• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.161-169
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• 2017

The present study investigated the effect of the rib arrangement and a guide vane for enhancing internal cooling of the blade. Two types of rib arrangements were used in the first and second passage in parallel. Aspect ratio of the channel was 5 and a fixed Reynolds number based on hydraulic diameter was 10,000. The attack angle of rib was $60^{\circ}$, rib pitch-to-height ratio (p/e) was 10, and the rib height-to-hydraulic-diameter ratio ($e/D_h$) was 0.075. The effect of an interaction between Dean vortices and the secondary vortices from the first passage was observed. Overall, the attack angle of rib in the first passage was dominant factor to heat transfer and flow patterns in turning region. Also, the channel with a guide vane showed enhanced heat transfer at the tip surface with reducing flow separation and recirculation.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.04a
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• pp.87-92
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• 1996

본 연구에서는 건조 마찰, 윤활제가 부족한 경우의 경계 윤활, 윤활제가 충분한 경우의 경계 윤활 상태에 대한 실험을 수행하여 각 윤활 상태에서의 요철표면의 성능을 알아 보고 요철 표면의 요철 표면의 성능에 영향을 주는 주된 요인을 알아보았다.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.65-74
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• 2007

There have been research and studies on rumble strip effectiveness in terms of accident reduction since rumble strips were first installed in 1950's. Research has shown that rumble strips reduce accidents from drowsy and inattentive driving. The present research statistically analyze the accident reduction effect of rumble strips based on accident reports obtained from rumble strip installed 377 places of nation wide freeway lines. Based on the results, rumble strips are effective in reducing accident frequencies 32.3%. The probable various factors inducing accidents are identified. These include drowsiness, speeding, inattentiveness, vehicle defectiveness, and short headways. It was found that rumble strips are effective in reducing A, B, C leveled accidents, and in reducing clear, cloudy, and rainy weather accidents. The results may make clear and expand probable types of accidents that rumble strips would reduce, then reduce the total accidents on freeway lines.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.200-200
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• 2001

백판지 면성은 표면 백색도의 변이, 불투명도의 변이, 광택도, 거치름도, 표면 지합, 표면 요철 등 다양한 인자들로 표현되고 있다. 인쇄소에서는 인쇄를 하기 때문에 화선 부에서의 백색도나 불투명도 등은 크게 불만 요소로 작용하지는 않으나 표면 요철의 경우에는 인쇄 후 화선부에서도 나타나기 때문에 고객 불만의 한 요소로 인식되어 진 다. 따라서 본 연구에서는 백판지 면성의 여러 인자 중 표면 요철의 평가에 대해 다루 고자 하였다. 백판지 표면 요철을 시각적으로 나타내기 위한 방법으로 3-Dimensinal topography를 얻을 수 있는 Zygo와 Stylus를 이용, FFT 변환을 통하여 2-dimensional topography를 얻는 방법이 연구되었다. 그러나 기자재 비용, 측정 시간 등의 문제 등으로 표면 요철 을 평가하기 어려운 점이 있다. 본 연구에서는 백판지를 T APIO를 이용하여 O.2mm간격으로 두께를 측정하였고 A verage slope와 Profile length라는 개념을 도입하여 수치 적으로 표면 요철을 정 량화 하였다. Average slope는 1mm 간격으로 이동하였을 때 높이의 편차를 평균하는 값이다. 또 한 Video eam을 이용하여 표면 요철의 형태를 촬영하여 시각적으로 판단할 수 있도록 하였다. 위의 측정 방법으로 국내, 외 12개의 Sample에 대해 Profile length와 Average s slope를 계산하였다. 고객의 주관적 평가를 의사결정 방법 중 하나인 AHP법을 이용하여 주관적인 정성 평가를 수치적으로 정량화할 수 있었으며 실제 측정 결과와 비교, 상관분석을 실시 하 였다. 고객의 평가 결과와 Profile length, average slope의 상관성을 분석한 결과 A Average slope에서 유의성 있는 상관성을 얻을 수 있었고 표면 사진을 비교하였을 때 C Coating 방식 등을 유추할 수 있었다. 이러한 평가 방법을 현장에 적용하였으며 그 결과, 공정 개선 전, 후의 표변을 측정, 개선 유무를 쉽게 판단할 수 있었다.

