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    Graph homomorphisms through random walks [electronic resource]

    , Article Journal of Graph Theory ; 2003, Volume 44, Issue 1, pages 15–38 Daneshgar, A. (Amir) ; Hajiabolhassan, Hossein ; Sharif University of Technology
    Abstract
    In this paper we introduce some general necessary conditions for the existence of graph homomorphisms, which hold in both directed and undirected cases. Our method is a combination of Diaconis and Saloff–Coste comparison technique for Markov chains and a generalization of Haemers interlacing theorem. As some applications, we obtain a necessary condition for the spanning subgraph problem, which also provides a generalization of a theorem of Mohar (1992) as a necessary condition for Hamiltonicity. In particular, in the case that the range is a Cayley graph or an edge-transitive graph, we obtain theorems with a corollary about the existence of homomorphisms to cycles. This, specially, provides... 

    Unique list-colourability and the fixing chromatic number of graphs [electronic resource]

    , Article Discrete Applied Mathematics ; Volume 152, Issues 1–3, 1 November 2005, Pages 123–138 Daneshgar, A. (Amir) ; Hajiabolhassan, Hossein ; Sharif University of Technology
    Abstract
    In this paper we introduce a chromatic parameter, called the fixing chromatic number, which is related to unique colourability of graphs, in the sense that it measures how one can embed the given graph G in G∪Kt by adding edges between G and Kt to make the whole graph uniquely t-colourable. We study some basic properties of this parameter as well as its relationships to some other well-known chromatic numbers as the acyclic chromatic number. We compute the fixing chromatic number of some graph products by applying a modified version of the exponential graph construction  

    Circular colouring and algebraic no-homomorphism theorems

    , Article European Journal of Combinatorics ; Volume 28, Issue 6, August 2007, Pages 1843–1853 Daneshgar, A. (Amir) ; Hajiabolhassan, Hossein ; Sharif University of Technology
    Abstract
    In this paper, we apply some new algebraic no-homomorphism theorems in conjunction with some new chromatic parameters to estimate the circular chromatic number of graphs. To show the applicability of the general results, as a couple of examples, we generalize a well known inequality for the fractional chromatic number of graphs and we also show that the circular chromatic number of the graph obtained from the Petersen graph by excluding one vertex is equal to 3. Also, we focus on the Johnson–Holroyd–Stahl conjecture about the circular chromatic number of Kneser graphs and we propose an approach to this conjecture. In this regard, we introduce a new related conjecture on Kneser graphs and we... 

    Density and power graphs in graph homomorphism problem

    , Article Discrete Mathematics ; Volume 308, Issue 17, 6 September 2008, Pages 4027–4030 Daneshgar, A. (Amir) ; Hajiabolhassan, Hossein ; Sharif University of Technology
    Abstract
    We introduce two necessary conditions for the existence of graph homomorphisms based on the concepts of density and power graph. As corollaries, we obtain a lower bound for the fractional chromatic number, and we set forward elementary proofs of the facts that the circular chromatic number of the Petersen graph is equal to three and the fact that the Coxeter graph is a core  

    Design and Manufacturing of an Assay System by Lateral Flow Method and Optimize the Model by Lattice-Boltzmann Numerical Solution

    , M.Sc. Thesis Sharif University of Technology Gholami Poshtehani, Abbas (Author) ; Shamloo, Amir (Supervisor)
    Abstract
    Lateral Flow Immunoassay kits are one of the most important instrument in laboratories and houses for diagnosing diseases, hormones, food toxins and etc. fast, exactly and by low cost. Since one of the most expensive parts in the mentioned kits, is using antibodies in their construction, an attempt has been made in this project for descending usage of antibody and consequently final cost of these sensors besides keeping desired and necessary sensitivity of these diagnostic kits. For this purpose, first of all with the help of simulating flow’s behavior in Lattice-Boltzmann method, provisions has been made to predicting flow’s movement behavior in Nitrocellulose membrane, Based on its results... 

    On the isoperimetric spectrum of graphs and its approximations [electronic resource]

    , Article Journal of Combinatorial Theory, Series B ; Volume 100, Issue 4, July 2010, Pages 390–412 Daneshgar, A. (Amir) ; Hajiabolhassan, Hossein ; Javadi, Ramin ; Sharif University of Technology
    Abstract
    In this paper1 we consider higher isoperimetric numbers of a (finite directed) graph. In this regard we focus on the nth mean isoperimetric constant of a directed graph as the minimum of the mean outgoing normalized flows from a given set of n disjoint subsets of the vertex set of the graph. We show that the second mean isoperimetric constant in this general setting, coincides with (the mean version of) the classical Cheeger constant of the graph, while for the rest of the spectrum we show that there is a fundamental difference between the nth isoperimetric constant and the number obtained by taking the minimum over all n-partitions. In this direction, we show that our definition is the... 

