• Journal of Korean Society for Geospatial Information Science
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• v.24 no.4
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• pp.105-113
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• 2016

Fire radiative power(FRP), which means the power radiated from wildfire, is used to estimate fire emissions. Currently, the geostationary satellites of East Asia do not provide official FRP products yet, whereas the American and European geostationary satellites are providing near-real-time FRP products for Europe, Africa and America. This paper describes the first retrieval of Himawari-8 FRP using the mid-infrared radiance method and shows the comparisons with MODIS FRP for Sumatra, Indonesia. Land surface emissivity, an essential parameter for mid-infrared radiance method, was calculated using NDVI(normalized difference vegetation index) and FVC(fraction of vegetation coverage) according to land cover types. Also, the sensor coefficient for Himawari-8(a = 3.11) was derived through optimization experiments. The mean absolute percentage difference was about 20%, which can be interpreted as a favourable performance similar to the validation statistics of the American and European satellites. The retrieval accuracies of Himawari FRP were rarely influenced by land cover types or solar zenith angle, but parts of the pixels showed somewhat low accuracies according to the fire size and viewing zenith angle. This study will contribute to estimation of wildfire emissions and can be a reference for the FRP retrieval of current and forthcoming geostationary satellites in East Asia.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.665-672
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• 1997

We applied mechanical alloying process by ball milling to produce molybdenum silicides $MoSi_2$ and $Mo_5Si_3$ using a mixture of elemental molybdenum and silicon powders at room temperature. The intermetallic compound MoSi$_3$ have been obtained by ball milling of $Mo_{33}Si_{67}$ mixture powders for 100 h, which is transformed to single $MoSi_2$ phase by subsequent heat treatment up to $725^{\circ}C$. The grain size of the $MoSi_2$ powders thus obtained was 19 nm, being approximately four times smaller than that of the commercial alloy. The intermetallic compound $MoSi_2$ with grain size of 30 nm have been also obtained by ball milling of $Mo_{62}Si_{38}$ mixture powders for 500 h, which is transformed to single $MoSi_2$ phase by heating up to $1000^{\circ}C$. We believe that the retarded ball milling time for the formation of $MoSi_2$ phase is attributed to its complicated crystal structure and large unit cell. The finer grain size in the ball-milled molybdenum silicides powders is expected to improve room-temperature mechanical properties for high-temperature structural materials.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.300-309
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• 2017

A spacecraft obtains a reaction momentum required for an orbit correction and an attitude control by exhausting a combustion gas through a small thruster in space. If the exhaust plume collides with spacecraft surfaces, it is very important to predict the exhaust plume behavior of the thruster when designing a satellite, because a generated disturbance force/torque, a heat load and a surface contamination can yield a life shortening and a reduction of the spacecraft function. The purpose of the present study is to ensure the core technology required for the spacecraft design by analyzing numerically the exhaust gas behavior of the 10 N class bipropellant thruster for an attitude control of the spacecraft. To do this, calculation results of chemical equilibrium reaction between a MMH for fuel and a NTO for oxidizer, and continuum region of the nozzle inside are implemented as inlet conditions of the DSMC method for the exhaust plume analysis. From these results, it is possible to predict a nonequilibrium expansion such as a species separation and a backflow in the vicinity of the bipropellant thruster nozzle.

• Journal of Environmental Impact Assessment
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• v.27 no.5
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• pp.431-446
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• 2018

In this study, chemical characteristics of $PM_{2.5}$ samples collected in an agricultural area in Nonsan of Korea were investigated focusing on of black carbon, 3 inorganic ions and 22 trace elements. It was found that the relative error and relative standard deviation of many trace elements fell below 10%, which indicates good analytical accuracy and precision. The mean values of $PM_{2.5}$ in an agricultural area were exceeded by new Korean air quality standard of March 2018. The concentration of $PM_{2.5}$ was well correlated with those of black carbon and ions. The concentrations of trace elements were in a wide range of seven orders of a magnitude. Based on these $PM_{2.5}$ data sets, a total of 6 sources were identified using PMF (Positive Matrix Factorization; secondary aerosol (34.4%), soil/road dust (20.1%), biomass burning (16.9%), incineration/fuel combustion (13.2%), vehicle exhaust(12.2%), sea-salt (3.17%). Results of our study indicate that it is very important to control illegal burning activities in agricultural area.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.459-466
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• 2012

The accurate engine output is basically one of important factors for the analysis of engine performance. Nowadays in-cylinder pressure analysis in internal combustion engine is also an indispensable tool for engine research and development, environment regulation and maintenance of engine. Here, it is essential more than anything else to find the correct TDC(Top Dead Center) position for the accuracy of engine output for diesel engine. Therefore this study is to analyze affecting factors to TDC position in 2-stroke large low speed engine and to suggest new method for determining correct TDC position. In the previous paper, it was mentioned that the accuracy of engine output is influenced by the determination of exact TDC position, and that 'Angle based sampling' method is better than 'Time based sampling' method in terms of precision. It was confirmed that there is 'Loss of angle', which is a difference between compression pressure peak and real TDC caused by heat loss and blow by of gas leakage. Consequently we invented new method, called "An improved method of time based sampling", which can obtain the correct engine output. The results by this method with compensating loss of angle was shown the same result by the 'Angle based sampling' method in encoder setting cylinder. This study is to suggest the new measuring method of exact engine output, and to examnine the reliance on the outcome.

