• International Journal of Aeronautical and Space Sciences
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• 제17권3호
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• pp.352-357
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• 2016

An investigation of ribbed divergent channel was undertaken to determine the effect of rib pitch to height ratio on total friction factor and heat transfer results in the fully developed regime. The ribbed divergent rectangular channel with the channel exit hydraulic diameter ($D_{ho}$) to inlet channel hydraulic diameter ($D_{hi}$) ratio of 1.16 with wall inclination angle of 0.72 deg, at which the ratios (p/e) of 6,10, and 14 are considered. The ribbed straight channel of $D_{ho}/D_{hi}=1.0$ were also used. The ribbed divergent wall is manufactured with a fixed rib height (e) of 10 mm and the ratio of rib spacing (p) to height 6, 10, and 14. The measurement was run with range of Reynolds numbers from 24,000 to 84,000. The comparison shows that the ratio of p/e=6 has the greatest thermal performance in the divergent channel under two constraints; identical mass flow rate and identical pressure drop.

• 한국수정란이식학회지
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• 제12권2호
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• pp.203-209
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• 1997

This study was carried out to compare the actual size(length and height) of ovaries, follicles and corpora lutea of Korean native cow with those on sonograms. We used 3 different probes(3.5 MHz abdominal probe, 6.5 MHz transvaginal probe and 5.0 MHz transrectal probe) and a calipher for measurements of ovaries, follicles and corpora lutea on sonograms and actual size. Under water immersion, 157 ovaries were scanned with 3 probes and measured in actual size and compared each other. The average height and width of ovaries of Korean native cows were 17.40$\pm$3.99 and 34.23$\pm$6.02mm, respectively. In comparison of height, length of ovaries and preovulation follicles, we found that image with a transvaginal probe was nearly the same as the actual size(p<0.01), but with an abdominal probe the image was appeared larger than the actual size. In measurement(diameter) of preovulation follicles the transvaginal probe was proven to be more accurate to the actual size than other probes and in corpus luteum measurement all probes were accurate. In the comparison of number of follicles by different size ranges, there was no statistical difference in the count of follicles over 10 mm in diameter between the transvaginal probe and naked eyes.

• 한국정밀공학회지
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• 제34권2호
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• pp.89-94
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• 2017

Micro-screws can be defined by their outer diameter of generally less than 1 mm. They are manufactured by head forging and thread rolling processes. In this study, the thread rolling process was numerically analyzed for a micro-screw with a diameter and pitch of 0.8 and 0.2 mm, respectively. Through finite element (FE) analysis, the effects of two design parameters (die gap and chamfer height) on the dimensional accuracy were investigated. Three combinations of chamfer heights were chosen first and the corresponding die gap candidates selected by geometric calculation. FE analyses were performed for each combination and their results indicated that the concave chamfer height should be less than 0.3 mm, while a 10 ?m difference in the die gap might cause degeneration in dimensional accuracy. These results conclude that ultra-high accuracy is required in die fabrication and assemblies to ensure dimensional accuracy in micro-screw manufacturing.

• 한국유기농업학회지
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• 제6권1호
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• pp.109-116
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• 1997

This experiment was carried out to examine the effect of various functional materials such as bioceramic podwers, crushed shells and elvanites supplemented to the each substrate on the seedlings growth of cucumber, watermelon and tomato. The seedlings were grown in pots filled with substrates of bioceramic podwers, crushed shell and elvanites. The growth of cucumber seedlings in terms of plant height, stem diameter, leaf width, leaf area, plant fresh and dry weight was promoted by adding the bioceramic. powder (1 to 2g/kg), crushed shells (20 to 80g/kg) or elvanites (20 to 80g/kg). Watermelon seedlings in terms of plant height, number of leaves and leaf area were greater than those of the control by adding bioceramics (1 to 2g/kg). Plant height was also promoted by the adding of bioceramic power from 16 days after treatment. But leaf area was increased from 8 days after treatment, while stem diameter was not affected. Watermelon seedlings were also influenced by adding curshed shells (20 to 80g/kg) and elvanites (20 to 40g/kg) into each substrate. The growth of characteristics of tomato seedlings were promoted by adding 1 to 3g/kg of bioceramics, 10 to 80g/kg of crushed shell or 20 to 40g/kg of elvanites, respectively. Especially, root growth was greatly influenced by bioceramic powder, whereas the shoot growth(leaves and stem) was stimulated by crushed shells and elvanites suppemented into substrate.

