• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.113-114
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• 2008

Conventional furnace annealing (CFA) for activating Mg-doped p-type GaN films had been performed in pure $N_2$ ambient. All sample activated the same gas ambient. The annealing process change temperature: the first process is performed at $550^{\circ}C$ for 10 min. but, the first process is the same bulk. From second to five process increase activation temperature to change $50^{\circ}C$ and annealing time keeping for 10 min. It is found that the samples characteristic measure hall measurement. Similar results were also evidenced by photoluminescence (PL) measurement.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.55-65
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• 1999

An experimenta investigation of unsteady impinging DI diesel spray on the unheated plate and heated plate has been conducted in a pressurized chamber using high speed shadowgraphy. The ambient agas pressure was varied using nitrogen with chamber pressure of 1.1MPa, 2.1MPa and 2.6MPa. As the increase of ambient gas pressure of ambient gas pressure, the height of spray is increased if entrainment and circulation . At higher temperature of impinging plate, the radial penetration of the impinging spary is incresed , but the height of impinging spray is decreased.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.99-106
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• 2010

A piezo-driven injector was applied with a purpose to evaluate the effect of induced voltage on spray characteristics. For this, injection rate, macroscopic imaging, ambient gas entrainment and particle sizing were carried out. It was shown that initial slope of injection rate was steeper as induced voltage increased, while slope of injection rate became mostly constant with fully opened needle. From macroscopoic imaging, longer spray tip penetration was produced with higher induced voltage. Moreover, wider spray angle was detected in the early stage of spray development, when higher induced voltage was applied. Ambient air entrainment rate was increased and particle size was reduced with higher induced voltage.

• Analytical Science and Technology
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• v.18 no.5
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• pp.419-424
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• 2005

In recent years, dioxins which were designated as persistent organic pollutants and endocrine disrupters are treated as substance of environmental pollution and studied about human health risk assessment, emission pollutants estimation, analytical methods and so on. It is easy that dioxins are accumulated to soil because of the atmosphere circulation of burning up the waste. This is the comparative studies on the distribution relationship of dioxin isomers in exhausted gas of industrial waste and urban waste incinerators, ambient air and soil. A basis of PCDDs and PCDFs based on OCDD was drawn up to the curve and they correspond to dioxin isomers in exhausted gas of industrial waste and urban waste incinerators and ambient air. On comparing these results, It was found that the ambient air and exhausted gas of industrial waste incinerators were very similar in curve and ratio. Consequently, environmental by exposed dioxin depends on the exhausted gas of industrial waste incinerators than urban waste incinerators. In case of soil, even though we can not completely rule out the possibility of pollution source bring on pesticide and other factors, and naturally biological dissociations, the curve shape is very similar to exhausted gas of industrial waste incinerators and ambient air. So, we inform here that it was mainly caused by these environmental factors.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.8
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• pp.448-455
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• 2009

A performance analysis of the regenerative gas turbine system with afterfogging is carried out. Because of the high temperature at the outlet of air compressor, afterfogging has a potential of improved recuperation of exhaust heat than inlet fogging. Thermodynamic analysis model of the gas turbine system is developed by using an ideal gas assumption. Using the model, the effects of pressure ratio, water injection ratio, and ambient temperature are investigated parametrically on thermal efficiency and specific power of the cycle. The dependency of pressure ratio giving peak thermal efficiency is also investigated. The results of numerical computation for the typical cases show that the regenerative gas turbine system with afterfogging can make a notable enhancement of thermal efficiency and specific power. In addition, the peak thermal efficiency is shown to decrease almost linearly with ambient temperature.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.44.2-44.2
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• 2018

