• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.423-430
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• 2005

In this paper. a microphone array beamforming algorithm that reduces the signal distortion caused by reverberation and near-field effect in car environment is proposed. When reverberation or near-field effect is present, an optimum beamformer should be constructed with a steering vector consisting of transfer functions between source and microphones, but it is generally difficult to estimate transfer functions on-line without knowledge of the source signal. Instead, a sub-optimal beamforming algorithm that reduces signal distortion is proposed. It is constructed with steering vectors consisting of relative transfer functions between reference sensor and other sensors. In order to evaluate the performance of the proposed algorithm. we had recorded noisy speech database in a car, and performed speech recognition experiments with HMM Toolkit (HTK) released by Cambridge University. The recognition rate of the proposed algorithm was 15 percents higher than that of the conventional far-field beamformers in best case.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1055-1061
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• 2002

A numerical and experimental study on the flow fields behind the fan outlet was carried out to improve the performance of a conventional fan-sink(fan and heat sink). Conventional fan-sinks have a heat sink of which fin configurations tend to increase the flow resistance, thus decreasing the performance and the cooling capabilities of a fan-sink. Lifting surface method is used for the prediction of flow fields behind the fan outlet. Oil-dot flow visualization technique is applied for the validation of numerical results. The numerical results and experimental data show agreement each other. A conventional heat sink is modified and redesigned using flow patterns behind the fan outlet. The newly designed heat sink has the configuration of curved fins which minimize flow resistance. It showed improvements in both cooling: capabilities and volumetric flow rate compared to the conventional one.

• Journal of Aerospace System Engineering
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• v.9 no.3
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• pp.12-16
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• 2015

인간동력 항공기 TORUK MAKTO I에 대하여 양력선이론 및 XFOIL을 사용하여 도출한 공력계수 및 미계수 값과 CATIA를 사용한 관성모멘트 추정 값을 사용하여 지면효과 및 주익과 무게중심 사이의 수직거리 변화가 인간동력 항공기의 세로 정안정성에 미치는 영향과 수평미익(스테빌레이터) 변위각제어에 따른 세로 동안정성 해석 연구를 수행하였다. 연구결과 지면효과가 정적여유에 미치는 영향은 미미했다. 공력중심과 무게중심 사이의 수직거리가 세로 정안정성에 미치는 영향은 매우 컸으며, 수직거리 증가는 세로 정안정성을 증가시켰다. 수평미익 변위각 제어에 따른 세로 동안정성 해석 결과 장주기 진동특성과 감쇄특성이 매우 나쁜 것으로 나타났다. 향후 항공기의 동특성을 고려한 세로 동안정성 해석 및 측풍에 의한 가로 및 방향 안정성 해석연구를 수행할 예정이다.

• Journal of Institute of Convergence Technology
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• v.11 no.1
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• pp.29-32
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• 2021

편대비행 항공기들은 선행항공기에서 발생시킨 후류의 영향으로 후행항공기의 공력효율이 증가하는 것으로 잘 알려져 있다. 비점성 비회전 유동장에 관한 연속방정식을 지배방정식으로 사용하는 패널법은 비교적 빠른 시간 이내에 항공기의 공력특성 변화를 계산할 수 있는 장점이 있다. 본 연구에서는 편대비행 항공기들 사이의 항공기들 사이의 흐름방향 거리는 스팬길이의 2.5배로 위치시키고, 수평상대거리는 스팬길이의 -0.4~0.3배로, 수직상대거리는 스팬길이의 -0.25, -0.15.0.15.0.25배로 변화시키며 계산을 수행했다. 연구결과 선행항공기와 후행항공기의 수평상대거리 변화의 경우 주날개들이 안쪽으로 겹침이 발생하고, 수직 상대거리가 가까울수록 더 큰 공력성능 향상을 얻을 수 있었다. 편대비행 하는 후행항공기의 공력성능 향상은 선행 항공기로부터 발생한 익단 와류의 올려흐름 영향에 기인한 것이다. 선행항공기로부터 발생한 익단와류는 후행항공기의 모멘트 특성을 변화시켜 비행안정성에 영향을 미치게 된다. 향후 연구에서는 선행항공기로부터 발생한 와의 영향이 후행항공기의 모멘트 특성에 미치는 영향을 연구 할 것이다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.33 no.3
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• pp.209-214
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• 1988

