• 대한기계학회논문집B
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• 제23권3호
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• pp.419-430
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• 1999

Measurements of local blowing ratio and ammonia-diazo flow visualizations have been conducted for a shower-head film cooling on a first-stage turbine stator. In this study, six rows of normal holes are drilled symmetrically on the semicircular leading edge of a simulated blunt body. The measurements show that for an average blowing ratio based on freestream velocity, M, of 0.5, local average mass flow rate through the first two rows of the holes is less than those through the second and third two rows of the holes, and the fraction of mass flow rate through the first two rows to total mass flow rate has a tendency to increase with the increment of M. The flow visualizations reveal that the injection through the first two row results in inferior film coverage even In the case of M = 0.5, meanwhile the row of holes situated at farther downstream location provides higher film-cooling performances for all tested M. This is because film-cooling effectiveness depends on local mainflow velocity at the hole location as well as the mass flow rate through each row.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1632-1639
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• 2001

Control of drag farce on a circular cylinder using a detached splitter plate is numerically studied for laminar flow. A splitter plate with the same length as the cylinder diameter(d) is placed horizontally in the wake region. Its position is described by the gap ratio(G/d), where G represents the gap between the cylinder base point and the leading edge of the plate. The drag varies with the gap ratio; it has the minimum value at a certain gap ratio for each Reynolds number. The drag sharply increases past the optimum gap ratio; this seems to be related to the sudden change in bubble size in the wake region. This trend is consistent with the experimental observation currently available in case of turbulent flow. It is also found that the net drag coefficient significantly depends on the variation of base suction coefficient.

• 대한기계학회논문집B
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• 제27권7호
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• pp.920-928
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• 2003

The objective of the present study was to investigate the characteristics of flow and wall shear stress under steady and pulsatile flow in the aneurysm. The numerical simulation using the software were carried out for the diameter ratios ranging from 1.5 to 3.0, Reynolds number ranging from 900 to 1800 and Womersley number, 15.47. For steady flow, it was shown that a recirculating vortex occupied the entire bulge with its core located closer to the distal end of the bulge and the strength of vortex increased with increase of the Reynolds number and diameter ratio. The position of a maximum wall shear stress was the distal end of the aneurysm regardless of the Reynolds number and diameter ratios. For the pulsatile flow, a recirculating flow at the bulge was developed and disappeared for one period and the strength of vortex increased with the diameter ratio. The maximum values of the wall shear stress increased in proportion to the diameter ratio. However, the position of a maximum wall shear stress was the distal end of the aneurysm regardless of the diameter ratios.

• 대한기계학회논문집B
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• 제20권4호
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• pp.1363-1375
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• 1996

Oil-film flow visualizations and three-dimensional flow measurements using a five-hole probe have been conducted to investigate three-dimensional flow characteristics and total pressure losses of a row of film-cooling jets injected in spanwise direction. For several span-to-diameter ratios, experiments are performed in the case of three velocity ratios of 0.5, 1.0 and 1.5. The flow measurements show that downstream flow due to the injection is characterized by a single streamwise vortex instead of a pair of counter-rotating vortices, which appear in the case of streamwise injection, and the vortex strength strongly depends on the velocity ratio. Regardless of the velocity*y ratio, presence of the spanwise film-cooling jets always produces total pressure loss, which is pronounced when the velocity ratio is large. It has also been found that the production of the total pressure loss is closely related to the secondary vortical flow. In addition, effects of the span-to-diameter ratio on the flow and total pressure loss are discussed in detail.

• Journal of Ecology and Environment
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• 제35권4호
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• pp.313-322
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• 2012

A 2-year study (2010-2011) was carried out in order to evaluate the effects of bean and maize intercropping. The experiment tested five different cropping systems: sole cropping of each crop, as well as intercropping of maize/bean with the ratios of 1:3 ($M_1B_3$), 2:2 ($M_2B_2$) and 3:1 ($M_3B_1$), each of which took place in the presence of two weed management systems (no weed control and weed eradication through manual removal), in a factorial experiment based on randomized complete block design using three replicates. Tests of homogeneity of variance for combined data over two years showed that data of both years could be analyzed together. The results showed that the effect of intercropping treatments on all measured traits in maize and bean were significantly different. A minimum land equivalent ratio (LER) for maize (0.78) was obtained for $M_3B_1$ under conditions of no weed control, while the highest LER (1.03) was observed in $M_3B_1$ under weed-free conditions. The highest (0.99) and lowest (0.70) LER values for beans were recorded for $M_1B_3$ under weed-free conditions and $M_3B_1$ under conditions of no weed control, respectively. $M_1B_3$ under weed-free conditions showed the highest total LER (2.02), while $M_3B_1$ under conditions of no weed control showed the lowest (1.48). Results of this study indicated that intercropping bean and maize can be an effective method to increase total productivity, and that the $M_1B_3$ system was the best cropping system for high productivity.

• 한국통신학회논문지
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• 제34권4C호
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• pp.446-452
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• 2009

OFDM 시스템은 전송단자 수신단의 오실레이터의 불일치로 인해 발생하는 주파수 오프셋의 영향에 민감하다는 단점이 있다. 또한 주파수 오프셋은 ICI(Inter Carrier Interference) 문제를 발생시키고 부반송파 사이에 직교성을 왜곡한다. 본 논문에서는 ICI 영향을 분석하고, 기존의 SC 기법을 응용하여 새로운 알고리즘을 제안한다. 제안된 기법의 BER(Bit Error Rate)과 신호 품질을 결정짓는 CR(Carrier to Interference Ratio)을 분석하기 위하여 MATLAB 프로그램을 사용한다. 모의실험 결과, 주파수 오프셋이 0.3과 0.5 일 때 $10^{-3}$의 BER에서 BPSK 변조는 0.5dB, 1dB 이상, QPSK 변조는 1.6dB, 1.5dB 이상의 SNR 성능 향상을 보이며, CIR 성능도 최대 15dB 이상 향상 되었다. 결과적으로 제안한 기법이 기존의 기법보다 시스템 성능 향상에 효과적이다.

