Vol. 19, No. 3 (1963)
1963-02-05
CONTENT
1963, 19 (3): 151-159.
doi: 10.7498/aps.19.151
Abstract +
This paper is a preliminary report on acoustical studies of the sugar-cane fiber-board, emphasis being made for cases in which the fiberboard was perforated.Experiments with the non-perforated fiberboard indicated the existence of "mechanical vibration" determined by its boundary conditions including peripheral constraint, as well as of resonance absorption of thin panels backed by an air-space. When the fiberboard was perforated, resonance peaks became less prominent but the over-all absorption was higher than ordinary perforated panel absorbers previously investigated. In addition, two new types of perforated sound absorbers were briefly discussed.For most cases theoretical interpretations were given, especially on the basis of specific acoustic resistance, and both advantages and disadvantages for these fiberboard sound absorbers were discussed in the conclusion.
1963, 19 (3): 160-164.
doi: 10.7498/aps.19.160
Abstract +
An electron bombardment furnace for laboratory use for the production of refractory metal single crystals is described. Molybdenum single crystals have been prepared and examined. Technique for the production of single crystals with controlled orientation is described. Microscopic examinations disclosed numerous terraces on the surfaces of Mo crystals, these terraces were tentatively identified as evaporation terraces.
1963, 19 (3): 165-168.
doi: 10.7498/aps.19.165
Abstract +
Oxalic acid solutions are used for producing etching pits on the surfaces of molybdenum crystals grown from electron-beam floating zone melt. By taking {100} as observation plane, dislocation densities along traces of three intersecting subboundaries are measured and the Read-Shockley formula for asymetrical tilt boundaries has been verified. The one-to-one correspondance between etching pits along these subboundaries and edge dislocations with Burgers vector < (100) is demonstrated.
1963, 19 (3): 169-175.
doi: 10.7498/aps.19.169
Abstract +
The radiation of a thin linear monopole antenna of any length erected at the tip and along the axis of a metallic spheroid of any length and eccentricity is analized. The monopole is excited at its base. General expressions for the fields are obtained.
1963, 19 (3): 176-190.
doi: 10.7498/aps.19.176
Abstract +
A new method for measuring the life time of minority current carriers in semiconductors is described. Measurements are made by observing the photoconductive decay of the spreading resistance under a point contact. This method possesses the following advantages: (1) It is not necessary to cut the specimen into special form. (2) No fixed electrode has to be made to the specimen. (3) It is applicable to test inhomo-geneous specimen. (4) No particular surface treatment is necessary. (5) Apparatus used is simple and easy to operate. (6) Enough accuracy is obtainable. A theoretical analysis is given of the effects of surface recombination velocity and of varying absorption depth of the light in specimen. Experimental details and discussions are given for Ge and Si specimens. Results are in agreement with those obtained by other methods.
1963, 19 (3): 191-201.
doi: 10.7498/aps.19.191
Abstract +
The photo-conductive decay of the spreading resistance of Ge and Si is investigated. The influence of the surface recombination velocity and the depth of absorption of the exciting light on the shape of the decay curve are studied in detail. The decay curves obtained are consistent with those predicted by the theory. The conditions required for accurate measurement of bulk lifetime are also discussed.
