3 성분계 유기용제의 인화특성에 관한 연구

최재욱,하동명,목연수,임우섭,최일곤,조태제 한국산업안전학회 1999 한국안전학회지 Vol.14 No.3

This study was accomplished by measuring the lower and upper flash point with air blowing method and grasping the characteristics of flammability for the three component systems, which are made up of the Benzene-Toluene-o-Xylene and Methylethylketone-Toluene-o-Xylene. These three component systems are widely used in the various industrial fields together with the development of industry. The results are as follows ; 1) Isothermal line is plotted on the triangular diagram for flash points determined in each solutions. From this line, the mixed compositions which indicated the same lower and upper flash points in each different composition could be read on this diagram, if the composition of mixtures are known. 2) Lower and upper explosion limits obtained from the flash points determined for the three component solution are compared with the value calculated from Le Chatelier's law. Especially the lower explosion limits are in a good agreement with the calculated values.

원자력발전소 인간신뢰도 분석의 한계점 분석과 차세대 방법을 위한 요건 개발

김재환,정원대,장승철,하재주 한국산업안전학회 1999 한국안전학회지 Vol.14 No.2

More than twenty methods were suggested for Human Reliability Analysis (HRA) in the field of safety analysis for Nuclear Power Plants (NPPs). However, there is still a high uncertainty on the analysis and a difficulty in performing HRA. New methods and approaches are under studying to overcome such limitations of current HRA. This paper presents some results of study to analysis limitations of current HRA in viewpoint of user, i.e., HRA analyst. The limitation analysis was based on 89 human error events modeled in a Probabilistic Safety Assessment (PSA) project for NPPs in Korea. Total 17 specific limitations were identified and categorized into seven groups. Important analysis has also been undertaken to assess the order of priority among those limitations. Finally, seven requirements with priority ranking were generated for an advanced framework and methodology of HRA.

Zn-0.3wt.% Al 합금의 초소성 변형에 따른 미세조직의 변화

이원절,박찬경,하태권,손중락,장영원 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9

The superplastic deformation of Zn-0.3wt.%Al alloys were investigated at room temperature under various strain rate. These alloys were highly elongated up to 1400% at the initial strain rate of 2×10^(-4)/s, revealing the rate sensitivity parameter of about 0.4. In order to investigate the microstructural change during superplastic deformation, the transmission electron microscopy(TEM) studies were performed on the specimen elongated up to the 100% tensile strain at various strain rate. The microstructure was composed of zinc rich matrix phase, with 1㎛ in grain size, and Al rich second phases precipitated generally at grain boundaries and/or triple point. In region III(5×10^(-2)/s), the high density of dislocations were observed within the grains and deformation twins were also formed within the grains. In region II(2^*10^(-4)/s), however, the dislocations were highly localized along the grain boundaries and deformation twins were not observed. Observation of severe deformation along the grain boundaries and grain boundary migration(GBM) suggest that grain boundary sliding(GBS) is a dominant mechanism of superplastic deformation in this alloy.

Zone melting furnace 온도와 성장속도가 90 % Bi2Se3n 형 단결정의 열전특성에 미치는 영향

현도빈,황종승,심재동,오태성,하헌필 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.1

The effects of the zone melting temperature and growth rate on the thermoelectric properties for 0.15 wt% CdI₂ and 0.05 wt% CdCl₂ doped 90% Bi₂Te₃-10% Bi₂Se₃ single crystals were investigated. The Seebeck coefficient and electrical resistivity of the 0.15 wt% CdI₂ doped single crystals were initially decreased along the ingots due to the condensation of iodine in the melts. The sharp increase of the Seebeck coefficient and electrical resistivity at the last-to-freeze region were considered as results of the evaporation of iodine from the molten zone and the compensation of electrons due to the formation of the antistructure defects. The figure-of-merit was enhanced with increasing the zone melting temperature and lowering the growth rate. The single crystels grown at the zone melting temperature of 800℃ and the growth rate of 0.1 ㎜/min exhibited the maximum figure-of-merit of 2.8×10^(-3)/K.

2-프로판올과 톨루엔 혼합물질의 인화점 측정에 관한 연구

최일곤,최재욱,목연수,김영일,하동명 한국산업안전학회 1997 한국안전학회지 Vol.12 No.3

The lower flash points and upper flash points of 2-propanol and toluene mixtures were determined by air-blowing method instead of Tag-closed flash point tester. The relations between the flash points and the composition of the mixtures are as follows ; T_(F.J) =4.3182+6.0909X₁ T_(F.U) =39.3636-2.9091X₁ As results, the experimental data and the estimated values from the relations are considerably agreed, and we could plotted the relative diagram between flash points and the explosive range.

Sbi3 를 첨가한 25% Bi2Te3-75% Sb2Te3 와 15% Bi2Te3-85% Sb2Te3 단결정의 전기적특성과 열전특성

현도빈,황종승,심재동,오태성,하헌필 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.8

The temperature dependences of the electrical and thermoelectric properties of the SbI₃-doped 25% Bi₂Te₃-75% Sb₂Te₃ and 15% Bi₂Te₃-85% Sb₂Te₃ single crystals, grown by the Bridgman method, were measured at temperatures ranging from 77 K to 600 K. For the Sb₂Te₃-rich single crystals, the temperature dependence of the Hall mobility was T^(-1.0) regardless the Sb₂Te₃ contents and added amount of SbI₃. The temperature dependences of (m*/m_o)^(3/2)·μ_c and effective mass m*/m_o were T^(-1.5) and T^(-1/3), respectively. The decrease of the saturated hole concentration and the change of the slope of the Seebeck coefficient with temperature were considered in the view point of the two sub-bands in the valence band. The maximum figure-of-merit at 300 K of 0.2 wt% SbI₃-doped 25% Bi₂Te₃-75% Sb₂Te₃ and 0.4 wt% SbI₃-doped 15% Bi₂Te₃-85% Sb₂Te₃ single crystals were 2.25×10^(-3)/K and 1.95×10^(-3)/K, respectively.

