• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.9
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• pp.545-551
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• 2004

CBTC(Communication Based Train Control) System can improve train operation efficiency by realizing moving block system which makes a continuous train interval control in accordance with the position and speed of train. Adopting radio transmission to make a continuous detection of train position and transmit the control data from the ground to a train, CBTC needs dedicated train operation and control algorithm which should be quite different from the conventional track-circuit-based train control system. This paper provides a train operation display and control algorithm for CBTC system in making train interval control, train route control and train supervision. Signalling pattern diagram is devised to analyze the train interval control mechanism of moving block system, and interlocking logic is devised to represent the train route control mechanism of moving block system. For train supervision, train occupation status on railway are displayed by using the segment which virtually divide the whole railway. The proposed method has been successfully applied to the development of CBTC system for the standardized AGT(automatic guided transit) which is under construction now in Korea, and also can be applied to any other CBTC system.

• Journal of Power Electronics
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• v.13 no.1
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• pp.51-58
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• 2013

This paper proposes the power conversion mechanism of a bailer-charge-transfer zero-current-switching (CT-ZCS) circuit. The operation modes are analyzed and researched using state trajectory equations. The topology of CT-ZCS based on soft-switching inverters offers some merits such as: tracking the input reference signal dynamically, bearing load shock and short circuit, multiplying inverter N+1 redundancy parallel, coordinating power balance for easy control, and soft-switching commutation for high efficiency and large capacity. These advantages are distinctive from conventional inverter topologies and are especially demanded in AC drives: new energy generation and grid, distributed generation systems, switching power amplifier, active power filter, and reactive power compensation and so on. Prototype is manufactured and experiment results show the feasibility and dynamic voltage-tracking characteristics of the topology.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.216-222
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• 2003

Train control by radio based communication is one of the interesting new fields in train signal. The radio based control has more benefits, low headway and low construction and maintenance cost, than conventional control. In this paper, a safe and efficient train operation is introduced. Triple radio communications, train to train, train to station, and train to central traffic control, are used to increase the reliability. One of these communications channels has a fault; the others can take the functions of it. Absolute position of a train is transmitted to station via radio communication. In the station, the interlocking mechanism should be activated as the legacy.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.1-6
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• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the construction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have beem deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechanism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical program is developed using these joint models.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.47-53
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• 2018

Various types of robotic arms are being used for industrial purposes, particularly with the small production of multi-products, and the importance of the gripper, which can be used in industrial fields, is increasing. This study evaluated a variable stiffness mechanism gripper that can change the stiffness using the nonlinearity of a flexible material. A prototype of the gripper was fabricated and examined to confirm the change in stiffness. The previous gripper was unable to grip objects in some situations with three variable stiffness mechanism. In addition, these mechanisms were not balanced and rarely rotated when the object was gripped. Therefore, a new type of gripper was needed to solve this problem. Inspired by the movements of the human palm and Venus Flytrap, a new type of a variable stiffness soft robot hand was designed. The possibility of grasping could be increased by interlocking the palm folding mechanism by pulling the tendon attached to the variable stiffness mechanism. The soft robotic hand was used to grasp objects of various shapes and weights more stably than the previous variable stiffness mechanism gripper. This new variable stiffness soft robot hand can be used selectively depending on the application and environment to be used.

• Journal of Surface Science and Engineering
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• v.32 no.6
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• pp.647-657
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• 1999

Due to the inherently poor adhesion strength of Cu-based leadframe/EMC (Epoxy Molding Compound) interface, popcorn cracking of thin plastic packages frequently occurs during the solder reflow process. In the present work, in order to enhance the adhesion strength of Cu-based leadframe/EMC interface, black-oxide layer was formed on the leadframe surface by chemical oxidation of leadframe, and then oxidized leadframe sheets were molded with EMC and machined to form SDCB (Sandwiched Double-Cantilever Beam) and SBN (Sandwiched Brazil-Nut) specimens. SDCB and SBN specimens were designed to measure the adhesion strength between leadframe and EMC in terms of critical energy-release rate under quasi-Mode I ($G_{IC}$ ) and mixed Mode loading ($G_{C}$ /) conditions, respectively. Results showed that black-oxide treatment of Cu-based leadframe initially introduced pebble-like X$C_2$O crystals with smooth facets on its surface, and after the full growth of $Cu_2$O layer, acicular CuO crystals were formed atop of the $Cu_2$O layer. According to the result of SDCB test, $Cu_2$O crystals on the leadframe surface did not increase ($G_{IC}$), however, acicular CuO crystals on the $Cu_2$O layer enhanced $G_{IC}$ considerably. The main reason for the adhesion improvement seems to be associated with the adhesion of CuO to EMC by mechanical interlocking mechanism. On the other hand, as the Mode II component increased, $G_{C}$ was increased, and when the phase angle was -34$^{\circ}$, crack Kinking into EMC was occured.d.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.667-672
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• 2009

