• Journal of Chest Surgery
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• v.30 no.6
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• pp.598-606
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• 1997

Among 136 patients having undergone mitral valve surgery from September of 1994 through August of 1995 in Sejong Heart Institute, forty four patients(18 males, 26 females) underwent mitral valve reconstruction using prosthetic rings and their clinical results were evaluated. Patients'ages ranged from 5 to 63 years(mean age 38.2 years). Mitral valvular diseases were due to rheumatic origin in 30 patients(68%), degenerative in 13(30%), and congenital in one patient(2%). Mitral regurgitation(MR) was in 33 patients(76%), mitral stenosis 2(5%), and mitral stenoinsufaciency 9 patients(19%). The patients were divided into Carpentier's functional groups : type I, 5 patients(11%) : type I, 24 patients(55%) ; type III, 4 patients (9%) i and mixed(II + III), 11 patients(25%). Average number of anatomic lesions of mitral valve per patient was 3.7. The techniques included prosthetic ring amluloplasty(44 patients, 32 Carpentier ring and 12 Duran ring), leaflet mobilization(24, 55%), chordae shortening(23, 52%), chordae transposition(23, 52%), commissurotomy(16, 35%), leaflet resection(9, 20%), papillary muscle splitting(8, 18%), and chordae reimplantation(1, 2%). Average 3.4 surgical procedures were applied on mitral valve per patient. There were two hospital mortality and one reoperation due to development of MR(grade III) after 2 weeks. During the mean follow up of 12 months, patients improved in terms of functional class of the New York Heart Association, which was mean 3.0 preoperatively and 1.3 postoperatively. Doppler echocardiographic studies showed adequate valve area(2.07$\pm$0.11 cm2 mean $\pm$standard error), improved ventricular contractiliy in 41 patients(93%), ab ence of MR in 23(53%), trace MR in 18(42%), and garde II MR in 2 patients(5%).

• The KSFM Journal of Fluid Machinery
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• v.15 no.4
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• pp.33-41
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• 2012

In the present work, a parametric study on double-jet film-cooling has been carried out to enhance the film-cooling effectiveness using three-dimensional Reynolds-averaged Navier-Stokes analysis. The shear stress transport turbulence model is used as the turbulence closure. The lateral ejection angles and the lateral and streamwise distance between the centers of the cooling holes are chosen as the geometric parameters. The spatially averaged film-cooling effectiveness averaged over an area of 8 hole diameters in width and 30 hole diameters in streamwise length is used to evaluate the performance of film-cooling. The parameter of the lateral distance has the largest impact on the film cooling effectiveness compared to the others. On the other hand, the parameter of streamwise distance gives the least influence on the film cooling effectiveness.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.208-210
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• 2009

5성분계 Ti-Al-Si-C-N 코팅막은 하이브리드 코팅 시스템을 사용하여 실리콘 (Si) 웨이퍼와 SUS 304 기판위에 합성되었다. 본 연구에서는 Si 첨가에 의해 Ti-Al-Si-C-N 코팅막의 미세구조와 기계적 특성의 변화를 체계적으로 조사하였다. Si 함량이 증가됨에 따라 Ti-Al-Si-C-N 코팅막의 미세구조는 주상정에서 나노복합체를 가지는 미세구조로 변화하였다. 나노복합체의 고유한 특성에 의하여 미소경도는 약 56GPa로 증가하였고, Si가 증가함에 따라 평균 마찰계수도 크게 줄어들었다.

• Journal of the Korean Vacuum Society
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• v.4 no.3
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• pp.301-305
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• 1995

습식 분위기로 성장한 게이트 산화막 위에 다결정 실리콘(poly-Si)과 텅스텐 폴리사이드(WSix/poly-Si)게이트 전극을 형성하여 제작한 금속-산화물-반도체(metal-oxide-semiconductor:MOS)의 전기적 특성을 순간 절연파괴(time zero dielectric breakdown: TZDB)로 평가하였다. 텅스텐 폴리사이드 게이트 전극에 따른 게이트 산화막의 평균 파괴정계는 다결정 실리콘 전극보다 1.93MV/cm 정도 낮았다. 텅스텐 폴리사이드 게이트 전극에서 게이트 산화막의 B model(1-8 MV/cm)불량률은 dry O2 분위기에서 열처리함으로써 증가하였다. 이것은 열처리함으로써 게이트 전극이 silane(SiH4)에 의한 것보다 B mode 불량률이 감소하였다. 그것은 dichlorosilane 환원에 의한 텅스텐 실리사이드내의 불소 농도가 silane에 의한 것보다 낮기 때문이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.217.2-217.2
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• 2013

