Showing papers by "Japan Aerospace Exploration Agency published in 2005"

Simulation of climate response to aerosol direct and indirect effects with aerosol transport‐radiation model

Abstract: [1] With a global aerosol transport-radiation model coupled to a general circulation model, changes in the meteorological parameters of clouds, precipitation, and temperature caused by the direct and indirect effects of aerosols are simulated, and its radiative forcing are calculated. A microphysical parameterization diagnosing the cloud droplet number concentration based on the Kohler theory is introduced into the model, which depends not only on the aerosol particle number concentration but also on the updraft velocity, size distributions, and chemical properties of each aerosol species and saturation condition of the water vapor. The simulated cloud droplet effective radius, cloud radiative forcing, and precipitation rate, which relate to the aerosol indirect effect, are in reasonable agreement with satellite observations. The model results indicate that a decrease in the cloud droplet effective radius by anthropogenic aerosols occurs globally, while changes in the cloud water and precipitation are strongly affected by a variation of the dynamical hydrological cycle with a temperature change by the aerosol direct and first indirect effects rather than the second indirect effect itself. However, the cloud water can increase and the precipitation can simultaneously decrease in regions where a large amount of anthropogenic aerosols and cloud water exist, which is a strong signal of the second indirect effect. The global mean radiative forcings of the direct and indirect effects at the tropopause by anthropogenic aerosols are calculated to be −0.1 and −0.9 W m−2, respectively. It is suggested that aerosol particles approximately reduce 40% of the increase in the surface air temperature by anthropogenic greenhouse gases on the global mean.

Efficient Optimization Design Method Using Kriging Model

Abstract: The Kriging-based genetic algorithm is applied to aerodynamic design problems. The Kriging model, one of the response surface models, represents a relationship between the objective function (output) and design variables (input) using stochastic process. The kriging model drastically reduces the computational time required for objective function evaluation in the optimization (optimum searching) process. ‘Expected improvement (EI)’ is used as a criterion to select additional sample points. This makes it possible not only to improve the accuracy of the response surface but also to explore the global optimum efficiently. The functional analysis of variance (ANOVA) is conducted to evaluate the influence of each design variable and their interactions to the objective function. Based on the result of the functional ANOVA, designers can reduce the number of design variables by eliminating those that have small effect on the objective function. In this paper, the present method is applied to a two-dimensional airfoil design and the prediction of flap’s position in a multi-element airfoil, where the lift-to-drag ratio (L/D) is maximized.

Discovery of the short |[gamma]|-ray burst GRB 050709

Abstract: Gamma-ray bursts (GRBs) are either ‘long and soft’, or ‘short and hard’. The long-duration type leave a strong afterglow and have been extensively studied. So we have a good idea of what causes them: explosions of massive stars in distant star-forming galaxies. Short GRBs, with no strong afterglow, were harder to pin down. The Swift satellite, launched last November, is designed to study bursts as soon as they happen. Having shown its worth with long GRBs (reported in the 18 August issue of Nature), Swift has now bagged a short burst, GRB 050509B, precisely measured its location and detected the X-ray afterglow. Four papers this week report on this and another recent short burst. Now, over 20 years after they were first recognized, the likely origin of the short GRBs is revealed as a merger between neutron stars of a binary system and the instantaneous production of a black hole. Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts1,2,3. The latter are now known to have X-ray4 and optical5 afterglows, to occur at cosmological distances6 in star-forming galaxies7, and to be associated with the explosion of massive stars8,9. In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow10 and (for the first time) the optical afterglow10,11 of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.

