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    Adsorption and Conversion of Heavy Oil Asphaltene on Composite Nanostructures

    , M.Sc. Thesis Sharif University of Technology Torka Bidokhti, Mostafa (Author) ; Ghotbi, Siros (Supervisor) ; Khodadadi, Abbasali (Supervisor)
    Abstract
    The aim of this project was to upgrade and reduce viscosity of heavy oils by adsorbing of asphaltene on Ni-Mo/CB and converting it into lighter and more valuable gas and liquid compounds. Asphaltene has been extracted from a heavy crude oil sample of Soroush oil field in Iran. After adsorption, Asphaltene conversion to lighter components (gas/liquid) was studied through hydrocracking process. To prepare the support of catalyst, Carbon Black, initially a thermal treatment step under the argon gas atmosphere followed by acid-washing process was performed. Afterward, the catalysts was prepared through dry impregnation method. In order to activate catalyst for hydrocracking, the catalysts has... 

    A generalized multi-layer information hiding scheme using wet paper coding

    , Article 2014 11th International ISC Conference on Information Security and Cryptology, ISCISC 2014 ; 2014 , p. 210-213 Bidokhti, A ; Ghaemmaghami, S ; Sharif University of Technology
    2014
    Abstract
    Multi-layer schemes have been proposed for steganography. Also some authors have combined these methods with the idea of wet paper codes and gained higher embedding efficiency. This paper proposes a generalized multi-layer method for wet paper embedding. First, the cover bits are divided into blocks and, by combining these bits in groups of 3, a pyramid is formed. Next, the secret message is embedded through a layer-by-layer procedure. The proposed method has higher embedding efficiency in some cases and provides more flexibility for choosing the embedding payload, especially in lower payload conditions  

    Detection of regional copy/move forgery in MPEG videos using optical flow

    , Article Proceedings of the International Symposium on Artificial Intelligence and Signal Processing, AISP 2015, 3 March 2015 through 5 March 2015 ; March , 2015 , Pages 13-17 ; 9781479988174 (ISBN) Bidokhti, A ; Ghaemmaghami, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    With rapid proliferation of affordable video capturing devices and state-of-the-art video editing software tools, it is now easier than ever to manipulate video contents. In this paper a passive method for copy/move video forgery detection in MPEG videos is proposed. The method first divides each video frame into suspicious and apparently innocent parts. Subsequently, an optical flow coefficient is computed from each part. Forgeries are located when an unusual trend in the optical flow coefficient of the suspicious object is detected. Experiments on a set of forged and original sequences validate the justifications made by the proposed method  

    Compound short- and long-term memory for memory augmented neural networks

    , Article Engineering Applications of Artificial Intelligence ; Volume 116 , 2022 ; 09521976 (ISSN) Bidokhti, A ; Ghaemmaghami, S ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Adding memory to artificial intelligence systems in an effective way has been addressed by researchers for many years. Recurrent neural networks and long short-term memories (LSTMs), among other neural network systems, have some inherent memory capabilities. Recently, in memory augmented neural networks, such as neural Turing machine (NTM) and its variants, a separate memory module is implemented, which can be accessed via read and write heads. Despite its capabilities in simple algorithmic tasks, such as copying and repeat copying, neural Turing machines fail when doing complex tasks with long-term dependencies due to their limited memory capacity. In this paper, we propose a new memory... 

    Detection of Forgeries in Moving Objects in Digital Video

    , M.Sc. Thesis Sharif University of Technology Bidokhti, Amir (Author) ; Ghaemmaghami, Shahrokh (Supervisor)
    Abstract
    This project aims at forgery detection in digital videos. Most of existing methods are based on similar methods for image forgery detection. Therefore, they do not have sufficient accuracy in case of video forgery detection. In this project, we focus on local copy/move attacks in digital videos and propose 3 solutions for 3 problems in this field: 1) detection of copy/move along time axis (temporal copy/move), 2) detection of copy/move along x and y axes (spatial copy/move) and 3) detection of original and fake part in case of finding a duplication. For each of these 3 problems a feature extraction algorithm and a forgery detection algorithm are proposed. Feature extraction algorithms are... 

    Flow visualization of internal waves and wakes of a streamlined body in a stratified fluid

    , Article Journal of Applied Fluid Mechanics ; Volume 9, Issue 2 , 2016 , Pages 635-641 ; 17353572 (ISSN) Bidokhti, A. A ; Bidokhti, A. A ; Sharif University of Technology
    Isfahan University of Technology  2016
    Abstract
    The wake and internal waves of a moving three dimensional (3D) airfoil body in a stratified fluid has been investigated in a large stratified tank with a finite depth using movies of shadowgraphs of the flow fields. Typical Reynolds and Froude numbers of the flow varied between 103 and 104, and 0.3 and 2 respectively. The flows are generated often by towing the body in a uniformly stratified flow, while limited cases are carried out with body stationary and the channel was in recirculating mode. For some experiments the density profile had a stepped like shape. The wake flow is often consisted of internal waves including random and coherent ones. Distortion of density fields was also... 

