Sharif Digital Repository

Internet of Things means making the all of things smart to access them anytime, anywhere through the Internet. Existing of IoT as a novel way of networking, opens up new issues round the communication and network world. One of them is how to establish the security in such a diffuse network. Because the members of this network are not smart phones, computers or any other usual networking technologies, but they are the normal things and appliances in our daily lives, such as refrigerators. Smart things are mostly resource-constrained and power-limited so the former ways of securing networks cannot be applicable in IoT. Thus, Security bootstrapping has is introduced a solution for establishing... 

In this study, we intend to investigate the effect of pollution levels on the valuation of residential units in Tehran. The method used in this research is Hadanik pricing method. Data required for the project, in relation to the intrinsic characteristics of housing including number of bedrooms, building life, area and… air pollution index by regional stations on a daily basis and housing environmental characteristics including per capita green space, day and night pollution index, density The population of the area and… are collected. According to the results, they have the greatest impact on determining the value of the building area and building life, and after controlling for other... 

The main objective of all managers of the economic organizations, manufacturing and industrial companies and service providers is to take steps toward improvement and effective use of different resources like workforce, capital, materials, energy and information. To attain the desired productivity, managers have to observe requirements such as establishment of a working organizational structure, effective implementation methods, safe equipment and tools, balanced working atmosphere and qualified human force as the most important factor. Therefore productivity culture should be publicized throughout the organization, and human force should be considered as the main component of this process.... 

Considering the advantages of optical communications and code division multiple access technique, Optical Code Division Multiple Access Networks (OCDMANs) was introduced. Thence, many researchers have suggested methods for creating Quality of Service (QoS) differentiated classes in OCDMANs. In this thesis, we have comprehensive review on the QoS assignment methods and enhance them by offering new techniques. In physical layer, we concentrate on variable chip rate OCDMANs and in MAC sub-layer, a new algorithm named Adaptive Level Control (ALC) is introduced. Then, we focus on the physical design of OCDMANs. Firstly, we solve the problem of one-class OCDMAN and introduce few simple and... 

In this study, the cooperative inertial navigation systems are used to prevent the error growth of the inertial navigation system in unmanned aerial vehicles that fly in group. Here, the navigation problem is defined for a group of unmanned vehicles, flying with full six degrees of freedom and the objective is to estimate the navigation information of all cooperators. Due to the nonlinear equations, the decentralized extended Kalman filter is used to estimate the states of the system. This means that there is a Kalman filter in each vehicle. The inputs of this filter are the range and the bearing angles between the vehicle and the cooperators, the estimated position of the cooperators and... 

Consistent growth in volume and dynamic behavior of traffic mandates new requirements for fast and adaptive resource allocation in modern optical networks.Elastic optical networks have been proposed to provide a competitive and scalable solution by creating tunable high-capacity optical communication networks in which network elements are configured according to the actual need to minimize resource usage for the specified service requirements. Resource allocation with quality of service constraints is one of the most challenging problems in elastic optical networks which is conventionally formulated as a complex mixed-integer nonlinear optimization program.In this research work, we focus on... 

In this study, integrated navigation systems that utilize velocity-matching algorithm and are used in automatic landing of Unmanned Aerial Vehicles (UAV) are investigated. At first, the accuracy of the navigation system in the landing phase is analyzed and the relationship between the accuracy of inertial sensors, flight parameters and the accuracy of the navigation system is derived analytically. Then, by integrating the dynamic model of the UAV and the inertial measurement unit, a new algorithm for navigation of fixed-wing UAVs is presented. The integration mechanism of the proposed algorithm is tightly coupled; hence, it is capable to eliminate the errors of UAV model and inertial system.... 

The perpuse of this thesis is to design and fabricate a laboratory one degree of freedom stable platform under turbulences by model-based design method. To do this, different parts of the system were first modeled in the Solidworks software and then fabricated with various tools. With proper assembly of electronic and mechanical components, the original body of the system was created. Then, the controller motor with a stable platform which is attached to it was modeled and simulated in MATLAB software. Then, the parameters of the equations were calculated using standard identification tests and TCACS optimization algorithm. One of the challenges of this thesis is the malfunction of the... 

In this research, a cooperative terminal guidance algorithm has been derived for simultaneous multi-interceptor collision with a target. This algorithm is obtained using the combination of model predictive control method and differential game theory. One of the features of this method is the calculation of the optimal guidance command in the form of an explicit relationship. Another feature of this method is its resistance to disturbances due to the use of differential game theory. The first innovation of this research is the use of this hybrid method to create a guidance algorithm, even in the non-cooperative guidance problem. The next innovation is in creating a cooperative terminal... 

