FDTD is an electromagnetic field computation method with the ability of considering circuit elements. Traditional lump element method is insufficient for simulating circuit. In this thesis, we use equivalent source method to combine non-linear circuit elements like active devices into the FDTD simulation. The advantages of this is powerful and time-saving. The accuracy of this method is checked of transmission line driving by CMOS circuits. By employing this method, we find that it will increase EMI phenomenon by strengthening current of driving load, and the load of coupling line will affect noise due to impedance mismatch.

With the gain in momentum of the structural health monitoring field in the last two decades, the popularity of ultrasonic nondestructive testing (NDT) has grown. However, ultrasonic NDT requires an expert to perform the testing and can be time consuming and costly when measured wave patterns in testing become extremely complex. A computer simulation of these tests can be utilized as a guide during actual evaluations or as a tool to train technicians. Presented in this dissertation is the development of models which simulate such acoustic phenomena as may arise in NDT. These models were developed using the distributed point source method (DPSM) for its proven capability to represent ultrasonic fields.Four sets of boundary conditions that arise from different types of commonly used acoustic transducers are modeled, enabling the visualization of the ultrasonic fields produced by the transducers. The transducer models exhibit good agreement with existing analytical solutions.In addition, the effect of a small cavity located at or near the focal point of an acoustic microscope is discussed. For this application the DPSM technique is modified so that inversion of a large global matrix is avoided, significantly improving the computational efficiency. The model shows that, as the pressure goes to zero, the velocity increases at the location of a cavity. Simulations demonstrate that the microscope is able to sense changes in position of the cavity by variations in the measured ratio of reflected to incident acoustic force.The field generated by an interferometric acoustic microscope is also presented. Qualitative agreement between the DPSM model and the experimental results of fields generated in a homogeneous fluid are obtained for a three-element lens. In the presence of a solid interface, the pressure on the edges of a converging beam near the fluid-solid interface is greater for a three-element lens than for single-element lens. A multi-element lens is also shown to exhibit oscillations in the pressure slightly above the interface.

The distributed point source method, or DPSM, developed in the last decade has been used for solving various engineering problems-such as elastic and electromagnetic wave propagation, electrostatic, and fluid flow problems. Based on a semi-analytical formulation, the DPSM solution is generally built by superimposing the point source solutions or Green's functions. However, the DPSM solution can be also obtained by superimposing elemental solutions of volume sources having some source density called the equivalent source density (ESD). In earlier works mostly point sources were used. In this paper the DPSM formulation is modified to introduce a new kind of ESD, replacing the classical single point source by a family of point sources that are referred to as quantum sources. The proposed formulation with these quantum sources do not change the dimension of the global matrix to be inverted to solve the problem when compared with the classical point source-based DPSM formulation. To assess the performance of this new formulation, the ultrasonic field generated by a circular planer transducer was compared with the classical DPSM formulation and analytical solution. The results show a significant improvement in the near field computation.

Time Reversal (TR) is a technique that may be used to focus an acoustic signal at a particular point in space. While many variables contribute to the quality of TR focusing of sound in a particular room, the most important have been shown to be the number of sound sources, signal bandwidth and absorption properties of the medium [Ribay et al., J. Acoust. Soc. Am. 117(5), 2866-2872 (2005)]. However, the effect of room size on TR focusing has not been explored. Using the image source method algorithm proposed by Allen and Berkley [J. Allen and D. A. Berkley, J. Acoust. Soc. Am. 65(4), 943-950 (1979)], TR focusing was simulated in a variety of rooms with different absorption and volume properties. Experiments are also conducted in a couple rooms to verify the simulations. The maximum focal amplitude, the temporal focus quality, and the spatial focus clarity are defined and calculated for each simulation. The results are used to determine the effects of absorption and room volume on TR. Less absorption increases the amplitude of the focusing and spatial clarity while decreasing temporal quality. Dissimilarly, larger volumes decrease focal amplitude and spatial clarity while increasing temporal quality. This thesis also explores the placement of individual transducers within a room. It also compares the layout of several source transducers used for a reciprocal time reversal process. Maximum focal amplitude and spatial clarity are found to increase when the focus location is dual coplanar to the source location while temporal quality is found to decrease in comparison to the case when source and focal location share only one plane. Maximum focal amplitude is found to be at a minimum when the focus location is at the critical distance and increases closer and farther away from the source, while temporal quality steadily decreases and spatial clarity steadily increases farther from the source. The maximum focal amplitude and the temporal quality are not greatly affected by the type of array layout, but a circular array is ideal for maximizing spatial clarity.

