Threshold stress during crack-healing treatment of structural ceramics having the crack-healing ability

Alumina/15 vol.% SiC particles composite and mullite/15 vol.% SiC particles composite, that have excellent crack-healing ability are subjected to crack-healing under elevated static and cyclic stresses at 1373 K or 1473 K. The bending strengths of the specimens crack-healed under stress were investigated at the crack-healing temperature. From the results, the threshold stresses during crack-healing were determined. Crack-healing was found to occur although the pre-crack is grown by the applied stress. It is found that crack-healing can eliminate the pre-crack under stress below 64% fracture stress of the cracked specimen, if the ceramic components have an adequate crack-healing ability.     

Application of a commercial immunoassay to the direct determination of insecticide imidacloprid in fruit juices

An ELISA was used to directly determine residual imidacloprid in fruit juices. Imidacloprid could be determined by only diluting samples without any pre-treatments such as filtration, centrifugation, and clean-up procedures. The ELISA enabled imidacloprid to accurately determine down to about 5 μg/L in apple and grape juice samples and down to about 20 μg/L in orange juice sample. Recovery and precision of the ELISA were evaluated by spiking fruit juice samples with imidacloprid in the 10–400 μg/L ranges. Coefficients of variation were lower than 20% in all cases, and average recoveries were 94.2%, 113.2%, and 104.2% for apple, grape, and orange juice samples, respectively. No false positive results were found. The results obtained with the proposed ELISA well correlated with the reference HPLC for each fruit juice sample (r > 0.99).     

Applying Micro-Texture to Cast Iron Surfaces to Reduce the Friction Coefficient Under Lubricated Conditions

The tribological properties of cast iron have been investigated to determine the effects of micro-texturing the surfaces. The micro-textured surfaces were prepared by shot blasting or milling using a shaper. The surfaces with groove patterns and mesh patterns had higher friction coefficients than the flat surfaces. The surfaces with dimpled patterns had lower friction coefficients than the flat surfaces. The results indicated that the dimpled pattern had a beneficial effect by decreasing the friction.     

Cyclic testing of beam-to-column connections with weld defects and assessment of safety of numerically modeled connections from brittle fracture

This paper concerns the assessment of significance of weld defects in beam-to-column connections. Four full-sized beam-to-column connections with weld defects were tested under cyclic loads. When the unfused regions created by partial joint penetration groove welds were reinforced by fillet welds so that the welded joints have a sufficient cross-sectional area, ductile cracks grew stably and, in consequence, the connections showed sufficient deformation capacity. The connections with weld defects at the root of welds sustained a quick extension of ductile cracks and, eventually, failed by brittle fracture. Test results were reproduced well by non-linear FE analyses. Fracture toughness properties of numerically modeled weld defects were evaluated by using a recently developed fracture mechanics approach. The results of evaluation were found to correspond well with test results.     

Changes in evaporation rate and vapor pressure of gasoline with progress of evaporation

The evaporation properties of motor gasoline are expected to change markedly with the progress of evaporation because gasoline is a multi-component fuel. The aim of this paper was to develop a prediction model of the amount of vapor generated from gasoline spill. The risks associated with gasoline spills can be accurately evaluated by the models. Degraded samples of regular gasoline and high-octane gasoline were prepared by leaving them under conditions of no wind at 20 °C, and their vapor pressures and flash points were measured. The evaporation rate was measured by determining weight loss using an electronic balance, and the relation between the weight loss fraction and the evaporation rate was investigated. “Weight loss fraction” was used as a parameter signifying the progress of evaporation and expressed the changes in vapor pressure and evaporation rate as a function of the weight loss fraction. The vapor pressure and the evaporation rate could be shown by exponential functions of the weight loss fraction, and a prediction model of the amount of gasoline vapor was obtained. Furthermore, the prediction model of the flash point of degraded gasoline was derived from the relational expression of temperature and vapor pressure, and the predicted flash points were compared with the measured values.     

