Engineering Commons^™

Theoretical Throughput Capacity: Capabilities Of Human Information Processing During Multitasking, Aerial N. Camden

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Technological advancements in automation have allowed humans to collect data at exorbitant rates. As a result, human multitasking as become an integral part of many government, industrial, and routine activities. However, multitasking can be difficult to study, primarily due to the lack of objective metrics. The Human Operator Informatic Model (HOIM) is an information-theory based model that has been recently developed to combat these difficulties. The HOIM is based on Shannon information theory and can provide an objective, meaningful measure to describe system complexity and overall multitasking performance. The main goal of this work was to validate the HOIM as …

Anterior Cruciate Ligament Biomechanics, Computational Modeling Of Mechanical Behavior And Injury Risk, Bharadwaj Cheruvu

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Knee joint involves interactions from various structures such as cartilage, bone, muscles, ligaments, tendon, as well as neural control. Anterior cruciate ligament (ACL) tears are one of the most frequent soft tissue injuries of the knee. A torn ACL leaves the joint unstable and at risk for further damage to other soft tissues manifested as pain, dislocation, and osteoarthritis. This injury is quite common in sports such as basketball, soccer and football. Females often tear their ACL 2-8 times more frequently than their male counterparts. An ACL injury can be devastating and significantly increases the athlete's risk for osteoarthritis long …

Hierarchical Porous Structures With Aligned Carbon Nanotubes As Efficient Adsorbents And Metal-Catalyst Supports, Hema Vijwani

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The overall goal of this study is two-fold: synthesis of multiscale nanostructures by growing aligned carbon nanotubes on porous foam substrates and investigation of their applicability as adsorbents and catalyst supports for environmental remediation applications. High purity, vertically-aligned arrays of carbon nanotubes (CNT) are grown on open-cell interconnected porous carbon foams by pre-activating them with an oxide buffer layer followed by chemical vapor deposition (CVD). This type of hierarchical morphology provides the capability of increasing surface area by several orders of magnitude, while tuning its morphology for targeted applications. Analytical models are also proposed in this study for specific surface …

Mathematical Models And Solution Approach For Staff Scheduling With Cross-Training At Call Centers, Taskiran, Gamze Kilincli

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Call centers face demand that varies throughout the week across multiple service categories and typically employ non-standard workforce schedules to meet this demand. In call centers, cross-training provides a buffer against fluctuation of demand between categories and is widely used. Full cross-training, however, is financially impractical in most cases, which has created a challenging problem in how to optimize a cross-trained workforce, i.e., a) what categories should be cross-trained, b) what portion of the workforce should be cross-trained, and c) how to schedule their weekly assignments. This problem is motivated by the need of a Fortune 50 company's technology support …

Pwm Buck Converter As A Dynamic Power Supply For Envelope Tracking And Amplitude Modulation, Thomas R. Salvatierra

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Modern energy transmission and signal reproduction techniques rely upon power amplifier (PA) architectures that must operate with high efficiency. Current-source PAs are linear but inherently inefficient; switch-mode PAs are efficient-yet-nonlinear systems, often lacking an efficient means of amplitude modulation (AM) for power transmission. A promising technique for addressing these problems involves replacing the fixed PA supply voltage V_dd with a controlled, variable voltage provided by a dynamic power supply. High-efficiency envelope tracking and amplitude modulation can thereby be provided to both current-source and switch-mode PAs, respectively. This work presents a pulse-width modulated (PWM) dc-dc buck converter for use as the …

Unsteady Physics And Aeroelastic Response Of Streamwise Vortex-Surface Interactions, Caleb J. Barnes

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Streamwise vortex-surface interactions can occur in aviation intentionally in the context of formation flight as an energy saving mechanism, unintentionally in wake crossings when aircraft fly in close proximity, and as a consequence of aircraft design through the interaction of fluid dynamics between different aerodynamic surfaces. The bulk of past work on streamwise vortex-surface interactions has focused on steady inviscid analysis for optimizing aerodynamic loads in the context of formation flight or experimental analysis on fin buffeting problems. A fundamental understanding of the viscous and unsteady effects that may occur is both important and currently lacking in the literature. This …

Improved Spare Part Forecasting For Low Quantity Parts With Low And Increasing Failure Rates, Albert Frank Lowas Iii

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Part demand forecasting methods assume that the demand for a part over time follows a predictable pattern, and that the patterns observed in historical data provide a reliable indication of future demands. Generally, forecasting studies focus on topics such as: the span of time from which to sample the historical data, an assessment of data in order to find weekly or annual patterns, and the assignment of probabilities of different demand quantities in any given time period. Using the demand models derived from these forecasting methods, inventory decisions are made--decisions which directly impact operating cost and equipment availability.

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Integrated Magnetic Components For Rf Applications, Sheena Hussaini

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Integrated r-f passive components such as inductors, transmission lines, transformers etc, form the basic building blocks in r-f integrated circuits (RFICs) such as matching networks, low noise amplifiers (LNAs), synthesizers and r-f mixers. One main challenge faced by current technology developers in integrating r-f components on integrated chip (IC) are related to operation and size. Tremendous efforts were made for overcoming challenges of r-f integrated circuits to meet growing technology demands.

In general, r-f devices utilize magnetic materials such as ferrites for their operation for improving device performance and scaling. However, due to material properties and size ferrite materials are …