• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.3
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• pp.70-81
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• 1996

Solutions of geotechnical engineering problems require predictions of deformation and stresses during various stages of loading. Powerful numerical methods are available to make such predictions even for complicated problems. To get accurate results, realistic stress-strain relationships of soils are dependent on a number of factors such as soil type, density, stress level and stress path. Attempts are continuously being made to develope analytical models for soils incorporating all such factors. Isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress path for Baekma river sand were performed to investigate stress-strain and volume change characteristics of Lade's single work hardening model dependant on the stress path. In order to predicted of stress-strain and volumetric strain behavior were determined the values of parameters for the mode by the computer program based on the regression analysis. Predicted stress-strain behavior of triaxial compression tests and optional stress path tests for increasing confining pressure with parameters obtained conventional triaxial compression tests agreed with several test results but the prediction results for decreasing confining pressure reduced triaxial compression tests make a little difference with test results.

• Journal of Navigation and Port Research
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• v.36 no.5
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• pp.395-400
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• 2012

The stress-strain relationship of soil is dependent on a number of factors such as soil type, density, stress level and stress path. Th accurate stress-stain relationship can be predict using a constitutive model incorporated all influencing factors. In this study, an isotropic compression-expansion test and a series of drained conventional triaxial tests with several stress paths were performed on Baekma river sand to investigate parameters characteristics of Lade's single work hardening model depending on the stress path.. Based on test results, the parameters of yield function (h, ${\alpha}$) are not much influenced by stress level and stress path, the these parameters do affect a little bit of stress-strain behavior. The parameters h and ${\alpha}$ are closely related to failure criterion ${\eta}_1$, they can be replaced by failure criterion parament. We also observed that predicted values from the Lade's single hardening constitutive model are well matched with the observed data.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.728-737
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• 2003

To evaluate microbial data and salivary measurements from clinically compatible, culture-based screening procedures employed with children younger than 36 months old. Plaque and stimulated saliva specimens were collected from 87 children. The pH of each saliva sample was measured before and after 0.94% lactic acid was added. Specimens were diluted and plated on selective media and non-selective media. Data collected were counts of mutans streptococci (MS) and lactobacilli (LB). In addition, total viable counts (TVC) of specimens, salivary pH and buffering capacity were also assessed. Each variable was compared to caries status of subjects. According to this study, the results were as followed: 1. Highly significant correlation with caries rates were found for counts of MS and LB. 2. The specific counts/ml saliva or plaque above which caries is predicted, or below which caries is not predicted were as follows: 1) Saliva MS; $10^5$ 2) Plaque MS; $2{\times}10^5$ 3) Saliva LB; $10^3$ 4) Plaque LB; $10^3$. 3. Salivary pH and buffering capacity versus caries status were not significant. 4. Microbial screening methods based on mutans streptococci had higher predictive values and odds ratios than methods for lactobacilli. 5. MS counts were clearly the best indicators of caries status in young children. This measurement can easily be obtained in a dental clinical setting both by conventional culture techniques, or commercial kits for MS recovery.

• The Journal of Engineering Geology
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• v.18 no.4
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• pp.459-470
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• 2008

Types of slope failure related to cut slope stability are interpreted through case analyses, and also factors affecting structurally controlled instability investigated, which are developed by geologic structures along a national road No. 25 across the Cheongwon and Boeun-Guns, Chungbuk. Engineering properties such as orientation, persistence, roughness and uniaxial compressive strength of joints are analyzed by square-inventory method in three areas with well-preserved outcrops. The study area is located in Ogcheon folded bet, and are composed of quartz-schist and quartzite in the Midongsan Formation and phyllite in the Ungyori Formation. Flexural beds by folding, schistosity and cleavage besides joints are developed due to slight metamorphism. Various types of joints developed by folding are formed such as strike-parallel, strike-perpendicular, wedge and wrench joint sets by both initially regional and later superposed folding. Factors of slope instability are created by crossing the orientations of joint, cleavage, bedding and slope one another. In the case that the orientation of a slope is coincident with one of beds, factors causing large-scale failure including plane failure are increased greatly. Also in the region that orientations of the slope and bed are crossed each other at high angle, only local and minor failures are shown in the slope.

• Journal of Bio-Environment Control
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• v.6 no.2
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• pp.80-85
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• 1997

This study was conducted to select useful medium material as a replacement for the rockwool in long term bag-culture of sweet pepper. The sole use of perlite and carbonized rice hull(CRH) as well as their mixture with various combinations were compared to the rockwool. The results are summarized as the followings : 1. Plant height and number of leaves did not significantly differ among media. However, in the mixture of CRH(1) : Perlite(1), stem diameter was thicker; plant weight and root weight were heavier, and T/R ratio was lower. 2. Although fruit length and number of fruits did not significantly differ among media, the mixture of CRH(1) : Perlite(1) provided longer fruit length, more fruits, heavier fruit weight, and greater yield. 3. Monthly yield was continuously increased from the first harvest in November to the harvest in May next year. The amount of increase in the fruit yield of the mixture of CRH(1) : Perlite(1) from the first harvest to the final harvest was significantly greater than the amount of increase of other media. 4. The amount of total nitrogen and phosphate was higher in mixture of CRH (1) : Perlite(1), while the amount of other elements did not significantly differ among mixtures.

