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Combination of inertial focusing and magnetoporetic separation in a novel microdevice
Afshin Shiriny,Morteza Bayareh,Afshin Ahmadi Nadooshan 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.8
Separation of microparticles is of great importance in diagnostic, chemical, and biological analysis, as well as food processing and environmental assessments. In the present work, a novel microfluidic device is designed to focus microparticles based on inertial and magnetophoretic impacts. Three permanent magnets are mounted in the vicinity of the microchannel to separate the diamagnetic particles suspended in a ferrofluid by applying a negative magnetophoretic force. Polystyrene particles with three sizes of 5, 10, and 15 m are separated from each other using the proposed device with 100% separation efficiency. The results show that high purity of particle collection can be achieved using Halbach array of magnets at Reynolds numbers of 100 and 110. The influence of inlet flow velocity, magnets’ configuration, and their distance from the microchannel is investigated and the optimal situations are determined.
A developed model predictive control scheme for vibration attenuation of building structures
Afshin Bahrami Rad,Mahdi Nouri,Javad Katebi,Seyyed Arash Mousavi Ghasemi 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.4
Model predictive control (MPC) is an optimal control algorithm in which the current control action is obtained by solving an optimization problem in the presence of hard and soft constraints in the finite time horizons sequentially. In most cases, neglecting the effects of the external loads in predicting the future responses of the structures lead to inaccurate control action. Therefore, it could be beneficial to consider the effects of external loads in the future within the MPC to improve its accuracy. In this paper, a developed model predictive control (DMPC) scheme is introduced. For this purpose, a forecasting seismic excitation model is formulated by two sequential autoregressive (AR) models. One of those estimates the future output of the seismic excitation and the second one enhances the estimation accuracy. Then, the efficiency of the presented approach is demonstrated by the numerical study of two benchmark buildings equipped with an active tuned mass damper (ATMD). The performance of the proposed MPC is finally compared with the conventional and ideal MPCs. The numerical outputs prove the competency and higher conformity of the proposed MPC with the ideal one almost in all of the cases. Twelve benchmark performance indices are also utilized for determining the superiority of the method. The average conformity values for all of the performance indices for the proposed method in the three- and nine-story buildings are by up to 17.75% and 9% more than the values in conventional one, respectively.
Adsorption of hexavalent chromium by metal organic frameworks from aqueous solution
Afshin Maleki,주상우,Bagher Hayati,Maryam Naghizadeh 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.28 No.-
A metal–organic frameworks (MOFs) based on copper-benzenetricarboxylates is applied to theadsorption of hexavalent chromium from aqueous solution. Characterization of Cu-BTC was achieved byXRD, SEM micrographs, nitrogen adsorption–desorption analysis and FT-IR spectra. The kineticcharacteristics and thermodynamic parameters are also analyzed. The experimental isotherm data areanalyzed using Langmuir and Freundlich isotherm equations. Thermodynamic parameters arecalculated by the Gibbs free energy function, confirming that the adsorption process was spontaneousand accompanied by exothermic. The maximum removal has been achieved at pH = 7.0. Possiblemechanism and adsorption behavior of hexavalent chromium onto Cu-BTC are investigated.
Afshin Amini,Babak Amini,Afsaneh Nejadzadeh,Habib Sharif 대한수학회 2018 대한수학회지 Vol.55 No.5
In this paper, we define right singular clean rings as rings in which every element can be written as a sum of a right singular element and an idempotent. Several properties of these rings are investigated. It is shown that for a ring $R$, being singular clean is not left-right symmetric. Also the relations between (nil) clean rings and right singular clean rings are considered. Some examples of right singular clean rings have been constructed by a given one. Finally, uniquely right singular clean rings and weakly right singular clean rings are also studied.
Afshin Dehghani Kiadehi,Majid Taghizadeh,Mohammad Darzinezhad Rami 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.81 No.-
In this study, palladium composite membranes were fabricated on porous stainless steel (PSS) supports using silicoaluminophosphate (SAPO) zeolite (SAPO-34) as a diffusion barrier and substrate modifier. The vacuum-assisted seeding and secondary growth method was used to coat the SAPO-34 zeolite layer on the PSS substrates. The morphologies and microstructures of the membranes were analyzed by AFM, XRD, BET, ICP–AES, FESEM and EDX techniques. The effect of crystallization time (24, 48 and 72 h) on the morphology and quality of SAPO-34 modified supports was studied. A continuous palladium layer with a thickness of about 9 μm was deposited on the SAPO-34 modified PSS support (72 h crystallization time) by electroless plating (ELP) route. The hydrogen permeation tests were carried out in the feed pressures range of 2–4 bar and various temperatures (623, 673 and 723 K). The values of the hydrogen permeance and ideal selectivity of H2/N2 for the PSM3 membrane were achieved 7.1 × 10–7 mol m–2 s–1 Pa–1 and 866, respectively a feed pressure of 2 bar and 723 K. In addition, the PSM3 membrane showed perfect stability during 260 h hydrogen permeation experiment at a feed pressure of 2 bar and 623 K.
