• Journal of the Korean Society of Hazard Mitigation
• /
• v.10 no.5
• /
• pp.109-116
• /
• 2010

Infiltration and the rising level of groundwater caused by rainfall are a major cause of the landslide and sliding. In order to secure the safety factor of slope, the slope stabilization and reinforcement works are used to enhance consistency. Nailing, Slope Drainage method and the surface vegetation measures can be simultaneously applied in the Mass Nail method, which is also environmental friendly reinforcement method. To demonstrate the reinforcement effect of a strengthened slope by Mass Nail, the changes in water contents by rainfall were considered while performing Scale Model Test. As a result, safety factor of reinforced slope was about 1.4~2.3 times increased on the unstrength slope. In the case of increasing water content 10% to 22%, The maximum stress was reduced to 12%~24% at the average rate of 18% on the unstrength slope and the reinforced slope by the Mass Nail Method was reduced to 4%~23% at the average rate of 14%.

• Water for future
• /
• v.19 no.2
• /
• pp.139-148
• /
• 1986

The hydrologic response function in a small basin is expressed by the distribution function of slope length. The characteristics of topographical factors is represented to the concentration time, and the instantaneous unit hydrograph is derived as a hydrologic rsponse function by application of probobility density function. The averaging process of runoff characteristics within watershed was analyzed for a few small watershed where was split up the small basin itself. The method of calculation of the effective rainfall should play important roles in the transformation process from hydrologic response function to runoff hydrograph. In this paper, the Horton's infiltration quation is used as a method of calculation of effective rainfall, a new response function of runoff process is derived. The $\Phi$-index method and the infiltration method are tested by comparing the observed and estimated values.

• Journal of the Korean Ceramic Society
• /
• v.39 no.10
• /
• pp.948-954
• /
• 2002

Porous reaction bonded SiC with high fracture strength was developed using Si melt infiltration method for use of the support layer in high temperature gas filter that is essential to develop the next generation power system such as integrated gasification combined cycle system. The porosity and pore size of porous RBSC developed in this study were in the range of 32∼36% and 37∼90 ${\mu}m$ respectively and the maximum fracture strength of porous RBSC fabricated was 120 MPa. The fracture strength and thermal shock resistance of porous RBSC fabricated by Si melt infiltration were much improved compared to those of commercially available porous clay bonded SiC due to the formation of the strong SiC/Si interface between SiC particles. The characteristics of pore structure of porous RBSC was varied depending on the amounts of residual Si as Well as the size of SiC particle used in green body.

• Childhood Kidney Diseases
• /
• v.21 no.2
• /
• pp.47-52
• /
• 2017

Purpose: Renal ultrasonography has been widely used in children with renal disease. However, the relationship of renal echogenicity with renal pathology and function in children is not well known. Method: Ultrasound examination was performed in 75 patients undergoing renal biopsy for suspected renal disease in Konkuk University Medical Center from August 2005 to November 2015. We compared renal echogenicity to pathologic findings and renal function. Renal echogenicity was scored as 0 to 2 by comparing adjacent liver echogenicity. Three histologic characteristics were evaluated: glomerular changes, interstitial infiltration or fibrosis, and tubular atrophy. These were graded as 0 to 3, according to increasing severity. Laboratory results included urine albumin excretion and estimated glomerular filtration rate (eGFR). Results: Among pathologic findings, renal echogenicity revealed a positive correlation with interstitial infiltration or fibrosis (r=0.259, P=0.025), and with tubular atrophy (r=0.268, P=0.02). Renal echogenicity and glomerular changes were not correlated. Renal echogenicity showed a positive correlation with microalbuminuria (r=0.283, P=0.014), but a negative correlation with eGFR (r=-0.352, P=0.002). Conclusion: Increased renal echogenicity suggested severe interstitial infiltration or fibrosis and tubular atrophy among the pathologic findings. Moreover, increased echogenicity is correlated with increased urine albumin excretion and decreased eGFR. Echogenicity on ultrasonography is useful for determining the status of renal pathology and function.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.43 no.2
• /
• pp.59-68
• /
• 2001

