The effect of ceria content in nickel–ceria composite anode catalysts on the discharge performance for solid oxide fuel cells

Optimum ceria content in nickel–ceria composite anode catalyst from the point of discharge performance is discussed. The ohmic loss increased when the ceria content was higher than 30 mol%. Even though the electrical conductivity of the anode decreased with increasing ceria content in the anode catalyst in association with decreasing nickel content, the ohmic loss was kept low until the ceria content was ≤30 mol% because the semiconducting ceria compensated for the decreased current path owing to the decreasing nickel content. The lowest activation loss was observed when the ceria content in the nickel anode catalyst was 30 mol% and the maximum activation loss was obtained for ceria content of 2 mol%. Ceria content in nickel anode influenced microstructure of the anode matrix. When the CeO₂ content was 2 mol%, sintering of anode catalyst was evident and the porosity of anode matrix was almost 57% - highest in this study. Whereas sintering of anode catalyst was not evident and the porosity of anode matrix was 46% when the ceria content in the nickel anode catalyst was 30 mol%. Activation loss was strongly influenced by microstructure of anode matrix, and highest activation loss when the CeO₂ content was 2 mol% was owing to the inappropriate microstructure for electrochemical reaction: sintering of the anode catalyst and excessive porosity of the anode.     

A method for aerosol particle removal by applying condensation phenomena

This paper describes an experimental study on a method of removing aerosol particles from air by condensing heated and humidified air. In the experiment, air, including aerosol particles, is circulated by a fan in a closed clean room system consisting of a closed vessel, a humidifier, two condensers, and an after-heater. The concentration of aerosol particles at the inlet of the closed vessel, the relative humidity, and the temperature in the system are measured for several humidification and condensation conditions. We find that the removal rate of aerosol particles in air increases when the mass flow rate of the condensate increases, by means of enlarging the temperature difference between the heating water in the humidifier and the cooling water in the condensers. We also show that this method is more effective when the temperature level in the humidifier is increased. The aerosol particle removal mechanism of this method is considered to be related to the generation of mist using aerosol particles as nuclei, inertia trapping, and the suction effect of condensation. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(6): 398–409, 1997     

Growth and structural characterization of molecular superlattice of quaterrylene and N,N′-dioctyl-3,4,9,10-perylenedicarboximide

A molecular superlattice consisting of alternate layers of N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈) and quaterrylene was prepared by using an ultra-slow deposition technique. Film growth under equilibrium conditions with precise optimization of the substrate temperature enabled the layer-by-layer stacking of hetero-molecules at a single-layer level. The morphology of the films and the orientation of the molecules in each layer were analyzed by atomic force microscopy (AFM) and an X-ray reflection (XRR) technique.     

Far infrared absorption spectra of amorphous (As2S3)−(Sb2S3) semiconductors and the spatial charge fluctuation

Far infrared absorption spectra of amorphous (As₂S₃)_1?x(Sb₂S₃)_x system (x=0.0～0.6) were measured in the wavenumber region 7～25 cm^?1 with Lamellar grating far infrared Fourier Transform Spectrometer, and the spatial fluctuation of charges and its correlation range were estimated with charge fluctuation model. The charge fluctuation of (As₂S₃)_1?x(Sb₂S₃)_x system increases with Sb₂S₃ concentration x. On the other hand, the correlation length of the charge fluctuation decreases from 7 A to 4.5 A with an increase in x. As a result, it can be found that the medium range order of As₂S₃ changes drastically with an incease in Sb₂S₃ concentration x.     

Laser‐induced burst corona and streamer corona for a positive DC nonuniform field gap in N2/NO mixtures

The characteristic of sparkover in a DC nonuniform field gap is closely related to the discharge mode at the onset time of corona. In order to investigate the transition mechanism from burst corona to glow corona or streamer corona, a discharge experiment which is controlled by a pulsed laser in N₂/NO mixture has been performed. From highly sensitive observation of discharge luminescence which corresponds to the discharge current wave, the transition from burst corona to streamer corona is identified by the electron avalanche, which is formed initially at the tip of the rod electrode with the highest electric field, and the effect of secondary ionization. Moreover, it is verified that the measured electron burst drift time with laser irradiation in the discharge gap is determined by the electric field of the discharge gap. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 10–17, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10007     

Consideration on safety research strategy toward commercialization of FBRs

The situation of FBR enters upon development stage expecting to commercialize upto 2030's and has not yet established the concept of commercialized FBR plant. The primary subject is remarkable improvement of economy which can be accomplished through higher performance of plant systems, reduction of the amount of materials of the plant due to simplification of the plant systems and maximization of plant availability. This subject can be solved by development of foresighted plant design through full utilization of the inherent safety characteristics of FBR's. The secondary subject is acquirement of public confidence of FBR safety. If recriticality accident can be eliminated from the safety analysis for licensing of future FBRs with firm experimental evidences, then safety logic for the FBRs will more simple and thus friendly to the public. Then the public will be quite confident of safety securement of the FBR system and will be free from any anxiety. Discrepancy of the confidence level of FBR safety between the experts and the public will be significantly improved by showing experimental evidence of elimination of recriticality accidents. In addition, an optimized plant design for further reduction of the plant construction cost can be accomplished by elimination of recriticality accidents in an FBR plant design. In order to realize the above experiments and clarify these phenomena with a subassembly scale, development of new in-pile experimental facility using real materials in an FBR core is essential. Considering requirements of prototypicality or objectives for demonstration, it is concluded that the new in-pile experimental facility should be built early in the next century. The tertiary subject is reinforcement of FBR safety and reliability technologies in a more broad sense developed by the industry's voluntary safe-ensuring activities. These requirements have been realized through lessons learned from the sodium leak incident in the secondary heat transport system of Monju occurred on December 8th, 1995. For acquirement of social confidence on FBR safety by the public, significant amount of sodium leakage should be precluded, even if spilled sodium is non-radioactive and thus gives no radiological consequence to the public. Countermeasures for prevention and mitigation against such sodium leakage should be reinforced not as regulation-based activities but as the voluntary safe-ensuring activities by the utilities/development organizations. It thus appears that development of rules, standards and guidelines made by the industries in addition to reinforcement of wide range of sodium-related fundamental technology are essential for the future commercialization of FBRs.

