• 한국광물학회지
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• 제17권1호
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• pp.23-35
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• 2004

울산시 사연댐 상류에 위치하여 주기적으로 침수되는 퇴적암의 풍화특징을 연구하였다. 현장조사, 전자현미분석기, Χ-선 회절분석기 및 Χ-선 형광분석기를 이용하여 암석의 풍화조직 및 광물의 조성변화 조사를 통해 주기적으로 침수되는 암석의 기계적 및 화학적 풍화양상을 연구하였다. 수장암석의 풍화작용은 퇴적층리와 수직방향으로 발달한 파쇄대 및 균열과 박리현상과 같은 기계적 풍화작용이 현저하다. 이러한 물리적인 풍화현상은 물과 암석과의 접촉면적을 넓혀 화학적 풍화작용을 가속화시킨 결과 풍화대와 약풍화대에서 석영을 제외한 거의 모든 광물이 용해작용 또는 변질작용을 받았으며, 특히, 탄산염광물의 용해작용이 현저하여 약풍화대에서 조차 방해석이 완전히 용해되어 빈 공간으로 남아있다. 그러나 점토광물과 같은 이차광물의 형성은 미약한 특징을 보인다. 이 지역의 암석은 일정기간 동안 물에 잠긴 상태로 유지되고, 동결과 해빙이 반복됨으로써 물리적 풍화작용이 상대적으로 빠르게 진행되어 물의 침투가 용이한 투수성 구조를 형성하였고, 그 결과 탄산염광물의 용해작용이 급속하게 일어났다. 자유로운 물의 순환으로 인하여 용해된 원소들이 점토광물과 같은 풍화광물로 침전되지 않고 용탈됨으로써 암석조직이 이완되어 풍화작용이 가속되었다. 퇴적암중 풍화에 극히 약한 탄산염광물의 높은 함량이 강한 화학적 풍화작용의 주 요인으로 보인다.

• 해양환경안전학회지
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• 제14권4호
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• pp.333-338
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• 2008

해안 지역은 해수의 운동에너지의 대부분은 해안에서 소산되며 이 과정에서 해안의 토사 등이 유실된다. 수면에 돌출된 방파제에 비해 수중구조물은 해수의 유통을 가능하게 하고 해안선을 따라 해수순환을 가능케 한다. 이 연구에서는 해안 침식을 방지 기능을 갖는 수중구조물을 하부틈새를 갖는 수중장애물로 형상화 하고 후방의 흐름특성을 규명하였다. 실험은 Re =$1.2{\times}10^4$ 조건에서 2프레임 입자영상유속계를 이용하여 속도장을 계측하여 고찰하였다. 측정된 시간평균 속도분포를 분석한 결과 유선의 곡률 효과가 현저히 나타났으며 전단층 주위 유체의 유입 등의 영향으로 박리 전단층 내에서 커다란 와구조가 연속적으로 발생하였다. 또한 하부틈새의 크기가 증가할수록 재순환 영역의 중심이 후류로 이동하고 재순환영역의 강도도 약해지는 결과를 보였다.

• 한국해양공학회지
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• 제10권3호
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• pp.14-23
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• 1996

The corrosion fatigue test were carried out to evaluate the fatigue characteristics of accelerated cooled (ACC) TMCP high tensile strength steels and weld joint with high heat input by one side one run submerged are welding. In this paper, the fatigue crack growth behaviors were investigated with the center crack tension specimen of base metal and heat affected zone in substitute sea water and air, respectively Main results obtained are sunnarized as follows: 1. The fatigue crack growth rates in sea water faster than those in air environment for the different heat input values, crack growth rate of base metal is very fast and effect of heat input is not remarkable. 2. In HAZ (82kJ/cm, 116kJ/cm), the crack branching phenomena were observed in both air and sea water environment, 3. In SEM observation, the corrosion effect on base metal was larger than that on HAZ in corrosion environment.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.278-280
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• 2003

• Journal of Periodontal and Implant Science
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• 제45권4호
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• pp.152-155
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• 2015

Purpose: This case report discusses the effect of a root submergence technique on preserving the periodontal tissue at the pontic site of fixed dental prostheses in the maxillary anterior aesthetic zone. Methods: Teeth with less than ideal structural support for fixed retainer abutments were decoronated at the crestal bone level. After soft tissue closure, the final fixed dental prostheses were placed with the pontics over the submerged root area. Radiographic and clinical observations at the pontic sites were documented. Results: The submerged roots at the pontic sites preserved the surrounding periodontium without any periapical pathology. The gingival contour at the pontic site was maintained in harmony with those of the adjacent teeth, as well as the overall form of the arch. Conclusions: The results of this clinical report indicate that a root submergence technique can be successfully applied in pontic site development with fixed dental prostheses, especially in the maxillary anterior esthetic zone.