A water balance analysis was performed for a paddy field neighboring the Dongchang stream, downstream of the Unmun reservoir, which is constructed for the urban water supply. Daily rainfall data were collected and irrigation water flow rate, drainage flow rate, evaportranspiration, infiltration, and piezometeric head were measured in the field. The flow rates were continuously observed by water level logger during the growing season. The evaportranspiration and the infiltration were measured by N-type depletion meter and cylindrical infiltrometer, respectively. PVC pipes with 12mm diameter were used for piezometric head measurement. Total Irrigation and drainage flows were 3,608mm and 1,170mm in 1999, and 3,971mm and 1,548mm in 2000, respectively. The mean and range of the daily infiltration rate were 4.4mm/d and 3.4mm/d to 5.5mm/d in 1999 and 5.1mm/d and 4.1mm/d to 6.5mm/d in 2000, respectively. The net ground water flow including the change of soil water storage was 2,855mm in 1999 and 2,540mm in 2000. The evapotranspiration was 458.3mm in 1999 and 553.5mm in 2000. The range of daily evapotranspiration rate was from 1.6 to 8.7mm/d. The return flow ratio was about 32% in 1999 and 39% in 2000 and three year average was 35% including previous study in 1997. The amount of irrigation water was much higher than design standards or references in this study, 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.

• Journal of Korean Society on Water Environment
• /
• v.34 no.3
• /
• pp.293-300
• /
• 2018

Ihe purpose of this study is to evaluate the effects the storage type of permeable concrete block paving (ST-PCBP) have on runoff reduction and infiltration increasement at Andong Maskdance Festival Square. This was accomplished using the NRCS-curve number method over the last 10 years. Two different scenarios were developed in this study for low impact development (LID) design. For the $1^{st}$ scenario, the walking path and parking lot were install using the ST-PCBP and runoff from the inline skating rink ($3,808m^2$) and lawn ($11,191m^2$) were routed to the ST-PCBP, but the rooftop runoff flowed into the storm water drainage system. For the $2^{nd}$ scenario, one of the non-structural BMPs, disconnected impervious surface (DIS), was applied so additional runoff from rooftop would enter the ST-PCBP. It was determined that ST-PCBP could significantly reduce surface runoff from the study area and increase infiltration with 71% and 88% of surface runoff reduction and 151% and 215% of infiltration increasement for scenarios 1 and 2, respectively. The effect of LID in the $2^{nd}$ scenario was better than the $1^{st}$ scenario, therefore DIS in conjunction with ST-PCBP could be a more cost-effective LID application.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.29 no.4
• /
• pp.93-105
• /
• 1987

This Study was carried out at the experimental Plot of Kang-Weon Province, Institute of Agriculture experiment, to find out Irrigation Water requirement and suitable calculating formula of evapotranspiration on Spreading Varieties of rice plant such as Seul Oak, Bokkwang and Teaback in Chuncheon Area. The evapotranspiration, infiltration, and consumptive use of water were measured by Micro Lysimeter for four years from '86yr. Also, yield of rice was investigated during same period. With the Kc Value taken from experimental value, evapotranspiration was calculated by methods of Blaney & criddle, Penman, Hargreaves and Thornthwaite by Computer using meteorological data in Chuncheon Area for twenty one yrs from '66yr to '86yr. All analyses were conducted based on average value of experiment for four years and the results are summarized as follows : 1) The yield by varieties through this experiment showed 1.06 times in Seul Oak, 1.94 times in Bokkwang and 1.89 times in Teaback more than Standard Yield. 2) The consumptive use of water including infiltration were 1.068.4mm in Seul Oak, 1,102. 6mm in Bokkwang and 1,195.6mm in Teaback 3) The evapotranspiration by Actual measurement presented 520.lmm in Seul Oak, 540.lmm in Bokkwang and 598.4mm in Teaback 4)The ratio of evapotranspiration and infiltration over Panevaporation showed 1.2 to 1.4. 5) The irrigation water reguirement by water balance were shown to be irrigated more than 584 mm / yr in average during 21 years from '66yr to '86yr for all Varieties and those for loyr frequency 693 mm in Seul Oak, 712 mm in Bokkwang and 728 mm in Teaback respectively. 6) Crop Coefficient (Ke Value) of the tested rice plant during the period were shown as Table 10. 7) Penman Method was the formula the most close to experiment Value among four different methods of Blaney & Griddle Penman, Hargreaves, and Thornthwaite.

