DCT를 이용한 프랙탈 블록 부호화 방법

이정렬,정원용,박영석 慶南大學校 附設 工業技術硏究所 1999 硏究論文集 Vol.17 No.-

본 논문에서는 프렉탈 부호화 속도를 개선하기 위해 DCT(discrete cosine transform)를 이용한 유사 블록 제거 알고리즘을 제안한다. 이 알고리즘은 DCT 변환계수의 평균값과 분산값의 유사도에 따라 유사블록들을 찾아 제거한다. 이 접근법은 부호화를 위한 정의역(domain)과 치역(range)를 줄임으로써 프랙탈 부호화 처리 속도를 개선한다. 알고리즘의 유효성을 확인하기 위해 정의역 블록만 제거시키는 경우 그리고 치역과 정의역 블록을 함께 제거시키는 경우 각각에 대한 실험을 행하고 기존의 프랙탈 블록 부호화 방법과 부호화 속도와 복원이미지의 PNSR을 비교한다. 실험결과 PNSR이나 시각적으로 큰 손실없이 부호화 속도를 약 20%정도까지 개선시킬수 있었다. In this paper, we propose a similar block removal a1gorithm using DCT(discrete cosine transform) to improve the fractal encoding speed. The proposed algorithm removes similar blocks depending to the similarity of the average and variance of the DCT transformed coefficients. This approach improves the fractal encoding speed by reducing the domain and range blocks for encoding. We perform an experiment for both the case of removing only domain and the case of removing together the range and domain to show the effectiveness of the algorithm. The experimental results show that the encoding speed is improved up to about 20% with a little PNSR and visual loss

제철 분진 슬래그를 이용한 열용사 코팅 막의 물리화학적 특성분석

이영석,정성기,유승화,조규진 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.3

제철소 제강공정 부산물인 분진은 탄소와 산화철이 전체의 90wt%를 차지하는 미세분말로서, 이를 환원하면 카본과 철이 주성분이 된다. 본 연구에서는 이들 환원 분진을 고부가가치 재료인 열용사 코팅 분말로 사용하여 열용사 코팅 후 코팅 막의 물리 화학적 특성을 조사하였다. 환원 분진은 입도별로 65-90㎛, 90-106㎛와 106-125㎛ 입자들로 분리하여 열용사를 동일한 조건하에서 수행하였으며, 이때 106-125㎛의 입도를 지닌 환원 분진을 이용한 열용사 증착 효율이 가장 우수하였으며, 코팅 막의 미세구조를 XRD와 XPS를 이용하여 조사하였고 코팅 막의 접착강도 및 내 부식성을 조사하였다. The steel powder slags, consisted of 90 wt% of carbon and iron oxides, can ba simply reduced to carbon and iron. In this research, we studied the physicochemical characteristics of thermal spray coated films prepared using the reduced powder slags as a highly valuable powders for the thermal spray coatings. After the reduced powder slags were divided into three fractions(65 to 90㎛, 90 to 106㎛, and 106 to 125㎛) based on the particle sizes, we carried out the thermal spray coating using each samples under the same thermal spray coating condition and found out that the particles with the sizes of 106 to 125㎛ had the best deposition efficiency. The microstructures of the coated films were investigated using XRD and XPS, and the adhesion strength and corrosion resistance were studied as well.

불소화방법을 이용한 탄소재료의 수소저장 연구동향

이영석 충남대학교 산업기술연구소 2006 산업기술연구논문집 Vol.21 No.1

ACF-카트리지를 이용한 수중 페놀의 흡착

이영석,문일식 순천대학교 공업기술연구소 1998 工業技術硏究所論文集 Vol.12 No.-

Adsorption characteristics of phenol in water using batch adsorption and activated Carbon Fiber (ACF)- cartridge were investigated. Adsorption capacities of the ACFs for phenol in water were found to be comparable with those of activated carbons (ACs) which have been widely used for phenol adsorption. In practices, phenol in water was rapidly removed at the first stage by ACF-cartridge. There are neither pressure changes between inlet and outlet nor shape change of cartridge. These studies enabled identification of an activated carbon fibers suitable for use in adsorption of low concentration phenol in water.

