However, its selectivity toward dimethyl ether was rather low. For this reason, the H-Mordenite was modified. Modification of zeolites was performed by wet impregnation method and considered catalysts were characterized by AAS, XRD and NH3-TPD analyses. Results of catalytic tests indicated that H-Mordenite modified with 8 wt% aluminum oxide was the best catalyst for synthesis of dimethyl ether from...
Coordination of process integration and exergoeconomic methodology for analysis and optimization of a pulp and paper mill
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 301-312 ; 10263098 (ISSN) ; Mozafari, A. A ; Farhanieh, B ; Sharif University of Technology
2009
Abstract
By simultaneously applying pinch technology and the exergoeconomic method to a complex process system, beneficial and energy-efficient measures are identified. The "three-link-model" exergoeconomic methodology optimizes the design and operability of a system. In this work, contrary to traditional exergoeconomic methods, a reversed method is used. The approach proposed for the optimization of such a complex system is to iteratively optimize subsystems. Since the reversed exergoeconomic method is used, assumptions considered by Tsatsaronis (based on four assumptions for calculating the cost-optimal exergetic efficiency and relative cost difference) are not applicable and new assumptions are to...
Effect of different geometries in simulation of 3D viscous flow in francis turbine runners
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 363-369 ; 10263098 (ISSN) ; Dadfar, R ; Pirali, A. P ; Ahmadi, G ; Sharif University of Technology
2009
Abstract
Overall turbine analysis requires large CPU time and computer memory, even in the present days. As a result, choosing an appropriate computational domain accompanied by a suitable boundary condition can dramatically reduce the time cost of computations. This work compares different geometries for numerical investigation of the 3D flow in the runner of a Francis turbine, and presents an optimum geometry with least computational effort and desirable numerical accuracy. The numerical results are validated with a GAMM Francis Turbine runner, which was used as a test case (GAMM workshop on 3D computation of incompressible internal flows, 1989) in which the geometry and detailed best efficiency...
Magnetite nanoparticle as a support for stabilization of chondroitinase ABCI
, Article Artificial Cells, Nanomedicine and Biotechnology ; Volume 47, Issue 1 , 2019 , Pages 2721-2728 ; 21691401 (ISSN) ; Vossoughi, M ; Khajeh, K ; Alemzadeh, I ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Chondroitinase ABCI (cABCI) is a drug enzyme that can be used to treat spinal cord injuries. Due to low thermal stability of cABCI, this enzyme was immobilized on Fe3O4 nanoparticle to increase its thermal stability. The size and morphology, structure and magnetic property of the Fe3O4 nanoparticles were characterized by the analyses of SEM, XRD and VSM, respectively, and FTIR spectroscopy was employed to confirm the immobilization of cABCI on the surface of Fe3O4 nanoparticles. The results indicated that the optimum conditions for pH, temperature, cABCI-to-Fe3O4 mass ratio and incubation time in immobilization process were 6.5, 15 °C, 0.75 and 4.5 h, respectively, and about 0.037 mg cABCI...
Appraising the impacts of SiO2, ZnO and TiO2 nanoparticles on rheological properties and shale inhibition of water-based drilling muds
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 581 , 2019 ; 09277757 (ISSN) ; Shams, R ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In recent decades, utilizing of water-based muds (WBMs) in drilling oil and gas wells is ever increasing comparing to oil-based muds and synthetic-based muds due to the lower environmental issues. However, the main drawbacks with WBMs are rheological properties inefficiency and shale swelling which have caused attentions turn to improvement of WBMs’ rheological properties. In this study, the effects of various nanoparticles (NPs) namely titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) on improving rheological properties and shale recovery rate of a WBM sample at two temperatures (25 and 50 °C) were investigated. The concentrations of NPs in the base mud were set at 0.01,...
Design of an effective piezoelectric microcantilever biosensor for rapid detection of COVID-19
, Article Journal of Medical Engineering and Technology ; Volume 45, Issue 6 , 2021 , Pages 423-433 ; 03091902 (ISSN) ; Merati, M ; Abdekhodaie, M. J ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
Acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, is one of the most contagious viruses resulting in a progressive pandemic. Since specific antiviral treatments have not been developed yet and its fatal rate is almost high, early and fast detection is critical for controlling the outbreak. In this study, a piezoelectric microcantilever biosensor has been designed for detecting COVID-19 samples directly without requiring preparation steps. The biosensor acts as a transducer and is coated with the related antibody. When the SARS-CoV-2 antigens adsorbed on the microcantilever top surface through their spike proteins, a surface stress due to the mass change would be...
