Phase diagram of the one-dimensional anisotropic Kondo-necklace model

, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 77, Issue 2 , 2008 ; 10980121 (ISSN) Mahmoudian, S ; Langari, A ; Sharif University of Technology

2008

Abstract

The one-dimensional anisotropic Kondo-necklace model has been studied by several methods. It is shown that a mean field approach fails to gain the correct phase diagram for the Ising-type anisotropy. We then applied the spin wave theory which is justified for the anisotropic case. We have derived the phase diagram between the antiferromagnetic long range order and the Kondo singlet phases. We have found that the exchange interaction (J) between the itinerant spins and local ones enhances the quantum fluctuations around the classical long range antiferromagnetic order and finally destroy the ordered phase at the critical value Jc. Moreover, our results show that the onset of anisotropy in the...

Mass Reconstruction of XMM-NEWTON06 Data Based on KSB Method

, M.Sc. Thesis Sharif University of Technology Mahmoudian, Hanieh (Author) ; Mansouri, Reza (Supervisor)

Abstract

Gravitational lensing affects not only the position and number of images of cosmic objects but also their shapes. In the so-called weak gravitational lensing effects related to shape of the cosmic objects are studied. These require high quality images and wide field of view. Because of technology development and production of multi-chip CCD cameras in recent decades, we are witnessing an increase in the number of projects using weak lensing techniques. Taking instrumental errors into account, the first step in weak lensing studies should be the proper data reduction to produce final images in which instrumental errors are removed and have sufficient precision to be processed. In This thesis...

On Graph Reconstruction Conjecture

, M.Sc. Thesis Sharif University of Technology Farhadian, Ameneh (Author) ; Mahmoudian, Ebadollah (Supervisor)

Abstract

The reconstruction conjecture is an open and interesting problem that attracts some reserchers. Although some work toward this problem has been done; but no one have been able to solve it comlpetely. In this thesis, some new theorms are developed which extend the domain of reconstructible graphs. Also, a generalization of graph spectrum -called Alpha Spectrum- is introduced that is very effective in recognization of graphs

Some Problems and Methods on Tournaments

, M.Sc. Thesis Sharif University of Technology Abdi, Maryam (Author) ; Mahmoudian, Ebadollah (Supervisor)

Abstract

In 1953, Landau expressed the conditions for the existence of tournaments with a prescribed score vector R. Eleven years later, Ryser proposed an algorithm for constructing the tournament matrix with score vector R and showed that any two tournaments with the same score vector can be obtained from one another by a sequence of 3-cycle switches. Last year (2014) Brualdi and Fristcher explained in an article, similar to this process, the existence of, algorithm and switches for loopy tournament and Hankel tournament and similar structure skew-Hankel tournament. This paper is discussed in a chapter of this thesis. In 1991, De Caen found a lower bound for the real rank of a tournament matrix....

Regularity of the Convex Solutions of the Monge-Ampère Equation

, M.Sc. Thesis Sharif University of Technology Mahmoudian, Sahand (Author) ; Fotouhi. Morteza (Supervisor)

Abstract

Partial Differential Equations (PDEs) play a crucial role in modeling various physical, biological, and engineering phenomena. One of the most important and complex of these equations is the Monge-Ampère equation, which appears in various fields including differential geometry and optimization theory. In this thesis, after defining and examining the preliminary properties of the Monge-Ampère measure and defining the Alexandrov weak solution, the existence and uniqueness of this weak solution for the Dirichlet problem are addressed, and finally, the regularity problem is studied

Thermal Simulation of Bioheap

, Ph.D. Dissertation Sharif University of Technology Mahmoudian, Alireza (Author) ; Sadrnezhad, Khatiboleslam (Supervisor)

Abstract

Nowadays, because of drastically decrease of copper sulfide ore’s grade, and difficulties in leaching of them, new processes of copper production like bioleaching technique become significant. Finding the optimal conditions for bioleaching, require investing a lot of time and cost. Computer simulation is useful in this case. Temperature, affects the kinetics of dissolution reactions, type and growth rate of bacteria, and finally, rate and amount of recovery of valuable copper metal from ores, so determination of temperature within the bioheap is very important. Thermophiles are better than mesophiles in chalcopyrite bioleaching and in the range of 55 to 65 degree centigrade, thermophiles...