납사분해 잔사유 및 콜타르 핏치로부터 중공형 탄소섬유의 제조 및 특성

이영석,인세진,오인석 順天大學校 1998 論文集 Vol.17 No.1

Hollow carbon fibers(HCFs) are produced from pitches which are isotropic and anisotropic(mesophase) through two cylinder annular type spinnerette specially designed to obtain hollow fibers. The amount of N₂ flowing inside of spinnerette decides both thickness of fiber and the surface area, which are affected by temperature and the winding velocity. The thicker the isotropic and mesophase pitch-based fibers are, the longer the oxidation time is, and the thinner, the shorter, however, they are easily broken. Mesophase pitch-based HCFs were oriented along the line corresponding with maximum velocity during melt spinning. It was concluded that a pitch precursor could be melt-spun, and produced uniformly into hollow carbon fibers if the spinning temperature, stabilization, and carbonization conditions were well controlled. In comparision the results of tensile testing with normal round CFs, the mechanical properties of HCFs were improved except tensile strength of isotropic HCFs.

메조페이스 핏치계 탄소섬유의 안정화

이보성,이영석,정두환 한국화학공학회 1991 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.29 No.1

본 연구는 산화안정화가 메조페이스 핏치계 난소섬유의 물성에 미치는 영향을 파악하기 위하여 수행 되었다. 실험은 방사섬유극 230℃, 280℃, 320℃의 산화온도에서 0-3시간 동안 공기 분위기에서 안정화시켜 화학적, 광학적 관찰을 통해 산화제의 섬유 내부로의 침투 과정을 관찰하고, 탄화섬유의 기계적 물성값을 측정하여 산화안정화 조건을 도출코져 하였다. 메조페이스 핏치섬유가 산화안정화되는 과정은 섬유속으로 산소가 침투되고 탄소 및 수소가 탈리되면서 랜덤한 모자이크 조직이 섬유 표층으로부터 중심부 쪽으로 발달되는 skin-core 구조를 가지면서 진행됨을 알 수 있었다. 안정화시 형성된 조직 특성은 탄화섬유의 단면조직을 제어하는 역할을 하며, 이는 섬유의 기계적 물성값에 큰 영향을 미친다는 것을 알 수 있었다. 안정화 시간, 온도, 도입된 산소량은 탄화섬유의 기계적 물성치를 변화시킴을 알 수 있었으며, 320℃에서 1시간 산화안정화하여 산소의 도입량이 8.9wt%인 안정화섬유를 탄화하였을 때가 인장강도 및 탄성율이 가장 우수한 탄소섬유를 제조할 수 있는 안정화 조건임을 알 수 있었다. This study was performed to investigate the properties of mesophase pitch based carbon fibers during stabilization. The stabilization of those was carried out in the range of 230, 280, 320℃ under atmospheric condition for 0-3 hours. The characteristics of the reactions were observed by chemical and optical analysis. The condition of stabilization was determined by testing the mechanical properties of carbonized fibers. The stabilization of mesophase pitch based carbon fibers was progressed with permeating oxygens to fibers, escaping hydrogens and carbons from those. The skin-core structure, a random and mosaic structure is progressed by oxidant from the surface of stabilized fibers to the center of those, was confirmed by using the polarized micrograph. The cross-sectional structure of carbonized fibers was controlled by the structure of stabilized fibers. The mechanical properties of carbonized fibers were determined using the stabilization time, temperature and the introduced oxygen contents. The tensile strength and Young's modulus of carbonized fibers stabilized at 320℃ for 1 hour with 8.9wt% of oxygen contents were founded to be superier to others.

