• Journal of Chest Surgery
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• v.31 no.7
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• pp.650-659
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• 1998

Between August 1996 and August 1997, 22 patients underwent extracardiac Fontan operations. The basic diagnoses included univentricular heart of the right ventricular type (n=12); univentricular heart of the left ventricular type (n=4); tricuspid atresia (n=4); left isomerism, transposition of great arteries, ventricular septal defect and pulmonary stenosis (n=1); and criss-cross heart with uneven ventricle (n=1). The median age of the 14 men and 8 women was 29 months (range from 21 months to 26 years). Previous procedures included bidirectional cavopulmonary shunt (n=15, interval=15.6$\pm$3.4 months), Kawashima operation (n=4, interval=37.5$\pm$20 months), and classic Glenn shunt (n=1, interval=14 years). In 2 patients, extracardiac Fontan operations were done without any previous procedures. A 16- to 22-mm flexible Gore-Tex tube graft (n=18), Hemashield graft (n=3), or, alternatively, a nonvalved aortic allograft (n=1) was cut and anastomosed end-to-end between inferior vena cava and undersurface of pulmonary artery using Gore-Tex or Prolene suture in a running fashion. In risk Fontan patients (n=12), a communication between the extracardiac conduit and the right atrium was constructed. In the most 13 recent patients, the procedures were done without cross-clamping of the aorta and with a beating heart. Operative mortality was 9.1% (n=2). Complications included persistent chest tube drainage for more than 7 days (n=5), chorea (n=2), and low cardiac output (n=1). There were no late deaths. Follow-up echocardiogram (mean: 6 months) demonstrated satisfactory hemodynamic results in the surviving 20 patients. Potential advantages of this technique consist of minimization of surgical manipulation of atrial tissue, reduction or elimination of myocardial ischemia, creationof a uniform and stable inferior vena cava-to-pulmonary artery conduit, and increased flexibility and safety in certain high-risk patients such as those with increased pulmonary vascular resistance, pulmonary hypertension, and impaired ventricular function. Further investigations during a longer follow-up are needed to confirm the intermediate and long-term results, especially the reduction of late atrial arrhythmias.

• Journal of the Korean GEO-environmental Society
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• v.20 no.1
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• pp.5-11
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• 2019

The main objective of this study was to analyse polycyclic aromatic hydrocarbons in surface sediments obtained from near Nakdong estuary, and to estimate ecological risks of PAHs using PAHs concentrations. The main constituents of sediments were $SiO_2$, $Al_2O_3$, CaO, $Fe_2O_3$, and ignition loss of sediments ranged from 2.97% and 8.39%. Total concentrations of PAHs ranged from $128.4ng\;g^{-1}$ and $507.4ng\;g^{-1}$, and the major PAHs were 2 ring and 4 ring aromatic hydrocarbons. Each concentrations of PAHs are all below effect range low, which indicated that each PAHs in 8 studying sites show low ecological risk. From M-ERM-Q analyses, M-ERM-Q values of 8 studying sites are below 0.1 indicating low ecological risk. From source apportionment analyses, PAHs come from grass, wood, charcoal combustion for N-1 and N-7, petroleum combustion for N-5 and N-6, petroleum pollution for N-2, N-3, N-4, N-8.

• Korean Journal of Plant Tissue Culture
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• v.21 no.4
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• pp.193-200
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• 1994

The effects of sucrose concentration and nitrogen source on shoot growth and in vitro formation of garlic (Allium sativum L. cv Seosan) bulblet were investigated in order to systematize propagation of high quality garlic through a shoot apical meristem culture. Shoot differentiation was not affected by sucrose concentration and nitrogen source, but plantlets which contain medium of NH$_4$- N or NH$_4$ + NO$_3$ were vigorous and healthy in .appearance. Shoot growth was vigorous in changeing of nitrogen source. The best quality of in vitro bulblets was obtained in culture on the medium containing 8% sucrose and NH$_4$ - N, and the formation of bulblet was more effective when plantlets were subjected to cold treatment before use. NH$_4$-N was a major factor for shoot growth and bulblet development, but NO$_3$-N was not and suppressed $K^{+}$absorption. The level of ethylene production was not affected by different nitrogen sources, however this production was enhanced in medium containing a higher concentration of sucrose.e.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.188-192
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• 2006

