Sharif Digital Repository

Algorithms for online identification of parameters of a satellite’s moment of inertia tensor based on two methods (recursive least squares and Kalman Filter) is presented and compared with each other. It is assumed that the satellite actuators are three orthogonal reaction wheels. The only available sensor is a 3-axis rate gyro, which measures the angular velocity of satellite in body coordinate system. For validation of algorithms on earth, a similar identifier was designed for a satellite simulator. Due to difference in Dynamics of satellite and satellite simulator, capability of identifying center of gravity was added to algorithms. In order to account for friction in air bearing of... 

In this thesis, gas sensors were fabricated based on resonance frequency shift of quartz crystal with covering of polymer fibers and carbon nanostructure materials.¬ Sensing materials were used in two different types of polyvinylpyrrolidone (PVP) and Graphene oxide. Electrospining was used as an efficient, simple and low cost approach for producing polymer and composite fibers with 280nm to 4um diameters. In addition, the effects of changing various parameters such as the concentration of polymer solution and electrospining process time were investigated. Images taken with a scaning electron microscope indicated that the concentration of polymer solution effectively can affect morphology,... 

Considering the importance of maintaining palm trees, this research focuses on the design of a climbing robot utilizing wheels. The goals of this robot include easy installation on the tree, climbing despite variations in trunk diameter and surface irregularities, maintaining static balance to prevent falling in a stationary state, and enabling tree pruning. Additionally, descending from the tree is an essential capability of this robot. For climbing, a rotating wheel and four auxiliary wheels are employed. A motor with a gearbox drives the rotating wheel, while the auxiliary wheels, supported by spring-lock mechanisms, provide the necessary force to prevent slipping and ensure stable... 

Stabilizing periodic orbit of fractional order chaotic system via linear state feedback is the subject of this research. Firstly, for detection of the unstable periodic orbits (UPO) in fractional order chaotic systems, the famous shooting method for integer order systems is extended to fractional order systems. After that, for stabilizing the fractional order system a hypothesis is stated and a theorem is proved in a specific condition. Besides the proven theorem, some examples are presented as evidences that verify the hypothesis. So, through the hypothesis, common methods for stabilizing integer order systems can be extended to the fractional order systems. Finally, for stabilizing the... 

The present research has dealt with developing theoretic basis for technology of a modern and beneficial robot. There has been an old aspiration to attain some machine which can enclose body and move exactly in concert with it so as to maximize human might and endurance via powerful actuators. Exoskeleton robot is a recent successful invention regarding this aspiration, the lower-limbs type of which being sufficient for enhancing gait and load carrying capabilities.
Modeling the dynamics of this robot is very fundamental and was done thoroughly for the first time in this research. In the available articles, at most, simplified models are investigated. Mechanical structure was selected... 

There are two ways for quality control testing of power transmission systems in various industries. A method of testing the specific positions of power transmission, and final testing (Automotive road tests), respectively. In various stages of design, manufacturing and quality control components, power transmission systems, require detailed information on the performance of parts. It's a special place for each transmission experiment designed and manufactured. Gearbox as an important component of the transmission of this issue is no exception. Magnetic gearbox has a new generation of power transmission systems in the last decade of the optimization is presented. In recent years, several... 

The synthesis and usage of TiO2/ZnO nanocomposite thin film in antibacterial activity against E-coli were experimented through a systematic research. TiO2/ZnO nanocomposite films can demonstrate different properties like gas sensing, self cleaning and treatment of the broad range of aqueous pollutants when it is exposed to light with wavelengths less than 400 nm. This phenomenon happens because of the photocatalytic reactions in the nanocomposite thin film which cause active species production on the surface of the thin film. The nanocomposite synthesis was based on sol-gel process in atmospheric pressure. In this study titanium dioxide is prepared by sol gel method from titanium... 

This thesis is related to the identification and design of a robust controller for an electrohydrodynamic printer system. As an emerging technology, this printer uses a strong electric field to deliver fluid ink from various conductive materials to the substrate. Modeling this system is complex due to the effect of different variables on its performance. In this project, first a simplified model with numerical solution data of the COMSOL model that is validated experimentaly is proposed. Then, by presenting a new control method that is a variant of an active disturbance rejection control baesd on extended state observer has been controlled. The new control method is actually an amendment to... 

There is a specific focus in sustainable transportation to three domains of safety, air pollution, and energy consumption. All these three domains are affected by the vehicle type choice. An important factor to estimate the impact of vehicle type choice on safety, air pollution, and the energy consumption is self-selection, defined as the tendency of people to make their travel-related choices based on their abilities, needs, and preferences. Ignoring the self-selection effect may cause a bias in the estimation of the coefficients of affecting variables on the travel-related choice. The main objective of this thesis is to study the self-selection effect in vehicle type choice considering the... 

The Iran-Iraq war between 1980 to 1988 involved Iran's western borders and inflicted heavy casualties. This war was also spread to the central provinces of Iran in several periods as a result of Iraqi missile attacks, known as the War of Cities. The attacks were mainly intended to intimidate people, leaving relatively few deaths and injuries. In this study, we seek to estimate part of the hidden and long run impacts of these attacks. Using a two-percent sample of Iran’s 1990 census and the information of the location and timing of missile attacks, and by incorporating the difference in difference method, we estimate the causal impact of missile attacks on the years of education of those who... 