Covering Arrays for Graphs and Their Construction Algorithms

, M.Sc. Thesis Sharif University of Technology Jahdasa, Rahman (Author) ; Mahmoudian, Ebadollah (Supervisor)

Simulation of bioleaching heat effects for enhancement of copper recovery from sarcheshmeh chalcopyrite [electronic resource]

, Article Metallurgical and Materials Transactions B ; Volume 45, Issue 4 , pp 1204-1212 Mahmoudian, A. R. (Ali Reza) ; Sadrnezhaad, K ; Manafi,Z ; Sharif Univercity of Technology

Abstract

A heat-transfer model was formulated to determine the distribution of temperature within a bioheap of chalcopyrite of Sarcheshmeh copper mine. Bioleaching employs mixed mesophilic and thermophilic microbes for Cu extraction. Thermophiles are better than mesophiles to dissolve CuFeS2. The solution irrigation and aeration rates were taken into account as the main operational factors. The model was validated by comparing the temperature profiles of test columns with those of bioheap. The model was used to find the optimal ratio of irrigation to aeration. It was found that when the solution was fed at a flow rate of 5 kg/m2 h and air was blown at a flow rate of 7.5 kg/m2 h, the transition from a...

Brain waves evaluation of sound therapy in chronic subjective tinnitus cases using wavelet decomposition

, Article Frontiers in Integrative Neuroscience ; Volume 12 , 2018 ; 16625145 (ISSN) Asadpour, A ; Jahed, M ; Mahmoudian, S ; Sharif University of Technology

Frontiers Media S.A 2018

Abstract

Management and treatment of subjective tinnitus is an ongoing focus of research activities. One of the most viable assessments of such treatment is the evaluation of brain activity in addition to patient response and clinical assessment. This study focuses on sound therapy and evaluation of patients’ electroencephalogram (EEG) in order to verify the potency of this approach. Broadband sound therapy was applied to nineteen participants aging from 25 to 64 and suffering from chronic subjective tinnitus to study the difference of brain activity, a) before fake treatment, b) after fake treatment and c) after the main treatment, using EEG and Visual Analog Scale (VAS) for evaluating Residual...

Aberrant frequency related change-detection activity in chronic tinnitus

, Article Frontiers in Neuroscience ; Volume 14 , 2020 Asadpour, A ; Jahed, M ; Mahmoudian, S ; Sharif University of Technology

Frontiers Media S.A 2020

Abstract

Tinnitus is the perception of sound without the occurrence of an acoustic event. The deficit in auditory sensory or echoic memory may be the cause of the perception of tinnitus. This study considered the mismatch negativity (MMN) to investigate the potential difference between and within groups of persons with normal hearing (NH) and tinnitus. Using an auditory multi-feature paradigm to elicit the MMN, this study considered the MMN peak amplitude at two central frequencies for two MMN subcomponents. These central frequencies were 1 and 5 kHz, which the latter was closer to the perceived tinnitus frequency in the group with tinnitus. The deviants were higher frequency, lower frequency, higher...

An Algorithmic Approach to the Intersection Problem in Latin Squares

, M.Sc. Thesis Sharif University of Technology Mohammadi Nevisi, Maysam (Author) ; Mahmoudian, Ebadollah (Supervisor)

Abstract

The so-called intersection problem has been considered for many different combinatorial structures, including Latin squares. This intersection problem basically takes a pair of structures, with the same parameters and based on the same underlying set, and determines the possible number of common sub-objects (such as blocks, entries, etc.) which they may have. The intersection problem has also been extended from consideration of pairs of combinatorial structures to sets of three, or even sets of , where may be larger than 3. In this thesis, we study the related problem of determining, for all orders n, the set of integers k for which there exists = 4 Latin squares of order n having...

Existence and Regularity of Renormalized Solutions for Boltzmann Equation

, M.Sc. Thesis Sharif University of Technology Mahmoudian, Hamid Reza (Author) ; Fotouhi, Morteza (Supervisor)

Abstract

In 1989 DiPerna and Lions proved the stability of Boltzmann’s evolution equation using their theory of renormalized solutions. Their result , for the first time, proved the existence of solutions without extra assumptions on the initial condition and on arbitrary time intervals. While the wellknown Grad’s cut-off assumption is present in the original theory, there have been successful generalizations to account for the singular case. Also the renormalization theory has shed light on limiting regimes of the Boltzmann equation. Here we discuss the new techniques that are essential for such generalizations

Evaluating Modal Accessibility Gap Between Public Transport and Bicycle: A Case Study of Tehran

, M.Sc. Thesis Sharif University of Technology Mahmoudian, Khashayar (Author) ; Kermanshah, Amir Hassan (Supervisor)

Abstract

This thesis examines the accessibility gap between different modes of transportation in Tehran Province, with a particular focus on public transportation and cycling. The main objective of this research is to calculate and analyze accessibility indicators to various land uses (such as commercial, service, and recreational) around metro stations using two modes of travel: cycling and bus-walking. The study utilizes simulations in Python and geographic libraries to compare these two modes of travel based on four key accessibility indicators: 1) nearest Opportunity, 2) cumulative opportunity, 3) average distance, and 4) gravity-based accessibility to measure the accessibility gap between the...

