Sharif Digital Repository

The goal of this thesis is the development and application of the finite volume method (FVM) with a same solution procedure in the fluid and structure domains for the simulation of fluid-structure interaction (FSI) problems in the compressible fluid flow. The unsteady Euler equations written in the arbitrary Lagrangian–Eulerian (ALE) form are considered as the governing equations of the compressible fluid flow and the moderate/large nonlinear deformation of the elastic structure is considered to be governed by the Cauchy equations in the Lagrangian/total Lagrangian forms. Therefore, the nonlinear phenomena in the unsteady compressible fluid flow and the large deformation of the elastic... 

Medical imaging is of interest because of information that will provide for doctors and registration is inevitable when we need to compare two or more images, taken from a subject at different times or with different sensors or when comparing two or more subjects together. Registration methods can be categorized in two major groups; methods based on feature and methods based on intensity. Methods in first group have three steps in common: feature extraction, finding matches and transform estimation. In second group it’s important to define a similarity measure and find the transform that minimizes this measure.
Manifold learning algorithms are mostly used as a dimensionality reduction... 

Medical imaging is a crucial part of modern healthcare, providing vital information for diagnosis, treatment, and monitoring of diseases. Physicians utilize various imaging modalities to obtain valuable information that aids in improving the treatment process. Ultrasound, due to its easy accessibility and lack of side effects, is one of the most commonly used modalities. Its alignment with 3D images such as CT scans and MRI provides useful information for treatment planning. Deep learning in image processing, including image alignment, has made significant advancements. One of the main challenges in this field is the lack of data for training deep networks, which becomes even more crucial in... 

Cooperative coexistence of two kinds of users with different priorities in random access wireless networks has been studied in this thesis. Source burstiness, a phenomenon in data communication networks, allows using silence periods of primary users (PUs) to have a better spectrum utilization. In this respect, new users, known as secondary users (SUs), are considered to exploit the resources opportunistically. In usual spectrum sharing systems, SUs have to act in a way to be transparent for the PUs. Therefore, they are allowed to access the common spectrum band only when PUs are silent. However, seeking such opportunities needs sensing capability of secondary nodes.In this thesis, sensing... 

Network coding, as a promising method for data exchange in wireless communication network, is investigated by many researchers. However, the random nature of packet generation and transmission as well as the collision among transmitted packets have not been fully addressed in network codingrelated literature. In this dissertation, we analyze the network coding-based wireless network from this point of view. In order to achieve this goal, we apply mathematical tools such as probability theory and queuing theory. In the first part of this dissertation, we address the interaction between MAC and network coding. In this respect, we consider a multihop tandem wireless network, where each node is... 

In this dissertation we discuss various results presented in the literature on single user channels with causal or noncausal side information and multiuser channels with side information such as multiple access channel and broadcast channel. The Series Relay Networks (SRN) with delays, with and without channel state information (CSI) are investigated from an information theoretic point of view. For SRN with unlimited look ahead where the relays can use the whole received block to encode, upper and lower bounds on the capacity are derived which are tight for the degraded case. For SRN without-delay where the relays have access to the present received symbols in addition to the past symbols,... 

Network coding generalizes conventional routing algorithms. It considers data streams as mathematical entities which can be processed in the nodes of networks. In this work, after a concise introduction to network coding, we focus on security issues in network coding form an information theoretic point of view. First we introduce fundamental concepts of network coding such as linear network coding and random network coding. Then, we accentuate the advantages and disadvantages of network coding. To investigate security in network coding, we introduce perfect security and weak security as two different levels of security against wire tapper. Then we scrutinize the prerequisite for reaching... 

Wireless Sensor Network (WSN) is a set of cheap wireless sensors that can collect, process and send environment’s data. WSN nodes are battery powered, therefore energy management is a key factor for long live network. One way to prolong lifetime of network is to utilize routing protocols to manage energy consumption. To have an energy efficient protocol, we can apply ZigBee protocols. ZiBgee standard is originated from IEEE802.15.4 standard that is defined for personal wireless networks with low bit rate. Now there are many different routing methods that are defined for ZigBee networks that have applications in different circumstances. These methods usually have been proposed in the network... 

Matrix completion is an emerging field that is proposed after new and attractive field of compressed sensing. Matrix completion is concerned with the problem of recovering an unknown matrix from a small fraction of its entries. In general, accurate recovery of a matrix from a small number of entries is impossible, but the knowledge that the unknown matrix has low rank radically changes this premise, making the search for solutions meaningful. Matrix completion problem comes up in great number of applications,including collaborative filtering, machine learning, control, image processing, sensor networks, system identification and communications (spectrum sensing and network coding). In this... 