4성분계 가연성 혼합용액의 끓는점 예측 및 표현

하동명,김문갑,이영세 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4

MRSM(modified response surface methodology)-2 model is presented for the prediction of boiling points in combustible solution of quaternary systems. This model requires only normal boiling points of pure substances and group-group parameters which are based on the group-group concepts without the use of experimental data under consideration. By means of this methodology, it is possible to predict the boiling points of the combustible mixture of quaternary systems by plotting of isothermal lines using computer graphics. The proposed methodology has been tested and compared successfully with reported boiling points in journals for the combustible solution of quaternary systems. It is hoped eventually that this methodology will permit prediction of the flash point and flammability limit for the combustible mixture of multicomponent systems.

Dieulafoy 양 병변에 의한 십이지장게실 출혈 1 예

김상현,김경환,이동현,송철수,정노원,박상제,김은규,하홍성,나일환,황윤이,성은영,최익수,신영기 대한소화기내시경학회 2001 Clinical Endoscopy Vol.23 No.1

Duodenal diverticula are first reported by Chomel in 1710. Duodenal diverticula are relatively common in adults with a prevalence of 23% in SRCP. The most duodenal diverticulum is asymptomatic. Complications such as obstruction, cholangitis, blliary stones, ulceration, perforation and hemorrhage can occur in approximately 10%. However, relatively few cases of bleeding from a duodenal diverticulum have been reported. The cause of bleeding from a duodenal diverticulum is uncertain and various suspected etiologies were suggested, such as ectopic gastric mucosa, stasis-induced ulceration, erosion into major vessels, aortoenteric fistuias, intradiverticujar polyp, aspirin-induced erosion. We report a case of a bleeding duodenal diverticulum by a Dieulafoy-like lesion and suggest this 1esion as one of posslble causes of blee4ng in duodenal diverticulum.

Preparation of Thermo-Responsive and Injectable Hydrogels Based on Hyaluronic Acid and Poly(N-isopropylacrylamide) and Their Drug Release Behaviors

Ha Dong In,Lee Sang Bong,Chong Moo Sang,Lee Young Moo,Kim So Yeon,Park Young Hoon The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.1

Copolymers composed of hyaluronic acid (HA) and poly(N-isopropylacrylamide) (PNIPAAm) were prepared to create temperature-sensitive injectable gels for use in controlled drug delivery applications. Semi-telechelic PNIPAAm, with amino groups at the end of each main chain, was synthesized by radical polymerization using 2-aminoethanethiol hydrochloride (AESH) as the chain transfer agent, and was then grafted onto the carboxyl groups of HA using carbodiimide chemistry. The result of the thermo-optical analysis revealed that the phase transition of the PNIPAAm-grafted HA solution occurred at around 30$\∼$33$^{circ}C$. As the graft yield of PNIPAAm onto the HA backbone increased, the HA-g-PNIPAAm copolymer solution exhibited sharper phase transition. The short chain PNIPAAm-grafted HA ($M_{w}$=6,100) showed a narrower temperature range for optical turbidity changes than the long chain PNIPAAm-grafted HA ($M_{w}$=13,100). PNIPAAm-grafted HA exhibited an increase in viscosity above 35$^{circ}C$, thus allowing the gels to maintain their shape for 24 h after in vivo administration. From the in vitro riboflavin release study, the HA-g-PNIPAAm gel showed a more sustained release behavior when the grafting yield of PNIPAAm onto the HA backbone was increased. In addition, BSA released from the PNIPAAm-g-HA gels showed a maximum concentration in the blood 12 h after being injected into the dorsal surface of a rabbit, followed by a sustained release profile after 60 h.

Hyaluronic Acid Stimulated Enterocytic Differentiation of Intestinal Stem Cells and Enhanced Enteroid Grafting on Scaffolds

Siu Chung Ha,Ya-Hui Tsai,Shinn-Gwo Hong,Yun Chen,Chao-Ling Yao 한국생물공학회 2023 Biotechnology and Bioprocess Engineering Vol.28 No.3

Hyaluronic acid (HA) is one of the main components of the extracellular matrix, and functions as a stabilizing molecule for cell-niche interactions. Although the mechanism of HA in supporting cell attachment is debatable, HA-based scaffolds are increasingly being applied in tissue engineering owing to their excellent mechanical properties and biocompatibility. HA reportedly enhances the intestinal growth in postnatal mice. In the present study, we aimed to investigate the effects of HA on intestinal stem cells (ISCs) using an in vitro enteroid culture system. A high-concentration of HA (0.5 mg/mL) significantly lowered the proliferative activity of ISCs with decreased enteroid-forming efficiency compared to the control ISCs. In contrast, a low-concentration of HA (0.1 mg/mL) did not affect the enteroid-forming efficiency of ISCs, but up regulated markers of enterocytic differentiation, villin, and HA receptor, CD44 and TLR4, in the enteroid cells. When enteroid fragments were seeded on an intestinal submucosa bioscaffold, HA treatment enhanced the growth and differentiation of enteroid cells on the material with a high villin expression level in the cell grafts. These results suggest that HA treatment is effective in promoting enterocytic differentiation of ISCs and enteroid grafting on scaffolds.