Sharif Digital Repository

With the increasing tendency of consumers to purchase from online stores and the remarkable growth of this industry in recent years, timely and cost-efficient delivery of goods to the final customer has become one of its major challenges. Accordingly, last-mile delivery has attracted significant attention from both researchers and practitioners. This study addresses a vehicle routing problem that considers customers’ ability to pick up their orders from selected centers and their possible presence at different locations within the planning horizon. This thesis aims to enhance customer satisfaction and reduce distribution costs by employing two innovative vehicle routing approaches. The first... 

Several nanostructured photocatalysts were prepared by sol-gel, hydrothermal and precipitation methods. The products were characterized by X-ray diffraction (XRD), nitrogen adsorption, UV-VIS diffuse reflectance spectroscopy, fourier transform infrared absorption spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM). Their Photocatalytic activities were evaluated by degradation of organic pollutants in liquid-solid system. In this research work, the influence of metal oxide, copper oxide, on structure of nanocrystalline mesoporous titanium dioxide were evaluated. Different molar percentages of copper oxide on the surface of titanium dioxide were... 

Nuclear energy is one of the most important sources of energy from the economical point of view and also in terms of cleanliness and safety. Hence, strategically, uranium is one of the most basic elements of the earth and nowadays, the importance of this element is more marked due to the nuclear industry developement. Therefore, uranium recovery from the wastes generated during nuclear fuel production in Isfahan’s uranium conversion plant- in which yellow cake is converted to uranium hexafluoride- is quite pivotal. In this experimental research, uranium is extracted from the sludge of evaporation lagoons of Isfahan’s UCF plant via solvent extraction method. Execution of this project in an... 

In this thesis, We propose and test a method for controlling the size of nanoparticles, which plays a fundamental role in their electrical, optical, and mechanical properties. The method utilizes turbulent mixing, and is applicable to the fabrication of any type of nanoparticle that uses a solution environment in the preparation process. We show by well-controlled experiments on the CdS nanoparticles, which are semiconducting materials, that the average size < d > of the particles decreases with Reynolds number Re. To gain a deeper understanding of the phenomena reported here, we have carried out molecular dynamics simulations of the processes. In second investigation, We provide a simple... 

While Cloud providers face problems during providing services to their clients, such as lack of resources or increasing idle resources in low workload; they can share their resources with other providers by participating in Cloud Federations, and take advantage of Cloud Computing benefits like high scalability and resource extension. Moreover collaborating Cloud Federations expands Geographical area of providers. The Resource Allocation Problem has been considered in many researches, but in fields like Cloud environment and Federated Clouds it comes with complications. This thesis analyzes an optimized mechanism based on game theoretic approach for Resource Allocation Problem in Federated... 

In comparison to attitude control of a satellite which is widely used in practical missions, orbit control (espescialy autonomous orbit control) has been only recently paid attention. Autonomous, on-board orbit control, also called autonomous stationkeeping, means the automatic maintenance of all of orbital elements by the satellite itself. In this thesis, an autonomous absolute orbit control strategy for a single Low Earth Orbit (LEO) satellite is presented. When the satellite violates the control trigger error limits, then the controller is activated and calculates a sequence of orbital maneuvers that move the satellite towards its desired states. The absolute orbit control of the... 

In this thesis, the problem of failure-tolerant control of the satellite in coupled orbital and rotational motion is investigated. All of the actuators of the satellite are thrusters and only the failure of the actuators is considered. At first, the equations of coupled relative translational-rotational motion of the satellite are derived. Then, the required specifications of the approapriate control method for the problem is explored with the conclution that the controller must be able to predict the behavior or planning the future trajectory of the satellite. In the next step, model predictive control, which has the required specifications, is used to control the coupled... 

The primary goal of this thesis is to develop a Fault Tolerant Control (FTC) system for a flexible satellite in presence of actuators fault and failure. The actuators of the satellite are including three magnetorquers and three reaction wheels on each principal axis. At first, the three-degree-of-freedom rotational motion of a rigid satellite with two flexible solar panels is modeled. The flexible panels are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using the Lagrange’s equation. Then, the dynamic model is validated by comparing the simulation results of the model to the NX... 

Traffic flow modeling on different levels was always the topic of many studies. In this regard, many researchers have tried to eliminate traffic problems by developing precise models. Therefore, in this study and in its two major parts, we developed two models: one macroscopic and one microscopic. Like previous studies, the main purpose here was the development of traffic flow models that have better precision and give more information about the mechanism behind the traffic phenomena. Our focus was on the free spaces in front of drivers which were considered in a macroscopic traffic flow model and resulting microscopic traffic flow model.First part, addresses the first-order extension of the... 

In this thesis, first, random lasing in a three dimensional disordered medium has been simulated using FDTD method and some properties of random lasers which were observed by others in the previous experiments have theoretically been shown. Our simulation results show that when the density of particles increases to an upper limit, the intensity of lasing modes is enhanced. Also, the effects of pumping rate and particle size on the number of lasing modes and their intensity are studied. Lasing threshold of laser modes in different disordered systems is calculated and it is shown that by an appropriate selection of the central frequency of gain line-shape, the output power intensity of random... 

This dissertation investigates the Multiple-Horizon Multiple-Model Predictive Control method and its application in soft landing problem on an irregular-shaped asteroid. In this way, a predictive framework including a heuristic guidance law named Predictive Path Planning and Multiple-Horizon Multiple-Model Predictive Control (MHMM-PC) as the control scheme is introduced for soft landing on an asteroid. Obviously, reducing the fuel consumption is a priority in space missions. Thus, the employed control framework should minimize the required control effort. Furthermore, the control method should be robust enough to deal with the effects of model uncertainties and disturbances. The unique... 

The problem of path simplification is an important problem in computer science. With the advances in navigation and geographical information based systems, simplification and data compression have gained considerable importance. The intends to find a path with less weight than the provided path while estimating the initial path with good accuracy and simplifying the storage and process cost of path information. This problem is not only useful in Geographical Information Systems, but it also has use cases in image processing and computer graphics and has been studied a lot in computational geometry. In this research, we introduce a simplification game that models the limited version of the... 

The observations of the cosmic background radiation and large-scale structures show that the standard cosmological model is in good agreement with observational data. The standard model is based on the cosmological constant, dark matter, and Gaussian, nearly scale-invariant, adiabatic, and isotropic initial conditions. Although this model has been phenomenologically successful, but the problems of dark energy, dark matter, missing baryons and early universe remain unresolved. One of the most important theoretical questions in cosmology is whether the cosmological constant is the reason for accelerated cosmic expansion. In other words, is Einsteinian gravity the correct theory on the cosmic... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Digital computers, comprising universal logic gates, are tremendously versatile. This versatility associated with the increasing integrability of digital electronics due to Moore’s law has left nearly no room for analog computers in the last few decades. However, in the case of some specific problems such as modeling complex and nonlinear systems or pro-cessing large amounts of data, computation time and power is still a serious restriction of digital computing. Optical phenomena are fast enough and offer novel approaches to overcome the mentioned restrictions about the system speed and power consumption. Therefore, optical structures make possible to perform ultra-fast spatial analog... 

Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related...