• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.3
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• pp.466-470
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• 2001

Response surface methodology was used for monitoring extraction conditions, based on quality properties of old pumpkin extracts. Hunter's color L value of extracts was maximized at 101℃, 2.6 hr and decreased gradually after maximum point. The polynomial equation for Hunter's color L value showed 10% of significance level and 0.8799 of R². Hunter's color a value was minimized at 117℃, 3.9 hr and R² of polynomial equation was 0.9852 within 1% significance level. Hunter's color b value and ΔE value increased as the extracting temperature and time increased. Extraction yield of old pumpkin was maximized at 110℃, 4 hr and increased in proportional to the extracting temperature and time, but decreased after 113℃ and 2 hr. Viscosity of pumpkin extracts were maximized at 120℃, nearly 3 hr. R² of polynomial equations for yield, viscosity and sugar content were 0.9532, 0.9812 and 0.8869, respectively. Optimum ranges of extraction conditions for quality properties of old pumpkin were 102∼109℃, 2.5∼3.5 hr, respectively. Predicted values at the optimum extraction condition agreed with experimental values.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.17-24
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• 1995

The TEA complex polymeric sol was prepared by the alkoxide sol-gel method. The purpsoe of this experiment was to vefity the particle shape in the sol from the investigation of the rheological properties. TEA retarded hydrolysis rate by the reaction with alkoxide enough to make a stable transparent sol in the wide range of composition. From the results of the viscosity change with time, the optimum mole ratio for spinning was selected as 0.5 mole of TEA, 3 mole of H2O and the optimum viscosity was 104 cPs. The rheological behavior of the sol showed that the particle shape in the sol was linear, which was adequate for fiber drawing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.905-913
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• 2003

Generally, most of optimization have been performed with fixed sizes and variables. But, the optimum value considering tolerance of design variables and material properties, might be useless owing to exist in infeasible region. It is needed that the tolerance of design variables and material properties is considered for a real design problem. A deterministic optimal solution can be in the feasible region by performing robust optimization considering tolerance. In the paper, robust design is suggested to gain an optimum insensitive to variation of design variables and it is applied for optimization problem of caliper disc brakes for vehicles.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.93-99
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• 2000

The physical properties of freshly mixed steel fiber reinforced recycled concrete(SFRRC) were_investigated. Physical state and quality of fresh concrete were monitored batch by batch. the properties of freshly mixed SFRRC were determined in terms of slump, air content, superplasticizer, and bleeding ratio. Concrete mixtures were produced for three kinds of aggregate proportions. So, the experimental variables are various aggregate proportions, steel fiber contents(0, 0.5, 1.0, 1.5%) and steel length(30, 50, 60mm). From experimental results, optimum s/a by various experimental variables, variations of the slump by the air contents, and optimum superplasticizer to decrease unit water were presented.

• Journal of Korea Foundry Society
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• v.18 no.4
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• pp.373-382
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• 1998

Particulate reinforced aluminum alloys produced by indirect squeeze casting are difficult to shape by cutting or milling. Therefore near net shape forming of complex shapes is of high economic and technical interest. The complex shape products of $SiC_p/6061$ Al composites are fabricated by the melt-stirring and indirect squeeze casting process. The mold temperatures are $200^{\circ}C$ and $300^{\circ}C$ and applied pressures are 70, 100, and 130 MPa. The volume fractions of the reinforcements are in the range of 5 vol% to 15 vol%. The reinforcement dispersion state are observed using on optical microscope. By employing observed results systematically a correlation is demonstrated among the microstructure, particles behavior, mechanical properties and processing parameters for an optimum melt-stirring(compocasting) and indirect squeeze casting process of MMCs. A procedure to establish the optimum squeeze casting of Al-MMCs is proposed.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.242-243
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• 2009

Friction stir welding and friction stir processing is a new solid state processing technique for ioining and micro..structural modification in metallic materials. It has been applied not only joining for light metals but also modification of the microstructure to enhance mechanical properties. In thin study, we investigated the mechanical properties for applied friction stir welding and processing under various parameters such as probe diameter, probe type, traveling speed and rotating speed for 5456-H116 AI allov. As a result of experiments, optimum condition of friction stir welding is traveling speed of 15mm/min, rotating speed of 500RPM at 6mm diameter probe. Moreover, in the case of friction stir processing, the optimum condition is traveling speed of 15mm/min, rotating speed of 250RPM at full screw probe. As above mentioned, the mechanical characteristics enhanced with the decreasing of traveling speed and the increasing of friction areas because of plastic flow due to high friction heat. These result can be used as reference data for ship repairment.

