• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.177.1-177.1
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• 2014

단일벽 탄소나노튜브(single-wall carbon nanotube)와 그래핀(graphene)과 같은 저차원 구조의 탄소물질은 우수한 기계적, 전기적, 열적 광학적 특성으로 인해 투명하고 유연한 차세대 전자소자로의 응용(투명전극, 투명트랜지스터, 투명센서 등)을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 단일벽 탄소나노튜브와 단일층 그래핀을 이용한 하이브리드 박막을 제작하여 투명전극(transparent electrode)과 전계효과 트랜지스터(field effect transistors)로의 응용 가능성을 연구하였다. 하이브리드 박막의 제작은 간단한 방법으로 단일벽 탄소나노튜브가 스핀 코팅된 구리 호일 위에 열 화학기상증착법(thermal chemical vapor deposition)을 통해 제작 하였다. 제작 과정 중 탄소나노튜브의 스핀코팅 조건을 최적화하여 하이브리드 박막에서 탄소나노 튜브의 밀도와 정렬을 제어하였으며 하이브리드 박막 제작 후 스핀 코팅 방향에 따른 박막의 저항을 측정하여 단일벽 탄소나노튜브의 코팅 방향에 따라 박막의 저항이 달라지는 모습을 확인할 수 있었다. 하이브리드 박막의 투명전극 특성을 확인 한 결과 $300{\Omega}/sq$의 면저항에 96.4%의 우수한 투과도를 보이는 것을 확인 할 수 있었다. 또한 하이브리드 박막은 CVD 그래핀과 비교하여 향상된 와 on-state current를 보이는 것을 확인 할 수 있었다. 우리는 단일벽 탄소나노튜와 단일층 그래핀으로 이루어진 하이브리드 박막이 앞으로의 투명하고 유연한 소자제작 연구에 있어 새로운 투명 전극 및, 트랜지스터 제작 방법을 제시 할 수 있을 것이다.

• Journal of Wetlands Research
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• v.22 no.3
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• pp.217-224
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• 2020

Waterlogging and unintended lake formation become the main problem in some parts of the world. Starting from 1989, the waterlogging problem was observed in the farmland of the Jarso community of Konso Woreda adjacent to the Segen River in Ethiopia. Therefore, the objectives are determining the extent and causes of unintended lake formation using GIS/RS in addition to a preliminary field survey to mitigate the problem. The analysis of satellite images revealed that over the years invasion of the irrigable land by unwanted water had increased, as, in 1989, the size of the wetland area was about 8 Km²; in 2000 the size of the un-intended lake was only 8.23 ㎢. Alarmingly the size of the lake increased to 19.68 Km² in 2014. Silting up of Weir and changing the flow of River Segen and Human Intervention and changing the natural flow of River Yanda were the main causes of this unwanted prolonged water-logging. The ecological and social environment has been degrading as the people of the waterlogged area have been experiencing some settlement and losing their land. Another problem encountered was flooding from River Barka and invasion of the farmland. Sediment control best management practices (BMPs) i.e, Removal of sediment, providing sandbags and well-scheduled maintenance; Changing the junction point of Yanda and Segen River were suggested for the long-term and short term possible remedial measures. Gabion retaining wall on the bank of the Segen River to the face of Barka River was suggested to protect the farmland from flooding.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.25.2-25.2
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• 2010