탄소섬유의 CVD-SiC 증착특성에 미치는 CH₃SiCl₃대 H₂의 비율의 영향

박병배,심환보,이보성,이영석,김종환 忠南大學校 産業技術硏究所 1994 산업기술연구논문집 Vol.9 No.2

Chemical vapor deposition of SiC on carbon fibers was investigated to improve oxidation resistance of carbon fibers, which was performed at the horizontal hot-wall reactor using the reactant mixtures of CH₃SiCl₃and H₂ with carrier gas Ar. The chemical composition, oxidation resistance, and tensile strength of SiC-coated carbon fiber were investigated as functions of CH₃SiCl₃/H₂ ratio, reaction temperature, coating thickness, and so on. The composition of deposited layer revealed C rich β-SiC at low hydrogen concentration and Si rich β-SiC at high hydrogen concentration. Because Si rich β-SiC layer is easy to be converted into SiO₂ favorable to oxidation resistance, high input value of H₂/CH₃SiCl₃ mole ratio resulted in good oxidation resistance in the SiC coating layer of carbon fibers.

미역 폐기물의 중금속 흡탈착 특성

조주식,박일남,허종수,이영석 한국환경농학회 2004 한국환경농학회지 Vol.23 No.2

본 연구에서는 생물흡착제인 미역을 사용하여 인공폐액 내의 중금속의 흡착 특성을 조사하였으며, 다음과 같은 결론을 얻었다. 미역 폐기물을 이용하여 제조된 생물흡착제의 단일 중금속 흡착효율은 각 중금속 100 mg/L인 용액에 biosorbent 3 g을 처리했을 때 Pb는 거의 100%였고 Cu와 Cd가 약 85~86% Zn과 Cr은 약 60~64%, Co와 Ni은 약 57%, Mn은 약 48%였다. 복합중금속 흡착효율은 단일중금속 흡착효율에 비하여 Pb를 제외한 다른 중금속들은 크게 감소되었으나 biosorbent g당 전체 중금속 흡착량은 더 증가되었다. 온도, pH에 따른 중금속 흡착효율은 별 차이가 없었으며 전반적으로 pH는 pH 5~6 범위, 온도는 20~30℃ 범위의 실온이 적당한 것으로 나타났다. 생물흡착제의 흡착평형은 모든 중금속이 1시간 이내에 이루어졌다. Freundlich와 Langmuir 등온흡착식을 구하여 실제 폐수처리에 적용여부를 검토한 결과 Pb, Cu, Cr, Cd, Co 순으로 비교적 친화도가 큰 것으로 나타났다. Freundlich 등온흡착식에 가장 잘 일치하였다. 모든 중금속의 Freondlich 지수 1/n값이 0.1~0.5 범위에 포함되어 흡착이 용이하고, Pb, Cr, Cu, Cd 순으로 비교적 평형 흡착량이 큰 것으로 나타났으며, 이 결과는 Langmuir 흡착등온식의 결과와 거의 유사하였다. 따라서, 중금속 농도범위에 따른 한계범위를 설정하여 등온흡착식을 적용시키면 매우 높은 중금속 처리효율을 나타낼 것으로 판단된다. 생물흡착제가 중금속 흡착 후의 구조적인 특성을 조사하기 위하여 FT-IR 분석 결과, 중금속 이온과 치환될 것으로 생각되는 functional group을 확인할 수 있었으며, 3,400/cm에서의 -OH group, 1,648/cm에서의 C=O bond, 1,426/cm에서의 C-O bond 그리고 850/cm에서의 S=O등이 전반적으로 중금속 흡착 후에 peak가 커지는 것이 관찰되었다. 생물흡착제의 재사용 가능성을 검토하기 위하여 최적의 중금속 탈착조건 검토하였는데, 탈착제 종류에 따른 중금속 탈착효율은 탈착제 종류와 중금속 종류에 따라 차이가 있었고, 전반적으로 NTA>H₂SO₄>HCl>EDTA 순으로 우수하였으며, 전체적으로 특정 중금속의 탈착효율이 떨어지지 않는 NTA가 탈착제로 가장 적합하였다. NTA농도에 따른 중금속 탈착효율은 NTA 0.1~0.3% 농도범위에서는 농도 증가에 따라 탈착효율도 약간 증가되었으나 그 이상의 농도에서는 별 차이 없었다. 온도와 pH 변화에 따른 중금속 탈착효율은 Cr을 제외한 다른 중금속들은 크게 영향을 받지 않는 것으로 나타났으며 전반적으로 온도는 30℃, pH는 2에서 높았다. 탈착제 접촉 반응시간에 따른 탈착효율은 10분 이내에 전체 탈착량의 80%이상이 탈착 되었으며 1시간 이후에는 거의 변화가 없었다. The adsorption and desorption of Pb, Cd, Co, Zn, Cr, Co, Ni, and Mo on the waste Undaria sp. were studied. Except for Pb, the mono adsorption rate for all heavy metals were lower than that of the heavy metals mixed. However, the adsorption capacity of the heavy metals by 1 g of biosorbent in mixed heavy metals increased. According to FT-IR analysis of the biosorbent after heavy metal biosorption, the replacement of the functional group by the heavy metals ions could be confirmed and the inverted peaks became larger after heavy metals adsorption. The adsorption equilibrium of heavy metals was reached in about 1 hour. The equilibrium parameters were determined based on Langmuir and Freundlich isotherms. The affinity of metals on the biosorbent decreased in the following order: Pb>Cu>Cr>Cd>Co. The desorption rate decreased in the following sequence: NTA>H₂SO₄>HCl>EDTA. The desorption rate of heavy metals by NTA increased with increase in the concentration from 0.1 to 0.3% but the desorption rate became constant beyond 0.3%. Therefore, it represented that desorption rate of heavy metals was suitable under optimized condition (30℃, pH 2 and 0.3% NTA solution) and was fast with 80% or more the uptake occurring within 10 min of contact time.

