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Arash Kiyoumarsi,Mohhamad Ataei,Rahmatollah Hooshmand,Arash Dehestani Kolagar 대한전기학회 2010 Journal of Electrical Engineering & Technology Vol.5 No.1
Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.
Kiyoumarsi, Arash,Ataei, Mohhamad,Hooshmand, Rahmat-Allah,Kolagar, Arash Dehestani The Korean Institute of Electrical Engineers 2010 Journal of Electrical Engineering & Technology Vol.5 No.1
Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.
Arash Poorsattar Bejeh Mir,Morvarid Poorsattar Bejeh Mir 대한구강악안면방사선학회 2012 Imaging Science in Dentistry Vol.42 No.3
Purpose: ANSI/ADA has established standards for adequate radiopacity. This study was aimed to assess the changes in radiopacity of composite resins according to various tube-target distances and exposure times. Materials and Methods: Five 1-mm thick samples of Filtek P60 and Clearfil composite resins were prepared and exposed with six tube-target distance/exposure time setups (i.e., 40 cm, 0.2 seconds; 30 cm, 0.2 seconds; 30 cm, 0.16 seconds, 30 cm, 0.12 seconds; 15 cm, 0.2 seconds; 15 cm, 0.12 seconds) performing at 70 kVp and 7 mA along with a 12-step aluminum stepwedge (1 mm incremental steps) using a PSP digital sensor. Thereafter, the radiopacities measured with Digora for Windows software 2.5 were converted to absorbencies (i.e., A=-log (1-G/255)), where A is the absorbency and G is the measured gray scale). Furthermore, the linear regression model of aluminum thickness and absorbency was developed and used to convert the radiopacity of dental materials to the equivalent aluminum thickness. In addition, all calculations were compared with those obtained from a modified 3-step stepwedge (i.e., using data for the 2nd, 5th, and 8th steps). Results: The radiopacities of the composite resins differed significantly with various setups (p⁄0.001) and between the materials (p⁄0.001). The best predicted model was obtained for the 30 cm 0.2 seconds setup (R2=0.999). Data from the reduced modified stepwedge was remarkable and comparable with the 12-step stepwedge. Conclusion: Within the limits of the present study, our findings support that various setups might influence the radiopacity of dental materials on digital radiographs.
Modeling the permeability of heterogeneous oil reservoirs using a robust method
Arash Kamari,Farzaneh Moeini,Mohammad-Javad Shamsoddini-Moghadam,Seyed-Ali Hosseini,Amir H. Mohammadi,Abdolhossein Hemmati-Sarapardeh 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.2
Permeability as a fundamental reservoir property plays a key role in reserve estimation, numerical reservoir simulation, reservoir engineering calculations, drilling planning, and mapping reservoir quality. In heterogeneous reservoir, due to complexity, natural heterogeneity, non-uniformity, and non-linearity in parameters, prediction of permeability is not straightforward. To ease this problem, a novel mathematical robust model has been proposed to predict the permeability in heterogeneous carbonate reservoirs. To this end, a fairly new soft computing method, namely least square support vector machine (LSSVM) modeling optimized with coupled simulated annealing (CSA) optimization technique was utilized. Statistical and graphical error analyses have been employed separately to evaluate the accuracy and reliability of the proposed model. Furthermore, this model performance has been compared with a newly developed multilayer perceptron artificial neural network (MLP-ANN) model. The obtained results have shown the more robustness, efficiency and reliability of the proposed CSA-LSSVM model in comparison with the developed MLP-ANN model for the prediction of permeability in heterogeneous carbonate reservoirs. Estimations were found to be within acceptable agreement with the actual field data of permeability, with a root mean square error of approximately 0.42 for CSA-LSSVM model in testing phase, and a R-squared value of 0.98. Additionally, these error parameters for MLP-ANN are 0.68 and 0.89 in testing stage, respectively.
Arash Ghorbani-Choghamarani,Maryam Hajjami,Mohammad Ali Zolfigol* 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.12
Sodium periodate (NaIO4) and potassium iodide (KI) in aqueous ammonia has been used for the one-pot synthesis of nitriles from the corresponding aldehydes and alcohols in moderate to good yield. This transformation, proceeds via an in situ oxidation- imination-aldimine oxidation sequence.
Arash Fakharnezhad,Peyman Keshavarz 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.34 No.-
In this study, hollow fiber membrane contactors have been applied for gas dehumidification using triethyleneglycol as absorbent. The effects of gas and liquid flow rates, inlet concentration of tri-ethyleneglycol and flow direction on dehumidification efficiency have been investigated. The results reveal thatmembrane contactors can remove water vapor very effectively using tri-ethylene glycol, and very lowwater dew point as low as 50 8C can be achieved. It also shows that liquid phase is not the limitingresistance in this system, as a result of very high solubility of water in tri-ethylene glycol.