• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.101-104
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• 1998

A new planar-type micro gas sensor was designed and fabricated on silicon substrate and the operating characteristics of the sensor were investigated. The thin sensitive film of the sensor was fabricated by spin-coating of the SnO$_2$ sol solution which was synthesized by hydrothermal method. The spin-coating method for preparation of sensing layer was adopted to improve the long-term stability of the fabricated sensing film instead of physical methods such as rf sputtering and thermal evaporation. The fabricated microsensor showed a fairly good sensing performance for CO gas in air at 250$^{\circ}C$ The sensitivity(S=Ra/Rg) was shown to be about 5 to 2000ppm CO with heating power of 50mW.

• Journal of ILASS-Korea
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• v.19 no.3
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• pp.101-108
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• 2014

The current paper reviews the main characteristics and the operating principles of major fuel atomizers used for gas turbine combustors, including various empirical SMD equations for each atomizers. We have summarized various methodologies for evaluation of the combustion efficiency and for combustor sizing from the selected SMD data. It is found that the combustor sizing as well as the combustion efficiency are totally dependent upon the SMD calculation results, which means that special cares should be taken in choosing the SMD empirical equations.

• Journal of the Korean Society of Combustion
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• v.3 no.2
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• pp.51-63
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• 1998

Air-assisted atomizer flames are investigated numerically to study spray structures in nonburning and burning conditions based on experimental data. A PDA is used to measure droplet size, velocity, and number density for both nonburning and burning spray. Computations utilize time-averaged gas-phase equations and $k-{\varepsilon}$ turbulence model for simplicity. The major features of the liquid-phase model are that a SSF approach is used to represent the effect of gas-phase turbulence on droplet trajectories and vaporization, an infinite-diffusion model is employed to represent the transient liquid-phase process. Computation and experiment results show that the droplet acceleration and evaporation proceed quickly in near the atomizer, characterizing high number densities and a strong convective effect. The primary combustion zone, however, is dorminated by the gas phase reaction and exhibits a sheath combustion.

• Journal of Sensor Science and Technology
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• v.15 no.6
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• pp.457-461
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• 2006

To use the porous silicon as gas sensors, we made the MOPS structure from the porous silicon with Al evaporation and investigated the sensing characteristic of ethanol. When the MOPS structure is in contact with ethanol gas, the maximum peak of PL changes and it return to original intensity without contact. The MOPS structure had response time 0.78s and recovery time 4.13s when it is in contact with ethanol, which satisfied the required sensor standards. Further complimentary researches, however, are required to investigate the contact mechanism between MOPS structure and ethanol and to solve the surface contamination problem.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2418-2425
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• 1993

A two-dimensional transient heat transfer model for reactive gas assisted laser cutting process with a moving Gaussian heat source is developed using a numerical finite difference technique. The kerf width, melting front shape and temperature distribution were calculated by using the boundary-fitted coordinate system to handle the ejection of workpiece material and heat input from reaction and evaporation. An analytical solution for cutting front movement was adopted and numerical simulation was performed to calculate the temperature distribution and melting front thickness. To calculate the moving velocity of cutting front, the normal distribution of the cutting gas velocity was used. The kerf width was revealed to be dependent on the cutting velocity, laser power and cutting gas velocity.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.99-105
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• 2014

This paper presents a comparison of operating characteristics for industrial water cooler with variation control methods. The performance analysis regarding the characteristics of condensation capacity, evaporation capacity, compressor load, COP of an on-off type cooler, a hot gas-bypass control type cooler and an inverter control type cooler with respect to the system load is reviewed, respectively. The primary results are as following: the variation of required compressor load of an on-off type cooler with respect to load is 5%, that of hot gas-bypass type is 18% and 66% for an inverter control type cooler. As the result shows, an inverter control type yields relatively huge difference of required compressor load compared to other types of control system. In terms of partial load, COP of an inverter control type cooler presents the highest value, and is considered as the optimized type for the used of the system involving frequent partial load.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.41-48
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• 2014

A urea-SCR system suffers from some issues associated with the ammonia slip phenomenon, which mainly occurs because of the shortage of evaporation and thermolysis time, and this makes it difficult to achieve an uniform distribution of injected urea. A numerical study was therefore performed by changing such various parameters as installed injector angle and application and angle of mixer to enhance evaporation and the mixing of urea water solution with exhaust gases. As a result, various parameters were found to affect the evaporation and mixing characteristics between exhaust gas and urea water solution, and their optimization is required. Finally, useful guidelines were suggested to achieve the optimum design of a urea-SCR injection system for improving the DeNOx performance and reducing ammonia slip.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.1
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• pp.135-140
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• 2019

Upon chemical agent release, it is of importance to study the characteristic persistence and evaporation of chemical agents from surfaces for the prediction of dispersion hazard. We have recently developed a fast and near real-time wind tunnel system proving the controlled environment(air flow, temperature, and humidity), continuously collects agent vapor and analyzes it. A thermal sorber/desorber is unnecessary to collect the vapor in the system we have developed. Instead, a tandem thermal sorber collects the vapor, which is then directly transferred to a fast gas chromatography(GC) for analysis. As a proof of concept, the evaporation of sulfur mustard agent(HD) was studied from glass, sand and concrete. The results were in an excellent agreement with those obtained from the conventional wind tunnel system.

• Bulletin of the Korean Chemical Society
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• v.34 no.6
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• pp.1632-1636
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• 2013

$Ga_2O_3$ one-dimensional (1D) nanostructures were synthesized by using a thermal evaporation technique. The morphology, crystal structure, and sensing properties of the $Ga_2O_3$ nanostructures functionalized with Pt to $NO_2$ gas at room temperature under UV irradiation were examined. The diameters of the 1D nanostructures ranged from a few tens to a few hundreds of nanometers and the lengths ranged up to a few hundreds of micrometers. Pt nanoparticles with diameters of a few tens of nanometers were distributed around a $Ga_2O_3$ nanorod. The responses of the nanorods gas sensors fabricated from multiple networked $Ga_2O_3$ nanorods were improved 3-4 fold at $NO_2$ concentrations ranging from 1 to 5 ppm by Pt functionalization. The Pt-functionalized $Ga_2O_3$ nanorod gas sensors showed a remarkably enhanced response at room temperature under ultraviolet (UV) light illumination. In addition, the mechanisms via which the gas sensing properties of $Ga_2O_3$ nanorods are enhanced by Pt functionalization and UV irradiation are discussed.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.93-100
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• 2009

An exergy analysis is carried out for the regenerative wet-compression Brayton cycle which has a potential of enhanced thermal efficiency owing to the reduced compression power consumption and the recuperation of exhaust energy. Using the analysis model, the effects of pressure ratio and water injection ratio are investigated on the exergy efficiency of system, exergy destruction ratio for each component of the system, and exergy loss ratio due to exhaust gas. The results of computation for the typical cases show that the regenerative wet-compression gas turbine cycle can make a notable enhancement of exergy efficiency. The injection of water results in a decrease of exergy loss of exhaust gas and an increase of net power output.