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Kinetically Investigation of Catalyst Deactivation in Catalytic Reforming Process
, M.Sc. Thesis Sharif University of Technology ; Baghalha, Morteza (Supervisor) ; Taghikhani, Vahid (Supervisor)
Abstract
Catalytic reforming of naphtha is an important process to convert of low-octane number naphtha into high-octane number gasoline. Deactivation of catalysts, is the major problem for this process. In this study, catalytic reforming unit of Tabriz oil refinery investigated, and Smith’s kinetic model used for modeling. Also, several models presented for activity of catalysts. To find the parameters of presented models, the difference between the calculated and experimental values of outlet temperatures of each bed and aromatics, paraffin and naphthene yields simultaneously must be minimized. Using Genetic Algorithm Toolbox in Matlab software, optimization was performed and results indicated that...
Reducing speech recognition costs: By compressing the input data
, Article IS'2012 - 2012 6th IEEE International Conference Intelligent Systems, Proceedings ; 2012 , Pages 102-107 ; 9781467327824 (ISBN) ; Shouraki, S. B ; Sharif University of Technology
2012
Abstract
One of the key constraints of using embedded speech recognition modules is the required computational power. To decrease this requirement, we propose an algorithm that clusters the speech signal before passing it to the recognition units. The algorithm is based on agglomerative clustering and produces a sequence of compressed frames, optimized for recognition. Our experimental results indicate that the proposed method presents a frame rate with average 40 frames per second on medium to large vocabulary isolated word recognition tasks without loss of recognition accuracy which result in up to 60% faster recognition in compare to usual 100 fps fixed frame rate sampling. This value is quite...
Smart fault classification in HVDC system based on optimal probabilistic neural networks
, Article 2012 2nd Iranian Conference on Smart Grids, ICSG 2012, 23 May 2012 through 24 May 2012 ; May , 2012 , Page(s): 1 - 4 ; 9781467313995 (ISBN) ; Mobarake, A. S ; Gharehpetian, G. B ; Fathi, S. H ; Sharif University of Technology
IEEE
2012
Abstract
Optimal probabilistic neural network-based method has been porposed in this paper to identify different types of fault in high voltage direct current (HVDC) system. Probabilistic neural network is a type of artificial neural networks capable of approximating the optimal classifier. The particle swarm optimization is porposed to achive an optimal value of smoothing factor for PNN which is an important parameter. The main purpose of this paper is fast and accurate fault classification, for this purpose simple HVDC system has been evaluated under various fault type condition to examine the efficacy of the proposed method. The performance of the proposed method is investigated using...
Bioleaching kinetics of a spent refinery catalyst using Aspergillus niger at optimal conditions
, Article Biochemical Engineering Journal ; Volume 67 , 2012 , Pages 208-217 ; 1369703X (ISSN) ; Mousavi, S. M ; Yaghmaei, S ; Barati, M ; Sharif University of Technology
Elsevier
2012
Abstract
The kinetics of bioleaching of Mo, Ni, and Al from spent hydrocracking catalyst, using Aspergillus niger was studied. The four most effective bioleaching variables were selected in accordance with the Plackett-Burman design and were further optimized via central composite design (CCD). The optimal values of the variables for maximum multi-metal bioleaching were as follows: particle size 150-212. μm, sucrose 93.8. g/L, pulp density 3%. w/v, and pH 7. The maximum metal recoveries corresponding to these conditions were 99.5 ± 0.4% Mo, 45.8 ± 1.2% Ni, and 13.9 ± 0.1% Al. The relatively low Ni extraction was attributed to the precipitation of Ni in the presence of oxalic acid. Under the optimal...
Application of the variational iteration method for nonlinear free vibration of conservative oscillators
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 513-518 ; 10263098 (ISSN) ; Fattahi, M ; Amjadian, A ; Sharif University of Technology
2012
Abstract
In this paper, an analytical solution for the nonlinear free vibration of a conservative oscillator is presented. The nonlinear governing equation is solved by employing the Variational Iteration Method (VIM). This method is based on the use of Lagrange multipliers for identification of optimal values of parameters in a function. Obtained results reveal that the proposed method is very effective, simple and exact. In the present investigation, the results of this method are compared with those of the Homotopy Analysis Method (HAM), as well as those predicted by the Runge-Kutta method. The excellent accuracy of the obtained results is demonstrated by comparing them with available analytical...
