• Tunnel and Underground Space
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• v.24 no.1
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• pp.89-96
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• 2014

Rock joint surface roughness, which is known to be one of the most important factors for defining shear strength of rock mass, has been researched in various methods. However, approaches to separate a roughness into two groups (primary and secondary) for evaluating the roughness have been rarely performed. In this study, elements of secondary roughness were eliminated through direct shear testing with tensile joint specimen and they were quantified with joint parameters. It is revealed that roughness parameters decrease with increasing the normal stress and sampling intervals, except for the case in which the normal stress is larger than 1.5 MPa. Also it is analyzed that ratio of area reduction in the opposite direction of shearing decreases with increasing the roughness parameter.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.3
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• pp.184-191
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• 1996

The purpose of this paper is to investigate components of surface roughness in turning with respect to the tool configuration and the changes of working conditions. Tool configurations of SNMG120404, SNMG120408 and DNMG150404, DNMG150408 are used, and working conditions such as cutting speed 3nd feed are varied. That is, the changes of cutting speed and feed were 150, 200, 250 m/min and 0.05, 0.1, 0.3 mm/rev, respectively. From the results obtained by the frequency analysis with spectrum, it is noted that the surface roughness was influenced most significantly by the feed. It is also observed that the vibration of bite had an effect on both the surface roughness and the surface waviness. Moreover, the influence of surface roughness increases as the feed decreases. Lastly, the vibration of the spindle was found to have little influence on the surface roughness in normal cases and the tool configuration was not the components of the surface roughness.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.33.1-33.1
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• 2011

풍력발전기가 점차 대형화되어가는 추세에 따라 블레이드 역시 점차 길어지고 무거워지는 경향을 보이고 있다. 이는 블레이드뿐만 아니라 풍력발전기 시스템 전체의 하중 및 비용의 증가를 불러오게 되므로, 시스템의 성능 및 하중에 가장 큰 영향을 끼치는 블레이드의 공력특성에 대한 연구가 전 세계적으로 지속되고 있다. 그 중에서도 특히 작동 중 오염에 의한 블레이드 표면 거칠기 변화는 블레이드의 공력특성을 변화시켜, 발전기 전체의 성능뿐만 아니라 전체 하중에도 영향을 끼치는 주요 인자이다. 따라서 풍력발전기 블레이드 설계 시에 예측된 설계하중과 실제 운용 환경에 의해 변화된 운용하중 간의 차이를 예측할 수 있다면, 블레이드 설계 시에 표면 거칠기 변화에 따른 영향을 고려함으로써 실제 운용 환경에 맞는 최적의 블레이드 및 풍력발전기 시스템 설계를 수행할 수 있다. 본 연구에서는 블레이드의 표면 거칠기 변화에 따라 풍력발전기 하중이 어떻게 영향을 받는지에 대하여 분석하였다. 이를 위하여 표면 거칠기 민감도를 고려하지 않고 설계된 기준 블레이드와, 운용 중 표면 거칠기가 변화된 블레이드의 2개 모델에 대한 하중해석을 수행하고 그 결과를 비교하였다. 보다 실제적인 해석을 위해 Multi-MW 급 풍력발전기 시스템 모델을 대상으로 최적 설계된 블레이드를 기준 모델로 삼았다. 하중계산방법은 IEC 및 GL 2010 가이드라인을 참고하였으며, 일부 주요 극한하중 상황에 대하여 해석을 수행하여 설계하중상황(design load case, DLC) 별로 하중의 증감 및 경향을 비교하였다.

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.237-249
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• 2019

The roughness changes on a fracture surface were analyzed via a multi-stage compression test under high temperatures to assess how the cracks in a rock mass affect groundwater movement. The analyzed samples consist of coarse granitic rocks from approximately 40 and 270 m depth, and fine granitic rocks from 500 m depth. The compression test was conducted on $20{\times}40{\times}5mm$ samples using a loading system where the pressure increases in 10 MPa increments to 120 MPa. A high-resolution 3D confocal laser scanning microscope (CLSM) was used to observe the surface changes, including the roughness changes, at each pressure step. The roughness change was calculated based on the roughness factor. The experimental results indicate that the roughness of the fracture surface varies with rock type under the stepwise pressure conditions. These data provide a basis for predicting groundwater flow along rock fractures.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.5-13
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• 2003

The domestic design method for the shaft resistance of drilled shafts into a bedrock is based on the empirical method, where the uniaxial compressive strength of rock specimen is utilized for calculation of the shaft resistance. This method has uncertainties in prediction of capacity of drilled shafts and result in uneconomic engineering design. Recently a new improved design method was suggested, which reflects important factors that affect the strength of pile sockets. Socket roughness is one of the significant factors influencing the shaft resistance of drilled shaft socketed into rock. In this paper roughness information for the shaft resistance design of socket pile was suggested on the basis of statistical analysis of data measured from wall surface in the bore holes of drilled shafts.

