Sharif Digital Repository

Nowadays, due to expansion of the cities, growth in population and developments in technology, energy demand has increased extremely. Therefore responding this increased demand is a great challenge in political and economical management of all countries. Thus in recent years, cogeneration has become so popular between experts in the energy field because of its great efficiency and performance. The goal of this research is to design a controller based on a model which can predict the behavior of the cogeneration system. This controler is called “Mode Based Predictive Controller”. It utilizes the system in such a manner which has the lowest operation costs. This goal is obtained via modeling... 

Financial and monetary markets are appropriate areas of applying Chaos Theory. Firstly, current theories of financial and monetary economics state that economic and financial variables such as exchange rates and stock prices are stochastic, so forecasting them is almost impossible. Secondly, if we find the hidden ordered and deterministic trends, we can achieve considerable profits. In this piece of research, we evaluate different methods and tests of detecting chaos in financial time series, and choose the most applicable methods to test financial markets’ indices. The main three indices of Tehran Stock Exchange, including Price, Finance and Industry indices, are examined. A sample of the... 

One of the important tasks of operation manager is keeping system in safe and reliable situation. There are many tools that supply safety in the power system. One of them is operation reserve. Operation reserve is any type of capacity being used to support active power balance. In this thesis, an approach for optimal determining reserve capacity with considering dynamic constraint is presented. This thesis describes a method for setting the optimum value of reserve capacity based on the cost of its provision, the benefit derived from its availability and Frequency stability. The method that used is D-SCRM algorithm. However, as the size of power systems increases, the current centralized... 

In opportunistic networks, the nodes have ad-hoc communications that are formed directly between them, without any infrastructure, and not by any using any other intermediate node. In case that the destination node is not in the same region as the source during the sending of a message, the source will send the message to one or a few of its neighbors so that they can store and carry out the message to the original destination in cooperation known as Store-Carry-Forward Mechanism. Remarkably, in most cases, the devices involving in this type of network, e.g., smartphones, have limited source of energy or they use a battery, there is a need to minimize the energy consumption in the nodes.... 

The use of nanocomposite materials in various industries such as aerospace, oil and gas, automotive, etc. has become increasingly widespread due to its unique thermal and mechanical properties. Due to the problems and costs of the production process and experimental testing for optimal construction, it is necessary to propose a low-cost method for estimating the mechanichal properties of these materials. In this research, the mechanical properties of polymetric nano carbon nanocomposites have been estimated by multi-scale method with using finite element analysis by Abaqus software. the mechanical properties of nanocarbon composites have been extracted by using the multi-scale method that... 

The purpose of this thesis is to use experimental and numerical tools to develop new constitutive models based on the Johnson Cook's model to predict the plastic deformation and failure of metallic diaphragms. Initially as the first case study, by designing and constructing a bulge test mechanism, the elastic-plastic behavior of 0.05 mm thickness pure aluminum diaphragms for a temperature range of 25-150℃ and large strains was extracted. Then, by presenting an innovative method, the biaxial stress-strain curves are transformed into uniaxial curves. By examining the observed behavior, a new constitutive model is developed based on the Johnson Cook's model. The ability of this constitutive... 

In this thesis, both experimental and numerical approaches are conducted to present a constitutive equation for 5052 aluminum diaphragms under quasi-static strain rate loadings. For this purpose the stress-strain curves at different strain rates are obtained using tensile tests. Brittle behavior during tensile tests is observed due to samples thin thicknesses. Employing Johnson-Cook constitutive equation no yields in reasonable agreement with these tensile tests results. Therefore, developing a more suitable constitutive equation for aluminum diaphragms is taken into consideration. This equation is then implemented into the commercial finite element software, ABAQUS, via a developed user... 

Can economics be a value-free science? The issue of values in science is a topic of discussion in the philosophy of science, and obviously in the social sciences, especially in economics, this issue becomes more controversial. Throughout the history of economics, these controversies have been the source of challenging debates among economists, philosophers, and sociologists. This question is still posed to philosophers and social scientists. Certainly, the answer to this question will have methodological implications. The issue of values has been an issue for economists from the very beginning of the Austrian school of economics. This dissertation deals with a view presented by a group of... 

