• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.310-310
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• 2014

ZnO박막은 넓은 밴드갭 (3.37 eV), 높은 여기 결합 에너지 (60 meV)를 가지는 육방정계 우르자이트(hexagonal wurtzite) 결정구조를 가지는 II-VI족 화합물 반도체로, 가시광선 영역에서의 높은 광학적 투과도 특성과 자외선 파장에서 발광이 가능한 장점을 가진다. 최근, ZnO박막 성장 기술이 상당히 발전하였지만, 아직까지도 p-형 ZnO박막 성장 기술은 충분히 발전하지 못하여 ZnO의 동종접합 LED는 아직 상용화되지 않고 있는 실정이다. 따라서, 많은 연구 그룹에서 p-GaN, p-SiC, p-diamond, p-Si 등과 같은 p-type 물질 위에 n-type ZnO를 성장시킨 이종접합 다이오드가 연구되고 있다. 특히, p-GaN의 경우 ZnO와의 격자 불일치 정도가 1.8 % 정도로 작다는 장점이 있어 많은 연구가 이루어 지고 있다. 일반적으로 c-축을 기반으로 한 극성ZnO 발광다이오드에서는 자발 분극과 압전 분극 현상에 의해 밴드 휨 현상이 발생하고, 이로 인해 전자와 정공의 공간적 분리가 발생하게 되어 발광 재결합 효율이 제한되고 있다는 문제가 발생한다. 따라서, 본 연구에서는 극성 (0001) 및 비극성 (10-10) n-ZnO/p-GaN 발광다이오드의 성장 및 발광 소자의 전기 및 광학적 특성에 대한 비교 연구를 진행하였다. 금속유기 화학증착법을 이용하여 c-면과 m-면 위에 각각 극성 (0001) 및 반극성 (11-22) GaN박막을 $2.0{\mu}m$ 성장시킨 후 Mg 도핑을 한 p-GaN을 $0.4{\mu}m$ 성장시켜 각각 극성 (0001) 및 반극성 (11-22) p-GaN템플릿을 준비하였다. 이후, N2분위기 $700^{\circ}C$에서 3분동안 열처리를 통하여 Mg 도펀트를 활성화시킨 후 원자층 증착법을 이용하여 동시에 극성 및 반극성 p-GaN의 위에 n-ZnO를 $0.11{\mu}m$ 성장시켜 이종접합구조의 발광소자를 형성하였다. 이때, 극성 (0001) p-GaN 위에는 극성의 n-ZnO 박막이 성장되는 반면, 반극성 (11-22) p-GaN 위에는 비극성 (10-10) n-ZnO 박막이 성장됨을 HR-XRD로 확인하였다. 극성 (0001) n-ZnO/p-GaN이종접합 발광다이오드의 전계 발광 스펙트럼에서는 430 nm 와 550 nm의 두 피크가 동시에 관찰되었다. 430 nm 대역의 파장은 p-GaN의 깊은 준위에서 발광하는 것으로 판단되며, 550 nm 피크 영역은 ZnO의 깊은 준위에서 발광되는 것으로 판단된다. 특히, 10 mA 이하의 저전류 주입시 550 nm의 피크는 430 nm 영역보다 더 큰 발광세기를 나타내고 있다. 하지만, 10 mA 이상의 전류주입 하에서는 550 nm의 영역보다 430 nm의 발광세기가 더욱 증가하는 것을 확인할 수 있었다. 이것은 ZnO의 밴드갭이 3.37 eV로 GaN의 밴드갭인 3.4 eV다 작기 때문에 우선적으로 ZnO의 깊은 준위에서 발광하는 550 nm가 더욱 우세하지만, 지속적으로 전류주입 증가에 따른 캐리어 증가시 n-ZnO에서 p-GaN로 전자가 넘어가며 p-GaN의 깊은 준위인 430 nm에서의 피크가 우세해지는 것으로 판단된다. 반면에, 비극성 (10-10) n-ZnO/반극성 (11-22) p-GaN 구조의 이종접합 발광다이오드로 전계 발광 스펙트럼에서는 극성 (0001) n-ZnO/p-GaN에 비하여 매우 낮은 전계 발광 세기를 나타내고 있다. 이는, 극성 n-ZnO/p-GaN에 비하여 비극성 n-ZnO/반극성 p-GaN의 결정성이 상대적으로 낮기 때문으로 판단된다. 또한, 20 mA 영역에서도 510 nm의 깊은 준위와 430 nm의 발광이 관찰되었다. 동일한 20 mA하에서 두 피크의 발광세기를 비교하면 430 nm의 영역은 극성 n-ZnO/p-GaN에 비하여 매우 낮은 값을 나타내고 있다. 이는 반극성 (11-22) p-GaN의 경우 극성 (0001) p-GaN에 비하여 우수한 p-형 특성에 기인한 것으로 판단된다.

