Rail brake system using a linear induction motor for dynamic braking

One type of braking system for railway vehicles is the eddy current brake. Because this type of brake has the problem of rail heating, it has not been used for practical applications in Japan. Therefore, we proposed the use of a linear induction motor (LIM) for dynamic braking in eddy current brake systems. The LIM reduces rail heating and uses an inverter for self excitation. We estimated the performance of an LIM from experimental results of a fundamental test machine and confirmed that the LIM generates an approximately constant braking force under constant current excitation. At relatively low frequencies, this braking force remains unaffected by frequency changes. The reduction ratio of rail heating is also approximately proportional to the frequency. We also confirmed that dynamic braking resulting in no electrical output can be used for drive control of the LIM. These characteristics are convenient for the realization of the LIM rail brake system. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 29–38, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21209     

Influence of seed sludge and pretreatment method on hydrogen production in packed-bed anaerobic reactors

Several studies have reported on the effects of inoculums source and pretreatment on biological hydrogen production. However, there have been few studies on continuous reactors. This paper investigated the influence of different seed sludge sources and pretreatment methods on biohydrogen production in up-flow anaerobic fixed-bed reactors fed with sucrose. The following inoculum sources were included in the study: (1) anaerobic sludge from an up-flow anaerobic sludge blanket (UASB) reactor used to treat poultry slaughterhouse wastewater (Sl), (2) anaerobic sludge from a UASB reactor used to treat swine wastewater (Sw) and (3) autofermentation (A). Heat (He) and acid (Ac) shock were used to increase hydrogen production and suppress hydrogen consumption. The average hydrogen yields (HY) in the experiment were 2.1 (A), 2.0 (SlHe), 2.0 (SlAc), 1.0 (Sl), 1.0 (SwAc), 0.7 (SwHe) and 0.7 (Sw) mol H₂ mol⁻¹ sucrose. Although heat shock produced the maximum HY value (SlHe), acid pretreatment (SlAc) resulted in more stable hydrogen production with the largest average value, which could be an advantage of using pH shock. The autofermentation process presented HY values similar to those produced with SlAc and SlHe, making it a suitable seed sludge for biohydrogen production because pretreatment was not required.     

Chemical states of fallout radioactive Cs in the soils deposited at Fukushima Daiichi Nuclear Power Plant accident

The chemical states of radioactive Cs (caused by Fukushima Daiichi Nuclear Power Plant accident) in the contaminated soils have been characterized by the desorption experiments using appropriate reagent solutions and size fractionation of the contaminated soils. More than 65% of radioactive Cs remained in the residual fraction of the soil samples after treatment of 1 mole L^?1 NH₄Cl solution and 1 mole L^?1 CH₃COOH solution. Approximately 70% of radioactive Cs in the residual fraction were associated with the size fractions larger than the elutriated one, even though mica-like minerals were present in the elutriated one. These results strongly suggest that radioactive Cs was irreversibly associated with soil components other than mica-like minerals in the contaminated soil.     

Microstructural stability of Ag sinter joining in thermal cycling

As a heat-resistant die attach technology processed at low temperatures, three Ag filler-based sinter joining materials have been proposed. Among these, Ag flake pastes exhibited the greatest potential. Joining was carried out by sintering Ag nanoparticles/flakes in air at 200 °C for 60 min. All of the joined samples survived up to 1,000 thermal cycles in a temperature range from ?40 to 180/250 °C with a 30 min dwell time. In particular, the joining strengths with the Ag micron and, Ag nano-thick flake pastes maintained excellent strength. Neither thermal fatigue cracks nor large voids were observed in the Ag sintered layers. Thus, low-temperature and low-pressure sinter joining with Ag flakes is expected to have an application in high power semiconductor devices for ultra-high temperature operation.     

Electrical resistivity changes due to interstitial hydrogen in palladium-rich substitutional alloys

The changes in electrical resistivity of palladium solid solution alloys (alloying element = silver, gold, copper, yttrium, cerium, titanium, zirconium, vanadium, niobium and tantalum) with hydrogen concentration were measured at 301 K up to aboutr(H/M) = 1.5×10^–2; the hydrogen was introduced by electrolysis and measurements of electrode potential were also made. The specific electrical resistivity increment per unit change of hydrogen concentration, 1r, generally increases with increase of the solute contents, although for silver, gold and copper there are no notable changes in the slopes with their concentrations. The increase in /g9/r with the alloying contents cannot be related to the lattice dilatation effect due to the solute, but it is associated approximately with a decrease in the density-of-states at the Fermi level caused by pre-filling of the 4 d band of palladium by the solute atoms.     

