• Food Science and Biotechnology
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• 제17권5호
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• pp.904-911
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• 2008

Covalent cross-links between a number of proteins and peptides explain why transglutaminase may be widely used by food processing industries. The objective of this work was optimization of the fermentation process to produce transglutaminase from a new microbial source, the Streptomyces sp. P20. The strategy adopted to modify the usual literature media was: (1) fractional factorial design (FFD) to elucidate the key medium ingredients, (2) central composite design (CCD) to optimise the concentration of the key components. Optimization of the medium resulted in not only an 86% increase in microbial transglutaminase activity as compared to the media cited in the literature, but also a reduction in the production cost. Optimal fermentation conditions - namely temperature and agitation rate - were also studied, using CCD methodology. Usual conditions of $30^{\circ}C$ and 100 rpm were within the optimal area. All other parameters for enzyme production were experimentally proven to be optimum fermentation conditions.

• International Journal of Fluid Machinery and Systems
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• 제9권3호
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• pp.229-236
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• 2016

Exergetic analysis was introduced in optimization of a rotating equilateral triangular internal cooling channel with staggered square ribs to maximize the net exergy gain. The objective function was defined as the net exergy gain considering the exergy gain by heat transfer and exergy losses by friction and heat transfer process. The flow field and heat transfer in the channel were analysed using three-dimensional Reynolds-averaged Navier-Stokes equations under the uniform temperature condition. Shear stress transport turbulence model has been selected as a turbulence closure through the turbulence model test. Computational results for the area-averaged Nusselt number were validated compared to the experimental data. Three design variables, i.e., the angle of rib, the rib pitch-to-hydraulic diameter ratio and the rib width-to-hydraulic diameter ratio, were selected for the optimization. The optimization was performed at Reynolds number, 20,000. Twenty-two design points were selected by Latin hypercube sampling, and the values of the objective function were evaluated by the RANS analysis at these points. Through optimization, the objective function value was improved by 22.6% compared to that of the reference geometry. Effects of the Reynolds number, rotation number, and buoyancy parameter on the heat transfer performance of the optimum design were also discussed.

• 한국산학기술학회논문지
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• 제18권1호
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• pp.15-20
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• 2017

볼밸브는 밸브의 가운데 구멍이 뚫린 구 모양의 볼이 회전에 의해 구멍을 닫거나 열어 밸브를 개폐시킨다. 본 연구에서는 플랜트장치용 고온용 볼밸브에 관한 것으로써, 사용되는 유체는 고온의 스팀을 사용하는 볼밸브이다. 고온의 스팀을 유체로 사용함에 따라 볼밸브에 열응력이 발생하기 때문에 초기모델에서의 열-구조 연성해석을 실시하여 고온용 볼밸브의 구조적 안정성을 검토하였다. 검토한 결과 폴리테트라 플루오르에틸렌 재질의 시트에서 항복응력 이상의 값이 나타나였다. 본 연구에서는 시트의 최적화를 실시하여 항복응력 이내의 구조적 안정성을 찾고자 하였다. 시트의 최적화를 위해 2개의 형상설계 변수를 선정하였고, 최적화 과정 중에 설계요구조건으로 시트의 길이와 두께에 관련하여 기준을 고려하였다. 시트의 응력과 질량을 고려한 30개의 표본점을 만들어 최적화 과정을 진행하였으며, 최적화 기법으로서 크리깅 내삽법을 이용한 메타모델 최적화 방법을 적용하였다. 그 결과 항복응력 이내의 구조적 안전성을 만족하는 시트의 두께와 길이를 찾을 수 있었고, 이에 따른 개도별 유동해석을 실시하여 볼밸브의 성능지표를 나타내는 유량계수 값을 구하여 볼밸브의 성능을 검토하였다.

