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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...
Budgeted experiment design for causal structure learning
, Article 35th International Conference on Machine Learning, ICML 2018, 10 July 2018 through 15 July 2018 ; Volume 4 , 2018 , Pages 2788-2801 ; 9781510867963 (ISBN) ; Salehkaleybar, S ; Kiyavash, N ; Bareinboim, E ; Sharif University of Technology
International Machine Learning Society (IMLS)
2018
Abstract
We study the problem of causal structure learning when the experimenter is limited to perform at most k non-adaptive experiments of size 1. We formulate the problem of finding the best intervention target set as an optimization problem, which aims to maximize the average number of edges whose directions are resolved. We prove that the corresponding objective function is submodular and a greedy algorithm suffices to achieve (1 - approximation of the optimal value. We further present an accelerated variant of the greedy algorithm, which can lead to orders of magnitude performance speedup. We validate our proposed approach on synthetic and real graphs. The results show that compared to the...
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...
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...
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...
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...
Concurrent project scheduling and material planning: a genetic algorithm approach
, Article Scientia Iranica ; Volume 16, Issue 2 E , 2009 , Pages 91-99 ; 10263098 (ISSN) ; Shadrokh, S ; Hassanzadeh, F ; Sharif University of Technology
Abstract
Scheduling projects incorporated with materials ordering results in a more realistic problem. This paper deals with the combined problem of project scheduling and material ordering. The purpose of this paper is to minimize the total cost of this problem by determining the optimal values of activity duration, activity finish time and the material ordering schedule subject to constraints. We employ a genetic algorithm approach to solve it. Elements of the algorithm, such as chromosome structure, unfitness function, crossover, mutation and local search operations are explained. The results of the experimentation are quite satisfactory
An integrated vendor-buyer cooperative model under stochastic supply lead-time
, Article International Journal of Advanced Manufacturing Technology ; Volume 41, Issue 9-10 , 2009 , Pages 1043-1050 ; 02683768 (ISSN) ; Akbari Jokar, M. R ; Sharif University of Technology
2009
Abstract
This paper presents a single-vendor, single-buyer integrated inventory model. We relax the assumption of deterministic lead-time in the hitherto existing joint economic lot sizing (JELS) models and analyze the problem where the buyer lead-time is a stochastic variable. Moreover, we consider the situation in which shortage is allowed. The vendor produces the product in batches and periodically delivers final goods at a fixed lot size to the customer, who has a constant demand rate. The proposed model, based on the integrated expected total relevant costs of both buyer and vendor finds out optimal values of reorder point, order quantity, and number of shipments, using a solution procedure....
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...
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...
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...
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...
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...
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...
Different optimization criteria for vehicle seat suspension control: Position versus acceleration
, Article Proceedings of the ASME Design Engineering Technical Conference, 30 August 2009 through 2 September 2009, San Diego, CA ; Volume 6 , 2009 , Pages 1053-1059 ; 9780791849033 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
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...
Model predictive control versus traditional proportional delay differentiation algorithms
, Article Canadian Journal of Electrical and Computer Engineering ; Volume 34, Issue 1 , 2009 , Pages 3-9 ; 08408688 (ISSN) ; Taheri, H ; Haeri, M ; Sharif University of Technology
Abstract
An approximated quadratic programming optimization is proposed to determine a model predictive controller to guarantee end-to-end delay in the DiffServ architecture. The proposed algorithm, called the suboptimal model predictive control scheduler (SMPCS), regulates the service rates of aggregated traffic classes dynamically, such that some constraints on proportional or absolute delay can be guaranteed. This paper investigates SMPCS complexity and its implementation problems in high-speed routers. The main problem of model predictive control (and one which has limited its use to slow processes) is its complexity. Optimization is the most computationally complex part in a model predictive...
Friction damper for vibration control in offshore steel jacket platforms
, Article Journal of Constructional Steel Research ; Volume 65, Issue 1 , 2009 , Pages 180-187 ; 0143974X (ISSN) ; Gholizad, A ; Sharif University of Technology
2009
Abstract
The performance of friction dampers to mitigate the wave-induced vibrations in jacket-type offshore platforms has been investigated in this study. Due to the random nature of ocean waves, a full stochastic analysis method has been used to evaluate the response of the structures equipped with these devices. A stochastic linearization technique has also been used to take the nonlinear behavior of these hysteretic dampers into account. At last, the developed mathematical formulation has been applied to evaluate the response of realistic models, and to find out the optimal values for the adjustable parameters of the friction dampers to dissipate the wave induced vibrations of the platforms. ©...