Sharif Digital Repository

In recent years, Network Coding has received a great attention as an effective approach to increase the network throughput. Due to its promising advantages, in this thesis, we consider cooperative protocols based on Network Coding in two basic channels, namely MAC and MARC. We propose three cooperative transmission protocols for these channels along with their proper receivers at the destination node. The first one is for a typical two-user MAC, in which direct conventional network coding (i.e., XORing the packets of the users) is used. The proposed protocol requires the transmission of only one additional (repeated) packet for any arbitrary number of information packets transmitted by the... 

Image steganalysis is the technique and art of detecting covert communication via images.Reduction of features dimentionality is an important issue according to accuracy and time complexity. In this thesis, GA (genetic algorithm) and PSO (Particle Swarm Optimization) are used to reduce the dimentionality of JRM, a recently proposed feature set containing 11255 features which looks high dimentional compared to other feature sets which has been reduced by evolutionary algorithms so far. So, inspite of other works done using evolutionary algorithms in this field, we use the class sepearability criterion as fitness function instead of the accuracy of the classifier. Investigating these features,... 

The corrosion rate of steel (EN 10130 DC-04) in the presence of oleuropein in aqueous corrosive solutions (of different concentrations in 1M and 0.5M hydrochloric acid and also 3.5% sodium chloride) evaluated and results was shown that oleuropein can protect steel surfaces and it acts as good inhibitor. This means that the observations of linear polarization and weight loss experiments showed inhibitor efficiency more than 97% in acidic corrosive medium and above 74% for aqueous solution of 3.5% sodium chloride. Adding oleuropein at different concentrations (i.e. 300 ppm, 700 ppm, and 1000 ppm) to three different types of polymeric paint structures (nitrocellulose alkyd base, acrylic base,... 

AdS/CFT Correspondence since it origination has found numerous applications in various aspects of Physics such as ion collision in Accelerators, Condensed matter Physics and etc. this orrespondence is a consequence of String Theory. In this project we have tried to analyze some of its applications in Condensed matter Physics and in the controversial phenomenon of superconductivity without resorting to the complexities of String Theory. Having applied this approach we have found a dual for it in Gravity and having calculated some common physical quantities and equations in these two sets such as Energy gap, Conductivity, London Equations and etc, we have tried to show the correspondence,... 

Nowadays, using of digital cameras is streaming across the world dramatically. Application of these devices is very diverse. One of the most interesting application of those is face verification. For example, imagine your smartphone has an application which verifies faces in front of its front camera, if that face be your face (with variation from original) then application automatically unlocks your phone. Face verification systems are also deployed in airports to verify passport photos and in smart homes. One of the most regular problems in face verification is occlusion. When your face is occluded with natural or random changes we can say your face is occluded. All of the recent papers... 

AC/DC/AC converters are widely being used in a variety of power applications. Continuity of service of these systems, as well as their reliability and performance are now of the major concerns. Indeed, the failure of the converter can lead to the total or partial loss of the control of the phase currents and can cause serious system malfunction or even shutdown. Thus, uncompensated faults can quickly endanger the system. Therefore, to prevent the spread of the fault to the other system components and to ensure continuity of service, fault tolerant converter topologies associated with quick and effective fault detection and compensation methods must be implemented. In this thesis, the... 

Steganalysis is the process of discovering existence of hidden data in a file or image. Recent advances in steganographic methods result in their wide use in secure communications applications. Reports of using information hiding by criminals to send messages, and malwares to communicate to servers, emphasizes importance of steganalysis in real time applications. Due to wide use of JPEG images in social media and internet, steganalysis of JPEG images is a highly active research topic in information hiding. Number of steganographic tools available for steganography in JPEG domain, shows importance of steganalysis of this image format. Classic Steganalysis techniques combine feature... 

In the last 4 years, while the annual investment return on 5 years bank deposits was 25 percent; the total index of Tehran Stock Exchange on average grew by 155 percent. Why the investors are not so willing to invest in the stock market? This research deals with existence of equity premium puzzle in Tehran Stock Exchange. Therefore, the Total Price Index of exchange market is considered as a risky asset and the return on long-term (5 years) deposit is a proxy for risk free asset. Data is monthly and covers the first month of 1380 (Persian Calendar) to the beginning of the second month of 1391 (equivalent to Aug 2010 to Jan 2013); which is converted to real term using monthly inflation rate.... 

Hyperbolic branching Brownian motion is a branching diffusion process in which individual particles follow independent Brownian paths in the hyperbolic plane H2, and undergo binary fission(s) at rate λ > 0. It is shown that there is a phase transition in λ : For λ ≤ 1/8 the number
of particles in any compact region of H2 is eventually 0, w.p.1, but for λ > 1/8 the number of particles in any open set grows to ∞ w.p.1. In the subcritical case (λ ≤ 1/8) the set Λ of all limit points in ∂H2 (the boundary circle at ∞) of particle trails is a Cantor set, while in the supercritical case (λ > 1/8) the set Λ has full Lebesgue measure. For λ ≤ 1/8 it is shown that w.p.1 the Hausdorff dimension of Λ... 

