• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.321-327
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• 2014

In this paper, linear dynamic equations are derived from nonlinear dynamic equations of constrained multibody systems using the QR decomposition method. The derived linear equations are applied to a railway vehicle bogie. The vibration characteristics of the railway vehicle are investigated by calculating the natural mode and transfer function of the bogie frame in relation to rail-roughness input. The main modes of the bogie were found below 35Hz, and the local modes above 198Hz. The magnitude of the vertical transfer function varied with the forward velocity due to vertical and pitch modes, which were influenced by the forward velocity. The magnitude of the lateral transfer function was negligibly small, and the mode in the longitudinal direction was excited for longitudinal transfer function regardless of the forward velocity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1587-1592
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• 2010

The effects of specimen geometry and loading conditions on the stress distribution in a sandwich specimen under combined loads are investigated by elastic finite element analysis. A commercial software NASTRAN is used in plain-strain two-dimensional finite element analysis of sandwich specimens; the analysis was performed for three different specimen shape factors and four different combined displacement conditions. The results of computational analysis suggest that the effect of the combined displacement angle, which is defined as the ratio of the shear displacement to the normal displacement, on the size of the non-homogeneous stress distribution is observed only in the case of the shear stress and von Mises stress. Also as the combined displacement angle increases, the size of the nonhomogeneous stress distribution decreases in the case of the shear stress and increases in the case of the von Mises stress. In addition, as the specimen shape factor, which is defined as the ratio of the specimen length to the height, increases, the size of the non-homogeneous stress distribution under combined displacement conditions decreases significantly.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.92-93
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• 2001

주파수 안정화 레이저 광원은 10-6 이상의 상대 불확도가 필요한 간섭계에서 널리 쓰이고 있으며 특히 변위 측정 시스템에서는 반드시 쓰이고 있다. 상용화된 많은 변위 측정 시스템은 신호 대 잡음비가 우수하고 광학계의 정렬이 더 쉬운 헤테로다인 방식을 채택하고 있으며 이를 위해서 서로 수직 선형 편광인 다른 주파수의 광을 내보내는 광원이 필요하다. 현재 헤테로다인 변위 측정 시스템에 쓰이고 있는 광원은 이중 주파수 광원을 만드는 방식에 따라 지만 효과(Zeeman effect)를 이용한 지만 레이저(HP사)와 음향-광 변조기(Acousto-optic modulator)를 이용한 이중 주파수 레이저(Zy해사)가 있다. (중략)

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.93-103
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• 2018

Behaviors of splices between bolts and welding spliced PHC piles using the tensile strength test were analyzed. The bolts spliced PHC piles, which were tightened over $200N{\cdot}m$ tightening torque, showed straight V shaped line at splices at the lowest 20 N load. Both sides of PHC piles stayed straight, so the full section of bolts spliced piles did not show the unifying behavior, which was the most important performance requirement as pile. Other bolts spliced PHC piles, tightened with $20N{\cdot}m$ loosening torque, also showed the same straight V shaped line at splices for each step of loading. The full section of bolts spliced piles did not return to the initial position after each step of unloading and did not show the elastic material behavior. The splices quality of bolts spliced piles is much lower than that of welding spliced piles with respect to displacement of splices during each step of loadings, residual displacements during each step of unloadings, and failure loads. Results showed that bolts spliced PHC piles, tightened with both over $200N{\cdot}m$ and as low as $20N{\cdot}m$ torque, fell short of performance requirements of spliced PHC pile.

• The korean journal of orthodontics
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• v.41 no.5
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• pp.337-345
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• 2011

Objective: The purpose of this study was to evaluate the effect of force and moment produced by Nickel-titanium wires of different sizes at activation and deactivation according to differing vertical bracket displacement. Methods: Superelastic NiTi wires of 3 different sizes (0.014", 0.016", and 0.016" ${\times}$ 0.022") were tied with elastomeric or 0.009-inch stainless steel ligations in a twin-bracket, 0.018-inch slot. A testing machine recorded the effects of simulated activation of 5 distances from 1 to 5 mm and deactivation of 5 distances from 4 to 0 mm, in increments of 1 mm. Results: Frictional force increased the wire stiffness during loading. Ligation of 0.014-inch NiTi wire with O-ring resulted in a significant increase in the stiffness. On application of orthodontic force for 5 mm of vertical displacement of teeth, the effective displacement in the case of the 0.014", 0.016", and 0.016" ${\times}$ 0.022" NiTi wires was 2 mm, 3 mm, and 4 mm, respectively. Conclusions: Our results showed that movement of teeth with large vertical displacement was ineffective because of excessive friction. This finding might contribute to the understanding of the force system required for effective teeth movement and thereby facilitate the application of the appropriate light wire for leveling and alignment.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.193-205
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• 2001

In this study the behavior of pile groups is investigated experimentally. Special attention is given to the load transfer characteristics of pile groups and to the evaluation of the group effects under vertical and horizontal loadings. In the laboratory experiments, vertical and lateral loadings were imposed on model piles in sand. Model piles made of PVC embedded in Joomoonjin sand were used in this study. Pile arrangements($2\times2,\; 3\times3$) and pile spacings(2.5D, 5.OD, 7.5D) were considered. Load-transfer curves(t-z, q-z and p-y curves), load-deflection curves and group interaction factors were obtained from the experimental results. The group interaction factors under both vertical and horizontal loadings were proposed for the cases of $2\times2\; and\; 3\times3$ pile groups with varying ratios of pile spacings. p-multipliers in this study were found for the individual piles in $2\times2\; and\; 3\times3$ pile groups.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.10
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• pp.777-788
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• 2006

This paper describes a displacement mapping technique which represents protruded shapes on the surface of an object. Previous approaches for image-based displacement mapping can represent only shapes depressed from the polygon surface. The proposed technique can represent shapes protruded from the underlying surface in real-time. Two auxiliary surfaces which are perpendicular to the underlying surface are added along the boundary of the polygon surface, in order to represent the pixels which overflow over the boundary of the polygon surface. The proposed approach can represent accurate silhouette of protruded shape. It can represent not only smooth displacement of protruded shape, but also abrupt displacement such as perpendicular protrusion by means of adding the supplementary texture information to the steep surface of protruded shape. By per-pixel instructions on the programmable GPU this approach can be executed in real-time. It provides an effective solution for the representation of protruded shape such as high-rise buildings on the ground.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.157-164
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• 2010

This research was conducted to analyze the behavior of Single-PTAS (Single Post-Tensioned Approach Slab) under tensioning and environmental loads by performing field tests when the demonstration Single-PTAS was being constructed. The temperature measurement sensors were installed at different depths, and the displacements in the approach slab under environmental loads and tensioning were measured using displacement transducers. As an experimental result, an abrupt change in the longitudinal displacement due to tensioning was not observed. The daily temperature change in the approach slab was negligible where the depth is over about 35cm. The temperature gradient in the approach slab adjacent to bridge was smaller than that adjacent to pavement. The patterns and magnitudes of vertical displacements were directly related to the temperature gradient at the measuring location. The behavior of Single-PTAS was very similar to that of concrete pavement. Therefore, a new design methodology for approach slabs is needed to include the pavement concept and to overcome drawback of current design procedures based on the simple beam concept.

• Journal of the Korean Professional Engineers Association
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• v.26 no.3
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• pp.44-50
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• 1993

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.1.2-12
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• 1995