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.

Experimental and Numerical Study of a Seismic Rotating Mass Damper (RMD) in an Isolated Floor

Afshin Kalantari,Reihane Shafie Panah 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4

Negative stiffness has shown a capable characteristic in reduction of seismic response of structures. In this paper a passive Rotating Mass Damper (RMD) with negative stiffness characteristic, which was conceptually introduced in an earlier study, has been employed experimentally and numerically on an isolated floor to protect the building content during strong ground motions. The equipment was assumed as a rigid block on the isolated floor. The RMD devices force results indicate the negative stiffness characteristic of the damper. It was also observed that the RMD could increase the natural period of the system up to 50 percent without increasing the mass or reducing the stiffness. A numerical model of a seven storey building was employed to investigate the seismic response of the isolation floor in fourth storey. Two RMD models with different specifications and a viscous damper providing 10 percent of critical damping were applied in the study. Seven ground motion records were selected from PEER ground motion database. The time history analysis results indicate that RMD dampers show acceptable performance in terms of reducing both acceleration up to 40% and displacement responses up to 68% simultaneously in comparison with the viscous damper under the applied ground motions. The model was also analyzed employing seven artificial seismic waves. The results in this part also show the capability of the damper model in generating negative stiffness characteristics and a successful performance during excitation.

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.

Singular clean rings

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.

Computer Forensics Approach Based on Autonomous Intelligent Multi-Agent System

Afshin Jahanbin,Ahmad Ghafarian,Seyed Amin Hosseeini Seno,Samane Nikookar 보안공학연구지원센터 2013 International Journal of Database Theory and Appli Vol.6 No.5

Reliability assessment of concrete bridges subject to corrosion-induced cracks during life cycle using artificial neural networks

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.

Simulation of phenol biodegradation by Ralstonia eutropha in a packed-bed bioreactor with batch recycle mode using CFD technique

Afshin Amani,Elham Jalilnejad,Seyyed Mohammad Mousavi 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.59 No.-

Packed-bed reactors are widely used in biological treatment processes. The complete simulation of the reactions and concentration profiles of the reactors, which are necessary for a successful reactor design, operation, and scale-up, are now possible due to extensive improvements of numerical methods and computational power. In the present work, phenol biodegradation was studied in a packed-bed bioreactor operating in the recycling batch mode using the computational fluid dynamics (CFD) method. A transient comprehensive 3D CFD was developed to simulate the dynamic behavior of batch phenol biodegradation by Ralstonia eutropha in a Kissiris-immobilized cell bioreactor. The model combined the porous medium CFD model with two kinetic equations, namely the Haldane and Luong inhibition models, to consider the inhibitory effect of phenol at high concentrations. The simulation results of the phenol concentration variation in different initial phenol concentrations (2.13, 4.26, 6.39, and 8.52 mol/m3) and recirculation flow rates (10, 25, and 40 ml/min) were validated against experimental data. Despite the assumptions, the simulation results create an acceptable assurance of the simulation precision with good agreement with experimental data.

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.

Springback Investigation of a Thick-Walled Tube Under Combined Torsion-Bending and Internal Pressure by Using Continuum Damage Mechanics

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.

Effect of Earthquake Disruptions of Freight Transportation in A Megacity: Case Study for The Los Angeles Area

Afshin Abadi,Petros Ioannou,James E. Moore II,Jean-Pierre Bardet,박지영,조성빈 아시아기술혁신학회 2022 Asian Journal of Innovation and Policy Vol.11 No.1

Many megacities are exposed to natural hazards such as earthquakes, and when located in coastal regions, are also vulnerable to hurricanes and tsunamis. The physical infrastructures of transportation systems in megacities have become so complicated that very few organizations can understand their response to extreme events such as earthquakes and can effectively mitigate subsequent economic downfalls. The technological advances made in recent years to support these complex systems have not grown as fast as the rapid demand on these systems burdened by population shift toward megacities. The objective of this paper is to examine the risks imposed on and recoveries of transportation systems in megacities as the result of extreme events such as earthquake. First, the physical damage to transportation infrastructure, loss of the transportation system performance, and the corresponding economic loss from disruptions to passenger and freight traffic is evaluated. Then, traffic flows are rerouted to reduce vehicles’ delay due to earthquake using a microscopic traffic flow simulator with an optimization model and macroscopic terminal simulator. Finally, the economic impact of earthquake is estimated nationwide. Southern California is regarded as the region of study. The results demonstrate the effectiveness of the integrated model and provide what and how to prepare innovative resilience policies of urban infrastructure for a natural disaster occurrence.