Hydrogen permeation through a Pd/Ta composite membrane with a HfN intermediate layer

Dense hafnium nitride (HfN) layers were prepared between Pd protection films and a Ta substrate in a composite hydrogen separation membrane to prevent a reaction between the Pd and the substrate at high temperatures. No significant reduction in hydrogen permeation rate was observed for the membrane with 50-nm-thick HfN layers at 873 K through at least 35 h, whereas the specimen without HfN layers rapidly deteriorated within 5 h. Hydrogen permeability of the former specimen was 4 × 10⁻⁹ mol m⁻¹ s⁻¹ Pa^−0.5 at 873 K at steady state. This value was smaller than the initial permeability of Pd-covered Ta before deterioration by an order of magnitude. The measurements of pressure–composition isotherms by using a HfN powder specimen showed that the hydrogen solubility in HfN was sufficiently high and comparable with the solubility in Ta. Therefore, the low permeability observed with the HfN intermediate layers was ascribed to low hydrogen diffusivity in HfN.     

An Approach to Use a Raw Single Crystal Whisker as Intrinsic Josephson Junctions Stack

We have developed a technique to observe the intrinsic Josephson effect in Bi₂Sr₂CaCu₂O_8+δ (Bi-2212) single crystal whiskers. In this technique, a raw Bi-2212 single crystal whisker used as intrinsic Josephson junctions (IJJs) along the c-axis. The technique is simple, quick, and less-cost processing. First, a whisker made to stand on ac-plane and then two electrodes were made in ab-planes on either side. The standing whisker with this configuration worked as IJJs. The standing whisker (1.6 mm×40 μm×3 μm) showed the transition temperature of about 84 K. The critical current was about 15 mA at 8 K (critical current density ～23 A/cm²). We observed voltage gap of about 500 mV in current–voltage (I–V) characteristics. This corresponds to a few hundred of IJJs out of ～2,000 IJJs in the whisker thickness. Observations reflect that the technique can be further improved with the single crystal quality, shape of single crystal whisker, and annealing conditions.     

Dynamic range improvement by narrow-channel effect suppression andsmear reduction technologies in small pixel IT-CCD image sensors

Technologies for narrow-channel effect suppression in photodiodes (PDs) and vertical CCDs (V-CCDs) and for smear reduction in PDs have been developed in order to improve dynamic range in small pixel interline-transfer CCD (IT-CCD) image sensors. The new technologies have been applied to a progressive-scan IT-CCD image sensor with 5 μm square pixels and have (1) increased the charge handling capability of its V-CCDs to 4500 electrons/V; (2) improved its smear value to -95 dB; and (3) increased the saturation charge of its PDs to 2.3×10⁴ electrons     

DC characteristic simulation for floating gate neuron MOS circuits

An original approach to DC characteristic SPICE simulation for floating gate neuron MOS circuits is demonstrated. A novel macromodel which calculates the floating gate potential by combining resistances and dependent voltage and current sources is introduced. Utilising this method, DC characteristics for neuron MOS circuits have been confirmed to be successfully simulated using SPICE     

基于开放式网络的远程照明控制系统

本文介绍了一种基于开放式网络的远程照明控制系统。通过连入局域网或广域网的客户端计算机上的Web浏览器,用户能够方便地对照明设备进行监视、控制、设定和管理。本文将对这种基于开放式网络的远程照明控制系统的结构、功能作详细介绍。     

[NCO]/[OH] and acryl-polyol concentration dependence of the gelation process and the microstructure analysis of polyurethane resin by dynamic light scattering