Virtual acoustic prototyping (auralization) is the rendering of a virtual sound field that is created from the calculated acoustic response of a modeled structure. Auralization is useful in the design and subjective evaluation of buildings, automobiles, and aircraft. The virtual acoustic prototyping method in this thesis uses finite element modeling (FEM), the equivalent source method (ESM), and head-related transfer functions (HRTFs). A tradeoff exists between the accuracy of the auralization process and the number of equivalent sources (and thus computational power) that are required. The goal of this research is to validate (numerically and subjectively) a virtual acoustic prototyping method for use in structural design; this thesis illustrates the first attempt to apply the aforementioned methods to a structure that represents a typical building or automobile. The structure's acoustics were modeled using FEM, ESM, and HRTFs. A prototype of the modeled structure was built. A 36% correlation was achieved between the model and prototype. Slight variations in boundary conditions caused significant FEM error, but the data represented a typical structure. Psychoacoustic comparison testing was performed to determine the number of equivalent sources that must be used in an auralization to accurately recreate the sound field. The number was found to be dependent on the type of noise that is played to the test subject. A clear relationship between the numerical correlation of two sounds and the percentage of subjects who could hear a difference between those two sounds was established for impulsive, broadband, and engine noises. / Master of Science

Il y a actuellement un vif intérêt pour des méthodes rigoureuses qui effectuent l’analyse électromagnétique des milieux diélectriques avec une distribution de permittivité diélectrique complexe. L’intérêt est motivé par des applications actuelles et futures dans la conception et la fabrication d’éléments optiques et optoélectroniques. Le niveau que les technologies de microstructuration ont maintenant atteint requiert des appels pour méthodes numériques rapides, économes en mémoire et rigoureuses capables de résoudre et d’optimiser des grandes parties de structures dont les caractéristiques représentent la fonction optique de la structure complète. Bien que la majorité des problèmes de modélisation en microoptique sont non périodiques (par exemple, une section d’une couche diffusante d’OLED, la cellule d’un réticule microélectronique, une microlentille diffractive de haute NA), ils peuvent être efficacement résolus par la périodisation de la distribution de l’indice. Une nouvelle méthode numérique puissante pour la modélisation exacte de structures périodiques 2D est décrite avec toutes les fonctionnalités et les expressions nécessaires à son exécution. La puissance de cette méthode est dans sa forme spécifique unique qui permet d’appliquer rapidement des algorithmes numériques et, par conséquent, de diminuer de façon spectaculaire la complexité de calcul en comparaison avec les méthodes établies. La comparaison avec des solutions de référence a montré que, d’abord, la nouvelle méthode donne les mêmes résultats que celles-ci sur les structures de référence et, d’autre part, que le temps de calcul nécessaire et le recours en mémoire représentent une percée vers la résolution de grandes structures périodiques ou périodisées. La méthode développée a été appliquée à analyser le problème de diffusion non périodique d’une couche diélectrique plan avec micro / nanoparticules sphériques. Une référence numérique proposée a démontré la possibilité d’obtenir environ 1% de précision. En outre, il a été développé un modèle numérique basé sur des matrices S pour la simulation des structures planes électroluminescentes. La validité de la méthode a été démontrée par comparaison avec les résultats expérimentaux. Enfin, les deux méthodes de calcul de la diffusion de la lumière et de simulation des structures multicouches ont été groupées, et une couche diffusante a été démontrée augmentait l’efficacité externe d’une OLED de quelques pour cents / There is presently a strong interest for rigorous methods that perform the electromagnetic analysis of dielectric media with complex dielectric permittivity distribution. The interest is motivated by both present and future applications in the design and manufacturing of optical elements and optoelectronic devices. The level that the microstructuring technologies have now reached calls for fast, memory sparing, and rigorous numerical methods capable of solving and optimizing large structure parts whose characteristics do represent the optical function of the whole structure. Although the majority of modeling problems in microoptics are non-periodic (e.g., a section of an OLED extraction layer, the cell of a microelectronic reticle, a high NA diffractive microlens) they can be efficiently solved by periodizing the index distribution. A new powerful numerical method for the exact modeling of 2D periodic structures is described with all features and expressions needed to implement it. The power of this method is in its unique specific form which permits to apply fast numerical algorithms and, consequently, to decrease dramatically the calculation complexity in comparison with established methods. The comparison with reference solutions has shown that, first, the new method gives the same results as the latter on benchmark structures and, secondly, that the needed calculation time and memory resort represent a breakthrough towards solving larger periodic or periodized structures. The developed method was applied to analyze nonperiodic scattering problem of a plane dielectric layer with spherical micro/nanoparticles. Proposed numerical benchmark demonstrated the possibility to get about 1% accuracy. In addition there was developed a numerical S-matrix based method for planar electroluminescent structures simulation. Validity of the method was demonstrated by comparison with experimental results. Finally both methods for the light scattering calculation and multilayer structures simulation were joined, and a scattering layer was demonstrated to increase an OLED external efficiency by several percent

