Correct time intervals ranging from 0.1 second to 1 minute for operating photographic printing lamps and other control apparatus are provided by a simple device using an electro-nic tube and a delay circuit. By checking up to 0.001 second with an electronic counter of the accuracy of ±0.0001 second, the device showed an accuracy very much higher than that of customary timers. The principle of operation is based upon the change of plate current, which operates a relay, in accordance with the change of the charging time, i.e. the delay time, of capacitor through an adjustable resistance in C-r delay circuit. A noticeable feature is that as it has a stabilizing tube each in the B electric power supply and the bias circuit, the current characteristic varies according as which one of the two tubes is operated. We may, therefore, choose the one that suits the purpose. Thus, in face of fluctuating line voltage of say ±10%, error in timing can be made as small as ±1.0%.
In rochelle salt crystals a peculiar type of ferroelectric domain (as Fig. 2) is observed around a hole which is filled with saturated solution. Another peculiar type of domain (as Fig. 3) is observed around a group of fine crystals which has been crystallized by a certain treatment. These peculiar types of domain are understood to result from stress concentration around the hole and the group of fine crystals.
The machining of hard metals can easily be performed nowadays by the method of electro-machining, which was first introduced by Lazarenko and was developed by many engineers. The machining, however, can be done only when condenced discharges or quenched sparks are initiated between a metal plate to be machined and an electrode, which is in incomplete contacts or in repeated contacts to the plate. Further, to increase the accuracy of machining and the working speed the plate must be connected as the anode in a direct current circuit. In the present method, the plate and the electrode, which are connected in an alternating current circuit, are separated to each other keeping a small gap, and are dipped into water. Applying high frequency oscillations between them in every other half cycles, at which the plate is in the positive potential, we can initiate quenched discharges only in the half cycles and are able to perform the electro-machining of the plate. Thus, with no use of the direct current source and repeated contacts of the electrode we can easily machine hard metals, especially tungsten plates, which are considered as being not easy to drill by both electro-mechanical and pure mechanical methods. Peculiallity of the present method is that even minute cracks do not grow in the machined surface and that screw cutting can be done easily by a screw of an electrode which progress-es by a guidance of a screw of the same pitch. Time for drilling a tungsten plate 3mm in thickness by a tungsten rod 1.54mm in diameter is 4 minutes with discharge current about 1 Amp., and the diameter of a hole drilled is 1.75mm. In the last section mechanisms of the electro-mechanical machining due to quenched discharges are explained qualitatively; the drilling effect being ascribed to electric attraction action on the melt of the plate, and loss of the electrode to a bluster effect of positive ions.
Hydrodynamical properties of hairy body are studied by using plane, hemi-spherical models bristled with thistle (sawa-azami) pappi which are cylindrical. By measuring the terminal velocity and introducing the effective projected area, the drag coefficient is determined. Rey-nolds number is varied by the mass of center of the model. The drag is found approximately proportional to the ath power of the terminal velocity. The relation of the exponent a to the number of bristle is shown by a figure. The drag coefficient at Reynolds number 300 is nearly constant, is independent of the number of bristle, but at 2000, it decreases slightly with the latter. The drag of a plane model is calculated by using the theoretical drag coef-ficient of an infinitely long cylinder and compared with the experimental value.
Many kinds of growths are obtained on the surface of brass, copper and platinum wires by heating for a few hours in air in an electric furnace or an infrared-ray furnace. The growths are studied by an electron microscope and some new characteristic features are found.