Sharif Digital Repository

Three distinct areas in linguistic studies are typically considered, namely, syntax, semantics and pragmatics. Each category has a specific realm and deals with special linguistic phenomena. Presenting exact definition and clarification of the corresponding boundaries of each area is considered in both linguistics and philosophy of language. In order to explain the “meaning” for sentences of a language, this issue turns out to be vital. Representing the definition and evaluating the domain of each area, is the objective of the first chapter. In chapter two, some important semantic theories have been investigated. Since at first one semantic theory ought to clear its position about reference,... 

DNA is big protein molecule consisting of two strands intertwining each others. Recently DNA molecule has drawn attention of researchers to be used in electronic circuits and molecule electronic field. Therefore, many experiments have been carried out to measure DNA conductivity in different temperature in single molecule or bundle mode with varying size and shape. In this thesis, metallic bundle DNA at normal room temperature is studied and their resistance characteristic is obtained and compared. In order to improve DNA conductivity Metal Ions like zinc are adulterated to each of its structure period. DNAs with these metallic impurities are called metallic DNAs.
Thus, golden electrodes... 

In this study, thermal and rheological properties of nanofluids of water/carbon nanotubes, water/spherical silica nanoparticles and water/hybrid nanoparticles (hybrid of carbon nanotubes and spherical silica nanoparticles) have been investigated. To do so, carbon nanotubes have been synthesized by CCVD process and spherical silica nanoparticles and hybrid nanoparticles by wet chemical method. After synthesis of nanomaterials, nanofluids have been prepared by using SDBS as a dispersant with the concentration of 1.5 times of concentration of nanomaterials and then thermal conductivity, kinematic viscosity, dynamic viscosity and density of nanofluids have been investigated. As the results show,... 

With the advent of new computer technologies, computational analysis on the human organs has become tremendously popular in the field of medical science. Every year thousands of people suffer irreversible eye damages pertaining to lack of adequate medications. In this regards, enormous amount of money is spent annually but mostly in vain due to the irreversibility and silent nature of eye diseases like glaucoma. Yet more precise studies on the topic are requisite. In this thesis, a validated half 3D finite volume model of human eye considering the fluid flow in collaboration with heat transfer in the steady state utilizing the well known discretized bio-heat transfer equation coupled with... 

Application of nanotechnology in the field of heat transfer has increased recently. The need to increase heat transfer rate yet decrease the size of cooling equipment, brought about lots of attention to thermal properties of Nanofluids. Nanofluid is the suspension of nanometer-sized solid particles in base liquid. Research on convective heat transfer of nanofluids which is only two decades old, shows great potential in increasing heat transfer rate. Although there is a remarkable research on thermal conductivity of Nanofluids, negligible research was conducted on combined Nanofluids . Developed Theory for thermal conductivity of combined nanofluid can be used to modeling the thermal... 

Increasing of human demanding for energy and limiting of fossil fuels and bio-logical problems, it seems necessary to access new and clean source of ener-gy. For instance, one of these sources of energy is sun. If we can impart from this infinite energy source so health and natural life can be pictured for human. Nanostructure dye sensitized solar cells in compare with other photovoltaic cells are more economical and practical as a result of lower material cost and simpler manufacturing process. In general, a typical dye sensitized solar cell is a sandwich structure based on two transparent conducting oxide (FTO) glasses. The FTO glass substrates are expensive and account for most of... 

In several electro-optic and optoelectronic devices, we require the structures with simultaneous high electrical conductivity and optical transparency so as to transmit the incident light. Transparent Conductive Electrodes (TCEs) that are both highly conductive and transparent were introduced to be an answer to the mentioned challenge. Periodic arrays of metallic holes are amongst the most important structures that are used as transparent electrodes. Using the metals with low electrical resistivity, such as Au and Ag, provides these structures with high electrical conductance. On the other hand, since these micro/nano structures support the propagation of guided electromagnetic waves, light... 

The global wind energy capacity has been increased rapidly in the past few years and became the fastest developing renewable energy technology. Small Permanent Magnet Synchronous Generators (PMSG’s) are widely used in low power wind turbines because they don’t need a gearbox and complicated control systems. In order to inject the electrical power generated by PMSG to the grid, an AC-DC-AC power electronic converter is required. A novel low cost efficient AC-DC converter is proposed to obtain the maximum power per ampere of PMSG. The new structure for the rectifier stage of the AC/AC converter is based on a DCM operated SEPIC converter and can convert the variable voltage and frequency of... 

In recent years lithium-air batteries captured worldwide attention because of their high energy density. Solid state electrolytes is one of the main components of lithium-air batteries. Lithium almunium titanium phosphate(LATP) is a nasicon type ion conduction which may be of great potential as solid electrolyte. The object of this thesis was the preparation of LATP solid electrolyte which can be used in a lithium-air battery. To reach this goal LATP powder was synthesized using a solution-based method and an appropriate crystallization temperature was selected based on obtained results of X-ray diffraction analysis. In the next step solid electrolytes was prepared under different pressing... 

Due to the growing need for plasmonic wavs in microwave and terahertz spectra, a periodic arrangement of one-dimensional cut-through slits is investigated and an equivalent model based on the effective medium theory is derived. In contrast to the all previous attempts that were successful in mimicking only the zeroth-order diffracted waves, the proposed effective medium is capable of mimicking all diffraction orders. The parameters of the equivalent model are established by comparing the scattered waves of the semi-homogeneous medium and those of the main structure obtained by invoking the rigorous mode matching approach based on the single mode approximation inside the slits. This medium is... 

