• Solar Energy
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• v.17 no.4
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• pp.3-11
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• 1997

Because grain boundaries in polycrystalline silicon act as potential barriers and recombination centers for the photo-generated charge carriers, these defects degrade conversion effiency of solar cell. To reduce these effects of grain boundaries, we investigated various influencing factors such as thermal treatment, various grid pattern, selective wet etching for grain boundaries, buried contact metallization along grain boundaries, grid on metallic thin film. Pretreatment above $900^{\circ}C$ in $N_2$ atmosphere, gettering by $POCl_3$ and Al treatment for back surface field contributed to obtain a high quality poly-Si. To prevent carrier losses at the grain boundaries, we carried out surface treatment using Schimmel etchant. This etchant delineated grain boundaries of $10{\mu}m$ depth as well as surface texturing effect. A metal AI diffusion into grain boundaries on rear side reduced back surface recombination effects at grain boundaries. A combination of fine grid with finger spacing of 0.4mm and buried electrode along grain boundaries improved short circuit current density of solar cell. A ultra-thin Chromium layer of 20nm with transmittance of 80% reduced series resistance. This paper focused on the grain boundary effect for terrestrial applications of solar cells with low cost, large area, and high efficiency.

• Journal of Technology Innovation
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• v.17 no.2
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• pp.25-53
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• 2009

The purpose of this paper is to analysis sectoral patterns of technological innovation in Korean manufacturing sector. Pavitt(1984) put forward a well-known taxonomy that industries three groups of industries characterized by markedly different innovative modes, namely science-based, production-intensive and supplier-dominated industries. Using Pavitt's taxonomy as a framework, we try to explain similarities and differences among sectors in the sources and impact of innovations. Based on a sample of 2,371 firms in manufacturing industry, this paper investigated its relevance to explain the sources and directions of innovative activities in Korean industries. Empirical study shows that in supplier dominated firms most process innovations come from suppliers of equipment and materials. In science-based firms product innovation is produced internally, based on the rapid development of the underlying sciences in the universities and research institutes. It also shows that production-intensive firms have a positive association between innovativeness and customer collaboration. This explanation has implications for our understanding of the sources and directions of technical changes, the formation of technological advantages at the level of both region and country.

• Journal of Life Science
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• v.21 no.2
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• pp.257-264
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• 2011

Seventy five methicillin- resistant Staphylococcus aureus (MRSA) strains and 24 methicillin- susceptible S. aureus (MSSA) were isolated from clinical specimens obtained from a hospital in Suncheon, Jeonnam province, Korea, from July to December, 2009. Antibiotic resistance was determined using the disc diffusion method. Genes encoding enterotoxin (SE), toxic shock syndrome toxin-1 (TSST-1), exfoliative toxin (ET) and Panton-Valentine leukocidin (PVL) were detected by multiplex PCR-mediated amplification using specific primers. Sixty (80%) MRSA isolates possessed either one or more toxin genes and the most common pattern that coexisted in MRSA was seb, sec, seg, sei and tst (22.7%) followed by coexistence of sec, seg, sei and tst genes (18.7%). Gene pvl encoding leukocidin was not found. Significant correlation between the production of sec, seg, sei and tst genes was found. MRSAs were resistant to erythromycin (89% of the isolates), gentamicin (70.7%), ciprofloxacin (69.3%), clindamycin (61.3%) and tetracycline (58.7%), while MSSAs were susceptible to the antibiotics with the exception of erythromycin. Toxin genes seb, sec and tst were related to the tetracycline resistance of MRSA.

• Nuclear Engineering and Technology
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• v.4 no.2
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• pp.132-136
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• 1972

The mechanism for activated sintering of UO$_2$by an addition of 0.05 w/o TiO$_2$was investigated using a high temperature X-ray diffractometer. The diffraction pattern of UO$_2$pellets was studied in a temperature range from room temperature to 120$0^{\circ}C$ in hydrogen atmosphere. At 120$0^{\circ}C$, the expansion of UO$_2$lattice were 1.448% and 1.354% greater when it was compared with those at room temperature for pellets with and without the 0.05 w/o TiO$_2$addition, respectively-The effect of the TiO$_2$addition is to increase the lattice constant of UO$_2$by 0.094% at 120$0^{\circ}C$. The lattice constant at 120$0^{\circ}C$without the TiO$_2$addition is equal to that at 108$0^{\circ}C$ with the 0.05 w/o TiO$_2$addition. This temperature difference could be well compared with the suppression of sintering temperature by TiO$_2$hat had been observed Previously. It is believed that the increase in lattice expansion due to the TiO$_2$addition would give rise to the activated sintering of UO$_2$by the lattice-expansion-induced-enhancement of self diffusion.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.2
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• pp.61-70
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• 2019

Geopolymer is an eco-friendly construction material that has various advantages such as reduced $CO_2$ emission, fire resistance and low thermal conductivity compared to cement. However, it has not been many studies on the thermal behavior of the surface of the geopolymer panel when flame is applied to the surface. In this study, surface characteristics of hardened geopolymer on flame exposure was investigated to observe its characteristics as heat-resistant architectural materials. External structure changes and crack due to the heat shock were not observed during the exposure on flame. According to the residue of calcite and halo pattern of aluminosilicate gel, decarboxylation and dehydration were extremely limited to the surface and, therefore, it is thought that durability of hardened geopolymer was sustained. Gehlenite and calcium silicate portion was inversely proportional to quartz and calcite and significantly directly proportional to BFS replacement ratio. Microstructure changes due to the thermal shock caused decarboxylation and dehydration of crystallization and it was developed the pore and new crystalline phase like calcium silicate and gehlenite. It is thought that those crystalline phase worked as a densification and strengthening mechanism on geopolymer panel surface.

