GRAPE-6: The massively-parallel special-purpose computer for astrophysical particle simulation

In this paper, we describe the architecture and performance of the GRAPE-6 system, a massively-parallel special-purpose computer for astrophysical $N$-body simulations. GRAPE-6 is the successor of GRAPE-4, which was completed in 1995 and achieved the theoretical peak speed of 1.08 Tflops. As was the case with GRAPE-4, the primary application of GRAPE-6 is simulation of collisional systems, though it can be used for collisionless systems. The main differences between GRAPE-4 and GRAPE-6 are (a) The processor chip of GRAPE-6 integrates 6 force-calculation pipelines, compared to one pipeline of GRAPE-4 (which needed 3 clock cycles to calculate one interaction), (b) the clock speed is increased from 32 to 90 MHz, and (c) the total number of processor chips is increased from 1728 to 2048. These improvements resulted in the peak speed of 64 Tflops. We also discuss the design of the successor of GRAPE-6.Comment: Accepted for publication in PASJ, scheduled to appear in Vol. 55, No.

Photothermally controlled Marangoni flow around a micro bubble

We have experimentally investigated the control of Marangoni flow around a micro bubble using photothermal conversion. Using a focused laser spot acting as a highly localized heat source on Au nanoparticles/dielectric/Ag mirror thin film enables us to create a micro bubble and to control the temperature gradient around the bubble at a micrometer scale. When we irradiate the laser next to the bubble, a strong main flow towards the bubble and two symmetric rotation flows on either side of it develop. The shape of this rotation flow shows a significant transformation depending on the relative position of the bubble and the laser spot. Using this controllable rotation flow, we have demonstrated sorting of the polystyrene spheres with diameters of 2 μm and 0.75 μm according to their size

Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer

Efficient photoacoustic emission from Au nanoparticles on a porous SiO2 layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO2/SiO2/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO2 layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO2 layer (0.93). The contribution of the porous SiO2 layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature

Ring-shaped Pottery (kanjō hei) - (Vessels with a Ring-shaped Body Made of Tubeshaped Clay): Manufacturing Techniques and Lineages

Sue ware (wheel thrown stoneware) was manufactured from the Middle Kofun period on and includes ring-shaped vessels (kanjō hei). Their shapes resemble flat water bottles (sagebe; hanging bottle) or sake vessels (hirabe; funnel-shaped jug, flagon with closed, wide vessel body). This Sue ware was initially thought to yield only from the first half of the 7th century AD in the ancient province Aki (western part of Hiroshima Prefecture), but recently they have been unearthed all over the country. One discovered them not only in corridor-style stone chambers with horizontal lateral entrance from the first half of the 7th century AD but also in kiln sites which are dated between the second half of the 7th century AD and the middle of the 8th century AD. It can be classified into three types according to the manufacturing technique. To distinguish between older and younger types one can make judgements on the basis of the cross sections and decorative patterns of the bodies. The later evolve from circular to quadrilateral ones. Older body patterns also consist of a row of punctions while newer ones comprise wavy line patterns. The most recent ones are undecorated. Ring-shaped vessels were made between the first half of the 7th century AD and the middle of the 8th century AD. Although manufacturing technique and pattern composition changed during this production phase, it indicates that the cultures of the Kofun and Nara periods were not mutually exclusive

遷音速航空機用ボルテックス・ジェネレータの近似設計最適化

要約のみTohoku University大林茂課

Water Droplet Bouncing on a non-Superhydrophobic Si Nanosprings

Self-cleaning surfaces often make use of superhydrophobic coatings that repel water. Here, we report a hydrophobic Si nanospring surface, that effectively suppresses wetting by repelling water droplets. We investigated the dynamic response of Si nanospring arrays fabricated by glancing angle deposition. The vertical standing nanospring arrays were approximately 250 nm tall and 60 nm apart, which allowed the droplets to rebound within a few milliseconds after contact. Amazingly, the morphology of the nanostructures influences the impact dynamics. The rebound time and coefficient of restitution were also found to be higher for Si nanosprings than vertical SI columns. It has been proposed that the restoring force of the Si nanosprings may be responsible for the water droplet rebound and can be explained by considering the droplet/nanospring surface as a coupled spring system. These nanospring surfaces may find applications in self-cleaning windows, liquid-repellent exteriors, glass panels of solar cells, and antifouling agents for roof tiling.Comment: 19 pages, 5 figures, 2 table

Experimental Evidence of a Twofold Electromagnetic Enhancement Mechanism of Surface-Enhanced Raman Scattering

The electromagnetic enhancement mechanism is a major contributor to surface-enhanced Raman scattering enhancements, which are a direct consequence of the roughness present on noble metal surfaces. The electromagnetic enhancement mechanism is a twofold phenomenon that involves the enhancement of both the incident excitation and scattered Raman fields. In this paper, we report a direct observation of the double-enhancement mechanism using a Ag nanorod array/SiO₂ dielectric layer/Ag mirror multilayer thin-film “local plasmon resonator”. The effect of light interference was controlled by adjusting the film thickness of the SiO₂ phase control layer (PCL), and the absorption rate in the Raman scattering wavelength range was tuned from 90 to 0%. In addition to the characteristic Raman peak of an aqueous solution of 4, 4-bipyridine, the background of the Raman scattering spectrum was also enhanced. By examining the relationship between the background Raman emission and the absorption spectrum, we demonstrated that the intensity of the background emission is closely related to the surface-enhanced Raman scattering (SERS) enhancement. We further illustrated that the Raman scattered field and background were enhanced when the absorption was high in the wavelength range of the scattering field. The present results not only suggest that the PCL layer may increase the intensity of plasmon-mediated broadband emission but also provide us with sufficient evidence for a twofold SERS enhancement mechanism