• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1595-1603
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• 2003

Droplet combustion at high ambient pressures is studied numerically by formulating one dimensional combustion model in the mixture of n-heptane fuel and air. The ambient pressure is supercritical conditions. The modified Soave-Redlich-Kwong state equation is used in the evaluation of thermophysical properties to account for the real gas effect on fluid p-v-T properties in high pressure conditions. Non-ideal thermodynamic and transport property at near critical and supercritical conditions are also considered. Several parametric studies are performed by changing ambient pressure and initial droplet diameter. Droplet lifetime decreased with increasing pressure. Surface temperature increased with increasing pressure. Ignition time increased with increasing initial droplet diameter. Temporal or spatial distribution of mass fraction, mass diffusivity, Lewis number, thermal conductivity, and specific heat were presented.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.23-27
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• 2011

Due to the rapid development of construction technology with effective land utilization in this nation, many tunnels were and are being built across the country. However, the smoke and the heat generated from tunnel fire are the most important critical factors which may results in both massive personal injury and property damage, especially, due to the closed surrounding of the tunnel. Considering this particular nature of the tunnels, this study aims to install a fire detection system using an optic fiber cable to measure the temperature changes, compare, and analyze the resulted values with the times of temperature changes of the sensor by performing fire simulations under the same condition as a real fire test. From the results, it has been found that the temperature sensor detects a fire occurrence and generates an alarm within one minute after ignition for both a real fire test and a fire simulation alike, and also that the characteristics of temperature changes of the sensor has close relations with the speeds of the currents inside the tunnel. In addition, considering the tunnel fires can affect the evacuation efficiency and the fire extinguishing activities of the fire brigade inside the tunnel, the temperature sensor must be able to search and find the locations and directions of the fires correctly.

• Fire Science and Engineering
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• v.24 no.6
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• pp.1-6
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• 2010

A smoldering ground fire can be a probable cause of reignition of surface fire when transmitted from Fermentation layer to Humus layer with temperature higher than that of ignition. Purpose of this paper is to identify experimental methodology on the potential risk of a smoldering ground fire, which is similar to the real surface fuel bed, and its combustion characteristics. The fuel model designed in this study is composed of 3 layers such as Litter layer, Fermentation layer and Humus layer and 8 Thermocouples are set through 3 layer at each boundary and in between to detect the temperature change and duration of smoldering and propagation velocity. As a result, it was observed that ignition conditions in the boundary between L layer and F layer determined transmission and non-transmisstion to F-H layer. In addition, range of critical humidity at which a smoldering ground fire was transmitted in a material layer was 33~44% and when temperature exceeds $350^{\circ}C$, likelihood of transmission of a smoldering ground fire was high. In the research, the experimental model for multi-layer smoldering ground fire is suggested and information about propagation of smoldering fire, possibility of reignition according to moisture content, propagation velocity and temperature change are obtained, Also, the built-up methods were established to help analyze basic characteristics of smoldering ground fire.

• Journal of the Korean Vacuum Society
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• v.20 no.5
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• pp.322-326
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• 2011

Etch process of silicon dioxide layer by using capacitively coupled plasma (CCP) is currently being used to manufacture semiconductor devices with nano-scale feature size below 50 nm. In typical CCP plasma etcher system, plasmas are generated by applying the RF power on upper electrode and ion bombardment energy is controlled by applying RF power to the bottom electrode with the Si wafer. In this case, however, etch results often drift due to heating of the electrode during etching process. Therefore, controlling the temperature of the upper electrode is required to obtain improvement of etch repeatability. In this work, we report repeatability improvement during the silicon dioxide etching under extreme process conditions with very high RF power and close gap between upper and bottom electrodes. Under this severe etch condition, it is difficult to obtain reproducible oxide etch results due to drifts in etch rate, critical dimension, profile, and selectivity caused by unexpected problems in the upper electrode. It was found that reproducible etch results of silicon dioxide layer could be obtained by controlling temperature of the upper electrode. Methods of controlling the upper electrode and the correlation with etch repeatability will be discussed in detail.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.1-6
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• 2003

