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Advanced Techniques of Image Dehazing and Object Detection in Hazy Environments
No full textIntelligent Transportation Systems (ITS) represent the future of smart city transportation, heavily reliant on computer vision for tasks such as object detection and recognition. However, real-world scenarios often introduce challenges such as haze, which can significantly impact the effectiveness of computer vision systems. This dissertation addresses these challenges through the proposal of innovative methods aimed at enhancing object detection in hazy environments.
Firstly, a novel Multiple Linear Regression Haze-removal model based on Dark Channel Prior (MLDCP) is introduced. This model achieves state-of-the-art dehazing performance by optimizing the estimation of transmission maps and atmospheric light. Additionally, pre-dehazing test images using MLDCP significantly enhance object detection accuracy by improving visibility. Secondly, a Synthetic Haze Generation Model is proposed to augment existing image datasets. By introducing synthetic haze, this model enables the training of object detectors robust to hazy conditions. This approach enhances the generalizability of object detection models, enabling them to perform effectively in diverse environmental conditions. Furthermore, depth estimation is addressed using a Dilated Fully Convolutional Neural Network. By incorporating dilated convolution, this model achieves depth estimation with reduced computational costs while maintaining high accuracy. This enhancement contributes to a more comprehensive understanding of the geometric relations within a scene, further improving object detection performance. Lastly, a Local Dehazing algorithm based on Dark Channel Prior is proposed. Leveraging object coordinates obtained from object detection tasks, this algorithm optimizes dehazing over specific regions, leading to improved detection accuracy on targeted objects.
Collectively, these contributions advance the field of computer vision for intelligent transportation systems and related applications in hazy environments. By addressing the challenges posed by haze, these methods offer promising solutions for improving the reliability and effectiveness of ITS in real-world settings
Three Essays on the Economics of Resource Conservation in Agriculture
No full textThis dissertation presents three essays that explore the economics of water and soil conservation in agriculture. The overarching focus of this work is on the impact and cost of conservation programs and policies aimed at conserving natural resources, as well as studying potential barriers to their implementation.
The first essay is an empirical study assessing the cost of reducing water use from irrigated agriculture in the Colorado River Basin. Utilizing basin-wide farm-level data into an econometric choice modeling framework, I simulate farmers��� crop choices under different hypothetical conservation prices paid for per acre-foot of water. I use the predicted crop shares to derive the abatement cost curve of water, which estimates the cost of an additional unit of water conserved in agriculture. My findings suggest that water abatement appears negligible at prices below $200 per acre-foot, but increases thereafter with a significant regional heterogeneity in the marginal cost of additional conserved water. Specifically, my results suggest that marginal abatement cost is smaller in the Lower Basin states of the river, suggesting opportunities for higher levels of conservation at relatively lower costs in this region.
The second essay studies the direct and spillover effect of an extension-based contest program in Arkansas, designed to promote the adoption of irrigation best management practices among pro-ducers. Specifically, I study how participation in the ���Most Crop per Drop��� irrigation yield contest, which ranks participants by water use efficiency and provides feedback on their performance, influences their adoption of irrigation practices. Results show that participation in the contest is positively correlated with a four percent increase in the average adoption of irrigation practices. Additionally, there appears to be an indirect positive spillover effect from the contest, which has influenced the behavior of those producers who were not participants of the program but were indirectly linked to it.