    Simulation of Regenerator in a Pulse Tube Refrigerator and Comparison of Performance in Two Conditions of Thermally Equilibrium and Thermally Non-Equilibrium

    , M.Sc. Thesis Sharif University of Technology Ali Akbari Bidokhti, Amin (Author) ; Saeedi, Mohammad Hassan (Supervisor)
    Abstract
    Pulse tube refrigerator due to the relatively high efficiency, high reliability of linear compressor and the absence of moving parts in the cold area is known as one of the best options to generate up to one kW of cooling power at temperatures from 4 to 123 K. More recently, the use of the device at a temperature of about 150 K, makes use of it even outside of cryogenic temperature. The most important part of the device is regenerator, so understanding the nature of the flow and interaction of gas and solid network in the retrievers is necessary. In this study, Inertance pulse tube refrigerator (IPTR) is simulated using Ansys Fluent in two different conditions. In the first condition the... 

    Application of artificial neural networks and mathematical modeling for the prediction of water quality variables (Case study: Southwest of Iran)

    , Article Desalination and Water Treatment ; Volume 57, Issue 56 , 2016 , Pages 27073-27084 ; 19443994 (ISSN) Salami, E. S ; Salari, M ; Ehteshami, M ; Bidokhti, N. T ; Ghadimi, H ; Sharif University of Technology
    Taylor and Francis Inc  2016
    Abstract
    River water quality monitoring using traditional water sampling and laboratory analyses is expensive and time-consuming. The application of artificial neural network (ANN) models to simulate water quality parameters is cost-effective, quick, and reliable. This study provides two methods of mathematical and ANN modeling to simulate and forecast five important river water quality indicators (DO, TDS, SAR, BOD5, HCO3) correlated with variables such as EC, temperature, and pH which can be measured easily and almost with no cost. The mathematical method is based on polynomial fitting with least square method and the neural network model was developed using a feed-forward algorithm. The 35 years’... 

    Periodic solutions for a semi-ratio-dependent predator-prey dynamical system with a class of functional responses on time scales

    , Article Discrete and Continuous Dynamical Systems - Series B ; Volume 9, Issue 2 , 2008 , Pages 267-279 ; 15313492 (ISSN) Mostafa, F ; Hesaaraki, M ; Sharif University of Technology
    2008
    Abstract
    In this paper we explore the existence of periodic solutions of a nonautonomous semi-ratio-dependent predator-prey dynamical system with functional responses on time scales. To illustrate the utility of this work, we should mention that, in our results this system with a large class of monotone functional responses, always has at least one periodic solution. For instance, this system with some celebrated functional responses such as Holling type-II (or Michaelis-Menten), Holling type-III, Ivlev, mx (Holling type I), sigmoidal [e.g., Real and mx2/((A + x)(B +x))] and some other monotone functions, has always at least one ω-periodic solution. Besides, for some well-known functional responses... 

    Modified Load Scheduling Using Smart Meters

    , M.Sc. Thesis Sharif University of Technology Bahrami, Shahab (Author) ; Parniani, Mostafa (Supervisor)
    Abstract
    Implementation of various incentive-based demand response strategies has great potential to decrease peak load growth and customer electricity bill cost. Using advanced metering and automatic demand management makes it possible to optimize energy consumption, to reduce grid loss, and to release generation capacities for the sake of providing sustainable electricity supply, and reducing electricity bills for the customers. With these objectives, this thesis examines the previously suggested load scheduling programs in both residential and industrial sectors, and proposes new practical strategies for load management. This thesis has mainly focuses on three subdivisions of load management... 

    The Analysis of Total Productive Maintenance Based on Computerized Maintenance Management System

    , M.Sc. Thesis Sharif University of Technology Behshad, Amir (Author) ; mostafavi, mostafa (Supervisor)
    Abstract
    The main purpose of this thesis is to analyze the total productive maintenance based on computerized maintenance management system. At first, a detailed study on total productive maintenance is performed and then the requirements of this maintenance strategy are specified. Also, a computerized maintenance management system is defined which can help total productive maintenance to reach to its requirements. Finally, a conceptual model and entity-relationship model for computerized maintenance management system data base has been created  

    Study of HVDC Transmission for Offshore Wind Farms Based on Voltage Source Converters

    , M.Sc. Thesis Sharif University of Technology Safaeian, Reza (Author) ; Parniani, Mostafa (Supervisor)
    Abstract
    In this thesis, DC transmission of offshore wind farms is studied thoroughly. Various system configurations that are introduced in the literatures are discussed and their control scheme for normal conditions and grid faults are studied. Then, the HVDC transmission based on voltage source converter, located between a local offshore ac grid and the onshore ac system is investigated as the most practical choice. The HVDC linke circuit elements are calculated and the control strategies of the offshore and onshore converters are introduced. DFIGs are considered to be the best choice for the offshore wind turbine generators. Then, the system is simulated and the frequency of the offshore grid is... 

