• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.401-407
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• 2011

The conventional method of magnetic abrasive polishing is not suitable for non-magnetic materials because such polishing is basically possible when magnetic force exists and the magnetic force in non-magnetic materials is very low. The installation of an electromagnet under the working area of a non-magnetic material, which is called second-generation magnetic abrasive polishing in this study, can enhance the magnetic force. Experimental evaluation and optimization of process parameters for polishing magnesium alloy steel was performed by adopting the design of experiments and the response surface method. The results indicated that the intensity of the magnetic force and spindle speed are significant parameters that affect the improvement of surface roughness. A prediction model for the surface roughness of the magnesium alloy steel is developed using the second-order response surface method.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.987-992
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• 1998

Titanium aluminide intermetallic compound was formed from high purity elemental Ti and A1 foils by selfpropagating, high-temperature synthesis(SHS1 in hot press. Formation of $TiAl_3$ intermetallics at the interface between Ti and Al foil was observed to be controlled by temperature, pressure and heating rate. Especially, the heating rate is the most important role to form intermetallic compound by SHS reaction. According to DTA experiment, the SHS reactions appeared at two different temperatures below and above the melting point of Al. It was also observed that both SHS reaction temperatures increased with increasing the heating rate. After the SHS reaction of alternatively layered 10 Ti and 9 A1 foils at the heating rate of $20^{\circ}C$/min, the $700\mu\textrm{m}$ thick titanium aluminide sheet was formed by heat treatment at $810^{\circ}C$ for 4hours.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.04a
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• pp.168-168
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• 2001

제지공정의 지절 현상은 많은 공정 변수들이 복합적으로 작용하여 발생하는 가장 큰 공정 트러블 중의 하나이다. 지절은 생산량 감소 뿐만 아니라 발생 후 공정의 복구 와 정리, 생산재가동 및 공정의 재안정화를 위해 많은 시간과 비용, 그리고 노력이 투 입되어야 하므로 공정의 효율과 생산성을 크게 저하시키는 요인이다. 그러나 지절 현상 의 복잡성 때문에 이에 대해 쉽게 접근하거나 해결하지 못하고 있는 것이 현실이지만 그 필요성은 더욱 더 증대되고 있다. 본 연구에서는 최근 들어 각종 산업분야에서 복잡 한 공정상의 결점 발견 및 진단에 효과적이라고 인정받고 있는 예측 분석기법인 인공 신경망(artificial neural network) 시율레이션과 일반적인 통계기법 중의 하나인 주성분 분석을 이용하여 제지 공정의 지절 현상의 검토 가능성을 타진하였다. 인공신경망이란 인간두뇌에서 일어나는 자극-반응-학습과정을 모사하여 현실세계에 존재하는 다양한 현상들의 업력벡터와 출력상태 간의 비선형 mapping올 컴퓨터 시율 레이션을 통하여 분석하고자 하는 기법으로, 여러 가지 현상들을 학습을 통해서 인식하 는 신경망 내의 신경단위들이 병렬처리에 의해 많은 양의 자료에 대한 추론이나 판단 을 신속하고 정확하게 해주는 특징이 있으며 실시간 패턴인식이나 분류 응용분야에도 매우 매력적으로 이용되고 있는 방법이다. 이러한 인공 신경망 기법 중에서도 본 연구 에서는 퍼셉트론의 한계점을 극복하기 위하여 입력총과 출력층에 한 개 이상의 은닉층 ( (hidden layer)을 사용하여 다층 네트워으로 구성하고, 모든 입력패턴에 대하여 발생하 는 오차함수를 최소화하는 방향으로 연결강도를 조정하는 back propagation 학습 알고 리즘을 사용하였다. 지절의 원인으로 추정 가능한 공정인자들을 변수로 하여 최적의 인 공신경망을 구축하기 위해 학습률과 모멘트 상수의 변화 및 은닉층의 수와 출력층의 뉴런 수를 조절하는 동의 작업을 거쳐 네트워크의 정확도가 높은 인공신경망을 설계하 였다. 또한 이러한 인공신경망과의 비교분석을 위해 동일한 공정 데이터들올 이용하여 보편적으로 사용하는 통계기법 중의 하나인 주성분회귀분석을 실시하였다. 주성분 분석은 여러 개의 반응변수에 대하여 얻어진 다변량 자료의 다차원적인 변 수들을 축소, 요약하는 차원의 단순화와 더불어 서로 상관되어있는 반응변수들 상호간 의 복잡한 구조를 분석하는 기법이다. 본 발표에서는 공정 자료를 활용하여 인공신경망 과 주성분분석을 통해 공정 트러블의 발생에 영향 하는 인자들을 보다 현실적으로 추 정하고, 그 대책을 모색함으로써 이를 최소화할 수 있는 방안을 소개하고자 한다.

