• The Transactions of the Korean Institute of Electrical Engineers
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• v.32 no.12
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• pp.419-426
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• 1983

This study is to analyze the nonlinear characteristics of magnetic flux distribution of a transformer by Finite Element Method using 2-dimensional elements. To accomplish this, first a single phase shell-type transformer is selected a model to be analyzed, and the element equation is derived by the vriational approach. And then using the numerical approximation of a magnetization curve and the Direct Convergence Method which is presented in this study, the magnetic nonlinear characteristic is analyzed. In this consequence, the resultant values are converged within 10 iterations of calculation. And in the comparison with the case of linear analysis, these results are more accurate and reasonable.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.648-657
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• 2015

Soil organic matter (SOM) plays an important role in the continuous production and environmental conservation in arable soils. In particular, the decomposition of organic matter in soil might promote soil organic matter and fertility due to the mineralization of N. In this study, to evaluate the effect of organic matter amendment on the C mineralization and N dynamic, $CO_2-C$ flux, extractable N and $N_2O$ emission were determined using closed chamber for 4 weeks at 10, 15, $20^{\circ}C$ of incubation temperature after the mixture of $2Mgha^{-1}$ rice straw compost and rye in sandy loam and clay loam. Regardless of soil texture, decomposition rates of rice straw compost and rye at $10{\sim}20^{\circ}C$ of incubation temperature ranged from 0.9 to 3.8% and 8.8 to 20.3%, respectively. Rye application in soil increased $NH_4-N$ and $NO_3-N$ content as well as the $N_2O$ emission compared to the rice straw compost. After incubation for 4 weeks, total C content in two soils was higher in rice straw compost than in rye application. In conclusion, application of rice straw compost and rye to soil was able to improve the soil organic matter and fertility. However, organic matter including the recalcitrant compounds like rice straw compost would be effective on the management of soil organic matter and the reduction of greenhouse gases in soil.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.147-160
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• 2015

In 2014, on 31 August and 1 September, the emissions of $CH_4$, $CO_2$, and $O_2$ gases were measured six times using the closed chamber method from exposed tidal flat sediments in the same position relative to the low point of the tidal cycle in the Eoeun-ri, Taean-gun, on the Mid-western Coast of Korea. The concentrations of $CH_4$ in the air sample collected in the chamber were measured using gas chromatography with an EG analyzer, model GS-23, within 6 hours of collection, and the other gases were measured in real time using a multi-gas monitor. The gas emission fluxes (source (+), and sink (-)) were calculated from a simple linear regression analysis of the changes in the concentrations over time. In order to see the surrounding parameters (water content, temperature, total organic carbon, average mean size of sediments, and the temperature of the inner chamber) were measured at the study site. On the first day, across three measurements during 5 hours 20 minutes, the observed $CO_2$ flux absorption was -137.00 to $-81.73mg/m^2/hr$, and the $O_2$ absorption, measured simultaneously, was -0.03 to $0.00mg/m^2/hr$. On the second day using an identical number of measurements, the $CO_2$ absorption was -20.43 to $-2.11mg/m^2/hr$, and the $O_2$ absorption -0.18 to $-0.14mg/m^2/hr$. The $CH_4$ absorption before low tide was $-0.02mg/m^2/hr$ (first day, Pearson correlation coefficient using the SPSS statistical analysis is -0.555(n=5, p=0.332, pronounced negative linear relationship)), and $-0.15mg/m^2/hr$ (second day, -0.915(n=5, p=0.030, strong negative linear relationship)) on both measurement days. The emitted flux after low tide on both measurement days reached a minimum of $+0.00mg/m^2/hr$ (+0.713(n=5, p=0.176, linear relationship which can be almost ignored)), and a maximum of $+0.03mg/m^2/hr$ (+0.194(n=5, p=0.754, weak positive linear relationship)) after low tide. However, the absolute values of the $CH_4$ fluxes were analyzed at different times. These results suggest that rate for $CH_4$ fluxes, even the same time and area, were influenced by changes in the tidal cycle characteristics of surface sediments for understanding their correlation with these gas emissions, and surrounding parameters such as physiochemical sediments conditions.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.181-184
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• 2003

