Development of a high power density 2.5 kW class solid oxide fuel cell stack

We have developed a 2.5 kW class solid oxide fuel cell stack. It is constructed by combining 70 power generation units, each of which is composed of an anode-supported planar cell and separators. The power generation unit for the 2.5 kW class stack were designed so that the height of the unit were scaled down by 2/3 of that for our conventional 1.5 kW class stack. The power generation unit for the 2.5 kW class stack provided the same output as the unit used for the conventional 1.5 kW class stack, which means that power density per unit volume of the 2.5 kW class stack was 50% greater than that of the conventional 1.5 kW class stack.     

Influence on moisture and hydrocarbons on conversion rate of tritium in catalytic reactors of fusion-DEMO detritiation system

Thoughtful consideration of abnormal events such as fire is required to design and qualify a detritiation system (DS) of a nuclear fusion facility. Since conversion of tritium to tritiated vapor over catalyst is the key process of the DS, it is indispensable to evaluate the effect of excess moisture and hydrocarbons produced by combustion of cables on tritium conversion rate considering fire events. We conducted demonstration tests on tritium conversion under the following representative conditions: (I) leakage of tritium, (II) leakage of tritium plus moisture, and (III) leakage of tritium plus hydrocarbons. Detritiation behavior in the simulated room was assessed, and the amount of catalyst to fulfill the requirement on tritium conversion rate was evaluated. The dominant parameters for detritiation are the concentration of hydrogen in air and catalyst temperature. The tritium in the simulated room was decreased for condition (I) following ventilation theory. An initial reduction in conversion rate was measured for condition (II). To recover the reduction smoothly, it is suggested to optimize the power of preheater. An increase in catalyst temperature by heat of reaction of hydrocarbon combustion was evaluated for condition (III). The heat balance of catalytic reactor is a point to be carefully investigated to avoid runaway of catalyst temperature.     

Fabrication and morphological control of ion-induced zinc nanostructures

An efficient method for the fabrication of zinc (Zn) nanostructures (nanoneedles and nanofibers) of controllable density and morphology without any catalyst, hazardous chemicals or external heat supply has been investigated. By varying the ion irradiation time and the ion current density, morphological control and the density of Zn nanostructures were successfully achieved using a fast and viable ion irradiation technique. Scanning (SEM) and transmission electron microscopy (TEM) results revealed that the sputtered surface was almost entirely covered with densely distributed conical and needle-like protrusions with linear shaped (sometimes curved) nanostructures (such as nanoneedles and nanofibers) with diameters and lengths of about 20-50 nm and several hundred nanometers, respectively. Detailed analysis of selected area electron diffraction (SAED) patterns with TEM analysis indicates that the Zn nanofibers were polycrystalline in nature. A possible mechanism of the formation of Zn nanostructures is briefly discussed. These aligned arrays of Zn nanoneedles/nanofibers could be a promising material for the fabrication of zinc oxide nanostructures by subsequent oxidation of Zn nanostructures and their future application in nanodevices. Thus, it is believed that this ion irradiation technique could open up a new approach for the fabrication of many kinds of nanomaterials of controllable density.     

Numerical verification of a simplified model for vapor bubble lift-off from a hydrophilic heated flat-wall

Three-dimensional interface tracking simulations were carried out to investigate the role of surface tension force in the process of vapor bubble lift-off from a hydrophilic heated surface in nucleate boiling. Since bubbles are frequently flattened along the heated surface in photographic experiments reported in literature, a bubble was assumed to be spheroidal in shape in the initial condition. The effect of phase change at the bubble interface was not taken into consideration for the sake of simplicity. In the present numerical simulations, the initially spheroidal bubble approached the spherical shape due to the surface tension force and was eventually lifted off the surface. The change in bubble shape induced local liquid flow directing toward the bubble base, that was the direct cause of the occurrence of the bubble lift-off. The dependence of the bubble migration velocity on several important parameters including the bubble size, surface tension coefficient and the density of surrounding liquid was also investigated. The change in bubble shape from flattened to more rounded causes the reduction of the surface energy, while the formation of local liquid flow leads to an increase in the kinetic energy. It was demonstrated that the bubble migration velocity after the lift-off can successfully be interpreted from the standpoint of energy conservation during the lift-off process.     

Basic Study of a Ship Navigator's Stress Using Salivary Amylase Activity

Evaluation of ship handling mental workload/training has usually depended on professionals (captain, pilot) who have a lot of experience on board. We are attempting to evaluate a ship navigator's mental workload (stress) based on a physiological index. The physiological indices, heart rate variability (R-R interval) and nasal temperature, are good indices of the stress found in ship handling. It is best if we get response and evaluation results quickly on the spot. A recent study shows salivary amylase activity is induced by the sympathetic nervous system; however, a research on ship navigator has not yet accepted worldwide. This article proposes that salivary amylase activity shows a ship navigator's stress during ship handling. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis of Extensible Reinforcement Subject to Oblique Pull

