Low-energy Electron Effects on the Sterility and Viscosity of Grains

Microbial load and viscosity of brown rice, rough rice, wheat and buckwheat exposed to electrons at different acceleration voltages were examined and compared with those irradiated with gamma-rays. Electrons at acceleration voltages of 180–225 kV reduced microbial loads of grains to <100 CFU/g. The viscosities of aqueous suspensions of grains treated with such low-energy electrons were almost the same or higher than those irradiated with gamma-rays at 0.1 kGy, much lower than necessary to disinfect grains. Results suggest that low-energy electrons can decontaminate grains with little starch degradation compared to gamma-rays.     

Ultrasonic echo signal fetures of dissimilar material bonding joints

An ultrasonic evaluation method of echo feature of diffusion bond joint between two dissimilar materials is presented. The echo signal was acquired by an automatic ultrasonic C-scan test system. It is found that the intensity of echo and its phase can he used to evaluate the joint quality, and interface products of dissimilar materials bonding can be evaluated by ultrasonic method.     

Aflatoxin Contamination in Nutmeg: Analysis of Interfering TLC Spots

When a mixture of ground nutmeg and ground cinnamon leaves was subjected to thin layer chromatography (TLC), spots that hampered detection of aflatoxins appeared on the TLC plate. These spots represented oxidation or heat-induced degeneration products of the cinnamon leaves. Between 1986 and 1991, 67 samples of nutmeg, that were commercially available in Japan, were examined for aflatoxin contamination. Aflatoxins were detected in 29 (43%) of the 67 samples.     

Automatic restraint and visual detection of fatigue crack growth by applying an alumina paste

A paste comprising fine alumina particles was applied on surfaces of steel plate specimens and a welded joint specimen, and the effects of the paste on restraint and visual detection of fatigue crack growth were experimentally investigated by performing fatigue tests with in situ observations by a c harge c oupled d evice (CCD) microscope and through various kinds of fractographic observations and elemental analyses using an scanning electron microscope (SEM) and an electron probe microanalyser (EPMA). As a result, the crack growth rate in the plate specimen was drastically retarded by the wedge effect of the alumina particles, and a 311% increase in failure life was produced on an average. The restraint of crack opening displacement (COD) value by the wedge materials was estimated by elastic finite element (FE) analyses, and the results were compared with the experimental data. Similar crack growth restraint effects were also observed on the welded joint specimen, producing a 117% increase in failure life. In the fatigue tests of the specimens on which the alumina paste was applied, a remarkable black colour developed in the white alumina paste along the paths of crack propagation, facilitating the visual detection of the cracks. An analysis using an X‐ray diffractometer showed that the black matter in the paste consists of fine debris derived from the base metal.     

12Cr-ODS钢中氧化物强化相（Y2O3）辐照损伤行为研究

本文采用电子束（e^－） 氦离子（He⁺）、氢离子（H⁺）束同时复合辐照方式研究12Cr-ODS铁素体钢中氧化物弥散强化相（Y₂O₃）辐照损伤行为,对不同辐照方式下辐照区内的氧化物形貌变化进行原位观察。研究结果表明,15dpa辐照后,氧化物周围出现微小高密度空洞,相界面变得不规则,氧化物在此特定条件下发生体积收缩或长大,尺寸有少量变化,但无明显溶解现象,对钢的性能不会产生影响。     

Numerical Study on Periodic Structure Evolution of Output Power in MHD Generator by Using Pulse‐Assisted Ionization Discharge

A pulse‐assisted ionization discharge applied to a magnetohydrodynamic (MHD) generator is proposed as a technique to increase an electrical conductivity of working fluid. In this study, a periodic structure of output power in the MHD generator by using pulse‐assisted ionization discharge was evaluated. As a result, the discharge electrode length and the velocity of working fluid affect the discharge current distribution. The periodic structure of output power was observed in the several conditions. When the velocity of working fluid is roughly same as the sound speed, the periodic structure of output power was not observed.     

Effect of aging treatment on irradiation-induced segregation of high Mn-Cr steel

To investigate the effect of aging treatment on irradiation-induced segregation of high Mn-Cr steel, specimens for electron-beam irradiation were prepared from the high Mn-Cr austenitic steel which was solution treated at 1 373 K for 1 h and aging treated at 573 K for 1 000 h, respectively. The electron-beam irradiation was performed at 573 K up to doses of 5.4 dpa in a 1 250 kV HVEM and irradiation-induced segregation analyses were carried out by an EDX in a 200 kV FE-TEM. The results show that void formation is not observed in both solution treated and aging treated ones. The amount of Cr segregation at the grain boundary decreases in the aged one; however, that of Mn is not changed in solution treated one.     

Relationship between histological complexity and elemental composition of the cuspal enamels among human deciduous teeth

The purpose of this study is to clear the difference of histology and elemental composition of the cuspal enamels among the human deciduous teeth. The reground surfaces at the cuspal enamels of them were observed under SEM. The contents of seven elements were analyzed quantitatively with EPMA. It is thought that not only the first zone but also the second zone of the inner enamel in the deciduous molar causes the lateral enlargement of the dental caries along the dento-enamel junction because the second zone of the inner enamel in the deciduous molar was more porous than that in the permanent premolar. It is thought that the cuspal enamel in the deciduous teeth is low calcified than that in the permanent teeth because the contents of calcium and phosphorus in the former were significantly lower than those in the latter. It is considered that the cuspal enamel in the deciduous teeth may include less magnesian whitlocki-te than that in the permanent teeth because the content of magnesium in the former was significantly lower than those in the latter. A relationship was recognized between the complexity level in the histological structure and the elemental composition of the cuspal enamels among the human deciduous teeth.     

Sluggish Pansition Between Tetragonal and Rhombohedral Phases of Pb(Zr,Ti)03 Prepared by Application of Electric Field

Tetragonal and rhombohedral phases always coexist in Pb(Zr_xTil_1−x)0₃ near the morphotropic phase boundary compositions (0.52≤x≤0.55) when prepared by solid-solid reaction among the constituent oxides. A special technique was developed to obtain perovskite ceramics exhibiting no co-existence in the boundary compositions, in which no compositional fluctuation occurred in the B site of the perovskite structure. Even these monophasic perovskite ceramics of the morphotropic phase boundary compositions were two-phase with the lapse of time after poling. This phenomenon is interpreted in terms of thermodynamics. It is suggested that this phenomenon may closely relate to the origin of aging in piezoelectrics.     

Crack-healing and mechanical behaviour of Al2O3/SiC composites at elevated temperature

Alumina/silicon carbide (Al₂O₃/SiC) composite ceramics with large self‐crack‐healing ability, high strength and high heat‐resistance limit temperature for strength were developed and subjected to three‐point bending. A semicircular surface crack 100 μm in diameter was made on each sample. Crack‐healing behaviour was systematically studied, as functions of crack‐healing temperature and healing time, and the fatigue strengths of the crack‐healed sample at room temperature and 1373 K were investigated. Four main conclusions were drawn from the present study. (1) Al₂O₃/SiC composite ceramics have the ability to heal after cracking from 1273to 1673 K in air. (2) The heat‐resistance limit temperature for strength of the crack‐healed sample is ?1573 K, and ?68% of the samples fractured from outside the crack‐healed zone in the testing‐temperature range 873–1573 K. (3) The crack‐healed sample exhibited very high fatigue limit at room temperature and also 1373 K. (4) The large self‐crack‐healing ability is a desirable technique for the high structural integrity of ceramic component.