Sharif Digital Repository

Production of nano-particles using arc-discharge method in a liquid nitrogen environment is a proficient way of forming nitride Particles whose formation by other methods is difficult and expensive. Amongstall, Titanium nitride (TiN) is of significant importance because of its high formidability and its optical and electrical metal properties due to plasmonic electrons. This research studies the production of titanium nitride Nano-particles using arc-discharge method and investigates optical properties and features, specially dielectric constant and optical extinction coefficient. Modeling interband Transitions is also discussed to revise Drude's electron theory. First, in experimental... 

New development in material fabrication resulted in functionally graded materials (FGM) with properties, can vary continuously based on the desired purpose. Vast applications of these materials attracted scientists to extend the researches in this area. One of the promising applications of these materials is in the optimized spherical and cylindrical pressure vessels. Optimization is usually based on the minimization of heat transfer and maximization of the strength of the vessel under pressure. In the present dissertation, spherical and cylindrical pressure vessels are designed and characteristics of the material distribution for certain pressure and temperature is developed. In this... 

Atomic force microscope (AFM) has a significant capability of imaging surface topography on an atomic scale. It is also widely used for Nanolithography in MEMS/NEMS (micro/nanoelectromechanical systems). Conventional AFMs consist of a cantilever with a sharp conical or pyramidal tip located at the free end of the cantilever that plays an important role in AFM measurements. Scanning across a surface, AFM interacts with the sample surface through its tip. Although the dynamic behavior of the AFM cantilever is complicated, the researchers have been interested in studying AFM dynamic behavior because it has a great influence on the surface imaging process. The imaging rate and contrast of... 

Co-movement between inflation and nominal interest in response to an interest rate shock, dubbed neo-fisherianism, has been the subject of contentious debate since the advent of non-inflationary ZLB environment. We design an economic model rich with banking features to understand the economic responses to permanent and long-term interest rate shocks. We find that responses to a permanent positive interest rate shock depend on the monetary authorities’ speculation of the new long-term inflation rate, with the most probable outcome being a permanent increase in inflation. Responses to a long-term positive interest rate shock depict an increase and then decrease in inflation. We also discover... 

FE simulations have been widely used to investigate the response of the brain tissue in various circumstances. The accuracy of the material models critically affects the results of the numerical simulation. However, despite the numerous studies aiming for the material modeling of the brain, there is still divergence between the results reported in the literature. A part of this discrepancy is due to the inherent difference between samples. Nonetheless, another part of it is resulted from the differences between testing protocols used by researchers. In some protocols multiple mechanical tests are performed on each sample. Enough recovery time should be considered between consecutive test... 

Shoreline monitoring and predicting has a very important role for policymakers and managers of coastal areas in future planning and achieving sustainable development. In this regard, to monitor the shorelines and predict its changes, a study has been conducted considering the effect of tides. In this study, the shoreline obtained from satellite images has been modified by using slope maps, slope direction and tidal data. Then these lines were monitored using the Digital Shoreline Analysis System (DSAS) and finally Bruun's rule along with the RCP scenario was used to predict changes in the shoreline. In this research, the coastlines of Bushehr Province in the Persian Gulf have been selected... 

Accurate modeling of clutter and detection of low observable targets within clutter are the major problems in radar signal processing applications. Recently, fractal geometry is applied to the analysis of high range resolution radar sea clutters. The intrinsic difference in the fractal dimension between sea clutter and the echoes from targets is extracted and used to detect targets. The box-counting method is widely used to estimate fractal dimension but it has some drawbacks never or rarely considered in literature. We explain the drawbacks and propose a new fractal dimension based detector to increase detection performance in comparison with traditional detectors. Both statistically... 

The synthetic aperture radar (SAR) is a microwave imaging radar that achieves high resolution while taking advantage of pulse compression technology and the Doppler effect. In typical radar systems, in order to obtain a good azimuth resolution, one should use an antenna with big aperture. However this is not possible in many cases. SAR has overcome this problem by moving the antenna and so making a synthetic aperture. In inverse SAR (ISAR) the radar antenna is static and synthetic aperture is created by the movement of target. Typical SAR imaging aims at the static targets and when the target is moving, it does not operate well. When detecting moving targets by SAR, both radar and target are... 

Shallow geothermal energy is a renewable and sustainable form of energy that has the potential to help alleviate the growing climate and energy crisis. The most common system used to extract shallow geothermal energy is the ground source heat pump (GSHP) system. The concept of using underground structures in exploiting shallow geothermal energy for space heating and cooling has received increasing attention. This study focuses on the use of geothermal tunnels as a means of extracting shallow geothermal energy.This research examines the effects of different heat transfer mechanisms, and highlights the effects of this phenomenon by focusing on the effects of natural convection around the... 

This study aims to propose a new correlation between in-situ horizontal stress and cone tip resistance in soils. Knowing the field in-situ stress state condition has an important role in stability assessment and stress-deformation analysis in a common geotechnical system. Although vertical stress could be measured easily, horizontal stress is still known as challenging work. Due to the difficulty in sampling undisturbed sand specimens, in-situ tests have been proposed in the previous literature to investigate the different characteristics of this soil. Cone Penetration Test (CPT) is one of the most used and accepted soil methods for soil investigation, identifying different soil parameters... 