CNT(Carbon Nanotube)는 특이한 구조 및 뛰어난 물성을 갖고 있어, 여러가지 분야에 응용 가능한 신소재로서 연구되어 왔다. 또한 모양 및 구조에 따라 기계, 전기, 화학적인 특성이 달라 다양한 분야에서 활용이 가능하다. 외국에서는 FED tip, TR, 디스플레이 소자, 수소저장체, 고강도 복합체 및 대 표면적 전극 등 CNT의 다양한 특성을 이용한 응용이 연구되고 있는 반면, 국내에서는 이론연구와 합성연구에 편중되어 있다. 본 연구에서는 열 화학 기상법 (Thermal CVD)을 이용하여 MWNT(Multi-wall nano tube)를 성장시켜 촉매두께, 온도, gas변수에 따른 CNT의 양상을 분석하였다. Ni catalyst는 DC magnetron sputter를 이용하여 5~50nm 두께로 증착하였으며, 성장온도는 $800^{\circ}C$에서 $950^{\circ}C$까지 변화시켰다. 기판의 pre-treatment 로 ammonia($NH_3$) gas를 주입한 후, carbon precursor인 methane($CH_4$) gas와 $H_2$ dilute gas를 1:4의 비율로 주입하여 CNT를 성장시켰다. FE-SEM과 TEM, 그리고 XRD를 이용해 성장된 CNT의 형상 및 구조를 분석한 결과, 낮은 온도에서는 100nm이상의 두께를 갖는 수직형상의 MWNT가 성장되었으며, $900^{\circ}C$이상의 높은 온도에서는 20nm이하의 amorphous carbon nano rod가 성장되었다. 각각의 MWNT, carbon nano rod는 온도가 높을수록 직경이 증가하는 추세를 나타냈으며, Ni catalyst가 얇아질수록 수직형상을 갖는 결과가 나타났다. 또한 ammonia gas의 pre-treatment여부에 따라 CNT의 수직 형상이 좌우되는 결과를 확인하였다. 향후 성장된 MWNT의 최적 조건을 도출하여 디스플레이 소자인 FED(Field Emission Display)분야 등에 응용 가능할 것으로 전망된다.

• Journal of the Korea Computer Industry Society
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• v.8 no.2
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• pp.73-80
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• 2007

In this reaearch, our goal is to find the representative adjectives which express the sensitivity for wall paper. We want to make a model which can explain the whole by using the representative adjectives. We got the adjectives through the questionnaire survey, field survey, and internet survey. To find the representative adjectives, we used modified factor analysis. The factor analysis used in preceding research can not control the individual difference of sensitivity, because the distribution information of data is concentrated into the mean. So, we used the modified factor analysis to control it. The experimental result showed that the reduced factors could account about 79.5% when the number of factor are three. The individual difference of sensitivity was reflected in some adjectives. This result can be used to make a recommending model for wallpaper.

• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.489-497
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• 1994

The most serious problems related to the cardiovascular prothesis are thrombosis and hemolysis. It is known that the flow pattern of cardiovascular prostheses is highly correlated with thrombosis and hemolysis. Laser Doppler Anemometry (LDA) is a usual method to get flow pattern, which is difficult to operate and has narrow measure region. Particle Image Velocimetry (PIV) can solve these problems. Because the flow speed of valve is too high to catch particles by CCD camera, high-speed camera (Hyspeed : Holland-Photonics) was used. The estimated maximum flow speed was 5m/sec and maximum trackable length is 0.5 cm, so the shutter speed was determined as 1000 frames per sec. Several image processing techniques (blurring, segmentation, morphology, etc) were used for the preprocessing. Particle tracking algorithm and 2-D interpolation technique which were necessary in making gridrized velocity pronto, were applied to this PIV program. By using Single-Pulse Multi-Frame particle tracking algorithm, some problems of PIV can be solved. To eliminate particles which penetrate the sheeted plane and to determine the direction of particle paths are these solving methods. 1-D relaxation fomula is modified to interpolate 2-D field. Parachute artificial heart valve which was developed by Seoul National University and Bjork-Shiely valve was testified. For each valve, different flow pattern, velocity profile, wall shear stress and mean velocity were obtained.

• Korean Journal of Digital Imaging in Medicine
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• v.13 no.3
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• pp.99-103
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• 2011

Radiation Therapy has been used in the treatment of breast cancer for over 80 years. Technically, it should include a part or all of such areas as chest wall or breast, axilla, internam mammary nodes and supraclavicular nodes. The purpose of this study is treated breast cancer patient to use 6 MV, 10 MV with bolus so that we observe changing of skin dose and evaluate those usefulness. Using woman's phantom, after CT simulate scanning, Through RTP system to make treatment plan, select three any place. And then, we measure that dose rate. After moving the phantom to linac, we put for TLD to three point same as RTP system which we put on the phantom. We exposed 6 MV, 10 MV with bolus and without so that it is measured dose by TLD device(4000 Harshaw). As a reult expose 6 MV,10 MV, it differences 10%, 15% according to bolus and withoout bolus where lateral point from RAO, LPO beam, other one is 20% where the furthest from both beams. To use bolus in the hospital is material to include closely part at skin among tissue of breast cancer. Acquired skin dose from RTP system is uncertainity. So it has to test another system likely TLD or other dosimetry system. Also exposed field of breast cancer is included inhomogeneity such as lung, bone and so on. Therefore it has to be accomplished a dose calculating of inhomogeneity part from treatment plan.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.432-435
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• 2006

