• Korean Journal of Soil Science and Fertilizer
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• v.17 no.3
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• pp.242-252
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• 1984

A port experiment was conducted to compare the effect of chemical forms of nitrogen fertilizers on the rice growth and soil characteristics. The nitrogen fertilizers used for this study were ammonium sulfate, ammonium nitrate, ammonium chloride and urea. The results are summarized as follows. 1. The differences in pH of the soil and surface water between treatments during the first week after fertilizer application were great and the pH values were in the order of urea > ammonium nitrate > ammonium sulfate > ammonium chloride treatment. However the differences were insignificant after the first week. 2. The differences in pH of the air-dried soil somewhat increased and pH values were in the order of urea > ammonium nitrate > ammonium chloride > ammonium sulfate treatment. 3. Sulfur contents of the soil and the rice leaf and N content of the rice leaf were highest when ammonium sulfate was applied. But there were few differences between the treatments in total N content of the soil and in P, K, Ca and Mg contents of the soil and the rice leaf. 4. Number of tillers and dry matter weight of the rice plant were highest in ammonium sulfate plot throughout all the growing stages. 5. Number of panicle per hill was highest in ammonium sulfate plot, and this brought the highest grain yield in ammonium sulfate plot. The lowest grain yield in ammonium nitrate plot resulted from the lowest number of panicle per hill and ripened grain ratio.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.4
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• pp.351-358
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• 2008

Purpose: This study examined the recovery of the dentin-resin bonding strength, and the difference in the bonding strength after applying pH hemostatic agents at various pH. Materials and methods: Bosmin, Hemodent, Astregedent, and Visine were used as the hemostatic agents in this study. The Bosmin, Hemodent, and Astrigedent hemostatic agents are acidic, and the Visine hemostatic agent is neutral and is used as a decongestant. Ninety human molar teeth were used as the specimen. The teeth were sectioned using a diamond wheel until the dentin was exposed and wet ground by silica paper. The specimens were divided into two groups according to the hemostatic agent used. The specimens were then subdivided into 9 groups according to the application of re etching (R group) or rinsing only (N group). A commonly used resin bonding procedure was used in the control group. The resin bonding procedure was managed dentin using celluloid capsule. In addition, the shear bond strength was measured using an Instron. Results: In general, samples with the applied hemostatic agent, with the exception of Visine, had a slightly weak bond that was similar to the control group. In addition, the rinsing only (N) group had slightly weak bond that was similar to the re etching (R) group. Conclusion: The application of a hemostatic agent on the dentin surface does not affect the shear bond strength after application for a short time. In addition, rinsing only can recover the shear bond strength making other management procedures redundant, particularly re etching.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.77-91
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• 2008

In this study, we developed a technique of applying DRASTIC, which is the most widely used tool for estimation of groundwater vulnerability to the aqueous phase contaminant infiltrated from the surface, and a groundwater flow model jointly to assess groundwater contamination potential. The developed technique is then applied to Buyeo-eup area in Buyeo-gun, Chungcheongnam-do, Korea. The input thematic data of a depth to water required in DRASTIC model is known to be the most sensitive to the output while only a few observations at a few time schedules are generally available. To overcome this practical shortcoming, both steady-state and transient groundwater level distributions are simulated using a finite difference numerical model, MODFLOW. In the application for the assessment of groundwater vulnerability, it is found that the vulnerability results from the numerical simulation of a groundwater level is much more practical compared to cokriging methods. Those advantages are, first, the results from the simulation enable a practitioner to see the temporally comprehensive vulnerabilities. The second merit of the technique is that the method considers wide variety of engaging data such as field-observed hydrogeologic parameters as well as geographic relief. The depth to water generated through geostatistical methods in the conventional method is unable to incorporate temporally variable data, that is, the seasonal variation of a recharge rate. As a result, we found that the vulnerability out of both the geostatistical method and the steady-state groundwater flow simulation are in similar patterns. By applying the transient simulation results to DRASTIC model, we also found that the vulnerability shows sharp seasonal variation due to the change of groundwater recharge. The change of the vulnerability is found to be most peculiar during summer with the highest recharge rate and winter with the lowest. Our research indicates that numerical modeling can be a useful tool for temporal as well as spatial interpolation of the depth to water when the number of the observed data is inadequate for the vulnerability assessments through the conventional techniques.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.317-324
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• 2012