• 한국연안방재학회지
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• 제4권spc호
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• pp.245-253
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• 2017

In this study, surface currents measured by small lagrangian GPS drifters (Aquadrifter) in Anmok coastal waters were analysed to account for the variability of nearshore surface current and wave-induced current to understand sediment transport mechanism near the crescentic bars in the surf-zone and near Kangneung breakwater and submerged breakwater in Anmok. The 8 times lagrangian drifter experiments were conducted mostly during in 2nd, 3rd, 4th intensive measurements in winter, summer, and spring seasons with long-term wave observation at the station W1. The analysed surface currents near the breakwaters in Anmok show that wave-induced currents at the middle of the submerged breakwater were separated and flowed toward the shoreline but offshore currents were dominant through the channels between the breakwaters. The longshore currents near the shoreline were flowed to the northwest (southeast) depending on the incoming waves from ENE (NNE). The surface nearshore offshore currents were generated mostly by waves and winds in case of high and low wave energy environments. Using the small-size lagrangian surface drifter experiments, we successfully measured longshore and offshore wave-induced currents in the surf-zone and near submerged breakwater close to Kangneung breakwater. The drifter experiment results show the availability of direct observation of nearshore surface currents to understand the mechanism of sediment transport analysing observed wave-induced current and ebb-current in the surf-zone generated by incoming waves and local winds.

• 한국해양공학회지
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• 제24권1호
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• pp.106-115
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• 2010

This study described the stability of riprap, which was examined by a two-dimensional physical model of a scattered riprap submarine breakwater. Artificial reef structures made of scattered riprap are used like artificial intertidal zone structures as waterfront seaside structures. To prevent topography change in such an artificial intertidal zone the energy is reduced at the scattered riprap submarine breakwater by intercepting high waves. The breaking waves are converted into flow on the front surface slope of the submarine breakwater, which follows the upper part of the artificial intertidal zone. Because of this phenomenon of resisting water flow, it is very important to calculate the required weight of the riprap to maintain its stability. The results of a physical model can be abstracted as shown below. First, distribute the wave breaking types occurring on the front surface slope of the submarine breakwater and arrange it in relation to the movement of riprap. Second, using the hydraulic phenomenon that occurs at the depth of the scattered riprap submarine breakwater, propose a calculation formula for the velocity distribution showing the influence on the stability of the riprap. Third, propose and compare values, which can be obtained by experiments and calculations for riprap stability on the front surface of the artificial intertidal zone. Fourth, calculate the required weight for riprap stability.

• 한국해양공학회지
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• 제24권2호
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• pp.18-24
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• 2010

Submerged rubble structures include artificial reef and the mound part of the rubble mound breakwater. Artificial reef is a type of the submerged wave absorbing structure installed in a coastal zone to prevent beach erosion and designed to initially reduce the energy of incoming waves so that its run-up height and overtopping quantity can be decreased. In order to ascertain the stability of such submerged rubble structures, minimum weight of the rubble has to be calculated first from the incoming wave height using Hudson's formula or Brebner-Donnelly formula. Based on the calculated minimum weight, a model is built for use in a hydraulic model test carried out to check its stability. The foregoing two formulas used to calculate the minimum weight are empirically derived formulas based on the result of the tests on the rubble mound breakwater and it is, therefore, difficult for us to apply them directly in the calculation of the minimum weight of the submerged structures. Accordingly, this study comes up with a numerical simulation method capable of deformation analysis for rubble structures. This study also tries to identify the deformation mechanism of the submerged rubble structures using the numerical simulation. The method researched through this study will be sufficient for use for usual preparations of the design guidelines for submerged rubble structures.

• 대한토목학회논문집
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• 제28권4B호
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• pp.429-439
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• 2008

본 연구에서는 잠제의 제원(천단수심, 천단폭, 사면경사, 제장)에 따라 해빈상을 전파하는 풍파의 처오름 높이 변화특성을 논의하기 위하여, 기존의 수리모형 실험치와 계산치를 비교 검토를 통해 타당성과 유효성이 검증된 수치모델로서, 파 투과성구조물 해빈의 상호간섭을 직접 해석할 수 있는 3D-수치모델(LES-WASS-3D; 허와 이, 2007)을 이용하여 잠제 2기의 제원에 따른 수치시뮬레이션을 실시하였다. 그 결과 천단수심, 천단폭, 사면경사, 제장의 변화가 연안에서의 처오름 높이에 미치는 영향에 관하여 검토하였으며, 아울러, 잠제 주변의 파고분포 및 상층흐름특성과의 관계에 대해서도 논의하였다.

• Journal of Welding and Joining
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• 제14권2호
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• pp.90-95
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• 1996

In order to investigate characteristics of surface fatigue crack propagation from a pit shaped surface defect which frequently exists around welded joints, SS400 steel with thickness of 12mm, which has been generally used for structure members, was welded with submerged-arc butt type and machined for both surface. An initial surface defect of pit shape with the aspect ratio of 2 was made on the specimen. The initial defect was located at 5 different zones over the weldment : weld metal zone, boundary between weld metal and HAZ, HAZ, boundary between HAZ and base metal. Characteristics of surface fatigue crack propagation from the defect on each region under the same loading condition were investigated and compared.