In this study, the basic absorption and scattering characteristics of acoustic scatterers, specifically Schroeder Diffusers, are investigated. Schroeder Diffusers are one of the most widely used acoustic scatterers in which the scattering phenomenon is predictable due to the geometry of the diffuser, based on a particular mathematical sequence. It is shown that it is possible to increase the amount of absorption by modifying the diffuser structure by means of adding perforated panels into the wells or narrowing diffuser wells. In room acoustics applications, diffusers are conventionally mounted to a wall or ceiling assumed to be rigid enough such that sound wave cannot penetrate through. This thesis proposes a new modification on these diffusers where the diffuser is not backed by a rigid surface / it is hung over a space instead. To construct such a configuration, diffuser wells are terminated with micro-perforated panels (MPP). Inclusion of MPP introduces additional losses / hence, higher absorption can be achieved. However, the most significant absorption in this configuration is achieved below the first resonance frequency of the panel-air space system due to the existence of non-rigid backing. This thesis aims to model the absorption and scattering mechanisms enabled with the non-rigid backing by improving a previously introduced mathematical model.

In this thesis work fluid flow and heat transfer in two-dimensional microchannels are studied numerically. A computer code based on Lattice Boltzmann Method (LBM) is developed for this purpose. The code is written using MATLAB and Jacket software and has the important feature of being able to run parallel on Graphics Processing Units (GPUs). The code is used to simulate flow and heat transfer inside micro and macro channels. Obtained velocity profiles and Nusselt numbers are compared with the Navier-Stokes based analytical and numerical results available in the literature and good matches are observed. Slip velocity and temperature jump boundary conditions are used for the micro channel simulations with Knudsen number values covering the slip flow regime. Speed of the parallel version of the developed code running on GPUs is compared with that of the serial one running on CPU and for large enough meshes more than 14 times speedup is observed.

The aim of this study is to develop a sound transmission model that can be used to predict the vibration and noise levels of a submerged vessel. The noise transmitted from the mechanical vibrations of the hull of a submarine and the turbulent boundary layer excitation on the submarine are investigated. A simplified physical model of the submarine hull including the effects of bulkheads, end enclosures, ring stiffeners and fluid loading due to the interaction of the surrounding medium is presented in the study. An energy approach, i.e., Statistical Energy Analysis (SEA) is used for the analysis because the characterization of the hull of the structure can be done by a very large number of modes over the frequency range of interest and the deterministic analysis methods such as finite element and boundary element methods are limited to low frequency problems. The application consists of the determination of SEA subsystems and the parameters and the utilization of power balance equations to estimate the energy ratio levels of each subsystem to the directly excited subsystem. Through the implementation of SEA method, the sound pressure levels of the hull of the structure are obtained. In terms of military purposes, the sound levels of the submarine compartments are vital in the aspects of the preserving of submarine stealth.

This thesis study is focused on experimentally investigating pump noise at design and off-design operations and its relations with pressure fluctuations. Small size pumps are placed in a semi-anechoic chamber and operated at various system conditions and various rotational pump speeds. Pump operational data, noise data and time dependent pressure data are recorded. Fast Fourier Transform spectra of noise and pressure data are compared. Coherence spectrum between sound pressure level and hydraulic pressures are obtained. Data processing, Fast Fourier Transform and cross correlation are conducted with specific software Soundbook SAMURAI. The experiments have indicated that system characteristics or pump size do not have any influence on the noise of pump. On the other hand, pump characteristics are found to be distinguishable by means of peak frequencies on the sound spectra which are proportional to blade passing frequency. Results of cross correlations also show that, pump outlet pressure is a more significant source of noise than pump inlet pressure.

In this study in order to simulate the acoustic waves, Ray Theory and Normal Mode models are used. These methods are analyzed using MATLAB simulation tool / differences between two models are examined and a region with a known bottom profile and sound velocity profiles is investigated. The Ray Theory is used in acoustic systems which is the one of the applications of wave modeling. Ray theory is solved with standard Ordinary Differential Equation solvers and normal mode with finite element method. Different bottom profiles and sound velocity profiles previously taken are interpolated to form an environment and examined in the case study. in the case study.

Two sample statistical energy analysis (SEA) models are generated for a section of the fuselage panel of an aircraft, namely the uniform panel model which includes the frames and stringers, and the ribbed panel model in which the frames and stringers are smeared into the skin. Turbulent boundary layer (TBL) excitation is used as the primary acoustic excitation source. Stress levels are estimated from the average velocity data of the panels. The stress results are found comply with those obtained by the AGARD method. Effect of radiation from panels to exterior and interior of the sample skin panel as well as the pressurization of the skin panels are investigated separately to analyze their effects on the stress levels. The method is then used in the analysis of center fuselage skin panels on a basic training aircraft. Two models are generated for the aircraft analysis, namely the complete aircraft model and the simplified model which excludes the wings and the empennage. In addition to TBL, propeller noise is used as the primary acoustic excitation source. The effects of the wings and the empennage on the stress levels in the center fuselage skin panels are also investigated along with the radiation from panels to the exterior and interior of the aircraft and pressurization of the pilot cabin.

