• Korean Chemical Engineering Research
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• 제59권2호
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• pp.191-199
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• 2021

화학 공정의 주요 설비 중 하나인 증류탑은 물질들의 끓는점 차이를 이용하여 혼합물에서 원하는 생산물을 분리하는 설비이며 증류 공정은 많은 에너지가 소비되기 때문에 최적화 및 운전 예측이 필요하다. 본 연구의 대상 공정은 공급처에 따라 원료의 조성이 일정하지 않아 정상 상태로 운전이 어려워 효율적인 운전이 어렵다. 이를 해결하기 위해 데이터 기반 예측 모델을 이용하여 운전 조건을 예측 할 수 있다. 하지만 미가공 공정 데이터에는 이상치 및 노이즈가 포함되어 있어 예측 성능을 향상시키기 위해 데이터 전처리가 필요하다. 본 연구에서는 인공 신경망 모델인 Long short-term memory (LSTM)과 Random forest (RF)를 사용하여 모델을 최적화한 후, 데이터 전처리 방법으로 Low-pass filter와 One-class support vector machine을 사용하여 데이터 전처리 방법 및 범위에 따른 예측 성능을 비교하였다. 각 모델의 예측 성능과 데이터 전처리의 영향은 R2과 RMSE를 사용하여 비교하였다. 본 연구의 결과, 전처리를 통해 LSTM의 경우 R2은 0.791에서 0.977으로 RMSE는 0.132에서 0.029로 각각 23.5%, 78.0% 향상되었고, RF의 경우 R2은 0.767에서 0.938으로 RMSE는 0.140에서 0.050으로 각각 22.3%, 64.3% 향상되었다.

• Earthquakes and Structures
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• 제5권6호
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• pp.753-779
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• 2013

One of the most important issues in progressive collapse mechanism of the buildings is evaluation of the collapse distribution in presence of the earthquake loads. Here, collapse propagation is investigated by tracking down the location and type of the collapsed beam and column elements, from the first element to the entire buildings. 6-story reinforced concrete ordinary moment resisting frame buildings with one directional mass eccentricity of 0%, 5%, 15% and 25% are studied to investigate differences among the progressive collapse mechanism of the regular and irregular buildings. According to the results of the nonlinear time history analyses, there are some patterns to predict progressive collapse scenarios in beam and column elements of the similar regular and irregular buildings. Results also show that collapse distribution patterns are approximately independent of the earthquake records.

• 한국공간구조학회논문집
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• 제13권3호
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• pp.65-72
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• 2013

Long span arch structure is composed of arch as relatively flexible structure and column as relatively rigid structure. In this study, the characteristic of dynamic response is analyzed according to the natural frequency ratio between arch and columns. The result of analysis for arch as relatively vertical vibration mode is dominant, the influence of columns mainly appears at relatively high frequency band according to increase of 1st mode frequency in column. However, the dynamic characteristic of arch structure is expected to vary with not only frequency ratio but interaction between vibration modes of arch and columns.

• 대한화학회지
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• 제7권2호
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• pp.115-121
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• 1963

Aliphatic hydrocarbon gases from rubber pyrolysis have been identified by gas chromatography with tetraethyleneglycol dimethylether column. Rubbers used in this work are polyisoprene, SBR, NBR, polybutadiene, buthyl rubber, polychloroprene and polyurethane rubber. The chromatogram is characteristic for each polymer. Author proposes a method of identification of synthetic rubbers by gas chromatograph of pyrolyzed gas. Sample is pyrolyzed at $450^{\circ}C$ under nitrogen or more effectively helium and gaseous portion, which eliminated liquid condensate, is passed to the column. The appearance of exclusively large peak of isoprene, isobutylene and carbon dioxide shows the presence of polyisoprene, polyisobutylene and polyurethane, respectively. Large peak of butadiene will appear in case of polybutadiene, SBR and NBR, but SBR can be identified through the styrene peak in gas chromatogram of liquid pyrolyzate and NBR can be identified by the evolution of hydrogen cyanide during pyrolysis. Polychloroprene is identified by the evolution of hydrogen chloride. This method could be applied to the identification of copolymer or polymer blend.

