Effect of Antimony Addition on Electrical and Optical Properties of Tin Oxide Film

Antimony-doped tin oxide films were prepared on Corning glass substrate by chemical vapor deposition from a gas mixture of SnCl₄–SbCl₅–H₂O. The electrical conductivity and optical transmission of tin oxide films were studied with antimony doping. The film conductivity increased largely without losing optical transparency with a small addition of antimony. The increase of the conductivity was attributed mainly to more electrons donated by pentavalent Sb ions in the SnO₂ lattice. Large additions of antimony, however, diminished the conductivity, optical transparency, and crystallinity of the film. The diminution was found to be caused by fine Sb₂O₅ phases codeposited with SnO₂.     

Preparation, Microstructure, and Mechanical Properties of Silicon Carbide–Dysprosia Composites

Composites of silicon carbide (SiC) with up to 30 vol% of dysprosia (Dy₂O₃) were fabricated by hot pressing and hot isostatic pressing. The effects of Dy₂O₃ dispersions on the microstructure and on selected mechanical properties of the composites were investigated. When 10-15 vol% of Dy₂O₃ was dispersed in the SiC matrix, the fracture toughness increased by ∼40%, whereas the flexural strength was comparable to that of unreinforced SiC. The increased fracture toughness was due to crack deflection, in conjunction with crack-interface grain bridging, and was not related to a phase transformation of Dy₂O₃ in the matrix.     

Price-based congestion control and local channel-link assignment for multi-radio wireless mesh networks

In multi-radio multi-channel wireless mesh networks, engineering the network capacity requires a complex cross-layer design. In this paper, in order to make the complex problem implementable in a distributed manner, we make a decoupling approach that breaks down the entire design space into routing and initial channel assignment, and distributed congestion control and local channel reassignment. We propose a unified priced-based framework for distributed congestion control and localized channel-link assignment algorithms. We demonstrate the convergence of the proposed algorithms with respect to different fairness objectives (i.e., proportional fairness and max–min fairness) via simulation on both grid and random topologies. The proposed algorithms achieve faster convergence with less overhead in the control and forwarding plane than previous multi-path based algorithms.     

Automatic learners with feedback queries

Automatic classes are classes of languages for which a finite automaton can decide whether a given element is in a set given by its index. The present work studies the learnability of automatic families by automatic learners which, in each round, output a hypothesis and update a long-term memory, depending on the input datum, via an automatic function. Many variants of automatic learners are investigated: where the long-term memory is restricted to be the current hypothesis whenever this exists, cannot be of length larger than the length of the longest datum seen, or has to consist of a constant number of examples seen so far. Learnability is also studied with respect to queries which reveal information about past data or past computation history; the number of queries per round is bounded by a constant.     

An X-ray photoelectron spectroscopic study of electrocatalytic activity of platinum group metals for chlorine evolution

A correlation of the catalytic activity for anodic chlorine evolution of platinum group metals to the nature of the surface film formed during chlorine evolution in a sodium chloride solution was studied by X-ray photoelectron spectroscopy. The change in the surface film with increasing potential was found on platinum, including an increase in the cationic valence. This seemed responsible for the decrease in the activity for chlorine evolution on platinum in the high potential region. Increasing potential did not result in the appreciable increase in the cationic valence in the surface film on the other platinum group metals. Replacement of hydroxyl ions in the surface film by chloride ions became easier in the order of rhodium, iridium and palladium, and the activity for anodic chlorine evolution increased in this order due possibly to an increase in the amount of chloride ions in the film which seemed to be one of the reactants in the rate determining electrochemical desorption of adsorbed chlorine atom. Chlorine molecules adsorbed on the surface film were also found. It was assumed that the activity for anodic chlorine evolution might be low when the metal surface was covered by a large amount of molecular chlorine which was the reaction product.     

Performance evaluation of electrodewatering system for sewage sludges

A laboratory-scale electrodewatering system, incorporating an electric field as an additional driving force to conventional pressure dewatering, has been developed to decrease the water content of sludges generated in wastewater treatment. Consisting of a piston-type filter press, a power supply and a data acquisition system, the electrodewatering system’s performance was evaluated as a function of applied pressure, applied voltage, sludge type and filtration time. Experiments were carried out using sewage sludges with the electric field up to 120 V/cm and pressure ranging from 98.1 to 392.4 kPa. Electrodewatering involving a combination of electric field and pressure enhances both the dewatering rate and final dewatered volume. The final water content of sewage sludges in the electrodewatering system can be reduced to 62 wt%, as compared to 78 wt% achieved with the pressure filtration alone. The electrodewatering system shows the potential to be an effective method for reducing the water content in sludges.     