This thesis presents turbulent partially premixed combustion modeling behind a bluff-body by using the Flamelet Generated Manifold. The objective of the present work is to develop a 4D FGM program to simulate partially premixed combustion at a reasonable computational cost. Pre-tabulated data of this manifold is obtained by using a correlated joint PDF. An in-house code is developed to build a pre-tabulated library in conjunction with a correlated PDF. Also, an exclusive OpenFOAM solver is created by employing the PIMPLE algorithm. This solver provides the link of the computational domain with the pre-tabulated chemistry. This program is used to simulate Cambridge-Sandia stratified burner... 

While Cloud providers face problems during providing services to their clients, such as lack of resources or increasing idle resources in low workload; they can share their resources with other providers by participating in Cloud Federations, and take advantage of Cloud Computing benefits like high scalability and resource extension. Moreover collaborating Cloud Federations expands Geographical area of providers. The Resource Allocation Problem has been considered in many researches, but in fields like Cloud environment and Federated Clouds it comes with complications. This thesis analyzes an optimized mechanism based on game theoretic approach for Resource Allocation Problem in Federated... 

Token offerings, one of the new methods of financing in the blockchain industry, have provided startups with significant opportunities. In previous studies, most of the factors that determine the success of an initial offering have been examined, and operational performance has been less studied. In this study, the relationship between environmental, social, and corporate governance activities on operational performance and adoption has been presented. Previous studies have shown that more attention to environmental, social, and corporate issues leads to a higher amount of capital raised in the offering. We also address these issues among crowdfunding platforms, which attract more... 

In recent years, with the growth of industrial societies, the amount of energy consumption in the world has been increasing. On the other hand, the most consumed energy sources in the world are non-renewable energy sources. For this reason, governments and industries have invested to facilitate and make renewable energy sources cheaper. One of these renewable energies is geothermal energy, which is one of the most economical ways to use this energy, using heat exchange systems in piles and foundations. Using a heat exchange fluid, energy piles transfer the heat of the earth's surface to the ground with a lower temperature in the hot seasons of the year and use the thermal energy of the... 

Micro electromechanical systems (MEMS) such as sensors and actuators are gaining more popularity in recent years. These systems have different application in automation, medicine and other industries. Mechanical structures are governed by electrical systems in MEMS devices and this is one of the challenges of MEMS studies. Usually these systems made by one deformable beam or plate over a fixed substrate. Due to applied voltage between substrate and deformable plate or beam, the deformable plate deflects toward the fixed substrate. The voltage at which the system becomes unstableis called pull-in voltage. Pull-in voltage is the most important characteristics of MEMS beyond which pull-in takes... 

In this thesis, the influence of nonideal boundary conditions on the vibration of a functionally graded beam excited by a moving oscillator on Pasternak-type viscoelastic foundation has been investigated. The beam has simply-supported boundary conditions and is assumed that the right-hand-side boundary conditions allows for small deflection, moment and axial force. The beam property gradient is assumed to be in the thickness direction and varies according to the power law distribution. The Hamilton's principle is utilized to obtain the governing equations of motion under the assumptions of Euler-Bernoulli beam theory. The equations of motion of the beam are solved using an... 

Epistemic logic gets its start with the recognition of the systematic properties of epistemic concepts. These properties make epistemic concepts amenable for formal study, and become our tools to present logical models for them.“Certainty” is one of these epistemic concepts for which no comprehensive logical model has been presented so far.
Among the logical models that have been presented for “Certainty”, there are two main models which are more comprehensive than the others and all the other models may be extendable to one of them. In this thesis, these two main logical models that have been proposed for the concept of certainty are introduced and described from a philosophical... 

Due to special characteristics, nowadays functionally graded materials are of great interest of researchers. Continuous change of properties in these materials,decreases undesirable phenomena such as stresscon centration. On the other hand knowing vibration parameters of structures such as natural frequencies, to avoid damage, is important. So far, many researches have been devoted to vibration analysis of structures, such as beams.In this dissertation, free vibration analysis of FGM beams, are investigated, using RKPM, a meshlesh method. The system of equations of motion is derived using Lagrange’s method under the assumption of Euler-Bernoulli beam theory. Buckling analysis of FGM beams... 

The ossicular chain of the human middle ear has a key role in sound conduction since it transfers vibrations from the tympanic membrane to the cochlea, connecting the outer and the inner part of the hearing organ. This study reports firstly a description of the main anatomical features of the middle ear to introduce a detailed survey of its biomechanics,focused on model development, with a collection of geometric, inertial and mechanical/material parameters. The joint issues are particularly discussed from the perspective of developing a model of the middle ear both explanatory and predictive. Such a survey underlines the remarkable dispersion of ... 

After Alzheimer and brain attack, the most common neurological disorder is epilepsy, which often involves seizures. In two-thirds of patients with epilepsy, the seizures can be controlled by antiepileptic drugs, and about 8% of patients can use epilepsy surgery; but unfortunately there is no acceptable treatment for the other 25% of these patients. Therefore preventing from epilepsy losses is a very important topic.
The gold standard for the diagnosis of the epilepsy is EEG monitoring. In this method, electrodes are placed on the scalp. Electrodes are uncomfortable to wear, and cause invasion to the patient, hence long-term monitoring and home monitoring is not feasible. In some...