• Journal of Biosystems Engineering
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• 제41권1호
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• pp.34-42
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• 2016

Purpose: This study was performed to improve the drying quality and drying rate of ginseng slices by combining microwave and far-infrared drying techniques. Methods: Based on single-factor experiments and analyses, a quadratic regression orthogonal rotation combination design was adopted to study the effects of the moisture content at the conversion point between the microwave and far-infrared techniques, the ginseng slice thickness and the far-infrared drying temperature on the chip drying time, the surface color difference value, the nutritional composition and the surface shrinkage rate index. Results: Compared to the far-infrared drying alone, the combined microwave and far-infrared drying resulted in an increase in the saponin content of the ginseng slices and reductions in the drying time, surface color difference, and shrinkage rate. Conclusions: We established a mathematical model of the relationships between the surface shrinkage rate index and the experimental factors using the multi-objective nonlinear optimization method to determine the optimal parameter combination, which was confirmed to be the following: microwave and far-infrared moisture contents of 65%, a ginseng slice thickness of 1 mm, and a far-infrared drying temperature of $54^{\circ}C$.

• 한국자동차공학회논문집
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• 제24권1호
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• pp.90-98
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• 2016

Currently government certified test method for an automobile remanufactured products is insufficient. Thus many automotive parts in the remanufacturing market are lacking proper evaluation criteria and production of defective products are causing customer dissatisfaction. In this paper a power steering oil pump, which requires stringent manufacturing standards, is studied by the failure mode and effect analysis approach. The research suggested that the test criteria such as discharge flow characteristic test, tightness test, pulley run-out test, pressure switch operation test, low temperature test and rotation pressure durability test should be performed to evaluate the reliability of remanufactured power steering oil pumps. As a result of tests, the performance of remanufactured power steering oil pump satisfied the evaluation criteria of pressure switch operation test and low temperature test. However, the remanufactured power steering oil pump failed to satisfy the evaluation criteria on discharge performance test, tightness test and pulley run-out test. These performance evaluation tests proved the necessity of standard process for the remanufactured power steering oil pump.

• 대한기계학회논문집A
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• 제41권11호
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• pp.1125-1130
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• 2017

$170^{\circ}C$의 고온에서 작동하는 자동변속기 토크컨버터의 리액터와 끝단 레이스 두 부품간 이빨이 서로 맞닿는 부분의 응력을 분산시키고, 수명을 증가시키기 위하여 치(이빨), 스플라인 두 형태의 리액터의 치형상을 FEM 최적화하였다. 최적화에 선행하여 서로 다른 재료로 된 두 부품의 열팽창에 의한 간격을 해석하였으며, 그 결과 열팽창 후에 치형 리액터는 약 0.1 mm, 스플라인형 리액터는 약 0.08 mm의 추가 간격이 발생한다는 것을 확인하였다. 형상최적화 결과 두 가지 형태의 리액터 치가 모두 비대칭 사다리꼴 형상으로 최적화 되었다. 이로 인해 치형 리액터의 경우 기존 비최적화 모델 대비, 최대등가응력이 24.5 % 감소하였으며, 스플라인형 리액터는 기존 비최적화 모델 대비 최대등가응력은 9.3 % 감소하였으며, 축 방향 두께는 13 % 감소하였다.

• 산업경영시스템학회지
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• 제39권1호
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• pp.130-139
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• 2016

The purpose of this paper is to analyze the problems and the sources of defective products and draw improvement plans in a small plastic boat manufacturing process using TOC (Theory Of Constraints) and statistical analysis. TOC is a methodology to present a scheme for optimization of production process by finding the CCR (Capacity Constraints Resource) in the organization or the all production process through the concentration improvement activity. In this paper, we found and reformed constraints and bottlenecks in plastic boat manufacturing process in the target company for less defect ratio and production cost by applying DBR (Drum, Buffer, Rope) scheduling. And we set the threshold values for the critical process variables using statistical analysis. The result can be summarized as follows. First, CCRs in inventory control, material mix, and oven setting were found and solutions were suggested by applying DBR method. Second, the logical thinking process was utilized to find core conflict factors and draw solutions. Third, to specify the solution plan, experiment data were statistically analyzed. Data were collected from the daily journal addressing the details of 96 products such as temperature, humidity, duration and temperature of heating process, rotation speed, duration time of cooling, and the temperature of removal process. Basic statistics and logistic regression analysis were conducted with the defection as the dependent variable. Finally, critical values for major processes were proposed based on the analysis. This paper has a practical importance in contribution to the quality level of the target company through theoretical approach, TOC, and statistical analysis. However, limited number of data might depreciate the significance of the analysis and therefore it will be interesting further research direction to specify the significant manufacturing conditions across different products and processes.

