• Restorative Dentistry and Endodontics
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• v.31 no.4
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• pp.269-281
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• 2006

This study evaluated the effectiveness and safety of an experimental bleaching strip (Medison dental whitening strip. Samsung medical Co., Anyang, Korea) containing 2.9% hydrogen peroxide. Twenty-three volunteers used the bleaching strips for one and a half hour daily for 2 weeks. As control group. the same strips in which hydrogen peroxide was not included were used by 24 volunteers with the same protocol. The shade change (${\Delta}E^{*}$, color difference) of twelve anterior teeth was measured using Shade Vision (X-Rite Inc., S.W. Grandville, MI, USA). Chroma Meter (Minolta Co., Ltd. Osaka. Japan) and Vitapan classical shade guide (Vita Zahnfabrik, Germany). The shade change of overall teeth in the experimental group was significantly greater than that in the control group (p < 0.05) and was easily perceivable. The change resulted from the increase of lightness (CIE $L^{*}$ value) and the decrease of redness (CIE $a^{*}$ value) and yellowness (CIE $b^{*}$ value). The shade change of individual tooth was greatest in canine. and smallest in central incisor. The safety of the bleaching strip was also confirmed.

• Restorative Dentistry and Endodontics
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• v.30 no.4
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• pp.335-343
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• 2005

Hemolytic property is a specific feature of bacteria to obtain iron which is essential for its survival in host tissues. Therefore, it is thought to be one of several factors of virulence. The purpose of this study was to investigate the hemolytic properties of Prevotella nigrescens isolated from the teeth diagnosed as pulp necrosis and apical periodontitis under the presence of hemolysin inhibitors such as $NaN_3$ and dithiothreitol. heat, various pH and cultural conditions. The results were as follows; 1. Clinically isolated P. nigrescens strains and standard P. nigrscens ATCC 33563 showed hemolytic activity. 2. P. nigrescens showed higher hemolytic activity against human erythrocytes than sheep or horse erythrocytes. 3. $NaN_3$ and dithiothreitol (DTT) reduced the hemolytic activity of P. nigrescens in a dose dependent manner (p<0.05). 4. Optimal pH for the maximum hemolytic activity of P. nigrescens was 4.0 and the hemolysin was stable under the $50^{\circ}C$, but the hemolytic activity was significantly decreased at $95^{\circ}C$. 5. P. nigrescens cultured in $10\%\;CO_2$ condition showed higher hemolytic activity than the bacteria cultured in the anaerobic condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.1126-1139
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• 2014

World is experiencing abnormal weather caused by urbanization and industrialization increasing greenhouse gas and one of these phenomenon domestically happening is flood and drought. The increase of green-house gases is due to urbanization and industrialization acceleration which are causing abnormal climate changes such as the El Nino and a La Nina phenomenon. It is expected that there will be many difficulties in water management, especially considering the topography and seasonal circumstances in Korea. Unlike in the past, a variety of water conservation initiatives have been undertaken like the river-management flow and water capacity expansion projects. To meet the increasing demand for water resources, new environmentally-friendly small and medium-sized dams have been built. Therefore, the development of a new paradigm for water resources management is essential. This study shows that additional security is needed for potential water resources through diversion tunnels and is very important to consider for future water supplies and situations. Using RCP 6.0 and RCP 8.5 in representative concentration pathway climate change scenario, specific hydrologic data of study basin was produced to analyze past observed basin rainfall tendency which showed both scenario 5%~9% range increase in rainfall. Through sensitivity analysis using objective function, population in highest goodness was 1000 and cross rate was 80%. In conclusion, it is expected that the results from this study will help to make long-term and stable water supply plans by using the potential water resource evaluation model which was applied in this study.

