• Journal of Power System Engineering
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• v.1 no.1
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• pp.61-69
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• 1997

본 연구는 동심환형관에서 거칠기가 없이 매끈한 경우, 내측벽에 만, 외측벽에 만, 그리고 양측 모두에 거칠기가 있는 4경우에 대해 직경비가 0.26, 0.39, 그리고 0.56일 때 벽면에 설치된 거칠기 위치들이 난류유동장에 미치는 효과를 실험적으로 조사하고자 한다. 최대속도와 전단응력이 0인 지점들, 시간평균속도의 구배들, 그리고 와확산계수들을 X형 열선풍속계와 이중 피토튜브를 사용하여 측정하였다. 본 연구를 통하여 동심환형관에 설치된 거칠기들이 난류유동에 미치는 효과에 대한 정량적자료를 제시할 수 있었다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.4
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• pp.269-283
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• 2005

To figure out the cause of underestimating the roughness and shear strength of rock joints suggested by numerous researchers, we analyzed roughness mobilization characteristics, characteristics of roughness parameters, effects of sampling interval, and waviness for roughness parameters. It was found out that lack of understanding of the roughness mobilization characteristics, inappropriate applications of roughness parameters, and effect of aliasing provide a main reasons for those problems. Several practical alternatives for improving those problems were suggested. As far as digitizing methods are concerned, we can find that using a 3D scanner can give a relatively effective result. To avoid aliasing, sampling interval should be less than one-quarter of the minimum asperities. As for the quantification of roughness, it was analyzed that the roughness parameter should be classified into two components depending on the scale of roughness to apply the shear strength model. For classifying the roughness, a framework of the criterion was suggested based on the plastic flow concept for the asperity failure, and the basis for proposing a new alternative shear strength model was established.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.22 no.1
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• pp.60-69
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• 1996

3-APPA는 생체내 물질 Υ-amino butyric acid와 유사한 구조를 갖는 물질로서 human fibroblasts 3-dimensional culture system 등의 in vitro 시험에서 collagen 합성촉진 효과, 세포증식 효과를 나타내며, hairless mouse를 이용한 동물시험에서도 collagen 합성이 증가되는 것으로 보고된 바 있다. 또한 피부 안정성에서도 우수한 결과를 보여줌으로서 화장품 분야에서 새로운 노화억제 물질로서 주목을 받게 되었다. 본 시험에서는 180명의 피검자를 대상으로 3개월간의 임상시험을 통하여 새로운 노화억제 물질인 3-APPA의 효능을 기존의 GABA 유사물질, aminopropane sulfonic acid와 비교하였다. 본 시험은 double-blind, randomized, vehicle-controlled clinical study로서 180명의 피검자를 APSA군, 3-APPA군, vehicle군으로 분류한 후 3개월간 매일 저녁 취침 전, 안면에 시험제품을 사용하도록 하였으며, 사용 전, 사용 1주후, 2주후, 6주후, 12주후 5회 설문지를 통하여 피부상태를 조사하였다. 각 설문내용은 피부 건조도, 피부 탄력도, 피부 주름량, 피부 윤기도, 피부 거칠기 정도에 대한 5개 질문으로 구성된 효능에 관한 질문과 흡수정도, 끈적임, 매끄러움, 보습력, 보습지속성, 전체적인 사용감에 대한 6개 질문으로 구성된 사용성에 관한 것이었다. 각 질문에 대하여는 매우 좋음 1점, 좋은 2점, 보통임 3점, 나쁨 4점, 매우 나쁨 5점 사이에서 답할 수 있도록 하였다. 시험 결과 APSA군은 6주와 12주후 피부 건조도, 피부 거칠기 항목에서 사용전에 비하여 유의한 차이를 나타내었다. 3-APPA군은 6주후 피부 건조도, 피부 거칠기, 피부 탄력도 항목에서 시료사용전에 비해 유의한 차이를 나타내었으며 12주후에는 피부 건조도, 피부 탄력도, 피부 윤기도, 피부 거칠기 항목에서 유의한 차이를 나타내었다. 12주후 APSA군은 피부 주름, 피부 탄력도 항목에서 vehicle 사용 피검자군에 비하여 유의적인 차이를 나타내었으나 3-APPA군은 피부 탄력도, 피부 주름량, 피부 윤기 항목에서 vehicle군에 비하여 유의적인 차이를 나타내었다. 결론적으로 3-APPA와 APSA 사이에 유의적인 차이가 있지는 않았으나 3-APPA군은 APSA군에 비하여 6주, 12주에서 사용전과 유의한 차이를 나타내는 항목이 많았으며 12주에서 vehicle과 유의적인 차이를 나타내는 항목도 많으므로 3-APPA가 APSA 보다 광범위한 피부노화 억제 효과를 갖는 물질이라고 할 수 있다.

