• Journal of dental hygiene science
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• v.15 no.4
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• pp.437-444
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• 2015

Due to the attractive benefits with regard to bone health, digestion, and hydration, carbonated water consumption have rapidly grown over the past few years. However, the acidic drink has latent potential for enamel erosion. The most experimental studies about the enamel erosion have focused on the carbonated beverages with sugar and artificial sweeteners. Here, we determined the enamel erosion potential by commercially available carbonated waters with bovine teeth. The erosion was verified by pH value, calcium concentration, and scanning electron microscope. Then plaque accumulation by bacterial adhesion was determined on the enamel erosion surface to measure roughness. In the present study, we observed that the increased calcium content after being immersed in carbonated waters result from the overall enamel erosion. There were no significant differences between general carbonated waters and mineral waters for erosive capacity. Therefore, commercially available carbonated waters are potentially erosive. In addition, oral bacteria strongly adhered to the erosive enamel surfaces thereby facilitating the development of dental plaque. Thus, it is urgently necessary to provide food safety information on the carbonated water as acidic drink to prevent the enamel erosion.

• Journal of the Korea Convergence Society
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• v.12 no.12
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• pp.153-159
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• 2021

The purpose of this study is to determine the demage of tooth surface changes according to exposure time of commercially available green grape juice and pomegranate juice. Extracted healthy human premolar enamel surfaces were used. Control group immersed in phosphate-buffered saline (PBS) and 10 ml of commercially available green grape juice and pomegranate juice applied experimental group was divided into 7 groups. The pH of the experimental juice was measured, and the change and micrographics of the surface were confirmed through a Scanning Electron Microscope (SEM). It was found that the more the immersion time between the tooth surface and acid juice, such as damage to the tooth surface, has a greater effect on the surface damage. Based on the results of this study, it is necessary to reduce the number of drinking times and retention time in the oral cavity.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.378-379
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• 2003

도로에서의 비산먼지는 건설현장 트럭에 의한 토사의 유입, 운반 중에 날리는 토사, 토양의 침식, 겨울철 모래살포, 타이어의 마모등에 의하여 도로표면에 쌓인 먼지가 차량의 운행이나 바람으로 인하여 발생한다 국내 주요도시 및 산업단지는 대부분이 포장도로로서 주변환경에서 유입되는 먼지와 함께 차량의 운행으로 인한 비산먼지(Fugitive dust)의 영향이 지대하며, 건설현장에서 발생되는 비산먼지와 함께 도시ㆍ산단지역의 미세먼지 배출량에 큰 기여를 하는 것으로 조사되었다. (중략)

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.133-133
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• 2008

본 연구에서는 임상적으로 사용후 임플란트시스템의 안정성을 조사하기 위하여 인위적으로 풀림 조임을 1회와 20회로 반복한 후 0.9% NaCl에서 부식을 시키고 파괴한 후 임플란트시스템의 안정성에 대하여 조사하였다.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.291-295
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• 2003

Many steam turbine components encounter solid particle erosion damage. It has been reported that particle erosion damage is caused by oxide scale exfoliation from boiler tubes. One of the most effective solutions to combat the erosion damage is the application of erosion resistant coatings on the turbine components. In this study, particle erosion resistance for various hard coatings such as nitride, Cr carbide and boride coatings was evaluated under the simulated erosion conditions of steam turbines. Based on the particle erosion tests, the boride coating was found to be more superior to others.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.617-623
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• 2004

Acidic drink has been known as a cause of tooth erosion. The purpose of this study is to verify the acid levels of orange juices in market and evaluate the erosion effects on the enamel of deciduous teeth by orange juices in relatively short period of time. With four kinds of orange juice selected from market, pH, buffering capacity and concentration of Ca and P ion were measured. And forty segments of normal enamel of deciduous incisors were divided into four groups and level of erosion was measured by surface hardness test before and after soaking at 50ml of orange juice for 10 minutes. The results of this study showed that the average pH of orange juices was 4.0 and this pH value was so acidic as to cause the tooth erosion. There were differences in small quantity for each group of teeth, however, the result was statistically so significant that orange juices can cause enamel erosion in relatively short period of time.

• Journal of Plant Biology
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• v.38 no.1
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• pp.79-86
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• 1995

Visible injury symptoms such as necrosis, chlorosis and premature senscence in the leaves of Ginkgo bloba and Pinus thunbergii treated with acid rain of pH 3.2 or below were observed. The epicuticular wax erosions were observed by SEM after exposure to acid rain of pH 2.4 and 3.2 in G. biloba and pH 4.0 below in P. thunbergii. The adaxial epidennal cells and sponge parenchyma cells were compressed, and those were distorted in the leaves of G. biloba treated with simulated acid rain of pH 3.2 or below. However, vascular tissue was intact. With increase of acidity, mesophyll cells were smaller than those of control while intercellular space in mesophyU was increased. In P. thunbergii, sponge parenchyma cells and vascular tissue except epidennis were distorted after exposure to acid rain of pH 2.4. The size change of stomata in foliar injury was not observed, but the stomatal index and size of stomatal aperture in leaves treated with acid rain increased. The stomata of injured leaf were opened in both species examined.amined.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.79-79
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• 2018

