• 유기물자원화
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• 제15권4호
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• pp.131-137
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• 2007

황산염 환원조건에서의 리그노셀룰로오스의 분해에 대하여 고찰하였다. 특히, 리그닌에 대한 셀룰로오스의 비(C/L 비)를 각각 42.15, 4.59, 2.51, 1.14, 0.7로 하여 리그닌과 셀룰로오스의 상호작용에 대하여 고찰하였다. 셀룰로오스의 분해율은 1차 반응식에 의해 계산되어져, C/L 비가 감소할수록 반응상수는 감소하여 셀룰로오스의 분해에 대한 리그닌의 저해작용을 보여 주였다. 1차 반응식에 의한 반응상수와 리그닌의 함량의 증가에 대한 셀룰로오스의 분해율은 0.97의 $R^2$ 값을 가지며 로그힘수에 의해 표현할 수 있었다. 리그노셀룰로오스의 분해율 또한 C/L 비와 로그함수의 관계를 가지며 리그닌의 함량이 많을수록 감소하였다. 리그닌의 분해율은 C/L 비가 2.51 및 1.14인 조건에서 4.59 및 0.7의 조건보다 높게 나타나, 공동기질로서의 과도한 탄소원은 리그닌분해에 장애가 됨을 보여 주였다.

• 설비공학논문집
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• 제8권4호
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• pp.519-526
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• 1996

A 2D-LDV system was employed to investigate the flow field characteristics in fully developed drag reducing turbulent channel flows. The additive used in this study was Habon-G which showed splendid drag reduction effect and minimum mechanical degradation trend in the closed flow circulation loop. In order to have better understanding of the drag reduction mechanism, the instantaneous velocities were carefully measured under various experimental conditions and the flow characteristics including time-averaged velocity, turbulent intensity and Reynolds shear stresses were carefully assessed. The time-averaged velocity profiles of surfactant flows showed more parabolic shape(typically shown in a laminar flow) together with significant suppression of turbulent production, yielding the shear induced micelle structure orienting in the flow direction due to its isotropic characteristics. Especially it was observed that the maximum intensity for drag reducing flows was shifted away from the wall and that the streamwise and normal turbulent intensities were strongly altered. This phenomenon strongly suggests that the viscous sublayer becomes thicker with addition of surfactant. Turbulent momentum transport was drastically suppressed across the whole drag reducing channel flow.

• 미생물학회지
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• 제50권3호
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• pp.254-260
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• 2014

황화합물은 혐기성환경에서 혐기성호흡을 위한 매우 중요한 전자수용체이다. 본 연구를 통하여 한국의 다양한 습지에서 배양을 통한 황산염/황-환원세균의 특성연구를 실시하였다. 이를 분리하기 위하여 혐기성 roll tube법을 통해 총 11개의 순수 배양체를 확보하였다. 16S rDNA를 이용한 계통분석 및 상동성 분석을 실시하여 Desulfovibrio 속의 세균 8종, Sulfurospirillum 속의 세균 2종, Desulfitobacterium 속의 세균 1종을 얻을 수 있었다. 이들 황산염/황-환원세균은 모두 lactate와 pyruvate를 전자공여체로 이용하였으며, sulfite and thiosulfate를 전자수용체로 이용할 수 있었다. 앞으로, 다양한 전자공여체와 배양조건을 통하여 유용한 절대혐기성 황산염/황-환원세균의 생물자원 확보에 기여할 것으로 기대된다.

• 한국조리학회지
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• 제23권8호
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• pp.90-97
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• 2017

This study investigated optimal extraction conditions for application of Hippophae rhamnoides leaves as a natural antioxidant. Hippophae rhamnoides leaves were extracted using ethanol at various concentrations (0, 30, 50, and 70%) and extraction times (4, 8, and 12 hrs) at $70^{\circ}C$ and then evaluated for extraction yield (22.51%), total phenolic contents (84.21~149.25 mg/g), total flavonoid contents (63.10~124.14 mg/g), as well as antioxidant activities DPPH, ABTS radical scavenging activity, reducing power, and FRAP. Antioxidant activities (DPPH, ABTS radical scavenging activity, reducing power) were correlated with total phenolic and flavonoid contents. 70% EtOH extracts for 12 h at $70^{\circ}C$ showed the highest total phenolic and flavonoid contents with strong antioxidant activities, and that the leaves of Hippophae rhamnoides could be considerd as a candidate of new functional antioxidant agents. This extract could be a good source for natural antioxidants and good health food. This work offers would be useful for chemical and biological studies of natural plants and its products.

