Vol. 25, No. 2 (1976)
1976, 148 (2): 97-104. doi: 10.7498/aps.25.97
It has been observed experimentally that the height of the microwave induced step in half-wavelength Josephson tunnel junction varies with the microwave voltage approximately as the square of the Bessel function; Also Odd-numeral steps disappear sometimes.A theoritical explanation is given for the above phenomena.
ANOMALOUS EDDY CURRENT LOSSES OF ISOPERM THIN STRIPS UNDER SUPERPOSED MAGNETIZATION BY ALTERNATING AND DIRECT CURRENTS
1976, 148 (2): 105-114. doi: 10.7498/aps.25.105
The eddy current loss at low frequencies in thin strips of isoperm under superposed magnetization by alternating and direct currents has been analyzed with a model of coherent rotation in magnetic domains. It is considered that the eddy current loss anomaly is not only caused by the displacement of the domain walls, but also by the rotation of magnetization. As the magnetic permeability is a tensor in the rotation process, it gives rise to a "laterat eddy current" term in addition to that given by the classical theory. Thence an expression has been derived for the anomaly coefficient ηr of the eddy current loss due to rotation. The theory has been extended to certain applied fields, and corresponding conclusions have been obtained.
1976, 148 (2): 115-121. doi: 10.7498/aps.25.115
Investigation has been made on the losses in magnetic cores consisting of strips of iron-nickel-cobalt alloy after annealment in a longitudinal magnetic field. It has been found that the p/f-f curve shows obvious anomalous behaviour. Explanation is given for this behaviour with a Theoretical model of the anomalous eddy current loss caused by the wall displacement in the 180?domains. Possible ways of minimizing the loss are suggested.
1976, 148 (2): 124-128. doi: 10.7498/aps.25.124
A noncoherent optical method for processing images blurred by large relative motions has been developed. The blurred image is directly differentiated by means of a pair of positive and negative plates, the optical densities of which are strictly "mutually compensated", thus giving the deblurred image. This method can be used to process both translation-blurred and rotation-blurred images; the latter are still difficult to process by coherent methods at present.
ENHANCEMENT OF NEUTRON DIFFRACTION INTENSITIES OF α-LiIO3 SINGLE CRYSTALS WITH THE APPLICATION OF A DC FIELD (Ⅱ)
1976, 148 (2): 129-134. doi: 10.7498/aps.25.129
The following investigations have been carried out on the basis of our previous work . The (002) intensities of neutron diffraction from α-LiIO3 single crystals under a DC or AC field along the c-axis were measured in various eases. (1) With a DC field applied at a temperature below 180 K or so, no enhancement is found to appear. When the DC field is applied at room temperature and the sample then cooled down to 180 K or even lower (e. g liquid nitrogen temperature), the magnitude of the diffraction intensity enhancement initially observed at room temperature remains the same, even after removing the applied voltage. (2) When a narrow neutron beam is scanned across a thicker crystal and a DC field applied, the diffraction intensity enhancement is not limited to the region near the electrodes, but also appears in each scanned region. (3) When a low-frequency AC field is applied, the enhancement decreases as the frequency increases for the same Vs.m.s. Above 1500 c/s the effect becomes negligible.
1976, 148 (2): 135-145. doi: 10.7498/aps.25.135
In this paper we give different types of generalized Watson expansions, therefore the total scattering process occurring in a N-body system can be decomposed into local processes (process involving only a few particles).
AN IONIC GROUPING THEORY OF THE ELECTRO-OPTICAL AND NON-LINEAR OPTICAL EFFECTS OF CRYSTALS (Ⅰ)——A THEORETICAL CALCULATION OF ELECTRO-OPTICAL AND SECOND OPTICAL HARMONIC COEFFICIENTS OF BARIUM TITANATE CRYSTALS BASED ON A DEFORMED OXYGEN-OCTAHEDRA
1976, 148 (2): 146-161. doi: 10.7498/aps.25.146
In order to elucidate the relationship between the structure and the electro-optical and nonlinear optical effects in crystals of the perovskite type, we have here proposed a deformed oxygen-octahedra model for these crystals. On the basis of quasi-molecular orbitals and ionic bond orbitals for the ionic grouping TiO6 formulated under the imposed crystal field, we have calculated the various electro-optical and second optical harmonic coefficients for the BaTiO3 crystal without introducing any adjustable parameters. It is gratifying to note that the calculated values of the electro-optical and second optical harmonic coefficients agree satisfactorily with the experimental values. As is to be expected, the quasi-molecular orbitals contribute very little to these optical effects. We have been led to the following conclusions:1) The electro-optical and second optical harmonic effects of the BaTiO3 crystal arise as a direct consequence of the deformation of the TiO6 oxygen-octahedra. The more these octahedra are deformed, the larger are these optical effects.2) When BaTiO3 is present as the ferroelectric phase, a strong odd ordered-term crystal field arises as a result of the spontaneous polarization within the crystal. This explains why BaTiO3 possesses such large electro-optical and second harmonic optical effects. The covalent bonds in the ionic group TiO6 tend to cancel each other in their contribution to these effects.3) The electro-optical and second harmonic optical coefficients are directly proportional to the degree of spontaneous polarization.