Sharif Digital Repository

In recent years, advances in computer technology and widespread use of computers have alleviated the wide usage of network-based services in contrast to traditional services like radio and television. These facilities made it possible to integrate various type of services with adding new features whenever is necessary.
Video has specific characteristics that its transport over the network imposes some challenges to service providers. In the literature several solutions have been offered for solving the problems of network-based video services. A set of these solutions use routers and other network assisted devices to gather information for better transportation. These router-assisted... 

Overlay Peer-to-Peer networks opposed to their high scalability and more robustness against network errors, are more considerable rather than other content distribution approaches such as Client/Server and multicast video streaming. At this thesis we investigate the video streaming over these networks, which includes more than half of internet traffic nowadays.Localized video streaming is one of the techniques for improving quality of service (QoS) over peer-to-peer networks. With localization techniques, video chunks distribute among neighbors that have more proximity with each other and traffic is held localized over the network.We proposed a new metric for estimating network proximity of... 

Scene classification and understanding is one of the most important fields in computer vision. Its applications are such as exploring robot navigation enviroment, content-based image retrieval (CBIR), organization in image databases, highly semantic describing images and videos and content extraction of videos.Many methods and algorithm are proposed till today to deal with diversity of this field by emphesizing on feature based methods or machine learning based methods. In this research we have focoused on proposing a new algorithm which is using principals of NBNN image classification method but major changes in how to exract distance metric from Nearest neighbour and how to use local... 

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... 

Nowadays with development of applications that stream video over internet, compression efficiency of video has become very important. On the other hand, Watermarking and video coding are two conflicting technologies. One adds redundancy and other tries to remove it. We have proposed a H.264 watermarking method that does not increases the bit rate. Unlike most of watermarking schemes, this methods embeds the watermark in inter coded frames. Abundance of these frames in video is impressively more than intra frames, so a lot of capacityis eventuated. But these frames are highly compressed using motion compensation, and are very sparse. To avoid from bit rate increment, this method only embeds... 

In the recent years, emerging vehicular ad hoc networks offer a wide variety of applications, including safety, convenience and entertainment. One of the beneficial applications in these fields is video streaming. However, according to the features like high mobility and loss of links, establishment of video streaming which requires stringent Quality of Service is a daunting task. In this thesis, the goal is introducing approaches in two levels, one for resilient video coding and the other one for network routing. For resilient video coding, the concentration is on the scalable video coding, which supports various applications for users with different requirements. The introduced approach... 

Video communications over mobile ad hoc networks is increasingly deployable as these networks become deployed in various applications such as disaster recovery. Error-prone nature of the mobile ad hoc networks and the vulnerability of compressed video to packet losses have brought many challenges to realize video transmission over MANETs. In this thesis, it is tried to achieve a good quality of service by resilient video coding and multipath transmission over mobile ad hoc networks. To generate error resilient video, a hybrid method is used by combining scalable video coding and multiple description video coding techniques. First, the video sequence is coded to two layers and then each layer... 

In content based image retrieval, low level features are used to find similar image. To do this, many system has been proposed by other people, in which in many of them, combination of features in the same time are used as a step of retrieval to increase accuracy. Feature combination are divied in two category: vector based and weight based which in weight based approach, features can get different weight, based on their importance and role in retrieval accuracy. Each image contain different partition, which some of them like background, base on their lower discrimintivity power, have lower importance. Based on our study, some image have powerfull color features and some of them have... 

The main objective of this study is to identify the contribution of different damping mechanisms in equivalent damping of inelastic soil- structure systems which can be used to reach a better estimation of inelastic soil- structure systems response using some simplified methods. This mechanisms include the material damping of soil and structure, radiation damping of soil and also the structure’s nonlinear behavior. Despite the studies have been done, even in the fixed base systems, there is not an exact prediction for the contribution rate of inherent damping and energy absorption related to nonlinear behavior in equivalent damping of system. Considering the flexibility of soil under the... 

Brain is the most complicated organ of body which controls the activity of all other organs. Understanding its function and its language could give us a direct communication pathway for connecting injured motor organ and it could be useful for functional repairing. Neurons are atoms of a vast network that generate the brain signals. Processing these signals would help to translate brain’s language and has three main stages: spike detection from signal, spike sorting, and intention extraction from encoded signal.
In this research, we use a dataset of rat’s extracellular recordings during a time interval in which a rat pressed the liver several times to receive water as an award. Since... 

In this thesis, the efficiency of bump modeling has been investigated on brain signals, in a variety of aspects including analysis, detection, classification and prediction. The aim of bump modeling is to provide an optimized representation of the signal in time-frequency domain. This would be done by discriminating oscillatory bursts from background signal and then showing them by half-ellipsoid functions called bump. Consequently, the problem of dealing with large numbers of parameters and hence complicated calculations, which are serious concerns in similar methods, can be overcome. This is in addition to the benefits of using time-frequency representation of the signal.The aim of bump... 

