• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.441-442
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• 2006

It is attempted to find out the optimal shape of U-type bellows using the finite element analysis. The design factors, mountain height, length, thickness, and the number of convolutions are considered and the proper values are chosen fur the simulation. The results show that as the number of convolutions reduces, the volume decreases while the stress increases. However, as the number of convolutions increases, the volume increases above the standard volume and the stress obviously increases. In addition, the effect of the thickness of bellows on the stress is very large. Both of the mass and stress are decreasing at a certain lower value region. Also, we investigated shape optimization with considering maximum stress distribution tendency.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.2
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• pp.141-147
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• 2015

This paper deals with thermal characteristic analysis of induction motors for machine tool spindle for motion error prediction. Firstly, the inverse design of general induction motors for machine tool spindle has been performed by design principles. Characteristics considering VVVF inverter of induction motors were analyzed. Secondary, power loss and thermal characteristics of induction motors analyzed by equivalent thermal resistance model from Motor-CAD S/W. To develop a second-order fitted power-loss distribution model for the constant-torque operating range of the induction motor, we employed the design of experiment and response surface methodology techniques. Finally, the analysis results were experimentally verified, and the validity of the proposed analysis method was confirmed.

• Food Science and Biotechnology
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• v.18 no.1
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• pp.31-35
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• 2009

Total folate content was determined by microbiological assay using Lactobacillus casei spp. rhamnosis (ATCC 7469) with a 96-well microplate technique. Using roasted peanut and red kidney beans as representative legume samples, response surface methodology (RSM) was supplied to optimize the trienzyme procedures for the determination of folate in legumes. After response surface regression (RSREG), the second-order polynomial equation was fitted to the experimental data. Ridge analysis showed that the optimal digestion times were <2 hr for $Pronase^{(R)}$ and $\alpha$-amylase, and <5 hr for conjugase to obtain maximal folate values for legume samples. This study confirms that established digestion times for cereal products (AOAC Method 2004.05) of 3 for protease and 2 hr for $\alpha$-amylase are applicable to legumes. Conjugase treatment can be reduced to 5 from 16 hr and the conjugase level to 5 from 20 mg per sample, providing significant cost saving.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.3
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• pp.312-317
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• 2014

In this paper, the wave run-up height and depression depth around air-water interface-piercing circular cylinder have been numerically studied. The Reynolds Averaged Navier-Stokes equations (RANS) and continuity equations are solved with Reynolds Stress model (RSM) and volume of fluid (VOF) method as turbulence model and free surface modeling, respectively. A commercial Computational Fluid Dynamics (CFD) software "Star-CCM+" has been used for the current simulations. Various Froude numbers ranged from 0.2 to 1.6 are used to investigate the change of air-water interface structures around the cylinder and experimental data and theoretical values by Bernoulli are compared. The present results showed a good agreement with other studies. Kelvin waves behind the cylinder were generated and its wave lengths are longer as Froude numbers increase and they have good agreement with theoretical values. And its angles are smaller with the increase of Froude numbers.

• Journal of the Korean Dietetic Association
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• v.26 no.1
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• pp.1-13
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• 2020

This study was undertaken to optimize preparation of sweet rice muffins using lotus (Nelumbo nucifera Gaertn) seed powder. The experimental conditions used in the preparation included lotus seed powder (X₁) and soybean oil (X₂). The muffin formulation was optimized using rheology. Lightness (P<0.01) displayed a quadratic model pattern, whereas yellowness (P<0.01) and redness (P<0.05) was presented a linear model. Texture properties significantly differed in cohesiveness (P<0.05). Evaluating the sensory characteristics of muffins, except for flavor and texture, the remaining properties of color (P<0.01), taste, overall quality, and appearance (P<0.05) were found to be significantly different. The overall quality was also affected by the proportion of lotus seed powder, rather than the amount of soybean oil. The optimal ratio for palatability of muffins was determined to be 47.80 g lotus seed powder and 95.28 g soybean oil. Taken together, our results indicate that sweet rice muffins prepared using lotus seed powder are sufficiently competitive in terms of function and quality.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.14-24
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• 2011

