An algebraic method for processing colored images

An 8-valued commutative ring is developed to process colored images. Algebraic operators are defined to perform a number of operations such as the extraction of the primary colors and contours of different colors.     

Spouted and spout-fluid bed combustors 1: Devolatilization and combustion of coal volatiles

The devolatilization and volatile combustion of a single coal particle in spouted and spout-fluid beds have been studied. The results showed that the flame extinction time increases with the particle diameter, and decreases with the bed temperature. When the bed temperature and the air flow rate were fixed, the operation modes (spouted or spout-fluid bed) showed less effect on the mean flame extinction time. A mathematical model of the spouted bed mode for preignition and postignition periods has also been developed assuming the devolatilization rate to be controlled by heat transfer and multireaction pyrolysis kinetics based on volatile products. Ignition, heat transfer back from the volatile flame to the particle surface, variation in flame temperature, and the hydrodynamics of SB are taken into account. The model predictions, with some adjusting parameters, were in good agreement with experimental results.     

Role of mixing parameters in the preparation of poly(ethylene vinyl acetate) nanocomposites by melt blending

Polymer/layered‐silicate nanocomposites have gathered momentum as cost‐effective and versatile materials since the middle of the 20th century. Many publications discuss the chemistry of organomodification and properties of nanocomposites, but relatively few deal with the significance of processing conditions. This article takes into account three mixing parameters and discusses the contribution of each toward nanocomposite formation. Organomodified natural sodium‐type bentonite clay was used in this study. The nanocomposites formed were characterized by X‐ray diffraction and mechanical property tests. Response surface regression was used to optimize the tensile modulus. The analysis shows that nanocomposite formation is promoted by a diffusion mechanism and that the interactions of parameters are as important as individual parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2652–2658, 2006     

Nanocrystalline orthoferrite powders: Synthesis and magnetic properties

Nanocrystalline orthoferrite powders were synthesised at low temperatures by employing an aqueous sol–gel process. Colloidal sols and water re-dispersible gels of orthoferrite precursors were prepared by room-temperature processing of inexpensive metal salts. The average diameter (Z_av) of the precursor particles was in the size range from 4 to 7 nm; the diameters had a narrow size distribution. Water re-dispersible translucent gel monoliths were obtained by concentrating the aqueous sols followed by drying them under reduced pressure (10⁻² Torr) at room temperature. The sol–gel transition was found to be completely reversible. Nanocrystalline fine powders of orthoferrites of general formula, LnFeO₃ (Ln = La, Sm, Gd, Dy, Er, Yb and Y) having a crystallite size of about 25 nm were prepared by heating the gel precursors at 650–700 °C in air. Powder X-ray diffraction and thermogravimetry, respectively, were employed to identify perovskite phase formation and delineate thermal events that lead to gel to crystallite conversion. Magnetic measurements were carried out on the resultant powders at room temperature and down to 40 K. Nanocrystalline orthoferrite powders exhibited weak ferromagnetic behaviour, and reduced magnetic moments.     

Fast algorithms for computing the diameter of a finite planar set

Three algorithms for computing the diameter of a finite planar set are proposed. Although all three algorithms have (O(n ²) worst-case running time, an expected-complexity analysis shows that, under reasonable probabilistic assumptions, all three algorithms have linear expected running time. Experimental results indicate that two of these algorithms perform very well for some distributions, and are competitive with an existing method. Finally, we exhibit situations where these exact algorithms out-perform a published approximate algorithm.Research of the first author was supported by grant NSERC A 2422. Research of the second author was supported by grants NSERC A 9293, FCAC EQ-1678 and a Killam Senior Research Fellowship awarded by the Canada Council     

Corrosion failure of Zn–Al detonator housing

Some batches of detonator housings made up of Chromium plated Zn–Al alloy were found in an extensively cracked condition after few months of storage at room temperature. An analysis of the failure showed that the cracks were due to intergranular corrosion facilitated by segregation of lead at the grain boundaries. Improper chromium plating further aggravated the corrosion problem. This failure case emphasises the need for strict control of chemical composition for components made from Zn–Al alloy and the process of Cr plating of the components.     

Rhodopsin mutations in autosomal dominant retinitis pigmentosa

Retinitis pigmentosa is an inherited progressive disease which is a major cause of blindness in western communities. It can be inherited as an autosomal dominant, autosomal recessive, or X-linked recessive disorder. In the autosomal dominant form (adRP), which comprises about 25% of total cases, approximately 30% of families have mutations in the gene encoding the rod photoreceptor-specific protein rhodopsin. This is the transmembrane protein which, when photoexcited, initiates the visual transduction cascade. So far, 41 single-base-pair (bp) substitutions, one two-bp substitution, and four deletions ranging from 3 to 42 bp have been identified in this gene. These mutations do not appear to be significantly clustered in a specific part of the protein, but occur in all three major domains, namely the intradiscal, transmembrane, and cytoplasmic regions. Different mutations appear to cause differences in the severity of the disease, though there is considerable variability in severity even within the same family, at least in certain of these mutations. Identification of all the mutations involved in rhodopsin-RP should allow accurate and early detection of affected individuals, informed genetic counselling, as well as furthering our knowledge of the disease process involved.     

Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

cDNA sequence and gene locus of the human retinal phosphoinositide-specific phospholipase-C beta 4 (PLCB4)

Defects in the Drosophila norpA (no receptor potential A) gene encoding a phosphoinositide-specific phospholipase C (PLC) block invertebrate phototransduction and lead to retinal degeneration. The mammalian homolog, PLCB4, is expressed in rat brain, bovine cerebellum, and the bovine retina in several splice variants. To determine a possible role of PLCB4 gene defects in human disease, we isolated several overlapping cDNA clones from a human retina library. The composite cDNA sequence predicts a human PLC beta 4 polypeptide of 1022 amino acid residues (MW 117,000). This PLC beta 4 variant lacks a 165-amino-acid N-terminal domain characteristic for the rat brain isoforms, but has a distinct putative exon 1 unique for human and bovine retina isoforms. A PLC beta 4 monospecific antibody detected a major (130 kDa) and a minor (160 kDa) isoform in retina homogenates. Somatic cell hybrids and deletion panels were used to localize the PCLB4 gene to the short arm of chromosome 20. The gene was further sublocalized to 20p12 by fluorescence in situ hybridization.