• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.217-226
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• 2003

This study is focused on the finding out load transfer mechanism in the ground near the tunnel during tunnel excavation in the jointed sandy ground. Laboratory model tests were performed on various cases of the overburden heights above tunnel crown, location, and degree of discontinuity planes. For model tests, a movable plate was installed in the midst of the bottom of sandy ground. This plate, moving downwards, was intended to model the stress relaxation during tunnel excavation. The load transfer was measured at the fixed separated bottom plates adjacent to the movable plate. As the result, the loosening zone and the load-transfer form around the tunnelling site were affected by the overburden height and the characteristics of discontinuous planes. And large loosening zone was developed along the discontinuous planes which were close to the tunnel.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.2
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• pp.151-161
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• 2012

The present study numerically investigates the aerodynamic characteristics of two-dimensional wings in the vicinity of the ground by solving two-dimensional steady incompressible Navier-Stokes equations with the turbulence closure model of the realizable k-${\varepsilon}$ model. Numerical simulations are performed at a wide range of the normalized ground clearance by the chord length ($0.1{\leq}h/C{\leq}1.25$) for the angles of attack ($0^{\circ}{\leq}{\alpha}{\leq}10^{\circ}$) in the prestall regime at a Reynolds number (Re) of $2{\times}10^6$ based on free stream velocity $U_{\infty}$ and the chord length. As the physical model of this study, a cambered airfoil of NACA 4406 has been selected by a performance test for various airfoils. The maximum lift-to-drag ratio is achieved at ${\alpha}=4^{\circ}$ and h / C = 0.1. Under the conditions of ${\alpha}=4^{\circ}$ and h / C = 0.1, the effect of the Reynolds number on the aerodynamic characteristics of NACA 4406 is investigated in the range of $2{\times}10^5{\leq}Re{\leq}2{\times}10^9$. As Re increases, $C_l$ and $C_d$ augments and decreases, respectively, and the lift-to-drag ratio increases linearly.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.193-204
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• 2008

This paper describes laboratory experiments modelling multiple tunnel construction in soft ground. A series of small-scale model tests have been conducted at approximately 1/50 scale in order to investigate the behaviours of existing tunnels in response to the construction of new tunnels in close proximity. The model tunnels were constructed in a consolidated Speswhite Kaolin clay using a tunnelling device involving an auger type cutter within a shield. Strain gauges and LVDTs were used for instrumenting the existing tunnels. The findings obtained from the analyses of these tests were compared to the field measurements involving the reconstruction of the Northern Line London Underground Ltd. tunnels at Old street, United Kingdom. The results were also compared to the ground movement measurements obtained from a separate set of tests undertaken using the same apparatus and experimental procedures.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.3
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• pp.97-108
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• 1995

A 3-dimensional double track vehicle model, that has 12-degress-of-freedom, was proposed to analyze handling and riding behaviours of an automotive car. Nonlinear characteristics of the suspension and steering systems of the vehicle model were considered in its equations of motion, which were solved by using the 4th-order Runge-Kutta integration method. Computer simulations for lane change, steady-state handling, and running-over-bump manoeuvres were made and verified by vehicle tests on proving ground. The computed results of the proposed model showed better agreement with test results than those of the conventional 2-dimensional single track model did. Especially they showed good accuracy near the characteristic speed and in high lateral accelerated manoeuvres.

• Journal of the Korean GEO-environmental Society
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• v.9 no.1
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• pp.5-10
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• 2008

In this study, laboratory model test was performed to estimate pullout behavior of pipe type anchor with surface roughness, embedment and diameter. The design of buried pipe anchors in areas of vertical ground movement is governed, in part, by magnitude of the forces imposed on the pipe and displacements at which they are developed. In this paper, uplift resistance and displacement characteristics of pipe anchors caused by ground condition and embedment ratio, surface roughness, pipe diameter through the analysis of pipe anchor model test were compared and analyzed. The test results of the buried pipe showed that as the relative density increases, ultimate uplift resistance increase in 20%. When pipe anchor is failed with the relative density of the ground, the change of surface roughness, it was shown that the deformation increases as the ratio of penetration increases from 2 to 8 in five times approximately. And most anchor-based theories overestimate the breakout factor.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1799-1804
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• 2010