태양전지의 기본구조는 전면전극, 후면전극, 그리고 이들 사이에 위치하는 광흡수층으로 구성된다. 여기에 더하여 광흡수층에서 반사되거나 투과되는 빛 에너지의 손실을 줄이기 위해 윗면에는 반사방지막을, 아랫면에는 고반사막을 적용한다. 투명 태양전지의 경우 고반사막을 대신하여 선택적 투과막을 적용할 경우 변환효율을 향상 시킬 수 있다. 본 연구에서는 투명 태양전지의 구성물질로서 이용 가능한 선택적 투과 특성을 보이는 지르코니아 박막의 광학적 특성을 보고한다. RF magnetron sputtering 방식을 이용하여 지르코니아 박막을 증착하고 두께에 따른 광학적 특성 및 표면 형상 변화를 관찰하였다. 투과율 및 반사율을 측정한 결과 지르코니아 박막의 투과율은 400 nm 이상의 파장에서 약 85% 이상의 양호한 값을 나타내었다. 반사율은 평균적으로 적외선 영역에서 약 35%의 수치를 나타내었다. 이러한 광학적 특성으로부터 지르코니아 박막은 선택적 투과막으로 적합한 물질이라는 결론을 얻을 수 있다.

• Membrane Journal
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• v.20 no.2
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• pp.97-105
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• 2010

This study was to evaluate the performance of the Double stage Pore controllable fiber (DP) filter system as the pre-treatment of the RO membrane. The evaluation for the pre-treatment filter was performed through the indirect method, SDI (Silt Density Index) measurement of the filtrate. This study was done during Jan. 3 of 2009 to Dec. 3 of 2009 at OO Water Treatment Plant that was suppling industrial water to plants, and the raw water was contaminated lake water and it was fed to the system after clarification with coagulation. The average turbidity of the feed water and that of the filtrate was 0.79 NTU (0.28~4.01 NTU), and 0.16 NTU (0.04~0.50) respectively. And so the average turbidity removal efficiency was 77%. The filtrate flow rate and the backwash water flow rate was about 230 $m^3$/day and about 8.7 $m^3$/day respectively, and so the backwash rate was 3.8%. The data for some samples were obtained after a few days storage, and it caused the higher turbidity and SDI15 as the storage time was increased. But average SDI value of the filtrate was 3.6 (2.26~5.00) which was lower than minimum value required by the RO membrane manufacturer as the RO feed water to guarantee the life time of the RO membrane. So, the DP filter system was enough for the application as the pre-treatment of the RO membrane.

• Proceedings of the Membrane Society of Korea Conference
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• 1994.06a
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• pp.1-31
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• 1994

국내 에너지 수급여건 : 에너지소비증가율이 경제성장율을 상회하는 비효율적 에너지 소비구조가 지속 에너지의 불안정한 수급구조 장가화 추세 -세계 11위 에너지수입국, 세계2위 석유소비 증가세 시현('92) -에너지수입 의존도 : 95% 수준 -화석에너지 의존도 : 85% 상회 (OECD 평균 65% 수준) -고급에너지 수요의 상대적 고증가율 지속 (전력, 가스) -에너지수입액의 총 수입액중 비중증가 : '91년 15.1% $\to$ '93년 18.0%

• Childhood Kidney Diseases
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• v.9 no.1
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• pp.31-37
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• 2005

