EFFECT OF ISOTHERMAL AGING ON SAC305 HARMONIC VIBRATION DURABILITY

The effect of isothermal aging on the harmonic vibration durability of Sn3.0Ag0.5Cu solder interconnects is examined. Printed wiring assemblies with daisy-chained leadless chip resistors (LCRs) are aged at 125°C for 0, 100, and 500 hours. These assemblies are instrumented with accelerometers and strain gages to maintain the same harmonic vibration profile in-test, and to characterize PWB behavior. The tested assemblies are excited at their first natural frequencies until LCRs show a resistance increase of 20%. Dynamic finite element models are employed to generate strain transfer functions, which relate board strain levels observed in-test to respective solder strain levels. The transfer functions are based on locally averaged values of strains in critical regions of the solder and in appropriate regions of the PWB. The vibration test data and the solder strains from FEA are used to estimate lower-bound material fatigue curves for SAC305 solder materials, as a function of isothermal pre-aging.

Hauntings

The thesis paper is about the process of creating and directing Hauntings, a dance theater work, performed in the 2016 MFA Spring Thesis Concert. The concert was shared with Curtis Stedge, fellow cohort and MFA candidate in the Department of Theater, Dance and Performance Studies at the University of Maryland, College Park. This document is meant to accompany the archival footage of the dance. Hauntings is a moving lyric poem depicting themes and motifs of the emotional landscape of its characters. It is a time-less world rendering the complexities of the psyche and soul. Love, obsession, loss, and nostalgia emerge as Smith and her fellow artists represent characters struggling with impermanence and mortality. The work is seeped in symbolism and metaphor. The dances/scenes draw inspiration from the music of Chopin, Liszt, Stravinsky, Charles Trenet, Rina Ketty, and poetry by John Keats, Sylvia Plath, Ted Hughes, W.B Yeats, and Claire Clemons Cowan.

Quantifying the impacts of urban wind sheltering on the building energy consumption

Common building energy modeling approaches do not account for the influence of surrounding neighborhood on the energy consumption patterns. This thesis develops a framework to quantify the neighborhood impact on a building energy consumption based on the local wind flow. The airflow in the neighborhood is predicted using Computational Fluid Dynamics (CFD) in eight principal wind directions. The developed framework in this study benefits from wind multipliers to adjust the wind velocity encountering the target building. The input weather data transfers the adjusted wind velocities to the building energy model. In a case study, the CFD method is validated by comparing with on-site temperature measurements, and the building energy model is calibrated using utilities data. A comparison between using the adjusted and original weather data shows that the building energy consumption and air system heat gain decreased by 5% and 37%, respectively, while the cooling gain increased by 4% annually.

An Investigation of Child and Adolescent Dental Sealant Predictors, NHANES 2011-2012

Objective: To examine sociodemographic and dental factors for associations with dental sealant placement in children and adolescents aged 6-18 years old. Methods: Secondary data analysis of 2011-2012 NHANES data was conducted. Multiple logistic regression models were used to assess relationships between predictor variables and sealant presence. Results: More than a third (37.1%) of children and adolescents have at least one sealant present; 67.9% of children compared with 40.4% of adolescents. Racial/ethnic differences exist, with Non-Hispanic black youth having the lowest odds of having sealants. Sealant placement odds vary by presence of dental home; the magnitude of the odds varies by age group. Those with untreated decay have lower odds of having sealants than those who do not have untreated decay (child OR: 2.6, 95% CI: 1.83-3.72; adolescent OR: 3.9, 95% CI: 2.59-6.07). Conclusion: Disparities exist in odds of sealant prevalence across racial/ethnic groups, income levels, and dental disease and visit characteristics. Further research is necessary to understand the reasons for these differences and to inform future interventions.

Heat Transfer Measurements in a Supersonic Film Flow

This thesis presents measurements of wall heat flux and flow structure in a canonical film cooling configuration with Mach 2.3 core flow in which the coolant is injected parallel to the wall through a two-dimensional louver. Four operating conditions are investigated: no film (i.e. flow over a rearward-facing step), subsonic film, pressure-matched film, and supersonic film. The overall objective is to provide a set of experimental data with well characterized boundary conditions that can be used for code validation. The results are compared to RANS and LES simulations which overpredict heat transfer in the subsonic film cases and underpredict heat transfer in supersonic cases after film breakdown. The thesis also describes a number of improvements that were made to the experimental facility including new Schlieren optics, a better film heater, more data at more locations, and a verification of the heat flux measurement hardware and data reduction methods.

