• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.123-133
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• 1996

From the experimental study of wire-cut Electric Discharge Machining of alloyed tool steel and tungsten carbide, the characteristics such as cutting speed, surface roughness has been observed and evaluated for various conditions. Cutting speed is improved as peak discharge current and wire tension become increased, and gap voltage and spark cycle decreased. Surface roughness can be better when peak discharge current and gap voltage become smaller, or spark cycle and wire tension become larger. Secondary cut is recommended to obtain high precision and good quality.

• Membrane Journal
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• v.1 no.1
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• pp.55-64
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• 1991

The ultrathin membranes of cellulose acetate and polyvinyl chloride were prepared by the method of watercasting. The spreading ability of polymer solutions on water doereased with increasing the surface tention and the viscosity of polymer solutions, and the temperature of water surface, respectively. The aggregation states of water-casting membranes were dense and dense with increasing the concentration of polymer solutions and the temperature of water surface. The surface structure of the air sides showed more dense than that of the water sides. In the case of the 3 wt% cellulose acetate/acetone system, the thickness of the membrane was about $0.1{\mu}.$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.555-562
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• 1998

Under the influence of non-uniform magnetic field, melt flow in steady state and oxygen concentration in unsteady state are numerically investigated. The strength of the applied characteristic magnetic fields are B=0.1T, 0.2T, and 0.3T, respectively. The buoyancy effects due to the crucible wall heating and the thermocapillary effects due to the surface tention at the free surface are suppressed differentially by the non-uniform magnetic fields. As the intensity of characteristic magnetic fields is increasing, the recirculation region in the meridional plane is moving toward the growing crystal, and is diminishing. The oxygen concentration on the growing surface of crystals is decreasing and the uniformity of the oxygen concentration is increasing as the intensity of the magnetic fields is increasing.

• Journal of the Korean Applied Science and Technology
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• v.17 no.3
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• pp.149-157
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• 2000

The synthesis of N-methyl glucamine was performed in two step reaction. The first step involves the amination between methylamine and glucose in methane. The N-methyl glucamine was obtained by the reduction of using Ni catalyst under the high pressure. The second step was glucamide anionic derivatives synthesis from N-methyl glucamine, maleic anhydride, lauryl alcohol and laurylamine by Schotten Banmann reaction respectively. Their molecular structures of N-methyl glucamine and glucamide (EG-MAS and AC-MAS) were investigated by IR and $^{1}H-NMR$. Basic physical properties and biodegradability of there glucamide anionic surfactant was investigated. The range of cmc values determined by measurements of surface tention was $10^{-5}{\sim}10^{-4}mol/l$ and the surface tension of the aqueous solution revealed in the range $28{\sim}30$ dyne/cm and their biodegradability was very good in the pH $5{\sim}10$.

• Journal of the Korean Applied Science and Technology
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• v.38 no.4
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• pp.1003-1009
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• 2021

A study on the associative properties of sodium hyaluronate (NaHA) and Alkane-bis (dimethylalkylammonium bromide) surfactants in aqueous solution was investigated in relation to the chemical structure of surfactants. As a result of measuring the interfacial tension, a parabolic graph showing the minimum value (c_min) at a specific concentration was shown. Above this minimum concentration the increase in interfacial tension is thought to be related to the formation of aggregates of NaHA chains and dimeric surfactants. The plot of viscosity vs surfactant concentration shows a slight maxium at c_min and a viscosity decrease at high surfactant concentrations. Viscosity nonlinear behavior is related to the size increase due to the complex growth and to the size shrinkage following from the interaction with electrolyte ions and free micelles. The results of surface tension measurements show a broad region of surface tension decrease, indicating the NaHA-surfactant interaction. The increase in surface tension above c_min may be related to the adsorption of clusters, consisting of free NaHA chains and dimeric surfactant. The strong adsorption of surfactant is observed at high concentrations.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.301-307
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• 1997

In field fabrication of steel members, the oversize hole is frequently required due to reaming and mismatching. But, there are no provisions and investigations about oversize hole in the Korean specifications. So, in this study, the tension test of friction type high-tention bolted joints is performed with parameters of bolt hole size, surface treatment and tightening force, and investigate the effect of slip behavior with those parameters. From the results, the enough tightening force is needed to obtain some degree slip load in shot blast treatment case, although tightening force is reduced somewhat, it is no problem to guarantee slip load in zincrich primer case. The slip behavior of joints with oversize hole(26mm) is similar to the slip behavior of joints with hole of nominal size.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.4
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• pp.266-277
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• 1991

To catch the surf clam, Mactra chinensis, in sand bottom using the excavating performance of water jet, the authors had constructed the experimental hydraulic jet dredge by the result of water tank experiment of previous report, and also were carried out the field experiments in the surf clam fishing ground near Kunsan, Korea from 5th to 30th of October, 1990. The results obtained are as follows. 1) Excavating depth was more than 10~11cm at the 1500cm/s water-jet velocity in the fine sand and muddy sand. 2) Towing tention was only 105$\pm$5kg in the 6.7cm/s towing speed. 3) Average catch amount per unit towing area was 0.42kg/m super(2) and it was 1.2~1.6 times comparing on the conventional dredge. 4) Experimental hydraulic jet dredge did not nearly brake the surf clam. 5) Turbidity variation by the water jet of dredge was not serious in the fishing ground; On the surface, when the depth is more than 5.2m, turbidity variation was not found at all, and on the 3m layer above the bottom, turbidity variations was increased 9~11ppm at 1m backward from the dredge, but it was gradually decrease, and it was nearly not at 9m backward from the dredge.