• 대한건축학회논문집:구조계
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• 제35권7호
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• pp.171-178
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• 2019

Auto Climbing Formwork System (ACS) for construction of high-rise building is a construction method for automatically lifting the formwork system supported by the anchor on the pre-constructed concrete wall. It has excellent construction speed and quality, but it has the possibility of structural failure depending on the quality of concrete and also has low economical efficiency due to the use of foreign technology. In order to overcome these problems, this study conducted an optimum design for the development of a new concept of Corner Supported Auto Climbing System (CS-ACS) in conjunction with the development of corner steel-reinforced concrete core wall system. For the design the formwork system, the basic module and structural member compositions were planned, and the structural analysis program was used to analyze the optimum member's cross section and spacing. As a result, the horizontal displacement and the stress of the horizontal members were influenced by the spacing more than the cross-section of the member. On the other hand, vertical members did not affect the displacement and stress of the formwork system. The form tie was very effective in controlling the displacement when adjusting the spacing of the horizontal members, but when the spacing of the form tie is more than 1,500mm, it is analyzed that form tie is yielding in basic module. When the span of the formwork system is more than 30m, it is analyzed that the basic module needs to be changed because of the increase of overall displacement.

• 한국환경농학회지
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• 제34권3호
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• pp.204-209
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• 2015

본 연구는 시장점유율이 가장 높은 가을무 두 품종을 이용하여 적정 재식거리를 구명하고자 실시하였다. 열간거리 $55{\times}25$, $45{\times}25$, $35{\times}25$ 및 $25{\times}25cm$ 등 4 실험구로, 주간거리 $35{\times}28$, $35{\times}25$, $35{\times}22$ 및 $35{\times}19cm$ 등 4 실험구로 파종하여 파종 58일 후 수확하여 지상부 및 지하부 생육과 뿌리 품질을 조사하였다. 두 품종 모두 열간거리에 따른 지상부 생육의 차이는 없었다. 하지만 열간거리 25 cm에서 S품종의 근장 및 C품종의 근중이 각각 20.5 cm, 1,422 g으로 다른 처리에 비해 통계적으로 유의하게 적었다. 따라서 가을무의 두 줄 재배시 열간거리는 근중이 감소하지 않고 무의 품질에도 영향을 미치지 않는 35 cm가 적절한 것으로 판단된다. 주간거리는 두 품종 모두 28, 25 및 22 cm에서는 평균 1,500 g 이상의 적절한 크기의 무가 생산되었으나 C품종의 경우 19 cm 실험구에서 근중이 1148.3 g으로 다른 실험구에 비해 크게 감소하였다. S품종의 경우, 주간거리는 무의 수량 및 품질에 큰 영향을 미치지 않았으나 C품종의 경우 주간거리에 의해 지상부 및 지하부 생육이 크게 영향을 받는 것으로 나타났다. 당도와 바람들이는 재식거리에 따라 영향을 받았지만 그 차이는 적었다. 따라서 가을무 두 줄 재배시 적정 재식거리는 최소 열간거리 25 cm, 주간거리 19 cm 이상 설정하는 것이 가을무 재배에 유리할 것으로 판단된다.

• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1801-1810
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• 2005

The effect of longitudinal thin rectangular riblets aligned with the flow direction on turbulent channel flow has been investigated using direct numerical simulation. The thin riblets have been modeled using the immersed boundary method (IBM) where the velocities at only one set of vertical nodes at the riblets positions are enforced to be zeros. Different spacings, ranging between 11 and 43 wall units, have been simulated aiming at getting the optimum spacing corresponding to the maximum drag reduction while keeping the height/spacing ratio at 0.5. Reynolds number based on the friction velocity ${\mu}_\tau$ and the channel half depth $\delta$ is set to 150. The flow is driven by adjusted pressure gradient so that the mass flow rate is kept constant in all the simulations. This study shows similar trend of the drag ratio to that of the experiments at the different spacings. Also, this research provides an optimum spacing of around 17 wall units leading to maximum drag reduction as experimental data. Explanation of drag increasing/decreasing mechanism is highlighted.

• 대한기계학회논문집
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• 제13권2호
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• pp.299-306
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• 1989

본 연구에서는 밀집형 열교환기에 사용되고 있는 루우버 핀에 해당되는 간단한 형상인 등온, 수직, 평행평판에서의 혼합대류 열전달에 관하여 Pr=0.7, Gr=$10^{4}$ 및 50＜Rｅ$_{L}$＜500인 경유 평판간격과 평판길이를 변수로 하여 유한차분법으로 수치해석하였다. 속도분포, 온도분포 및 Nusselt수를 구하여 평판의 간격과 길이가 열전달에 미치는 영향에 관하여 연구하였다.