    Structural Health Monitoring Using Optimal Finite Element Model Based on Digital Image Correlation

    , M.Sc. Thesis Sharif University of Technology Amir Hossein Amir Ahmadi (Author) ; Khaloo, Alireza (Supervisor)
    Abstract
    The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

    Molecular Engineering of Recombinant Human Transglutaminase 2 with Correct Folding ( Soluble ) for Studying Promiscuous Organic Reactions

    , M.Sc. Thesis Sharif University of Technology Gholami, Amir Hossein (Author) ; Kalhor, Hamid Reza (Supervisor)
    Abstract
    Transglutaminases of family enzymes are implicated in different functions in cell including cellular division and cell adhesion. Several members of this family catalyze formation of isopeptide bond that involved in wound restoration and angiogenesis. Transglutaminase 2 that have been studied in this project, are found in almost every human cell tissue. This enzyme has multiple functions depending on its cell location. In cytoplasm TG2 act as GTPase and is involve in post translational modifications. This enzyme by using calcium form a isopeptide bond between two proteins, isopeptide bond is function in brain cortex and cells creates amyloid structures that including brain diseases, Parkinson... 

    Semisolid Stir Joining of As-Cast Silicon-Aluminum Bronze

    , M.Sc. Thesis Sharif University of Technology Ferasat, Keyvan (Author) ; Kokabi, Amir Hossein (Supervisor) ; Ashuri, Hossein (Supervisor)
    Abstract
    Aluminum Bronzes have many applications in marine environments. These alloys suffer from both hot cracking and cold cracking. In order to overcome the hot cracking and cold cracking, Semisolid Stir Joining method and a proper thermal cycle was used respectively. Effects of temperature, stirring rate, and tool type were investigated in Semisolid Stir joining method. In this method, butt joint design was used in order to place specimens, and the specimens were heated up to specific temperatures (920, 925, 930°C). A stirrer (Cylindrical and Grooved tool) with three rotational speeds (800, 1200, 1600 RPM) was introduced into the stir weld seam. Welded specimens were cooled to the 900°C... 

    Electrochemical Hydrogen Generation Using Metal Organic Frameworks Derived Catalysts

    , M.Sc. Thesis Sharif University of Technology Koohdareh, Amir Reza (Author) ; Gholami, Mohamad Reza (Supervisor)
    Abstract
    In recent years, the widespread investigation on multi-transition metal oxides that with two or more transition metal oxides, have been increased rapidly for electrochemical application due to low cost, high conductivity and good electrochemical performance other than single metal oxides. In this project, CuCo2O4 nanoparticles were firstly fabricated by decomposing of CuCo-MOF as the template. The as prepared samples were used to synthesis a new nanocomposite of MoS2 and CuCo2O4. The best ratio of the two component were optimized to prepare the best electrocatalyst for Hydrogen evolution reaction (HER). The structure of prepared nanocomposite were investigated by various techniques such as... 

    Analysis and Evaluation of Routing Protocols Conformance Test

    , M.Sc. Thesis Sharif University of Technology Tabatabaee, Hosein (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Nowadays, one of the problems of network designers and users is the correctness of network equipment functionality. Since routers play an important role in information transfer between various networks and communicate with each other through a routing protocol, any violation of such protocol can result in the network's failure or defective transfer of data. Thus, being assured of the conformance of the implemented protocol in a router with what has been defined in the protocol's standard is of great significance. To this end, before using or exposing a router, network equipment testers should run protocol conformance tests on it and insure its correct functionality. This brings up the... 

    Network Traffic Analyzer

    , M.Sc. Thesis Sharif University of Technology Silavi, Ehsan (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    In order to increase the network performance, to discover network security threats, to guarantee the quality of services, to simulate networks and develop new network protocols, network designers and operators need software tools to analyze the network traffic. The first step to do this analysis is network monitoring. This can be done by using various software and hardware tools.
    In this research we developed a tool which analyzes the network traffic using appropriate statistical methods. The models which are analyzed in this application are: Poisson, Self-similar and Weibull. This application analyzes the network traffic based on this statistical models and calculates their parameters.... 

    Analysis and Evaluation of Real Timeliness and Safety of VANET

    , M.Sc. Thesis Sharif University of Technology Ahmadvand, Hossein (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    The increasing number of road accidents and fatalities have yielded the introduction of several solutions by related industries such as automobile manufacture. Proposed solutions can be classified into two categories: passive, such as airbags, and active such as ABS ad ITS-based technologies. Inter vehicles communication let the communication between vehicles(V2V) or between vehicles and road infrastructure (V2I) by relying on DSRC technology and standards. Intelligent Transportation System (ITS) has three main types of applications namely safety, traffic and commercial. Safety applications are the main goal of vehicular communication, and real time guarantee in safety applications is so... 