In the third essay, I investigate the difference in the adoption of conservation practices among different groups of producers based on their tenure status. I use operation-level data from the Census of Agriculture for all 48 contiguous states to test whether the enrollment in land retirement programs, and the use of on-farm conservation practices differ among full-owner, part-owner, and full-tenant operations. My results suggest that part-owners and full-tenants are more likely than full-owners to adopt practices such as reduced-tillage and using cover crops. Based on my findings, full-owners are using no-till practice at higher rates than other tenure categories, and are also enrolling higher shares of their operation into land retirement programs
Megahertz Rate Spectroscopic Investigation of Hypervelocity Impact Flash
No full textUnderstanding hypervelocity impacts (HVI) has become crucial to several fields, such as space exploration, planetary science, aerospace engineering, and defense-related applications. HVIs are highly dynamic and extreme phenomena characterized by the immense and rapid transfer of energy between colliding bodies. One manifestation of this transformation of kinetic energy during and immediately following an HVI is the emission of an intense flash of light. Researchers investigating these optical emissions emanating from HVIs refer to this phenomenon as the ���impact flash.��� The impact flash can be noticed across a wide range of impact scenarios: both high and low impact velocities; in the vacuum of outer space, as well as the atmosphere of the earth; with both solid and liquid objects; and across metallic, ceramic, and polymer materials. Investigations into the impact flash have sought to establish connections between impact conditions, temporal evolution of different spectroscopic features, and underlying material failure mechanisms. Characterization of this phenomenon can also act as an indicator for a spatial and temporal evolution of material damage. Typical studies of the impact flash make use of a diverse array of optical diagnostics tools and methods. These include high-speed cameras, photodiodes and photomultiplier tubes, pyrometers, laser interferometers, and spectrometers. Stop-motion or relatively low-rate spectral analysis systems have been employed to measure HVI-induced light emission, providing some spectral information related to the dynamic material behavior and projectile-to-target energy transfer. The relatively short time scales (microseconds) and rapidly evolving impacted material response characteristics of HVI events necessitate the use of highspeed detectors with superior temporal resolution to capture the impact flash evolution with sufficient temporal resolution.
Hence, the objective of this thesis research is to develop two high-speed transient spectral analysis systems for investigating the evolution of the impact flash. The first system, an ultrahigh-speed spectrometer (UHSS), has been developed to capture and analyze the transient light emission induced by HVIs in a two-stage light gas gun (2SLGG) facility, with sub-microsecond (i.e., megahertz-rate) temporal resolution. The UHSS makes use of a MHz-rate complementary metal��� oxide���semiconductor (CMOS) camera coupled to an imaging spectrometer, resulting in MHz-rate spectral imaging characterization. This system was used to record time-resolved spectral images of HVIs at speeds up to 6 km/s from spherical aluminum projectiles impacting both aluminum and stainless-steel targets. The high-speed spectral images recorded allowed us to compare the evolutionary behavior of energized metallic species and combustion byproducts in the nano- and microsecond time scales following the impacts. This study found that even at similar impact conditions, the light emission behavior of aluminum-on-aluminum and aluminum-on-stainless-steel impacts can be substantially different. Aluminum target impacts showed one temporal peak in light intensity, whereas the stainless-steel targets showed an additional secondary peak of emitted light. Additionally, in stainless-steel impacts, combustion byproducts were seen to feature a stronger second peak than pure metallic species.
The second high-speed spectral analysis system, a fiber-based multi-spectral diagnostics (FMSD) system, makes use of a fiber bundle to direct light from the impact flash into a collection of highspeed silicon photodiodes. A gigahertz-rate oscilloscope receives the output voltage from these photodiodes as light reaches each photodiode. By placing unique spectral filters in front of each photodiode, these photodiodes are used to capture signals from a specific species. The design of the FMSD was validated using laser-induced plasma experiments. Engineering improvements and subsequent implementation in future HVI studies are discussed
Professional Mental Health Help-Seeking Behaviors
No full textThis dissertation examined the mental health help-seeking behaviors of undergraduate students and the retrospective help-seeking experiences of professors, while they were college students. Past research has noted disparate mental health outcomes for minoritized and first-generation students. However, research exploring their help-seeking attitudes, styles, and sources in general college populations is limited. This dissertation aims to address some of those gaps by including the perspectives of traditionally underrepresented groups.
The dissertation employed a mixed-methods approach. The first study used a quantitative approach with over 200 self-identified Black, Latine, and White students through surveys. Data was analyzed via numerous versions of Analysis of variances. The second study employed a qualitative focus group design with 10 students from the first study. The third study used a single case design via an exploratory, qualitative inquiry with 8 self-identified Black and Latine professors. Data collection methods for both qualitative studies included face-to-face interviews. Data for both qualitative studies were also analyzed via the constant comparative method.