The gelation process and the microstructure after the gelation of polyurethane resin consisting of acryl-polyol and polyisocyanate was investigated by dynamic light scattering (DLS) as a function of stoichiometric ratio, [NCO]/[OH], and the concentration of acryl-polyol, C_polyol. The following conclusions were obtained. First, the sol-gel transition was explained by the so-called site-bond percolation theory. Here polyol groups act as site-occupants, and isocyanate groups act as chemical cross-linkers. Second, the scattering inhomogeneities increased rather gradually around the gelation point, which are the characteristics of the gelation process not from monomeric but from oligomer units. Third, at the gelation point, the characteristic decay time of the fast mode, τ_fast, decreased, and the fraction of the collective diffusion mode, A, increased with [NCO]/[OH], which are due to introduction of cross-linking and/or increase of the rigidity of the network. Finally, the ensemble average scattering intensities, 〈I〉_E, the static inhomogeneities, 〈I_C〉_E, the time-average dynamic fluctuating component, 〈I_F〉_T and the collective diffusion coefficient, D, showed remarkable dependence not only on C_polyol but also on [NCO]/[OH]. These are due to the competition between the cross-linking and the progress of micro-phase separation.     

Hydrogen production by catalytic near-critical water gasification and steam reforming of glucose

Near-critical water gasification (NCWG) and steam reforming (SR) were investigated for the production of hydrogen from a biomass model compound (glucose) using fixed bed tubular reactor. Ruthenium/carbon and nickel/yttria stabilized zirconia (YSZ) were utilized to enhance the reaction rates of the two processes for NCWG and SR, respectively. NCWG experiments were performed at 200 bar and 360–450 °C, while SR experiments were conducted at 500–800 °C and atmospheric pressure. Although in both cases complete carbon gasification is achieved, gas composition, hydrogen selectivity and overall energy efficiency show strong dependencies on the type of process itself and the associated operating conditions. It is shown that operating the reforming reaction of glucose at high pressures and low temperatures (NCWG) results in a significant amount of methane and trace amounts of carbon monoxide. In contrast, gasification of glucose at atmospheric pressures and high temperatures (SR) leads to a methane-free gas stream that contains few percents of carbon monoxide. Considering energy recovery and neglecting the heat losses, the maximum cold gas efficiency of the NCWG and SR reached 78% and 91%, respectively. The features of the two catalytic reaction processes are discussed in terms of the experiments and process simulations.     

Improvement of high temperature stability of Pd coating on Ta by HfN intermediate layer

Hafnium nitride (HfN) was chosen as a material for non-porous intermediate layer to improve the high temperature stability of Pd–Ta composite membranes for hydrogen separation. A layer of dense HfN (70 nm) was prepared between Ta substrate and thin Pd film (300 nm), and the high temperature stability of Pd coating was examined by hydrogen absorption experiments at 573 K after the heat treatments at 873 and 973 K. The HfN layer showed obvious hydrogen permeability, though the permeation rate in HfN appeared to be smaller than that in Pd and Ta. In addition, the degradation in coating effects of Pd at elevated temperatures was substantially retarded by HfN layer. Such improved stability was ascribed to retardation of open porosity development in Pd films and interdiffusion between Pd and Ta. It was concluded that HfN is a potential candidate material for intermediate layer to improve high temperature stability of Pd-group 5 metal composite hydrogen separation membranes.     

Artificially layered Bi2Sr2Ca n−1Cu n O2n+4 (n≥3) films by sequential sputter deposition

Uniformly layered mixture of the succeeding members in the structure series was found in artificially layered Bi₂Sr₂Ca _n?1Cu _n O_2n+4 films synthesized by a three-target sequential sputter deposition technique. The intergrowth structure was quantitatively evaluated by X-ray analysis technique. An averagedc-axis (half) unit length and a plane spacing d₀～-0.31 nm $\left( { \simeq d_{CaCuO_2 } } \right)$ in the intergrowth structure are considered as a modulation wavelength and an average lattice of superlattice in the analysis. It is shown that the X-ray diffraction patterns observed in our films are in good agreement with that predicted by the superlattice model.     

Distraction detection of lectures in e-learning using machine learning based on human facial features and postural information

Artificial Life and Robotics - While e-learning lectures allow students to learn at their own pace, it is difficult to manage students’ concentration, which prevents them from receiving...