A Study of the Sensitivity of Energy Conversion Efficiency to Load Variation in Class-E Resonant Power Inverter

In this thesis the sensitivity of energy conversion efficiency (ECE) and output power of a class-E resonant inverter under variable resistive and inductive load assignments is examined for wireless power transfer (WPT) applications. By performing simulation and mathematical analysis, it was found that the on-resistance of the switching device has minor effect on the design’s efficiency. Additional comparisons between the simulation and mathematical analysis show reasonable output power and ECE load variation performance for the design, but with unique load impedances where zero voltage switching (ZVS) and zero derivative switching (ZDS) are achieved. These comparisons also expose inaccurate mathematical assumptions. Experimental test results are presented to validate simulation and mathematical assumptions. These tests also show invalid assumptions used in the simulation and mathematical analysis and the performance of the class-E resonant power inverter suffer due to the difference in resonant frequencies during switch on and off state periods, nonlinear shunt capacitance, and parasitic impedances

Samuel Jennings, Phineas Pemberton, May 1, 1697

Letter dated April 1, 1697 (March 22, 1696 Old Style) from Samuel Jennings to Phineas Pemberton

Evaluating the Consistency of a Breathing Flow Recording Device Across Different Elastomeric Half-Mask Respirators

The National Institute of Occupational Safety and Health (NIOSH) is the organization in charge of approving respiratory devices in the United States, as permitted by 42 CFR Part 84. Standards that NIOSH uses to certify powered air-purifying respirators (PAPRs) are based on respiratory data collected before the 21st century. With new technologies, it is possible to gain a more accurate understanding of breathing flow of healthcare workers (HCWs). A new portable breathing flow recording device developed by The S.E.A. Group was intended for use with a Sundström SR100 mask with a P100 filter. This study tests the device with a North 7700 mask with a P100 filter as well to evaluate the device’s consistency of measurement among other types of elastomeric half-mask respirators (EHMRs). The respirators are first calibrated for use with the device, then each is exposed to four different measurement conditions. Each condition is tested at varying flow rates from 5 liters per minute to 75 liters per minute. The results are analyzed using a two-sided hypothesis test of difference in independent population means, with a null hypothesis (H0) being: H0 = μ1 – μ2 = 0. A two-tailed t-test is performed, assuming equal variances. The results show that the hypothesis is accepted (p \u3e 0.05), therefore the results obtained by the device are not significantly different. These results suggest the device can potentially be used to measure the breathing flow rate of HCWs using various types of EHMRs. With the consistency and reliability of new devices in measuring breathing flow of HCWs in a real-time work environment, new data can be gathered to supplant the outdated information used to shape current NIOSH respirator certification standards

Frequency stability characterization of a broadband fiber Fabry-Perot interferometer

An optical etalon illuminated by a white light source provides a broadband comb-like spectrum that can be employed as a calibration source for astronomical spectrographs in radial velocity (RV) surveys for extrasolar planets. For this application the frequency stability of the etalon is critical, as its transmission spectrum is susceptible to frequency fluctuations due to changes in cavity temperature, optical power and input polarization. In this paper we present a laser frequency comb measurement technique to characterize the frequency stability of a custom-designed fiber Fabry-Perot interferometer (FFP). Simultaneously probing the stability of two etalon resonance modes, we assess both the absolute stability of the etalon and the long-term stability of the cavity dispersion. We measure mode positions with MHz precision, which corresponds to splitting the FFP resonances by a part in 500 and to RV precision of ~1 m/s. We address limiting systematic effects, including the presence of parasitic etalons, that need to be overcome to push the metrology of this system to the equivalent RV precision of 10 cm/s. Our results demonstrate a means to characterize environmentally-driven perturbations of etalon resonance modes across broad spectral bandwidths, as well as motivate the benefits and challenges of FFPs as spectrograph calibrators.Comment: 15 pages, 9 figures, accepted to Opt. Expres

Samuel Jennings, Phineas Pemberton, March 2, 1701

Letter dated March 2, 1701 (February 19, 1700 Old Style) from Samuel Jennings to Phineas Pemberton. The original letter is not extant in the collection; the only record is a photocopied image of the letter