Effective promotion of g–C3N4 photocatalytic performance via surface oxygen vacancy and coupling with bismuth-based semiconductors towards antibiotics degradation
, Article Chemosphere ; Volume 287 , 2022 ; 00456535 (ISSN) ; Moradi, M ; Aghaebrahimi Samani, S ; Kakavandi, B ; Rahman Setayesh, S ; Noorisepehr, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In this research, the potential of bismuth chromate (BCO), a new bismuth-based semiconductor belongs to the family of Bi2XO6 (X = Mo, W, or Cr), was introduced by a novel 1D/2D structure consist of BCO nanobelts and N2-freezed ultra-wrinkled graphitic carbon nitride (N–CN) nanosheets. To enhance intimate contact between BCO and N–CN (BCO/N–CN composite), surface oxygen vacancy (VO) was created as an efficient electron transfer highway using a simple alkaline-treatment-assisted method. Various characterization techniques, including XRD, FT-IR, EPR, FE-SEM, TEM, BET, DRS, PL, EIS, and photocurrent transient analyses were conducted to elucidate the physicochemical aspects of catalysts. The...
Aniline-silica nanocomposite as a novel solid phase microextraction fiber coating
, Article Journal of Chromatography A ; Volume 1238 , May , 2012 , Pages 22-29 ; 00219673 (ISSN) ; Roostaie, A ; Sharif University of Technology
2012
Abstract
A new unbreakable solid phase microextraction (SPME) fiber coating based on aniline-silica nanocomposite was electrodeposited on a stainless steel wire. The electropolymerization process was carried out at a constant deposition potential, applied to the corresponding aqueous electrolyte containing aniline and silica nanoparticles. The scanning electron microscopy (SEM) images showed the non-smooth and the porous surface structure of the prepared nanocomposite. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some environmentally important polycyclic aromatic hydrocarbons (PAHs), as model compounds, from aqueous samples....
Towards obtaining more information from gas chromatography-mass spectrometric data of essential oils: An overview of mean field independent component analysis
, Article Journal of Chromatography A ; Volume 1217, Issue 29 , 2010 , Pages 4850-4861 ; 00219673 (ISSN) ; Parastar, H ; Sereshti, H ; Sharif University of Technology
2010
Abstract
Mean field independent component analysis (MF-ICA) along with other chemometric techniques was proposed for obtaining more information from multi-component gas chromatographic-mass spectrometric (GC-MS) signals of essential oils (mandarin and lemon as examples). Using these techniques, some fundamental problems during the GC-MS analysis of essential oils such as varying baseline, presence of different types of noise and co-elution have been solved. The parameters affecting MF-ICA algorithm were screened using a 25 factorial design. The optimum conditions for MF-ICA algorithm were followed by deconvolution of complex GC-MS peak clusters. The number of independent components (ICs) (chemical...
Effective factors in the treatment of kerosene-water emulsion by using UF membranes
, Article Journal of Hazardous Materials ; Volume 161, Issue 2-3 , 2009 , Pages 1216-1224 ; 03043894 (ISSN) ; Roostaazad, R ; Hesampour, M ; Nyström, M ; Ghotbi, C ; Sharif University of Technology
2009
Abstract
The effects of different parameters including membrane type (regenerated cellulose and polysulphone), transmembrane pressure (TMP), the content of oil in the feed, the flow velocity of the feed and pH on the ultrafiltration of an emulsion of kerosene in water were studied. It was found that the important factors affecting ultrafiltration were, in order, membrane type, pressure and oil concentration. The greatest flux at the optimum conditions here of 3 bar, an oil content of 3% (v/v) and with membrane type C30F was predicted as 108 L/(m2 h) that was within the range of the confidence limit of the measured value of 106 L/(m2 h). The normalised FTIR results of the virgin cellulosic membranes...
A novel niosome formulation for encapsulation of anthocyanins and modelling intestinal transport
, Article Food Chemistry ; Volume 293 , 2019 , Pages 57-65 ; 03088146 (ISSN) ; Akay, S ; Sharifi, F ; Sevimli Gur, C ; Ongen, G ; Yesil Celiktas, O ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The bioavailability of drugs can be improved by regulating the structural properties, particularly lipoid systems, such as niosomes, can increase cellular uptake. Herein, we optimized double emulsion and niosomal formulations for encapsulating anthocyanin-rich black carrot extract. Nanoparticles obtained by selected formulation were characterized in terms of morphology, particle size, drug encapsulation efficiency, in vitro release and cytotoxicity. The optimum conditions for niosomal formulation were elicited as 30 mg of cholesterol, 150 mg of Tween 20 and feeding time of 1 min at a stirring rate of 900 rpm yielding the lowest average particle size of 130 nm. In vitro release data showed...