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Evaluation of the effect of organic pollutants exposure on the antioxidant activity, total phenolic and total flavonoid content of lettuce (Lactuca sativa L.) using UV–Vis spectrophotometry and chemometrics
, Article Microchemical Journal ; Volume 170 , 2021 ; 0026265X (ISSN) ; Parastar, H ; Sharif University of Technology
Elsevier Inc
2021
Abstract
In the present contribution, the effects of different contaminants of emerging concerns (CECs), including parabens, drugs, and polycyclic aromatic hydrocarbons (PAHs) on antioxidant activity of Lactuca sativa L. in different concentration levels (10–500 µg L−1) were evaluated using ultraviolet–visible (UV–Vis) spectrophotometry combined with chemometric techniques. The extracts of lettuce samples were investigated for the antioxidant activity (AA), total phenolic content (TPC), and total flavonoid content (TFC) after 39 days of planting and 14 days of exposure. Then, the spectroscopic data were arranged in two different data matrices, including (i) the control lettuce samples and PAHs...
Effect of Alternative Electromagnetic Vibration on Joining of 2024 Aluminum Alloy
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
2024 Aluminum alloy has an abundant application in the aerospace and automobile industries. One of the most important problems of the alloy is hot cracking during the fusion welding process. It is stated that the solidified grains can be refined by a static magnetic field and an alternative electric field applied simultaneously during solidification. To make the alternative electric field, an alternative current was passed through the specimen. In order to prevent hot cracking, electromagnetic vibration was used. Then the effect of intensity of the static magnetic field and alternative electric current on joint was examined. Joining was carried out at electric currents of 40, 60, and 80A and...
Colorful paths in vertex coloring of graphs
, Article Electronic Journal of Combinatorics ; Volume 18, Issue 1 , 2011 , Pages 1-9 ; 10778926 (ISSN) ; Liaghat, V ; Nikzad, A ; Sharif University of Technology
2011
Abstract
A colorful path in a graph G is a path with χ(G) vertices whose colors are different. A v-colorful path is such a path, starting from v. Let G ≠ C7 be a connected graph with maximum degree Δ (G). We show that there exists a (Δ(G)+1)-coloring of G with a v-colorful path for every v ∈ V (G). We also prove that this result is true if one replaces (Δ (G) + 1) colors with 2 χ(G) colors. If χ (G) = ω(G), then the result still holds for χ(G) colors. For every graph G, we show that there exists a χ(G)-coloring of G with a rainbow path of length ⌊ χ(G)/2⌋ starting from each v ∈ V (G)
Development of a Neuro-muscular Model for Stroke Patient in Reaching Motion and Experimental Evaluation
, M.Sc. Thesis Sharif University of Technology ; Behzadipour, Saeed (Supervisor)
Abstract
Paralysis is one of the most common disabilities resulting from stroke. Usually injury to one hemisphere of the brain affects the opposite side of the body. This one-sided paralysis is called hemiplegia Damage to a lower part of the brain, the cerebellum, can affect the body's ability to coordinate movement, a disability called ataxia, leading to problems with body posture, walking, and balance. Reaching tasks are building blocks of most daily functional movements. The purpose of such a movement is to transfer a specific point of hand (e.g. fingertip) toward a special location in space around. In people with ataxia, trajectories of reaching movements are far different from healthy people in...
Mechanism of Al-Si codeposition on In738LC through single-step diffusion process
, Article International Journal of Surface Science and Engineering ; Volume 11, Issue 1 , 2017 , Pages 1-11 ; 1749785X (ISSN) ; Abdi, M ; Rastegari, S ; Sharif University of Technology
2017
Abstract
The out-of-pack cementation method was applied to coat the Nickel-based super alloy IN738LC with Si-modified aluminide. Different mixtures of the pack containing pure Al, Si, alumina powders as an inert filler, and NH4Cl as a halide salt activator were used for co-deposition at 950 and 1,050°C. The results showed although the amount of subhalide vapour pressures of Al and Si were equal at 1,050°C, Al atoms diffused only after Si atoms had been deposited. Before heat treatment, the coating thickness formed by the pack containing 2.3 wt.% Al was 6 μm more than that containing 3.5 wt.% Al. After heat treatment, thickening coatings formed within the pack containing 2.3 wt.% Al was less than that...