Groundwater is the most important freshwater resource in the coastal zones. There are some factors contaminate fresh groundwaters. Sea water intrusion (SWI) is one of the most important components of groundwater salinization. Also Submarine groundwater discharge (SGD) occurs when hydraulic gradient is from landside to seaside in coastal aquifers. There are many factors intensify SWI and SGD. In this research at the first part, coastline shape effect on SWI and SGD is investigated. For to this 4 different aquifers with different coastline shapes as stepped coastline, vertical coastline, steep slope coastline, and mild slope coastline are simulated with the same hydraulic parameters and... 

In this study, transparent conductive thin film of Aluminum doped ZnO (ZnO:Al) have been fabricated thorough RF sputtering. The main goal of fabrication of these layers is achieving thin films with minimum resistivity and maximum optical transparency in visible range of spectrum employing as transparent electrodes and buffer layer at the entirely oxidized solar cells. To achieve the suitable structure, various parameters including pressure, power and the thickness of the deposition and annealing on morphologies of thin film has been investigated. According to these results, thin film of ZnO:Al has the transparency of 80% in the visible light range . Doping of ZnO with Aluminum caused... 

In this project, we were intended to study the ultra-strong coupling in optical waveguides. Hence, we analyze the interaction of an electromagnetic wave with a quantum well embedded in a dielectric slab waveguide. First, we designed a QW with and alloys, which the energy of its electron-heavy holes transition is . By exploiting the envelope function approximation, we derived the wavefunction of electrons and holes, their eigen-energies, and the dipole moment of electon-holes. For finding the wavefunction of holes and their eigen-energies, we used the Luttinger Hamiltonian. Next, we calculated the electrical susceptibility of a three level quantum system (as a model for QW), by using... 

In this research convective heat transfer coefficient enhancement of nanofluids prepared from high surface area graphene has been investigated in laminar flow in the developing region. The nanofluid has been prepared from nanoporous graphene with high surface area and with concentration of 0.025 to 0.1 %wt. Deionized water has been used as the base fluid and a type of Ter-Polymer has been utilized as the surfactant. The results indicate that thermal conductivity of nanofluid with concentration of 0.1 %wt remains quite constant, with only %3.8 enhancement, while convective heat transfer coefficient improves significantly, with 34% enhancement. The behavior of this enhancement related to the... 

In the present study, the thermal behavior of human teeth during laser radiation has been discussed. The high laser power, as well as its low emission, can allow deviations from the Fourier heat transfer model. To overcome this problem, the non- Fourier heat transfer method, dual phase lagged (DPL), has been used. Wisdom considered in this study to evaluate the thermal behavior of tooth. Using the finite volume method, the DPL equations are solved and the thermal response of the teeth is obtained during laser irradiation. The effect of delay times, which are the parameters of the DPL model and depart from the Fourier model, is fully demonstrated on the temperature behavior of the tooth, and... 

Attaining accurate information about satellite attitude is one of the most important requirements in space missions in order to improve the accuracy of the satellite control and mission objectives. Many different sensors such as sun sensor, star sensor, horizon sensor, etc. are used to estimate spacecraft’s attitude. Attitude estimation using temperature sensors is a topic that has recently been addressed by some related researchers because, they need less power and budget to operate in comparison with the other sensors.Accuracy and heat model performance improvement is the main purpose of this project. To achieve a more accurate perspective of space thermal model, and the way heat transfers... 

This dissertation argues that bi-conductive textured surfaces increase both Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) simultaneously. Surface modification is applied to stainless steel specimens by the anodizing method in an electrolyte containing Ammonium Fluoride and DI-Water and Ethylene Glycol as the based solvent. The process of oxidation was under constant DC voltage and constant temperature. The contact angle on self-aligned Nano-porous oxide layer fabricated on the substrate substantially decreases to about 5.7 degree which has a dramatic effect on CHF. Furthermore, the oxide layer augments the boiling efficiency by increasing the number of active sites and... 

To reduce material consumption needed in production as well as avoiding thousands of tons of contaminations produced by spent materials in the battery industry, recycling was taken into consideration. In this study silica was recycled from spent lead-acid battery separators by the pyrolysis process. silica along with high-density polyethylene (HDPE), can be used as supporting material for fabricating form-stable phase change materials (FSPCM). FSPCMs are of great ability to be used as thermal energy storage (TES) in different parts of a building e. g. wallboards to reduce energy consumption. In this line, an eutectic mixture of lauric acid, palmitic acid and paraffin with the melting point... 

“How can we generate a random point with uniform distribution over a convex body ?” According to it’s applications, it’s important for a solution to this problem to be applicable in high dimensions. Here, we are interested in algorithms with polynomial order with respect to the dimension. All existing methods for dealing with this problem are based on the Markov chain Monte Carlo method, i.e. a random walk is constructed in such that its stationary distribution is the uniform distribution over. Then, after simulating “enough” steps of this random walk, the distribution of the resulting point is “approximately” uniform. The real problem in Monte Carlo method is analyzing its “mixing time”,... 

Double channel and coreless induction furnaces are used extensively in many processing industries due mainly to their good heating efficiency, high production rate, clean working environments and relatively low operating costs. The study of heat transfer treatment and evaluation of the heat losses of these furnaces becomes an important issue in melting industries. In this dissertation, a heat transfer analysis will be performed for an induction furnace and heat losses by conduction, convection, Eddy-Current and Hysteresis in a furnace structure, and radiation from the body of a specific induction furnace will be modeled considering the symmetry of the furnace chamber. The models presented in...