• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.136-142
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• 2014

Nowadays, dental zirconia is widely used as a framework material for a fixed dental prosthesis as well as a single restoration. However, clinical studies have reported high incidence of veneer chipping of zirconia-ceramic restorations compared to that of metal-ceramics. Several factors were raised as the possible causes of veneer ceramic chipping, however, it is still in debate. Recently, residual stresses in the veneer ceramics after cooling process gathers attention as one possible cause of chipping and many studies reported that the rate of cooling significantly influenced the types and the amount of residual stress. The purpose of current review was to briefly describe the effect of cooling rate on the residual stress in zirconia-ceramics. It was also described that the different behavior of residual stress between zirconia-ceramics and metal-ceramics following different cooling rate.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.1
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• pp.15-20
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• 2009

The concentration of residual chlorine should be kept at over 0.1 mg/L in the circular water tank used in a water purification system. Generally, the concentration of residual chlorine depends on the structure and the volume of water tank, and also the water flow rate. To secure the diffusion time is important to the concentration of residual chlorine. For that reason, the baffles are installed in the circular water tank. In the present study, the variations of water and chlorine concentration were obtained with time using the numerical analysis. And also, the streamlines were shown according to the number of baffles. As a results, the vortex flow appeared between baffles, and the diffusion time of chlorine increased with the more number of baffles.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.133-139
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• 2000

In this study, activated carbon was prepared from solid residue after lignin pyrolysis by using zinc chloride as an activation agent. The steam activation method was adopted to manufacture activated carbon from solid residue after lignin pyrolysis. The effect of process operation variables such as activation temperature, activation time and mass of activation agent added to char on the pore structure and specific surface area of the activated carbon was investigated. Activated carbon with high surface area and well-developed pore structure could be prepared, when solid residue after lignin pyrolysis was mixed with zinc chloride of 300 wt% and then the mixture was activated for 1 hour at $1000^{\circ}C$ in a stream of nitrogen.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.181-181
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• 2022

상수도 관망은 비정상상황에서도 안전한 물을 안정적으로 공급하는 것을 목표로 한다. 따라서 상수도 관망의 최적 설계는 수리학적 제약조건 (i.e., 절점의 압력, 관의 유속)을 만족하는 설계안을 제시한다. 하지만 점차 커지는 도시 규모에 따라 수질적으로 안전한 물을 공급하지 못하는 문제가 발생하고 있다. 또한, 상수도시스템의 형식 (i.e., 수지상식, 혼합식, 순환식)에 따라 용수의 체류 시간, 절점의 압력 등이 상이하다. 따라서, 본 연구에서는 도시 규모 및 형식과 잔류염소 농도를 고려한 상수도시스템 최적 설계를 진행하였다. 절점의 개수에 따라 도시의 규모를 분류하였으며, BI(BI; Branch Index) 지수를 통해 상수도시스템의 형식을 분류하였다. 또한, 수리학적 제약조건(i.e., 절점의 압력)과 수질적 제약조건 (i.e., 잔류염소 농도)을 설정하여 수리-수질을 동시에 만족하는 최적 설계안을 도출하였다. 비상시에도 물을 안정하게 공급하기 위하여 시스템의 탄력성과 설계비용을 목적함수로 설정하여 다목적 최적 설계를 진행하였다. 이러한 연구는 압력만을 고려한 기존 설계단계에서 수질적 측면을 동시에 고려하여 수질 측면의 안전성을 향상할 수 있다. 또한, 시스템의 탄력성을 고려하여 비정상상황에서도 물을 공급하여 사용성을 향상하는 설계안을 도출하여 수리학적 안정성을 만족하며, 경제적 측면도 향상할 수 있다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.11-20
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• 2013

In this paper, the quantitative damage index for reinforced concrete (RC) columns with non-seismic details were presented. They are necessary to carry out the postearthquake safety evaluation of RC buildings under 5 stories without seismic details. The static cyclic test of the RC frame sub-assemblage that was an one span and actual-sized was first conducted. The specimen collapsed by the shear failure after flexural yielding of a column, lots of cracks on the surfaces of columns and beam-column joints and the cover concrete splitting at the bottom of columns occurred. The damage levels of these kinds of columns with non-seismic details were classified to five based on the load-displacement relationship by the test result. The residual story drift ratios and crack widths were then adapted as the quantitative index to evaluate the damage limit states because those values were comparatively easy to measure right after earthquakes. The highest one among the residual story drift ratios under the similar maximum story drift ratio decided on the residual story drift ratio of each damage limit state. On the other hand, the lowest and average ones among the respective residual shear and flexural widths under the similar maximum story drift ratio decided on the residual shear and flexural widths of each damage limit state, respectively. These values for each damage limit state resulted in being smaller than those by the international damage evaluation guidelines that are for seismically designed members under the same deformations.

