• Journal of Electrochemical Science and Technology
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• v.7 no.2
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• pp.91-96
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• 2016

Oxidation behaviours of ash free coal (AFC), carbon, and H₂ fuels were investigated with a coin type molten carbonate fuel cell. Because AFC has no electrical conductivity, its oxidation occurs via gasification to H₂ and CO. An interesting behaviour of mass transfer resistance reduction at higher current density was observed. Since the anode reaction has the positive reaction order of H₂, CO₂ and H₂O, the lack of CO₂ and H₂O from AFC results in a significant mass transfer resistance. However, the anode products of CO₂ and H₂O at higher current densities raise their partial pressure and mitigate the resistance. The addition of CO₂ to AFC reduced the resistance sufficiently, thus the resistance reduction at higher current densities did not appear. Electrochemical impedance results also indicate that the addition of CO₂ reduces mass transfer resistance. Carbon and H₂ fuels without CO₂ and H₂O also show similar behaviour to AFC: mass transfer resistance is diminished by raising current density and adding CO₂.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.478-483
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• 2003

In this paper, in order to fabricate the circularly polarized diversity system which will mitigate multipath fading, 5.8GHz band microstrip array antenna were designed and fabricated. These antenna were designed using Ensemble 6.0 program and the fabricated antenna were vertical and horizontal polarized antenna, left-handed circularly polarized antenna, and right-handed circularly polarized antenna. The designed antenna parameters included S11 and impedance characteristics of fabricated antenna were measured using Network Analyzer(8753ES). From the measurement results, the S11 for each polarization antenna at resonance frequency of 5.8GHz band was showed -38dB, -44dB, and -50dB respectively and it was similar to the simulation result, and also the impedance can be matched at $50{\Omega}$. In order to compare polarization characteristics, broadband measurement was also conducted in this paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.978-984
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• 2015

In this paper, we designed a RF transceiver operating up to 200 km operating range and 45 Mbps data rate. The RF transceiver operates in Ku band and composed of up/down converter, high power amplifier, front-end elements. To satisfy the operating range of RF transceiver, 10W power amplifier was required and realized by using GaN power amplifier. Moreover, to mitigate mutual interference for different bandwidth signals due to the adaptive transmission speed control function, SAW filter bank structure was used. To verify system requirement satisfaction AWR simulation tool was used.

• Journal of Environmental Science International
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• v.20 no.3
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• pp.309-319
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• 2011

In this study, we investigated the effects of Upo-swamp upon local thermal environment with nighttime cooling rate. To do this, we set up the AWS(Automatic Weather observation System) over the central part of Upo-swamp on the early October 2007. We conducted the study by comparing the AWS data with another weather data observed by several meteorological observations of the Korea Meteorological Administration located at the vicinity of Upo-swamp for one year. The air temperature of Upo-swamp was higher than that of the surrounding in cold-climate season. But it was opposite in warm-climate season. We confirmed that Upo-swamp roles to mitigate the daily and annual air temperature ranges. And the daily air temperature variation of Upo-swamp lagged behind the land one. This phenomenon represent that the heat reservoir capacity of Upo-swamp is much larger than that of the ground.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.916-924
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• 2015

Electromagnetic Interference (EMI) is a system to system or environment to system phenomenon. The literature survey proved that the Randomized Pulse Width Modulation (RPWM) technique is a promising technique to reduce EMI. A new Constant Trailing Edge, Randomized Pulse Width Modulation (CTERPWM) technique is proposed in this paper. The effect of the proposed RPWM technique for mitigation of conducted-EMI on Cuk converter operating in Continuous Conduction Mode (CCM) is simulated and tested. In this paper, the analytical expressions for the Power Spectral Density (PSD) are derived for the proposed RPWM technique and are validated by experimental measurements. The effectiveness of the proposed RPWM technique on the mitigation of conducted-EMI is verified comparing simulation and experimental results and it is identified that both the results are almost similar with allowable experimental deviations. The comparative investigation proves that the proposed RPWM technique can mitigate and spread the dominant peaks of conducted-EMI over the complete spectrum for the Cuk converter. Based on the investigation the CTERPWM technique is recommended for adoption.

