• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1470-1471
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• 2008

We present a front-side micromachined thermopile with high sensitivity in the 3-5${\mu}m$ window, and discuss its application to a novel non-dispersive infrared (NDIR) $CO_2$ gas sensor with a light source emitting collimated light. The micromachined thermopile shows a measured sensitivity of 30 mV/W and a $D^*$ of $0.3{\times}10^8cm^{\surd}Hz/W$. Using this newly fabricated thermopile, we also have successfully developed a small, sensitive NDIR $CO_2$ detector module for accurate air quality monitoring systems in energy-saving building and automotive applications. The novel sample cavity comprising specular reflectors around the light bulb is configured to uniformly emit collimated light into the entrance aperture of the cavity in order to enhance the sensitivity of NDIR $CO_2$ detector.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.322.1-322.1
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• 2014

Many research groups have studied tandem or multi-junction cells to overcome this low efficiency and degradation. In multi-junction cells, band-gap engineering of each absorb layer is needed to absorb the light at various wavelengths efficiently. Various absorption layers can be formed using multi-junctions, such as hydrogenated amorphous silicon carbide (a-SiC:H), amorphous silicon germanium (a-SiGe:H) and microcrystalline silicon (${\mu}c$-Si:H), etc. Among them, ${\mu}c$-Si:H is the bottom absorber material because it has a low band-gap and does not exhibit light-induced degradation like amorphous silicon. Nevertheless, ${\mu}c$-Si:H requires a much thicker material (>2 mm) to absorb sufficient light due to its smaller light absorption coefficient, highlighting the need for a high growth rate for productivity. ${\mu}c$-SiGe:H has a much higher absorption coefficient than ${\mu}c$-Si:H at the low energy wavelength, meaning that the thickness of the absorption layer can be decreased to less than half that of ${\mu}c$-Si:H. ${\mu}c$-SiGe:H films were prepared using 40 MHz very high frequency PECVD method at 1 Torr. SiH4 and GeH4 were used as a reactive gas and H2 was used as a dilution gas. In this study, the ${\mu}c$-SiGe:H layer for triple solar cells applications was performed to optimize the film properties.

• Applied Science and Convergence Technology
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• v.25 no.6
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• pp.138-144
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• 2016

The discharge characteristics of pulse-driven coplanar micro barrier discharges for an ultraviolet (UV) light source using Ne-Xe mixture have been investigated using a two-dimensional fluid simulation at near-atmospheric pressure. The densities of electrons, the radiative excited states, the metastable excited states, and the power loss are investigated with the variations of gas pressure and the gap distance. With a fixed gap distance, the number of the radiative states $Xe^*(^3P_1)$ increases with the increasing driving voltage, but this number shows weak dependency on the gas when that pressure is over 400 Torr. However, the number of the radiative states increases with the increase of the gap distance at a fixed voltage, while the power loss decreases. Therefore, a long gap discharge has higher efficiency for UV generation than does a short gap discharge. A slight change in the electrode tilt angle enhances the number of radiative species 2 or 3 times with the same operation conditions. Therefore, the intensity and efficiency of the UV light source can be controlled independently by changing the gap distance and the electrode structure.

• International Journal of Automotive Technology
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• v.6 no.5
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• pp.445-451
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• 2005

Most of the pollutants from passenger cars are emitted during the cold-transient phase of the FTP-75 test. In order to reduce the exhaust emissions during the cold-transient period, it is essential to warm up the catalyst as fast as possible after the engine starts, and the Unburned Exhaust Gas Ignition (UEGI) technology was developed through our previous studies to help close-coupled catalytic converters (CCC) reach the light-off temperature within a few seconds after cold-start. The UEGI system operates by igniting the unburned exhaust mixture by glow plugs installed upstream of the catalyst. The flame generates a high amount of heat, and if the heat is concentrated on a specific area of monolith surface, then thermal crack or failure of the monolith could occur. Therefore, it is very important to monitor the temperature distribution in the CCC during the UEGI operation, so the local temperatures in the monolith were measured using thermocouples. Experimental results showed that the temperature of CCC rises faster with the UEGI technology, and the CCC reaches the light-off temperature earlier than the baseline case. Under the conditions tested, the light-off time of the baseline case was 62 seconds, compared with 33 seconds for the UEGI case. The peak temperature is well under the thermal melting condition, and temperature distribution is not so severe as to consider thermal stress. It is noted that the UEGI technology is an effective method to warm up the catalyst with a small amount of thermal stress during the cold start period.