To evaluate geology and extent of leachate migration around the landfills, electrical resistivity survey were conducted in area of uncontrolled landfills in Cheonan and Wonju. The Cheonan landfill is located above the paddy fields and the resistivity survey lines were crossed to confirm possible pollution of the paddy fields by leakage of the landfill leachate. In Wonju, the landfill and the downgradient paddy fields are divided by a concrete barrier wall. At the bottom of the landfill, there is a leachate settlement system but has not been in operation. And a total of 4 survey line installed (1 parallel and 3 perpendicular to mean groundwater flow direction). According to the resistivity survey results, the landfill leachate in Cheonan appeared to be restricted only within the interior of the landfill, not to migrate into the subsurface of the paddy fields. These results are well consistent with electrical conductivity values of groundwaters obtained from a periodic analysis of water qualities. In Wonju, however, it was inferred that the leachate emanating from the landfill migrated beneath the abandoned leachate settlement system and it would reach the downgradient paddy field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.451-457
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• 2014

Recently, as a means of resolving the issue of legal liability in the event of an accident or a disaster, a wide variety of simulation techniques, such as structural and structure-fluid interaction analysis, have been used in the field of forensic engineering. The plate girder bridge discussed in this paper was being constructed between a pier and an abutment to expand an existing bridge, but an accident whereby the bridge overturned occurred at the end of the concrete laying process for a protective wall. This accident was caused by additional loads not being considered at the time of the design as well as the actual construction being different from the design. The additional loads ultimately generated a negative support force. In this study, we determined the cause of the accident by comparing the structural stability of the original design with that of the additional, non-conforming construction using MIDAS structural analysis.

• Journal of the Korean Wood Science and Technology
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• v.29 no.3
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• pp.1-13
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• 2001

Compression, lateral, and opposite woods in the stem and branch of rimu (Dacrydium cupressinum Lamb.), a softwood species indigenous to New Zealand, were described and compared in the anatomical aspects. Qualitatively, growth rings were wide in the compression wood, intermediate in the lateral wood, and narrow in the opposite wood. Tracheid transition from early wood to late wood was very gradual in the compression wood but was more abrupt in both the lateral and opposite woods. When viewed transversely, compression wood tracheids showed a roundish outline except at the growth ring boundary but lateral and opposite wood tracheids were angular to rectangular in outline. Intercellular spaces were occasionally detected in the compression wood except in the late wood at the growth ring boundary but were absent from both the lateral and opposite woods. Slit-like extensions of the bordered pit openings caused by the location of pit apertures within short and narrow helical grooves were observed in the compression wood tracheids but not in the opposite or lateral wood tracheids. In the compression wood tracheids, fine striations in the form of fine checks or grooves were observed on the lumen surfaces and the innermost $S_3$ layer of secondary wall was absent. In the tracheids of lateral and opposite woods, the $S_3$ layer was sometimes absent but occasionally highly developed. Cross-field pits in the compression wood appeared to be piceoid due to slit-like pit apertures but those in the lateral and opposite wood tracheids showed cupressoid to taxodioid. Quantitatively, compression wood tracheids were somewhat shorter than those of opposite or lateral wood in stem but not different from the opposite or lateral wood tracheids in branch. The walls were thicker in the compression wood than in the lateral or opposite wood. Uniseriate rays in the compression wood were fewer than in the lateral or opposite wood.

• Korean Journal of Organic Agriculture
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• v.21 no.2
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• pp.265-270
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• 2013

Cooking oil and yolk mixture (COY) was applied to control the powdery mildew of sweet persimmon at the research field of Gyeongsangnam-do Agricultural Research and Extension Services from 2010 to 2011. COY was sprayed three times with 10 days interval on foliar parts of sweet persimmon and the disease development was monitored after 5 days of final spray. Diseased leaf area rate was 13.4% and the control efficacy of COY against powdery mildew was 80.5%. Disease rate was 68.6% on negative control. Using scanning electron microscope (SEM), the morphological changes of the powdery mildew fungus on the leaf surface were observed. On COY-treated leaves, fungal mycellia were morphologically characterized by a loss in cell volume, shriveling, plasma membrane rupture, and subsequent loss of intracellular contents. It may due to the destruction of fungal cell wall or membrane structure.