Design and Analysis of Magnetic Encondor
, M.Sc. Thesis Sharif University of Technology ; Nasiri Gheidari, Zahra (Supervisor)
Abstract
Measuring the speed and position of the rotating part and using the speed and position information in the closed loop control of electric machines is very important. Various sensors are available for this purpose, including resistive sensors, capacitive sensors, encoders, synchros, resolvers, Halleffect sensors, and etc. Common encoders include optical and magnetic types. There are two main problems in using an encoder as a sensor: determining/maintaining accuracy during change of rotational direction and determining the absolute position. Both of the mentioned challenges have been investigated in the case of optical encoders and some solutions have been provided to overcome them. Although...
Reliability enhancement and price reduction of restructured power system with probabilistic day-ahead real time pricing contract
, Article IEEE Power Engineering Society (IEEE/PES); Chinese Society for Electrical Engineering (CSEE) ; 2010 ; 9781424459407 (ISBN) ; Mozafari, B ; Ranjbar, A. M ; Sharif University of Technology
2010
Abstract
Lack of demand response has always been the main reason for price increasing, shortage of production capacity and system risk increasing as the electricity markets have been greatly involved during the past years. In Electricity market, the exchanges are profitable for producers and consumers when both can participate freely. Based on this new environment, we are currently facing with a new concept as demand-side participation or demand response. There are several demand response programs that accurate pricing of each them is the major challenge that retailers and market operators are facing with. In this article the day-ahead real time pricing contract (DA-RTP) based on two different...
Development a planar neuro-musculoskeletal arm model in post-stroke patients
, Article 26th National and 4th International Iranian Conference on Biomedical Engineering, ICBME 2019, 27 November 2019 through 28 November 2019 ; 2019 , Pages 236-241 ; 9781728156637 (ISBN) ; Asghari, M ; Behzadipour, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Computational models of the central nervous system after a stroke helps to reveal the physiological mechanisms that may have strong impacts on the neuro-motor rehabilitation approaches. This paper studies the stroke subject's motor control mechanism in reaching movements by extending the previous study by incorporating the kinematics of motion as well as neural disconnection between the muscles and the CNS to further develop a planar patient specific neuro-musculoskeletal model of arm. The developed model was calibrated to eight post-stroke individuals by altering the Muscle Significance Factors (MFS) using numerical optimization to match the simulated motions with those measured...
Resource Allocation in a Hybrid CDN-P2P Video Streaming
, M.Sc. Thesis Sharif University of Technology ; Akbari, Behzad (Supervisor) ; Khansari, Mohammad (Supervisor)
Abstract
Since the contribution bandwidth of each CDN (Content Delivery Network) node and also each peer are limited, optimal allocation of their bandwidth to their partners is an interesting issue. In this work, an efficient resource allocation algorithm in a hybrid CDN-P2P (Content Delivery Network- peer to peer) video streaming network has been designed and each peer will receive the video chunks with the bit rate according to the number of nodes that the peer supports. We have added this algorithm to Coolstreaming because it does not have a resource allocation mechanism. In Coolstreaming each peer when requests chunks from its neighbors, the neighbors will send the peer the requested chunks with...
Microstructural modification of Al–30Si–5Fe Alloy using a combination of rapid solidification and thixoforming processes
, Article Metallography, Microstructure, and Analysis ; Volume 5, Issue 3 , 2016 , Pages 217-228 ; 21929262 (ISSN) ; Aashuri, H ; Ferasat, K ; Nikzad, S ; Sharif University of Technology
Springer New York LLC
2016
Abstract
It is commonly known that the properties of materials are strongly related to their microstructure. This paper introduces a method that is a combination of rapid solidification (melt spinning) and semisolid forming (thixoforming) processes, which are used to refine the microstructure of “as-cast” Al–30Si–5Fe alloy and improve its mechanical properties. Produced Al–30Si–5Fe ribbons by melt-spinning process, were pulverized and subsequently consolidated at 300 °C in argon atmosphere. Prepared specimens were thixoformed at temperatures ranging from 580 to 700 °C in various holding times. Some samples were also directly thixoformed from as-cast condition. Microstructure of the as-cast, meltspun,...
