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Modeling Electrical Activities of the Brain and Analysis of the EEG in General Anesthesia
, M.Sc. Thesis Sharif University of Technology ; Shamsollahi, Mohammad Bagher (Supervisor)
Abstract
In this thesis, an enhanced local mean-field (MF) model that is suitable for simulating the electroencephalogram (EEG) in different depths of anesthesia is presented. The main building elements of the model (e.g. excitatory and inhibitory populations) are taken from two pioneer MF models designed by Steyn-Ross et al and Bojak & Liley, and then a new slow ionic mechanism is included in the main model. Generally, in mean-field models, some sigmoid-shape functions determine firing rates of neural populations according to their mean membrane potentials. In the enhanced model, the sigmoid function corresponding to excitatory population is redefined to be also a function of the slow ionic...
Scattering of SH-Waves by a Cylindrical Multi Inhomogeneity Embedded in a Piezo-Electromagnetic Medium Using an Analytical Innovative Micromechanical Approach
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
This work examines the problem of the fully coupled magneto-electro-elastic (MEE) scattering of SH-waves incident upon a heterogeneous MEE scatterer which is embedded in an unbounded medium. The scatterer consists of a circular core and a circular encapsulator with eccentricity. All three regions: the core, encapsulator, and the surrounding matrix have distinct MEE properties and fully coupled constitutive relations. The generated coupled MEE fields coexist simultaneously in all these regions without resort to any simplifying assumptions. The precise description of the multifunctionality involves the solution of three fully coupled partial differential equations in three different regions....
Design and Simulation (& Manufacturing) of A Micro-Gyroscope
, M.Sc. Thesis Sharif University of Technology ; Akbari, Javad (Supervisor)
Abstract
Nowadays, microgyroscopes are among the most important products of MEMS. The production of small, precise and inexpensive gyroscopes has become possible as the result of recent developments in fabrication technology. In this thesis it is intended to introduce a new method for manufacturing more precise microgyroscopes regarding manufacture facilities. Using this new method, sensitivity and resistance of microgyroscopes are increased against noises which are primarily caused by vibration and rotation about undesirable axes. The rotational movement imposed on the gyro is detected through fluid flow within its torus channel. This transformation facilitates the measurement of the initial motion....
Propagation of SH Wave in Elastic Media with Cylindrical Inhomogeneity at Micro and Nano Scales by Couple Stress Theory
, M.Sc. Thesis Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
It is well known that the classical continuum theory does not consider size effect in predicting material’s behavior, however at the micro and nano scales, this effect is not negligible and the classical theory has deficiencies at these scales. To take into account the size effect, higher order continuum theories introduce new material constants into the formulation. One famous version of these theories is couple stress which is applied in this research. This theory considers size effect of inhomogeneity by employing Characteristic length of materials. Quasi-static couple stress and classical dynamic approaches do not include explicitly the size of the material unit cell in the formulation...
The Effect of Electroporation on Ultrasund Signals
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor)
Abstract
In this thesis, a cellular model of electroporation process and its detection by ultrasound signals is proposed. Electroporation is permeabilization of the cell membrane, caused by an external electric field. The resulted pores open cell’s membrane to large or hydrophilic molecules. The process of Electroporation has been used in Gene therapy and treatment of solid tumors. In this project, first we made a phantom of electroporated tissue and a phantom of normal tissue and then we simulated their responses to a linear array ultrasound transducer. By comparision of received signals from phantoms the probable effect of electroporation on ultrasound RF signals revealed. Results show up to 5 %...
Development of a Model to Investigate Energy Production Potential from Sea Applying GIS Technique
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Majid (Supervisor)
Abstract
The growing requirements for renewable energy production lead to the development of a new series of systems, including wave and tidal energy conversion systems. Due to their sensitivity and the impact of the aggressive marine environment, the selection of the most adequate location for these systems is a major and very important task. Several factors, such as technological limitations, environmental conditions, administrative and logistic conditions, have to be taken into account in order to support the decision for best location. The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called ‘the Atlas’) to map out wave and tidal resources...
Analysis of Nonuniform Superconducting Transmission Lines and Microstrips in Microwave Regime
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor) ; Fardmanesh, Mehdi (Supervisor)
Abstract
Nonuniform superconducting microstrip transmission lines in microwave regime have been investigated. Nonuniform transmission lines provide the capability of controlling line parameters. Photonic structures with subwavelength features can be homogenized and thus be accurately approximated by homogeneous yet spatially dispersive structures. This idea is here applied to nonuniform superconducting transmission lines with subwavelength nonuniformities, i.e. subcentimeter features in the microwave regime. This modelling is quite useful in geometrical and optical control of quasi-TEM wave propagation and dispersion engineering along microwave superconducting lines. This approach has applications...