• Journal of Wetlands Research
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• v.6 no.3
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• pp.71-81
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• 2004

In recent, the heavy rainfall is frequently occurred and the damage tends to be increased. So, more careful hydrologic analysis is required for the designs of the hydraulic or disaster prevention structures. The time distribution of a rainfall is one of the important factors for the estimation of peak flow in hydrologic and hydraulic designs. This study is to suggest a methodology for the estimation of a rainfall time distribution which can reflect the meteorologic and topographical characteristics of Daejeon area. We collect the 34 years' rainfall data recorded in the range of 1969 to 2002 for Daejeon area and we performed the rainfall analysis with the data in between May and October of each year. According to the Huff method, the collected data corresponds to the first quartile which the rainfall is concentrated in the primary stage but the suggested method shows the different rainfall distribution with the Huff method in time. The reason is that the Huff method determines the quartile in each storm event while the suggested one determines it by estimating the dimensionless distribution of rainfall in duration after the accumulation of rainfall in time. The rainfall distributions estimated by two methodologies were applied to the Gabcheon basin in Daejeon area for the estimation of flood flow. Here we use the SCS method for the effective rainfall and unit hydrograph for the flood discharge. As the results, the peak flow for 24-hour of 100-year frequency was estimated as a $3421.20m^3/sec$ by the Huff method and $3493.38m^3/sec$ by the suggested one. We can see the difference of $72.18m^3/sec$ in between two methods and thus we may carefully determine the rainfall time distribution and compute the effective rainfall for the estimation of the peak flow.

• The Korean Journal of Mycology
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• v.13 no.1
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• pp.41-47
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• 1985

Eighteen plant residues were added to soil and the amended soil was inoculated with chlamydospores (5,000 cells/g soil) of Fusarium solani causing root rot of ginseng in soil to test the effects of amendment using pea (Pisium sativa L.) as an index plant. Distributional conditions of microogranisms in soil were compared with each other before and after dealing with soil amendment by plant debries. Infection rate by index plant's infectivity showed a higher degree in the treatment of wheat crushed than in control group, and followed by stalk of sweet potato, chinese cabbage, ginseng leaves and soybean pod. On the other hand, the de­creasing order of infection rate was root of garlic, welsh onion, cabbage leaf and stalk, green onion stalk, wheat straw and barley straw. In comparison with control group, the propagules of fungi increased in the treatment of ginseng leaves, soybean ground, wheat crushed, maize stalk, and chinese cabbage, but decreased in the root of garlic, cabbage, and barley straw. Population of total bacteria increased in the treatment of soybean ground, chinese cabbage, radish stalk, welsh onion, and wheat crushed, but decreased in barley straw, tobaco root, ginseng stalk, and wheat straw. The numbers of actinomycetes increased only in the treatment of soybean ground in a comparison with control and also decreased in the garlic stalk and tobaco root. The propagules of Fusarium spp increased in the treatment of chinese cabbage, welsh onion, radish stalk, wheat crushed, and sweet potato stalk, wheat crushed, and sweet potato stalk, but decreased in the treat­ment of wheat straw, ginseng leaves, and cabbage than control.