• 한국도로학회논문집
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• 제9권3호
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• pp.101-110
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• 2007

국내 줄눈콘크리트 포장의 줄눈간격은 6m로 획일적으로 설계 건설되어 왔으며 이에 대한 과학적 근거는 제시된 바 없었다. 현재 진행중인 한국형 포장설계법 개발에서는 국내 지역별 기후조건 등을 고려하여 줄눈간격 변화에 따른 줄눈콘크리트 포장의 장 단기 파손을 역학적-경험적 방법을 토대로 분석하여 줄눈간격을 지역별로 $6{\sim}8m$로 설계할 것을 제시한 바 있다. 본 연구는 한국형 포장설계법에서 제시한 줄눈간격 잠정안에 대한 타당성을 검증하기 위한 연구의 일환이다. 줄눈간격이 증가할 경우 시공초기에 하중전달률의 변화, 무작위균열 등의 발생가능성에 문제점이 없는지를 검증하기 위해서 한국형 포장설계법의 줄눈간격 잠정안에서 줄눈간격이 7m로 제시된 지역에 대해서 7m 줄눈간격으로 시험시공하고 초기거동을 모니터링 하였다. 하중전달률, 무작위균열, 줄눈폭변화 등 모니터 링 결과를 시공조건이 동일한 인접 6m 줄눈간격 비교구간의 초기거동과 비교분석하였다.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1998년도 춘계학술대회논문집
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• pp.161-166
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• 1998

In this study, the optimum criteria of space between the lines and the letters which could largely affect the legibility were found by the experiment and were presented as guidelines to design Korean VDT screens. Since the experiment was designed to test the human performance based on the VDT screen design, searching speed (S.S) and error rate (E) were used as the criteria of performance, and CFF value was measured to evaluate user's visual fatigue. The EOG value was also measured for the visual restriction during the experiment for the space between the lines and letters.

• The Journal of the Acoustical Society of Korea
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• 제18권4E호
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• pp.37-42
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• 1999

This paper concerns a modified perturbation method and a least square approach to synthesize an optimum beam pattern of a thinned sensor array with respect to element spacing. In the modified perturbation, the antenna spacing is perturbed iteratively such that the sidelobes are equalized via a linear programming approach. The least square approach is proposed to improve the array performance for the thinned array using the fact that the number of sidelobes is more than the number of element spacings. It is demonstrated that the least square approach performs better than the modified perturbation method.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.386-389
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• 2004

Beamforming for underwater acoustic communication is affected by the broadband feature of underwater acoustic communication signal, which has the low center frequency compared to the signal bandwidth. In this paper, the baseband equivalent array signal model is derived and we present computer simulation results for the broadband finite impulse response (FIR) beamformer performance according to the FIR filter order and the tap spacing. If the FIR filter order is increased above the optimum value, the beamformer performance is degraded. Also the tap spacing is related to the optimum FIR filter order.

• 대한기계학회논문집B
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• 제22권4호
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• pp.520-529
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• 1998

Heat and mass transfer behaviors of metal hydride beds were predicted by solving a set of volume-averaged equations numerically both for the gas (hydrogen) and the solid(metal hydride) phases. Time variations of temperature and hydrogen concentration ratio distributions were obtained for internally cooled, cylindrical-shaped beds with metal(aluminum) fins imbedded in them. Also, time variations of the space-averaged hydrogen concentration ratio were obtained. Temperature and velocity of the coolant, hydrogen pressure at the gas inlet, and the fin spacing were taken as the parameters. The hydrogen absorption rate increases with the higher velocity and the lower temperature of the coolant, and with the decrease of the fin spacing. Increasing of the hydrogen pressure at the gas inlet also promotes the rate of absorption though the increasing rate gradually slows down. The amount of the hydrogen storage per unit volume of the bed decreases with the tighter fin spacing despite of the higher absorption rate ; therefore, there should be an optimum fin spacing for a given volume of the system and the amount of the hydrogen storage, in which the absorption rate is the highest.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.605-608
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• 1993

Breakdown characteristics of a small rod-to-rod microairgap has been studied for obtain an optimum breakdown voltage and an airgap spacing to be used as an emission control means by the electrical arc-burning unburnt carbon particulates exhausted from a power station burner. It is found that the breakdown voltage at the rod-to-rod airgap spacing in the rang of $1{\sim}100{\mu}m$ decreased with decrease in the rod-to-rod airgap spacing. And there were no minimum breakdown voltage on a $V_b$-Pd characteristics which is known as the minimum voltage in Paschen's law in air atmosphere. Breakdown voltages of the airgap at the constant airgap spacing were $V_{b-dc}>V_{b-ac}>V_{b-pulse}$, and it was lowest for the pulse voltage applied. As a result, it is found that a pulse power was one of effective power compared with dc or ac to be used as such an unburnt carbon particulate emission control means and the airgap spacing became to several tens ${\mu}m$, then the breakdown voltages were down to several handreds voltages.