• Resources Recycling
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• v.7 no.3
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• pp.42-51
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• 1998

Hydrogen in atmosphere can easily dissolve in melt of light metal alloys. Increasing demand for recycling of light metal a alloys has, therefore, focused attention on the removal of hydrogen gas, and alloy addition in melt has become an imporLant r refining process. For this purpose behaviors of mixing and hydrogen degassing in impeller agitated refming vessel with/without barnes were investigated. Flow patterns, mixing time behavior and kinetics of degassing in various agitating conditions were analysed in watet model experiments. And, numerical analysis on turbulent flow pattern in impeller agitated vessels was performed.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.1019-1029
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• 2006

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.

• Applied Biological Chemistry
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• v.29 no.4
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• pp.366-371
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• 1986

Fatty acid compositions of Panax ginseng leaves (6 year) grown under different light intensity in field and of the detached leaves exposed to high temperature (20 hours) were investigated by gas chromatography. Linoleic, linolenic, palmitic and palmitoleic acid were the major components(80%) of leaf lipid. The higher the growth light intensity, the lower the percentage of unsaturated acids or bonds, indicating metabolic adaptation to high temperature. Pattern similarity of fatty acid composition was little changed until 20% light but significantly different at 30%, suggesting 20% as limitation light intensity. The close similarity of fatty acid composition between the loaves grown under 30% light and the one at harvest rises uncertainty between adaptation to high temperature and senescence. Total fatty acid content decreased with the increase of light intensity. Short term high temperature $(25^{\circ}C\;or\;35^{\circ}C)$ increased total fatty acid content, unsaturated acid percentage and insignificant difference in pattern similarity of composition.

• Journal of Sensor Science and Technology
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• v.32 no.2
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• pp.75-81
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• 2023

The significance of gas sensors has been emphasized in various industries and applications, owing to the growing significance of environmental, social, and governance (ESG) management in corporate operations. In particular, the monitoring of hazardous gas leakages and detection of fugitive emissions have recently garnered significant attention across several industrial sectors. As industrial workplaces evolve to ensure the safety of their working environments and reduce greenhouse gas emissions, the demand for high-performance gas sensors in industrial sectors dealing with toxic substances is on the rise. However, conventional gas-sensing systems have limitations in monitoring fugitive gas leakages at both critical and subcritical concentrations in complex environments. To overcome these difficulties, recent studies in the field of gas sensors have employed techniques such as mobile robotic olfaction, remote optical sensing, chemical grid sensing, and remote acoustic sensing. This review highlights the significant progress made in various technologies that have enabled accurate and real-time mapping of gas distribution and localization of hazardous gas sources. These recent advancements in gas-sensing technology have shed light on the future role of gas-detection systems in industrial safety.

• Journal of Korean Society on Water Environment
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• v.23 no.3
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• pp.303-308
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• 2007

Three types dyeing wastewater (dark, medium, light color) discharged from cotton textile dyeing with reactive dye was collected at each step of process. Each process dying wastewater was analyzed and treated by ionized gas. The analysis focused on $COD_{Cr}$, SS and color. Bleaching & scouring process wastewater has the highest $COD_{Cr}$ value in the three type dyeing wastewater. SS shows the highest value at dyeing process wastewater in dark and medium color but light color has at finishing process wastewater. The result of process wastewater treatment by ionized gas was that the ionized gas was effective in $COD_{Cr}$ removing of bleaching & scouring process and finishing process wastewater but was not good at dyeing process wastewater. From that result it is estimated that the ionized gas could not work in opening the aromatic ring and react only in aliphatic component of the molecule. Because the surfactants contained in bleaching & scouring process and finishing process wastewater have only one aromatic ring in its molecular structure, in contrast with the reactive dye compounds consist of aromatic rings great part of its molecular structure. The color almost removed in 1.5 hrs reaction time but $COD_{Cr}$ removal effiency was only 30.7% through 3hrs in 1500 mL of total dyeing wastewater treated by 10 L/min ionized gas.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.232-242
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• 2005

It has been recognized that solar water heating systems are economically inferior to conventional gas water-heaters and boilers using light oil as fuel in spite of having practical possibilities among other alternative energy facilities in Korea. The solar system, however, should be revaluated due to the sharp rise of oil prices recently. We have calculated the energy amount and cost through a series of research projects for the system by experiment and simulation, which lead to analyzing reliable life cycle costs. For the economic analysis, the gas water-heater and light oil boiler were taken as base cases while the solar systems implemented with these facilities were compared as alternatives. As a result, the solar system using the light oil as an auxiliary fuel surpassed the light oil boiler in economics. And a $50\%$ government subsidy for the initial cost is needed to maintain competitiveness with the gas hot-water heater. With this support, the simple payback period of the system can approach 12.8 years under $20\%$ additional curtailment of expenditure.