• 한국방재학회 논문집
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• 제3권2호
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• pp.139-145
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• 2003

본 연구에서는 다양한 크기의 원환에 따른 균등원통교각 주위의 세굴심을 분석하여 세굴심 감소효과 및 원환의 적정 크기를 제시하였다. 이를 위하여 수리모형실험을 실시하였으며, 교각에 원환을 설치한 경우 원환을 하상 위보다 하상 아래에 설치하는 것이 더욱 효과적이었으며, 원환의 크기가 클수록 세굴심 감소 효과가 뚜렷하였다. 교각 직경에 대한 원환 직경의 비(W/D)가 2인 경우 약 67% 세굴심이 감소하였으며, 퇴적고는 약 70%정도 증가하였다. 세굴심 감소 효과, 세굴공 및 퇴적고의 분석 결과를 토대로 W/D=2인 원환을 최적 크기로 제안하였다.

• 생명과학회지
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• 제13권6호
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• pp.889-895
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• 2003

장미 삽목묘에 돌리도를 주기적으로 관주하여 초장, 경직경, 엽수, 엽면적, 최대 근장 등 생육반응을 검정한 결과 돌리도의 관주처리는 삽목묘의 초기생육에 큰 차이는 없었으나 60일 후의 후기생육은 향상되었다. 장미 유목에 돌리도를 관주 처리하면 초장, 경직경의 향상과 줄기의 부피생장 더불어 엽수 및 엽면적이 증가되었다. 돌리도를 주기적으로 관주한 장미유목은 이를 처리하지 않은 대조구에 비해 초장이 6.4∼11.0 cm, 경직경은 0.70∼l.14 cm증가하였고, 엽면적도 $136cm^2$ 높았다. 또한 돌리도의 처리에 의해 총 생체중 및 총 건물중을 증가시켰는데, 그 효과는 생육후기로 갈수록 현저하였다.

• 한국환경과학회지
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• 제32권3호
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• pp.161-171
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• 2023

The present study evaluated growth factors affecting oak community plantations through literature review and a field survey. Specifically, 41 related literature sources were analyzed and field surveys were conducted to collect growth data. Previous studies were analyzed to identify variables with high frequency of use. The frequency of use was in the order of tree size > environment > planting density > forest age. Analysis of factors impacting height and diameter growth revealed that the growth rate of species other than Quercus variabilis was negative in the field survey. This may be because of differences between the actual trees planted and specifications in the construction drawings, which may be attributed to the site conditions and decisions made by the project subject during construction. Furthermore, simple linear regression analysis was conducted with time, height at planting, density, and species code as the independent variables and growth rate as the dependent variable. A strong positive linear correlation was noted between height and diameter. This work builds a foundation for developing a forest restoration model and simulation program based on a regression model derived from the four variables tested.

• Advances in concrete construction
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• 제13권3호
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• pp.223-231
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• 2022

The problem is formulated by applying the Kirchhoff's conception for shell theory. The longitudinal modal displacement functions are assessed by characteristic beam ones meet clamped-clamped end conditions applied at the shell edges. The fundamental natural frequency of rotating functionally graded cylindrical shells of different parameter versus ratios of length-to-diameter and height-to-diameter for a wide range has been reported and investigated through the study with fractions laws. The frequency first increases and gain maximum value with the increase of circumferential wave mode. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing height-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The trigonometric frequencies are lower than that of exponential and polynomial frequencies. Stability of a cylindrical shell depends highly on these aspects of material. More the shell material sustains a load due to physical situations, the more the shell is stable. Any predicted fatigue due to burden of vibrations is evaded by estimating their dynamical aspects.

