• 한국음향학회지
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• 제21권4호
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• pp.164-164
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• 2002

This paper proposes a hybrid method for vibration analysis in the medium to high frequency ranges using Power Flow Analysis (PFA) algorithm and Statistical Energy Analysis (SEA) coupling concepts. The main part of the developed method is the application of coupling loss factor (CLF) suggested in SEA to the power transmission, reflection coefficients in PI' A boundary conditions. The developed hybrid method shows very promising results with regard to the applications for the various damping loss factors in wide frequency ranges. And also this paper presents the applied results of Power Flow Finite Element Method (PFFEM) by forming the new joint element matrix with CLF to analyze the various plate structures in shape. The analytical results of automobile, complex plate structures show good agreement with those of PFFEM using the PFA coefficients.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.291-300
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• 2000

This paper proposes the new hybrid analysis of vibration in the medium to high frequency ranges including PFA and SEA concept. The core part of this method is the applications of coupling loss factor(CLF) instead of power transmission, reflection coefficients in boundary condition. This method shows very promising compared to the classical PFA for the various damping loss factors and wide ranges of frequencies. Besides this paper presents the applicable method in Power Flow Finite Element Method by forming the joint element matrix with CLF. These hybrid concepts are expected to improve SEA and PFA methods in vibration analysis.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2945-2950
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• 2015

경질 폴리우레탄 폼(RPUF) 제조에서의 단열성 향상을 위하여 사용되는 PFA (Perfluoroalkane)는 액상의 발포 기핵제로서 성능은 뛰어나지만 매우 고가일 뿐만 아니라 불소화합물로서 환경 유해성 물질이다. 따라서 이를 대체할 수 있는 고성능의 대체 기핵제 개발에 대한 많은 연구가 진행되고 있다. 본 연구에서는 이에 대하여 다중벽 탄소나노튜브(MWCNT)를 고상 기핵제로 사용하여 제조한 샘플에서의 셀 크기 및 단열 성능과 기계적 물성에 미치는 영향을 비교 연구하여 보고자 하였다. 셀의 평균크기는 $165.6{\mu}m$에서 $162.9{\mu}m$로 상대적으로 더 작아졌으며, 표준 편차 역시 각각 45.6 및 35.2로서 상대적으로 더 균일한 셀 크기 분포를 가진 것으로 나타났다. k-factor 값 역시 0.01763 및 $0.01745kcal/m.hr.^{\circ}C$의 값으로서 1.02%가 감소된 더 작은 값을 나타내었다. 또한 압축 응력 시험에서의 초기 모듈러스는 상대적으로 더 큰 값을 나타내었으나 압축항복 응력은 약 $0.030{\times}105Pa$로서 거의 같은 값을 나타내었다. 이러한 결과들로 부터 MWCNT는 매우 우수한 기핵제로 작용함을 알 수 있었고, 따라서 소량의 MWCNT를 기핵제로 사용하여 경제적이면서도 우수한 단열효과와 기계적 물성을 지닌 친환경적인 경질 폴리우레탄 폼을 제조할 수 있음을 알 수 있었다.

• 대한토목학회논문집
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• 제29권1A호
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• pp.75-84
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• 2009

본 연구에서는 혼합 콘크리트의 염소이온 고정화 능력, 수화물의 부식 억제 능력(Buffering capacity) 및 모르타르 내 철근 부식 측정을 통하여 콘크리트 내 철근 부식의 임계 염소이온 농도를 도출하였다. 실험 시 결합재로서 보통 포틀랜드 시멘트(OPC), 30% 플라이애시(PFA), 60% 고로슬래그 미분말(GGBS), 10% 실리카퓸(SF)를 치환한 혼합 시멘트를 사용하였다. 염소이온 고정화는 수분추출방법을 이용하여 측정하였으며, 시멘트의 부식 억제 능력은 결합재에 따른 산에 대한 저항성 측정을 통해 평가하였다. 염소이온이 함유된 모르타르 내 철근 부식은 재령 28일에 선형 분극 방법을 이용하여 측정하였다. 실험 결과, 염소이온 고정화 능력은 결합재 내의 $C_{3}A$ 함유량과 물리적 흡착에 의해 크게 영향을 받음을 알 수 있었다. 염소이온 고정화 정도는60% GGBS > 30% PFA > OPC > 10% SF 의 순으로 나타났다. pH 감소에 따른 시멘트의 부식 억제 능력은 같은 pH 값에서 결합재의 종류에 따라 다양하게 나타났다. 부식전류가 $0.1-0.2{\mu}A/cm^{2}$에 이를 때 부식이 발생한다는 가정하에, 부식에 대한 임계 염소이온 농도에 대하여 OPC는 1.03, 30% PFA는 0.65, 60% GGBS는 0.45, 10% SF는 0.98%로 각각 계산되었다. 그에 비해 임계 염소이온 농도의 새로운 표현방법으로 제시한 [$Cl^{-}$]:[$H^{+}$] 몰 농도비의 단위로 계산하였을 때, 임계 염소이온 농도는 결합재에 관계없이 0.008-0.009로 도출되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.311-318
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• 1998

