The conventional mushroom-like Sievenpiper structure is re-visited in this thesis and a relationship is established between the dispersion and reflection phase characteristics of the structure. It is shown that the reflection phase frequency at which the structure behaves as a Perfect Magnetic Conductor (PMC) can be predicted for varying angles of incidence from the modal distribution in the dispersion diagrams and corresponds to the supported leaky modes within the light cone. A methodology to independently tune the location of the PMC frequency point with respect to the surface wave band-gap location is then presented. The influence of having said PMC frequency point located inside or outside the surface wave band-gap on a dipole radiation pattern is then studied numerically. It is demonstrated that the antenna exhibits a higher gain when the PMC frequency and band-gap coincide versus when they are separated. Two design cases are then presented for when the aforementioned properties coincide and are separated and a gain improvement of 1.2 dB is measured for the former case.

The conventional mushroom-like Sievenpiper structure is re-visited in this thesis and a relationship is established between the dispersion and reflection phase characteristics of the structure. It is shown that the reflection phase frequency at which the structure behaves as a Perfect Magnetic Conductor (PMC) can be predicted for varying angles of incidence from the modal distribution in the dispersion diagrams and corresponds to the supported leaky modes within the light cone. A methodology to independently tune the location of the PMC frequency point with respect to the surface wave band-gap location is then presented. The influence of having said PMC frequency point located inside or outside the surface wave band-gap on a dipole radiation pattern is then studied numerically. It is demonstrated that the antenna exhibits a higher gain when the PMC frequency and band-gap coincide versus when they are separated. Two design cases are then presented for when the aforementioned properties coincide and are separated and a gain improvement of 1.2 dB is measured for the former case.

Nondestructive testing (NDT) uses different wave propagation modes to evaluate the internal structure of materials, revealing internal damage such as corrosion and fracturing that cannot be detected by traditional methods. Civil infrastructures are considered high priority assets in Ontario and Canada because of their value, high consequence of failure, and the continual influence of aging effects. Unexpected failure of infrastructure not only costs more than planned replacements but also results in increased safety risks. The in-situ condition assessment of civil infrastructure is critical for the successful implementation of maintenance and safety programs. Therefore, reliable nondestructive methods of inspection are required for the implementation of economical and efficient maintenance and asset management programs. Continuing technological developments in data collection, acquisition equipment, and data processing techniques have provided useful applications of nondestructive methods in many engineering fields. Among the many applications, this research study examines three applications of nondestructive testing in civil engineering: (1) condition assessment of construction joints in asphalt pavements, (2) average thickness evaluation of steel pipes, and (3) void and debonding detection in grouted steel tanks. The study on asphalt focuses on the improvement of the coupling system between the transducers and the asphalt surface, and the development of a new data processing technique to reduce user input and increase the reliability of the condition assessment of longitudinal joints. The current wavelet transmission coefficient (WTC) method requires user input, making the automatic data processing difficult. In the WTC method, the coupling between the transducers and the asphalt surface requires the use of epoxy and aluminum plates. This procedure is not practical for testing in-service roads. A new coupling mechanism using polyurethane foam to provide a spring action on the transducers and calibrated weights to generate a compression force was developed and showed good results, reducing the testing time by up to 50%. A new and robust data analysis methodology, called instantaneous transmission coefficient (ITC), is proposed based on measured instantaneous frequencies and damping ratios. The main advantage of the ITC procedure is that it can be performed automatically, reducing user input. A laboratory scale asphalt slab is used to evaluate the new methodology. Results show good agreement between the WTC and ITC measurements for both jointed and joint-free areas. The second study investigates the feasibility of the multichannel analysis of surface waves (MASW) technique for the evaluation of the average wall thickness of steel pipes. Electromagnetic NDT methods, such as the eddy current and the remote field testing, are common tools for thickness measurement of conductive materials. However, these methods give only localized results where measurements are made, making the process time consuming and inaccurate for assessing the full cross-sectional area of the pipe. Lamb waves have been used previously in the evaluation of steel pipes; however, the existing techniques require prior calibration to a theoretical wave mode, and their accuracy decreases with the length of the pipe evaluated due to wave attenuation effects. Preliminary results show the capability of the MASW test for providing reliable thickness information. The measured dispersion curves include information of fundamental modes and the higher modes, providing an improved characterization of the medium. Thicknesses between 3.2 mm and 12.7 mm are tested with an error of less than 2%. The third study explores the detection of voids in a steel tank filled with lightweight grout. A joint analysis of surface waves and Lamb waves is used for void detection and the identification of debonding conditions in a laboratory scale model of a steel tank filled with grout. Different configurations of the MASW method are conducted using an instrumented hammer (large wavelengths, 10 cm < λ < 25 cm) and a 50 kHz piezoelectric transmitter (small wavelengths, 5 cm < λ < 9 cm) as sources. The attenuation coefficient computed from the Fourier spectra of the measured signals indicates that the presence of a void has an effect on the propagation of the wave. The comparison between experimental and theoretical dispersion curves show that mainly Lamb waves are generated during the testing of the steel tank; thus, detecting the debonding conditions between the steel plate and the grout. Lamb modes are used successfully for detecting the presence of a void beneath the steel wall. The laboratory measurements are effective in the detection of the void, showing amplitudes up to 50% higher, likely because the deformation of the wall is attenuated by the grout.

