Sharif Digital Repository

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... 

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... 

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... 

The need for independent power generation has been increased in recent years with the growing demand in micro grid systems. Losses in power systems are unavoidable. These losses occur in transmission to distributionnetworks from the generation sites to the end-user loads. Reduction of power losses has been one of the reasons for engineers to be attracted by micro grid systems which include small size independent power generation units. However, in a micro grid with several DGs of different types and with all kinds of loads of variable nature, an optimal power balance in the system has to be achieved. This optimal objective, which results in minimal energy losses over a specific period of... 

The main focus of this project is the fabrication of surface engineering scaffolds based on polyurethane and titanium dioxide. The research's aim is the creation of the synergistic properties of TiO2 and PU as a new strategy for engineering artificial autologous blood vessels. In the first section, PU-TiO2 nanocomposites were synthesized by co-insitu synthesis of nanoparticles and polymer. The nanocomposite films were prepared by solvent casting and thermally induced phase separation methods. Mechanical and biological properties of films were compared with pure PU film. In solvent casting method, the outcomes revealed that the rate of endothelialization of the nanocomposite scaffold after 7... 

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... 

Nowadays, the use of gas turbines with low capacity have acceptance in large quantity. This type of gas turbines with a capacity of approximately 5-200kW are known as microturbines. This type of turbines due to the existence of limitations on increasing of turbine inlet temperature and compressor pressure ratio has low efficiency compared to the turbine with high capacity. Therefore the use of a recuperator in the cycle is necessary. Optimum design of heat recuperator has important effect on improving of gas turbine cycle efficiency. In this project for optimum design of heat recuperator, the effect of recuperator on gas turbine cycle efficiency is studied. By determining geometric... 

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... 

In this thesis, we consider multiple-antenna K-user interference channels with backhaul collaboration in one side (among the transmitters or among the receivers) and investigate the trade-off between the rate in the channel versus the communication load in the backhaul. In this investigation, we focus on a first order approximation result, where the rate of the wireless channel is measured by the degrees of freedom (DoF) per user, and the load of the backhaul is measured by the entropy of backhaul messages per user normalized by log of transmit power, at high power regimes. This trade-off is fully characterized for the case of even values of K, and approximately characterized for the case of... 

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... 

The commercial breakthrough of micro-tubular solid oxide fuel cells (MT-SOFCs) is still facing so many challenges because of the complexity of their manufacturing process and the high cost associated with them. By deploying electrophoretic deposition as a simple and cost-effective method, the different components of the fuel cells (the anode, electrolyte, and cathode) can deposit on the graphite rod as a sacrificial substrate. The next step is eliminating the sacrificial substrate which will make hollow rods of cell components. The results of this study show that the use of a particular type of pencil lead will have a minimal negative impact on the overall fuel cell performance, leading to a... 

Nanostructured graphene based membranes demonstrated excellent capabilities in various applications in nanofiltration and energy conversion due to unique atomically smooth surfaces and adjustable pore size or interlayers spacing at Angstrom scales.In addition to graphitic surface and physical confinement on ions in Graphene-oxide (GO) laminates, surface charges on such 2D-slits provide an attractive aspects to have more channels walls interactions with ions. There are some reports on the osmotic power generation using physical confinements and electrostatic interactions between ions and GO membranes. However, the results indicated insufficient power densities (1 W=m2 ) can be achieved... 

Digital microfluidics has emerged as a promising tool in engineering and biomedicine over the past decade, with applications in drug delivery, biochemistry, sample manipulation in lab-on-chip systems, and tissue engineering. These systems enable the precise control of droplets and microfluids independently, which can be utilized as contamination-free chambers for conducting chemical reactions in medical applications. The precise control of the position of a ferrofluidic marble is also crucial in the field of digital microfluidics. Given the importance of this issue, this dissertation investigates, for the first time, the closed-loop control of a ferrofluidic marble’s position using a... 

In this study, the impact of imposed financial sanctions on Iranian banks is being estimated using micro-level data. Using a panel regression while controlling on some variables and other shocks, we find a decline in both level and slope of granted loans by sanctioned banks. Moreover, we examine the varying characteristics of banks and how they respond to sanctions. Granted loans by big banks are found to decline drastically
and from the prospective of ownership, private banks are also more vulnerable toward sanctions. At last, we seek for balance sheet channels for sanction transmission, and in almost every case the existence of such channel is supported which means, the impact of... 

Residual stresses are stress fields that exist in the absence of any external loads. All mechanical processes can cause deformation that may lead to residual stresses. It is well established that virtually no material, no component and no structure of technical importance exists free of residual stresses. However, in practice, the knowledge of the true distribution of exiting residual stress is rare. The residual stress fields are very challenging to evaluate, independent of the measurement techniques. The important aspect about the residual stress determination is that often true distribution is unknown in the engineering specimen. A simple and non-destructive method to measure residual... 

The epidemic of Covid 19 has killed millions of people worldwide. Despite the efforts of scientists around the world, there is still no cure for this disease. Approval of newly designed drugs due to clinical trial periods is time-consuming and costly. For this reason, in the current emergency situation, it is important to have a solution for screening available approved drugs in order to find effective substances for this disease.High-throughput assays are a good option for such problems. In this field of research, image-based high-throughput assays are amongst the most effective and cost-effective methods that help quantify the response of treated cells by measuring cell... 

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...