Study on control characteristics for HTTR hydrogen production system with mock-up test facility: System controllability test for fluctuation of chemical reaction

The Japan Atomic Energy Research Institute has a demonstration test plan of a hydrogen production system by steam reforming of methane coupling with the High-Temperature Engineering Test Reactor (HTTR). Prior to the coupling of a hydrogen production plant with the HTTR, simulation tests with a mock-up test facility of the HTTR hydrogen production system (HTTR-H2) is underway. The test facility is a 1/30-scale of the HTTR-H2 and simulates key components downstream from an intermediate heat exchanger of the HTTR. The main objective of the simulation tests is the establishment and demonstration of control technology, focusing on the mitigation of a thermal disturbance to the reactor by a steam generator (SG) and on the controllability of the pressure difference between the helium and process gases at the reaction tube in a steam reformer (SR). It was confirmed that the fluctuation of the outlet helium gas temperature at the SG and the pressure difference in the SR can be controlled within the allowable range for the HTTR-H2 in the case of the system controllability test for the fluctuation of chemical reaction. In addition, a dynamic simulation code for the HTTR-H2 was verified with the obtained test data.     

First-principles simulations of removal process in EEM (Elastic Emission Machining)

Interactions between ultra-fine powder [SiO₂] and work [Si (1 0 0) surface] in EEM (Elastic Emission Machining) has been investigated by employing first-principles molecular dynamics (MD) simulations. Calculated results show the possibilities of the atomic removal through the solid phase chemical interaction between surfaces of ultra-fine powders and works.     

重离子射线照射后家蚕胚胎造血器官的修复再生

为了研究重离子射线照射后家蚕造血器官的修复再生作用，用碳离子射线局部照射家蚕接近孵化时紧贴翅原基内侧的胚胎造血器官，局部细微手术损伤造血器官，观察了对幼虫造血功能的影响，了解了造血器官的修复程度。100Gy以上剂量照射，家蚕出现变态困难，幼虫和蛹的生存率下降，眠中、化蛹或羽化时期出现死亡个体等缺血生理障碍，其影响程度随射线剂量增加而加重。200Gy照射组5龄存活幼虫血细胞含量下降，但其中部分个体的血细胞含量接近对照未照射处理，其体内出现了再生的造血器官。家蚕幼虫有很强的修复再生造血器官功能。     

Visualization of hydrogen diffusion in steels by high sensitivity hydrogen microprint technique

Hydrogen diffusion in steels was examined by both a high sensitivity hydrogen microprint technique (HMT) and an electrochemical hydrogen permeation method. The main diffusion path in an extremely low carbon steel was lattice within grains; grain boundaries were not accelerated diffusion paths. In the case of a hypo-eutectoid steel, hydrogen diffused through proeutectoid ferrite and ferrite in pearlite under steady-state of hydrogen diffusion. The diffusion paths, however, were carbide/ferrite interfaces when hydrogen charging was interrupted before achievement of the steady state. This is probably ascribable to the reversible trapping effect of the interface. The detection efficiency of the high sensitivity HMT was 75% for the low carbon steel and 40% for the hypo-eutectoid steel.     

The effect of the preparation conditions on the optical properties of transparent silica aerogels

Hemispherical and specular transmittance in visible wavelength region and small-angle neutron-scattering of silica aerogels were measured to investigate the effects of supercritical drying media and heat treatment on the optical properties and structure of them. Silica aerogels were prepared by using methanol, ethanol, 2-propanol and carbon dioxide as supercritical drying medium. The analysis of transmission spectra suggested that a reduction of transmittance in visible light can be attributed to Rayleigh scattering, and the scattering intensity depended on the supercritical drying medium. The difference of the scattering intensity among the samples was related to the difference of the cluster size of aerogels from the results of small angle neutron scattering. Heat treatment affected the scattering intensity, but the change of the cluster size was not observed.