This dissertation is focused on design of compact electromagnetic magnetic band-gap structures (EBG). Several popular compact techniques are introduced and analyzed with equivalent surface impedance model. A novel compact EBG structure is investigated. Compared to the conventional uniplanar compact photonic band gap (UC-PBG) structure, a size reduction of 64.7% is achieved. A distinctive band gap is observed at 2.45 GHz with around 100 MHz bandwidth and zero reflection phase. Antenna applications of this novel EBG structure, including EBG patch antenna and EBG antenna array, have been presented. Simulation results further verify its characteristic of suppressing surface waves. For the EBG patch antenna, a more focused radiation pattern is obtained compared to a normal patch antenna. For an antenna array, the presence of EBG structure reduces the mutual coupling between the two radiating elements by 6 dB.

The propagation of acoustic plate-mode waves in composite membranes is studied. A computer program has been developed and used to calculate the wave velocity and electromechanical coupling factor in these structures which may consist of any combination of piezoelectric layers with arbitrary orientation and surface metallization. In particular, shear modes (SH) in zinc-oxide and selenium membranes, as well as stiffened-Lamb modes in ZnO membranes and ZnO/Si, ZnO/GaAs composite membranes are studied. / The surface-acoustic-wave propagation in selenium and in selenium layers on tellurium has been extensively studied using an improved computer program. The study shows that surface-wave coupling factors in the range of 0.5 to 1.5% are possible with these structures. The calculated sensitivity of the velocity and coupling factor to errors in material constants shows that an accurate value of the e(,11) constant for selenium is necessary for an accurate estimate of the coupling factor. / A technology for fabricating selenium-tellurium layered structures for SAW propagation has been successfully developed. Measurements on fabricated SAW delay lines were carried out and estimates of the coupling factor and the acoustic attenuation obtained. These measurements, taken together with previously published results, confirm that the published value of e(,11) = 0.32 C/m('2) is too small.

Thesis (Ph. D.)--State University of New York at Binghamton, Mechanical Engineering Department, 2006. / Includes bibliographical references.

Thesis (Ph.D.)--Biomedical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: William D Hunt; Committee Member: Bruno Frazier; Committee Member: Dale Edmondson; Committee Member: Marie Csete; Committee Member: Peter Edmonson; Committee Member: Ruth O'Regan

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 150-157).

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Electrical and Computer Engineering." Includes bibliographical references (p. 142-149).

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xvii, 169 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 147-155).