Formation and Evolution of Cellular Structures in Two Dimensional Weakly Unstable Detonation Waves
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
In this investigation, cellular structure of a weakly unstable detonation wave in H2/O2/Ar mixture is studied. The detonation is simulated using 2D reactive Euler equations and one step Arrhenius type reaction model developed by Mr. Barkhordari. The numerical technique is the high order Piecewise Parabolic Method on the basis of Godonov method. The numerical fluxes are computed based on a high-order extension of the Godunov's method; the piecewise parabolic method (PPM). The initial cell formation processes and different machanisms involved in cell size changes are studied. This study shows that the form of initial perturbation used to intrigate the instability of detonation is not important...
Experimental Study of the Performance of a Multi-Tube Pulse Detonation Engine
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor) ; Ghorbanian, Kaveh (Supervisor)
Abstract
Performance of a multi tube pulse detonation engine has been investigated experimentally. A pulse detonation engine uses detonation phenomena and simply consists of a large narrow tube which has closed head, and has feeding system and ignition system. In this tube, detonation is produced periodically to generate thrust. In multi-tube mode, several tubes are arranged in parallel which detonate sequentially. Our PDE consists of 2 tubes with 70 cm length and 25 mm inner diameter which have several places performed for high speed pressure sensors installation. The premixed hydrogen-oxygen mixture are controlled by solenoid valve and injected on head-end and ignited by conventional spark plug....
Experimental Study on Ship Added Resistance in Wave
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor) ; Mehdigholi, Hamid (Supervisor)
Abstract
In the ship designing, it is preferable to access to a good performance in waves and low efficiency loss. Accordingly, modeling and estimation of added resistance would be an important issue. Added resistance in wave is an important part of ship's performance due to many technical and economic effects on the ship's performance. With understanding and awareness of the added resistance that comes from ship accident to the waves, we can reduce this parameter by changing in specifications and hull form of ships. Designers are also interested in optimizing the ship from this aspect. In previous works, added resistance in waves was obtained from experimental, numerical and analytical methods. In...
Wideband Electromagnetic Wave Propagation Modeling In Indoor Environments Using Ray Tracing Method
, M.Sc. Thesis Sharif University of Technology ; Shishegar, Amir Ahmad (Supervisor)
Abstract
Ray-tracing method is extensively used for wave propagation analysis of indoor and outdoor environment for narrowband systems. The main goal of this research is to extend ray-tracing method for site-specific modeling of wideband electromagnetic propagation. In this thesis, Time-domain reflection and transmission coefficients have been computed for dielectric half-space and dielectric slab with frequency dependent permittivity. First, analytical form of Fresnel reflection coefficient for vertical and parallel polarizations in time-domain have been computed for dispersive half-spaces with lossy, extended Debye, two-pole Debye and multi-pole Debye models. By using these time-domain...
Assessment of Existing Jacket Type Offshore Platform against Environmental Wave Loading Utilizing Theory of Reliability
, M.Sc. Thesis Sharif University of Technology ; Golafshani, Ali Akbar (Supervisor)
Abstract
Assessment of existing jacket type offshore platform against environmental wave loading hazard is the central component of this work. Two general approaches exist in this context, deterministic and probabilistic assessment. In this study, a new probabilistic method (reliability analysis) to assess offshore structures under environmental loading (extreme wave) is introduced. Before describing this approach, several necessary elements such as collapse analysis, sampling methods and wave hazard analysis should be investigated. First of all, deterministic assessment of SPD2 platform located in Persian Gulf, which is the case study considered in this dissertation, is conducted utilizing...
Simulation of Gravity Drainage in Oil Reservoirs Using Black-Oil Model
, M.Sc. Thesis Sharif University of Technology ; Taghizadeh Manzari, Mehrdad (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)Experimental Study on Ship Motions in Regular Waves
, M.Sc. Thesis Sharif University of Technology ; Seif, Mohammad Saeed (Supervisor) ; Mehdigholi, Hamid (Supervisor)
Abstract
Regarding the increasing application of fast boats in the world, studying the dynamic performances of these boats is consequently effective and vital. So one can evaluate the hull performance in different sea forces. Vast activities take place in all over the world yearly. General performances hull tests occur in marine laboratories such as Wave maker and carriage. Model hull test is one of effective branches of the naval architecture engineering. This method is also based on dimensional analysis. In this thesis, after understanding the waves and the methodology some experimental tests are done in the conditions of frontal static waves, and heave, pitch and roll activities of the craft are...
