Sharif Digital Repository

In this research, role of zirconia nanoparticles as a biocompatible material which has great mechanical properties, was investigated on corrosion behavior and bonding strength of HA coating. HA- ZrO2 composite prepared by a 2-step pulse electrodeposition method. Effect of pH (3.5, 4.5), bath temperature (60, 80 ͦC), current density (0.5, 1, 2 mA/cm2) and zirconia concentration (5, 10, 15 g/L) on coating characteristics were studied. X-ray diffraction was employed for phase analysis. Morphology and microstructure of samples observed utilizing scanning electron microscope (SEM) and elemental analysis was done by EDS. In order to corrosion studies electrochemical impedance spectroscopy (EIS)... 

In some of object recognition problems, labeled data may not be available for all categories. Zero-shot learning utilizes auxiliary information (also called signatures) describing each category in order to find a classifier that can recognize samples from categories with no labeled instance. On the other hand, with recent advances made by deep neural networks in computer vision, a rich representation can be obtained from images that discriminates different categorizes and therefore obtaining a unsupervised information from images is made possible. However, in the previous works, little attention has been paid to using such unsupervised information for the task of zero-shot learning. In this... 

A Mobile Ad hoc NETwork (MANET) is a set of wireless mobile nodes that form a self configured network. MANETs do not have infrastructure and are not currently deployed on large scales. So research in this area is simulation based. Mobility model in a mobile ad hoc network explains the movement pattern of mobile users and is designed to describe the change of their location, velocity and acceleration over time. One of the challenges in this field is the definition of a common mobility model that provides an accurate and realistic movement description of mobile nodes. In this thesis we want to study the mobility pattern of vehicles on Kish Island and compare it with different kinds of... 

Congestion is an important issue in the network environment. To keep stable the perfor-mance of the network, congestion control algorithms have been extensively studied. Queue management method employed by the routers is one of the important issues in the congestion control study. Active Queue Management (AQM) has been proposed for early detection of congestion inside the network. AQM mechanisms control the queue length in a router by dropping arriving packets. The Random Early Detection (RED) is the most popular AQM mechanism used in routers on the Intenet to allow network users to simultaneously achieve high throughput and low average delay. The RED algorithm may cause heavy oscillation of... 

Multi-objective optimization is an important branch of optimization. One of the most common methods to solve multi-objective problems is to find the Pareto efficient points. In practical applications, there are many instances in which there are no analytical formula for the function and only approximate values at some points are available. Derivative-free optimization is one approach to solve these problems.Here, we consider one of the multi-objective derivative-free optimization techniques called direct multisearch (DMS), recently proposed in the literature. In this method, a commonly used single objective optimization method is generalized to the multiobjective case. A popular category of... 

Estimation of runoff in the ungauged basins is a challenge for hydrologists. The main objective of this research is to produce runoff coefficient map using SCS-CN (1972) and Kennessey (1930) as empirical models to for Urmia Lake basin between for 2006-2011.Both SCS-CN and Kennessey methods use slope, land use, and soil permeability data to estimate surface runoff. Accuracy of each model is tested along with the observed runoff using the Root Mean Square Error (RMSE).Urmia Lake basin includes about 400,000 hectares irrigated land, which constitutes around 10 percent of the entire basin area. To exclude the anthropological activities from the estimations, methods were applied only for 28... 

This study attempts to describe and analyze Persian speakers’ linguistic knowledge of different types of causative and inchoative constructions within the framework of Lexical Functional Grammar (LFG). In order to do so, different studies on Persian causative alternations within theories other than LFG as well as causative alternations in other languages within LFG are reviewed. Next, different types of causative constructions are categorized conceptually and structurally after they are extracted from Bijankhan corpus (2005). Then they are analyzed syntactically and semantically. In this regard, we represent syntactic and semantic structures based on LFG as a monostratal theory. After that,... 

Resources management is essential duo to sustainable development and marine resources limitations. There are several ways to restore coastal damaged ecosystems, one of the best and most cost effective solution is establishment of artificial reefs. A popular type of artificial reef is named Reef ball, a hollow hemisphere. In some regions these habitats has also been used as submerged breakwater. These structures recover and protect endangered species ecosystem although they provide aesthetic view to a beach. Main application of these structures is to provide a safe environment for marine creature. In this study initially Transmission coefficient variation in two-dimensional model experiments... 

Motorcycle has one of the most complicated geometries and mechanisms and its kinematic, according to the articles surveyed, has always been expressed with approximation and simplification in the degrees of freedom and especially in the magnitude of the angles. Analyzing the dynamic model of bodies, using methods like Kane, Lagrange, Boltzmann-Hamel, Gibbs-Apple, Newton, Hamilton and Ross, lead to mechanism’s equations of motion. While the equations of motions, obtained from alternative methods, lead to the same result, but the number of differential equations and sometimes their order, are different in different methods, and therefore their numerical solving time for the body’s motion, are... 

In this thesis, graphene/titanium oxide and graphene/tungsten oxide composites were synthesized using arc discharge in liquid and their photocatalytic behavior was studied. Based on physical principles of the arc discharge in liquid, geometry of point-point was used for metallic Ti and W electrodes. TiO2 and WO3 nanoparticles and their nanocomposites with graphene and graphene oxide (GO) were studies using DLS, UV-vis, PL, ICP, FTIR, XRD, Raman and TEM characterization. The concentration of aqueous solution of Rhodamine B mixed with graphene/WO3 and GO/WO3 composites and WO3 nanoparticles under ultraviolet light was measured versus time and reached to 0.1, 0.6 and 0.6 of the initial value... 

Positron Emission Tomography (PET) imaging is a modern sectional imaging technique widely used due to its advantages in visualizing the physiological functions of body tissues. In this method, a radiotracer is injected into the body, concentrating in the area of interest. As the positron-emitting radionuclide decays, positron annihilation occurs, resulting in the emission of two gamma rays in opposite directions. The PET scanner detects these gamma rays; however, scattering may occur during their journey from the patient’s body to the detector, which can introduce errors in tumor localization. To reconstruct images and correct for these scatter effects, various techniques such as iterative... 

Nowadays, self-healing process, repairing minor damages automatically without the need for detection or any type of manual intervention, becomes a hot topic of general interest. In this research, the effect of addition of carbon nanocontainers doped with film forming epoxy and polyamine agents in various contents on the self-healing properties of epoxy resin was investigated. Carbon nanocontainers were synthesized via the silica templating method and carbonization of polysaccharide shells at the high temperature. Loading of the film forming agents into carbon nanocontainers was performed using vacuum jar method in the presence of epoxy/acetone and polyamine/acetone dilute solutions....