Enhancement of bioleaching of a spent Ni/Mo hydroprocessing catalyst by Penicillium simplicissimum
, Article Separation and Purification Technology ; Volume 80, Issue 3 , August , 2011 , Pages 566-576 ; 13835866 (ISSN) ; Mousavi, S. M ; Yaghmaei, S ; Sharif University of Technology
2011
Abstract
Statistically based experimental designs were applied to screen and optimize the bioleaching of spent hydrocracking catalyst by Penicillium simplicissimum. Eleven factors were examined for their significance on bioleaching using a Plackett-Burman factorial design. Four significant variables (pulp density, sucrose, NaNO3, and yeast extract concentrations) were selected for the optimization studies. The combined effect of these variables on metal bioleaching was studied using a central composite design (CCD). Second-order polynomials were established to identify the relationship between the recovery percent of the metals and the four significant variables. The optimal values of the variables...
On optimal replacement-repair policy for multi-state deteriorating products under renewing free replacement warranty
, Article Computers and Mathematics with Applications ; Volume 61, Issue 4 , February , 2011 , Pages 840-850 ; 08981221 (ISSN) ; Chukova, S ; Mahlooji, H ; Sharif University of Technology
2011
Abstract
In this paper a replacement-repair model is developed to study a renewing free replacement warranty (RFRW) for a class of multi-state deteriorating repairable products. After a replacement, the product warranty is renewed. Two parameters affect the manufacturer's decision to minimally repair or replace a failed item: the product deterioration level at the time of failure and the remaining warranty time. We derive an optimal replacement-repair policy to minimise the expected warranty servicing cost per item sold. In the case of a product with two different working states, we are able to explicitly find the optimal values of the replacement-repair parameters using the Adomian decomposition...
Characterization of nanocrystalline CuCo2 O4 spinel prepared by sol–gel technique applicable to the SOFC interconnect coating
,
Article
Applied Physics A: Materials Science and Processing
;
Volume 119, Issue 2
,
May
,
2015
,
Pages 727-734
;
09478396 (ISSN)
; Askari, M
; Ghorbanzadeh, M
;
Sharif University of Technology
Springer Verlag
2015
Abstract
CuCo2 O4 spinel nanopowders were synthesized by sol–gel method. The optimal values of pH and molar ratio of citric acid to metal ions (RC), and the influence of the calcination temperature and time were investigated. As-prepared materials were characterized by XRD, TGA, DSC, FE-SEM and electrical and coefficient of thermal expansion (CTE) measurements. It was found that pH = 4.5 and RC = 1 are the optimum conditions to produce pure CuCo2 O4 nanopowders. The electrical conductivity was increased remarkably from 15.2 to 27.5 S cm−1 with an increase in temperature from 500 to 800 °C. Over the temperature range of 25–800 °C, the CTE of...
ON-line learning of a Persian spoken dialogue system using real training data
, Article 10th International Conference on Information Sciences, Signal Processing and their Applications, ISSPA 2010, 10 May 2010 through 13 May 2010 ; May , 2010 , Pages 133-136 ; 9781424471676 (ISBN) ; Sameti, H ; Setareh, H ; Sharif University of Technology
2010
Abstract
The first spoken dialogue system is developed for the Persian language is introduced. This is a ticket reservation system with Persian ASR and NLU modules. The focus of the paper is on learning the dialogue management module. In this work, real on-line training data are used during the learning process. For on-line learning, the effect of the variations of discount factor (γ) on the learning speed is investigated as the second contribution of the research. The optimal values for γ were found and the variation pattern of the action-value function (Q) in the learning process was obtained. A probabilistic policy for selecting actions is used in this work for the first time instead of greedy...
A framework for compromising between power generation cost and power system security in regulated market using MO-OPF
, Article EPEC 2010 - IEEE Electrical Power and Energy Conference: "Sustainable Energy for an Intelligent Grid", 25 August 2010 through 27 August 2010 ; 2010 ; 9781424481880 (ISBN) ; Sotoodeh, P ; Khosravi, H ; Pishvaie, M ; Sharif University of Technology
Abstract
Transmission line congestion in electricity market is lead to increase the energy cost and change in local marginal prices. So, it is probable that the market power is manifested. Market power may prevent the full competition in Electricity Market. Moreover, in this condition, with operating of power system in its boundary conditions, the system may be damaged and the security of the system may be disturbed. On the other hand, decreasing the line flows from their optimal value, cost and consequently, price of energy are increased. So, there is need to have a compromise between the line flow decrease and the cost those impose. In this paper, a framework for compromising between social cost...