• Composites Research
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• v.31 no.6
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• pp.323-331
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• 2018

The effect of stainless steel jagged-pin reinforcement on the pull-off strength of the composite hat-joint was studied by the test. The pins were physically and chemically surface-treated and inserted in the thickness direction over the interface where the skin and stiffener meet. The specimens including the jagged-pins were made by co-curing process. Diameters of the jagged-pins were 0.3, 0.5 and 0.7 mm. The pin areal densities were set to 0.5 and 2.0% based on the interface area where the skin and stiffener meet. The specimens using 0.3 mm diameter normal (un-jagged) pins with 2.0% areal density were additionally fabricated and tested to investigate the pin shape effect on the pull-off strength. The pull-off strengths of specimens reinforced with 0.5% areal density by 0.3, 0.5, and 0.7 mm diameter pins were 45, 19 and 9% higher than those of un-reinforced specimens, respectively. In case with 2.0% pin areal density, the strengths were 127, 45, and 11% higher than those of un-reinforced specimens, respectively. The test results show that the higher pin areal density results in the higher strength when the pin diameter is the same. When the pin areal density is the same, the smaller pin diameter leads to higher strength. When the joints using jagged-pins and normal pins in 2.0% areal density with 0.3 mm diameter, the joints of jagged-pins showed the 64% higher strength. From the results of this study, it was confirmed that jagged-pin reinforcement can be an effective method for improving the pull-off strength of composite hat-joint.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.259-266
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• 2020

In this study, required drill bits and excavation methods were developed for an uneven drilling method that can solve the problem of performance degradation of rock bolts. The developed drill bit's excavation performance was verified using rock with a strength of 100 MPa or more. In addition, for the relative evaluation of the uneven excavation method, experimental specimens were prepared for models with and without irregularities, and tests were performed. As a result of the experiment, the model with unevenness exhibited an average critical draw resistance of 801.6 kN, which is about 1.7 times the value of 468.7 kN for the model without unevenness, thus confirming the effect sufficiently. Therefore, it is expected that the resistance performance will significantly increase despite an increase in the uneven hole diameter of 20 mm. In the future, the results of this study could be used as basic data when performing other studies using numerical analysis models and performance verification through experiments to obtain an optimized rock forming method.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.77-87
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• 2007

Traffic accidents on freeway are occurred by various factors, and driver inattention is one of the most important factors causing traffic accidents. To warn drivers about unexpected dangerous events and diminish driver inattention problems, traffic safety facilities including warning and regulatory traffic signs; delineators; rumble strips are installed. In this study, the traffic safety effect of shoulder rumble sips were investigated using "Comparison Croup (C-G)" method developed by Hauer. Through the analyses, it was found that numbers of run-off-the road crashes were reduced as 2.43 crashes per year after the installation of shoulder rumble strips on the freeway. Based on the analysis results in this study, it was concluded that shoulder rumble strips on the freeway contribute to reduce traffic accidents, especially run-off-the road crashes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.41-49
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• 2014

In this study, experimental research was carried out to evaluate the structural performance of the reinforced concrete beam using hybrid retrofitting with two materials (groove and embedding FRP rod, CFRP sheet) in existing reinforced concrete buildings. Seven reinforced concrete beams, retrofitted groove and embedding FRP rod (NER series) and groove and embedding FRP rod with CFRP sheet (NERL series), and standard specimen (NBS) were constructed and tested under monotonic loading. Design parameters of test specimens are the amount of groove and embedding FRP rod and lapping CFRP sheet. Test results showed that the maximum load carrying capacity of specimens with groove and embedding FRP rod and groove and embedding FRP rod with CFRP sheet (NERL series) were increased the by 12~46% and 22~77% respectively in comparison with the standard specimen NBS. Test specimens NER series were failed with the adhesion slip and concrete cover separation. And test specimens NERL series were failed with the adhesion slip due to the confining effect of lapping CFRP sheet.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.54-54
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• 2011

