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해상용 가스터빈의 흡음형 소음기 성능에 대한 3차원 해석적 연구
이창헌(Changheon Lee),백성현(Seonghyeon Baek),권대훈(Baek, Daehun Gwon),이일재(Iljae Lee) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10
Acoustic behavior of dissipative silencers with splitters was analyzed by using 3-dimensional commercial software. An impedance tube setup was used to obtain the flow resistivity of mineral wool. The resistivity is used as an input parameter for the calculation of insertion loss of silencers. The comparison of insertion loss predictions with the experimental results shows reasonable agreements. For large silencers, it needs a large number of elements especially at high frequencies and thus long computation time. To reduce computation time without sacrifice of accuracy, predictions for various partial models were presented. Partial model can be used as a representation of the full model with relatively short computation time. It can be concluded from more predictions with different flow resistivity that lower flow resistivity may decrease the insertion loss, but higher resistivity slightly improves it.
반응표면분석법을 활용한 다시마 김치 유래 유산균의 신바이오틱스 최적화
이창헌(Changheon Lee),심진하(Jin Ha Sim),김진현(Jin Hyeon Kim),송예준(Ye-Jun Song),손은익(Eun-Ik Son),김영목(Young-Mog Kim),유대웅(Daeung Yu) 한국식품영양과학회 2021 한국식품영양과학회지 Vol.50 No.12
Encapsulation 기술은 식품, 화장품 및 제약 등 산업계 전반에서 광범위하게 활용되는 기술로 식품 산업에서도 소재화 등에 널리 활용되고 있다. 본 연구에서는 이러한 encapsulation 기술 및 RSM을 활용하여 대체 피복물질인 프리바이오틱스(INL) 적용에 따른 다시마 김치 유래 Lactobacillus plantarum D-12의 신바이오틱스 최적화를 하고자 하였다. 분무건조 입구 온도의 증가에 따른 유산균 생존율 감소를 확인할 수 있었으며, 제조 수율에서의 피복물질 농도 증가는 일정 농도 초과 시 점도 상승으로 인해 수율의 감소를 야기하였다. 신바이오틱스 제조 조건 최적화에 있어서 최적 프리바이오틱스 농도(x₁)는 32%(w/v), 입구 온도(x₂)는 80℃로 예측되었으며, 이는 예측 최적값 적용에 따른 실측값과 큰 차이가 없었다. 구조분석 결과, 분무건조 적용 시 신바이오틱스 분말 입자가 더 균일하고 encapsulation이 더 규칙적으로 치밀하게 형성되어 분무건조를 적용하는 게 더 적합하다. 본 연구 결과는 INL을 활용한 Lactobacillus plantarum D-12의 신바이오틱스 최적화를 통하여 기존 피복물질 대체 제로 프리바이오틱스의 가능성을 확인하여 프로바이오틱스 산업에 크게 기여할 것으로 사료된다. The purpose of this study was the optimization of the synbiotics of Lactobacillus plantarum D-12 isolated and identified from kelp kimchi with inulin, which is widely used as a prebiotic, using encapsulation technology and response surface methodology (RSM). Inulin concentration [x₁, (w/v)], inlet temperature [x₂, ℃], synbiotics yield (Y₁), and survival rate of L. plantarum D-12 (Y₂) were designated as independent and dependent variables for the optimization of the synbiotics of L. plantarum D-12 using RSM. Y₁ was increased by increasing x₁ and x₂, whereas it decreased at x₁ over 30% due to adhesion loss in the spray dryer vessel due to the increasing stickiness of the synbiotic solution. Y₂ was decreased by increasing x₁ and x₂. Based on the ANOVA result, response models for Y₁ and Y₂ obtained from RSM were suitably fitted to a quadratic model. The predicted optimum x₁ and x₂ were 32% and 80℃. Based on the predicted optimum x values (x₁, x₂), the predicted Y values were 71.70% and 97.43% for Y₁ and Y₂ and the measured Y values were 75.35±0.58% and 98.12±0.46% for Y₁ and Y₂, respectively. The results of this study are expected to contribute to the probiotic industry by confirming the potential of prebiotics as a replacement for existing coating materials through the synbiotic optimization of L. plantarum D-12 with inulin.