• Journal of Convergence for Information Technology
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• v.10 no.7
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• pp.138-146
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• 2020

The paper deals with comparative study of characteristics of surrogate models and sensitivity evaluation using design of experiments in order to enhance and analysis the structure design of an automatic salt collector under various design load conditions. Orthogonal array design based on numerical analysis was used for the design of experiments. The thickness sizing variables of main structure member were considered the design factors, and the output responses were selected from the strength performances as well as the weight. The quantitative effects on responses for each design factor were evaluated from the orthogonal array experiment. Optimum design case was also identified to improve the strength performances with weight minimization. Using the orthogonal array experiment. various surrogate models such as response surface model, Kriging model, and Chebyshev orthogonal polynomial were generated. The orthogonal array experiment results were validated by the surrogate modeling results. The most suitable surrogate model was the response surface model for the exploration of design space of the automatic salt collector.

• Journal of the Korean Institute of Gas
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• v.26 no.5
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• pp.16-21
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• 2022

The reaction rate of a catalyst for producing hydrogen using the methanol steam reforming reaction was studied. It was prepared by impregnating copper, which is often used in methanol synthesis, as the main active metal, using hydrotalcite, which has excellent porosity and thermal stability, high specific surface area, weak Lewis acid point, and basicity, as a support. Activation energy and Pre-exponential factors were identified. In this study, the activation energy of the hydrotalcite catalyst impregnated with 20 wt% copper was calculated to be 97.4 kJ/mol and the Pre-exponential was 5.904 × 10¹⁰. Process simulation was performed using the calculated values and showed a similar tendency to the experimental results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.244-249
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• 2023

In this study, various experimental parameters were investigated for high-purity C₃A synthesis. As a results of experiment, it was verified that the calcined temperature was the most important parameter for the synthesis of high-purity C₃A. In addition, more synthesis time was needed when large amount of C₃A synthesis to achieve high-purity. Meanwhile, the C₃A blended with CaCO₃ showed different reaction products compared to normal cement because C15 and C30 had monocarbocaluminate as a reaction product at early stage of hydration. Furthermore, the production amount and formation rate of monocarboaluminate formation was different varying with the CaCO₃ a mounts.

• Microbiology and Biotechnology Letters
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• v.44 no.1
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• pp.48-54
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• 2016

In this study, biosugar production by the red-algae Eucheuma cottonii was investigated using dilute sulfuric acid-catalyzed hydrolysis and data analysis by response surface methodology. This approach yielded 25.8 g/l total reducing sugar under the conditions of $160.1^{\circ}C$, 1% (v/v) sulfuric acid, and 13.1 min. The sugar concentration showed a linear inverse correlation with the combined severity factor (CSF) of the reaction conditions. CSF was calculated as $log(t{\cdot}e{xp}[(T_H-T_R)/14.75])-pH$, where t is the coupling reaction time, $T_H$ is the target temperature, and $T_R$ is the reference temperature ($100^{\circ}C$). In addition, levulinic acid production showed a linear positive correlation with CSF. E. cottonii may represent a useful feedstock for sugar production in the field of bioenergy.

• Clean Technology
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• v.20 no.3
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• pp.256-262
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• 2014

Catalytic oxidation characteristics of benzene as a VOC was investigated in a fixed bed flow reactor using $Cu/{\gamma}-Al_2O_3$ catalyst. The parametric tests were conducted at the reaction temperature range of $200{\sim}500^{\circ}C$, benzene concentration of 400~650 ppm, gas flow rate of 50~100 cc/min, and space velocity range of $7,500{\sim}22,500hr^{-1}$. The property analyses by using the BET, SEM, TGA and the conversion of catalytic oxidation of benzene were examined. The experimental results showed that the conversion was increased with decreasing benzene concentration, gas flow rate and space velocity. Benzene oxidation reaction over $Cu/{\gamma}-Al_2O_3$ catalyst could be expressed as the first order homogeneous reaction of which the activation energy was 17.2 kcal/mol and frequency factor was $1.33{\times}10^6sec^{-1}$.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.651-659
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• 2000

The characteristics of ammonia removal by natural neutralizer were studied by using a scrubber type equipment. As operation parameters, neutralizer dilution ratio, neutralizer inlet flowrate, air flowrate and initial ammonia concentration were selected and their effects on ammonia removal efficiency were investigated. The optimal removal effect was achieved at neutralizer dilution ratio of 1.0% and neutralizer inlet flowrate of $60m{\ell}/min$. On the other hand, with respect to air flowrate and initial ammonia concentration, there was no significant effect on removal efficiency, when loading rate was considered. In addition, ammonia removal reaction was investigated by analyzing the ammonia oxides, such as nitrites and nitrates, after reacting ammonium solution with natural neutralizer. The result shows a partial oxidation by natural neutralizer besides dominant absorption of ammonia.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.547-553
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• 2017

Thermal analysis of three energetic materials used in pyroelectric device was performed using Differential Scanning Calorimetry (DSC). The theoretical method for extracting the reaction rate equation of energetic materials using DSC experimental data is proposed and the reaction rate extraction is performed. The results of the DSC were analyzed by the conversion method such as Friedman. Activation energy and frequency factor according to mass fraction were extracted to complete the reaction rate equation. The extracted reaction rate equation has a form that represents the entire chemical reaction process, not the assumption that the chemical reaction process of the high energy material is a main step in several stages. It has considerable advantages in terms of theoretical and accuracy as compared with the chemical reaction rate form extracted through conventional thermal analysis experiments. Using the derived reaction rate equation, we predicted the performance change of three energetic materials operating on actual storage condition over 20 years.