• Structural Engineering and Mechanics
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• 제35권2호
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• pp.127-140
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• 2010

This paper focuses on a number of criteria that enable controlling the influence of geometric simplification on the quality of finite element (FE) computations. To perform the mechanical simulation of a component, the corresponding geometric model typically needs to be simplified in accordance with hypotheses adopted regarding the component's mechanical behaviour. The method presented herein serves to compute an a posteriori indicator for the purpose of estimating the significance of each feature removal. This method can be used as part of an adaptive process of geometric simplification. If a shape detail removed during the shape simplification process proves to be influential on mechanical behaviour, the particular detail can then be reinserted into the simplified model, thus making it possible to readapt the initial simulation model. The fields of application for such a method are: static problems involving linear elastic behaviour, and linear thermal problems with stationary conduction.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.161-161
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• 2008

The oxide film of silicon wafer has been mainly polished by fumed silica, colloidal silica or ceria slurry. Because colloidal silica slurry is uniform and highly dispersed composed of spherical shape particles, by which the oxide film polished remains to be less scratched in finishing polishing process. Even though the uniformity and spherical shape is advantage for reducing the scratch, it may also be the factor to decrease the removal rate. We have studied the correlation of silica abrasive particles and CMP characteristics by varying pH, down force, and table rotation rate in polishing. It was found that the CMP polishing is dependent on the morphology, aggregation, and the surface property of the silica particles.

• 한국기계가공학회지
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• 제18권7호
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• pp.8-13
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• 2019

As increasing demand for precise machining in advanced disciplines, especially in semi-conductor, aeronautical and automotive industries, the magnetic abrasive deburring(MAD) which is able to eliminate micro-sized burr on complex surface in less time has drawn the attention in the last decades. However, the performance of MAD is subject to shape and size of a tool. Therefore, this study aim to identify deburring behavior of MAD in U-type flow channel by measuring the length rate of burr removal in radial distance of the cylindrical tool under four process factors. In order to evaluate the deburring effect of MAD on the surface, finishing regions are divided based on center of the circular cutting tool. As a results, it was defined that the amount of burr removal in a downward direction moving toward flow channel from the top surface was higher than upward direction. This is because the magnetic abrasives were detached from magnetic lines of force due to geometrical shape.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.74-78
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• 2002

Ultra-Precision CNC polishing system including on-machine measurement system, a corrective polishing algorithm is developed. The unit removal profiles for various polishing tools and analyzed and tested and dwell time distributions and residual errors for a target removal shape are calculated. The corrective polishing algorithm is tested with various workpieces. This result will be used for the software development of the CNC polishing system.

• 상하수도학회지
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• 제33권1호
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• pp.79-86
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• 2019

In order to measure the filtration characteristics of a cotton ball shape filter, the experiments of suspended solids(SS) surrogate material selection and filtration performance have been carried out in this study. Between the two materials of powdered activated carbon(PAC) and powdered red-clay, PAC is more suitable surrogate material in terms of experimental criteria and particle size distribution in the non-point source pollutants removal system. As a result of the filtration experiments with the cotton ball shape filter, the initial headloss was about 8 cm, and the headloss slightly increased over filtration time. The Kozeny-Carman equation was used to analyze the changes of pressure and porosity during the filtration. The initial porosity was calculated as 0.945 and it decreased to 0.936 at the end of design filtration time. As the filtration continued, the SS concentration of the filtered water gradually increased and the SS removal rate gradually decreased. When the SS target removal efficiency is assumed to be 80%, the cumulative SS removal capacity is expected as $28.8kg/m^2$. This means the volume loading rate of the cotton ball shape filter can be $115m^3/m^2$ when the typical SS concentration of non-point source water pollution is assumed as 250 mg/L.

• 한국대기환경학회지
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• 제19권3호
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• pp.315-323
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• 2003

The goal of this study if the optimization of discharge electrode for pulsed corona discharge reactor located in thermal power plant. For this purpose, we have performed experiments of NO$_{x}$ removal rate by exchange of discharge electrode diameter and arrangement of discharge electrode in the non -thermal plasma reaction facility using a ethylene as additive. If the diameter and numbers of discharge electrode were larger, the NO$_{x}$ removal rate was higher. From these results, if we optimized the shape and installed numbers of discharge electrode at the pilot plant, we could increase the NO$_{x}$ removal rate with less amount of additive than current amount.mount.

