• Journal of Advanced Marine Engineering and Technology
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• 제21권4호
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• pp.421-429
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• 1997

This study is theoretically examined the influences on the performance of diesel engine super¬charged by exhaust gas turbine with the change of excess air factor, admission ratio, total efficien¬cy of turbine and compressor, scavenging pressure ratio, and scavenging temperature. In this study, all calculations are carried out by computer, and the theoretical engine performance is com¬pared with the actual engine performance which is offered from engine manufacturer. Following results are acquired by this study. The mean effective pressure is increased with decrease of excess air factor or increase of scavenging pressure ratio. As the admission ratio or total efficiency of tur¬bine is increased, the mean effective pressure is increased but the specific fuel consumption is decreased. Mean calculation error compared with the actual engine performance is under 5 per¬cents, therefore, this calculation method can be used in the design of diesel engine.

• 대한환경공학회지
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• 제36권8호
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• pp.534-541
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• 2014

본 논문은 먹는물 처리공정에 적합한 고도산화공정 중 하나인 자외선/과산화수소공정의 효율적인 운전을 위한 최적 운전 조건을 도출하는 방법을 연구하였다. 자외선/과산화수소 공정에서 대상물질의 제거효율을 예측하고 그에 따른 운전조건을 도출하기 위한 핵심 인자인 수산화라디칼 소모인자를 보다 쉽고 빠르게 측정하기 위해 새로운 지표물질인 로다민 비(Rhodamin B, RhB)를 선정하여 검증하였다. 그 결과, 기존 지표물질인 para-Chlorobenzoic acid (pCBA)와 비교해 약 1.1% 이하의 오차율로 높은 신뢰성을 가진 것을 확인하였다. 검증된 RhB를 이용하여 측정한 수산화라디칼 소모인자 및 모델링을 통해 대상물질(Ibuprofen)의 제거효율 예측 가능성을 평가한 결과, 실제 실험값과 평균 오차율 약 5% 내외로 거의 일치하였다. 약 8개월간의 자외선/과산화수소공정 파일럿 플랜트 유입수의 수산화라디칼 소모인자 모니터링 결과, 최대 두 배 정도의 차이로 크게 변화하였다. 이 차이는 미량오염물질 중 하나인 Caffeine의 목표 제거율을 만족하기 위한 자외선 에너지를 약 1.7배 증가시켜야 할 정도로 큰 값이다. 이상의 결과를 통해 자외선/과산화수소 공정을 안전하고 효율적으로 운전하기 위해서는 수산화라디칼 소모인자의 측정이 매우 중요하며, 측정된 소모인자, 자외선 흡광도($A_{254}$), 대상물질의 정보만 입력하면 자외선/과산화수소 공정을 쉽게 제어할 수 있음을 확인하였다.

• 한국자원식물학회지
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• 제36권6호
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• pp.549-555
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• 2023

Hijikia fusiforme (HF), a member of brown algae family, exerts various pharmacological effects, including preventing arteriosclerosis and menopausal disorders. This study aimed to elucidate the ameliorative effect of HF on skin inflammation. We investigated the antioxidant and anti-inflammatory effect of HF extract to evaluate its potential as a functional materials. The antioxidant activity of HF was determined using 2,2-diphenyl-1-picrylhydrazy (DPPH) scavenging and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) scavenging. To determine the pharmacological mechanism of HF in inflammatory reaction, we evaluated the effects of HF on interleukin (IL)-8, IL-6 and tumor necrosis factor (TNF)-α production and nuclear factor-κB (NF-κB) activation in activated- human mast cells (HMC)-1. Results showed that HF had the high DPPH and ABTS+ radical scavenging activity, and it suppressed IL-8, IL-6 and TNF-α production in a concentration-dependent manner. Moreover, HF significantly ameliorated NF-kB activation in activated-HMC-1. Hence, these results provide evidence that HF's potential for skin inflammation therapy.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.55-63
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• 2003

In a diesel engine, air-fuel mixture formation and ignition delay period have great influence on the performance of engine. Their main factors are combustion chamber shape, fuel injection system. air volume, air flow and so on. So, the combustion process in the cylinder is complex because of many factors which have direct and indirect effects on it. In this study, we take into consideration of scavenging pressure and scavenging temperature that are hewn as the main factor to the combustion process of two-stroke D.1. diesel engine. It is taken a picture of the combustion flame process for combustion chamber of re-entrant type and cylindrical type. So, it is applied to the basis data of combustion chamber design from an image analysis.

• 한국자동차공학회논문집
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• 제2권5호
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• pp.48-57
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• 1994

The specific power output and thermal effeciency of any two-stroke engine are dependent on its scavenging behavior. Among the many factors which influence on the scavenging process, the cylinder head shape is one of the important factor. Hence in this study three different type models of cylinder head shape which are the cylindrical, the spherical and the arbitrary shape are studied to show the effects of the turbulent scavenging process in the cylinder with one inlet port, two side ports and one exhaust port. A modified version of KIVA-II which strip out of or add planes of cells across the mesh above the piston for flow simulation of two-stroke engine is used. The $k-{\varepsilon}$ turbulent model is used. The results show that the flow in a two-stroke engine cylinder of the spherical head shape among the three different type model is a desirable for efficient scavenging.

