Coverage Of Patches Research Articles

Optimization of zinc phosphate coating on 7075-T6 aluminum alloy

A zinc phosphate coating process on 7075-T6 aluminum alloy has been significantly improved through a combined approach of titanium colloid pretreatment, pH level adjustment, fluoride additive and ZnO H 3PO 4 ratio adjustment. In particular, optimum phosphate coatings were formed in coating baths with a ZnO H 3PO 4 ratio of 0.205 and 0.256. Coating morphology studied by SEM reveals that the adjustment in the coating procedure produces an improved crystalline coating layer with high coverage and small grain size. For coatings formed in a bath with a ratio of 0.205, the coverage of the crystalline patches on top of the amorphous coating base is almost complete. The chemical composition of the coating layers has been characterized by XPS and SIMS. The crystalline and amorphous coating phases formed in the bath with a ratio of 0.205 were found to have compositions given schematically as Zn x(PO 4) and Zn xAl y(PO 4), respectively. In contrast, neither coating phase formed in the bath with a ratio of 0.256 shows the presence of Al.

Architecture and development in Fagus japónica ‐ Fagus crenata forest near Mount Takahara, Japan

Abstract. The architecture and development of forest eco‐units in a mixed Japanese beech forest were studied by means of aerial photographs and belt‐transects. Fagus japónica dominates in this forest because it has the ability to reproduce through root‐collar sprouts. Each individual has a number of stems that reach the canopy. Two eco‐unit types are recognized. Most abundant is the type dominated by multiple‐stem F. japónica individuals (type A). The other type is dominated by other tall tree species, mostly Fagus crenata (type B). The most common cycle of development for type A is mature / stem‐breakage / growing / mature. After stem‐breakage, suppressed sprouts of the same individual replace the broken stem by growing quickly into the canopy. This accounts for the low coverage of patches in the early growing phases and the high coverage in mature phases in the aerial photographs. After uprooting off. japónica or after death of other canopy tree species, a seedling phase will be necessary, during which canopy species establish themselves from seed and F. japónica may establish itself from sprouts. Dwarf bamboo appeared to inhibit the establishment of seedlings but it does not affect the establishment of F. japónica sprouts.It is concluded that the dominance of F. japónica over other tall tree species is the result of F. japónica reproducing by sprouts.