• 상하수도학회지
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• 제23권5호
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• pp.669-678
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• 2009

The reduction of excess activated sludge from petrochemical plant was investigated by the electro fenton (E-Fenton) process using electrogenerated hydroxyl radicals which lead to mineralization of activated sludge to $CO_2$, water and inorganic ions. Factors affecting the disintegration efficiency of excess activated sludge in E-Fenton process were examined in terms of five criteria: pH, $H_2O_2/Fe^{2+}$ molar ratio, current density, initial MLSS (mixed liquid suspended solids) concentration, $H_2O_2$ feeding mode. TSS total suspended solid and $TCOD_{cr}$ reduction rate increased with the increasing $H_2O_2/Fe^{2+}$ molar ratio and current density until 42 and $6.7 mA/cm^2$, respectively but further increase of $H_2O_2/Fe^{2+}$ molar ratio and current density would reduce the reduction rate. On the other hand, as expected, increasing pH and initial MLSS concentration of activated sludge decreas TSS and $TCOD_{cr}$ reduction rate. The E-Fenton process was gradually increased during first 30 minutes and then linearly proceed till 120 minutes. The optimal E-Fenton condition showed TSS reduction rate of 62~63% and $TCOD_{cr}$ (total chemical oxygen demand) reduction rate of 55~56%. Molar ratio $H_2O_2/Fe^{2+} = 42$ was determined as optimal E-Fenton condition with initial $Fe^{2+}$ dose of 5.4 mM and current density of $6.7{\sim}13.3 mA/cm^2$, initial MLSS of 7,600 mg/L and pH 2 were chosen as the most efficient E-Fenton condition.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.205-209
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• 1998

Unlike the drawing of round section from round bar, the shaped drawing like polygonal section is known to have influence not only drawing stress but also comer filling. Therefore, this study analyze the drawing process of suqare rod from round bar using nonsteady state rigid-plastic FEM. To investigate effects of process variables of the drawing process of square rod from round bar, FE-simulations with variety of reduction in area and semi-die angle for a given frictional condition have been conduction. By this results, it has to suggest optimal process condition on the drawing stress and the comer filling. In addition, it has determined forming limit considering necking and bulging.

• Structural Engineering and Mechanics
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• 제32권3호
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• pp.371-382
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• 2009

Response of harbor structure to environmental loads such as wave load, impact load, ship's contacting load, is a fundamental factor in designing of the structure's optimal configuration. In this paper, typical environmental loads against coastal structures are investigated for designing of the optimal harbor structure. Loads to be considered here are wave load, impact load and contacting load due to ship mooring. Statistical analysis for several harbor structure types under the corresponding loads is carried out, followed by investigation of effect of individual environmental load. Based on these, the optimal configuration for the harbor structure is obtained after considerable engineering process. Estimation of contacting load of the ship is suggested using effective energy concepts for the load, and analysis of structural behavior is done for the optimal designing of the structure in the particular load. A guideline for the design process of the harbor structure is established, and safety of the structure is examined by proposed scheme. For verification of the analytical approach, various steel-piled coastal structures and caissons are chosen and relevant structural analyses are carried out using the Finite Element Methods combined with MIDAS/GTS and ANSYS code. It is found using the Morison equation that impact load cannot be a major load in the typical harbor structure compared with the original wave load, and that configuration shape of the structure may play an important role in consideration of the response criteria.

• 청정기술
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• 제9권2호
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• pp.87-100
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• 2003

본 연구는 청정생산기술의 개념을 염색가공분야에 도입시키기 위한 방법론을 제시한 것이다. 먼저 각 분야별 전문가로 이루어진 진단지도팀을 구성하여 대상업체에서 진행중인 제조공정 진행상태를 파악하고 사용하는 원부자재의 성능 및 환경적 분석과 폐수의 환경적 분석을 실시하였다. 원부자재(조제 및 염료)의 환경성은 TOC, CODMn, CODCr, $BOD_5$의 항목으로 평가하였고, 발생되는 폐수는 TOC, CODMn, CODCr, $BOD_5$, TDS, pH의 항목으로 평가하였다. 또 물질수지 분석과 LCA 평가 후 다음 단계로 공정, 에너지, 원부자재, 생산관리, 일반관리에서의 문제점을 도출한 후 그 중에서 개선 대상을 선정하고 마지막 단계에서 각 부분에 대해 지도하여 개선토록 한 후 최종 개선 효과를 분석하였다.