In order to solve the above-mentioned subjects, it is essential to optimize and clarify the roles between the government and industries, to execute safety researches based on the well-organized long-term plan and to make the most use of international cooperation.     

Flashover phenomena in positive rod-to-plane air gaps under impulse and DC voltages

Discharge phenomena in positive rod-to-plane air gaps under lightning impulse and dc voltages were investigated. Under impulse voltages, the 50 percent flashover voltages agree with the 50 percent corona inception voltages only in a gap shorter than a certain value d_c which increases with the rod diameter φ. The 50 percent flashover voltage at d_c rises at a rate of about 14 kV/cm with d_c in the range of d_c < 2.8 cm (φ ? 1.5 cm), and then it rises at a rate of about 5 kV/cm. Experimental results show that the flashover process in the former region (termed the Gp process) is different from that in the latter region (the Lp process). Under dc voltages, the critical gap length, at which the first corona may lead to flashover without any succeeding streamer corona, corresponds to d_c under impulse voltage. In a gap shorter than d_c flashover occurs through the Gp process (φ ? 1 cm) or Lp process (φ ≥ 2 cm), but in gap longer than d_c flashover may occur through another process which cannot be seen under impulse voltages. In this paper, those flashover characteristics and processes are described on the basis of experimental results and photographic observations with an image converter camera.     

A combined engineering model for the analysis of switching surge flashover characteristics of long air gaps

The flashover characteristics of long air gaps submitted to switching surge voltages may be predetermined by use of a mathematical model of leader propagation. The present model is developed from each combination of previous engineering models, and is also applied to positive rod-to-plane geometries with gap lengths up to 20 m. However, four parameters to determine leader propagation with respect to our model are adjusted in the present calculation so as to fit experimental flashover voltages and calculated flashover voltages which depend on waveforms of the applied voltage and gap length. The calculations show that these parameters are only a function of gap length. Our combined engineering model using parameters that depend on gap length allows the flashover characteristics of long air gaps to be easily determined with a microcomputer.     

Proteasome from rabbit skeletal muscle: Some properties and effects on muscle proteins

Rabbit proteasome, likely to be a 20S proteasome, was purified and its properties were investigated to clarify its contribution to proteolysis during meat conditioning. The purified enzyme migrated as a single band on non-denaturing polyacrylamide gel and dissociated to a number of subunits (20000–29000 Da) under denaturing conditions. The molecular mass of this enzyme was found to be 580 000–800 000 Da by Sephacryl S-300 column chromatography. The isoelectric point of this enzyme was 5.5. The optimum pH for hydrolysis of succinyl-Leu-Leu-Val-Tyr-(4-methylcoumaryl-7-amide) (Suc-LLVY-MCA) was 8. This enzyme was almost stable in the range of pH 5–9 and up to 60 °C at pH 7.2. The enzyme activity was inhibited by diisopropyl fluorophosphate (DFP) and chymostatin, but was not affected by EDTA, leupeptin, E-64, bestatin, monoiodoacetic acid or pepstatin. The enzyme was activated about 8-fold by 0.01% sodium dodecyl sulfate (SDS), but was not by ATP or CaCl₂. Remarkably, SDS increased the V_max value of the enzyme. Rabbit proteasome was shown to degrade myosin heavy chain, -actinin, actin, tropomyosin, troponins and myosin light chains in the presence of SDS. In the absence of SDS, no change in myofibrillar proteins was observed. This enzyme did not degrade any sarcoplasmic proteins regardless of the presence of SDS.     

Study on Ag/Sn multilayer thin film bonding for 3D stacked semiconductor

Through-silicon via (TSV) technology for 3D stacking is attracting much attention as a means of alleviating the miniaturization limits on advanced semiconductor devices. Despite a great deal of research, low load (<1 MPa), low temperature (<473 K) and short time (<300 s) solid phase bonding with high heat resistance (>623 K) to prevent the damage of weak low-k dielectric material, etc. has not been realized. In this work, we examine a new Ag–Sn thin film bonding system to replace Cu–Cu direct bonding. It is found that Ag/Sn/nano Ag-nano Ag/Sn/Ag thin film bonding systems (especially when the film thickness of the surface Ag is controlled to around 10 nm) is a promising approach because (1) it enables low load (<0.4 MPa), low temperature (<453 K) and short time (<300 s) bonding, and (2) the bonded interface has a high heat resistance (>673 K) and joint strength (>29 MPa). It is found that it may be possible to realize an optimal solid-phase bonding system for wafer-level 3D-stacking for 3D-IC which can satisfy a hierarchical temperature-based bonding method that includes TSV formation.