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Optimization of a radiator for a MPFL system in a GEO satellite
Afshari, Behzad Mohasel,Abedi, Mohsen,Shahryari, Mehran Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.6
One of the components that used in the satellite thermal control subsystem is the Mechanically Pumped Fluid Loop (MPFL) system; this system mostly used in geosynchronous orbit (GEO) satellites, and can transfer heat from a hot point to a cold point using the fluid which circulated in a closed loop. Heat radiates to the deep space at the cold plate to cool down the fluid temperature. In this research, the radiative heatexchanger (RHX) for a MPFL system is optimized. The genetic algorithm has been used for minimizing the total mass and pressure drop by considering a constant transferred heat rate at the heat exchanger. The optimization has been done in two cases. In case I, two parameters are considered as a goal function, so optimization is performed using NSGA-II method. Results of optimization are shown in the pareto diagram. In case II, the diameter of pipe is considered constant, so the optimized value for distances of the parallel pipes is obtained by using the genetic algorithm, in which the system has the least total mass. Results show that in the RHX, by increasing the pipe diameter, pressure drop decreases and total mass increases. Also by considering a constant value for pipe diameter, an optimum distance between pipes and pipe length are obtained in which the system has a minimum mass.
EXISTENCE OF FIXED POINTS OF SET-VALUED MAPPINGS IN b-METRIC SPACES
Afshari, Hojjat,Aydi, Hassen,Karapinar, Erdal The Youngnam Mathematical Society 2016 East Asian mathematical journal Vol.32 No.3
In this paper, we introduce the notion of generalized ${\alpha}-{\psi}$-Geraghty multivalued mappings and investigate the existence of a xed point of such multivalued mappings. We present a concrete example and an application on integral equations illustrating the obtained results.
Afshari, Behzad Mohasel,Mirjavadi, Seyed Sajad,Barati, Mohammad Reza Techno-Press 2022 Advances in concrete construction Vol.13 No.5
The present paper deals with nonlinear deflection analysis of hyperelastic plates rested on elastic foundation and subject to a transverse point force. For modeling of hyperelastic material, three-parameter Ishihara model has been employed. The plate formulation is based on classic plate theory accounting for von-Karman geometric nonlinearity. Therefore, both material and geometric nonlinearities have been considered based on Ishihara hyperelastic plate model. The governing equations for the plate have been derived based on Hamilton's rule and then solved via Galerkin's method. Obtained results show that material parameters of hyperelastic material play an important role in defection analysis. Also, the effects of foundation parameter and load location on plate deflections will be discussed.
EXISTENCE OF FIXED POINTS OF SET-VALUED MAPPINGS IN b-METRIC SPACES
Hojjat Afshari,Hassen Aydi,Erdal Karap nar 영남수학회 2016 East Asian mathematical journal Vol.32 No.3
In this paper, we introduce the notion of generalized α-ψ-Geraghty multivalued mappings and investigate the existence of a xedpoint of such multivalued mappings. We present a concrete example andan application on integral equations illustrating the obtained results.
Nanohybrid Nanoparticles Based on Chitosan/Functionalized Carbon Nanotubes as Anti-HIV Nanocarrier
R. Afshari,S. Mazinani,M. Abdouss 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.1
Carbon nanotube-natural biopolymer nanovectors have important potential applications in delivery system for drugs and biomolecules. In this work, the use of multi-walled carbon nanotubes (MWCNT) as nanoreservoirs for drug loading and controlled release is demonstrated. We synthesized different carbon nanotube-based drug delivery systems including acid and amide-functionalized MWCNT; chitosan (CS) covalently grafted to functionalized MWCNT and MWCNT-CS nanoparticles (NPs) using an ionotropic gelation method as a sustained-release systems for delivery of Tenofovir (hydrophilic anti-retroviral drug). The prepared NPs as different drug delivery systems were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). As it is shown, in vitro drug release studies indicated that the cumulative release rate of Tenofovir from MWCNT–CS NPs shows the best result and it reaches the maximum value (90%) after about 120 h. Moreover, comparing to ungrafted CNTs, MWCNT–CS shows high dispersability and long-term stability in aqueous medium which approves the effective solubilization of MWCNT followed by grafting with CS.
Reza Afshari,Majid Khadem-Rezaiyan,Hoda Khatibi Moghadam,Mahdi Talebi 한국독성학회 2020 Toxicological Research Vol.36 No.1
Withdrawal syndrome is one of the initial focuses of opioid detoxification. Very low dose naltrexone (VLNTX) has been found to reduce opioid tolerance and dependence in animal and human clinical studies. The aim of this study was to determine the safety and efficacy of VLNTX during early stages of detoxification. In a multi-arm parallel, double-blind, randomized controlled trial, 63 opioid-dependent male participants referring to Imam Reza Rehabilitation Center were allocated to three equal groups using block randomization method. They received 0.125 mg, 0.250 mg of VLNTX or placebo daily for 10 days, together with the routine clonidine-based protocol. Self-reported and observer ratings of withdrawal severity and adverse events were measured on the 1st, 4th and 10th day of treatment. Runny eyes (p = 0.006), anxiety (p = 0.031) and dehydration (p = 0.014) were reduced during the whole 10 days in the 0.125 mg VLNTX-treated group compared to placebo. Only drowsiness (p = 0.043) and dysphoric mood (p < 0.001) were reduced in the 0.250 mg VLNTX-treated group. Results of 1st, 4th, and 10th-day assessment showed that most symptoms reductions were for the 0.125 mg VLNTX and the placebo group in the 1st and 4th days, respectively. On the 10th day, there was not any significant difference between 0.250 mg VLNTX-treated group and placebo group. No adverse effect was observed. In the starting days of detoxification, VLNTX can reduce the withdrawal symptoms, but the efficacy declined by passing time. Further studies are needed to test the utility of this new therapeutic approach.
Investigation of a nonlinear dynamic hydraulic system model through the energy analysis approach†
Hamed Hossein Afshari,Mostafa Ehramianpour,Morteza Mohammadi 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.11
The dynamics of a pressure regulator valve have been studied using the through Bondgraph simulation technique. This valve consists of several elements that can transmit, transform, store, and consume hydraulic energy. The governing equations of the system have been derived from the dynamic model. In solving system equations numerically, various pressure-flow characteristics across the regulator ports and orifices have been taken into consideration. This simulation study identifies some critical parameters that have significant effects on the transient response of the system. The results have been obtained using the MATLAB-SIMULINK environment. The main advantage of the proposed methodology is its ability to model the nonlinear behavior of the hydraulic resistance of system elements as a function of the fluid flow rate.
An analytical guidance law of planetary landing mission by minimizing the control effort expenditure
Hamed Hossein Afshari,Alireza Basohbat Novinzadeh,Jafar Roshanian 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.12
An optimal trajectory design of a module for the planetary landing problem is achieved by minimizing the control effort expenditure. Using the calculus of variations theorem, the control variable is expressed as a function of costate variables, and the problem is converted into a two-point boundary-value problem. To solve this problem, the performance measure is approximated by employing a trigonometric series and subsequently, the optimal control and state trajectories are determined. To validate the accuracy of the proposed solution, a numerical method of the steepest descent is utilized. The main objective of this paper is to present a novel analytic guidance law of the planetary landing mission by optimizing the control effort expenditure. Finally, an example of a lunar landing mission is demonstrated to examine the results of this solution in practical situations.