An improved single-stage PFC AC-DC power supply

peer-reviewedThis letter describes an enhancement to a previously reported single-stage transformer-leakage-inductance-based power-factor-corrected isolated power supply. An improved switch timing calculation algorithm is developed to achieve zero current switch on of the active rectifier switches. The algorithm is based on an analytical model of the system relating the gate timing to the input and output voltages and control inputs. Remarkably, a closed-form expression for the switch timing can be derived and used to calculate and apply the timings in real time without the need for high-speed measurements or resonant structures. A prototype 1.25 kW prototype power supply is implemented using the proposed technique and performance measurements presented.ACCEPTEDpeer-reviewe

Intrinsic Linking and Knotting in Virtual Spatial Graphs

We introduce a notion of intrinsic linking and knotting for virtual spatial graphs. Our theory gives two filtrations of the set of all graphs, allowing us to measure, in a sense, how intrinsically linked or knotted a graph is; we show that these filtrations are descending and non-terminating. We also provide several examples of intrinsically virtually linked and knotted graphs. As a byproduct, we introduce the {\it virtual unknotting number} of a knot, and show that any knot with non-trivial Jones polynomial has virtual unknotting number at least 2.Comment: 13 pages, 13 figure

Towards Cultural Inclusion: Using Mobile Technologies to Increase Access to Audio Description

This paper describes a National Park Service (NPS) and University of Hawaii research project that is developing a mobile application for audio describing NPS print brochures for blind and visually impaired park users. The project has the potential to expand access to cultural and aesthetic material for blind and visually impaired people

Indefinite integrals involving the exponential integral function

publishedVersio

Case Study in Modeling Accessibility for Online Instruction.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017