G33.92+0.11, classified as a core-halo UC HII region at a distance of 7.1 kpc, contains several sub-clumps (~20-200 solar masses) as identified by dust continuum emission. This source shows very complicated features associated with vigorous massive star-forming activities with a nearly face-on projection. The ambient gas is still accreting to the massive molecular clumps dynamically, while the whole cloud is under disruption by newly formed stars. Using the recent high resolution (< 0.2") ALMA observations, we investigate the detailed structure associated with the star-forming activities by comparing different chemical tracers. The sub-clumps having extremely complex morphologies still preserve cold dense gas together with the turbulent and dense warm gas resulted by newly formed stars and interaction with accreting gas. The accretion of the ambient gas may have occurred episodically to this source. Most recent star formation, which probably the third generation of star formation in this region, is taking place in the northern part (A5 clump). The relatively small mass (~ 1/3 of A1 or A2) and the lack of turbulent gas of this star-forming core may suggest that this core was formed already during the overall collapse of the whole cloud for the first star formation. We think that gravitational collapse of these sub-clumps appears as sequential star formation of this region. The later interaction with accreting gas may have not been a direct cause of the star formation activities of this source.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.377-381
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• 2016

NDIR $CO_2$ gas sensor was prototyped with ASIC implemented thermopile sensor which included temperature sensor and White-Cell structure in this paper. The temperature dependency of dual infrared sensors ($CO_2$ and reference IR sensors) has been characterized and their output voltage ratios according to the temperature and gas concentration were presented in this paper for achieving temperature compensation algorithm. The initial output voltages of NDIR $CO_2$ gas and reference IR sensors showed $3^{rd}$ order polynomial and linear output voltages according to the variation of ambient temperatures from 253 K to 333 K, respectively. The output voltages of temperature sensor presented a linear dependency according to the ambient temperature and could be described with V(T) = -3.0069+0.0145T(V). The characteristics of output voltage ratios could be modeled with five parameters which are dependent upon the ambient temperatures and gas concentration. The estimated $CO_2$ concentrations showed relatively high error below 300 ppm (maximum 572 % at 7 ppm $CO_2$ concentration), however, as the concentration increased from 500 ppm to 2,000 ppm, the overall estimated errors of $CO_2$ concentrations were less than ${\pm}10%$ in this research.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.1023-1029
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• 2013

The integration between a gas turbine and an air separation unit (ASU) is important in IGCC plants. The portion of ASU air extracted from the gas turbine and the degree of nitrogen supply from the ASU to the gas turbine side are important operating parameters. Their effect on the gas turbine performance and operability should be considered in a wide ambient temperature range. In this study, appropriate nitrogen dilution rate and turbine inlet temperature that satisfy the two limitations of turbine blade temperature and maximum allowable power output were predicted. The air integration was set at zero. The simulation showed that the power output increases and turbine blade temperature decreases as the nitrogen dilution increases. The maximum allowable power output can be obtained under medium and low ambient temperature ranges. Under a high ambient temperature range, the achievable power is less than the maximum power.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.1
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• pp.69-76
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• 1995

Water content and strong acidity are estimated for ambient particles measured between Fall, 1991 and Summer, 1992 in Seoul using a gas/aerosol equilibrium model, called SCAPE. Particle water content and formation of solid species are closely related to ambient relative humidity and ionic concentrations. Generally, water content of particles is high during the night and summer. Estimated particle strong acidity level of Seoul is similar to that of Los Angeles, U.S.A. Acidity of wet and dry depositions in Seoul is discussed.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.315-322
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• 2005

This work was performed to investigate the effect of a split injection on spray characteristics of fuel sprays injected from a common rail system. In order to analyze the spray behavior and atomization characteristics at various rates of split injections, the injection durations of pilot and main injections were varied in experiments. The injection rate of split injection was measured to study the effect of the pilot injection on the main injection. By using a Nd:YAG laser and an ICCD camera, the development of the injected spray was visualized at various elapsed time from the start of injection. The microscopic characteristics such as SMD and axial velocity were analyzed by using a phase Doppler particle analyzer system. The results indicate that the ambient gas flow generated by the pilot injection affects the behavior of main spray, whereas the effect of pressure variation on the main spray is little. The spray tip penetration of a main spray with pilot injection is longer than that of the single injection by the effect of ambient gas flow. Also the main spray produces larger droplets than the pilot spray due to a small relative velocity between the droplets and ambient gas.