• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.362-362
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• 2023

한정된 수자원의 이용 및 관리로 매년 물 부족과 물 배분 의사결정 문제가 발생하고 있다. 50년간(1965~2014년) 수자원의 총량은 약 1.2배 증가한 반면 인구수 약 1.8배, 생·공·농업용수의 수요는 약 5배가 증가(국회입법조사처, 2018) 했을 뿐 아니라, 기후변화의 영향으로 인한 강수량의 변화와 지역별 편차가 커져 지속가능한 물관리 필요성이 증대되고 있다. 따라서 효율적인 물관리를 위해서는 관리부처가 분절되어 있는 물순환 계통의 데이터를 통합하는 것이 우선시되어야 하고 이를 통해 물순환 모니터링/평가/예측 기술을 개발할 수 있다. 본 연구에서는 생활용수 물순환 계통 통합 DB를 정의 및 구축하였다. 도시의 관점에서 물순환 시스템을 순차적으로 물 유입(수원~취수장)/전달(정수장~급수지역)/유출(하(폐)수처리장~방류구)의 개념으로 설정하고 DB정의서를 마련하였다. 연구대상지는 가뭄이 장기화가 되고 있는 전라남도중 물순환 계통이 비교적 단순한 네트워크로 형성되어 있는 함평군 도시지역으로 선정하였다. 연구 기간은 총 5년(2017년 1월 1일~2021년 12월 31일)이고 일 단위 실계측자료 위주의 원자료를 구축하였다. 이를 이상치 탐지, 제거, 대체의 과정을 거쳐 품질 보정하고 정제된 시계열 자료에 대한 특성 분석을 하였다. 그 결과, 물순환 계통 내 주요 지점 간의 상관관계 및 지연시간을 통한 물흐름의 시계열적 특성을 파악할 수 있었으며 모형의 적합도를 판단하는 데 활용되는 통계량과 유의미하지 않은 잔차의 자기상관성을 볼 때 물 유입-전달-유출의 단기 예측을 위한 ARIMA(Auto-regressive Integrated Moving Average) 모형의 구축도 가능할 것으로 판단되었다. 다만 여름철 발생하는 방류량의 첨두값을 설명하기 위해서는 강우에 의한 불명수 발생으로 증가하는 방류량을 묘사할 수있어야 하므로 향후에는 물순환계통 외 해당 지역의 불명수(강우 효과)도 하수 방류량의 주요 입력 요인으로 추가 검토할 필요가 있다.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1429-1433
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• 2010

수공구조물의 설계, 수자원 관리계획의 수립, 재해영향 검토 등을 수행할 때, 재현기간에 따른 확률개념의 강우량, 홍수량, 저수량 등을 산정하여 사용하게 되며, 보통 대상지역의 장기 수문관측 자료를 이용하여 수문사상의 확률분포를 산정한 후 재현기간을 연장하여 원하는 설계빈도에 해당하는 양을 추정하게 된다. 미계측지역 또는 관측자료의 보유기간이 짧은 지역의 경우는 지역빈도 분석 결과를 이용하게 된다. 지역빈도해석을 위해서는 강우자료들의 동질성을 파악하는 것이 가장 기본적인 과정이 되며 이를 위해 통계학적인 범주화분석이 선행되어야 한다. 지점 빈도분석의 수문학적 동질성 판별을 위해 L-moment 방법, K-means 방법에 의한 군집분석 등이 주로 사용되며 관측소 위치좌표를 이용한 공간보간법을 적용하여 시각화하고 있다. 강수량은 시공간적으로 변하는 수문변량으로서 강수량의 시간적인 특성 또한 강수량의 특성을 정의하는데 매우 중요한 요소이다. 이러한 점에서 본 연구를 통해 강수지점의 공간적인 좌표 및 강수량의 양적인 범주화에 초점을 맞춘 기존 지역빈도분석의 범주화 과정에 덧붙여 시간적인 영향을 고려할 수 있는 요소들을 결정하고 이를 활용할 수 있는 범주화 과정을 제시하고자 한다. 즉, 극치강수량의 발생 시기에 대한 정량적인 분석이 가능한 순환통계기법을 이용하여 관측 지점별 시간 통계량을 산정하고, 이를 극치강수량과 결합하여 시 공간적인 특성자료를 생성한 후 이를 이용한 군집화 해석 모형을 개발하는데 연구의 목적이 있다. 분석 과정에 있어서 시간속성의 정량화 및 일반화는 순환통계기법을 사용하였으며, 극치강수량과 발생시점의 속성자료는 각각의 평균과 표준편차를 이용하였다. K-means 알고리즘을 이용해 결합자료를 군집화 하고, L-moment 방법으로 지역화 결과에 대한 검증을 수행하였다. 속성 결합 자료의 군집화 효과는 모의데이터 실험을 통해 확인하였으며, 우리 나라의 58개 기상관측소 자료를 이용하여 분석을 수행하였다. 예비해석 단계에서 100회의 군집분석을 통해 평균적인 centroid를 산정하고, 해당 값을 본 해석의 초기 centroid로 지정하여, 변동적인 클러스터링 경향을 안정화시켜 해석이 반복됨에 따라 군집화 결과가 달라지는 오류를 방지하였다. 또한 K-means 방법으로 계산된 군집별 공간거리 합의 크기에 따라 군집번호를 부여함으로써 군집의 번호순서대로 물리적인 연관성이 인접하도록 설정하였으며, 군집간의 경계선을 추출할 때 발생할 수 있는 오류를 방지하였다. 지역빈도분석 결과는 3차원 Spline 기법으로 도시하였다.

