• 한국물환경학회지
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• 제26권6호
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• pp.943-947
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• 2010

Runoff ratio of paddy fields for the application of Event Mean Concentration (EMC) method was studied. To measure actual runoff ratio of paddy fields, a field monitoring was conducted for 2008 ~ 2009 period. Long-term rainfall data of four cities in major river basins were analyzed and weighting factors were developed to consider temporal and spatial variation of rainfall distribution of Korean peninsula. The observed runoff ratio ranged 0.00 ~ 1.20 and arithmetic mean were 0.25, respectively. However, the representative runoff ratio for paddy fields was determined as 0.41 according to the method suggested by National Institute of Environmental Research (NIER).

• 한국물환경학회지
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• 제29권4호
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• pp.504-513
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• 2013

Water quality trends for major tributaries (66 sites) in the Yeongsan River basin of Korea were examined for 12 parameters based on water quality data collected every month over a period of 12 months. The complex data matrix was treated with multivariate analysis such as PCA, FA and CA. PCA/FA identified four factors, which are responsible for the structure explaining 78.2% of the total variance. The first factor accounting 27.3% of the total variance was correlated with BOD, TN, TP, and TOC, and weighting values were allowed to these parameters for grade classification. CA rendered a dendrogram, where monitoring sites were grouped into 5 clusters. Cluster 2 corresponds to high pollution from domestic wastewater, wastewater treatment and run-off from livestock farms. For grade classification of tributaries, scores to 10 indexes were calculated considering the weighting values to 3 parameters as BOD, TN and TP which were categorized as the first factor after FA. The highest-polluted group included 10 tributaries such as Gwangjucheon, Jangsucheon, Daejeoncheon, Gamjungcheon, Yeongsancheon. The results indicate that grade classification method suggested in this study is useful in reliable classification of tributaries in the study area.

• 한국물환경학회지
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• 제29권4호
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• pp.523-530
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• 2013

This study has been carried out to clarify the characteristics of discharge and pollutant loading according to flow conditions at jiseok stream watershed (JSW). A flow rate and pollutant load in the study watershed were estimated by equation of stage-discharge and discharge-loads rating curve. By using the methods above, I've evaluated the water quality (WQ) of the JSW if it is satisfied with the standard target. I've collected the data of BOD and T-P from the JSW every 8 days for the duration of 12 months. And then, I've schematized the data upon the load duration curve and the results showed me that the WQ of JSW was satisfied with the standard target. I've also collected the same data every each day for the duration of 12 months from JSW and have schematized the data again. And the results showed that it also was satisfied with the standard target. To be concluded, I've determined that point pollution sources of JSW gives more significant impacts to the WQ than non-point pollution sources of JSW and hence, as time goes, point pollution sources will keep depriciating the WQ of JSW. Therefore, further efforts will be required to JSW to maintain the WQ.

• 한국재료학회지
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• 제27권11호
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• pp.590-596
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• 2017

We demonstrated a CNT synaptic transistor by integrating 6,6-phenyl-C61 butyric acid methyl ester(PCBM) molecules as charge storage molecules in a polyimide(PI) dielectric layer with carbon nanotubes(CNTs) for the transistor channel. Specifically, we fabricated and compared three different kinds of CNT-based synaptic transistors: a control device with $Al_2O_3/PI$, a single PCBM device with $Al_2O_3/PI:PCBM$(0.1 wt%), and a double PCBM device with $Al_2O_3/PI:PCBM$(0.1 wt%)/PI:PCBM(0.05 wt%). Statistically, essential device parameters such as Off and On currents, On/Off ratio, device yield, and long-term retention stability for the three kinds of transistor devices were extracted and compared. Notably, the double PCBM device exhibited the most excellent memory transistor behavior. Pulse response properties with postsynaptic dynamic current were also evaluated. Among all of the testing devices, double PCBM device consumed such low power for stand-by and its peak current ratio was so large that the postsynaptic current was also reliably and repeatedly generated. Postsynaptic hole currents through the CNT channel can be generated by electrons trapped in the PCBM molecules and last for a relatively short time(~ hundreds of msec). Under one certain testing configuration, the electrons trapped in the PCBM can also be preserved in a nonvolatile manner for a long-term period. Its integrated platform with extremely low stand-by power should pave a promising road toward next-generation neuromorphic systems, which would emulate the brain power of 20 W.

• 환경영향평가
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• 제21권6호
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• pp.917-925
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• 2012

In this study, we report the runoff characteristics of pollutants for Tamjin A and B watershed in Tamjin river basin using statistical analysis, such as correlation analysis and regression equation. Flow rate and water qualtiy data collected from 2 sampling sites(Tamjin A and B watershed) during 3 years(2009~2011) were analyzed for biochemical oxygen demand(BOD), total nitorgen(TN), total phosphorus(TP) and suspended solid(SS). The results showed that strong correlations were observed between flow rate and SS in Tamjin A, while weak correlations were observed among the BOD, TN, and TP. In Tamjin B, strong correlations were observed among the flow rate, SS and T-P except BOD and TP. Meanwhile, the values of $R^2$ for regression equations between flow rate and pollutants load were greater than 0.7. Results of these statistics indicated that there was a good agreement between flow rate and pollutants load. Also, the flow rate exponents of regression equations for BOD, TN, and TP were smaller than 1 in Tamjin A. In Tamjin B, flow rate exponents of regression equation for BOD and TP were smaller than 1. These results indicated that concentrations of BOD, TN, TP in Tamjin A and concentrations of BOD and TP were decreased as the flow rate was increased. This means that rater than nonpoint sources, point sources affect BOD, TN and TP in Tamjin A and BOD and TP in Tamjin B.

