Thermal expansion behavior of LDEF metal matrix composites

The thermal expansion behavior of Long Duration Exposure Facility (LDEF) metal matrix composite materials was studied by (1) analyzing the flight data that was recorded on orbit to determine the effects of orbital time and heating/cooling rates on the performance of the composite materials, and (2) characterizing and comparing the thermal expansion behavior of post-flight LDEF and lab-control samples. The flight data revealed that structures in space are subjected to nonuniform temperature distributions, and thermal conductivity of a material is an important factor in establishing a uniform temperature distribution and avoiding thermal distortion. The flight and laboratory data showed that both Gr/Al and Gr/Mg composites were stabilized after prolonged thermal cycling on orbit. However, Gr/Al composites showed more stable thermal expansion behavior than Gr/Mg composites and offer advantages for space structures particularly where very tight thermal stability requirements in addition to high material performance must be met

Polymer matrix composites on LDEF experiments M0003-9 and M0003-10

Over 250 polymer matrix composites were exposed to the natural space environment on Long Duration Exposure Facility (LDEF) experiments M0003-9 and 10. The experiments included a wide variety of epoxy, thermoplastic, polyimide, and bismalimide matrix composites reinforced with graphite, glass, or organic fibers. A review of the significant observations and test results obtained to date is presented. Estimated recession depths from atomic oxygen exposure are reported and the resulting surface morphologies are discussed. The effects of the LDEF exposure on the flexural strength and modulus, short beam shear strength, and coefficient of thermal expansion of several classes of bare and coated composites are reviewed. Lap shear data are presented for composite-to-composite and composite-to-aluminum alloy samples that were prepared using different bonding techniques and subsequently flown on LDEF

Changes in American and British Stature Since the Mid-Eighteenth Century: A Prelimanary Report on the Usefulness of Data on Height...

This paper is a progress report on the usefulness of data on physical height for the analysis of long-ten changes in the level of nutrition and health on economic, social, and demographic behavior. It is based on a set of samples covering the U.S. and several other nations over the years from 1750 to the present. The preliminary results indicate that native-born. American Revolution, but there were long periods of declining nutrition and height during the 19th century. Similar cycling has been established for England. A variety of factors, including crop mix, urbanization, occupation, intensity of labor, and immigration affected the level of height and nutrition, although the relative importance of these factors has changed over time. There is evidence that nutrition affected labor productivity. In one of the samples individuals who were one standard deviation above the mean height (holding weight per inch of height constant) were about 8% more productive than individuals one standard deviation below the mean height. Another finding is that death did not choose people at random. Analysis of data for Trinidad indicates that the annual death rate for the shortest quintile of males was more than twice as great as for the tallest quintile of males.

The impact of LDEF results on the space application of metal matrix composites

Over 200 graphite/aluminum and graphite/magnesium composites were flown on the leading and trailing edges of LDEF on the Advanced Composites Experiment. The performance of these composites was evaluated by performing scanning electron microscopy and x-ray photoelectron spectroscopy of exposed surfaces, optical microscopy of cross sections, and on-orbit and postflight thermal expansion measurements. Graphite/aluminum and graphite/magnesium were found to be superior to graphite/polymer matrix composites in that they are inherently resistant to atomic oxygen and are less susceptible to thermal cycling induced microcracking. The surface foils on graphite/aluminum and graphite/magnesium protect the graphite fibers from atomic oxygen and from impact damage from small micrometeoroid or space debris particles. However, the surface foils were found to be susceptible to thermal fatigue cracking arising from contamination embrittlement, surface oxidation, or stress risers. Thus, the experiment reinforced requirements for carefully protecting these composites from prelaunch oxidation or corrosion, avoiding spacecraft contamination, and designing composite structures to minimize stress concentrations. On-orbit strain measurements demonstrated the importance of through-thickness thermal conductivity in composites to minimize thermal distortions arising from thermal gradients. Because of the high thermal conductivity of aluminum, thermal distortions were greatly reduced in the LDEF thermal environment for graphite/aluminum as compared to graphite/magnesium and graphite/polymer composites. The thermal expansion behavior of graphite/aluminum and graphite/magnesium was stabilized by on-orbit thermal cycling in the same manner as observed in laboratory tests

Exploration of Flow Among Collegiate Marching Band Participants

The purpose of this study was to explore the extent to which collegiate marching band participants experience flow. While much research has been done in relation to athletes in flow, very little has been done using music as a basis, especially on the collegiate level. Participants for this study were 155 college students attending the 2005 Kappa Kappa Psi and Tau Beta Sigma National Convention. Results demonstrate that collegiate marching band members do experience flow in varying intensities. The research also indicates that the flow experiences of the participants were similar to the experiences of athletes in regards to flow dimensions and flow facilitators.School of Teaching and Curriculum Leadershi