This experiment was carried out to determine the effect of nitrogen rate and maturity on the yield, quality, nitrogen compound, protein pattern, and nitrate reductase activity. The results were as follow. As the nitrogen rate increased, the degree of red color of cured leaf increased. According to the time of harvesting at their leaf position, the price of the lugs is lowest in immature stage compared with mature and over mature stage but the upper leaves were lower than mature and immature stage in price. Yield are equal in immature stage and mature stage but over mature stage is lower than mature and immture stage. There was no different protein pattern and nitrate reductase activity in nitrogen rate and mature stage.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.422.2-422.2
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• 2014

가스장 이온원(GFIS: Gas Field Ionization Source)은 전자현미경보다 분해능이 향상된 이온현미경의 광원으로 사용하기 위하여 연구되고 있고, 큰 각전류 밀도, 작은 크기의 가상 이온원 그리고 좁은 에너지 퍼짐을 특징으로 한다. 여러 가지 장점을 가지고 있는 GFIS을 개발하기 위해서는 GFIS에서 발생된 이온빔의 형상을 관찰 것이 매우 중요하며, 이러한 관찰을 위한 시스템에는 주로 마이크로 채널 플레이트 (MCP: Micro Channel Plate)가 사용된다. MCP는 채널내부에 입사한 입자의 에너지에 의해서 생성된 이차전자를 수 천 배에서 수 백 만 배 이상 증폭시켜 형광판에 조사하고 발광시키는 방법으로 작은 신호를 영상으로 관찰 할 수 있도록 한다. MCP의 큰 증폭비는 작은 크기의 신호를 큰 신호로 증폭하여 관찰하는데 용이하여, GFIS 방법으로 생성된 이온빔(이온빔 전류 값은 pA 수준)을 관찰하기에 적합하다. 그러나 MCP를 이용하여도 증폭된 이온빔의 세기가 매우 작기때문에 생성된 이온빔 형상을 정확하게 관찰하기 위해서는 MCP의 형광판을 촬영하는 카메라 노출시간을 길게하여 데이터 수집 시간을 늘려야 하는 문제가 있다. 본 발표에서는 이온빔 형상 관찰에 소요되는 시간을 단축하기 위하여 MCP의 잡음이 GFIS의 이온빔 이미지 관찰에 미치는 영향을 분석하고 이를 제거 방법을 소개한다. 본 연구에서는 GFIS 방출 이온빔의 이미지에 포함된 MCP 잡음 특성을 장(전계)이온현미경 (Field Ion Microscope)실험을 통하여 분석하였고, 디지털 이미지 처리 방법을 이용하여 방출 이온빔 이미지에서 MCP 잡음을 제거하여 방출 이온빔 이미지만 추출할 수 있었다. 본 연구에서 제안한 방법을 GFIS 방출 이온빔 관찰시스템에 적용함으로써 기존 방법에 비해 노출시간을 단축하여 방출 이온빔을 관찰 할 수 있었으며, 노이즈 제거 효과로 향상된 이온빔 형상을 얻을 수 있었다. 본 연구결과의 관찰시간 단축과 향상된 이온빔 형상 획득은 이온현미경 개발에 필수적인 단원자 이온빔을 보다 효율적으로 개발할 수 있으며 디지털 이미지 처리로 GFIS 이온빔 생성을 자동화하는데 응용할 수 있다. 더불어 기존방법에 비해 이미지 획득을 위한 MCP의 노출시간을 단축할 수 있으므로 실험장비 수명 단축 방지 및 관리에 큰 장점이 있다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.32 no.1
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• pp.40-47
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• 1987