• Journal of Chest Surgery
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• v.31 no.10
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• pp.945-951
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• 1998

Background: Although profound hypothermia with total circulatory arrest(TCA) is a valuable maneuver in cardiac surgery, its applications have been limited due to serious complications, especially cerebral damage. In this study, the possible role of creatinine kinase-BB(CK-BB), an index enzyme of ischemic cerebral damage, was assayed as a parameter for the assessment of the cerebral complications after TCA. Hemoglobin(Hb), ionized calcium(Ca++), and blood glucose levels were also assessed as clinical parameters involved in cerebral damage. Materials and methods: Among patients with congenital heart disease, 18 patients who had been operated on with TCA were randomly selected and divided into two groups: 6 with acyanotic and 12 with cyanotic heart disease. Arterial blood from each patient was collected before and after TCA at scheduled times(15 min., 30 min, 1, 2, 4, 8, and 12hr). The levels of CK-BB, Hb, Ca++, and blood glucose were assessed in each sample. Results: As a whole, correlation between CK-BB level and blood sampling time after TCA was not statistically significant. Also, the difference in the level of CK-BB after TCA was not significant between the acyanotic and cyanotic groups. The levels of Hb and CK-BB correlated significantly. Conclusions: The results, which showed no correlation between the alterations in CK-BB level and the TCA duration, suggest that the single assay of the CK-BB level is not a representative measurement for the assessment of cerebral damage after TCA. Also, the cyanotic congenital heart disease group is not more vulnerable to cerebral damage induced by TCA.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2B
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• pp.191-198
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• 2010

Assessing seasonality of precipitation is necessarily required to establish future plans and policies for water resources management. In this regard, a main objective of the study is to introduce an effective approach for assessing the seasonality of the precipitation and evaluate the seasonality through the proposed one. We have used circular statistics to characterize the seasonality on the precipitation in Korea. The circular statistics allow us to effectively assess changes in timing of the seasonality in detail. It was found that peak time on monthly rainfall occurred between end of June and early July in southern coastal area while the timing was delayed in northern part of Korea because of monsoon moving in from south to north. In case of annual daily peak precipitation, spatio-temporal variation of the peak time was increased. It is mainly because of geophysical effects, frequency and paths of typhoons. Finally, temporal variations on the timing of the peak seasons were evaluated through circular statistics by 30-year moving average data. The peak season in the Northen part of Korea (e.g. Seoul and Gangrung) has been moved back from early July to end of July while the peak season has been moved up from middle of July to early July in the Southern part of Korea (e.g. Busan and Mokpo). It seems that changes in seasonality are mostly modulated by variability in the east-asia monsoon system.

• Journal of Chest Surgery
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• v.38 no.2 s.247
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• pp.101-109
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• 2005

