• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.316-323
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• 1991

We calculated a difference between the YBa$_2Cu _3O_{7-x}$ superconductor (123 system) of critical temperature, 95 K and the YBa$_2Cu_4 O_8$ superconductors (124 system) of critical temperature, 80 K in Y-system superconductors using Extended Huckel Theory (EHT). The valence electron population (VEP), reduced overlap population (ROP) and net charge for the charged cluster models relating to the layer and the chain in 123 and 124 systems were compared. The VEPs of Cu atom in the layer of 123 and 124 systems populated d$_{z^2}$ orbital more than d$_{x^2-y^2}$ orbital, and in the chain of 123 and 124 systems populated d$_{y^2-z^2}$ orbital more than d$_{z^2}$ orbital. The ROP of the Cu(1)-O(1) in the layer of 123 system was larger than the value of the Cu(1)-O(2), but the ROP of the Cu(1)-O(2) in the layer of 124 system was larger than the value of the Cu(1)-O(1). The ROP of Cu(2)-O(4) in the chain of 123 and 124 systems were larger than the value of the Cu(2)-O(3). In 123 system the net charge values of the Cu in the layer was larger than the value of the Cu in the chain. However, in 124 system the net charge value of the Cu in the chain was larger than the value in the layer.

• Korean Journal of Remote Sensing
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• v.39 no.5_3
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• pp.979-995
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• 2023

As wildfires are difficult to predict, real-time monitoring is crucial for a timely response. Geostationary satellite images are very useful for active fire detection because they can monitor a vast area with high temporal resolution (e.g., 2 min). Existing satellite-based active fire detection algorithms detect thermal outliers using threshold values based on the statistical analysis of brightness temperature. However, the difficulty in establishing suitable thresholds for such threshold-based methods hinders their ability to detect fires with low intensity and achieve generalized performance. In light of these challenges, machine learning has emerged as a potential-solution. Until now, relatively simple techniques such as random forest, Vanilla convolutional neural network (CNN), and U-net have been applied for active fire detection. Therefore, this study proposed an active fire detection algorithm using state-of-the-art (SOTA) deep learning techniques using data from the Advanced Himawari Imager and evaluated it over East Asia and Australia. The SOTA model was developed by applying EfficientNet and lion optimizer, and the results were compared with the model using the Vanilla CNN structure. EfficientNet outperformed CNN with F1-scores of 0.88 and 0.83 in East Asia and Australia, respectively. The performance was better after using weighted loss, equal sampling, and image augmentation techniques to fix data imbalance issues compared to before the techniques were used, resulting in F1-scores of 0.92 in East Asia and 0.84 in Australia. It is anticipated that timely responses facilitated by the SOTA deep learning-based approach for active fire detection will effectively mitigate the damage caused by wildfires.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.678-683
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• 2012

Ceria is one of the most important catalytic materials which can be used in three-way catalysts, waste water treatment, petroleum refining, etc. So far, many methods have been studied to produce ceria nanoparticles. In this study, ceria nanoparticles were prepared via solvothermal synthesis using supercritical methanol in short reaction time using a batch reactor. The size of synthesized ceria nanoparticles in supercritical methanol is 6 nm without capping agent, which is smaller than that made in supercritical water at the same conditions of $400^{\circ}C$ and 30 MPa. Size difference results from density and critical point difference between water and methanol and slow reaction rate at the surface of ceria particles in supercritical methanol which reduces crystal growth rate. Several organic compounds were added to modify the surface of ceria nanoparticles, and in-situ surface modification was confirmed by FT-IR and TGA analysis. Surface modified ceria nanoparticles have excellent dispersibility in organic solvent. Size and shape of surface modified ceria particles can be controlled by adjusting molar ratio of modifier to precursor and selection of modifier.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.4
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• pp.45-53
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• 2013

Global warming causes sea levels to rise and global changes apparently taking place including coastline changes. Coastline change due to sea level rise is also one of the most significant phenomena affected by global climate change. Accordingly, Coastline change detection can be utilized as an indicator of representing global climate change. Generally, Coastline change has happened mainly because of not only sea level rise but also artificial factor that is reclaimed land development by mud flat reclamation. However, Arctic coastal areas have been experienced serious change mostly due to sea level rise rather than other factors. The purposes of this study are automatic extraction of coastline and identifying change. In this study, in order to extract coastline automatically, contrast of the water and the land was maximized utilizing modified NDWI(Normalized Difference Water Index) and it made automatic extraction of coastline possibile. The imagery converted into modified NDWI were applied image processing techniques in order that appropriate threshold value can be found automatically to separate the water and land. Then the coastline was extracted through edge detection algorithm and changes were detected using extracted coastlines. Without the help of other data, automatic extraction of coastlines using LANDSAT was possible and similarity was found by comparing NLCD data as a reference data. Also, the results of the study area that is permafrost always frozen below $0^{\circ}C$ showed quantitative changes of the coastline and verified that the change was accelerated.