Low Energy High flux Plasma Source인 Stationary Plasma thruster (SPT)를 이용하여 폴리이미드의 표면개질 후 접촉각과 표면에너지의 변화를 조사하고 접착력과의 관계를 조사하였다. 이온에너지는 180 eV - 200 eV, 이온전류 밀도는 수백 ${\mu}A/cm^2$, 이온선량은 $5\times10^{15}/cm^2$부터, $10\times^{18}/cm^2$로 $Ar^+,\;N_2^+,\;O_2^+$를 이온 주입시켰다. 표면 처리된 폴리이미드에 대한 접촉각 변화는 dual contact anglemeter로 증류수와 에틸렌글리콜을 이용하여 측정하였고, 표면에너지의 변화량을 구하였다. 접촉각의 변화는 아르곤 이온의 경우는 최저 $35^{\circ}$, 질소와 산소의 경우 $1\times10^{17}/cm^2$에서 각각 $14^{\circ},\;10^{\circ}$정도의 전촉각을 보였으며, $5\times10^{17}/cm^2$이상에서는 측정하기 불가능하였다. 산소 이온빔으로 처리된 PI의 표면을 x-ray photoelectron spectroscopy를 통하여 측정하여본 결과, 친수성기가 많이 형성되었음을 확인할 수 있었다. 접촉각 측정으르부터 PI의 표변에너지는 42.1 mN/m에서 아르곤 이온빔의 처리 시 65.2 mN/m로 산소 이온빔의 처리 시 81.2 mN/m로 각각 1.5배, 1.9배 정도 증대하였다. 산소 이온빔으로 처리된 PI 표면위에 스퍼터링으로 300 nm 정도의 clad layer 형성 후 $20{\mu}m$ 정도의 구리 전기 도금막을 형성하여, peel 강도를 측정한 결과 0.79 kg/cm의 강도를 얻을 수 있었다.

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.59-65
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• 1988

To develop porous glass membranes used for a effective membrane-separation process, porous glasses and glass membranes were prepared from the sodium borosilicate parent glass by the phaseseparation technique and effects of heat-treatment and leaching conditions on their characteristics were investigated. The crack-free glass membranes could be fabricated from the 9.4 Na2-O-30.7 B2O3-59.2 SiO2-0.7 Al2O3(wt%) parent glass by heat-treatment at the lower temperature(550-570$^{\circ}C$) and for longer than 45 hrs for the phase separation, followed by leaching with 3N-HCl＋60% ethylene glycol solution at 90$^{\circ}C$ over 25 hrs. Porous glasses prepared in this work showed large specific surface areas(400㎡/g) and narrow pore size distribution with the mean pore radius of 14${\AA}$ enough for the application as reverse osmosis membranes. The salt-rejection efficiency and product-flux of the glass membranes heat-treated at 570$^{\circ}C$ for 80 hrs were found to be 51.8% and 270cc/㎡. hr, respectively. This result suggests that the porous glass membranes fabricated in this study could be applied for the reverse osmosis process.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.2
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• pp.46-49
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• 1964

1. 본 시험에 사용된 선량범위내에서는 기건종자에 의한 Thermal neutron이나 X-ray의 처리가 발아율에 크게 영향을 미치지 못하였는데 Fast neutorn 처리종자의 발아율은 선량의 증가에 따라 거의 직선적 저하를 보였다. 2. 선량의 증가에 따라 기형엽발생율은 증가하였으며 특히 Fast neutron에서는 동일 flux일망정 Thermal neutron 조사구에 비해 발생율은 높다. 3. 저선량에서의 기형엽출현은 유식물기에서만 봇 수 있으며 성장함에 따라 회복한다. 이는 정상세포와 이상세포간의 분열속도의 차에 기인되는 상 싶다. 4. 같은 선량에서는 Fast neutron이 Thermal neutron에 비해 그 영향력이 크다는 것이 확실하며 이는 Energy의 차에서 오는 결과이다. 5. 일반적으로 선량의 증가에 따라 성숙이 연장되는 경향이 있었으며, 반면에 아주 희귀하기는 하나 개화와 성숙이 촉진되는 고체도 발견되었다. 6. 선량의 증가에따라 다소 왜소화되기는 하나 저선량에서는 오히려 유의성은 없으나 초장이 증가하였다. 7. 생육초기와 생육종기에 있어서의 선량에 따르는 초장에 대한 영향은 그 초기에 있어서 더 현저하며 성장함에 따라 회복되는 경향을 보인다. 8. 발아와 생육에 별 지장이 없이 재배할 수 있는 선량범위는 Thermal neutron에서 $1O^13$ N/$cm^2$, Fast neutron에서 5$\times$$1O^12$N/$cm^2$ 이하이면 무난할 것이며, X-ray는 본 시험에 이용한 32 Kr 이상에서도 이용에 지장이 없을 것이다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.101-106
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• 1996

