Three different types of generators for plasma jet have been designed; they are stabilized by running water, argon, or nitrogen gas respectively. In the type of using running water, the anode is a carbon rod and the cathode a carbon disk with a circular hole. Water is injected tangentially into a glass cylinder making a vortex flow. The arc is pinched by the so-called “thermal pinch”. The plasma jets out from the hole of the cathode. The mean arc current and voltage are 400 amperes and 80 volts respectively. Details of electrical characteristics have not been obtained as the disintegration of the anode is so fast. In the generator of plasma jet, in which argon is used for cooling, tungsten for the cathode and copper for the anode, both being cooled by running water, stabilized arc plasma and jet are obtained. The electrical characteristics-the voltage dependences on discharge current, diameter of the pinched plasma and distance between electrodes-have been measured. The structure of the nitrogen plasma jet generator is similar to that of the argon type except an additional outlet of the cooling gas which is provided in order to stabilize the arc.
Results of experiments on the relation between the thickness of diffusion layer adjacent to evaporating surface and the velocity of air relative to the surface are reported. The experiments are carried out by three methods of (1) blowing air paralell to a wetted flat plate, (2) moving a wetted endless belt fiat over two rotating rollers, and (3) rotating a wetted circular cylinder. The thickness of the diffusion layer is determined graphically from the data of humidity distribution measured by using a small electric resistance hygrometer and thermistor thermometer. As the thickness of the diffusion layer, the effective thickness, i.e., the distance from the evaporating surface to the point at which the vapour pressure becomes equal to that in the ambient air, obtained by extending the straight line of the linear portion of the vapour pressure curve, is taken. The effective thickness defined above is a quantity which is inversely proportional to the rate evaporation. It is shown that at relative velocities up to about 10cm/s, the effect of natural convection is predominant over that of forced convection and that, as the relative velocity becomes greater than about 30 to 50cm/s, the effect of natural convection almost disappears. From the results obtained it is concluded that the rate of evaporation of water per unit surface area by forced convection is proportional to the 0.50 to 1.0 power of the relative velocity depending upon the conditions of the air flow over the surface.
For measuring correctly the internal friction of wood three kinds of spruce, two kinds of maple and one kind each of lime and cherry used for the making of violin-in the range of frequency from 100 to 10000 cps, the method of measurement is first investigated. Fixing of the specimen at one end, electromagnetical excitation at the free end and picking-upp of the vibration by a small microphone seem to be the method suited for measuring at high frequencies the internal friction of inhomogeneous materials such as wood. By means of this method the frequency dependence of internal friction of four specimens of every kind, twenty-eight specimens in all, is determined. Internal friction of all these specimens increases with the fre-quency; spruce in particular, it shows an remarkable increase. Young's modulus, rigidity and internal friction for bending and tortion of these specimens are also measured at a low frequency and several suggestions regarding the relation between dynamic mechanical properties of wood and sound quality of violin are obtained.
Methods of examining silicon single crystals by means of an image tube and outline of the results are given. Observation is made on the dislocation lines by “decorating” them with copper and the birefringent patterns after the method developed by Dash and also on the forming state of an alloyed p-n junction. Furthermore, the authors adopted the infra-red photoelastic technique for detecting the residual stress produced around the alloyed p-n junctions and succeeded in observing the near-infra-red emission from a grown p-n junction at room temperature. Lastly, the future role of the image converting devices in the research of semiconductor materials is discussed.
Of late, automatization of magnetic susceptibility measurement has been dealt with by several persons. But when it comes to the automatization of high sensitive apparatus for measuring the susceptibility of the order of 10-6_??_10-7 e.m.u./g in reproducible 2_??_3 figures, the case of the apparatus used by McGuire in 1949 for the examination of Hg single crystal at liquid helium temperature is the only example. An automatized apparatus, capable of measuring accurately and in good reproducibility the susceptibility of the order of 10-9 e.m.u./g of a sample, 0.1g or less in weight, in a magnetic field of 6•10-3 Oe was produced by the author. The apparatus incorporates with a magnetic torsion balance similar to the one used by McGuire and an improved phase sensitive Inoue detection circuit coupled with a pick-up condenser. The frequency used is 16 Mc/s which is modulated by 635 c/s. The detected voltage is added to the feed-back circuit after the low frequency amplification. For paramagnetic salts of iron group, 20-50 mg of sample mass suffices to obtain accurately the susceptibility in 3 figures in a 2_??_3•10-3 Oe field.
A new photoelectric ellipsometer is devised and with it a polarization spectrometer is constructed. This photoelectric polarization spectrometer is characterized by: 1) The two parameters of elliptically polarized light are modulated by two polarization modulators which are subjected to alternating electric field. These modulators are composed of ADP crystals and quarter wave plates. 2) Two modulated signals are separated by an simple and ingenious electro-mechanical circuit and are fed back to optical compensators. With this photoelectric polarization spectrometer, two parameters of elliptically polarized light, for instance reflection ratio Rp/Rs, and retardation δs are automatically determined.
To the six UCS systems already dealt with, four more systems represented by the chromatic value diagram of Adams and the color spaces of Munsell, Wright and MacAdam reported by Farnsworth are added. From the result of comparison made among these ten systems by using MacAdam ellipses and Munsell scales, the authors' new projective diagram (q1, q2) is found to be a good uniform chromaticity scale diagram.
In order to compare various formulas for specification of whiteness, the relations between visual impressions of white papers and the colorimetric assessments of their whiteness are examined by means of both Kendall's rank correlation τ1) and Spearman's ρ1). For the assessment of whiteness of non-fluorescent papers, the NBS color-difference unit with the proximity factor k of 100 and a new whiteness formula by using the author's (q1, q2) UCS system are found very good and the TAPPI-method a good and the simplest one.
The wavelengths of three spectral lines of krypton and two of mercury in the infrared near 1μ are obtained by radiometric-interferometric method using a germanium phototransistor as a photosensitive detector and at the path differences of 0, 4 and 20mm. A preliminary Michelson type interferometer equipped with a sliding wedge-shaped compensator is constructed for this purpose. Dark current of the phototransistor is eliminated by 400 Hz modulation of the incident beam and the output current is rectified through a mechanical synchronizing device. Fractional order of interference is calculated from eight successive readings of the current intensity corresponding to eight positions, arranged at equal intervals, of the sliding compensator. The final values of the wavelengths found in the present work are: _??_ _??_ of which the uncertainty is estimated to be ±0.01 A.
A Seya-Namioka type vacuum spectrophotometer incorporated with a concave grating of 1200 lines/mm and 1m radius has been constructed. In consideration of the discussion given by Greiner and Shäffer, the spectrum of positive 1st order with the angle of 69°45' between the incident and exit light beams is used instead the negative 1st order spectrum with the angle of 70°15' used by Seya and Namioka. The grating is rotated simply about its vertical axis through the grating center, and good focus is obtained over a wide range of wavelength from 0 to 3500Å, but actually the spectrometer is available to longer wavelength of about 6200Å, the limit of the response of RCA 5819 or 1P21 photo-multiplier. The spectral lines can be resolved down to 1Å and the relative intensity of scattered light does not exceed 2 percent in the extreme ultraviolet region. The spectrometer is designed to be used also as a spectrograph and may easily be modified into a 3m radius grating spectrometer if necessary. As the light source for photometry in the extreme ultraviolet region, hydrogen discharge of 1 ampere at about 1mm Hg is used. Obtained spectra of light sources are shown and results of absorption measurements on LiF single crystals are given.