To reduce non-point source pollutants in Juam Lake eco-wetlands, purification efficiencies of pollutants were investigated at three different systems. The constructed wetlands (CWs) consisted of A system, B system and C system. A system consisted of $1^{st}$ free water surface (FWS) CW, $2^{nd}$ FWS CW, $3^{rd}$ FWS CW, $4^{th}$ subsurface flow (SSF) CW and $5^{th}$ SSF CW. B system consisted of $1^{st}$ FWS CW, $2^{nd}$ FWS CW, $3^{rd}$ FWS CW, $4^{th}$ FWS CW and $5^{th}$ SSF CW. C system consisted of $1^{st}$ FWS CW, $2^{nd}$ FWS CW, $3^{rd}$ FWS CW, $4^{th}$ FWS CW and $5^{th}$ SSF CW. The concentrations of BOD, COD, SS, T-N and T-P in inflow ranged 0.20 ~ 0.91, 1.24 ~ 8.00, 0.60 ~ 8.60, 0.04 ~ 2.50 and $0.001{\sim}0.685mg\;L^{-1}$ from March to October in 2011, respectively. Removal rates of BOD, SS, T-N and T-P were high in Autumn, Spring, Spring and Summer, respectively. In A system, $1^{st}$ FWS CW, $2^{nd}$ FWS CW and $3^{rd}$ FWS CW were dominated by Leersia oryzoides. In B system, $1^{st}$ FWS CW, $3^{rd}$ FWS CW and $4^{th}$ FWS CW were dominated by Leersia oryzoides. In C system, $2^{nd}$ FWS CW and $3^{rd}$ FWS CW were dominated by Nymphaea teragona.

• Membrane Journal
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• v.22 no.2
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• pp.95-103
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• 2012

To treat nitrate and non-biodegradable organics effectively in sewage, industrial wastewater and livestock wastewater, the activated sludge process integrated by a membrane separation and a porous electrode- electrolysis was proposed and its efficiency was investigated. The proposed system was consisted of 3 processes; activated sludge, membrane filtration and electrolysis. In the study, the membrane filtration played a role in reducing the load of the electrolysis to operate the proposed process stably. The electrolysis consisted of a porous electrode to increase the efficiency due to the extension of the specific surface area. Additionally, redox reaction in the electrolysis was induced by decomposing influent water as current was applied. As a result, hydrogen free radicals and oxygen radicals as intermediates were produced and they acted as oxidants to play a role in decomposing non-degradable organics. It was environmentally-friendly process because intermediates produced by porous electrode were used to treat waste matters without supplying external reagent. Experimental data showed that the proposed process was more excellent than activated sludge process. SS removal efficiencies of the proposed process, membrane filtration and activated sludge process were about 100%, about 100% and about 90%, respectively. COD removal efficiencies of the proposed system, membrane filtration and activated sludge process were about 92%, about 84% and about 78%, respectively. T-N removal efficiencies of the proposed system, membrane filtration and activated sludge process were about 88%, about 67%, and about 58%, respectively. The SS data showed that SS was efficiently removed in the single of the membrane filtration. The COD/T-N data showed that COD/T-N of membrane hybrid process was treated by removing a little soluble organics and SS, and that COD/T-N of electrolysis hybrid process was treated by oxidize organics with high removal rate.