Impressive progress in hardwares and developing encryption algorithms in last two decades are caused increase in using encryption protocols in network communications. In last decade, users use privacy preserving networks like Jap and Tor to protect their privacy. These networks protect users' data from eavesdroppers by using three-layer encryption and intermediate nodes between user and target website. Recent researches show that Deep Neural Networks can predict websites viewed by users with high accuracy. In other words, privacy preserving networks suffer from information leakage. In this research, we introduced some of the most powerful methods in encrypted traffic classification and then... 

Procedural Content Generation (PCG) is a critical challenge in video game design, aimed at automating the creation of complex maps and levels. This thesis presents a novel deep learning-based approach for PCG that integrates transformer architectures with reinforcement learning techniques. Building on previous works, this research seeks to enhance the quality, diversity, and success rate of generated playable levels. The proposed method utilizes transformer architectures to model sequences of actions, states, and rewards, predicting optimal game content based on past trajectories. Offline datasets, generated by semi-expert agents trained in the PCGRL framework, serve as the foundation for... 

In the present work the stability analysis for the coupled aeroelasticity and fuel sloshing in supersonic wings is represented. The wing and store structure is modeled using the finite element method. The supersonic wing aerodynamic is modeled by the linear piston theory and store aerodynamic is modeled by the semi-stable slender body piston theory. Fuel sloshing in the store with desired geometry is modeled by the boundary element method. The coupled structure, aerodynamic and sloshing governing equations are drawn by using the Galerkin method and reduce order modeling teqnique for them and an effective numerical model was developed that is capable to analyze the stability for... 

In this thesis, by taking into account the phonetic information contained in the signal spectrum we have been looking for, compact Parameterization and less redundancy, in feature extraction phase. In order to access the consecutive dependency nformation contained in the frame, we’ve put on the agenda, using a linear regression model based on the phonetic structure and developments. Then, to describe the phonetic symbols, it has been considered to the tone modeling and ways of expression and modeling of speaker and background. In fact, we have expressed the speaker and the background as dependent functions to speech phonetics classes. According to phonetic subspaces and time
speech... 

LSB embedding in spatial domain with very low rate can be easily performed and its detection in spite of many researches is very hard, while BOSS competition has been held to break an adaptive embedding algorithm with low rate. Thus, proposing powerful steganalyzer of very low rate in spatial domain is highly requested. In this thesis it has been tried to present some algorithms to detect secret message with very low rate in spatial domain using eigenvalues analysis and relative auto-correlation of image.First approach is based on the analysis of the eigenvalues of the cover correlation matrix that we used for the first time. Image partitioning, correlation function computation,... 

Talking face synthesis is a process in which is made using audio-visual data or its features. Because the face is the first output, face animation plays a crucial role in this process. A high-quality face, a balance between different facial regions, natural movements of facial organs, and the like are basic requirements to synthesize a relatively realistic talking face. There are a wide variety of applications for the photo-realistic talking face. For instance, as a teaching assistant, or reading emails and e-books are only two simple ones to mention. To reach a realistic talking face with mentioned necessary requirements, we set a goal to consider all face regions and their movements. To... 

In this thesis, the aim is to stating some of the noncommutative geometry(NCG) applications in formulating and describing the gravity. So, in the first chapter, we will work on some of metric aspects of NCG. In this chapter, we will review elements of the spin geometry, specifically we will define the Dirac operator which is the most important object in this thesis. Then, we will try to find counterparts of some of Riemannian geometric notions like integral and distance in the NCG framework. We will define some notions such as noncommutative infinitesimals, Dixmier trace, Wodzicki residue, noncommutative integral and spectral triples. Then, in the second chapter, we will work on some of the... 

In this study, through explaining a micromechanical model of progressive damage, failure in a composite conical structure under mechanical and thermal loads with 36 layers of carbon/phenolic material have been studied. To this end, first, mechanical behaviors of composite layers in micro and macro scale and their properties via fiber and matrix characterizations are discussed. In the following, selection of a proper RVE along with different types of boundary conditions on RVE are discussed. Then stress reinforcement coefficients in order to convert the mechanical and thermal stresses from macro to micro scale for carbon / phenolic material are extracted through defining appropriate RVE for... 

Banks are not only money brokers but also money creators. The ability of a bank to create money is due to its unique feature in issuing debts (deposits) that are accepted as a medium of exchange by economic agents. Although this bank function has been discussed under the "liquidity transformation" heading under the micro-banking literature, it has been less discussed in macro literature. In this study, we want to examine the consequences of the bank's liquidity transformation function by developing a New-Keynesian model in which banks can finance the economy by voluntarily expanding their balance sheet. To identify the mechanisms that the money creator bank creates in the model, we have... 

Deep neural networks have not progresses comparative until last decade due to computational complexity and principal challenges as gradient vanishing. Thanks to newly designed hardware architecture and great breakthroughs in 2000s leading to the solution of principal challenges, we currently face a tsunami of deep architecture utilization in various machine learning applications. Sparsity of a representation as a feature to make it more descriptive has been considered in different deep learning architectures leading to different formulations where sparsity is impose on specific representations. Due to the gradient based optimization methods for training deep architecture, smooth regularizers...