• Journal of Korean Society of Forest Science
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• v.89 no.3
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• pp.397-404
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• 2000

This study was carried out to investigate the influence of the road structure and site conditions on side-ditch stability of forest road. For experimental purposes, the forest road in the Kwangrung Experimental Forest, Korea Forestry Research Institute, was chosen as a study site. A total of 556 plots wes set up as every longitudinal gradient changing points by belt-transect method. Data of 10 road structural characteristics and side-ditch stability were collected from each plot and analysed by Quantification II. The main factors in order of partial correlation coefficient were longitudinal gradient, road position, inclination of cut-slope, constituent material of cut-slopes, distance of surface flow, cross-sectional shape of road, pavement material, vegetation of cut-slopes and length of cut-slope. The erosion of side-ditch of forest road occurred in the following cases; more than 8% of the longitudinal gradient, road position of hill under side and foot hill, more than $50^{\circ}$ of inclination of cut-slope, constituent material of cut-slopes of hard soil and gravel soil, more than 80m of distance of surface flow, pavement material with earth or gravel, more than medium covered of vegetation of cut-slopes, and the straight and convex form of road-bed.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.775-784
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• 2009

Weathered foliation could act as a critical failure plane because this type of plane tend to have low roughness and long extensions. A big constructed slope at $\bigcirc\bigcirc$ road construction site was failed due to the block movement along a fault zone which is parallel to foliation. Tectonic activity reactivated a fault zone parallel to foliation, and the fault clay within the shear zone metamorphosed retrogressively to chrolite. The failed block moved when the block weigh lost the balancing with the resisting force of the retrogressively metamorphosed chrolite. Evaluating the three dimensional distribution of the foliation was critical for establishing a plan for the stabilization of the slope. For this purpose, 10 boreholes were drilled as a lattice distribution, and the BIPS analyses are performed at each boreholes. The fractures measured in the boreholes are projected into 15 cross sections and their distributions are analysed, using Fracjection software. The projection analyse show that the strike of the foliation gets dipper towards left side of the slope. This geometry indicates that there are more failure block geometry at left side of the slope. Potential failure planes are searched using the projection method, and these information are provided for further support design.

• The Journal of Engineering Geology
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• v.15 no.2 s.42
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• pp.201-212
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• 2005

A photogrammetric camera system and a software have been built for capturing planned stereo images. To evaluate the system,25 planar data from a constructed rock slope were measured using both geological compass and photo system. Comparison of the data groups from both system showed matching relationship that falls within the error range of $5.25\pm4.53$ in strike and $3.18\pm3.17$ in dip angles, when the 2 standard deviation error distributions were considered. To evaluate the errors of the Photo matching and non planarity of the surface, orientations of the same plane were repeatedly measured 20times. These measurements showed error ranges of $8.2\pm3.4$in strike and $6.6\pm3.4$ in dip angle, considering the same error distributions. Measured strikes and dips were compared with the corresponding compass measurements in 5 constructed. slopes to test the system. Stereonet plots showed that the photo system measured data coincided well with the compass measurements. With these evaluations, the photo system can measure the planar structure in inaccessible locations with reliable accuracy at the same time reducing the data gathering period therefore resulting to an efficient geological survey.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.122-129
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• 2007

The purpose of this study was to evaluate the effects of a various light curing time on the residual monomers released from light-cured dental sealant, and to examine the effectiveness of surface treatment in reducing the oxygen-inhibited layer of light-cured dental sealant($Helioseal^{(R)}$ F, Vivadent, Liechtenstein). Specimens were cured with a halogen light curing unit(XL 3000, 3M, USA) for 20, 40, 60s. Surface treatment of a light-cured dental sealant included no treatment(control group), a 10-seconds exposure to distilled water(Group I), 10-seconds manual application using a cotton pellet wetted with 75% alcohol(Group II), and 10-seconds application of a water/pumice slurry using a rubber cup on a slow-speed handpiece The specimens were eluted in distilled water for 10 minutes. All elutes were analyzed by HPLC for identification and quantitive analysis of monomers. The results of this study can be summarized as follows. 1. None of the chromatograms of the tested sealant displayed peaks with the same retention time as that of the standard solution, except for TEGDMA. 2. The release of TEGDMA decreased with increasing curing time in conventional halogen light. 3. All surface treatment group had a decrease of monomer release in comparison with no treatment group. 4. Treatment that Group III eliminated the greatest amount of any type of residual monomers. 5. The elution of unreacted monomers from curing with halogen curing unit for 60s and Group III was less than other groups.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.1
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• pp.70-76
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• 2006

The aim of this study was comparison of effectiveness of surface treatment methods in reducing the oxygen-inhibited layer of a commercially available freshly polymerized, light cured dental sealant($concise^{TM}$, 3M, St Paul, USA). Surface treatment groups were consisted of no treatment(negative control group) and 3 experimental groups according to surface treatment of light-cured sealant. Experimental group I was 10 seconds' exposure to distilled water syringe, group II was 10 seconds' manual application using a cotton pellet wetted with 75% alcohol and group III was 10 seconds' prophylaxis with pumice/water slurry using rubber cup on a slow-speed handpiece. All specimens were immersed in 5ml distilled water and stored at 37c water bath for 10 minutes. All eluates were analyzed by HLPC for identification and quantitive analysis of monomers. The results of this study can be summarized as follows. 1. None of the chromatograms of the tested sealant displayed peaks with the same retention time as that of the standard solution, except for TEGDMA. 2. All surface treatment group had a statistically significant decrease of monomer release in comparison with no treatment group. 3. Removal effects of unreacted monomer in group III was statistically significant in comparison with group I and group II. These results revealed that mechanical method using pumice and rubber cup is the most effective in removing residual monomer and may be valuable to be used effectively in clinic.