Infrared Telescope in Space Observations of the Near-Infrared Extragalactic Background Light

Abstract: We have searched for near-infrared extragalactic background light (EBL) in the data from the Near-Infrared Spectrometer (NIRS) on the Infrared Telescope in Space (IRTS). After subtracting the contribution of faint stars and the zodiacal component based on modeling, a significant isotropic emission is obtained in the wavelength bands from 1.4 to 4.0 ?m. The spectrum is stellar-like but shows a spectral jump from the optical EBL. The emission obtained is isotropic over the observed sky, and the in-band flux amounts to ~35 nW?m-2?sr-1, which is too bright to be explained by the integrated light from faint galaxies. Analyses of COBE DIRBE data, after removal of starlight, show essentially the same result within the uncertainty in the zodiacal light model, which implies that the isotropic emission observed by IRTS NIRS is of extragalactic origin. Significant fluctuations in sky brightness were also detected that cannot be explained by fluctuations due to faint stars, zodiacal components, and normal galaxies. The excess fluctuation amounts to ~1/4 of the excess emission over the integrated light of galaxies and is consistent with fluctuations observed by COBE DIRBE. A two-point correlation analysis shows that IRTS NIRS data have an angular scale of fluctuations of a few degrees. The spectrum and brightness of the observed excess EBL emission could be explained by the redshifted UV radiation from the first generation of massive stars (Population III stars), which caused the reionization of the universe. Recent Wilkinson Microwave Anisotropy Probe (WMAP) observations of the cosmic microwave background (CMB) polarization have indicated that reionization occurred at z ~ 17 or earlier, while the spectral jump around 1 ?m in the observed excess EBL suggests that the Population III star formation terminated at z ~ 9. The observed fluctuations, however, are considerably larger than the theoretical predictions for the Population III stars.

Total Galaxy Magnitudes and Effective Radii from Petrosian Magnitudes and Radii

Abstract: Petrosian magnitudes were designed to help with the difficult task of determining a galaxy's total light. Although these magnitudes [taken here as the flux within 2RP, with the inverted Petrosian index 1/?(RP) = 0.2] can represent most of an object's flux, they do of course miss the light outside the Petrosian aperture (2RP). The size of this flux deficit varies monotonically with the shape of a galaxy's light profile, i.e., its concentration. In the case of a de Vaucouleurs R1/4 profile, the deficit is 0.20 mag; for an R1/8 profile this figure rises to 0.50 mag. Here we provide a simple method for recovering total (S?rsic) magnitudes from Petrosian magnitudes using only the galaxy concentration (R90/R50 or R80/R20) within the Petrosian aperture. The corrections hold to the extent that S?rsic's model provides a good description of a galaxy's luminosity profile. We show how the concentration can also be used to convert Petrosian radii into effective half-light radii, enabling a robust measure of the mean effective surface brightness. Our technique is applied to the Sloan Digital Sky Survey Data Release 2 (SDSS DR2) Petrosian parameters, yielding good agreement with the total magnitudes, effective radii, and mean effective surface brightnesses obtained from the New York University Value-Added Galaxy Catalog S?rsic R1/n fits by Blanton and coworkers. Although the corrective procedure described here is specifically applicable to the SDSS DR2 and DR3, it is generally applicable to all imaging data where any Petrosian index and concentration can be constructed.

InGaP/GaAs-based multijunction solar cells

Abstract: The conversion efficiency of InGaP/(In)GaAs/Ge -based multijunction solar cells has been improved up to 29–30% (AM0) and 31–32% (AM1·5G) by technologies, such as double-hetero wide band-gap tunnel junctions, combination with Ge bottom cell with the InGaP first hetero-growth layer, and precise lattice-matching to Ge substrate by adding 1% indium to the conventional GaAs lattice-match structure. Employing a 1·95 eV AlInGaP top cell should improve efficiency further. For space use, radiation resistance has been improved by technologies such as introducing of an electric field in the base layer of the lowest-resistance middle cell, and EOL current matching of sub-cells to the highest-resistance top cell. A grid structure and cell size have been designed for concentrator applications in order to reduce the energy loss due to series resistance, and 38% (AM1·5G, 100–500 suns) efficiency has been demonstrated. Furthermore, thin-film structure which is InGaP/GaAs dual junction cell on metal film has been newly developed. The thin-film cell demonstrated high flexibility, lightweight, high efficiency of over 25% (AM0) and high radiation resistance. Copyright © 2005 John Wiley & Sons, Ltd.

