Tokyo Institute of Technology

About: Tokyo Institute of Technology is a education organization based out in Tokyo, Tôkyô, Japan. It is known for research contribution in the topics: Thin film & Catalysis. The organization has 46775 authors who have published 101656 publications receiving 2357893 citations. The organization is also known as: Tokyo Tech & Tokodai.

Double-Layer Full-Corporate-Feed Hollow-Waveguide Slot Array Antenna in the 60-GHz Band

Abstract: In order to achieve a wide bandwidth characteristic of high gain and high efficiency antennas, a double-layer hollow-waveguide slot array is proposed, where a full-corporate-feed waveguide is arranged in the lower layer. This antenna can be built up easily by the process of diffusion bonding of laminated thin metal etching plates, which has high precision and is possibly a low cost technique. The radiating elements and the feed waveguide are designed to suppress the reflection over a wideband. The predicted bandwidth of the reflection less than -14 dB is 8.3% for a 16 × 16-element array antenna. A test antenna is fabricated in the 60-GHz band, and about 80% antenna efficiency with more than 32 dBi is achieved over 4.8 GHz.

Dynamically Stabilized Bright Solitons in a Two-Dimensional Bose-Einstein Condensate

Abstract: We demonstrate that a matter-wave bright soliton can be stabilized in 2D free space by causing the strength of interactions to oscillate rapidly between repulsive and attractive by using, e.g., Feshbach resonance.

Cepstral analysis synthesis on the mel frequency scale

Abstract: This paper presents a new technique of cepstral analysis synthesis on the mel frequency scale, the log spectrum on the mel frequency scale (the mel log spectrum) is considered to be an effective representation of the spectral envelope of speech. This analysis synthesis system uses the mel log spectrum approximation (MLSA) filter which was devised for the cepstral synthesis on the mel frequency scale. The filter coefficients are easily obtained through a simple linear transform from the mel cepstrum defined as the Fourier cosine coefficients of the mel log spectral envelope of speech. The MLSA filter has a low coefficient sensitivity and a good coefficient quantization characteristics. The spectral distortion caused by interpolation of the filter parameters of two successive frames is small. Accordingly, the data rate of this system is very low. The same quality speech is synthesized at 60-70 % of data rates in the conventional cepstral vocoder or the LPC vocoder.

Phase transitions in pyrolitic mantle around 670‐km depth: Implications for upwelling of plumes from the lower mantle

Abstract: [1] Phase relations in the natural pyrolitic mantle composition (KLB-1) around 670-km depth have been determined at 1600–2200°C by high-pressure experiments using multianvil apparatus. A phase transition between majorite garnet and Al-bearing Mg-rich perovskite occurs at depths similar to the postspinel phase transition. The seismic discontinuity observed at this depth could be caused by a combination of both transitions. The majorite-perovskite transition boundary has a positive Clausius-Clapeyron slope (+0.0013 GPa/°C for majorite-out curve), in contrast to the negative slope of the postspinel phase boundary (−0.0028 GPa/°C). Both transition boundaries cross each other at 1700–1800°C. Below this temperature, formation of Mg-perovskite starts at the majorite-perovskite or akimotoite-perovskite transition coexisting with ringwoodite but is predominantly formed by the postspinel phase transition at higher pressures. On the other hand, the stability of majorite significantly expands relative to Mg-perovskite at higher temperatures. Majorite becomes a dominant postspinel phase, and a majority of Mg-perovskite is formed by the majorite-perovskite transition with a positive Clapeyron slope. Phase transition within high-temperature plumes (>1800°C at 670-km depth) assists their upwelling from the lower mantle through the 670-km boundary. The depth of the 670-km seismic discontinuity becomes much less temperature-sensitive and is greater in such a higher temperature region.