Preparation and Evaluation of High-Purity La2O3

A separation procedure based on extraction chromatography using the di(2-ethylhexyl) phosphoric acid (D2EHPA) impregnated resin, anion exchange with DIAION SA 10 resin, and oxalate precipitation has been developed for the preparation of high-purity La₂O₃ in hydrochloric acid media at a high La concentration. The metallic impurities Ce, Pr, Nd, Sm, K, Mg, Ca, Zn, Cu, Co, Mn, Pb, Al, In, and Fe, but not Bi, were removed efficiently from La by extraction chromatography using a D2EHPA impregnated resin. The Bi was separated from the La by anion exchange (DIAION SA 10) separation. Thus, a high-purity LaCl₃ solution was obtained by anion exchange separation and extraction chromatography. La₂O₃ was prepared from the purified LaCl₃ solution by oxalate precipitation. Glow discharge mass spectrometry was applied for purity evaluation of the prepared La₂O₃. The purity of the prepared La₂O₃ was more than 99.9998 pct total rare earth oxide.     

Removal of boron from coal fly ash by washing with HCl solution

Boron as an environmentally regulated substance is well known to condense in the coal fly ash generated from coal combustion plants. Since boron in the coal fly ash tends to elute into the soil easily, a technology for its stabilization or removal from fly ash is required. An acid washing process is proposed and studied as one of the candidate technologies for the removal of boron from coal fly ash. A laboratory-scale investigation is conducted on the dissolution behavior of boron in the coal fly ash in a diluted HCl solution. The dissolution of boron and alkaline species is considerably fast and exhibits a behavior different from that of aluminum and silicon, which are major components of the ash. From the kinetic model, it is expected that boron in the ash may mainly be in the form of alkaline or alkaline earth borates that are deposited on the surface of relatively large ash particles of alumino-silicate or may be precipitated as fine particles during coal combustion. This acid washing process is extended to a bench-scale plant and boron is successfully removed from the coal fly ash until its content is less than the regulation limit.     

A node configuration algorithm with bandwidth bottleneck resolution for WDM ring networks

The wavelength-division multiplexing (WDM) technology has been extensively studied and actually deployed as a key technology to solve global information explosions by multiplexing plural signal paths using different wavelengths into one optical fiber. Among WDM-based network architectures, this article focuses on a double-ring one for a next-generation metropolitan area network (MAN), where each node is normally equipped with two pairs of fast-tunable transmitters and wavelength-fixed receivers (TT-FR) as interface to two fibers. To enhance the network performance, additional transmitters/receivers at nodes and receiver wavelengths should be assigned optimally, so that the bandwidth bottleneck can be resolved both on nodes and fiber links. This article formulates this node configuration problem with bandwidth bottleneck resolution as a combinatorial optimization problem, and proves the NP-completeness of its decision version. Then, it presents the two-phase heuristic algorithm composed of a greedy method and a variable depth search (VDS) method. Our algorithm is evaluated through extensive network simulations, where the results support the effectiveness of this joint assignment approach.

Ion beam deposition of α-Ta films by nitrogen addition and improvement of diffusion barrier property

Ta thin films were deposited on Si (100) substrates by an ion beam deposition method at various substrate bias voltages under Ar + N₂ atmosphere with different pressure ratios of Ar and N₂. The effects of nitrogen pressure in the plasma gas and the substrate bias voltage on the surface morphology, crystalline microstructure, electrical resistivity and diffusion barrier property were investigated. It was found that the fraction of a metastable β-phase in the Ta film deposited at the substrate bias voltage of − 50 V films decreased by adding nitrogen gas, while the α-Ta phase became dominant. As a result, the Ta films deposited at the substrate bias voltage of − 50 V under Ar (9 Pa) + N₂ (3 Pa) atmosphere showed a dominant α-phase with good surface morphology, low resistivity, and superior thermal stability as a diffusion barrier.     

