Apatite crystal in hard tissue of conodont fossils

The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis (EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present. Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is not hydroxyapatite but fluorapatite.     

Quantum-Mechanical Properties of Protons in Solid Molecular Hydrogen at Megabar Pressures

Quantum distributions of protons in three high-pressure phases of solid molecular hydrogen are investigated by the first-principles path integral molecular dynamics (FP-PIMD) method, in which interatomic forces are calculated precisely based on the density functional theory. The distributions have entirely different symmetries from those predicted by conventional simulation with classical treatment of protons. Especially in phase II, we found that molecular rotation is hindered by quantum fluctuation of protons, having a strong resemblance to a quantum distribution of impurity muonium in crystalline silicon. The mechanism of this “quantum localization” is clarified by a detailed study of the potential energy surface for the molecular rotation.     

Optimal periodic maintenance strategy under an intermittently used environment

In this paper, the optimal periodic replacement-like strategy with minimal repairs is considered under an intermittently used environment. Suppose that transactions or jobs with exponential service times arrive at a system according to a homogeneous Poisson process and the system is alternatively in either a busy or an idle period subject to demand for use. We derive approximately the optimal preventive maintenance schedule which minimizes the relevant expected cost criterion for the system which behaves intermittently on an M/M/1 queueing process, and compare it with the usual maintenance schedule for the continuously used system.     

Study on dominant mechanism of high-cycle fatigue life in 6061-T6 aluminum alloy through microanalyses of microstructurally small cracks

The mechanism controlling the fatigue life of a precipitation-hardened Al–Mg–Si alloy (6061-T6) at a high-cycle fatigue (HCF) regime of over 10⁷ cycles was investigated in detail. It was found that over 90% of the total fatigue life was occupied by the growth process of a microstructurally small crack at relatively low stress amplitude. The small crack was often found to be arrested and halted for a long period (more than 10⁶ cycles) before it began to grow again, which resulted in a significantly slow growth process. The small crack was then analyzed not only by the conventional fractography but also by the cross-sectional observation of the crack tip region using a focused ion beam and transmission electron microscopy. These observations, supplemented also by a grain orientation analysis using electron backscattered diffraction, explicitly revealed the following points: (i) the small crack growth observed on the specimen surface is primarily related to facet-type cracking that occurs exclusively at the specimen surface; (ii) the growth direction of the small crack has strong anisotropy (i.e. surface-induced growth); (iii) the facet-type cracking is related to the formation of persistent fine slip bands that accompany no structural change of the matrix. On the basis of these results, the micromechanism of small crack growth and its relation to the concept of fatigue limit at the HCF regime is discussed in detail.     

An outcome of nuclear safety research in JAERI: case study for LOCA

An outcome of nuclear safety research (NSR) done by JAERI (Japan Atomic Energy Research Institute) was case studied by the bibliometric method. (1) For LOCA (loss-of-coolant accident) a domestic share of JAERI in monoclinic research paper was 63% at the past (20) 1978–1982 but was decreased to 40% at the present 1998–2002. For co-authored papers a domestic share between JAERI and PS (public sectors) was zero at past (20) but increased to 4% at the present. Research cooperation is active between Tokyo University and JAERI or between JAERI and Nagoya University. (2) It is revealed that LOCA outputs born by NSR-JAERI reflected partly to those of the Safety Licensing Guidelines, however, a share of NSR-JAERI could not determined due to the lack of necessary information in the Guideline.     

A background optimization method for PLL by measuring phase jitter performance

This paper describes a background (BG) optimization method for a phase-locked loop (PLL) by changing the circuit parameters of the PLL circuits. Measuring the phase shift of the voltage-controlled oscillator (VCO) at each input reference clock, we can determine the phase jitter performance with accuracy equal to a time interval analyzer (TIA). Using the combination of the global optimization method at initial stage and the local optimization method for the background calibration always gives the PLL the smallest jitter performance under process variation, supply voltage modulation, and temperature variation. The test environment fabricated by the 0.15-/spl mu/m CMOS controlled by an external FPGA demonstrates enough ability to suppress the impacts of the environmental variations.     

Control of nano-sized interlayer space of lamellar vanadyl benzylphosphate

Nano-sized interlayer space of lamellar vanadyl benzylphosphate was controlled by water content in starting solution. Depending on the water content, three types of lamellar vanadyl benzylphosphate having basal spacings of 1.4 nm, 1.9 nm and 2.3 nm were obtained. It was suggested that the difference in the concentrations of benzyl and hydroxyl groups in the interlayer leads to the variation of the interlayer space.     

Abnormality of electric field at a wedgelike edge of a conductor or a dielectric interface and methods for its relaxation

Abnormal electric field appears at a wedgelike edge of a conductor (electrode) or a dielectric interface, which usually becomes infinitely high. This paper analyzes the electric field near such an edge by the analytical variable separation method and by the numerical one of the charge simulation method. The analysis focuses on the special conditions where the electric field becomes zero at an edge. These conditions are important for the insulation design to suppress the discharge inception at such edges of conductors and dielectric interfaces. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 1–8, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20280     

Integral controller design based on disturbance cancellation: Partial LTR approach for non-minimum phase plants

For non-minimum phase plants, the loop transfer recovery (LTR) design of integral controllers based on the disturbance cancellation is considered. Since the design requires an unstabilizable extended plant, the standard LTR method cannot be applied. A new partial LTR method is proposed to overcome the difficulty. The target of the proposed design is a fictitious controller including a disturbance estimator based on the measurement of the minimum phase state. It is shown that the Riccati equation including the gain matrix of the disturbance estimator in the target can be used to recover the target feedback property in the output feedback controller. A simple design example is presented to show the effectiveness of the proposed method.