• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.234-234
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• 2013

VOx 박막은 마이크로볼로미터 적외선 센서의 감지재료로 주로 사용된다. 일반적으로 VOx 박막은 RF sputtering 방법으로 증착이 되며, 이 때 저항 값은 수 kohm~수 Mohm, TCR 값은 -1.5~-2.0%/K까지 다양하게 변화되어 나타난다. 이는 산소의 phase가 여러가지로 변화되기 때문에 재현성이 떨어지는 단점이 있으며, 결정성있는 박막을 증착하기 어려운 문제들이 있다. 본 연구에서는 VOx 박막의 재현성 및 재료의 안정성을 위해 ZnO 물질을 첨가하여 sandwich 구조의 나노박막을 증착하여 산소 열처리를 통해 산소의 phase가 어떻게 변화되는가를 XRD 측정을 통해 조사하였다. ZnO 나노박막을 첨가함으로써 갓 증착되었을 때의 XRD는 V2O5 주된 상을 이루고 있었으며, 산소열처리에 의해 VO2상이 나타남을 알 수 있었다. 또한 V2O5 phase가 표면쪽의 얇은 층에서 주로 나타나고, 중간층은 V2O5와 VO2 phase 가 혼합된 형태로 존재함을 X-ray diffraction 분석을 통해 알 수 있었다. 또한 GIXRD 측정을 통해 깊이에 따른 혼합 phase가 주로 VO2에 의해 형성된 것임을 확인할 수 있었다. 또한 산소열처리의 온도 및 시간에 따라 XRD 특성을 조사하였으며, 최적의 열처리 조건을 XRD 피크를 통해 찾고자 하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.178.1-178.1
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• 2013

산화물 반도체는 가시광선영역인 380~780nm에서의 투과율이 80% 이상이고, 3.2eV 이상의 밴드갭과 높은 이동도를 가지는 물질로 투명하고 휘어지는 디스플레이에 전도유망한 물질로 연구되고 있다. $10cm^2/V{\cdot}s$ 이상의 이동도를 확보하기 위해 IGZO에서 Ga대신 Sn을 첨가한 ITZO 산화물 반도체에 대한 연구가 되고 있다. 본 연구에서 ITZO 산화물 반도체 박막 증착 시 가장 중요한 특성으로 알려진 산소의 영향에 따른 광학적 특성을 알아보기 위한 실험이다. RF 마그네트론 스퍼터링을 이용하여 산소 가스 분압에 따라 ITZO 박막을 증착하였다. $(Ar+O_2)$의 합을 20으로 고정하고 $O_2/(Ar+O_2)$의 비율을 0~40%까지 가변하였고, $O_2$의 비율이 증가함에 따라 증착율은 감소하는 경향을 보였다. 투명 소자로서의 가능성을 판단하기 위하여 밴드갭과 투과도를 측정하였다. 광학적 밴드갭은 증착 시 산소 분압이 0%에서 40%로 증가할수록 3.46eV에서 3.32eV로 감소하였고, 또한 투과도가 가시광 영역(380~770nm)에서 87%에서 85% 감소하였다. In, Sn, Zn 의 금속 원자와의 결합 과정에서 산소의 빈자리가 줄어들어 전도도가 감소하여 광학적 밴드갭이 감소함에 따라 투과도가 감소하는 것을 확인하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.7
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• pp.854-862
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• 2016

In summer 2010, we measured the concentration of dissolved oxygen (DO) and nutrients in the water collected at the bottom of Cheonsu Bay, off the west coast of Korea. We also measured nutrient fluxes across the sediment-water interface by deploying a fully-automated benthic lander, which collected time-series water samples inside a benthic chamber. We confirmed on-going hypoxia in the northern parts of the bay where polluted lake water was discharged. DO content in the water at the bottom was 2 mg/l, compared to 5 mg/l at the mouth of the bay in the south. Nutrient concentrations showed a trend that was opposite to that of DO. The variation of N/P ratios implies phosphate desorption and a release of nutrients caused by hypoxia. The organic carbon oxidation rate and oxygen consumption rate in the northern parts of the bay were about twice as fast as those at the mouth of the bay. Benthic fluxes of nutrients in the northern part of the bay were 4 to 6 times higher than those at the mouth. Our results imply that it is important to understand the role of hypoxia events to make an accurate estimation of material fluxes across the sediment-water interface.

