We proposed the anisotropic charged layered XY lattice model for phase transition in high Tc superconducting oxide. It is capable of describing from Kosterlitz-Thouless transition in two dimension to standard second-order phase transition in three dimension. This model is investigated using the mean field plus two loop effective energy approach. We find the tricritical point above Tc that is suggest the possibility of first order phase transition.
In our previous paper, the anisotropic charged layered XY lattice model in high Tc superconducting oxide was introduced and the phase transition of this model was investigated using the mean field plus two loop effective energy without magnetic fluctuation. In this paper, the critical temperature and tricritical point were investigated using the mean field approximation plus anisotropic magnetic fluctual correction. It was found that the critical temperature and tricritical point were inversely propotional to the anisotropic parameter γ of the Josephson-coupling constant.
The paper summarizes the investigation of physico-chemical properties of hydrides of RE3Ni6X2 (RE-rare earth metal, X-Al, Ga, Si) intermetallic compounds. A decrease of hydrogen affinity of intermetallic compounds in the sequence Tb3Ni6Al2-Tb3Ni6AlGa-Tb3Ni6Ga2-Tb3Ni6Si2 was observed. Considering the results of crystal structure analysis, hydride formation studies and neutron diffraction investigation, it was suggested that the phenomenon is caused by the decrease of unit cell size and increase of nonmetallic properties of the p-elements in the same sequence.
The resistivities ρ of the solidified n- and p-type PbTe and plasma activated sintered n-type PbTe were measured as a function of temperature during heating and cooling cycles to progressively higher temperatures until 903K in Ar atmosphere. The hysteresis of the temperature dependence of ρ appeared for all specimens after heated above 703K, which indicates that the change of thermoelectric properties will occur during the operation as a thermoelectric generator. This phenomenon was more remarkable for the sintered specimen than that for the solidified one. However, X-ray analysis did not detect the evidence such as the apperance of the secondary phase or oxidation. Then, it is pointed out that the mechanism of the aging effect for PbTe can not be explained by solely the evaporation of constituents such as Pb, Te and I.
In this work, we study the PSS (polysilastylene) concentration dependence on the thermoelectric properties of SiC/Cu (0.5wt.%) samples, whose figure of merit is about 10 times larger than SiC/B4C 2.0wt.% at room temperature. The thermoelectric properties of SiC/Cu 0.5wt.% density controlled samples depend on the PSS concentration. The figure of merit increases with temperature in experimental temperature range (room temperature-700°C). The figure of merit of the sample with PSS 5.0wt.% is estimated to be 1×10-5K-1 at 700°C.
Single crystals of K-doped p-type PbTe were prepared by Bridgman method. The carrier concentration and Hall mobility were measured from 77 to 300K. The hole concentration was successfully controlled in the range from 8.0×1024 to 4.0×1025m-3 with 1000 to 20000 molppm K at 300K. By calculating κel on the basis of Fermi integration, κph was estimated to be 2.15Wm-1K-1. By using the observed thermoelectric power and electrical conductivity value and the calculated κ value, figure-of-merits Z of PbTe at 300K were 8.0×10-4K-1 for p-type at a hole concentration of 1.0×1025m-3 (2000 molppm K). The μH monotonously decreased with an increase of carrier concentration. Z remains low due to the low values of μH and μH/κph.
In order to develop C14 type alloys having excellent electrochemical properties, alloys with enthalpy-ΔH for hydride formation in the range of 35-37kJ/molH2 were designed by using relations between ΔH, cell volume VC14 of C14 structure and average atomic radius rav. Observed cell volume VC14 was in highly good agreement with designed value. Only small error around 1kJ/molH2 was found between the observed and designed ΔH values. Discharge capacities of these alloy electrodes were in the range of 367-412mAh/g at discharge current density of 17mA/g and 334-353mAh/g at 110mA/g. Good high-rate capability was also observed.
In the foregoing study [J. Adv. Sci. 7, 1 (1995)] supercooling solidifications of NaCl aqueous solution, as an example, were reported. In the present study, the solidification of other two kinds of binary solution such as aqueous solutions of sucrose and ethylne glycol has been investigated. Liquid layer is about 0.2mm thick. Fractal analyses are made for dendrite-patterns obtained for various concentrations of these solution. Dendrite grown from these solutions are found to be fractal over two orders of dimensions, and their fractal dimensions D are determined by the use of the box-counting method. The fractal dimension D changes their values as they grow. They vary according as a kind of saturation curve. D approaches a constant D∞. Values of D∞ for these two solutions are alomost the same: D∞=1.919 for ethylene glycol and 1.917 for sucrose aqueous solutions in case of the concentration of 8.0wt%. In the case of thick layer of 0.08mm, dendritic ices grow which forms multilayer dendrites. Therefore, dendrites have a slightly larger D value for those grown in the thick liquid layer than in a thin layer.
