Characterizing uncertainty to manage risk in spacecraft development with application to structures and mass

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 101-104).Most space programs experience significant cost and schedule growth over the course of program development. Poor uncertainty management has been identified as one of the leading causes of program cost and schedule overruns. Traditional methods of uncertainty management are deterministic, using industry standards to predict worst-case inputs and designing systems accordingly. However, this method can lead to inefficient use of resources due to excessive need for redesign of subsystems when other subsystems evolve. Improvements in computational power now allow more sophisticated uncertainty analysis methods using probabilistic techniques. We propose a spacecraft design methodology that uses Monte Carlo and Gradient-based Sensitivity Analysis of system models to reduce program cost and schedule overruns by identifying design issues early when redesign is less expensive. We cover applications to mass budgets and finite element analysis to illustrate this methodology. The META complexity metric is a measure of uncertainty of a quantity of interest based on exponential entropy from information theory. The Trapped Energetic Radiation Satellite (TERSat) structural design process is used as a test case to evaluate the methodology, with a focus on the mass budget and finite element analysis. While traditionally mass budget uncertainty is treated with margins and contingencies, we present a way to model the mass of a system and its components as probability distributions using studies of historical data to model the means and standard deviations. We propagate the uncertainties in the mass budget analysis through the TERSat finite element model to determine the effects of the uncertainty on structural analysis outputs. We show that uncertainty analysis and sensitivity analysis can help to identify design issues early and guide the redesign and refine processes for spacecraft development.by Emily Baker Clements.S.M

Views of addiction etiology predict religious individuals’ willingness to help.

Abstract Views of addiction etiology predict religious individuals’ willingness to help. Emily Brady, Valerie Hoots, Joseph Barnet, and Andrea Clements, Department of Psychology, East Tennessee State University. Addiction to drugs and alcohol is an accrescent societal problem. Individuals with substance addiction face stigma in their daily lives, specifically from religious individuals as explored in this study. The stigma these religious individuals might portray could be related to their ideas on addiction etiology. The purpose of this project is to evaluate if different views of addiction etiology predict religious individuals’ willingness to help individuals with substance addition. Our hypothesis for this sample consists of two parts. (1) Religious individuals who hold the belief of a moral etiology of addiction will be less willing to help individuals with substance addiction. (2) Religious individuals who hold the ideology of a physical etiology of addiction will be less willing to help individuals with substance addiction. A survey, which contained the Addiction Attitudes and Beliefs Scale (AABS) and the Tobacco, Alcohol, Prescription medication, and other Substance use Tool (TAPS), was administered to a sample of 215 individuals recruited through social media advertising via Facebook and Reddit platforms, email, and East Tennessee State University’s SONA research portal. Results showed significance in beliefs of moral etiology and willingness to help across religious individuals. One limitation for this project is a lack of generalizability due to the majority of participants being female (73.6%) and white (92.1%). Another limitation is that the measure is based on self-report, and given the sensitivity on the topic, individuals may not be willing to report accurately

Prospective cohort study of body mass index and the risk of hospitalisation: findings from 246 361 participants in the 45 and Up Study.

OBJECTIVE: To quantify the risk of hospital admission in relation to fine increments in body mass index (BMI). DESIGN, SETTING AND PARTICIPANTS: Population-based prospective cohort study of 246 361 individuals aged X45 years, from New South Wales, Australia, recruited from 2006–2009. Self-reported data on BMI and potential confounding/mediating factors were linked to hospital admission and death data. MAIN OUTCOMES: Cox-models were used to estimate the relative risk (RR) of incident all-cause and diagnosis-specific hospital admission (excluding same day) in relation to BMI. RESULTS: There were 61 583 incident hospitalisations over 479 769 person-years (py) of observation. In men, hospitalisation rates were lowest for BMI 20–o25 kgm2 (age-standardised rate:120/1000 py) and in women for BMI 18.5–o25 kgm2 (102/1000 py); above these levels, rates increased steadily with increasing BMI; rates were 203 and 183/1000 py, for men and women with BMI 35–50 kgm2, respectively. This pattern was observed regardless of baseline health status, smoking status and physical activity levels. After adjustment, the RRs (95% confidence interval) per 1 kgm2 increase in BMI from X20 kgm2 were 1.04(1.03–1.04) for men and 1.04(1.04–1.05) for women aged 45–64; corresponding RRs for ages 65–79 were 1.03(1.02–1.03) and 1.03(1.03–1.04); and for agesX80 years, 1.01(1.00–1.01) and 1.01(1.01–1.02). Hospitalisation risks were elevated for a large range of diagnoses, including a number of circulatory, digestive, musculoskeletal and respiratory diseases, while being protective for just two—fracture and hernia. CONCLUSIONS: Above normal BMI, the RR of hospitalisation increases with even small increases in BMI, less so in the elderly. Even a small downward shift in BMI, among those who are overweight not just those who are obese, could result in a substantial reduction in the risk of hospitalisatio