• Journal of Marine Life Science
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• v.2 no.2
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• pp.62-69
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• 2017

In order to assess the potential environmental factors in the vicinity of a fish cage farm, we investigated the biotic and abiotic factors during a short-term period in summer 2016 in two inner stations of Tongyeong Obi. High water temperature on August 10^th was apparent among the full depth of up to 29℃, which might have been related to the abnormally high temperatures of large amounts of the Changjiang River discharge along the Tongyeong coast. The concentration of nitrate+nitrite, ammonium, phosphate, and silicate ranged from 0.08 to 5.11 μM, 0.08 to 34.62 μM, 0.01 to 1.15 μM, and 1.46 to 31.79 μM, respectively. The nutrients were mainly supplied by precipitation and leaching from the bottom sediments in the fish culture farm area. It was not retained for a long duration because of the phytoplankton consumption and diffusion by water currents. The chlorophyll a concentration varied from 0.49 ㎍ l^-1 to 7.39 ㎍ l^-1. At that time, Chaetoceros debilis, C. pseudocurvisetus, and Pseudo-nitzschia delicatissima were rapidly proliferated and reached the level of 4.74 × 10⁹ cells l^-1. In particular, the lowest dissolved oxygen was recorded at 4.52 ㎍ l^-1 at the bottom layer after bloom. Therefore, even though phytoplankton blooms in summer have frequently occurred in a fish culture farm area, the oxygen-deficient environments were not found in neither the surface nor bottom layers, which implied that the water masses might be well exchanged from the mouth of the northwest and southeast between Obi and Mireuk Island in the study area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.165-170
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• 2004

MLCC의 주재료인 $BaTiO_3$는 금속전극의 산화를 방지하기 위해 환원분위기에서 소결하는데 이는 비화학양론적 조성 및 전기적 성질, 결함 그리고 상의 변화를 가져온다. 본 연구에서는 상의 변화를 다양한 온도 범위에서 BaO 또는 $TiO_2$를 첨가시킨 $BaTiO_3$ powder을 가지고 급냉시킨 후 이를 X-선 회절 분석을 통하여 이들의 이차상 형성 여부 등을 조사하였다. $1320^{\circ}C$에서는 $TiO_2$의 고용도가 BaO의 고용도에 비해 상당히 큰 값을 가짐을 알 수 있었다. 이런 결과를 바탕으로 Ba/Ti 비, 산소분압 및 온도에 따른 $BaTiO_3$의 전기전도도 거동에 의하면, 고용범위내에서 BaO 첨가량이 증가할수록 전기전도도의 최소점은 낮은 산소분압쪽으로 이동함을 관찰하였으며 이는 $Ti^{4+}$빈자리에 따른 산소빈자리가 형성되는 결함 모델로 설명되어진다.

• Proceedings of KOSOMES biannual meeting
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• 2009.06a
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• pp.161-161
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• 2009

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.177-186
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• 2003

The influences of horizontal and vertical flow components including the stratification of water column and the wind field on the formation of oxygen-deficient water in summer in Jindong Bay, northern part of Chinhae Bay, were examined. Temperature, salinity and dissolved oxygen in seawater, and direction and velocity of wind were observed in Jindong Bay from March 1998 to February 1999. Low concentration of 5 mg/L in dissolved oxygen (DO) appeared at the bottom layer from May to September. Extremely low DO concentration less than 3 mg/L was investigated in summer (July to August) when stratification was strongest due to abrupt vertical gradients of temperature and salinity in water column. Bottom waters with the extremely low DO concentration were observed even in spring (May to June) at the inner part of the bay. In summer (August to September), the bottom waters with the low DO concentration (less than 5 mg/L) existed at the water depth from 4 to 6 m, being moved upward to the surface layer compared to other seasons. Vertical components of residual flow, calculated by the direction and velocity of wind, in Jindong Bay in summer showed that locally prevailed northerly and westerly wind resulted in downwelling flow at the outer part of the bay and conversely, upwelling at the inner part of the bay. In addition, bottom current at the outer part corresponding to the downwelling area directed to the inner part, probably resulting in a transport of the particulate organic matter settled at the bottom waters to the inner part of the bay. The oxygen-deficient watermass, which was formed at the bottom layer of the inner part, was likely to transported to the surface layer by the upwelling flow.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.4
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• pp.56-64
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• 2000