Mechanical properties improvements in two-phase and three-phase composites using carbon nano-fiber dispersed resin

Abstract: Static strength tests were carried out for cured carbon nano-fiber (CNF) dispersed resin as tow-phase composites and for CFRP laminates using CNF dispersed resin as three-phase composites. To obtain these CFRP laminates, the CNF dispersed resin was impregnated to CF reinforcement and cured by hot press. The CNF used was a cup-stacked type of nano-fiber, CARBERE®, made by GSI CREOS Corporation, Japan. Two CNF aspect ratios of 10 and 50 were employed. These fiber lengths of the CNF were controlled about 1000 nm (AR10) and 5000 nm (AR50), respectively. The CNF was dispersed to EPIKOTE 827® epoxy resin in two values of CNF weight ratios, 5 and 10% to the resin. TORAYCA® C6343 plain woven fabric was used for reinforcement of the CFRP laminates. The cure condition with the agent of aromatic amine EPIKURE W® was 100 °C for two hours followed by a post cure of 175 °C for 4 h. The static strength tests led to the conclusion that the dispersion of CNF into epoxy improves mechanical properties of the tow-phase composites, and that CFRP laminates with CNF dispersed resin also exhibit higher compressive strength than CFRP laminates without CNF as control. Possibilities of improvement in mechanical properties were confirmed in the two and three-phase composites. Moreover, a proportional tendency in strength improvements to CNF weight content was found in the two present composites so far in the present test results.

Near-Infrared Imaging Survey of Bok Globules: Density Structure

Abstract: On the basis of near-infrared imaging observations, we derived the visual extinction (AV) distribution toward 10 Bok globules through measurements of both the color excess (EH-K) and the stellar density at J, H, and Ks (star count). Radial column density profiles for each globule were analyzed with the Bonnor-Ebert sphere model. Using the data of our 10 globules and four globules in the literature, we investigated the stability of globules on the basis of ξmax, which characterizes the Bonnor-Ebert sphere, as well as the stability of the equilibrium state against gravitational collapse. We found that more than half the starless globules are located near the critical state (ξmax = 6.5 ± 2). Thus, we suggest that a nearly critical Bonnor-Ebert sphere characterizes the typical density structure of starless globules. The remaining starless globules show clearly unstable states (ξmax > 10). Since unstable equilibrium states are not long maintained, we expect that these globules are on the way to gravitational collapse or that they are stabilized by nonthermal support. It was also found that all the star-forming globules show unstable solutions of ξmax > 10, which is consistent with the fact that they have started gravitational collapse. We investigated the evolution of a collapsing gas sphere whose initial condition is a nearly critical Bonnor-Ebert sphere. We found that the column density profiles of the collapsing sphere mimic those of the static Bonnor-Ebert spheres in unstable equilibrium. The collapsing gas sphere resembles marginally unstable Bonnor-Ebert spheres for a long time. We found that the frequency distribution of ξmax for the observed starless globules is consistent with that from model calculations of the collapsing sphere. In addition to the near-infrared observations, we carried out radio molecular line observations (C18O and N2H + ) toward the same 10 globules. We confirmed that most of the globules are dominated by thermal support. The line width of each globule was used to estimate the cloud temperature including the contribution from turbulence, with which we estimated the distance to the globules from the Bonnor-Ebert model fitting.

