An Astronaut's Risk of Experiencing a Critical Impact from Lunar Ejecta During Lunar EVA

The Moon is under constant bombardment by meteoroids. When the meteoroid is large, the impact craters the surface, launching crater ejecta far from the impact potentially threatening astronauts on the lunar surface. In the early 1960s, the ejecta impact flux was thought no more than the sporadic meteoroid flux but with speeds one to two orders of magnitude smaller. However, the Lunar Module designers realized by 1965 that meteoroid bumpers do not perform well at the smaller ejecta impact speeds. Their estimates of the Lunar Module risk of penetration by ejecta were 25 to 50% of the total risk. This was in spite of the exposure time to ejecta being only a third of that to sporadic meteoroids. The standard committee based the 1969 NASA SP-8013 lunar ejecta environment on Zooks 1967 flux analysis and Gault, Shoemaker and Moores 1963 test data for impacts into solid basalt targets. However, Zook noted in his 1967 analysis, that if the lunar surface was composed of soil, that the ejected soil particles would be smaller than ejected basalt fragments and that the ejection speeds would be smaller. Both effects contribute to reducing the risk of a critical failure due to lunar ejecta. The authors revised Zooks analysis to incorporate soil particle size distributions developed from analysis of Apollo lunar soil samples and ejected mass as a function of ejecta speed developed from coupling parameter analyses of soil impact-test data. The authors estimated EVA risk by assuming failure occurs at a critical impact energy. At these impact speeds, this might be true for suit hard and soft goods. However, these speeds are small enough that there may be significant strength effects that require new test data to modify the hypervelocity critical energy failure criterion. With these caveats, Christiansen, Cour-Palais and Freisen list the critical energy of the ISS EMU hard upper torso as 44 J and the helmet and visor as 71 J at hypervelocity. The authors then assumed that the lunar EVA suit fails at 50 J critical energy. This results in a 1,700,000 years mean time to failure using the results of this analysis and a 3,800 years mean time to failure using NASA SP-8013

What Every Coach Should Know Before Graduation

Becoming a successful Strength and Conditioning Coach is a rewarding career in which you will improve the physical and mental strength of your clients. The path it takes to become a successful coach requires dedication, hard work, and sacrifice. My Professor’s at Farquhar helped me become the professional I am today by challenging me to work hard. There are many facets of building a successful Strength and Conditioning facility and I will share what I have learned from my success and failures. I will also pre sent a road map to improve success as a coach

Kepler planet occurrence rates for mid-type M dwarfs as a function of spectral type

Previous studies of planet occurrence rates largely relied on photometric stellar characterizations. In this paper, we present planet occurrence rates for mid-type M dwarfs using spectroscopy, parallaxes, and photometry to determine stellar characteristics. Our spectroscopic observations have allowed us to constrain spectral type, temperatures, and, in some cases, metallicities for 337 out of 561 probable mid-type M dwarfs in the primary Kepler field. We use a random forest classifier to assign a spectral type to the remaining 224 stars. Combining our data with Gaia parallaxes, we compute precise (~3%) stellar radii and masses, which we use to update planet parameters and occurrence rates for Kepler mid-type M dwarfs. Within the Kepler field, there are seven M3 V to M5 V stars that host 13 confirmed planets between 0.5 and 2.5 Earth radii and at orbital periods between 0.5 and 10 days. For this population, we compute a planet occurrence rate of ${1.19}_{-0.49}^{+0.70}$ planets per star. For M3 V, M4 V, and M5 V, we compute planet occurrence rates of ${0.86}_{-0.68}^{+1.32}$, ${1.36}_{-1.02}^{+2.30}$, and ${3.07}_{-2.49}^{+5.49}$ planets per star, respectively.Published versio

Further Evidence on Hedge Funds Performance.

