Specimens are suspended equidistantly in a line with weights at their ends to give initial tension and instantaneous photographs are taken when they are shot through by a bullet at 130_??_400m/sec velocity. Gist of experimental results are: 1) Under the impact with velocities above a certain value, the specimen can no longer be stretched but torn up at the point of impact. This “critical impact velocity” is 350, 300 and 300 m/sec for silk yarn, cotton yarn and nylon cord respectively under the initial tension of 21g. 2) Propagation velocity of transverse deformation along the specimen is not influenced by the impact velocity except the cotton yarn with which the propagation velocity is slowed down in some measure as the impact velocity increases. 3) The propagation velocity is not greatly influenced by the value of initial tension; it decreases only slightly with light initial tensions. 4) As the initial elongation with the initial tension is obtained by a tension-elongation curve, the limit of allowable elongation under impact can be estimated by combining geometrically the impact velocity and the propagation velocity. 5) Under high speed impact, the allowable elongation of silk yarn, cotton yarn and nylon cord are 36, 35 and 35% while their statical breaking elongations are 16, 15 and 20% respectively. Thus, the breaking elongation of these materials under high speed impact is far greater than that in static test.
By means of the probe method (1) the distribution of resistance in a coating layer, (2) Iemission-Vprove characteristics and (3) the grid action of the probe are studied. Ex-perimental results show that the resistance near the emitting surface is a few times higher than the resistance of the inner bulk oxide while the resistance of the interface layer is not so high. Thus the substantial potential drop is supposed to exist near the emitting surface. At a large anode current, the potential drop across the coating layer becomes extremely high by the poisoning of gas released slightly from the plate leading to the thermal breakdown near the emitting surface. Cathode sparking of a diode often experienced in the earlier stage of working may perhaps be such type of breakdown.
Calculations already reported are verified by measurements. Electromagnetic wavelength used in the measurements is 3.14cm. In the preceding calculations of directional characteristics of doublet antenna with ribbon-shaped reflector, the antenna is treated as a radiator, but in the measurements, it is taken as a receiving antenna and its directional characteristics are observed. This reversing is justifiable as there are reciprocal relations between radiating and receiving. Two sets of measurement are made by using 1/4λ and λ (λ, the wavelength) for the distance between the antenna and the reflector. In both cases the reflector is 2 A in width and 8 λ in length. Although in the preceding calculations the reflector is treated as infinitely long, 8 λ is practically long enough to assume as infinite, for an antenna with reflector longer than 8 λ has almost the same characteristics as an infinitely long one. Results of measurement are in very good agreement with those of computations. Formulas already reported can also be applied to computations of directional characteristics of doublet antenna with rectangular reflector. Experiments with a rectangular reflector show also good results.
Structure of evaporated gold films of thicknesses from 5 to 2350A are investigated by electron microscope and diffraction method. Evaporation conditions, such as pressures of argon atmosphere, temperatures of substrates at evaporation and substrates materials, and also the annealing conditions after evaporation are widely varied. Above a certain critical pressure of argon atmosphere, gold blacks are found to be pro-duced due to collision with argon atoms near the evaporation source, not due to impurity. Particles aggregate in relatively large crystals, and gold particles change their shape above the temperature of recrystallization. Fibre structure of the films under various conditions are also studied, and the origin of electric resistivity of the black films are considered.
One method for vectorial stability criteria of an automatic control circuit having a minor feedback loop and its example are described. Characteristic equation of the system is divided into two parts, one being the main circuit characteristic equation and the other the equation which depends on the minor loop. The former gives the stability region, and if the vector notation of the latter remains in the stability region given by the former, the system is stable. This method can be used for both the analysis and the synthesis of linear systems.
A few glass beads (0.85 mm dia.) are sintered in a small vessel under compressive loads and the relations between the load, sintering time and sintering temperature for the begin-ning of sintering are determined by the testing method deviced by the author. The sintering temperature is not so low as expected by the author. For example, the beads are sintered at 520°C for two hours under the load of 3.5 kg. or at 740°C for 5 minutes under no load. These temperatures are about 1/2 and 2/3 of the melting point or are about 4/5 and 1.1 of the softening point of glass. The formula expressing the rate of growth of the area of adhesion between two beads (Alt) as a function of load W, coefficient of viscosity 71, and surface energy o is obtained theoretically which is given by:_??_ where r is the radius of the bead, cl and c2 are constants, 4×10-2 and 1×10-2 respectively. It is in agreement with the experimental results. The activation energy for the beginning of sintering between the beads is about 100-140 kcal/mol.