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abdoli--majid
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Complexity- Rate- Distortion Optimization for Video Compression in H.264/AVC Standard
, M.Sc. Thesis Sharif University of Technology ; Ghanbari, Mohammad (Supervisor)
Abstract
As the applications of digital video is becoming elementary parts of our daily life both in entertainment and business, the amount of digital video data being transferred by or stored in PDAs rapidly increases. Despite the fact that H.264/AVC is very efficient in terms of compression efficiency, however it is too complex to be used in devices in which their battery energy is restricted and cannot bear this complexity. In this thesis, a fast mode decision algorithm is proposed which brings into play the correlation in content of the video frames and reduces the number of candidate inter modes to be evaluated.For each macroblock, the proposed method performs two steps: first step attempts to...
Investigating the Seismic Behaviour of Split-Level Building Structures
, M.Sc. Thesis Sharif University of Technology ; Khonsari, Vahid (Supervisor)
Abstract
Observations made after previous earthquakes have shown the crucial role of irregularities in initiating damage in buildings with irregularity, either in Plan or in Elevation. Since in existing Building Codes, there is no provision for the distribution of the Equivalent Static Loads for such buildings, designers have no option but to resort to Dynamic Analysis. In this work, the seismic behaviour of a group of two-dimensional steel building structures with irregularity in elevation, namely Split-Level buildings, was studied. The studied structures consist of a series of 5- and 15-storey frames having two parts with splitting distance of 150 cm. Both, moment-resisting and braced frames were...
Investigation of Economic Incentives for Reducing Energy Intensity in Industrial Sector
, M.Sc. Thesis Sharif University of Technology ; Maleki, Abbas (Supervisor)
Abstract
The trend of increasing energy intensity in the country, despite awareness of the officials and managers of the need to take action to improve it, is ongoing. Various studies conducted worldwide to improve the productivity of energy. These studies suggest ways for improving energy intensity; suggestions that will never be implemented, because of lack of utility consideration of actors. In this research, in search for energy intensity reduction barriers in the industrial sector of the country, a game theoretical approach has been applied. In this study’s modeling, energy consuming firms as an actor, compete with each other and the government as an important actor in the implementation or...
The Effects of Intentional Process Models on Goal Modeling and Process Conformance Checking
, M.Sc. Thesis Sharif University of Technology ; Rafiei, Majid (Supervisor) ; Khedmati, Majid (Supervisor)
Abstract
In recent years, requirement engineering and goal modeling have gained more attention among different organisations. Therefore, different methods have been designed to discover stakeholders’ requirements and translate them into process and organizational goals. Various goal models have been introduced to represent these goals and their relations towards each other. Still, these methods are manual representations of different process scenarios and do not relate to the actual behavior. In 2014, Map Miner Method (MMM) was introduced to discover intentional process models from event logs. MMM uses Hidden Markov Model (HMM) as a means to represent the process as a map model of strategies and...
Sintering behavior of Al-AlN-nanostructured composite powder synthesized by high-energy ball milling
, Article Journal of Alloys and Compounds ; Volume 473, Issue 1-2 , 2009 , Pages 116-122 ; 09258388 (ISSN) ; Asgharzadeh, H ; Salahi, E ; Sharif University of Technology
2009
Abstract
High strength Al-AlN composites were synthesized via high-energy milling and sintering technique. Al-X wt.% AlN (X = 0, 2.5, 5 and 10) composite powders were milled in a planetary ball mill for 25 h. Morphology, particle size distribution, crystallite size, micro-strain, and microhardness of milled powders were studied. Ball-milled powders were degassed at 400 °C for 30 min. After uniaxial cold compaction, composite compacts were sintered at 650 °C for 20, 30 and 60 min under N2 atmosphere. Effects of reinforcement content, degassing treatment and sintering time on the sinterability of powders were investigated. The results revealed that the sinterability was degraded by increasing the...
