Partial Discharge Testing and Detection under PWM Voltage

Partial Discharge detection and measurement is an important part of electric insulation design. However, in PWM (pulse width modulation) voltage source converter environments, the noise resulting from switching voltage (rise and fall times of tens of nanoseconds) makes detection and extraction of partial discharge difficult. Unique methods of partial discharge detection are needed to address and decouple the noise from partial discharge measurements. PWM voltage can feature high switching speeds and high dv/dt during voltage switching. These PWM voltage behaviors are not found in traditional utility high voltage applications, and the effects that this type of voltage has on insulation and associated partial discharge behavior are not well understood. A good understanding of partial discharge behavior is vital to effective insulation design in high voltage power electronic systems. \\ To better understand the behavior of partial discharge in a PWM voltage source environment, a partial discharge testing platform is designed. This testing platform features a 3kV Si half-bridge converter to apply PWM voltage at varying switching frequency (5-60kHz) and dv/dt (11-16V/ns). An additional full-bridge 10kV SiC converter provides extra voltage capability for partial discharge testing. Converters with wide bandgap semiconductors can feature high switching frequency and dv/dt not currently possible with Si converters. The effect that switching frequency and dv/dt has on partial discharge behavior will become more of an issue as wide bandgap semiconductors are operated at full potential. The output voltage from this converter will be applied to test subjects chosen to model types of partial discharge: surface, internal, and corona discharge. This testing platform requires an effective method of partial discharge detection that is not interfered by voltage switching transient noise. Three electrically isolated methods of detection are explored to determine the most effective methods of partial discharge detection in the presence of PWM voltage switching transient noise: optical detection, electromagnetic detection, and acoustic detection. Post-processing wavelet denoising techniques are applied to remove any remaining noise from partial discharge signals. With effective partial discharge detection and a testing platform with test subjects chosen to model types of discharge, the effects of PWM voltage on partial discharge behavior are demonstrated. Methods of partial discharge classification and identification are demonstrated as well to show methods to effectively identify defects in insulation caused by partial discharge due to PWM voltage

Understanding the Health-related Challenges Experienced by Former State Prisoners Living with HIV: A Qualitative Study

Background: Human Immunodeficiency Virus (HIV) disproportionately affects certain populations, specifically those passing through correctional facilities. It is estimated that about 1.4% of the approximately two million people residing in correctional facilities are living with HIV. Although the health services offered in correctional facilities are limited, health status may improve substantially for individuals during their placement. Often this progress is lost once a person is released back into the community. Lack of access to care and/or financial assistance inhibits the ability to make health a priority, especially when individuals are faced with the struggle to obtain basic needs such as food, shelter, housing, and employment. This population also bears an unequal burden of non-HIV health conditions. Of those individuals currently incarcerated in the state of Georgia, 1.6% are HIV positive, 26% suffer from chronic illness, 52% have mental health issues, and 25% have reported using drugs or alcohol. In an effort to provide support for this population, Georgia State University partnered with Georgia Department of Corrections Pre-Release Planning Program (PRPP) to establish the Community Connections (CC) Program in 2009. CC program was designed to connect participants with resources that assist with successful reintegration into the community. Exit interviews were conducted with individuals after their participation, and were used to gather information about post-release challenges and outcomes associated with the CC Program. This qualitative study used these interviews to analyze the specific health-related challenges experienced by CC participants. The results from this analysis were used to provide recommendations for further improvements that address the needs of former inmates living with HIV at the policy level. Methods: This study analyzed a set of 16 in-depth, semi-structured interviews with individuals that participated in the post-release CC program during 2010 to 2012. These participants were recruited via convenience sampling, and informed consent was obtained prior to each interview. Interview questions were focused around topics pertaining to housing, employment, risk behaviors, sexual activity, social interactions, HIV care, mental health, substance abuse, and access to medication or treatment. A modified grounded theory approach was used in the analysis. Interviews were openly coded for words and phrases that pertained to health status. The results were used to determine the most pressing health-related challenges associated with this population, and to provide recommendations at the policy level for addressing such issues. Results: Commonly reported co-occurring conditions from this study were as follows: high blood pressure, epilepsy, high cholesterol, anemia, insomnia, arrhythmia, migraines, kidney disease, neuropathy, blood clots, and diabetes. Depression was the most frequently reported mental illness, followed by bipolar disorder and schizophrenia. Over half of participants reported using drugs or alcohol before, during, or following incarceration. Additional barriers to maintaining positive health outcomes included lack of medical insurance or financial assistance, the need for oral health care, and frequent hospitalization. Conclusions: Findings illustrate the need for policy-level changes that specifically address post-release challenges for former inmates, and aim to improve health-related outcomes for this population. Linking this population to services that provide basic needs such as housing and employment would enable them to focus on maintaining their health status. Further, linking this population to insurance or other forms of financial assistance immediately following release is crucial to avoiding gaps in healthcare and treatment relapse. In the state of Georgia, expanding Medicaid to make former inmates eligible would provide a major source of relief for some of these issues. Policy-level changes will not only benefit the individual, but the community as a whole by improving overall health outcomes, reducing the spread of diseases, preventing the occurrence of relapse, and reducing the likelihood of recidivism attributable to illness