• Journal of the Korean Geotechnical Society
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• v.28 no.7
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• pp.41-53
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• 2012

During rainfall period, to identify the characteristics of the infiltration of moisture, electrical resistivity monitering survey was carried out to weathered zone. Four regions of geophysical exploration areas with different rock types, four regions were selected. An area consists of mafic granite and three areas are composed of sedimentary rocks (Sandstone, Shale, Unconsolidated Mudstone). Survey was conducted from June (rainy season) to November (dry season), and during the period the change in resistivity was observed. According to the result of monitoring exploration on Geumjeong and Jinju areas, for the estimation of the standard rainfall, it is necessary to estimate the effects of the antecedent rainfall during the rainy season based on the overall rainfall from June till October and also necessary to consider this for the estimation of the half period. Also, the vertical distribution of the low resistivity anomaly zone does not show that the infiltration of moisture does not occur uniformly from the surface of the ground to the lower ground but shows that it occurs along the relaxed gap of the crack or soil stratum of the weathering zone. In Pohang area, the type of moisture infiltration is different from that of the granite or sedimentary rock. Since, after the rainfall, the rate of infiltration to the lower ground is high and the period of cultivation to the lower bedrock aquifer is short, it has similar effect to that of the antecedent rainfall applied for the estimation of the standard rainfall being presently used. In Danyang, due to the degree of water content of the ground, the duration period of the low resistivity anomaly zone observed in the lower ground of the place where clastic sedimentary rock is distributed is similar to that in Pohang area. The degree of lateral water diffusion at the time of localized heavy rain is the same as that of the sedimentary rock in Jinju. According to the above analysis results, in Danyang area, the period when the antecedent rainfall has its influence is estimated as three weeks or so.

• Journal of the Korean Association of Geographic Information Studies
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• v.13 no.2
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• pp.94-106
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• 2010

Understanding of the amount of energy resources and site selection are required prior to develop Ocean Thermal Energy (OTE). It is necessary to calculate the appearance probability of difference of seawater temperature(${\Delta}T$) between sea surface layer and underwater layers. This research mainly aimed to calculate the appearance probability of ${\Delta}T$ using frequency analysis(FA) and harmonic analysis(HA), and compare the advantages and weaknesses of those methods which has used in the South Sea of Korea. Spatial scale for comparison of two methods was divided into local and global scales related to the estimation of energy resources amount and site selection. In global scale, the Probability Differences(PD) of calculated ${\Delta}T$ from using both methods were created as spatial distribution maps, and compared areas of PD. In local scale, both methods were compared with not only the results of PD at the region of highest probability but also bimonthly probabilities in the regions of highest and lowest PD. Basically, the strong relationship(pearson r=0.96, ${\alpha}$=0.05) between probabilities of two methods showed the usefulness of both methods. In global scale, the area of PD more than 10% was less than 5% of the whole area, which means both methods can be applied to estimate the amount of OTE resources. However, in practice, HA method was considered as a more pragmatic method due to its capability of calculating under various ${\Delta}T$ conditions. In local scale, there was no significant difference between the high probability areas by both methods, showing difference under 5%. However, while FA could detect the whole range of probability, HA had a disadvantage of inability of detecting probability less than 10%. Therefore it was analyzed that the HA is more suitable to estimate the amount of energy resources, and FA is more suitable to select the site for OTE development.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.1
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• pp.44-50
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• 2016

The purpose of this study was to compare and evaluate the remineralization effect of three types of fluoride varnishes on demineralized enamel of primary teeth. 40 primary teeth were decalcified by soaking them in artificial acidic solution and stored at $37^{\circ}C$ for 7 days. Then 3 varnishes - Cavity shield$^{TM}$, V varnish$^{TM}$ and MI varnish$^{TM}$ were applied respectively one time a week, for 3 weeks on the demineralized enamel surface. For the first week, MI varnish$^{TM}$ showed the highest microhardness value, V varnish$^{TM}$ was in second position, and Cavity shield$^{TM}$ showed the lowest microhardness value. However, there was no significant difference among the three groups(p > 0.05). For the second week, V varnish$^{TM}$ showed the highest microhardness value, and MI varnish$^{TM}$ came next in second position noting no significant difference (p > 0.05). Cavity shield$^{TM}$ was significantly lower than the other groups (p < 0.05). For the third week, V varnish$^{TM}$ showed the highest microhardness value, noting a significant difference from the other groups (p < 0.05). MI varnish$^{TM}$ came next, while Cavity shield$^{TM}$ showed the lowest microhardness value. However, there was no significant difference between MI varnish$^{TM}$ and Cavity shield$^{TM}$ (p > 0.05). The increase in the microhardness of groups V varnish$^{TM}$ and MI varnish$^{TM}$ were higher than that of group Cavity shield$^{TM}$ (p < 0.05), while no significant difference was noted between groups V varnish$^{TM}$ and MI varnish$^{TM}$ (p > 0.05).

