• Composites Research
• /
• v.30 no.2
• /
• pp.108-115
• /
• 2017

Among several fabrication processes of $SiC_f/SiC$ composites, the chemical vapor infiltration (CVI) process has attractive advantages in manufacturing complex net-or near-net-shape components at relatively low temperatures, easily controlling the microstructure of the matrix and obtaining the highest SiC purity level. However, it has disadvantages in that the ratio of residual pores in matrix is higher than other processes and processing time is relatively long. To reduce the residual porosity, the whisker-growing-assisted CVI process, which is composed of whisker growth and matrix filling steps has been developed. The whiskers grown before matrix filling may serve to divide the large natural pores between the fibers or bundles so that the matrix can be effectively filled into the finely divided pores. In this paper, the fundamentals of the CVI process for preparation of $SiC_f/SiC$ composites and some experimental results prepared by CVI and whisker-growing-assisted CVI processes are briefly introduced.

• Journal of Korea Water Resources Association
• /
• v.37 no.3
• /
• pp.249-255
• /
• 2004

To investigate the return flow ratio of irrigation water, lots of observations were made during the irrigation periods in 2003 crop year. This Area is a portion of Dae-Am pumping station basin which is located in Changryung-gun, Gyeongnam province. A water balance analysis was performed for a paddy field in Dae-Am pumping station in the Nakdong river basin, which is constructed for irrigation water supply. Daily rainfall data in the this area were collected and irrigation water flow rate, drainage water flow rate, infiltration and evaportranspiration were measured in field area. Irrigation water flow rate and drainage water flow rate were continuously observed by water level logger(GTDL-L10) during the growing season. The infiltration and evaportranspiration were measured by cylindrical 300mm depletion meter and cylindrical 200mm infiltrometer, respectively. Total irrigation and drainage flows were 654.7mm and 281.2mm in 2003. Total infiltration and evaportranspiration were 36.0mm and 160.0mm respectively. The mean of the daily evaportranspiration rate was 4.3mmm/d. The prompt return flow and retard return flow ratio were 43.0％ and 5.5％, respectively. Total return flow ratio was 48.5％. Therefore, it can be concluded that the amount of irrigation water was much higher than design standard or reference in this study. It means that this was caused by the inadequate water management practice in the area where water was oversupplied on farmers' request rather than following sound water management principles, and design standard should be changed in the future.

• Journal of Environmental Science International
• /
• v.6 no.6
• /
• pp.637-644
• /
• 1997

The purpose of thins study was to quantitatively determine the Indoor Infiltration of pollutants of outdoor origin. The relationship between Indoor and outdoor air is dependent, to a large extent. on the rate of k exchange between these two environments. Mean Indoor/outdoor ratios measured from thins study were: 0.70 for HNO3; 1.60 for HNO2: 0.56 far SOg: 1.30 for mf3: 0.96 for PM2.5(dP<2.5mm: 0.89 for SO4a': 0.87 for NO3· and 0.79 for NH4 'Mean Indoor concentrations for PMa s, SO4a., HNO9, NO3 and NIL' were similar to outdoor levels. Indoor HNO2 and mB3 values were h19her than outdoors. However, the Indoor level of SO2 was lower than ambient level.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.56 no.6
• /
• pp.113-119
• /
• 2014

This study aims to evaluate the behavior of poorly-compacted raised reservoir levee with water level raising by using centrifugal model test. From the test results, it seems that the hydraulic fracturing at the core of the raised reservoir levee with low degree of compaction possibly occurs due to the drastical increase of pore water pressure by water level raising. Additionally, the continuous infiltration may induce crack and/or sinkhole on the surface of the poorly-compacted raised reservoir levee owing to the increase of the subsidences at the crown and the front side of that. Therefore, reasonable construction management for the compaction of the raised reservoir levee is needed.

