Sharif Digital Repository

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... 

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... 

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... 

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... 

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... 

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... 

The physics of the flow around the wing in the oscillatory motion of the wing has various patterns, including the leading edge vortex, the tip vortex and trailing edge vortex escape. The interaction of these vortices forms a complex flow structure around the wing, which will have a direct effect on the aerodynamic performance of the wing. Therefore, controlling these structures can be considered as a way to improve the performance of the flapping wing. One of the passive flow control techniques that has recently been taken into consideration is a leading-edge protuberance method. Another type of passive flow control is geometric correction, using corrugation method. According to studies, two... 

In this thesis, the nonlinear vibrations of the circular plate is examined using multiple scale methods and experimental tests. At first step, the nonlinear equations governing the problem are written using von Karman's assumption. In the next step, to solve nonlinear equations and calculate natural frequency, the problem is solved using multiple scale method and frequency charts are extracted as a function of the amplitude of vibration. . The design of the setup has been done in such a way that it is possible to simulate the boundary conditions. In the first phase, experimental tests was performed on a 0.3 mm thick aluminum sheet, which did not produce the desired results due to the... 

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... 

The unsteady phenomena occur in rotors of helicopters, wind turbines and compressors. Investigation of the unsteady flow is a very important test, since it can affect and restrict the performance of rotors of helicopters and wind turbine's blades when operating at high angles of attack. Dynamic tests, such as pitching and plunging oscillations are one of the best methods for studying these phenomena due to the complexity of the unsteady flows. In analyzing the results of dynamic tests one must consider the interference effects of wind tunnel walls. Different investigations show that in dynamic tests, the interference effects of flow field around the model, wind tunnel walls and support of... 

Jet into cross-flow interaction is one of the complex and fundamental problems in fluids dynamics and heat transfer, which is observed in various applications, such as pollutant discharges, film cooing of turbine blades, combustion chamber design of jet engines, trust vectoring systems, boundary layer control, and vertical short take-off and landing (VSTOL) aircrafts. One of the applications of this kind of flow is injection of supersonic jet into subsonic compressible cross-flow, which is used in trust vectoring systems of missiles. In this research, the two-dimensional interactions of supersonic jet into subsonic compressible cross-flow were investigated as two cases: "without a fin" and... 

Chatter in machining systems is a limiting factor of workpiece surface, tool and machine life and material removal rate. Because of this, studying and modeling of vibrations is very important in the machining. This study is much importer in the boring operation because boring bar's length to diameter ratio is very high and so it is very sensitive to vibrations. As we know, vibration characteristics of a machine change between its operating condition and its resting mode. Because of this it's better to study machine's vibrations when it's working. This study requires some methods that can find operating parameters of machine. The aim of this work is to find these parameters. For finding these... 

High purity titanium nanoparticles were synthesized by utilizing Electromagnetic Levitation Melting Gas Condensation (ELM-GC) method. High purity titanium samples were melted by electromagnetic levitation to a temperature of 1700 ± 20 °C in a silica tube. High purity argon and helium were employed as carrier gases and cooling agent. Particlesize, morphology, and Purity of the produced nanoparticles were studied by Field-Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), Dynamic Light Scattering (DLS), X-ray fluorescence (XRF), and ICP-AES analysis. The FE-SEM, DLS and XRF studies confirmed narrow size distribution of almost spherical shape pure titanium nanoparticles...