• Korean Journal of Occupational Health Nursing
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• v.18 no.2
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• pp.153-164
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• 2009

Purpose: This study investigates the relationship between job stress, depression, health-related behavior and type A behavior patterns among male workers at a steel factory. Methods: The study was done on 171 male workers, using the structured questionnaire. The data were collected in April, 2009 and analyzed by descriptive statistics, t-test, ANOVA, and pearson correlation coefficient. Results: The results showed that 65.5% of workers were under moderate stress, 25.7% high stress and 0.6% extremely high stress. The overall score of these workers' occupational stress was 41.9, lower than the Korean workers' average. Occupational stress was correlated with depression, type A behavior patterns, a very poor physical condition without sufficient sleep. Conclusion: Stress management program is strongly needed for these subjects working over 45 hours a week, with a very poor subjective physical condition, insufficient sleep, type A behavior patterns and signs of severe depression. Further longitudinal study is recommended to show the effect of such worker's stress management program to mitigate job-related stress.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.247-248
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• 2015

Wind turbines causes instabilities on the grid as their penetration increase. To mitigate harmful effects from wind turbines, transmission system operator(TSO) set up some requirements to obligate for wind generation operator for grid connection. So wind farm management system(WFMS) has important role to follow requirement from TSO, WFMS calculates available real power by considering wake effects, and dispatches real power order to each wind turbine in wind farm to optimize for decreasing load fatigue. To verify operation of WFMS, real-time simulator(RTS) is necessary. This paper deals with RTS configuration to verify WFMS operation. RTS includes wind farm model and power flow code. Normally, wind farm equivalent simple model makes wind turbines in wind farm to one wind turbine mode which cannot verify power flow in wind farm and WFMS operation. Thus, this paper makes wind farm model using simple wind turbine model with transfer function. Matlab is used for make power flow code and wind farm model to impose RTS and those model is certified by PSCAD/EMTDC.

• Journal of the Korean Society of Safety
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• v.32 no.2
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• pp.147-152
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• 2017

The external reactor vessel cooling (ERVC) is well known strategy to mitigate a severe accident at which nuclear fuel inside the reactor vessel is molten. In order to compare the heat removal capacity of ERVC between the nuclear reactor designs quantitatively, numerical method is often used. However, the study for ERVC using computational fluid dynamics (CFD) is still quite scarce. As a validation study on the numerical prediction for ERVC using CFD, the subcooled boiling flow and natural circulation of coolant at the ULPU-V experiment was simulated. The commercially available CFD software ANSYS-CFX was used. Shear stress transport (SST) model and RPI model were used for turbulence closure and wall-boiling, respectively. The averaged flow velocities in the downcomer and the baffle entry under the reactor vessel lower plenum are in good agreement with the available experimental data and recent computational results. Steam generated from the heated wall condenses rapidly and coolant flows maintains single-phase flow until coolant boils again by flashing process due to the decrease of saturation temperature induced by higher elevation. Hence, the flow rate of coolant natural circulation does not vary significantly with the change of heat flux applied at the reactor vessel, which is also consistent with the previous literatures.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.32-38
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• 2016

In general, lots of containers including various dangerous materials are transported to the port located in big cities such as Busan where massive residents live. Thus, it's really important how to make the emergency response for the leak accidents of dangerous materials and evaluate the direct or indirect damages to adjacent areas. In this study, in order to make reasonable emergency plans, CA (Consequence Analysis) is employed after selecting a key hazardous and noxious material, hydrogen fluroide. This material accounts for the third largest portion of cargo volume among all dangerous materials and can cause a huge damage in case of leakages. As a case study, Busan North port is selected as a test port since the portion of dangerous materials is higher than that of other ports in Busan. It is assumed that 1 ton of hydrogen fluoride is spilled at Busan North port. CA is performed to assess the impact of this accident. Throughout CA, the ERPG-2 range of a leak accident can be evaluated and this result can be used for decision making tools for mitigating the impact of a leak accident. To mitigate the damage of this accident, suitable a protective equipment and resident evacuation procedures should be prepared. Finally, this study can provide a systematic approach to make the emergency plan for reducing economical and personal losses.

• Korean Journal of Adult Nursing
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• v.26 no.3
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• pp.275-286
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• 2014

Purpose: The purpose of this study was to explore the meaning and essence of good nursing from the perspective of patients undergoing hemodialysis. Methods: The data were collected through in-depth interviews of five hemodialysis patients who have been dialyzed for one year or longer. The data analysis was conducted using the Giorgi's phenomenological method. Results: The findings included six constituents and 13 sub-constituents. The six constituents were 'prompt and skillful response to mitigate distress', 'careful attention to provide relief', 'individualized education to promote self-management', 'an intimate relationship to regain isolated ego', 'warmhearted support to encourage strength to live in a exhausting life', and 'providing of comfortable environment to maintain stability'. Conclusion: From the perspective of the hemodialysis patients, the concept of good nursing should stem from the integration of nurses' scientific knowledge, expert skills, and moral sensitivity. The finding suggests that strategies to develop nursing interventions for hemodialysis patients will be required on the basis of understanding of their sociocultural contexts and familism.