In case of high-levelled platform in the urban railway system, a certain width of gap is inevitably formed between the train and the platform, and the gap gets wider when it is concerned with curved portion of the tracks at platform. This gap greatly contributes to decrease of passengers' safety while boarding and alighting a train. In particular, it endangers children's safety. Gap filler system is often fitted out to minimize gap and to overcome this safety problem at platform. However, as existing gap fillers are in most case structurally complex and organized to be powered from separate supply unit, there are a range of non-favorable points from the viewpoint of cost, installation and maintenance. In addition, existing gap fillers are due to cause disruptions in operation of train, with failures such as malfunctioning of control system. In this study, the authors will review on the gap filler applicable to the platforms of various height types, which neither requires any modifications of the train nor causes any operational disruptions. The proposed gap filler system here is a by-stage retractile type and based on the idea of interlocking it with train doors open-close mechanism, without any additional power supply unit or control system.

• Tribology and Lubricants
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• v.37 no.5
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• pp.195-202
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• 2021

This paper presents a numerical analysis of the lubrication characteristics of condensed water molecules on a solid surface by conducting molecular dynamics simulations. We examine two models consisting of a simple hexahedral substrate with and without water molecules to reveal the lubrication mechanism of mono-layered water molecules. We perform a sliding simulation by contacting and translating a single asperity on the substrate under various normal loads. During the simulation, we measure the friction coefficient and atomic stress. When water molecules were interleaved between solid surfaces, atomic stress exerted on individual atom and friction coefficient were smaller than those of model without water molecule. Particularly, at a low load, the efficacy of water molecules in the reduction of atomic stress and friction is remarkable. Conversely, at high loads, water molecules rarely lubricate solid surfaces and fail to effectively distribute the contact stress. We found a critical condition in which the lubrication regime changes and beyond the condition, significant plastic deformation was created. Consequently, we deduce that water molecules can distribute and reduce contact stress within a certain condition. The reduced contact stress prevents plastic deformation of the substrate and thus diminishes the mechanical interlocking between the asperity and the substrate.

• Earthquakes and Structures
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• v.25 no.3
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• pp.209-221
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• 2023

The Mw=7.7 (Pazarcık-Kahramanmaraş) and Mw=7.6 (Elbistan-Kahramanmaraş) earthquakes that occurred in Türkiye on 06.02.2023 with 9 hours' intervals, caused great losses of life and property as the biggest catastrophe in the instrumental period. The earthquakes affecting an area of 14% of the country were enormous and caused a great deal of loss of life and damage. Numerous buildings have collapsed or damaged at different levels, both in the city centers and in rural areas. Within the scope of this study, masonry structure damage built from different types of materials in the earthquake region was taken into consideration. In this study, the damage and causes of such masonry structures that do not generally receive engineering services were examined and explained in detail. Insufficient interlocking between wall-wall and wall-roof, inadequate masonry, lack of horizontal and vertical bond beams, usage of low-strength materials, poor workmanship, and heavy earthen roof are commonly caused to structural damages. Separation at the corner point and out-of-plane mechanism in structural walls, and heavy earthen roof damages are common types of damage in masonry structures.

• Journal of Surface Science and Engineering
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• v.32 no.4
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• pp.531-537
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• 1999

A copper based leadframe was oxidized in brown-oxide forming solution, then the growth characteristics of brown oxide and the effect of brown-oxide formation on the adhesion strength of leadframe to epoxy molding compound (EMC) were studied by using sandwiched double cantilever beam (SDCB) specimens. The brown oxide is composed of fine acicular CuO, and its thickness increased up to ~150 nm within 2 minutes and saturated. Bare leadframe showed alomost no adhesion to EMC, while once the brown-oxide layer formed on the Surface of leadframe, the adhesion strength increased up to ~80 J/$\m^2$ within 2 minutes. Correlation between oxide thickness, $\delta$ and the adhesion strength in terms of interfacial fracture toughness, $G_{c}$ was linear. Considering the above results, we might conclude that the main adhesion mechanism of brown-oxide treated leadframe to EMC is mechanical interlocking, in which fine acicular CuO plays a major role.e.