Dynamic mechanical properties of three different combinations taken from styrene-co-itaconate, styrene-co-methacrylate, and styrene-co-sulfonate ionomers

Dynamic mechanical properties of three different styrene-based ionomer blends containing ca. 5 mol% of ionic repeat units were investigated; the three ionic units were itaconate (ITANa), methacrylate (MANa), and styrenesulfonate (SNa). For SNa-MANa ionomers, it was observed that this ionomer system showed only two loss tangent peaks, implying that this ionomer system resembles a typical miscible system. When the ion content increased, however, the ionomer blend showed two cluster loss tangent peaks, indicating the presence of phase-separated cluster regions. This suggests that, with increasing ion content, the role of ionic units becomes more important than that of host non-ionic units to determine ionomer properties. In the case of ITANa-MANa and ITANa-SNa ionomers, however, it was suggested that the multiplets of the MANa and SNa ionomers might be disrupted upon the addition of the ITANa ionomers. In addition, the SEM images showed that the fracture surfaces of ionomers changed upon blending.     

Measurement and modeling solubility of bioactive coumarin and its derivatives in supercritical carbon dioxide

To design a supercritical fluid extraction process for the separation of bioactive substances from natural products, a quantitative knowledge of phase equilibria between target biosolutes and solvent is necessary. How-ever, mostly no such information is available in literature to date. Thus in the present study, illustratively the solubility of bioactive coumarin and its various derivatives (i.e., hydroxy-, methyl-, and methoxy-derivatives) in supercritical CO₂ were measured at 308.15–328.15 K and 10–30 MPa. Also, the pure physical properties such as normal boiling point, critical constants, acentric factor, molar volume and standard vapor pressure for coumarin and its derivatives were estimated. By these estimated information, the measured solubilities were quantitatively correlated by an approximate lattice equation of state proposed recently by the present authors.     

Recognition of substrates by membrane potential of immobilized glucose oxidase membranes

The shifts in membrane potential, caused by the injection of glucose into a permeation cell, were measured using immobilized (entrapped) glucose oxidase membranes. No, pH change in the permeation cell was observed upon injection of glucose, but the shift in membrane potential was definitely detected. The shift in membrane potential was observed under nitrogen bubbling (in the absence of oxygen) using initially used enzyme membranes. It was, therefore, suggested that the shifts in membrane potential were not caused by an enzyme-substrate reaction, but by binding of the substrate to the enzyme, which indues a conformational change in the enzyme and leads to a change in charge density in the enzyme membrane. This mechanism is also supported by the fact that the shifts in membrane potential were observed upon injection of not only D-glucose but also L-glucose as reported in our previous study [J. Chem. Soc. Faraday Trans., 87 , 695 (1991)]. © 1994 John Wiley & Sons, Inc.     

Preparation and characterization of modified starch‐based plastic film reinforced with short pulp fiber. II. Mechanical properties

Native corn starch‐ and hydroxypropylated starch (HPS‐) based plastic films were prepared using the short pulp fiber as the reinforcement and the glycerol as the plasticizer. The results of tensile test showed that the strain and stress at break and elastic modulus increased with pulp content. With glycerol content, the strain at break increased considerably, but the breaking stress and elastic modulus decreased. And the stress–strain curves showed that the brittleness problem of films was overcome by the pulp, glycerol, and water content. The hydroxypropyl starch films showed results similar to those of the native starch films. The results of the three‐point bending test showed that maximum deflection, flexural strength, and specific work increased with pulp content, but the flexural modulus was the highest at a pulp content of 20%. And with the glycerol content, the maximum deflection and specific work of rupture increased, but the bending elastic modulus decreased. The hydroxypropyl starch films showed results similar to those of native starch films as far as the maximum deflection and flexural strength were concerned, but the bending elastic modulus and specific work of the hydroxypropyl starch films were considerably lower than those of starch films. So it was concluded that the flexibility of films was improved by the hydroxypropylation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2108–2117, 2003