• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.1
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• pp.19-22
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• 1999

N-doped and low-hydrogenated DLC thin films were coated on the Mo-tip FEAs in order to improve the field emission performance and their electrical properties were evaluated. The fabricated devices showed improved field emission performance in terms of turn-on voltage, emission current and current fluctuation. This result might be caused both by the shift of Fermi level toward conduction band by N-doping and by the inherent stability of DLC material. Furthermore, the transconductance of the DLC-coated Mo-tip FEA and electrical conductivity and optical band-gap of the deposited DLC films were investigated.

• Journal of ILASS-Korea
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• v.27 no.2
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• pp.94-100
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• 2022

Even in non-road UTV (Utility Terrain Vehicle), spark ignition engines are often used to reduce emissions. In this study, gasoline and LPG (Liquified Petroleum Gas) fuels were applied to UTV engines, and the exhaust gas and combustion stability were compared through engine tests. A 0.8-liter two-cylinder SI engine was used in the experiment. Experiments were conducted while changing the IVO (Intake Valve Open) and EVC (Exhaust Valve Close) at 1500 rpm 14 N·m, 40 N·m, and 3000 rpm 17 N·m, 44 N·m conditions. As a result of the experiment, when the valve overlap increased according to the change of IVO and EVC, combustion stability decreased and THC emission increased, but NOx decreased. Comparing the LPG engine with the gasoline engine, the amount of CO₂ and PN (Particulate Number) generation decreased in the LPG engine, and the combustion stability was good.

• Asian Journal of Atmospheric Environment
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• v.11 no.3
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• pp.153-164
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• 2017

Odor dispersion around a cubic building from rooftop odor emissions was investigated using computational fluid dynamics (CFD). The Shear Stress Transport (here after SST) $k-{\omega}$ model in FLUENT CFD code was used to simulate the flow and odor dispersion around a cubic building. The CFD simulations were performed for three different configurations of cubic buildings comprised of one building, two buildings or three buildings. Five test emission rates were assumed as 1000 OU/s, 2000 OU/s, 3000 OU/s, 4000 OU/s and 5000 OU/s, respectively. Experimental data from wind tunnels obtained by previous studies are used to validate the numerical result of an isolated cubic building. The simulated flow and concentration results of neutral stability condition were compared with the wind tunnel experiments. The profile of streamline velocity and concentration simulation results show a reasonable level of agreement with wind tunnel data. In case of a two-building configuration, the result of emission rate 1000 OU/s illustrates the same plume behavior as a one-building configuration. However, the plume tends to the cover rooftop surface and windward facet of a downstream building as the emission rate increases. In case of a three-building configuration, low emission rates (<4000 OU/s) form a similar plume zone to that of a two-building configuration. However, the addition of a third building, with an emission rate of 5000 OU/s, creates a much greater odorous plume zone on the surface of second building in comparison with a two-building configuration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.325-326
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• 2009

We studied the effect of ITO surface treatment by using $O_2$ plasma to enhance the emission efficiency of the Organic Light Emitting Diodes (OLEDs). The luminance efficiency and the operational stability were improved with an ITO anode treated at the optimized conditions.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.368.1-368.1
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• 2014

We proposed amorphous GeSe-based ReRAM device of metal-insulator-metal (M-I-M) structure. The operation characteristics of memory device occured unipolar switching characteristics. By introducing the concepts of valance-alternation-pairs (VAPs) and chalcogen vacancies, the unipolar resistive switching operation had been explained. In addition, the current transport behavior were analyzed with space charge effect of VAPs, Schottky emission in metal/GeSe interface and P-F emission by GeSe bulk trap in mind. The GeSe ReRAM device of M-I-M structure indicated the stable memory switching characteristics. Furthermore, excellent stability, endurance and retention characteristics were also verified.

• Vacuum Magazine
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• v.4 no.4
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• pp.14-17
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• 2017

Recently, quantum-dots light emitting diodes (QLEDs) are considered as a next-generation display due to the superior luminescence behaviors, photo stability and narrow spectral emission bandwidth. Moreover, the emission color of QLEDs can be easily controlled by changing the dimension of quantum dots (QDs). A flexible display based on QLEDs can be achieved using low-cost solution process, such as a printing technology. Therefore, QLEDs are expected as a next generation display. In this document, recent progresses in QDs technology will be introduced.

