• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.789-792
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• 1993

We have proposed a fuzzy model for behavior of vehicles in the road traffic simulation system with microscopic model for analyzing traffic jam in the broad areas. It can exactly simulate each vehicle's behavior. We propose a new hardware processor to simulate fuzzy decision-making mechanism for its model. This paper describes the functions, performance and structure of the hardware processor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3028-3044
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• 1993

A metallic bond of great strength for the same or dissimilar metals can be produced by the explosive welding. The formation of a metallic jet at the interface between the two impacting plates has been simulated using the numerical hydrocode DYNA2D. The mechanism of explosive welding for the wave formation is also analyzed by the computer simulation technique. The microscopic with the experimentally observed behaviour of the explosive welding. The computer simulations of the explosive welding process have proven especially useful for analyzing the mechanism of metallic bones.

• Journal of ILASS-Korea
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• v.3 no.3
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• pp.1-13
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• 1998

In this study, an experimental study was performed to investigate the breakup mechanism of vaporizing droplet. A well-controlled experimental apparatus was used to study breakup mechanisms of a monodisperse stream of drops injected into a transverse high temperature and velocity air stream. The experiments gave information$ about the microscopic structure of the liquid drop breakup process, drop breakup regimes, and drop trajectories in high temperature flow region. The breakup time, drop acceleration and wavelength of surface instability wave were measured from a high-magnification and double spark photography. The two instability theories, i.e., Kelvin-Helmholtz instability and Rayleigh-Taylor instability, were estimated by comparing the calculated data with the measurements. The results showed that the breakup time in high temperature flow condition is shortened because the surface tension is decreased by the increase of gas temperature.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.180-184
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• 2004

The tribological behavior of carbon epoxy composites whose surfaces have many small grooves of $100\mu m$ width was experimentally investigated with respect to the sliding direction against groove orientation, surface pressure (P) and velocity (V). The wear mechanism of the composites was observed to calculate the wear volume with respect to the friction coefficient using scanning electron microscopic (SEM). Experimental results show that the abrasive wear is dominant wear mechanism for the grooved composite surface and the friction and wear are greatly reduced when the sliding direction is parallel to the axis of groove because abrasive particles are removed through the grooves effectively.

• Journal of Applied Reliability
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• v.13 no.2
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• pp.129-140
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• 2013

As a fundamental experimental study for reliability improvement of lithium ion secondary battery, degradation mechanism was investigated by microscopic observation and acoustic emission monitoring. Microstructural observation of the decomposed battery after cycle test revealed mechanical and chemical damages such as interface delamination, microcrack of the electrodes, and solid electrolyte interphase (SEI). Acoustic emission (AE) signal was detected during charge and discharge of lithium ion battery to investigate relationships among cumulative count, discharge capacity, and microdamages. With increasing number of cycle, discharge capacity was decreased and AE cumulative count was observed to increase. Observed damages were attributed to sources of the detected AE signals.

• Corrosion Science and Technology
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• v.20 no.5
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• pp.242-248
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• 2021

Unforeseen failures of boilers in power plants may affect the continuation of electricity generation. Main failures in boilers are influenced by the tube material, tube position, boiler service temperature and pressure, and chemical composition of the feed water and coal. This investigation was intended to find answers on the causes and mechanism of failure of the fire-side boiler water-wall tubes, due to perforation and corrosion. The tube conformed to the material requirements in terms of its chemical composition and hardness. Microscopic examination showed ferrite and pearlite indicating no changes in its microstructure due to the temperature variation. SEM test showed a single layer and homogenous film density particularly on the area far from perforation. However, layers of corrosion product were formed on the nearby perforation area. EDX showed that there were Na, Ca, S, and O elements on the failed surface. XRD indicated the presence of Fe₂O₃ oxide. The failure mechanism was identified as a result of significant localized wall thinning of the boiler water wall-tube due to oxidation.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.247.2-247.2
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• 2002

A synthetic naphthoquinone alkaloid. 2-amino-3-ethoxycarbonyl-l-methyl pyrolo (3,2-b) naphtho-4,9-dione (compound 1), showed a potent cytotoxicity in a panel of cancer cell lines with an IC50 ranged from 0.1 to 0.3 microgram/mL. Prompted by a potent cytotoxic activity, the mechanism action study was performed with cultured A549 of human lung cancer cells. Flow cytometric G2-M cell cycle arrest and microscopic investigation was also characterized with apoptotic morphological features. (omitted)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.104-111
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• 1997

Accounting for the additional damages come out from non-proportional loading path effect, material damage according to crystal structure dependence was studied. Microscopic observations of damaged material by SEM(Scanning Electron Microscope) showed crystal structure dependence. Biaxial in-phase loaded specimens showed the slips of same direction, which pararell each other, but biaxial 90.deg. out-of-phase loaded specimens showed multiply crossed slips. S. H. Doong and D. F. Socie reported that wavy/planar or planar slip material showed the increase in the cyclic hardening level during non-proportional cycling. From these results, the additional hardening and non-proportional loading effects were related with slip mechanism, and the slip mechanism was related with crystal structure. In the present study, a damage mechanism which accounts for the non-proportional loading effect from crystal structure dependence was considered and applied to A17075-T651.

• Bulletin of the Korean Chemical Society
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• v.29 no.8
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• pp.1459-1463
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• 2008

Second-order rate constants (kN) have been measured spectrophotometrically for reactions of 3,4-dinitrophenyl 2-thiophenecarboxylate (2) with a series of alicyclic secondary amines in 80 mol % $H_2O$/20 mol % dimethyl sulfoxide at 25.0 ${^{\circ}C}$. The Brønsted-type plot exhibits a downward curvature for the aminolysis of 2. The curved Brønsted-type plot is similar to that reported for the corresponding reactions of 2,4-dinitrophenyl 2- thiophenecarboxylate (1). The reactions of 1 and 2 have been suggested to proceed through the same mechanism, i.e., through a zwitterionic tetrahedral intermediate ($T^{\pm}$) with a change in the rate-determining step. Substrate 2 is less reactive than 1 toward weakly basic amines (e.g., $pK_a$ < 10.4) but becomes more reactive as the basicity of amines increases further. Dissection of kN into the microscopic rate constants has revealed that the reaction of 2 results in a smaller $k_2/k_{-1}$ ratio but larger $k_1$ than the corresponding reaction of 1. Steric hindrance exerted by the ortho-nitro group has been suggested to be responsible for the smaller $k_1$ value found for the reactions of 1.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1722-1726
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• 2013

A kinetic study on nucleophilic substitution reactions of phenyl Y-substituted-phenyl carbonates (5a-5j) with ethylamine in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$ is reported. The plots of $k_{obsd}$ vs. [amine] are linear for the reactions of substrates possessing a strong electron-withdrawing group (EWG) but curve upward for those of substrates bearing a weak EWG, indicating that the electronic nature of the substituent Y in the leaving group governs the reaction mechanism. The reactions have been concluded to proceed through a stepwise mechanism with one or two intermediates (a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$) depending on the nature of the substituent Y. Analysis of Bronsted-type plots and dissection of $k_{obsd}$ into microscopic rate constants have revealed that the reactions of substrates possessing a strong EWG (e.g., 5a-5f) proceed through $T^{\pm}$ with its formation being the rate-determining step, while those of substrates bearing a weak EWG (e.g., 5g-5j) proceed through $T^{\pm}$ and $T^-$.