In regard to fill loading structures such as bridge abutments and retaining walls on soft ground, the soft ground undergoes excessive deformation, which causes the lateral movement of the ground, resulting in increased risk of much damage. In this study, a centrifuge model test was conducted to check the possibility of lateral movement of a bridge abutment during back filling in a field, and a numerical analysis considering the lateral movement of the bridge abutment under the influence of the counterweight fill method applied during construction was carried out by using MIDAS/GTS as the FEM(Finite Element Method) program. The results of this study showed that the lateral movement of the abutment can exceed the allowable lateral movement value(15mm), and that the counterweight fill method was effective for the stability of the lateral movement.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.183-188
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• 2008

Engine control/performance model for helicopter simulator is one of the most important models which affect flight performance and handling quality. It is typical to develop the model based on the raw data and models from the engine designers/manufacturers. The approaches in this study were to develop the basic model based on the available resources and to tune and verify it based on the ground/flight test results. The maintenance manuals of TB3-117 which is installed in KA-32T were reviewed and the components to be simulated for the engine control model were categorized and modeled. Piece-wise linear modeling method was used for the engine performance model. The engine performance data in the engine maintenance manuals were incorporated into the engine steady state performance tables, which were incorporated with the transfer functions for the dynamic performance. Engine control/performance model was compared and tuned with the ground/flight test results. It was verified that the fidelity of the model was within the tolerances in FAA AC120-63.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.512-520
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• 2020

Recently, the applications of the standing column well (SCW) ground heat exchanger (GHX) have increased significantly in Korea as a heat transfer mechanism of ground source heat pump systems (GSHP) because of its high heat capacity and efficiency. Among the various design and operating parameters, bleeding was found to be the most important parameter for improving the thermal performance, such as ground thermal conductivity and borehole thermal resistance. In this study, a bleeding analysis model was developed using the thermal response test data, and the effects of bleeding rates and bleeding locations on the thermal performance of anSCW were investigated. The results show that, when the ground water flows into the top of anSCW, the time variation of circulating water temperature decreased with increasing bleeding rate, and the ground thermal conductivity increases by as much as 179% with a 30% bleeding rate. When the ground water flows into the bottom of the SCW, the circulating water temperatures become almost constant after the increase in the beginning time because the circulating water exchanges heat with the ground structure before mixing with the ground water at the bottom.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.241-252
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• 1998

The objective of the research stated herein is to observe the actual responses of a low-rise nonseismic moment-resisting reinforced concrete frame subjected to varied levels of earthquake ground motions. First, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used and the model was manufactured according to the similitude law. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelations (PGAs) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The lateral accelerations and displacements at each story and local deformations at the critical reginos of the structure were measured. The base shear was measured by using self-made load cells. Before and after each earthquake simulation test, free vibration tests were performed to find the change in the natural period and damping ratio of the model. The test data on the global and local behaviors are interpreted. The model showed the linear elastic behavior under the Taft N21E motion with the PGA if 0.12g, which represents the design earthquake in Korea. The maximum base shear was 1.8tf, approximately 4.7 times the design base shear. The model revealed fairly good resistance to the higher level of earthquake simulation tests. The main components of its resistance to the high level of earthquakes appeared to be 1) the high overstrength, 2) the elongation of the fundamental period, and 3) the minor energy dissipation by inelastic deformations. The drifts of the model under these tests were approximately within the allowable limit.

• Journal of Advanced Navigation Technology
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• v.28 no.3
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• pp.278-287
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• 2024

In this paper, telemetry link budget model for small launch vehicle is proposed, and telemetry link budget simulator is implemented. The proposed link budget model consist of geometry model and propagation loss model. The geometry model is calculation of look angle between ground station and small launch vehicle. The propagation loss model consist of free space loss, polarization loss, and de-pointing loss which are appropriate to the small launch vehicle flight environment. The proposed propagation loss model can be calculate propagation loss without complex calculation of propagation environments. The link budget simulator is implemented in MATLAB. The simulator calculate look angle, free space loss, polarization loss parameter, de-pointing loss and received signal level in ground station by using position of ground station, routing of small launch vehicle, 3-D radiation patterns of antennas.