A Trajectory Recommendation System for Efficient Finding of Passengers
, M.Sc. Thesis Sharif University of Technology ; Khedmati, Majid (Supervisor) ; Rafiee, Majid (Supervisor)
Abstract
Recommending routes to city taxis in order to improve their performance in finding passengers can reduce traffic, pollution and waiting time for passengers, as well as this, increasing the efficiency of taxis can increase their income. In this study, by analyzing trajectory data obtained from 536 taxis in San Francisco over a period of one month, we generated networks of cells, each of which has time-dependent characteristics such as the probability of finding a passenger, the capacity of each cell, or the amount of demand exists is in the cell and the average speed of passing through that cell. also, the connections between these cells in order to make more use of the experiences of taxi...
Improving Artificial Neural Network Predictive Performance Using Panel Data
, M.Sc. Thesis Sharif University of Technology ; Khedmati, Majid (Supervisor) ; Rafiee, Majid (Supervisor)
Abstract
The purpose of the present study is to develop neural network estimation method for hybrid or panel data which have a combination of two cross-sectional and time series structures and because of the features of both structures, their use in different sciences offers many advantages; and the analytical methods for this data structure are also different from other one-dimensional structures, so different and specific regression models are presented for this data structure. However, in the artificial neural network method, modeling the development for this data structure is neglected, so in the present study, using the concepts of panel regression methods and their application to the...
Gaussian mixture model-based contrast enhancement
, Article IET Image Processing ; Volume 9, Issue 7 , 2015 , Pages 569-577 ; 17519659 (ISSN) ; Sarikhani, H ; Ghanbari, M ; Brault, P ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In this study, a method for enhancing low-contrast images is proposed. This method, called Gaussian mixture model-based contrast enhancement (GMMCE), brings into play the Gaussian mixture modelling of histograms to model the content of the images. On the basis of the fact that each homogeneous area in natural images has a Gaussian-shaped histogram, it decomposes the narrow histogram of low-contrast images into a set of scaled and shifted Gaussians. The individual histograms are then stretched by increasing their variance parameters, and are diffused on the entire histogram by scattering their mean parameters, to build a broad version of the histogram. The number of Gaussians as well as their...
Evolutions during synthesis of Al-AlN-nanostructured composite powder by mechanical alloying
, Article Journal of Alloys and Compounds ; Volume 461, Issue 1-2 , 11 August , 2008 , Pages 166-172 ; 09258388 (ISSN) ; Salahi, E ; Farnoush, H ; Pourazrang, K ; Sharif University of Technology
2008
Abstract
High-energy milling technique was used to synthesize Al-10 wt.%AlN-nanostructured composite powder in a planetary ball-mill under argon atmosphere up to 25 h. To show the role of AlN particles, process was conducted for monolithic aluminum. The changes in powder characteristics were investigated by time. Microstructure of powders was studied after different milling times by scanning electron microscope (SEM). The morphological evolutions showed that relative equiaxed powder could be synthesized after 25 h milling. Structural analysis was performed by X-ray diffraction method (XRD) to determine the grain sizes and lattice strain. Furthermore, particle size analysis (PSA) revealed the...
The Effects of Organizational Mindfulness on Covid-19 Crisis Management and Business Survival: Case Study of Health Tourism SMEs in Iran
, M.Sc. Thesis Sharif University of Technology ; Najmi, Manouchehr (Supervisor) ; Tasavori, Misagh (Supervisor)
Abstract
In the world of today, the high rate of change, instability and uncertainty leave organizations under the constant effect of crises and unforeseen events. The prediction, prevention and control of crises alongside sustained performance and stability are now vital to the survival of organizations. The COVID-19 pandemic has created innumerable challenges for many businesses in Iran, including Small and Midsize Enterprises involved with health tourism, and has placed their subsistence at risk. The concept of Organizational mindfulness can help organizations avert crises and unexpected incidents, while rapidly bringing such events under control and mitigating the associated damage, should they...
