Acoustic properties of foamed polymer are affected largely by its cell structure and, to a small extent, by chemical structure of polymer itself. In this paper, examination is made on the relation between acoustic properties and resistance to air flow which is a physical quantity related to cell structure. Acoustic impedance is measured with a standing wave apparatus under various. mounting conditions. Theoretical value of acoustic impedance for a porous material with rigid skeleton is compared with experimental result. For samples with small resistance to air flow, a good agreement is found over a wide range of frequency. When samples are stuck on a rigid wall with adhesive, the resonance occurs in the rigion between 500 and 1000 c/s.
An automatically controlled apparatus for measurement of angular dependence in ESR spec-troscopy of crystalline solids has been designed and constructed for use in automatic observation of externally resonant magnetic field, the intensity of which varies by the rotation of sample in the resonant cavity. The apparatus consists of a microwave bridge with reflection cavity as the error detector, a servo-amplifier and a magnetic field control device. Such an automatic control system is regarded as a self-contained system of feeding back through the magnetic field. The variation of the resonant magnetic field due to continuous rotation of sample in the cavity is traced on paper as a function of rotation by the use of an X-Y recorder.
In a previous paper, a study was made on nineteen ruby rods concerning the relation between their nterferograms and laser emission. The study is furthered to investigate in detail how the quality of ruby affects the radiation pattern. One ruby rod, more or less devoid of homogeneity, is divided into several portions which, are examined with a Twyman interferometer about their optical properties. When subjected to laser operation, their near- and far-field radiation patterns disclosed various characteristics inherent in ruby rod, which are the inhomogeneity and its distribu. tion, presence of minute foreign particles which cause scattering, composite radiation pattern of primary and scattering' modes, primary and scattering mode radiations and their respective nature, relation between these two radiations in respect of near- and far-field patterns, and formation of interference rings in far field pattern.
Mass of copper whiskers of the order of 109 in number are successfully obtained in a single run of reducing CuO in a CO-CO2 atmosphere in the presence of small amounts of CuCI and graphite. The whiskers are observed to grow on the surface of graphite particles mostly in length of 0.1-1.5mm with maximum of 15mm, their diameter of between 0.5 and 3μ being fairly uniform. Under favorable conditions, as much as 99% of copper in the used materials changed into whiskers. The fundamental properties of the whiskers thus obtained are nearly the same as those formed by the known method of hydrogen reduction of cuprous halide.
It is well known that many changes are effected on the physical properties of plastics by the addition of fillers. The purpose of this paper is to present thermal conductivity data of amorphous resin filled with various inorganic crystalline substances and to compare these data with those of partially crystalline polymers. Binary mixtures of amorphous and crystalline components are pre-pared by adding powdered fillers to polyester resin of ethylene glycol and maleic acid cross-linked by styrene, and their thermal conductivity is measured by the steady-state method in the temper-ature range of approximately 20 to 100°C. The fillers used are Al2O3, Alundum, CaF2, graphite, Al and Cu. The thermal conductivity of the systems increases with increase of the content of crystalline component. The results are discussed by analogy with the electrical resistivity of-multicomponent systems. It is difficult to find a simple relation which can predict the conductivity of the composite system by the conductivity and amount of each component. The temperature. dependence of thermal conductivity of the systems filled with Al2O3 and Alundum of various particle, sizes are compared with that of partially crystalline polymers.
The compacting behavior of various kinds of powder under tablet compression is studied. Dry powdered mass of about 3cm3 is compressed in a steel die by a flat headed steel piston. Change of volume of the sample is measured with a measuring microscope while the pressure is being increased gradually up to 3 tons/cm2. In general, powder of common nonspherical particles has its initial porosity of more than 40%, and the change of porosity due to the applied pressure is comparatively large. The compacting behavior of these kinds of powder fits in well with Kawakita's equation. On the other hand, powder of spherical glass or metal particles has its initial porosity of about 40% which does not change much by pressure. In this case, Athy's equation becomes applicable.