The comparison of student engagement rates during classroom discourse, cooperative learning, and lecture methods of instruction in secondary schools

The purpose of this study was to examine the degree to which cooperative learning affects the active participation or engagement of students in the classroom. Previous research has found that students were more engaged during lecture and classroom discourse methods of instruction (anderson & Scott, 1978). This study attempted to determine whether the instructional strategy of cooperative learning affected this result.;The sample for this study was selected from the students of two English and two social studies teachers for each instructional method (cooperative learning, lecture, and classroom discourse). Videotapes were made of each teacher\u27s class for analysis. Each class had five students whose engagement levels were studied. The participants were students at a suburban high school in southeast Virginia.;Percent of time engaged in the learning process was estimated by dividing the number of behaviors coded as task-relevant by the total number of behaviors coded. After the rate of engagement of each instructional strategy was determined, a one-factor between-subjects design with three levels of the dependent variable, engagement of students, was used. Planned comparisons using the multiple F test were used to analyze the engagement rates for each of the three instructional strategies (lecture, classroom discourse, and cooperative learning) for each instructional area (English and social studies) and for combined subject areas to determine whether the prediction that cooperative learning had the highest engagement level was verified. Alpha was set at 0.05.;The results showed that cooperative learning techniques resulted in statistically significantly (p {dollar}\u3c{dollar}.05) higher levels of engagement of students in the secondary classrooms studied (English and social studies) than instructional strategies using lecture or classroom discourse. In addition, there was statistically significant higher levels of engagement when cooperative learning was used in each of the subject areas English and social studies than instructional strategies using lecture or classroom discourse.;Comparisons of engagement rates in each of the subject areas studied (English and social studies) showed no statistical difference between the instructional strategies of classroom discourse and lecture.;Further research is needed to determine the effect of cooperative learning techniques in secondary subject classes other than English and social studies, to determine the amount of time needed for cooperative learning techniques to be effective, to determine whether cooperative learning techniques ultimately result in higher achievement for secondary students, to determine if a teacher\u27s preferred teaching method influences these results and to compare the rates of engagement for English and for social studies classes when teachers are using classroom discourse and lecture methods of instruction

Cut Out of Place: The Geography and Legacy of Otto Ege\u27s Broken Books

Otto Ege cut apart hundreds of medieval manuscripts during the first half of the twentieth century, claiming to do so to provide wider access to them. His destruction resulted in the loss of provenance, material history, and context of these manuscripts. Moreover, he made mistakes when identifying and dating the manuscript leaves he cut, and the loss of the bindings and front matter of the manuscripts makes it difficult to correct these. Much of the research concerning Ege focuses on his identity as a biblioclast, yet even scholars who denounce his book-cutting admit he allowed for places and people to have access to these manuscripts that otherwise would not. In this thesis, I examine how place impacted not only Ege’s motivations to distribute medieval manuscript leaves, but how place further impacts the accessibility of these leaves to people of lower socio-economic status. By mapping the locations of Ege’s Fifty Original Leaves of Medieval Manuscripts portfolios against the percentage of the population with college degrees, I make the argument that Ege’s portfolios are not as accessible to underrepresented populations as they could be, because most of these portfolios are located at university special collections and archives. I draw on social and geographic theory to show that non-college educated people are less likely to visit a college campus than those who attended college. I then explore current scholarship in archives and special collections to show the importance of public outreach programs and how bridging the gap between university archives and special collections and public libraries or other community institutions can make Ege’s portfolios more accessible to a broader audience. I conclude that while Ege did irreparable damage to the historical value of these medieval manuscript leaves, they do indeed still have value in their ability to allow more people to learn from and appreciate them. Ege’s vision of democratizing medieval book history may not have been perfect, but with the damage done, we can move in a more positive direction so as not to waste the potential benefits of these portfolios

