Improved methodology for measuring the emissivity of metal powders

A specially designed chamber is proposed to accurately measure the emissivity coefficient of metal powders over a wide temperature range using an infrared (IR) camera. This measurement setup significantly reduces the oxidation of metal powders during heating to high temperatures. As a result, it enables precise determination of the actual emissivity values, which is crucial for accurate IR camera calibration when studying sintering or melting processes in additive manufacturing.Mechanical Engineerin

Switch-mode active EMI filtering

Power converters often require EMI filtering which usually involves bulky passive components. Active EMI filters (AEF) can reduce size but incur heavy losses in their linear amplifiers when designed to filter large ripple currents. This work proposes two different approaches for active EMI filters with a switch-mode amplifier to achieve reduced size and low loss penalty: a high-frequency AEF and a synchronous AEF. The high frequency AEF features a switching amplifier operating at 31 MHz to keep its own EMI out of the regulated EMI range. A fractional-order filtering technique is used to design the feedback compensation loop, achieving a high loop gain and thus high current attenuation of 30 dB from the active circuit at the dc-dc boost fundamental frequency of 150 kHz, while consuming only 1W for an output power of 120 W. The proposed high frequency AEF is compared to a passive LC filter for the same application and is shown to have a volume that is eight times smaller than that of the size-optimized LC filter. The proposed synchronous AEF, in contrast to the high-frequency AEF and other typical AEF circuits, does not use feedback, thereby avoiding the bandwidth and attenuation limitations associated with feedback stability. This AEF also has very low energy storage requirements compared to passive EMI filters and achieves very high efficiency compared to typical AEF circuits with linear amplifiers. Furthermore, it can simplify circuitry by directly utilizing the same gate signals as the main power converter. Additionally, the AEF does not interfere with the closed-loop controller of the main converter, a common challenge in the design of passive EMI filters or feedback-based AEFs. We demonstrated the proposed synchronous AEF through simulations and hardware prototypes for both a boost power factor correction (PFC) and a dc-dc boost converter, operating at different current control modes and switching frequencies. The AEFs achieved high differential-mode current attenuation from 20 dB to 65 dB at different harmonic frequencies and provided significant common-mode current attenuation of over 29 dB by injecting a common-mode current that largely cancels the common-mode current generated by the boost PFC. Additionally, the volumes of the synchronous AEFs are significantly smaller than those of conventional passive LC filters — approximately 1/16 to 1/32 of the size-optimized LC filter. They also have very low power consumption, with a maximum efficiency penalty of less than < 0.7% when filtering high current ripple ratios of up to R = 100% from the boost PFC, in contrast to AEFs based on linear amplifiers. Both AEF proposals present very promising approach to (mostly) replace the conventional LC filter and linear-mode AEFs for smaller volume and high efficiency. At the end of this work, we present the design and implementation of two ultra-fast isolated gate drivers with 2-8 ns propagation delays, one of which will be used to design the gate driver of the high-frequency AEF. This will help improve the compensator bandwidth of the high-frequency AEF, which is limited by propagation delays primarily caused by the bootstrap gate driver and the comparator in the previous design.Electrical and Computer Engineerin

Physical activity participation, physical fitness, psychosocial characteristics and academic achievement among adolescents

In this dissertation we will examine the effects of physical activity (PA) and physical fitness (PF) on academic achievement (AA), mediated by the psychosocial constructs of grit, self-efficacy (SE) and modality of physical education (PE). Given the known relationship between PF and AA (Castelli, Hillman, Buck & Erwin, 2007) the purpose of study one was to determine how psychosocial characteristics of grit and SE contribute to this relationship. Students completed the Perceptions of Barriers to PA (Motl, 2000) and the Short Grit Scale (Duckworth, Peterson & Mathews, 2007) at the beginning and end of the school year. PF was measured using the FitnessGram® test (Cooper Institute; Dallas, TX.). Results revealed students with higher grit (r [subscript s] = 0.21, P < 0.001) and had less school absences (r [subscript s] = -0.35, P < 0.001) performed better on AA (β = 0.13, P < 0.01and β = -0.35, P < 0.001, respectively). Despite PA’s connection to optimized cognitive functioning, the results among adolescents have been equivocal based on PA sampling technique (Tremblay, Inman, & Williams, 2000; Donnelly et al., 2016). The purpose of study two was to determine if objectively measured PA is related to AA in a low SES school setting and whether the psychosocial characteristics of grit and SE mediate this relationship. Student PA was sampled across four ten-hour periods. Results revealed that PF accounted for 5.8% of the variance in AA suggesting a non-significant relationship among the sample population. In study three a PE alternative (APE) was compared to traditional PE (TPE) examining if modality moderates the relationship of PF, AA, and grit. APE was a running club offered at low SES schools in the district as an option to TPE. Study methods were similar to previous studies, with the added independent variable of PE modality (traditional or APE). Results of MANOVA revealed despite the two populations similarity at onset for PF and grit. There was a 6.5% variance in AA that was accounted for by modality to the benefit of the APE (Pillais’ Trace = .065, F (14,700), p <.01 with η² = .065).Curriculum and Instructio