Proposed test program and data base for LDEF polymer matrix composites

A survey of the polymer matrix composite materials that were flown on Long Duration Exposure Facility (LDEF) is presented with particular attention to the effect of circumferential location (alpha) on the measured degradation and property changes. Specifically, it is known that atomic oxygen fluence (AO), VUV radiation dose, and number of impacts by micrometeoroids/debris vary with alpha. Thus, it is possible to assess material degradation and property damage changes with alpha for those materials that are common to three or more locations. Once the alpha-dependence functions were defined, other material samples will provide data that can readily be used to predict damage and property changes as a function of alpha as well. What data can be realistically obtained from these materials, how this data can be obtained, and the scientific/design value of the data to the user community is summarized. Finally, a proposed test plan is presented with recommended characterization methodologies that should be employed by all investigators to ensure consistency in the data base that will result from this exercise

Long-Term Trends in Health, Welfare, and Economic Growth in the United States

We present evidence showing that the course of economic growth and of health, as measured by stature, Body Mass Index (BMI), mortality rates, or the prevalence of chronic conditions, diverged in the nineteenth century and converged in the twentieth. To analyze the change in welfare resulting from changes in health, we estimate a Human Development Index and a Borda Ranking and we calculate Usher- adjusted incomes and the willingness to pay for a reduction in mortality risk. Prior to the Civil War the increase in income was insufficient to compensate for the decline in health, whereas improvements in health outpaced economic growth in the twentieth century. We identify numerous possible causes of the nineteenth century decline in health, including greater exposure to disease, hardship created by the Civil War, and rising inequality. Our evidence on trends in waist-hip ratio, BMI, and the prevalence of chronic conditions at older ages suggests that early life conditions may exert an impact on mortality and morbidity that is not manifest until older ages. The dramatic twentieth century improvement in early life conditions implies that cohorts who are now approaching their sixties will experience a much greater rate of increase in health and longevity than past generations.

Spacecraft materials studies on the Aerospace Corporation tray on EOIM-3

A passive tray was flown on the Effects of Oxygen Interaction with Materials experiment on STS-46 (EOIM-3) with 82 samples from The Aerospace Corporation. A variety of advanced materials related to potential uses on future spacecraft were included for evaluation representing optical coatings, lubricants, polymers, composites, carbon-carbon composite protective coatings, graphite protective coatings, thermal-control materials, and some samples of current materials. An overview of the available results from the investigations of these materials is presented

Carbon supported CdSe nanocrystals

Insights to the mechanism of CdSe nanoparticle attachment to carbon nanotubes following the hot injection method are discussed. It was observed that the presence of water improves the nanotube coverage while Cl containing media are responsible for the shape transformation of the nanoparticles and further attachment to the carbon lattice. The experiments also show that the mechanism taking place involves the right balance of several factors, namely, low passivated nanoparticle surface, particles with well-defined crystallographic facets, and interaction with an organics-free sp2 carbon lattice. Furthermore, this procedure can be extended to cover graphene by quantum dots.Comment: 5 pages, 5 figure

Distributional impacts of carbon pricing in developing Asia

Understanding who would be affected in which way by carbon pricing is pivotal for effective and socially equitable policy design, addressing climate change and reducing inequality. This paper focuses on eight key countries in developing Asia (Bangladesh, India, Indonesia, Pakistan, Philippines, Thailand, Turkey and Vietnam). By combining national household surveys with input-output data, we compare the distributional effects of four carbon pricing design options, including a globally harmonized carbon price, a national carbon price and sectoral carbon prices in the power and transport sectors, respectively. Our analysis reveals a substantial degree of variation regarding who would be affected across policy designs and countries. Looking into national carbon pricing as the most favourable policy option from an economic point of view, we find that differences in distributional outcomes are generally more pronounced within income groups than across income groups. These differences are mainly driven by households' energy use patterns, which vary across countries. Equally recycling revenues back to all citizens would overcompensate the burden of a carbon price for the poorest households in all countries. Carbon pricing can alter income distribution. With a focus on Bangladesh, India, Indonesia, Pakistan, Philippines, Thailand, Turkey and Vietnam, this study compares four types of carbon pricing schemes and finds substantial variation in distributional effects across policy designs and countries.Industrial Ecolog