• 한국산학기술학회논문지
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• 제18권10호
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• pp.8-14
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• 2017

최근 들어 국민 식생활 문화가 개선되고 생활수준이 향상됨에 따라 소프트 아이스크림, 슬러시와 같은 일회용 냉동 유제품의 소비가 급증하고 있다. 이들 냉동 유제품은 소형 냉동 시스템에서 만들어진다. 소프트 아이스크림 제조기의 경우 냉각기는 동심 원통으로 구성되며 냉매는 환형부에서 증발하고 냉각기 표면에 형성된 얼음 결정이 내측에서 회전하는 스크레이퍼에 의해 빙삭되어 아이스크림이 만들어진다. 본 연구에서는 냉각기 체적 2.8 리터인 R-404A를 사용하는 소프트 아이스크림 제조기에 대하여 최적화와 성능평가를 수행하였다. 최적화는 냉각기 스크레이퍼 회전수 및 냉매 유로 개선에 주안점을 두고 실제 아이스크림 제조기에서 요소 부위의 온도와 압력 그리고 소비동력을 측정함으로써 수행되었다. 실험 결과 최적 회전수는 124 rpm으로 나타났다. 이 회전수에서 아이스크림 제조 시간은 6분 2초이고 이 때 성적계수는 0.90이었다. 또한 물-공기를 사용한 가시화 실험을 통하여 냉매측 유로 개선을 시도하였다. 유로가 개선된 제품은 아이스크림 제조 시간을 현저히 감소시켰다. 본 연구 결과는 냉동식품 제조기를 비롯한 여타 냉동 사이클의 최적화에도 활용될 수 있을 것이다.

• Korean Chemical Engineering Research
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• 제53권3호
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• pp.327-332
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• 2015

A large amount of dye wastewater poses a threat to environmental safety. Disperse blue, an anthraquinone dye that is widely used in textile dyes, is difficult to degrade in wastewater. In this work, one fungus was screened according to the decolorization rate of disperse blue. The fungus was identified and named Aspergillus XJ-2 on the basis of its morphological characteristics and 18s rDNA. Response surface method was used to optimize culture conditions for A. XJ-2. The optimum values of obtained responses were as follows: temperature, $35^{\circ}C$; pH, 5.2; carbon-to-nitrogen ratio, 30:5.5; and rotation ratio, $175r{\cdot}min^{-1}$. Under optimized conditions, the decolorization rate of A. XJ-2 was up to 94.8% in 48 h.

• Macromolecular Research
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• 제17권6호
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• pp.411-416
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• 2009

The color stabilization of antimicrobial blends was studied by using poly(hexamethylene guanidine) phosphate (PHMG) as a highly efficient biocidal and nontoxic agent. The Taguchi method was used to determine the optimum conditions for the blending of PHMG in polypropylene (PP) matrix. To improve the yellowing phenomena, two kinds of stabilizer were used together: tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)](IN1010) from phenol and tris(2,4-di-t-butylphenylphosphite) (IF168) from phosphorus. According to blend composition and mixing condition, six factors were chosen, with five levels being set for each factor. The orthogonal array was selected as the most suitable for fabricating the experimental design, L25, with 6 columns and 25 variations. The-smaller-the-better was used as an optimization criterion. The optimum conditions for these parameters were 10 phr for PHMG, 2 phr for IN1010, 1 phr for IF168, 10 min for mixing time, $210^{\circ}C$ for mixing temperature, and 30 rpm for rotation speed. Under these conditions, the yellowness index of the blend was 1.52. The processibility of the blends was investigated by Advanced Rheometric Expansion System (ARES). The blend with 0.5 w% PHMG content, diluted with PP, exhibited an antimicrobial characteristic in the shake flask method.