A rational analysis of extensible sheet reinforcement subjected to an oblique end force has been presented that properly accounts for complex soil-reinforcement interaction and involves stress-deformation relationship implicitly. The results can be used for internal design of geosynthetic reinforced soil walls against pullout failure and tension failure. The pullout force and the end displacement at pullout for an extensible reinforcement are found to be almost the same as those for an inextensible reinforcement if the ratio of the reinforcement stiffness to the axial pullout capacity J* is greater than 15. With decrease in J* below 15, the maximum strain increases, the pullout failure becomes irrelevant, the tension failure dominates and the maximum allowable oblique force decreases. A minimum stiffness of about 25 times the axial pullout capacity is required to avoid the tension failure before the pullout provided the failure strain is 0.1. The predicted results have been calibrated against the finite-element analysis of pullout tests and detailed back analyses of published test data on model reinforced walls constructed with a wide range of extensible materials. The present analysis gives better predictions of the critical height against the pullout and the tension failure in model reinforced soil walls constructed with extensible reinforcements as compared to that of Rankine’s method.     

Amorphous In-Ga-Zn-O thin-film transistor with coplanar homojunction structure

Amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with a coplanar homojunction structure are demonstrated. The coplanar source and drain regions made of a-IGZO were formed by depositing a hydrogenated silicon nitride (SiN_X:H) layer onto the a-IGZO layer. The a-IGZO regions on which the SiN_X:H layer was directly deposited showed the low resistivity of 4.7 × 10⁻³  Ω cm and degenerated conduction. The fabricated TFT showed excellent transfer and output characteristics with a field-effect mobility of 11 cm² V^− 1 s^− 1, a subthreshold swing of 0.17 V decade^− 1, and an on-to-off current ratio larger than 1 × 10⁹. The width-normalized source-to-drain resistance (R_sdW) calculated using a channel resistance method was 51 Ω cm. This TFT also showed good stability over environment change and under electrical stress.     

Cloning and expression of chitin deacetylase gene from a Deuteromycete, Colletotrichum lindemuthianum

The chitin deacetylase gene was cloned from cDNA of Colletotrichum lindemuthianum ATCC 56676, and the open reading frame consisted of a possible prepro-sequence of 27 amino acids at the N-terminus and a mature chitin deacetylase. The deduced amino acid sequence of the mature enzyme revealed 26% identity and 46% similarity with a chitin deacetylase from Mucor rouxii. The molecular mass of the protein estimated from the amino acid sequence data was 24.3 kDa, which was in good agreement with the MALDI-TOF MS analysis data of the purified protein (24.17-24.36 kDa). The gene product was overexpressed in Escherichia coli cells as a fusion protein with six histidine residues at its C-terminus. The fusion protein formed inclusion bodies, but chitin deacetylase activity was restored from the inclusion bodies by a simple renaturation step with 8 M urea treatment. The recombinant enzyme was purified by affinity chromatography and gel filtration steps, and had a final specific activity of 4.22 units mg(-1) of protein. Trypsin digestion of the recombinant enzyme resulted in 2.1-fold increase in activity, suggesting that the removal of the prepro-domain from the recombinant enzyme resulted in an increase in its activity.     

Establishment of Intestinal Organoid from Rousettus leschenaultii and the Susceptibility to Bat-Associated Viruses,SARS-CoV-2 and Pteropine Orthoreovirus

Various pathogens, such as Ebola virus, Marburg virus, Nipah virus, Hendra virus, Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and SARS-CoV-2, are threatening human health worldwide. The natural hosts of these pathogens are thought to be bats. The rousette bat, a megabat, is thought to be a natural reservoir of filoviruses, including Ebola and Marburg viruses. Additionally, the rousette bat showed a transient infection in the experimental inoculation of SARS-CoV-2. In the current study, we established and characterized intestinal organoids from Leschenault’s rousette, Rousettus leschenaultii. The established organoids successfully recapitulated the characteristics of intestinal epithelial structure and morphology, and the appropriate supplements necessary for long-term stable culture were identified. The organoid showed susceptibility to Pteropine orthoreovirus (PRV) but not to SARS-CoV-2 in experimental inoculation. This is the first report of the establishment of an expandable organoid culture system of the rousette bat intestinal organoid and its sensitivity to bat-associated viruses, PRV and SARS-CoV-2. This organoid is a useful tool for the elucidation of tolerance mechanisms of the emerging rousette bat-associated viruses such as Ebola and Marburg virus.     

Electron microscopic study on residual defects of Al+ or B+ implanted 4H-SiC

The residual defects of Al⁺- or B⁺-implanted 4H-SiC were studied in combination with annealing temperature and implantation temperature using cross-sectional transmission electron microscopy technique. Noticeable defects structure is not observed before post-implantation annealing. But after annealing, a lot of black spots appear in the implanted layer. These black spots are composed of a dislocation loop, parallel to {0001} of 4H-SiC, and strained area at the upper and lower sides of the dislocation loop. This defect structure and its size do not depend on implantation temperature and implanted ion species. The size of defect area depends only on post-implantation annealing temperature. The size grows, when post-annealing temperature is raised.