In this paper, the power flow analysis(PFA) method is applied to the prediction of the vibrational energy density and intensity of coupled co-planar plates. To cover the energy transmission and reflection at the joint of the plates, the wave transmission approach is introduced with the assumption that all the incident waves are normal to the joint. By changing the frequency ranges and internal loss factors, we have obtained the PFA results, and compared them with the analytical exact solutions.

• Corrosion Science and Technology
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• 제8권2호
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• pp.74-80
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• 2009

The high alkaline property in the concrete pore solution protects the embedded steel in concrete from corrosion due to aggressive ions attack. However, a continuous supply of those ions, in particular, chlorides altogether with a pH fall in electrochemical reaction on the steel surface eventually depassivate the steel to corrode. To mitigate chloride-induced corrosion in concrete structures, finely grained mineral admixtures, for example, pulverized fuel ash (PFA), ground granulated blast furnace slag (GGBS) and silica fume (SF) have been often advised to replace ordinary Portland cement (OPC) partially as binder. A consistent assessment of those partial replacements has been rarely performed with respect to the resistance of each binder to corrosion, although the studies for each binder were extensively looked into in a way of measuring the corrosion rate, influence of microstructure or chemistry of chlorides ions with cement hydrations. The paper studies the behavior of steel corrosion, chloride transport, pore structure and buffering capacity of those cementitious binders. The corrosion rate of steel in mortars of OPC, 30% PFA, 60% GGBS and 10% SF respectively, with chloride in cast ranging from 0.0 to 3.0% by weight of binder was measured at 7, 28 and 150 days to determine the chloride threshold level and the rate of corrosion propagation, using the anodic polarization technique. Mercury intrusion porosimetry was also applied to cement pastes of each binder at 7 and 28 days to ensure the development of pore structure. Finally, the release rate of bound chlorides (i.e. buffering capacity) was measured at 150 days. The chloride threshold level was determined assuming that the corrosion rate is beyond 1-2 mA/$m^3$ at corrosion and the order of the level was OPC > 10% SF > 60% GGBS > 30% PFA. Mercury intrusion porosimetry showed that 10% SF paste produced the most dense pore structure, followed by 60% GGBS, 30% PFA and OPC pastes, respectively. It was found that OPC itself is beneficial in resisting to corrosion initiation, but use of pozzolanic materials as binders shows more resistance to chloride transport into concrete, thus delay the onset of corrosion.

• 한국해양바이오학회지
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• 제12권1호
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• pp.20-28
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• 2020

Symbiodinium is a dinoflagellate genus that coexists with coral reefs and is known to provide ultraviolet (UV) protection in nature through the synthesis of mycosporin-like amino acids (MAA). In order to develop a natural and ecofriendly sunblock for use in summer resorts, the possibility of using a Symbiodinium microbiome extract or an MAA was investigated. Two sunblocks, one containing 7% Symbiodinium extract and the other containing MAA were prepared to be tested on hairless mice and human skin. In this clinical study, the sun protection factor (SPF) and Protection factor of UV A (PFA) values of the sunblock containing either Symbiodinium extract or MAA were determined. The SPF values of the sunblock containing Symbiodinium extract and MAA were 10.43 and 10.83, respectively, and the PFA values were 3.42 and 3.39, respectively. Based on their PFA values of ≥2, the UV A protection can be graded as PA+ (low) for both the sunblocks. In addition, the UV-blocking extract of Symbiodinium has a low phototoxicity and cytotoxicity, reducing the possibility of a heavy feeling to the skin or a foreign-body sensation caused by residue build-up. The low toxicity feature of the major sunblock component will also prevent side effects, such as allergic reactions. Although Symbiodinium extract or MAA alone do not provide effectiveprotection against UV irradiation, their protection capacity can be complemented by the addition of inorganic UV-protecting compounds.

