Depolymerization of Molten-Moisturized-Starch Molecules by Shearing-Force under High Temperature

Potato, corn and wheat starch containing 20% moisture were treated with a flow tester under heated and heated-sheared conditions. Then heated and heated-sheared starch specimens were prepared from three kinds of intact starches. Small amount of glucose was detected in water-soluble fractions of heated and heated-sheared specimens in spite of almost no detection in intact starches. By viscometry, the viscometric molecular weight of intact potato, intact corn and intact wheat starch with 20% moisture were 104kDa, 527kDa and 605kDa, respectively. While for heated specimens their molecular weights were depolymerized into 986kDa, 34kDa and 511kDa, respectively, and for heated-sheared specimens, they were significantly depolymerized into 539kDa, 169kDa and 279kDa, respectively. Those facts were also supported from gel filtration profiles. As the results from glucose formation, viscometric molecular-weight depolymerization and gelfiltration profiles, the considerable depolymerization in melt starchmolecules is yielded by the physical shearing-force on starch melt despite starch varieties.     

Effect of heated length on the critical heat flux of subcooled flow boiling. Part 1: Observation of bubbles and slug length at atmospheric pressure

The effect of the heated length on the Critical Heat Flux (CHF) of subcooled flow boiling with water was experimentally investigated by means of a direct current heated plate made of stainless steel with various lengths. The motion of bubbles at near burnout was observed by a high‐speed video camera under atmospheric pressure conditions. Consideration was made of the critical wavelength of the Helmholtz instability in several CHF mechanistic models. The slug length at CHF almost coincided with the critical wavelength. It is further confirmed that when the heated length is shorter than the critical wavelength, a large enhancement of the CHF is seen. © 2000 Scripta Technica, Heat Trans Asian Res, 29(2): 132–143, 2000     

Resonance Shear Measurement of Confined Alkylphenyl Ether Lubricants

The tribological properties of four phenyl ether lubricants, monoalkydiphenyl ether (MADE), dialkyldiphenyl ether (DADE), m-phenoxyphenoxy m-biphenyl (m-4P2E), and m-bis(m-phenoxyphenoxy) benzene (m-5P4E), confined between mica surfaces have been investigated using the resonance shear measurement (RSM). The RSM study revealed that the viscous parameter of these lubricants increased when they were confined in a nano-space. The viscous parameter b ₂ values of these lubricants confined in a gap smaller than ca. 2–3 nm were in the order of MADE > DADE > m-4P2E ≈ m-5P4E, while their bulk viscosities were in the order of m-5P4E > m-4P2E > DADE > MADE. Further, the MADE, which has better hydrodynamic lubrication property because of the lowest bulk viscosity, was relatively easily squeezed out from the gap compared to others. These results have demonstrated that phenyl ether lubricants confined in a nano-space behave quite differently from those of the bulk phase, and the direct characterization of confined lubricants is imperative for designing efficient lubricants, especially for boundary lubrication.     

Tuning the luminescence color and enhancement of afterglow properties of Sr(4−x−y)CaxBayAl14O25:Eu,Dy phosphor by adjusting the composition

Color point tuning is an important challenge for improving the practical applications of various displays, especially there are very limited white color single hosts that emits in the white spectrum. In this paper, the possibility of color tuning by substituting part of host lattice cation (Sr²⁺ ions) by Ca²⁺ or Ba²⁺ ions in an efficient strontium aluminate phosphor, Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺, is reported and found to be very promising for displays. A detail study by replacing part of Sr²⁺ with Ca²⁺ or Ba²⁺ has been investigated. X-ray diffraction study showed that crystal structure of Sr₄Al₁₄O₂₅ is preserved up to 20 mol of Ca²⁺ ion exchange while it is limited to 10 mol of Ba²⁺ ions exchange. Substantial shift in the emission band and color were observed by substitution of Sr²⁺ by Ca²⁺ or Ba²⁺ ions. A bluish-white emission and afterglow was observed at higher Ca²⁺ ions substitution. Further, partial Ca²⁺ substitutions (up to 0.8 mol) resulted in enhanced afterglow of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor. However, Ba²⁺ substitution decreased the fluorescence as well afterglow of the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor significantly. The enhanced phosphorescence by partial Ca²⁺ substitution is explained on the basis of increased density of shallow traps associated with higher solubility of Dy³⁺ ions in to the host lattice due to equivalent size of Ca²⁺ and Dy³⁺ ions. Thus, Ca²⁺ substitution in the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor is a promising method for tuning the emission color and improving the afterglow intensity of the phosphor.     

Effect of Molecular Weight Distribution of Mineral Oils on Life of Thrust Ball Bearings

In order to investigate the effect of molecular weight distributions of mineral oils on bearing life, the authors carried out systematic tests using thrust ball bearings, type 51104.

Besides the general trend of increasing life with viscosity, blended oils characterized by wide-ranged molecular weight distributions exhibited longer life compared with base oils with narrow-ranged distributions corresponding to the same viscosity grade. These results were obtained by estimating states of oil film and oxide film formations, and furthermore, by measuring coefficients of friction, oil temperatures, and viscosity at the glass transition points.