Analysis of high‐frequency oscillations in voltage transformers

High‐frequency oscillations in voltage transformers are analyzed by the FFT method, using an equivalent lumped circuit. Such an analysis has been regarded as difficult because the transformers used in high‐voltage distribution systems have a large number of turns. The constants of the equivalent circuit are evaluated on a turn‐to‐turn basis. The frequency domain analysis is followed by time domain analysis using the FFT technique. Both characteristics are verified by an experiment on a 6.6‐kV voltage transformer. The nature of the high‐frequency oscillation is shown for a simpler model. It is found that the interlayer voltage becomes highest at the entrance to the incoming surge. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 8–15, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20643     

A study on spot distortion for an in‐line self‐converging system for color CRTs

Abstract— The spot distortion at the screen periphery of an in‐line self‐converging CRT is formulated by considering four factors; (a) oblique incidence of the beam at the screen periphery, (b) increased path length of the beam, (c) beam compression due to the deflection, and (d) the astigmatism due to the deflection field. The analytic spot size calculated with the formulas agrees well with measurement, though the effects of a particular gun system, spherical aberration, and space‐charge repulsion are not taken into consideration in the formulas while assuming an ideal deflection field. The analytic formulas enable easy evaluation of spot distortion at the screen periphery because they give an intuitive understanding of beam behavior in the in‐line self‐converging system. In addition to the derivation of the formulas, “transposed scanning” is analyzed with the use of the formulas for one of the ways to optimize the spot distortion at the screen periphery.     

Relationship between microstructure of plasma-sprayed 8YZ coatings and thermal fatigue life of thermal barrier coatings

Microstructure of plasma-sprayed yttria-stabilized zirconia coatings (8YZ) was characterized by the measurement of surface roughness, hardness, and pore size distribution and was correlated with thermal fatigue life. It was confirmed that the coatings which had greater roughness tended to show both lower hardness and higher porosity. Furthermore, such coatings were found to have a longer thermal fatigue life. We propose that measurement of the roughness of 8YZ coatings is useful as a non-destructive evaluation method for predicting thermal fatigue life.     

Thermal Behavior of Nitrocellulose with Inorganic Salts and their Mechanistic Action

In this study, we investigated the effects of inorganic salts on the stability of NC and its reaction mechanism. Under isothermal conditions at 120 °C in an O₂ atmosphere, the induction time period for NC heat release was prolonged in the presence of Li₂CO₃, Na₂CO₃, CaCO₃, Mg(OH)₂, Ca(OH)₂, and MgO, all of which produce alkaline saturated solutions with a pH value of 10–12. In addition, the induction time period depended on this pH value. This suggests that these salts stabilized NC by neutralizing acids that would otherwise accelerate the hydrolysis of the O‐NO₂ bond. However, Sr(OH)₂ ⋅ 8H₂O and K₂CO₃, which produce strongly alkaline saturated solutions with pH>13, decreased the induction time period. It is possible that these strong bases caused alkaline decomposition of NC. In addition, for Sr(OH)₂ ⋅ 8H₂O, the released water of crystallization appeared to be related to NC destabilization. SrCO₃, NaHCO₃, K₂SO₄, CaSO₄, ZnSO₄, NaCl, CaCl₂, AgCl, and NaNO₂, which produce near‐neutral saturated solutions, slightly decreased the NC induction time period. The NC induction time period with these salts depended upon the solubility of the added salt. This may indicate that in the presence of these inorganic salts, the boiling point of water is increased, which reduces the vaporization of water from NC and thus accelerates the hydrolysis of NC.     

Study of Image Quality of Superimposed Projection Using Multiple Projectors

In this correspondence, we discuss the quality of images realized by a recently proposed method of generating a high-resolution image by superimposing multiple low-resolution images projected by different projectors. We show several fundamental properties of this method: 1) the accuracy of the image realization (e.g., resolution of the realized image) is heavily affected by the structures of the images to be realized, and 2) there is a tradeoff between the image quality and the maximum brightness of the images to be realized. These are properties peculiar to multiprojector super-resolution and are in contrast with multicamera super-resolution. The results will be helpful in evaluating the usefulness of the method.     