Study of the densification of a nanostructured composite powder. part 1: effect of compaction pressure and reinforcement addition
, Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 580-584 ; 09215093 (ISSN) ; Farnoush, H ; Salahi, E ; Pourazrang, K ; Sharif University of Technology
2008
Abstract
The compressibility behavior of Al-AlN nanostructured composite powder with different amount of reinforcement content was studied. The composite powder was synthesized by blending and high-energy milling process for 25 h. Williamson-Hall method was applied to determine the crystallite size after milling process. To investigate the role of reinforcement particles in consolidation of composite powders, monolithic aluminum powder was examined. Samples were made at different pressures and relationships were established between the compaction pressure and the density of the compacts. The modified Heckel equation was used to assume the pressure effect on yield strength and then was compared with...
Simulation of body force field effects on airfoil separation control and optimization of plasma actuator
, Article Journal of Physics D: Applied Physics ; Volume 41, Issue 17 , 2008 ; 00223727 (ISSN) ; Mirzaee, I ; Anvari, A ; Purmahmod, N ; Sharif University of Technology
2008
Abstract
Among all active flow control methods, EHD, MHD and EMHD are the only methods which operate on the basis of body force induction on flow field. The EHD plasma actuator is the proper method which has been used in various flow control applications recently. In this paper, the effects of different body force fields on different domains have been studied for separation control on NACA 0021 and the results have been discussed. The airflow velocity has been assumed to be 35 m s-1 at a post-stall angle of attack of 23°. Three different domains have been used around the airfoil to investigate body forces with different strengths and directions and those which give the best result in separation...
Study of Micropollutants Adsorption from Water by Nanoporous Silica Aerogels
, M.Sc. Thesis Sharif University of Technology ; Bastani, Daruoosh (Supervisor) ; Bargozin, Hassan (Co-Advisor)
Abstract
Phenolic compounds are important environmental pollutants that the removal and separation of them from the water and industrial wastewater especially in the oil industry is essential before entering the environment. In the present study, the removal efficiency of the adsorbent silica aerogel 4-Chlorophenol and 4-Bromophenol as phenolic compounds from aqueous solution was surveyed. In this research, the effects of various factors such as contact time, pH, and initial concentration of the pollutant and the adsorbent on the adsorption were studied. It was observed that there is a large amount of adsorption in acidic pH and this amount increases by incrementing the concentration of the...
Fabrication of aluminum nitride coatings by electrophoretic deposition: Effect of particle size on deposition and drying behavior
, Article Ceramics International ; Volume 37, Issue 1 , 2011 , Pages 313-319 ; 02728842 (ISSN) ; Zarabian, M ; Alizadeh, P ; Sadrnezhaad, S. K ; Sharif University of Technology
2011
Abstract
Electrophoretic technique was used to deposit micro- and nano-sized aluminum nitride coatings on stainless steel surfaces by using a well-dispersed stable suspension produced by addition of AlN powder plus a small amount of iodine to ethanol. Parabolic regime governed the deposition. Electrophoretic deposition for 240 s at 100 V resulted in formation of a uniformly dense film on the top, but a porous inhomogeneous layer at the bottom. This was attributed to fast deposition of coarse particles and/or agglomerates at large electric fields. After drying, micro-sized particles led to a uniform crack-free interface while nano-particles resulted in fragmented non-cohesive layers. Weight loss...
Welding Metallurgy and Weldability of Martensitic Advanced High Strength Steel and Duplex Stainless Steels during Resistance Spot Welding
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor)
Abstract
Duplex stainless steels and advanced high strength steels are both known as new materials in automobile industry applications. Process of resistance spot welding is the main process in welding of auto-body structures. Hence investigating the welding metallurgy and weldability of similar and dissimilar joints of duplex stainless steels and advanced high strength steel are crucial. The purpose of this study is to analyse the relationship between welding process and geometric characteristic of weld nugget, phase transformations of Weld nugget and heat affected zone, mechanical properties (i.e force bearing capacity and energy absorption capability) and failure mode (interfatial or pullout). in...