Comparison of ARIMA and NNAR Models for Forecasting Water Treatment Plant's Influent Characteristics
Afshin Maleki,Simin Nasseri,Mehri Solaimany Aminabad,Mahdi Hadi 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.9
A reliable forecasting model for each Water Treatment Plant (WTP) influent characteristics is useful for controlling the plant's operation. In this paper Auto-Regressive Integrated Moving Average (ARIMA) and Neural Network Auto-Regressive (NNAR) modeling techniques were applied on a WTP's influent water characteristics time series to make some models for short-term period (to seven days ahead) forecasting. The ARIMA and NNAR models both provided acceptable generalization capability with R2s ranged from 0.44 to 0.91 and 0.45 to 0.92, respectively, for chloride and temperature. Although a more prediction performance was observed for NNAR in comparison with ARIMA for all studied series, the forecasting performance of models was further examined using Time Series Cross-Validation (TSCV) and Diebold-Mariano test. The results showed ARIMA is more accurate than NNAR for forecasting the horizon-daily values for CO2, Cl and Ca time-series. Therefore, despite of the good predictive performance of NNAR, ARIMA may still stands as better alternative for forecasting task of aforementioned series. Thus, as a general rule, not only the predictive performance using R2 statistic but also the forecasting performance of a model using TSCV, are need to be examined and compared for selecting an appropriate forecasting model for WTP's influent characteristics.
Afshin Firouzi,Alireza Rahai 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.1
Corrosion of RC bridge decks eventually leads to delamination, severe cracking and spalling of the concrete cover. This is a prevalent deterioration mechanism and demands for the most costly repair interventions during the service life of bridges worldwide. On the other hand, decisions for repairs are usually made whenever the extent of a limit crack width, reported in routine visual inspections, exceeds an acceptable threshold level. In this paper, while random fields are applied to account for spatial variation of governing parameters of the corrosion process, an analytical model is used to simulate the corrosion induced crack width. However when dealing with random fields, the Monte Carlo simulation is apparently an inefficient and time consuming method, hence the utility of neural networks as a surrogate in simulation is investigated and found very promising. The proposed method can be regarded as an invaluable tool in decision making concerning maintenance of bridges.
Afshin Farhadi,Amir Hosseini-Hooshyar,Ali Nayebi 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.6
The choice of material behavior models, as well as the forming procedures such as loadings and their sequences are essential in plastic flow and springback. In this study, the combined torsion and bending of a thick-walled tube under an internal pressure is simulated to predict bending and torsion springback. Continuum Damage Mechanics and the nonlinear kinematic hardening models are assumed and a numerical tool is developed to predict the springback analytically. The numerical model is verified by comparing the experimental results of simultaneous bending and torsion of a pure aluminum tube conducted by Wu et al. (Int J Mech Sci 131–132:191–204, 2017) with the numerical results. The experimental results of Sorour et al. (Thin-Walled Struct 144:106336, 2019), which studied the bending of a tube with internal pads, are also modelled with the present numerical model. The effects of loading sequences on the springback are also investigated.
Afshin Davoodi,Mahnaz Maddahfar,Majid Ramezani 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.22 No.-
In this work, In2S3 nanostructures have been successfully prepared via a simple wet chemistrymethod atroom temperature. By using mercaptoacetic acid (TGA) as a capping agent, solvent, and sulfide precursorwith different concentrations, In2S3 nanostructures were obtained. The effects of reaction time, reactiontemperature, and concentration of precursor on the morphology and the particle size was also studied. The as-prepared In2S3nanoparticles were characterized extensively by techniques like XRD, TEM, SEM,PL, and EDX. Photoluminescence study of the In2S3 nanoparticles displayed quantum confinementbehavior with band gap of 2.74 eV.