Comparison of 80-keV D+ Ion Implantation with Thermal D2 Doping in Silica by FTIR and ESR Spectroscopy

Behavior of deuterium atoms in fused silica, which were implanted by 80-keV D⁺ (D₂⁺, D₃⁺) ions or doped thermally by D₂ (or D₂O), was studied by infrared Fourier transform spectroscopy (FTIR) and by ESR spectroscopy. When 80-keV deuteron ions are implanted into fused silica, OD bonds are formed. The OD bonds are also formed by thermal doping with D₂ or D₂O. When the deuterated silica is γ-ray irradiated at 77 K, D atoms are formed by rupture of the OD bonds. The efficiency of the OD bond rupture in the deuteron-implanted silica is much less than that in the D₂-doped silica. It is concluded from the results of thermal annealing that the low efficiency of the OD bond rupture in the deuteron-implanted silica is due to the radiation damage accompanying the implantation process. However, the decay rate and detrapping energy of deuterium atoms, once formed in the silica, are similar in both cases.     

Capsule-Packed Freezing of Cooked Rice and Glutinous Rice Cakes

Cooked rice and commercial glutinous rice cakes were frozen by a capsule-packed freezing method we developed, then stored. Characteristics of samples frozen by this new method were compared with those of samples frozen in deep freezers (–20°C and –50°C), or chilled in an ordinary (5°C) or Cold Fog refrigerator (0°C). Texturometer measurements, glucoamylase digestion, and X-ray diffraction analysis of specimens thawed to room temperature indicated that the samples prepared by our new method were superior to those frozen in conventional freezers or chilled in refrigerators. Simulation experiments in a program freezer showed that rapid freezing and adequate tempering were characteristic of our capsule-packed method.     

Design of servo systems for distributed parameter systems by finite dimensional dynamic compensator

The design problem of servo systems for distributed parameter systems is investigated. The output regulator of integral type is designed in order to guarantee internal stability and output regulation. The design procedure based on a dynamic stabilizing compensator is discussed. The output regulation of a wide class of distributed parameter systems is proved under the condition that a closed-loop system is stabilized by a dynamic compensator of general type. Then a closed-loop system can be stabilized by a finite dimensional dynamic compensator under some additional conditions. The reducabitity of the design procedure to a purely finite dimensional one is discussed.     

Selective O–H Bond Cleavage in the Radiolysis of Quartz

Cleavage of the O–H bond in quartz was studied by Fourier transform infrared spectroscopy and ESR spectroscopy. When quartz single crystals and fused silica glass are γ-irradiated at 77 K, hydrogen atoms are produced by rupture of O–H bonds. The initial efficiency of O–H bond cleavage in quartz single crystals, i.e. the initial yield of H atoms, was three times as great as that in fused silica glass, although the concentration of O–H bonds in quartz single crystals (70 ppm) is much lower than that in fused silica glass (4000 ppm). The efficiency of O–H bond cleavage in quartz single crystals indicates that energy transfer from the irradiated single crystal to the O–H bonds takes place effectively at 77 K. The efficiency of O–H bond cleavage decreases with increasing γ-ray dose, i.e. with increasing amounts of radiation-induced defects in quartz single crystals. When the radiation-induced defects are removed by annealing the irradiated quartz single crystal at 773 K, the O–H bonds are ruptured again as effectively as for a fresh quartz single crystal. The distance of the energy transfer, estimated by a target model, is ∼15 nm.     

Kinetic Behavior of H and D Atoms in γ-Irradiated SiO2 as Studied by ESR Spectroscopy

The decay of hydrogen atoms, produced by γ irradiation of fused silica and quartz, was studied by ESR spectroscopy. The decay of H atoms in silica cannot be explained by a secondorder kinetics nor by a simple first-order kinetics. Also, the decay is not composed of several first-order processes with different activation energies. The data for the decay of H atoms can be described by a first-order kinetic equation with a timedependent rate constant of the form k(t) = Bt ^α−1, where B and α are constants. The decay kinetics of D atoms in deuterated fused silica and H atoms in a single crystal of quartz are also explained by use of the time-dependent rate constant. The apparent activation energies for the decay of H and D atoms in the silica are 15 to 16 kJ/mol and 14 to 15 kJ/mol, respectively. The decay rates for D and H atoms in the silica are similar.     

Compositional Trends in Photoelastic Constants of Borate Glasses

The stress-optical coefficients of binary and ternary borate glasses were measured and the factor ( p·q ), where p and q are the Neumann strain-optical coefficients, was determined. As a modifier oxide was added to B₂O₃ glass, the stress-optical coefficient decreased monotonically. It was found that the stress-optical coefficient is determined mainly by the elastic modulus, but the factor ( p·q ) becomes significant when the content and polarizability of the modifier cation are high. It was also found that the factor ( p·q ) decreases when the content and polarizability of the modifier cation increase. The ( p·q ) was divided into the lattice effect and the atomic effect, and their compositional dependences were discussed.     

THE CATEGORY THEORY OF TIME SYSTEMS

In this paper we show a categorical treatment of general time systems using the categorization method presented in our previous paper. Various concepts about general time systems are categorized in the unified framework. Some category theoretical tools for the investigation of such time systems are presented. Using those tools some basic properties of time systems are explored in our framework. In particular, a conceptual equivalence between the causality and the state space representability is proved in the categorical terms. These results show that our method can be a universal tool for a categorization and a categorical treatment of mathematically defined general systems.     

Multirate digital control design of an optimal regulator via singular perturbation theory

In this paper a multirate digital control design of an optimal regulator is investigated via singular perturbation theory. It is shown that the singularity perturbed continuous-time regulator leads, under slow and fast sampling rates, to two different discrete-time versions. They are decomposed into slow and fast subsystems, and then these solutions are combined in a proper way. Within the framework of such a decomposition-coordination principle, a multirate control design is developed naturally. Furthermore, the problem of the asymptotic stability of a multirate controlled system is investigated and the relationship between the original continuous-time version and the multirate controlled version is discussed.     

人类学如何着眼景观？——景观人类学之新课题

景观人类学兴起于20世纪90年代的英语圈,21世纪后传入日本、中国。人类学家之所以于20世纪90年代后开始讨论景观,是因为当时景观作为新的分析概念正广受关注。人类学着眼景观概念后,开拓了新的学术领域,也直面新的课题。由此可以探讨人类学应用景观概念的意义和可能性。     

EFFECT OF WAVEFORM ON CORROSION FATIGUE CRACK GROWTH

Abstract A study was made on the effects of stress rise time T ₁, maximum stress holding time T ₂, stress decreasing time T ₃ and minimum stress holding time T ₄ of a cycle on fatigue crack growth for a low alloy carbon steel in 3% NaCl solution. Measurements of the effective stress intensity range ratio U and observations of crack tip response were performed to clarify the causes of waveform effects.
The results were summarized as follows; T ₁ had a strong accelerating effect due to corrosive dissolution of the fresh surfaces of the crack which were formed during T ₁. The crack growth rate was enhanced as T ₁ increased and reached a constant value (about 3 times that in air) after T ₁= 10s. The crack growth rate at low Δ K , however, decreased as T ₁ increased more than T ₁= 1 s. T ₂, T ₃ and T ₄ decreased the crack growth rate. The extent of decrease not only depended on the period of T ₂ (or T ₃, T ₄), but also on Δ K and T ₁. A previously derived crack growth law which considered waveform and frequency effects, is also valid to a first approximation for the present results.