Generation of terahertz radiation by photomixing with dual- and multiple-mode lasers

Abstract: Photomixing with dual-mode and multi-mode lasers in the sub-terahertz frequency region is presented with a description on the principle and efficiency of photomixing on low-temperature-grown-GaAs photoconductive antennae for generation of continuous-wave terahertz (THz) radiation. The difference frequency stabilization by the common-mode-rejection effect in the dual-mode lasers is discussed with several reported experimental results. It is also shown that generation and detection of broadband sub-THz radiation is possible by photomixing with multi-mode semiconductor lasers on the emitter and detector photoconductive antennae (multi-mode-laser-diode-based terahertz time-domain spectroscopy, MLD-TDS). The MLD-TDS system can be a low-cost and broadband spectrometer in the sub-THz frequency region, which is useful for measurement of complex refractive indices and carrier densities of semiconductor wafers.

Distributed hydrogen determination with fiber-optic sensor

Abstract: In order to develop a distributed hydrogen sensor, a fiber-optic evanescent-wave sensor was characterized using optical time domain reflectometry (OTDR). A silica core (O = 100 μm) fiber was coated with platinum-supported tungsten trioxide (Pt/WO 3 ) thin film as hydrogen sensitive cladding. The fiber-optic sensors of 15 cm length were spliced into a transmitting fiber cable. Light pulse of 20 ns emitted from laser diode at 1.3 μm wavelength was applied in OTDR measurement. The power loss of about 5 dB in backscattering light at spatial position of the sensor was observed with the exposure to 1 vol.% H 2 /99 vol.% N 2 . This indicates that the sensor has the potential for distributed measurement to detect the location of hydrogen leakage points along a fiber. The response to hydrogen increased as the fiber sensor length increases (62 dB/m). On the other hand, the OTDR measurement revealed 14 dB/m of propagation loss associated with the sensor device in air. Then, step index (SI) and quasi step index (QSI) multimode optical fiber sensors, which have different refractive index profile were prepared and optical responses were compared. Although the QSI type sensor showed lower sensitivity, light level was higher than that of SI type sensor. Finally, multipoint sensing using three sensors spliced in series was demonstrated.

Spatial and diurnal variation of precipitation systems over Asia observed by the TRMM Precipitation Radar

Abstract: [1] The spatial and diurnal variation of rainfall over Asia was investigated using the spaceborne radar data for four seasons during 1998–2003. The regional variation of the prevailing precipitation systems most closely associated with the maximum hourly rainfall was shown by examining the fine spatial distribution of rainfall amount and scale-based precipitation systems. Small precipitation systems ( 104 km2) developed mostly in the evening over nearly flat landmasses. Wide-spread systems with intense rain pixels developed over the foothills of the Himalayas in late night–early morning period, which was distinct from the daytime convection. Over ocean, in addition to the morning signature, spatially inhomogeneous and systematic characteristics were evident over the offshore region, for example, around the maritime continent. Large systems, which are strongly associated with terrain, have a great influence on the total number of rain pixels and the total amount of rainfall. For 86% of the region where large system is dominant the time of maximum rainfall is within 3 hours of the time of maximum rainfall for large systems.

Delamination monitoring of laminated composites subjected to low-velocity impact using small-diameter FBG sensors

Abstract: Small-diameter fiber Bragg grating (FBG) sensors were applied for the monitoring of delamination induced by low-velocity impact. The FBG sensors were embedded into carbon fiber reinforced plastic (CFRP) laminates [04/904/04]. Using a drop-weight impact tester, an impact loading was applied to the laminates at four impact energy levels. After the impact tests, the internal damages including delaminations were observed by ultrasonic C-scan, and the reflection spectra from the embedded FBG sensors were measured. The form of the spectrum changed sensitively depending on the delamination size. Furthermore, the spectra were calculated theoretically for confirmation of the measured spectra. Since the change in the measured spectrum was consistent with that in the calculated spectrum, the relationship between the delamination size and the form of the spectrum could be clarified. From the results, the present method using small-diameter FBG sensors was found to be effective for the monitoring of the delamination.

