• Nuclear Engineering and Technology
• /
• 제33권6호
• /
• pp.605-618
• /
• 2001

For the mechanical stability assessment of a deep underground high-level waste repository. computer simulations using FLAC3D were carried out and important parameters including stress ratio, depth, tunnel size, joint spacing, and joint properties were chosen from sensitivity analysis. The main effect as well as the interaction effect between the important parameters could be investigated effectively using fractional factorial design . In order to analyze the stability of the disposal tunnel and deposition hole in a discontinuous rock mass, different modelings were performed under different conditions using 3DEC and the influence of joint distribution and properties, rock properties and stress ratio could be determined. From the three dimensional modelings, it was concluded that the conceptual repository design was mechanically stable even in a discontinuous rock mass.

• Wind and Structures
• /
• 제5권5호
• /
• pp.393-406
• /
• 2002

Aerodynamic pressures and forces were measured on a model of a solar panel containing six slender, parallel modules. Of particular importance to system design is the aerodynamically induced torque. The peak system torque was generally observed to occur at approach wind angles near the diagonals of the panel ($45^{\circ}$, $135^{\circ}$, $225^{\circ}$ and $315^{\circ}$) although large loads also occurred at $270^{\circ}$, where wind is in the plane of the panel, perpendicular to the individual modules. In this case, there was strong vortex shedding from the in-line modules, due to the observation that the module spacing was near the critical value for wake buffeting. The largest loads, however, occurred at a wind angle where there was limited vortex shedding ($330^{\circ}$). In this case, the bulk of the fluctuating torque came from turbulent velocity fluctuations, which acted in a quasi-steady sense, in the oncoming flow. A simple, quasi-steady, model for determining the peak system torque coefficient was developed.

• Wind and Structures
• /
• 제4권6호
• /
• pp.481-494
• /
• 2001

Wind tunnel pressure tests were conducted on a 1:100 scale model of a large industrial building with solar panels mounted parallel to the flat roof. The model form was chosen to have the same aspect ratio as the Texas Tech University test building. Pressures were simultaneously measured on the roof, and on the topside and underside of the solar panel, the latter two combining to produce a nett panel pressure. For the configurations tested, varying both the lateral spacing between the panels and the height of the panels above the roof surface had little influence on the measured pressures, except at the leading edge. The orientation of the panels with respect to the wind flow and the proximity of the panels to the leading edge had a greater effect on the measured pressure distributions. The pressure coefficients are compared against the results for the roof with no panels attached. The model results with no panels attached agreed well with full-scale results from the Texas Tech test building.

• Advances in aircraft and spacecraft science
• /
• 제4권2호
• /
• pp.125-144
• /
• 2017

This paper summarises the design of a gust generator and the comparison between high fidelity numerical results and experimental results. The gust generator has been designed for a low subsonic wind tunnel in order to perform gust response experiments on wings and assess load alleviation. Special attention has been given to the different design parameters that influence the shape of the gust velocity profile by means of CFD simulations. Design parameters include frequency of actuation, flow speed, maximum deflection, chord length and gust vane spacing. The numerical results are compared to experimental results obtained using a hot-wire anemometer and flow visualisation by means of a tuft and smoke. The first assessment of the performance of the gust generator showed proper operation of the gust generator across the entire range of interest.

• 터널과지하공간
• /
• 제7권3호
• /
• pp.202-207
• /
• 1997

Jointed rock is often modeled using ubiquitious joint models, anisotropic plasticity models with yield condions that simulate slip along joint sets. In this paper, a ubiquitous joint model is derived for a rock mass cut by two sets of continuous joints. The model is used to compute the bearing capacity of a footing resting on jointed rock. Comparison to a series of Distinct Element simulations with different joint spacings, suggests that ubiquitous joint modles are only appropriate when the joint spacing is small.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
• /
• pp.587-587
• /
• 2012

Supercapacitors, which can deliver significant energy with high power density, have attracted a lot of attention due to their potential application in energy storage. Among various oxide materials, sodium vanadate has been recognized as one of the most promising electrode materials because of high electrical conductivity. In addition, larger layer spacing of ${\beta}$-Na0.33V2O5 compared to V2O5 makes easier Li+ insertion. Moreover, ${\beta}$-Na0.33V2O5 has a tunnel like structure along b axis with 3 kinds of V site allowing it to enhance the ion intercalation by introducing three different intercalation sites along the tunnel. The tunnel can act as a fast diffusion path for ion diffusion, which can improve the overall charge storage kinetics. In this study, high quality single crystalline sodium vanadate (${\beta}$-Na0.33V2O5) nanowires were grown directly on Pt coated $SiO_2$ substrate by a facile chemical solution deposition method without employing catalyst, surfactant or carrier gas. The results show that great enhancement in capacitance was observed compared with previous reports.