Israel’s Newfound Petroleum Wealth: A Critique of the “Resource Curse”

In 1999, a company in Israel did what no one thought could be done – it struck natural gas and lots of it. Since then, two of the largest offshore natural gas fields have been found in Israel’s waters, disproving the belief that Moses led the Jews to the only Middle Eastern country to not have petroleum. In 2011, it found what is believed to hold 250 billion barrels of shale oil – an amount that rivals the 260 billion barrels of crude oil in Saudi Arabia. Most economists argue, however, that this is not good news for Israel due to the “resource curse.” The concept claims that finding an abundant amount of natural resources actually harms the local economy, politics and society as a whole through means of abuse of power, manipulation and pure disregard for societal welfare. This usually is applied to small, poor and previously corrupt governments. Currently, Israel is in a good position to avoid the resource curse. It is a militarily and economically strong, democratic nation. It has many resources available to it as well as lessons from the past to help it avoid the turmoil that historically faces nations with newfound petroleum wealth. This paper argues that not only can Israel beat the resource curse, but that the concept of the resource curse itself is flawed. Through historical examples of Nigeria and Canada, it is proven that not only small and weak governments fall victim to the greed and temptation that follows new resource wealth. The United States and Norway will show that with correct policy response, governments can avoid the curse highlighting the fact that an avoidable “curse” is, in fact, no “curse” at all. Finally, this paper will outline the appropriate political response for Israel containing several policies that limit sector transfers and exports as well as outlines the establishment of two sovereign wealth funds. Israel, like others before, can avoid the resource curse and boost all parts of its economy by taking several intricate steps

Pressure and Flow Validation of a Second Generation Gas Extraction Probe for a Hybrid Rocket Gas Extraction System

A gas extraction system (GES) has been designed for use with the hybrid rocket facility at the University of Arkansas at Little Rock (UALR) for spectroscopic analysis of rocket plumes. While monitoring gas flow-rate and pressure, the GES extracts gases from the hybrid rocket plume and transports them to a mass spectrometer. This paper describes design and construction of a gas extraction probe (GEP) prototype capable of extracting gases directly from the plume. Gas dynamics equations were used to design two venturi-type GEP, converging and converging-diverging. The probe was tested with air to verify design assumptions. Flow rate through the U-arm and pressures for each probe were measured and compared

Resampling to accelerate cross-correlation searches for continuous gravitational waves from binary systems

Continuous-wave (CW) gravitational waves (GWs) call for computationally-intensive methods. Low signal-to-noise ratio signals need templated searches with long coherent integration times and thus fine parameter-space resolution. Longer integration increases sensitivity. Low-mass x-ray binaries (LMXBs) such as Scorpius X-1 (Sco X-1) may emit accretion-driven CWs at strains reachable by current ground-based observatories. Binary orbital parameters induce phase modulation. This paper describes how resampling corrects binary and detector motion, yielding source-frame time series used for cross-correlation. Compared to the previous, detector-frame, templated cross-correlation method, used for Sco X-1 on data from the first Advanced LIGO observing run (O1), resampling is about 20x faster in the costliest, most-sensitive frequency bands. Speed-up factors depend on integration time and search setup. The speed could be reinvested into longer integration with a forecast sensitivity gain, 20 to 125 Hz median, of approximately 51%, or from 20 to 250 Hz, 11%, given the same per-band cost and setup. This paper's timing model enables future setup optimization. Resampling scales well with longer integration, and at 10x unoptimized cost could reach respectively 2.83x and 2.75x median sensitivities, limited by spin-wandering. Then an O1 search could yield a marginalized-polarization upper limit reaching torque-balance at 100 Hz. Frequencies from 40 to 140 Hz might be probed in equal observing time with 2x improved detectors.Comment: 28 pages, 7 figures, 3 table