• Journal of Korean Society of Forest Science
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• v.112 no.3
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• pp.374-381
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• 2023

The travel time of flash floods along mountain streams is mainly governed by reach-average velocity, rather than by the point velocity of the locations of interest. Reach-average velocity is influenced by various factors such as stream geometry, streambed materials, and the hydraulic roughness of streams. In this study, the reach-average velocity in mountain streams was measured for storm periods using rhodamine dye tracing. The point cloud data obtained from a LiDAR survey was used to extract the average hydraulic roughness height, such as R_a, R_max, and R_z. The size distribution of the streambed materials (D₅₀, D₈₄) was also considered in the estimation of the roughness height. The field experiments revealed that the reach-average velocities had a significant relationship with flow discharges (v = 0.5499Q^0.6165 ), with an R² value of 0.77. The root mean square error in the roughness height of the R_a-based estimation (0.45) was lower than those of the other estimations (0.47-1.04). Among the parameters for roughness height estimation, the R_a -based roughness height was the most reliable and suitable for developing the reach-average velocity equation for estimating the travel time of flood waves in mountain streams.

• 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.

• Journal of the Korean Chemical Society
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• v.66 no.6
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• pp.436-441
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• 2022

Because the nanoporous electrodes has large electrochemical surface areas, extensive studies have been focused on their fabrication methods. In this paper, a method for introducing a nanoporous gold (NPG) structure on the surface of an ultramicroelectrode (UME) using potentiostatic anodization was investigated. A well-defined NPG structure was introduced on the surface of the UME when a potential of 1.3 V was applied in 0.1 M phosphate buffer solution (pH 8) containing 1 M KCl. The anodic oxidation efficiency was investigated by observing the effect of the applied potential, the reaction time, and the size of the electrode on the roughness factor (R_f) of the prepared NPG-UMEs. In a short time of about 10 minutes, NPG-UME with a large R_f value of about 2000 could be prepared, which could be effectively used for electrochemical glucose detection. The results shown in this work are expected to have great applicability when performing electrochemical analysis with a small sample volume.

• 전자공학회논문지 IE
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• v.44 no.3
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• pp.42-50
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• 2007

In this paper, elastic and plastic adhesion index was very important in deciding adhesive characteristics and varying elastic and plastic index, dimensionless load and pull-off force were analyzed and simulated. Finally, using AFM, experimental surface roughness parameters of substrates and pull-off force between tip and substrates were produced. Using these values, pull-off forces were calculated and were compared with experimental pull-off forces. Through simulation and experiment, it was found that interaction of asperity also had very important influence on adhesive contact.

• Proceedings of the KOSOMBE Conference
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• v.1994 no.12
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• pp.52-57
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• 1994

간 기능 진단에 초음파 영상이 가장 많이 이용되고 있다. 간이 나빠지면 간 표면의 입자가 굵어지고 이것이 영상에서는 밝기(intensity)와 입자의 거칠기(Coarseness)가 높아지는 등의 특성이 나타난다. 진단에 사용되는 인자는 표면의 거칠기와 밝기 외에도 소엽의 크기와 모양 그리고 문맥 혈관의 크기 등도 고려가 된다. 초음파상으로 이러한 크기와 모양의 구분은 그렇게 어렵지 않다. 그러나, 영상의 밝기와 거칠기의 미세한 변화는 구분하기가 어렵다. 본 연구는 밝기와 거칠기를 나타내는 변수를 제시하고 이를 기준으로 간 질환을 분류하였다. 간 조직의 거칠기에 따라 크게 정상(Normal), 만성 간염(Chronic), 간경변증(Cirrhosis) 세단계로 질환의 상태를 진단하고 영상의 밝기에 따라 다른 간질환과 지방간(fat liver)을 구별해 낸다. 본 분석에 이용된 임상 영상은 주로 만성 간염과 간경변증을 갖고 있는 환자들의 것과 약간의 지방간 영상들이다.