기존의 착저식 방파제를 보완하기 위하여 부유식 방파제가 개발되었고, 많은 연구가 선행되어 왔다. 부유식 방파제의 최대 장점은 경제성과 친환경성이다. 그러나 부유식 방파제는 소파성능이 떨어진다는 단점이 있으며, 이를 개선하기 위해 잠재와 혼용, 배열형에 관한 연구등이 선행되어왔다. 그러나 이것은 경제성이라는 강점을 고려하지 못하였다. 그래서 본 연구에서는 부유식 방파제의 중요한 장점중 하나인 경제성을 고려해, 단면현상 변화만을 이용하여 부유식 방파제의 소파성능 개선하고자 하였다. RANS(Reynolds averaged Navier-Stokes) 방정식에 기초하여 VOF법과 $k-{\varepsilon}$ 난류모델을 결합한 수치모델인 CADMAS-SURF를 이용하였으며, 구조물 단면형상 변화를 이용해 와의 상호 간섭을 유도하였고, 이에 따른 투과율 변화를 관찰 하였다. 결과를 살펴보면 요철1 단면에서는 구조물 전면 하단부분과 구조물 후면 하단부분에서 와의 간섭이 일어났으며 가장 아래 요철 부분에서 유속의 전달현상이 보인다. 투과계수는 일반적인 부유식 방파제와 마찬가지로 L/B가 1~4사이 값인, 비교적 단주기에서는 0.3~0.4의 투과율을 보였으나 L/B가 5를 넘어가면서 0.45~0.55의 투과율을 보였고, 요철2 단면에서는 전면과 후면에서 발달한 와가 전, 후면 돌출부에 의해 바닥까지 전파되지 못하는 양상을 보였으며, 돌출부 사이 중앙부분에서 가장 활발한 와의 간섭을 관찰 할 수 있었다. 돌출부 아래에서 역시 강력한 와의 간섭을 보이고 있다. 투과율 역시 가장 낮은 값을 보였으며 비교적 단주기 구간인 B/L 1~4 에서는 0.2~0.35 사이의 값을 가졌으며 5~10사이구간에서는 0.35~0.34의 값을 보이고 있다. 이 같은 결과는 와의 간섭이 가장 활발하게 나타난 결과로 보인다. 그리고 요철 3단면에서는 전면 돌출부 끝단에서의 활발한 와의 간섭을 관찰 할 수 있었다. 투과율은 세 단면 중 가장 높은 값의 투과율을 보이지만 B/L 3~4 구간에서 요철1 경우보다 낮은 값의 투과율을 보이고 있다. 결과에서 보듯이 도출부의 적절한 조합과 배치를 통해 언급한 연구목표(와의 생성과 간섭, 방파효율 개선)를 달성하였고 추후에 돌출부의 크기와 배치, 흘수의 영향, 수심의 영향 등을 고려한 연구가 진행된다면 더욱 우수한 단면형상을 개발 할 것이라 예상된다.

• Journal of Korean Society of Transportation
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• v.24 no.7 s.93
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• pp.7-14
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• 2006

Most researches about rumble strips have Presented only the before-and-after analysis of the accidents. So, Researchers have not dealt with the estimation of rumble strip's effectiveness on the driver's alertness. In this study. the effectiveness of the rumble strips on the driver's alertness was estimated by measuring the bio-signal transmitted from the driver. The bio-signal acquired for this experiments were theta wave in central lobe. The experimental results revealed that the theta waves as measured form the drivers's head while in the rumble strip section differed from those while in non-rumbled section; 74 percent decrease in theta wave value, respectively. This fact finding could mean that the driver's alertness increased from 74 percent while in the rumble strip section of the road. In all five trials of driving experiments on the rumble strip section, all the drivers showed the best alertness as measured by the theta waves in the first driving trial.