Takayuki Yamamoto

Abstract We report on the in-orbit performance of the Gas Slit Camera (GSC) on the MAXI (Monitor of All-sky X-ray Image) mission carried on the International Space Station (ISS). Its commissioning operation, which started on 2009 August 8, confirmed the basic performances of the effective area in the energy band of 2–30 keV, the spatial resolution of the slit-and-slat collimator and detector with 1 $^\circ\!\!\!.$ 5 FWHM, the source visibility of 40–150 seconds for each scan cycle, and the sky c

We have presented a novel design of a photonic crystal slab (PCS) nanocavity, in which the electric field of the cavity mode is strongly localized in free space. The feature of the cavity is a linear air slot introduced to the center of the mode-gap confined PCS cavity. Owing to the discontinuity of the dielectric constant, the electric field of the cavity mode is strongly enhanced inside the slot, allowing strong matter-field coupling and large interaction volume in free space. Using finite-dif

The physicochemical and electrochemical properties of the binary ionic liquid, K[FSA]–[C3C1pyrr][FSA] (FSA = bis(fluorosulfonyl)amide; C3C1pyrr = N-methyl-N-propylpyrrolidinium), were investigated at 253–393 K, with the aim of developing a new electrolyte for potassium-ion batteries (K-ion batteries; KIBs). A phase diagram was constructed from the results of differential scanning calorimetry measurements and revealed that the melting point of this ionic liquid is below room temperature for compo

Abstract We report on the discovery of a cyclotron resonance scattering feature (CRSF) in the X-ray spectrum of GX 304 $-$ 1, obtained by RXTE and Suzaku during major outbursts detected by MAXI in 2010. The peak intensity in August reached 600 mCrab in the 2–20 keV band, which is the highest ever observed from this source. The RXTE observations on more than twenty occasions and one Suzaku observation revealed a spectral absorption feature at around 54 keV, which is the first CRSF detection from

Fluoride shuttle batteries (FSBs) are attracting considerable interest as next-generation energy storage devices, owing to their superior energy density. We focused on fluorohydrogenate ionic liquids (FHILs) as new electrolytes for FSBs operating at room temperature, because they show much higher ionic conductivities compared with those of conventional electrolytes. In the present study, the charge–discharge behavior of CuF2 positive electrodes was investigated in the [C2C1im][(FH)2.3F] (C2C1im

We performed variable-temperature synchrotron powder X-ray diffraction measurements and impedance spectroscopy under pressure for silver iodide (AgI) nanoparticles with a diameter of 11 nm. The superionic conducting α-phase of AgI nanoparticles was successfully stabilized down to at least 20 °C by applying a pressure of 0.18 GPa, whereas the transition temperature was 147 °C in bulk AgI at ambient pressure. To our knowledge, this is the first example of the α-phase of AgI existing stably at room

In this study, submicron-sized tin particles were used as the negative electrode material for potassium secondary batteries. With a bis(fluorosulfonyl)amide-based ionic liquid electrolyte, K[FSA]-[C3C1pyrr][FSA], the tin negative electrodes showed improved capacity retention of over 170 mA h (g-Sn)-1 after 100 cycles at room temperature.

A summary of the material and tribological properties of amorphous carbon films for the overcoat of thin film media is presented. Two families of film are considered. One is the family of sputtered DLC film including amorphous carbon, amorphous hydrogenated, and nitrogenated carbon films, which are all widely used as overcoats for commercially available thin film media. The other film is amorphous hydrogenated carbon film, which is deposited by hot filament plasma CVD and is being developed for

Potassium-ion batteries (K-ion batteries; KIBs) are attractive as high-voltage, low-cost energy storage devices. Ionic liquids (ILs) are potential candidates as safe and high-performance electrolytes for large-scale devices. Imidazolium-based ILs are known to possess high ionic conductivities and moderate electrochemical stabilities. In this study, we report the physicochemical and electrochemical properties of K[FSA]–[C2C1im][FSA] (FSA = bis(fluorosulfonyl)amide; C2C1im = 1-ethyl-3-methylimidaz

We developed a Stiction Free Slider that has pads on the air bearing surface to reduce the stiction between the head and disk. This paper presents our extended experimental data on the SFS for use on lightly textured disks. The SFS shows excellent CSS performances on disks having an average roughness of 0.8 nm with 1.5 -2.5 nm thick lubricant. The wear of pads is negligible after 100,000 Contact Start/Stop cycles. This novel technique has an excellent potential to overcome the tribology obstacle

PLANET-B is the Japanese Mars orbiter program. The spacecraft will begin its journey to Mars in July 1998, and will be inserted into Mars orbit in October 1999. It will collect data for at least one Martian year (about two Earth years). The primary objective of the program is to study the Martian aeronomy, with emphasis on the interaction of the Martian upper atmosphere with the solar wind. The periapsis altitude and the apoapsis distance are 150 km and 15 Mars radii, respectively. The dry weigh