• Preventive Nutrition and Food Science
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• 제18권3호
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• pp.196-202
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• 2013

Citron seed extracts (CSEs) were made using distilled water (CSEW), ethanol (CSEE), and n-hexane (CSEH), to measure the total polyphenol contents, DPPH and ABTS radical scavenging activities, and anti-complementary activity. The total polyphenol content was observed the highest in CSEE (188.71 ${\mu}g/mL$), and occurred in the following order: CSEE>CSEW (141.11 ${\mu}g/mL$)>CSEH (26.19 ${\mu}g/mL$) at 10 mg/mL. CSEE (63.56%) and CSEW (56.61%) showed significantly higher DPPH radical scavenging activities when compared with CSEH (28.57%). ABTS radical scavenging activities of CSEE (45.53%) and CSEW (40.02%) were also observed to be higher, whereas CSEH did not show ABTS radical scavenging activity. Anti-complementary activity of CSEE (26.85%) showed a greater activity than that of CSEW (7.84%) at 1,000 ${\mu}g/mL$. Limonin and nomilin contents had the highest values (1.882% and 2.089%) in CSEE, and with 0.327% and 0.139% in CSEW; however, CSEH showed relatively very low values at 0.061% and 0.026%, respectively. Among the CSEs tested, CSEE as a by-product from citron may provide an important source of dietary antioxidant compounds with rich polyphenol and limonoid contents, and immunopotentiating activity, including the complement activation factor.

• Fisheries and Aquatic Sciences
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• 제25권6호
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• pp.335-349
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• 2022

To optimize the hydrolysis conditions in the production of antioxidant hydrolysates from tuna cooking juice concentrate (TC) to maximize the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, TC containing 48.91% protein was hydrolyzed with Alcalase 2.4 L, and response surface methodology (RSM) was applied. The optimum hydrolysis conditions included a 2.2% (w/v) Alcalase concentration and 281 min hydrolysis time, resulting in the highest DPPH radical scavenging activity of 66.49% (0.98 µmol Trolox/mg protein). The analysis of variance for RSM showed that hydrolysis time was an important factor that significantly affected the process (p < 0.05). The effects of different drying methods (freeze drying, hot air drying, and vacuum drying) on the DPPH radical scavenging activity and amino acid (AA) profiles of TC hydrolysate (TCH) were evaluated. Vacuum-dried TCH (VD) exhibited an increase in DPPH radical scavenging activity of 81.28% (1.20 µmol Trolox/mg protein). The VD samples were further fractionated by ultrafiltration. The AA profiles and antioxidant activities in terms of the DPPH radical scavenging activity, 2,2'-azino-bis(3-ethylbenzthiazoline)-6-sulfonic acid (ABTS) radical scavenging activity, ferric reducing antioxidant power, and ferrous ion chelating activity were investigated. Glutamic acid, glycine, arginine, and cysteine were the major AAs found in the TCH fractions. The highest DPPH radical scavenging activity was found in the VD-1 fraction (< 5 kDa). The VD-3 fraction (> 10 kDa) exhibited the highest ABTS radical scavenging activity and ferric reducing antioxidant power. The ferrous ion chelating activity was the highest in VD-1 and VD-2 (5 to 10 kDa). In conclusion, this study provided the optimal conditions to obtain high antioxidant activities through TCH production, and these conditions could provide a basis for the future application of TCH as a functional food ingredient.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.35-43
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• 2006

A four-stroke four-cylinder turbocharged diesel engine can be fitted with various types exhaust system. In this paper, the impacts of exhaust system design on scavenging performance and wave action characteristic during valve overlap are investigated by using one-dimensional gas dynamic code. This work shows that a huge reflected exhaust pressure waves which reaches the exhaust port during valve overlap period is crucial design factor which determines quality and quantity of the fresh charge. Hence pressure wave that reaches the exhaust port of the cylinder during the valve overlap sequence should be weakened for good scavenging performance. This paper describes advantages and disadvantages of the various exhaust systems applied to a turbocharged and intercooled 4-cylinder diesel engine system in terms of scavenging efficiency and engine performance. To verify the computational results, experimental comparison has also performed.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.487-492
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• 2010

For developing a two-stroke free-piston hydrogen engine with high efficiency and low emission, determination of the scavenging type is one of the most important factor. In this research, backfire characteristics for loop scavenging were analyzed with the number of piston crevice volume and piston expansion speed. Rapid Compression Expansion Machine, RCEM was used for combustion research of the free piston $H_2$ engine in the experiment. As the results, it was shown that although backfire occurring in a loop scavenging type can be partially controled by a complete exhaust of burned gas, possibility of backfire basically exist due to the structure which piston crevice volumes contact with fresh mixture in a scavenging port. However, a loop scavenging may be considered as combustion chamber of a free piston $H_2$ engine from the point of view that backfire does not occur nearby lean equivalence ratio obtained high thermal efficiency. It was also analyzed that an advances of backfire occurrence timing with increase of the fuel-air equivalence ratio were due to promotion of flame propagation into piston crevice volumes by decrease of the quenching distance.

• 한국해양바이오학회지
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• 제9권2호
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• pp.43-48
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• 2017

Temperature is a major factor that affects the physiochemical properties of compounds. This study focus on the determination of thermostability and the effect of temperature on antioxidant activities of Ecklonia cava (E. cava) ethanoic extract. The ethanoic extracts of E. cava were evaluated at $30^{\circ}C$, $60^{\circ}C$ and $90^{\circ}C$ for 0 to 7 days. The antioxidant activities were determined by DPPH, hydroxyl radical and hydrogen peroxide scavenging activities. The intracellular reactive oxygen species (ROS) scavenging activity was investigated using DCFH-DA assay. Results revealed that the ethanoic extract of E. cava incubated at different temperatures for 0 to 7 days, showed stable scavenging activities on DPPH, hydroxyl radical and hydrogen peroxide. The ROS scavenging activities of ethanoic extract and ascorbic acid were also investigated. The extract showed a stable ROS scavenging activity from 0 to 7 day at $90^{\circ}C$. However, the scavenging activity of ascorbic acid at $90^{\circ}C$ decreased starting from day 3. These results indicated that the antioxidant effects of this food grade ethanoic extract of E. cava could remain stable during the employed temperatures of food processing.