Size-controlled oxidation-resistant copper fine particles covered by biopolymer nanoskin

Size-controlled oxidation-resistant copper fine particles were prepared from insoluble CuO micron-sized particles. The particle sizes were quite uniform and could be varied only by the concentration of the complex reagent from 45 to 175 nm. No template material was needed for size control. Gelatin was selected as the protective polymer. Addition of protease after formation of copper fine particles decomposed preferentially loop and tail parts of gelatin. The remaining nanoskin gelatin layer, covered on the particle surface, prevents oxidation of copper.     

Roles of rare earth oxide additives in millimeter-wave sintering of AlN

Roles of rare earth oxide (RE2O3) additives in millimeter-wave(MM) sintering of AlN were investigated from the standpoints of phase diagram, heating characteristics of rare earth oxides, and morphology of intergranular oxide phase. In the millimeter-wave sintering of AlN, densification temperature decreased with the decrease of the ionic radius of rare earth ion and was closely related with the eutectic temperature in the RE2O3-Al2O3 binary system. The lowest densification temperature in the millimeter-wave sintering of AlN with Yb2O3 additive was attributed to the largest heating rate of Yb2O3·Al2O3 binary oxide under millimeter-wave radiation. Furthermore, the lowest densification temperature could be attained while selecting the Yb2O3 content so as to form the intergranular phase with the eutectic composition in the Yb2O3-Al2O3 binary system. The result showed good agreement with the above mentioned during the sintering of Si3N4 with Yb2O3-Al2O3 additive. From TEM observation, it was verified that film-like intergranular oxide phase formed under millimeter-wave radiation was favorable for attaining high thermal conductivity in the Yb2O3 added AlNs.     

7xxx系铝合金凝固过程中收缩行为的测定

应用自主设计的测量装置对7xxx系铝合金凝固过程中的收缩行为进行了系统的测量。主要研究了3种7xxx系铝合金的收缩行为和微观组织对热裂敏感性的影响。研究发现,在凝固过程中,3种7xxx系铝合金表现出了非常不同的收缩行为。7050和7075铝合金的热膨胀系数曲线从收缩起始点(固相率fs分别为0.69和0.73)开始陡然增加至峰值,之后随着温度的降低减小至一个常数值;7022铝合金的热膨胀系数曲线与以上两种不同,从收缩起始点(固相率为0.8)开始先出现一个波动上升,其后随着温度降低数值单调递增。微观组织显示,收缩过程的起始点是枝晶搭接的开始点。凝固过程中,7050合金的热膨胀系数大于7022合金,可以认为凝固过程的收缩行为能作为热裂敏感性的一种判断准则。     

The study of activity median aerodynamic diameter using imaging plate technique for assessment of effective dose from radon and its decay products

The indoor workplace environment was evaluated for exposure to radon and its decay products at two Universities in two metropolises of Japan. The mean radon concentrations in Nagoya University (NU) and Hokkaido University (HU) were 16.7 Bq m(-3) and 18.0 Bq m(-3), respectively. Activity median aerodynamic diameter (AMAD) of particles at NU ranged from 172 nm approximately 205 nm and at HU from 186 nm approximately 300 nm. Estimated effective doses for five usual sites of NU by ICRP approach was 0.15 mSvy(-1) approximately 0.76 mSvy(-1) and by UNSCEAR approach was 0.05 mSvy(-1) approximately 0.24 mSvy(-1). The effective dose for the same of HU by ICRP 66 approach was 0.16 mSvy(-1) approximately 0.79 mSvy(-1) and by UNSCEAR 2000 approach was 0.05 mSv y(-1) to 0.26 mSv y(-1). The two approaches differs on an average by a factor 2.3- approximately 4.7. The AMAD of obtained particle size distribution at NU has an average total deposition of 23% in human respiratory tract and 20% at HU.     

Polyurea thin film ultrasonic transducers for nondestructive testing and medical imaging

Ultrasonic transducers using polyurea piezoelectric thin film are studied in this paper. Aromatic polyurea thin films, prepared by vapor deposition polymerization, have useful characteristics for use as an ultrasonic transducer. This paper presents the fabrication and experimental evaluation of ultrasonic transducers formed using polyurea films. First, the vapor deposition polymerization process using two monomers is briefly reviewed, and the temperature conditions for higher piezoelectric constants are explored. Second, in order to test the fundamental characteristics of this material as a high-frequency, ultrasonic transducer, a polyurea film of 2.5 microm thickness was deposited on a silicon substrate. In the pulse/echo experiment results, a resonant frequency of about 100 MHz was observed. Third, we fabricated a concave point focus transducer and a cylindrical line focus transducer. To examine the performances of the focus transducers, two-dimensional images of a coin and V(z) curve measurements for an aluminum surface were demonstrated.     