Today, energy has a great impact on the economy, political relations, prosperity, and lifestyle of human societies. Energy sustainable development has become inevitable because of factors such as increasing population growth and as a result, increasing the energy consumption, consuming more energy from fossil fuels, decreasing in reserves of fossil fuel resources, environmental damage caused by the burning down of fossil fuels and greenhouse gas emissions,high cost of energy from burning fossil fuels.Generally, the sustainable development isall steps in order to comply with economic development and protecting the environment, resources and living standards. Considering that a large part of... 

Support vector regression (SVR) in the field of machine learning attracted much attention because of its attractive features and high efficiency for high-dimensional and nonlinear data. Although support vector regression has shown to be very effective for prediction problems, it is necessary to adjust the parameters contained therein to obtain the desired output with error rates. In the past, this was done manually, by trial and error. Over time and by development of optimization algorithms, one of the newest methods to solve such problems is the meta-heuristic optimization algorithms. Therefore, in this thesis, we use the firefly optimization algorithm, which is a population-based... 

Using Peer-to-Peer (P2P) overlay networks have become a progressively popular approach for streaming live media over the Internet due to their scalability and deployment simplicity. In this project, we have proposed a hybrid push-pull live P2P video streaming protocol called PPM that combines the benefits of pull and push-based mechanisms for video delivery. The main goal of this research is to minimize the network end-to-end delay in comparison to pure mesh networks. The low end-to-end delay is achieved through two phases: the first phase is to select a parent node based on peers’ overlay hop count in a mesh topology and the second is to construct a dynamic tree in order to push the most... 

Structural best management practices (BMPs) are often used to mitigate the impact of storm water runoff on receiving waters. Vegetative filter strips (VFS) are an example of a structural BMP that has been used to treat storm water and highway runoff. In this study (the first in Iran), field-quality data were collected from a native VFS treating urban runoff in North of Tehran. At first field data were used to test the design concepts of the VFS treatment train and to modify and calibrate simulation model for evaluating the impact of physical factors such as slope, type of vegetation and impermeable surface on sediment removal then more field data were used to evaluate and modify the... 

Given many computing errors in current systems, a method appears necessary for predicting the nuclear parameter quickly and accurately. In this thesis, a neural network was used to predict safety in a nuclear power plant in order to develop an operating aid tool for preventive measures.First, some studies were conducted on appropriate feature selection for training neural networks. Some case studies have also been carried out on parameter prediction through soft computing in a power plant. In the next section, an expert judgment was taken into account to select DNBR (Departure from Nucleate Boiling Ratio) as a criterion for safety evaluation in the exploitation of a nuclear power plant (PWR)... 

Following heart coronary artery occlusion, heart stroke (HS) happens which leads to the creation of a dead zone on heart tissue named Myocardial Infarction (MI), the presence of which on a patient’s heart will result in succeeding HSs and the death of the patient. In this study, porous microcarriers capable of being utilized in cardiovascular tissue engineering is fabricated using a mixture of myocardium ectracellular matrix (ECM) and Chitosan (Cs). Results of Elasticity tests, SEM images, swelling behavior, biodegradability test, and cell proliferation assay showed that the scaffold consisting of 3.5% (w/w) Chitosan and 0.66% (w/w) ECM has the best potential in providing cardiovascular... 

In this project, in continuation of a PhD resreach undertaken in this research group in 2017, the synthesis and study of two new tweezer and linker molecule bearing azobenzene moiety were carried out, characterized by applying IR spectroscopy, ¹H and ¹³C {¹H} NMR, fluorescence spectroscopy, UV-visible spectroscopy, elemental analysis and X-ray crystallography. Firstly, interaction of T2 with meso-tetraphenylporphyrinato zinc(II) and aluminium tetraphenylporphyrinato were studied using the fluorescence spectroscopy. The formation constant of T2 in cis and trans isomer with ZnTPP was measured as 5.1(±0.4) ×108 and 2.0×108(±1074) dm6mol-2, respectively. The formation constant of T2 in with... 

Nowadays, H.264 is a popular format to data transfer. The growing use of video signals and importance of its ownership in the digital world, requires careful study of robust video watermarking. Distorting the watermark through recompression is a common attack to robust video watermarking schemes. It is aimed in this thesis to design a recompression resistant watermarking scheme and to address real-time extraction of the watermark from both compressed video bitstream and decoded video. In this thesis, we employ an objective quality metric, which is highly correlated with human perception, as a cost function in image/video watermarking optimization. We show that by embedding in the selected... 

The goal of this project was study on coordination behavior of the 14-membered macrocyclic ligand of type N2O2 aza-crown while it is attached to fullerene C60 nano-particle. For this purpose, firstly the macrocyclic ligand (Fig 3-1, L1) was synthesized and then was reacted with C60 (Fig 3-1, L2) of which the product was characterized by elemental analysis. Since the product was insoluble in any solvents, further study on its coordination chemistry was impossible. In a second procedure, the macrocyclic ligand was reacted with benzylbromide. The reaction mixture gave two macrocyclic ligands with different number of benzylic pendant groups (Fig 3-1, L3-L4). The products were separated by column...