High temperature superconductor micro-superconducting-quantum-interference-device magnetometer for magnetization measurement of a microscale magnet

We have developed a high temperature superconductor (HTS) micrometer-sized dc superconducting quantum interference device (SQUID) magnetometer for high field and high temperature operation. It was fabricated from YBa2Cu3O7-delta of 92 nm in thickness with photolithography techniques to have a hole of 4x9 microm2 and 2 microm wide grain boundary Josephson junctions. Combined with a three dimensional magnetic field coil system, the modulation patterns of critical current Ic were observed for three different field directions. They were successfully used to measure the magnetic properties of a molecular ferrimagnetic microcrystal (23x17x13 microm3), [Mn2(H2O)2(CH3COO)][W(CN)8]2H2O. The magnetization curve was obtained in magnetic field up to 0.12 T between 30 and 70 K. This is the first to measure the anisotropy of hysteresis curve in the field above 0.1 T with an accuracy of 10(-12) J T(-1) (10(-9) emu) with a HTS micro-SQUID magnetometer.     

Te concentration dependent photoemission and inverse-photoemission study of FeSe1?xTex

We have characterized the electronic structure of FeSe_1−xTe_x for various x values using soft x-ray photoemission spectroscopy (SXPES), high-resolution photoemission spectroscopy (HRPES) and inverse photoemission spectroscopy (IPES). The SXPES valence band spectral shape shows that the 2 eV feature in FeSe, which was ascribed to the lower Hubbard band in previous theoretical studies, becomes less prominent with increasing x. HRPES exhibits systematic x dependence of the structure near the Fermi level (E_F): its splitting near E_F and filling of the pseudogap in FeSe. IPES shows two features, near E_F and approximately 6 eV above E_F; the former may be related to the Fe 3d states hybridized with chalcogenide p states, while the latter may consist of plane-wave-like and Se d components. In the incident electron energy dependence of IPES, the density of states near E_F for FeSe and FeTe has the Fano lineshape characteristic of resonant behavior. These compounds exhibit different resonance profiles, which may reflect the differences in their electronic structures. By combining the PES and IPES data the on-site Coulomb energy was estimated at 3.5 eV for FeSe.     

Decoupling properties of singular LQ regulation problem

Some properties of a limiting solution derived from a standard LQ regulator problem are discussed in the case where the input weighting matrix tends to zero, for a discrete time system. The explicit limiting solution is given in some literature. It is shown that the limiting solution is closely connected with a disturbance decoupling problem. Moreover it is pointed out that the limiting feedback gain with the help of feedforward gain constructs the decoupled system with the maximum number of blocks.     

The formation of graphene–titania hybrid films and their resistance change under ultraviolet irradiation

We report the fabrication of hybrid films of graphene and monolayer titania using a simple electrostatic self-assembly method. Ultraviolet (UV) responses of the hybrid films based on the graphene–titania structure were investigated. We observed that the resistance of the graphene–titania hybrid increased exponentially with UV irradiation time and decreased exponentially when UV was turned off. Time constants of the order of hundreds of seconds were identified and found to be sensitive to the gas environment of graphene. The UV response as well as the time constant is tunable by varying the number of titania layers. Our results confirmed that UV irradiation played a significant role in the resistance modulation of graphene as well as graphene–titania hybrid films.     

Influence of temperature on the fatigue strength of compressed-hydrogen tanks for vehicles

The influence of environmental temperatures on the fatigue strength of compressed-hydrogen tanks for vehicles was investigated. The fatigue strength of Type-3 tanks was found to decrease in a low-temperature environment and increase in a high-temperature environment. The Type-3 tank has been subjected to autofrettage to improve fatigue strength. The investigation clarified that the effect of autofrettage changes according to the environmental temperature due to the difference between the coefficients of thermal expansion of carbon fiber reinforced plastic and aluminum alloy. This causes fatigue strength to change with changes in temperature. The Type-4 tank has a very long fatigue life and did not break after 45,000 cycles in a room-temperature or low-temperature environment. In a high-temperature environment, however, the tank broke in fewer than 45,000 cycles. The fatigue of carbon fiber reinforced plastic was promoted in the high-temperature environment, resulting in breakage of the tank. These results indicate that the fatigue strength of the tanks is influenced by the environmental temperature.     

Syntheses and properties of B-C-N and BN nanostructures

The current status of research on boron-carbon-nitrogen (B-C-N) and boron nitride (BN) nanotubes is presented. The latest achievements in syntheses, analyses and property measurements of these nanoscale tubular architectures are reviewed. The characteristic features of B-C-N and BN nanotubes, compared with conventional C nanotubes, are paid special attention. In particular, the latest breakthroughs in the chemical vapour deposition synthesis of BN nanotubes and an insight into their unique structures are highlighted. A wide range of potential applications is also envisaged, based on the recent progress, which includes pioneering results in BN nanocable fabrication, gas adsorption, electron transport and field emission measurements.     

Sellmeier dispersion for phase-matched terahertz generation in ZnGeP2

A Sellmeier dispersion of zinc germanium diphosphide (ZnGeP2) crystal has been formulated to determine the phase-matching characteristics of the crystal for the generation of coherent tunable terahertz radiation by difference-frequency mixing techniques. The results computed with the formulated Sellmeier dispersion provide an excellent fit to the experimental data.     

An Approximation for the Production Efficiency of Automatic Transfer Lines with In-Process Storages

This paper considers the production efficiency of automatic transfer lines where in-process storages are provided for stochastic station breakdowns. A simple approximation method is developed in order to readily obtain the production efficiency and show the benefit of providing storages even for long lines. Additionally, the optimal partitioning of the line and the method of allocating capacities for storages are numerically investigated.