• Advances in environmental research
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• 제4권4호
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• pp.263-271
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• 2015

In this study, the effect of initial nitrate loading on nitrate removal and byproduct selectivity was evaluated in a continuous system. Nitrate removal decreased from 100% to 25% with the increase in nitrate loading from 10 to $300mg/L\;NO_3-N$. Ammonium selectivity decreased and nitrite selectivity increased, while nitrogen selectivity showed a peak shape in the same range of nitrate loading. The nitrate removal was enhanced at low catalyst to nitrate ratios and 100% nitrate removal was achieved at catalyst to nitrate ratio of ${\geq}33mg\;catalyst/mg\;NO_3-N$. Maximum nitrogen selectivity (47%) was observed at $66mg\;catalyst/mg\;NO_3-N$, showing that continuous Cu-Pd-NZVI system has a maximum removal capacity of 37 mg $NO_3{^-}-N/g_{catalyst}/h$. The results from this study emphasize that nitrate reduction in a bimetallic catalytic system could be sensitive to changes in optimized regimes.

• 상하수도학회지
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• 제26권5호
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• pp.659-668
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• 2012

In Korea, almost every water treatment plant suffers from seasonal problem of algae and turbidity which result from eutrophication and heavy rainfall. To relieve this problem, experimental investigation was performed to study the applicability of a floating-media and sand filter to preliminary water treatment in terms of algae and turbidity removal. Experimental results using pure-cultured algae influent showed that the shape of algae species as well as filtration velocity affects the removal efficiency. From the experiments using natural river water, it was concluded that algae removal is more sensitive to floating-media depth but turbidity more sensitive to sand depth. As the filtration velocity increased, the removal of turbidity decreased but that of algae was not affected. The floating-media and sand filter removed more than 30 % of TP, TN, turbidity, Chl-a and CODcr, and less than 20 % of DOC and $UV_{254}$.

• 상하수도학회지
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• 제26권1호
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• pp.131-139
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• 2012

Field experiment was performed from June 2010 to July 2011 to evaluate pollutants removal efficiency in the constructed wetland system for the treated wastewater and the river water. The wetland systems were constructed near Gyungan river. Two different systems with meandering shape were compared for seasonal base and operational period base. Several kinds of aquaculture are planted through the corridor of wetland system. Average removal rate of BOD, T-N and T-P for A system were 15.8%, 14.8% and 26.5%, respectively. Average removal rate of BOD, T-N and T-P for C system were 23.5%, 27.8% and 10.6%, respectively. The effluent from two wetland systems often exceeded effluent water quality standards for wastewater influent, however effluent water quality standards for river water. However, the wetland system can be useful to treat polluted river water and effluent from wastewater plant. Removal rate of pollutants in seasonal variation was the highest in summer for BOD and T-N, however the removal rates of T-P were higher in spring and autumn than in summer.

• KSBB Journal
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• 제14권6호
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• pp.731-736
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• 1999

동두천과 반월공단에서 87가지의 균주를 분리하였다. 그 중 5가지 균주가 색도 제거율이 우수함을 보였으며, 동정을 통해 Shewanella putrefaciens, Aeromonas salmonicida(서로 다른 3종), Pseudomonas vesicularis로 각각 동정되었다. 동정된 5종의 미생물들은 성장에 최적인 pH와 온도는 각각 7.0과 30$^{\circ}C$이었으며, Gram negative, catalase nagative, rod shape, 그리고 비운동성을 보였다. 500 mL 플라스크에서 분리된 균주 중 단일균주를 사용하여 염색폐수를 처리한 경우 약 35%의색도 제거율을 보였다. 2균주를 조합하여 적용하였을 때는, 색도 제거율이 65%까지 증가한 반면, 3균주 조합 혹은 그 이상의 균주 조합에서는 2균주 조합보다 더 좋은 효율은 보이지 않았다. 염색폐수 분해시 $Mn^{2+},\;Fe^{3+}$와 같은 중금속의 영향을 조사하였는데, 70 ppm 이하의 농도에서는 별로 영향을 주지 않았다.