• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.737-742
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• 1994

The fracture energy of glass fiber/carbon fiber/epoxy resin hybrid composite system was investigated in the aspect of fracture mechanism. Epoxy resin matrix was DGEBA-MDA-SN-HQ system. On the interface of glass fiber and matrix, post debone friction energy provided a major contribution to the fracture energy, and debonding energy and pull-out energy were of the similar value. In the case of fracture on the interface of carbon fiber and matrix, pull-out energy was the major contributor.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.446-450
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• 2013

TRISO coated particles with a ZrC barrier layer were fabricated by a fluidized-bed chemical vapor deposition (FBCVD) method for a use in a very high temperature gas-cooled reactor (VHTR). The ZrC layer was deposited by the reaction between $ZrCl_4$ and $CH_4$ gases at $1500^{\circ}C$ in an $Ar+H_2$ mixture gas. The amount of free carbon codeposited with in ZrC was changed by controlling the dilution gas ratio. Near-stoichiometric ZrC phase was also deposited when an impeller was employed to a $ZrCl_4$ vaporizer which effectively inhibited the agglomeration of $ZrCl_4$ powders during the deposition process. A near-stoichiometric ZrC coating layer had smooth surface while ZrC containing the free carbon had rough surface with tumulose structure. Surface roughness of ZrC increased further as the amount of free carbon increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.791-799
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• 2015

This study focuses on the algae growth restraining. Many researches on a critical damage from algae growth are published, but it is hard to find how th restrain. Abnormal algae increasing is a problem, because it makes red tides, biodeterioration, etc. Therefore this study aims to decrease the damage from algae growth. Some metal ions have been used microorganism killing materials from old times. Especially, Cu ions are highly effective. Based on these uses of the metal ions, a functional mortar which restrains algae growth is developed. The mortar contains soluble glass which dissolve in water. The soluble glass was made of Cu ions and phosphates. When the soluble glass is dissolved, Cu ions are soaked out stably from the soluble glass. Culture mediums which incubate algae were made to evaluate the developed mortar specimens. Culture mediums were filled with fresh water and sea water. Algae were incubated for fourteen days in culture mediums. The evaluating methods are measuring volume of the dissolved organic carbon and the chlorophyll. Using these two measurements, the mortar specimens are judged that can restrain algae or not. According to the result, the functional mortars of culture medium filled with fresh and sea water shows similar trend. The functional mortar for restraining algae growth performs that's role well.

• Korean Journal of Remote Sensing
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• v.31 no.5
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• pp.449-459
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• 2015

The conventional National Forest Inventory(NFI)-based forest carbon stock estimation method is suitable for national-scale estimation, but is not for regional-scale estimation due to the lack of NFI plots. In this study, for the purpose of regional-scale carbon stock estimation, we created grid-based forest carbon stock maps using spatial ancillary data and two types of up-scaling methods. Chungnam province was chosen to represent the study area and for which the $5^{th}$ NFI (2006~2009) data was collected. The first method (method 1) selects forest type map as ancillary data and uses regression model for forest carbon stock estimation, whereas the second method (method 2) uses satellite imagery and k-Nearest Neighbor(k-NN) algorithm. Additionally, in order to consider uncertainty effects, the final AGB carbon stock maps were generated by performing 200 iterative processes with Monte Carlo simulation. As a result, compared to the NFI-based estimation(21,136,911 tonC), the total carbon stock was over-estimated by method 1(22,948,151 tonC), but was under-estimated by method 2(19,750,315 tonC). In the paired T-test with 186 independent data, the average carbon stock estimation by the NFI-based method was statistically different from method2(p<0.01), but was not different from method1(p>0.01). In particular, by means of Monte Carlo simulation, it was found that the smoothing effect of k-NN algorithm and mis-registration error between NFI plots and satellite image can lead to large uncertainty in carbon stock estimation. Although method 1 was found suitable for carbon stock estimation of forest stands that feature heterogeneous trees in Korea, satellite-based method is still in demand to provide periodic estimates of un-investigated, large forest area. In these respects, future work will focus on spatial and temporal extent of study area and robust carbon stock estimation with various satellite images and estimation methods.

