• 한국태양에너지학회 논문집
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• 제22권4호
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• pp.77-84
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• 2002

In order to investigate forced convection heat transfer due to the wind from the inner surface of a cavity receiver for a parabolic dish type solar energy collecting system, a two-dimensional rectangular cavity receiver is prepared and installed in a wind tunnel. The convection heat transfer coefficient of the inner surface of the receiver is dependent on the direction and the velocity of the wind. The attack angle of the cavity and the air velocity in the tunnel are controlled in a wide range so that the effects of the attack angle and the wind velocity on the heat transfer coefficient can be studied. The skirt is installed at the aperture of the cavity in order to reduce convective heat loss. The effects of the length and the installation angle of the skirt on convection heat transfer of the cavity are tested. It is found that convection heat loss can be significantly reduced by installing the skirt. Also, it is known that heat transfer from the cavity can be minimized if the angle of the skirt is $90^{\circ}$ to the outer surface of the cavity.

• Advances in concrete construction
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• 제1권3호
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• pp.201-213
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• 2013

While recognizing the problem of reinforcement corrosion and premature structural deterioration of reinforced concrete (RC) structures as a combined effect of mechanical and environmental actions (carbonation, ingress of chlorides), emphasis is given on the effect of the latter, as most severe and unpredictable action. In this study, a simulation tool, based on proven predictive models utilizing principles of chemical and material engineering, for the estimation of concrete service life is applied on an existing reinforced concrete bridge (${\O}$resund Link) located in a chloride environment. After a brief introduction to the structure of the models used, emphasis is given on the physicochemical processes in concrete leading to chloride induced corrosion of the embedded reinforcement. By taking under consideration the concrete, structural and environmental properties of the bridge investigated, an accurate prediction of its service life is taking place. It was observed that the proposed, and already used, relationship of service lifetime- cover is almost identical with a mean line between the lines derived from the minimum and maximum critical values considered for corrosion initiation. Thus, an excellent agreement with the project specifications is observed despite the different ways used to approach the problem. Furthermore, different scenarios of concrete cover failure, in the case when a coating is utilized, and extreme deicing salts attack are also investigated.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.248-249
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• 2014

Photocatalytic cement is receiving attention due to its high oxidation power that oxidizes nitrogen oxides (NOx), thus contributing to clean atmospheric environment. However, there has not been a thorough investigation on durability of a parent material, cementitious material, as a result of photocatalytic reactions. In this study, durability of photocatalytic cementitious materials exposed to nitrogen dioxide (NO₂) gas was examined. Titanium dioxide (TiO₂) nanoparticles containing cement paste samples were exposed to cycles of NO₂ with UV light, followed by wetting and drying to simulate environmental condition. The surface of samples was characterized mechanically, chemically, and visually during the cycling. The results indicate that the photocatalytic efficiency decreased with continued NO₂ oxidation due to calcium carbonate formation. The pits found from SEM demonstrate that chemical deterioration have occurred, such as acid attack or leaching. In conclusion, the photocatalytic reactions and its product could alter cementitious materials chemically and mechanically which could further affect long-term durability.

• Korean Chemical Engineering Research
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• 제44권6호
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• pp.597-601
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• 2006

고분자 전해질 연료전지에서 산소라디칼(OH, $HO_2$)에 의한 나피온 고분자막의 열화를 연구하였다. 산소라디칼 형성을 위해 과산화수소(10-30％)와 황산암모늄철(1-4ppm)을 이용해 Fenton 용액을 제조하고, $80^{\circ}C$에서 막을 일정 시간 열화 하여 막의 특성 변화를 측정하였다. 열화 후 고분자 막의 C-F, S-O, C-O 결합이 산소 라디칼의 공격으로 끊어짐을 보였다. C-F 결합의 끊어짐으로 인해 막의 기계적 강도가 감소하고 pinhole이 발생했으며 이로 인해 수소가 막을 통과하는 양이 증가하였다. S-O와 C-O결합의 파괴로 전해질 막의 이온교환능력(IEC)이 감소함을 보였다. 30％ $H_2O_2$에 4 ppm $Fe^{2+}$이 첨가된 용액에서 48시간 열화시킨 막을 이용해 단위전지 성능을 측정한 결과 정상적인 막 성능의 약 1/2로 감소했다.

• Archives of Pharmacal Research
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• 제22권2호
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• pp.157-164
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• 1999

LB50016 was characterized as a selective and potent$ 5-HT_{1A}$ receptor agonist and evaluate it anxiolytic and antidepressant activities. It shows high affinity for $ 5-HT_{1A}$receptor, moderate affinity for $\alpha$2 adrenergic and $ 5-HT_{2A}$receptors and no significant affinity for other receptors tested. Hypothermia and increased serum corticosterone level were observed in LB50016-treated rats, which are mediated mostly by post synaptic $ 5-HT_{1A}$ receptor activation. In the mouse forced swim model for depression, LB50016-elicited dose-dependent reductions in immobility time, showing $ED_{50}$ of approximately 3 mg/kg i.p., which was blocked by pretreatment of NAN-190, $ 5-HT_{1A}$antagonist. In face-to-face test for anxiolytic activity in mice, estimated $ED_{50}$ was 2 mg/kg, i.p.. In isolation-induced aggression test with mice, fifty-fold increases in latency to attack were observed at 30 min and last up to 4 h after LB50016 treatment (3 mg/kg, i.p.). Taken together, LB50016-induced pharmacological activities are mediated by activation of $ 5-HT_{1A}$receptors, offering an effective therapeutic candidate in the management of anxiety and depression in humans.

