Sharif Digital Repository

As more renewables step in, the ongoing change will be drastic for the electrical grid. The energy sector must find new ways to balance energy production and consumption. Electric vehicle (EV) batteries are by far the most cost-efficient form of energy storage since they require no additional investments in hardware. A bidirectional EV charger is a new technology that enables energy to be pushed back to the power grid and auxiliary loads from the battery. The electrical requirements of the EV charger are examined in detail to find an appropriate power electronics converter to meet all the requirements. The CLLC resonant converter is a promising candidate for high efficient, bidirectional... 

In this project rotational barrier around the C-N bond in 4-ethyle-morpholine- carboxylate has been studied using DNMR spectroscopy. Spectra were taken at variable temperature, and then with simulation of bandshape broadening pattern at coalescence region, rate constants of exchange were obtained for all temperatures. For simulation of line-shape broadening Spinworks software was used, that with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from simulations, were used for calculation of thermodynamic activation parameters (∆G#, ∆H#, ∆S# and Ea). ∆G# 298 value of 13.66 Kcal/mol for 4-ethyle-morpholine- carboxylate... 

The Barrier of the internal rotation around C-N bond in O-ethyle morpholine-4-carbotioate were calculated using dynamic NMR spectroscopy (DNMR) in DMSO solvent. 1H and 13C NMR spectra were recorded at different temperatures (295-350K). Band shape broadening patterns at coalescence regions were simulated to extract rate constants of NMR spectera. Transition state thermodynamic properties of internal rotation around C-N bond in O- ethyle morpholine -4- carbotioate are estimated: , , , . To assay reliability of the estimated values, transition state thermodynamic properties were calculated using PCM model at method and basis set B3LYP/6-311++G(d,p). Theoretical values of thermodynamic... 

Prediction and calculation of shielding tensors of H, C, F and P nuclei of different molecules has been the subject of much research, because these nuclei have the greatest importance in NMR experiments. The optimum wave functions and calculation method were obtained using empirical models and factorial design. Based on preliminary experiences, the following four factors at two levels were selected: electron correlation, triple-ξ valence shell, diffuse function and polarization function. The wave functions for calculating gas phase 1H and 13C chemical shifts of various types of alcohols, amines and simple hydrocarbons were optimized using empirical model. The B3LYP/6-311+G wave function is... 

Image segmentation is a technique which divides an image into significant parts. The accuracy of this technique plays an important role when it applies on medical images. Among various image segmentation methods, clustering methods have been extensively investigated and used. Since it is an unsupervised method, the existence of a small amount of side-information which is extracted from a specific application (in this case, medical image) could improve its accuracy. Using this side-information in clustering methods introduces a new generation of clustering approaches called semi-supervised clustering. This information usually has a format of pair-wise constraints and can be prepared easily... 

In this project rotational barrier around the C-N bond in Ethyl N-(pipyridin carbotioate) has been studied by using DNMR spectroscopy. Spectra were taken at various temperatures , and then with simulation of bandshape broadening pattern at coalescence region, the exchange rate constant of were obtained for all temperatures. For simulation of line-shpe broadening Spinworks software was used, that with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from the simulation were used for calculation of thermodynamic activation parameters (... 

Ring and disk resonator are studied in this thesis. First, the complex resonance frequencies of two-dimensional homogeneous ring and disk resonators are extracted by following the standard approach and then a novel method is proposed to extract the complex eigen-frequencies of two-dimensional inhomogeneous ring and disk resonators. The inhomogeneity of the refractive index is arbitrary along the radial direction. The proposed method is shown to be more efficient than the standard approach based on the stair-case approximation. It is therefore appropriate for resonator design and is thus employed for systematic study of the opposing trends of geometrical parameters in maximization of... 

In this project rotational barrier of C-N bond in Ethyl N-(pyrrolidine carbotioate) has been studied using DNMR spectroscopy. Spectra were taken at various temperatures, and then with simulation of bandshape broadening pattern, rate constants of exchanges were obtained for all temperatures. For simulation of line-shape broadening SpinWorks software was used,which with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from simulations, were used for calculation of thermodynamic activation parameters (?G#, ?H#, ?S# and Ea#).Experimental ?G# 298value(Experimental) of 18.3 Kcal/mol for Ethyl N-(pyrrolidine... 

In recent years, multiport bidirectional converters have been a center of attention in renewable energy systems. This research focuses on three-port bidirectional converters. First, series resonant bidirectional converter is precisely analyzed. This analysis includes sinusoidal, exact state space and small signal analysis through phasor concept. This converter can work in higher switching frequencies and higher power ratings in comparison with common DAB bidirectional converter due to its inductor impedance cancellation. To increase power rating a three-phase version is proposed which has reduced output filter capacitance. Then, three-port bidirectional resonant converter is proposed and... 

Constantly rising fuel prices and environmental consciousness have caused alternative transport solutions to be considered.Recently, batteries and electric vehicle industries have developed to become a reasonable alternative for gasoline powered cars. Plug-In hybrid electric vehicles could be connected to the electrical grid to be recharged. To ease the charging process, one solution could use an on-board charger to charge the electric vehicle. This charger should be able to be connected to a conventional outlet for convenience reasons and moreover, it should be a grid friendly charger in order not to pollute the electrical network. After studying the introduced structures for electric... 