Chemical solution processing of sr2(nb,ta)2o7 thin films

Abstract

Sr₂(Nb,Ta)₂O₇ thin films have been synthesized by chemical solution deposition. Homogeneous and stable Sr₂(Nb,Ta)₂O₇ precursor solutions with various Nb/Ta ratios were prepared by controlling the reaction of metal alkoxides in ethanol with a key additive of 2-ethoxyethanol. The crystallization temperature of the perovskite-type Sr₂(Nb,Ta)₂O₇ slabs structure decreased with increasing Nb substitution in amount. The crystallization temperature of Sr₂(Nb_0.2Ta_0.8)₂O₇ films on Pt/Ti/SiO₂/Si and Pt/Ir/Ti/SiO₂/Si substrates was above 800°C. On the other hand, by using Pt(100)/MgO(100) as a substrate, Sr₂(Nb,Ta)₂O₇ thin films crystallized into the Sr₂(Nb,Ta)₂O₇ phase at 700°C.     

Chemical Processing and Properties of (Sr,Ca) 2 (Nb,Ta) 2 O 7 Thin Films

Ca-doped Sr 2 (Nb,Ta) 2 O 7 thin films have been synthesized by the chemical solution deposition. Homogeneous and stable (Sr,Ca) 2 (Nb,Ta) 2 O 7 precursor solutions were prepared by optimizing the reaction of starting metal alkoxides in ethanol with a key additive of 2-ethoxyethanol. The improvement of ferroelectric properties of the Sr 2 (Nb,Ta) 2 O 7 based films were achieved through the Ca substitution into Sr 2 (Nb 0.3 Ta 0.7 ) 2 O 7 as well as the optimization of heating conditions. The crystallization temperature of the layered perovskite (Sr 0.9 Ca 0.1 ) 2 (Nb 0.3 Ta 0.7 ) 2 O 7 thin films on Pt/Ir/Ti/SiO 2 /Si substrates was found to be above 750C. (Sr 0.9 Ca 0.1 ) 2 (Nb 0.3 Ta 0.7 ) 2 O 7 thin films crystallized at 750C exhibited P r of 0.51 w C/cm 2 and E c of 69 kV/cm.     

A field study of lightning overvoltages in low‐voltage distribution lines

The number of home electric appliances, such as personal computers and telephones, has been rapidly increasing. Lightning damage to these home electric appliances has a great impact on a highly sophisticated information society. There are cases in which lightning overvoltages in low‐voltage distribution lines cause malfunctions in them, even though they are equipped with surge protective devices to protect against lightning overvoltages. Therefore, for lightning protection of low‐voltage equipment including home electric appliances, it is important to understand the phenomenon of lightning overvoltages in low‐voltage power distribution lines. However, many aspects of this problem are not entirely clear, in particular how they are generated. The Tokyo Electric Power Company carried out lightning observations on low‐voltage distribution lines. The observation results provide a statistical distribution of lightning overvoltages in low‐voltage distribution lines. A mechanism for generating lightning overvoltages in low‐voltage distribution lines is inferred from the observed waveforms and facilities data. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(2): 12–21, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21299     

Optimum operating conditions for a two-stage gasification process fueled by polypropylene by means of continuous reactor over ruthenium catalyst

We studied fuel gas production by means of pyrolysis and steam reforming of waste plastics for applications in solid oxide fuel cells. More specifically, we evaluated the effects of pyrolytic gasification temperature, catalyst content, steam reforming temperature, and weight hourly space velocity for a Ru catalyst used in a 60 g h^− 1-scale continuous experimental apparatus, which consisted of a tank reactor for pyrolysis and a packed-bed catalytic reactor for steam reforming. Polypropylene (PP) pellets were used as a model waste plastic. Ru/γ-Al₂O₃ catalysts with two different Ru contents were investigated. To suppress residue formation, the optimum operating temperature of the pyrolyzer was 673 K. To ensure suppressed coke formation, sufficient carbon conversion to gaseous products, and minimized heat loss from the reactor, the optimum operating conditions for the reformer were determined to be 903 K and 0.11 g-sample g-catalyst^− 1 h^− 1 with a 5 wt.% Ru/γ-Al₂O₃ catalyst. The composition of the gas produced with the 5 wt.% catalyst was almost the same as that predicted by chemical equilibrium laws, and it was applicable for a direct hydrocarbon fuel cell.