• Journal of the Korean Chemical Society
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• v.23 no.6
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• pp.358-367
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• 1979

EHT and CNDO/2 calculations have been performed to determine conformations of acetamides and diacetamides, and of their protonated forms. Results show that: protonation is always favored on the cis position with respect to N due to greater attractive potential between $H^+$ and N; the trans-trans conformer of diacetamides gives the most preferred protonated form although the cis-trans conformer is the most stable one for the unprotonated diacetamides. Protonation on a carbonyl oxygen is predicted to increase both charge and orbital controlled $S_N$SN reactivities of the protonated carbonyl carbon due to increases in positive charge and AO coefficient of ${\pi}$-LUMO of the carbon atom. In the acid catalyzed hydrolysis of diacetamides therefore it appears highly probable that the rate determining attack by a water molecule occurs at the carbon of the protonated carbonyl group and the carbonyl carbon-nitrogen bond scission follows subsequently. This mechanism is consistent with that generally accepted for the hydrolysis of amides in dilute acid solution but disagrees with that proposed by Laureut et al., for acid hydrolysis of N-acetyl-lactams.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.439-445
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• 2006

For investigating self-diagnosis applicability, a method based on monitoring the changes in the electrical resistance of hybrid FRP(having electrical property) reinforced concrete has been tested. Then after examining change in the value of electrical resistance of carbon fiber in CFRP(non-hybrid type), CFGFRP and CFAFRP(hybrid type) before and after the occurrence of cracks and fracture in non-hybrid and hybrid FRP reinforced concrete at each flexural weight-stage, the correlations of each factors(the changes in electrical resistance and load as a function of strain, deflection) were analyzed. As the results, it is clarified that when the carbon fiber tows fracture, the electrical resistance of it increase largely, and afterwards hybrid FRP composites can be resist the load due to the presence of the reinforced fiber, for example, glass fiber or aramid fiber tows. Therefore, it can be recognized that hybrid FRP(including carbon fiber) reinforcing bar could be applied for self-diagnosis of fracture in reinforced FRP concrete fracture.

• KSBB Journal
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• v.11 no.5
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• pp.613-621
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• 1996

The effects of important medium components such as carbon, nitrogen sources and amino acids on the production of cyclosporin A(CyA) were investigated in an immobilized fungal cell fermentation using Tolypocladium inflatum. As carbon sources in the synthetic medium, fructose and maltose stimulated CyA production remarkably compared to glucose when ammonium sulfate was supplemented as a nitrogen source. In the absence of ammonium sulfate in the medium, however, CyA biosynthesis was reduced considerably without regard to C-sources tested. Ammonium sulfate was found to be the best N-source, and also ammonium phosphate and ammonium citrate showed some positive effects on CyA production. Optimum concentration of ammonium sulfate was 10g/L, and supplementation of ammonium sulfate at the start of fermentation was found to be the most efficacious for maximal production of CyA. Among the constituent amino acids of cyclic peptide, CyA, L-valine had the most significant effect on the biosynthesis of CyA, and maximum CyA production was observed when 10 g/L of L-valine was initially added.

• Composites Research
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• v.28 no.5
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• pp.311-315
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• 2015

Measuring fiber volume fraction properly is very important in designing composite materials because the fiber volume fraction mainly determines mechanical and thermal properties. Conventional Ignition methods are effective for ceramic fiber reinforcing composite materials. However, these methods are not proper for applying to carbon fiber reinforcing composites because of the venerable characteristic against oxidation of carbon fiber. In the research, fiber volume fraction of carbon fiber composites was obtained by a thermogravimetric analysis considering oxidation characteristic of the carbon fiber and the method was compared and verified with the results from microscopic cross section images.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.176.1-176.1
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• 2011