Background: In sudden cardiac arrest, the effective maintenance of coronary artery blood flow is of paramount importance for myocardial preservation as well as cardiac recovery and patient survival. The purpose of this study was to directly compare the effects of pulsatile and non-pulsatile circulation to coronary artery flow and myocardial preservation in cardiac arrest condition. Material and Method: A cardiopulmonary bypass circuit was constructed in a ventricular fibrillation model using fourteen Yorkshire swine weighing $25\~35$ kg each. The animals were randomly assigned to group I (n=7, non-pulsatile centrifugal pump) or group II (n=7, pulsatile T-PLS pump). Extra-corporeal circulation was maintained for two hours at a pump flow of 2 L/min. The left anterior descending coronary artery flow was measured with an ultrasonic coronary artery flow measurement system at baseline (before bypass) and at every 20 minutes after bypass. Serologic parameters were collected simultaneously at baseline, 1 hour, and 2 hours after bypass in the coronary sinus venous blood. The Mann-Whitney U test of STATISTICA 6.0 was used to determine intergroup significances using a p value of < 0.05. Result: The resistance index of the coronary artery was lower in group II and the difference was significant at 40 min, 80 min, 100 min and 120 min (p < 0.05). The mean velocity of the coronary artery was higher in group II throughout the study, and the difference was significant from 20 min after starting the pump (p < 0.05). The coronary artery blood flow was higher in group II throughout the study, and the difference was significant from 40 min to 120 min (p < 0.05) except at 80 min. Serologic parameters showed no differences between the groups at 1 hour and 2 hours after bypass in the coronary sinus blood. Conclusion: In cardiac arrest condition, pulsatile extracorporeal circulation provides more blood flow, higher flow velocity and less resistance to coronary artery than non-pulsatile circulation.

• The korean journal of orthodontics
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• v.39 no.6
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• pp.393-401
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• 2009

Objective: The purpose of this study was to compare the shear bond strength (SBS) of brackets and microleakage of a tooth-adhesive-bracket complex bonded with a direct and an indirect bonding technique after thermocycling. Methods: Fifty non-carious human premolars were divided into two equal groups. In the direct bonding group a light-cured adhesive and a primer (Transbond XT) was used. In the indirect-bonding group, a light-cured adhesive (Transbond XT) and chemical-cured primer (Sondhi Rapid Set) were used. After polymerization, the teeth were kept in distilled water for 24 hours and thereafter subjected to thermal cycling (500 cycles). For the microleakage evaluation, 10 teeth from each group were further sealed with nail varnish, stained with 0.5% basic fuchsin for 24 hours, and examined under a stereomicroscope. Fifteen teeth from each group were used for SBS testing with the universal testing machine and adhesive remnant index (ARI) evaluation. Data were analyzed using the Mann-Whitney U test, Chi-square test, and Fisher's exact test. Results: There were no statistical differences on SBS and microleakage between the two bonding techniques. The indirect bonding group had a significantly lower ARI score. Bracket failures were obtained between enamel-resin interfaces. Conclusions: The type of bonding technique did not significantly affect the amount of microleakage and SBS.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.197-197
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• 2012

본 연구에서는 대기 순환패턴 및 수문 환경변화에 영향을 미치는 주요인자인 El Ni$\tilde{n}$o-Southern Oscillation (ENSO)의 서로 다른 형태인 Warm-pool (WP) El Ni$\tilde{n}$o, Cold-tongue (CT) El Ni$\tilde{n}$o에 따른 한강유역의 봄철 (March~May)과 여름철 (June~August) 강수 및 유출의 특성을 분석하였다. 봄철 강수량의 경우, WP El Ni$\tilde{n}$o 시기에 증가추세를 보이며, 강수의 변동특성 또한 크게 나타났다. 여름철 강수량의 경우, CT El Ni$\tilde{n}$o 시기에는 평년보다 대체로 건조한 경향을 보이나, WP El Ni$\tilde{n}$o 시기에는 유역 전체에서 습한 경향을 보였으며 강수의 변동성은 매우 작은 것으로 분석되었다. 봄철 유출량의 경우, CT El Ni$\tilde{n}$o 시기와 WP El Ni$\tilde{n}$o 시기에 모두 평년치보다 크게 나타났으며, WP El Ni$\tilde{n}$o 시기에 한강 남부 대부분 유역에서 유출량이 통계적으로 유의한 증가 경향을 보였다. 여름철 유출량의 경우, CT El Ni$\tilde{n}$o 시기에는 대부분 유역에서 평년치보다 감소하나 수문 변량의 변동성은 큰 것으로 분석되었다. WP El Ni$\tilde{n}$o 시기에는 거의 모든 유역에서 유출이 증가하는 것으로 나타났으며, 특히 13개 중권역에서는 유출의 변동성이 작고 통계적으로 유의한 증가패턴이 분석되었다. 따라서 본 연구는 서로 다른 두가지 형태의 El Ni$\tilde{n}$o패턴에 대하여 한강유역의 봄철과 여름철 수자원 변동성에 민감하게 영향을 미치고 있음을 확인하였으며 수자원의 효율적인 예측 및 관리와 안정적인 용수공급을 위한 수문기상인자와 수문자료간의 관계 규명에 유용하게 활용될 것으로 기대한다.

• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.282-289
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• 2006

The purpose of this study was to compare the ability of three resin surface sealants to prevent microleakage in Class V composite resin restorations. Forty Class V cavities with the occlusal margin in enamel and gingival margin in dentin were prepared on the buccal surfaces of sound extracted molars, and restored with composite resin. Restorations were randomly assigned into one of four equal groups (n = 10): a control group, without resin sealing, and three experimental groups in which margins were sealed with Fortify Plus, Biscover and Permaseal, respectively. Specimens were thermocycled, immersed in a 2% methylene blue solution for 4 hours, sectioned longitudinally, and observed the leakage at the occlusal and gingival margins. The result was analyzed using Kruskal-Wallis test, Mann-Whitney test and Wilcoxon signed rank test. In conclusion, the ability to reduce microleakage at occlusal margins was similar in all of three sealants. However at gingival margin, it depended on the type of used resin surface sealant. At gingival margin. control and Fortify Plus group showed statistically higher microleakage than PermaSeal group. and Fortify Plus group also showed higher microleakage than BisCover group (p < 0.05).

• Restorative Dentistry and Endodontics
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• v.32 no.3
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• pp.222-235
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• 2007

The objectives of this study was to evaluate the effect of thermocycling on the ${\mu}TBS$ (microtensile bond strength) to dentin with four different adhesive systems to examine the bonding durability. Freshly extracted $3^{rd}$ molar teeth were exposed occlusal dentin surfaces, and randomly distributed into 8 adhesive groups 3-steps total-etching (Scotchbond Multi-Purpose Plus; SM, All Bond-2; AB), 2-steps total-etching (Single Bond; SB, One Step plus; OS), 2-steps self-etching (Clearfil SE Bond; SE, AdheSE AD) and single-step self-etching systems (Promp L-Pop; PL, Xeno III; XE) Each adhesive system in 8 adhesives groups was applied on prepared dentin surface as an instruction and resin composite (Z250) was placed incrementally and light-cured. The bonded specimens were sectioned with low-speed diamond saw to obtain $1\times1mm$ sticks after 24 hours of storage at $37^{\circ}C$ distilled water and proceeded thermocycling at the pre-determined cycles of 0, 1,000 and 2,000. The ${\mu}TBS$ test was carried out with EZ-tester at 1mm/min. The results of bond strength test were statistically analyzed using one-way ANOVA/ Duncan's test at the a < 0.05 confidence level. Also, the fracture mode of debonded surface and the interface were examined under SEM. The results of this study were as follows ; 1. 3-step total etching adhesives showed stable, but bond strength of 2-step adhesives were decreased as thermocycling stress. 2. SE showed the highest bond strength, but single step adhesives (PL, XE) had the lowest value both before and after thermocycling. 3 Most of adhesives showed adhesive failure. The total-etching systems were prone to adhesive failure and the single-step systems were mixed failure after thermocycling. Within limited results of this study, the bond strength of adhesive system was material specific and the bonding durability was affected by the bonding step/ procedure of adhesive Simplified bonding procedures do not necessarily imply improved bonding performance.

• Restorative Dentistry and Endodontics
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• v.30 no.5
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• pp.355-362
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• 2005

The purpose of this study was to compare the effect on marginal leakage of a resin surface sealant (Biscover) applied before or after polymerization of composite resin to unsealed composite restorations. Thirty Class V cavities with the occlusal margin in enamel and cervical margin in dentin or cementum were prepared on the buccal surfaces of sound extracted molars and restored with a microfilled light-cured composite resin (Micronew). Restorations were randomly assigned into one of three equal groups (n = 10): a control group - no surface sealing, group 1 - applied Biscover after polymerization of the composite resin. and group 2 - applied Biscover before polymerization of the composite resin. Specimens were thermocycled, immersed in a $20\%$ methylene blue solution for 4 hoots, sectioned longitudinally, and analyzed for leakage at the occlusal and gingival margins. The results of this study were as follows 1. In sealed group, group 2 showed higher microleakage than group 1 at both occlusal and gingival margins. but there was no significant difference between two groups (p > 0.05). 2. Unsealed control group showed a little higher microleakage than sealed group at occlusal margins, and a little Higher or similar microleakage than sealed group at gingival margins (p > 0.05) 3. Control group and group 2 showed significantly less microleakage at the occlusal margins, but group 1 showed no significantly difference between microleakage at the occlusal and gingival margins.