• 치위생과학회지
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• 제19권3호
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• pp.154-161
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• 2019

Background: The market for vitamin drinks is expanding both in Korea and worldwide. However, it was difficult to find studies regarding the possibility of tooth erosion induction due to vitamin drinks. The purpose of the present in vitro study was to evaluate the effect of tooth erosion caused by a few commercial vitamin beverages on bovine teeth enamel in terms of erosion depth and fluorescence loss. Methods: Three experimental groups (vitamin drinks), a positive control group (Coca-Cola), and a negative control group (mineral water) were established. Each group consisted of 5 specimens obtained from sound bovine teeth. The pH and titratable acidity of beverages were measured. Specimens were immersed in the beverages and artificial saliva for 6 and 18 hours, respectively. This cycle was repeated for 5 days. The depth of the tooth loss caused by tooth erosion (erosion depth) and maximum loss of fluorescence (Max ${\Delta}F$) were measured using the microscope and quantified light-induced fluorescence-digital, respectively. For the statistical analysis, the Kruskal-Wallis test and ANOVA were used to compare the erosion depth and Max ${\Delta}F$ of the enamel surfaces. In addition, Spearman correlations were estimated. Results: The pH of the three vitamin beverages ranged from 2.65 to 3.01, which is similar to that of the positive control group. All beverages, except mineral water, had sugar and acidic ingredients. Vitamin drinks and the positive control, Coca-Cola, caused tooth erosion lesions, and showed significant differences in erosion depth compared to mineral water (p<0.05). The vitamin beverages with low pH were associated with high erosion depth and Max ${\Delta}F$. Conclusion: Vitamin drinks have the potential to cause tooth erosion.

• 한국환경복원기술학회지
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• 제14권5호
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• pp.53-67
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• 2011

The major objective of this study was to quantify the effects of substrate depth and substrate composition on the development of sedum etc., in a sloped rooftop (6 : 12 pitch) environment during a 4-year period. The experiment was conducted from 2006 October to 2010 December under several conditions without soil erosion control : two substrate depth (5cm, 10cm), four substrate composition (A5N3C2, A3N3C4, A6C4, G5L3C2: A: artificial lightweight soil, N : natural soil, G : granite decomposed soil, C : leave composite, L : loess), four sloped roof direction ($E40^{\circ}W$, $W40^{\circ}N$, $S40^{\circ}W$, $N40^{\circ}E$). In this experiment 4 sedum etc., were used: Sedum sarmentosum, Sedum kamtschaticum, Sedum rupestre, Sedum telephium, flowering herbs (mixed seed : Taraxacum platycarpum, Lotus corniculatus, Aster yomena, Aster koraiensis), western grasses (mixed seed : Tall fescue, Creeping redfescue, Bermuda grass, Perennial ryegrass). The establishment factor had two levels : succulent shoot establishment (sedum), seeding (flowering herbs, western grasses). 1. Enkamat, as it bring about top soil exfoliation, was unsuitable material for soil erosion control. 2. Sedum species exhibited greater growth at a substrate depth of 10cm relative to 5cm. All flowering herbs and western grasses established only at a substrate depth of 5cm were died. A substrate depth of 5cm was not suited in sloped rooftop greening without maintenance. If additional soil erosion control will be supplemented, a substrate depth of 10cm in sloped rooftop greening without maintenance was considered suitable. 3. For all substrate depth and composition, the most abundant species was Sedum kamtschaticum. The percentage of surviving Sedum kamtschaticum was 73.4% at a substrate depth of 10cm in autumn 2007 one year after the roof vegetation had been established. But the percentage of surviving other sedum were 33.3%~51.9%, therefor mulching for soil erosion control was essential after rooftop establishment in extensive sloped roof greening was proved. To raise the ratio of plant survival, complete establishment of plant root at substrate was considered essential before rooftop establishment. 4. There was a significant interaction between biomass and substrate moisture content. There were also a significant difference of substrate moisture and erosion among substrate composition. The moisture content of A6C4 was highest, the resistance to erosion of A5N3C2 was highest among substrate composition. The biomass of plants were not significantly higher in A5N3C2 and A6C4 relative to A3N3C4 and G5L3C2, For substrate moisture and erosion resistance, A5N3C2 and A6C4 were considered suitable in sloped rooftop greening without maintenance. 5. There were significant difference among roof slope direction on the substrate moisture. Especially, the substrate moisture content of $S40^{\circ}W$ was lower relative to that of $N40^{\circ}E$, that guessed by solar radiation and erosion.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권2호
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• pp.60-64
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• 2001

The degradation process of silicone rubber was investigated by leakage current monitoring in Inclined-Plane method. DAS (Data Acquisition System) with 12-bit, 8-channel A/D converter was prepared. Average current, cumulative charge, current waveform and the number of peak pulses were measured on-line. And, FFT (Fast Fourier Transform) analysis was performed with stored current waveform. Besides, maximum erosion depth was measured in order to use as the indicator of the degradation process. So, the results of leakage current components and maximum erosion depth measurements were compared to find one or more components which have trends of changing similarly to that of erosion process. The result suggests that the ratio of peak current to r.m.s. current, harmonic contents and the number of peak pulses are well corresponding with the degradation process.

• 한국세라믹학회지
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• 제45권7호
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• pp.405-410
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• 2008

Ceramics are widely used as plasma resistant materials in semiconductor industries. However, the plasma erosion resistance has not been properly evaluated in terms of microstructural changes during the exposure to plasma. In this study, microstructure developments of $Al_2O_3$ were investigated under the fluorine plasma conditions. In polycrystalline alumina, uniform erosion throughout the specimen as well as spatially distributed local erosion were observed. Local erosion was much more severe in lower purity alumina. In contrast to the polycrystalline alumina, only uniform erosion was observed in single crystalline sapphire. These specimens, however, had practically the same erosion depth, which results in the incorrectly similar plasma resistance. This implies that the plasma erosion resistance of ceramics should be evaluated in terms of the microstructural changes, as well as the conventionally accepted erosion depth.