Cosmic-Ray Spectra and Composition in the Energy Range of 10-1000 TeV per Particle Obtained by the RUNJOB Experiment

Abstract: This is a full report on the cosmic-ray spectra and composition obtained by the emulsion chambers on board 10 long-duration balloons, launched from Kamchatka between 1995 and 1999. The total exposure of these campaigns amounts to 575 m2 hr, with an average flight altitude of ~32 km. We present final results on the energy spectra of two light elements, protons and helium nuclei, and on those of three heavy-element groups, CNO, NeMgSi, and Fe, covering the very high energy region of 10-1000 TeV particle-1. We additionally present the secondary/primary ratio, the all-particle spectrum, and the average mass of the primary cosmic rays. We find that our proton spectrum is in good agreement with other results, but the intensity of the helium component is nearly half that obtained by JACEE and SOKOL. The slopes of the spectra of these two elements obtained from RUNJOB data are almost parallel, with values of 2.7-2.8 in the energy range of 10-500 TeV nucleon-1. RUNJOB heavy-component spectra are in agreement with the extrapolation from those at lower energies obtained by CRN (Chicago group), monotonically decreasing with energy. We have also observed secondary components, such as the LiBeB group and the sub-Fe group, and present the secondary/primary ratio in the TeV nucleon-1 region. We determine the all-particle spectrum and the average mass of the primary cosmic rays in the energy region of 20-1000 TeV particle-1. The intensity of the RUNJOB all-particle spectrum is 40%-50% less than those obtained by JACEE and SOKOL, and the RUNJOB average mass remains almost constant up to ~1 PeV.

Search for cosmic-ray antideuterons

Abstract: We performed a search for cosmic-ray antideuterons using data collected during four BESS balloon flights from 1997 to 2000. No candidate was found. We derived, for the first time, an upper limit of 1.9x10{sup -4} (m{sup 2}s sr GeV/nucleon){sup -1} for the differential flux of cosmic-ray antideuterons, at the 95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the atmosphere.

The Motions of the Hard X-Ray Sources in Solar Flares: Images and Statistics

Abstract: On the basis of the Yohkoh Hard X-Ray Telescope (HXT) data, we present a statistical study of different types of the hard X-ray (HXR) source motions during solar flares. A total of 72 flares that occurred from 1991 September to 2001 December have been analyzed. In these flares, we have found 198 intense HXR sources that are presumably the chromospheric footpoints of flare loops. The average velocity V and its uncertainty σ were determined for these sources. For 80% of them, the ratio of V to 3 σ is larger than 1, strongly suggesting that (1) the moving sources are usually observed rather than stationary ones and (2) the regular displacements of HXR sources dominate their chaotic motions. After co-alignment of the HXT images with the photospheric magnetograms, we have conducted an additional analysis of 31 flares out of 72 and distinguished between three main types of the footpoint motions. Type I consists of the motions preferentially away from and nearly perpendicular to the neutral line (NL). About 13% of flares (4 out of 31) show this pattern. In type II, the sources move mainly along the NL in antiparallel directions. Such motions have been found in 26% of flares (8 out of 31). Type III involves a similar pattern as type II, but all the HXR sources move in the same direction along the NL. Flares of this type constitute 35% (11 out of 31). In 26% of flares (8 out of 31) we observed more complicated motions that can be described as a combination of the basic types or some modification of them. For the most interesting flares, the results of analysis are illustrated and interpretation is suggested.

