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Parametric design models were created to optimize cable sensitivities in a structural health-monitoring system. Experiments were also conducted to determine the sensitivity of a working system. The system consists of time domain reflectometry (TDR) signal processing equipment and specially designed sensing cables. The TDR equipment sends a high-frequency electric pulse (in the gigahertz range) along the sensing cable. Any change in electric impedance along the cable reflects some portion of the electric pulse back to the TDR equipment. The time delay, amplitude, and shape of the reflected pulse provides the means to respectively locate, determine the magnitude, and indicate the nature of the change in impedance. The change in the sensing cable impedance may be caused by cable elongation (change in resistance), shear deformation (change in capacitance), corrosion of the cable or the materials around the cable (change in inductance), etc. The sensing cables are an essential part of the health-monitoring system because the cable design parameters determine the cable impedance sensitivity to structural changes. By using parametric design models, the optimum cable parameters can be determined for specific cases and used to select or design an appropriate cable. Proof-of-concept and resolution experiments were also conducted to provide, respectively, verification and sensitivity of the system. / Master of Science

Effective and efficient system identification techniques for discrete, time domain, linear, MIMO, heavily damped modal systems from input/output sequences have been developed and simulated. This will facilitate a better understanding of the possible errors in the estimated model and lead to a more accurate compensator and estimator design. Three different time domain system identification algorithms have been developed in this work. The first algorithm determines the state space model in a pseudo controllable/observable canonical form. The second method is a computational simplification of the Eigensystem Realization Algorithm using pseudo observability and controllability indices. The third algorithm tested is the Pseudo Linear Identification Algorithm (PLID). The PLID algorithm is extensively tested on simulated data. This algorithm is also applied to identify a rectangular plate which gives a realistic idea of the identification capabilities of the PLID algorithm to real measured data. / Master of Science

In this dissertation a new time domain approach for the determination of material properties such as the complex permittivity and the complex permeability in a stripline geometry is presented. The new technique uses both Time Domain Reflectometry (TDR) and Time Domain Transmission (TDT) measurements for determining an optimum frequency dependent lossy transmission line model for the stripline under test. The optimization is done in the time domain by comparing the experimental TDR and TDT response waveforms with the simulated ones using a non-linear least squares fit. The conventional optimization algorithms have shown to be inefficient in this specific application. In this dissertation an efficient optimization algorithm which has been developed to suit this application is also presented. In general, the material properties in a stripline under test are related with the geometrical parameters of the line through complicated integral expressions. Using the proposed approach, the use of complicated integral expressions are avoided. The material properties such as the complex permittivity and the complex permeability are determined from the optimum lossy transmission line model. For this purpose, the frequency behavior of the line parameters have to be known beforehand in the form of causal mathematical models. The literature survey shows that, no causal model exists for the complex permittivity of thick film and polymer materials. The dissertation proposes a new causal model for this purpose. / Ph. D.

In this thesis, the conventional low voltage power line communication methods is investigated in the axis of automated meter reading applications and the classification and experimental verification of common noise types for low voltage power line communication network. The investigated system provides the real time transmission of electricity consumption data recorded by electricity meters, initially to a local computer via a low voltage line through a low speed PLC (Power Line Carrier) environment and subsequently to a corporate network through a high speed data transmission medium. The automated meter system provides a more effective tracking and data acquisition, a more detailed and vigorous knowledge about consumer behavior for subscriber assessment in electricity distribution in association with a brand new management and system supervision concept in electricity distribution control and management technology. The theoretical studies are experimentally verified for the Turkish low voltage power infrastructure through laboratory experiments performed in METU Electrical and Electronics Engineering Department, Electrical Machines and Drives Laboratory and R&amp / D Laboratories of MAKEL facilities in Hadimk&ouml / y. The single phase voltage of the mains line between the phase and neutral is monitored to exhibit the disturbing effects of various noise sources. The resulting voltage spectrum is logged by using digital data acquisition devices in time and frequency domain. The waveforms are converted to frequency domain using the Fast Fourier Transform (FFT) functions of the MATLAB. The experimental results are compared to the theoretical findings obtained through literature survey.