• Journal of Environmental Science International
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• v.21 no.1
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• pp.113-123
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• 2012

A unit emission reduction of nitrous oxide ($N_2O$) from anthropogenic sources is equivalent to a 310-unit $CO_2$ emission reduction because the $N_2O$ has the global warming potential (GWP) of 310. This greatly promoted very active development and commercialization of catalysts to control $N_2O$ emissions from large-scale stationary sources, representatively nitric acid production plants, and numerous catalytic systems have been proposed for the $N_2O$ reduction to date and here designated to Options A to C with respect to in-duct-application scenarios. Whether or not these Options are suitable for $N_2O$ emissions control in nitric acid industries is primarily determined by positions of them being operated in nitric acid plants, which is mainly due to the difference in gas temperatures, compositions and pressures. The Option A being installed in the $NH_3$ oxidation reactor requires catalysts that have very strong thermal stability and high selectivity, while the Option B technologies are operated between the $NO_2$ absorption column and the gas expander and catalysts with medium thermal stability, good water tolerance and strong hydrothermal stability are applicable for this option. Catalysts for the Option C, that is positioned after the gas expander thereby having the lowest gas temperatures and pressure, should possess high de$N_2O$ performance and excellent water tolerance under such conditions. Consequently, each de$N_2O$ technology has different opportunities in nitric acid production plants and the best solution needs to be chosen considering the process requirements.

• Tunnel and Underground Space
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• v.27 no.3
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• pp.121-131
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• 2017

We studied the time-dependent behaviors of rock and concrete materials by conducting the static and dynamic long-term strength tests. In particular, acoustic emission(AE) signals generated while the tests were analyzed and used for the long-term stability evaluation. In the static subcritical crack growth test, the long-term behavior and AE characteristics of Mode I and Mode II were investigated. In the dynamic long-term strength test, the fatigue limit and characteristics of generation of AE were analyzed through cyclic four points bending test. The graph of the cumulative AE hits versus time showed a shape similar to that of the creep curve with the first, second and third stages. The possibility for evaluating the static and dynamic long-term stability of rock and concrete is presented from the log - log relationship between the slope of the secondary stage of cumulative AE hits curve and the delayed failure time.

• Asian Journal of Atmospheric Environment
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• v.12 no.1
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• pp.47-58
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• 2018

The aim of this work is to investigate the effect of atmospheric stability on near-field pollutant dispersion from rooftop emissions of a single cubic building using computational fluid dynamics (CFD). This paper used the shear stress transport (here after SST) k-${\omega}$ model for predicting the flow and pollutant dispersion around an isolated cubic building. CFD simulations were performed with two emission rates and six atmospheric stability conditions. The results of the simulations were compared with the data from wind tunnel experiments and the result of simulations obtained by previous studies in neutral atmospheric condition. The results indicate that the reattachment length on the roof ($X_R$) obtained by computations show good agreement with the experimental results. However, the reattachment length of the rooftop of the building ($X_F$) is greatly overestimated compared to the findings of wind tunnel test. The result also shows that the general distribution of dimensionless concentration given by SST k-${\omega}$ at the side and leeward wall surfaces is similar to that of the experiment. In unstable conditions, the length of the rooftop cavity was decreased. In stable conditions, the horizontal velocity in the lower part around the building was increased and the vertical velocity around the building was decreased. Stratification increased the horizontal cavity length and width near surface and unstable stratification decreased the horizontal cavity length and width near surface. Maintained stability increases the lateral spread of the plume on the leeward surface. The concentration levels close to the ground's surface under stable conditions were higher than under unstable and neutral conditions.

• Environmental and Resource Economics Review
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• v.30 no.1
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• pp.129-167
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• 2021

The emission trading system is an essential policy for reducing greenhouse gas emissions and converting low-carbon society. EU ETS is a good benchmark that is ahead of Korea's emission trading system in terms of operating period and design know-how. Therefore, this study focused on the key design elements of EU ETS phase 4 such as total emission allowances issued (Cap), free allocation method, carbon leakage list, market stability reserve, and innovation supporting system. In addition, we analyzed the impact of key design elements and their changes during EU ETS Phase 1 to 4 on the design and operation of Korea emission trading system in the future. First of all, the expected impact on the design of Korea emission trading system is to increase three demands: preparing benchmark renewal plans, establishing criteria for selecting free allocation industries that reflect domestic industrial structure and characteristics and introducing two-stage evaluations for free allocation industries, and preparing specific plan to support innovation and industries using allowance auction revenues. The next three impacts on the operation of Korea emission trading system are the increased needs for objective and in-depth impact assessment of plan and amendments, provision of system stability and response opportunities by quickly confirming plan and amendments prior to the implementation, and coordination of the emission trading system governance and stakeholder participation encouragement.