A brief review is given of recent theoretical and experimental studies on superconductivity irk semiconductors. After discussions on empirical and theoretical criterions of superconductivity is metals, theories of superconductivity in polar and many-valley semiconductors are reviewed in some detail. Experiments on superconductivity in Ge-Te and SrTiO3 are discussed with a comment on. superconductivity in semiconductors and semimetals under high pressures. Lastly, a brief comment is given on a possibility of organic superconductors (or room-temperature superconductors) and of surface superconductors.
The desorbed water vapour from walls of conduit pipe has a large effect on measurement of very low humidity below -40°C in terms of dew-point temperature. This effect is investigated by the use of a vinyl tube and a copper pipe as the conduit pipe and the following are concluded to be important for the reduction of the effect. 1) The conduit pipe must be as thin and short as possible. 2) The pipe wall temperature must be kept below 30°C. 3) The flow rate of gas must be above 10l/min. Furthermore, the relation between the Reynold's number, Re, and the relative error of indicated dew-point temperature, (p-pi)/pi, is obtained, where p is the water vapour pressure corresponding to the indicated dew-point temperature at the outlet of the conduit pipe and pi is the water vapour pressure corresponding to the dew-point temperature of gas entering the conduit pipe, therefore (p-pi)/pi means the relative error of indicated dew-point temperature.
In order to measure the fluidity of powder kept in flowing state, the movement of powder in a rotating horizontal cylinder is first analyzed in analogy of that of fluid. The stationary angle of inclination between the free surface of fluid in a rotating horizontal cylinder and the horizontal plane is measured from the profile of the fluid at one end of the cylinder, and the relations of this angle to the amount, viscosity, density of the fluid and the rate of rotation are theoretically derived, which are verified by measurements on several liquids. By applying this derivation to the case of powder, a quantity which may be called the viscosity of powder is obtained. Though this quantity can reasonably be applied to flowing powder mass as viscosity, observation made on velocity distribution of powder particles proved that the whole mass is not actually flowing, it consists of two parts: the one is actually flowing with velocity gradient between particle layers, the other one which is close to the cylinder walls follows the motion of the cylinder in bulk with no relative movement between particles.
A compensation method of voltage drop due to stray capacitance is investigated. Compensation coils of an arbitrary number are used in a generator circuit in a certain definite manner. This multiple loading coil method improves markedly the voltage efficiency of the generator, even when the stage number is larger and/or the capacitance ratio (capacitance of column capacitor to stray capacitance arising parallel to rectifier) is not high. As the coil number increases, the optimum coil inductance becomes larger and the voltage efficiency becomes high. Since the input impedance of a cascade circuit rises with the coil number, the leading input current and therefore the reactive input power decreases. The results are comfirmed by model experiments. In the present paper, the characteristics relating to multiple loading coils concerning Cockroft-Walton type, inverse type, symmetrical type, and symmetrical inverse type circuits are discussed and the equations for the optimum inductance of the compensation coil and the voltage efficiency are given.
Main factors which decide the dynamic viscoelastic properties of a plastic foam are the viscoelastic characteristics of the elastomer constituting the plastic foam and the cell structure. Another important factor that affects the dynamic viscoelastic property is the existence of air, for the flow of air is disturbed by the cell structure. The present paper describes the effect of air examined by the apparatus made in the authors' laboratory, which is also designed to be operated in vacuum. Experiments are carried out on cylindrical flexible polyurethan foam samples of various flow resistance at compressive strains of 20_??_150c/s. The experimental results show that the presence of air mainly acts to increase the value of tangent of loss angle, or tan d, and its increment is proportional to the flow resistance, frequency and square of specimen radius. These results can be explained by the behavior of inner air pressure, and the amount of inner air pressure can be calculated by the flow resistance of the specimen.
A penetrometer of an improved type is devised on the basis of the principles described in a previous paper (Japan. J. Appl. phys. 1, 174 (1962)). With this penetrometer one can obtain not only the penetration depth in a given interval of time but also the automatic record of time required for the penetration of a given range of depth. This recorded time is found closely related to the viscosity of samples as predicted by the theory. Effects of load and conical angle of needlepoint on the penetration time are studied, and the needle of 90° tip is concluded to be most suitable. The scale reading of this penetrometer is compared with that of the conventional one for a series of asphalt samples. For the design of this penetrometer, care was taken to control the sample temperature and to obtain easy setting of zero point.
The factors that are accountable for the error of film thickness monitored by the photoelectric extremum method are derived for a monolayer film. By using the Balzers G.S.M. monitoring apparatus, the relations between these factors and the standard deviation of measured values of film thickness are experimentally investigated.
Beam pulsing by means of a grid electrode fitted outside the source canal is described. Pulsed beams of the width up to 0.2μs are obtained. The wave form of the pulsed beam is similar to that of the applied voltage pulse. The same result is obtained in the case of einzel lens where voltage modulation is applied to the electrode which is usually grounded.