The characteristics of ferrite cores with low Curie temperature and their application

The utility of ferrite cores which have the Curie temperature in the vicinity of the room temperature and suddenly change the permeability vs. temperature characteristic near the Curie temperature is described in this paper. Using the characteristics of these ferrite cores, the author made an overcurrent relay and a long delay circuit, and investigated their application to a temperature control device and to the thermomagnetic generator. These devices are smaller than usual, and operate with good accuracy. The author finds that ferrite cores with low Curie temperature are materials important to the development of a new field in electrical engineering.     

Electron microscopic determination of orientation

The martensites of titanium binary alloys, containing 1, 2, and 5.3 wt pct Cu, were studied by transmission electron microscopy techniques. Roughly parallel plates with different variants of the orientation relationship, as well as colonies of identical variant plates, prevail in the structures. A stereographic projection analysis of super-imposed diffraction patterns from two adjacent plates is shown to be sufficient for the deduction of the orientation relationship that existed during transformation, which is found to be the Burgers’ relationship -(110)_β∥ (0001)_α′; 〈111〉_β∥ 〈2110〉_α′. A graphical method was developed for the derivation of the habit plane and its particular variant, in spite of the absence of retained β phase in quenched Ti-Cu alloys. The habit plane of Ti-Cu martensite is found to be (1079)_β with 4 deg accuracy, and to best agree with Class A (α^- ω⁺) solution of the Bowles and Mackenzie theory, rather than with (α⁺ ω⁺) or with Class B solutions.     

Analysis of the coupled effect of plastic damage and creep damage in nimonic 80A at finite deformation

The coupled effect and the anisotropic feature of plastic damage and creep damage in Nimonic 80A are analysed with special emphasis on the finite deformation and the material spin of the damaged material. In view of that both the plastic and the creep damage are governed by the formation of grain boundary cavities, it is first assumed that the states of plastic damage and creep damage are represented in terms of symmetric second-rank damage tensors Ω^P and Ω^C, the sum of these tensors Ω = Ω^P + Ω^C represents the damage state of the material. The evolution equations of these variables are established on the basis of the experimental observations on the nucleation and growth of microscopic cavities. The creep constitutive equation of the material, on the other hand, is formulated by taking account of the acceleration due to material damage as well as the material softening caused by the formation of the dislocation network at particle interfaces. Finally, creep damage process at finite deformation of Nimonic 80A at 750°C subjected to prior plastic damage brought about by the plastic prestrain at room temperature is analysed. The numerical results are compared with the corresponding experimental results to discuss the validity of the proposed theory. Though considerable rotation of principal damage direction was observed in the process of torsional creep, its effect on the creep damage process was found to be rather small.     

Sputtering of silicon carbide coatings by low-energy hydrogen ions

Various types of silicon carbide coatings made by reactive ion-plating have been bombarded with a 3.0 keV H⁺₃ ion beam at temperatures around 500°C. The sputtering yield in stoichiometric samples (i.e. Si : C = 1 : 1) at 500°C was $\text{1.15 × 10}{}^{\mathrm{?2}}$ atoms/H⁺. As the stoichiometry deviates from this point, the sputtering yield has larger values. The temperature dependence of the sputtering yield in stoichiometric samples was negligible below 600°C. No surface topography changes occurred in stoichiometric samples even at a high fluence of $\text{2 × 10}{}^{20}\text{H}{}^{\mathrm{+}}\text{/cm}{}^2$, while severe erosion took place in non-stoichiometric samples. By Auger electron spectroscopy (AES), carbon exists on the surface in the form of carbide in stoichiometric SiC before and after bombardment, while it exists in the form of graphite in carbon rich samples, which suggests that the bound state of carbon in the form of carbide should correspond to the low sputtering yield in stoichiometric SiC coatings. The surface stoichiometry changes due to hydrogen bombardment were observed by AES, where the carbon population increases in stoichiometric SiC, while it decreases in carbon rich samples, which was supported as well by the results from electron probe X-ray microanalysis.     

Theoretical Comparison Between DPCM and Transform Coding Regarding the Robustness of Coding Performance for Variation of Picture Statistics

Since DPCM and transform coding are two fundamental approaches to high-efficiency (bit reduction) coding, it is important to clarify the basic coding characteristics of these approaches and the differences between them in order to utilize the high-efficiency coding method effectively. It is important to compare them not only from the standpoint of coding performance as optimized coding schemes based on the statistics of the input picture signal, but also from that of the robustness of coding performance for the variation of picture statistics to be coded. This paper theoretically compares the robustness of the coding performance of DPCM having a two-dimensional predictor with that of a two-dimensional Hadamard transform coding in an intrafield coding method of the NTSC composite signal. The comparison provides theoretical evidence that transform coding is more stable than DPCM, and this tendency is marked at lower bit rates such as 1 or 2 bits/pel, while DPCM has a higher coding performance for pictures with high autocorrelation.     

Study of the structure and crystallization of an Fe-17 at % B amorphous alloy

The structure of an Fe₈₃B₁₇ amorphous alloy was examined in detail, mainly by means of small-angle X-ray scattering (SAXS) measurements. The electron density-density correlation derived from the observed intensity had the following characteristic features: a strong correlation concentrated in the short radial distances within about 1.2 nm and a rather weak correlation towards larger distances. After quantitative analysis, it was concluded that a compositional fluctuation occurs on a fine scale of about 1 nm in the amorphous Fe-B alloys, even though phase separation is not present as completely as in the structure model proposed by Boudreaux. Electrical resistivity measurements as well as transmission electron microscope (TEM) observations were performed to investigate the crystallization process. By using the theoretical equation of electrical resistivity reported by Landauer, the temperature dependence for the partially aged amorphous alloys was analysed. The volume fraction of crystalline phase estimated from the present analysis was in good agreement with the results obtained from TEM observation.     

Chemorheological study of vulcanized rubbers under mechanical stress

At lower than the glass transition temperature, the cleavage of the molecular chains of extended vulcanized rubbers will occur. The crosslinking density of vulcanized rubbers, which were placed at room temperature for about 4 hr in nitrogen atmosphere, increased about 17% after extension of 200% at ?76°C. This may be due to the recombination of cleft chains, and this can be shown by the Maxwellian type of curves between crosslinking density and forced strain. Considering the decreasing proportion of crosslinking density by the radical acceptors included in the rubbers and the fact that crosslinking density increases because of recombination of cleft chains, this was attributed to the recombination of unstable chains produced by the added mechanical stimulus.