X-ray Photoelectron Spectroscopic Analysis of Modified MWCNT and Dynamic Mechanical Properties of E-beam Cured Epoxy Resins with the MWCNT

Young-Seak Lee,Ji-Sun Im,Seok-Min Yun,Young-Chang Nho,Phil-Hyun Kang,Hang-Kyo Jin 한국탄소학회 2009 Carbon Letters Vol.10 No.4

The surface treatment effects of reinforcement filler were investigated based on the dynamic mechanical properties of mutiwalled carbon nanotubes (MWCNTs)/epoxy composites. The as-received MWCNTs(R-MWCNTs) were chemically modified by direct oxyfluorination method to improve the dispersibility and adhesiveness with epoxy resins in composite system. In order to investigate the induced functional groups on MWCNTs during oxyfluorination, X-ray photoelectron spectroscopy was used. The thermo-mechanical property of MWCNTs/epoxy composite was also measured based on effects of oxyfluorination treatment of MWCNTs. The storage modulus of MWCNTs/epoxy composite was enhanced about 1.27 times through oxyfluorination of MWCNTs fillers at 25℃. The storage modulus of oxyfluorinated MWCNTs (OF73-MWCNTs) reinforced epoxy composite was much higher than that of R-MWCNTs/epoxy composite. It revealed that oxygen content led to the efficient carbon-fluorine covalent bonding during oxyfluorination. These functional groups on surface modified MWCNTs induced by oxyfluorination strikingly made an important role for the reinforced epoxy composite.

Improvement of Thermal Stability of Electrospun PAN Fibers by Various Additives

Young-Seak Lee,Min-Il Kim,Ji-Sun Im,Se-Jin In 한국탄소학회 2008 Carbon Letters Vol.9 No.3

In order to improve the thermal stability of PAN-based electrospun fibers, AP-PER-MEL and TiO2 were added in to the fibers as additives. The polymer composite with uniformly mixed additional agents was obtained. In case of non-treated sample, the fibers were burn off completely with high rate within 620℃. But in case of treated samples (EF-M and EF-MT), it is sure that the thermal stability was improved by studying TGA data and ISO flammability test about 20 and 30%, respectively. A synergy effect of adding two kinds of agents (AP-PER-MEL and TiO2) into PAN-based electrospun fibers was confirmed. Through SEM images, it is confirmed that the fiber shape can be kept even after addition of agents (AP-PER-MEL and TiO2). Finally the thermal stability of fibers was largely developed with keeping the nature of PAN-based fibers effectively.