Effects of car coating treatment on resistance to environmental corrosion and on cracks formed by collision were studied by microscopical, spectroscopical and mechanical methods. Treated and untreated samples aged for three years were used to examine the surface brightness, the water repellency and the crack appearance. From the results, it was verified that this excellent coating material mainly consists of silicone polymer and the treated car-body surface has resistance to corrosion and superelasticity.
Radical-assisted metal organic chemical vapor deposition of ZnSe thin films was performed using nitrogen trifluoride (NF3) as the co-reactant and source of nitrogen atoms. The growth rate showed a gradual increase with an increase of NF3 flux. The photoluminescence (PL) spectra of all the films showed the intense donor-acceptor pair (DAP) emission and the weak excitonic emission bound to neutral nitrogen atom pair (I1N-N). The results gave a direct evidence of N-doping in ZnSe thin films by radical-assisted MOCVD. The I1N-N emission intensity was dependent upon NF3 flux, indicating that non-radiative recombination centers were introduced at high NF3 flux. In case of the growth at high NF3 flux, the additional PL emission was observed at 2.4-2.5eV, the intensity of which decreased after the heat-treatment. The result suggests that the heat-treatment might be effective for quality enhancement through the decrease of undesirable defects and nonradiative recombination centers.
The irradiation temperature effect on polytetrafluoroethylene (PTFE) was investigated by tensile test and thermal analysis. The behavior of mechanical properties and changes of crystallinity on irradiation indicated the network formation in PTFE molecules by radiation induced crosslinking under oxygen-free atmosphere in the molten state around 613K. The radiation resistance of PTFE was much improved by crosslinking, that is, the irradiation dose at a half value of ultimate elongation was about 1MGy for 500kGy-crosslinked PTFE, while the dose for non-crosslinked PTFE was only 3.5kGy, so it is expected that the crosslinked PTFE can be applied for the nuclear facilities with relatively high radiation environment. Also, the crosslinked PTFE had light transparency due to the decrease of crystallites, and held the electrical insulation and heat resistance. The abrasion factor in frictional test was greatly improved by crosslinking.
Influence of tourmaline on sour taste is studied for hot coffee. The tourmaline pelletized samples soak in the hot coffee for long time. The hydrogen ion concentration of treated coffee by tourmaline is smaller than that of untreated one. Therefore, tourmaline treatment prevents to become sour taste.
Sterilization process by sheet electron beam irradiation is investigated on a medical glass. Number of colony of E. coli on the surface of the medical glass was reduced by SEBI. SEBI is effective for the sterilization of medical glass.
In our previous study [J. Adv. Sci. 8, 57 (1996)], results of the indoor performance test of a tilted-tray, wick type solar still with a condensing chamber have been reported. In the present study, this solar still has been improved so as to be a circulation type, where the moist air can circulate between the evaporator and the condenser. Performance tests were done and their results have been compared with those of the non-circulation type. The distillation efficiency was considerably improved, especially at lower solar insolation, and its performance characteristics became more stable to irradiation changes.
The present study has been initiated to observe the effect of randomization on a passivity-maintaining current density (Ip) in anodic polarization curve in a liquid-quenched Fe-4 at% Cr-10 at% Si-15 at% B alloy glass. The randomization decreases both a passivity current density and passivity-maintaining current density, thus improving the corrosion resistance of the glassy alloy.
We synthesized Polyallylamine (PAA) quaternary salt gel and examined the behavior of the swelling and the shrinkage due to the change of solvent composition, the salt concentration, pH and the temperature. It was found that PAA quaternary salt gel showed the behavior described below. A definitive discontinuous change was observed for the variation of the solvent compsition and the temperature, but for the variation of the salt concentration and pH, the change was ambiguously discontinuous. The behavior of this swelling and the shrinkage which PAA quarternary salt gel showed will offer possible applications of the macromolecule material to the sensor and the actuator.
Far-infrared(F-IR) reflection spectra were measured for Bi2(SeTe)3 single crystal, and analyzed using dispersion analysis. Dispersion parameters such as damping factor, plasma frequency and ε ∞ were derived by fitting caluculated spectrum to experimental one. It was estimated that and HgBr2 doping rate dependence of a mobility is mainly contributed by ionized impurity scattering.