Investigation of Microstructural Evolutions During Dissimilar TLP Bonding of IN792 and Hastelloy X Nickel Based Superalloys
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor)
Abstract
In this thesis, macrostructural evolutions in dissimilar TLP bonding of as-cast nickel based supperalloy IN792 to wrought HX was investigated. In the first step of this study solidification behavior of Ni-Cr-Fe-Si-B (MBF-15) interlayer in presence of HX as base metal at 1120 °C was surveyed. In second step, bonding of HX/HX, IN792/IN792 and HX/IN792 systems with MBF-15 interlayer at 1120 °C and different times were studied and isothermal solidification time and factors that affect this stage were discussed. In third step, synchronization of dissimilar bonding with standard heat treatment cycle of IN792 was investigated and effect of this cycle on aging response of different zones, isothermal...
An Online Portfolio Selection Algorithm Using Pattern-matching Principle
, M.Sc. Thesis Sharif University of Technology ; Khedmati, Majid (Supervisor)
Abstract
According to the rise of turnover and pace of trading, accelerating of analysis and making decision is unavoidable. Humans are unable to analyze big data quickly without behavioral biases so, using machines to analyze big data seems critical. Hence, financial markets tend to apply algorithmic trading in which some techniques like data mining and machine learning are notable. OLPS which sequentially allocates capital among a set of assets aiming to maximize the final return of investment in the long run, is the core problem in algorithmic trading. This article presents an online portfolio selection algorithm. The online portfolio selection sequentially selects a portfolio over a set of assets...
Prioritizing and Clustering Customers in a Supply Chain with Perishable and Fast Moving Consumer Goods (FMCG) (Case Study of Ramak Company)
, M.Sc. Thesis Sharif University of Technology ; Rafiee, Majid (Supervisor)
Abstract
Knowing different groups of customers and building effective communication with them in such a way as to guarantee the future economic interests of the organization is a very important issue in today's businesses. The attraction of profitable customers, as well as the preservation of valuable old customers, are both important, except for the precise identification of their features. The value of customer longevity plays an important role in customer segmentation, and there are numerous researches that focuses on customer value with the aim of making more profit for the organization, most of which have life-cycle customer value models as the main inputs for segmentation cCustomers have been...
Providing a Method Based on Signal Transformations and Machine Learning Tools for Forecasting in Stock Market
, M.Sc. Thesis Sharif University of Technology ; Khedmati, Majid (Supervisor)
Abstract
Obtaining high profit is the ultimate goal of an investor in the financial market. The key to achieve high profits in stock trading is to find the right time to trade with minimum business risk. However, it is difficult, often, to make decision about the best time to buy or sell some stocks due to the extremely dynamic and volatile behavior of the stock market. In order to resolve these problems, two steps have been followed in this research:1) Create a model to predict the final price of the stock with small error rate, and 2) Suggest the best stocks for trading to the trader. In order to achieve the goals of the first step, the stock price data of Hcltech, Maruti, Axisbank is selected and...
Studying of Micro-structure and Mechanical Properties of Resistant Spot Welds of Nickel Base Super Alloys
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor)
Abstract
Resistance spot welding is one of the fabrication processes of gas turbines. Due to few published works about using RSW for joining participation hardened nickel base super alloys like Nimonic C263 and solid solution hardened ones like Hastelloy X, this work tries to investigate the microstructure and mechanical properties of RSW joints of these super alloys. In phase one, effect of welding current on structural properties of welds, hardness profile from the center of the weld to the edge of it, failure mod and failure energy were investigated. In phase two, effect of standard heat treatment of Nimonic C263 and the initial microstructure of the base metal on the micro-structure and...