• 한국산림과학회지
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• 제95권1호
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• pp.131-138
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• 2006

본 연구는 우리나라 천연활엽수림의 대표적 수종인 신갈 굴참나무를 대상으로 흉고직경 생장량 패턴을 알아보고, 14개의 임목 측정인자와 직경생장량과의 관계를 규명하기 위하여 실시하였다. 본 생장량 자료는 강원도 천연활엽수림지역에서 벌도 된 83본의 신갈 및 굴참나무에 대하여 수간석해를 통하여 분석하였다. 두 수종 모두 우세목의 경우 평균적으로 15~20년까지 흉고직경생장률이 높게 나타나다가 그 이후부터는 일정한 생장량을 갖고, 매년 0.09~0.83 cm/yr의 흉고직경생장을 하는 것으로 나타났다. 최근 5년간의 연년직경생장량은 신갈나무가 평균 0.28 cm/yr로 굴참나무 평균 0.27 cm/yr 자라는 것으로 실측되었으며, 두 수종 모두 우세목, 준우세목, 중간목, 피압목 순으로 생장이 좋은 것으로 확인되었다. 특히, 신갈나무의 경우는 수관급간에 직경생장량이 매우 유의적인 차이 (p<0.0001)가 있는 것으로 나타났다. 또한, 14개의 입목 측정인자와 조제변수를 이용하여 최근 5년간의 연년직경생장량과 Pearson 상관분석을 실시한 결과, 신갈나무의 경우 상대직경(r=0.64), 상대수고(r=0.61), 노출된 수관투영면적(r=0.58), 전체 수관투영면적(r=0.56)순으로 상관관계가 높게 나타났으며, 굴참나무는 흉고직경(r=0.57), 수관폭(r=0.55), 연령(r=0.39), 경쟁지수(r=-0.39), 수고(r=0.35)순으로 상관관계가 있는 것으로 나타났다.

• 농업생명과학연구
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• 제45권6호
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• pp.9-19
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• 2011

작물의 묘소질은 정식 후 본포에서의 생육이나 수량, 품질에 영향을 미치기 때문에 작물 재배에서 있어서 육묘는 매우 중요하다. 본 연구는 야간온도 수준을 10, 15, $20^{\circ}C$로 조절하여 토마토묘와 수박 접목묘의 생육에 어떠한 영향을 미치는지 살펴보고 야간온도에 따라 변화된 초장, 건물중, 경경 등의 건묘를 나타내는 중요한 생육지표간의 상관관계를 분석하였다. 야간온도 $10^{\circ}C$로 관리하였을 때 토마토묘에서 엽면적지수와 건물중이 다른 처리에 비하여 유의적으로 감소하였으며, 야간온도를 $20^{\circ}C$로 관리하였을 때 수박 접목묘에서 초장이 길어지고 경경이 감소하는 것으로 나타났다. 재배기간 동안의 누적온도에 대한 반응은 토마토의 경우 야간온도가 낮을 경우 누적온도가 같더라도 엽면적이 감소되어 결과적으로는 건물중을 감소시켰으며, 수박 접목묘의 경우 초장이 유의적으로 길어졌다. 주요 생육지표간의 상관관계를 살펴보면 토마토묘의 경우 초장과 경경의 경우 온도처리와 상관없이 선형적인 상관관계가 있는 것으로 나타나 묘소질을 판단하기에는 부적절한 것으로 판단되며, 수박 접목묘의 초장과 경경은 야간기온 처리에 따라 달라지며 상관성을 보이지 않았으므로 묘소질을 판단하는데 이용 가능할 것으로 판단된다.