• Economic and Environmental Geology
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• v.44 no.1
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• pp.49-57
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• 2011

Water budget analysis in the groundwater system was conducted in order to understand water budget distributions in the ground water system in Geum-gang watershed. The annual amounts of precipitation, runoff, evapotranspiration, dam storage change and water supply over the sub-watershed in Geum-gang watershed were evaluated the residual groundwater from 2002 to 2006, based on the water budget considering inflow and outflow. Then we are able to expect residual groundwater of each sub-basin. According to the result of study, the year 2003 and 2006 were recorded the highest and the lowest precipitation value, respectively. Average run-off percentage against precipitation was 60.44%. Annual evapotranspiration in each of years didn't show the remarkable variations but the values were high in the lower reaches of the basin. The residual waters in Geum-gang basin were determined to be 133.36 in 2002, 77.64 in 2003, -19.40 in 2004, -82.25 in 2005 and -128.07 mm in 2006. The residual water in Geum-gang basin was high in the main and up stream such as Maepo. Also the residual water showed low distributions in Nonsan and Seokhwa.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.3
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• pp.183-191
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• 1991

A study was conducted to determine the influence of soil chemical properties on the distribution and forms of cadmium (Cd), lead (Pb), copper(Cu) and Zinc(Zn) in paddy soils near zinc mines. A sequential extraction procedure was used to fractionate the heavy metals in soils into the designated from of water soluble, exchangeable, organically bound, oxide/carbonate, and sulfide/residual. The predominant form of Cd, Pb, Cu and Zn in the soils was found to be sulfide/residual form. Oxide/carbonate Cd and Pb and organically bound Cu were high, while exchangeable Pb and Cu were very low. Water soluble Cd, Pb and Cu were not detected in the soils. The percentages of the heavy metals content in exchangeable fractions were inversely correlated with those in sulfide/residual fractions in the soils. Exchangeable Cd and Zn and the oxide/carbonate Pb were shifting to the sulfide/residual form with soil depth and the chemical forms of Cu were not changed. Organically bound Cu was positively correlated with soil organic matter content but Cd, Pb and Zn were not. The percentages of Cd, Pb and Zn content in exchangeable forms decreased with soil pH, while those in oxide/carbonate and sulfide/residual forms increased with soil pH. The amounts of oxide/carbonate and sulfide/residual forms of pb were higher than those of Cd and Zn at same soil pH.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.2
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• pp.9-15
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• 2024

The effect of the residual impurity on the prepreg surface on the wettability of encapsulant for chip on board package was analyzed with microstructure, compositions and chemical bonds using a scanning electron microscope and X-ray photoelectron spectroscopy. As a result, the contact angle of w/ residual impurity sample was measured to be 28° higher than that of w/o residual impurity sample, and the C-O bond was decreased to be 4% lower than that of w/o residual impurity sample. The surface energy of the prepreg decreased because the impurity ions, Na and F, generated by the manufacturing process and wet etching, reacted chemically with the C on the prepreg surface, forming C-F bonds and breaking the C-O bonds on the prepreg surface. Therefore, the wettability of the encapsulant was degraded because the contact angle between the encapsulant and the prepreg was increased.

• Journal of Food Hygiene and Safety
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• v.34 no.2
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• pp.140-147
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• 2019

An analytical method was developed for the determination of quinoxyfen in agricultural products using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted with 1% acetic acid in acetonitrile and water was removed by liquid-liquid partitioning with $MgSO_4$ (anhydrous magnesium sulfate) and sodium acetate. Dispersive solid-phase extraction (d-SPE) cleanup was carried out using $MgSO_4$, PSA (primary secondary amine), $C_{18}$ (octadecyl) and GCB (graphitized carbon black). The analytes were quantified and confirmed by using LC-MS/MS in positive mode with MRM (multiple reaction monitoring). The matrix-matched calibration curves were constructed using six levels ($0.001-0.25{\mu}g/mL$) and the coefficient of determination ($R^2$) was above 0.99. Recovery results at three concentrations (LOQ, 10 LOQ, and 50 LOQ, n=5) were in the range of 73.5-86.7% with RSDs (relative standard deviations) of less than 8.9%. For inter-laboratory validation, the average recovery was 77.2-95.4% and the CV (coefficient of variation) was below 14.5%. All results were consistent with the criteria ranges requested in the Codex guidelines (CAC/GL 40-1993, 2003) and Food Safety Evaluation Department guidelines (2016). The proposed analytical method was accurate, effective and sensitive for quinoxyfen determination in agricultural commodities. This study could be useful for the safe management of quinoxyfen residues in agricultural products.

• Journal of the Korean Vacuum Society
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• v.13 no.4
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• pp.157-163
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• 2004

Dependence of residual compressive stress of diamond-like carbon (DLC) films on relative humidity was investigated. Polymeric, graphitic and diamond-like carbon films were prepared by r.f.-PACVD using methane or benzene with the negative self bias voltage of the substrate ranging from -100 to -800 V. In-situ measurements of the residual stress were carried out in an environment chamber where the relative humidity was varied from 10％ to 90％. In dense DLC film of high residual compressive stress and hardness, we could not observe any change in the residual compressive stress with relative humidity. However, in the cases of graphitic and polymeric DLC films, abrupt change in the residual stress occurred by changing the relative humidity. The quantity of the stress change was inversely proportional to the film thickness, which means that the stress change with humidity is not due to the penetration of the water molecule into the film structure, but due to surface interaction between water molecules and film surface.