세계적으로 석유 기반 자원의 고갈에 따른 부족, 기후변화협약 및 환경규제 강화에 의해 세계적으로 바이오소재를 이용하고자 하는 연구와 더불어 유리강화복합재료의 대체물질로 적합한 천연섬유를 보강재로 사용하는 바이오복합재료의 연구 또한 활발하게 진행되고 있다. 최근 새로운 신재생에너지원으로 각광 받고 있는 바이오에너지 중 해조류는 가장 자연친화적이고 생산력이 뛰어난 바이오매스로 알려져 있다. 해조류는 바닷물 속에 녹아 있는 탄소를 흡수할 뿐만 아니라 광합성을 통해서도 탄소를 흡수하면서 성장하기 때문에 탄소흡수원의 역할을 하게 되며, 해조류 바이오에너지를 생산할 경우 화석연료를 대체하여 지구온난화의 주범인 온실가스를 감축하는 기능을 한다. 본 연구에서는 해조류를 이용한 바이오에너지 생산 공정에서 2차적으로 발생하는 부산물을 보강재로 사용한 바이오복합재료의 제조와 제조된 바이오복합재료의 열적 특성 및 동역학적 특성을 분석하였다. 해조류 부산물의 화학적 전처리에 따른 Thermogravimetric analysis(TGA) 분석 결과로 cellulose 함량이 가장 높고 불순물이 적은 황산 처리한 파래를 이용해 파래/Polypropylene(PP) 바이오복합재료를 다양한 보강비율 (20-50wt%)로 압축성형 하였다. 파래/PP 바이오복합재료의 저장탄성률은 파래 함량이 40wt%일 때 4.0 Gpa으로 최대값을 보였으며 이는 PP 매트릭스와 비교했을 때 약 8.1% 향상된 결과이다. 파래/PP 바이오보합재료의 열팽창 특성은 파래 함량이 증가함에 따라 열팽창계수가 낮아지는 경향으로 50wt%일 때 가장 낮은 값을 나타내었으며 이는 PP 매트릭스와 비교했을 때 약 56% 향상된 결과이다. 따라서 비생분해성 고분자에 새로운 신재생 바이오매스인 해조류를 보강재로 사용하여 열적 특성 및 동역학적 특성이 향상된 친환경적인 바이오복합재료의 제조 가능성을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.67-67
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• 2010

탄소나노튜브(CNT)는 우수한 기계적, 화학적, 전기적 특성으로 인해 다양한 분야에서 차세대 응용재료로서 각광을 받고 있다. 다양한 CNT의 합성방법 중 CNT 구조제어가 가장 용이한 방법으로는 열화학증기증착법(TCVD)와 플라즈마지원(PE) CVD법이 있으며, 대량합성을 위해서는 TCVD가 보다 일반적으로 이용되어지고 있다. 일반적으로 CNT를 합성하기 위해서는 전이금속의 촉매가 필요하며 촉매의 활성화 및 탄소를 포함하는 원료가스의 분해를 위하여 고온공정이 요구된다. 그러나 향후 산업적 응용을 고려한다면 저온합성법의 개발은 시급하게 해결해야 할 과제로 인식되고 있다. 또한 기판 위에 CNT를 합성하는 경우 촉매와 기판재료 사이의 합금화를 방지하기 위하여 산화막층을 삽입하게 되는데, 이는 CNT의 높은 전도성을 이용하고자 할 경우 저해요소로 작용하게 된다. 따라서 CNT를 완충층의 도움 없이 금속기판 위에 직접 성장시키는 기술 역시 향후 CNT응용에 있어서 중요한 과제라 할 수 있다. 상기와 같은 배경으로 본 연구에서는 금속기판 위 CNT의 저온성장을 목적으로 연구를 진행하였다. CNT 합성기판으로는 SUS316L 및 Inconel과 같은 촉매금속을 자체 함유한 금속기판을 선정하였고, 플라즈마 전처리를 통한 기판표면 제어를 통하여 CNT의 저온성장을 도모하였다. 직류전원의 아르곤 플라즈마를 이용하여 금속기판을 처리하였을 때 기판온도 및 플라즈마 파워가 증가함에 따라 기판의 표면조도가 증가하는 것을 AFM분석을 통해 확인할 수 있었다. 아세틸렌 가스를 원료가스로 이용한 TCVD합성에 있어서는 플라즈마 처리한 기판이 무처리 기판보다 동일 합성온도에서 더 두꺼운 CNT박막을 형성하였고, 합성온도는 $400^{\circ}C$ 부근까지 내릴 수 있었다. 이는 플라즈마 처리로 증가된 기판의 표면조도가 저온에서 CNT의 핵생성에 유리하게 작용했음을 추측하게 한다.