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.153-162
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• 2014

Purpose: This study was assessed to investigate the change of subjective and/or objective symptoms and the light transmittance of lens caused by the use longer than recommended wearing time of daily disposable circle contact lenses (circle lens) in dry eyes. Methods: Three daily disposable circle lenses made of etafilcon A, hilafilcon B, and nelfilcon A were applied on 30 dry eyes with smaller tear volume than normal eyes in their twenties free from any eye diseases by when subjects complained any kind of discomfort. On the first and the last days of lens wearing, subjective discomfort, blinking rate, lens centration on corneal surface and visible light transmittance of lens were recorded at every case and compared. Results: The circle lens wearers complained subjective discomfort and quit the lens wearing when they wore the circle lens longer than 10 hours even though there were some difference according to the lens materials of daily disposable circle lens. However, around 20% of dry eyes could wear the circle lens made of non-ionic materials longer than 40 hours. Dry eyes showed most sensitive feeling of subjective discomfort against the circle lens made of etafilcon A among three different lens materials. On the last day of lens wearing, the representative subjective discomforts were irritation, stiffness, dryness and tiredness. When the subjects wore circle lens more than the recommended time, blinking rate was significantly increased about 20~30% regardless of lens materials when it compared with the values right after lens wearing. On the last day of lens wearing, the vertical direction of lens centration was shifted to pupil center however, its distribution in horizontal direction was wide compared with the distribution right after lens wearing. Especially, the centration of etafilcon A lens was unstable. Furthermore, the visible light transmittance of 3 different circle lenses in dry eyes has significantly been reduced around 15% averaged. Conclusions: From these results, it was known that the increase of dryness and stiffness caused by overusage of daily disposable circle lens induced excess irritation and decreased visible light transmittance and caused significant more blinking, which provoked lens decentration. It was also revealed that dry eyes showed sensitive reaction subjectively and objectively against the overusage of circle lens made of high water content/ionic lens material even there were some difference of the degree depending on the individual and the lens material. Thus, this research can be suggested as the basic reference for the education about some unexpected problems and the side effect caused by the wearing of circle lens in dry eyes.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.409-415
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• 2011

Purpose: To design applied anamorphic lens that focal length ratio is 3:1 optical system to improve detecting distance. Methods: We defined a boundary condition as $50^{\circ}{\sim}60^{\circ}$ for viewing angle, horizontal direction 36mm, vertical direction 12 mm for focal length, f-number 4, $15{\mu}m{\times}15{\mu}m$ for pixel size and limit resolution 25% in 33l p/mm. Si, ZnS and ZnSe as a materials were used and 4.8 ${\mu}m$, 4.2 ${\mu}m$, 3.7 ${\mu}m$ as a wavelength were set. optical performance with detection distance, narcissus and athermalization in designed camera were analyzed. Results: F-number 4, y direction 12 mm and x direction 36 mm for focal length of the thermal optical system were satisfied. Total length of the system was 76 mm so that an overall volume of the system was reduced. Astigmatism and spherical aberration was within ${\pm}$0.10 which was less than 2 pixel size. Distortion was within 10% so there was no matter to use as a thermal optical camera. MTF performance for the system was over 25% from 33l p/mm to full field so it was satisfied with the boundary condition. Designed optical system was able to detect up to 2.9 km and reduce a diffused image by decreasing a narcissus value from all surfaces except the 4th surface. From sensitivity analysis, MTF resolution was increased on changing temperature with the 5th lens which was assumed as compensation. Conclusions: Designed optical system which used anamorphic lens was satisfied with boundary condition. an increasing resolution with temperature, longer detecting distance and decreasing of narcissus were verified.