Sharif Digital Repository

Active Learning Method (ALM) is a soft computing methodology which has been used for modeling and control. Unlike the good results of ALM’s ability, there is not any analytic expression to prove its power, because ALM’s main operators don’t satisfy fuzzy S-norm & T-norm properties. This problem considered from three viewpoints: Mathematics, Geometry and fuzzy sets. In this paper, we try to introduce two new operators based on morphology to satisfy three conditions: at first, they must be fuzzy S-norm and T-norm to confirm the committal of fuzzy set theory. Secondly, they must satisfy Demorgans law, because they are complement of each other. And finally, they resemble the main operators of... 

Mode I and II stress intensity factors are derived for an inclined crack breaking the surface of a half-plane which is subjected to an un-symmetrical singular contact loading due to the contact of a tilted wedge with the half-plane. The method used is that of replacing the crack by a continuous distribution of edge dislocations and assume the crack to be traction-free over its entire length. A traction free crack is achieved by cancelling the tractions along the crack site that would be present if the half-plane was un-cracked. The stress distribution for an elastic uncracked half-plane subject to a tilted wedge shaped indenter is derived analytically using the Muskhelishvili’s potential... 

Ag / AgCl /TiO2 , 2 Ap / Ag / AgCl /TiO , 2 AgI /TiO and 2 Ap / AgI /TiO were prepared by the deposition-precipitation method on 2TiO (P25) nanoparticles and their photocatalyctic activities have been investigated under visible light and dark environments. Cationic surfactant plus 2 PVPI (topical solution and dry powder) as an iodine ion source and nonionic surfactant plus KI as an iodide ion source were used to prepar 2 AgI /TiO . In less than 30 minutes, 2 AgI /TiO which has been resulted from combination of cationic surfactant and 2 PVPI showed high efficiency on Escherichia coli under visible light when small quantities of it is used . However, AgCl sample prepared with cationic... 

In this thesis, cavitating flow over 2D/3D geometries of cavitators and projectile bodies in stationary and moving conditions are simulated using the "Volume of Fluid" (VOF) technique. The main application of VOF model is for simulating free surface flows. In this work, another capability is added to the VOF algorithm to solve for gas phase and by applying analytical-numerical mass transfer models, cavitation phenomenon is simulated. The developed algorithm precisely simulates the geometrical parameters of supercavities such as dimension and shape in a wide range of cavitation numbers. In addition, the flow parameters of supercavity such as drag coefficient, pressure coefficient inside the... 

Nowadays, there is a focus on developing a propulsion system with higher efficiency and performance in comparison to conventional systems. Many diverse systems have been designed for the vessel propulsion and everyday, utilizing new ideas, their performance and energy consumption are being improved. Direct use of steam energy is a noble and new idea. In this research, the steam jet propulsion system has been explained and current worldwide research on the topic has been investigated. Considering the shortage of primary data in the field and the novelty of subject, required information for the manufacturing of a sample model of this special propulsion system has been gathered and a design for... 

The primary objective of this dissertation is to obtain a mechanism from the family of 5-dof parallel mechanisms of type 3T2R which gains the advantages of higher kinematic performance, low coupling of motion, and simple kinematics and control commands. Based on this aim, at first a method for structural synthesis of this type of mechanisms is introduced. The method is based on the theory of linear transformation and a geometrical analysis. By using this method, a set of novel 5-dof 3T2R parallel mechanism are introduced for the first time in the literature. In order to compare the designed mechanisms and to identify the promising ones, some important criteria which are a) low coupling... 

Ship maneuverability is so important from different aspects. According to the regulations of International Maritime Organization (IMO), every vessel has to meet the minimum requirements of mentioned rules. Consequently, prediction of ship maneuverability in early stages of ship design has become to one of the most necessary steps for shipbuilding and design companies. There are a variety of options in order to prediction of maneuverability of vessels, for instance, one important way is Free running model tests which is capable of direct calculation of the required parameters, provided if some certain conditions are met. In this work, firstly, an introduction to the importance of vessel... 

In the present study, waves maker and its effective parameters has been investigated. Different kind of wave makers have been investigated and compared with each others. Then, according to marine laboratory requirnents such as Dimensions, seakeeping tests, installation place and budget, a proper wave maker is designed. In design procedure, differential equations of waves and paddle wavemaker, wavemaker's power, forces on paddle and mechanical system with servo motor are used. For improving efficiency of system and converting the rotary motion to linear motion, a ball screw is utilized.
 

In this thesis the tow-dimensional wave propagation in a functionally graded elastic medium is considered. It is assumed that the stiffness and density of the medium vary continuously in one direction. This work presents analysis in both time and frequency domain. In time domain, a graded element is presented for static and dynamic analyses in FGMs. This element clearly simulates wave propagation in inhomogeneous materials. The most important property which an element must have to be reasonable in wave propagation analyses in FGMs is simulating reflection only from boundaries. In frequency domain a dynamic stiffness matrix is generated using stiffness and mass matrix used in time domain... 