• 터널과지하공간
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• 제14권5호
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• pp.339-344
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• 2004

침식에 따른 횡방성 암반의 초기응력비 변화를 수치해석적으로 구하여 등방성의 경우 및 이론해와 비교한 결과 횡등방성의 영향은 크지 않아 초기지응력비가 작고 침식심도가 깊을 때만 고려하는 것이 좋을 것으로 판단되었다. 수치해석에 의한 응력과 이론적인 값의 차이는 초기 지응력비가 클수록 또 침식되는 깊이가 증가할수록 증가하였다. 또 침식 후의 초기응력비는 심도가 깊어짐에 따라 초기 응력비로부터 발산하였다. 이를 감안하여 침식에 따른 초기응력비 산정식을 제안하였다.

• 해양환경안전학회지
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• 제7권3호
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• pp.75-84
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• 2001

Ultrasonic vibrator is an equipment which atomizes and homogenizes the oils by breaking the oil particles with ultrasonic vibration cavity, and possibly improves the properties. There are various parameters on the effect of ultrasonic irradiation. Especially, this study intended to investigate the matrix structure of sludge oils and the erosion damages for horn disc SS41 according to the variation of the oil temperature and the immersing depth of horn disc. Sludge oils were irradiated with ultrasonic vibration and then observed the aspects of the change of oil particles. From these, the recycling feasibility of sludge oil for useable oil to be burnt was determined. The erosion damages for horn disc SS41 were examined with weight loss, weight loss rate and the irradiation time to max. erosion rate. These data will be useful to the development of ultrasonic breaking systems to recycle sludge oil and to consider a countermeasure for the prevention of erosion damages.

• 전기학회논문지
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• 제62권12호
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• pp.1694-1699
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• 2013

Frequency accelerated partial discharge resistance (PDR) aging of epoxy/layered silicate nanocomposite with 1.5wt % additions of layered silicate was investigated in comparison with that of epoxy without layered silicate in terms of PD(partial discharge) erosion depth. It was found that the change in the erosion depth is far smaller in specimens with layered silicate than those without layered silicate nano particles. Frequency acceleration can be done from 60Hz to 1000Hz. But the depth of erosion is less proportional to frequency. Acceleration factor is almost 2 times between 500Hz and 1000Hz, but it is much less than about 8.3 times between 60Hz and 500Hz. This superior PD resistance is caused by the presence of nanofillers, anano-effect due to closely packed nanofillers, and strong chemical bonds at layered silicate nanofillers /resin interfaces.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.151-159
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• 2017

The action of rainwater on reinforced concrete walls has led to an erosion phenomenon. The erosion is very apparent when the walls are inclined. This phenomenon is studied on a real site characterized by different architectural forms. The site dates back to the seventies; it was designed by the architect, modeler of concrete, Oscar Nie Meyer. On this site, the erosion has damaged the cover of the reinforcements and reduced its depth. In this research work, a method of quantification of the erosion is developed. Using this method, the amount of mass loss by erosion was measured on imprints taken from the site. The results are expressed by the rate of mass loss by erosion; they are associated to the height and the inclination of the walls. Moreover, laboratory analysis was carried out on samples taken from the site. From this study, it is recommended to consider the erosion, in any building code, to determine the cover thickness.

• 한국수자원학회논문집
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• 제44권6호
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• pp.487-495
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• 2011

본 연구는 식생호안의 안정성 평가에 중요한 인자인 식생 근모량의 채취와 산정방법을 제시하였다. 또한 근모량에 따른 식생호안의 침식특성을 수리모형실험을 통하여 분석하였다. 수리모형실험에 사용한 식생으로는 국내 최우점종으로 확인된 달뿌리풀과 잔디이다. 유속별 근모량에 따른 침식특성으로 침식깊이와 침식률을 분석하고 그 관계식을 제시하였다. 실험결과 근모량이 증가함에 따라 침식깊이가 현저하게 감소하는 것을 확인할 수 있었다. 침식률의 산정결과 근모량이 증가함에 따라 침식에 대한 저항능력이 현저하게 증가함을 알 수 있었으며, 달뿌리풀과 잔디 각각의 식생별 및 전체 cases별 관계곡선식을 도출하여 높은 결정계수를 가짐을 확인하였다. 또한 달뿌리풀보다 잔디의 침식저항능력이 더욱 뛰어남을 확인하였다.

• Journal of Forest and Environmental Science
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• 제29권4호
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• pp.314-323
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• 2013

To examine surface erosion and sediment export patterns on a hillslope, which was devastated by a shallow landslide and which was slowly revegetating by natural plant species, we surveyed variations in surface erosion depth on the upper-, middle- and lower-section of the hillslope, and subsequent sediment yield from the whole hillslope. The result showed that, with the passing of year, surface erosion on the devastated hillslope was regulated by higher rainfall intensity due to the supply-limitation of exportable sediment, and its variation range decreased. In addition, surface erosion on the upper-section with steep slope was regulated by higher rainfall intensity, which might result in raindrop erosion, compared to it on the lower-section with relatively gentle slope. Besides, the sediment yield from the devastated hillslope had nonlinear relationship with surface erosion depth on the hillslope because sediments on the hillslope are exported downwards while repeating their cycle of transport and redistribution. Our findings suggest the establishment of management strategy to prevent sediment-related disasters occurred during torrential rainfall events, which was based on the continuous field investigation on the hillslope devastated by landslides.