• 한국분말재료학회지
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• 제20권3호
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• pp.191-196
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• 2013

Nano-sized cobalt powder was fabricated by wet chemical reduction method at room temperature. The effects of various experimental variables on the overall properties of fabricated nano-sized cobalt powders have been investigated in detail, and amount of NaOH and reducing agent and dropping speed of reducing agent have been properly selected as experimental variables in the present research. Minitab program which could find optimized conditions was adopted as a statistic analysis. 3D Scatter-Plot and DOE (Design of Experiments) conditions for synthesis of nano-sized cobalt powder were well developed using Box-Behnken DOE method. Based on the results of the DOE process, reproducibility test were performed for nano-sized cobalt powder. Spherical nano-sized cobalt powders with an average size of 70-100 nm were successfully developed and crystalline peaks for the HCP and FCC structure were observed without second phase such as $Co(OH)_2$.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.11-19
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• 2020

In recent years, oil prices have continued to be low owing to the development of unconventional resources such as shale gas, coalbed methane gas, and tight gas. However, shipping companies are still experiencing difficulties because of recession in the shipping market. Hence, they devote considerable effort toward reducing operating costs. One of the important parameters for reducing operating costs is the frictional resistance of vessels. Generally, a vessel is covered with paint for smoothing its surface. However, frictional resistance increases with time owing to surface roughness, such as that caused by fouling. To prevent this, shipping companies periodically clean or repaint the surfaces of vessels using analyzed operating data. In addition, studies using various methods have been continuously carried out to identify this phenomenon such as fouling for managing ships more efficiently. In this study, numerical simulation was used to analyze the change in the resistance performance of a ship owing to an increase in surface roughness using commercial software, i.e., Star-CCM+, which solves the continuity and Navier eStokes equations for incompressible and viscous flow. The conditions for numerical simulation were verified through comparison with experiments, and these conditions were applied to three ships to evaluate resistance performance according to surface roughness.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.543-547
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• 2000

Power factor and harmonics are increasingly important for high speed train auxiliary block. This paper presents experimental results of the power factor and harmonic performance of two parallel PWM circuits under various supply and load conditions. For reducing harmonics the harmonic content is eliminated by the phase shift between two converters switching phase. Experimental results show the usefulness of the proposed method and applicability to PWM converter in auxiliary block of high speed train.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.274-277
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• 2000

Power factor and harmonics are increasingly important for high speed train auxiliary block. This paper presents experimental results of the power factor and harmonic performance of four parallel PWM converter circuits under various supply and load conditions. For reducing harmonics the harmonic content is eliminated by the phase shift between four converters switching phase. Experimental results show the usefulness of the proposed method and applicability to PWM converter in auxiliary block of high speed train.

• 소성∙가공
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• 제6권2호
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• pp.161-175
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• 1997

The effects of various process paramenters on the detailed aspects of the thermo-mechanical behavior of work roll and on the roll life are investigated via a series of process simulation, using a mathematical model presented previously. The process conditions are discussed that are favorable or optimal in terms of reducing roll wear in the front finishing stands.

• 대한한방소아과학회지
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• 제28권1호
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• pp.61-70
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• 2014

Objectives The purpose of this study is to report three cases of epileptic children who were treated by oriental medicine. Methods Three epileptic children were treated by Gwakhyangjeonggi-san and Kuibiondam-tang. Two children had took combination therapy; anti-epilepsy drugs and oriental medicines and the other one took only oriental medicines. We measured frequency and intensity of seizure, and observed general conditions. Results The oriental medicine treatment is not only reducing seizures, but also improving general condition like digestion, constipation and reducing frequency of common cold and symptom of rhinitis. Conclusions Epilepsy in childhood is induced by various factor like Fung (風), Dam (痰), Sik (食), Kyung (驚). We administrated oriental medicine and prevented seizures.