A paired-dominating set of a graph G is a dominating set of vertices whose induced subgraph has a perfect matching, and a double dominating set is a dominating set that dominates every vertex of G at least twice. We show that for trees, the paired-domination number is less than or equal to the double domination number, solving a conjecture of Chellali and Haynes. Then we characterize the trees having equal paired and double domination numbers.

A paired dominating set of a graph G is a dominating set of vertices whose induced subgraph has a perfect matching, and a double dominating set is a dominating set that dominates every vertex of G at least twice. First a necessary and sufficient condition is given for a double dominating set (respectively, paired dominating set) to be minimal in G. We show that for clawfree graphs, the paired domination number is less than or equal to the double domination number. Then bounds on the double and paired domination numbers are presented. Sums involving these parameters are also considered.

The double angle connection (sometimes referred to as a cleat connection) is one of the most commonly used simple shear connections, and many investigations have been conducted on this type of connection. However, most of these investigations have focused on either the strength or the moment-rotation relationship under shear loading. Several investigations have recently been performed on the behavior of double angle connections subjected to shear plus axial tensile loads. In these investigations, analytical models and design formulas have been proposed to model the complex behavior of these connections when subjected to the combined loading. However, a complete design model has not been developed. To fulfill the need for a design procedure, double angle connections were studied for three different loading cases. The first case was used to establish the load-displacement relationship under axial tensile loads. The second case was to establish the moment-rotation relationship under shear loads. Finally, the third case was to find the effects of combined axial tensile loads and shear loads on the behavior of double angle connections. For these purposes, 3D-nonlinear finite element models were developed to simulate the connection behavior under the three loading cases. The commercial software package, ABAQUS, was used for the study. The complex phenomena of contact problems and the pretension forces in the bolts were simulated. A simplified angle model and an equivalent spring model were developed from the 3D results. / Ph. D.

It is known that the 1-18 GHz Double Ridge Guide Horn (DRGH) antenna is highly sensitive to tolerances in manufacturing. Since a typical DRGH antenna is constructed from a number of individual parts, tolerances in the machining, even when numerically controlled, and errors in the assembly can easily lead to gaps between subsections. Performance deviations, most notably resonances in the boresight gain and VSWR was observed in a number of manufactured 1-18 GHz DRGH antennas. The exact cause of the performance deviations had to be determined in order to identify which sections of the antenna need to be redesigned in such a way that the effects of the manufacturing and assembling tolerances on the performance of typical mass produced DRGH antennas are reduced or eliminated. It was hypothesised that gaps most notable in the waveguide launcher section and especially the coaxial feeding section is the cause of the sharp resonance effects. This hypothesis was confirmed during the study. A highly accurate Method of Moments (MoM) numerical model of the 1-18 GHz DRGH antenna was developed, gaps were then implemented in between various parts of the model and the results observed. Based on these results a new improved 1-18 GHz DRGH antenna was designed with reduced sensitivity to manufacturing tolerances and improved performance. / Dit is alombekend dat die 1-18 GHz Dubbel Rif Golfleier Horing (DRGH) antenna baie sensitief is vir vervaardigings toleransies. 'n Tipiese DRGH antenna bestaan uit verskeie individuele onderdele. Toleransies in vervaardiging, selfs al word die proses numeries beheer, kan dus lei tot spasies tussen verskillende dele. Die waarneming van verswakte werkverrigting, meer spesifiek resonansies in die wins en Spannings Staande Golf Verhouding (SSGV) by 'n aantal vervaardigde 1-18 GHz DRGH antennes het gelei tot verdere studie. Om die 1-18 GHz ontwerp minder sensitief te maak ten opsigte van toleransies, moes die presiese oorsaak van die verswakte werkverrigting bepaal word. Aan die begin van die studie was die vermoede dat spasies in veral die golfleierlanseerder en meer spesifiek die koaksiale voer seksie, die oorsaak is van die resonansies. Die hipotese is in die daaropvolgende ondersoek bevestig. 'n Hoogs akkurate Metode van Momente (MvM) numeriese model is vir die 1-18 GHz DRGH antenna ontwikkel. Spasies is tussen verskeie parte van die model ge-inkorporeer en die resultate is ondersoek. 'n Nuwe verbeterde 1-18 GHz DRGH antenna op die ondersoek gebaseer, is ontwikkel. Die antenna het verminderde sensitiwiteit ten opsigte van vervaardigings toleransies sowel as verbeterde werkverrigting. / Dissertation (MEng)--University of Pretoria, 2011. / Electrical, Electronic and Computer Engineering / Unrestricted