• Nutritional Sciences
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• 제4권1호
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• pp.20-25
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• 2001

The dietary vitamin $B_6$ intake of 218 Korean young women (aged 20-26y), who had no health problems, and their sources were estimated using a modified Korean vitamin $B_6$ database. The average daily vitamin $B_6$ intake was 0.987 mg for the subjects. About 87.2% of the subjects consumed less than the Korean Recommended Dietary Allowance (RDA) of vitamin $B_6$. The average ratio of vitamin $B_6$ intake to daily protein intake was 0.014 mg/g protein, and approximately 91% of subjects consumed 〈 0.02 mg/g protein. Vitamin $B_6$ intake was significantly (p〈.01 -p〈.001) positively correlated to the intakes of all other nutrients. Between animal and vegetable protein, animal protein had a stronger positive correlation with vitamin $B_6$. Major dietary sources of vitamin $B_6$, the top 10 foods provided nearly 64% of total vitamin $B_6$, and dietary contributors of vitamin $B_6$ for Koreans are less varied than those for Americans.

• 한국작물학회지
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• 제62권2호
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• pp.79-86
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• 2017

본 연구는 전남지역 시군에서 생산, 유통되고 있는 브랜드쌀의 품질평가를 실시하여 연차간 변이와 유통쌀의 품질에 미치는 요인을 분석하고자 수행되었으며 그 결과는 다음과 같다. 1. 전남의 연중 브랜드쌀 품질 변이는 도요윤기치 3.1%, 백도 2.1%, 단백질함량 1.6%, 수분함량 1.0%, 완전미율 0.4% 순으로 컸고 4월 이후부터 품질특성이 저하되었다. 2. 연차별 브랜드쌀 품질 변이는 단백질함량(5.6%), 도요윤기치(5.2%)가 컸고 백도(2.7%), 완전미율(1.8%)은 상대적으로 낮았다. 3. 식미치와 단백질함량은 최저기온, 일조시간, 강수량, 일교차와 높은 상관을 보였고 완전미율은 일교차와 부의 상관을, 분상질립율은 강수량과 높은 정의 상관을 보였다. 4. 단백질함량, 수분함량, 백도, 완전미율 등 밥맛과 상관이 높은 항목을 이용한 식미추정회귀식 산정 결과 y = - 6.71a + 2.27b + 1.29c + 0.51d - 15.34 ($R^2$=0.51*)이었으며 이 때 y는 관능식미, a는 단백질함량(%), b는 수분함량(%), c는 백도, d는 완전미율(%)이었다.

• Journal of Microbiology and Biotechnology
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• 제18권1호
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• pp.135-137
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• 2008

The metabolic engineering of epothilones, as secondary metabolites, was investigated using Sorangium cellulosum to achieve the selective production of epothilone B, a potent anticancer agent. Thus, the propionyl-CoA synthetase gene (prpE) from Ralstonia solanacearum was heterologously expressed in S. cellulosum to increase the production of epothilone B. Propionyl-CoA synthetase converts propionate into propionyl-CoA, a potent precursor of epothilone B. The recombinant S. celluloslim containing the prpE gene exhibited a significant increase in the resolution of epothilones B/A, with an epothilone B to A ratio of 127 to 1, which was 100 times higher than that of the wild-type cells, demonstrating its potential use for the selective production of epothilone B.

• 한국지능시스템학회논문지
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• 제15권2호
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• pp.230-235
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• 2005

본 논문에서는 잡음에 열화된 대역에서 지능적으로 잡음의 패턴을 추정하여 지각 필터의 성능을 개선시켜 오디오 신호의 음질을 개선하는 알고리즘을 제안한다. 제안된 알고리즘은 묵음 구간에서 추정한 고정된 추정 잡음을 사용하는 기존의 방식을 사용하지 않고, 신호 구간마다 달라지는 신호의 세기와 잡음의 영향 정도를 고려하여 신호가 열세하고 잡음이 대부분을 차지하는 대역, 즉 잡음에 열화된 대역에서 잡음 패턴을 추정하여 신호를 열화시키는 잡음을 효과적으로 제어하는 방식으로 지각적으로 개선된 음질의 신호를 얻을 수 있다. 기존 방식과의 비교를 위해 다양한 신호 대 잡음 비(signal-to-noise ration, SNR)에서 열화된 오디오 신호를 입력으로 사용하였다. 입력 SNR이 $5\cal{dB},\;10\cal{dB},\;15\cal{dB}$와 $20\cal{dB}$의 각각의 경우에 대하여 객관적인 평가인 세그멘탈 신호 대 잡음비(Segmental SNR, SSNR)와 잡음 대 마스킹 비(Noise-to-mask ratio, NMR), 또한 주관적인 평가인 청감 테스트(Mean opinion score, MOS test)를 비교하였다. 그 결과, SSNR 측면에서는 각각의 경우에 대해 $7.4\cal{dB},\;6.8\cal{dB},\;5.7\cal{dB},\;5.1\cal{dB}$ 그리고, NMR 측면에서는 $15.7\cal{dB},\;15.5\cal{dB},\;15.2\cal{dB},\;14.8\cal{dB}$ 의 개선을 확인할 수 있었다. 또한 주관적인 측정 결과인 테스트의 개선 확인 및 음질 개선에 의한 성능을 확인할 수 있었다.