• 한국지반환경공학회 논문집
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• 제9권7호
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• pp.45-51
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• 2008

강도이방성 암석의 파괴규준에 관한 연구를 위해 대구지역에 널리 분포되어 있는 beddding-plane을 지닌 즉, 고유 이방성 암석인 셰일(shale)을 대상으로 삼축압축시험을 수행하였다. 시험과정에 있어 구속압력은 5, 10, 20, 30, 40MPa으로 단계적으로 증가시켜 시험을 수행하였으며, 시료의 파괴를 위한 전단속도는 대상시료가 5~15분안에 파괴가 일어나도록, 0.1%/min을 적용하였다. beddding-plane을 포함한 고유 이방성 암석에 대한 시험결과는 최대주응력축과 beddding-plane사이의 각도에 따라 전형적인 shoulder-type으로 나타났으며, 구속압력이 증가할수록 이방성 효과가 줄어드는 경향을 나타내었다. 불연속면의 각도에 따른 암석의 강도 변화는 무결암 상태와 유사한 조건인 ${\beta}=0^{\circ}$와 $90^{\circ}$에서 최대의 압축강도를 보였고, 최소의 강도를 갖는 ${\beta}$ 값은 대략 $30^{\circ}$ 정도로 나타났다. 또한 Hoek & Brown 파괴규준은 암석의 강도이방성을 나타내는데 모든 ${\beta}$ 값의 범위에서 실측치와 잘 부합되는 결과를 주었으나 Jaeger의 파괴규준은 ${\beta}=15^{\circ}{\sim}45^{\circ}$ 범위에서만 실측치에 접근하는 경향을 보였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.137-145
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• 2004

Limestone zone in korea have been distributed to diagonal line so that it is wide from the Gangwondo to the Jeonlanamdo. The limestone cavity and fractured zone were formed by chemical weathering. Limestone cavity and fractured zone was reinforced with cemented milk(w/c=60%)by high pressure jet grouting by tripple -pipe to establish bridge foundation on the ground condition like limestone cavity. To analyze property of limestone and solid of cement milk(w/c=65%), mixed solid of cement, core NX size in the limestone cavity and fractured zone and compressive strength. Seismic tomograpy exploration was pcrforn1cd to analyze deformation modulus of limestone. The analysis suggests that deformation modulus of limestone has effect on uniaxial compressive strength, seismic velocity, seismic elasticity modulus. Average static elasticity modulus of limestone is $5.08{\times}10^5kgf/cm^2$, cement and coal mixed solid is $0.25{\times}10^5kgf/cm^2$, $0.095{\times}10^5kgf/cm^2$. Average seismic velocity of limestone is 5.240m/sec, cement and coal mixed solid is 2,211.3m/sec, 1,447.5m/sec. Average uniaxial compressive strength of limestone was $1,221.3kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $125.22kgf/cm^2$, $35kgf/cm^2$ each other. Average friction angle of limestone was $49.14^{\circ}$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $38.39^{\circ}, 25.83^{\circ}$ each other. Average cohesion of limestone was $137.7kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $23.5kgf/cm^2$, $15.5kgf/cm^2$ each other. Average deformation modulus of limestone was $2.84{\times}10^5kgf/cm^2$ and limestone specimen mixed with cement milk and solid of cement milk mixed with coal were $0.4{\times}10^5kgf/cm^2, 0.12{\times}10^5kgf/cm^2$ each other. It was analyzed that the elasticity and uniaxial compressive strength, seismic velocity of solid of cement milk mixed limestone pieces and coal had an highly interrelation regardless of existence of limestones pieces and coal but it had shown that limestones had an lower interrelation. In case of field seismic velocity and deformation of limestone, SIC solid of cement milk mixed with coal and limestone pieces had an highly interrelation.

• 한국세라믹학회지
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• 제41권5호
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• pp.370-374
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• 2004

