Development of Multi-Axial Fatigue Retrofits for Lock Gate Components

Lock gates are essential infrastructure components to the United State (US) supply chain. They create large cost savings and environmental benefits when compared with traditional methods of transport (freight and rail). Because of the large quantity of goods and dependence on these shipping chains, the US economy can be drastically affected by an unexpected gate closure. Unfortunately, many lock gates within the US have reached or exceeded their designed life. Due to the intensity of cyclic loads and the environment, fatigue cracks have become a prominent issue. Developed cracks near the pintle region (a joint which the gate rotates and rests upon) have shown to be difficult to mitigate due to the complex stresses that flow through this area. Mitigation methods commonly used for mode I cracking have been futile in the arrestment of cracks seen around the pintle because of this. These stresses are known to be multi-axial stresses which cause multi-mode cracking at the crack tips of the developed fatigue cracks. The thesis herein presents an analytical and experimental investigation into multi-axial fatigue crack mitigation by the use of carbon fiber reinforced polymer (CFRP) capable of extending gate life into a time frame where permanent repair can occur. Detailed finite element analysis (FEA) models are used to develop and validate CFRP retrofit geometries capable of mitigating crack propagation on generalized, scaled specimens as well as a detailed model of the pintle geometry itself. Additionally, experimental crack mitigation is conducted in an attempt to validate what is found through the FEA models

Stream benthic algal relationships with multi-metric indices of sensitivity, exposure, and vulnerability to watershed land use change, with an emphasis on unconventional natural gas development

Unconventional natural gas (UNG) is harvested using a unique fossil fuel extraction method that uses horizontal drilling and hydraulic fracturing techniques. The combined methods have expanded the industry both nationally and globally, and development has the ability to transform landscapes and impact freshwater resources. Natural gas wells are often near streams, yet substantial knowledge gaps remain as to how and the extent to which development affects surface waters. Stream algal biomass can respond positively to anthropogenic stressors associated with different types of land use, including agriculture. Benthic algal biomass can also positively correlate with UNG well density and proximity to streams in the Fayetteville shale, but wells are often associated with agricultural land that may confound the relationship. The first objective of the present study was to determine if stream benthic algal biomass related to previously developed metrics of sensitivity, exposure, and vulnerability to land use change. These metrics incorporated landscape measures of UNG development, an emerging human land use change that may affect stream ecosystems. The second objective was to determine if the relationships among algal biomass and the metrics differed in streams draining lands with and without the presence of UNG wells. Forty stream reaches in the Fayetteville shale were sampled that represented a gradient of vulnerability scores (hereafter, Vulnerability), and analysis of covariance was used to determine if algal biomass, measured as Chlorophyll a, differed based on land use type across a covariate score. The results indicated no relationship between Chlorophyll a and Vulnerability or its two individual metrics, Sensitivity and Exposure (p\u3e0.50 for all scores). There was no difference in Chlorophyll a between sites with and without UNG wells present. I suggest modifications to the vulnerability index that might yield an overall Vulnerability effect as well as additional considerations for choosing a response metric

A Study of the Influence of Women Clients on Residential Architectural Design through the Work of E. Fay Jones

This thesis aims to determine the influence of women clients on residential architectural design in the United States throughout the twentieth century. In the late nineteenth and twentieth century, waves of feminism and women’s rights movements pushed traditional views of men, women, family and relationships in America to change. At the same time, modernity brought about a shift in architectural thinking. Therefore, if architectural ideas about housing and the home and cultural ideas regarding gender roles and domesticity are directly related, these cultural changes would be present in housing designs of the period. Architect Frank Lloyd Wright was known to have progressive and controversial views on women gender roles. Because Fay Jones was a student and disciple of Wright, some of Wright’s views would be passed on to him. To illustrate these changes, I examined four houses designed and built for women clients in America in the twentieth century: The Susan Lawrence Dana House (Frank Lloyd Wright, 1902), the Goetsch-Winckler House (Frank Lloyd Wright, 1940), the Goetsch-Winckler House III (E. Fay Jones, 1965), and the Alice Walton House (E. Fay Jones, 1982). These houses were constructed at fairly regular intervals throughout the nineteen-hundreds, and illustrate the interaction between social changes and design changes. The placement of these houses on a timeline of the twentieth century yields the conclusion that each woman was pushing the envelope and working to break down traditional boundaries of separate spheres, but they were doing so within the restrictions of each time period

Ultrafast extreme ultraviolet absorption spectroscopy of methylammonium lead iodide perovskite