Effects of key, controversial dietary factors on inflammation, glycemic control and expression of circulating microRNAs, novel biomarkers with identified signatures in cardiometabolic disease

Dysregulation of metabolism is a common factor across obesity, type 2 diabetes (T2D) and cardiovascular disease (CVD) and disturbs metabolic pathways that are tightly regulated at the genetic level. At this level, post-transcriptional modifiers known as microRNA are aberrantly expressed in a state of dysregulation, released into circulation and contribute to the development and severity of chronic conditions. Although a number of dietary factors influence cardiometabolic health, it is unclear whether they do so through altered miRNA expression. Therefore, we aimed to examine the impact of consuming 1) diets with and without fresh, lean beef; 2) energy-restriction diets containing higher- vs normal-protein, animal source foods; and 3) breakfasts varying in protein content on 12 a priori circulating miRNA associated with cardiometabolic disease risk in healthy, overweight populations. In our first study, we aimed to identify whether a healthy dietary pattern containing fresh, lean beef influences the expression of miRNA compared to a healthy dietary pattern void of fresh, lean beef. Further, this study sought to understand the potential associations between changes in circulating miRNA expressions and markers of cardiometabolic disease risk. The expression of miR-15b-5p was higher following the consumption of a diet containing 2 servings of fresh, lean beef/d vs. a diet void of fresh lean beef. In our second study, we aimed to identify whether an energy-restriction, higher-protein diet, containing approximately 4 servings of fresh, lean beef alters expression of circulating miRNA selected based on their recorded signatures in obesity, T2D and CVD compared to an energy-restriction, normal protein diet containing approximately 1 serving of fresh, lean beef. No differences in miRNA expression were detected between diets. The third and final study sought to examine whether the consumption of breakfast, varying in protein quantity, alters the expression of miRNA associated with cardiometabolic disease risk compared to skipping breakfast. The habitual consumption of HP breakfast resulted in higher expression of miR-126-3p and miR-223-3p compared to breakfast skipping. Collectively, these studies aid in informing future dietary recommendations concerning the impact of key dietary factors on metabolic disease risk and assist in understanding the contribution of miRNA activity in this context.Nutritional Science

An observational study on fathers’ self-disclosure and vulnerability in conversations with their adolescent children

Self-disclosure and vulnerability are two constructs that play an important role in relational intimacy. To date, almost no research investigates if or how fathers engage in self-disclosure or express vulnerability with their adolescent children. This study addresses this gap by providing a qualitative, thematic account of paternal self-disclosure and vulnerability obtained through observations of fathers engaging in conversations with their adolescent children. Results from this study suggest that, in certain contexts, fathers do self-disclose and express vulnerability with their adolescent children. Additionally, results from this study provide four distinct dimensions of self-disclosure that can be used for further research investigating individuals’ self-disclosure tendencies. Finally, several themes engorged from the data that demonstrate possible methods fathers can use to engage in self-disclosure and vulnerability with their adolescent children.Educational Psycholog

A comparative analysis of cost and schedule performance in public and private construction projects

This research investigates the cost and schedule performance differences between construction projects from public and private organizations, emphasizing the significance of effective management for successful project execution. Utilizing data from the Construction Industry Institute (CII), the study analyzes 481 projects from both sectors through statistical methods and benchmarking techniques. The analysis did not find statistically significant differences in the overall cost and schedule performance between public and private projects in the dataset, with an average cost factor of 0.99 for both and average schedule factors of 1.08 for public projects and 1.06 for private projects. However, a few specific subsets of projects did show statistically significant differences. For instance, projects with budgets over 100 million dollars and modernization projects with budgets under 50 million dollars demonstrated that private projects outperformed public projects, showing better performance and greater consistency in term of cost performance. Thus, the study's findings indicate that while both public and private sectors generally manage costs effectively, schedule management poses a more significant challenge across the board. Public projects, in particular, show higher variability in scheduling, often leading to delays.Civil, Architectural, and Environmental Engineerin

