• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.309-314
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• 2003

Impact Echo method has been successful in detecting a variety of defects in concrete structure. This study has the objectives to show important aspects of applying the Discrete Wavelet Transform(DWT) to signal processing of Modified Impact Echo(ModIE) Measurement systems and to the understanding of the seismic wave propagation. The data of ModIE were processed by DWT and compared with the results of conventional ModIE Analysis. Although it is inconsistent in the evaluated thickness of concrete lining, the DWT provides the features of separation, synthesis and de-noising in the original signal. The application of technique by wavelet was explained numerically with ABAQUS and performed experimentally with a real scale model in this work. Further works on the possible ways for creating new mother wavelet are specially needed for the enhancement of seismic signal analysis.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.11
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• pp.127-133
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• 2003

Pin-on-disk and hardness tests using mechanical components of M-20J aircraft braking system were performed to identify the friction and wear characteristics. The intention of this work was also to analyze a 5-year term maintenance record of an M-20J aircraft. used for flight training at Hankook Aviation University, and to determine the reliability of the brake system of an M-20J aircraft. The mean wear coefficients of the lining sliding against the brake disk were compared between the test and reliability estimation to obtain a predictive wear model.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.199-207
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• 2006

Before getting to the actual study of the load distribution factor in various excavating methods, this research is preliminarily focused on the comparison of two different excavation methods, CD cut method and Ringcut method. Especially, the purpose of this research is to study the behavioral mechanism of two tunnels which share the same construction environment but different excavating method. Two numerical analysis models with the same tunnel section and material properties are compared in this study, and they are analyzed by 3D Finite Element Analysis. In each model, face stability, crown displacement, ground settlement, and shotcrete-lining stress are computed. Thus, the general behavior of CD cut method and Ringcut method are studied, and it certified what should be considered for the calculation of the load distribution factor.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.911-917
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• 2018

This paper concerns a numerical investigation on the effect of construction sequence on three-arch (3-Arch) tunnel behavior. A three-arch tunnel section adopted in a railway tunnel construction site was considered in this study. A calibrated 3D finite element model was used to conduct a parametric study on a variety of construction scenarios. The results of analyses were examined in terms of tunnel and ground surface settlements, shotcrete lining stresses, loads and stresses developed in center column in relation to the tunnel construction sequence. In particular, the effect of the side tunnel construction sequence on the structural performance of the center structure was fully examined. The results indicated that the load, thus stress, in the center structure can be smaller when excavating two side tunnels from opposite direction than excavating in the same direction. Also revealed was that no face lagging distance between the two side tunnels impose less ground load to the center structure. Fundamental governing mechanism of three-arch tunnel behavior is also discussed based on the results.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.201-210
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• 1995

In Resent years, urban tunnels have been more deeply constructed due to the congestion of buried steuctures. In such conditions, the shield method has become one of the popular urban tunnelling method by reason of several characteristics ; safety of construction, mimium environmental damage, and workbility. In tunnelling, the space which is tail-void are created between the ground and the other face of the primary lining. in other to reduce the ground seformation, it is important backfilling in tail-void. In this paper, the result of an experimental investigation undertaken to evaluate the physical and mechanical propeties of grouts composed of various mixtures of backfill materials. And the backfill injection model test was carried out considering the effects of tail-void.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1518-1525
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• 2008

This paper concerns optimum design of 2-Arch tunnel. A 2-Arch tunnel adopted in a subway tunnel construction site is considered in this study. A calibrated 3D finite element model was adopted to conduct a parametric study on the lagged distance between left and right tunnel faces. The results of analysis were examined to determine optimum lagged distance for minimizing the interaction between the left and right tunnels. The results indicated that the shotcrete lining stress and the center pillar load are more influenced by the second tunnel excavation than the tunnel deformation. Also shown is that a lagged distance of 20m is sufficient to minimize the interaction between two tunnels. Fundamental mechanism of 2-arch tunnel was also investigated based on the results.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2149-2153
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• 2008

A large-scale fire test was done for interior materials from a vehicle installed within a fire test room. The interior materials are satisfied with the Korean guide for the safety of rail vehicle. The guide has taken effect since December 2004 in Korea. Ignition source (gas burner) was increased in several controlled steps. The objectives of this test are to assess the fire performance in terms of ignition and flame spread on interior lining materials and to provide data on an enclosure fires involving train interior materials that grow to flashover. This data will be used to develop and calibrate an Fire Dynamics Simulator (FDS) model for fire growth on the interior vehicle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.876-876
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• 2001

Axisymmetric finite element model is developed to determine sound propagation characteristics in a circular duct lined with a poroelastic foam. The foam and air models are derived based on the Biot's theory and the Helmholtz equation respectively and finally result in a quadratic eigenvalue problem in the wave number. Some cross sectional mode shapes are shown and sound attenuations and phase speeds of some acoustic modes are given. Those of fundamental modes are compared with those by forced response solutions and those from measurement results. The influence of lining thickness is also described on sound propagation characteristics.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.590-595
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• 2008

A large-scale fire test was done for interior materials from a vehicle installed within a fire test room. The interior materials are the old style before interior replacement by the Korean guideline for the safety of rail vehicle. Ignition source (gas burner) was increased in several controlled steps. The objectives of this test are to assess the fire performance in terms of ignition and flame spread on interior lining materials and to provide data on an enclosure fires involving train interior materials that grow to flashover. This data will be used to develop and calibrate an Fire Dynamics Simulator (FDS) model for fire growth on the interior vehicle.

• Journal of Drive and Control
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• v.12 no.1
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• pp.1-8
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• 2015

The stability of friction characteristics and thermal management for a dry type dual clutch transmission (DCT) are inferior to those of a wet clutch. Too high temperature resulting from frequent engagement of DCT speeds up degradation or serious wear of the pressure plate or burning of the clutch disk lining. Even though it is significantly important to estimate the temperature of a dry double clutch (DDC) in real-time, few meaningful study of the thermal model of DDC has been known yet. This study presented a thermal analytical model of lumped parameters for a DDC by analyzing its each component firstly. Then a series of experimental test was carried out on the test bench with a patented temperature telemetry system to validate the proposed thermal model. The thermal model, whose optimal parameter values were found by optimization algorithm, was also simulated on the experimental test conditions. The simulation results of DDC temperature show consistency with the experiment, which validates the proposed thermal model of DDC.