The Pulse Laser Deposition (PLD), Sputtering, Evaporation and Metal-Organic Chemical Vapor Deposition are the common methods for thin film fabrication. The mentioned methods are very costly for commercials application. Due to the importance of cost in large thin film fabrication, scientist tried to find a low-cost method. The low-cost non-hazardious Metal Organic Deposition (MOD), method which is based on chemical manufacturing method was developed. The type of the solvent and removal the destructive residual materials are the main challenge in this method. In this project, by utilizing acetyl acetone method, high quality MOD YBCO superconducting thin film has been fabricated and will be... 

With the increasing development in the field of electronics and information technology, the required dimensions and power of electronic devices and sensors have decreased. The range of applications of these electronic devices is very large, which is the product of technological progress development. There is a problem in the development and application of such devices, the supply of electrical power used in them, especially in the set of wireless sensors, this problem is more significant.The use of piezoelectric materials is one of the methods of converting mechanical energy into electrical energy. The voltage generated by the piezoelectric material can be used to charge the capacitor or... 

In this study, through explaining a micromechanical model of progressive damage, failure in a composite conical structure under mechanical and thermal loads with 36 layers of carbon/phenolic material have been studied. To this end, first, mechanical behaviors of composite layers in micro and macro scale and their properties via fiber and matrix characterizations are discussed. In the following, selection of a proper RVE along with different types of boundary conditions on RVE are discussed. Then stress reinforcement coefficients in order to convert the mechanical and thermal stresses from macro to micro scale for carbon / phenolic material are extracted through defining appropriate RVE for... 

A biocompatible ferrofluid containing ?Fe?_3 O_4 nanoparticles was produced using co precipitation of ?FeCl?_2.?4H?_(2 )O and ?FeCl?_3 ?6H?_2 O under ultrasonic irradiation power with NaOH being the alkaline. Two variables studied in this research were concentration and molecular weight of PEG, as the coating agent. The impact of these variables were carefully monitored on shape, size distribution and magnetic behavior of nanoparticles through SEM, DLS, XRD and VSM characterization techniques. Moreover, MRI relaxation times,T_1and T_2, were calculated using synthesized nanoparticles as contrast agents. Accordingly these nanoparticles were biologically evaluated by MTT assay. Results... 

A 3-D CFD model was developed to study effects of early/late intake valves opening/closing on flow field characteristics in the Intake Manifold (IM) of a spark-ignited gasoline 1.5 Litre, 4-cylinder engine. The main task of IM is to prepare essential air for combustion process into cylinder which should distribute air to total runners of IM properly. In this modeling, combustion process and valve behaviors and how to pass fluid flows through intake valves are simulated separately and they are added to it.HyperMesh, Fluent, GT-Power, and MATLAB were used to create a mathematical model on the geometries of IM in TIBA engine, one National Engine of Iran, obtained from MEGA motor Company. The... 

Adaptive vibration control of a structure under different condition of exciting forces or structural response is the main scope of this research.Using a combination of the pole placement and online Empirical Mode Decomposition (EMD) methods, a new algorithm is proposed for adaptive active control of structural vibration. For this purpose, by structural response which is evaluated from Hilbert-Huang Transform (HHT) and using prior knowledge for corresponding conditions, proper and optimum control forces are applied to structure. Hence, error sources of EMD method in the HHT such as end effects error, mode mixing problem and decomposition resolution are being studied. A modified method based... 

The two-dimensional composites are benefited from different advantageous; however, they may not be good enough in terms of strength along the thickness, manufacturing speed, cost management and resistance to delamination. To overcome these unpleasant challenges, the three-dimensional composites are defined as having a 3D pattern of yarns which not only includes yarns along the length and width, but also in thickness or vertical direction. One of these common types of composites is 3D-orthogonal woven composites. In this comprehensive research study, the 3D orthogonal woven composite modelling is conducted through a specialized and advanced software, TexGen software. Then Voxel mesh were... 

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... 

In this thesis, we provide a comprehensive overview of the efforts made towards achieving the goals of Hilbert’s program, and evaluate how successful They are. We begin by discussing Gödel’s incompleteness theorems, and then as a first attempt we present a brief presentation of Gentzen’s consistency theorem. Subsequently, various research fields that branched out from these initial efforts are explored, encompassing the application of the Omega-Rule, reverse mathematics, and self-verifying systems. Furthermore, we present the concept of “Almost Finitistic Consistency” as an alternative approach within Hilbert’s program. In conclusion, a thorough assessment of the success of Hilbert’s program... 

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...