Evaluation of Dynamic Properties of Plastic Concrete Using Bending Disk Tests in Small Strain Range
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Evaluation of the compression wave velocity (Vp ) and small strains elastic modulii of various types of plastic concrete specimens in unconfined and triaxial compression tests using piezoelectric transducers was performed in this study. Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable cut-off wall for seepage control in highly permeable dam foundations. A plastic concrete cut-off wall acts essentially as a barrier to stop or reduce the groundwater flow. In this study the effect of specimen age, water-cement ratio, bentonite-cement ratio, confining pressure, wave...
Ultrasound Intensity Exposimetry in Physiotherapy Devices using Micro-Bubbles
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor)
Abstract
Routine ultrasound calibration methods have some restrictions such as: low bandwidth, low frequency resolution, limited spatial resolution, the high cost of test and risk of damage to the transducer when exposed to high powers. In this thesis, a new technique based on microbubble resonance is proposed. Non-linear resonating microbubbles produce harmonics;the first harmonic may be masked by reflection from larger microbubbles as well as unwanted reflections which cause ambiguity in the determination of the amplitude of the excited pressure. Therefore, the second harmonic is used, with a single characteristic peak. In order to model the physical phenomenon, the second harmonic generated in the...
Love Wave Propagation in a Functionally Graded Magneto-Electro-Elastic Half-Space with Quadratic Variations
, M.Sc. Thesis Sharif University of Technology ; Eskandari, Morteza (Supervisor)
Abstract
The propagation behavior of Love wave in functionally graded magneto-electro-elastic half-spaces with a quadratic variation is addressed. The magneto-electromechanical coupling factor, the dispersion relations, electric potential, magnetic potential and displacement are obtained analytically for both magneto-electrically open and short conditions. The effect of gradient coefficient on phase velocity, group velocity and magneto-electromechanical coupling factor are plotted and discussed. Research on the wave propagation in magneto-electro-elastic materials is still very limited. This work provides us with a theoretical foundation to design and practically apply SAW devices with high...
Production of Zn-Tio2 Nanocomposite Coating by Electrochemical Method and Investigation of its Properties
,
M.Sc. Thesis
Sharif University of Technology
;
Ghorbani, Mohammad
(Supervisor)
;
Afshar, Abdollah
(Supervisor)
Abstract
Pure zinc coating and Zn-TiO2 composite coating were deposited from two methods: Direct and Pulse Current from a sulphate bath. D.C. section, current density and particle concentration in electrolyte were investigated. Moreover in Pulse section, frequency, duty cycle and maximum current density were investigated as parameters. Morphological properties of these coatings were investigated by FE-SEM and corrosion behavior by potentiodynamic polarization in 1M NaCl. In D.C. section, in investigation of the effect of current density, an optimum was observed in case of obtaining the highest amount of deposited particles at 0.1 A/cm2 and amount of 2.93%. This amount is the highest one in D.C....
Numerical Modeling of Sediment Transport in Souza Gheshm Island
, M.Sc. Thesis Sharif University of Technology ; Raie, Mohammad (Supervisor) ; Ataei Ashtiani, Behzad (Supervisor)
Abstract
Complicated theories dominated toward interacting of coastal regions resulted from its nature. Besides of that interference of human activities for acquiring beneficial aspects of shorelines causes environmental considerations to be challenged. One of the main factors for resolving this challenge is to obtain adequate information from hydrodynamic process and sediment regime. In spite of scientific researches that carried out along past three decades for understanding the exact mechanism of along shore sediment transport, it was not fully developed. One of the main reasons of uncertainty for forecasting the sediment regime regarded not exact knowledge of how sediment act in different...
Structural Health Monitoring of Oil Pipeline Using Guided Lamb Waves
, M.Sc. Thesis Sharif University of Technology ; Zabihollah, Abolghasem (Supervisor) ; Selk Ghafari, Ali (Supervisor)
Abstract
Pipeline systems are one of the cheapest ways for distribution and transportation of petroleum and natural gas. The testing of pipes used in the petroleum industry is necessary to avoid unplanned process interruptions, environmental pollution and provide good safety. One of the methods which is used for pipeline inspection is the ultrasonic non-destructive testing (NDT) technique. The use of conventional NDT techniques such as ultrasonic thickness gauging is a slow inspection process, which becomes very expensive when full inspection is needed. Ultrasonic guided waves provide an appropriate fast screening technique. These waves stress the whole pipe wall and propagate along the length of the...