Vol. 9, No. 1 (1953)
1953-01-05
Original Articles
1953, 9 (1): 3-14.
doi: 10.7498/aps.9.3
Abstract +
An attempt has been made to determine the half-life for spontaneous fission for the average uranium atom with on argon-filled parallel-plate ionization chamber, employing the method of electron collection. The high vohage electrode contained an aluminum disk of 6.2 cm diameter on which was deposited a layer of uranium oxide prepared in the following manner. A known amount of uranium nitrate crystals was dissolved in alcohol and mixed with properly thinned colorless lacquer. The procedure then consisted in applying a small amount of the solution on the disk, baking it on an electric furnace to about 400℃ for five minutes, and repeating the process again and again until the desired amount of uranium had been deposited. The ionization pulses were observed on a Cenco cathode ray oscilloscope to which the output of the amplifier was connected.
1953, 9 (1): 15-35.
doi: 10.7498/aps.9.15
Abstract +
The approach to magentic saturation in the cases of iron, nickel, and a number of iron-cobalt alloys at various temperatures has been studied in the range of field from a few hundred to 6,000 oersteds. It has been found that for annealed and moderately cold-worked specimens the differential susceptibility can be represented fairly accurately by a formula of the form ((?I)/(?H))T=A/H2+(2B)/H2+ C/H1/2+D where I is the magnetization, H the applied field, and T the temperature. Near room temperature, the last two terms taken together are so small compared to the first two that they can be approximated by a single constant. For a specimen starting in the annealed state both the coefficients A and B increase at first tremendously with the amount of cold-work the specimen receives, but the formula fails to apply when the specimen is severely cold-worked For annealed specimens these coefficients decrease with increasing temperature, vanishing at considerable distances below the Curie point. In general, D cannot be evaluated with certainty from the present data. However, the coefficient C evaluated by neglecting D is in satisfactory agreement with the theoretical results of Holstein and Prima-koff in so far as its order of magnitude and the way in which it varies withthe temperature are concerned. B is undoubtedly proportional to K12/I5 where K1 is the first magnetocrystalline anisotropy coefficient and I5 thesaturation magnetization. However, values of K1 obtained by comparing theory and experiment are satisfactory only in regard to the order of magnitude.
1953, 9 (1): 36-44.
doi: 10.7498/aps.9.36
Abstract +
It was shown in the preceding paper The S-Matrix in Meson Theory that the S matrix for certain types of meson theories can be made divergence-free by charge and mass renormnalizations if the radiation effect of the meson self-energy part has been taken into account properly. This amounts to replacing the following function occurring in integralsby the function
专题: 癌症生物物理
1953, 9 (1): 45-56.
doi: 10.7498/aps.9.45
Abstract +
A method based upon simple diffraction theory is described for the calculation of modified paraboloid reflectors to produce from a point source a shaped beam of arbitrary shape in one plane and uniformly narrow in the perpendicular planes. A specific application of the shaped beam antennas is in connection with radar antennas designed for height finding. In this case the antenna must have a sharp elevation beam for obtaining precise elevation information and a rapid elevation scan. The beam must be relatively broad in azimuth in order that the target will be held in the beam long enough to obtain height information. If a fixed minimum of illumination is to be achieved at a given linear distance on both sides of the center line of the azimuth beam, the amplitude pattern must have the so-called “double cosecant” or “beavertail' shape.