Subaru Mid-Infrared Imaging of the Quadruple Lenses PG 1115+080 and B1422+231: Limits on Substructure Lensing*

Abstract: We present mid-infrared imaging at 11.7 μm for the quadruple lens systems PG 1115+080 and B1422+231 using the cooled mid-infrared camera and spectrometer (COMICS) attached on the Subaru Telescope. These lensed QSOs are characterized by their anomalous optical and radio flux ratios, as obtained for A1 and A2 images of PG 1115+080 and A, B, and C images of B1422+231, respectively, i.e., such flux ratios are hardly able to be reproduced by lens models with a smooth mass distribution. Our mid-infrared observations for these images have revealed that the mid-infrared flux ratio A2/A1 of PG 1115+080 is virtually consistent with smooth lens models (but inconsistent with the optical flux ratio), whereas for B1422+231, the mid-infrared flux ratios among the A, B, and C images are in good agreement with the radio flux ratios. We also identify a clear infrared bump in the spectral energy distributions of these QSOs, thereby indicating that the observed mid-infrared fluxes originate from a hot dust torus around a QSO nucleus. Based on the size estimate of the dust torus, we place limits on the mass of a substructure in these lens systems causing the anomalous optical or radio flux ratios. For PG 1115+080, the mass of a substructure inside an Einstein radius ME is 16 M☉, corresponding to either a star or a low-mass CDM subhalo having a mass of M 2.2 × 104 M☉ inside a radius of 100 pc if modeled as a singular isothermal sphere (SIS). For B1422+231, we obtain ME 209 M☉, indicating that a CDM subhalo is more likely, having a mass of M 7.4 × 104 M☉.

Simulations of a QuasiTaylor State Geomagnetic Field Including Polarity Reversals on the Earth Simulator

Abstract: High-resolution, low-viscosity geodynamo simulations have been carried out on the Earth Simulator, one of the fastest supercomputers, in a dynamic regime similar to that of Earth's core, that is, in a quasi-Taylor state. Our dynamo models exhibit features of the geodynamo not only in spatial and temporal characteristics but also in dynamics. Polarity reversals occurred when magnetic flux patches at high latitudes moved poleward and disappeared; patches with reversed field at low and mid-latitudes then moved poleward.

Data mining for aerodynamic design space

Abstract: Analysis of variance (ANOVA) and self-organizing map (SOM) were applied to data mining for aerodynamic design space. These methods make it possible to identify the effect of each design variable on objective functions. ANOVA shows the information quantitatively, while SOM shows it qualitatively. Furthermore, ANOVA can show the effects of interaction between design variables on objective functions and SOM can visualize the trade-offs among objective functions. This information will be helpful for designers to determine the final design from non-dominated solutions of multi-objective problems. These methods were applied to two design results: a fly-back booster in reusable launch vehicle design, which has 4 objective functions and 71 design variables, and a transonic airfoil design performed with the adaptive search region method.

Chandra observations of galactic supernova remnant Vela Jr. : A new sample of thin filaments emitting synchrotron X-rays

Abstract: The Galactic supernova remnant (SNR) Vela Jr. (RX J0852.0-4622, G266.6-1.2) shows sharp filamentary structures on its northwestern edge in the hard X-ray band. The filaments are very smooth and located on the extreme outside edge of the remnant. We measured the averaged scale width of the filaments (wu and wd) with excellent spatial resolution with Chandra, and they are on the order of the size of the point-spread function of Chandra on the upstream side and 495 (360-888) on the downstream side. The spectra of the filaments are very hard and have no linelike structure; they were well reproduced with an absorbed power-law model with Γ = 2.67 (2.55-2.77) or a SRCUT model with νroll = 4.3 (3.4-5.3) × 1016 Hz under the assumption of p = 0.3. These results imply that the hard X-rays are synchrotron radiation emitted by accelerated electrons, as mentioned previously. Using a correlation between the function ≡ νroll/w and the SNR age, we estimated the distance and the age of Vela Jr.: the estimated distance and age are 0.33 (0.26-0.50) kpc and 660 (420-1400) yr, respectively. These results are consistent with previous reports, implying that the -age relation may be a useful tool for estimating the distance and the age of synchrotron X-ray-emitting SNRs.

