• Journal of the Korean Geosynthetics Society
• /
• v.6 no.3
• /
• pp.17-23
• /
• 2007

To construct an ideal geosynthetic reinforced soil retaining wall (GRS-RW), the facing of the wall should be flexible enough to accommodate a large deformation of the supporting ground and to develop the large tensile force in reinforcements during wall construction as long as the stability is ensured, but should be rigid enough to be stiff and stable as well as durable and aesthetically acceptable for a long life time when the wall is in service. Facing conditions during the construction and service of the wall are quite different. So it is difficult to be satisfied all these conditions with the current construction method which is mainly used in reinforced wall construction in Korea. Most of this contradiction could be solved by the staged construction procedure. According to the results of cases and references analyses, stage construction procedures make it possible to accommodate large deformation of the supporting ground and backfill without losing the stability of the wall, and to derive the tensile strength of reinforcement causing deformation of the facing. When the facing is a full-height rigid one, it also appeared almost impossible to occur a local shear failure of the active zone, and pull-out failure of reinforcements. Therefore, GRS-RWs having a full-height rigid facing have been constructed by the staged construction procedures that matched well with the theory of reinforced soil, which had outstanding stability and durability, and thus could be used for railways and bridge abutments in Korea in the future.

• The Journal of the Convergence on Culture Technology
• /
• v.4 no.3
• /
• pp.139-147
• /
• 2018

This study starts with the consciousness of what should be the public pension service that meets the 4th Industrial Revolution era. To do this, we review the current status of non-facing services of domestic and foreign public institutions, and draw out implications for revitalizing non-facing services of the National Pension over the medium to long term. First, we reviewed the status of non-face-to-face service and the authentication method of the National Pension Service. Next, we reviewed the status of non-facing services in public pension and private agencies in the United States, the United Kingdom, Canada, and Australia. Based on the results of the analysis, we needs to analyze the impact of the 4th Industrial Revolution on the National Pension Service and extract future strategies, to expand channels of non-facing by business, to introduce PinTech as a non-facing authentication method, and to propose a unified service channel through the construction of an internet integrated portal. In the 4th industrial revolution era, it is possible to secure the connectivity of government portal for civil affairs and intelligence and automation introducing artificial intelligence robots.

• Architectural research
• /
• v.18 no.4
• /
• pp.151-155
• /
• 2016

It is necessary to improve the performance of buildings with respect to the energy efficiency while improving the quality of occupants' lives through a sustainable built environment. During the design and development process, building projects must have a comprehensive, integrated perspective that seeks to reduce heating, cooling and lighting loads through climate-responsive designs. The aim of this study is to find an optimal thermal transmittance (U-values) for building envelope elements for low energy multi-rise residential buildings in the early design phase in Korea. The study found that using small U-values of $0.15w/m^2K$ for exterior walls, ceilings and floors and $1.0w/m^2K$ for south and north facing windows has resulted in energy reduction of 22.1%-59.4% in the south facing rooms and 43%-77.6% of the north facing rooms. It has also found the energy load reduction potential of using small U-values are higher on the north facing rooms. The findings of this study can be suggested to be used as a baseline case for low energy consumption studies. It can also be used to determine appropriate envelope materials and insulation values.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.6
• /
• pp.33-41
• /
• 2015

Scaled model of a dual-mode ramjet engine with large backward-facing step, as a component of the rocket-based combined cycle engine, was designed. Design parameters were derived for this engine with the consideration of application for the rocket-based combined cycle engine. Design methodology was established for these design parameters. The design was partially verified through numerical study. Flow characteristics of the dual-mode ramjet engine with large backward-facing step was investigated experimentally. The design methodology for relevant design parameters established in this study was verified as feasible.

• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.506-511
• /
• 2001

This paper presents how redevelopment of the boundary layer in a backward-facing step flow is affected by boundary conditions imposed on velocity at the inlet, top and exit of the flow. A two-dimensional, laminar, incompressible flow over a backward-facing step with an open top boundary has been computed by using numerical methods of second-order time and spatial accuracy and a fractional-step method that guarantees a divergence-free velocity field at all time. The inlet velocity profile above the step is of Blasius type. Along the top boundary, shear-tree and Dirichlet conditions on the streamwise velocity were considered and at the exit fully-developed and convective boundary conditions were examined. (The vertical velocity at all boundaries were assumed to be zero explicitly or implicitly.) From the computed flow fields, the reattachment on the bottom side of shear layer separated from the tip of the step and succeeding redevelopment of the boundary layer were investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.10
• /
• pp.840-845
• /
• 2012

An ARX(Auto-Regressive eXogenous) modeling technique for vortex dynamics in the BFS(Backward Facing Step) flow field is proposed in this paper. In order for the modeling of the dynamics, the spatial and temporal modes are extracted through POD(Proper Orthogonal Decomposition) analysis. Determining the orders of the inputs and outputs for an ARX structure is carried out by the spectrum analysis and temporal mode analysis, respectively. The order of input delay terms is also determined by the flow velocity. Finally the coefficients of the ARX model are designed by using an artificial neural network.

• Conservation Science in Museum
• /
• v.5
• /
• pp.43-47
• /
• 2004

The five pieces (Bon 4054, 4074, 4077, 4096 and Bon 4097)of the Central Asia murals housed in the National Museum of Korea were conserved for approximately 2 years. The Central Asia murals conserved for this time have undergone the processes of cleaning, reinforcing pigment layers, facing to protect the pigment layers disassembling, separating wooden frames reinforcing the wall layers, attaching supports to the wall layers, removing facing and making picture frames. They were conserved with emphasis placed on reinforcing the peeled pigment layers and the weakened walls and on improving the structural problem of the exhibit frames.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.9
• /
• pp.2328-2341
• /
• 1995

An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purposes of the present study are to investigate the effect of the free stream turbulence intensity on the reattachment length and to understand the turbulence structure of the recirculating flows. Local mean and fluctuating velocity components were measured in the separated and reattaching axisymmetric turbulent boundary layer over the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. As the free stream turbulence intensity increased, the reattachment length became shorter due to the enhanced mixing in the separated shear layer. It was also observed that the reverse flow velocity and turbulent kinetic energy increase with increasing free stream turbulence intensity. Spectral data and flow visualization showed that low-frequency motions occur in the separated flow behind a backward-facing step. These motions have a significant effect on the time-averaged turbulence data.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.247-254
• /
• 2000

The base pressure of vacuum vessel of the KSTAR (Korea Superconducting Tokamak Advanced Research) Tokamak is to be a ultra high vacuum, $10^{-6}{\sim}10^{-7}Pa$, to produce clean plasma with low impurity containments. For this purpose, the KSTAR vacuum vessel and plasma facing components need to be baked up to at least $250^{\circ}C,\;350^{\circ}C$ respectively, within 24 hours by hot nitrogen gas from a separate baking/cooling line system to remove impurities from the plasma-material interaction surfaces before plasma operation. Here by applying the implicit numerical method to the heat balance equations of the system, overall temperature distributions of the KSTAR vacuum vessel and plasma facing components are obtained during the whole baking process. The model for 2-dimensional baking analysis are segmented into 9 imaginary sectors corresponding to each plasma facing component and has up-down symmetry. Under the resulting combined loads including dead weight, baking gas pressure, vacuum pressure and thermal loads, thermal stresses in the vacuum vessel during bakeout are calculated by using the ANSYS code. It is found that the vacuum vessel and its supports are structurally rigid based on the thermal stress analyses.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.4 s.247
• /
• pp.364-372
• /
• 2006

The objective of this study is to evaluate the efficiency and the prediction accuracy of developed large eddy simulation (LES) program for complex turbulent flows, such as recirculating and swirling flows. To save the computational cost, a Beowulf cluster system consisting 16 processors was constructed. The flows in backward-facing step and dump combustor were examined as representative recirculating and swirling flows. Firstly, a direct numerical simulation (DNS) for laminar backward-facing step flows was previously conducted to validate the overall performance of program. Then LES was carried out for turbulent backward-facing step flows. The results of laminar flow showed a qualitative and quantitative agreement between simulations and experiments. The simulations of the turbulent flow also showed reasonable results. Secondly, LES results for non-swirling and swirling flows in a dump combustor were compared with the results of Reynolds-averaged Navier-Stokes (RANS) using standard $k-{\varepsilon}$ model. The results show that LES has a better performance in predicting the mean axial and azimuthal velocities, comer recirculation zone (CRZ) and center toroidal recirculation zone (CTRZ) than those of RANS. Finally, it was examined the capability of LES for the description of unsteady phenomena.