Thermodynamic modeling and optimization of cogeneration heat and power system using Evolutionary algorithm (Genetic Algorithm)
, Article Proceedings of the ASME Turbo Expo, 14 June 2010 through 18 June 2010 ; Volume 3 , 2010 , Pages 745-752 ; 9780791843987 (ISBN) ; Karrabi, H ; Ghadami, S ; Barzegar, H ; Rasoulipour, S ; Kebriyaie, M ; Sharif University of Technology
Abstract
A gas-turbine cogeneration system with a regenerative air preheater and a single-pressure exhaust gas boiler serves as an example for application of CHP Plant. This CHP plant which can provide 30 MW of electric power and 14kg/s saturated steam at 20 bars. The plant is comprised of a gas turbine, air compressor, combustion chamber, and air pre-heater as well as a heat recovery steam generator (HRSG). The design Parameters of the plant, were chosen as: compressor pressure ratio (rc), compressor isentropic efficiency (ηac), gas turbine isentropic efficiency (ηgt), combustion chamber inlet temperature (T3), and turbine inlet temperature (T4). In order to optimally find the design parameters a...
New solutions of LR fuzzy linear systems using ranking functions and ABS algorithms
, Article Applied Mathematical Modelling ; Volume 34, Issue 11 , November , 2010 , Pages 3363-3375 ; 0307904X (ISSN) ; Mahdavi Amiri, N ; Sharif University of Technology
2010
Abstract
We propose an approach for computing the general compromised solution of an LR fuzzy linear system by use of a ranking function when the coefficient matrix is a crisp m×n matrix. The solution is so that mean values of a compromised solution satisfies the corresponding crisp linear system. We show that if the corresponding crisp system is incompatible, then the fuzzy linear system lacks any solution. Otherwise, we solve a constrained least squares problem to compute a compromised solution. If the optimal value of the constrained least squares problem is zero, then we obtain the LR solution, namely the exact solution, of the system with respect to a ranking function. On the other hand, if the...
A practical model for transfer optimization in a transit network: Model formulations and solutions
, Article Transportation Research Part A: Policy and Practice ; Volume 44, Issue 6 , 2010 , Pages 377-389 ; 09658564 (ISSN) ; Khani, A ; Sharif University of Technology
2010
Abstract
This paper studies the transit network scheduling problem and aims to minimize the waiting time at transfer stations. First, the problem is formulated as a mixed integer programming model that gives the departure times of vehicles in lines so that passengers can transfer between lines at transfer stations with minimum waiting times. Then, the model is expanded to a second model by considering the extra stopping time of vehicles at transfer stations as a new variable set. By calculating the optimal values for these variables, transfers can be better performed. The sizes of the models, compared with the existing models, are small enough that the models can be solved for small- and medium-sized...
A parameter-tuned genetic algorithm to solve multi-product economic production quantity model with defective items, rework, and constrained space
, Article International Journal of Advanced Manufacturing Technology ; Volume 49, Issue 5-8 , July , 2010 , Pages 827-837 ; 02683768 (ISSN) ; Akhavan Niaki, S.T ; Mirhosseyni, S. S ; Sharif University of Technology
2010
Abstract
The economic production quantity (EPQ) model is often used in manufacturing environments to assist firms in determining the optimal production lot size that minimizes the overall production-inventory costs. While there are some unrealistic assumptions in the EPQ model that limit its real-world applications, in this research, some of these assumptions such as (1) infinite availability of warehouse space, (2) all of the produced items being perfect, and (3) the existence of one product type are relaxed. In other words, we develop a multi-product EPQ model in which there are some imperfect items of different product types being produced such that reworks are allowed and that there is a...
A queueing approach to production-inventory planning for supply chain with uncertain demands: Case study of PAKSHOO Chemicals Company
, Article Journal of Manufacturing Systems ; Volume 29, Issue 2-3 , July , 2010 , Pages 55-62 ; 02786125 (ISSN) ; Modarres, M ; Ghasemzadeh, F ; Fathi, M ; Sharif University of Technology
2010
Abstract
In some industries such as the consumable product industry because of small differences between products made by various companies, customer loyalty is directly related to the availability of products required at that time. In other words, in such industries demand cannot be backlogged but can be totally or partly lost. So companies of this group use make-to-stock (MTS) production policy. Therefore, in these supply chains, final product warehouses play a very important role, which will be highlighted by considering the demand uncertainty as it happens in real world, especially in the consumable product industries in which demand easily varies according to the customer's taste variation,...