Le contrôle de la température d'un milieu thermique reste d'une grande importance en raison du coût économique qu'il peut engendrer. Ainsi, un moyen efficace de réduire les coûts de chauffage/refroidissement est de fournir un bon système de contrôle qui limite l'énergie nécessaire pour exécuter ces tâches. À cette fin, nous étudierons le contrôle d'une interface diffusive homogène finie utilisant le contrôleur CRONE de trois générations et contrôlons leurs comportements. La nouveauté de ce travail existe dans l'utilisation d'un contrôleur de commande fractionnaire (le contrôleur CRONE) appliqué à une unité d'ordre fractionnaire et l'utilisation d'un contrôleur complexe (la troisième génération) qui n'est pas si familier dans le domaine des contrôleurs. Les résultats montrent le comportement et la robustesse des contrôleurs CRONE de trois générations. / Controlling thermal medium’s temperature remains of a great importance, because of the economic cost that it may engender. Thus, one effective way to reduce heating/cooling cost is by providing a good control system that limits power needed to run these tasks. For this purpose, we will study the control of a finite homogeneous diffusive interface using the three generations CRONE controller and control their behaviors. The novelty of this work exists in the use of a fractional order controller (the CRONE controller) applied to a fractional order plant and the use of a complex controller (the third generation) which is not so familiar in the controllers domain. The results show the behavior and the robustness of the three generations CRONE controllers.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In this work we investigate a new method to measure the electric field of ultrafast laser pulses by extending a known measurement technique, ptychography, in the spatial domain to the time domain which we call time domain ptychography. The technique requires the measurement of intensity spectra at different time delays of an unknown temporal object and a known probe pulse. We show for the first time by measurement and calculation that this technique can be applied with excellent results to recover both the amplitude and phase of a temporal object. This technique has several advantages, such as fast convergence, the resolution is limited by the usable measured spectral bandwidth and the recovered phase has no sign ambiguity. We then extend the technique to pulse characterization where the probe is derived form the temporal object by filtering meaning the probe pulse is also unknown, but the spectrum of the probe pulse must be the same as the spectrum of the temporal object before filtering. We modify the reconstruction algorithm, now called ptychographic iterative reconstruction algorithm for time domain pulses (PIRANA), in order to also reconstruct the probe and we show for the first time that temporal objects, a.k.a laser pulses, can be reconstructed with this new modality. / AFRIKAANSE OPSOMMING: In hierdie werk het ons ’n nuwe metode ondersoek om die elektriese veld van ’n ultravinnige laser puls te meet deur ’n bekende meettegniek wat gebruik word in die ruimtelike gebied, tigografie, aan te pas vir gebruik in die tyd gebied genaamd tyd gebied tigografie. Die tegniek vereis die meting van ’n reeks intensiteit spektra by verskillende tyd intervalle van ’n onbekende ‘tyd voorwerp’ en ’n bekende monster puls. Ons wys vir die eerste keer deur meting en numeriese berekening dat hierdie tegniek toegepas kan word met uitstekende resultate, om die amplitude en fase van ’n ‘tyd voorwerp’ te meet. Hierdie tegniek het verskeie voordele, die iteratiewe proses is vinnig, die resolusie van die tegniek word bepaal deur die spektrale bandwydte gemeet en die fase van die ‘tyd voorwerp’ word met die korrekte teken gerekonstrueer. Ons het hierdie tegniek uitgebrei na puls karakterisering waar die monster pulse afgelei word, deur ’n bekende filter te gebruik, van die onbekende ‘tyd voorwerp’ nl. die inset puls. Ons het die iteratiewe algoritme wat die ‘tyd voorwerp’ rekonstrueer aangepas om ook die monster puls te vind en ons wys dat ons hierdie metode suksesvol kan gebruik om laser pulse te karakteriseer

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Terahertz (THz) radiation is often used in many promising applications such as information and communication technology and airport security. Optimized and adapted terahertz fields hold huge promise for leading this technology further. This study is focused on terahertz time domain spectroscopy (THz-TDS). In THz-TDS the electric field is measured, therefore both amplitude and phase information of the THz pulse can be obtained. We used the pump-probe technique in order to measure a THz pulse from the photoconductive antenna. A pulsed fiber laser with FWHM of ' 100 fs was used for this. The frequency spectrum of the measured THz pulse was obtained via a fast Fourier transform. We studied the principles of the THz pulse generation as well as detection, with a photoconductive antenna as emitter and detector. In this study terahertz spectroscopy has been used to investigate the refractive index and absorption coefficient of different types of materials in the terahertz region. The last part of this study deals with a simple process for material parameter extraction of a polymer sample using commercial software called Teramat1.0. It uses the sample thickness, the reference THz pulse and the transmitted THz pulse to retrieve the complex refractive index of the sample. / AFRIKAANSE OPSOMMING: Terahertz (THz) straling word gereeld gebruik vir belowende toepassings soos inligting en kommunikasie tegnologie en lughawe sekuriteit. Geoptimeerde en aangepaste terahertz velde dra by tot die bevordering van die tegnologie. Hierdie studie fokus op terahertz tyd domein spektroskopie (THz-TDS). In THz-TDS word die elektriese veld gemeet en dus word beide amplitude en fase inligting van die THz puls verkry. Ons gebruik ’n pomp en toets tegniek om die THz puls deur ’n fotogeleidende antenna te bepaal. ’n Gepulseerde vesel laser met FWHM van 100 fs word hiervoor benut. Die frekwensie spektrum van die gemete THz puls word bereken deur ’n vinnige Fourier transvorm te bereken. Die beginsels van die generering en deteksie van THz pulse is bestudeer met ’n fotogeleidende antenna as sender en ontvanger. In die studie is terahertz spektroskopie gebruik om die brekingsindekse en die absorpsie koeffisiënte van verskillende materiale in die terahertz gebied te bepaal. Die laaste gedeelte van die studie handel oor ’n eenvoudige proses om die materiaal parameters van ’n polimeer te bepaal deur gebruik te maak van kommersiële sagteware Teramat 1.0. Die monster dikte, die THz verwysingspuls en die deurgelate puls word gebruik om die komplekse brekingsindeks van die materiaal te bereken.