The Effect of Package Geometry on Moisture Driven Degradation of Polymer Aluminum Capacitors

Polymer aluminum electrolytic capacitors were introduced to provide an alternative to liquid electrolytic capacitors. Polymer electrolytic capacitor electric parameters of capacitance and ESR are less temperature dependent than those of liquid aluminum electrolytic capacitors. Furthermore, the electrical conductivity of the polymer used in these capacitors (poly-3,4ethylenedioxithiophene) is orders of magnitude higher than the electrolytes used in liquid aluminum electrolytic capacitors, resulting in capacitors with much lower equivalent series resistance which are suitable for use in high ripple-current applications. The presence of the moisture-sensitive polymer PEDOT introduces concerns on the reliability of polymer aluminum capacitors in high humidity conditions. Highly accelerated stress testing (or HAST) (110ºC, 85% relative humidity) of polymer aluminum capacitors in which the parts were subjected to unbiased HAST conditions for 700 hours was done to understand the design factors that contribute to the susceptibility to degradation of a polymer aluminum electrolytic capacitor exposed to HAST conditions. A large scale study involving capacitors of different electrical ratings (2.5V – 16V, 100µF – 470 µF), mounting types (surface-mount and through-hole) and manufacturers (6 different manufacturers) was done to determine a relationship between package geometry and reliability in high temperature-humidity conditions. A Geometry-Based HAST test in which the part selection limited variations between capacitor samples to geometric differences only was done to analyze the effect of package geometry on humidity-driven degradation more closely. Raman spectroscopy, x-ray imaging, environmental scanning electron microscopy, and destructive analysis of the capacitors after HAST exposure was done to determine the failure mechanisms of polymer aluminum capacitors under high temperature-humidity conditions.

Assessment and Life-Cycle Analysis of Recycled Materials for Sustainable Highway

Recycled materials replacing part of virgin materials in highway applications has shown great benefits to the society and environment. Beneficial use of recycled materials can save landfill places, sparse natural resources, and energy consumed in milling and hauling virgin materials. Low price of recycled materials is favorable to cost-saving in pavement projects. Considering the availability of recycled materials in the State of Maryland (MD), four abundant recycled materials, recycled concrete aggregate (RCA), recycled asphalt pavement (RAP), foundry sand (FS), and dredged materials (DM), were studied. A survey was conducted to collect the information of current usage of the four recycled materials in States’ Department of Transportation (DOTs). Based on literature review, mechanical and environmental properties, recommendations, and suggested test standards were investigated separately for the four recycled materials in different applications. Constrains in using these materials were further studied in order to provide recommendations for the development of related MD specifications. To measure social and environmental benefits from using recycled materials, life-cycle assessment was carried out with life-cycle analysis (LCA) program, PaLATE, and green highway rating system, BEST-in-Highway. The survey results indicated the wide use of RAP and RCA in hot mix asphalt (HMA) and graded aggregate base (GAB) respectively, while FS and DM are less used in field. Environmental concerns are less, but the possibly low quality and some adverse mechanical characteristics may hinder the widely use of these recycled materials. Technical documents and current specifications provided by State DOTs are good references to the usage of these materials in MD. Literature review showed consistent results with the survey. Studies from experimental research or site tests showed satisfactory performance of these materials in highway applications, when the substitution rate, gradation, temperature, moisture, or usage of additives, etc. meet some requirements. The results from LCA revealed significant cost savings in using recycled materials. Energy and water consumption, gas emission, and hazardous waste generation generally showed reductions to some degree. Use of new recycled technologies will contribute to more sustainable highways.

Not Very Far, But Not Close Either

In “Not Very Far, But Not Close Either”, formal lyrics, free verse poems, and translations from the first century Latin of Martial and Horace explore ideas of distance: the physical distance between bodies, the psychological distance between (and within) human minds, the temporal distance between past, present, and future. A speaker considers his relationship to the image in a foggy bathroom mirror, another to the bird living behind his house, another to the ghosts of his dead parents, whom he asks to watch over a beloved and recently departed child. In exploring these distances—between self and semblance, man and bird, living and dead—the speakers of these poems attempt to locate themselves the only way we can ever locate anything: in relation to something—or someone—else. In this spirit, the manuscript incorporates not only translations and original poems, but poems adapted from and taken after the work of poets who have explored similar themes, questions, and concerns.

PARTICIPATORY PLANNING PILOT CASE STUDY IN CHINA: REALITY, CHALLENGES & LESSONS LEARNED FROM US

Urban planning in China is in a period of change, where participatory planning may supplement the traditional planning system. Since the beginning of the 21st century, several pilot participatory planning projects have responded to the new challenge. The author collected eight cases from the Chinese planning institution to explore the possible models of and barriers to participatory planning. On the other hand, public participation has been a concrete component of planning and implementation process in the United States. The author will also elaborate on one practical case of the planning process in the United States to compare the two countries on planning methods and barriers.