Comparison of Skin Biomechanics and Skin Color in Puerto Rican and Non-Puerto Rican Women

Objective: Skin biomechanics are physical properties that protect the body from injury. Little is known about differences in skin biomechanics in racial/ethnic groups and the role of skin color in these differences. The purpose of this study was to determine the relationship between skin biomechanics (viscoelasticity, hydration) and skin color, when controlling for demographic and health-related variables in a sample of Puerto Rican and non-Puerto Rican women. Methods: We performed a secondary analysis of data from 545 women in a longitudinal, observational study of skin injury in Puerto Rico and the United States. Data included measures of skin viscoelasticity, skin hydration, skin color, demographic, and health-related variables. Skin color was measured by spectrophotometry (L* - lightness/darkness, a*- redness/greenness, b* - yellowness/blueness). The sample was 12.5% Puerto Rican, 27.3% non-Puerto Rican Latina, 28.8% Black, 28.6% White, and 2.8% Other. Results: Regression analyses showed that: 1) higher levels of skin viscoelasticity were associated with lower age, higher BMI, and identifying as non-Puerto Rican Latina as compared to Puerto Rican; (all p \u3c .001); and 2) higher levels of hydration were associated with lower L* values, higher health status, lower BMI, and identifying as non-Puerto Rican Latina, White, or Other as compared to Puerto Rican (all p \u3c .05). Conclusion: When adjusting for skin color, Puerto Rican women had lower viscoelasticity and hydration as compared to other groups. Puerto Rican women may be at long-term risk for skin alterations, including pressure injury, as they age or become chronically ill

Telehealth Services to Improve Nonadherence: A Placebo-Controlled Study

This is the publisher's version, also available electronically from http://online.liebertpub.com/doi/abs/10.1089/tmj.2006.12.289.The objective of this study was to test whether a telehealth intervention could improve the compliance with continuous positive airway pressure (CPAP) by patients with sleep apnea. These patients had been nonadherent for the initial 3 months of therapy even after receiving the initial standard and then supplemental audiotaped/videotaped patient education for adhering to CPAP nightly. The materials and methods included a randomized testing of experimental and placebo interventions. Interventions were delivered by nurses to two groups in their homes by telehealth over a 12-week period. The placebo intervention was used to control for Hawthorne effect, time and attention influences and the novelty of having telehealth in the home. Results following the telehealth interventions were that significantly more patients in the experimental group 1 (n = 10) than the placebo group 2 (n = 9) were adhering nightly to CPAP (χ2 = 4.55, p = 0.033). Group 1 patients reported greater satisfaction with their intervention. However, both groups rated telehealth delivery positively. The mean cost of each 20-minute telehealth visit was $30 while the total cost of the telehealth intervention for each patient was$420. These costs included telehealth equipment, initial installation, longdistance telephone charges, nurse salary, and intervention materials. Conclusions are that telehealth interventions are a potentially cost-effective service for increasing adherence to prescribed medical treatments. Replication studies with large samples and in other clinical groups are recommended

Validity of self-reported height and weight and derived body mass index in middle-aged and elderly individuals in Australia

Background: Body mass index (BMI) is an important measure of adiposity. While BMI derived from self-reported data generally agrees well with that derived from measured values, evidence from Australia is limited, particularly for the elderly. Methods: We compared self-reported with measured height and weight in a random sample of 608 individuals aged ≥45 from the 45 and Up Study, an Australian population-based cohort study. We assessed degree of agreement and correlation between measures, and calculated sensitivity and specificity to quantify BMI category misclassification. Results: On average, in males and females respectively, height was overestimated by 1.24cm (95% CI: 0.75-1.72) and 0.59cm (0.26-0.92); weight was underestimated by 1.68kg (-1.99-1.36) and 1.02kg (-1.24-0.80); and BMI based on self-reported measures was underestimated by 0.90kg/m2 (-1.09-0.70) and 0.60 kg/m2 (-0.75-0.45). Underestimation increased with increasing measured BMI. There were strong correlations between self-reported and measured height, weight and BMI (r=0.95, 0.99 and 0.95, respectively, p<0.001). While there was excellent agreement between BMI categories from self-reported and measured data (kappa=0.80), obesity prevalence was underestimated. Findings did not differ substantially between middleaged and elderly participants. Conclusions: Self-reported data on height and weight quantify body size appropriately in middle-aged and elderly individuals for relative measures, such as quantiles of BMI. However, caution is necessary when reporting on absolute BMI and standard BMI categories, based on self-reported data, particularly since use of such data is likely to result in underestimation of the prevalence of obesity