Ti-Ni alloy of an approximately equiatomic concentration has been attraction by its unique nature of shape memory effect (SME). SME is associated with reversible thermoelastic martensitic transformation. Therefore, shape memory alloy (SMA) has the energy convertible function from thermal into mechanical energy.
Shape memory alloy is influenced by liquid-quenching condition and composition. The twin-type piston anvil apparatus is easy to control the quenching condition and the sample composition. We investigated characteristics of Cu-Al-Ni alloy prepared by the twin-type piston anvil apparatus.
High Tc superconductors have many pinning center. While the pinning center traps magnetic flux strongly, high Tc superconductor may be used for a permanent magnet. We have studied the properties of oxide high Tc superconductors prepared by sintering and melt-growth processes as a new type of permanent magnets.
An artificial synaptic model was constructed by assembling an actuator and a sensor. The actuator was consist of a square pipe cell with two carbon electrodes. The actuator was filled with acrylic acid gel microparticles swelled with glucose solution which were shrunken under an electric field. The sensor was a glucose sensor which was constructed by combining an oxygen electrode with an immobilized glucose oxidase membrane. The out put current of glucose sensor in the synaptic model was observed under the application of DC field to the actuator. The amount of glucose released from the actuator increased time-dependently with increasing voltage above 5V, however, little release was observed below 5V.
Microbiosensor for the determination of glutamate was constructed by combining hydrogen peroxide electrode with immobilized glutamate oxidase. The biosensor was applied for the measurement of glutamate (0.1-1mM), glutamine (0.1-0.6mM) and γ-aminobutylate (0.25-0.1mM).
In this study, using brain wave (EEG) measurement and psychological tasks, ergonomic aspect of the Sitzball was investigated. Peak frequency of the alpha components in the Sitzball sitting condition were higher than that in control condition. Alertness and behavioral responses were stably maintained in the Sitzball sitting condition compared with control condition.
In order to investigate early visual perception, an experiment of direction discrimination task was carried out using a computer controlled tachistoscope. Effective interval of stimulus onset and masking presentation was not different from that under partial masking condition. Identification performed in the central view is influenced by all the stimulus including peripheral view. It suggests the unknown image processing argorithm.
To investigate detailed characteristics of human sleep cycle, all night polysomnograms were recorded in healthy and sleep deprived subjects. R-R interval series extracted from the ECG data were analysed using FFT. Estimated low and high frequency components of R-R power spectra were evaluated. Specific change of autonomic function during sleep was observed in sleep deprived subjects.
To investigate characteristics of circadian rhythm, all day holterrecording were analyzed. Power spectra were estimated from R-R interval series via FFT. High and low frequency components of R-R fluctuation were observed. We discussed the circadian profiles of R-R spectra and its sleep-related changes.
To analyse visual cognitive process, a location estimation task of moving target in hidden area with two different background stimuli were carried out. Result shows that accuracy of estimation under the depth sensible background was greater than that of random background. Identification performed in the central view is infiuenced by all the stimulus including peripheral view. It suggests the unknown image processing algorithm.
To investigate visual perception mechanisms, 3-D stereogram perception time was measured using computer controlled tachistoscope. In this experiment, minimum required time to discriminate the 3-D images was relatevely short (<20ms). Cognitive and neurological aspects of early perception for stereographical imeges were discussed.
In this study, flavonoid glycosides contained in horsetails have been isolated by column chromatography. The produced flavonoid was confirmed by TLC, HPLC, UV/VIS spectroscopic and 1H-NMR spectra. The structure of flavonoid as 5, 7, 3′, 4′-tetrahydroxyflavon-3-O-β-D-glucoside (Isoquercitrin) was proved on the basis of chemical evidence.
In this paper, precurser of carthamin was confirmed from pistil and petal, which weregathered from the fresh flower of safflower. The extracted precarthamin from petal was isolated by cellulose and gel calumn chromatography. The isolated precarthamin was confirmed by TLC, HPLC and UV/VISspectroscopic.
A nickel-metal hydride battery for a solar car was manufactured. This battery has a size of W11×D7×H9cm, a weight of 1.5kg and an energy capacity of 9.6V-7Ah. The energy density of this battery is higher by a factor of 1.5 than those of lead-acid batteries for conventional vehicles.
Optical surface mount technology (O-SMT) is proposed on the analogy of surface mount technology widely employed in current, in order to meet growing serious problem in manufacturing processe for partical optoelectronic system.
We fabricated of a feedback loop phase conjugate mirror (RING-SPPCM) using photorefractive Rh:BaTiO3 crystal, and measured the reflectivity of this mirror with nanosecond pulses at 1064nm. The reflectivity of about 33% was obtained. A demonstration of the correction of phase distortions was made with this arrangement.