• Journal of Ginseng Research
• /
• v.38 no.1
• /
• pp.8-15
• /
• 2014

Helicobacter pylori-induced gastric inflammation includes induction of inflammatory mediators interleukin (IL)-8 and inducible nitric oxide synthase (iNOS), which are mediated by oxidant-sensitive transcription factor NF-${\kappa}B$. High levels of lipid peroxide (LPO) and increased activity of myeloperoxidase (MPO), a biomarker of neutrophil infiltration, are observed in H. pylori-infected gastric mucosa. Panax ginseng Meyer, a Korean herb medicine, is widely used in Asian countries for its biological activities including anti-inflammatory efficacy. The present study aims to investigate whether Korean Red Ginseng extract (RGE) inhibits H. pylori-induced gastric inflammation in Mongolian gerbils. One wk after intragastric inoculation with H. pylori, Mongolian gerbils were fed with either the control diet or the diet containing RGE (200 mg RGE/gerbil) for 6 wk. The following were determined in gastric mucosa: the number of viable H. pylori in stomach; MPO activity; LPO level; mRNA and protein levels of keratinocyte chemoattractant factor (KC, a rodent IL-8 homolog), IL-$1{\beta}$, and iNOS; protein level of phospho-$I{\kappa}B{\alpha}$(which reflects the activation of NF-${\kappa}B$); and histology. As a result, RGE suppressed H. pylori-induced mRNA and protein levels of KC, IL-$1{\beta}$, and iNOS in gastric mucosa. RGE also inhibited H. pylori-induced phosphorylation of $I{\kappa}B{\alpha}$ and increases in LPO level and MPO activity of gastric mucosa. RGE did not affect viable H. pylori colonization in the stomach, but improved the histological grade of infiltration of poly-morphonuclear neutrophils, intestinal metaplasia, and hyperplasia. In conclusion, RGE inhibits H. pyloriinduced gastric inflammation by suppressing induction of inflammatory mediators (KC, IL-$1{\beta}$, iNOS), MPO activity, and LPO level in H. pylori-infected gastric mucosa.

• Journal of Korea Water Resources Association
• /
• v.51 no.spc
• /
• pp.1161-1169
• /
• 2018

In this study, a new methodology was proposed to evaluate the flood vulnerability of river levee and to investigate the effect on the levee where the water level changes according to climate change. The stability of levee against seepage was evaluated using SEEP/W model which is two-dimensional groundwater infiltration model. In addition to the infiltration behavior, it is necessary to analyze the vulnerability of the embankment considering the environmental conditions of the river due to climate change. In this study, the levee flood vulnerability index (LFVI) was newly developed by deriving the factors necessary for the analysis of the levee vulnerability. The size of river levee was investigated by selecting the target area. The selected levees were classified into upstream part, midstream part and downstream part at the nearside of Seoul in the Han river, and the safety factor of the levee was analyzed by applying the design flood level of the levee. The safety ratio of the levee was analyzed by applying the design flood level considering the current flood level and the scenario of climate change RCP8.5. The degree of change resulting from climate change was identified for each factor that forms the levee flood vulnerability index. By using the levee flood vulnerability index value utilizing these factors comprehensively, it was finally possible to estimate the vulnerability of levee due to climate change.