• 응용통계연구
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• 제26권4호
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• pp.611-622
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• 2013

Mudholkar와 Tian (2002)이 제시한 엔트로피 기반 검정은 위치모수와 척도모수가 모두 알려져 있지 않거나 척도 모수만 알려져 있는 역가우스분포의 적합을 알아보고자 하는 경우에만 사용이 가능하다. 본 논문에서는 위치모수와 척도모수가 모두 알려져 있거나 위치모수만 알려져 있는 역가우스분포의 적합에도 적용할 수 있는 엔트로피 기반 적합도 검정을 소개한다. 이 검정은 확률적분변환에 기초를 두고 있다. 모의실험을 통해서 추정한 표본크기와 윈도크기에 따른 검정통계량의 기각값과 근사기각값을 얻기 위한 계산공식을 제시한다. 제안한 검정과 Mudholkar와 Tian (2002)의 검정을 검정력 측면에서의 성능을 비교하고자 모의실험을 수행한다. 모의실험 결과에서 제안한 검정은 기존의 엔트로피 기반 검정보다 더 좋은 검정력을 가지는 것으로 나타난다.

• Journal of Periodontal and Implant Science
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• 제47권6호
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• pp.381-387
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• 2017

Purpose: The aim of this study was to evaluate volumetric and histologic changes in edentulous alveolar ridge areas after ridge preservation using basic fibroblast growth factor-2 (bFGF-2) in combination with collagenated biphasic calcium phosphate (BCP). Methods: The experiments were performed in 6 adult male beagle dogs. The following 3 groups were created: 1) ridge preservation with bFGF-2 and collagenated BCP (experimental group), 2) ridge preservation with collagenated BCP (positive control group), and 3) a negative control group in which no ridge preservation procedure was performed. Volumetric change analysis was performed using an optical scanner and casts. Histological observations were made using light microscopy. Results: After the initial swelling subsided, the magnitude of the volumetric change in the experimental group and positive control group was smaller than in the negative control group. In the experimental group, a distinct trend was observed for the resorption of residual bone and collagen fibers at 4 weeks and for more mature bone and faster healing at 12 weeks. Conclusions: Based on the findings of the present study, bFGF-2 may be considered for use as a therapeutic molecule in ridge preservation procedures.

• 응용통계연구
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• 제26권1호
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• pp.37-47
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• 2013

Q-Q 플롯은 자료에 대한 분포적 가정을 평가하기 위해서 사용되는 편리하고 효과적인 그래프 방법이다. Q-Q 플롯은 자료의 분포와 이론적 분포를 비교하기 위한 확률플롯으로 자료에서의 분위수와 이에 대응하는 이론적 분위수를 각각 수직축과 수평축으로 해서 그린 산점도의 형태를 취한다. 본 논문에서는 확률변수 X가 위치모수 ${\mu}$와 척도수 ${\lambda}$를 가지는 역가우스분포를 따르면, 변환된 확률변수 $Y={\mid}\sqrt{\lambda}(X-{\mu})/{\mu}\sqrt{X}{\mid}$는 평균이 0이고 분산이 1인 표준반접정규분포를 하게 되는 분포적 결과를 활용하여 역가우스분포 Q-Q 플롯의 구축방법을 소개한다. 역가우스분포와 다른 분포를 따르는 자료를 대상으로 그린 Q-Q 플롯에서 나타나는 점들의 형태를 알아보고자 모의실험을 수행하고 그 결과를 제시한다. 실제 자료에 대한 사례분석을 통해 제안한 Q-Q 플롯의 유용성을 보인다.

• 한국물환경학회지
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• 제28권6호
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• pp.813-818
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• 2012

BOD and COD are currently used for water quality indices, but adoption of TOC for TMDL (Total Maximum Daily Load) is being suggested. Estimation of TOC using existing BOD and COD data is very important to diagnosis water quality trend when TOC is used for water quality index of organic matter in the future. The relationships between BOD COD and TOC in runoff from paddy fields were investigated during 2008-2011. The observed mean concentration of EMCs (Event Mean Concentration) for BOD, COD, TOC were 3.87, 10.97, 7.26 mg/L respectively. The correlation coefficients between BOD-TOC and COD-TOC were 0.42, 0.73, respectively. The coefficient of determination of regression equation for BOD-TOC and COD-TOC were 0.18, 0.53 respectively. Even though, conversion of COD data to TOC seems to be rather reliable than that of BOD-TOC, further monitoring is recommended to ensure better interpretation of relationship among BOD, COD and TOC.

• 상하수도학회지
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• 제18권6호
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• pp.731-741
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• 2004

The purpose of this study was to evaluate the potential of a gamma ray irradiation to decompose hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in an aqueous solution. The decomposition reaction of RDX by gamma ray irradiation was a first-order kinetic over the applied initial concentrations (10-40mg/L). The dose constant was strongly dependent on the initial concentration of the RDX. The removal of RDX was more efficient at pH below 3 and at pH above 11 than at neutral pH (pH 5-9). The required irradiation dose to remove 99% of the RDX (40mg/L) was 4, 8 and 1 kGy, at pH 2, 7 and 13, respectively. The dose constant was increased by two folds and over twelve folds at pH 2 and 13, respectively, when compared with that at pH 7. When an irradiation dose of 20 kGy was applied, the removal efficiencies of TOC were 80, 57 and 91% at pH 2, 7 and 13, respectively. Ammonia and nitrate were detected as the main nitrogen byproducts of RDX and formic acid was detected as an organic byproduct. The results showed that a gamma ray irradiation was an attractive method for the decomposition of RDX in an aqueous solution and it was found that a strong alkaline pH over 12 should be applied to the decomposition reaction of RDX.