본 연구에서는 수열합성법으로 SrAl$_2$O$_4$:Eu 형광체 분말을 합성하여 이들의 발광 특성과 장잔광 특성 등에 대해서 고찰하였다. 증류수에 Sr(NO$_3$)$_2$, Al(NO$_3$)$_3$ㆍ9$H_2O$, Eu(NO$_3$)$_3$$.$6$H_2O$ 등의 금속염을 용해시킨 용액을 NH$_4$OH 수용액으로 pH 률 적당히 조절하고 고온고압의 Autoclave 반응용기 내에서 반응시켰다. 이렇게 합성된 분말은 균일한 입도 분포를 나타내었으며, sub-micron 크기의 초미세 분말이었다. 합성된 SrAl$_2$O$_4$:Eu 초미세 분말을 Ar-H$_2$ 가스 환원분위기에서 1100 -140$0^{\circ}C$ 온도로 2시간동안 열처리시켜서 형광 특성을 나타내도록 만들었다. 분말의 여기 및 발광 특성을 측정한 결과, 발광파장을 520 nm 로 고정시켜 측정한 여기스펙트럼은 250 ∼ 450 nm 의 넓은 파장영역에 걸쳐 여기가 일어났고, 발광스펙트럼은 520 nm에서 최대 피크를 나타내었다. 또한 10분간 여기시킨 후 520 nm 파장에 대한 잔광 특성이 1000초 이상 지속되는 우수한 장잔광 특성을 나타내었다. 그 밖에 SEM, XRD를 이용하여 SrAl$_2$O$_4$:Eu 형광체 분말에 대한 미세구조 및 결정구조를 고찰하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.66-66
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• 2008

본 연구에서는 ITO/Ag/ITO 다층 박막을 유기발광소자와 플렉시블 광전소자의 전극으로 적용하기 위하여 선형 대항 타겟 스퍼터(Linear facing target sputter) 시스템을 이용하여 성막하였고, ITO/Ag/ITO 다층박막의 전기적, 광학적, 구조적 특성을 분석하였다. 선형 대항 타겟 스퍼터 시스템은 강한 일방항의 자계와 타겟에 걸린 음극에 의해 전자의 회전, 왕복 운동이 가능해 마주보는 두 ITO 타겟 사이에 고밀도의 플라즈마를 구속 시켜 플라즈마 데미지 없이 산화물 박막을 성막시킬 수 있는 장치이다. 대항 타겟 스퍼터 시스템을 이용하여 성막한 ITO 전극을 DC power, working pressure, Ar/O2 ratio 에 따른 특성을 각각 분석하였다. glass 기판위에 최적화된 ITO 전극을 bottom layer로 두고, bottom ITO layer 위에 thermal evaporation 을 이용하여 Ag 박막을 6~20nm의 조건에 따라 두께를 다르게 성막하고, Ag 박막을 성막한 후에 다시 bottom ITO 전극과 같은 조건으로 ITO 전극을 top layer로 성막 하였다. 두 비정질의 ITO 전극 사이에 매우 앓은 Ag 박막을 성막 함으로 해서 glass 기판위에 ITO/Ag/ITO 다층 박막전극은 매우 낮은 저항과 높은 투과도를 나타낸다. ITO/Ag/ITO 박막의 전기적 광학적 특성을 보기 위해 hall measurement와 UV/visible spectrometer 분석을 각각 진행하였다. ITO/Ag/ITO 다층 박막 전극이 매우 얇은 두께임에도 불구하고 $4\Omega$/sq.의 낮은 면저항과 85%의 높은 투과도를 나타내는 이유는 ITO/Ag/ITO 전극 사이에 있는 Ag층의 표면 플라즈몬 공명 (SPR) 현상으로 설명할 수 있다. ITO/Ag/ITO 전극의 Ag의 거동을 분석 하기위해 FESEM분석과 synchrotron x-ray scattering 분석을 하였다. ITO/Ag/ITO 전극의 Ag층이 islands의 모양에서 연속적으로 연결되는 변화과정 중에 SPR현상이 일어남을 알 수 있다. 여기서, 대항 타겟 스퍼터 시스템을 이용하여 성막한 ITO/Ag/ITO 다층박막을 OLED 또는 inverted OLEDs의 top 전극으로의 적용 가능성을 보이고 있다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.400-403
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• 2002

The fundamental experiments for measuring soft x-ray characteristics from the vacuum capillary are described. These experiments were primarily performed in order to generate line spectra such as x-ray lasers. The generator consists of a high-voltage power supply, a polarity-inversion ignitron pulse generator, a turbo-molecular pump, and a radiation tube with a capillary. A high-voltage condenser of 200 nF in the pulse generator is charged up to 20 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing the ignitron. During the discharge, weakly ionized plasma forms on the inner and outer sides of a capillary. In the present work, the pump evacuates air from the tube with a pressure of about 1 mPa, and a demountable capillary was developed in order to measure x-ray spectra according to changes in the capillary length. In this capillary, the anode (target) and cathode elements can be changed corresponding to the objectives. The capillary diameter is 2.0 mm, and the length is adjusted from 1 to 50 mm. When a capillary with aluminum anode and cathode electrodes was employed, both the cathode voltage and the discharge current almost displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were -10.8 kV and 4.7 kA, respectively. The x-ray durations observed by a 1.6 ${\mu}$m aluminum filter were less than 30 ${\mu}$s, and we detected the aluminum characteristic x-ray intensity using a 6.8 ${\mu}$m aluminum filter. In the spectrum measurement, two sets of aluminum and titanium electrodes were employed, and we observed multi-line spectra. The line photon energies seldom varied according to changes in the condenser charging voltage and to changes in the electrode element. In the case where the titanium electrode was employed, the line number decreased with corresponding decreases in the capillary length. Compared with incoherent visible light, these rays from the capillary were diffracted and diffused greatly after passing through two slits.