• Journal of Korean Society of Forest Science
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• v.101 no.1
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• pp.130-137
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• 2012

This study has conducted to develop new gabion wall systems with vegetation base materials for stream bank stability and rapid rehabilitation. Vegetation base materials are primarily compounded with fine soil, organic composts and peat moss as plant fibers, a water retainer and a soil improver. Normally gabion wall systems resist the lateral earth pressures or stream power by their own weight. Therefore, fill material must have suitable weight, compressive strength and durability to resist the loading, as well as the effects of water and weathering. In this project, 100 to 200-mm clean, hard stones are basically specified, and about 50-mm rubbles are also used. Test application of new gabion wall system carried out in the stream bank of a small stream in the Gwangreung experimental forest, belonging to Korea Forest Research Institute (KFRI) in December 16th, 2006. As a result of the analysis of hydraulic stability of new gabion wall system, gabion wall system has highest threshold shear stress when the gabion wall covered by vegetation. New gabion wall system is highly resistant to sliding and overturning because safety coefficients exceed 1.5. As a result of term of slope stability analysis of new gabion wall system by Bishop and Fellenius methods, stability of stream bank was highly increased after the construction of gabion wall. Therefore, new gabion wall system is effective to stabilize unstable stream bank.

• International Journal of Highway Engineering
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• v.4 no.4 s.14
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• pp.23-39
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• 2002

This study dealt with developing a new approach for finding properties which might represent rut resistance characteristics of asphalt mixture under static loading. Two aggregates, a normal asphalt (pen 60-80) and 5 polymer-modified asphalts were used in preparation of 12 dense-graded mixtures. Marshall mix design was used in determination of OAC and each mixture at the OAC was prepared for a newly-developed Kim test on Marshall specimen (S=10cm) and gyratory specimen (S=15cm), and for wheel tracking test. Kim test used Marshall loading frame and specimens were conditioned for 30min at $60^{\circ}C$ before loading through Kim tester an apparatus consisting of a loading column and a specimen and column holder Diameter (D) of column was 3cm and 4cm with each column having different radius (r) of round cut at the bottom. The static load was applied at 50mm/min in axial direction of the specimen, not in diametral direction. The maximum load ($P_{max}$) and vertical deformation (y) at $P_{max}$ point were obtained from the test. A strength value was calculated based on the $P_{max}$ r, D and y by using the equation $K_D = 4P_{max}/{\pi}(D-2(r-\sqrt{2ry-y^2}))^2$ and is defined as the deformation strength ($kgf/cm^2$). The values of $P_{max}$/y and $K_I=K_D/y$ were also calculated. In general the leading column diameter and radius of round cut were significant factors affecting $K_D$ and $P_{max}$ values while specimen diameter was not. The statistical analyses showed the $K_D$ had the best correlation with rut depth and dynamic stability. The next best correlation was found from $P_{max}$ which was followed by $P_{max}$/y and $K_I$ in order.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.39-39
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• 2018

