FIR system identification based on a nonparametric Bayesian model using the Indian buffet process

In this paper, we propose a nonparametric Bayesian model combined with the Indian buffet process (IBP) for a finite impulse response (FIR) system. We develop an FIR system identification method that can simultaneously estimate the number of FIR taps and coefficients. In the proposed model, each FIR tap consists of a coefficient and a gain, and the gain is a binary value. An infinite-dimensional binary vector is composed of binary values, and we assume that this binary vector is generated by the IBP. To identify the FIR system, we specify the likelihood function and prior distributions of the parameters and derive their posterior distributions. We can simultaneously estimate the number of FIR taps and coefficients by sampling from posterior distributions using the Gibbs sampler. Our simulations demonstrate that although the number of FIR taps is unknown, the identification performance of the proposed method in a high signal-to-noise ratio environment is similar to or better than that of the conventional least square solution.     

Littrow-type external-cavity blue laser for holographic data storage

An external-cavity laser with a wavelength of 405 nm and an output of 80 mW has been developed for holographic data storage. The laser has three states: the first is a perfect single mode, whose coherent length is 14 m; the second is a three-mode state with a coherent length of 3 mm; and the third is a six-mode state with a coherent length of 0.3 mm. The first and second states are available for angular-multiplexing recording; all states are available for coaxial multiplexing recording. Due to its short wavelength, the recording density is higher than that of a 532 nm laser.     

Tunable blue laser compensates for thermal expansion of the medium in holographic data storage

A tunable laser optical source equipped with wavelength and mode-hop monitors was developed to compensate for thermal expansion of the medium in holographic data storage. The laser's tunable range is 402-409 nm, and supplying 90 mA of laser diode current provides an output power greater than 40 mW. The aberration of output light is less than 0.05 lambdarms. The temperature range within which the laser can compensate for thermal expansion of the medium is estimated based on the tunable range, which is +/-13.5 degrees C for glass substrates and +/-17.5 degrees C for amorphous polyolefin substrates.     

Application of femtosecond laser ablation for detaching grown protein crystals from glass capillary tube

We developed a novel technique for detaching protein crystals from glass capillary tube using the counter diffusion crystallization technique by femtosecond laser irradiation. X-ray diffraction analysis demonstrated that femtosecond laser irradiation has little effect on crystallinity. This technique will contribute to progress in structural genomics as a powerful tool.     

Purification and characterization of enzyme responsible for N-myristoylation of octapeptide in aqueous solution without ATP and coenzyme a from Pseudomonas aeruginosa

The enzyme that catalyzes N-acyl linkage between myristic acid and the NH(2)-terminal glycine residue of the octapeptide Gly-Asn-Ala-Ala-Ala-Ala-Arg-Arg-NH(2) in aqueous solution without ATP and coenzyme A was found in Pseudomonas aeruginosa. The enzyme was purified from cell-free crude extract using DEAE-Cellulose, Sephadex G-200, CM-Sephadex C-50, and hydroxyapatite column chromatographies, and then purified approximately 1900-fold with about 1.5% recovery of enzyme activity from the crude extract. Finally, the purified enzyme showed a main band on SDS polyacrylamide gel electrophoresis after staining with Coomassie Brilliant Blue. The band corresponded to a molecular mass of approximately 60 kDa. The K(m)s of the purified enzyme for the substrate myristic acid and the octapeptide were 0.36 and 2.6 mM, respectively. When myristoyl-CoA instead of myristic acid was used as the substrate for the enzyme reaction, myristoyl octapeptide could be synthesized as observed in the case of myristic acid. The K(m) of myristoyl-CoA was 0.17 mM.     

Quantum States of Helium Atoms Confined in Nanocage in Na-Y Zeolite

We have studied the heat capacities of heliums adsorbed in Na-Y zeolite down to 70 mK. The Y-type zeolite has void cages 1.3 nm in diameter connected through narrow apertures 0.8 nm in diameter. In the nanopores at low temperatures, the second-layer He adatoms can be confined in each cage by the first solid layer. In the quantum fluid region above the second-layer promotion, where the heat capacities show qualitative differences between ⁴He and ³He, the heat capacities of ³He adatoms and the thermal relaxation processes show large and non-monotonic changes when one ³He atom is added in each cage. These results strongly suggest that the quantum fluid formed in Na-Y zeolite is not fluid film spread over the entire substrate but quantum clusters confined in each cage.     

Quantification of SOFC anode microstructure based on dual beam FIB-SEM technique

The three-dimensional microstructure of an SOFC anode is quantified using a dual beam focused ion beam scanning electron microscopy (FIB-SEM) system equipped with an energy dispersive X-ray spectroscopy (EDX) unit. The microstructure of the Ni-YSZ anode is virtually reconstructed in a computational field using a series of acquired two-dimensional SEM images. The three-phase boundary (TPB) density and tortuosity factors are carefully evaluated by applying two different evaluation methods to each parameter. The TPB density is estimated by a volume expansion method and a centroid method, while the tortuosity factors are evaluated by a random walk calculation and a lattice Boltzmann method (LBM). Estimates of each parameter obtained by the two methods are in good agreement with each other, thereby validating the reliability of the analysis methods proposed in this study.     

Blow-off process of highly under-expanded hydrogen non-premixed jet flame

Relationships between flame lift-off heights and reservoir pressure were experimentally investigated in order to clarify blow-off process of hydrogen non-premixed jet flames with a highly under-expanded jet structure. In this study, straight nozzles with diameters of 0.34, 0.53, 0.75 and 1.12 mm were used with maximum reservoir pressure for spouting hydrogen of 13.2 MPa. Experimental results are shown that lift-off heights in stable under-expanded jet flames do not vary significantly and are independent of the reservoir pressure in the range of studied pressure. However, the lifted heights are affected by the nozzle diameters and become smaller as the nozzle diameters increase. From experimental results, the condition for the blow-off process of under-expanded subsonic jet flames was proposed. It was concluded that the under-expanded jet flame could be blown off when the maximum waistline position, where radial distance from the jet axis to an elliptic stoichiometric contour reaches its maximum comes closer to the nozzle exit than the edge of the jet flame base.     

JSFR key technology evaluation on fuel handling system

A simplified fuel handling system design for the demonstration Japan sodium-cooled fast reactor (JSFR) has been proposed. Fast Reactor Cycle Technology Development project phase I results of key technology evaluations on a pantograph fuel handling machine (FHM), a fuel transfer pot with two core component positions, dry spent fuel cleaning and minor actinide-bearing fresh fuel shipping cask are summarized. A full-scale FHM mockup has been fabricated and tested in the air accumulating performance and seismic tolerance data. A mockup fuel transfer pot with fins and chromium carbide coating has been fabricated and tested with sodium accumulating heat transfer performance data. Several sodium cleaning tests using a dummy subassembly has been conducted accumulating cleaning performance data. For fresh fuel shipping cask, a design tool for evaluation of heat transfer capability has been developed and a helium gas cask shows cooling capability of minor actinide-bearing fresh fuel. Those experimental and analytical efforts have shown that key technologies to develop simplified fuel handling system are matured enough to proceed large-scale sodium experiments and conceptual design study for the demonstration JSFR.