하천시설물 설계, 시공 및 관리에 재료에 따른 호안이나 제방의 보호능력이 저하되어 설계 시 예상하지 못한 조건에서 쉽게 파손될 수 있으며, 하천환경의 변화를 야기시킬 수 있다. 제방 표면재료는 제외 비탈면의 침식 방지를 목적으로 사용되는 재료로 주로 호안블록. 식생 매트, 사석, 돌망태, 식생등이 주로 사용되며 국내에서는 2000년대 이전에는 자연 흙사면의 식생, 돌망태, 단순 돌기형 콘크리트 블록 등이 주로 사용되었으며 2000년대 이후에는 하천환경을 고려하여 식생의 생장이 가능한 친환경 호안 블록 및 식생 매트의 적용이 일반적인 실정이다. 제방의 수리적 설계를 위해서는 표면 재료의 수리 특성, 즉, 조도계수 및 한계 유속, 한계 소류력이 제시되어야 하는데 이는 실험을 통해서 결정되어야 한다. 때문에 본 연구에서는 자연형 하상재료를 이용하여 바이오 폴리머 첨가시 증가하는 방어능력에 대한 향상도를 평가하는 실험적 평가 방법을 제안하기위해 홍수시 수리조건을 반영하여 상류에서부터 사류까지 다양한 유속범위에 따른 세굴 및 침식에 대한 실험을 진행하였다. 본 연구에서는 실험연구를 통해 연구에 사용된 재료 외 추가적인 재료에 대해서도 평가방법이 적용될 수 있도록 제방 재료의 안정성 평가시스템을 개발하였고, 안정성 평가를 위한 실험진행은 기 개발된 바닥응력을 직접측정하는 장치와 PIV시스템을 이용하여 수리특성을 측정하였다.(Park J.H. et al. 2016, Flow Measurment and instrumentation.) 이러한 측정 장치를 이용하여 바이오폴리머의 첨가에 유무에 따라 세굴에 대한 방어능력의 향상정도를 측정하고자 세굴 및 침식에 대한 평가 방법을 제시하고 있다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.107-107
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• 2018

무전해 니켈도금 용액의 성분은 Ni(II)염, 환원제, 적합한 금속 배위 리간드, 안정제 및 특정 특성 요구에 대한 첨가제를 포함한다. 일반적으로 도금 욕에는 미량의 안정제가 함유되어 있다. 만약 적절한 안정화 시스템이 없는 도금 욕에서 도금 공정 시 도금 시작 직후에 많은 양의 니켈 플레이크(Ni flake)가 생성되어 빠르게 도금 용액이 분해되어 더 이상 도금이 어렵게 된다. 그러나 무전해 도금 욕에서 안정제의 역할 및 도금 층에 미치는 영향에 대한 연구는 여전히 부족한 실정이다. 따라서 본 연구에서는 $Pb^{2+}$ 안정제 농도가 도금 층에 미치는 영향과 캐비테이션 침식 실험을 통해 그 내구성을 평가하고자 하였다. 무전해 니켈코팅을 위한 모재는 회주철(FC250)을 $19.5mm{\times}19.5mm{\times}5mm$의 크기로 가공하였다. 회주철의 인장강도는 $330N/mm^2$이며, 그 성분 조성(wt.%)은 3.23 C, 1.64 Si, 0.84 Mn, 0.016 P, 0.013 S 그리고 나머지는 Fe이다. 시험편은 SiC 페이퍼 #1200까지 연마하여 시험편의 표면 거칠기는 $1.6-2.1{\mu}m$ 범위 내로 제작하였다. 무전해 도금 전 시험편은 탈지를 위해 상온의 아세톤 용액에서 3분간 초음파 세척하고, $90^{\circ}C$의 알카리 수용액으로 5분간 세척하였다. 그리고 표면 활성화를 위한 산세척은 5% 황산용액에서 30초 동안 실시하였다. 도금조로 500mL 비커를 사용하였으며, 모든 시험편은 2시간 동안 무전해 니켈도금을 실시하였다. 그리고 니켈도금 층의 내식성과 내구성을 평가하기 위해 전기화학적 분극 실험을 통한 타펠분석과 ASTM G32 규정에 의거한 캐비테이션 침식 실험을 실시하였다. 그 결과 안정제 농도가 도금 속도와 도금 층의 성분 변화에 크게 영향을 미쳤으며, 그에 따라 도금 층의 내식성과 내구성이 크게 변화되었다.

• Journal of Korean Society of Forest Science
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• v.99 no.4
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• pp.534-545
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• 2010

To examine 1) rainfall pattern (i.e., type and intensity) regulating surface erosion on hillslopes in postwildfire area and 2) its effect on variation in sediment yield along the gradient of severity wildfire regimes and elapsed years, we surveyed the amount of sediment yield with respect to daily or net-effective rainfall in 9 plots in eastern coastal region, Republic of Korea. Before field investigation, all plots classified into three groups: low-, mixed- and high-severity wildfire regimes (3 plots in each group). We found that, with decreasing wildfire regimes and increasing elapsed years, the rainfall type regulating surface erosion changed from daily rainfall to net-effective rainfall (considering rainfall continuity) and its intensity increased continuously. In general, wildfires can destroy the stabilized forest floors, and thus rainfall interception by vegetation and litter layer should be reduced. Wildfires can also decrease soil pores in forest floors, and thus infiltration rates of soil are reduced. These two processes lead to frequent occurrence of overland flows required to surface erosion, and sediment yields in post-wildfire areas should increase linearly with increasing rainfall events. With the decreasing severity wildfire regimes and the increasing elapsed years, these processes should be stabilized, and therefore their sediment yields also decreased. Our findings on variations in sediment yields caused by the wildfire regimes and the elapsed years suggest understanding of hydrogeomorphic and ecologic diversities in post-wildfire areas, and these should be carefully examined for both watershed management and disaster prevention.