• 한국결정성장학회지
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• 제19권5호
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• pp.228-236
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• 2009

본 연구에서는 $SF_6$ 가스 포접 하이드레이트 결정이 생성되고 성장하는 메커니즘의 특성을 기술하였다. 실험은 일정한 압력과 온도에서 2상 실험($SF_6$ 기상/수용액상)과 3상 실험($SF_6$ 기상/수용액상/$SF_6$ 액상)의 서로 다른 두 가지 상 조건에서 이루어졌다. 두 조건 모두 기체 영역과 수용액 영역 사이의 경계면에서 하이드레이트 결정의 수지상이 섬유상 형태로 상향 성장하는 거동을 보였다. 3상 실험의 경우 하이드레이트 생성이 진행됨에 따라, 반응기 내부압의 감소로$SF_6$ 액상에서 생성된 기포가 기체와 수용액 계면의 막에 도달하여 기포의 표면이 하이드레이트로 전환되었다. 본 논문에서는 결정의 핵생성과 이동, 성장, 간섭을 중심으로 $SF_6$ 가스하이드레이트 결정의 성장 특성을 기술하였다.

• 펄프종이기술
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• 제40권5호
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• pp.60-69
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• 2008

The principal reasons for applying a pigment coating to paper are to improve appearance and printability. The pigment coating provides a surface that is more uniform and more receptive to printing ink than are the uncoated fibers and, in turn, both facilitates the printing process and enhances the graphic reproduction. The improvement in print quality is readily apparent, especially in image areas or when multiple colors are involved. Although pigment coating of paper is to improve the printability, coated paper is not completely free from printing defects. Actually there are a number printing defects that are observed only with the coated papers. Among the printing defects that are commonly observed for coated papers, print mottle during multi-color offset printing is one of the most concerned defects, and it appears not only on solid tone area but also half dot print area. There are four main causes of print mottle ranging from printing inks, dampening solution, paper, and printing press or its operation. These indicates that almost every factors associated with lithographic printing can cause print mottle. Among these variation of paper quality influences most significantly on print mottle problems in multicolor offset printing, and this indicates that paper is most often to be blamed for its product deficiency as far as print mottle problems are concerned. Furthermore, most of the print mottle problems associated with paper is observed when coated papers are printed. Uncoated papers rarely show mottling problems. This indicates that print mottle is the most serious quality problems of coated paper products. Overcoming the print mottle is becoming more difficult because the operating speeds of coating and printing machines are increasing, coating weights are decreasing, and the demands on high-quality printing are increasing. Print mottle in offset printing is caused by (a) nonuniform back trap of ink caused by a nonuniform rate of ink drying, referred as "back trap mottle, and (b) nonuniform absorption of the dampening solution. Furthermore, both forms of print mottle have some relationship to the structure of the coated layer. The surest way of eliminating ink mottling is to eliminate unevenness in the base paper. Coating solutions, often easier to put into practice, should, however, be considered. In this paper the principal factors influencing print mottle of coated papers will be discussed. Especially the importance of base paper roughness, binder migration, even consolidation of coating layers, control of the drying rate, types of binders, etc. will be described.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2008년도 제33회 펄프종이기술 국제세미나
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• pp.47-70
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• 2008

Cost efficiency is today the primary requirement in the paper and board industry. This has led therefore, to a greater preponderance of products with specifically designed functionality to take account of current industry needs. Continually increasing machine coating speeds together with these new coating colour components have put more emphasis on the importance of the correct rheology and water retention of the coating colours to achieve good runnability and end product quality. In the coating process, some penetration of the aqueous phase, to the base paper or board must occur to anchor the pre-coating to the base or the topcoat to the pre-coat. The aqueous phase acts as a vehicle not only for the binder, but also for the other components. If this water or material penetration is not controlled, there will be excessive material shift from the coating colour to the base, before immobilization of the coating colour will stop this migration. This can result in poor machine runnability, unstable system and uneven coating layer, impacting print quality. The performance of rheology modifiers or thickeners on the coating color have tended to be evaluated by the term, "water retention". This simple term is not sufficient to explain their performance changes during coating. In this paper we are introducing a new concept of "material retention", which takes note of the total composition of the coating colour material and therefore goes beyond the concept of only water retention. Controlled material retention leads to a more uniform z-directional distribution of coating colour components. The changes that can be made to z-directional uniformity will have positive effects on print quality as measured by surface strength, ink setting properties, print gloss, mottling tendency. Optical properties, such as light scattering, whiteness and light fastness delivery should also be improved. Additionally, controlled material retention minimizes changes to the coating colour with time in re-circulation giving less fluctuation in quality in the machine direction since it more closely resembles fresh coating for longer periods. Use of the material retention concept enables paper and board producers to have more stable runnability (i.e. lower process costs), improved end product quality (i.e. better performance of used chemicals) and/or optimized use of coating colour components (i.e. lower total formulation cost)

