Microstructures and luminescent properties of Ce-doped transparent mica glass-ceramics

Transparent mica glass-ceramics were prepared by heating parent glasses that had been doped with 0.5–15 mol% CeO₂. During the melting and heat treatment, Ce⁴⁺ ions in the specimens were reduced to Ce³⁺ ions, and one or both of these ion species were then replaced with Li⁺ ions in the interlayers of the separated mica crystals. However, scanning transmission electron microscope (STEM) and Z-contrast imaging revealed that the mica crystals did not contain the same amount of Ce. On excitation at 254 nm, the parent glasses and glass-ceramics emitted blue light, which originated from the 5d to 4f transition of the Ce³⁺ ions. The emission of the glass-ceramic containing a smaller amount of Ce was attributed to the Ce³⁺ ions in both the glass phase and the mica crystals, whereas that of the glass-ceramics containing a larger amount of Ce was caused mainly by Ce³⁺ ions in the mica crystals. The dependence of the emission band of the parent glasses on the amount of Ce was a unique feature of the Ce-doped transparent mica glass-ceramics and was not observed in previous studies of Eu-doped parent glasses and mica glass-ceramics.     

Pyrolysis and gasification characterization of sewage sludge for high quality gas and char production

A study on pyrolysis, steam gasification, and carbonization-activation was conducted to produce energy and resource from waste sewage sludge. Carbonization-activation is a sequential process of pyrolysis and steam gasification. The experiment was conducted with a batch-type fixed bed reactor. A comparative analysis on the formation characteristics of products, such as gas, tar, and char, was conducted to evaluate the three cases. For sludge char, carbonization-activation showed the largest amount of porosity in the char, and its specific surface area was 80.28 m²/g with an average pore diameter of 6.229 nm. The best adsorption ability of benzene, a light tar, was 175 mg/g. For the producer gas, steam gasification obtained the largest amount of 20.1 L. Similarly, carbonization-activation showed a large value of 16.6 L. Hydrogen and carbon monoxide concentrations were higher in the producer gas due to steam reforming compared with carbonization-activation. Energy yields were 209 kJ and 226 kJ for steam gasification and carbonization-activation, respectively. The amount of tar formation did not show a significant difference, but the largest one was found in steam gasification. The gravimetric tar amount for steam gasification was 23.5 g/Nm³. However, the selected light tar displayed the lowest concentration for the carbonization-activation. Such concentrations were 2.79 g/Nm³, 0.75 g/Nm³, 0.14 g/Nm³, and 0.14 g/Nm³ for benzene, naphthalene, anthracene, and pyrene, respectively. Therefore, carbonization-activation was found to be the most effective process for producing high quality sludge char and producer gas for utilizing waste sludge into renewable energy and resources.     

Relationship between current waveform just before current zero and interruption ability of high‐speed VCB

A high‐speed vacuum circuit breaker which forces the fault current to zero was investigated. The test circuit breaker consisted of a vacuum interrupter and a high‐frequency current source. A vacuum interrupter with an axial magnetic field electrode and a disk‐shaped electrode was tested. The arcing period of the high‐speed vacuum circuit breaker is much shorter than that of a conventional circuit breaker. The arc behavior of the test electrodes immediately after the contact separation was observed by a high‐speed video recorder. The relation between the current waveform just before the current zero point and the interruption ability was investigated experimentally by varying the high‐frequency current source. The results demonstrate the interruption ability and the arc behavior of the high‐speed vacuum circuit breaker. Effective current interruption is made possible by a low current period just before the current zero point, even though the arcing time is short and the arc is concentrated. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(2): 20–27, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20915     

Estimating mean life of an aged power equipment group with operation data sequence

This paper proposes a systematic method of estimating the mean life of an aged power equipment group based on the approach of Dr. W. Li of BCTC, Canada (IEEE Transactions on Power Systems, February 2004). In order to estimate the mean life of aged power equipment systematically and effectively with the operation data sequence, a linear estimation method is developed on the assumption that the stochastic behavior of aged equipment life determines the probability distribution model, such as the normal model or the Weibull model. Introductory and practical examples are illustrated for verification of the proposed approach. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 18–25, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20961