The Ballad of Ravolo Soto

Set in 2008 Puerto Rico, this novel aims to explore the relationship between constructed masks of personal identity, the increasingly interconnected nature of community, and their confluence in the worlds of politics, media, social activism, and business through a narrative examination of the ways in which three primary characters affect the lives of those around them. Jaime, a meditative young man with a penchant for planes, comes home to find the power shut off and his drug-addict mother gone. His best friend, Yarique, a disaffected stoner with a false sense of machismo, becomes an overnight sensation after an escalating series of violent run-ins with his abuelo’s neighbor. Ravolo Soto, a reclusive pitorro distiller, drinks to keep The Other in check, but takes off into the jungles of Lares, hiding out in his father’s mountain shack, after a violent encounter with the police leaves one officer dead.

The Cameraman

In this novel segment titled The Cameraman, a fictionalized version of silent film icon Buster Keaton grapples with his newfound role at big picture studio MGM, which has stripped him of his creative influence. For the first time in his career, Buster must operate with little authority in what was the beginning of the Hollywood studio system. This excerpt’s narrative present takes place in New York City in 1928 during the filming of The Cameraman, with flashbacks to Los Angeles in 1927, prior to the filming. The close third-person narrator examines what it means for Buster to be famous, to be an artist, and what happens when public and private identities are conflated.

Green Circle

The speaker in this collection explores the quotidian experiences of daily life. Often restless, she attempts to find beauty or significance in these occurrences. The speaker looks into her personal history in a variety of locations. Many of the poems are set in Washington DC, California, Massachusetts and South Korea and as such, they explore the intersection of memory and present reality.

Octavia's Brood: Riding the Ox Home

Octavia’s Brood: Riding the Ox Home was an evening-length dance concert performed October 15 and 16, 2015, at the Clarice Smith Performing Arts Center in partial fulfillment of the Master of Fine Arts degree from the University of Maryland’s School of Theatre, Dance, and Performance Studies. Inspired by the prophetic envisioning of Harriet Tubman and Octavia Butler, it explores race, otherness, ownership and story-telling from the perspective of Black women’s dancing bodies and histories. Borrowing its title from Octavia’s Brood: Science Fiction Stories from Social Justice Movements, it utilizes visionary story-telling, where science fiction provides a foundation for imagining socially just worlds inhabited by richly diverse protagonists. This paper is a written account of the research by which I composed this immersive dance event, leaping back and forth through time, landing between antebellum Maryland of the mid-1800s and an unknown place at an unknown date of a foreseen future.

Examining the Association between Acculturation and Hypertension among Asian Americans in the Washington D.C. Metropolitan Area

Objective: To evaluate the association between Acculturation and hypertension among Asian Americans in the Washington, D.C. metropolitan area. Methods: A cross-sectional study was conducted of 600 Chinese, Korean, and Vietnamese adults. Logistic regression was used to investigate the relationship between acculturation variables (years in the U.S., self-rated acculturation, self-rated English fluency) and hypertension, determined from a mean of 3 blood pressure readings taken on site. Results: Compared to those who resided in the U.S. for 0-5 years, individuals who resided for 6-10 years were about 60% less likely to have hypertension (aOR= 0.36; 95% CI: 0.12, 1.05; p-value=0.06). No significant association was observed between self-rated identity and hypertension. Compared to those with poor English fluency, those who speak “so-so” English have increased odds of hypertension (aOR=1.57; 95%CI: 0.93, 2.64; p-value= 0.09). Disaggregated analysis was conducted for Asian American subgroups, which showed differences in trends of acculturation and hypertension. Conclusion: Findings suggest an association between acculturation and hypertension, guiding future studies to investigate further into these observed effects. Some subgroup differences were observed among Asian American subgroups, potentially suggesting a subgroup-focused intervention.

Fully Anisotropic Solution of the Three Dimensional Boltzmann Transport Equation

The development of accurate modeling techniques for nanoscale thermal transport is an active area of research. Modern day nanoscale devices have length scales of tens of nanometers and are prone to overheating, which reduces device performance and lifetime. Therefore, accurate temperature profiles are needed to predict the reliability of nanoscale devices. The majority of models that appear in the literature obtain temperature profiles through the solution of the Boltzmann transport equation (BTE). These models often make simplifying assumptions about the nature of the quantized energy carriers (phonons). Additionally, most previous work has focused on simulation of planar two dimensional structures. This thesis presents a method which captures the full anisotropy of the Brillouin zone within a three dimensional solution to the BTE. The anisotropy of the Brillouin zone is captured by solving the BTE for all vibrational modes allowed by the Born Von-Karman boundary conditions.