• The Korean Journal of Mycology
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• v.36 no.2
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• pp.153-162
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• 2008

Pinewood nematode (PWN) trapping by nematophagous fungi, Arthrobotrys conoides, A. dactyloides and A. oligospora and the fungal growth were characterized. The three Arthrobotrys species each was inoculated into the PWN cultured on Botrytis cinera fungal colony on potato dextrose agar (PDA). The effects of temperature, pH, PWN inoculation density and nutrients on the growth of the three Arthrobotrys spp were measured. A. conoides grew fast, 13.9 mm/day while A. dactyloides grew slow, 3 mm/day. PDA medium was the best for the fungal growth at $25^{\circ}C$ and pH 4.5. The Arthrobotrys spp growth was stimulated by 500 nematodes inoculation but not by 1000 inoculation. A. dactyloides did not grow below pH 4.5 and at high PWN density. A. conoides and A oligospora formed trapping organs with thick constricting hyphal network only when PWN present, while A. dactyloides formed the organ with circular hyphae constitutively. A. conoides formed trapping organs faster than A. oligospora did. The nematode trapping hyphae of the fungi penetrated into PNW inside to form many tiny infection bulbs and to digest the nematode. However, A. dactyloides formed a few trapping organs but no trapping was observed. Infection rate of PWN was 95% by A. conoides, 80% by A. oligospora and 92% by the combination inoculation of A. conoides and A. oligospora. In contrast A. dactyloides increased PWN density without infecton. There was no interaction effect in any combination inoculation of the three Arthrobotrys spp. A. conoides enhanced PWN infection rate by rapid hyphal growth and early trapping, while A. oligospora did it by increasing hyphal density. In conclusion A. conoides is the most effective in both hyphal growth and infection, and thus these characteristics can be utilized as a biological control of PWN.

• The Korean Journal of Mycology
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• v.41 no.2
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• pp.104-111
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• 2013

Phellinus baumii is a medicinal mushroom used in Asian countries for a long period of time. The purpose of this study was to investigate the skin whitening activities of methanol extracts from fruiting bodies of P. baumii. To evaluate the antioxidant activities of the extract, polyphenol and flavonoid contents, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and chelating activity on ferrous ions were studied. For assay of skin whitening activities, tyrosinase and DOPA inhibitory activities, and tyrosinase and melanin synthesis inhibitory activities of B16/F10 melanoma cells treated with the methanol extract were investigated. The total polyphenol content of P. baumii methanol extract was 4.19. DPPH scavenging ability of P. baumii methanol extract was 88.26% in $25{\mu}g/mL$ concentration. We tested tyrosinase inhibitory activity and melanin contents in melanoma cells. The tyrosinase activity was inhibited to 65.17% at the concentration of $125{\mu}g/mL$ and melanin synthesis was inhibited to 57.61% at the concentration of $25{\mu}g/mL$. Overall, the experimental results showed that P. baumii methanol extract had inhibitory activities of tyrosinase and melanin synthesis by dose dependent manner in B16/F10 melanoma cells. Strong ultra-violet absorption spectra in the range of 270~370 nm indicated that ethanol extract of P. baumii could protect the skin from UV. Therefore, P. baumii methanol extract might be used for development of skin whitening, anti-UV and skin care agents.

• Korean Journal of Heritage: History & Science
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• v.53 no.3
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• pp.258-277
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• 2020