Fourier transform spectrometer for Greenhouse Gases Observing Satellite (GOSAT)

Abstract: Global warming has become a very serious issue for human beings. In 1997, the Kyoto Protocol was adopted at the Third Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change (COP3), making it mandatory for developed nations to reduce carbon dioxide emissions by six (6) to eight (8) per cent of their total emissions in 1990, and to meet this goal sometime between 2008 and 2012. The Greenhouse gases Observing SATellite (GOSAT) is designed to monitor the global distribution of carbon dioxide (CO2) from the space. GOSAT is a joint project of Japan Aerospace Exploration Agency (JAXA), the Ministry of Environment (MOE), and the National Institute for Environmental Studies (NIES). JAXA is responsible for the satellite and instrument development, MOE is involved in the instrument development, and NIES is responsible for the satellite data retrieval. The satellite is scheduled to be launched in 2008. In order to detect the CO2 variation of boundary layers, both the technique to measure the column density and the retrieval algorithm to remove cloud and aerosol contamination are investigated. Main mission sensor of the GOSAT is a Fourier Transform Spectrometer with high optical throughput, spectral resolution and wide spectral coverage, and a cloud-aerosol detecting imager attached to the satellite. The paper presents the mission sensor system of the GOSAT together with the results of performance demonstration with proto-type instrument aboard an aircraft.

Detection of PAH Emission Features from Nearby Elliptical Galaxies with the Spitzer Infrared Spectrograph

Abstract: According to the current understanding, the presence of a considerable amount of dust in elliptical galaxies is quite common. Recent studies with ISO and Spitzer even suggest the presence of polycyclic aromatic hydrocarbon (PAH) emission features in the spectral energy distributions of several elliptical galaxies. Hot ionized gas filling the interstellar space of elliptical galaxies, however, is expected to easily destroy such very small grains through sputtering by plasma ions. Here we present the results of mid-IR spectroscopic observations of four elliptical galaxies with the Spitzer Infrared Spectrograph (IRS). We succeeded in detecting PAH emission features from elliptical galaxies. The observed spectra seem to be quite unusual; the PAH features at 6.2, 7.7, and 8.6 ?m are very faint or even absent, in contrast to prominent emission features at 11.3 and 12.7 ?m, which may reflect peculiar physical conditions of the interstellar medium. The detection of the PAHs provides strong constraints on evolution scenarios for the interstellar medium of elliptical galaxies.

A numerical study on the formation of diffusion flame islands in a turbulent hydrogen jet lifted flame

Abstract: This paper presents a numerical study on the formation of diffusion flame islands in a hydrogen jet lifted flame. A real size hydrogen jet lifted flame is numerically simulated by the DNS approach over a period of about 0.5 ms. The diameter of hydrogen injector is 2 mm, and the injection velocity is 680 m/s. The lifted flame is composed of a stable leading edge flame, a vigorously turbulent inner rich premixed flame, and a number of outer diffusion flame islands. The relatively long-term observation makes it possible to understand in detail the time-dependent flame behavior in rather large time scales, which are as large as the time scale of the leading edge flame unsteadiness. From the observation, the following three findings are obtained concerning the formation of diffusion flame islands. (1) A thin oxygen diffusion layer is developed along the outer boundary of the lifted flame, where the diffusion flame islands burn in a rather flat shape. (2) When a diffusion flame island comes into contact with the fluctuating inner rich premixed flame, combustion is intensified due to an increase in the hydrogen supply by molecular diffusion. This process also works for the production of the diffusion flame islands in the oxygen diffusion layer. (3) When a large unburned gas volume penetrates into the leading edge flame, the structure of the leading edge flame changes. In this transformation process, a diffusion flame island comes near the leading edge flame. The local deficiency of oxygen plays an important role in this production process.