The Rotating Compensator Ellipsometer (RCE) which are measured comparatively fast and higher accuracy can be determined all Stokes-parameters. But alignment of the RCE equipped with many optical components is tedious work. Use of the RCE and its attendant problems are discussed.
The purpose of this research is to obtain an information experimentally for the basic parameters relating with a weak localization of light. It is examined the effect of absorption dye on the line shape of the coherennt back-scattering peak from a disordered medium where latex beads are dispersed in water. The optical path length through the scattering medium was estimated by using an absorption dye with differennt optical densities.
The ion temperature in the magnetized sheet plasma were measured by two kinds of Faraday cup which is located the direction of the axial and parallel to the sheet plasma. As a result, the ion temperature (-10eV) is maxmaum value to the half width of the density of the sheet plasma.
In order to investigate the effect of an oblique the target on plasma paramerters, we measured the electron density, electron temperature and the loss of charged particles at the end-target in a magnetized sheet plasma. The profiles of the electron density, the electron temperature and loss of charged particles are unsymmetric at the upper and lower sides of the target.
We produced OH radicals by means of injecting O2 and H2 gasses against the Ar-sheet plasma vertically. Density of OH radicals is measured by LIF (laser induced fluorescence) spectroscopy. As a result, the density of OH radicals was obtained about 3.6×109cm-3.
In order to investigated the Oxygen radicals in the discharge tube, the 3p3P state of O is populated by two-photon absorption at 226nm is detected by the Laser-Induced Fluorescence (LIF) spectroscopy. The O fluorescence emission (845nm) increases with increasing the discharge current.
The negative ion in the edge region of the sheet plasma were measured by the electrostatic probe technique, that is, the Druyvesteyn method for the measurrement of electron energy distribution, The density and the temperature of the negative ions are 1.5×1011cm-3 and 2eV, respectively.
The isotope separation in a magnetized sheet plasma has been studied by using the ion cyclotron resonance (ICR) heating. In order to remove a potential well of the sheet plasma, a double slit type orifice was provided between the discharge region and the experimental region. The resonant helium ions with a shallow potential well was clearly observed. It was found that the resonant frequencies for 4He+ shift to the higher fregency than the cyclotron freqency of those ions.
The fundamental study on the isotope separation in the sheet plasma by using ion cycloton resonance has been carried out. The newly designed orifice is used to reduce the electron density in sheet plasma, the results, however, indicate only the separation between the different species.
The transverse deflection measurement between a head and a disk varying a lensless head height against Bernoulli base plate under various measurement conditions of dynamic characteristics for the floppy disk are performed. In this experment in order to find a suitable value for both the disk rotation speed and the head hight. both optica method and capacitive method were applied to measure the gap.
Preparation of single-phase CdS thin-films suitable as a window-layer for CuInSe2 has been studied by means of a chemical deposition method. CdS thin-films, although contain trace of γ-Cd(OH)2, were grown from solutions consisting of 0.5M-CdSO4, 1.4M-NH4OH, 1M-SC(NH2)2 and 1.48M-Triethanolamine, holding at 80°C. The films showed a direct band gap of 2.38eV and had a high transparency at room temperature.
Deformation resistance of Czochralski-grown (100) silicon single crystals is investigated. Denuded zone (DZ), which is prepared by H2 or Ar annealing, decreases deformation resistance of silicon wafer. It also decreases interstitial oxygen concentration of silicon wafer.
We measured Pressure-Composition-Temperature relation for the Pd-H system using 150μm, 1μm particle size of Pd powder samples and a Pd powder with 150μm after alkaline pretreatment, respectively. These different samples have marked influence on equilibrium reaction of the Pd-H system.
The characteristics of the hydrogen absorption by Sm2Fe17 were investigated with respect to equilibrium and kinetics properties. The measurd pressure-composition-isotherms showed no pressure plateau, indicating the Sm2Fe17 forms only the hydrogen solid solution phase at the temperature below 773K. In addition, the isotherms suggest that Sm2Fe17 absorbs hydrogen in hydrogen concentrations up to H/Sm2Fe17=5.0. The reaction kinetics of hydrogen absorption revealed that the initial reaction rate was controlled by the dissociation of H2 molecules on the surface.
Misting vision is serious problem of end scope sapphire lens. It often induces excess fatigue and wrong diagnosis. The clear vision is induced by the wettability enhancement. The enhancement can be achieved by sheet electron beam irradiation.