• 대한화학회지
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• 제44권5호
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• pp.429-434
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• 2000

Styryldiphenylphosphine(SDPO)의 가수분해 속도상수를 자외선 분광법으로 측정하여 넓은 pH에서 잘 맞는 반응속도식을 구하였다. pH에 따르는 속도상수의 변화, 가수분해 생성물의 확인, 일반염기 및 치환기 효과 등으로부터 실험 결과에 잘 맞는 반응 메커니즘을 제안하였다. 즉 pH 4.5 이하에서는 phosphine oxide기의 산소에 양성자가 첨가된 다음 탄소 이중결합에 물의 첨가가 일어나 가수분해가 진행되며, pH 4.5-8.0 사이에서는 물분자와 수산와 음이온의 첨가가 경쟁적으로 일어나 반응이 진행되었고, pH 8.0 이상에서는 반응속도 상수가 수산화 음이온의 농도에만 비례함을 알았다.

• Mycobiology
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• 제46권1호
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• pp.33-46
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• 2018

Gray mold (Botrytis cinerea) is one of the most common diseases of strawberries (Fragaria${\times}$ananassa Duchesne) worldwide. Although many chemical fungicides are used for controlling the growth of B. cinerea, the risk of the fungus developing chemical resistance together with consumer demand for reducing the use of chemical fungicides have necessitated an alternative method to control this pathogen. Various naturally occurring microbes aggressively attack plant pathogens and benefit plants by suppressing diseases; these microbes are referred to as biocontrol agents. However, screening of potent biocontrol agents is essential for their further development and commercialization. In this study, 24 strains of yeast with antagonistic ability against gray mold were isolated, and the antifungal activity of the volatile and diffusible metabolites was evaluated. Putative mechanisms of action associated with the biocontrol capacity of yeast strains against B. cinerea were studied through in vitro and in vivo assays. The volatile organic compounds produced by the Galactomyces candidum JYC1146 could be useful in the biological control of plant pathogens and therefore are potential alternative fungicides with low environmental impact.

• 보존과학연구
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• 통권11호
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• pp.87-105
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• 1990

Chemical and micro morphological changes of archaeological waterlogged woods from shipwrecked materials in marine situations were investigated which were submerged in seabed for over 900 years. Tested Wood species were Pinusdensiflora, Zelkova serrata, Quercus acutissima and Camellia japonica. The obtained results were summarized as follows; Chemical analysis showed that lignin content was increased, whereas the amout of holocellulose was heavily decreased in the degraded archaeological lwoods(DAW), when compared to the recent woods. The amount of alkalineextractives in the DAW was extremley high. IR spectra showed that disappearance of absortion band at $1,730㎝^-1$ intensity increase at 1,600, 1,500 and $1,270㎝^-1$ and the emergence of single band around $1,050㎝^-1$.Microscopic investigation showed that cell wall of latewood tracheids and fiber in the DAW were severely degraded while, early wood tracheids less degraded. Degradation in the cell wall was mainley occurred in $S_2$layer, while the middle lamella was the least degraded. The micro morphological characteristics of DAW were separation of secondary wall from middle lamella, cavities aligned with micro fibril angle in $S_2$layer and granular appearance of secondary wall by the bacterial attack.

• 한국재난관리표준학회지
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• 제1권1호
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• pp.63-67
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• 2008

본 연구는 위험성 분석 기법을 통해 화학 산업 시설에서 발생 가능한 화학 테러에 대한 원인 을 규명하고, 기존의 테러 대응 방법에 대한 분석 및 평가를 함으로써 효과적 대응 개선 방안을 마련하기 위 한 프로그램 개발이다 테러 위험성 평가 프로그램은 자산 분석(Asset Characterization), 위협 평가(Threat Assessment), 취약성 분석(Vulnerability Analysis), 위험성 평가(Risk Assessment), 대응책 제시(New Countermeasure)의 총 5단계의 순차적 알고리즘으로 구성되어 있다. 개발된 프로그램을 항만에 위치한 석유 저장 및 정제 공정에 적용하여 테러 위험성과 그 원인을 분석함으로써 위험성 평가 프로그램의 효용성과 신뢰성을 검증하였다. 화학 산업 시설에서의 보안 및 테러리즘에 대한 문제성 제기를 통해 그 해결책을 제시하고 테러의 취약점과 원인을 규명함으로써 테러나 재해(extreme event) 발생 시 효과적인 대응책 마련이나 대응 전략 수립에 기여하고자 개발된 프로그램이다.

• Korean Chemical Engineering Research
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• 제47권4호
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• pp.441-445
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• 2009

고분자전해질 막의 전기화학적 열화에 미치는 온도의 영향에 대해 연구하였다. 가속 열화 조건(OCV, anode 무가습, cathode 65% RH)에서 셀 온도를 변화시켜 144시간 운전한 후 셀 성능은 12에서 35%까지 감소하였다. 이러한 성능 감소는 FER(Fluoride Emission Rate) 측정에서 알 수 있듯이 과산화수소 혹은 산소라디칼(${\cdot}OH$, $HO_2{\cdot}$)의 공격에 의한 막의 열화에 따른 것으로 라디칼 형성을 위한 가스 crossover의 증가를 가져왔다. 전극에서의 라디칼 생성은 ESR로 확인하였다. 고분자막 열화의 온도 의존성을 나타내는 Arrhenius plot에 얻어진 활성화 에너지 값은 66.2 kJ/mol이었다. 셀 작동온도 증가는 라디칼 형성속도와 라디칼이 막을 공격하는 반응 속도뿐 아니라 가스 crossover 속도도 증가시켜 막 열화를 가속화시켰다.