With the proliferation of mass media such as smartphones and the use of social networks, the exchange of video data between users has increased, and according to forecasts in the coming years we will see significant growth in the amount of this data on mobile networks. In this dissertation, we examine the effect of sending video packets via LTE and WiFi and try to calculate two parameters that affect the quality of experience, namely the probability of interruption and the amount of delay. The modeling results show that if the packets are optimally routed to these two paths, there is about a 15% improvement in the probability of interruption. Sending packets from two separate routes Although... 

In this research a systemic framework for recognizing and using international opportunities has been generated based on the Viable System Model (VSM). This framework consists of designing required functions, recognizing capabilities and assigning requirements in the different levels of the system. Based on this framework a systemic analysis for diagnosing Iran’s problems and barriers in implementing Clean Development Mechanism (CDM) which is a part of international carbon trade has been done. This research results show that the generated systemic framework has a good diagnosing power for identifying systemic problems in different systems  

OFDMA multi-hop cellular network (MCN) is the topic of a wide range of research today. In this thesis, we analyse this type of networks, regarding shadowing status, mobility patterns and different service requirements. In the multi-hop (MH) scenario, six fixed relays are set up in each cell, which split the cell into seven subcells. For mobility modeling, each subcell is split into several sub-regions. Mobile nodes are able to maintain at each sub-region with a random time distribution and migrate from it to one of its neighboring sub-regions. We also consider three types of services requiring specific number of subcarriers with specific BERs. The set of subcarriers is distributed among... 

In this thesis, we evaluate the maximum stable throughput of a cognitive multi-hop IEEE 802.11-based WLAN overlaid on a cellular network. In the considered scenario, the secondary users operate in the downlink or uplink frequency band of primary network and transmit their data in free primary channels using OFDM technique. The activity of primary nodes is modeled independently by ON-OFF alternating states. To model the scenario, each secondary user is modeled with an open queueing network. The queueing network can model the transmission of data as well as the effect of primary users. By writing the traffic equations of the queueing network and applying the stability conditions, we are able... 

In this thesis the effect of frame aggregation mechanism in maximizing throughput in Wireless Local Area Networks (WLANs) have been investigated. Frame aggregation has become a part of the IEEE 802.11 standard as the amendment IEEE 802.11n. First, we have a quick review on access control layer in IEEE 802.11 standard then illustrate the necessity of frame aggregation. Afterwards, we propose an analytical model for the analysis of an IEEE 802.11n network comprised of an Access Point (AP) and several conventional nodes, all in the coverage area of each other. This analytical model focuses on downlink throughput; therefore only AP uses frame aggregation and the other nodes use basic IEEE 802.11... 

In this thesis, we propose two new network coding-based packet relaying schemes suitable for multiple unicast scenarios in a random access network. In such networks the channels may have memory dependent upon the random access scheme. Thus, the optimal scheme for memoryless channels reported recently in the literature is not necessarily optimal in random access networks. In our proposed schemes, we convert a multiple unicast scenario to a combination of multiple anycast and a few multicast scenarios. By such an approach, we exploit the channels between relay node and the other nodes, instead of using only one channel at each packet transmission, for as many as possible. By simple analytical... 

Car accident damages take about 7 percent of GPD of Iran every year. As a result of car accidents, the economy of the country is damaging irreparably. The amount of road casualties equals casualties in a complete war. Considering the aforementioned conditions, the researchers are thinking about new technologies to reduce the cost of the accidents. So the use of Vehicular ad-hoc Networks (VANET) is inevitable in the near future. Content distribution service is one of the emerging services of VANETs. This service is used in both safety and comfort related applications. Content distribution describes delivery of media content such as Video, Audio, Image, Text, Software, and Video Games over... 

In cognitive radio networks, secondary users try to use empty channels that primary users provide for transmitting data. First, the secondary users sense the target channels. If the selected channel is empty, they send their data. When the primary user returns, the secondary user has to find another empty channel for transmitting data. The process of changing channel is called hand off. In recent years, there are challenges in the spectrum mobility of for reducing delay time of secondary users packet. In this thesis, we assume that the secondary users network is an ad-hoc network. We use contestation based method for reducing collision between secondary users. In this thesis, we present an... 

In this dissertation, we focus on two types of EH cooperative networks. In the first type, the source and relay nodes access a shared channel according to a random access protocol. Also, they harvest energy from non-RF environmental resources. The relay node has data and energy buffers to store the packets of the source and the harvested energy, respectively. Our main goal is to find the optimal relaying protocol at the relay node. In this regard, the first type of the EH cooperative networks are investigated in two different scenarios. In the first one, the MAC channels of the nodes are independent of the applied policy at the relay node, and thus the throughput of the network is fixed....