by Ng Chi-Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 127-134). / Abstract also in Chinese. / Abstract --- p.2 / 摘要 --- p.3 / Acknowledgements --- p.4 / Chapter Chapter 1 --- Introduction --- p.7 / Chapter Chapter 2 --- Packaging Effects of Integrated Circuits --- p.9 / Chapter 2.1 --- The Structure of the IC Package --- p.9 / Chapter 2.2 --- Microstrip Discontinuities --- p.11 / Chapter Chapter 3 --- The Finite-Difference Time-Domain Method --- p.19 / Chapter 3.1 --- Basic Theory --- p.19 / Chapter 3.2 --- Stability Criterion --- p.25 / Chapter 3.3 --- Formulation of Source --- p.30 / Chapter A. --- Source Function --- p.30 / Chapter (i) --- Sinusoidal --- p.30 / Chapter (ii) --- Gaussian Pulse --- p.31 / Chapter B. --- Source Realization --- p.36 / Chapter (i) --- Electric Field Source --- p.36 / Chapter (ii) --- Lumped Source --- p.38 / Chapter (iii) --- Current Source --- p.40 / Chapter C. --- Source Placement --- p.41 / Chapter 3.4 --- Parameter Extraction --- p.42 / Chapter A. --- Voltage and Current --- p.42 / Chapter B. --- Characteristic Impedance --- p.44 / Chapter C. --- Effective Dielectric Constant --- p.45 / Chapter D. --- Scattering Parameters --- p.46 / Chapter 3.5 --- Termination and Boundary Treatment --- p.48 / Chapter A. --- Perfect Electric Conductor (PEC) --- p.48 / Chapter B. --- Perfect Magnetic Conductor (PMC) --- p.49 / Chapter C. --- Interface between Two Materials --- p.50 / Chapter 3.6 --- Perfectly Matched Layer (PML) --- p.54 / Chapter A. --- Theory of PML in Three Dimensions --- p.56 / Chapter B. --- Incorporation of PML as Absorbing Boundary Condition (ABC) --- p.65 / Chapter C. --- Discretization of Maxwell's Equations in PML --- p.73 / Chapter 3.7 --- Flowcharts --- p.75 / Chapter A. --- Free Space Radiation by a Dipole Antenna --- p.77 / Chapter B. --- Parameters of a Microstrip Line --- p.79 / Chapter C. --- Scattering Parameters of Planar Network --- p.85 / Chapter 3.8 --- Summary --- p.87 / Chapter Chapter 4 --- Effects of Ground Via Allocation --- p.88 / Chapter 4.1 --- Introduction --- p.88 / Chapter 4.2 --- Simulation and Experimental Results --- p.91 / Chapter 4.3 --- Equivalent Circuit Modelling --- p.108 / Chapter 4.4 --- Summary --- p.124 / Chapter Chapter 5 --- Conclusions --- p.125 / Chapter Chapter 6 --- Recommendation for Future Work --- p.126 / References --- p.127 / Publication --- p.134

This thesis presents a study of the sub-light year regions of Active Galactic Nuclei (AGN). These environments contain accretion discs that orbit a central super-massive black hole. The luminosity of the AGN inner regions varies over time across all wavelengths with variability at longer wavelengths lagging behind that at shorter wavelengths. Since the AGN themselves are too remote and too compact to resolve directly, I exploit these time lags to infer the physical characteristics of the accretion disc and surrounding gas clouds that emit broad emission lines. These characteristics include the inclination and temperature profile of the accretion disc, and the shape (or light curve) of the luminosity fluctuations that drive the accretion disc variability. This thesis details the work in the first author papers of Starkey et al. (2016, 2017), in which I detail the statistical code, CREAM (Continuum REverberting AGN Markov Chain Monte Carlo), that I developed to analyse AGN accretion disc variability. I apply the code to a set of AGN light curve observations of the Seyfert 1 galaxy NGC 5548 by the AGN STORM collaboration (De Rosa et al., 2015; Edelson et al., 2015; Fausnaugh et al., 2016a; Goad et al., 2016; Starkey et al., 2017). I also present work detailing my variability analysis of the Seyfert galaxies NGC 6814, NGC 2617, MCG 08-11-11 and NGC 4151. This work has contributed to the analysis presented in (Troyer et al. 2016, Fausnaugh et al. submitted). I also investigate the implications of a twin accretion disc structure (Nealon et al., 2015) on the disc time lag measurements across near UV and optical wavelengths. I finish by detailing a modification to CREAM that allows it to merge continuum light curves observed in a common filter, but taken by multiple telescopes with different calibration and instrumental effects to consider.