• 한국구조물진단유지관리공학회 논문집
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• 제16권5호
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• pp.112-120
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• 2012

본 연구는 고강도 콘크리트 부재의 고온 하에서의 내화성능을 평가하기 위하여 내부증발 및 크리프를 고려한 해석적 모델들을 제시하였다. 내화성능의 평가는 열팽창, 수분확산, 크리프 모델 및 구조해석을 통하여 폭렬진행과 내화시간의 2가지 단계로 구분하였으며, 해석프로그램을 사용하여 사전재하조건에서부터 화재에 따른 부재의 폭렬 및 파괴까지의 전반적인 해석을 수행하였다. 콘크리트가 화재에 노출되면 콘크리트 표면에서의 수분뿐만 아니라 콘크리트 내부에서의 수분도 수분의 평형 및 전달조건에 의하여 증발이 발생된다. 화재시 콘크리트 부재 내부의 수분변화를 예측하기 위하여 부재 내부의 임의의 위치에서의 상대함수율을 산정하기 위하여 유한요소방식을 적용하였다. 이러한 해석적 모델 및 해석프로그램의 정확성을 검증하기 위하여 해석적 결과와 다른 연구자들에 의한 여러 가지의 실험데이터와 비교하였으며, 그 결과 해석프로그램은 하중, 단면조건, 부재길이, 콘크리트 강도 등 여러 가지 변수들에 대하여 고강도 콘크리트 부재의 내화성능을 해석적으로 잘 평가하고 있는 것으로 나타나고 있다.

• 한국재료학회지
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• 제17권8호
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• pp.447-451
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• 2007

We investigated the dependence of the various annealing conditions and thickness ($6\sim45nm$) of the Ti-doped $Al_2O_3$ coating on the electrochemical properties and the capacity fading of Ti-doped $Al_2O_3$ coated $LiCoO_2$ films. The Ti-doped-$Al_2O_3$-coating layer and the cathode films were deposited on $Al_2O_3$ plate substrates by RF-magnetron sputter. Microstructural and electrochemical properties of Ti-doped-$Al_2O_3$-coated $LiCoO_2$ films were investigated by transmission electron microscopy (TEM) and a dc four-point probe method, respectively. The cycling performance of Ti-doped $Al_2O_3$ coated $LiCoO_2$ film was improved at higher cut-off voltage. But it has different electrochemical properties with various annealing conditions. They were related on the microstructure, surface morphology and the interface condition. Suppression of Li-ion migration is dominant at the coating thickness >24.nm during charge/discharge processes. It is due to the electrochemically passive nature of the Ti-doped $Al_2O_3$ films. The sample be made up of Ti-doped $Al_2O_3$ coated on annealed $LiCoO_2$ film with additional annealing at $400^{\circ}C$ had good adhesion between coating layer and cathode films. This sample showed the best capacity retention of $\sim92%$ with a charge cut off of 4.5 V after 50 cycles. The Ti-doped $Al_2O_3$ film was an amorphous phase and it has a higher electrical conductivity than that of the $Al_2O_3$ film. Therefore, the Ti-doped $Al_2O_3$ coated improved the cycle performance and the capacity retention at high voltage (4.5 V) of $LiCoO_2$ films.

