Abstract – HTS current lead have been prepared by the TFA-MOD processed YBCO tapes. A current lead unit is composed of eight YBCO tapes, Cu end caps and a pair of stainless steel boards. The YBCO tape is 5 mm in width and around 108 μm in overall thickness. The YBCO superconducting layer with 1.5 μm is formed on oxide buffered layers on Hastelloy substrate tape. The critical current of eight YBCO tapes ranges from 160 to 180 A at 77 K and self-field. The transport current of 750 A at 77 K was stably carried with no voltage generation on the YBCO tapes of the current lead. Rogowski coils and Hall sensors were attached on eight YBCO tapes to evaluate current distribution of the current lead. The current imbalance of 8 A occurred between eight YBCO tapes at transport current of 700 A.
In order to explain the relationship between “pinch” and nail, a sphygmograph was used for measuring blood flow changes in a nail while pinching several weight, and frequency characteristics of sphygmogram were analyzed by continuous wavelet transform(CWT). From the results of CWT, frequency components (1-4Hz) were increased as compared with sphygmogram without weights. This indicates a blood flow fluctuation caused by the stimulation of tactile receptors in the nail bed.
In an effort to fabricate thin film thermoelectric generators, we prepared p-type antimony telluride and n-type bismuth telluride thin films by using a RF magnetron sputtering, after which a thermal annealing was implemented. We investigated the relationship between the annealing temperatures and the properties of both types of the thin films. The structural properties were analyzed by x-ray diffraction patterns and scanning electron microscope. The in-plane electrical properties, which were the electrical conductivity, Seebeck coefficient and power factor, were estimated at room temperature. As a result, the surface morphology of both types of the thin films exhibited nano-sized pores as the annealing temperature increased possibly because of the evaporation of tellurium atoms. This evaporation also induced to increase the defect density of both types of the thin films, and to be degraded their electrical properties. Therefore, we resulted in the higher thermoelectric properties at the annealing temperature of 300°C; antimony telluride: σS2 = 18.8 μW⁄(cm∙K2) and bismuth telluride: σS2 = 20.9 μW⁄(cm∙K2).
Micro air vehicle (MAV) is highly focused by many researchers because the MAV can investigate the condition of disaster site and accident site that is difficult to investigate for human being. Usually, design of the aircraft wing is inspired by birds and flying insects. Resently, dragonfly is a good research target because the dragonfly has high flight performances and high robustness. In order to develop the MAV that is inspired by the dragonfly, it is important to investigate the aerodynamic characteristics of micro structures on the dragonfly’s wing. The cross section of the dragonfly’s wing is corrugated. The effect of the corrugated shape is already investigated and applied to windmills for weak wind. On the other hand, the effect of micro spikes on the dragonfly’s wing is not investigated in spite that the number of the spikes are more than three thusands. So, we focus on the micro spikes on the wing vein of dragonfly. Firstly, we prepared the handmade artificial wings with micro spikes. The fabricated artificial wing had 150 micro spikes whose length wass 600~700 μm. We investigated the aerodynamic characteristics of the micro spikes on these artificial wings. Some merits of micro spikes were observed in spite that the length and the number of spikes were different from those of the natural wing. So, we challenged to fabricate highly realistic artificial wing and investigate the aerodynamic characteristics of the wing. A metal mold with micro holes was fabricated by the electrical discharge machining (EDM) process. Melted chitosan was applied on the mold and spread into the hole of the mold. After the solidification of chitosan, artificial wing with 400 micro spikes was fabricated. These wings had 400 micro spikes whose height is 100 μm.
MgB2 wires have been prepared through diffusion process in pure Mg metal tube. Amorphous B powder mixed with 5 mol% SiC nano-sized powder addition was encased in a Mg tube, and then the tube was inserted into a pure iron tube to form the Fe/Mg/B(powder) composite wires. The composite was initially drawn into around wires of 1.0 ~ 0.8 mm in diameter without intermediate annealing. The composite wires were heat treated at 630℃ for 5 h in Ar gas atmosphere. Some of the specimens were hot isostatic pressed (HIP treated) under 100 MPa during heat treatment. The MgB2 core was synthesized through the diffusion reaction between outside Mg metal tube and inside B powder with SiC addition. The MgB2 core forms denser structure without voids and cracks in comparison with conventional in-situ powder in tube (PIT process) MgB2 wires. The Ic values at 4.2 K for MgB2 wire of 1.0 mm and 0.8 mm in diameter with HIP reach to 145 A and 164 A at 5 T, which correspond to the Jc of 1680 A/mm2 and 2930 A/mm2, respectively. These values are much higher than that of PIT processed MgB2 wire.
MgB2 bulks have been prepared by hot pressing method in order to fabricate high density MgB2 structure. Mixed Mg and B powder were enclosed in stainless steel mold. The bulk samples were treated at 850°C for 3 h under 30-300 MPa in Ar gas atmosphere. The hot pressed sample size is 20 mm in diameter and 5.6~10 mm in thickness. The XRD patterns of the bulks show that MgB2 phase is synthesized and dominant with small amount of MgO in the whole range of 0~300 MPa. The density of the bulks increased with increasing hot pressing pressure, and reached a peak of 2.34 g/cm3 at 200 MPa which corresponded to the relative density of 90 %.
An imaging system for gaseous ethanol transpired from human palm skin, based on an enzymatic reaction, was assembled and validated. This system uses a highly sensitive camera that measures gaseous ethanol concentrations as intensities of chemiluminescence from luminol’s reaction induced by alcohol oxidase (AOD) and a luminol-hydrogen peroxide-horseradish peroxidase (HRP) system. Conversion of gaseous ethanol concentrations and distributions proceed on an enzyme-immobilized mesh substrate with luminol solution in a dark box. In order to visualize ethanol transpired from human palm skin, we improved the chemiluminescence sensitivity of the imaging system with a mixture of a high-purity luminol solution of luminol sodium salt HG solution and an enhancer of eosin Y solution. The detection limit of the ethanol concentration was 4.9 ppm. This highly sensitive imaging allows successful visualization of ethanol transpired from palm skin.