우리나라는 전체 국토의 약 70%가 산악지형으로 이루어져 있고 연중 강우가 6월에서 9월에 집중되는 기후적 특성을 가지고 있다. 최근 기후변화의 영향까지 더해지면서 시간당 300mm 이상의 집중호우를 보이는 이상강우가 빈번하게 발생하고 있다. 대부분의 도시지역은 하천을 중심으로 발달되어 있어 인구 및 사회기반시설의 집약정도가 매우 높고 하천변 저지대 지역에 주거 및 상업시설이 밀집되어 있다. 기후적 지역적 특성으로 인한 홍수피해를 미연에 방지하고 피해를 최소화하기 위하여 치수 중심의 수자원 관리를 위해 노력하고 있다. 하지만 우리나라의 하천관리는 시기별 하천 수량의 급격한 변동으로 어려움을 겪고 있다. 이러한 어려움을 극복하고 효율적인 수자원 관리 및 홍수피해 저감을 위해 수계를 중심으로 20개의 다목적댐을 건설하여 운영 관리 중에 있다. 특히, 홍수기 시 댐 운영은 예상 강우에 따라 적절한 예비방류와 강우 시 효율적인 댐 운영계획이 필수적이다. 본 연구에서는 강우가 집중되는 홍수기 댐 운영 시에 예상 강우량에 따라 댐 유역 내 유량 증가에 기여하는 정도를 예측할 수 있는 유출율 예측 회귀식을 개발하였다. 유출율은 강우와 유출량의 비로 지역특성, 강우특성, 관개여부, 선행강우량, 강우이동 방향 등 다양한 요인에 의해 복잡한 메케니즘을 갖는다. 단순히 예상되는 총강우량에 따른 유출율 만으로 상호관계를 정의하기가 쉽지 않기 때문에 한국수자원공사에서 개발한 댐군 홍수조절 연계운영시스템(COSFIM)인 수문학적 연계운영모형을 활용하였다. 최근 10년간 홍수기에 발생한 강우사상별 시간단위의 수문자료(총강우량, 기저유량, 유출율, 무강우일수, 강우지속시간 등) 분석을 실시하였다. COSFIM 모형을 통한 결과를 토대로 고려항목 간 교차검증을 통해 사분위수범위의 이상치 경계를 설정하고 상관분석 결과에 따라 0.5 이상의 상관성이 높은 항목을 활용하여 예측 강우량에 따른 유출율 예측 회귀식을 도출하였다. 본 연구에서 개발한 예측 강우에 따른 유출율 예측 산정식은 댐 유역에 예상되는 강우량에 대하여 하천의 유량 증가 예측 정도를 정량적으로 제시할 수 있으며, 실제 홍수기 댐 운영 시 예상 강우량에 따라 신속하고 적절한 수문 방류 계획 수립에서 용이하게 활용할 수 있을 것으로 기대한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.75-75
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• 2019

첨두홍수량 자료는 홍수예경보 및 치수계획수립 등 하천관리에 있어서 매우 중요한 요소이다. 그러나 대규모 홍수가 발생 시 악천후가 동반된 기상상황이나, 현장 접근이 어려운 환경적 조건과 예산 및 인력 부족 등에 의한 불가피한 문제로 첨두홍수량을 측정하는데 어려움 있다. 따라서 일반적으로 수위-유량관계곡선식을 이용하여 첨두홍수량을 산정하지만 단순 고수위 외삽 추정을 통해 개발된 곡선식을 이용한 첨두홍수량 산정에 있어서는 주의가 필요하다. 이러한 경우 홍수가 지나간 후 현장조사를 통해 획득한 위치, 표고, 횡단면적 등 홍수흔적(flood marks)을 가지고 경사면적법(slope-area method)과 같은 간접적인 방법으로 첨두홍수량을 추정할 수 있다. 본 연구에서는 2018년 큰 호우사상이 발생한 내성천의 지류인 서천의 영주시(월호교) 지점과 남강의 산청군(하촌리) 지점에서 홍수흔적 조사를 통해 지점별 두 개의 단면을 선정하였다. 영주시(월호교) 지점의 두 단면 간 거리는 약 90m, 높이차는 약 0.21m로 조사되었고, 산청군(하촌리) 지점의 두 단면 간 거리는 약 330m, 높이차는 약 0.47m로 조사되었다. 경사면적법을 이용한 첨두 홍수량 추정에 적용된 조도계수는 '서천 하천기본계획(2014)', '남강 하천기본계획(2013)'에서 계획 홍수량 산정에 적용된 조도계수 0.029와 0.025를 적용하였다. 영주시(월호교) 지점은 2018년 9월 4일 발생한 호우사상의 첨두수위 5.59m에서 수위-유량관계곡선식을 이용하여 산정된 유량은 $1,127.8m^3/s$이고 경사면적법을 이용하여 추정된 유량은 $1,105.9m^3/s$로 약 -1.98%의 편차율이 발생하였다. 산청군(하촌리) 지점은 2018년 8월 26일 발생한 호우사상의 첨두수위 6.75m에서 수위-유량관계곡선식을 이용하여 산정된 유량은 $3,435.0m^3/s$이고 경사면적법을 이용하여 추정된 유량은 $3,233.3m^3/s$로 약 -6.24%의 편차율이 발생하였다. 경사면적법을 이용하여 추정된 첨두홍수량은 수위-유량관계곡선식을 이용하여 산정된 유량과 편차율이 지점별 ${\pm}10%$ 이내의 근사한 범위로 산정되었다. 따라서 경사면적법을 이용한 첨두홍수량 추정 방법의 적용에 있어서 적절한 것으로 판단된다.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.117-125
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• 2011

