• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.119-124
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• 2004

In this study, a rotor blade of a Curtis turbine is investigated. Bezier curve is generally used to define the profile of turbine blades. However, this curve gives a feature of global control, which is not proper to a supersonic impulse turbine blade. Thus, a blade design method is developed by using B-spline curve so that local control is possible to obtain an optimized blade section. To design a Curtis turbine blade section systematically, the blade section has been changed by varying three design parameters using central composite design method. Flow analyses have been carried out for the blade sections, and the effects of design parameters are evaluated.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.47-50
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• 2002

Because of the environmental problems, automotive companies are trying to reduce the weight of car body. Therefore, TRIP(TRansformation Induced Plasticity) steels, which have high strength and ductility have been developed. Welding process is a complex process; therefore deciding the optimal welding conditions on the basis of experimental data is an effective method. However, trial-and-error method to decide the optimal conditions requires too many experiments. To overcome these problems, response surface methodology was used. Response surface methodology is a collection of mathematical and statistical techniques that are used in the modeling and analysis of problems in which a response of interest is influenced by several variables and the objective is to optimize this response. This method was applied to the resistance spot welding process of the TRIP steel to optimize the welding parameters.

• 대한기계학회논문집A
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• 제34권7호
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• pp.881-889
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• 2010

체적 적분방정식법(Volume Integral Equation Method)이라는 새로운 수치해석 방법을 이용하여, 서로 상호작용을 하는 등방성 함유체를 포함하는 등방성 무한고체가 정적 인장하중을 받을 때 무한고체 내부에 발생하는 응력분포 해석을 매우 효과적으로 수행하였다. 즉, 등방성 기지에 다수의 등방성 함유체가 1) 정사각형 배열 형태 또는 2) 정육각형 배열 형태로 포함되어 있는 경우에, 다양한 함유체의 체적비에 대하여, 중앙에 위치한 등방성 함유체와 등방성 기지의 경계면에서의 인장응력 분포의 변화를 구체적으로 조사하였다. 또한, 체적 적분방정식법을 이용한 해를 해석해 또는 유한요소법을 이용한 해와 비교해 봄으로서, 체적 적분방정식법을 이용하여 구한 해의 정확도를 검증하였다.

• 한국지구과학회지
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• 제22권4호
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• pp.292-300
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• 2001

1997년 12월 이후 남한 중부지역에서 방생한 지진 중 13개 지진에 대하여, 지역에 따라 5개 그룹으로 구분하여 P 파 극성을 이용하여 구한 복합단층면해와 P, S파 극성 및 진폭비(SV/P, SH/P, SV/SH)를 이용하여 구한 결과를 비교 해석하였다. 지진원에서의 단층운동은 NNE-SSW와 WNW-ESE 방향의 단층면을 나타내며 주향이동 혹은 역단층성 주향이동운동이 우세하게 나타났다. 단층운동에 작용한 주압축응력방향은 ENE-WSW 방향, 혹은 NE-SW 방향을 나타내며, 이는 남한지역에 발생하는 주요 지진에 대하여 구해진 주압축 응력장 방향과 거의 일치한다.

• Preventive Nutrition and Food Science
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• 제14권4호
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• pp.323-328
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• 2009

Cryotin F could be used for hydrolyzing shrimp byproducts into bioactive ingredients, which could be used as value-added products. The objective of this study was to investigate the optimum condition for antioxidative activities of the enzymatic hydrolysate produced with Cryotin F using response surface methodology with central composite rotatable design. Shrimp byproducts (shells and heads) were hydrolyzed with Cryotin F. The experimental ranges of the independent variables for 20 experimental runs were 28.2-61.8${^{\circ}C}$ reaction temperature, pH 6-10 and 0.5-5.5% enzyme concentration. The degree of hydrolysis for the reaction products was measured. Their antioxidative activities were measured using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging activity and Fe-chelating activity. The experimental method with central composite rotatable design was well designed to investigate the optimum condition for biofunctional ingredients with antioxidative activities using Cryotin F because of their high R2 values of 0.97 and 0.95 for DPPH-scavenging activity and Fe-chelating activity, respectively. Change in enzyme concentration did not significantly affect their antioxidative activities (p<0.05). Both DPPH scavenging activity and chelating activity against Fe for the enzyme hydrolysates were more affected by the pH of enzyme hydrolysis than by their action temperature. DPPH-scavenging activity was higher at acidic pH than alkali pH, while chelating activity against Few was inversely affected. Hydrolysate of shrimp byproducts showed high antioxidative activities depending on the treatment condition, so the optimum treatment of enzymatic hydrolysate with Cryotin F and other proteases can be applied to shrimp byproducts (shells) and other protein sources for biofunctional ingredients.

• Membrane and Water Treatment
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• 제7권2호
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• pp.127-141
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• 2016

Electrodialysis (ED) is known to be a useful membrane process for desalination, concentration, separation, and purification in many fields. In this process, it is desirable to work at high current density in order to achieve fast desalination with the lowest possible effective membrane area. In practice, however, operating currents are restricted by the occurrence of concentration polarization phenomena. Many studies showed the occurrence of a limiting current density (LCD). The limiting current density in the electrodialysis process is an important parameter which determines the electrical resistance and the current utilization. Therefore, its reliable determination is required for designing an efficient electrodialysis plant. The purpose of this study is the development of a predictive model of the limiting current density in an electrodialysis process using response surface methodology (RSM). A two-factor central composite design (CCD) of RSM was used to analyze the effect of operation conditions (the initial salt concentration (C) and the linear flow velocity of solution to be treated (u)) on the limiting current density and to establish a regression model. All experiments were carried out on synthetic brackish water solutions using a laboratory scale electrodialysis cell. The limiting current density for each experiment was determined using the Cowan-Brown method. A suitable regression model for predicting LCD within the ranges of variables used was developed based on experimental results. The proposed mathematical quadratic model was simple. Its quality was evaluated by regression analysis and by the Analysis Of Variance, popularly known as the ANOVA.