In this study, the micro and nano particles of substituted strontium hexaferrites with nominal composition of SrFe12-xTix/2Znx/2O19 (x=0, 0.5, 1, 1.5, 2 and 2.5) were prepared by a co-precipitaion method. Ferrite-PVA composites (70:30) with thickness of 1.8mm were prepared at 220°C and 50Mpa. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer (EDS), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) were employed for characterization of synthesized powders and composites. XRD and FTIR results showed that single phase hexaferrite were obtained for almost all of the... 

In this work we have studied conformation of ranitidine by dynamic nuclear magnetic resonance spectroscopy (DNMR) in four different solvents: chloroform, acetone, dimethylsulfoxide, and deuteriumoxide. Ranitidine has three tatumeric forms of enamine, nitoic acid, and imine, but its stable structure is enamine. Temperature dependent 1HNMR spectra of ranitidine which reportet at 500MHz were consistent with the following free activation of energies ΔG# (kcal mol-1): chloroform = 16.2; acetone = 15.4; dimethylsulfoxide = 15.1. The experimental results were confirmed by DFT theoretical calculations at the B3LYP/6-311++G (d, p) level of theory. It was also proved that ranitidine has the form of... 

Magnetic Resonance Imaging (MRI) is a non-invasive imaging modality which can represents the structure, metabolism and the function of inner tissues and organs. Unlike other imaging modalities MRI does not use ionizing radiation.Reducing the imaging time will result in cost reduction and patient comfort. Therefore since the invention of MRI, increasing the speed of imaging has drawn a lot of attention. This was mainly done by improving and upgrading the data collecting hardware of the imaging module.With the advances in technology, a point has been nearly reached, that due to the physical and physiological constraints, such as nerve stimulation, quickening the hardware is impractical.... 

Vibrations with high amplitudes in continuous systems and models with multiple degrees of freedom, in specific conditions, is concomitant with a phenomenon called internal resonance. In the presence of this phenomenon, energy is transferred from one directly excited mode to the other vibrating modes of the structure results in response of the structure to be combination of the excited modes. In that situation occurrence of the internal resonance may decrease the level of undesired vibrations of the structure. This behavior is of interest especially in sandwich structures with viscoelastic cores that are designated to improve the damping characteristics of the structure and the property may... 

Breast cancer is considered as the most common type of cancer in women worldwide and mammography is currently utilized as the principal method for screening the breast cancer. Breast Magnetic resonance imaging (MRI) can be used as a complementary imaging technique besides mammography. MRI technique involves scanning a patient before and repeatedly after the injection of the contrast agent (DCE-BMRI). This examination often takes 7-10 minutes and any movement of the patient’s breasts due to breath, heartbeat or deliberate movement, made in this relatively long acquisition period, leads to a distortion in images called motion artifact. This problem makes the quantitative analysis of the images... 

Image registration is defined as matching two or more than two images which are taken from a same scene in different times, from various views and using different sensors. By matching, we mean finding the transformation function between the images. Image registration
has many application in medical domains such as analyzing changes in body limbs, supervision of the tumors growth, and robotic surgery. The challenges of image registration are unavailability of the transformation function, existence of the outliers in the images, changes in the images intensity, changes in the image geometry, noise, etc. Image registration consists of four steps: (i) feature extraction, (ii) choosing a... 

One of the different sensing techniques for biosensors is based on surface plasmon resonance which provides high reliability and efficiency. In this project working operating principles of biosensors based on surface plasmon resonance will be examined. For investigation of sensing meachanism we assume that there an array consisting of alternating graphen ribbons which by applying light leads to an effective magnetic field coupling to the localized surface plasmon. The numerical calculations are based on the exact solution of Maxwell's equation using Fuorier Model Method and Matlab coding. In these calculations, the coefficients of transmission, reflection and absorption of light versus... 

Circular polarization (CP) is one of the common polarization types used in wireless systems for frequency identification (RFID), global positioning (GPS) and wireless local area networks (WLAN), since it can provide greater flexibility in orientation angle between transmitter and receiver, and better mobility and weather penetration than the linearly polarized antennas. Magnetic permeability in ferrites can be tuned by external magnetic field ; So ferrites can be good candidates for new reconfigurable CP antenna technology. In this project, we will consider circularly polarized slot antenna with a wide axial ratio beamwidth that consists of a normally magnetized ferrite substrate mounted... 

Magnetic resonance imaging is one of non-invasive methods to measure the hemodynamic and morphologic parameters of tissues, especially brain tissues. Hemodynamic parameters monitoring in brain tissue is of significant importance in many majors such as detection of tumor occurrence, brain abnormalities, and track of treatment procedures. Blood is a suspension, comprised of plasma, red blood cells, white blood cells, platelet, etc. Plasma is a Newtonian fluid which is composed of proteins and has a constant viscosity in body temperature. Rheological properties of blood are highly dependent on mechanical and rheological properties of its cells and this dependence is multiplied in narrow vessels... 

Magnetic Resonance Imaging is one of the most advanced medical imaging procedure that noninvasively played in most applications. However, this imaging method is a good resolution, but not in the conventional high speed imaging method, in fact, the main problem is slow. In recent years many studies have been done to accelerate MRI that compressed sensing can be mentioned among them. Such methods, however, have had very good results but MRI systems are very complex. This project investigates the reconstruction of MR images using data from partial non-Cartesian samples aimed at reducing sampling time and also speed up the process of reconstruction of MR images have been studied. In this regard,...