ケイチョクガタ ノウセイ マヒ ニヨル ケイド シタイ フジユウシャ ノ チョウキ トレーニング ニカンスル ケンキュウ : ソノ ユウコウセイ ト モンダイテン

国立情報学研究所『研究紀要公開支援事業』により電子化

JASMINE: Near-infrared astrometry and time-series photometry science

The Japan Astrometry Satellite Mission for INfrared Exploration (JASMINE) is a planned M-class science space mission by the Institute of Space and Astronautical Science, the Japan Aerospace Exploration Agency. JASMINE has two main science goals. One is Galactic archaeology with a Galactic Center survey, which aims to reveal the Milky Way’s central core structure and formation history from Gaia-level (∼25 ${\mu}$as) astrometry in the near-infrared (NIR) Hw band (1.0–1.6 ${\mu}$m). The other is an exoplanet survey, which aims to discover transiting Earth-like exoplanets in the habitable zone from NIR time-series photometry of M dwarfs when the Galactic Center is not accessible. We introduce the mission, review many science objectives, and present the instrument concept. JASMINE will be the first dedicated NIR astrometry space mission and provide precise astrometric information on the stars in the Galactic Center, taking advantage of the significantly lower extinction in the NIR. The precise astrometry is obtained by taking many short-exposure images. Hence, the JASMINE Galactic Center survey data will be valuable for studies of exoplanet transits, asteroseismology, variable stars, and microlensing studies, including discovery of (intermediate-mass) black holes. We highlight a swath of such potential science, and also describe synergies with other missions

Cost-effective approach for structural evolution of Si-based multicomponent for Li-ion battery anodes

Silicon-based composite materials have been attracting significant attention because they offer an effective strategy for resolving the drawbacks of Si anodes, such as mechanical failure caused by significant volume changes and the resulting unstable interface. These drawbacks significantly affect the electrochemical properties of Si anodes and thereby inhibit their commercialization. Coupling Si anodes with inactive Al2O3 materials is one possible way of addressing these issues. In this study, we developed Si-based multicomponent anode materials comprising a multiscale porous silicon framework uniformly passivated with thin Al2O3 layers. This was achieved using a cost-effective, simple process of selective etching and wet oxidation. We found that the structural properties depended strongly on the Al residue in the core, which later generated asymmetries in the structure and the effective passivation layers. Our novel materials exhibited an excellent battery performance because of the structural robustness conferred by the Al/Al2O3 core support combined with the mechanical stability of the Al2O3 layers. The outermost protecting layers were also shown to enhance Li-ion diffusion through the Li-ion-conducting layers; this stabilized the solid-electrolyte-interphase layers. The wet oxidized Al-Si alloy (ASWO) exhibited an improved cycling performance with 81.9% capacity retention after 500 cycles at 0.2C in a Li half cell. In addition, a full cell using an ASWO-natural graphite (NG) anode and a lithium cobalt oxide (LCO) cathode exhibited excellent cycling performance with 75.3% capacity retention after 200 cycles at 1C.clos