Reversible CO2 capture by ZnO slurry leading to formation of fine ZnO particles

ZnO powders were synthesized by heating precursors, prepared by the addition of ethylene diamine tetraacetate to an aqueous solution of zinc acetate, at 500?°C in air. A ZnO slurry was prepared by adding distilled water to the synthesized ZnO powder. X-ray diffraction studies confirmed that the ZnO slurry adsorbed CO₂ at 25?°C under a CO₂ gas flow to produce Zn₅(CO₃)₂(OH)₆. The CO₂ adsorption ratio of the ZnO slurry was influenced by the amount of added water. When the weight ratio of water/ZnO was 1, the ZnO slurry had the largest CO₂ adsorption ratio. Scanning electron microscopy and thermal gravimetry showed that the plate-like Zn₅(CO₃)₂(OH)₆ particles thermally decomposed at 300?°C in air leading to a single-phase ZnO powder consisting of nanoparticles with approximately 20?nm in diameter. The specific surface area of the reformed ZnO powder increased to approximately 82?m²/g through the thermal decomposition of Zn₅(CO₃)₂(OH)₆. The ZnO slurry was capable of adsorbing CO₂ under a CO₂ flow at 25?°C and desorbing CO₂ under an air flow at 300?°C. The CO₂ adsorption ratio of the ZnO slurry reached 80%–90% at 25?°C even after the fifth CO₂ adsorption and desorption cycle.     

Ductile fracture behavior of circumferentially cracked type 304 stainless steel piping under bending load

A ductile pipe fracture test program has been conducted in Japan Atomic Energy Research Institute (JAERI) to investigate the ductile fracture behavior of circumferentially cracked pipes and to demonstrate the validity of the leak before break concept in LWR pipings.In the paper are described the scope of the pipe test program and current test results for 6-inch diameter type 304 stainless steel pipes. Test pipes with a through-wall or a part-through crack in the circumferential direction were bent under low or high compliance condition, and stable or unstable pipe fracture behavior was investigated. J based tearing instability criterion and the net section collapse criterion are compared with the pipe test results, and the validity of these fracture criteria is discussed. Furthermore, geometries of acceptable flaws in pipes are evaluated considering the leak before break condition.     

Optimization of 3-D nonlinear magnetic circuit by using the magnetization integral equation method

To design optimal electrical machines, it is necessary to develop an optimal design method for determining the shapes, sizes, positions of the cores, permanent magnets and windings which produce such specified values as flux distributions and torques. In this paper, a design method for determining the optimal sizes of cores taking into account the nonlinearity of the core has been developed by using the nonlinear programming method and the magnetization integral equation method. The pole shape of an electromagnet which produces the uniform flux distribution is determined by using the design method for determining the optimal sizes of cores. The effectiveness of the method is shown by designing the pole piece of the permanent magnet-type MRI device.     

A future satellite communications system using millimetre-wave bands and an on-board processor

This paper proposes the system concept of a personal satellite communications system that will be available in the first decade of the 21st century. Technologies of millimetre-wave bands and an onboard processor with baseband switching promise to meet the requirements of a personal communications system: portability, low-cost, and large capacity. Based on the prospects of these technologies, the most likely parameters for the future personal satellite communications system and the configuration of a suitable on-board processor are proposed. A trial model of such an on-board processor has been made. In this paper, details of the trial model on-board processor and its future developments are described.     

Hydrodynamics of longitudinally discontinuous,vertically double layered and partially covered rigid vegetation patches in open channel flow

