Loading...
Search for:
nikzad-goltapeh--a
0.144 seconds
Total 14708 records
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...
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...
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....
Swing up and arm trajectory tracking of the furuta pendulum with sliding mode control
, Article 5th RSI International Conference on Robotics and Mechatronics, IcRoM 2017, 25 October 2017 through 27 October 2017 ; 2018 , Pages 346-351 ; 9781538657034 (ISBN) ; Nikzad Goltapeh, A ; Sharif University of Technology
2018
Abstract
In this paper, the swing-up problem of the Furuta pendulum has been solved by introducing a new combined method based on the frequency response, and the sliding mode method. Furthermore, a trajectory tracking controller has been introduced and applied to the Furuta pendulum; which the pendulum remained regulated at the upward position, while the arm tracks a desired time-varying trajectory. The hierarchical sliding mode control (HSMC) approach has been employed to achieve the mentioned goals. The Furuta system is made up of two subsystems. Based on this physical structure, the hierarchical structure of the sliding surfaces is designed as follows: first, the sliding surface of each subsystem...
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)
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...
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...
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...
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...
Resolution improvement of hall effect gear tooth magnetic encoder
, Article 2023 3rd International Conference on Electrical Machines and Drives, ICEMD 2023 ; 2023 ; 979-835039374-3 (ISBN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Magnetic encoders as position sensors are widely used in industrial applications. They have numerous benefits, including resilience, cheap maintenance costs, minimal sensitivity to EMI noise, and a wide temperature range. However, they suffer from relatively low resolution. Therefore, the highest resolution that a magnetic encoder may achieve is estimated in this study. Then, a low-cost output circuit is proposed to increase the resolution of magnetic encoder without changing its primary parameters. The experimental measurements on the porotype of the sensor approve the success of the proposed method. © 2023 IEEE
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...
Designing time-of-use program based on stochastic security constrained unit commitment considering reliability index
, Article Energy ; Volume 41, Issue 1 , May , 2012 , Pages 541-548 ; 03605442 (ISSN) ; Mozafari, B ; Bashirvand, M ; Solaymani, S ; Ranjbar, A. M ; Sharif University of Technology
2012
Abstract
Recently in electricity markets, a massive focus has been made on setting up opportunities for participating demand side. Such opportunities, also known as demand response (DR) options, are triggered by either a grid reliability problem or high electricity prices. Two important challenges that market operators are facing are appropriate designing and reasonable pricing of DR options.In this paper, time-of-use program (TOU) as a prevalent time-varying program is modeled linearly based on own and cross elasticity definition. In order to decide on TOU rates, a stochastic model is proposed in which the optimum TOU rates are determined based on grid reliability index set by the operator. Expected...
The Effect of Temperature and Rotational Speed on Structure and Mechanical Properties of Cast Cu Base Alloy (Cu-Al-Si-Fe) Welded by Semisolid Stir Joining Method
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 46, Issue 12 , 2015 , Pages 5782-5788 ; 10735623 (ISSN) ; Aashuri, H ; Kokabi, A. H ; Shafizadeh, M ; Nikzad, S ; Sharif University of Technology
2015
Abstract
Semisolid stir joining has been under deliberation as a possible method for joining of copper alloys. In this study, the effect of temperature and rotational speed of stirrer on macrostructure evaluation and mechanical properties of samples were investigated. Optical microscopy and X-ray diffraction were performed for macro and microstructural analysis. A uniform micro-hardness profile was attained by semisolid stir joining method. The ultimate shear strength and bending strength of welded samples were improved in comparison with the cast sample. There is also lower area porosity in welded samples than the cast metal. The mechanical properties were improved by increasing temperature and...
Newly developed technique to eliminate hot cracking with electromagnetic vibration for joining of 2024 aluminum alloy
, Article Metallography, Microstructure, and Analysis ; Volume 5, Issue 1 , 2016 , Pages 7-15 ; 21929262 (ISSN) ; Ashuri, H ; Kokabi, A. H ; Shafizadeh, M ; Ferasat, K ; Sharif University of Technology
Springer New York LLC
2016
Abstract
In this study, the effect of electromagnetic vibration on joining of aluminum alloy 2024 was investigated. Simultaneously applying a static magnetic field and alternating electrical current passing through a conductor produced electromagnetic vibration. Joining was accomplished using constant electric current (60 A) and the magnetic flux of 75, 110, and 145 mT in the presence of argon gas. After joining, samples were cooled first by argon gas as a shielding gas and then by water. The microstructure and mechanical properties of the welded samples were studied for different electromagnetic vibrations. The optimum microstructure and mechanical properties were obtained when applied...
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...
Optimal iterative pricing over social networks (extended abstract)
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 13 December 2010 through 17 December 2010 ; Volume 6484 LNCS , December , 2010 , Pages 415-423 ; 03029743 (ISSN) ; 3642175716 (ISBN) ; Ghodsi, M ; Haghpanah, N ; Mirrokni, V. S ; Mahini, H ; Nikzad, A ; Sharif University of Technology
2010
Abstract
We study the optimal pricing for revenue maximization over social networks in the presence of positive network externalities. In our model, the value of a digital good for a buyer is a function of the set of buyers who have already bought the item. In this setting, a decision to buy an item depends on its price and also on the set of other buyers that have already owned that item. The revenue maximization problem in the context of social networks has been studied by Hartline, Mirrokni, and Sundararajan [4], following the previous line of research on optimal viral marketing over social networks [5,6,7]. We consider the Bayesian setting in which there are some prior knowledge of the...
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...
Chemometrics-assisted-liquid phase microextraction based on deep eutectic solvents followed by gas chromatography for determination of polycyclic aromatic hydrocarbons in aqueous and juice samples
, Article Microchemical Journal ; Volume 191 , 2023 ; 0026265X (ISSN) ; Keyvan, N ; Nikzad, N ; Parastar, H ; Sharif University of Technology
Elsevier Inc
2023
Abstract
In the present study, an optimized liquid-phase microextraction technique based on the deep eutectic solvent (LPME-DES) followed by gas chromatography-flame ionization detector (GC-FID) is developed to determine 13 carcinogenic polycyclic aromatic hydrocarbons (PAHs) in water and juice samples. In this regard, central composite design (CCD) was used to design, multiple linear regression (MLR) to model, and Nelder-Mead simplex optimization to optimize the effective LPME-DES factors. The optimum values for DES volume, temperature, extraction time, and salt amount were 112 µL, 72 °C, 9.14 min, and 2.5% (w/v), respectively. Afterward, multivariate calibration based on partial least squares...