• Journal of Korean society of Dental Hygiene
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• v.17 no.5
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• pp.817-826
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• 2017

Objectives: The aim of this study was to investigate the effects of bamboo salts on remineralization effects on subsurface of artificial carious enamel. Methods: Incipient carious enamel was formed in permanent bovine incisors and then specimens were divided into three groups randomly: 3% bamboo salt (BS), 2% (NaF) and the solution of mixed 3% BS and 2% NaF. For remineralization, specimens of each of the three groups were treated for 24 hrs at $37^{\circ}C$ incubator. After treatment, specimens were analyzed using SEM and VHN. Statistical analysis used was one-way ANOVA. Results: In SEM observation, the BS group showed narrower distances between enamel rods than the cases of incipient subsurface caries enamel. The NaF and BS+NaF groups showed that the enamel rods near the surface were destructed, and innumerable round small particles were deposited near the surface of enamel. The BS+NaF group showed more minerals attachment between enamel rods than the cases of other groups. The differences in subsurface microhardness (${\Delta}VHN$) increased all of three groups in total by $80{\mu}m$. The ${\Delta}VHN$ of the BS+NaF group increased significantly more than NaF and BS groups in depth of $50{\mu}m$, $80{\mu}m$. Conclusions: The 3% bamboo salt with 2% NaF solution was found to increase subsurface hardness of incipient caries enamel. Thus, bamboo salt will be used to contribute to prevention on dental caries.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.372-378
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• 2015

Growing crops under different soil textures may affect crop growth and yield because of soil N availability, soil N leaching, and plant N uptake. The objective of this study was to evaluate effects of three different soils (sandy loam, loam, and clay loam) on cucumber (Cucumis sativus L.) yield, nitrogen (N) use efficiency (NUE), and water use efficiency (WUE) by subsurface drip fertigation in the greenhouse. Three different soil textures are sandy loam, loam, and clay loam with 3 replications. The dimension of each lysimeter was $1.0m(W){\times}1.5m(L){\times}1.0m(H)$. Cucumber was transplanted on April $8^{th}$ and Aug $16^{th}$ in 2011. The subsurface drip line and tensiometer was installed at 30 and 20 cm soil depth, respectively. An irrigation with $100mg\;NL^{-1}$ concentration was automatically applied when the tensiometer reading was 10 kPa. Volumetric soil water content for cucumber cultivation was the highest in 30 cm soil depth regardless of soil texture and was lowered when soil depth was deeper. The volumetric soil water contents at soil depths of 10, 30, 50, and 70 cm were the highest at clay loam, followed by loam, and sandy loam. The growth of cucumber at the $50^{th}$ day after transplanting was the lowest at sandy loam. Cucumber fruit yields were similar for all three soil textures. The highest amount of water use at sandy loam was observed. Nitrogen and water use efficiencies for cucumber were higher for clay loam, followed by loam and sandy loam, while the amount of N leaching was the greatest under sandy loam, followed by loam, and clay loam. Overall, growing cucumber on either loam or clay loam is better than sandy loam if subsurface drip fertigation is used in the greenhouse.

• Journal of Soil and Groundwater Environment
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• v.27 no.spc
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• pp.64-74
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• 2022

The conceptual site model (CSM) is used as a key tool to support decision making in risk based management of contaminated sites. In this work, CSM was applied in Jeonju Industrial Complex where site investigation for groundwater contamination was conducted. Site background information including facility types, physical conditions, contaminants spill history, receptor exposure, and ecological information were collected and cross-checked with tabulated checklist necessary for CSM application. The CSM for contaminants migration utilized DNAPL transport model and narrative CSMs were constructed for source to receptor pathway, ecological exposure route, and contaminants fate and transport in the form of a diagram or flowchart. The component and uncertainty of preliminary CSM were reviewed using the data gap analysis while taking into account the purpose of the survey and the site management stage at the time of the survey. Through this approach, the potential utility of CSM was demonstrated in the site management process, such as assessing site conditions and planning follow-up survey work.

