Thermal crystallisation of amorphous calcium phosphate to α-tricalcium phosphate

Dehydration and thermal change in amorphous calcium phosphate (ACP) have been studied by thermogravimetry, differential thermal analysis and X-ray diffractometry. ACP retained water up to about 773 K. Immediately after the dehydration, a high-temperature form of calcium phosphate, α —Ca₃(PO₄)₂ (α -TCP), was obtained by ignition of ACP precipitated from the solution with a high degree of supersaturation. The kinetics of thermal crystallisation of α-TCP from ACP were also studied.     

Uptake of fluoride ion by amorphous calcium phosphate

Fluor-bearing apatites were obtained by suspending amorphous calcium phosphate in NaF solutions, The amounts of absorbed F increased with lowering of pH in the fluoride solutions and elevation of temperature. The apatite formation may be interpreted in terms of a certain dissolution-crystallisation mechanism.     

Behavior of a tip of non-propagating fatigue crack during one stress cycle

Measurements and observations were made on the crack closure for the so-called non-propagating crack of notched specimens and for the non-propagating microcrack of unnotched specimens, which were formed in a rotating bending test of annealed carbon steel. Under the condition which produces the non-propagating crack, the ratio of stress range where the crack tip is open, to the full range of the cyclic stress tends gradually to zero with the increase in length of the crack initiated from a notch root.The tip of a non-propagating microcrack on the surface of a plain specimen is also recognized to be closed under the maximum stress level after 10⁷ cycles of the repetitions of the stress slightly below the fatigue limit.From these facts, it can be said that the tip of a so-called non-propagating crack or a non-propagating microcrack is hardly damaged by the repetition of stress which has produced each crack.     

Cold rolling of polymers 3. Properties of rolled crystallized polycarbonates

Amorphous polycarbonate sheets up to 1/4 inch in thickness have been crystallized both thermally and by acetone vapor sorption. For thick sheets acetone vapor sorption is the superior technique and a method has been developed for assuring homogeneous crystallized sheets. The crystallized polycarbonate can be cold rolled providing there is a residual acetone content to act as a plasticizer for the sheet. The tensile stress strain characteristics of the as-crystallized sheets as well as the rolled crystallized sheets have been determined as a function of the residual acetone content. It is shown that a crystallized polycarbonate whose thickness is reduced by 74 percent can achieve a true stress at fracture of 27,180 psi and a strain of 33 percent. These values are significantly greater than the values obtained for rolled amorphous polycarbonates.     

The mechanisms of in-pile fission gas release from UO2

In-pile release mechanisms of fission gas from UO₂ at low temperatures were studied. The release of ¹³³Xe, ¹³⁵Xe, ¹³⁸Xe, ^85mKr, ⁸⁸Kr and ⁸⁷Kr from a sintered UO₂ pellet was measured at temperatures ranging from 250 to 930°C using a graphite specimen holder. The release from the holder, in which a fraction of fission gas was recoil-implanted, was subtracted to obtain the net release from the UO₂ pellet. Knock-out release from the UO₂ was measured directly, and it was found that it was not the main release mechanism, at least not for short-lived nuclides. A ‘pseudo-recoil’ release model is proposed to explain the low temperature release under irradiation. In the model, some of the defects produced by fission fragments act as short-lived carriers for fission gas.     

Far-infrared spectroscopy by synchrotron radiation at the UVSOR Facility

At the UVSOR Facility, Institute for Molecular Science, the practical use of the synchrotron radiation as a far-infrared light source has started. A spectroscopic system has been constructed at the beam line BL6A1 of UVSOR storage ring, which covers the wavenumber region from 5 to 250 cm^?1. The cross sectional diameter of the light beam at the sample position is as small as 3 mm with the angular divergence of about 100 mrad. The system has been made mainly for the transmission and reflection measurements of small samples with small angular divergence by the use of the high brightness of the synchrotron radiation. Examples of observed transmission and reflectivity spectra are shown.     

Targets and results from phase one and two of the fifth generation computer systems study

This article presents an introduction to the fifth generation computer systems.

Fifth generation computers are under development to meet the knowledge information processing needs for the advanced information-oriented society of the 1990s. This clearly requires overcoming the technical limitations of conventional computers. A fifth generation computer requires problem solving and inference functions for inference of solutions to problems from accumulated knowledge, knowledge base management functions for acquirement and retrieval of knowledge, intelligent interface functions for fluent conversations using natural language, drawings, images, etc., and intelligent programming functions for automatic conversion of problem specifications submitted in natural language, drawing etc., into efficient programs.

Fifth generation computers with these functions will have far-reaching impact finding applications in all areas of industry and society. However, research and development (R&D) of these computers requires an extremely wide variety of leading-edge technology, and the risks are high. Accordingly, a long-term R&D plan was established for this project that extends over ten years with the initial stage lasting from 1982 to 1984, the intermediate stage from 1985 to 1988, and the final stage will begin in 1989 and the project will end in 1991.