Time varying electromagnetic field, produced by electrodes or coils with configuration that has a central axis and azimuthal and axial periodicities, is analysed in general. As special cases of such a configuration, many types of electromagnetic fields, such as helical type, line cusp type and mirror type, are found, and the characteristics of these fields are outlined. Many configurations of electromagnetic fields used for plasma heating can be reduced to these special cases.
Diesel engine exhaust gas changes in colour between light gray and black according to the state of combustion, the density of colour indicating the amount of contained soot which tells how far the combustion is from completion. In measuring the smoke density, the lenses for observation are generally air-curtained to prevent them from being contaminated. Concerning this device, the :author points out the trouble of exhaust gas being mixed with or its flow rate being disturbed by the curtaining air causing inaccuracy of measurement. The author's method of obtaining the true smoke density and the result of experiment by this method are described.
Bending and annealing behavior of α-brass single crystal is studied by the etch-pit technique, the bending being by a four-point bending device and the annealing being for various durations at a high temperature. The results show that the ease with which polygonization occurs depends on the orientation of the bending crystal. When the crystals in a given region are so oriented that only the single slip is realizable, a homogeneous aggregation of dislocations is produced. This dislocation configuration develops readily to a large. scale polygonization. When, however, sets of intersecting dislocations are produced locally, Lomer-Cottrell's dislocation reaction is liable to occur, and since climbing of the groups of dislocations thus originated is not easy, no clearly polygonized structure arises. Furthermore, the orientation effect of polygonization reported in a previous paper is confirmed in the present experiment.
The optical properties of plane grating monochromators such as of Ebert and Czerny-Turner type are examined by the method of geometrical optics. The grating equation and the expression for the focal plane are derived, and by using them the expressions of image form are given. Further the optical system that minimizes the wavelength impurity is discussed and such residual aberrations as coma and astigmatism are examined. In any monochromator the focal plane depends. upon the grating position and the off-axial amount of collimator. In Ebert type monochromator with a circular-arc shaped entrance slit the image form is circular-arc only in a symmetric arrangement and elliptic in other arrangements, and the light through a circular-arc shaped exit slit is free from the wavelength error, and even if the slit is long, the image will be not so much blurred by residual aberrations. Therefore it is advisable to use a long circular-arc slits if the system is of Ebert type. In Ebert or Czerny-Turner type monochromator with a straight entrance slit the image form is parabolic. In Czerny-Turner type both the image form and focal plane are affected by its non-concentric quantity.