• 품질경영학회지
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• 제30권2호
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• pp.86-98
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• 2002

Defining the relationship between the quality of injection molded parts and the process condition is very complicate because of lots of factor are involved and each factor has a non-linearity. With the development of CAE(Computer Aided Engineering) technology, the estimation of volumetric shrinkage of injection mold parts is possible by computer simulation even though restricted application. In this research, Neural Network applied for finding optimal processing condition. The percent of volumetric shrinkage compared on each case and show neural network can be successfully applied selecting optimum condition not only within factor level but also between factor level.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.639-642
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• 2004

The pH as a control parameter for oxidation-reduction potential (ORP) was investigated through the denitrification by Ochrobactrum anthropi SY509 under non-growing condition. The optimal pH of nitrate reductase was 7.0, and the minimal ORP level was －250 mV for the denitrification under aerobic condition. In the case of anaerobic condition, the optimal pHs of nitrate and nitrite reductase were shifted to 10.0 and 9.0, respectively, and the minimal ORP levels of nitrate and nitrite reductase were decreased to －370 mV and －340mV, respectively. In the case of alkaline pH and anaerobic condition, the denitrification efficiency of nitrate was increased up to about 2-fold over that of neutral pH and anaerobic condition. Therefore, the combined control of pH and ORP in the anaerobic condition is shown to be an important parameter in the biological denitrification process.

• 대한전기학회논문지
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• 제34권5호
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• pp.173-178
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• 1985

The control of a linear system with random coefficients is discussed here. The cost function is of a quadratic form and the random coefficients are assumed to be completely observable by the controller. Stochastic Process involved in the problem by the controller. Stochastic Process involved in the problem formulation is presented to be the unique strong solution to the corresponding stochastic differential equations. Condition for the optimal control is represented through the existence of solution to a Cauchy problem for the given nonlinear partial differential equation. The optimal control is shown to be a linear function of the states and a nonlinear function of random parameters.

• 소성∙가공
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• 제11권4호
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• pp.363-370
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• 2002

In this study, an optimal design technique was investigated for determining appropriate dimensions of components of the die set used in the extrusion process. For this, an axi-symmetric elastic finite element program for the analysis of deformation of the shrink fitted die set was developed with the Lagrange multiplier method to implement the constraint condition of shrink fit of stress ring. By coupling the rigid-viscoplastic analysis of extrusion process by CAMPform and elastic analysis of the die set, the optimization study was made by employing optimization program DOT. Considering the various assembly conditions, optimal design was determined for a single stress ring case. It is construed that the proposed design method can be beneficial for improving the tool life of cold extrusion die set at practice.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.19-22
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• 1997

The objective of this research is to use an analytical and experimental approach to develop optimal tool geometry for high speed machining. The tool geometry parameters and cutting process have complex relationships. Until now, numerous cutting tests were needed to acquire optimal design of endmill for the purpose of high speed machining, dut to the insufficient knowledge about process in high speed machining. In order to improve the cutting ability of endmill, a model for optimal cutter shape was developed to minimize resultant cutting force by combing cutting force and wear test and surface roughness test from optimized and conventional cutter with the same cutting condition. Using various tools with different geometry, relationships between the tool geometry parameter, rake angle, clearance angle, lengh of cutter have been stuied.

• 한국기계가공학회지
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• 제13권3호
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• pp.89-95
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• 2014

The increasing level of demand for multi-tasking machines requires a saddle with an ultra-precise machining accuracy level of $15{\mu}m$, as such a saddle is one of the main components of these machines. The manner of achieving ultra-precise machining accuracy mainly depends on the fixed forces. In this paper, we optimized the number of contact points and the contact positions to reduce the deformation of the saddle while it is machined. The performance levels of the proposed optimal jig and fixture are determined by measuring the flatness, parallelism and perpendicularity of a machined saddle. The machining accuracy is found to be lower than $15{\mu}m$ at all measured points.