• Korean Chemical Engineering Research
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• 제45권4호
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• pp.400-409
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• 2007

메탄/프로판 혼합기체의 포접 하이드레이트를 다양한 과냉 조건 하에서 생성시키며 결정의 성장 특성을 연구하였다. 먼저 내압 용기를 물과 고압의 혼합기체로 충진하고 충분히 교반하여 용액을 포화시킨 후, 내부 온도를 하이드레이트 생성온도 이하로 급격히 떨어뜨리고 이후에는 일정하게 유지하며 하이드레이트 결정의 핵생성, 이동, 성장 및 간섭을 현미경을 통하여 관찰하였다. 수행한 모든 실험조건에서 하이드레이트의 생성은 기체와 액체의 상경계면에서 막의 형태로 시작되었으며, 이후 용기 하부에서 생성된 다수의 소결정들이 부상하여 일부는 막의 밑면에 부착하고 일부는 하이드레이트 막으로부터 자라는 결정과 간섭하며 아래 방향으로 성장하였다. 막 근처에서 성장하는 결정들은, 비교적 작은 과냉 조건에서는 다면 기둥의 형태를 가지며 과냉이 커짐에 따라 형상이 수지상(dendrite)으로 천이하고 성장속도는 증가하며 가지간격은 감소하였다. 액체 영역 내부에서 관찰 된 부유 결정(floating crystals)들은 팔면체, 삼각판 및 육각 판 등 다양한 형태를 보이며, 과냉이 작을수록 팔면체 형태가 지배적이었다. 과냉이 커짐에 따라 부유 결정 역시 수지상으로 천이하며 성장하였다. 상세한 하이드레이트 결정의 성장 특성을 과냉과 기억효과(memory effect; 하이드레이트가 분해된 후에도 액체에 물분자의 입체 그물 결합구조가 잔존하는 현상)가 미치는 영향을 중심으로 기술하였다.

• 대한기관식도과학회지
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• 제6권1호
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• pp.29-37
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• 2000

Background and Objectives : The concentration of sulfur dioxide($SO_2$) gas in the ambient air appears increasing in the industry and urban area day by day. It was known that $SO_2$ is noxious gas. $SO_2$ can be irritating to the eyes, nose, throat, upper respiratory tract and skin. It produces sulfurous acid on contact with water and is extremely irritating to the nasopharynx and respiratory tract. Laminin is a family of extracellular matrix glycoproteins localized in the basement membrane that separates epithelial cells from the underlying stroma. The biological activities of laminin are to promote cell migration, wound healing, growth and differentiation. Meterials and Methods : The histologic changes and the expression of laminin in tracheal mucosa sacrificed at every weeks (to 7 weeks) after continued $SO_2$ exposure of 250ppm for 30 minutes a day were studied in rats. Results : Pathologic tissue was formed at the tracheal mucosa and the underlying tissue by the infiltration of monocytes and epithelium was transformed to the single cell layered epithelium above 5 weeks after exposure. At the 6 weeks after exposure, epithelial cells were partially lost and epithelial cell layer was transformed to be leaf-shaped. Submucosal tissue was transformed to be lymphatic tissue. An intense positive staining for laminin was found in apical cytoplasm and lateral surface of the normal epithelial cells and basement membrane but at the 5 and 6 weeks after exposure, laminin activity was decreased to the moderate activity. At the 7 weeks after exposure, laminin activity was decreased to the weak activity. Conclusion : Our finding suggests that $SO_2$ makes histologic damage on the tracheal mucosa and decreases immunoreactivity for laminin. Longer duration of the exposure of $SO_2$ makes more histologic damage on the tracheal mucosa and decreases immunoreactivity for laminin.

• 분석과학
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• 제18권6호
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• pp.511-519
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• 2005

식품 포장재에 사용되는 접착제의 원료로 사용되는 우레탄의 주원료인 톨루엔 디이소시아네이트(TDI)는 인체에 노출될 경우에 독성을 일으킬 수 있다. GC/MS를 사용하여 식품 포장재에 잔류하는 TDI를 분석하기 위한 시료 전처리 조건과 분석조건을 확립하였다. 포장재 중에 포함된 TDI는 n-헵탄, 4%아세트산 등과 같은 식품유사용매를 사용하여 추출된 후, 기체 크로마토그래프/질량분석기 (GC/MS)에 의해 분석되었다. 26개의 식품 포장재를 측정한 결과 10개의 시료에서 $0.51{\sim}60.88{\mu}g/ml$ 농도 범위에서 TDI가 검출되었다. 포장재의 절단된 면에 대한 추출 용매의 접촉을 피하고 포장재 면만이 접촉하도록 한 후 추출시간을 달리하면서 실험한 결과 2시간 추출 조건에서도 0.7% 수준으로 감소되어 실제 식품 조리시에 TDI가 다량 검출될 위험은 미미한 것으로 평가되었다. 본 연구에서 확립된 톨루엔 디이소시아네이트에 대한 분석법은 외국의 유해물질에 대한 관리기준을 만족시키는 정량한계를 확보한 신뢰성 있는 방법으로 추후 관련 연구를 위한 기초 분석기술로 활용도가 높을 것으로 예상된다.