The purpose of this paper is to examine the paintings and symbols of the Jeju Guandeokjeong murals, Treasure No. 322. Gwandeokjeong Pavilion in Jeju is one of the oldest buildings in Jeju and was built in 1448 during the reign of King Sejong (世宗) of the Joseon Dynasty to serve as a training ground for soldiers. Unlike Gwandeokjeong Pavilions in other regions, Jeju's Gwandeokjeong Pavilion has a long history and is of cultural value due to its beautiful architecture. In addition, it contains various murals which are a further source of attention. There are four murals on the front and back of the two Lintels on the left and right sides of the building. Their contents include of 『The Three Kingdoms (三國志)』 and and on the back. Towards the right, is depicted, with on the back. Based on a replica of the murals from 1976, the plan, style, and age of the Gwandeokjeong Pavilion murals have been studied, together with their meanings. The contents of the mural are broadly divided into five parts, which are identified by the tacit signatures atop the screen, which provide such details as the painting titles. The paintings on the left and right sides of the center appear to inspire the spirit of the military's commerce in order to boost soldiers' morale, protect the country, and protect the people in line with the purpose of Gwandeokjeong Pavilion. The following and figuratively depict guidelines for the behavior and mindset of officials. In particular, is a painting concerned with concepts of longevity and an auspicious (吉祥), which shows how court paintings became popular as folk paintings at that time. The paintings of tangerines and other specialties of Jeju Island, the ritual paintings of Jeokbyeokdaejeon, and the expressions of Mt. Halla (漢拏山) and Oreum (오름) indicate the existence of Jeju artists that belonged to the Jeju government office at that time. The five themes and styles of the murals also show that the murals of Gwandeokjeong Pavilion were produced in the late 19^th and early 20^th centuries.

• Macromolecular Research
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• v.14 no.4
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• pp.408-415
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• 2006

Temperature-dependent, wide-angle, x-ray diffraction (WAXD) patterns and infrared (IR) spectra were measured for biodegradable poly(3-hydroxybutyrate) (PHB) and its copolymers, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(HB-co-HHx) (HHx=2.5, 3.4, 10.5, and 12 mol%), in order to explore their crystal and lamellar structure and their pattern of C-H...O=C hydrogen bonding. The WAXD patterns showed that the P(HB-co-HHx) copolymers have the same orthorhombic system as PHB. It was found from the temperature-dependent WAXD measurements of PHB and P(HB-co-HHx) that the a lattice parameter is more enlarged than the b lattice parameter during heating and that only the a lattice parameter shows reversibility during both heating and cooling processes. These observations suggest that an interaction occurs along the a axis in PHB and P(HB-co-HHx). This interaction seems to be due to an intermolecular C-H...O=C hydrogen bonding between the C=O group in one helical structure and the $CH_3$ group in the other helical structure. The x-ray crystallographic data of PHB showed that the distance between the O atom of the C=O group in one helical structure and the H atom of one of the three C-H bonds of the $CH_3$ group in the other helix structure is $2.63{\AA}$, which is significantly shorter than the sum of the van der Waals separation ($2.72{\AA}$). This result and the appearance of the $CH_3$ asymmetric stretching band at $3009 cm^{-1}$ suggest that there is a C-H...O=C hydrogen bond between the C=O group and the $CH_3$ group in PHB and P(HB-co-HHx). The temperature-dependent WAXD and IR measurements revealed that the crystallinity of P(HB-co-HHx) (HHx =10.5 and 12 mol%) decreases gradually from a fairly low temperature, while that of PHB and P(HB-co-HHx) (HHx = 2.5 and 3.5 mol%) remains almost unchanged until just below their melting temperatures. It was also shown from our studies that the weakening of the C-H...O = C interaction starts from just above room temperature and proceeds gradually increasing temperature. It seems that the C-H...O=C hydrogen bonding stabilizes the chain holding in the lamellar structure and affects the thermal behaviour of PHB and its copolymers.

• Korean Journal of Microbiology
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• v.50 no.3
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• pp.201-209
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• 2014

This study was carried out in order to develop a biological control of anthracnose of red pepper caused by fungal pathogens. In particular, this study focuses on the Colletotrichum species, which includes important fungal pathogens causing a great deal of damage to red pepper. Antagonistic bacteria were isolated from the soil of pepper fields, which were then tested for biocontrol activity against the Colletotrichum gloeosporioides anthracnose pathogen of pepper. Based on the 16S rRNA sequence analysis, the isolated bacterial strain CS-52 was identical to Bacillus sp. The culture broth of Bacillus sp. CS-52 had antifungal activity toward the hyphae and spores of C. gloeosporioides. Moreover, the substances with antifungal activity were optimized when Bacillus sp. CS-52 was grown aerobically in a medium composed of 0.5% glucose, 0.7% $K_2HPO_4$, 0.2% $KH_2PO_4$, 0.3% $NH_4NO_3$, 0.01% $MnSO_4{\cdot}7H_2O$, and 0.15% yeast extract at $30^{\circ}C$. The inhibition of spore formation resulting from cellulase, siderophores, and indole-3-acetic acid (IAA), were produced at 24 h, 48 h, and 72 h, respectively. Bacillus sp. CS-52 also exhibited its potent fungicidal activity against anthracnose in an in vivo test, at a level of 70% when compared to chemical fungicides. These results identified substances with antifungal activity produced by Bacillus sp. CS-52 for the biological control of major plant pathogens in red pepper. Further studies will investigate the synergistic effect promoting better growth and antifungal activity by the formulation of substances with antifungal activity.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.12 no.1
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• pp.42-62
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• 2008

