• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.364-371
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• 2017

TPMS is a vehicle electric system that measures the air pressure of a tire, and informs the driver of current tire states. The TPMS sensor typically uses unidirectional communication for small size, light weight, and low power. The transmission period of the sensor indicates the service quality of monitoring the tire. In order to determine the optimal transmission period, frame collision probability and the life time of the sensor should be analyzed. In this paper, collision probability model using Venn diagram is designed in low power TPMS with the normal and warning mode. And the life time and a collision probability were analyzed with the ratio(n) of the normal mode to warning mode transmission period. As a result, $T_{nP}=31sec$ and $T_{wP}=2.4sec$ at 5 years, and $T_{nP}=71sec$ and $T_{wP}=2.5sec$ at 7 years.

• Atmosphere
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• v.18 no.3
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• pp.237-248
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• 2008

A thermal index which considers metabolic heat generation of human body is proposed for operational forecasting. The new thermal index, Perceived Temperature (PT), is forecasted using Weather Research and Forecasting (WRF) mesoscale model and validated. Forecasted PT shows the characteristics of diurnal variation and topographic and latitudinal effect. Statistical skill scores such as correlation, bias, and RMSE are employed for objective verification of PT and input meteorological variables which are used for calculating PT. Verification result indicates that the accuracy of air temperature and wind forecast is higher in the initial forecast time, while relative humidity is improved as the forecast time increases. The forecasted PT during 2007 summer is lower than PT calculated by observation data. The predicted PT has a minimum Root-Mean-Square-Error (RMSE) of $7-8^{\circ}C$ at 9-18 hour forecast. Spatial distribution of PT shows that it is overestimated in western region, while PT in middle-eastern region is underestimated due to strong wind and low temperature forecast. Underestimation of wind speed and overestimation of relative humidity have caused higher PT than observation in southern region. The predicted PT from the mesoscale model gives appropriate information as a thermal index forecast. This study suggests that forecasted PT is applicable to the prediction of health warning based on the relationship between PT and mortality.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.5
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• pp.21-28
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• 2009

This experimental study was performed to find the important design parameters and the starting characteristics of a supersonic exhaust diffuser. The experimental study was carried out on a scaled down model of straight cylindrical supersonic exhaust diffuser, in order to evaluate the effects of operating fluid(air, nitrogen), the diffuser inlet area over the primary nozzle throat area($A_d/A_t$), the inlet pressure of primary nozzle, diffuser length over diffuser inner diameter($L_d/D_d$) and existence or nonexistence of diffuser divergence. The test results showed that the starting pressure increased with decrease in diameter of primary nozzle, and the measured starting pressure of the diffuser had approximately 90~98% efficiency as compared with the predicted starting pressure. Also, the diffuser was started at all case, regardless of $L_d/D_d$ (above 8.4) and diffuser divergence. The result of this study can be used as an essential database for developing a simulated high-altitude facility for real-scale model.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.27-34
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• 2014

Buzz margin scheduling and control technique which are suitable to regulate stable and high pressure air in wide range of Mach number are suggested for fixed geometry of a supersonic intake. From the analysis of preceding study, most effective control variable is induced and scheduling law is newly suggested in a real application point of view. The appropriateness of the control law in wide range of Mach number is addressed by numerical simulation of controlled propulsion system. Also, the simulation for stabilization and tracking performances of the controller are studied to investigate the phenomena under flight maneuver and disturbances.

• Journal of the Korean association of regional geographers
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• v.12 no.1
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• pp.124-141
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• 2006

Fiji is referred to as the hub of the South Pacific as it lies on the major sea and air transport routes in the region. Tourism, the fastest growing industry within the global economy, is already well established within the country. This paper aims to explore the characteristics of ecotourism in Fiji Islands as a foreign area study. To achieve the objectives, this research carried out a literature review before taking several field surveys in Fiji Islands. Research areas are Raintree Lodge in Suva, Kula Ecopark near Sigatoka, Sigatoka Sand Dunes National Park, Nalesutale Fijian indigenous village near Nadi. Most of all facilities and ecotour programs are developed for environmental, economical and educational effects. The case studies of Fiji present a good model of how to succeed in ecotourism and conservation management to Korea. In addition, this research will provide effective regional policies for the environmental friendly tourism in Korea.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.5
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• pp.435-444
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• 2017