• Journal of the Korean Ceramic Society
• /
• v.44 no.7
• /
• pp.381-386
• /
• 2007

A porous reaction bonded silicon carbide (RBSC) was fabricated by a molten Si infiltration method. The porosity and flexural strength of porous RBSC fabricated in this study were dependent upon the amount of carbon source used in the SiC/carbon preform as well as the amount of Si infiltrated into the SiC/carbon preform. The porosity and flexural strength of porous RBSC were in the range of $20 vo1.{\sim}49 vo1.%$ and $38{\sim}61 MPa$, respectively. With increase of carbon contents and molten Si for infiltration, volume fraction of the pores was gradually decreased, and flexural strength was increased. The porous RBSCs fabricated with the same amount of molten Si show less residual Si around neck with increase of carbon source, as well as a new SiC was formed around neck which resulted in the decreased porosity and improvement of the flexural strength. In addition, decrease of the porosity and increase of the flexural strength were also obtained by increase of the amount of molten Si with the same amount of carbon source. However, it was found that the flexural strength of porous RBSC depends on the porosity rather than the amount of the newly formed SiC in neck phase between SiC particles used as a starting material.

• Journal of Powder Materials
• /
• v.28 no.1
• /
• pp.51-58
• /
• 2021

The conversion of carbon preforms to dense SiC by liquid infiltration is a prospectively low-cost and reliable method of forming SiC-Si composites with complex shapes and high densities. Si powder was coated on top of a 2.0wt.% Y2O3-added carbon preform, and reaction bonded silicon carbide (RBSC) was prepared by infiltrating molten Si at 1,450℃ for 1-8 h. Reactive sintering of the Y2O3-free carbon preform caused Si to be pushed to one side, thereby forming cracking defects. However, when prepared from the Y2O3-added carbon preform, a SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C → SiC reaction at 1,450℃, 3C and 6H SiC phases, crystalline Si, and Y2O3 were generated based on XRD analysis, without the appearance of graphite. The RBSC prepared from the Y2O3-added carbon preform was densified by increasing the density and decreasing the porosity as the holding time increased at 1,450℃. Dense RBSC, which was reaction sintered at 1,450℃ for 4 h from the 2.0wt.% Y2O3-added carbon preform, had an apparent porosity of 0.11% and a relative density of 96.8%.

• Korean Journal of Materials Research
• /
• v.31 no.5
• /
• pp.301-311
• /
• 2021

The conversion of all carbon preforms to dense SiC by liquid infiltration can become a low-cost and reliable method to form SiC-Si composites of complex shape and high density. Reactive sintered silicon carbide (RBSC) is prepared by covering Si powder on top of 0.5-5.0 wt% Y₂O₃-added carbon preforms at 1,450 and 1,500℃ for 2 hours; samples are analyzed to determine densification. Reactive sintering from the Y₂O₃-free carbon preform causes Si to be pushed to one side and cracking defects occur. However, when prepared from the Y₂O₃-added carbon preform, an SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C = SiC reaction, 3C and 6H of SiC, crystalline Si, and Y₂O₃ phases are detected by XRD analysis without the appearance of graphite. As the content of Y₂O₃ in the carbon preform increases, the prepared RBSC accelerates the SiC conversion reaction, increasing the density and decreasing the pores, resulting in densification. The dense RBSC obtained by reaction sintering at 1,500 ℃ for 2 hours from a carbon preform with 2.0 wt% Y₂O₃ added has 0.20 % apparent porosity and 96.9 % relative density.