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farajpour-niri--farid
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Elastic Analysis of Brazilian Test of Transversely Isotropic Material
, M.Sc. Thesis Sharif University of Technology ; Eskandari, Morteza (Supervisor)
Abstract
In Former research we determinate elastic response of Brazilian Test of transversely Isotropic material . In Bio-mechanic science surveying mechanical properties and modeling biological organ such as bone , tooth and bio-material such as titanium, zirconium with application in joint replacement is very important . One of method to determine properties of bio-material which mostly has transversely Isotropic behavior is Brazilian Test. Also most rocks has transversely Isotropic behavior, so choosing efficient test is so important. In current issue , load apply in limited area and it is also considered friction in area of jaw loading area .By use of displacement potential function ...
Improvement of Robustness of Deep Neural Networks in Adversarial Environments
, M.Sc. Thesis Sharif University of Technology ; Jalili, Rasul (Supervisor)
Abstract
Increasing the volume of data and processing power of computing systems, resulted in using machine learning algorithms to solve a variety of problems, including automatic security threat detection and user anomaly detection. Despite of efficient performance of machine learning algorithms, especially deep neural network models, they have some fundamental vulnerabilities. Their confidentiality, integrity, or availability can be threaten in an adversarial environment. Adversarial example is one the most significant attacks which cause the model to misclassify the perturbed input. Another threat is model extraction attack. A machine learning model can be accessed by a user interface and label...
A new experimental and theoretical approach for viscosity Iranian heavy crude oils based on tuning friction theory and friction volume theory parameters
, Article Inorganic Chemistry Communications ; Volume 139 , 2022 ; 13877003 (ISSN) ; Jafari Behbahani, T ; Ghotbi, C ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this research work, Friction Theory and Free Volume Theory are applied to live oil characterized based on SARA TEST for viscosity modeling and make a new model in combination with two equation of state (PR and PC-SAFT). Parameters for pseudo-components are obtained by tuning the viscosity at atmospheric pressure and temperatures of 10, 20, and 40 ℃. A new fitting approach is suggested where the number of fitting parameters is 17 and 12 for FT and FVT model, respectively. These parameters are tuned using the Genetic Algorithm and Particle Swarm Optimization and make eight new models. The results show that PC-SAFT provides viscosity predictions for all models with less deviation from...
Prediction of Crude Oil Viscosity Using Equations of State
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Sirous (Supervisor) ; Jafari behbahani, Traneh (Supervisor)
Abstract
experimental data of crude oil for viscosity are available in limited conditions of temperature and pressure. Therefore, the use of empirical equations and relations to predict it at temperatures and pressures beyond the temperature and pressure of the reservoir is inevitable. In order to reduce the cost of the laboratory, the use of a comprehensive model in this project is considered. For this purpose, using two theories of friction and free volume, the Peng Robinson and PC-SAFT equation of states and genetic algorithms and particle swarm optimization are widely used to calculate the viscosity of pure hydrocarbons, binary mixtures of hydrocarbons and crude oil have been used. Obviously, by...
Knowledge active forgetting: the forgotten side of knowledge management
, Article PICMET 2009 - 2009 Portland International Conference on Management of Engineering and Technology, Portland, OR, 2 August 2009 through 6 August ; 2009 , Pages 1007-1018 ; 1890843202 (ISBN); 9781890843205 (ISBN) ; Bagherzadeh Niri, M ; Rahimi, M ; Yarmand, H ; Sharif University of Technology
2009
Abstract
As Gregory Bateson, the British social scientists, once said "You can't live without an eraser", the process of learning is not a unidirectional way toward accumulation of knowledge, rather, organizations should critically evaluate the value of their knowledge and if necessary, actively forget no-longer-useful knowledge. A brief review of related literature shows that the concept of knowledge active forgetting (KAF) is a crucial aspect of organizational learning and knowledge management. However, many aspects of this topic deserve more attention by researchers. The main gap in the literature seems to be related to the linkage between peculiar aspects of knowledge (such as stickiness, context...
Simvastatin-loaded nano-niosomes confer cardioprotection against myocardial ischemia/reperfusion injury
, Article Drug Delivery and Translational Research ; Volume 12, Issue 6 , 2022 , Pages 1423-1432 ; 2190393X (ISSN) ; Mousavi Niri , N ; Akbarzade, I ; Sharifi, M ; Aboutaleb, N ; Sharif University of Technology
Springer
2022
Abstract
Although simvastatin (SIM) has been proven to be a powerful agent against myocardial ischemia/reperfusion (MI/R) injury, poor water solubility, short half-life, and low bioavailability have made it futile while using conventional drug delivery system. Hence, this study aims to investigate therapeutic efficacy of SIM-loaded nano-niosomes on MI/R injury. Surface active agent film hydration method was used to synthesize nano-niosomes. The physicochemical properties of nano-niosomes were characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, niosomes were characterized in entrapment efficiency (EE) and releasing pattern. Male Wistar rats were...