• Journal of Food Hygiene and Safety
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• v.36 no.6
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• pp.520-527
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• 2021

In this study, toxin gene and antibiotic resistance of food poisoning strains isolated from indoor air in the cafeteria were analyzed to prevent food poisoning. Staphylococcus aureus (16 strains) and Bacillus cereus (37 strains) isolated from indoor air in child care center were tested. The toxin genes of S. aureus and B. cereus were detected by PCR assay. The antimicrobial susceptibility test followed the disc diffusion method described by the Clinical and Laboratory Standard Institute. The seg and sei toxin genes were detected in 11 of 16 S. aureus strains (68.6%). The nheA and nheB toxin genes were detected in 37 B. cereus strains. In this study, a total of 12 toxin gene patterns of B. cereus were found, among which the nheA-nheB-nheC toxin gene was found to be the most frequent pattern. The result of the antimicrobial susceptibility test of S. aureus revealed 93.8% and 87.5% resistance to ampicillin and penicillin antibiotics, but methicillin resistance S. aureus and vancomycin resistance S. aureus were not detected. All 37 B. cereus tested in this study were resistant to ampicillin and penicillin antibiotics. Based on the result of this study, it was judged that regular ventilation and air quality management were necessary to prevent food poisoning caused by S. aureus and B. cereus contaminated in the indoor air of child care centers.

• Korean Journal of Environment and Ecology
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• v.36 no.5
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• pp.507-524
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• 2022

In this study, we revealed the location environment and community structural characteristics after extensively investigating Korea's warm-temperate island areas and categorizing vegetation through TWINSPAN analysis. Based on it, this study aims to suggest the direction of the vegetation restoration plan for warm-temperate forests by deriving a restoration strategy for each vegetation type. The vegetation types were clearly divided into eight types, and communities I through IV were good evergreen broad-leaved forests dominated by Machilus thunbergii and Castanopsis sieboldii. On the other hand, communities V through VIII were Pinus thunbergii forest, deciduous broad-leaved forest, and artificial forest, and retrogressive succession vegetation in the warm-temperate areas. The environmental factors derived from the DCA analysis were altitude (average temperature of the coldest month) and distance from the coastline (salt tolerance). The distribution pattern of warm-temperate forests has been categorized into M. thunbergii, C. sieboldii and Cyclobalanopsis spp. forest types according to the two environmental factors. It is reasonable to apply the three vegetation types as restoration target vegetation considering the location environment of the restoration target site. In communities V through VIII, P. thunbergiiand deciduous broad-leaved formed a canopy layer, and evergreen broad-leaved species with strong seed expansion frequently appeared in the ground layer, raising the possibility of vegetation succession as evergreen broad-leaved forests. The devastated land where forests have disappeared in the island areas is narrow, but vegetation such as P. thunbergii and deciduous broad-leaved forests, which have become a retrogressive succession, forms a large area. The restoration strategy of renewing this area into evergreen, broad-leaved forests should be more effective in realizing carbon neutrality and promoting biodiversity.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• Microbiology and Biotechnology Letters
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• v.51 no.4
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• pp.500-506
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• 2023

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is emerging as a worldwide public health threat. Recently, Klebsiella pneumoniae carbapenemase-2 (KPC-2)-producing sequence type (ST) 307 was identified main clone of CRKP, and dissemination of ST307 was reported in South Korea. This study examined the molecular characteristic and antimicrobial resistance pattern of 50 CRKP isolated from a tertiary hospital in Daejeon, from March 2020 to December 2021. Epidemiological relationship was analyzed by Multilocus sequence typing (MLST) and antimicrobial susceptibility test was determined using disk-diffusion method. PCR and DNA sequence analysis were performed to identify carbapenemase genes. CRKP infections were significantly more frequent in males and the patients aged ≥ 60 years. Among the 50 CRKP isolates, 46 isolates (92.0%) were multidrug-resistant (MDR), and 44 isolates (88.0%) were carbapenemase-producing K. pneumoniae (CPKP). The major carbapenemase type was KPC-2 (36 isolates, 72.0%) and New Delhi metalloenzyme-1 (NDM-1) and NDM-5 were identified in 7 isolates (14.0%) and 1 isolate (2.0%), respectively. In particular, 88.9% (32/36) of KPC-2-producing K. pneumoniae belonged to ST307, whereas 87.5% (7/8) of NDM-1,-5-producing K. pneumoniae belonged to non-ST307. These results suggest that proper infection control and effective surveillance network need to prevent not olny the spread of ST307, but also the development of non-ST307.

• Journal of the Korean Society of Radiology
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• v.85 no.3
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• pp.682-690
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• 2024

Acute necrotizing encephalopathy (ANE) is a rare immune-mediated complication of a viral infection commonly involving the bilateral thalamus and has been reported mainly in children. Here, we describe the MRI findings of coronavirus disease 2019 (COVID-19)-associated ANE in two pediatric patients, including a 7-year-old girl with fever and mental change, and a 6-year-old girl with fever and generalized seizures. Brain MRI revealed symmetrical T2 fluid attenuated inversion recovery high-signal intensity lesions in the bilateral thalamus with central hemorrhage. In one patient, the thalamic lesions showed a tri-laminar pattern on the apparent diffusion coefficient map. This report emphasizes the importance of creating awareness regarding these findings in patients with COVID-19, particularly in children with severe neurological symptoms. Furthermore, it provides a literature review of several documented cases of COVID-19 presenting with bilateral thalamic hemorrhagic necrosis, suggesting a diagnosis of ANE.