• 한국식품과학회지
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• 제25권6호
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• pp.637-642
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• 1993

반응온도 $180^{\circ}C$, 수소압력 $2.0{\pm}0.3bar$, 니켈촉매량 0.048%(Ni/oil by wt.), 교반속도 300rpm 조건하에서 수소첨가하면서 시간별로 얻은 옥수수 수소첨가유의 트리글리세리드 분자종 조성의 변화 및 이화학적 항수의 변화를 연구하였다. 시간에 따른 요드값 감소율로 표현되는 수소첨가반응의 효율은 1차 반응으로 진행 되었으며, K>0.01 이었다. 요드값 감소율이 39.9%였던 수소첨가 30분 경과시 18 : 1 생성이 최고치(77.06%)였고, 그후로 18 : 1은 감소하고 18 : 0는 증가하였다. 트리글리세리드 조성의 변화에 있어서는 수소첨가가 진행됨에 따라 PLO, PLL, OLO는 30분만에 제거되었으며, OLL, LLL은 10분만에 급격히 감소하고 이후 서서히 제거되었다. 반면, POO, PLS 등의 CN52와 OOO, SLO 등의 CN54는 30분까지 크게 증가하고 이후 거의 일정하였다. 녹는점은 수소첨가 20분경과시 $27.8^{\circ}C$, 60분경과시 $44.1^{\circ}C$였고, 트란스산은 40분에 46.8%로 최고치를 나타내다가 이후 미약하게 감소하였다. 수소첨가시간의 경과에 따라 고체지함량은 증가하였다. 상기의 결과로 부터 본 실험의 수소첨가조건은 이중결합이 많은 불포화지방산부터 순차적으로 수소첨가되고, 트란스이성체 형성이 활발히 진행되는 선택적 조건임을 확인하였다. 이와같은 유지의 수식기술에 따라 생성된 수소첨가유는 여러 유지제품 생산에 적용되리라 사료한다.

• 한국진공학회지
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• 제6권2호
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• pp.122-128
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• 1997

본 연구는 건식 프로세스의 일종인 열증착법을 이용하여 PVDF유기박막을 제조하는 데 있다. 발열원과 기판간의 거리는 5cm로 하였고, 기판의 온도를 $30^{\circ}C$로 유지시키면서 반 응조의 진공도가 $2.0\times10^{-5}$Torr로 되었을 때 발열원의 온도를 6~$8^{\circ}C$/min로 상승시켜, 발열 원의 온도가 $270^{\circ}C$될 때 셔터(shutter)를 열고 증착을 개시하였다. 전계인가 강도의 증가에 따라 $\alpha$형 피크들인 $530\textrm{cm}^{-1},795\textrm{cm}^{-1},1182\textrm{cm}^{-1}$ 피크는 점점 작아지고 $\beta$형 피크 인 $510\textrm{cm}^{-1},1273\textrm{cm}^{-1}$ 피크가 증가함을 알 수 있었다. 전계인가강도 71.4kV/cm 이하에서는 $530\textrm{cm}^{-1}$ 피크가 $510\textrm{cm}^{-1}$피크의 강도보다 큰 것을 알 수 있는데 이는 $\beta$형 성분보다 $\alpha$형 성분이 필름의 특성을 지배함을 알 수 있었다. 이상의 결과로 전계인가 강도의 증가에 따라 PVDF 유기박막의 분자쇄는 $\alpha$형인 TGT 또는 TG'T에서 $\beta$형인 평면지그재그 TT형태로 변화함을 알 수 있다.