Synchronicity and Firm’s Network Structure
, M.Sc. Thesis Sharif University of Technology ; Fatemi, Farshad (Supervisor) ; Ebrahimnejad, Ali (Supervisor)
Abstract
There are two viewpoints about pyramid shareholding and cross ownership; first, shareholders want to increase their control over firms. Second, by pyramidal structure and cross ownership, firms internalize weakness of financial market and lack of some financial institutions. In order to identify reason(s) of this issue, we must first recognize affiliated firms and their networks. In this study, we identify firms’ networks in Iran by three definitions: shareholder network, owner network and director network. Then we estimate any correlation between returns synchronicity and being in a same network. Our results show that more than 40% of studied firms are affiliated. Also there is positive...
Throughput Analysis in Multi Hop Cellular Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
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...
Throughput Analysis of a Cognitive Multi-hop Wireless Network Overlaid on a Cellular Network
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
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...
Network Coding-based Packet Relaying in Wireless Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
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...
Analysis of the Effect of Frame Aggregation in IEEE 802.11 Standard
, M.Sc. Thesis Sharif University of Technology ; Ashtiyani, Farid (Supervisor)
Abstract
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...
Performance Analysis of Cognitive Radio Networks With Capability of Spectrum Mobility
, M.Sc. Thesis Sharif University of Technology ; Ashtinani, Farid (Supervisor)
Abstract
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...
Content Distribution Service Analysis in Vehicular Ad-Hoc Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
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...
Energy Harvesting in Wireless Communication Networks
, Ph.D. Dissertation Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
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....
Cooperative Networks from the MAC Layer Viewpoint
, Ph.D. Dissertation Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Cooperative networks have attracted much attention in the last decade. Being introduced to mitigate the inefficiencies in the physical layer, cooperation can also be beneficial in upper layers, such as MAC layer. Using cooperative communications is specifically more challenging in the random access networks, where collision is a main concern. Delay, as one of the main performance metrics in random access networks, can decrease significantly by using cooperative communications. Transmission delay, i.e., the required time for delivering one packet form its source to destination, is an important metric in many communication networks, such as the networks in which each node generates and...
Analysis of Age of Information in Multisource Communication Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In this thesis, we investigate the age of information in multisource networks. To this end, in the first phase of this thesis, we evaluate the Age of Information (AoI) in slotted ALOHA network. Regarding the interactions among the nodes in such a network, we model the memory of this network with a Trellis and find the peak Age of Information (PAoI) by using this Trellis. Then, we evaluate Age of Information-constrained regions and achievable throughput regions in the slotted ALOHA network and optimize Age of information in a symmetric case. In the second phase, we propose an efficient prioritizing scheme from AoI point of view and find the distribution of AoI and PAoI in such a scheme with...
Analysis and Reduction of the Age of Information in a Random Access Relay Network
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
In data transmission from a transmitter to a receiver, in some applications receiving updated data is crucial. To this end, a metric called Peak Age of Information has been introduced, the minimum of which is equivalent to having more updated packets. In this thesis, a method for calculating the probability distribution function of this random variable in a random access network with a transmitter, a relay, and a receiver in which the error probability of the channels between the transmitter and the relay and also the relay and the receiver is less than the error probability of the channel between the transmitter and the receiver, is proposed. The transmitter and the relay send their packets...
Latency Analysis and Improvement in Distributed Storage Systems
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Today, with the proliferation of smart devices and the advent of various innovative applications, there has been an exponential surge in the number of users in telecommunication networks. Consequently, the data traffic rate is escalating considerably. This has created a major predicament for wireless networks due to the limited frequency spectrum. Therefore, the conventional centralized architecture makes it difficult for the network to address these numerous simultaneous requests. This issue can be solved by designing new architectures. In a way, network information is disseminated to the network's periphery and the contents of the primary data center are provided temporarily in closer...
Traffic Analysis in Cellular Networks based on OFDMA Access
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
OFDMA modulation method is a multiple access technique that is resistant to fading effect in cellular communication systems. In OFDMA, multiple access is performed both in time and frequency, so more users can be served with less delay than other protocols. In this thesis, based on queuing theory, we seek to present a traffic model for OFDMA system traffic analysis in single-cell mode and in the next section in multi-cell mode. Then, by examining and comparing the analytical results and the simulation results, we show that our proposed model for traffic analysis of the OFDMA system is a suitable and effective model. Also, since users in the multimedia environment need different types of...
Throughput Analysis of Routing Algorithms in 802.11s-Based Wireless Mesh Networks
, M.Sc. Thesis Sharif University of Technology ; Ashtiani, Farid (Supervisor)
Abstract
Wireless Mesh Networks (WMNs) can be considered as the result of cooperation among two ad hoc networks, one composed of Mesh Points (MPs) and another one composed of Mesh Clients (MCs) as well as corresponding Access (Mesh) Points. Each one has its own functions and properties. This cooperation results in a flexible network that to fully demonstrate its potentials, requires special routing algorithms and access schemes.Here, we study and analyze three routing algorithms in IEEE 802.11s-based WMNs from throughput point of view. To this end, each node in the network is modeled by a queue during Contention-Free Periods (CFPs). During Contention-Based Period, however, to simplify modeling, we...