Quantitative intensity measurement of equal thickness fringes in Si and MgO crystal images with an energy-filtering transmission electron microscope using an imaging plate

Quantitative measurement of intensity profiles of equal thickness fringes has been carried out in Si and MgO crystal images with an energy-filtering transmission electron microscope using an imaging plate. The crystals have a 90 degrees wedge-shape with [110] surfaces for Si and with [100] surfaces for MgO, and are observed under the exact axial incidence of a 200 keV electron beam along the [100] axis for Si and along the [110] axis for MgO. The intensities are measured in bright field and 022 and 040 dark field images for Si, and in bright field and 111, 002, 220, 113, 222, and 004 dark field images for MgO, with and without an energy slit having +/- 5 eV energy width for incident electrons. The intensity profiles obtained from the images are presented as standard experimental data for calculation of electron diffraction intensities. A few simulation programs for high-resolution transmission electron microscopy are checked by comparing the calculated diffraction intensities with the experimental data. The complex potential suitable for matching the data is discussed.     

Diagnostic value of tomography in unilateral vocal cord paralysis

Tomographic studies were made on 56 patients with unilateral paralysis of the vocal cord. The findings were examined in relation to etiology, course, and laryngoscopic findings. In 74.1 percent of the cases, marked enlargement of the ventricle was noticed on the side of the paralysis, especially during inhalation. The paralyzed vocal cord was higher than the intact cord during phonation in 46.4 percent of the cases. The rest of the cases (53.6 percent) demonstrated no level difference between the vocal cords. The position of the paralyzed vocal cord, unilateral involvement of the cricothyroid muscle and other neck muscles were suggested as possible contributors to the findings.     

Studies on radiation-induced current in polymeric insulating materials and their fine structure

Radiation-induced current (conductivity) (RIC) has been investigated in polymeric materials degraded under combined conditions of heat and radiation. Crystalline materials such as polyethylene, and non-crystalline materials such as ethylene—propylene rubber used for the insulation of wire and cable have been studied. Fine structure changes have been investigated by studying X-ray crystallinity, melting behaviour, the glass transition temperature, and tensile properties. RIC and its decay are affected more by the degree of crystallinity than its perfection. In crystalline samples irradiation after heating causes less degradation than heating after irradiation. Numbers of short-lived carriers increase with a decrease in the degree of crystallinity, indicating the trapping of short-lived carriers in the non-crystalline region and long-lived carriers in the crystalline region.     

Low‐noise blue light generation of intracavity frequency‐doubled LD‐pumped Cr:LiSAF laser by single‐mode method

We have demonstrated the production of low‐noise blue SHG (Second Harmonic Generation) light by single‐mode oscillation in an intracavity frequency‐doubled laser diode (LD)‐pumped Cr‐doped LiSrAlF₆ (Cr:LiSAF) solid‐state laser. The SHG crystal was LiB₃O₅ (LBO). A birefringent filter and an etalon plate were used for the single‐mode Cr:LiSAF laser oscillation wave. A maximum blue SHG output power of 32 mW was obtained by using a 1‐mm‐thick birefringent filter and an etalon plate 200 μm thick with 20% reflectivity. The oscillation wavelength varied by 0.24 pm/hPa in response to changes in atmospheric pressure. A long‐term stability of 300 hours was obtained with the cavity enclosed in a barostat. © 2001 Scripta Technica, Electr Eng Jpn, 138(1): 49–55, 2002     

Oxidation Mechanism of Cu2O to CuO at 600–1050°C

To clarify the oxidation mechanism of Cu₂O to CuO, Cu₂O oxidation was studied at 600–1050 °C under 1atm O ₂. The Cu₂O specimens were prepared through completely oxidizing 99.99999 and 99.5 pure copper at 1000°C in an Ar + 1 O ₂ atmosphere. The oxidation kinetics of Cu₂O specimens prepared from both purity levels followed the logarithmic law, not the parabolic law or the cubic law as reported in the literature. The activation energy for Cu₂O oxidation is relatively high in the lower-temperature range, but becomes very small or even negative at higher temperatures. The logarithmic oxidation rate law can be explained by Davies et al.s model related to grain-boundary diffusion in the oxide layers. The very small or negative activation energies in the higher-temperature range can be attributed to the very small thermodynamic driving force and the fast lateral growth of CuO grains related to a sintering effect. The influence of small amount of impurities is also discussed.