The aim of this paper is to numerically investigate how the flow structures are affected through a longitudinally discontinuous and vertically two‐layered vegetation occupying half width of the channel, with steady flow rate and subcritical conditions. A three‐dimensional (3‐D) Reynolds stress turbulence model (RSM), incorporated by Computational Fluid Dynamics (CFD) code FLUENT, was first validated with the experimental data, and then used for simulation purpose. The results showed that the flow stream‐wise velocities within the gap regions are visibly slower than that in the vegetation patch regions. Along the cross section, the velocity in the vegetation region (VR) reduced significantly due to resistance offered by the vegetation, which affected the channel conveyance; as compared to the free (non‐vegetated) region. The flow instability in the lateral direction was triggered by the flow shear due to the presence of partly distributed vegetation, resulting in the formation of coherent vortices and exchange of momentum at the interface. The discharge percentage passing through the free region (FR) was found to be 144–525% larger than that passing through the VR. The flow resistance increased significantly with higher vegetation density, whereas it decreased when both the vegetation layers were submerged. Moreover, the flow characteristics profiles in large gaps were more stable than in small gaps. The turbulent kinetic energy (TKE) and turbulence intensity also increased significantly through the patch regions compared to that of the gap regions. The results indicated that the flow structures and the flow resistance are strongly influenced by partial and discontinuous vegetation.     

Preparation of semiconducting carbon fibre by pyrolysis of polyacrylonitrile precursor

Semiconducting carbon fibres were prepared from polyacrylonitrile precursor by pyrolysis in an inert atmosphere in temperature range 550–800 °C. The obtained fibres have an electrical resistivity between 10⁴ and 10^–2 cm^–1 and showed negative temperature coefficients. Electrical resistivity was mainly governed by the pyrolysis temperature and both electrical resistivity, , and thermistor constant,B, decreased with increasing pyrolysis temperature and duration. A linear relation between log and thermistor constantB was observed. Chemical analysis and infrared spectra indicated that the concentration of nitrogen and hydrogen decreased and basal plane structure developed accompanying an increase in carbon content as the pyrolysis temperature increased.     

Modeling and emergence of flapping flight of butterfly based on experimental measurements

The objective of this paper is to clarify the principle of stabilization in flapping-of-wing flight of a butterfly, which is a rhythmic and cyclic motion. For this purpose, a dynamics model of a butterfly is derived by Lagrange’s method, where the butterfly is considered as a rigid multi-body system. For the aerodynamic forces, a panel method is applied. Validity of the mathematical models is shown by an agreement of the numerical result with the measured data. Then, periodic orbits of flapping-of-wing flights are searched in order to fly the butterfly models. Almost periodic orbits are obtained, but the model in the searched flapping-of-wing flight is unstable. This research, then, studies how the wake-induced flow and the flexibly torsional wing’s effect on the flight stability. Numerical simulations demonstrate that both the wake-induced flow and the flexible torsion reduces the flight instability. Because the obtained periodic flapping-of-wing flight is unstable, a feedback control system is designed, and a stable flight is realized.     

Depletion of monolayer liquid lubricant films induced by high-frequency pulsed-laser heating in thermally assisted magnetic recording

In this study, lubricant depletion due to high-frequency pulsed-laser heating was investigated for lubricant films with thicknesses of both more than and less than one monolayer. A conventional lubricant, Zdol2000, was used. It was found that the critical temperature at which the lubricant begins to deplete owing to laser heating was strongly dependent on the lubricant film thickness. In the case in which the thickness of the lubricant film was less than one monolayer, this temperature was approximately 170?°C higher than it was when the thickness was more than one monolayer. To analyze the lubricant depletion mechanism, we examined the tested lubricant film using temperature programmed desorption (TPD) spectroscopy. It was found that the lubricant depletion characteristics due to laser heating could be explained using the experimental TPD results for the tested lubricant film, and that the depletion mechanism involves the desorption or decomposition of the lubricant molecules, which interact with the diamond-like carbon thin films when the lubricant film thickness is less than one monolayer. Further, the results of TPD and of a thermogravimetric analysis (TGA) of the lubricant were compared. The thermal robustness of the ultra-thin liquid lubricant films was found to be greater than that of the bulk lubricant materials.     

Highly Efficient 68-W Green-Beam Generation by Use of an Intracavity Frequency-Doubled Diode Side-Pumped Q-Switched Nd:YAG Rod Laser

An intracavity frequency-doubled diode side-pumped Nd:YAG laser was developed by use of an advanced cavity configuration and a diffusive close-coupled side-pumping design. A maximum green power of 68 W was generated at a 20-kHz repetition rate with 18.4% optical-to-optical conversion efficiency and 7.1% electrical-to-optical conversion efficiency.