In this thesis, localization of the underwater sound sources using matched field processing technique is considered. Localization of the underwater sound sources is one of the most important problems encountered in underwater acoustics and signal processing. Many techniques were developed to localize sources in range, depth and bearing angle. However, most of these techniques do not consider or only slightly takes into account the environmental factors that dramatically effect the propagation of underwater sound. Matched field processing has been developed as a technique that fully considers the environmental factors. Matched field processing has proven to be successful in many applications such as localization of sources in range and depth, the determination of environmental parameters, and the evaluation of model accuracies. In this study, first a comparative analysis of narrowband matched field processors is given. Namely four main processors: Bartlett processor, Minimum Variance Distortionless Response (MVDR) processor, MVDR with neighboring location constraints and MVDR with environmental perturbation constraints are compared in terms of their probability of correct localization under certain environmental conditions. Secondly, a performance assesment for the most common broadband matched field processors is made. The correct localization performances for incoherent broadband matched field processor, Tolstoy/Michalopoulo&#039 / s coherent matched field processor and broadband matched field processor with environmental perturbation constraints is given for certain environmental conditions. Finally, a new weighting approach to combine data for broadband matched field processing is introduced. The fact that information from different frequencies may have different reliability depending on the environmental conditions is considered to develop a weighting scheme. It is shown that a performance gain compared to existing processors can be achieved by using the weighting scheme introduced in this study.

The processes of grain boundary grooving and cathode voiding which are important in determining the life times of thin films connecting the transistors in an integrated circuit are investigated by introducing a new mathematical model, which flows from the fundamental postulates of irreversible thermodynamics, accounting for the effects of applied electric field and thermal stresses. The extensive computer studies on the triple junction displacement dynamics shows that it obeys the first order reaction kinetics at the transient stage, which is followed by the familiar time law as , in the normalized time and space domain, at the steady state regime in the absence of the electric field (EF). The application of EF doesn&rsquo / t modify this time law very / but puts only an abrupt upper limit for the groove depth and fixes the total elapse time for that event, which is found to be inversely proportional with the electron wind intensity parameter. The drift in the cathode edge due to the surface diffusion along the side walls is simulated under the constant current regime. An analytical formula is obtained in terms of system parameters, which shows well defined threshold level for the onset of electromigration induced cathode drift, showing an excellent agreement with the reported experimental values in the literature.

Our aim was to establish a methodology for laser assisted oxidation of semiconductor and metal surfaces. One advantage of laser oxidation is the fact that radiation is heavily absorbed in a thin surface layer of the sample and the other is its ability for local oxidation. In addition to this, laser beam can be directed into some areas that other processes cannot reach. For these reasons, Nd:YAG pulsed laser working at 1064 nm wavelength is used for the oxidation purposes of Si and Ta films. First, SiO2 layer was obtained for various O2 pressures and laser powers. The thickness, refractive index, structural, dielectric, electrical and optical characteristics of the SiO2 layers have been determined. We have established that there exists an interval of laser power in which the oxidation occurs without surface melting. The oxidation process is controlled by the laser power rather than by the substrate temperature (673 &ndash / 748 K). It was found that better film quality is obtained at higher substrate temperatures and laser power greater than 3.36 J/cm2. Second, rf-sputtered Ta films were oxidized by laser, because Ta2O5 appears to be a good promising candidate to replace SiO2 because of its high dielectric constant, high breakdown voltage and relevant small leakage current values. It was found that the substrate temperature is an important parameter to obtain denser layers with reduced amount of suboxides and the most suitable substrate temperature range is around 350 C to 400 C. &amp / #946 / -orthorhombic crystal structure was obtained when the substrate temperature is 350 &ndash / 400 C for thinner films (up to 20 &ndash / 25 nm) and 300 &ndash / 350 C for thicker films (40 nm). The refractive index values of laser grown thin tantalum oxide films were between ~1.9 and 2.2 being close to those of bulk Ta2O5 (2.0 &ndash / 2.2). Oxide thicknesses in uniform Gaussian&ndash / like shapes were measured as around the twice of those initial Ta films. Effective dielectric constant values reached ~26 when the substrate temperature was increased from 250 C to around 400 C. It was shown that the leakage current density level decreases with increasing substrate temperature. However, the refractive index values of the films were smaller than those of thermally grown films. Porous structure formed during laser oxidation might be the reason for lower refractive indices and can be improved by post&ndash / oxidation annealing.

In this thesis, using a general model independent form of the effective Hamiltonian, the CP-violating asymmetries in the b -&gt / d l l transition, when one of the leptons is polarized, is investigated. The sensitivity of the CP-violating asymmetries on the new Wilson coefficients are analyzed. Next, in the frame work of the same formalism, the polarized lepton pair forward&amp / #8211 / backward asymmetries in B-&gt / K l l decay are studied. We present the general expression for the nine double&amp / #8211 / polarization forward&amp / #8211 / backward asymmetries. It is obtained that, the zero point position of the forward&amp / #8211 / backward asymmetries of the doubly&amp / #8211 / polarized lepton pair does not depend on long distance effects but depends on short distance dynamics. Furthermore, it is shown that the zero position of AFB is very sensitive to the sign of the new Wilson coefficients. When sign of the Wilson coefficients is positive (negative) the zero position of the forward&amp / #8211 / backward asymmetries shifts to the left(right) compared to the SM. Moreover, the dependencies of the nine double&amp / #8211 / polarization forward&amp / #8211 / backward asymmetries on new Wilson coefficients, and the correlation of the averaged nine double&amp / #8211 / polarization forward&amp / #8211 / backward asymmetries with branching ratio, have been studied. It is observed that, the study of the nine double&amp / #8211 / polarization forward&amp / #8211 / backward asymmetries can serve as a good test in establishing new physics beyond the Standard Model. Finally, we observed that there are exist such regions of new Wilson coefficients for which the nine double&amp / #8211 / polarization forward&amp / #8211 / backward asymmetries considerably depart from the SM result, while the branching ratio coincides with that of the SM prediction. In other words, new physics effects can be established by analyzing polarized forwardbackward asymmetry in this region of the new Wilson coefficients.