Major findings from the first study indicated significantly higher avoidant help-seeking styles scores for first-generation students than their counterparts. Findings from the second study included various themes about generational differences, socioeconomic ideals, and differing help-seeking styles via ethnicity. Findings from the third study included various themes based on values, sociocultural factors, and how professors��� attitudes changed over time.
The data from this dissertation highlights the need for continued exploration and understanding the role that college settings, ethnicity, and first-generation status may or may not play in mental health help-seeking behaviors
Thermal Management and Defect Engineering in Reversible Transformations
No full textThis study delves into the nucleation behavior of thermoelastic martensitic transformations in Ni45Co5Mn36.7In13.3 microparticles, examining the influence of mesoscale order-disorder domains and phase boundaries between L21 and B2 phases on nucleation kinetics. The study compares microparticles with varying L21 domain interfacial area densities by employing solution heat treatment and secondary annealing. Characterization of 131 single particles reveals a range of undercooling from 11.3 to 59.4 K, with smaller volumes exhibiting the largest magnitude and variance. Surprisingly, nucleation site potency distributions between different domain sizes are statistically similar, suggesting that anti-site defects do not significantly impact nucleation at the length scales examined.
Additionally, our study explores the effects of helium and localized gallium irradiation on nucleation behavior. Helium irradiation induces Frenkel-pairs at our low doses (��� 0.1 dpa) and penetrates to about 4 ��m at 2 MeV. In comparison, localized gallium irradiation creates high-order defects (��� 140 dpa) and gallium implantation at depths of approximately 10 nm at 5 keV. Interestingly, helium irradiation and associated Frenkel-pairs do not statistically alter nucleation. In contrast, gallium irradiation leads to a notable reduction in the undercooling mean, indicating the potency of localized Ga+ irradiation to create potent nucleation sites.
Furthermore, this dissertation develops a theoretical framework based on thermal impedance to improve the melting efficiency of phase change material composites in transient power systems. The framework highlights the importance of the storage fraction in determining thermal impedance, offering insights into thermal design strategies for pulsed power systems. Finally, the study investigates the thermal impedance of PCM-intercalated copper foams with different pores per inch (40 ��� 90 PPI). Results show that at sufficiently small pores, the time for maximum thermal buffering decreased, peaking near on-times of 7.5 to 8 s, with diminishing returns observed for decreasing pore radii, independent of heat flux. However, the thickness of the foams was found to be a more prominent factor in reducing the observed timescales. This research contributes valuable insights into nucleation phenomena and thermal management strategies in materials science and engineering applications
The Effect of Mechanical Degradation on Sustained Fluoride-Releasing O-Rings: An In-Vitro Study
No full textTraditional methods for caries prevention focus on operator application or patient compliance, but the current study aims to establish a viable alternative to the current white spot lesion prevention techniques. O-rings incorporated with fluoride have been previously studied and assessed for a continuous release of fluoride, however, their ability to release fluoride after being mechanical degraded has not been assessed. The proposed research will provide more evidence on the efficacy of the O-rings and their ability to withstand mechanical degradation.
To assess the mechanical degradation these CaF��� O-rings they were brushed in a toothbrushing simulator for 2-weeks and 8-weeks in DIW at a force of 225g. Control and brushed calcium fluoride O-rings were placed on upper lateral incisor brackets, brushed, weighed, and soaked in distilled water. The amount of released fluoride was tested over a period of 7 weeks.
There were statistically significant differences between the control group and the 2-week and 8-week brushing groups throughout the entire duration of the study. The control and experimental groups dropped below the therapeutic range after the first week. When comparing the control group and experimental groups we see there were statistically significant difference between control and 2-week as well as control and 8-week groups at all time points in the study. All three groups experienced a tapering off of fluoride release. When looking at the cumulative release, the control group showed a statistically significant larger cumulative release of fluoride rate compared to both the 2- and 8-week groups (p<0.001). Weight analysis showed that there is a significant loss of material after mechanical abrasion when compared to before brushing. Additionally, there were several revisions to the protocol that were necessary to produce consistent results.
