• Tunnel and Underground Space
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• v.4 no.2
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• pp.77-86
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• 1994

The vibration resulting from track-train interaction is transmitted through the tunnel structure and the surrounding ground to adjacent buildings. This paper provides a review of the ground vibration propagation mechanism and the theoretical isolation effectiveness of each transit systems. Moreover, predictive vibration values estimated from various models are compared with measured results performed in Seoul Metropolitan Subways and evaluate the applicability of those models.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.79-80
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• 2003

In order to develop an indoor assistive mobility equipment, we paid attention to the mechanism of locomotion in a snail, or a terrestrial gastropod molluscs. It is known that the snail moves by propagation of a pedal wave generating on a pedal surface of the snail and a pedal locomotion has flexibility far ground condition. An air mattress with a function of a pedal-like locomotion mechanism was developed and the performance of the pedal locomotory air mattress as mobility equipment was discussed.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.39-47
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• 1999

A combustion flame visualization system, which is used as an engine diagnostics tool, was developed in order to understand the combustion reaction mechanism in the development stage for S.I. engines. The measurement system consists of an I-CCD camera and a computer-aided image processing system. By using optically accessible engine system, the flame structure was analyzed from the acquired graylevel image and the direction of flame propagation (shape of flame) has been measured to understand combustion phenomena. And combustion radical which involves combustion information were measured. As a result, strong relation between combustion radicals intensity ratio and air excess ratio was found.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.464-470
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• 1996

Toughening mechanism of boron carbide ceramics by the addition of titanium boride was investigated. Speci-men was prepared by hot pressing of boron carbide with upto 30vol% of titanium boride particulates. Toughness of boron carbide ceramics was increased from 4.7 MPa m1/2 to 6.3 MPa m1/2 with 15 vol% TiB2 addition. But further increase of TiB2 content results in slow decrease of toughness. From microstructure evaluation and crack propagation behavior it is concluded that the major toughening mechanism is crack deflection pheno-mena.

• IEMEK Journal of Embedded Systems and Applications
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• v.1 no.2
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• pp.64-72
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• 2006

The long propagation delay over satellite internet causes degradation of TCP performance in slow start phase. Especially, web traffic performance is greatly reduced by low throughput in slow start phase. To improve web traffic performance, we propose the Dynamic ACK Generation Scheme which generates ACKs and considers sender RTO in PEP (Performance Enhancing Proxy). The Normal ACK generation mechanism improves TCP throughput, and also decreases sender RTO. if PEP stops generating ACKs, TCP performance will be reduced by frequent RTO expiration. To solve this problem, our scheme adjusts RTO using ACK generation interval. And it supports retransmission mechanism for loss recovery in PEP. The results of the performance analysis provide a good evidence to demonstrate the efficiency of our mechanisms over satellite internet.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.121-124
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• 2005

A novel process to fabricate carbon nanotube (CNT)/alumina nanocomposites, consisting of a molecular level mixing process and an in situ spark plasma sintering process, is proposed. The CNT/alumina nanocomposites fabricated by this proposed process show enhanced hardness due to a load transfer mechanism of the CNTs and increased fracture toughness arising from the bridging mechanism of CNTs during crack propagation

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.3
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• pp.92-97
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• 2007

The overlay welding the automobile where the durability is demanded, it is used in the vessel engine valve, plant valve and pump parts. Cause of damage public opinion one what is thought is the fatigue load due to the opening and shutting operation right time repetition of the engine valve. The damage cause of the engine valve or explanation of destruction mechanism is very difficult. The research which it sees to make clear a overlay welding of Co-alloy by Plasma Transferred Arc Weld Surfacing Process reconsideration fatigue crack initiation and fatigue crack growth mechanism at high temperature.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.124-130
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• 1998

The wear characteristics and wear mechanisms of dental composite resins were investigated. Composite resins such as Metalii, Silux Plus, Heliomolar and Palfique Estelite were selected as specimens and contents of filler in specimens in order to analyze the effect of Prepolymerized Particle Fillers in friction and wear characteristics. Ball on flat wear tester was used for a wear test. Friction and wear tests are carried out at room temperature. The friction coefficient of Metafil was quite high relatively, and the wear resistance of Silux Plus and Palfique Estelite was better than that of Metafil and Hellomolar at the same experimental condition. The main wear mechanism is plastic flow and abrasive wear by crack propagation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.128-134
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• 2006

Topology optimization is an effective scheme to obtain the initial design concept: however, it is hard to apply in case of non-linear or multi-objective problems. In this study, a modified topology optimization method is proposed to generate a structure of a swing arm type actuator satisfying maximum compliance as well. as maximum stiffness using the multi-objective optimization. approach. The multi-objective function is defined to maximize the compliance in the direction of focusing of the actuator and the second eigen-frequency of the structure. The design of experiments are performed and the response surface functions are formulated to construct the multi-objective function. The weighting factors between conflicting functions are determined by the back-error propagation neural network and the solution of multi-objective function is acquired using the genetic algorithm.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.268-274
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• 1978

The kinetics of the bulk polymerization of propylene sulfide initiated by o-sulfobenzoic anhydride were investigated, which proceeded by a zwitterionic mechanism.The instantaneous concentrations of monomer and initiator were determined by means of ir-and nmr-spectroscopy. The rate constant of propagation was found to be about three order of magnitude higher than that of initiation and this should be caused by a zwitterion mechanism.