In this study, we investigated the effect of aerosol feedback on $PM_{10}$ simulation using a two-way coupled air quality model (WRF-CMAQ). $PM_{10}$ concentration over Korea in January 2014 was simulated, and the aerosol feedback effect on the simulated solar radiation was intensively examined. Two $PM_{10}$ simulations were conducted using the WRF-CMAQ model with (FB) and without(NFB) the aerosol feedback option. We find that the simulated solar radiation in the west part of Korea decreased by up to $-80MJ/m^2$ due to the aerosol feedback effect. The feedback effect was significant in the west part of Korea, showing high $PM_{10}$ estimates due to dense emissions and its long-range transport from China. The aerosol feedback effect contributed to the decreased rRMSE(relative Root Mean Square Error) for solar radiation (47.58% to 30.75%). Aerosol feedback effect on the simulated solar radiation was mainly affected by concentration of $PM_{10}$. Moreover, FB better matched the observed solar radiation and $PM_{10}$ concentration than NFB, implying that taking into account the aerosol direct effects resulted in the improved modeling performance. These results indicate that aerosol feedback effects can play an important role in the simulation of solar radiation over Korean Peninsula.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.583-589
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• 2016

Volatile organic compounds(VOCs) are regarded as a harmful cause substance not only causing air pollutions but also causing global warming phenomenon. For this reason, VOCs are managed politically to reduce emissions by each country. In particular, the vapor from the gas station contains VOCs which is harmful to the human body such as carcinogens benzene and pollute the atmosphere, the Ministry of Environment defined every gas station must install vapor recovery equipment to recover volatile organic compounds. Recently, there are many accidents caused by existing vapor treatment methods, the liquefaction recovery technology is getting the spotlight to cool the vapor at the field. However, because the liquefaction recovery technology have risks of fire or explosion in accordance with temperature, the real time monitoring is critical factor. In this paper, we implement an Android-based monitoring application for liquified vapor recovery device which attached sensor module for temperature and power to monitoring real time information.

• Journal of Korean Society for Atmospheric Environment
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• v.25 no.1
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• pp.15-25
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• 2009

Donghae city is one of the most representative cement industrial city in Korea. The area is faced with the East Sea to the East and with high montane region of Tae-Back mountain range to the West. Many pollutant sources of air pollution are located near the coast, but the largest point sources of the region are located at the bottom of the mountain area in Donghae city. The local wind is highly affected by local topography and plays an important role in transport and dispersion of contaminants from the pollution sources. This study was designed to evaluate enhancement of MM5 predictions by using Four Dimensional Data Assimilation (FDDA), the SONDE data and the national meteorological station, data only. The alternative meteorological fields predicted with and without FDDA were used to simulate spatial and temporal variations of NOx in combined with Atmospheric Dispersion Models (CALPUFF). For the modeling domain, the alternative meteorological fields with 1.1 km spatial resolution were interpolated to the CALMET with 0.5 km resolution. The vertical layers set to have 35 and 12 layers for MM5 and CALPUFF, respectively. MM5 with the FDDA did not resulted in significant improvement of meteorological field prediction in Donghae region, which is primarily because of complex geography and wind scheme. The result of CALPUFF, however, showed reduction of uncertainty errors by using the interpolation scheme of the actual measurement data.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.3
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• pp.128-134
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• 2016

An analysis of the main factors and its degree of impact on power production is performed against the landfill gas power plant in S landfill site. The number of normal operation (50 MWh & 24 hr) days was 70.9% to the total number of operation days from 2007 to 2014, and the percentage of the actual power production was 79.3% of 3,428,400 MW which is the theoretical maximum estimation. The ratio of factors that accounted for the efficiency of power production are: 44.0% of repairing of the defect and regular servicing, 37.4% of cut-down operation due to hydrogen sulfide, and 18.6% of air pre-heater washing, respectively. Yet, considering that the cut-down operation due to hydrogen sulfide was carried out for only two years, the high concentration of hydrogen sulfide was the most influential factors on landfill gas power production. The long-term power production was analyzed as 35.9 MWh in 2018, and the constant drop is anticipated, resulting in 16.6 MWh by 2028, and under 8.4 MWh in 2038.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.705-709
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• 2009

Based on experimental study of lycopodium dust particles' behavior, we suggest the flame propagation model through dust clouds. With dust concentration, flame velocity reaches a maximum value at $170g/m^3$ to exceed the stoichometric concentration for lycopodium-air mixture combustion and decreases slightly in the richer side of $500g/m^3$. At $47{\sim}200g/m^3$, mean velocity of particle increases in proportion to flame velocity. As the sum of burning rate and particle velocity is approximate in flame velocity, the flame propagation velocity with lycopodium dust concentration can be estimated by the calculation and it was found that behavior of particles is useful for better understanding of dust flame propagation velocity.