• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.18-24
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• 2011

In this paper, we present the load-deflection behavior of GRP pipes. GRP buried pipes are widely used in construction in the advantage of their superior mechanical and physical characteristics such as high chemical resistance, high corrosion resistance, right weight, smooth surface of the pipe, and cost effectiveness from soil-structure interaction. To design flexible pipes to be buried underground, it should be based on the ASTM D2412(2010). When applying ASTM D 2412(2010) to the design, pipe stiffness(PS) must be predetermined by the parallel-plate test which requires tedious and laborious working process. To overcome such problems, the finite element simulations for finding the load-deflection behavior of the GRP flexible pipes is installed at UTM testing machine. In the finite element simulations, basic data, such as the modulus of elasticity of the material and cross-sectional dimension, is used. From the investigation, we found that the difference between experimental result and analytical prediction is less than 15% when the pipe deflected 3% and 5% of its vertical diameter although the pipe material is not uniform across the cross-section.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.111-116
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• 2006

통신용 지하 관로 자재로는 주로 100mm관(PVC관, FC관)과 50mm관(FC관)이 사용되고 있으며, 이들 관자재의 품질은 관로 시공 품질 뿐 아니라 케이블 포설을 위한 선로 구성에 큰 영향을 미치고 있어, 관자재의 품질 확보는 매우 중요하다고 할 수 있다. 관자재의 품질 성능을 나타내는 방법으로는 편평시험(5% 및 100% 변형하중)과 충격시험 결과를 많이 사용하고 있으나, 관로 시공 현장에서 이러한 성능 시험을 한다는 것은 현실적으로 불가능하여, 대부분의 현장에서는 관자재의 두께나 무게와 같은 물성치 측정으로 품질관리를 하고 있다. 이에 본 논문에서는 관자재의 물성치와 품질 성능간 상호 관계를 분석한 후, 상관성이 높은 항목들을 도출함으로써, 관종 별의 관자재의 물성치와 품질 성능간에는 상관성이 매우 높은 인자들이 있다는 것을 규명하였으며, 이를 통하여 관자재의 물성치 만으로도 품질 성능을 객관적으로 판단할 수 있는 근거를 제시하였다. 이를 이용하여 관로 시공 현장에서 관자재 품질관리와 시공 품질 향상에 활용할 수 있도록 하였다.

• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.21-28
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• 2021

This study proposes a deep learning-based flat foot classification methodology using transfer learning. We used a transfer learning with VGG16 pre-trained model and a data augmentation technique to generate a model with high predictive accuracy from a total of 176 image data consisting of 88 flat feet and 88 normal feet. To evaluate the performance of the proposed model, we performed an experiment comparing the prediction accuracy of the basic CNN-based model and the prediction model derived through the proposed methodology. In the case of the basic CNN model, the training accuracy was 77.27%, the validation accuracy was 61.36%, and the test accuracy was 59.09%. Meanwhile, in the case of our proposed model, the training accuracy was 94.32%, the validation accuracy was 86.36%, and the test accuracy was 84.09%, indicating that the accuracy of our model was significantly higher than that of the basic CNN model.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.121-131
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• 2007

Recently, the probability of rock joints being exposed to free faces is getting higher for the scale of rock mass structures gets larger. Also, the frequency of occurring dynamic events such as earthquakes and blasting has been increasing. Thus, the shear behavior of rock joints under different conditions needs to be investigated. In this study, a series of direct shear tests were carried out under various conditions to examine the velocity-dependent shear behavior of saw-cut rock joints. Two types of direct shear test were carried out. The first was to examine the velocity-dependent shear behavior of saw-cut rock joints at seven different shear velocities, each with three different normal stresses. The second was to examine the shear behavior of saw-cut rock joints when three different instantaneous shear velocities changed. As a result, the coefficient of friction was affected by normal stress. The breakpoint velocity, the point when the change of shear velocity starts to affect the frictional behavior, became lower as normal stress increased. Also, as the shear velocity became lower, the degree of stress-drop on stick-slip behavior became larger. As a result of examining the changes of friction coefficient, velocity weakening (decrease of friction coefficient) was observed. The decrement of friction coefficient due to the changes of shear velocity under slow shear velocity was larger than that under fast shear velocity.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.70-79
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• 1997

Ni-base self-fluxing alloy powder particles were flame sprayed onto the SS400 mild steel substrate surface. The effects of both substrate temperature and spraying distance on the splat behavior of sprayed particles were examined. The results obtained are summarized as follows: 1) In the splat behavior of Ni-base self-fulxing alloy particles sprayed onto the SS400 mild steel substrate, splashing was observed under the room temperature condition. On the contrary, it showed circular plate pattern in the substrate temperature range over 373K. 2) It was cleared that there was close relationship between mechanical properties of coating layer and splat behavior of sprayed particles. 3) From the experimental results, optimum spraying conditions showed excellent mechanical properties in the case of Ni-base self fluxing alloy sprayed onto the SS400 mild substrate were 473K of substrate temperature and 250mm of spraying distance.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.53-59
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• 2009

The purpose of this research is particle shape evaluation of granular soil and aggregate using Digital Image Process(DIP). DIP is very useful to measure the roughness and particle shape of aggregates. Couple of aggregates, like standard sand, two different crushed stones, and two different marine aggregates, have been employed. Shape factor of two different marine aggregates is ranged 0.35 to 0.54. Crushed stone I is that of 0.74 which is highly flat, but standard sand is elongated shape. Especially, two marine aggregate showed a big difference of width and length which meaned a long shape. There is any significant difference of elongation ratio and flakiness for each aggregate with different measuring system, like direct measurement of vernier calipers and DIP method. Within the limited test results, DIP is one of useful to get the particle shape of aggregate with limitation of measuring errors and to apply the particle distribution curve.

