Cambering in the flapping wings of insects plays an important role in the aerodynamic performance of their flight. In a previous study, the authors proposed a wing model using shell finite elements to elucidate the mechanism of cambering. However, the analysis of a strongly coupled fluid–structure system using this model would be quite computationally expensive because of the necessity of robust mesh-moving techniques. Therefore, in this study, a new wing model using rectangular shell finite elements is proposed. In the proposed model, the veins and membranes are described as pseudo-elastic materials. The cambering of the proposed model is investigated by comparison with the previous model.
An all‐sky survey in two mid‐infrared bands covering wavelengths from 6 to 12 and 14 to 26 μm, with a spatial resolution of ∼94–10'', will be performed with the Infrared Camera (IRC) on board the ASTRO‐F infrared astronomical satellite. The expected detection limit for point sources is 80–130 mJy (5 σ). The all‐sky survey will provide data with a detection limit and a spatial resolution an order of magnitude deeper and higher, respectively, than those of the Infrared Astronomical Satellite survey. The IRC is optimally designed for deep imaging in staring observations. It employs 256 × 256 Si:As IBC infrared focal plane arrays for the two mid‐infrared channels. In order to make observations with the IRC during the scanning observations for the all‐sky survey, a new method of operation for the arrays has been developed—"scan mode" operation. In the scan mode, only 256 pixels in a single row aligned in the cross‐scan direction on the array are used as the scan detector, and they are sampled every 44 ms. Special care has been taken to stabilize the temperature of the array in scan mode, which enables the user to achieve a low readout noise, comparable to that in the imaging mode (20–30 e−). The accuracy of the position determination and the flux measurement for point sources is examined both in computer simulations and laboratory tests with the flight model camera and moving artificial point sources. In this paper we present the scan mode operation of the array, the results of the computer simulation and the laboratory performance test, and the expected performance of the IRC all‐sky survey observations.
Results: We found that the (B-V) v.s. (V-S9W) color-color diagram is useful to identify the stars with infrared excess emerged from circumstellar envelopes/disks. Be stars with infrared excess are well separated from other types of stars in this diagram. Whereas (J-L18W) v.s. (S9W-L18W) diagram is a powerful tool to classify several object-types. Carbon-rich asymptotic giant branch (AGB) stars and OH/IR stars form distinct sequences in this color-color diagram. Young stellar objects (YSOs), pre-main sequence (PMS) stars, post-AGB stars and planetary nebulae (PNe) have largest mid-infrared color-excess, and can be identified in infrared catalog. Finally, we plot L18W v.s. (S9W-L18W) color-magnitude diagram, using the AKARI data together with Hipparcos parallaxes. This diagram can be used to identify low-mass YSOs, as well as AGB stars. We found that this diagram is comparable to the [24] vs ([8.0]-[24]) diagram of Large Magellanic Cloud sources using the Spitzer Space Telescope data. Our understanding of Galactic objects will be used to interpret color-magnitude diagram of stellar populations in nearby galaxies which Spitzer Space Telescope has observed. Conclusions: Our study of the AKARI color-color and color-magnitude will be used to explore properties of unknown objects in future. In addition, our analysis highlights a future key project to understand stellar evolution with circumstellar envelope, once the forthcoming astronometrical data with GAIA are available.
For future space IR missions, such as SPICA, it is crucial to establish an experimental method for evaluating the performance of mid-IR detectors. In particular, the wavelength dependence of the sensitivity is important but difficult to be measured properly. We are now preparing a testing system for mid-IR Si:As/Si:Sb detectors on SPICA. We have designed a cryogenic optical system in which IR signal light from a pinhole is collimated, passed through an optical filter, and focused onto a detector. With this system, we can measure the photoresponse of the detector for various IR light using optical filters with different wavelength properties. We have fabricated aluminum mirrors which are adopted to minimize thermal distortion effects and evaluated the surface figure errors. The total wavefront error of the optical system is $1.3{\mu}m$ RMS, which is small enough for the target wavelengths ($20-37{\mu}m$) of SPICA. The point spread function measured at a room temperature is consistent with that predicted by the simulation. We report the optical performance of the system at cryogenic temperatures.
AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from the mid- to far-infrared. The instruments also have the capability for imaging and spectroscopy in the wavelength range 2 - 180 micron in the pointed observation mode, occasionally inserted into the continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90 percent of the whole sky with higher spatial resolution and wider wavelength coverage than that of the previous IRAS all-sky survey. Point source catalogues of the All-Sky Survey will be released to the astronomical community. The pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission.
We report on the detection of an H$\alpha$ emission line in the low-resolution spectrum of a quasar, RX J1759.4$+$6638, at a redshift of 4.3 with the Infrared Camera (IRC) onboard AKARI. This is the first spectroscopic detection of an H$\alpha$ emission line in a quasar beyond $z =$ 4. The overall spectral energy distribution (SED) of RX J1759.4$+$6638 in the near- and mid-infrared wavelengths agrees with a median SED of the nearby quasars; also, the flux ratio of $F$(Ly$\alpha$)$/$$F$(H$\alpha$) is consistent with those of previous reports for lower-redshift quasars.
The selective mesh stiffening in this study changes the stiffness of the element based on both the element area and shape. It includes the stiffening in the previous studies as a specific case, and leads to a general scenario in the pseudoelastic mesh–moving. This scenario gives better mesh quality in the mesh-moving of a rectangular domain with a structure consisting of a square and a fin undergoes large rotations. This is because the shear deformation of the element is adaptively considered.