The microstructures and mechanical properties of continuously porous $SiC-Si_3N_4$composites fabricated by multi-pass extrusion were investigated at different Si levels added. Si-powder with different weight percentages (0%, 5%, 10%, 15%, 20%) was added to the SiC powder to make the raw mixture powders, with $6wt%Y_2O_3-2wt%Al_2O_3$ as sintering additives, carbon ($10-15{\mu}m$) as a pore-forming agent, ethylene vinyl acetate as a binder and stearic acid ($CH_3(CH_2)_{16}COOH$) as a lubricant. In the continuously porous $SiC-Si_3N_4$ composites, $Si_3N_4$ whiskers like the hairs of nostrils were frequently observed on the wall of the pores. In this study, the morphology of the $Si_3N_4$ whiskers was investigated with the silicon addition content. In the composites containing of 10 wt% Si, a large number of $Si_3N_4$ whiskers was found at the continuous pore regions. In the sample to which 15 wt% Si powder was added, maximum values of about 101 MPa bending strength and 57.5% relative density were obtained.

• Membrane Journal
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• v.11 no.3
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• pp.116-123
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• 2001

Polyimide-silica hybrid membranes were prepared and the effect of silica content on the structural properties and the gas transport properties was studied. The hybrid membranes were obtained by the sol-gel process starting from 1,2,4,5-benzenetetracarboxylic dianhydride(PMDA), 4,4`-diamino- diphenyl oxide(ODA) and tetraethoxysilane(TEOS) in N,N` dimethylacetatmide (DMAc) solvent. The structural characterizations of the membrane were performed by FT-IR, EDX, TGA and SEM. The gas permeation experiments with ${N_2}, {O_2}, {H_2}, {CO_2}and ${CH_4}$ were carried out at the temperature of $25^{\circ}C$ and in the range of pressure from 3atm to 7atm. the hybrid membranes showed higher thermal stability than PI membranes. The silica patricles were uniformly embedded in the polyimide matrix and the size of silica particles increased with increasing silica content. The permeability coefficients of ${N_2}, {O_2}, {H_2}, {CO_2}and ${CH_4}$ increased with increasing silica content but the diffusion coefficients might appear to be a result of a solubility enhancement. In spite of the permeability enhancement, an increase in the selectivities of ${H_2}/{N_2}, ${H_2}/{O_2} and ${H_2}/{CO_2} was observed.

• Bulletin of the Korean Mathematical Society
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• v.48 no.3
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• pp.617-625
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• 2011

In [6], it was shown that hyponormality for Toeplitz operators with polynomial symbols can be reduced to classical Schur's algorithm in function theory. In [6], Zhu has also given the explicit values of the Schur's functions ${\Phi}_0$, ${\Phi}_1$ and ${\Phi}_2$. Here we explicitly evaluate the Schur's function ${\Phi}_3$. Using this value we find necessary and sufficient conditions under which the Toeplitz operator $T_{\varphi}$ is hyponormal, where ${\varphi}$ is a trigonometric polynomial given by ${\varphi}(z)$ = ${\sum}^N_{n=-N}a_nz_n(N{\geq}4)$ and satisfies the condition $\bar{a}_N\(\array{a_{-1}\\a_{-2}\\a_{-4}\\{\vdots}\\a_{-N}}\)=a_{-N}\;\(\array{\bar{a}_1\\\bar{a}_2\\\bar{a}_4\\{\vdots}\\\bar{a}_N}\)$. Finally we illustrate the easy applicability of the derived results with a few examples.