Image measurements of unsteady pressure fluctuation by a pressure-sensitive coating on porous anodized aluminium

Abstract: Pressure-sensitive luminescent coating on porous anodized aluminium (AA-PSP) was applied to measure non-periodic unsteady pressure distribution on a wind-tunnel model. A high-speed digital video camera was used to capture the PSP signal. The pressure-sensitive dye was tris(4,7-diphenylphenanthroline) ruthenium(II) ([Ru(dpp)3]2+). The coating has a short response time of O(10 µs), although it exhibits temperature and humidity sensitivities. A hydrophobic coating was applied on the anodized aluminium surface to suppress the humidity sensitivity. A temperature sensitive paint was used to obtain the temperature distribution instantaneously with the pressure. The temperature data were used to correct the PSP response. An appropriate data acquisition procedure as well as digital image processing algorithm was established to compensate for the error from the temperature and humidity sensitivities. The present system was applied to measure the pressure distribution on a delta wing at a high angle of attack in transonic flow, whose flow is unsteady due to the interaction between shock waves and leading edge vortices. The non-periodic unsteady pressure distribution on the delta wing was successfully measured with the sampling rate of 1 kHz and within a few per cent error in absolute pressure level.

Thermal infrared observations of the Hayabusa spacecraft target asteroid 25143 Itokawa

Abstract: We obtained N - and Q -band observations of the Apollo-type asteroid 25143 Itokawa during its close Earth approach in July 2004 with TIMMI2 at the ESO 3.6 m telescope. Our photometric measurement, in combination with already published data, allowed us to derive a radiometric effective diameter of $0.32 \pm 0.03$ km and an albedo of 0.19$^{+0.11}_{-0.03}$ through a thermophysical model. This effective diameter corresponds to a slightly asymmetrical and flattened ellipsoid of the approximate size of 520( ± 50) $\times$ 270( ± 30) $\times$ 230( ± 20) m, based on the Kaasalainen et al. (2005, Proceedings of the 1st Hayabusa Symposium, ASP Conf. Ser., submitted) shape model. Our studies show that the thermal observations lead to size estimates which are about 15% smaller than the radar results (Ostro et al. 2005, Met. Plan. Sci., submitted), slightly outside the stated radar uncertainties of ± 10%. We determined a rather high thermal inertia of 750 J m -2 s -0.5 K -1 . This is an indication for a bare rock dominated surface, a thick dust regolith can be excluded as well as a metallic surface. From our data we constructed a 10.0 μ m thermal lightcurve which is nicely matched in amplitude and phase by the shape and spin vector solution in combination with our TPM description. The assumed S-type bulk density in combination with radiometric size lead to a total mass estimate of $4.5^{+2.0}_{-1.8} \times 10^{10}$ kg.

Intercomparison of General Purpose Clear Sky Atmospheric Radiative Transfer Models for the Millimeter/submillimeter Spectral Range

Abstract: [1] We compare a number of radiative transfer models for atmospheric sounding in the millimeter and submillimeter wavelength range, check their consistency, and investigate their deviations from each other. This intercomparison deals with three different aspects of radiative transfer models: (1) the inherent physics of gaseous absorption lines and how they are modeled, (2) the calculation of absorption coefficients, and (3) the full calculation of radiative transfer for different geometries, i.e., up-looking, down-looking, and limblooking. The correctness and consistency of the implementations are tested by comparing calculations with predefined input such as spectroscopic data, line shape, continuum absorption model, and frequency grid. The absorption coefficients and brightness temperatures calculated by the different models are generally within about 1% of each other. Furthermore, the variability or uncertainty of the model results is estimated if (except for the atmospheric scenario) the input such as spectroscopic data, line shape, and continuum absorption model could be chosen freely. Here the models deviate from each other by about 10% around the center of major absorption lines. The main cause of such discrepancies is the variability of reported spectroscopic data for line absorption and of the continuum absorption model. Further possible causes of discrepancies are different frequency and pressure grids and differences in the corresponding interpolation routines, as well as differences in the line shape functions used, namely a prefactor of (n/n0 )o r (n/n0) 2 of the Van-Vleck-Weisskopf line shape function. Whether or not the discrepancies affect retrieval results remains to be investigated for each application individually.