• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1996년도 가을 학술발표회 논문집
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• pp.173-178
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• 1996

• Geomechanics and Engineering
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• 제31권3호
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• pp.305-318
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• 2022

Permeable reactive barriers used for groundwater treatment require proper estimation of the reactive material behavior regarding the emplacement method. This study evaluates the dry emplacement of zeolite (clinoptilolite) to be used as a reactive material in the barrier by carrying out several geotechnical laboratory tests. Dry zeolite samples, exhibited higher wetting-induced compression strains at the higher vertical stresses, up to 12% at 400 kN/m². The swelling potential was observed to be limited with a 3.5 swell index and less than 1% free swelling strain. Direct shear tests revealed that inundation reduces the shear strength of a dry zeolite column by a maximum of 10%. Falling head permeability tests indicate decreasing permeability values with increasing the vertical effective stress. Regarding self-loading and inundation, the porosity along the zeolite column was calculated using a proposed 1D numerical model to predict the permeability with depth considering the laboratory tests. The calculated discharge efficiency was significantly decreased with depth and less than 2% relative to the top for barrier depths deeper than 20 m. Finally, the importance of directional dependence in the permeability of the zeolite medium for calibrating 2D finite element flow analysis was highlighted by bench-scale tests performed under 2D flow conditions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.960-963
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• 2007

In this paper, development of the noise barrier analysis program is described. The upper part of barriers may have complicated shapes like "Y", "T", inverted L, and other shapes. The insertion loss of the barrier is predicted by summation of multiple diffractions occurring at top edge points. In addition, the program considers diffractions occurring at both vertical sides, while reflections from ground due to mirror images are also included. In case of two barriers at both sides of the road, reflections from the other side of barriers are considered, in which magnitudes are decreased by the ratio of absorption coefficient.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2004년도 학술발표회
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• pp.557-562
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• 2004

A surface-piercing barrier model is presented for understanding morphological development in the sheltered region and investigating the main factors causing the severe accumulation. Surface-piercing structures like vertical barriers, surface docks and floating breakwaters are recently favored from the point of view of a marine scenario since they do not in general partition the natural sea. The numerical solutions are compared with experimental data on wave profiles and morphological change rates within a rectangular harbor of a constant depth protected by surface-piercing thin breakwaters as a simplified problem. Our numerical study involves several modules: 1) wave dynamics analyzed by a plane-wave approximation, 2) suspended sediment transport combined with sediment erosion-deposition model, and 3) concurrent morphological changes. Scattering waves are solved by using a plane wave method without inclusion of evanescent modes. Evanescent modes are only considered in predicting the reflection ratio against the vertical barrier and energy losses due to vortex shedding from the lower edge of plate are taken into account. A new relationship to relate the near-bed concentration to the depth-mean concentration is presented by analyzing the vertical structure of concentration. The numerical solutions were also compared with experimental data on morphological changes within a rectangular harbor of constant water depth. Through the numerical experiments, the vortex-induced flow appears to be not ignorable in predicting the morphological changes although the immersion depth of a plate is not deep.

• Wind and Structures
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• 제20권5호
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• pp.643-660
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• 2015

The wind tunnel test of large-scale sectional model and computational fluid dynamics (CFD) are employed for the purpose of studying the aerodynamic appendices and mechanism on suppression for the vortex-induced vibration (VIV). This paper takes the HongKong-Zhuhai-Macao Bridge as an example to conduct the wind tunnel test of large-scale sectional model. The results of wind tunnel test show that it is the crash barrier that induces the vertical VIV. CFD numerical simulation results show that the distance between the curb and crash barrier is not long enough to accelerate the flow velocity between them, resulting in an approximate stagnation region forming behind those two, where the continuous vortex-shedding occurs, giving rise to the vertical VIV in the end. According to the above, 3 types of wind fairing (trapezoidal, airfoil and smaller airfoil) are proposed to accelerate the flow velocity between the crash barrier and curb in order to avoid the continuous vortex-shedding. Both of the CFD numerical simulation and the velocity field measurement show that the flow velocity of all the measuring points in case of the section with airfoil wind fairing, can be increased greatly compared to the results of original section, and the energy is reduced considerably at the natural frequency, indicating that the wind fairing do accelerate the flow velocity behind the crash barrier. Wind tunnel tests in case of the sections with three different countermeasures mentioned above are conducted and the results compared with the original section show that all the three different countermeasures can be used to control VIV to varying degrees.

• Journal of Periodontal and Implant Science
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• 제39권1호
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• pp.71-76
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• 2009

Purpose: Many researches showed loss of alveolar bone in fresh extraction socket and even in case of immediate implant placement. The aim of this study was to evaluate the effect of non-resorbable barrier membrane on the change of buccal and lingual alveolar bone in immediate implant placement into periapically infected extraction sockets. Materials and methods: Immediate implants were placed into artificially induced periapical lesion of mandibular premolars after complete debridement using buccal bone defect made by a 6mm trephine bur in 4 mongrel dogs. Before flap repositioning, a non-resorbable barrier membrane was placed on the buccal defect in the experimental group. No membrane was placed in the control group. In 12 weeks after placement, the dogs were sacrificed and undecalcified histologic specimens were prepared. The vertical distance from the smooth-rough surface interface(SRI) to gingiva, 1st bone contact and bone crest were measured in buccal and lingual side. The horizontal thicknesses of gingiva and bone at 0, 1, 2 and 3mm below SRI were measured. Results: The buccal bone was resorbed more than lingual bone in both groups and there was statistical significance(p<0.05). The distances from SRI to 1st bone contact were $2.45{\pm}2.35\;mm$ in experimental group and $4.49{\pm}3.10\;mm$ in control group. In all vertical level, lingual bone was thicker than buccal bone(p<0.05). Conclusion: Buccal bone was reduced more than lingual bone in immediate implant placement into periapically infected extraction sockets. Placement of non-resorbable barrier membrane reduced the buccal bone resorption. However there was no statistical significance.