• Journal of Korean Society of Water and Wastewater
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• v.13 no.2
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• pp.34-40
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• 1999

Aerobic night-soil treatment effluent containing high concentration of ammonia nitrogen was treated to remove nitrogen using Bardenpho process with Methanol addition. The objective of this study was to investigate the feasibility of complete nitrogen removal at three different HRTs such as 6.25d, 5d, and 3.75d, respectively. At each HRT, the nitrogen removal efficiencies are 92%, 99% and 97% and the required amount of methanol are 3.05gMeOH/gN, 2.75gMeOH/gN, and 3.38gMeOH/gN, respectively. Specific nitrification rates are decreased proportional to HRT and are $0.022gNH_4^+-N/g\;MLVSS{\cdot}day$, $0.0332gNH_4^+-N/g\;MLVSS{\cdot}day$ and $0.051gNH_4^+-N/g\;MLVSS{\cdot}day$ and specific denitification rate are decreased proportional to HRT and are $0.0210g\;N/gMLVSS{\cdot}day$, $0.0330g\;N/gMLVSS{\cdot}day$ and $0.0525g\;N/gMLVSS{\cdot}day$, respectively.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.13-20
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• 1989

After sintering Si3N4 containing 20wt% of variable composition ratio of Y2O3 and Al2O3 at 1$600^{\circ}C$, the specimens were annealed at 125$0^{\circ}C$ and 135$0^{\circ}C$ for 5, 10, 15 hours in order to crystallize the remanining oxynitride glass phases. The main grain-boundary crystalline phases in the Si3N4-Y2O3-Al2O3 system were melilite and YAG. By annealing 15hrs. at 125$0^{\circ}C$, almost all of the glasses were crystallized. During the growth of melilite, lattice volyume of $\beta$-Si3N4 was increased as Al3+ and O2- ions in the oxynitride glass diffuse into $\beta$-Si3N4 lattice, but during the growth of YAG, lattice volume of $\beta$-Si3N4 was decreased by reverse diffusion of Al3+ and O2- ions. In case of crystallization of glass phase to melilite, thermal expansion of sample was decreased, but in case of crystallization to YAG, inverse phenomen on was observed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.251.1-251.1
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• 2014

Oraganic Light Emitting Diodes (OLED) 소자의 광추출 효율을 향상시키기 위한 방안으로 나노급 사이즈의 고 굴절률 패턴을 기판의 내부 패턴에 적용하였다. 100 nm 및 300 nm의 직경을 갖는 Si3N4 나노 패턴을 나노 임프린트 리소그래피와 건식 식각 공정을 통하여 OLED의 유리기판에 형성을 하였다. 그리고 Silicon On Glass (SOG) 물질을 패턴이 전사된 기판에 스핀 코팅으로 평탄화 공정을 진행 함으로써 OLED소자의 전기적인 특성이 떨어지는 문제점을 개선하였다. 그러고 나서 Si3N4 나노 패턴이 형성되고 평탄화 공정을 마친 기판상 OLED 소자를 제작하였다. OLED의 발광층에서 발생한 빛은 Si3N4 나노패턴에 의해 산란되어 광 추출 효율을 개선할 수 있다. 본 연구에서 두 가지 종류 100nm, 300nm 높이의 Si3N4 나노패턴으로 높이에 따른 광 추출 효율을 비교하고자 OLED 소자를 제작하였다. 기판에 Si3N4 패턴이 형성된 OLED의 효율은 Si3N4 300nm에서 13.1% 증가하였다.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.358-362
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• 2004

$Si_3$$N_4$ ceramics have been identified as one of the promising structural ceramics. This study has been carried out to investigate of the synthetic behaviors of $Si_3$$N_4$ derived from domestic silica-stone by direct nitriding method. The silicon nitridation reaction has been studied in the temperature range of $1300～1550^{\circ}C$. Below the $1400^{\circ}C$, the nitriding rate was measured to be 16%. For the temperatures higher than the $1400^{\circ}C$, $\beta$-$Si_3$$N_4$ phase was formed mainly, and the nitriding rate showed above 98%. With the increasing of sample weight of silicon powder, the nitriding rate and $\beta$-$Si_3$$N_4$ phase increased at $1400^{\circ}C$ for 2 hours. The shape and particle size of$ Si_3$$N_4$ powder synthesized at $1400^{\circ}C$ for 2 hours showed the irregular angular-type and 10 $\mu\textrm{m}$, respectively.