Measurements of local elastic moduli by amplitude and phase acoustic microscope

A new method is suggested for the nondestructive measurement of elastic moduli in a localized area, 100–400 μm in diameter, by the complex V(z) curve using an amplitude and phase acoustic microscope. The inverse Fourier transform of the complex V(z) curve contains the reflectance function of a liquid-specimen interface. Therefore, the longitudinal, transverse and Rayleigh wave velocities for the specimen are simultaneously obtained by the inversion of the complex V(z) curve. The elastic moduli for glass obtained from wave velocities by acoustic microscope agree fairly well with those by other methods. The present method is applied to aluminium alloy, and it is shown that this method is useful in measuring the microscopic characteristics in inhomogeneous materials.     

Evaluation of the treatment performance of a multistage ozone/hydrogen peroxide process by decomposition by-products

The performance of a multistage ozone/hydrogen peroxide (O3/H2O2) process was evaluated with respect to total organic carbon (TOC) removal of waste waters. An aqueous humic acid solution (5.2 mgC l(-1) as TOC) and a sand filtered secondary sewerage effluent (5.6mgC l(-1) as TOC) were used as model waste waters. Appropriate range of hydrogen peroxide (H2O2) dose at each stage depended upon the components of the tested solutions that changed as the process proceeded. Higher hydrogen peroxide dose was required at later stages in which low reactivity compounds with hydroxyl radical (HO*), low molecular fatty acids, were predominant. And, oxalic acid concentration related to H2O2 demand at later stages. This was assumed that the slow decomposition of oxalic acid was rate-determining step for TOC removal after its accumulation. Also, it is important to maintain dissolved ozone at low concentration for efficient TOC removal because rapid ozone consumption is required for the rapid formation of hydroxyl radical (HO*).     

Boiling time effect on CHF enhancement in pool boiling of nanofluids

Using TiO₂–water nanofluids as the test liquid, pool boiling experiments were carried out to investigate the dependence of the nucleate boiling heat transfer, surface wettability and critical heat flux (CHF) on the boiling time in nanofluids. In the experiments performed at sufficiently high nanoparticle concentrations, the boiling heat transfer first degraded, then improved, and finally reached an equilibrium state. It was hence supposed that the present nanofluids had competing effects to deteriorate and enhance the nucleate boiling heat transfer. As for the surface wettability and CHF, the static contact angle asymptotically decreased whilst the CHF asymptotically increased with an increase in the boiling time. The maximum CHF enhancement measured in the present experiments was 91%, and strong correlation was found between the contact angle and the CHF. Although the boiling time needed to achieve the maximum CHF enhancement was less than a minute at high particle concentrations, a longer time of the order of 1 h was necessary at the lowest particle concentration tested in this work. This experimental result indicated that sufficient attention should be paid to the boiling time effect particularly in industrial applications of nanofluids to emergency cooling.     

Compact Reforming Process Using High-Performance and Long-Lived CO Preferential Oxidation over an Activated Ru/Al2O3 Catalyst for PEFC

Compact natural gas reforming process using high-performance and long-lived CO preferential oxidation (PROX) over an activated Ru/Al₂O₃ catalyst has been developed for residential polymer electrolyte fuel cell (PEFC) systems. The long-term durability of the catalyst was demonstrated for more than 40,000 h. After 40,000 h operation, CO was removed from a reformed gas to below 1 ppm on the activated Ru/Al₂O₃ catalyst at [O₂]/[CO] = 1.5. The high activity and selectivity of the catalyst were maintained for more than 40,000 h. Moreover, the start–stop durability for more than 3,000 cycles of the activated Ru/Al₂O₃ catalyst was also demonstrated without N₂ purge.     

Analytical study on energy consumption and damage to cylindrical and I-shaped reinforced concrete shear walls subjected to cyclic loading

An analytical study using the nonlinear finite-element method was conducted for reinforced concrete shear wall tests under cyclic loading to estimate the damage from the aspect of energy consumption. First, the validity of the analytical method was confirmed by studying the load–displacement relationship, the condition of the cracking, and a comparison between the total strain energy of the analysis and the loaded energy of the test. Next, the distribution of the energy consumption was investigated, and the division between rebars and concrete was studied. It was determined that energy consumption is an effective method for estimating damage of shear walls.     