• Korean Journal of Food Science and Technology
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• v.47 no.6
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• pp.757-764
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• 2015

Red ginseng was treated by subcritical water extraction (SWE) whose two parameters were the extraction temperature ($105-150^{\circ}C$) and time (5-20 min) under a high pressure. The oBrix value, solid content, color difference, and turbidity of the red ginseng extract increased with increasing extraction time and temperature, while the pH decreased. The total concentration of ginsenosides in the red ginseng extract was maximal at $120^{\circ}C$ and 20 min. The concentrations of ginsenosides Rg3 and Rh1 were maximal at $150^{\circ}C$ and 15 min. The concentrations of Rg3 and Rh1 were respectively 3.5-5 times and 2-2.5 times higher than those treated by conventional extraction methods with hot water, ethanol, and methanol. SWE is a particularly effective method for the selective extraction of less-polar ginsenosides such as Rg3 which is well known to exert strong anticancer effects.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.447-454
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• 2003

Samples were prepared by the solid-state reaction method. The nominal composition of the samples was B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{delta}$ prepared from powder of B $i_2$ $O_3$, PbO, SrC $O_3$, CaC $O_3$, and CuO. They were pulverized, mixed with AgO, A $u_2$ $O_3$and MgO of 50 wt%. Finally, they were sintered at 820 to 85$0^{\circ}C$ in air. The structural characteristics, the microstructure of surface and the critical temperature with respect to the each samples were analyzed by XRD, $T_{c}$, SEM and EDS respectively. It was found that the the critical temperature of the silver oxide additive samples (99.58 K) is higher than those of gold or magnesium oxides additive samples, but all those values are lower than that of pure Bi-2223 phase. The microstructure of surface showed the tendency which the AgO additive samples become more minuteness than A $u_2$ $O_3$ and MgO additive samples.s.samples.s.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.76-81
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• 1998

Physical adsorption on a silica gel(pore size of 80 nm, particle size of $10{\mu}m$)has been studied for binary mixture of acetone diluted in $CO_2$ by use of a FTIR transmission technique and we have compared the result of FTIR transmission technique with that of a chromatographic technique. Measurements were made at 313.2 K and under pressures up to 15MPa. As the pressure increases from 0.1MPa, the IA(Integral Absorbance) of the hydrogen-bonded OH groups interacting with acetone and adsorbed amount by use of a chromatographic technique increases at first, and reaches a maximum at a pressure below the critical pressure of $CO_2$, and then the intensities decrease gradually with increasing pressure. It is found that the pressure dependency of the chromatographic isotherm is a little larger than that of spectroscopic isotherm in the supercritical fluid region. This difference might be attributable to the weaker van der Waals force and relatively stronger hydrogen-bonding force influencing the adsorption of acetone on the sllica gel. The unique spectroscopic characteristics of amine group which vibrational frequencies of hydroxyl groups on the silica gel surface shift downward to about $1300cm^{-1}$ were measured from experimental result of triethylamine diluted in $CO_2$ or $N_2$.

• Journal of the Korean Vacuum Society
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• v.15 no.1
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• pp.81-88
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• 2006

Laterally self-aligned InGaAs/GaAs quantum-dots (QDs) have been fabricated by using a multilayer stacking technique. For the growth optimization, we vary the number of stacks and the growth temperature in the ranges of 1-15 periods and $500-540^{\circ}C$. respectively, Atomic force microscope (AFM) images and photoluminescence (PL) spectra reveal that the lateral alignment of QDs is enhanced in extended length by an increased stack period, but severely degrades into film-like wires above a critical growth temperature. The morphological and the photoluminescence characteristics of laterally self-aligned InGaAs QDs have been analyzed through mutual comparisons among four samples with different parameters. An anisotropic arrangement develops with increasing number of stacks, and high-temperature capping allows isolated QDs to be spontaneously organized into a one-dimensionally aligned chain-like shape over a few ${\mu}m$, Moreover, the migration time allowed by growth interruption plays an additional important role in the chain arrangement of QDs. The QD chains capped at high temperature exhibit blue shifts in the emission energy, which may be attributed to a slight outdiffusion of In from the InGaAs QDs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.54-54
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• 2003