Indiana University-Purdue University Indianapolis (IUPUI) / For regenerative endodontic procedures (REPs) to be successful an elimination of bacteria from the root canal system must be accomplished. Many different medicaments with antibacterial properties have been used to obtain complete disinfection. Double antibiotic paste (DAP) containing a mixture of ciprofloxacin and metronidazole has been shown to be a promising intracanal medicament. The addition of a radiopaque filler such as zirconium oxide to DAP may affect the antibacterial properties of DAP as well as allow precise placement and radiographic visualization of its position in the canal system. The aim of the proposed study was to evaluate the direct antibacterial properties of zirconium oxide radiopacifier combined with DAP (RoDAP) against a multispecies biofilm from a bacterial isolate from an infected immature tooth with a necrotic pulp and a known single species biofilm. 4x4 mm radicular dentin specimens (n = 112) obtained from human extracted teeth were used prepared and sterilized prior to use. A multispecies clinical bacterial isolate from an immature tooth with a necrotic pulp and a single species Enterococcus faecalis isolate were obtained. These bacterial isolates were used to inoculate dentin slabs and grown for 3 weeks. The dentin slabs were treated for 1 week with 1.0-mg/mL and 10- mg/mL RoDAP, 1.0-mg/mL DAP, and two placebo pastes consisting of methyl cellulose (MC) and methyl cellulose combined with zirconium oxide (RoMC), respectively, as well as two no-treatment controls. Following treatment, the grown biofilm was detached and spiral plated. The plated biofilm cells were cultured for 24 hours and each group examined using a colony counter to determine bacterial numbers (CFUs/mL). Data analysis, using a 5.0-percent significance level was conducted using one-way ANOVA followed by pair-wise group comparisons. Both 1.0-mg/mL and 10 mg/mL RoDAP demonstrated significant antibacterial effects against bacterial isolates from an immature tooth with a necrotic pulp as well as an E. faecalis isolate. The precise application of RoDAP confirmed radiographically with its direct antibacterial properties may be beneficial for intracanal disinfection during REPs.

The spatiotemporal evolution of temperature of leaves-on-branchlet carbon based electric double layer capacitors (EDLCs) under imposed constant current was studied using a continuum thermal model. The hot spot aggregated at the tips of graphene petals (GPs), particularly at the high concave surface, at the beginning of the charging step. As the charging proceeded, the overall temperature rose continuously, and the temperature distribution was likely uniform throughout the graphene petals due to an increasingly uniform distribution of ions on GPs surfaces. To elucidate the effects of electrode geometry on the change of temperature, several simple two-dimensional structures were also simulated in the charging step. Concave and planar structures contributed to high temperature change, while a convex structure tended to alleviate the hot spot. An insight into geometric effects on the thermal behavior may lead engineers to develop a new class of nanomaterials for supercapacitors.

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Double rotor machines, appearing in versatile forms and configurations thanks to the great flexibility of having a pair of rotors, are seen in a number of applications. Double rotor machines show promising prospect in the application of advanced hybrid electric vehicle powertrains due to the requirement of dual electro-mechanical ports in such systems. Integrating these powertrain systems with double rotor machines not only brings design freedom of laying out components, but also reduces number of parts and thus improves compactness. The switched reluctance type double rotor machines, offering unique characteristics of having a simple structure and no permanent magnets, are strong candidates for high performance applications. In this thesis, a family of double rotor switched reluctance machine with segmented rotors is proposed and studied. Compared to double rotor switched reluctance machines with a more conventional structure, the proposed designs exhibit potentials of achieving higher compactness and performance. A prototype double rotor machine of the segmented rotor design is constructed and tested to benchmark an existing double rotor switched reluctance machine. The experiment results show that the proposed design is able to achieve the same output with similar or higher efficiency than the benchmark machine, while occupying only about 60% of overall volume. The double segmented rotor switched reluctance machine demonstrates to be a promising double rotor topology and is worth further research. / Thesis / Master of Applied Science (MASc)

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