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The mystery of Canis Major overdensity is addressed. We discuss concurrent methods and their limitations on the determination of interstellar reddening. We establish a new way to determine line of sight interstellear reddening by observing stellar spectral lines and UBV colors. We observe and analyze spectra of 22 stars in different open clusters. We find that Hydrogen Balmer line at 4861 angstrom can predict the stellar atmospheric parameters and intrinsic colors with reasonable accuracy. Comparing with observed colors we derive the reddening of the stars. We compare our results with standard database WEBDA and find that within 90% probability limit the standard deviation of the error is 0.102798. This is improved by taking the absolute maximum probabilities and the scatter becomes 0.0688865.

In this thesis, the problem of overvoltage calculation on multiconductor transmission lines due to nonuniform external electromagnetic field excitations, such as lightning, is investigated by introducing a field-voltage macromodel. The main purpose of this thesis is to find a fast and efficient algorithm to model the effect of the radiated electromagnetic fields on transmission lines. This is done by replacing distributed voltage and current sources along the transmission line which are as a result of external electromagnetic field radiation, by voltage and current sources at the terminals of the transmission line. For this purpose, the knowledge of electromagnetic field at every point on the transmission line is required. A transfer function based pole-residue tracing technique will be introduced in this thesis. By using the proposed algorithm, a closed form solution for the lumped sources at the terminals of transmission line in the frequency domain is obtainable. This approach will enable us to bridge the software working in frequency domain with those working in the time domain. The effect of different parameters on calculated overvoltage such as finite conductivity of the ground and lightning return stroke channel (RSC) specifications are studied. The theoretical background and extent of validity of the proposed algorithm are reviewed in this thesis.

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Software product lines (SPLs) manage product variants in a systematical way and allow stakeholders to derive variants by selecting features. Finding a desirable variant is hard, due to the huge configuration space and usually conflicting objectives (e.g., lower cost and higher performance). This scenario can be reduced to a multi-objective optimization prob- lem in SPLs. We address the problem using an exact and an approximate algorithm and compare their accuracy, time consumption, scalability and parameter setting requirements on five case studies with increasing complexity. Our empirical results show that (1) it is feasible to use exact techniques for small SPL multi-objective optimization problems, and (2) approximate methods can be used for large problems but require substantial effort to find the best parameter settings for acceptable approximation. Finally, we discuss the tradeoff between accuracy and time consumption when using exact and approximate techniques for SPL multi-objective optimization and guide stakeholders to choose one or the other in practice.

Accurate, efficient and general computational techniques are developed to evaluate the scattering parameters of passive microstrip components composed of discontinuities in microstrip transmission lines on general two layer substrates with single and two level metallization. An open domain model is used. The Electric Field Integral Equation is examined and the Green's function for single and double layer dielectric substrates on a infinite ground plane are reviewed while emphasizing the important computational details to the model, including singularity of the kernel, evaluation of the Sommerfeld Integrals, and interpolation of the Green's functions. In order to model accurately complex circuit geometries, two dimensional currents are used. Different basis functions for expansion and for testing are chosen in order to make the computation more efficient and allow for structures having general shape in the moment method formulation. A transmission line current source is used to model the parameters are flowing in and circuit evaluated out of structure. Structures excitation and the scattering by calculating the currents each of the N-ports of the such as microstrip bends, microstrip crossovers of arbitrary angle, and coupled microstrip discontinuities are analyzed. To validate the model, results of some elementary structures are compared with published results of other models. / Graduation date: 1992

Typescript (photocopy) / iii, 152 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Applied Mathematics, University of Adelaide 1981

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A sample of 9 small-diameter radio sources has been selected from the Molonglo Galactic Plane Survey (MGPS) and observed with the Australia Telescope Compact Array (ATCA) in the radio recombination line (RRL) at 5 GHz, in a search for young Galactic SNRs. Since the RRL emission is an unambiguous indicator of a thermal source, this method has been used to eliminate HII regions from the selected sample. In addition, the IRAS and MSX infrared data and spectral index measurements have been combined with the RRL studies to distinguish thermal and non-thermal sources in the selected sample. One source (G282.8-1.2) is identified here as a possible new young Galactic supernova remnant, based on its relatively weak infrared emission, steep radio spectrum and possible x-ray emission. However, the ATCA data are inconclusive and further studies are needed to confirm this result. Radio recombination line emission (H107 alpha) has been detected in 3 of the selected sources, eliminating them from the sample of SNR candidates. In addition, the parameters of the RRL emission from the identified HII regions have been used to estimate their properties. The RRL data are inconclusive for the remaining low brightness, extended sources in the sample. However, some of these sources are likely to be thermal HII regions according to the infrared and spectral index data. The selected method for distinguishing thermal and non-thermal Galactic radio sources seems promising. The selected ATCA configuration was appropriate for imaging relatively bright, compact sources, but a slightly modified observing technique is needed to successfully image low surface brightness, extended sources.