• Journal of the Korean Ceramic Society
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• v.41 no.3
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• pp.235-242
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• 2004

Si, NH$_4$Cl, NaN$_3$, NaCl, $N_2$ were used as raw materials for preparation of $\alpha$-Si$_3$N$_4$ powder. NH$_4$Cl and NaN$_3$ were used as additives, and NaCl was used as a diluent. Initial $N_2$ gas pressure in the SHS reactor was 60 atm. In preparation of $\alpha$-Si$_3$N$_4$, the reactivity and the properties of the products were examined with the various kinds of additives and the content of diluent. At first, the optimum reaction system for the preparation of $\alpha$-Si$_3$N$_4$ is examined and then the optimum composition was examined in the optimum reaction system. The optimum reaction system was Si-$N_2$-additive(NH$_4$Cl+NaN$_3$)-diluent(NaCl) and the optimum composition was 38 wt%Si+50 wt%(NH$_4$Cl+NaN$_3$)+12 wt%NaCl. The maximum fraction of $\alpha$-phase of Si$_3$N$_4$ produced in this condition was 96.5 wt% and the shape of the $\alpha$-Si$_3$N$_4$ produced in this condition was an irregular fiber with a length of 10 ${\mu}{\textrm}{m}$ and a diameter of 1 ${\mu}{\textrm}{m}$.

• Fire Science and Engineering
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• v.24 no.3
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• pp.52-57
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• 2010

Fire protection countermeasure were considered on the straw thatched roof and wooden structure. For the fire resistant treatment, rice straw was soaked in the fire resistant liquid with different soaking time. After treatment, some rice straw sample was washed with water then the rice straws were tested to check the fire resistance performance. And the wood was soaked in the fire resistant liquid at an atmospheric pressure, vacuum-pressure condition and painted with brush on the surface. To analyse the fire resistant performance of rice straw, ignition delay time was measured under the radiant heat flux of cone heater. And the fire resistant performance of wood samples were tested with 45 degree fire resistant test apparatus and cone heater. Based on the cone heater test, the rice straw which most easily ignitable material shows the longer ignition delay time than not treated ones and even in the water washed straw show a longer ignition delay time than not treated ones. And fire resistant treated woods of vacuum-pressure treated sample showed the most excellent performance on fire resistance. And the fire resistant treated by brush and soaking showed a longer ignition delay time than not treated ones. From this experiment, it was found that a fire resistant treatment of rice straw and wood of the house can be protected from the fire spread.

• KOMUNHWA
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• no.57
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• pp.195-210
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• 2001

One kiln site of Koryo Earthenware in Hwakok-ri, Ansung was excavated from March 15, 1999 to May 15, 1999 by Museum Team of Ehwa Women's University, and also other one earthenware kiln site was confirmed as exposed figure on the ground. In this study, the

• Journal of Korean Society of Environmental Engineers
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• v.31 no.7
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• pp.531-540
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• 2009

In this study, thermo-gravimetric analysis(TGA) was used to investigate the effect of urea concentration and heating rate on the ammonia($NH_3$) formation process from urea solution. A newly designed pipe nozzle was inserted through a 1,000 N${\ss}$(C)/h oil firing boiler to compare the DeNOx efficiencies between the upward and downward nozzle. This experiment reveals the effect of path which an urea droplet goes through. Urea solution showed the same TGA graph without regard to the presence of oxygen. Heating rate had a great influence on the weight loss trend. But the concentration of urea solution between 10% and 40% did not affect so much the thermal decomposition temperature. Therefore, heating rate is more important factor on the thermal decomposition of urea than the concentration of urea solution. Three nozzles located at different positions showed similar DeNOx efficiencies such as 68.1%, 71.8%, 70.8% at the same temperature. Even though urea solution was injected for the same zone, the injection direction made much difference in DeNOx efficiency. A upward nozzle showed 68.1% and downward nozzle 9.5%. This results illustrate the importance of heating rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5376-5383
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• 2011

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose $CO_2$ because $CO_2$ is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of $CO_2$ at low temperature. Metal oxides, which converts $CO_2$ to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of $CO_2$. As the results, the reduction area of $H_2$ was high value at 15 wt% of NiO and the decomposition area of $CO_2$ was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of $H_2$ was 28.47wt% and oxidation area by $CO_2$ was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. $CO_2$ decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.