• 한국철도학회논문집
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• 제19권2호
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• pp.124-134
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• 2016

철도 선로에 근접하여 설치하는 근접 저상 방음벽은 방음벽 높이를 저감시키기 위한 방안으로 외국에서는 많은 연구가 수행되고 있으나 국내에서의 연구는 매우 미흡한 실정이다. 본 논문에서는 근접 저상 방음벽의 음향특성을 파악하고자 축척 모형을 제작하여 성능평가를 수행하였다. 실험결과, 'ㄱ'자형 방음벽 설치 시에는 방음벽의 안쪽뿐만 아니라 상부에도 흡음재를 설치하는 것이 삽입손실의 개선효과가 있는 것으로 분석되었고, 방음벽의 삽입손실 평가를 위해 단순한 경험식 대신에 경계요소법과 같은 보다 해석적인 방법으로 삽입손실을 예측할 필요가 있다. 또한, 흡음재를 부착한 근접 방음벽을 설치하면 승객 위치에서의 소음 증가현상은 미미한 것으로 분석되었다. 그리고, 근접 방음벽의 음향성능 예측을 위해 2차원 경계요소법을 이용한 소음해석을 수행하였으며, 측정결과와의 비교 분석을 수행함으로서 예측 프로그램의 활용 가능성을 검증하였다.

• 한국해양공학회지
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• 제19권2호
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• pp.1-11
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• 2005

In the present paper, the hydrodynamic properties of a Rahmen type flexible porous breakwater with dual fixed pontoon system interacting with obliquely or normally incident small amplitude waves are numerically investigated. This system is composed of dual vertical porous membranes hinged at the side edges of dual fixed pontoons, and a submerged horizontal membrane that both ends are hinged at the steel frames mounted pontoons. The dual vertical membranes are extended downward and hinged at bottom steal frame fixed into seabed. The wave blocking and dissipation mechanism and its effects of permeability, Rahmen type membrane and pontoon geometry, pretensions on membranes, relative dimensionless wave number, and incident wave headings are thoroughly examined.

• 한국음향학회지
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• 제26권7호
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• pp.353-360
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• 2007

급속한 도시화와 인구밀도의 증가로 도시의 주거지역은 점점 고층화, 고밀화 되어가는 추세이다. 그로 인하여 인구의 공간적 집중으로 발생하는 교통수요를 감당하기 위하여 도시내부 도로는 점차 증가하였으며, 주거지역은 도로에 바로 인접하여 개발되고 있다. 이에 따라 도로에 연접한 주거지역의 도로교통소음 문제를 해결하기 위하여 방음벽에 의존하는 실정이었으나, 경관저해, 소음차단성능저해 등 다양한 역기능이 발생하고 있다. 본 연구에서는 방음벽의 역기능을 해소하고 바람직한 개선방안을 제시하기 위하여 도로변에 위치한 주거지역의 현장측정을 통하여 시뮬레이션의 정확도를 검증한 후 방음시설별 성능평가 및 전체 지역을 분석하였다. 그리고 개선방안으로 건축물의 배치형태 변화와 도로단으로부터의 이격거리를 20m 증가시켰다. 분석 결과 도로변과 평행한 공동주택의 피해가 가장 심각하였고, 시설별 분석에서는 방음벽의 성능이 우수하였으며, 건물 배치형태는 $30^{\circ}$ 배치가 우수하며, 이격거리가 증가함에 따라 교통소음이 감소하는 것으로 나타났다.

• 한국화재소방학회논문지
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• 제32권1호
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• pp.66-75
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• 2018

랙크 내 설치되는 차단막은 초기 화재확산을 지연시키는데 큰 역할을 담당하고 있으나 소화를 목적으로 설치되는 천장형 스프링클러의 입장에서는 소화수의 원활한 공급에 장애물로서 비춰질 수도 있다. 이에 In-Rack 스프링클러와 차단막을 동시에 적용하는 방법 등이 제시되고 있으나 차단막의 설치조건에 따른 화재확산 지연성능 및 In-Rack 스프링클러에 미치는 영향 등에 관한 연구는 부족한 실정이다. 이에 본 연구에서는 축소모델 화재실험을 통해 차단막의 설치조건에 따른 화재확산 지연성능과 In-Rack 스프링클러에 미치는 영향 등을 분석하였다. 그 결과, 랙크 내에 수평과 수직 차단막을 동시에 설치한 경우, 4배 이상의 화재확산 지연성능이 발휘되는 것을 확인하였으며, 구획화로 인한 구획 내 온도 상승 또한 약 2~3배 가량 높은 것으로 나타나 In-Rack 스프링클러가 조기에 작동될 수 있도록 유도하는 긍정적인 효과 또한 존재하는 것으로 나타났다.