Sharif Digital Repository

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 purpose of this thesis is sliding mode control of a roll-pitch seeker by considering the zenith pass problem. This problem takes place when the target appears in front of the seeker’s head. First, the mathematical model of the roll and pitch frames is obtained by the Newton-Euler equations of motion. Then, a MIMO sliding mode controller is designed. The performance of the controller is investigated in the presence of model uncertainties and seeker disturbances. The results indicate that the designed controller is robust enough and provides a suitable performance in the stabilization, tracking and guidance loops.
 

In this research, a Ground-to-Ground axisymmetric flying vehicle is studied. In this flying vehicle the warhead is replaced by a nose having simple and cheap guidance and control. Commonly such systems include axial rotation to increase stability, which results in the malfunction of the added seekers. In this research, to overcome this problem, the rotation of the vehicle’s forward part is controlled by fuzzy control method, from the beginning of the fly. In addition, a strapdown seeker, which has high accuracy and low cost is used. This provides the system with employing Integrated Guidance and Control (IGC). The IGC, used in this research is based on fuzzy logic, which directly determines... 

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... 

The microstructures of stainless steels consist of an austenitic matrix with almost continuous network of primery carbides.This class of steel had replaced the traditional super alloys with a reduction in costs and has similar properties under conditions of creep, which is one of the principal degradation mechanisms leading to failure in service at elevated temperaturs , therefore, their mechanical properties such as tensile strength and creep resistance are particularly important in hot deformation. Recently the effects of temperature and aging time on static strain aging in worked stainless steel have been investigated. In this study the deformation behavior of HP-series austenitic... 

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... 

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 rapid growth of the Internet, edge computing, and artificial intelligence has intensified the demand for high-capacity and flexible networks, where packet switches play a fundamental role. With the increasing hardware resources and transceiver bandwidths of modern FPGAs, implementing such switches on reconfigurable platforms has become not only feasible but also highly attractive, offering advantages such as reconfigurability, integration with other network functions, and eliminating the need for separate ASIC-based solutions. In this thesis, we present a scalable switch fabric architecture on FPGA, which on the VU13P device enables the implementation of a switch with up to 128 ports at... 

With the advancement of technology and the increase in the scope and complexity of data communication networks due to the growth of the number of users and the volume of traffic, the need to increase the speed and quality of access for exchanging information at any point in the network is increasing day by day. In this regard, cell-free networks (CF) with a different architecture compared to traditional cellular networks have been introduced, which have advantages such as improving the total user rate, complete network coverage, and solving cell edge problems. In this type of network, a large number of access points (AP) serve users (UE) through AC connection on the traditional mobile radio... 

In this M.S. dissertation numerical study of slinger fuel distributer has been studied. This type of atomizer has been used in mini turbojets like Teledyne CAE.
The main purpose of this work was obtaining spray structure of slinger atomizers. This goal was achieved by implementing a UDF code in FLUENT® software to model the primary atomization that include variation of fluid from exit of slinger disk bores till formation of primary droplet. In FLUENT® the DPM method and its ability to utilizing Lagrangian approaches have been used. The result of this model is validated by the data from experimental test that can be found in Articles. This is the first time that spray structure of slinger... 

The process of injecting acid or acidizing, is one of the most common ways to stimulate oil and gas wells. The purpose of this process is to increase the productivity of the well by increasing the permeability of the reservoir rock around the well. This is especially important in carbonate reservoirs due to damage to the formation and low intrinsic permeability in some places. In order to minimize the effects of structural damage, conventional wormhole channels are created to pass through the injured area. One of the important factors in acid validation is achieving optimal injection rate, which means obtaining the highest permeability with the lowest amount of injected acid.Numerous... 

Electric vehicles (EVs) will be used rampantly in future transportation system. Although the uncontrolled charging of these EVs will be threatening for the stability and sustainability of the grid, a well-suited energy trading policy may provide a number of beneficial services to the grid as well as preserving the sustainability of the system along with heightening the performance of operation. In this paper, by taking advantage of block rate tariff, a wholesale pricing policy is introduced. A multi-objective approach is utilized to address the cost reduction and load levelling services, concurrently, in order to guarantee the profits of the both the grid and EVs. Due to the high... 

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... 

One of the proposed methods for enhancing optical networks and increasing their capacity is the use of the band multiplexing concept. This approach leverages additional available bands in optical fibers, enabling a significant boost in network capacity at much lower costs compared to other methods. However, fully utilizing the potential of this concept requires efficient resource allocation strategies to adequately counteract the nonlinear effects in optical fibers caused by increased bandwidth. In this research, we introduce an innovative method that simultaneously considers the physical layer constraints and user quality of service requirements for resource allocation in multi-band optical...