• Journal of the Korean Geotechnical Society
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• v.22 no.7
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• pp.45-54
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• 2006

Resistivity cone penetrometer test (RCPT) can be employed at a relatively low cost for in-situ delineation of subsurface contamination. While the resistivity measurement has a potential to investigate the subsurface contamination, resistivity measurements alone will lead to some degree of ambiguity in the results. In this study, capacitance measurement was incorporated into the RCPT to overcome the ambiguity inherent in electrical resistivity measurements. This study is focused on verifying the applicability of resistivity and capacitance measurements of CPT module to provide information on subsurface contaminated by heavy metal and petroleum hydrocarbon. Laboratory model tests were performed to evaluate the sensitivity of the measured resistivity and relative capacitance on the water content and different types of contaminants. Test results show that simultaneous measurement of electrical resistivity and capacitance can give more reliable information on subsurface contamination. Electrical measurements of the CPT module showed high applicability to be used in detecting saturated soils contaminated by heavy metal and diesel plume floating above the groundwater table.

• Economic and Environmental Geology
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• v.56 no.5
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• pp.501-514
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• 2023

Forest fires can generate numerous pollutants through the combustion of vegetation and cause serious environmental problems. The global warming and climate change will increase the frequency and scale of forest fires across the world. In Korea, many nuclear power plants (NPPs) are located in the East Coast where large-scale forest fires frequently occur. Therefore, understanding the sorption and transport characteristics of radionuclides in the forest fire areas is required against the severe accidents in NPPs. This article reviewed the physiochemical changes and contamination of groundwater and soil environments after forest fires, and discussed sorption and transport of radionuclides in the subsurface environment of burned forest area. We considered the geochemical factors of subsurface environment changed by forest fire. Moreover, we highlighted the need for studies on changes and contamination of subsurface environments caused by forest fires to understand more specific mechanisms.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.543-550
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• 1999

Hazardous substances produced from industrial sectors have caused serious contamination of soils and groundwater. The hydrophobic organic compounds in the subsurface are hard to be decomposed, and as they soil on the soil or last as a NAPL they might contaminate the groundwater for a long time. Although we recognize the danger of contaminated subsurface, very little was known about the effective remediation technique. This paper focuses on the remediation of the p-Cresol which contaminated subsurface by applying the surfactant-enhanced description technique. Sorption characteristics of soils and organic compounds are studied, and the applications of surfactant solution are studied for effective rededication. The results from this study could be used as some data for surfactant-enhanced rededication. The flexible-wall permeameter tests are performed in which in-situ remediation is simulated. Results show that triton X-100 at 2% solution disrobes p-Cresol 1.7 times as much as water description in the flexible-wall permeameter tests.

• Tribology and Lubricants
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• v.20 no.5
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• pp.252-258
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• 2004

In this study, using high cycle fatigue (HCF) criteria, the simulation of rolling contact fatigue is conducted under elliptical contact. The HCF criteria fall into three categories: the critical plane approach, the stress invariant approach and the approach based on the mesoscopic scale. The accurate calculation of contact stresses and subsurface stresses is essential to the prediction of crack initiation life. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsurface stress field is obtained using rectangular patch solutions. The simulation results show that the critical load is decreasing rapidly and the site of crack initiation also moves rapidly to the surface from the subsurface when the friction coefficient exceeds a specific value for all of three fatigue criteria.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.331-337
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• 2000

A numerical procedure for contact analysis and calculating subsurface stress was developed. The procedure takes the advantage of signal processing technique in frequency domain to achieve shorter computing time. Boussinesq's equation was adopted as a response function in contact analysis. The validity of this procedure was proved by comparing the numerical results with the exact solutions. The fastness of this procedure was also compared with other algorithm.

• Economic and Environmental Geology
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• v.27 no.3
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• pp.313-321
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• 1994

Structural interpretation by using subsurface attitude of coal seam and outcrop patterns of folds and faults shows that wrench and thrust tectonics took place simultaneously in the study area. From the interference patterns of fold axes, three generations of folding are suggested: $F_1$ (NE-SW), $F_2$ (N-S), and $F_3$ (E-W). Differential displacement of rock mass from north to south yields to E-W fold and Osypcheon Fault. Geometry of subsurface coal seam show different patterns comparing to those of surface outcrop because of shallow-depth crustal shortening which took place post Cretaceous.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.66-69
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• 2001

A subsurface containment system which is constructed by pumping a gelling liquid (Colloidal Silica) into the unsaturated medium is investigated by developing a mathematical model and conducting numerical simulations. The proposed model is verified by comparing experimentally and numerically determined hydraulic conductivities of gel-treated soil columns at different Colloidal Silica (CS) injection volumes. The numerical experiments indicate that an impermeable gel layer is formed within the time period twice the gel-point. At the Same normalized time, the CS solutions with lower NaCl concentrations result ill further migration and poor Performance in plugging the pore space.