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레이저형광여기(LIF)를 이용한 비등온 제트유동의 온도장 측정
윤정환,이상준,Yoon, Jong-Hwan,Lee, Sang-Joon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.10
A 2-dimensional temperature field measurement technique using PLIF (Planar Laser Induced Fluorescence) was developed and it was applied to an axisymmetric buoyant jet. Rhodamine B was used as a fluorescent dye. Laser light sheet illuminated a two-dimensional cross section of the jet. The intensity variations of LIF signal from Rhodamine B molecules scattered by the laser light were captured with an optical filter and a CCD camera. The spatial variations of temperature field of buoyant jet were derived using the calibration data between the LIF signal and real temperature. The measured results show that the turbulent jet is more efficient in mixing compared to the transition and laminar jet flows. As the initial flow condition varies from laminar to turbulent flow, the entrainment from ambient fluid increases and temperature decay along the jet center axis becomes larger. In addition to the mean temperature field, the spatial distributions of temperature fluctuations were measured by the PLIF technique and the result shows the shear layer development from the jet nozzle exit.
Seven-year Survival Rate of On-line Hemodiafiltration
윤정환,김남호 대한의생명과학회 2019 Biomedical Science Letters Vol.25 No.1
Conventional high-flux hemodialysis (HD) is not as good as normal kidney function. Morbidity and mortality rates of patients receiving HD are still very high. To increase mid-to-large molecule clearance by combining diffusion and convection, on-line hemodiafiltration (HDF) is required. The objective of this study was to compare long-term survival rate of patients treated with on-line HDF to those who received conventional high-flux HD by reviewing data from Chonnam National University Hospital (CNUH). We selected patients who attended the 'CUNH dialysis center' and agreed to participate in the study. Overall, 40 patients with ESRD switched from high flux HD to on-line HDF or started on-line HDF from August 2007 to December 2009. Additionally, a total of 42 patients receiving conventional high-flux HD during the same period were enrolled. We then reviewed long-term survival rate of patients receiving on-line HDF over the next seven years. When we compared survival rates for seven years, the survival rate of the group receiving on-line HDF was 65% (26/40) while that of the group receiving the conventional high-flux HD was 54.8% (23/42). Although the number of patients was small to see survival difference clearly by one specific dialysis modality, there was somewhat difference in survival rate between the two groups. Indicators such as anemia, calcium-phosphate metabolism, nutritional status, treatment adequacy, and hospitalization were also improved in the group receiving HDF. Overall, results of our study showed beneficial effects of on-line HDF on clinical outcomes and survival in chronic HD patients.
윤정환,김영남,이단비,김권래,김원일,김계훈 한국토양비료학회 2017 한국토양비료학회지 Vol.50 No.6
This study aimed to investigate correlations between concentrations of extractable Arsenic (As) with varyingchemical solutions (0.1 M Ca(NO3)2, 0.1 M (NH4)2HPO4, 0.5 M EDTA, Mehlich 3, and 0.5 M NaHCO3) andthose of As in crops, and then to seek the most suitable soil extraction method for predicting the potential of Asuptake in crops cultivated in soils contaminated with As. For a mesocosm experiment, pepper (Capsicumannuum L.), soybean (Glycine max L.), and rice (Oryza sativa L.) were cultivated for three months in potscontaining soils taken from the arable areas near abandoned mines in Korea. Following the cultivation, soil pHand DOC significantly increased by treatments of lime and lime plus compost, respectively, while insignificantinfluences in changing total and all extractable As concentrations were found in all soils. Arsenic concentrationin edible part of all crops considerably depended on the extractable As concentration in the soils, particularlywith Mehlich 3. All extractable As concentrations in the soils of C. annuum and G. max were significantlycorrelated with As concentration in their edible parts. For O. sativa, the extractable concentrations of Mehlich 3(R2: 0.18 at p: 0.006) and EDTA (R2: 0.11 at p: 0.036) showed only marked relationships with As concentrationin the edible part. These results may indicate that the Mehlich 3 and EDTA are soil extractants to determinephytoavailable As in soil that provide better prediction for As transfer from soil to crop.
윤정환,김계훈,양재의 한국토양비료학회 2022 한국토양비료학회지 Vol.55 No.1
In agricultural highland, soil properties change over time due to soil management methods, soil erosion, and cultivation. The objective of this study was to investigate the differences in soil properties according to land management in agricultural highland. As a result of the soil analysis, Anbandegi, Maebongsan, Yeongwol, and Jeongseon, located near the top of the mountain, had low bulk densities, and organic matter, CEC, exchangeable cation, water stable aggregation rate, and dehydrogenase activity, were relatively higher than those of Daegwallyeong and Punch bowl. In the Daegwallyeong and Punch bowl, saprolite soil was periodically piled to replace eroded top-soil, and as a result, soil characteristics differed significantly from those located near the top of the mountain. In the principal component analysis result, organic matter showed the largest eigenvalue in PC1, and pH was selected as PC2. The distribution of soil clusters by sampling point was PC1, and Daegwallyeong and Punch bowl were classified differently from highland areas near the top of the mountain, and coastal basins and Daegwallyeong were classified by PC2. In conclusion, highland soil showed different soil properties for each region, which was the result of differences according to the soil management methods. And considering the relationship between soil characteristics, it was confirmed that organic matter was the most important factor in the soil management methods.