발효 다시마(Saccharina japonica) 분말, 미역귀 후코이단 분말 및 이들 혼합분말의 수분 흡습 특성
이창헌 ( Changheon Lee ),심진하 ( Jin Ha Sim ),김진현 ( Jin Hyeon Kim ),유대웅 ( Daeung Yu ) 한국수산과학회(구 한국수산학회) 2021 한국수산과학회지 Vol.54 No.1
The goal of this study was to investigate moisture sorption characteristics of Lactobacillus brevis-fermented sea tangle Saccharina japonica, Mekabu fucoidan, and these mixture powders. Moisture sorption isotherms of powders were determined at 37°C using the static gravimetric technique in a water activity (a<sub>w</sub>) range of 0.11-0.93. Equilibrium moisture content (X<sub>eq</sub>) values of the fermented sea tangle powder were almost 3 times when a<sub>w</sub><0.7 and increased upto almost 4 times when a<sub>w</sub><0.9 higher than mekabu fucoidan powder. In these reason, to improve strong hygroscopic nature of the fermented sea tangle powder, fermented sea tangle and mekabu fucoidan powders were dissolved as ratios of 7:3, 5:5, and 3:7 (w/w) in a distilled water and then freeze dried. X<sub>eq</sub> values of mixture powders were around average value of sum of both powders at all a<sub>w</sub> ranges. All moisture sorption isotherms of powders exhibited typical J-shaped type III. X<sub>eq</sub> of mixture powders increased with increasing a<sub>w</sub> and decreased as increasing proportion of mekabu fucoidan powder. The Peleg model was found to accurately describe moisture sorption isotherms of powders. The results can be used to understand hygroscopic nature of powders, improve shelf life, and retain quality across postharvest processing.
이재윤(Jaeyoon Lee),이상혁(Sanghyeok Lee),김현택(Hyeontaek Kim),박용찬(Yongchan Park),이근진(Geunjin Lee),이창헌(Changheon Lee),최성규(Sunggyu Choi),홍순욱(Soonwook Hong) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.2
In this study, Yttria-stabilized zirconia (YSZ) functional layers were applied with different thin-film fabrication process such as sputtering and atomic layer deposition (ALD) to enhance oxygen reduction reaction (ORR) for solid oxide fuel cells. We confirmed that the YSZ functional layer deposited with sputtering showed relatively low grain boundary density, while the YSZ functional layer deposited with the ALD technique clearly indicated high grain boundary density through scanning electron microscopy (SEM) and X-ray diffractometry (XRD) results. The YSZ functional layer coated with the ALD technique revealed that more ORR kinetics can occur using high grain boundary density than the functional layer deposited with sputtering. The peak power density of the SOFC deposited with ALD YSZ indicates 2-folds enhancement than the pristine SOFC.
대형 스플리터 소음기 성능에 대한 3차원 수치해석적 연구
백성현(Seonghyeon Baek),이창헌(Changheon Lee),권대훈(Daehun Gwon),이일재(Iljae Lee) 한국소음진동공학회 2017 한국소음진동공학회 논문집 Vol.27 No.2
Acoustic performance of splitter silencers was investigated by using 3-dimensional commercial software and experiments. Flow resistivity of sound absorbing material was indirectly estimated by using an impedance tube setup and a curve fitting method. In addition the acoustic impedance of perforated plate was determined by an empirical formulation. Such properties have been used as input parameters in the commercial software. The prediction for a splitter silencer with 1000 ㎜ length was compared with the experimental result. The numerical method is then applied to identify the effects of number of splitters, length of splitters, absorptive material density, and porosity of a perforated plate on the performance of the splitter silencers. As the number and length of splitter increases, the acoustic performance significantly increases. Although the increase of density of absorptive material also increase the acoustic performance, a change in the density over a certain level hardly affect it. The increase of porosity will enhance the performance especially at higher frequencies.