Low significance of evidence for black hole echoes in gravitational wave data

Recent detections of merging black holes allow observational tests of the nature of these objects. In some proposed models, non-trivial structure at or near the black hole horizon could lead to echo signals in gravitational wave data. Recently, Abedi et al. claimed tentative evidence for repeating damped echo signals following the gravitational-wave signals of the binary black hole merger events recorded in the first observational period of the Advanced LIGO interferometers. We reanalyse the same data, addressing some of the shortcomings of their method using more background data and a modified procedure. We find a reduced statistical significance for the claims of evidence for echoes, calculating increased p-values for the null hypothesis of echo-free noise. The reduced significance is entirely consistent with noise, and so we conclude that the analysis of Abedi et al. does not provide any observational evidence for the existence of Planck-scale structure at black hole horizons.Comment: As accepted by Physical Review

Directed Searches for Continuous Gravitational Waves from Spinning Neutron Stars in Binary Systems.

Gravitational wave detectors such as the Laser Interferometer Gravitational-wave Observatory (LIGO) seek to observe ripples in space predicted by General Relativity. Black holes, neutron stars, supernovae, the Big Bang and other sources can radiate gravitational waves. Original contributions to the LIGO effort are presented in this thesis: feedforward filtering, directed binary neutron star searches for continuous waves, and scientific outreach and education, as well as advances in quantum optical squeezing. Feedforward filtering removes extraneous noise from servo-controlled instruments. Filtering of the last science run, S6, improves LIGO's astrophysical range (+4.14% H1, +3.60% L1: +12% volume) after subtracting noise from auxiliary length control channels. This thesis shows how filtering enhances the scientific sensitivity of LIGO's data set during and after S6. Techniques for non-stationarity and verifying calibration and integrity may apply to Advanced LIGO. Squeezing is planned for future interferometers to exceed the standard quantum limit on noise from electromagnetic vacuum fluctuations; this thesis discusses the integration of a prototype squeezer at LIGO Hanford Observatory and impact on astrophysical sensitivity. Continuous gravitational waves may be emitted by neutron stars in low-mass X-ray binary systems such as Scorpius X-1. The TwoSpect directed binary search is designed to detect these waves. TwoSpect is the most sensitive of 4 methods in simulated data, projecting an upper limit of 4.23e-25 in strain, given a year-long data set at an Advanced LIGO design sensitivity of 4e-24 Hz^(-1/2). TwoSpect is also used on real S6 data to set 95% confidence upper limits (40 Hz to 2040 Hz) on strain from Scorpius X-1. A millisecond pulsar, X-ray transient J1751-305, is similarly considered. Search enhancements for Advanced LIGO are proposed. Advanced LIGO and fellow interferometers should detect gravitational waves in the coming decade. Methods in these thesis will benefit both the instrumental and analytical sides of observation.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/110473/1/gmeadors_1.pd

Manifesto on the ledge: an American comic chamber

My thesis composition, Manifesto on the Ledge, is a thirty-minute long chamber opera for or soprano, mezzo-soprano and baritone, saxophone, violin, viola, cello, percussion and electric keyboard. It is the result of collaborating with librettist John Paul Carillo as well as with the vocalists of Rhymes With Opera, the company who commissioned the work. Our collaboration led to a novel approach to the creative process: rather than starting with a story and libretto, we began with music, which served as inspiration for the text. Ultimately, this approach resulted in a rich collaborative experience, with a great deal of give and take between composer and librettist. Many other collaborations were vital to the success of the project, including the work with the Rhymes with Opera vocalists, performers and leadership. As a result of this experience, I plan on continuing to work collaboratively in future projects. There will be a full-scale production of Manifesto on the Ledge in May 2015, presented by the commissioning organization