    Feasibility Study of Producing Active Pharmaceutical Ingredient from Conceptual Process to Mass Production-Case Study

    , M.Sc. Thesis Sharif University of Technology Tavakoli, Meysam (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    The main aim of this thesis is to develop the technical knowledge of designing and making active ingredients of domestically produced drugs, decreasing the costs, independency in producing these products, and checking outflow of currency. It also aims to reduce the financial challenges of patients who have to pay huge amounts for such drugs. Conducting research in the field of reverse engineering and using its definition, and attempt in made to get knowledge into the stages of product development process, to determine the technical standards associated with each stage, to recognize how knowledge is shared during this process, and to present some methods of establishing the infrastructure... 

    Performance Improvement of Maximum Power Point Tracker in Grid-Connected Photovoltaic Systems

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Hossein (Author) ; Parniani, Mostafa (Supervisor)
    Abstract
    Increase in growing concerns over environmental pollution and depletion of fossil fuel resources motivate the need for cleaner energy technologies and stimulate research in facilitating renewable energy systems. In recent years, photovoltaic systems have attracted great attention since they remove the need for energy storage systems and intermediate processess for energy conversion. However, high capital cost, low efficiency and low energy density per area of these systems, as compared with other technologies hinder its industrial use. To surmount these bottlenecks and improve technical performance of PV systems, it is crucial to optimize configuration of convertor connection and to improve... 

    Coordinated Voltage Control of Power Systems in Normal and Emergency Operation States

    , Ph.D. Dissertation Sharif University of Technology Rabiee, Abbas (Author) ; Parniani, Mostafa (Supervisor)
    Abstract
    One of the main objectives in operating a power system is to maintain the system voltage properly to avoid equipment damage and transfer power efficiently. Automatic control of transmission network voltage provides significant improvements in security, quality and efficiency of power system operation. This thesis investigates coordinated voltage control of power systems in normal, alert and emergency states. The aim is to propose a comprehensive framework for real-time operation of practical power systems, ensuring secure operation of the system in the normal state and after occurrence of sever contingencies.
    At the first, a new coordinated voltage control scheme is proposed to ensure... 

    The Analysis of Knowledge Management, Dimensions and Implementation Methods-Case study: Sardsaz Khodro Ind. Co

    , M.Sc. Thesis Sharif University of Technology Saghafian, Hamideh (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Today, organizations are surrounded by basic and continuous changes such as declining organizational resources, reduction of the production cycles, and the need for rapid adaption. Those organizations remain competitive while maintaining their productivity, that have following characteristics: accurately plan and assess their knowledge resources, create and absorb beneficial knowledge, store and organize their knowledge, disseminate knowledge to needed areas, and use knowledge in practice and decision making, to improve their products/services as well as their performance. Therefore, the human capital has been considered as knowledge owners and the most important organizational resource, on... 

    Feyerabend’s Point of View on Scientific Progress

    , M.Sc. Thesis Sharif University of Technology Yazdani, Homa (Author) ; Taghavi, Mostafa (Supervisor)
    Abstract
    Feyarabend’s philosophy of science is against method and rule such that he believes that “anything goes”. However, he sometimes applies the term “progress”. Reviewing his publications shows that from his point of view, progress is qualitative and relative. So, unlike other philosophers of science Feyarabend ignores the clarification of the concept; subsequently, his applications of the term “progress” are somewhat ambiguous. However, by studying his philosophy, one may realize what should be done to achieve progress in any sense. The affirmative aspect of Feyerabend’s philosophy, while highlights the social and ethical elements, considering his humanitarian outlook as well as his special... 

    Analyzing the Healthcare Wastes and Feasibility Study of Related Items (Plastics)

    , M.Sc. Thesis Sharif University of Technology Mesbah, Niousha (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Increasing population and competition for producing various productions and also more consumption in recent decades, result in producing more wastes. Therefore effective and continuous waste management is essential for monitoring the process (from the wastes generation source to the waste disposal) and establishing the efficient strategies to reduce wastes. One of the major sources of waste generation is hospitals that cause lots of environmental problem unless they are managed properly.Recycling is an important element of waste management that can reduce costs by innovative and proper management. The purpose of this research is identification of recyclable plastic items and estimates the... 

    Analyzing Cost Engineering Along With Presenting A Model To Reduce Cost Of industrial Products

    , M.Sc. Thesis Sharif University of Technology Shakeri, Ehsan (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Lack of financial sources for production and performing projects has been an effective issue in all governmental and non-governmental organizations. So, using a structure with capability of detecting and forecasting all expenses and costs, and being able to convert the mass of data into useful and instrumental reports for managerial decision such as estimating total cost, selecting the syntax of production and etc is obvious for recourse management of every organization. Among the various components of the cost engineering system, cost management system by recording and allocating cost is an important issue in efficiency of every cost engineering system.In this thesis, Automotive Industrial... 

    Feasibility Study of Manufacturing of Disposable Plant Containers

    , M.Sc. Thesis Sharif University of Technology Ansari, Mahmood (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Although laws vary in the competitive business world of today and the changing supply and demand parameters show that the process of delivering new products to market is very important.Most organizations today have found that spending more than ever on trusting in traditional competitive levers such as quality, cost reduction and differentiation in selling more products and services are not enough to be successful in market, instead notions such as speed, flexibility andagility can have a significant trend toward offering new products and services. There aresome good reasons for knew that organizations need new ways to develop their new products to survival, compete with its competitors and...