In order to use the high performance capabilities of a computing system, first it is required to provide a proper modelling for the job and the system's environment. Second, it is required to design scheduling and offloading algorithms based on the job and the system modeling and third for evaluating the performance of these algorithms. It is needed to either simulate them or prove their approximation factors. This project aims to carry out these three parts for the Edge Computing environment. The laid out model of the system in this thesis consists of many devices that are distributed around the network, which they can execute tasks parallel to each other, and between each two devices there... 

This work describes the effect of hydroxyapatite with different morphology including nanorods and whisker on the properties of hydroxyapatite/polycaprolactone (HA/PCL) composite. Biodegradable polymer/Hydroxyapatite (HA) composites with the morphology of nanorods and whisker of (HA) as bone replacement scaffolds are synthesized by sol-gel and hydrothermal methods, respectively with a Ca/P ratio of 1.67 and 20:80 (HA/PCL).The crystallization behavior and porosity of HA/PCL composite are studied by scanning electron microscope and X-Ray diffraction. The response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic... 

In the present work, we have designed a novel CdS/CdTe solar cell based on CdS nanowires, as a window layer, and CdTe nanoparticles, as a absorber layer. CdS nanowires and CdTe nanoparticles were synthesized by solvothermal method. The samples were characterized by X-ray diffraction diffractometer (XRD), field emission scanning electron microscope (FE-SEM), Atomic Force Microscope (AFM) and Ultraviolet–Visible (UV–vis) spectroscopy spectrometer. Photocurrent measurements were carried out using a 150 W xenon lamp with an air-mass (AM) 1.5 filter. The performance of the solar cell based on the CdS nanowire (NW-CdS) film with 225 nm thickness and CdTe nanoparticle (NP-CdTe) film with 6 μm... 

Perovskite solar cells are the new generation of solar cells, and are mainly introduced in two types of structures.1) planer and 2) mesoscopic structure. The difference between these two structures derives from the absence of mesoporous layer in the planer structures. The mesoporous layer acts as an electron transporting layer, and is mainly a titanium dioxide semiconductor. To apply the mesoporous layer, the preparation of the TiO2 paste is needed.The synthesis of titanium dioxide nanopowder for the preparation of TiO2 paste requires high temperature heat treatment and is not desirable in terms of energy consumption.Another weakness of this layer is the presence of surface defects, which... 

Typical Numerical Control Machines, mainly are made a mechanism with axes perpendicular to each other. Because of lower weight, the parallel mechanisms are focused by CNC manufacturers. the Hexaglide mechanism is popular in parallel mechanisms used in CNC.Today, software of Solid modelling, generate G-Codes but this Codes works for conventional Numerical Control machines. for use of this G-Code for Parallel Mechanism CNC, a new controller should be designed to convert the standard G-Code motion command for Hexaglide CNC.The End of this project, is design and manufacture a controller for Hexaglide CNC that convert conventional G-Code for that and initiate drivers.Finally, the controller is... 

In this work, the dynamic competition between firms providing internet services is studied. The framework is Markov equilibrium whereby structural parameters are obtained using two-step estimations, allowing for analyzing the situation in case of subsidies for service upgrade. The results show that such subsidy has little effect on the number of firms while increasing the number of fast firms  

In machining processes, chip formation is one of the most important methods to obtain the final shape of a work-piece. Improving the machining processes leads to the increase in the material removal rate (MRR) and reduction of high economical costs. Vibration is an undesirable phenomenon in machining processes because it results in reduction of material removal rate (MRR), poor surface finish and increased tool wear. Among various types of vibration, self-excited vibration or chatter is the most important one. It is obvious from previous investigations that for prediction of machine tools vibration, many simplifications were assumed while the linear and non-linear effects are not considered... 

Numerous strategies have been applied to deal with the drought crisis such as reusing the effluent wastewater in irrigating crops, sports spaces, parks, health, entertainment purposes etc.Although the common treatment of sewage can eliminate almost 95% to 99% of microorganisms but this level of treatment is not enough for reusing the sewage, due to the existence of Pathogenic microorganisms. Therefore, disinfecting the wastewater effluent is one of the crucial stages of sewage’s treatment for preserving water resources or reusing it. Chlorination is the most common method of disinfecting wastewater. However, using a wastewater which is disinfected through Chlorination has Harmful effect on... 

Tin sulfide with an energy gap of about 1.1 ev is a semiconductor suitable for applications such as solar cells, lithium-ion batteries, photocatalysts and other semiconductor-based devices. There are several methods for synthesizing this semiconductor at the nanometer scale, among which the solvothermal method is an efficient, controllable and inexpensive method. By precisely controlling the parameters of this process, two-dimensional tin sulfide nanosheets with high purity and desirable morphology can be produced. In this research, tin sulfide has been synthesized by solvothermal / hydrothermal chemical method and its metallurgical properties have been studied. Effect of solvothermal... 

Nowadays, heterogeneous photocatalytic processes have attained a particular importance among the other advanced oxidation processes in purification of organic polluted wastewaters. Titanium oxide is the most popular photocatalyst because of its strong oxidizing abilities for decomposition of organic pollutants, superhydrophilicity, chemical stability, long durability, non-toxic nature, and low cost. Same as other semiconductors, high recombination rate of charge carriers is the main weakness that cause decreases in photocatalytic efficiency. One of the solutions is coupling this material with other semiconductors. Core-shell nanoparticles are the type of these composites that show high...