Effects of thermal cycling on epoxy bonded materials

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 21-22).Thermal cycling is a concern to those who use epoxy as an adhesion in space applications due to the mechanical and thermal properties of both the epoxy and adhered materials. These properties include the thermal expansion coefficient, a, and the stress at which the epoxy will yield fracture. An experiment was carried out to find out if failure would occur by thermal cycling of epoxy bonded components in the propulsion components of a small satellite. Failure did not occur due to shear stress attributed to the thermal expansion coefficient but unexpectedly to the liquefaction of epoxy in 3 of the 6 samples. The samples with thicker epoxy layers failed in contrast to the thinner epoxy layer samples. Overall, thermal cycling is still a concern for failure of the epoxy bond.by Michelle Burroughs.S.B

Master of Science

thesisFlying rotorcraft, such as helicopters and quadrotors, can gather useful information without the need for human presence, but they consume a great deal of power and have limited on-board energy resources. Our work aims to provide a passive perching mechanism so that a rotorcraft is able to grip branch-like perches and resist external wind disturbances, using only the weight of the rotorcraft to maintain the grip. Deviating from previous bio-inspired approaches, in this thesis, we propose a mechanism that incorporates a Sarrus linkage to convert the weight of the rotorcraft into grip force. We provide an analysis of the mechanism's kinematics, we present the static force equations that describe how the weight of the rotorcraft is converted into grip force onto a cylindrical perch, and we describe how grip forces relate to the ability to reject horizontal disturbances such as wind gusts. The mechanism is then optimized for use on a single perch size, and then for a range of perch sizes. We conclude by constructing a prototype mechanism, and we demonstrate its use with a remote-controlled helicopter

Using Focus Groups in the Consumer Research Phase of a Social Marketing Program to Promote Moderate-Intensity Physical Activity and Walking Trail Use in Sumter County, South Carolina

INTRODUCTION: The use of social marketing approaches in public health practice is increasing. Using marketing concepts such as the "four Ps" (product, price, place, and promotion), social marketing borrows from the principles of commercial marketing but promotes beneficial health behaviors. Consumer research is used to segment the population and develop a strategy based on those marketing concepts. In a community-based participatory research study, 17 focus groups were used in consumer research to develop a social marketing program to promote walking and other moderate-intensity physical activities. METHODS: Two phases of focus groups were conducted. Phase 1 groups, which included both men and women, were asked to respond to questions that would guide the development of a social marketing program based on social marketing concepts. Phase 1 also determined the intervention's target audience, which was irregularly active women aged 35 to 54. Phase 2 groups, composed of members of the target audience, were asked to further define the product and discuss specific promotion strategies. RESULTS: Phase 1 participants determined that the program product, or target behavior, should be walking. In addition, they identified price, place, and promotion strategies. Phase 2 participants determined that moderate-intensity physical activity is best promoted using the term exercise and offered suggestions for marketing walking, or exercise, to the target audience. CONCLUSION: There have been few published studies of social marketing campaigns to promote physical activity. In this study, focus groups were key to understanding the target audience in a way that would not have been accomplished with quantitative data alone. The group discussions generated important insights into values and motivations that affect consumers' decisions to adopt a product or behavior. The focus group results guided the development of a social marketing program to promote physical activity in the target audience in Sumter County, South Carolina

Synchronous shedding of multiple bat paramyxoviruses coincides with peak periods of Hendra virus spillover

Within host-parasite communities, viral co-circulation and co-infections of hosts are the norm, yet studies of significant emerging zoonoses tend to focus on a single parasite species within the host. Using a multiplexed paramyxovirus bead-based PCR on urine samples from Australian flying foxes, we show that multi-viral shedding from flying fox populations is common. We detected up to nine bat paramyxoviruses shed synchronously. Multi-viral shedding infrequently coalesced into an extreme, brief and spatially restricted shedding pulse, coinciding with peak spillover of Hendra virus, an emerging fatal zoonotic pathogen of high interest. Such extreme pulses of multi-viral shedding could easily be missed during routine surveillance yet have potentially serious consequences for spillover of novel pathogens to humans and domestic animal hosts. We also detected co-occurrence patterns suggestive of the presence of interactions among viruses, such as facilitation and cross-immunity. We propose that multiple viruses may be interacting, influencing the shedding and spillover of zoonotic pathogens. Understanding these interactions in the context of broader scale drivers, such as habitat loss, may help predict shedding pulses of Hendra virus and other fatal zoonoses

Using Focus Groups in the Consumer Research Phase of a Social Marketing Program to Promote Moderate-Intensity Physical Activity and Walking Trail Use in Sumter County, South Carolina

IntroductionThe use of social marketing approaches in public health practice is increasing. Using marketing concepts such as the “four Ps” (product, price, place, and promotion), social marketing borrows from the principles of commercial marketing but promotes beneficial health behaviors. Consumer research is used to segment the population and develop a strategy based on those marketing concepts. In a community-based participatory research study, 17 focus groups were used in consumer research to develop a social marketing program to promote walking and other moderate-intensity physical activities. MethodsTwo phases of focus groups were conducted. Phase 1 groups, which included both men and women, were asked to respond to questions that would guide the development of a social marketing program based on social marketing concepts. Phase 1 also determined the intervention’s target audience, which was irregularly active women aged 35 to 54. Phase 2 groups, composed of members of the target audience, were asked to further define the product and discuss specific promotion strategies. ResultsPhase 1 participants determined that the program product, or target behavior, should be walking. In addition, they identified price, place, and promotion strategies. Phase 2 participants determined that moderate-intensity physical activity is best promoted using the term exercise and offered suggestions for marketing walking, or exercise, to the target audience.ConclusionThere have been few published studies of social marketing campaigns to promote physical activity. In this study, focus groups were key to understanding the target audience in a way that would not have been accomplished with quantitative data alone. The group discussions generated important insights into values and motivations that affect consumers’ decisions to adopt a product or behavior. The focus group results guided the development of a social marketing program to promote physical activity in the target audience in Sumter County, South Carolina

Heterogenized Pyridine-Substituted Cobalt(II) Phthalocyanine Yields Reduction of CO2 by Tuning the Electron Affinity of the Co Center.

Conversion of CO2 to reduced products is a promising route to alleviate irreversible climate change. Here we report the synthesis of a Co-based phthalocyanine with pyridine moieties (CoPc-Pyr), which is supported on a carbon electrode and shows Faradaic efficiency ∼90% for CO at 490 mV of overpotential (-0.6 V vs reversible hydrogen electrode (RHE)). In addition, its catalytic activity at -0.7 V versus RHE surpasses other Co-based molecular and metal-organic framework catalysts for CO2 reduction at this bias. Density functional theory calculations show that pyridine moieties enhance CO2 adsorption and electron affinity of the Co center by an inductive effect, thus lowering the overpotential necessary for CO2 conversion. Our study shows that CoPc-Pyr reduces CO2 at lower overpotential and with higher activity than noble metal electrodes, such as silver