EXPERIMENTAL PANEL FLUTTER RESULTS FOR SOME FLAT AND CURVED TITANIUM SKIN PANELS AT SUPERSONIC SPEEDS

Panel flutter results for flat and curved titanium skin panels at supersonic spee

MODELING AND TOPOLOGY EVALUATION FOR RECTIFIER CIRCUITS IN MEDIUM VOLTAGE DIRECT CURRENT SYSTEM

Naval ship propulsion design is evolving from the traditional structure with a main engine driving a shaft through a reduction gear, to a new architecture that uses electric drives powered from a direct current (DC) power distribution system. The goal of this thesis is to compare different medium voltage rectifiers interfacing an alternate current (AC) generator to a DC bus which can power the ship propulsion system. Power quality and efficiency of the power converters are the parameters used to compare four different rectifier circuit topologies: 2-level converter, 3-level converter, modular multi-level converter, and modular multi-level rectifier. Converter operating principles, design trade-offs, modeling characteristics, performance, and naval shipboard applicability are discussed in detail. Using a power electronics simulation platform, the four power rectifier circuits and their controls are connected between a 6.6kV AC generator and a regulated DC bus that represents the shipboard platform. Inside each rectifier circuit, thermal properties of the chosen semiconductor switching devices and diodes are built in and losses are captured and analyzed in steady state operation. This study shows that the modular multi-level rectifier circuit is the most efficient, easiest to maintain, and the recommended topology for Naval shipboard applications.Lieutenant, United States NavyApproved for public release. Distribution is unlimited

A Hybrid Jump Search and Tabu Search Metaheuristic for the Unmanned Aerial Vehicle (UAV) Routing Problem

In this research, we provide a new meta-heuristic, a jump search I tabu search hybrid, for addressing the vehicle routing problem with real-life constraints. A tour construction heuristic creates candidate solutions or jump points for the problem. A tabu search algorithm uses these jump points as starting points for a guided local search. We provide statistical analysis on the performance of our algorithm and compare it to other published algorithms. Our algorithm provides solutions within 10% of the best known solutions to benchmark problems and does so in a fraction of the time required by competing algorithms. The timeliness of the solution is vitally import to the unmanned aerial vehicle (UAV) routing problem. UAVs provide the lion\u27s share of reconnaissance support for the US military. This reconnaissance mission requires the UAVs to visit hundreds of target areas in a rapidly changing combat environment. Air vehicle operators (AVOs) must prepare a viable mission plan for the UAVs while contending with such real-life constraints as time windows, target priorities, multiple depots, heterogeneous vehicle fleet, and pop-up threats. Our algorithm provides the AVOs with the tools to perform their mission quickly and efficiently

Audit technology and preferences for auditing standards

This paper investigates factors associated with audit firm positions on Auditing Standards Board issues during the three-year period ending during 1984. The major finding is that firms with relatively structured audit technologies tend to favor proposed statements while firms with relatively unstructured technologies do not. Audit firm size is not associated with firm position. Also, Big 8 firms favoring proposed statements have lower staff-to-partner ratios and concentrate less in auditing. The staff-to-partner ratio is negatively associated with technology. The results' implications for auditing profession organization studies and auditing and financial reporting research are investigated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26243/1/0000323.pd

Three-Dimensional Mapping of Mineral Densities in Carious Dentin: Theory and Method

X-ray tomographic microscopy (XTM), a three-dimensional X-ray imaging technique, has been used to quantitatively map mineral concentrations in carious dentin. Data analysis from the XTM study indicates that variations in the mineral concentration surrounding the caries can be imaged in three dimensions with a spatial resolution that is sufficient to detect calcified and enlarged tubule spaces in the lesion. A three-dimensional image of the subsurface lesion indicates that lesion penetration is along the direction of the tubules. The mineral concentration in the uninfected dentin was measured by the XTM to be 1.29 ± 0.14 g/cm3 based upon the tabulated X-ray attenuation coefficients for apatite. This value is in excellent agreement with averaged estimates for the mineral concentration in dentin (1.4 g/cm3). Furthermore, the mineral concentration determined using XTM varies from 2.25 g/cm3 in the remineralized dentin to as low as 0.55 ± 0.17 g/cm3 in the demineralized tissue. The high concentration of mineral in the remineralized region suggests that organic matter is lost and mineral is deposited at some time during the caries process

Cross-cultural Adaptation, Validation and Reliability of the Brazilian Version of the Richmond Compulsive Buying Scale

Objective: To present the process of transcultural adaptation of the Richmond Compulsive Buying Scale to Brazilian Portuguese. Methods: For the semantic adaptation step, the scale was translated to Portuguese and then back-translated to English by two professional translators and one psychologist, without any communication between them. The scale was then applied to 20 participants from the general population for language adjustments. For the construct validation step, an exploratory factor analysis was performed, using the scree plot test, principal component analysis for factor extraction, and Varimax rotation. For convergent validity, the correlation matrix was analyzed through Pearson’s coefficient. Results: The scale showed easy applicability, satisfactory internal consistency (Cronbach’s alpha=.87), and a high correlation with other rating scales for compulsive buying disorder, indicating that it is suitable to be used in the assessment and diagnosis of compulsive buying disorder, as it presents psychometric validity. Conclusion: The Brazilian Portuguese version of the Richmond Compulsive Buying Scale has good validity and reliability