Behavior of trace metals in Masan Bay, Korea was studied in August 1998 when the oxygen deficient condition occurred. Dissolved Cd and Zn concentration in the surface waters decreased with increasing distance from Masan Harbor. Dissolved concentrations of Cd, Cu Pb and Zn in the surface waters were higher than bottom waters. Particulate(acid-teachable fraction) concentrations of Cu, Cd and Pb in the surface waters of Masan Bay decreased with increasing distance from Masan Harbor. Bottom waters contained higher concentrations of particulate Cd, Cu, Pb and Zn than surface waters. Distribution coefficients between dissolved and particulate phase (K/sub d/) of Cu and Cd decreased with the increasing distance from the Harbor, possibly due to reaction of these elements with sewage-derived particulate matter Al, Zn, Cu, Cd, and Pb in the surface sediment showed relatively high concentration in the inner Masan Bay.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.134-143
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• 2002

우리나라의 경우 항만 및 어항의 개발시 항내의 정온 및 가동률 확보를 위해서 설치되는 방파제 등 외곽시설이 외해로부터의 침입파랑을 효과적으로 차단하고 있으나 한편으로는 이러한 구조물이 해수에 대하여 비투과성이므로 항만의 폐쇄성을 증대시켜 해수순환성이 저하되어 항만 수질오염이 악화되는 경향이 있다. 일반적으로 비투과성 방파제가 설치되면 항내 외간의 해수교환력이 떨어져서 오염물질 등이 항내에 머무르는 시간이 길어지므로 항내의 오염이 가속될 뿐만 아니라 오염원에 포함됨 유기물이 분해됨에 따라 항내 해수의 용존산소가 다량 소모되어 빈 산소상태를 야기시켜 항내의 수질에 부정적인 영향을 미친다. (중략)

• Clinical and Experimental Pediatrics
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• v.53 no.3
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• pp.349-357
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• 2010

Purpose : Transient tachypnea of the newborn (TTN) is usually benign and improves within 72 hours. However, it can also progress to prolonged tachypnea over 72 hours, profound hypoxemia, respiratory failure, and even death. The aim of this study is to find predictable risk factors and describe the clinical courses and outcomes of prolonged TTN (PTTN). Methods : The medical records of 107 newborns, >$35^{+0}$ weeks of gestational age with TTN, who were admitted to the NICU at Seoul Asan Medical Center from January 2001 to September 2007 were reviewed. They were divided into 2 groups based on duration of tachypnea. PTTN was defined as tachypnea ${\geq}72$ hours of age, and simple TTN (STTN) as tachypnea <72 hours of age. We randomly selected 126 healthy-term newborns as controls. We evaluated neonatal and maternal demographic findings, and various clinical factors. Results : Fifty-five infants (51%) with total TTN were PTTN. PTTN infants had grunting, tachypnea >90/min, $FiO_2$ >0.4, and required ventilator care more frequently than STTN infants. PTTN had lower level of serum total protein and albumin than STTN. The independent predictable risk factors for PTTN were grunting, maximal respiration rate >90/min, and $FiO_2$ >0.4 within 6 hours of life. Conclusion : When a newborn has grunting, respiration rate >90/min, and oxygen requirement >0.4 of $FiO_2$ within 6 hours of life, the infant is at high risk of having persistent tachypnea ${\geq}72$ hours. We need further study to find the way to reduce PTTN.