Transmission-Line Models for Approximate Analysis of Electromagnetic Periodic Structures

, Ph.D. Dissertation Sharif University of Technology Khavasi, Amin (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

Full numerical methods are usually used for the analysis of periodic structures such as photonic crystals and diffraction gratings. The main drawback of these methods is that they are time-consuming and thus are not appropriate for the design process. In this thesis, approximate and fast methods, based on transmission line models, for the analysis of periodic structures are proposed. To this end, in the first part of the thesis, we investigate one-dimensionally periodic metallic gratings. Longitudinally homogenous metallic gratings, enhanced reflection phenomenon and longitudinally inhomogenous metallic gratings are examined, and simple, and efficient transmission line models for these cases...

Microwave Inspired Easy-to-Design Nano-Couplers for Hybrid Photonic-Plasmonic Waveguide Structures

, M.Sc. Thesis Sharif University of Technology Hodaei, Hossein (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

Potential of plasmonic waveguide structures to confine light in sub-wavelength scales attracted many attentions in recent years. Among these structures planar metal-insulator-metal waveguide and plasmonic slot waveguide are more promising. That is because of their easy fabrication process along with their various reported applications. However, there are some obstacles in the path of developing plasmonic integrated circuits, among whichhigh propagation loss can be named as the most important. To solve this issue, photonic waveguides can be used as the lossless interconnections between small footprint plasmonic components on optical chips. Therefore, application of plasmonic slot waveguide...

Multi-Conductor Transmission Line Models for Analysis of Metal-Dielectric -Metal Nanoplasmonic Structures

, M.Sc. Thesis Sharif University of Technology Bahadori, Meisam (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

The existing transmission line models of plasmonic nanostructures are modified in this thesis to study the electromagnetic characteristics of nano-plasmonic structures in a more efficeint yet accurate enough fashion. First, rectangular plasmonic cavities made by carving dielectric rectangles within a metallic region are modeled by trasnmission lines of finite length being appropriately terminated at their both ends. The resonance conditon in the proposed model yeilds the resonance frequencies, quality factors, and mode profiles of its correspondig plasmonic resonator. The accuracy of the proposed model is assessed by using the fully numerical finite-difference time-domain method (FDTD)...

Rigorous Calculation of Guided Modes in Photonic Crystal Waveguides and Contriving Homogenized Models

, M.Sc. Thesis Sharif University of Technology Habibi, Nasim (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

In this thesis an approximate method is proposed for analysis of two dimensional photonic crystal waveguides. In this method an equivalent impedance is assigned to photonic crystal regions and the waveguide region is modeled with a transmission line. Waveguide’s loss is also analysed and computed by this method. In other words the proposed method is able to determine the complex propagation constant of guided modes without computing any complex roots for dispersion equation. Although like any other approximate method, the accuracy of this method is dependent to some special conditions but it’s advantage over other numerical methods is its simplicity and its capability for waveguide designs....

Distributed Circuit Modeling of Plasmonic Nanostructures

, M.Sc. Thesis Sharif University of Technology Rezaei, Mohsen (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

The existing transmission line models of plasmonic nanostructures are modified in this thesis to study the electromagnetic characteristics of nano-plasmonic structures in a more efficeint yet accurate enough fashion. First, rectangular plasmonic cavities made by carving dielectric rectangles within a metallic region are modeled by trasnmission lines of finite length being appropriately terminated at their both ends. The resonance conditon in the proposed model yeilds the resonance frequencies, quality factors, and mode profiles of its correspondig plasmonic resonator. The accuracy of the proposed model is assessed by using the fully numerical finite-difference time-domain method (FDTD)...

Analysis and Design of the Dielectric Resonators Using Differential Transfer Matrix Method (DTMM) in the Cylindrical Coordinate

, M.Sc. Thesis Sharif University of Technology Jalaly, Sadegh (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

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...

Optical Circuits Made of Spoof Plasmonic Structures with Wide-Band Transmission Resonance and the Impact of Fano Resonance

, M.Sc. Thesis Sharif University of Technology Rahmani, Babak (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

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...