Superconducting properties of Ti-Nb-Hf alloys

To achieve improvements in superconducting properties of the Ti-Nb superconductor, effects of ternary additions of Hf have been extensively studied on 42 Ti-Nb-Hf alloys with compositions of 25 - 65at%Nb, 0- 15at%Hf and the balance Ti. Critical temperatures are found to depend upon Hf addition and aging temperature. In as-rolled Ti-40at%Nb-3at%Hf alloy the critical temperature is raised by about 0.3K over Ti- 40at%Nb alloy. Aging at 800°C can raise critical temperatures of high Hf alloys by 0.6 - 1.8K. The upper critical field at 4.2K of as-rolled Ti-40at%Nb-3at%Hf reaches 11.7 tesla, a value higher by 0.4 tesla than that of Ti-40at%Nb. High field critical current densities are also improved by the 3at%Hf addition. 2 step aging treatment is found effective in enhancing critical current densities of high Hf alloys. No degradation in fabricability is caused by a few at% Hf additions.     

Study on metallographic damage parameter in creep-damage-dominant condition under creep-fatigue loading

The microstructural changes of type 304 stainless steel in the creep-dominant condition under creep-fatigue loading were investigated and the representativeness of some metallographical damage parameters (MDPs) was studied. A series of creep-fatigue tests was conducted at low total strain range and long strain hold time. Some of these were interrupted during the periods of life cycle. Cross-section of all tests specimens were observed with a scanning electron microscope. Microstructures such as cavities, precipitate nucleation sites and internal microcrack initiation along grain boundaries were investigated. Cavity segregation phenomena which occur in an angular relationship between cavitated grain boundaries and the loading direction were also studied. Then the mechanism of cavity initiation and growth up to microcrack initiation was analysed. The number of cavities per unit area (NC), mean cavity area (MCA) and area fraction of cavity per unit area (AFC) were measured and studied in respect of their suitability to evaluate the damage under the present condition. Finally a more suitable MDP which should be possible to relate with both cavitation and grain boundary deformation quantitatively is discussed.     

Reciprocal Altruism-based Cooperation in a Social Network Game

Cooperative behaviors are common in humans and are fundamental to our society. Theoretical and experimental studies have modeled environments in which the behaviors of humans, or agents, have been restricted to analyze their social behavior. However, it is important that such studies are generalized to less restrictive environments to understand human society. Social network games (SNGs) provide a particularly powerful tool for the quantitative study of human behavior. In SNGs, numerous players can behave more freely than in the environments used in previous studies; moreover, their relationships include apparent conflicts of interest and every action can be recorded. We focused on reciprocal altruism, one of the mechanisms that generate cooperative behavior. This study aims to investigate cooperative behavior based on reciprocal altruism in a less restrictive environment. For this purpose, we analyzed the social behavior underlying such cooperative behavior in an SNG. We focused on a game scenario in which the relationship between the players was similar to that in the Leader game. We defined cooperative behaviors by constructing a payoff matrix in the scenario. The results showed that players maintained cooperative behavior based on reciprocal altruism, and cooperators received more advantages than noncooperators. We found that players constructed reciprocal relationships based on two types of interactions, cooperative behavior and unproductive communication.     

HPRT yeast artificial chromosome transfer into human cells by four methods and an involvement of homologous recombination

The transfer of a yeast artificial chromosome (YAC) into mouse and human cell lines was effected by four methods, and the efficiency and integrity of the incorporated YAC DNA were compared. A 500 kb YAC containing the human hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene was transferred more efficiently by polyethylene glycol-mediated fusion than by lipofection, electrofusion, or electroporation. Southern blot analysis demonstrated that PEG fusion lines yielded fragments of the size of the original YAC clone, whereas lipofection and electroporation did not. Two of 53 fusion lines showed 6-thioguanine resistance and confirmatory disruption of the HPRT gene in the YAC DNA, suggesting that the YAC DNA was integrated by homologous recombination with the endogenous HPRT gene region.     

Photocatalytic Decomposition of Lactic Acid in Water on a Photoelectrochemical Circuit System Consisting of a Rod-type TiO2 Electrode and Silicon Solar Cell

Lactic acid, a well-known substance causing dental caries, was dissolved in water and completely oxidized into CO₂ and H₂O on a powdered TiO₂ photocatalyst under UV light irradiation. Furthermore, a unique photoelectrochemical circuit system consisting of a rod-type TiO₂ electrode and counter electrode connected through a silicon solar cell was constructed and its photocatalytic activity for the decomposition of lactic acid was investigated. The photoelectrochemical circuit system was found to effectively mineralize the lactic acid in water into CO₂ while the negative bias applied on the rod-type TiO₂ electrode enhanced the photocatalytic decomposition rate of the lactic acid.