• Journal of Power System Engineering
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• v.8 no.4
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• pp.44-48
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• 2004

For many years researchers have been attempting to establish the relations among the preparation history, structure and properties of ceramics. In this study, the strength property of $Al_2O_3$ ceramics with components and giudes of the textile machinery was investigated. The optimized conditions of ressureless sintering were investigated in order to obtain the maximum strength of $Al_2O_3$ ceramics for using at the textile machinery. As the sintering conditions, $1,400{\sim}1,700^{\circ}C$ of temperatures and $30{\sim}150$ minutes of times were applied. Three-point bending test was conducted on the sintered materials to obtain the strength property. From test results, the optimum sintering temperature has $1,600^{\circ}C$. And the optimum sintering time in $1,600^{\circ}C$ has about 100 minutes.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.4
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• pp.555-562
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• 1990

Alloyed ohmic contact properties of Au-Zn/Au, Au-Be/Au,Au-Zn/Cr/Au, and Au-Be/Cr/Au metal system to p-InP were investigated. Optimum alloying conditions were obtained at the annealing temperature of 425\ulcorner for all the metal systems using a rapid thermal annealing system. Surface AES analysis and auger depth profiling were done for each metal system annealed at the optimum conditions. Outdiffusions of In and P from the InP substrate were found in the metal systems without Cr intermediate layer. Also, small amount of In. P and Cr were detected at the surface in the case of Au-Zn/Cr/Au system, while there were occured no outdiffusion of In, P, and Cr for Au-Be/Cr/Au system. The best surface morpholoty and specific contact resistivity of 4.5x 10**-5 \ulcornercm\ulcornerhave been obtained in this Au-Be/Cr/Au material system alloyed at 425\ulcorner for 60 second.

• Journal of the Korean Ceramic Society
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• v.24 no.2
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• pp.170-178
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• 1987

Changes of the properties of PECVD-SiN film with the variation of deposition process parameters were investigated and optimum process parameters were determined. The refractive index of the film increased with increasing substrate temperature and pressure, and decreasing rf-power, NH3/SiH4 gas ratio and total gas flow. BHF etch rate and deposition rate show a decreasing tendency with increasing refractive index. The step coverage of the film was not affected much by deposition rate and pressure, but improved apparently with increasing rf-power and NH3/SiH4 gas ratio. Also the optimum process parameters were determined by considering the characteristic properties as well as thickness uniformity of films. The refractive index of the film deposited under this condition was 2.06.

• Journal of Welding and Joining
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• v.15 no.6
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• pp.32-40
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• 1997

Solid state diffusion bonding is the joining process performed by creep and diffusion, which is accelerated by heating below melting temperature and proper pressing, in vacuum or shielding gas atmosphere. By this process we can obtain sufficient joint which can't be expected from the fusion welding. For Ti-6Al-4V alloy, the optimum solid state diffusion bonding condition and mechanical properties of the joint were found, and micro void morphology at bond interface was observed by SEM. The results of tensile test showed sufficient joint, whose mechanical properties are similar to that of base metal. 850$^{\circ}$C, 3MPa is considered as the optimum bonding condition. Void morphology at interface is long and flat at the initial stage. As the percentage of bonded area increases, however, small and round voids are found. Variation of void shape can be explained as follows. As for the void shrinkage mechanism, at the initial stage, power law creep is the dominant, but diffusion mechanism is dominant when the percentage of bonded area is increased.