Elastic Wave propagation in structures with irregular boundaries is studied by transforming the plates with irregular surfaces to sinusoidal wave-guides. Guided elastic wave in a two-dimensional periodically corrugated plate is studied analytically. The plate material is considered as homogeneous, isotropic and linearly elastic. In a periodically corrugated wave-guide, all possible spectral orders of wave numbers are considered. The dispersion equation is obtained by applying the traction free boundary conditions at the two surfaces. The analysis is carried out in the wave-number domain for both symmetric and anti-symmetric modes. Non-propagating 'stop bands' and propagating 'pass bands' are investigated. Experimental analyses with two different pairs of transducers are also performed and compared with the results from the mathematical analysis. Newly developed semi-analytical DPSM technique has been also adopted in this dissertation to model the ultrasonic field in sinusoidally corrugated plate. Distributed Point Source Method (DPSM) is gradually gaining popularity in the field of Non-Destructive Evaluation (NDE). DPSM can be used to calculate the ultrasonic field (pressure, velocity and displacement in a fluid or stress and displacement in a solid) generated by ultrasonic transducers. So far the technique has been used to model ultrasonic field in homogeneous or multilayered fluid structures. In this dissertation the method is extended to model the ultrasonic field generated in both fluid and solid media. The Prime objective of using DPSM technique in this dissertation is to model the ultrasonic field generated in the corrugated wave guide. This method has never been used to model ultrasonic field in solids. Development of stress and displacement Green's functions in solids are presented. In addition to the wave propagation problem in the sinusoidal wave guide, a few unsolved problems such as ultrasonic field generated by bounded acoustic beams in multilayered fluid structures, near a fluid-solid interface and in flat solid isotropic plates are also presented in this dissertation.

There is presently a strong interest for rigorous methods that perform the electromagnetic analysis of dielectric media with complex dielectric permittivity distribution. The interest is motivated by both present and future applications in the design and manufacturing of optical elements and optoelectronic devices. The level that the microstructuring technologies have now reached calls for fast, memory sparing, and rigorous numerical methods capable of solving and optimizing large structure parts whose characteristics do represent the optical function of the whole structure. Although the majority of modeling problems in microoptics are non-periodic (e.g., a section of an OLED extraction layer, the cell of a microelectronic reticle, a high NA diffractive microlens) they can be efficiently solved by periodizing the index distribution. A new powerful numerical method for the exact modeling of 2D periodic structures is described with all features and expressions needed to implement it. The power of this method is in its unique specific form which permits to apply fast numerical algorithms and, consequently, to decrease dramatically the calculation complexity in comparison with established methods. The comparison with reference solutions has shown that, first, the new method gives the same results as the latter on benchmark structures and, secondly, that the needed calculation time and memory resort represent a breakthrough towards solving larger periodic or periodized structures. The developed method was applied to analyze nonperiodic scattering problem of a plane dielectric layer with spherical micro/nanoparticles. Proposed numerical benchmark demonstrated the possibility to get about 1% accuracy. In addition there was developed a numerical S-matrix based method for planar electroluminescent structures simulation. Validity of the method was demonstrated by comparison with experimental results. Finally both methods for the light scattering calculation and multilayer structures simulation were joined, and a scattering layer was demonstrated to increase an OLED external efficiency by several percent