The 2-week and 8-week groups showed significantly less fluoride release over the duration of the study and had lower release rates when compared to the control, which can be affected by the coating protocol. In the first week of experimentation the 2-week group had a higher release rate, but this difference did not continue for the duration of the study
Impact of Astaxanthin Supplementation on Markers of Cardiometabolic Health and Tactical Performance Among Firefighters
No full textFirefighters are at risk for cardiovascular disease (CVD) due to increased oxidative stress, inflammation, and poor cardiorespiratory fitness (CRF). Astaxanthin (AX) possesses antioxidant/anti-inflammatory and purported ergogenic properties. This study examined the impact of 12 mg/d for four weeks of AX supplementation on markers of oxidative stress, inflammation, cardiometabolic health, cardiorespiratory fitness, and occupational performance in career firefighters. In a randomized, double-blinded, placebo-controlled, crossover fashion, 15 male career firefighters (34.5��7.4 years; 177.7��7.0 cm; 95.6��12.0 kg; 30.1��2.9 kg/m��; 11.03��6.85 years of service) ingested 12 mg/d of AX (AstaReal��, Burlington, NJ, USA) or placebo for four weeks while following a standardized resistance training program. After each treatment, testing sessions were completed to assess 1) blood cardiometabolic health, oxidative stress, and inflammatory and CRF parameters, and 2) salivary oxidative stress and inflammatory responses and tactical performance to fire suppressive activities. Data were analyzed using general linear model multivariate analysis with repeated measures (GLM). Clinical significance was assessed via mean changes from baseline (BL) with 95% confidence intervals (mean [LL, UL]). Analysis of mean changes from BL revealed AX lessened the inflammatory response to a cardiopulmonary exercise test. Additionally, the percent ventilatory anaerobic threshold (%VANT) was higher following AX compared to placebo (4.84 [0.27, 9.41] %, p<0.039, ����_p^2=0.114). Analysis of mean changes from BL revealed AX may lessen increases in IL-1��, cortisol, and UA response to fire suppressive activities. Cardiometabolic health markers were not affected in a statistically significant manner. These findings provide some evidence that AX supplementation may help mediate occupation-related inflammation and oxidative stress in response to high-intensity, short-duration exercise in firefighters. More research is warranted to determine if long-term supplementation can improve cardiometabolic risk in this population
Turbulent Spherical Flames in a Constant-Volume Fan-Stirred Vessel
No full textTurbulent flame speed is a measurement of the flame propagation rate in a turbulent flow field, combining chemical kinetics with fluid mechanics. Because turbulence is very influential to the flame propagation rate, it is a challenge to model turbulent combustion. The velocity field and relevant length scales of the test chamber flow must be determined to fully analyze the turbulent combustion. In spherically expanding turbulent flame speed experiments, wrinkles in the flame front form pockets and cause the flame to morph into a non-spherical shape. Because of this random non-spherical propagation, the experimental variability is higher for turbulent flame speed experiments than laminar flame speed experiments. The experiments in this study were conducted inside a fan-stirred flame vessel at Texas A&M University.
In this study, we aimed to verify the new heating system and reestablish the turbulent flame analysis method to prepare for future turbulent experiments. To verify the heating system, we performed laminar flame speed experiments and measured the pre-test temperature distribution with an array of thermocouples. Because of the interest in methane as a rocket propellant, the turbulent experiment matrix used methane as the chosen fuel. Methane-air turbulent flame speed experiments were performed for pressures of 1 and 5 atm; turbulent intensities of 1.4 and 2.8 m/s; and equivalence ratios of 0.8, 1.0, and 1.2. The data confirmed that increased turbulence increases the flame speed due to additional instability at the flame front and increased material transport due to turbulent flow. The experiments at higher turbulence intensity show an increased flame acceleration compared to the lower-turbulence tests. Turbulent flame speed increases with increased pressure due to stronger wrinkles increasing the surface area of the flame front
Targeted Therapeutic Strategies Against Triple-Negative and Metaplastic Breast Cancers
No full textBreast cancer is the second most common cause of cancer mortality in women in the United States. As a heterogenous disease, breast cancer is clinically classified by expression of estrogen receptor (ER), progesterone receptor (PR), and overexpression/amplification of human epidermal growth factor receptor 2 (HER2). Triple-negative breast cancer (TNBC), i.e., those not expressing ER, PR, or HER2, represent ~10-20% of all breast cancer cases, has the worst prognosis in comparison to ER+ or HER2+ breast cancers.