• The Journal of Engineering Geology
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• v.33 no.4
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• pp.717-724
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• 2023

Residual shear strength is an important parameter in landslide dynamics and may be considered the critical factor in landslide triggering. Tests were undertaken using Jumunjin sands to examine the effects of smooth and rough surfaces on ring-shear characteristics. Under dense and drained conditions, shear velocities were recorded as 0.01, 0.1, 1, 10, 50, 100 mm s^-1, with shear strength increasing with velocity and producing increasingly fine content. Particle fragmentation may thus increase landslide mobilization when the landslide body is mixed with ambient water in channelized flows.

• Tunnel and Underground Space
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• v.27 no.1
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• pp.58-68
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• 2017

According to the development of optical technology, the capacity of LIDAR equipments has been greatly improved to get rock mass characteristics precisely and accurately enough and it has been lightened and popularized so that it can be easily used in the field. In this study, we examined the applicability of roughness measurement for joints in a rock slope using LIDAR technique. A triangular irregular network was constructed using LIDAR and a patch, which is a plane structure of discontinuity on rock mass measured from LIDAR scanning, was extracted to estimate the roughness of the rock slope. Four different kinds of roughness parameters were analyzed to find out their correlation with JRC for various point intervals. Among them, $R_s$ parameter was used to measure the roughness of a patch. Regression analysis between four roughness parameters and JRC with respect to point interval was performed. All the roughness parameters decreased with the increase of point interval. In addition, the parameter value showed greater decrease for rougher surfaces. A method of roughness measurement using $R_s$ parameter on rock slope discontinuities was suggested which showed slight overestimation of the real roughness value.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.228-228
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• 2012

방사광 가속기의 좁은 간격 언듈레이터 진공용기를 지나는 전자의 진행을 방해하는 wakefield 효과를 최소화하기 위해서는, 진공용기의 내부 표면이 매끄럽게 제작되어야 한다. 알루미늄 진공용기의 일반 압출 직후 내부 표면 거칠기는 이러한 요구 조건을 만족하지 못하며, 다양한 표면처리를 통하여 원하는 표면 조도를 얻을 수 있다. 여기서는 일반 압출 공정만 거친 시료와 압출 이후 표면처리를 거친 시료의 내부 표면 조도를 비교하였다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.2
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• pp.120-124
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• 1991

An interaction of turbulent boundary layer and local roughness effects was evaluated to investigate the shear frictional coefficient in diffuser. Clauser roughness function was applied to Karman's integral equation for governing equation. The roughness of overall and local diffuser surfaces were calculated using Cole's wall and wake law and Clauser's roughness function for turbulent boundary layer characteristics. The calculating results were compared with the experimental results of other paper. It shows some significant improyements for shear frictional coefficient. Computer code was then used to confirm the behavior of local frictional coefficient along with diffuser roughness surface for some reduction of shear flow stress.

• Tunnel and Underground Space
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• v.19 no.1
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• pp.52-63
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• 2009

This is a study on large-scale rock joint roughness measurements using LIDAR (light detection and ranging) and the Split-FX point cloud processing software. The large-scale rock Joint Roughness Coefficient (JRC) is calculated using the maximum amplitude of joint asperities over the profile length on large-scale Joint surfaces of rock. As the profile length increases, JRC decreases due to scale-effects of rock specimens and is non-stationary. Also JRC shows anisotropy depending on the profile direction. The profile direction is measured relative to either dip or strike of the large-scale joint.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.409-415
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• 2016

In this study, we test the effects of the surface roughness on the hydro efficiency of double-suction centrifugal pumps ($Q=70.7m^3/min$, H = 87 m). The original surface of the impeller and inner casing were coated, resulting in surface-roughness reductions ranging from $100{\sim}110{\mu}m$ to $0{\sim}0.08{\mu}m$. We conducted experimental studies to measure the efficiency of the pumps and operating-pump electro energy variations with different surface roughness values. The experimental results showed that the efficiency of the pumps increased by about 0.8~1.79% and the electric energy of the operating pump was reduced by around 4.38 ~ 6.08%. These results indicate that the performance of the pumps depend largely on the surface roughness of the impeller and inner casing, and by reducing the surface roughness, we can improve the efficiency of the pump and reduce costs by reducing the electric energy consumption.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1681-1690
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• 2003

The effect of roughness is a change in the velocity and turbulence distributions near the surface. Turbulence models with surface roughness effect are applied to the fully developed flow in a two-dimensional, rough wall channel. Modified wall function model, low-Reynolds number k-$\varepsilon$ model, and k-$\omega$ model are selected for comparison. In order to make a fair comparison, the calculation results are compared with the experimental data. The modified wall function model and the low-Reynolds number k-$\varepsilon$ model require further refinement, while the k-$\omega$ model of Wilcox performs remarkably well over a wide range of roughness values.