No abstract

BABH(n)s exhibit two different Ia3̄d cubic phases depending on the chain length. We revealed the difference in molecular packing in the two Ia3̄d phases. Based on the difference, the reentrant behavior between the two Ia3̄d phases was clarified.

For total luminous flux calibration by a sphere-spectroradiometer system in 2π geometry, a new LED-based standard light source (standard LED) covering the full visible wavelength range has been developed. The developed standard LED has sufficient spectral power over the full visible wavelength range using UV-LED dies of different peak wavelengths in combination with red, green and blue phosphors. By evaluating spectrum flatness based on the magnitude of the second derivative, the spectrum of the standard LED was customised to minimise the measurement uncertainty. Properties of the standard LED such as the luminous intensity distribution, stability and reproducibility were also evaluated. The evaluation results indicate that the standard LED has good properties as a standard light source for the 2π total spectral radiant flux scale. Furthermore, the result of an operating current dependence suggests that the standard LED has benefits as a standard source that conventional standard lamps do not have.

The National Metrology Institute of Japan realized a total spectral radiant flux scale in the visible wavelength range (from 380 nm to 780 nm) for sphere-spectroradiometer calibration in 2π geometry. For a transfer standard in 2π geometry, a standard source based on a specially-designed broadband light-emitting diode (2π standard LED) was used. For the scale realization, we used the goniophotometer/spectroradiometer system. In the realization, an effect of a bandpass function of the array spectroradiometer was corrected by a matrix inversion approach. The relative expanded uncertainty (k = 2) for the scale is from 3.3% to 5.7% depending on the wavelength range. We also evaluated the contributions of the wavelength calibration and the bandpass function to the measurement of the total spectral radiant flux of typical white LEDs against the 2π standard LED. Our results demonstrate that the 2π standard LED achieves uncertainties comparable to those of a conventional standard lamp, within a practical wavelength range for LED measurements. These results show that the 2π standard LED is a useful transfer standard for the realization of the total spectral radiant flux scale and for evaluation of the total luminous flux of LEDs in 2π geometry.

Early nondestructive inspection of rebar corrosion in reinforced concrete structures is important, but a practical, accurate, high-speed, and high-resolution method has not yet been proposed. We have proposed a vibro-Doppler radar (VDR) method for quantitative evaluation of rebar corrosion based on vibration displacement of a rebar sinusoidally vibrated by an excitation coil. However, this method is not practical because it is not quick enough, requiring two minutes for a measurement at one point. In this paper, a VDR system based on a pulse radar, which is 100 times faster than the conventional system, was developed, and its effectiveness was verified using a concrete specimen. As a result, it was found that a 30-cm section could be scanned in about 2 min. Furthermore, the vibration displacements spatially distributed on the rebar were monitored while the rebar was corroded by electrolytic corrosion tests. As a result, it was found that the vibration displacement increased locally with a width of a few centimeters, and their positions corresponded to the positions of sectional loss of rebar due to corrosion, indicating that this method can be used for nondestructive evaluation of localized rebar corrosion.