In this analysis we identify dynamic hedge fund strategies quantitatively pursuing a Principal Component Analysis following Fung and Hsieh (1997). We extract five dominant hedge fund strategies each representing similar investment styles and analyse the performance of each strategy by employing a multi-factor model comprising both market indices and passive option strategies along the lines of Agerwal and Naik (2000). We find that the majority of the five homogenous strategies show superior performance. However, correcting for survivorship bias this superior performance disappears.Hedge funds; Investment in securities; Performance; Dynamic strategies; Hedge funds performance;

Characterization of GaN Nanorods Fabricated Using Ni Nanomasking and Reactive Ion Etching: A Top-Down Approach

Large thermal mismatch between GaN surface and sapphire results in compressive stress in Gallium Nitride (GaN) layer which degrades the device performance. Nanostructuring the GaN can reduce this stress leading to reduction in Quantum Confined Stark Effect. Aligned GaN nanorods based nanodevices have potential applications in electronics and optoelectronics. This paper describes the fabrication of GaN nanorods using Ni nanomasking and reactive ion etching. The morphology of GaN nanorods was studied by field emission scanning electron microscopy. The optical properties of GaN nanorods were studied by Cathodoluminescence (CL) spectroscopy. CL results revealed the existence of characteristic band-edge luminescence and yellow band luminescence. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3099

Linear Models for Estimating the Nutritive Value of Sheep Diets

Digestibility data were determined in 2 replications of a 2 x 3 x 2 x 2 factorial arranged experiment to: (1) determine the effects of forage type (grass vs alfalfa), forage maturity (late vegetative vs midbloom vs fullbloom), diet ingredients (forage only vs 50:50 forage plus corn), and diet texture (coarsely chopped vs pelleted) on the digestibility of diet chemical constituents by sheep; (2) develop equations to estimate digestible energy of sheep diets from nutrient content of the diet; and (3) compare popular chemical methods used to partition feed dry matter into fibrous and soluble components. Diets were fed to growing wether lambs. Crude protein (CP) and available carbohydrates (AC) of diets were nearly 100% digestible (true digestibility) regardless of diet source. However, the apparent digestibility of CP and AC varied significantly with concentration of these components in the diet. Apparent digestibility of cellulose (CL) was significantly different between grass and alfalfa, early and late maturity stages, and coarse and pelleted diet textures. Interactions between forage type and stage of maturity and between stages of maturity and energy level also significantly altered the apparent digestibility of all diet fibrous constituents except hemicellulose (HC). An energy level-by-diet texture interaction significantly affected the apparent digestibility of HC, CL, CW, NDF, ADF and CF. simple (equation 1) and complex (equation 2) models were generated for estimating nutrient digestible amounts (YN) or diet digestible energy (DE) (YN) from nutrient content (XN) of the diet. Complex models were developed to adjust the estimation of the nutrient digestible amount or DE estimations for effects due to forage type (αi), stage of maturity (βj), feed combination (γk) and texture (δl). Two-way interactions (βij, βγK , . . ., γβKl) between qualitative variables were added in the equations when significant. Interactions between qualitative variables and the quantitative variable (αiXl, βjXl, γKXl, δlXl, &&alhpa;βijXl, etc) were also tried but did not significantly change the precision of the equations. Complex models gave significantly better estimates of digestible CP, AC, total lipid (TL), HC, CL, CW, NDF, ADR or CF and DE than simpler models. DE in the diets was determined by two methods: First, DE was estimated by the summation of the predicted decimal fraction of digested protein, carbohydrates, and lipids times respective caloric values (Mcal/kg) (equation 3). DE was also estimated directly from CL, CW, NDF, ADF, or CF content in the diet. Both approaches gave comparably precise estimations of diet DE when complex models were used. The CF (1) YN = bo + blXN (2) YN = bo + blXN + αi + βj + γK + δl + αβij+ . . . + γδKl (3) DE = 5.65 (YCP) + 4.15 (YAC + YHC + YCL) + 9.40 (YTL) Simple model gave poorer estimates of DE (R2 = .56) than CL, CW, NDF, and ADF simple models (R2 = .69, .69, .71, and .71 respectively). Added indicator variables compensated for differences between CF and other chemical parameters. Cl, CW, NDF, ADF, and CF complex models were similar in estimation of DE (average R2 = .89 for DE complex models). Complex models could be effectively used in a computer program for balancing rations for sheep. Additional experiments should be conducted to provide added information for comparison

On protection of Freedom's solar dynamic radiator from the orbital debris environment. Part 2: Further testing and analyses

Presented here are results of a test program undertaken to further define the response of the solar dynamic radiator to hypervelocity impact (HVI). Tests were conducted on representative radiator panels (under ambient, nonoperating conditions) over a range of velocity. Target parameters are also varied. Data indicate that analytical penetration predictions are conservative (i.e., pessimistic) for the specific configuration of the solar dynamic radiator. Test results are used to define the solar dynamic radiator reliability with respect to HVI more rigorously than previous studies. Test data, reliability, and survivability results are presented