• Geotechnical Engineering
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• v.12 no.2
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• pp.107-114
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• 1996

A series of shear tests is performed to measure friction coefficients of the interface between different reinforcements and weathered granite soils. The reinforcements tested are smooth steel strip, Paraweb(friction tie) and geotextile with rough surface, while the weathered granite soils are composed of different, grain size distribution. Soils are compacted with the energy of 95% modified AASHTO and fully saturated before testing to simulate the worst site condition. Because of characteristics of the direct shear apparatus, shear strength is obtained in terms of drained condition. Test results show that the more fines the soils contain, the larger ratio of friction coefficient ($\mu=\frac{tan{\delta}}{tan{\Psi}}$) is obtained. Also the ratios are much higher for the Friction tie and the geotextile compared to the smooth steel strip. Those suggest that even weathered granite soils with 36% fines are possible to use as backfill of reinforced earth structures for the two reinforcements when a drainage system is provided.

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.58-72
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• 2006

In recent years, not only the occurrences but the magnitude of earthquakes in Korea are on an increasing trend and other sources of dynamic events including large-scale construction, operation of hi띤-speed railway and explosives blasting have been increasing. Besides, the probability of exposure fir rock joints to free faces gets higher as the scale of rock mass structures becomes larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, a shaking table test system was set up and a series of dynamic test was carried out to examine the dynamic frictional behavior of rock joints. In addition, a computer program was developed, which calculated the acceleration and deformation of the sliding block theoretically based on Newmark sliding block procedure. The static friction angle was back-calculated by measuring yield acceleration at the onset of slide. The dynamic friction angle was estimated by closely approximating the experimental results to the program-simulated responses. As a result of dynamic testing, the static friction angle at the onset of slide as well as the dynamic friction angle during sliding were estimated to be significantly lower than tilt angle. The difference between the tilt angle and the static friction angle was $4.5\~8.2^{\circ}$ and the difference between the tilt angle and the dynamic friction angle was $2.0\~7.5^{\circ}$. The decreasing trend was influenced by the magnitude of the base acceleration and inclination angle. A DEM program was used to simulate the shaking table test and the result well simulated the experimental behavior. Friction angles obtained by shaking table test were significantly lower than basic friction angle by direct shear test.

• Land and Housing Review
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• v.2 no.1
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• pp.69-78
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• 2011

The purpose of this research is particle shape evaluation of aggregate using Digital Image Process(DIP). DIP is very useful to measure the roughness and particle shape of aggregates. Couple of aggregates, like standard sand, two different crushed stones, and two different marine aggregates, have been employed. Shape factors of two different marine aggregates are ranged 0.35 to 0.54. Crushed stone I is 0.74 which is highly flat, but standard sand is elongated shape. Especially, two marine aggregate showed a big difference of width and length which meaned a long shape. There is any significant difference of elongation ratio and flatness for each aggregate with different measuring system, like direct measurement of vernier calipers and DIP method. Shape conversion coefficient and equivalent diameter for changing 2D image to 3D image by the Digital Image Process(DIP) have been suggested and modified particle size distribution curve has been showed. The measured flatness ratios of each aggregate were 0.30, 0.36, 0.47 and 0.83, respectively. Also, the conversion shape coefficients of each aggregate were determinded as 0.77, 0.78, 0.84 and 0.92. The size of aggregate has been modified by multiplying the shape conversion coefficient and the aggregate size from DIP. The modified gradation curve with modified volume and weight of aggregate has been suggested. Within the limited test results, DIP is one of useful to get the particle shape of aggregate with limitation of measuring errors and to apply the particle distribution curve.

• The Journal of the Korea Contents Association
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• v.13 no.8
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• pp.308-313
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• 2013

Among 179 specimen diagnosed with ASCUS but did not go through biopsy or other tests, 26 cases (14.52%) showed positivity in HPV Hybrid Capture II Test. There were 25 cases of HPV high risk factor(+), marking 13.96%, and 3 cases of low risk factor(+) at 1.67%. According to cytology manifestation, patients with over LSIL can increase their complete recovery rate with continuous tests, but most patients diagnosed ASCUS do not go through any tests at all. It is considered that in order to prevent and start early treatment on cervical cancer, the HPV Hybrid Capture II Test must be enforced to patients diagnosed with ASCUS. Negative patients should go through routine screening, and positive patients should receive treatment after colposcopy.