• Wind and Structures
• /
• 제8권5호
• /
• pp.325-342
• /
• 2005

This paper deals with the buckling behavior of thin-walled aboveground tanks under wind load. In order to do that, the wind pressures are obtained by means of wind-tunnel experiments, while the structural non linear response is computed by means of a finite element discretization of the tank. Wind-tunnel models were constructed and tested to evaluate group effects in tandem configurations, i.e. one or two tanks shielding an instrumented tank. Pressures on the roof and on the cylindrical part were measured by pressure taps. The geometry of the target tank is similar in relative dimensions to typical tanks found in oil storage facilities, and several group configurations were tested with blocking tanks of different sizes and different separation between the target tank and those blocking it. The experimental results show changes in the pressure distributions around the circumference of the tank for half diameter spacing, with respect to an isolated tank with similar dimensions. Moreover, when the front tank of the tandem array has a height smaller than the target tank, increments in the windward pressures were measured. From the computational analysis, it seems that the additional stiffness provided by the roof prevents reductions in the buckling load for cases even when increments in pressures develop in the top region of the cylinder.

• 한국터널지하공간학회 논문집
• /
• 제20권1호
• /
• pp.211-224
• /
• 2018

터널의 지보패턴 설계는 터널의 안정성에 직접적인 영향을 끼치기 때문에 터널에 작용하는 다양한 하중들을 적절히 고려하여야 한다. 국내에서는 프로젝트에 따라 암반분류법을 기반으로 표준 지보패턴을 정의하고 있으며, 시공 시 터널거동을 고려하여 적절히 수정되어야 한다고 기술되어 있다. 본 연구에서는 내공변위제어법, 토압, 록볼트의 축력 및 숏크리트의 모멘트 등을 종합적으로 고려하여 지보패턴을 최적화할 수 있는 방법을 제시하고자 한다. 차분진화알고리즘(DEA)을 적용하여 터널 심도에 따라 록볼트의 길이 및 간격, 숏크리트의 두께를 최적화하였으며, 도출된 결과를 철도터널의 표준지보패턴(3등급)과 비교하였다. 천층지반에서 록볼트의 길이는 표준지보패턴보다는 짧아질 수 있으며, 간격은 넓어질 수 있다. 터널의 심도가 깊어질수록 숏크리트의 두께는 선형적으로 증가하는 것으로 나타났다. 따라서, 숏크리트의 두께는 심도가 깊어질수록 표준지보패턴보다는 두꺼워져야 터널의 안정성을 확보할 수 있는 것으로 나타났다.

• 터널과지하공간
• /
• 제19권1호
• /
• pp.1-10
• /
• 2009

암반 내 구조물을 시공하는 경우 역학적 안정성을 평가하기 위하여 암반의 특성을 조사한다. 이 경우 암반의 특성은 주로 암반 내 절리의 특성에 의하여 좌우된다. 지금까지는 암반 내 절리의 특성을 조사하기 위하여 암반이 노출된 사면이나 노두에 접근하고 육안으로 직접 관찰하였다. 이때 급사면과 같은 곳에서 접근의 문제, 작업의 안전 문제, 많은 시판이 걸리는 문제, 조사시간에 비하여 얻은 정보량의 부족, 정보의 재현 문제, 측정 오차 문제 등의 제한이 있었다. 따라서 이와 같은 문제를 개선하기 위하여 LIDAR (light detection and ranging)로 암반을 스캔하여 얻은 포인트 클라우드(point cloud)글 Split-FX 소프트웨어로 처리한 결과 절기의 방향과 간격 및 절리면의 거칠기 등 절리의 특성을 정확하고 효율적으로 분석할 수 있었다.

• 터널과지하공간
• /
• 제13권5호
• /
• pp.344-352
• /
• 2003

시추공 또는 선형조사선과 같은 1D측선에서 측정된 절리 자료의 샘플링 편향을 보정하는 절차를 기술하였다. ID 측선에서 절리가 관측될 수 있는 확률은 측선 방향에 대한 절리의 상대적인 방향 이외에도 절리 크기, 절리 모양 및 측선 길이 등의 복합적 요인에 의하여 결정될 수 있다. 본 연구에서는 절리의 모양을 원판형이라 가정하고 절리의 방향 및 크기에 의하여 나타날 수 있는 절리 자료의 방향 편향 효과를 동시에 보정할 수 있는 방법론을 제시하고, 현장적용을 통하여 방향 편향 보정이 절리군의 방향분포에 미치는 영향에 대하여 고찰하였다. 또한, 유한 길이의 측선으로부터 산정된 절리군의 간격분포는 샘플링 영역인 측선 길이에 따라 다르게 나타날 수 있으며, 이와 같은 간격 편향에 대한 보정절차를 기술하였다.