• 한국산학기술학회논문지
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• 제17권9호
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• pp.1-11
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• 2016

본 연구에서는 벽면으로부터 균일한 열 유속 조건에서 나노유체의 층류유동에 의한 대류 열전달 향상과 관련하여 유동관 내 벽면에서의 나노입자 거동의 영향에 대한 수치해석 및 실험 연구에 대해서 논한다. $SiO_2$ 나노유체의 동적 열전도도는 스테인리스 원형 관(길이 1 m 및 직경 1.75 mm)의 외면에 부착된 T형 열전대를 활용하여 측정하였다. 실험에 사용된 나노유체는 직경이 24 nm인 구형의 $SiO_2$ 나노 입자를 초순수에 분산시켜 제조하였다. 나노 유체의 향상된 열전도도(즉, 최대 7.9 %의 증가)는 기본유체(즉, 초순수)와 나노유체 간 유동에서 벽면 온도 변화를 측정하여 비교함으로써 확인하였다. 하지만, 수치해석 결과에서는 실험으로부터 발견된 경향이 발견되지 못했는데, 이는 수치해석 모델이 기본적으로 연속체역학 및 안정된 콜로이드 용액에 나노 입자를 포함하는 유동특성에 기반을 두기 때문으로 분석된다. 이에 따라, 열교환 표면에서 나노입자와 벽면 간 상호작용(예: 나노입자의 고립된 침전)에 의한 표면특성 변화와 같은 비연속체역학 기반의 효과를 확인하기 위하여, 나노유체의 흐름 직후 정제수를 활용한 추가실험을 수행하였다.

• 대한한의학회지
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• 제40권2호
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• pp.17-34
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• 2019

Objectives: This study was carried out to observe and compare the effects of Pinellia ternata, Zingiber officinale and Sobanhatang on the reflux esophagitis induced by gastric fundus and pylorus ligation in mice with esomeprazole. Methods: Antioxidant effects were measured by DPPH radical scavenging activity at four different concentration of 0.125, 0.25, 0.5 and $1.0mg/102{\mu}{\ell}$. Zingiber officinale water extract(ZE), Pinellia ternata water extract(PE) and Sobanhatang water extract(SBE) and esomeprazole were treated orally for 14 days before gatric fundus and pylorus ligation. In the histochemistry, changes in suface mucous cells, muscle tissue and connective tissue in gastro esophageal junction(GEJ) and mast cell on the esophageal mucosa were observed. The change of Hemo oxygenase(HO)-1, ghrelin, gastrin and substance P in gastric body tissue were measured by immunohistochemistry. Results: DPPH radical scavenging activity exhibited concentration dependently increases in ZE, PE, SBE. ZE was significantly higher at all concentrations than PE. The gastric surface mucous cells were more in the treated group than in the reflux esophagitis elicited group(GE) in the order of PE, SBE, ZE and esomeprazole treateded group(PT, SBT, ZT, ET). Lower esophageal sphincter muscle damage and intercellular space in the GEJ were less in the treated group than GE. In the esophageal mucosa, the mast cell distribution and the migration of inflammatory cells were lower in the treateded troup than GE in order to ZT, SBT, PT and ET. The antioxidative enzyme, HO-1 was more in the order of ZT, SBT, control group, PT, ET than in GE. ZT was significantly higher than the other groups and SBT was significantly higher than ET. Ghrelin was found to be higher in ZT, ET, SBT and PT than in GE, and ZT was significantly higher than all other groups except ET. Gastrin showed the highest positivity in GE, and was lower in the order of ET, ZT, SBT, PT, and control group. Substance P was the highest in GE, and was lower in the order of ET, ZT, SBT, PT and control group, and PT were significantly lower than ET. Conclusion: ZT, PT and SBT showed superior antioxidative, anti-inflammatory and mucosal protective effects on mouse reflux esophagitis as compared with ET. In particular, ZE was more effective in antioxidant and gastric motility enhancement, while PE was more effective in mucosal protection and anti-inflammatory effects. Sobanhatang is expected to be effective treatment because it has advantages of both drugs and reduces toxicity.