Under the different conditions of planting density and compound fertilizer level, some agronomic and chemical characteristics of burley tobacco were investigated from 1982 to 1984. Leaf area and dry leaf weight per plant, crop growth rate, relative growth rate and net assimilation rate for 40-60 days after transplanting were higher with increasing plant spacing and fertilizer, but leaf area index was lower with increasing plant spacing. At topping stage, the leaf size was increased with increasing plant spacing and amount of fertilizer applied and the stem diameter was increased by increasing plant spacing. Leaf area, leaf weight per plant and weight per unit leaf area of harvested leaf were higher when plant spacing and fertilizer increased. It was estimated that the optimum plant spacing was 105cm x 34cm and level of com-pound fertilizer (N-P$_2$ O$\sub$5/ -K$_2$O =10-10-20) was 263kg/l0a for high yield. There were trends toward increase the contents of total alkaloid and total nitrogen with increasing plant spacing and fertilizer application. There was significant positive correlation between plant spacing and total nitrogen, and between fertilizer application and total nitrogen. The plant spacing of 105cm x 35 to 40cm and 227.5kg/l0a of fertilizer level may be profitable for farm economy and the low nitrogenous leaf.

• Solar Energy
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• v.12 no.3
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• pp.47-59
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• 1992

In the concentric tube type recuperator, which is the most typical type of radiation recuperator, installed on the exhaust-secion of industrial furnace, air flows between the adiabatic outer tube and the inner tube in which exhausted gas flows with high temperature. The waste heat of the exhausted gas is transferred to the inner tube, and transferred from the inner tube to the flowing air. The heat transfer by radiation In the concentric tube type recuperator is modeled using spherical harmonics approximation, namely, P-N method and numerically analyzed considering the effect of dynamic flow field. The results are compared with the existing empirical data. In addition, a theoretical method is presented for the analysis of the heat transfer characteristics of a recuperator with a reradiator installed in the inner tube, which causes re-radiant in the inner tube, and the characteristics of the recuperator is analyszed and defined.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.298-302
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• 2013

The experiment was carried out to examine the effect of planting date on the growth and marketable yield on rain shielding vinyl house in Busan area. Okra cultivars were 'Jukokra', 'Greensod', 'Marumichang', 'Betafive' and 'Akamarumichang'. Planting date were June and July. Plant height, stem length and leaf width were significantly different between various cultivars. Plant height and stem length were best at 'Akamarumichang' among all cultivars tested and the 'Betafive' cultivars showed the lowest plant growth of June treatment. There was no significant difference in planting of July treatment. Marketable yield of okra fruit was affected by planting date. In case of June planting date, 'Betafive' cultivars produced the highest marketable yield (4,286 kg/10a) in green fruit. Marketable yield of green okra fruit was increased at 'Betafive' and 'Greensod' cultivars, whereas 'Marumichang' cultivars was lowerd. Therefore, the optimum planting date was considered June planting in rain shielding culture of okra in Busan area.

• Korean Journal of Plant Resources
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• v.13 no.2
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• pp.111-117
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• 2000

In an attempt to select grape bag, which elevates grape quality and make easy maturation period determination, the following research was carried out at Chungbuk Institute of Agricultural Technology, Grape Experiment Station. Light transmittance rate of bag reached to 11-65% with non-woven fabric and non-dripped vinyl bags. Non-dripped vinyl perforation and white painting bag resulted in 50 and 75%, respectively. Berry weights in non-woven fabric and non-dripped vinyl bag were high than that in paper bag. Non-dripped vinyl perforation 50%, white painting bag brought into fruit cracking, shattering, and rotten fruit, making the investigation difficult. Maturation period preceded about 1-4 day with non-woven fabric and non-dripped vinyl compared with that in paper bag. Soluble solids content with non-woven fabric and non-dripped vinyl bags was high and acidity showed a reverse result. Coloring extent was developed rapidly with non-woven fabric and non-dripped vinyl than paper bag. During initial state of coloring, coloring was rapid with Maekban-Stone mixed non-woven fabric and non-dripped vinyl + non-woven fabric bag. This was rapid with non-woven fabric bag as long appropriate maturation period. Abnormal berry rate was 5.4-7.0% with paper and non-woven fabric bags but brought about as much as 16.6-100% with non-dripped vinyl and it's mixed bags. Appearance quality was the best with index 9.0 for non-woven fabric bag. Maekban-Stone mixed non-woven fabric but non-dripped vinyl performance 50% white painting bag was the least, showing index 1.0. The time consumed for maturation determination was reduced to 74-93% with non-woven fabric and non-dripped vinyl bag compared with 17.4h/10a with paper bag.