An ultraprecision positioning system using a twist-roller friction drive

For ultraprecision positioning, the use of the twist-roller friction drive is proposed. To improve the positioning accuracy of conventional twist-roller friction drives, the proposed design has two features: (1) the twist angle between the driving shaft and the driven rollers is very small, and (2) the driven rollers are supported by hydrostatic bearings. The twist-roller friction drive is mechanically a kind of lead screw, and the small twist angle makes the lead of the friction drive less than 0.1 mm. The use of hydrostatic bearing is effective for improving the rotational accuracy of the driven rollers and for eliminating the influence of the fluctuation in roller rotation on positioning accuracy. It has been shown by experiments that the resolution of positioning can be less than 10 nm, and the twist-roller friction drive is suitable for an ultraprecision positioning system.     

Flow structure and bubble characteristics of steam–water two-phase flow in a large-diameter pipe

The flow structure and bubble characteristics of steam–water two-phase upward flow were observed in a vertical pipe 155 mm in inner diameter. Experiments were conducted under volumetric flux conditions of J_G<0.25 m s⁻¹ and J_L<0.6 m s⁻¹, and three different inlet boundary conditions to investigate the developing state of the flow. The radial distributions of flow structure, such as void fraction, bubble chord length and gas velocity, were obtained by horizontally traversing optical dual void probes through the pipe. The spectra of bubble chord length and gas velocity were also obtained to study the characteristics of bubbles in detail. Overall, an empirical database of the multi-dimensional flow structure of two-phase flow in a large-diameter pipe was obtained. The void profiles converged to a so-called core-shaped distribution and the flow reached a quasi-developed state within a relatively short height-to-diameter aspect ratio of about H/D=4 compared to a small-diameter pipe flow. The PDF histogram profiles of bubble chord length and gas velocity could be approximated fairly well by a model function using a gamma distribution and log–normal distribution, respectively. Finally, the correlation of Sauter mean bubble diameter was derived as a function of local void fraction, pressure, surface tension and density. With this correlation, cross sectional averaged bubble diameter was predicted with high accuracy compared to the existing constitutive equation mainly being used in best-estimate codes.     

胞外多糖Pullulan处理养猪场污水的研究

对Pullulan处理养猪场污水进行了研究．结果表明,污水的稀释倍数与Pullulan的添加量对处理效果有极显著的影响,当Pullulan在2倍稀释污水中的添加量达到3mg／kg时,污水的BOD、COD、总P、N的去除率达到90％以上,大肠杆菌的去除率达到95％以上,透过率也从8％上升到92％．     

A 5‐MHz AT‐cut quartz crystal oscillating circuit functioning in 350 nA

An oscillating circuit functioning at ultra low power (350 nA) for a 5‐MHz AT‐cut quartz crystal oscillator was investigated. This circuit has a resistance between the power terminal of the CMOS‐IC and the power supply, and another between the earth terminal of the CMOS‐IC and the ground (GND). These resistances discourage an inrush of current, and set a gain (g_m) necessary for oscillating the circuit at minimum. The developed circuit is quite simple, but enables driving at once‐unthinkable, low power (below 1 µA). © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Electrical characterization of phosphorus-doped n-type homoepitaxial diamond layers

Electrical properties of phosphorus (P)-related donors have been investigated for P-doped homoepitaxial diamond layers grown by microwave plasma CVD. Temperature-dependent current–voltage (I–V), capacitance–voltage (C–V) measurements and frequency-dependent C–V measurements have been carried out with lateral dot-and-plane (with ring-shaped gap) Schottky barrier diodes. N-type Schottky junction properties were obtained. The ideality factor and the rectification ratio of the Schottky junction were obtained to be 1.9 and 1.7×10⁵ at ±10 V and 473 K, respectively. Frequency-dependent measurements on these Schottky barrier diodes have shown that the capacitance is reduced at high frequency, most likely due to the inability of deep centers to maintain an equilibrium ionization state under a high-frequency modulation. C–V measurements deduced that the net donor concentration was 6.2×10¹⁷ cm⁻³ and the corresponding built-in potential was 4.0 eV, when the P concentration was 8.3×10¹⁷ cm⁻³. Phosphorus electrical activity was 0.75 in the P-doped diamond layer. The carrier thermal activation energy (the donor level) was evaluated to be 0.6 eV from the relation between the net donor concentration and the carrier concentration.