• Tuberculosis and Respiratory Diseases
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• 제81권3호
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• pp.247-255
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• 2018

Background: Patients with acute respiratory failure secondary to tuberculous destroyed lung (TDL) have a poor prognosis. The aim of the present retrospective study was to develop a mortality prediction model for TDL patients who require mechanical ventilation. Methods: Data from consecutive TDL patients who had received mechanical ventilation at a single university-affiliated tertiary care hospital in Korea were reviewed. Binary logistic regression was used to identify factors predicting intensive care unit (ICU) mortality. A TDL on mechanical Ventilation (TDL-Vent) score was calculated by assigning points to variables according to ${\beta}$ coefficient values. Results: Data from 125 patients were reviewed. A total of 36 patients (29%) died during ICU admission. On the basis of multivariate analysis, the following factors were included in the TDL-Vent score: age ${\geq}65$ years, vasopressor use, and arterial partial pressure of oxygen/fraction of inspired oxygen ratio <180. In a second regression model, a modified score was then calculated by adding brain natriuretic peptide. For TDL-Vent scores 0 to 3, the 60-day mortality rates were 11%, 27%, 30%, and 77%, respectively (p<0.001). For modified TDL-Vent scores 0 to ${\geq}3$, the 60-day mortality rates were 0%, 21%, 33%, and 57%, respectively (p=0.001). For both the TDL-Vent score and the modified TDL-Vent score, the areas under the receiver operating characteristic curve were larger than that of other illness severity scores. Conclusion: The TDL-Vent model identifies TDL patients on mechanical ventilation with a high risk of mortality. Prospective validation studies in larger cohorts are now warranted.

• 한국수소및신에너지학회논문집
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• 제28권6호
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• pp.601-609
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• 2017

Hydrogen is a clean, endlessly produced energy and it is easy to store and transfer. So, hydrogen is regarded as next generation energy. Among various ways for hydrogen production, the way to produce hydrogen by water electrolysis can effectively respond to fossil fuel's depletion or climate change. As interest in hydrogen has increased, related research has been actively conducted in many countries. In this study, we analyzed the performance characteristics and safety of water electrolysis system. In this study, we analyzed the performance characteristics and safety of water electrolysis system. The items for safety performance evaluation of the water electrolysis system were derived through analysis of international regulations, codes, and standards on hydrogen. Also, a prototype of the overall safety performance evaluation station was designed and developed. The demonstration test was performed with a prototype $10Nm^3/h$ class water electrolysis system that operated stably under various pressure conditions while measuring the stack and system efficiency. At 0.7MPa, the efficiency of the alkaline water electrolysis stack and the system that used in this study was 76.3% and 49.8% respectively. Through the GC analysis in produced $H_2$, the $N_2$ (5,157ppm) and $O_2$ (1,646 ppm) among Ar, $O_2$, $N_2$, CO and $CO_2$ confirmed as main impurities. It can be possible that the result of this study can apply to establish the safety standards for the hydrogen production system by water electrolysis.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.344-344
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• 2014

Transparent amorphous oxide semiconductors such as a In-Ga-Zn-O (a-IGZO) have advantages for large area electronic devices; e.g., uniform deposition at a large area, optical transparency, a smooth surface, and large electron mobility >10 cm2/Vs, which is more than an order of magnitude larger than that of hydrogen amorphous silicon (a-Si;H).1) Thin film transistors (TFTs) that employ amorphous oxide semiconductors such as ZnO, In-Ga-Zn-O, or Hf-In-Zn-O (HIZO) are currently subject of intensive study owing to their high potential for application in flat panel displays. The device fabrication process involves a series of thin film deposition and photolithographic patterning steps. In order to minimize contamination, the substrates usually undergo a cleaning procedure using deionized water, before and after the growth of thin films by sputtering methods. The devices structure were fabricated top-contact gate TFTs using the a-IGZO films on the plastic substrates. The channel width and length were 80 and 20 um, respectively. The source and drain electrode regions were defined by photolithography and wet etching process. The electrodes consisting of Ti(15 nm)/Al(120 nm)/Ti(15nm) trilayers were deposited by direct current sputtering. The 30 nm thickness active IGZO layer deposited by rf magnetron sputtering at room temperature. The deposition condition is as follows: a rf power 200 W, a pressure of 5 mtorr, 10% of oxygen [O2/(O2+Ar)=0.1], and room temperature. A 9-nm-thick Al2O3 layer was formed as a first, third gate insulator by ALD deposition. A 290-nm-thick SS6908 organic dielectrics formed as second gate insulator by spin-coating. The schematic structure of the IGZO TFT is top gate contact geometry device structure for typical TFTs fabricated in this study. Drain current (IDS) versus drain-source voltage (VDS) output characteristics curve of a IGZO TFTs fabricated using the 3-layer gate insulator on a plastic substrate and log(IDS)-gate voltage (VG) characteristics for typical IGZO TFTs. The TFTs device has a channel width (W) of $80{\mu}m$ and a channel length (L) of $20{\mu}m$. The IDS-VDS curves showed well-defined transistor characteristics with saturation effects at VG>-10 V and VDS>-20 V for the inkjet printing IGZO device. The carrier charge mobility was determined to be 15.18 cm^2 V-1s-1 with FET threshold voltage of -3 V and on/off current ratio 10^9.