In this thesis we investigate the spectrum of the Laplacian matrix of a graph. Although its use dates back to Kirchhoff, most of the major results are much more recent. The first chapter of this thesis is devoted to the integral Laplacian eigenvalues of graphs. In Section 2, particular attention is given to multiplicities of integer eigenvalues and to the effect on the spectrum of various modifications. In Section 3, the Laplacian integral graphs are investigated. The Section 4 relates the degree sequence and the Laplacian spectrum through majorization.The second chapter presents the result on permanent of the Laplacian matrix of graphs and permanental roots. In Section 2, we investigate... 

Vortex engine has shown to be a credible substitute in thermal power and aerospace industries mainly due to their advantages such as better mixing, improved combustion, and considerable cooled walls of combustion chamber. The engine geometry and tangential inlet oxidizer create inner and outer vortices rotating in the same angular direction. The inner vortex moves from head to the end of engine in the axial direction and outer vortex moves in the opposite direction. In the vortex engine, vortices affect spray droplets and force them to have a spiral path and apply a centrifugal force on the droplets to push them towards sidewall. Also axial relative velocity of droplets and flow filed act as... 

Magnetic Shape Memory Alloys (MSMAs) are a category of active materials which can be excited by magnetic field. These alloys have been used in sensor and actuator applications recently. MSMAs posses special properties such as large magnetic field-induced strains (up to %10) and high actuation frequency (about 1kHz), while ordinary Shape Memory Alloys can’t act in frequencies above 5Hz due to the time involved with heat transformation. In this thesis, MSMAs are modeled by means of incremental modelling which is a useful method in analysis of nonlinear behaviour of materials. Furthermore, stress-strain curve of MSMA is approximated using an analytical expression whose parameters can simply be... 

ALM (Active Learning Method) is based on fuzzy concepts, striving for human-like information processing. Typical fuzzy methods for control and modeling applications rely on linguistic processing with membership functions of the kind in fuzzy rules. ALM, however, processes multiple features of a target by converting each into patterns. This simulates the human approach to the acquisition of knowledge from complex source targets in that it focuses on each feature of the target and processes that information in pattern-like images rather than utilizing numerical interpretations. In ALM, the ink drop spread (IDS) method has been proposed as a means of obtaining useful information... 

Different reasons, all structures have inside crack or surface crack when crack growth is more at the frequancy load and it is one of the main factor in the diagnosis of structural life that this sensitivity is much greater aerial parts industry. The aim of this project, designing a new structure for the auxiliary engine compartment of the aircraft with the damage tolerance theory for cargo aircraft within the country are making. In the first stage after reviewing activitation past, the evaluation design rules between each company design its obligations, standards in design and then conceptual plan to make. Then reload force plan to make. At this stage with regard to maneuver the airplane... 

In recent years, unmanned vehicles have intensively been developed to reduce human dangers for marine applications. Predicting the hydrodynamic coefficients of an autonomous underwater vehicle is important during the vehicle’s design phase. In other words to design an AUV, one must clarify its maneuverability and controllability based on a mathematical model. The mathematical model contains various hydrodynamic forces and moments expressed collectively in terms of hydrodynamic coefficients. Therefore, the correct values of the coefficients must be known to precisely design the controller of AUVs. SUT-2 is an AUV, being developed by Marine Engineering Laboratory of Sharif University of... 

Wide range application of high speed marine crafts in marine industry and other related industries results in attempts to improve the performance of such vessels. The main ideas of using control surfaces in high speed planing crafts are the change of the high speed planing craft‘s resistance due to change of their running attitudes and wave response mitigation of this vessels. Control surfaces produce forces and a pitching moment due to a pressure distribution caused by them, which can be used to alter the running attitude of high speed marine crafts. The present work contains a comprehensive study on trim tab as a control surface for the high speed crafts. The results of this study condense... 

In the first stage of this research, different amounts of glycidoxypropyltrimethoxysilane (GPS) were grafted as a coupling agent on the surface of nanosilica particles (NS). Surface characterization was done by Particle Size Analyzer and Thermal Gravimetric Analyzer (TGA) and that way, samples were distinguished from each other. More comparisons were taken by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Then the different amounts of modified NS were added into the matrix of an epoxy resin and the physical and mechanical properties of samples were tested with Abrasion Resistance test, Tensile Strength test, Thermal Mechanical Analysis (TMA),... 

Increasing the application of elastomeric structures in industries has caused an interest in the researchers for nonlinear elasticity and viscoelasticity of solids. Such materials which show large deformation and rate dependent behavior are treated by visco-hyperelastic constitutive equations. Based on visco-hyperelastic constitutive equations, total stress is divided into two parts: quasi-static and viscous stress. The method for determining the visco-hyperelastic constitutive equation is strictly dependent on the chosen rheological model. In this project, a new visco-hyperelasic constitutive equation in the integral form was introduced based on the Zener model. Also, based on the internal... 

In this research, penetration in a new confined ceramic-metal structure is studied experimentally and numerically. In this new structure, ceramic tile is confined on its front face by an aluminum foil. First, penetration experiment in 5 mm thick Al 1100 plate carried out. The ballistic limit velocity is obtained about 140 m/s. The difference between experiment and numerical simulation is lower than 5 percent. Then penetration analysis of 10 mm thick Alumina tiles is carried out experimentally and numerically in confined and unconfined conditions. Ceramic tiles are in square shape with 50 mm side length. The ballistic limit velocity for unconfined and confined ceramic tiles are obtained about...