For the application of the neutron flux mapping, an accurate calculation of the sensitivity is required because the sensitivity is proportional to the neutron flux density. Sensitivity is defined as the current per unit length per unit neutron flux and it mainly depends on the depression factor(f), the escape probability from the emitter($\varepsilon$1) and the charge build-up factor of the insulator layer(c). A Monte Carlo simulation was accomplished to calculate the sensitivity of rhodium emitter material and alumina(Al$_2$O$_3$) insulator with a cylindrical geometry, based on the (n,${\beta}$) interaction and on other interaction including the secondary electron generation for the more accurate estimation of the sensitivity. From the simulation results, factors fur the sensitivity were accurately calculated and compared with other theoretical and experimental values. In addition, the sensitivity linearly increases and saturates as the emitter radius increases. The accomplished method is useful in the analysis for the change of SPND sensitivity as a function of burn-up and in the optimum design of SPND.

• Progress in Superconductivity
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• v.2 no.2
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• pp.76-80
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• 2001

We have fabricated YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) ramp-edge Josephson junctions by modifying ramp edges of the base electrodes without depositing any artificial barrier layer. YBa$_2$Cu$_3$O/7-x//SrTiO$_3$ (YBCO/STO) films were deposited on SrTiO$_3$(100) by on-axis KrF laser deposition. After patterning the bottom YBCO/STO layer, the ramp edge was cleaned by ion-beam and then reacted with deionized water under various conditions prior to the deposition of counter-electrode layers. The top YBCO/STO layer was deposited and patterned by photolithography and ion milling. We measured current-voltage (I-V) characteristics, magnetic field modulation of the critical current at 77 K. Some showed resistively shunted junction (RSJ)-type I-V characteristics, while others exhibited flux-flow behaviors, depending on the dipping time of the ramp edge in deionized water. Junctions fabricated using optimized conditions showed fairly uniform distribution of junction parameters such as I$_{c}$R$_{n}$ values, which were about 0.16 mV at 77 K with 1$\sigma$~ 24%. We made a dc SQUID with the same deionized water treated junctions, and it showed the sinusoidal modulation under applied magnetic field at 77 K. 77 K.

• Journal of Environmental Science International
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• v.31 no.2
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• pp.195-213
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• 2022

This research summarizes the generating factors of greenhouse gas (carbon dioxide, methane, nitrous oxide) in hydropower dams and related domestic/foreign researches. Microorganisms and eutrophication are the main factors in greenhouse gases in hydropower dam reservoirs. The greenhouse gas emission from the hydropower dam is affected by meteorological factors and dam operation periods, and greenhouse gases are also emitted from the outlets. The fluxes of greenhouse gas emission from the hydropower dams were -926~180,806 mg CO₂ m^-2d^-1, -0.19~3800 mg CH₄ m^-2d^-1, and 0.01~16.1 mg N₂O m^-2d^-1. In South Korea, the study on the greenhouse gas emission from Korean hydropower dams has been rarely, and therefore it is inquired. This research suggested the methods on the greenhouse gas emission from Korean hydropower dams and flux calculation.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.04a
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• pp.200-202
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• 2000

온실가스의 배출자료는 기후변화협약 참여협상 및 저감대책 수립에 없어서는 안될 중요한 기초자료이다. 그러나 국내에서는 현재 에너지와 농업 분야를 제외하고는 온실가스의 배출원 및 배출량 조사가 미미한 실정이다. 이번 연구에서는 기후변화와 관련된 온실효과에 커다란 기여를 하고 있는 메탄($CH_4$)의 매립지 표면으로부터의 국내 배출량을 조사하고자 한다. $CO_2$, $CH_4$, $N_{2}O$, $O_3$, CFC 등의 주요 온실가스들은 여러 경로를 통해서 대기로 배출되고 있으며, 온실가스의 배출기여도를 보면 도시쓰레기의 매립이 전체 배출량에 약 3%정도 기여하는 것으로 보고되었다. (중략)