The Effects of Physical Exercise on Salivary microRNA Levels

Diagnosing concussions provides challenges for healthcare professionals due to current diagnostic protocols utilizing subjective input from patients. Recent studies have shown relationships between specific salivary microRNA levels and concussions, but it is unknown if this is due to concussive forces or physical exertion. Analysis of this distinction may contribute to further confirming the relationship of concussions and microRNA, improving techniques for objective assessments of concussion. Objective: To measure the effects of physical exertion through exercise on specific salivary microRNA. Methods: Twenty non-intercollegiate athletes (10:M, 10:F) were recruited for this case series. After ensuring the participants received a minimum of 6-hours of sleep the previous night, a baseline salivary sample was taken with the p-157: Nucleic acid stabilization kit (DNA Genotek; Ottawa, Canada). Participants completed a graded exercise test on a treadmill following the Bruce Protocol (VO2-Max). Participants began walking and investigators gradually increased the intensity at regular 3-minute intervals. Intensity increases were achieved by increasing both the speed and incline of the treadmill until maximal physical exhaustion was achieved. Physiological measures were measured to ensure safety. Immediately following the graded exercise test, a second salivary sample was collected. All samples were sent to Quadrant Biosciences for analysis and NextGen sequencing. Upon receiving normalized data from Quadrant Biosciences (Syracuse, NY), investigators performed paired t-tests (α Conclusions: The findings of this study reinforce the relationship between 6 salivary microRNA and concussions. The body of evidence of the aforementioned salivary microRNA’s relationship to concussions is strengthened as no significant differences were found, indicating the concentration of the 6 salivary microRNA are not affected by exercise.https://digitalcommons.odu.edu/gradposters2020_healthsciences/1001/thumbnail.jp

Pitt Political Review: GSPIA Edition (Spring 2011, Volume 3)

This volume of the Pitt Political Review: GSPIA Edition includes "Legal and Societal Injustice: Gender Inequality and Land Rights in Tanzania" and "The Transformation of Philanthropy in Sub-Saharan Africa: from Traditional Practices to the Establishment of Grantmaking Foundations." The aim of "Legal and Societal Injustice: Gender Inequality and Land Rights in Tanzania" is to increase awareness of the problems surrounding land rights and gender inequality in Tanzania's Karagwe District. "The Transformation of Philanthropy in Sub-Saharan Africa: from Traditional Practices to the Establishment of Grantmaking Foundations" discusses the effectiveness of African foundations in development over the long-term

Integration and Testing of the Nanosatellite Optical Downlink Experiment

CubeSat sensor performance continues to improve despite the limited size, weight, and power (SWaP) available on the platform. Missions are evolving into sensor constellations, demanding power-efficient high rate data downlink to compact and cost-effective ground terminals. SWaP constraints onboard nanosatellites limit the ability to accommodate large high gain antennas or higher power radio systems along with high duty cycle sensors. With the growing numbers of satellites in upcoming scientific, defense, and commercial constellations, it is difficult to place the high-gain burden solely on the ground stations, given the cost to acquire, maintain, and continuously operate facilities with dish diameters from 5 meters to 20 meters. In addition to the space and ground terminal hardware challenges, it is also increasingly difficult and sometimes not possible to obtain radio frequency licenses for CubeSats that require significant bandwidth. Free space optical communications (lasercom) can cost-effectively support data rates higher than 10 Mbps for similar space terminal SWaP as current RF solutions and with more compact ground terminals by leveraging components available for terrestrial fiber optic communication systems, and by using commercial amateur-astronomy telescopes as ground stations. We present results from the flight unit development, integration, and test of the Nanosatellite Optical Downlink Experiment (NODE) space terminal and ground station, scheduled for completion by summer of 2017. NODE’s objective is to demonstrate an end-to-end solution based on commercial telecommunications components and amateur telescope hardware that can initially compete with RF solutions at \u3e10 Mbps and ultimately scale to Gbps. The 1550 nm NODE transmitter is designed to accommodate platform pointing errors \u3c 3 degrees. The system uses an uplink beacon from the ground station and an onboard MEMS fine steering mirror to precisely point the 0.12 degree (2.1 mrad) 200 mW transmit laser beam toward the ground telescope. We plan to downlink to an estalblished ground terminal at the Jet Propulsion Laboratory (JPL) Optical Communications Telescope Laboratory (OCTL) ground station as well as the new low-cost 30 cm amateur telescope ground station design to reduce overall mission risk. Moving beyond our initial laboratory prototyping captured in Clements et al. 2016 we discuss recent progress developing and testing the flight electronics, opto-mechanical structures, and controls algorithms, including demonstration of a hardware-in-the-loop test of the fine pointing system, for both the space and ground terminals. We present results of over-the-air testing of the NODE system, as we advance from benchtop to hallway to rooftop demonstrations. We will present thermal and environmental test plans and discuss experimental as well as expected results