• The Journal of Korean Medicine
• /
• v.40 no.1
• /
• pp.63-77
• /
• 2019

Objectives: The purpose of this study is to examine the effect of water and fermentation extracts of KMS (Kami-Mihudeongsikjang-tang) on AD (atopic dermatitis). Additionally, by applying the fermentation extracts of KMS at the first sensitization and latency period, I investgated whether it could prevent AD. Methods: In this study, to test the effect and preventive efficacy of KMSs on AD. DNCB-induced BALB/c mice of AD model was used. Through histological observation, epidermis and dermis thickness, the infiltration of eoshiphils and mast cells in epidermis and dermis were examined. We measured the serum level of IgE and IL-6, TNF-alpha, and the expressions of $NF-{\kappa}B$ and MAPK protein. In order to examine the effect of KMSs on keratinocyte, HaCaT cells were treated TNF-alpha and IFN-gamma to induce an inflammatory response. The KMSs were applied at various concentration in the experimental group. We investigated TARC expression. Results: The treatment groups were reduced epidermis and dermis thickness, inhibited the infiltration of eosinophils and mast cells, reduced the serum level of IL-6. Moreover, sfKMS group reduced serum level of TNF-alpha, inhibited the protein expressions of $NF-{\kappa}B$ and the phosphoryllation of ERK, JNK and p38. Especially sfKMS-pre group were reduced the serum level of IgE, show significant inhibition on the protein expression of $NF-{\kappa}B$ and the phosphoryllation of ERK, JNK and p38. In the experiment on HaCaT cells, sfKMS group were reduced expression of TARC. Conclusions: These result suggest that wKMS and sfKMS was effective in the treament on AD, and sfKMS would prevent AD.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.04a
• /
• pp.63-66
• /
• 2003

This study applied a hydrogeological field survey and isotope investigation to identify source locations and delineate pathways of groundwater contamination by nitrogen compounds. The infiltration and recharge processes were analyzed with groundwater-level fluctuation data and oxygen-hydrogen stable isotope data. The groundwater flow pattern was investigated through groundwater flow modeling and spatial and temporal variation of oxygen isotope data. Based on the flow analysis and nitrogen isotope data, source types of nitrate contamination in groundwater are identified. Groundwater recharge largely occurs in spring and summer due to precipitation or irrigation water in rice fields. Based on oxygen isotope data and cross-correlation between precipitation and groundwater level changes, groundwater recharge was found to be mainly caused by irrigation in spring and by precipitation at other times. The groundwater flow velocity calculated by a time series of spatial correlations, 231 m/yr, is in good accordance with the linear velocity estimated from hydrogeologic data. Nitrate contamination sources are natural and fertilized soils as non-point sources, and septic and animal wastes as point sources. Seasonal loading and spatial distribution of nitrate sources are estimated by using oxygen and nitrogen isotopic data.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.40 no.5
• /
• pp.43-51
• /
• 1998

In design and management of sea0dikes, engineers need to study various transient seepage conditions through dikes not only for the sea water infiltration into dikes due to cyclic rises of sea water level also for the seepage flow out from dikes toward the sea due to cyclic drawdown of sea water level. Characteristics of seepage flow toward the sea from dikes are more complicated than as known and remained unclearly. The case of such seepage flow may be explained by figuring out seepage characteristics in filter as a part of sea-dikes. Filters in most sea-dikes in Korea are inevitably placed with reversely inclined shape due to field construction conditions. Most computer programs for seepage analysis based on the various numerical methods give practically acceptable results, but for the case of reversely inclined section of filters any verification to apply them might be needed. In this study, large scaled model tests were executed to verify and understand seepage flow through earth-filled sea-dikes. The results from numerical analysis and model tests show some remarkable differences in pore pressure distribution under cyclic changes of see level, and some of the results need to be considered in design and construction practices with further study.

• Journal of Soil and Groundwater Environment
• /
• v.19 no.4
• /
• pp.12-22
• /
• 2014

This study evaluated the pattern of groundwater fluctuation in cyrstalline rock using time series and factor analyses. From the results, groundwater level for the 18 wells was classified into 4 types reflecting the hydrogeological properties and rainfall event. Type 1 (DB1-5, DB1-6, DB2-2, KB-10, KB-13) was significantly influenced by groundwater flow through water-conducting features, whereas type 2 (DB1-3, DB1-7, KB-1~KB-3, KB-7, KB-11, KB-14, KB-15) was affected by minor fracture network as well as rainfall event. Type 3 (DB1-1, DB1-2) was mainly influenced by surface infiltration of rainfall event. Type 4 (DB1-8, KB-9) was reflected by the irregular variation of groundwater level caused by anisotropy and heterogeneity of crystalline rock.