Change all but defines the late nineteenth and early twentieth centuries in American history. In the midst of these tumultuous times, America experienced a revolution of reform meant to develop and enhance all areas of life from politics to society, which led historians to call this time period the Progressive Era. However, the progress of the nation was not always the winning ideology. At times, the backlash against progressive ideas restrained innovators and caused them to disappear into the mires of history. One reformer who experienced this backlash was Fred Morrow Fling. Although he was an internationally-known historian, he remained a rather invisible history education reformer because his ideas were overshadowed by the enormous human events of his lifetime, including the work of other reformers and his unexpected death in 1934. As a trained scientific historian, Fling was a pioneer of historical method and the application of what became known as “source method” in the classroom and he espoused a radical approach to critical education that sought to embed a scientific approach into the teaching of history that has clear parallels with best teaching practices today. Thus, using traditional historical research methods and archival records from both Bowdoin College and the University of Nebraska, the author presents in this dissertation a biographical portrait of Fling’s life. Through the analysis of these historical documents and the evidence of his life recorded in publications and the public press, this portrait will serve to uncover both how Fred Morrow Fling’s conception of history education influenced his practice as a history professor and researcher and how Fred Morrow Fling’s philosophy of education formed and developed over his lifetime. Specifically, this author will consider: how can the philosophy of history education created by Fred Morrow Fling inform our current history education practices today? By investigating Fling’s life, researchers will finally be able to acknowledge Fling’s myriad contributions to history education, which are vital to composing a fuller picture of the history of social studies education.

Temperature is a very important process parameter in Friction Stir Welding (FSW), but until lately active control of temperature has not been practiced. Recently, temperature control via a PID controller has proven to be effective. Model Predictive Control (MPC) is a control method that holds promise, but has not been attempted in FSW before. Two different model forms are developed for MPC and are evaluated. The first is a simple first-order plus dead time (FOPDT) model. The second is the Hybrid Heat Source model and is more complex; it combines the heat source method and a 1D discretized thermal model of the FSW tool. Model parameters were determined by fitting model predictions to actual weld data. The models were evaluated for their performance in modeled and unmodeled disturbances once the process was already at a quasi steady state condition and also were evaluated for control immediately after plunge. The FOPDT based MPC controller has very good performance and was comparable in performance to previously proven and well-tuned PID controllers. For small modeled disturbances the FOPDT controller settled within 1°C of the setpoint in 10s with almost no oscillations and only 2°C of overshoot. For large unmodeled disturbances, the FOPDT controller settled within 1°C of the setpoint in 30s with no oscillations and 16°C of overshoot. For the same disturbances, the PID servo controller settled in 30s with no oscillations and 9°C of overshoot, and the PID regulator controller settled in 15s but had almost a full oscillation and 13°C of overshoot.The Hybrid Heat Source MPC controller and the PID regulator controller were also able to control temperature within 5°C of the setpoint immediately after the plunge during the highly transient portion of the weld, which previously had been assumed to be too difficult to control. The PID regulator controller had a high degree of variability between the two runs (a settling time of 10s and 30s, and .5 and 4.5 oscillations before settling), but settled quickly and once settled was able to hold the temperature within 2°C of the setpoint. The HHS MPC controller on the other hand had far fewer oscillations (0 and 1 oscillation) before settling, but could only hold the temperature within 5°C of the setpoint. Both of these controllers performed far better than the FOPDT MPC and PID servo controllers.