최근 새로운 개념에 물성 구현을 위한 강유전체 산화물 인공격자의 연구가 활발히 진행되고 있다. 본 연구에서는 펄스레이져 증착법을 이용하여 산소분압 100 mTorr와 증착온도 50$0^{\circ}C$에서 LSCO/MgO 기판 위에 PbTiO$_3$(PTO) 와 PbZrO$_3$(PZO)을 주기적으로 적층하여 강유전체 산화물 인공격자를 형성하였다. 인공격자의 주기는 1~100 unitcell 까지 변화시켰다. 적층주기와 두께 변화에 따른 PZO/PTO 인공격자의 성장과 전기적 특성에 대하여 관찰하였다. X선 회절분석을 통하여 PZO/PTO 인공격자는 주기가 25 unit cell 이하의 적층구조에서 초격자의 형성으로 인한 위성피크가 관찰되었으며, 그 이하의 낮은 주기(1~10 unitcell)에서는 위성피크와 강한 (100)과 (200) 성장거동을 보였다. 높은 주기에서는 c축 성장된 PTO와 a축 성장된 PZO 각각의 성장거동을 보였다. 적층 주기가 감소함에 따라 a축 성장된 PTO와 c축 성장된 PZO가 초격자를 형성하였다. 적층주기가 감소함에 따라 유전상수와 잔류분극값이 향상되었다. 유전상수는 1 unitcell 주기에서 800정도의 값을 보였고, 잔류분극값은 2 unitcell 주기에서 2Pr=38.7 $\mu$C/$\textrm{cm}^2$ 정도의 가장 큰 값을 나타냈다. 적층주기가 2 unitcell에서 두께가 감소함에 따라 유전상수가 감소하였고, 20 nm 까지 분극반전에 의한 capacitance-voltage 특성곡선의 이력 현상(강유전성)을 관찰하였다. 이러한 산화물 인공초격자에서의 유전상수와 잔류분극값의 향상에 대하여 논의 할 것이며, 임계크기효과 관점에서 나노사이즈(50 nm~5 nm)에서 인공초격자의 전기적 분극의 안정성에 대하여 또한 논의 할 것이다.소수성 가스의 경우70% 이상 향상되었음을 알 수 있었으며, 본 연구를 통해 광분해를 이용한 스크러버가 기존설비의 장.단점을 충분히 보완 가능한 환경 설비임을 확인할 수 있었다. duty로 구동하였으며, duty비 증가에 따라 pulse의 on-time을 고정하고 frequency를 변화시켰다. dc까지 duty비가 증가됨에 따라 방출전류의 양이 선형적으로 증가하였다. 전압을 일정하게 고정시키고 각 duty비에서 시간에 따라 방출전류를 측정한 결과 duty비가 높을수록 방출전류가 시간에 따라 급격히 감소하였다. 각 duty비에서 방출전류의 양이 1/2로 감소하는 시점을 에미터의 수명으로 볼 때 duty비 대 에미터 수명관계를 구해 높은 duty비에서 전계방출을 시킴으로써 실제의 구동조건인 낮은 duty비에서의 수명을 단시간에 예측할 수 있었다. 단속적으로 일어난 것으로 생각된다.리 폐 관류는 정맥주입 방법에 비해 고농도의 cisplatin 투여로 인한 다른 장기에서의 농도 증가 없이 폐 조직에 약 50배 정도의 고농도 cisplatin을 투여할 수 있었으며, 또한 분리 폐 관류 시 cisplatin에 의한 직접적 폐 독성은 발견되지 않았다이 낮았으나 통계학적 의의는 없었다[10.0%(4/40) : 8.2%(20/244), p>0.05]. 결론: 비디오흉강경술에서 재발을 낮추기 위해 수술시 폐야 전체를 관찰하여 존재하는 폐기포를 놓치지 않는 것이 중요하며, 폐기포를 확인하지 못한 경우와 이차성 자연기흉에 대해서는 흉막유착술에 더 세심한 주의가 필요하다는 것을 확인하였다. 비디오흉강경수술은 통증이 적고, 입원기간이 짧고, 사회로의 복귀가 빠르며, 고위험군에 적용할 수 있고, 무엇보다도 미용상의 이점이 크다는 면에서 자연기흉에 대해 유용한 치료방법임에는 틀림이 없으나 개흉술에 비해 재발율이 높고 비용이 비싸다는 문제가 제기되고 있는 만큼 더 세심한 주의와 장기 추적관찰이 필요하리라 사료된

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.614-618
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• 2018

The changes in the mechanical properties according to the width of the tool shoulder, rotation speed and moving speed in friction stir welding (FSW) are evaluated using Al 6061-T6. The results indicated that the tensile strength value increases with increasing rotation speed. The higher the moving speed of the tool shoulder, the lower the tensile strength, regardless of the tool type. A higher tensile strength value was generally obtained with a tool shoulder diameter of 12mm (TSD12) than with 8mm. When the moving and rotation speeds exceed a limiting value, a stabilization stage is reached, in which (the tool shoulder diameter?) no longer affects the material properties. At a tool shoulder diameter of 8mm (TSD8), the material properties are decreased and the mixture of material in the welding area is incomplete in comparison with the tool type of TSD12. The tensile strength value is decreased at a rotation speed of 1500 rpm. As a result, a rotation speed higher than the threshold value is needed in order for and the transition temperature to be reached, which allows the complete mixing of the material in the welding area.