In this paper, design optimization for mixed-flow pump impellers and diffusers has been studied using a commercial computational fluid dynamics (CFD) code and DOE (design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser. Geometric design variables were defined by the vane plane development, which indicates the blade-angle distributions and length of the impeller and diffusers. The vane plane development was controlled using the blade-angle in a fixed meridional shape. First, the design optimization of the defined impeller geometric variables was achieved, and then the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Next, design optimizations of the defined diffuser shape variables were performed. The importance of the geometric design variables was analyzed using $2^k$ factorial designs, and the design optimization of the geometric variables was determined using the response surface method (RSM). The objective functions were defined as the total head and the total efficiency at the design flow rate. Based on the comparison of CFD results between the optimized pump and base design models, the reason for the performance improvement was discussed.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.27-32
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• 2013

A valve is a marine structure that is subjected to multiple seawater loads. Therefore, it is necessary to define the kind of loads applied to it to confirm whether the structure has sufficient strength. In this research, we aimed to find the optimal solution for the stress and deformation of valves under various loads. We first selected design variables and implement a finite element analysis according to changes in the thickness of each component of a valve based on a central composite design. Next we developed a regression model of the response surface. Using this model, we calculated the optimal objective value based on NSGA-II. Finally, to confirm the correspondence between the optimal objective value and the real FEM value, we compared the optimal result and structural analysis result to verify the performance of NSGA-II.

• Journal of the Korean Chemical Society
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• v.57 no.6
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• pp.761-768
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• 2013

Removal of COD and TSS from rice mill wastewater was investigated using continuous electrocoagulation method (CEC). The electrical energy consumption (EEC) of the process was also examined in order to evaluate the economic viability. The Box-Behnken statistical experiment design (BBD) and response surface methodology (RSM) were used to investigate the effects of major operating variables. Initial pH, current density, electrode distance and flow rate were selected as independent variables in BBD while COD removal, TSS removal and EEC were considered as the response functions. The predicted values of responses obtained using the response function was in good agreement with the experimental data. Optimum operating conditions were found to be pH of 7, current density of 15 mA $cm^{-2}$, electrode distance of 5 cm and flow rate of 70 ml/min. Under these conditions, greater than 89% removal of COD and TSS were obtained with EEC value of 7 KWh.

• Journal of the Korean Society of Food Culture
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• v.28 no.4
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• pp.392-400
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• 2013

The purpose of this study was to determine the optimal amounts and mixing condition of skim milk powder (A), and roselle (B) for the production of yogurt prepared with roselle. The experiment was designed according to the central composite design for estimating the response surface method, which yielded ten experimental points, including two replicates for the skim milk powder and roselle. The physicochemical and mechanical analysis of each sample, including pH (P<0.001), titratable acidity (P<0.001), color (P<0.05), viscosity (P<0.001), showed significant differences. Antioxidant properties (total phenolic content, DPPH free radical scavenging activity) and viable cell counts of lactic acid were significantly different (P<0.05). The sensory measurements were significantly different in color, flavor, sourness, texture, and overall quality (P<0.05). The optimal formulation, calculated by numerical and graphical methods, was 7.82 g of skim milk powder and 2.09 g of roselle. From findings of this study, the roselle may be used in yogurt and can be applied for other food industries.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.12
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• pp.627-632
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• 2001

There are claims that ESE(Early streamer emission) Air terminals offer a vastly increased zone of protection over that of traditional lightning rods by causing the emission of an upward streamer/leader that will propagate towards the tip of downward leader at an early stage in the attachment process than would occur for a simple rod in the same geometrical configurations. This paper shows the results of comparing test a particular type of ESE air terminals with a simple rod conducted in the KEH HV laboratory, which are lightning impulse voltage test, flashover direction test and corona emission current measurement. The results from this test show a completely random scattering of flashovers to the conventional and ESE air terminals under identical electrics] and geometrical conditions, and thus shows no advantage of one terminal over the other.