• Asian-Australasian Journal of Animal Sciences
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• 제29권9호
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• pp.1314-1321
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• 2016

We conducted this 10-wk experiment to evaluate the effects of dietary phytoncide, Korean pine extract as phytogenic feed additive (PFA), on growth performance, blood characteristics, and meat quality in finishing pigs. A total of 160 pigs ([Landrace${\times}$Yorkshire]${\times}$Duroc, body weight (BW) = $58.2{\pm}1.0kg$) were randomly allocated into 1 of 4 treatments according to their BW and sex, 10 replicate pens per treatment with 4 pigs per pen were used (2 barrows and 2 gilts). Dietary treatments were: CON, control diet; PT2, CON+0.02% PFA; PT4, CON+0.04% PFA; PT6, CON+0.06% PFA. Overall, average daily gain (ADG) was higher in PT4 (p<0.05) than in PT6, average daily feed intake (ADFI) was lower in PT6 than in CON (p<0.05). Besides ADFI decreased linearly (p<0.05) with the increased level of phytoncide and gain:feed ratio in PT4 treatment was higher (p<0.05) than CON treatment. During 5 to 10 weeks and overall, quadratic (p<0.05) effect was observed in ADG among the treatments. At the end of this experiment, pigs fed with PT4 diet had a greater (p<0.05) red blood cell concentration compared to the pigs fed CON diet. Water holding capacity increased linearly (p<0.05) with the increased level of phytoncide supplementation. Moreover, firmness, redness, yellowness, and drip loss at day 3 decreased linearly (p<0.05) with the increase in the level of phytoncide supplementation. In conclusion, inclusion of phytoncide could enhance growth performance without any adverse effects on meat quality in finishing pigs.

• 국제지역연구
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• 제13권2호
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• pp.789-812
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• 2009

논문은 아제르바이잔의 정체성을 형성해 온 역사적 문화적 원천을 페르시아, 투르크, 러시아의 영향이라는 측면에서 분석하여 그 복합적인 성격을 해명하고, 1991년의 독립 초기 그것이 아제르바이잔의 대외정책에 미친 영향과 그 귀결을 살펴보고자 한다. 오늘날의 세계에서 정체성은 사회적, 정치적, 경제적, 문화적 맥락에서 뿐만 아니라 복합적인 맥락에서 진행되는 다양한 변화 속에서 형성되고 표현된다. 이러한 정체성의 표출은 다원적인 환경에서 종종 배타적인 결과를 가져오기도 한다. 독립 이후 PFA 정부는 아제르바이잔의 풍부한 문화적 유산과 다면적인 정체성을 강조하기보다는 종족적 기원과 아제르바이잔의 터키성(Turkishness)을 강조하는 논리를 내세웠다. 국내적으로 볼 때, 종족 민족에 기반을 둔 대외정책은 소비에트 하에서 아제리 민족에 흡수되었던 아제르바이잔의 쿠르드인조차도 소외감과 배신감을 느꼈을 정도로 심각한 실패에 직면했다. 국제적으로 볼 때, PFA 정부의 대외정책은 러시아와 이란으로 하여금 등을 돌리게 만들었을 뿐만 아니라, 터키가 러시아와의 관계 악화를 우려함에 따라 터키에 대한 교섭력도 약화시켰다. 이에 따라, PFA 이후에 집권한 헤이다르 알리예프는 아제르바이잔 정체성의 네 가지 요소(페르시아적인 정체성, 투르크적인 정체성, 러시아적인 정체성, 아제르바이잔적인 정체성)를 모두 활용하여 대외정책의 방향을 결정하였던 것이다.

• Korean Membrane Journal
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• 제9권1호
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• pp.52-56
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• 2007

A proton exchange membrane was prepared by ${\gamma}-irradiation-induced$ grafting of styrene into poly(tetrafluoro-ethylene-co-perfluoropropyl vinyl ether) (PFA) and subsequent sulfonation reaction. The degree of grafting (DOG) increased with an increase in the absorbed dose. The prepared membranes showed high ion exchange capacity reaching 3.0 meq/g, which exceeded the performance of commercially available perfluorosulfonic acid membranes such as Nafion. The proton conductivity of PFA-g-PSSA membrane increased with the DOG and reached 0.17 S/cm for the highest sample at room temperature. The DMFC performance of the prepared membranes with 50% DOG was comparable to that of Nafion membrane.