Sharif Digital Repository

In the beginning of the 90’s a new type of robot was introduced by Fukuda. The brachiation is a type of mobile robot that moves from branch to branch like a long-armed ape. Here, as a new innovation, optimal control is used to obtain the optimal trajectories for two different problems. The first problem is “Brachiation between fixed branches with different distance and height” and the second is “Brachiating and catching the moving target branch”. Theoretical results show that the control effort in the proposed method is reduced by 25% in comparison with the “Target Dynamics” method which was proposed in prior articles for this robot. The obtained optimal trajectory also minimizes the... 

In recent years, various nanocars have been synthesized to provide controlled mechanical function, transport other nanoparticles, or enable bottom-up assembly capability. In this research, using molecular dynamics and quantum mechanics, the motion of nanoworm on the gold substrate was investigated. The incorporation of the azobenzene chromophore at the middle of the chassis allows for the potential motion of nanoworm by light as a source of external stimuli. The creators claimed that nanoworm could achieve controlled wormlike movement on gold substrate, which should be validated as the purpose of this research. In the first section, the movement of the p-carborane wheel on the gold surface... 

Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to... 

After the discovery of integer and fractional quantum Hall effects, a comprehensive effort started to understand the physics behind these findings thoroughly. At the end, these efforts resulted in the introduction of topological phases of matter and the notion of topological phase transition. With the recent developments in this field, as the introduction and synthesis of 3D topological insulators, many researchers began inspecting the effects of disorders and impurities in the lattice structure on the topological phases, As these imperfections are inevitable in the lab-created instances. Since, in the previous works only on-site disorders was studied, the concentration of this thesis is on... 

Today using of microwave integrated circuits in commercial and military applications is paid attention too much, especially with emerging of monolithic microwave integrated circuits that prepares for us producing of amplifier with mass production, enough accuracy and proper cost. Power amplifiers that used in the end of transmitter path are paid attention in this field. However,in transmitter systems which require high power to create stable link with the receivers, fabrication process like CMOS are unable to provide such level of power. Thus, designers employ another group of integrated circuits which names MMIC that offers this capability to designers.MMIC is the abbreviation of Microwave... 

In this thesis, heterogenous catalysts based on poly(ionic liquids) were synthesized. These catalysts were prepared by polymerization of functionalized ionic liquid monomers in the presence of an ionic cross-linker. Several types of poly(ionic liquids) such as acidic ionic liquid, basic ionic liquid and their complexs with copper and palladium were prepared. Some of these polymers were coated onto the magnetic nanoparticles to produce a catalyst with magnetic prppertise with easy magnetic separation from the reaction medium. Such catalysts have high loading level and high thermal stability. Most of prepared catalysts have high loading level due to the macromolecular nature of polymer. At the... 

Ultralow phase noise microwave oscillators with high stability are one of the key components required for many applications. With recent advances in ultrapure microwave oscillators, optoelectronic oscillators (OEOs) culminated in the state-of-the-art ultralow phase noise microwave oscillators. In this thesis, a nonlinear analytical approach is used to predict the main oscillation mode power and spurious levels in ultrapure microwave OEOs. Our analytical predictions are verified by numerical simulations and experimental data. Performance of an intensity-modulation direct-detection (IMDD) microwave photonic link (MWPL) operating under nonlinear conditions when its input consists of a sum of... 

The impact of ownership concentration on competitive conditions and profitability of industries has been studied and analyzed for decades. By using the Herfindahl-Hirschman concentration index, a range for the level of concentration in the industry has been determined, and some countries implement anti-trust laws based on this range. The new literature that has been discussed recently is the concentration of the market directly and through the common ownership of corporations by large shareholders. In the sense that two or more apparently independent companies may have a common owner who practically regulates their behavior as a company. The structure of ownership in Iran is complex and... 

In this research a robotic fish was designed and fabricated. For this propose different types of manufactured robotic fish were investigated and this model was developed and made with a one-piece flexible tail with an actuator that creates lateral movement through cable strings attached to the tail. Proposed mechanism has a simple, low cost structure that facilitates the control of the robotic fish movement. To control this robotic fish, a four-channel radio controller with 40 kHz frequency, was used. Swimming mode of this robotic fish is categorized in Subcarangiform swimming mode which is faster and has better maneuverability compared to its counterparts. It should be noted that the... 

High power, broadband amplifiers at microwave and millimeter wave frequencies are needed for military and civilian applications. High power, broadband, high linearity, low noise, high efficiency and graceful degradation on failure are among the most important features in amplifier design. Solid state and vacuum tube devices have many disadvantages. A promising solution has been spatial power combining technique. Spatial power combining is a method of coherently combining the power of many amplifying devices using free space as the power dividing/combining medium within a guided wave structure in contrast to traditional circuit based amplifiers. This thesis presents the design and fabrication... 

In this research, delamination in compound laminated materials under the I mode loading is studied. In this way, a Double Cantilever Beam is investigated, which is the only experiment to study delamination in standard compound laminated materials. At first, a survey and comprehension of the failure of these materials is performed and the major mode of failure, which is named Delamination Mode is understood. Next, a survey on the possible methods of investigating the delamination phenomena is presented. In the next chapter, possible numerical methods are analysed, and the better performance of Cohesive Zone Model and Virtual Crack Closure Technique is studied. In this research, using the... 

This dissertation is a survey on linear and nonlinear dynamics of single-walled carbon nanotubes (SWNTs) conveying fluid with different boundary conditions. A detailed review on Some of the most important studies on free vibration and instability of CNTs conveying fluid is done. By employing the nonlocal continuum field theory of Eringen and Von Karman nonlinear strains, an analytical model are developed. In linear analysis the natural frequencies and critical flow velocities are discussed. In nonlinear analysis effect of nonlocal parameter on Nonlinear dynamics of cantilevered SWNTs conveying fluid investigated by bifurcation diagram, phase plane and Poincare map. The numerical results... 

A metal cylinder tank with composite coating is a pressure vessel which is made of a thin metal layer and a composite layer; like Graphite, and most of the loading is carried by the composite layer. In this study the penny-shaped cracks in cylindrical pressure vessels with composite coating is studied. These kinds of cracks are mostly initiated in manufacturing processes and they have crucial rule in fatigue life and load carrying of the structure. Although there are numerous analytical and numerical methods, they have shortcomings in the case of penny-shaped cracks problems. The strain discontinuity in the interfaces of materials along with discontinuity and singularity due to the crack are... 

The J-integral, as a powerful tool in fracture mechanics, is used to analysis of fracture behavior of materials. In order to, evaluate of three dimensional J-integral, an integral evaluation of line and surface is required. However, because surface integral evaluation requires the calculation of the second derivative of displacement field, an commercial finite element codes cannot calculate it.In this thesis, a method for computing 3D J-integral is presented using finite element analysis. In the analysis, the second derivative evaluation of displacement field is employed. In this method, error-minimal points for stress computation are not suitable for second derivative displacement... 

This thesis focuses on how the dimensions and location of piezoelectric patches affect thedynamic behavior of multi layered sandwich panels by the use of finite element method (FEM). To accomplish this objective the finite element formulation of the problem, including coupling of electrical and mechanical characteristic equations for piezoelectric patches is derived. Finite element modeling of sandwich panels is presented on the basis of classic theory and also first order shear displacement hypothesis for multi-layered plates. To perform finite element analysis, ABAQUS is utilized and the development procedure of a finite element model by this software is also introduced. After verifying...