Transparency Under Takeover: Financial Ramifications of the TEA Takeover of Houston ISD

This paper examines the financial transparency and accountability practices before and after the 2023 state takeover of the Houston Independent School District (HISD). Superintendent Mike Miles and his Board of Managers reallocated critical district resources towards troubling new “priorities,” while the district was facing a sizable deficit. Parents and community members raised concerns about the district’s transparency and accountability practices, which sparked backlash throughout the first year and a half of the takeover. Using a historical case study methodology (Widdersheim, 2018) and qualitative document analysis (Bowen, 2009), we examined school board meeting content, online news articles, and state policy to analyze the financial changes that HISD underwent as they transitioned to a state appointed superintendent and school board during the first two years of the state takeover. Findings suggest patterns of concerning fiscal practices under the post-takeover administration. We make recommendations for local and state educational agencies that may improve financial transparency and solvency during state takeovers.Educatio

Negotiating Primacy: Strategic Stability, Superpower Arms Control, and the End of the Cold War (Spring 2025)

The United States successfully used the concept of strategic stability to tip the nuclear balance against the Soviet Union during the Strategic Arms Reduction Talks (START) of the 1980s and early 1990s. Both superpowers sought to employ strategic stability to legitimate their objectives for START, but differed significantly over how it should be operationalized in an arms control agreement. Despite appearances, the 1991 START I treaty did not reflect the reconciliation of these two divergent views of strategic stability, but rather the triumph of Washington’s conception over Moscow’s, thereby laying the groundwork for arms control in an era of US military primacy.LBJ School of Public Affair

On the Doppelperfekt in German dialects

This paper examines the periphrastic tense formation known as Doppelperfekt (DPF), used in various non-standard German dialects. The DPF, also referred to as doppelte Perfektformen, gesteigertes Perfekt, Perfekt II, and Ultraperfekt, involves adding an additional Partizip II of the auxiliary verb to a Perfekt construction. Examples include "Ich habe dem Kunden den Brief geschickt gehabt!" and "Er ist mit dem Zug angekommen gewesen." Historically marginalized in grammar books, the DPF's usage has often been overlooked. This study emphasizes the importance of non-standard tenses like the DPF for understanding language history and usage evolution. It explores the DPF's attributes, usage, history, and theorized origins, aiming to position the DPF within the German tense system both historically and in contemporary language.Germanic Studie

Tectonic and magmatic processes during extension in planetary lithospheres : rifting, spreading, delamination, and recycling on Earth and Venus

The contrast between Earth and Venus exemplifies how similar planets can dramatically diverge in their evolutionary pathways and highlights the importance of developing a theoretical framework for the origins of planetary diversity. A key aspect of planetary tectonic systems is how the lithosphere responds to driving forces such as the upwelling or downwelling of material in the mantle, especially for extensional systems. On Earth, the processes underpinning continental break-up are poorly understood despite decades of study. In this dissertation, I present a synthesis of numerical modeling, high resolution seismic experiments, and ophiolite geology to reveal how the mantle lithosphere controls the transition from continental rifting to seafloor spreading. The study finds that the transition is controlled by high temperature shear zones in the mantle and by a change in stress from gravitational collapse to buoyant upwelling of a melt-rich mantle. On Venus, extensional systems form a global network across the planet, superficially similar to seafloor spreading on Earth. Using the same numerical modeling methods, I present work showing that the global rift network on Venus is not consistent with the systemic formation of new crust. The exception to this are certain coronae along Venus’ rifts that may represent localized recycling of the crust driven by the delamination of eclogite roots at the base of the crust. Finally, we test that hypothesis for rift-embedded coronae formation and link their formation to global geodynamics, highlighting that Venus’ regional tectonics is highly sensitive to thermal conditions in the lithosphere and mantle. All of this shows the importance of understanding regional tectonics and local lithosphere dynamics, since they can alter or even overprint the expected signal from global geodynamics. The contrast between Earth and Venus also suggests that extension on Earth is dominated by slab-pull, slab-suction, and other far-field stresses associated with downwelling while Venus is dominated by mantle upwelling, despite regional variations. Because the behavior of Venus’ lithosphere is primarily a result of an elevated geothermal profile, this indicates that climate-tectonic coupling is the engine for terrestrial planetary diversity.Earth and Planetary Science