• 청정기술
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• 제20권3호
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• pp.314-320
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• 2014

이번 연구의 목적은 세계적으로 널리 이용되고 있고, 액화 효율이 높은 Air Products and Chemicals Inc. (APCI)사(社)의 C3MR(Propane Pre-cooled & Mixed Refrigerants) 천연가스 액화공정에 사용되는 혼합냉매의 최적 조성을 통계학적 기법으로 결정하는 것이다. 공정모사는 상업 공정 모사기를 이용했으며 혼합냉매는 methane ($C_1$), ethane ($C_2$), propane ($C_3$)과 nitrogen ($N_2$)로 선택하였다. 그리고 혼합물 설계(mixture design, MD)와 중심합성계획법(central composite design, CCD)을 이용하여 전체 공정의 에너지 소비가 최소가 되게 하는 최적의 혼합냉매 조성을 결정하였다. 연구결과 기존 설계 대비 최대 11.28%의 에너지 소비 절감을 확인하였다. 또한 주 극저온 열교환기(main cryogenic heat exchanger, MCHE)의 온도 프로파일을 통해 열적 효율성도 함께 비교하였다.

• Journal of Microbiology and Biotechnology
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• 제22권1호
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• pp.92-99
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• 2012

The optimal physical factors affecting enzyme production in an airlift fermenter have not been studied so far. Therefore, the physical parameters such as aeration rate, pH, and temperature affecting PLA-degrading enzyme production by Actinomadura keratinilytica strain T16-1 in a 3 l airlift fermenter were investigated. The response surface methodology (RSM) was used to optimize PLA-degrading enzyme production by implementing the central composite design. The optimal conditions for higher production of PLA-degrading enzyme were aeration rate of 0.43 vvm, pH of 6.85, and temperature at $46^{\circ}C$. Under these conditions, the model predicted a PLA-degrading activity of 254 U/ml. Verification of the optimization showed that PLA-degrading enzyme production of 257 U/ml was observed after 3 days cultivation under the optimal conditions in a 3 l airlift fermenter. The production under the optimized condition in the airlift fermenter was higher than un-optimized condition by 1.7 folds and 12 folds with un-optimized medium or condition in shake flasks. This is the first report on the optimization of environmental conditions for improvement of PLA-degrading enzyme production in a 3 l airlift fermenter by using a statistical analysis method. Moreover, the crude PLA-degrading enzyme could be adsorbed to the substrate and degraded PLA powder to produce lactic acid as degradation products. Therefore, this incident indicates that PLA-degrading enzyme produced by Actinomadura keratinilytica NBRC 104111 strain T16-1 has a potential to degrade PLA to lactic acid as a monomer and can be used for the recycle of PLA polymer.

• Journal of Microbiology and Biotechnology
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• 제29권7호
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• pp.1061-1070
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• 2019

In the present study, the optimization of poly(${\gamma}$-glutamic acid) (${\gamma}$-PGA) production by Bacillus sp. FBL-2 was studied using a statistical approach. One-factor-at-a-time method was used to investigate the effect of carbon sources and nitrogen sources on ${\gamma}$-PGA production and was utilized to select the most significant nutrients affecting the yield of ${\gamma}$-PGA. After identifying effective nutrients, response surface methodology with central composite design (CCD) was used to obtain a mathematical model to identify the optimum concentrations of the key nutrients (sucrose, $\text\tiny{L}$-glutamic acid, yeast extract, and citric acid) for improvement of ${\gamma}$-PGA production. The optimum amount of significant medium components appeared to be sucrose 51.73 g/l, $\text\tiny{L}$-glutamic acid 105.30 g/l, yeast extract 13.25 g/l, and citric acid 10.04 g/l. The optimized medium was validated experimentally, and ${\gamma}$-PGA production increased significantly from 3.59 g/l (0.33 g/l/h) to 44.04 g/l (3.67 g/l/h) when strain FBL-2 was cultivated under the optimal medium developed by the statistical approach, as compared to non-optimized medium.

• Bulletin of the Korean Chemical Society
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• 제27권7호
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• pp.991-994
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• 2006

Herein, insoluble single-walled carbon nanotube (SWNT) was successfully dispersed into water in the presence of a special kind of surfactant-dicetyl phosphate (DCP), subsequently, a SWNT-DCP composite film coated glassy carbon electrode (GCE) was fabricated. The electrochemical behaviors of 6-benzylaminopurine (6-BAP) at the unmodified GCE and SWNT-DCP modified GCE were examined. It is found that the SWNT-DCP modified GCE remarkably enhances the oxidation peak current of 6-BAP, indicating great potential in the determination of trace level of 6-BAP. Finally, a sensitive and simple voltammetric method with a good linear relationship in the range of ${\times}5.0\;\;10^{-8}\sim 2.5\;{\times}\;10^{-6}$ mol/L, was developed for the determination of 6-BAP. The detection limit is as low as $2.0\;{\times}\;10^{-8}$ mol/L for 3-min accumulation. This newly-proposed method was successfully demonstrated with practical samples.