Asphalt colloidal types differentiated by Korcak distribution

Asphalt in a colloidal context can be considered as a sol, sol-gel or gel type where in all three cases the asphaltene particle plays an important role. Usually the three colloidal types can be differentiated by refinery processes or by rheological properties. The aggregation or clustering of the asphaltene particles (or micelles) from sol to sol-gel and finally to the gel state with a fixed lattice can follow the stochastic process of fractal Brownian motion which can fit a hyperbolic (or Korcak) distribution. A test was carried out using the same mass of various asphalts of different colloidal types for floc formation with a series of n-alkanes (dispersion media) of increasing characteristic lengths. Results from floc formation studies indicate that the value of the size distribution for the gel type is small, is higher for the sol-gel type, and is highest for the sol type. On the other hand, the surface irregularities for all three types of asphalt do not have any correlation. These observed facts are consistent with principles based on the fractal approach.     

Mesophase formation in coal liquid solvent fractions

The single greatest influence on the mesophase microstructure is the chemical composition of the organic precursor. The effects of oxygen content and structural parameters of precursors from solvent fractions of coal liquefaction products on the microstructure and pyrolysis yields were determined. The fractions were analysed using the Brown-Ladner method to obtain average molecular structural parameters. It was found that pyrolysis yield increases with increased aromaticity and oxygen content and that mesophase microstructure is determined primarily by the oxygen content of the precursors.     

Subsolidus Phase Relationships in Si3N4–AlN–Rare-Earth Oxide Systems

The subsolidus phase relationships in Si₃N₄–AlN–rare-earth oxide (Me₂O₃ where Me=Nd, Sm, Gd, Dy, Er, and Yb) systems were studied. Solid-solution regions with the α-Si₃N₄ structure were delineated along the Si₃N₄–"Me₂O₃:9AIN" joins for all of the rare-earth oxide systems studied. The solubility limits of these solid solutions increased with decreasing size of the rare-earth ions.     

Sex pheromone components from asian corn borer,Ostrinia furnacalis (Hubner) (Lepidoptera: Pyralidae) in Taiwan

The female sex pheromone of the Asian com borer,Ostrinia furnacalis, widespread in Taiwan, was confirmed as (Z)-12-tetradecenyl acetate and its geometric isomer (E)-12-tetradecenyl acetate in a ratio of ca. 31 by gas chromatography and gas chromatography-mass spectrometry in selected ion monitoring mode. Males were attracted by the mixture of these two synthetic components in the field, but the attractiveness was less than by virgin females. The presence of minor components in the sex pheromone was therefore suggested.     

Laminar mixed convection in the entrance region of shrouded arrays of heated rectangular blocks

Laminar mixed convection in the entrance region of shrouded arrays of heated rectangular blocks is approximated numerically for large Prandtl number fluids. The problem considered is related to the convective cooling of electronic components mounted on horizontal circuit boards. Two heating conditions are investigated; in case 1, the uniformly heated components are facing upwards and, in case 2, the heated components are facing downwards. Typical fluid streamlines and isotherms, block wall temperature distributions and local Nusselt numbers are presented. It is found that the secondary flow leads to a significant enhancement in heat transfer for cases where the block faces upwards rather than downwards.     

Stability of some stationary solutions to the forced KdV equation with one or two bumps

Free-surface flows past submerged obstacles in a channel are considered. The fluid is assumed to be inviscid and incompressible and the flow to be irrotational. The first-order approximation of long nonlinear surface waves over one or two bumps results in a forced Korteweg?Cde Vries (fKdV) equation. Solutions of the stationary fKdV equation are constructed and their stability is studied, either analytically or numerically. These various solutions include solitary waves over a single bump, solitary waves with two humps over a double bump, table-top solutions over a double bump and fronts.     

Multistage treatment of high strength dye wastewater by coagulation and ozonation

Two types of wastewaters from the dye manufacturing process were treated by multistage chemical coagulation combined with ozonation. By using the coagulant iron(II) chloride and a commercial coagulant aid, the majority of COD was removed in advance of ozonation, a similar repeated treatment cycle was performed after settlement of the coagulant in each cycle. Results showed that the optimum concentrations to be used were 2·5% (v/v) iron(II) chloride and 35 mg dm⁻³ coagulant aid. The decolorization efficiency was >99% and the COD elimination was >90%. The multistage combined chemical coagulation ozonation treatment was found to be superior to the single-stage treatment. © 1998 SCI.     

Feasibility of a one–step process for desizing,scouring, bleaching and mercerisating cotton fabrics

In this study the desizing, scouring, bleaching and slack mercerising of cotton fabric by a one–step process at different sodium hydroxide concentrations, impregnation temperatures and curing times were examined. The results indicate that when the fabrics are mercerised at lower temperature, the strength retention and colour strength are enhanced. When the sodium hydroxide concentration is increased, these properties also increase. When cotton fabrics are mercerised for 3 min at 40C and cured for 30 s at 120C, their physical properties are similar to those obtained using a conventional two–step approach.     

Alkylation of aldehydes with methanol over titanium oxide catalysts

The methylation of various aldehydes, such as acetaldehyde, propionaldehyde, and phenylacetaldehyde over titanium oxidesupported vanadium oxide was studied under atmospheric pressure and temperatures of 250–400°C. The catalyst properties of titanium oxide can be enhanced only by addition of a fairly small amount of vanadium. High-temperature treatment transforms titanium oxide, the support, from anatase to rutile, which causes the catalysts to lose their catalytic properties. The reactivity of these can be ranked in the following order: acetaldehyde > propionaldehyde > phenylacetaldehyde. The steric effect of the substituted groups in propionaldehyde or phenylacetaldehyde may prevent self-condensation to form oligomers and to give a high selectivity of alkylated products.