Mechanical properties of Al–30Si–5Fe alloy using combination of rapid solidification and thixoforming processes
, Article Metallography, Microstructure, and Analysis ; Volume 6, Issue 6 , 2017 , Pages 502-511 ; 21929262 (ISSN) ; Aashuri, H ; Nikzad, S ; Ferasat, K ; Sharif University of Technology
2017
Abstract
In this study, a combination of rapid solidification (melt-spinning) and semisolid forming (thixoforming) processes was used to refine the coarse microstructure of “as-cast” Al–30Si–5Fe alloy and improve its mechanical properties. Al–30Si–5Fe ribbons produced by the melt-spinning process were pulverized and subsequently consolidated at 300 °C in an argon atmosphere. Prepared specimens were thixoformed at temperatures ranging from 580 to 700 °C for various holding times. Some cast samples were also directly thixoformed as reference. In all thixoformed samples, microstructures were modified and needle-like intermetallic compounds as well as silicon particles in the as-cast part were changed...
Prioritizing demand response programs from reliability aspect
, Article 2012 11th International Conference on Environment and Electrical Engineering, EEEIC 2012 - Conference Proceedings ; 2012 , Pages 229-234 ; 9781457718281 (ISBN) ; Bashirvand, M ; Mozafari, B ; Ranjbar, A. M ; Sharif University of Technology
IEEE
2012
Abstract
In this paper, the impact of demand response programs (DRPs) on reliability improvement of the restructured power systems is quantified. In this regard, the demand response (DR) model which treats consistently the main characteristics of the demand curve is developed for modeling. In proposed model, some penalties for customers in case of no responding to load reduction and incentives for customers who respond to reducing their loads are considered. In order to make analytical evaluation of the reliability, a mixed integer DCOPF is proposed by which load curtailments and generation re-dispatches for each contingency state are determined. Both transmission and generation failures are...
Fabrication of a highly flexible and affordable transparent electrode by aligned u-shaped copper nanowires using a new electrospinning collector with convenient transferability
, Article ACS Omega ; Volume 4, Issue 25 , 2019 , Pages 21260-21266 ; 24701343 (ISSN) ; Mohamadbeigi, N ; Sadrnezhaad, Kh ; Mahdavi, M ; Sharif University of Technology
American Chemical Society
2019
Abstract
By making aligned and suspended copper nanowires, a high performance, transferable, and flexible transparent electrode is reported. Indium tin oxide is often used in devices such as displays, solar cells, and touchscreens that require transparent and conductive plates. Because of problems such as brittleness, high cost, and environmental effects, this material is facing rivals, the most serious of which are metallic nanowire meshes, especially copper. We developed a simple technique which uses a U-shaped collector in the electrospinning process with three advantages including the enhancement of the figure of merit (which is related to the surface resistance Rs and the transmittance T) by...
Geometrical optimization for silver nanowire mesh as a flexible transparent conductive electrode
, Article Applied Optics ; Volume 59, Issue 10 , 2020 , Pages 3073-3080 ; Mahdavi, S. M ; Sadrnezhaad, S. K ; Sharif University of Technology
OSA - The Optical Society
2020
Abstract
We report the effect of the geometric parameters on transparency and conductivity in a metallic nanowire mesh as a transparent electrode. Today, indium tin oxide and fluorine-doped tin oxide are used as the transparent electrode for displays and solar cells. Still, there is a definite need for their replacement due to drawbacks such as brittleness, scarcity, and adverse environmental effects. Metallic nanowire mesh is likely the best replacement option, but the main issue is how to find the optimal structure and how to get the best performance. Since the interaction of light with nanowire mesh is complicated, there is no straightforward rule with a simple analytical solution. We developed a...
A study on Warm Rolling Behavior of an Austenitic Stainless Steel and the Mechanical Properties of the Rolled Product
, M.Sc. Thesis Sharif University of Technology ; Serajzade, Siamak (Supervisor)
Abstract
In this study, thermo-mechanical behavior of an austenitic stainless steel AISI316L was investigated using mathematical modeling and experimental analysis during warm rolling process. First, the thermo-mechanical analysis was carried out employing the finite element software, Abaqus CAE, to assess temperature, strain, velocity and stress distribution during rolling. Then, rolling operations on 316L austenitic steel were performed under different working conditions while mechanical testing as well as microstructural observations were made on the rolled steels. Using simulation results and practical data, microstructural events and mechanical properties after warm rolling of stainless steel...