Growth energetics of Lactococcus lactis subsp. lactis biovar diacetylactis in cometabolism of citrate and glucose

Certain strains of lactic acid bacteria present in commercial cheese starters, characterized by faint transparent colonies on an agar plate containing 1 mg kg ⁻¹ crystal violet (CVT), were identified as Lactococcus lactis subsp. (ssp) lactis biovar diacetylactis. The effect of citrate on the growth of these strains (CVT strains) in the presence of glucose was studied, in comparison with L. lactis strains. Molar growth yield from glucose (Y_G, g dry weight/mole of glucose consumed) for CVT strains grown on glucose plus citrate was significantly higher than the control (i.e. without citrate), but not for other L. lactis strains tested. Enhanced Y_G was also observed at a pH-controlled experiment, indicating that enhanced Y_G did not result from a buffering effect of citrate. CVT strains, in contrast to other strains of the same species, were shown to obtain enough energy to enhance Y_G on glucose–citrate mixtures.     

Influence of microwave roasting on positional distribution of fatty acids of triacylglycerols and phospholipids in sunflower seeds (Helianthus annuus L.)

Whole sunflower seeds were exposed to microwave roasting for 6, 12, 20 or 30 min at a frequency of 2450 MHz. The kernels were then separated from the sunflower seeds, and the lipid components and the positional distribution of fatty acids in triacylglycerols (TAGs) and phospholipids (PLs) were investigated. Major lipid components were TAGs and PLs, while steryl esters, free fatty acids and diacylglycerols were also present in minor proportions. The greatest PL losses (p < 0.05) were observed in phosphatidyl ethanolamine, followed by phosphatidyl choline or phosphatidyl inositol. Significant differences (p < 0.05) in fatty acid distributions occurred (with few exceptions) when sunflower seeds were microwaved for 20 min or more. Nevertheless, the principal characteristics for the positional distribution of fatty acids still remained after 20 min of microwave roasting; unsaturated fatty acids, especially linoleic, were predominantly concentrated in the sn‐2‐position and saturated fatty acids, especially stearic and palmitic acids, primarily occupied the sn‐1‐ or sn‐3‐position. These results indicate that no significant changes in fatty acid distribution of TAGs and PLs would occur within 12 min of microwave roasting, ensuring that a good‐quality product would be attained.     

The content of tocopherols and oxidative quality of oils prepared from sunflower (Helianthus annuus L.) seeds roasted in a microwave oven

Sunflower seeds ((Helianthus annuus were roasted for 6, 12, 20 or 30 min at a frequency of 2450 MHz using a domestic microwave oven. After the kernels were separated from the sunflower seeds, the quality characteristics and the compositions of the oils were investigated in relation to their tocopherol distributions, and they were further evaluated as compared with an unroasted oil sample. Only minor increases (p < 0.05) in chemical and physical changes of the oils, such as the carbonyl value, the p‐anisidine value and the color development, occurred at a prolonged roasting period. Significant decrease (p < 0.05) was observed in the amounts of phospholipids in the oils after microwave roasting. Nevertheless, compared to the original level, more than 92 wt‐% tocopherols still remained after 30 min of roasting. With a few exceptions, these results indicate that the exposure of sunflower seeds to microwaves for 12 min caused no significant (p < 0.05) loss or change in the content of tocopherols and polyunsaturated fatty acids in the kernels.     

Periodic overhaul planning system for electric power plants

Periodic overhaul planning for boilers and turbines in electric power plants has been done based on expert experience in order to satisfy various constraints that are hard to formalize, such as legal regulations, the overhaul interval restriction between units, the adjustment strategy in the case of including special events, the daily electric power requirement, and so forth. Although computer processing using the knowledge base approach has been tried, it does not lead to good results because of excessive hardware requirements, low performance, and no assurance of optimality. A two‐step approach is proposed based on the categorization of constraints that are hard to formalize into “strong constraints” and “weak constraints.” It replaces the nonlinear integer programming problem corresponding to “strong constraints” by a combination of integer programming and combinatorial analysis. Consequently, it can lead to optimal solution in terms of fuzzy satisfaction measures within an allowable time with a PC. © 1999 Scripta Technica, Electr Eng Jpn, 127(2): 24–31, 1999     

Construction of self‐organizing algorithms for vector quantization

Vector quantization is used for both storage and transmission of speech and image data, and an algorithm that minimizes the distortion error is often required. To obtain the minimum distortion error in neural networks for vector quantization, corrective competitive learning has been introduced. In a large number of algorithms, self‐creating neural networks and self‐deleting neural networks have performed well. In this paper, we improve the self‐deleting neural network and propose a generalized algorithm combining the creating and deleting neural networks. First, a few weight (reference) vectors are prepared, the self‐creating algorithm is applied, and vectors are created automatically. Next, the self‐deleting algorithm is applied, and weight vectors are deleted sequentially to reach a predetermined number. Experimental results show the effectiveness of the proposed algorithm. © 1999 Scripta Technica, Electr Eng Jpn, 127(1): 47–55, 1999