Sinterability of various high-purity magnesium oxide powders

The sinterability of high-purity MgO powders with different production histories was investigated to make clear the relationship between the powder characterization, the densification processes, and the changes in microstructure both with increasing temperature at a rate of 10° C min^–1 and at a fixed temperature of 1450° C for 5 h. The densification behaviour and the changes in microstructure of these compressed bodies were affected chiefly by their original surface activity and degree of agglomeration, depending on the production histories: (i) the ultra-fine and well-dispersed powder prepared by the vapour-phase oxidation process showed that densification proceeded with an appreciable grain growth with few closed pores remaining; (ii) powder derived from the sea-water magnesia process showed that the densification behaviour was affected by the species of magnesium salt, i.e. basic magnesium carbonate or magnesium hydroxide, used as a precursor; however, whichever magnesium salt was used, its sintered compact showed similar closed porosities and grain-size distributions; (iii) powder derived from the spark-discharge process contained skeletons of the original Mg(OH)₂ particles; however, the densification proceeded gradually with slow grain growth, reflecting the fact that the powder has a moderate surface area (36 m² g^–1). The sintered compact from (iii) had a small closed porosity and the smallest grain-size distribution among the compacts used in this investigation.     

Design study of PbBi- and NaK-cooled small deep sea fast reactors

The liquid lead-bismuth eutectic (PbBi) has good compatibility with water, which is different from sodium. It is expected that the PbBi could be used as a coolant of the deep sea fast reactor (DSFR). Physics analysis of the PbBi-cooled small reactor cores with and without inner control rods performed using the computer program of a neutronics code system (SRAC95) shows that PbBi is suitable for the coolant of small reactors as well as NaK.     

Noninvasive Measurement of the Volume Elastic Modulus in Finger Arteries Using Photoelectric Plethysmography

A method for the nonivasive measurement of the volume elastic modulus (Ev) in human finger arteries was developed. The volume change ratio and pulse pressure in the arteries were simultaneously determined by a transmittance type infrared photoelectric plethysmograph and a volume oscillometric sphygmomanometer using an occlusive cuff. The Ev values could be obtained at a desired transmural pressure level of the arteries which was controlled by the cuff. A clear difference was revealed between the Ev values obtained in the fingers of two male subjects of 33 and 65 years old. The values determined by this method were compared to those calculated from pulse wave propagation velocity (Evp) obtained simultaneously in the fingers of 11 subjects. The linear regression equation was Ev = 1.31 Evp ?0.117 with a correlation coefficient r = 0.893 (n = 39). These results suggest that this should be a useful and noninvasive method of evaluating changes in arterial elasticity accompanying aging and perhaps influenced by accompanying hypertension or arteriosclerosis.     

Fir laser emissions from population inversion transition by TEA-CO2 laser pumping

In this paper, the numerical analysis is given which is applicable for a TEA-CO₂ laser pumping in search of effective pumping method. The analysis also can estimate the optimum pressure for a given molecule and a given pulse laser. Also we report in this work many FIR laser emissions from population inversion transition which have never observed before using a TEA-CO₂ laser.     

Improved Filtration Performance of Continuous Alumina-fiber-reinforced Mullite Composites for Hot-Gas Cleaning

The effect of filtration layer morphology on filtration performance at 673 K was investigated for continuous alumina-fiber-reinforced mullite composite filters that capture fly ash on their outer surfaces. Two types of filtration layers were prepared on the outer surfaces: a mono-layer consisting of mullite agglomerated particulates and a bi-layer, with mullite whiskers formed by a vapor-phase reaction and strongly adhered to the particulates exposed on the outer surfaces. For filters with mono-filtration layers, the filtration efficiency was improved slightly by increasing the filtration layer thickness. However, the maximum differential pressure increased during the filtration tests. Adhesion of whiskers to the outer surface decreased the maximum differential pressure to about one-third less than that with the mono-filtration layer. This low differential pressure remained constant throughout the duration of the test, with corresponding increases in filtration efficiency.     

Complex impedance and admittance of a silver-conducting glass

From the analysis of complex impedance and admittance data of (Agl)₇₅(Ag₄P₂O₇)₂₅ glass, an Ag⁺-ion conductor, it was revealed that the sample can be approximated by a seriesRC ₁ circuit at high temperature, with the capacitorC ₁ arising from the charge-carrier depleted region near the anode which develops as conduction proceeds, and by a parallelRC ₂ circuit at low temperature, with the capacitorC ₂ arising from the saturated value for ionic polarization of, say, the silver-iodine pairs as well as from the relaxation effect of the Ag⁺ ions for conduction. TheC ₁ andC ₂ values were found to be almost temperature-independent at peak frequencies of the distorted semicircles in respective complex planes, with the ratioC ₁/C ₂ as large as 10⁴.