Japan Aerospace Exploration Agency

About: Japan Aerospace Exploration Agency is a facility organization based out in Tokyo, Japan. It is known for research contribution in the topics: Galaxy & Telescope. The organization has 4327 authors who have published 12054 publications receiving 208330 citations.

Effects of layup angle and ply thickness on matrix crack interaction in contiguous plies of composite laminates

Abstract: Matrix microcracking behaviors in constrained plies adjacent to a cracked ply are highlighted. Quasi-static tension tests of [0/ θ /90]s and [0/ θ 2 /90]s laminates with θ =30, 45 and 60° were conducted in order to investigate effects of the ply thickness and the intersecting angle of the cracked plies on the crack development in the adjacent plies. Matrix cracks developed along the fiber direction were the dominant damages observed in 30° plies of [0/ θ 2 /90]s laminates, whereas a high density form of matrix microcracking was mainly observed in θ ° plies of the other laminates. The difference of the matrix cracking behaviors in the adjacent plies among laminate configuration is characterized by calculating energy release rates associated with θ ° ply crack growth in the presence of 90° ply cracks using finite element analysis. It is clarified that microcracking in plies adjacent to a cracked ply is susceptible to formation in the cases of thin θ ° ply thickness and small intersecting angles of the cracked plies.

The global accretion rate of extraterrestrial materials in the last glacial period estimated from the abundance of micrometeorites in Antarctic glacier ice

Abstract: The accretion rate of micrometeorites in the last glacial period was estimated from the concentrations of micrometeorites in the blue ice around the Yamato Mts. in Antarctica. The samples from this study were collected from the five sampling points (M03, K02, K11, J09 and J10) in the blue ice. The blue ice was melted and filtered, and the micrometeorites were handpicked from the collected “glacial sands”. The weight of the micrometeorites in the blue ice was estimated from the abundance of recovered micrometeorites and the solar noble gas concentrations in the “residue” after handpicking. The age of the blue ice from the K area was estimated to be 27–33 kyr before present based on oxygen isotope data. The estimated accretion rate to the whole Earth ranges from 5300 × 103kg/a to 16000 × 103kg/a. However, the lower end of this range probably represents lower limits due to possible loss of solar noble gases during long residence in the glacier ice. Hence, we estimate that the accretion rate of micrometeorites 27–33 kyr before present to be in the range between (11000 ± 6600) × 103kg/a and (16000 ± 9100) × 103kg/a. These results, as well as the other estimates, suggest that the accretion rate of micrometeorites in the last glacial period was comparable to that in the present. Micrometeorite k]accretion rate k]Antarctica k]last glacial periods k]noble gas k]interplanetary dust particle

Albedo Properties of Main Belt Asteroids Based on the Infrared All-Sky Survey of the Astronomical Satellite AKARI

Abstract: We present an analysis of the albedo properties of main belt asteroids detected by the All-Sky Survey of the infrared satellite AKARI. The characteristics of 5120 asteroids detected by the survey, including their sizes and albedos, were cataloged in the Asteroid Catalog Using AKARI (AcuA). Size and albedo measurements were based on the Standard Thermal Model, using inputs of infrared fluxes and absolute magnitudes. Main belt asteroids, which account for 4722 of the 5120 AcuA asteroids, have semimajor axes of 2.06 to 3.27 AU. AcuA provides a complete data set of all main belt asteroids brighter than the absolute magnitude of H 20 km. We confirmed that the albedo distribution of the main belt asteroids is strongly bimodal as was already known from the past observations, and that the bimodal distribution occurs not only in the total population, but also within inner, middle, and outer regions of the main belt. We found that the small asteroids have much more variety in albedo than the large asteroids. In spite of the albedo transition process like space weathering, the heliocentric distribution of the mean albedo of asteroids in each taxonomic type is nearly flat. The mean albedo of the total, on the other hand, gradually decreases with an increase in semimajor axis. This can be explained by the compositional ratio of taxonomic types; that is, the proportion of dark asteroids such as C- and D-types increases, while that of bright asteroids such as S-type decreases, with increasing heliocentric distance. The heliocentric distributions of X-subclasses: E-, M-, and P-type, which can be divided based on albedo values, are also examined. P-type, which is the major component in X-types, are distributed throughout the main belt regions, and the abundance of P-type increases beyond 3 AU. This distribution is similar to that of C- or D-types.

Luminosity functions of local infrared galaxies with AKARI: implications for the cosmic star formation history and AGN evolution

Abstract: Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and active galactic nuclei (AGN) evolution, since their most intense stages are often obscured by dust. However, local IR luminosity function estimates today are still based on the IRAS survey in the 1980s, with wavelength coverage only up to 100 μm. The AKARI IR space telescope performed an all-sky survey in six IR bands (9, 18, 65, 90, 140 and 160 μm) with 3–10 times better sensitivity, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (L_(TIR)) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting modern IR spectral energy distribution (SED) models, we have remeasured L_(TIR) of the IRAS Revised Bright Galaxy Sample, which is a complete sample of local galaxies with S_(60μm) > 5.24 Jy. We present mid-IR monochromatic luminosity (νL_ν) to L_(TIR) correlations for Spitzer 8 μm, AKARI 9 μm, IRAS 12 μm, WISE 12 μm, ISO 15 μm, AKARI 18 μm, WISE 22 μm and Spitzer 24 μm filters. These measures of L_(MIR) are well correlated with L_(TIR), with scatter in the range 13–44 per cent. The best-fitting L_(MIR)-to-L_(TIR) conversions provide us with estimates of L_(TIR) using only a single MIR band, in which several deep all-sky surveys are becoming available such as AKARI MIR and WISE. Although we have found some overestimates of L_(TIR) by IRAS due to contaminating cirrus/ sources, the resulting AKARI IR luminosity function (LF) agrees well with that from IRAS. We integrate the LF weighted by L_(TIR) to obtain a cosmic IR luminosity density of Ω_(TIR) = (8.5^(+1.5)_(−2.3)) × 10^7 L_⊙ Mpc^(−3), of which 7 ± 1 per cent is produced by luminous infrared galaxies (LIRGs) (L_(TIR) > 10^(11) L_⊙), and only 0.4 ± 0.1 per cent is from ultraluminous infrared galaxies (ULIRGs) (L_(TIR) > 10^(12) L_⊙) in the local Universe, in stark contrast to high-redshift results. We separate the contributions from AGN and star-forming galaxies (SFGs). The SFG IR LF shows a steep decline at the bright end. Combined with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of Ω^(SF)_(TIR) ∝ (1 + z)^(4.0 ± 0.5) and Ω^(AGN)_(TIR) ∝ (1 + z)^(4.4 ± 0.4). For Ω^(AGN)_(TIR), the ULIRG contribution exceeds that from LIRGs already by z ~ 1. A rapid evolution in both Ω^(AGN)_(TIR) and Ω^(SFG)_(TIR) suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of Ω^(AGN)_(TIR) to that of X-ray luminosity density. The Ω^(AGN)_(TIR)/Ω^(AGN)_(X-ray) ratio shows a possible increase at z > 1, suggesting an increase of obscured AGN at z > 1.