Optimal online pricing with network externalities
, Article Information Processing Letters ; Volume 112, Issue 4 , February , 2012 , Pages 118-123 ; 00200190 (ISSN) ; Ghodsi, M ; Khajenezhad, A ; Mahini, H ; Nikzad, A ; Sharif University of Technology
2012
Abstract
We study the optimal pricing strategy for profit maximization in presence of network externalities where a decision to buy a product depends on the price offered to the buyer and also on the set of her friends who have already bought that product. We model the network influences by a weighted graph where the utility of each buyer is the sum of her initial value on the product, and the linearly additive influence from her friends. We assume that the buyers arrive online and the seller should offer a price to each buyer when she enters the market. We also take into account the manufacturing cost. In this paper, we first assume that the monopolist defines a unique price for the product and...
Indirect adaptive fuzzy sliding mode control of 3D inverted pendulum
, Article 2017 IEEE 4th International Conference on Knowledge-Based Engineering and Innovation, KBEI 2017 ; Volume 2018-January , 2018 , Pages 0919-0924 ; 9781538626405 (ISBN) ; Shokouhyan, M. R ; Motekallem, A ; Sharifi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
In this paper, an indirect adaptive fuzzy sliding mode controller for a 3-dimensional inverted pendulum as a fully actuated MIMO system is developed. This inverted pendulum, has four degrees of freedom and equations of the system are nonlinear and non-minimum phase. Thus, control of this system is a challenging issue. Accordingly, in this work, general basis of sliding mode control method with reaching rules is expressed for this system, then the fuzzy control theory is combined, and modeling uncertainties of the system are estimated by universal fuzzy approximation theory. Controller parameters are updated by a defined adaptation law to decrease the tracking error of the inverted pendulum....
Improving the multi-step fabrication approach of copper nanofiber networks based transparent electrode for achieving superb conductivity and transparency
, Article Materials Research Express ; Volume 6, Issue 9 , 2019 ; 20531591 (ISSN) ; Angizi, S ; Sadrnezhaad, S. K ; Nikzad, M. J ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
Transparent Conductive Electrode (TCE), as an essential part of the optoelectronic devices, has become popular owing to its unique properties such as high optical transmittance and conductivity. Among utilized materials for fabrication of TCE, copper nanofibers (NFs)-network have been attracting much attention due to its extraordinary properties such as low sheet resistance, the scalable manufacturing and low-cost fabrication method. However, many challenges exist in the way of multi-step fabrication of network to increase the NFs continuity and consequently, improvement of their electrical conductivity as TCE. Herein, we report a deep investigation of the effective parameters on diameter...
Improving the multi-step fabrication approach of copper nanofiber networks based transparent electrode for achieving superb conductivity and transparency
, Article Materials Research Express ; Volume 6, Issue 9 , 2019 ; 20531591 (ISSN) ; Angizi, S ; Sadrnezhaad, S. K ; Nikzad, M. J ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
Transparent Conductive Electrode (TCE), as an essential part of the optoelectronic devices, has become popular owing to its unique properties such as high optical transmittance and conductivity. Among utilized materials for fabrication of TCE, copper nanofibers (NFs)-network have been attracting much attention due to its extraordinary properties such as low sheet resistance, the scalable manufacturing and low-cost fabrication method. However, many challenges exist in the way of multi-step fabrication of network to increase the NFs continuity and consequently, improvement of their electrical conductivity as TCE. Herein, we report a deep investigation of the effective parameters on diameter...
Effect of Strain Path on Static Recrystallization Behavior of a Steel
, M.Sc. Thesis Sharif University of Technology ; Serajzadeh, Siamak (Supervisor)
Abstract
Static recrystllization in low carbon steel after two type of deformation –sidepress as an inhomogeneous deformation and rolling as a common industrial process - has been simulated using Cellular Automata (CA). The finite element method was utilized to compute the strain and stored energy distribution due to deformation. The initial microstructures were created by simulation of recrystallization with homogeneous site-saturated nucleation and topologic deformation was also considered in model. Subsequently using the result of FEM, stored energy of deformation was calculated and transferred into a two dimensional CA lattice. Nucleation rate and grain boundary velocity were considered...