Abstract: The temperature dependence of wettability (wetting
angle, Θ (T)) for Ag-based melts on graphite and Al2O3 substrates is
compared. Typical alloying effects are found, as the Ag host metal is
gradually replaced by various metallic elements. The essence of
alloying lies in the change of the electron/atom (e/a) ratio. This ratio
is also manifested in the shift of wetting angles on the same substrate.
Nevertheless, the effects are partially smeared by other
(metallurgical) factors, like the interaction between the oxygenalloying
elements and by the graphite substrate-oxygen interaction. In
contrast, such effects are not pronounced in the case of Al2O3
substrates. As a consequence, Θ(T) exhibits an opposite trend in the
case of two substrates. Crossovers of the Θ(T) curves were often
found. The positions of crossovers depend on the chemical character
and concentration of solute atoms. Segregation and epitaxial texture
formation after solidification were also observed in certain alloy
drops, especially in high concentration range. This phenomenon is
not yet explained in every detail.
Abstract: SiC reinforced Aluminum samples were produced by stir casting of liquid AA1200 aluminum alloy at 600-650ºC casting temperature. 83µm SiC particles were rinsed in 10g/l, 20g/l and 30g/l molar concentration of Sncl2 through cleaning times of 0, 60, 120, and 180 minutes. Some cast samples were tested for mechanical properties and some were subjected to heat treatment before testing. The SnCl2 rinsed SiC reinforced aluminum exhibited higher yield strength, hardness, stiffness and elongation which increases with cleaning concentration and time up to 120 minutes, compared to composite with untreated SiC. However, the impact energy resistance decreases with cleaning concentration and time. The improved properties were attributed to good wettability and mechanical adhesion at the fiber-matrix interface. Quenching and annealing the composite samples further improve the tensile/yield strengths, elongation, stiffness, hardness similar to those of the as-cast samples.
Abstract: Organic farming systems still depend on intensive, mechanical soil tillage. Frequent passes by machinery traffic cause substantial soil compaction that threatens soil health. Adopting practices as reduced tillage and organic matter retention on the soil surface are considered effective ways to control soil compaction. In tropical regions, however, the acceleration of soil organic matter decomposition and soil carbon turnover on the topsoil layer is influenced more rapidly by the oscillation process of drying and wetting. It is hypothesized therefore, that rapid reduction in soil organic matter hastens the potential for compaction to occur in organic farming systems. Compaction changes soil physical properties and as a consequence it has been implicated as a causal agent in the inhibition of natural disease suppression in soils. Here we describe relationships between soil management in organic vegetable systems, soil compaction, and declining soil capacity to suppress pathogenic microorganisms.
Abstract: This study presents a systematic analysis of wetted region due to cooling of aluminum plate by water spray impingement with respect to different water flow rates, spray nozzle heights, and subcooling. Unlike jet impingement, the wetting is not commenced upon spray impingement and there is a delay in wetness of hot test surface. After initiation, the wetting (black zone) progresses gradually to cover all test plate and provides efficient cooling in nucleate boiling regime. Generally, spray cooling is found function of spray flow rate, spray-to-surface distance and water subcooling. Wetting delay is decreasing by increasing of spray flow rate until spray impact area is not become bigger that test surface. Otherwise, higher spray flow rate is not practically accelerated start of wetting. Very fast wetting due to spray cooling can be obtained by dense spray (high floe rate) discharged from adjacent nozzle to the test surface. Highly subcooling water spray also triggers earlier wetting of hot aluminum plate.
Abstract: Thirty three re-wetting tests were conducted at
different combinations of temperatures (5.7- 46.30C) and relative
humidites (48.2-88.6%) with barley. Two most commonly used thinlayer
drying and rewetting models i.e. Page and Diffusion were
compared for their ability to the fit the experimental re-wetting data
based on the standard error of estimate (SEE) of the measured and
simulated moisture contents. The comparison shows both the Page
and Diffusion models fit the re-wetting experimental data of barley
well. The average SEE values for the Page and Diffusion models
were 0.176 % d.b. and 0.199 % d.b., respectively. The Page and
Diffusion models were found to be most suitable equations, to
describe the thin-layer re-wetting characteristics of barley over a
typically five day re-wetting. These two models can be used for the
simulation of deep-bed re-wetting of barley occurring during
ventilated storage and deep bed drying.