Puruose : Thin glomerular basement membrane disease(TGBMD) is found in patients with family history of hematuria. TGBMD is autosomal dominant and is known to be one of the commonest causes of asymptomatic hematuria. This study was conducted to evaluate the histological and clinical features of patients with TGBMD. Methods : 150 cases diagnosed with TGBMD by renal biopsy while admitted in the department of pediatrics, Kyungpook National University Hospital between January 1999 and December 2003 comprised the study group. The following parameters were retrospectively anaIyzed age of onset, hematuria pattern, existence of proteinuria, process of diagnosis, laboratory findings, thickness and character of basement membrane and family history. Results : The mean age at the time of diagnosis was 7.9 years. The male to female ratio was 65:77. 94 patients or 66% visited the hospital with a chief complaint of persistent microscopic hematuria. Gross hematuria accounted for 13 cases or 9%. 78 cases(55%) were found to have hematuria for the first time from a routine school urinalysis screening. The renal biopsy showed the thickness of basement membrane to be 186$\pm$36 nm. Focal lamellation of the basement membrane was found in eight cases. In the family history, hematuria was shown in 10 cases on the Paternal side, 13 on The maternal side and none on both sides. In seven cases, hematuria was shown among siblings. No significant differences were found among the laboratory test results which were conducted at an average interval of fifteen months. Conclusion : TGBMD is one of the major causes of asymptomatic hematuria in children, which was diagnosed in increasing numbers since school urinary mass screening test started in 1998. In cases with familial progressive renal disease or focal duplication in the basement membrane Alport syndrome should be considered.

• Journal of The Korean Ophthalmological Society
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• v.58 no.8
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• pp.960-967
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• 2017

Purpose: To compare the macular choroidal thickness in patients with thyroid-associated ophthalmopathy (TAO) with those with normal tension glaucoma (NTG). Methods: A total of 70 normal eyes, 74 eyes with TAO and 60 eyes with NTG were enrolled in this study. All patients underwent spectral-domain optical coherence tomography (SD-OCT) (Cirrus HD-OCT, Carl Zeiss Meditec Inc., Dublin, CA, USA). Macular choroidal thickness was assessed using enhanced depth imaging. The average macular choroidal thickness was defined as the average value of three measurements: at the fovea and at the points located 1.5 mm in the nasal and temporal directions from the fovea. Generalized estimating equations were used to uncover factors affecting the average macular choroidal thickness. Results: The average, superior and inferior quadrant retinal nerve fiber layer thicknesses were significantly thinner in the NTG group compared with the TAO and control groups (p < 0.001). The average macular choroidal thickness of the TAO group, NTG group and controls was $281.01{\pm}60.06{\mu}m$, $241.66{\pm}55.00{\mu}m$ and $252.07{\pm}55.05{\mu}m$, respectively, which were significantly different (p = 0.013). The subfoveal, nasal and temporal side choroidal thicknesses were significantly thinner in the NTG group compared with the TAO group (p = 0.014, 0.012 and 0.034, respectively). Subjects with TAO were associated with a thicker average macular choroidal thickness compared with the NTG group after adjusting for age, sex, spherical equivalent and intraocular pressure (${\beta}=32.61$, p = 0.017). Conclusions: Macular choroidal thickness was significantly thicker in patients with TAO compared with those with NTG. Further evaluation is required to determine if a thick choroid in subjects with TAO has any role in glaucomatous optic neuropathy.

• Polymer(Korea)
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• v.32 no.1
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• pp.70-76
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• 2008

The PES-g-BTCA membrane was synthesized by UV irradiation method and then used to be modified into the PES anion exchange membrane by the amination reaction. Their chemical structures and adsorption properties were investigated. The degree of grafting and amination were increased with increasing the reaction time and had the maximum values of 138% and 1.20 mmol/g at 80 min, respectively. The initial thermal degradation temperature of PES membrane was $400^{\circ}C$. Which was reduced as the surface modification reaction had proceeded. The values of contact angle for PES membrane were decreased from 68.1 to $40.2^{\circ}$ with increasing the extent of amination, the water up-take and ion exchange capacity were also increased with increasing UV irradiation time until 80 min. The average pore size and BET surface area were decreased in order of PES, PES-g-BTCA, and aminated PES ion exchange membrane. Their average pore sizes were 624.8, 359.7, and 138.5 ${\AA}$, and their surface areas were 10.1,9.7 and 1.7 $m^2/g$, respectively.