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H S Ku

Publications and source records attributed to H S Ku.

11 recordsLinked to original sources
PubMed2001

Permittivity measurement of thermoplastic composites at elevated temperature.

The material properties of greatest importance in microwave processing of a dielectric are the complex relative permittivity epsilon = epsilon'-jepsilon", and the loss tangent, tan delta = epsilon"/epsilon'. This paper describes two convenient laboratory based methods to obtain epsilon', epsilon" and hence tan delta of fibre-reinforced thermoplastic (FRTP) composites. One method employs a microwave network analyzer in conjunction with a waveguide transmission technique, chosen because it provides the widest possible frequency range with high accuracy. The values of the dielectric constant and dielectric loss of glass fibre reinforced (33%) low density polyethylene, LDPE/GF (33%), polystyrene, PS/GF (33%), and Nylon 66/GF (33%), were obtained. Results are compared with those obtained by another method using a high-temperature dielectric probe.

Electric Capacitance↗
PubMed1999

Microwave facilities for welding thermoplastic composites and preliminary results.

The wide range of applications of microwave technology in manufacturing industries has been well documented (NRC, 1994; Thuery, 1992). In this paper, a new way of joining fibre reinforced thermoplastic composites with or without primers is presented. The microwave facility used is also discussed. The effect of power input and cycle time on the heat affected zone (HAZ) is detailed together with the underlying principles of test piece material interactions with the electromagnetic field. The process of autogenous joining of 33% by weight of random glass fibre reinforced Nylon 66, polystyrene (PS) and low density polyethylene (LDPE) as well as 23.3% by weight of carbon fibre reinforced PS thermoplastic composites is discussed together with developments using filler materials, or primers in the heterogenous joining mode. The weldability dependence on the dielectric loss tangent of these materials at elevated temperatures is also described.

Microwaves↗
PubMed1976

Variables Affecting the CO(2) Compensation Point.

Some factors influencing dark respiration, photorespiration, and photosynthesis were examined for their effect on the CO(2) compensation point (70 mul/l) of detached soybean (Glycine max) leaf discs. A higher compensation point in young leaves decreased to the constant value after leaf expansion and maturation, but increased again during senescence. The compensation point was 40 to 50% higher in plants grown in the summer than in the winter. The compensation point and dark respiration increased with temperatures above 17 C. Below 17 C dark respiration continued to decrease, but the compensation point did not decrease further. Increasing light intensities did not affect the compensation point.The effect of selected chemicals on the compensation point were surveyed. Some buffer components did not greatly alter the compensation point but organic solvents lowered it. Potassium phosphate and pyrophosphate greatly increased it. Inhibitors of photosynthesis increased the compensation point. Hydroxypyridinemethanesulfonate and sodium bisulfite severely inhibited photosynthesis in soybean leaves, stimulated dark respiration, and increased the compensation point.

Journal Article↗
PubMed1968

Isolation of active mitochondria from tomato fruit.

An improved method for isolating mitochondria from tomato fruit (Lycopersicon esculentum Mill.) is described. The fruit is chilled, and the tissue of the fruit wall cut by hand into very thin slices with a razor blade while immersed in a buffer containing 0.4 m sucrose, 2 mm MgCl(2), 8 mm EDTA, 4 mm cysteine, 10 mm KCl, 0.5 mg per ml bovine serum albumin 50 mm tris-HCl, pH 7.6. The pH is monitored and kept within the range of 7.0 to 7.2 by dropwise addition of 1 n KOH during cutting. The tissue is strained through 8 layers of cheesecloth and centrifuged at 2000 x g for 15 minutes. The supernatant is then centrifuged at 11,000 x g for 20 minutes, and the sediment is washed once with a medium containing 0.4 m sucrose, 10 mm KCl, 1 mm MgCl(2), 10 mm tris-HCl, 10 mm KH(2)PO(4) and bovine serum albumin (0.5 mg per ml), pH 7.2. Electron microscope studies show that this method gives homogeneous, relatively intact mitochondria; they have a higher respiratory control ratio than those reported by other workers. The method was also tested successfully on fruits of cantaloupe and ;Honey Dew' melon.

Journal Article↗