River bed variation drops storage capacity of dams and reservoirs, and furthermore deteriorates safety of banks and peers. Therefore, understanding of bed variation is important to use and manage river water. Study section is downstream part of Ji- Cheon nearby Ji-Cheon Bridge which is located in Gum river basin. The river surveying at fourteen places with the length of 1,320m were undertaken on November 7, 2003 and September 24, 2004, and the results of river surveying were analyzed for the study. Real bed variation was compared with the simulation results of HEC-6 and GSTARS 3.0. Cross section data for the simulation of HEC-6 and GSTARS3.0 were composed of the basis of river surveying data on November 7, 2003. Hydrological data were acquired from Gu-Ryong watermark located at Ji-Chun Bridge. The research results revealed that when using Toffaleti equation, simulation results of two models were similar to the real bed variation. The bed variation simulated by using GSRARS 3.0 with only one stream tube was similar to the real bed variation. The bed variation simulated by using two models(HEC-6 and GSTRARS 3.0) with Toffaleti equation was also similar to the real bed variation. Therefore, it is expected that HEC-6 and GSTARS 3.0 models have applicability to predict the bed variation at the downstream of Ji-Cheon.

• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.127-138
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• 2021

The aim of this study is to demonstrate interaction as a describable field and tries to understand interaction from the perspective of attributes, thus building a theoretical to help interactive designer understand this field by common rule, rather than waste huge time and labor cost on iteration. Since the concept of interaction language has been brought out in 2000, there are varies of related academical studies, but all with defect such as proposed theoretical models are built on a non-uniform scale, or the analyzing perspective are mainly based on researcher's personal experience and being too unobjective. The value of this study is the clustered resource of research which mainly based on academical review. It collected 21 papers researched on interaction paradigm or interaction attributes published since 2000, extracting 19 interaction attribute models which contains 174 interaction attributes. Furthermore, these 174 attributes were re-clustered based on a more unified standard scale, and the two theoretical models summarized from it are respectively focuses on interaction control and interaction experience, both of which covered 6 independent attributes. The propose of this theoretical models and the analyzation of the cluster static will contribute on further revealing of the importance of interaction attribute, or the attention interaction attribute has been paid on. Also, in this regard, the interactive designer could reasonably allocate their energy during design process, and the future potential on various direction of interaction design could be discussed.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.605-618
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• 2018

Korea follows the slope design criteria during construction. It was enacted by the Ministry of Land, Transport and Maritime Affairs. There are cases where the Soil-nail is designed as a measure to secure slope stability. The arrangement of the soil-nail may be arranged at equal intervals or may be arranged differently depending on the soil failure model. The optimum design of the countermeasure method is determined by securing stability of the slope through optimization of dimensions and shape. However, when uniform nails are placed at low elevations in slopes, the standard safety factor is exceeded, which may hinder economic design. It is preferable to arrange the reinforcement of the nails over the entire slope. When the horizontal spacing of the nails was topology optimized according to the slope height, it was possible to minimize the amount of reinforcement while satisfying the standard safety factor. Since the active load is reduced in the section where the slope height is lowered, the safety factor after reinforcement may be excessively increased. Therefore, the phase optimization method is proposed as an economical optimal design method using the reinforcing shape density. In addition, a relational expression was designed to optimize the horizontal spacing by slope height.