Different optimization criteria for vehicle seat suspension control: Position versus acceleration
, Article Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference 2009, DETC2009, 30 August 2009 through 2 September 2009 ; Volume 6 , August–September , 2010 , Pages 1053-1059 ; 9780791849033 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2010
Abstract
This paper addresses the effect of different optimization criteria for the control purpose of vehicle suspension. In the present study, active vibration control system for a 5 degree-of-freedom (DoF) pitch-plane suspension model with bounce and pitch motions is investigated. In the proposed vehicle model, the impact of the wheel-axle-brake assemblies' masses is also considered. The developed model is controlled using a fuzzy logic controller (FLC) to minimize the vibration of the driver's seat. The controller is designed to control the applied force to the seat. Furthermore, in order to determine the optimal value of fuzzy system parameters, genetic algorithm (GA) optimization search is used...
General bounds for the optimal value of retailers' reorder point in a two-level inventory control system with and without information sharing
, Article International Journal of Advanced Manufacturing Technology ; Volume 48, Issue 1-4 , April , 2010 , Pages 383-393 ; 02683768 (ISSN) ; Eshragh Jahromi, A ; Akhavan Niaki, S ; Sharif University of Technology
2010
Abstract
In this study, an inventory system consisting of a single product, one supplier, and multiple identical retailers is considered. Each retailer replenishes inventory from the supplier according to the well known (R,Q) policy. Transit times are constant and retailers face independent Poisson demand. The supplier utilizing the retailers' information in decision making for replenishment policy with a given order size starts with m initial batches (of size Q) and places an order in a batch of size Q to an outside source when a new order is placed. In this inventory system, excess demand is backordered, delayed orders are satisfied on a first-come first-serve basis, and no partial shipment is...
Application of ozone treatment and pinch technology in cooling water systems design for water and energy conservation
, Article International Journal of Energy Research ; Volume 34, Issue 6 , 2010 , Pages 494-506 ; 0363907X (ISSN) ; Gharaie, M ; Parand, R ; Panjeshahi, E ; Sharif University of Technology
2010
Abstract
Re-circulating cooling water systems offer the means to remove heat from a wide variety of industrial processes that generate excess heat. Such systems consist of a cooling tower and a heat-exchanger network that conventionally has a parallel configuration. However, reuse of water between different cooling duties allows cooling water networks to be designed in a series arrangement. This results in performance improvement and increased cooling tower capacity. In addition, by the integration of ozone treatment into the cooling tower, the cycle of concentration can be increased. The ozone treatment also dramatically reduces the blow-down that, in turn, is environmentally constructive. In this...
On the prediction of CO2 corrosion in petroleum industry
, Article Journal of Supercritical Fluids ; Volume 117 , 2016 , Pages 108-112 ; 08968446 (ISSN) ; Ghaderi Ardakani, A ; Niknejad Khomami, M ; Karimi Malekabadi, F ; Rasaei, M. R ; Mohammadi, A. H ; Sharif University of Technology
Elsevier B.V
2016
Abstract
In this communication, a hybrid model based on Least Square Support Vector Machine (LSSVM) was constructed to predict CO2 corrosion rate. The input parameters of the model are temperature, CO2 partial pressure, flow velocity and pH. The data used for training and testing of the developed model are 612 and 109 data, respectively. In order to benefit LSSVM from Kernel learning, we compared three kernel functions to select the most efficient one. Furthermore, Coupled Simulated Annealing (CSA) optimization technique was adapted to choose the best optimal values of the model parameters. The results elucidate that Gaussian Kernel functions is the desired function which can afford high accuracy for...
Optimizing a joint economic lot sizing problem with price-sensitive demand
, Article Scientia Iranica ; Volume 16, Issue 2 E , 2009 , Pages 159-164 ; 10263098 (ISSN) ; Sheikh Sajadieh, M ; Sharif University of Technology
Abstract
This paper considers the problem of a vendor-buyer integrated production-inventory model. The vendor manufactures the item at a finite rate and delivers the final goods at a lot-for-lot shipment policy to the buyer. We relax the assumption of uniform demand in the hitherto existing joint economic lot sizing models and analyze the problem where the end customer demand is price-sensitive. The relation between demand and price is considered to be linear. The model proposed, based on the integrated expected total relevant profits of both buyer and vendor, finds out the optimal values of order quantity and mark-up percentage, using an analytical approach. Some numerical examples are also used to...