    An Efficient Approach for Improving the Performance of Real-time Flow Routing in SDN Controllers

    , M.Sc. Thesis Sharif University of Technology Heidari, Hossein (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    In real-time systems, jobs that miss their deadline are considered worthless or ineffective. Nowadays, real-time applications (such as multimedia) that communicate through software-defined networks (SDN) are widely used and will continue to expand in the future. SDN is an emerging network architecture in which control plane is separated from data plane to manage it directly. In this research, we make changes to the controller and the switch used in such network to deliver real time packets or real-time flows (such as video) on time, as much as possible. As missed deadline packets are worthless and they waste bandwidth, dropping them is a solution. Moreover, the controller can drop flows that... 

    Packet Processing Acceleration for Virtualized Network Functions

    , M.Sc. Thesis Sharif University of Technology Barati Sedeh, Amir Reza (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Network Function Virtualization (NFV) is a new paradigm in computer networks for implementing network functions on general-purpose common-of-the-shelf processors. The revolutionized NFV architecture has shown to be a suitable replacement for hardware middleboxes. NFV is in high demand because of its lower costs, increased flexibility, and more scalability. However, the ever-growing volume of network traffic and increased data transfer speed in computer networks have made achieving high performance the major issue in this area. With thousands of processing cores and high memory bandwidth, Graphical Processing Units (GPUs) are potentially an appropriate solution to accelerate network... 

    Conversion of Traditional Logistics Service Providers to 3PL Case Study: Persian Gulf Transportation Company

    , M.Sc. Thesis Sharif University of Technology Gholami, Amir Ebrahim (Author) ; Akbari Jokar, Mohammad Reza (Supervisor)
    Abstract
    In spite of logistics outsourcing benefits, Iranian companies usually do their logistics activities themselves, and logistics outsourcing are limited in performing of transportation and warehousing. One of the main reasons of these conditions is lack of a powerful and modern 3PL in Iran even though there are high potentials for 3PLs in Iran’s different industries such as automotive, oil and petrochemical, food and grocery, retail goods and etc. Therefore formation of powerful and modern 3PLs in Iran is necessary. Two styles for formation of 3PLs are common. In First style the companies start up directly the third party logistics business and in second style traditional logistics firms try to... 

    Analyzing and Evaluating Intrusion Detection Datasets and Providing a Solution to Solve their Weaknesses by Focusing on Benign traffic

    , M.Sc. Thesis Sharif University of Technology Rezaei, Farzam (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Today, with the increasing expansion and development of computer networks and information technology, network security has become an important concern for experts and researchers in this field. One of the main elements in the field of information and network security are intrusion detection systems. To maintain the accuracy and quality of these systems, we need to test and evaluate them frequently. The datasets of intrusion detection systems are one of the main tools for evaluating these systems. The quality and accuracy of these systems in detecting anomalies and attacks in the network largely rely on rich and complete data. Also, the main component of this datasets is the traffic data,... 

    Analysis and Evaluation of Security Vulnerabilities of Precision time Protocol (PTP) and Securing IEEE61850 based Digital Substations

    , Ph.D. Dissertation Sharif University of Technology Moradi, Mohsen (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Nowadays, power systems and substations are the most important components of the vital infrastructure of a country, which handle the production, transmission and distribution of the electrical energy. Automation systems increase the efficiency of the power industry while making remote control possible, but the use of computer-based control systems is a potential field for cyberattacks which may cause equipment destruction and electricity network destabilization. One of the main requirements for the utilization of digital substations is the synchronization between different equipment used in it. Several algorithms and protocols have been proposed so far for time synchronization in distributed... 

    A Suitable Approach to Detect Vulnerabilities in Windows-based HMI Used in Industrial Environments (SCADA)

    , M.Sc. Thesis Sharif University of Technology Soodi, Sanaz (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Supervisory Control and Data Acquisition (SCADA) systems are recognized as critical components of industrial infrastructure across various sectors. These systems consist of diverse hardware and software components designed for automated control and remote monitoring of industrial processes. One of the pivotal software components in SCADA systems is the Human-Machine Interfaces (HMI), which serve as the user interaction point with control systems. The security of HMI software is of paramount importance, as a breach in this area could compromise the entire SCADA system. In recent years, given the security oversights in industrial control systems compared to information technology sectors,... 

    Reconfigurable Architecture For Cryptanalysis Applications

    , M.Sc. Thesis Sharif University of Technology Noshadravan, Mohammad Reza (Author) ; Jahangir, Amir Hossein (Supervisor)
    Abstract
    Nowadays, the significance of securing data and information is undeniable. Cryptography is being used to provide data security. In addition, cryptanalysis is required to evaluate the effectiveness of cryptography methods, and hence, it is an essential concept for securing data. In general, the cryptography functions shall be designed in a way to impose a high load of time-intensive operations to prevent an adversary from accessing the main data from the encrypted data. As a result, cryptography and cryptanalysis algorithms need high performance computations. So far, a number of methods have been proposed to support the required performance. These methods include: distributed computing and...