The presence of stress or strain in a crystal changes its electric resistance. The relationship between the stress or strain and the change in the resistance is known to be represented by the expression. σijEi=Ij+πijklIjTkl where σij designates the electric conductivity tensor, Tkl the stress tensor, and πijkl is the piezoresistance tensor. No detailed data have so far been published as to the above expression in the vicinity of room temperature. The author studied the effect of piezoresistance and its temperature dependency of single crystalline, p type and n type, germanium with respect to  and  directions at temperatures ranging from 200°K to 370°K. This effect is applied for measuring the static strain in the crystal which is one of factors that determine the applicability of the crystal as a strain gauge element. Smith obtained the effect of piezoresistance of germanium from its tensile stress at 25°C while Herring and his coworker obtained that from compressive stress over a temperature range from 5° to 350°K. In comparison of their results with the author's obtained from tensile stress in the vicinity of room temperature, the latter is in good agreement with Smith's but is partially different from Herring's. It is found that a strain gauge element comprising a germanium crystal has a sensitivity several hundred times as large as that of any known wire strain gauge with the size only a very small fraction of the size of the latter.
The influence of directionality in sheet metal on its plastic bending is studied by using mild sheet steel. Specimens are taken from rolled materials which showed directionality and bended with V-shaped punch of zero radius and V-die, both of 90 degree. A specimen taken from annealed sheet is used for comparison. The results obtained are as follows. (1) No cracking and folding on the bend; effect of the directionality is not apparent. (2) The spring-back is clearly influenced by the directionality, probably by the directionality of inclusion and of roller-levelling. (3) By analysing the scratches on the specimens caused by the die corners, some theoretical derivations concerning the perfect plastic solid and the relation between stress and strain are obtained with which the experimental results are satisfactorily explained.
In order to find the relation between the surface-chemical properties of sand and the condition for the sand to produce musical sound, experiments have been made on the samples of musical sand collected on the sea-shore of Kotobuki, Aminocho, Takeno-Gun, Kyoto, Japan. By treating the surface of the sand particles with various reagents and by analyising the sound produced, it is made clear that the sound is independent of the shape of sand particles but is attributed to the friction of surface-clemical nature. Whether audible or not, the pitch of the sound is approximately 1700 c/s, the wave form being almost sinusoidal when the sound is musical. As to the origin of the musical sound, it is likely that, when the pressure is applied to the sand, layers of sand particles crumble one after another in steps because of the particular friction accompanied with sudden forcing out of air from the interspace between the particles producing the sound. Result of the experiments supports this supposition.
The conditions for obtaining a good imagery by rotating the concave grating around an axis that passes through a suitable point and is parallel to the grooves of the grating to change the wavelength of diffracted ray are obtained. Only the rays lying in the plane passing the vertex of the grating and normal to the grooves are considered to be the image-forming rays. The conditions for imagery are derived from the formulas given by Beutler. A group of mountings that are of good imaging performance and applicable to the photoelectricspectrometric use is found by equating the w2 and w3 terms of the Beutler's equations to zero. The well-known Eagle and Wadsworth mountings belong to this group as special cases. The formulas for determining the position of the axis of rotation, which gives a good imagery for a range of wavelength with a set direction of emerging rays, are derived.
A new chemical technique has been developed for obtaining mirror-finished surface of germanium without scratches and etch-pits by etching a germanium wafer in an etchant named CPD-2. Such a surface is very useful in the fabrication of transistors. This method is simpler and easier than polishing-on-a-lap method for obtaining mirror-finished surface on diffused-transistors. In this experiment, germanium wafers are etched after being polished with alundum powder of No. 2000 and No. 4000. Etching in CP-4 etchant gives mirror surface to germanium specimens, but under a microscope etch-pits are seen on them. The reaction of CP-4 with germanium goes slow initially and becomes violent after about 30_??_60 seconds. The mild reaction in the early period brings about etch-pits. Therefore, to obtain a perfect mirror-finished surface it is necessary to find out an etchant which reacts violently with germanium in the instant of throwing-in. Treatment in the new etchant, which is composed of fluoric acid 15 cc, nitric acid 15 cc and bromine 0.02 cc, gives always good mirror-finished surface without etch-pits even to germanium wafers with high dislocation density. Etching is completed in 1_??_2 minutes. Flatness of the etched surface is satisfactorily confirmed by interference fringe test. The effect of varying the composition of CPD-2 is studied. Solution, in which the volume ratio of HF to HNO3 is 1.5:1 or 1:1.5 and the volume of bromine is kept unchanged, roughens the etched surface and gives etch-pits on it. If more nitric acid is used, the surface becomes covered with yellow film. As the content of bromine is increased, more etch-pits are formed on the surface. Thus it was found that the optimum composition of the etchant which gave a perfect mirrorfinished surface corresponded to the composition of CPD-2. Diffused transistors produced from germanium wafers treated in CPD-2 solution showed an excellent high-frequency characteristics (ƒα=300_??_500 MC, b=30_??_200).
The effect of irradiation of beta rays or ultra-violet rays on the operating characteristics of a spark counter has been investigated. The Rosenblum spark counter which consists of a fine wire and a metal plate is known to be sensitive to dense ionization of alpha rays and insensitive to weak ionization of beta and gamma rays. However, according to the authors' experiments, counting rate of a spark counter for alpha rays of Po decreases when irradiated from outside by beta rays of Sr90. Further-more, the feeble A. C. current caused by burst pulses of corona is observed toy decrease remarkably when the counter is irradiated by beta rays or ultra-violet rays.
A new photoelectric method of determining the azimuth of polarized light has been devised. For measuring the relative retardation of birefringent crystals, Sénarmont compensator is being used. When this compensator, made up with a polarizer, a quarter-wave plate and an ADP Z-cut crystal, is subjected to a field of alternating voltage, the plane of polarization of light emerging from the compensator vibrates in accord with the applied voltage. This optical system is named “polarization azimuth vibrator” which is useful in determining the azimuth of linearly polarized light. Application of this element to polarimetry is reported.
Viscoelasticity of coating film and thin film has hitherto been measured by many but the data thereby obtained are not free from the effect of the load that hung at the lower end of the sample. In order to remove the influence of the load, a torsional pendulum is devised for low frequency measurements, with which satisfactory results are obtained. A piano wire suspends a cross made of a horizontal iron rod and a vertical steel rod to which the upper end of the sample strip is clamped, the lower end of the sample being fixed. Variation of complex rigidity modulus of polystyrene thin film with temperature in the range from 20°C to 120°C is observed at about 0.2 cps. Two maximum peaks of tan δ are found, the main peak at about 116°C and the small secondary one at about 56°C.
Orange and pink electroluminescent zinc sulfide phosphors are prepared, the orange phosphor, which contains copper and manganese, by firing in H2S atmosphere with NaCl flux and the pink phosphor, which contains manganese of low concentration and a trace of magnesium, by a similar process. Frequency and temperature dependencies of the electroluminescence are studied.
In the previous study on wearing of glass, the author arrived at a conclusion that the polishing is in the main the “molecular wearing”, the rubbing-off of particles of constituting mass in the form of molecules, atoms or ions. If this is the case, such torn-off particles from the rubbed and rubbing substances of stable structure and the vacant sites formerly occupied by these particles would both be in unstable and nascent state and react chemically with surrounding matter that comes into contact. Experiments are carried out and chemical changes observed on various kinds of metal when rubbed with sulphur are compiled in a table. It should be noted that Pt and Au combine directly with S by polishing while no usual method can produce such chemical combinations.