Objectives: It is well known that some parameters of the photoplethysmogram (PPG) acquired by time domain contour analysis can be used as markers of vascular aging. But the previous studies that have been performed for frequency domain analysis of the PPG to date have provided only restrictive and fragmentary information. The aim of the present investigation was to determine whether the harmonics extracted from the PPG using a fast Fourier transformation could be used as an index of vascular aging. Methods: The PPG was measured in 600 recruited subjects for 30 second durations, To grasp the gross age-related change of the PPG waveform, we grouped subjects according to gender and age and averaged the PPG signal of one pulse cycle. To calculate the conventional indices of vascular aging, we selected the 5-6 cycles of pulse that the baseline was relatively stable and then acquired the coordinates of the inflection points. For the frequency domain analysis we performed a power spectral analysis on the PPG signals for 30 seconds using a fast Fourier transformation and dissociated the harmonic components from the PPG signals. Results: A final number of 390 subjects (174 males and 216 females) were included in the statistical analysis. The normalized power of the harmonics decreased with age and on a logarithmic scale reduction of the normalized power in the third (r=-0.492, P<0.0001), fourth (r=-0.621, P<0.0001) and fifth harmonic (r=-0.487, P<0.0001) was prominent. From a multiple linear regression analysis, Stiffness index, reflection index and corrected up-stroke time influenced the normalized power of the harmonics on a logarithmic scale. Conclusions: The normalized harmonic power decreased with age in healthy subjects and may be less error prone due to the essential attributes of frequency domain analysis. Therefore, we expect that the normalized harmonic power density can be useful as a vascular aging marker.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.235-247
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• 2020

Simulation study and validation on 50 L/hr pilot-scale Bunsen process was carried out in order to investigate thermodynamics parameters, suitable reactor type, separator configuration, and the optimal conditions of reactors and separation. Sulfur-Iodine is thermochemical process using iodine and sulfur compounds for producing hydrogen from decomposition of water as net reaction. Understanding in phase separation and reaction of Bunsen Process is crucial since Bunsen Process acts as an intermediate process among three reactions. Electrolyte Non-Random Two-Liquid model is implemented in simulation as thermodynamic model. The simulation results are validated with the thermodynamic parameters and the 50 L/hr pilot-scale experimental data. The SO₂ conversions of PFR and CSTR were compared as varying the temperature and reactor volume in order to investigate suitable type of reactor. Impurities in H₂SO₄ phase and HI_X phase were investigated for 3-phase separator (vapor-liquid-liquid) and two 2-phase separators (vapor-liquid & liquid-liquid) in order to select separation configuration with better performance. The process optimization on reactor and phase separator is carried out to find the operating conditions and feed conditions that can reach the maximum SO₂ conversion and the minimum H₂SO₄ impurities in HI_X phase. For reactor optimization, the maximum 98% SO₂ conversion was obtained with fixed iodine and water inlet flow rate when the diameter and length of PFR reactor are 0.20 m and 7.6m. Inlet water and iodine flow rate is reduced by 17% and 22% to reach the maximum 10% SO₂ conversion with fixed temperature and PFR size (diameter: 3/8", length:3 m). When temperature (121℃) and PFR size (diameter: 0.2, length:7.6 m) are applied to the feed composition optimization, inlet water and iodine flow rate is reduced by 17% and 22% to reach the maximum 10% SO₂ conversion.