Engine emission regulations are becoming more stringent nowadays. In cold transient regime, about 80% THC is exhausted to the atmosphere in the first 200s (US FTP cycles). Accordingly, reducing emission levels in the cold period immediately after the engine start before the catalysts reach their working temperature will be an especially critical factor in meeting more stringent regulations in the future. In this study, the total hydrocarbon quantities are measured using a Fast FID with gasoline fuel for a 4-cylinde. Sl engine, including Secondary Air Injection (SAI) system. Commercial SAI device's direction is reverse to the exhaust flow. In this study, a swirl flow type SAI system which is positioned between the exhaust manifold and exhaust port, was developed. We compared the swirl type secondary air injection with a commercial secondary air injection of .everse flow. The swirl type SAI showed better results in reducing HC by 26% than the commercial flow type SAI of reverse flow which was caused by the better mixing between the exhaust gas and the secondary air.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.93-93
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• 2016

Large scale integrated circuits (LSIs) has been improved by the shrinkage of the circuit dimensions. The smaller chip sizes and increase in circuit density require the miniaturization of the line-width and space between metal interconnections. Therefore, an extreme precise control of the critical dimension and pattern profile is necessary to fabricate next generation nano-electronics devices. The pattern profile control of plasma etching with an accuracy of sub-nanometer must be achieved. To realize the etching process which achieves the problem, understanding of the etching mechanism and precise control of the process based on the real-time monitoring of internal plasma parameters such as etching species density, surface temperature of substrate, etc. are very important. For instance, it is known that the etched profiles of organic low dielectric (low-k) films are sensitive to the substrate temperature and density ratio of H and N atoms in the H2/N2 plasma [1]. In this study, we introduced a feedback control of actual substrate temperature and radical density ratio monitored in real time. And then the dependence of etch rates and profiles of organic films have been evaluated based on the substrate temperatures. In this study, organic low-k films were etched by a dual frequency capacitively coupled plasma employing the mixture of H2/N2 gases. A 100-MHz power was supplied to an upper electrode for plasma generation. The Si substrate was electrostatically chucked to a lower electrode biased by supplying a 2-MHz power. To investigate the effects of H and N radical on the etching profile of organic low-k films, absolute H and N atom densities were measured by vacuum ultraviolet absorption spectroscopy [2]. Moreover, using the optical fiber-type low-coherence interferometer [3], substrate temperature has been measured in real time during etching process. From the measurement results, the temperature raised rapidly just after plasma ignition and was gradually saturated. The temporal change of substrate temperature is a crucial issue to control of surface reactions of reactive species. Therefore, by the intervals of on-off of the plasma discharge, the substrate temperature was maintained within ${\pm}1.5^{\circ}C$ from the set value. As a result, the temperatures were kept within $3^{\circ}C$ during the etching process. Then, we etched organic films with line-and-space pattern using this system. The cross-sections of the organic films etched for 50 s with the substrate temperatures at $20^{\circ}C$ and $100^{\circ}C$ were observed by SEM. From the results, they were different in the sidewall profile. It suggests that the reactions on the sidewalls changed according to the substrate temperature. The precise substrate temperature control method with real-time temperature monitoring and intermittent plasma generation was suggested to contribute on realization of fine pattern etching.

• Journal of Korea Foresty Energy
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• v.21 no.2
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• pp.25-33
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• 2002

One of the critical problems to preserve books and documents in libraries and archives is the deterioration. Some of previous results showed that the major cause of paper deterioration was the acid-catalyzed hydrolysis of the cellulose in paper fibres and aging rate of acidic paper was faster than that of alkaline paper. Therefore, It is necessary to remove the acid in the paper for reducing the rate of paper deterioration. It has been reported to extend the useful life of acidic paper by three to five times. Recently, It has been recognized the need for an effective method of deacidifying large quantities of books and document. However, in the previous many reports little attention was paid to the effect of paper additives. In this paper, We carried out experiment about the effect of additives on paper aging and the effect of deacidification by the gaseous ethanolamines (monoehtanolamine, diethanolamine, triehtanolamine). In result, it was found that the strength of aging was in the order of the alum＋rosin＞alum ＞AKD＞ control and the rate of deacidification was in the order of the monoethanolamine＞diethanolamine＞triethanolamine. The treatment with the gaseous ethanolamines caused decreasing of brightness and dropping of fold endurances. However, deacidification by combination treatment of the various gaseous ehtnaolamines prevented from decreasing of brightness and dropping of folding endurances.