A novel approach has been proposed to describe the relationship between the conductivity and relative density of highly porous materials. As a first approximation, porous material was represented by a uniaxial string of spheres along the direction of the potential gradient. Then, a string of spheres was remodeled into a rotating body of sine‐wave functions, f(x) = (1 +r0)/2 + [(1 –r0)/2] sin (πx/c) for 0 ≤x < c and f(πx) = (1 +r0)/2 + [(1 –r0)/2] sin {π(x+ 1 − 2c)/(l −c)} for c≤x < 1, where the former represents the shape of a sphere, the latter that of the bottleneck between neighboring spheres, and r0 denotes the ratio of the minimum diameter at the bottleneck to the maximum diameter of the rotating body. It was shown that the calculated relationships reproduced the reported experimental results for the relationship between the porosity and conductivity of La0.5Sr0.5CoO3, BaF2, and (ZrO2)0.9(Y2O3)0.1. The relative conductivity to the bulk material was close to zero at 45–60% relative density, which is the density of green wares. It steeply increased with an increase in the relative density and then gradually approached that of the bulk material.

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An experimental programme was intended to analyse the heat feedback from a spreading wall fire to its unburned surface, one of the two important parameters determining its spread rate. The heat flux from PMMA fires was observed to be higher than those from previous investigations as plotted with normalised flame height (X/X f ). However, very good consistency was performed with another study as a parameter

The pyrometer fitted for the temperature measurement of exhaust gas of the rocket, was constructed, and the exhaust temperature of the JP4-nitric acid rocket having 100 kg. of thrust, was observed. From the obtained exhaust temperature, it has been ascertained that the expansion of the gas through the present nozzle proceeds with chemical equilibria neither shifting nor frozen, and that relaxation occurs. From the approximate analysis of chemically relaxed flow, the relaxational process is assumed to occur at −(dt⁄dT)=3∼8×10−8 sec./deg., T\fallingdotseq2600°K and T\fallingdotseq10 atm.

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