Gene profiling analysis has identified TNBC subtypes with unique molecular signatures that may be therapeutically targeted. Among the six known TNBC molecular subtypes, the mesenchymal subtype comprises 30% of all TNBCs and has the worst disease-free survival compared to other TNBC subtypes. Metaplastic breast cancer (MpBC) is a highly aggressive, and metastatic breast cancer malignancy that typically falls under the mesenchymal TNBC subtype, accounting for <5% of all invasive breast cancers. Patients with MpBC are generally diagnosed at a later age with a more aggressive disease, likely contributing to their dismal median survival of 8 months after metastasis. There are no standardized therapeutic options for patients with MpBC.
MpBC is characterized by one or more cell populations that have undergone metaplastic differentiation, i.e. cells convert from glandular to non-glandular morphology. MpBCs are enriched with epithelial-to-mesenchymal (EMT) and cancer stem cell (CSC) markers, with hyperactivation of phosphoinositide-3-kinase (PI3K) pathway and enhanced nitric oxide (NO) production. Patients diagnosed with metaplastic TNBC have a significantly worse prognosis compared to non-metaplastic TNBC (non-MpTNBC). Thus, the development of effective therapies for women with MpBC and non-MpTNBC represents a significant unmet clinical need.
The focus of my dissertation has been on evaluating novel therapeutic strategies in the preclinical setting to treat MpBC and non-MpTNBC. Using human breast cancer cell lines and patient-derived xenograft (PDX) models, my preclinical studies focused on evaluating targeted therapies, such as utilizing monoclonal antibodies against EGFR to treat TNBC, as well as combining PI3K and nitric oxide synthase (NOS) inhibitors to treat MpBC. I found that combined PI3K and NOS inhibition reverses EMT, decreases CSC populations, rendering MpBC tumors more chemosensitive
Shell Designs for Tailoring Dissolution Rates of Selective Laser Sintered Pharmaceutical Printlets
No full textWith the advent of personalized medicine, 'Just In Time' manufacturing of solid dosage pharmaceutical formulations is necessary, especially for a pediatric population that has a rapidly changing physiology. Solvent-free additive manufacturing is a promising approach that lends geometric and compositional flexibility to the process. The objective of this study is to investigate the behavior of shell-based designs, predominantly in their ability to affect dissolution rates of additively manufactured (AM) pharmaceutical pills/tablets (printlets). The primary motivation for this work lies in being able to leverage the tailorability of the AM process to control the geometric design of printlets and thus ���tune��� the eventual dissolution rates of these pills in a biological medium. For this, Selective Laser Sintering (SLS) was used to manufacture tablets using a powder mixture consisting of Carbamazepine (CBZ) as the active ingredient (drug), Kollidon VA64 as the excipient (polymer), and gold sheen as the agent with high laser absorptivity. A design of experiments was implemented to investigate the influence of compositional variance (% drug fraction) and geometrical differences (shell thickness) on the manufacturability and mechanical/pharmacokinetic performance of the printlets. Results show a general inverse relationship between structural integrity (as measured by pharmaceutical 'hardness' tests) and drug dissolution rates, as expected. Further, certain shell-breakup events were detectable via dissolution tests, as evidenced by sudden increases in dissolution magnitudes. FTIR and XRD analyses confirmed that there was no appreciable drug degradation. Altogether, this effort yielded a viable approach to 'tune' dissolution rates of certain solid dosage formulations