Mobile edge computing (MEC) is a promising technology that aims to resolve cloud computing’s issues by deploying computation resources at the edge of mobile network and in the proximity of users. The advantages of MEC include reduced latency, energy consumption, and load on access and mobile core networks, to name but a few. Despite all the aforementioned advantages, the mobility of mobile network users causes the traditional MEC architecture to suffer from several issues, such as decreased efficiency and frequent service interruption. One of the methods to manage users’ mobility is virtual machine (VM) migration, where the VM containing the user’s task is migrated to somewhere closer to... 

Hybrid engines are one of a variety of chemical propulsion systems that have been given special attention in recent years by various industries such as space and defense. The most important reasons for considering this type of system are its high safety, its affordable price compared with liquid fuel propulsion systems, the possibility of switching on and off and changing thrust. This system has a lot of disadvantages as well. This system cannot meet all the needs of different industries due to the low regression rate and, consequently, the limitation of the operating range, thrusts and special impulse. As a result, increasing the fuel regression rate in these engines can greatly expand... 

Optical impairments, as a challenging obstacle in optical communication systems, have been under deep attention of optical engineers in recent years. These impairments can be divided into two categories of linear and nonlinear impairments. Dispersion is a significant linear impairment leads to broadening of the optical signal and interference between transmitted symbols during detection. Nonlinear impairments such as cross-phase modulation (XPM) and self-phase modulation (SPM) also distort the transmitted signal through the fiber, causing interference at the receiver and degrading the system's performance. An appropriate solution for compensating optical fiber impairments is to utilize... 

The performance evaluation involves a process by which the employees are periodically and officially evaluated. Major reasons of performance evaluation include, among others, identification of efficient employees and granting bonuses to them to create stimuli to improve their and other employees' performances. The main objective of performance evaluation constitutes study of people's performances in the organization in order for directors to take proper and required decisions to enhance both quantities and qualities of the employees' works. The performance evaluation is deemed to be a major critical function of the management of human resources to facilitate organizational effectiveness. In... 

Quantum key distribution (QKD), as one of the applications in quantum information processing, allows two distant legitimate parties to establish a set of secure keys even in the presence of an untrusted environment controlled by an eavesdropper. In general, QKD mainly includes two families, namely, discrete variable quantum key distribution (DV-QKD) and continuous variable quantum key distribution (CV-QKD). In CV-QKD system, the sender Alice, encodes information on the quadratures of the optical field with Gaussian modulation, and the receiver Bob, decodes the secret information with homodyne or heterodyne detection so that this system promises a higher secret key rate than its DV-QKD... 

With the advancement of technology, the volume of network traffic has also increased dramatically. The optical network, as the main part of the backbone communication system, plays a significant role in the transmission of network traffic. Due to the limited network resources, an efficient resource allocation in optical networks is required to increase network performance and reduce costs. To solve resource allocation optimization problems, an effective tool is needed to provide a suitable solution in a reasonable time. Resource allocation problems are usually developed on a graph, which is derived from network topology or other properties of the network. As a result, graph-based tools seem to... 

Dynamic reconfigurability in optical and mobile networks can facilitate heterogeneous service provisioning while utilizing minimal resources. This allows cost-efficient service delivery resulting in increased revenues for network operators. Deployment of elastic mobile and optical networks is a key driver for enabling reconfigurability in modern networks. Elastic optical networks can be utilized as the fronthaul portion of new generation of mobile networks. Such elastic optical fronthaul networks facilitate joint reconfiguration of flexible radio and optical elements and provide considerable performance improvements. This thesis focuses on the joint dynamic selection of functional splits and... 

Optimal resource allocation sustains mobile operators' competitiveness by increasing profitability. Reducing system configuration costs and enhancing accepting new requests to boost revenue provide increasing profitability. A crucial strategy in modern communication frameworks is network slicing, which assigns specific network resources to each customer to ensure its required quality of service (QoS) without interference from other slices. In our study, focusing on the xhaul network structure within fifth-generation mobile networks, we delve into joint optimization of the allocation process across three dimensions of processing, radio, and communication resources to enhance operator... 

In this investigation, cellular structure of a weakly unstable detonation wave in H2/O2/Ar mixture is studied. The detonation is simulated using 2D reactive Euler equations and one step Arrhenius type reaction model developed by Mr. Barkhordari. The numerical technique is the high order Piecewise Parabolic Method on the basis of Godonov method. The numerical fluxes are computed based on a high-order extension of the Godunov's method; the piecewise parabolic method (PPM). The initial cell formation processes and different machanisms involved in cell size changes are studied. This study shows that the form of initial perturbation used to intrigate the instability of detonation is not important... 

In minimum cut problem we aim at finding a set of edges with minimum overall cost possible, such that removing them would separate two specific vertices, source and sink. This problem has been studied thoroughly, however the available algorithms were not proven to be time-wise optimal. Nowadays, planar graphs have attracted more attention because of their applications in cities and countries map. Moreover,their characteristics and properties, make some problems easier to solve in planar case. In this thesis, we will have a survey on algorithms for minimum cut on planar graphs. Our motivation to choose these algorithms is the balance between how easily they could be implemented and how fast...