Methylammonium lead iodide (perovskite) is a leading candidate for use in next-generation solar cell devices. However, the photophysics responsible for its strong photovoltaic qualities are not fully understood. Ultrafast extreme ultraviolet (XUV) absorption was used to investigate electron and hole dynamics in perovskite by observing transitions from a common inner-shell level (I 4d) to the valence and conduction bands. Ultrashort (30 fs) pulses of XUV radiation with a broad spectrum (40-70 eV) were generated via high-harmonic generation using a tabletop instrument. Transient absorption measurements with visible pump and XUV probe directly observed the relaxation of charge carriers in perovskite after above-band excitation in the femtosecond and picosecond time ranges

FilteredWeb: A Framework for the Automated Search-Based Discovery of Blocked URLs

Various methods have been proposed for creating and maintaining lists of potentially filtered URLs to allow for measurement of ongoing internet censorship around the world. Whilst testing a known resource for evidence of filtering can be relatively simple, given appropriate vantage points, discovering previously unknown filtered web resources remains an open challenge. We present a new framework for automating the process of discovering filtered resources through the use of adaptive queries to well-known search engines. Our system applies information retrieval algorithms to isolate characteristic linguistic patterns in known filtered web pages; these are then used as the basis for web search queries. The results of these queries are then checked for evidence of filtering, and newly discovered filtered resources are fed back into the system to detect further filtered content. Our implementation of this framework, applied to China as a case study, shows that this approach is demonstrably effective at detecting significant numbers of previously unknown filtered web pages, making a significant contribution to the ongoing detection of internet filtering as it develops. Our tool is currently deployed and has been used to discover 1355 domains that are poisoned within China as of Feb 2017 - 30 times more than are contained in the most widely-used public filter list. Of these, 759 are outside of the Alexa Top 1000 domains list, demonstrating the capability of this framework to find more obscure filtered content. Further, our initial analysis of filtered URLs, and the search terms that were used to discover them, gives further insight into the nature of the content currently being blocked in China.Comment: To appear in "Network Traffic Measurement and Analysis Conference 2017" (TMA2017

RAPID HOLE COOLING AND SLOW ELECTRON COOLING IN METHYLAMMONIUM LEAD IODIDE PEROVSKITE

Methylammonium lead iodide perovskite is a promising candidate for next-generation photovoltaics. One application for this perovskite is in hot-carrier collection devices. In a standard cell any excess energy from absorbed photons is lost as heat, but a cell can be designed to extract carriers before they cool to increase its efficiency above the Shockley-Queisser limit. In order to achieve this, the cooling rate of carriers must be sufficiently slower than the extraction time. Perovskite may fit this criterion due to the presence of a hot-phonon bottleneck for carrier cooling. Time-resolved XUV absorption from the core I4d level to the valence band (45-50 eV) after optical excitation (3.1 eV) was used to probe the hole distribution of photoexcited perovskite. The holes were found to cool rapidly (cooling time shorter than 400 fs) at high carrier density (10$^{19}$ cm$^{-3}$). In comparison, time-resolved optical absorption (1.5-2.5 eV) was used to probe the electron distribution, which was found to cool slowly (cooling time longer than 5 ps) for the same excitation density. This indicates that a hot-carrier collection device using perovskite should be designed to only extract hot electrons, not hot holes

ULTRAFAST EXTREME ULTRAVIOLET SPECTROSCOPY OF METHYLAMMONIUM LEAD IODIDE PEROVSKITE FOR CARRIER SPECIFIC PHOTOPHYSICS

Methyl ammonium lead iodide (perovskite) is a leading candidate for next-generation solar cell devices. However, the fundamental photophysics responsible for its strong photovoltaic qualities are not fully understood. Ultrafast extreme ultraviolet (XUV) spectroscopy was used to investigate relaxation dynamics in perovskite with carrier specific signals arising from transitions from the common inner-shell level (I 4d) to the valence and conduction bands. Ultrashort (30 fs) pulses of XUV radiation in a broad spectrum (40-70 eV) were obtained using high-harmonic generation in a tabletop instrument. Transient absorption measurements with visible pump and XUV probe directly observed the dynamics of charge carriers after above-band and band-edge excitation

F-CHEC Community Letter

Letter to the community represented by the Fernald Community Health Effects Committee, the seven townships within five miles of the former Fernhald uranium processing plant. This letter informs the community about the Committee and its research. The goal of the research was to determine whether contaminants from the plant existed in the water. Their findings were sent along with this letter. This research was completed money allocated during Round 4 of the Citizens’ Monitoring and Technical Assessment Fund (MTA Fund). Clark University was named conservator of these works. If you have any questions or concerns please contact us at [email protected]://commons.clarku.edu/fchec/1000/thumbnail.jp