The OAKTrust Digital Repository

The OAKTrust digital repository at Texas A&M is a digital service that collects, preserves, and distributes the scholarly output of the University. The repository facilitates open access scholarly communication while preserving the scholarly legacy of the Texas A&M community.

 

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Recent Submissions

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A Characterization of the Vertical Structure and Mixing of the Eastern Mediterranean Sea
(2024-05) Milton, Gianna F.; DiMarco, Steven F; Potter, Henry; Schumacher, Courtney
Observational data collected by THEMO (The Texas A&M - University of Haifa Eastern Mediterranean Observatory) is used to characterize the seasonal variability of the water-column to understand the vertical structure and vertical mixing of the Levantine Basin in the Eastern Mediterranean Sea. Previous studies have shown the marginal Eastern Mediterranean Sea is characterized by hypersaline waters, strong water-column stratification, and regular seasonal atmospheric patterns. THEMO is composed of two surface buoys located off the coast of Haifa, Israel: one shallow buoy (water depth of 125 m; 10 km from shore) in the coastal zone of the Levantine Basin, one deep buoy (water depth of 1430 m; 60 km from shore), and one StandAlone McLane Moored Profiler (MMP), which is deployed close to the deep buoy. These instruments and buoys provide in-situ near real-time subsurface physical oceanographic observations and atmospheric observations of the Eastern Mediterranean Sea. The objectives of this research are: 1) to characterize and identify the processes that force the seasonality of the surface mixed layer depth, 2) to quantify the mechanisms that drive the hydrographic variability of the upper (surface to 1400 m depth) water-column, and 3) to categorize the stability processes of the Eastern Mediterranean Sea upper water-column using Turner Angle (Tu). Results show that the mixed layer depth varies seasonality from 250 m in Winter to less than 85 m in non-Winter months and is correlated with relatively stronger winter wind speeds (average of 7.12 m/s (Winter) to 4 m/s (non-Winter)). The upper 100 m of the water-column also experiences warming of 2 degrees C during Winter due to enhanced downward mixing of warm surface water with cooler subsurface water. Statistical analysis using empirical orthogonal functional (EOF) analysis shows that outside Winter months, variance in the principal component time-series is most correlated with the geostrophic current direction and accounts for about 50% of the total variance of water-column temperature and salinity. Characterization of water-column stability shows stable waters (-45 degrees < Tu < 45 degrees), i.e., no overturning, are most likely to occur in the upper 200 m of the water-column, and double diffusive mixing through salt fingering occur in waters below the mixed layer depth. The depth of salt fingering and stability are similar to other areas of the deep Eastern Mediterranean Sea and mid-latitude marginal seas of the world ocean.
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Quantitative Analysis of Strain Response Measured by Low-Frequency Distributed Acoustic Sensing During Hydraulic Fracturing
(2024-05) Khatara, Sajan Zaverbhai; Wu, Kan; Kitajima, Hiroko; Akkutlu, Ibrahim Y.
This master's thesis investigates the pivotal role of strain measurements in hydraulic fracturing operations, employing Low-Frequency Distributed Acoustic Sensing (LF-DAS) technology to monitor strain changes during treatments. A significant gap in the existing research is addressed by systematically analyzing strain decay beyond the fracture domain corridor. The thesis investigates the impact of parent-well depletion and completion design on hydraulic fracture geometry, employing a decline factor of the strain decay curve as a key analytical tool. This analysis is supported by a geomechanics model, providing a comprehensive understanding of the dataset. Furthermore, the study conducts a comprehensive analysis of Hydraulic Fracture Test Site-2 (HFTS-2), considering the maximum cumulative strain change and decline factor of the strain decay curves. The thesis outlines a well-structured workflow for processing and analyzing LF-DAS cross-well strain data.
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Developing the Texas A&M Smart and Connected Homes Testbed
(2024-05) Firsich, Thomas; O'Neill, Zheng; Allaire, Douglas; Culp, Charles
The Texas A&M Smart and Connected Homes Testbed has been developed to support residential HVAC research. The flexible testbed enables the windows and walls to be replaced, the floorplan to be reconfigured, provides two separate duct networks, and incorporates on-site renewable energy. Heavy instrumentation is done at the testbed to capture information on local weather conditions, building envelope performance, occupant comfort, HVAC equipment performance, and the power consumption of all household end-uses. A smart thermostat is also incorporated to provide HVAC control capabilities. Occupants are simulated inside the home to mimic actual operation and internal loads. A Modelica model has been created for the building envelope and split system HVAC at the testbed. Using data from the experimental testbed, the model is tuned to ensure accurate implementation. Researchers can use these models to bridge the gap between simulation-based studies and their real-world application.
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Neoconservatives and Taiwan: Adherents of Conservative Precedent or Advocates for Liberal Interventionism?
(2024-05) Willadsen, Brandon Iliff; Parker, Jason; Cobbs, Elizabeth; Schuessler, John
During the 1990s neoconservatives grew concerned over a burgeoning People’s Republic of China (PRC) threatening the newly democratic government of Taiwan. They wanted the United States to bolster Taiwan’s standing in the international community, commit to defend Taiwan, end strategic ambiguity, prevent further entrenchment of the PRC in international organizations, and push for closer if not official relations between the United States and Taiwan. Neoconservatives frequently employed Wilsonian rhetoric to shore up support for Taiwan. Despite this liberal notion, their foreign policy positions and thinking built on the likes of the China Lobby and New Right. By analyzing neoconservative viewpoints on U.S. policy towards Taiwan one can see how evolved earlier conservative positions despite accusations that they carried on liberal tenets in foreign policy.
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An Epidemiologic Investigation on Arsenic Exposure and Its Association with Mental Health Outcomes
(2024-05) Datzman, Jared N.; Roh, Taehyun; Bolanos, Carlos; Xu, Xiaohui; Han, Daikwon
Mental health problems, characterized by a clinically important disturbance in cognitive, emotional, or behavioral aspects of an individual’s life, have garnered growing interest in the field of epidemiology due to their complex causal mechanisms, increasing prevalence, and substantial burden on modern populations. There are many causal factors suspected to impact mental health, mental illness, and emotional wellbeing including certain environmental toxins, like arsenic, although these associations are not well established. Arsenic has been shown to be a globally toxic substance that is associated with numerous health problems. Recent studies suggest that arsenic may have an impact on mental health due to its neurotoxicity. The present research investigates the possible association between arsenic and mental health problems through a systematic review, geographically weighted regression on a county level for the 48 contiguous states with soil arsenic, and a geographically weighted regression on a county level for Texas with water arsenic exposure estimates. The systematic review demonstrated associations between Arsenic and multiple mental disorders as well as generally poor mental health. The first geographically weighted regression of the contiguous 48 states found that soil arsenic was a significant predictor of both county suicide rates and the years of potential life lost due to suicide rate. The second geographically weighted regression found that estimated water arsenic exposure was a significant predictor of both county suicide rates and number of days reported with poor mental health. The present research suggests that arsenic may be a potential environmental risk factor for mental health outcomes. Further prospective studies with individual-level data are necessary to confirm causality and explore the interactions with other risk factors.