• Management Science and Financial Engineering
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• 제9권1호
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• pp.11-27
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• 2003

In this study, we propose a mathematical model based on the graph theory for the wavelength assignment problem arising in the design of SDH (Synchronous Digital Hierarchy) over WDM (Wavelength Division Multiplexing) ring networks. We propose a branch- and -price algorithm to solve the suggested models effectively within reasonable time in realistic SDH over WDM ring networks. By exploiting the structure of ring networks, we developed a polynomial time algorithm for efficient column generation and a branching rule that conserves the structure of column generation. In a computer simulation study, the suggested approach can find the optimal solutions within reasonable time and show better performance than the existing heuristics.

• Biotechnology and Bioprocess Engineering:BBE
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• 제6권6호
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• pp.363-375
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• 2001

Chromatography has been method of choice for the separation complex biologi-cal mixtures fro analytical purpose, particularly for the last fifty years. Its use has recently been extended to preparative separation where the productivity relative to the amount of resin and sol-vent used is a matter of concern. To overcome the inherent thermodynamic inefficiency of batch chromatography, as exemplified by the partial temporal usage of the resin and dilution of the product with the solvent, chromatography has been continually modified by separation engineers. Column switching and recycling represnet some of the process modifications that have brought high productivity to chromatography. Recently, the simulated moving bed (SMB) method, which claims a high separation efficiency based on counter-current moving bed chromatography. has be-come the mainstay of preparative separation, especially in chiral separation. Accordingly, this pa-per reviews the current status of SMB along with several chromatographic modification, which may be helpful in routine laboratory and industrial chromatographic practices.

• 한국가구학회지
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• 제13권2호
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• pp.53-62
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• 2002

Due to the industrial development some scholars insist that homo sapiens has become a new race--homo sedens. Since this great degree of behavioral change often cause problems in the spinal column, the appropriate sitting became critical. The nineteenth-century idea of sitting upright position is not considered as a proper sitting any longer. Recent studies by such psychological scientists as A. C. Mandal, Ernest McCormick, and Karl Kroemer show that the spinal column in s-curve with forward bends should be efficiently supported in that manner. Designing a chair sometimes focuses on aesthetic points rather than true ergonomic considerations. Therefore, these result in deleterious effects on human bodies such as lordosis and kyphosis. In fact, it has been overlooked due to the lack of technical and scientific supports. Also, in a mass production, it is hard to meet everyone's need. However, the well adapted ergonomic considerations should meet the needs for wide ranges of people. Indeed, in this study we will examine designing chairs in ergonomic perspectives and suggest additional controversial points and alternatives.

• Elastomers and Composites
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• 제22권1호
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• pp.11-19
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• 1987

A coil pyrolyzer and processor-controlled gas chromatograph were used for analysis of rubber for compounding ratio of the single and blend rubber vlucanizates. Variables such as sample size, pyrolysis temperature, time allowed for pyrolysis, the column packing material, its length and programmable temperature for gas chromatography were examined to obtain optimum condition for application to NR, BR and SBR blends. By application fixed conditions, three kinds of standard curves were finally obtained from thirty samples of blend vulcanizates which were prepared in the pilot plant, NIRI. It is possible to determine rubber composition and their ratio in NR, BR and SBR products by pyrolysis.

• 한국산학기술학회논문지
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• 제15권6호
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• pp.3851-3857
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• 2014

화물열차를 이용하는 화주의 화물열차 수요는 기간에 따라 변동성이 크나 화주의 요구에 따라 화물열차 스케줄을 조정하거나 증편하는 것은 상당한 시간이 소요된다. 그 이유는 해의 범위가 폭발적으로 증가하고 선로용량, 운영규정, 기존열차와의 경합 등을 고려해야하기 때문이다. 그러나 국내 철도 운영사에서 화물열차 증편일정 조정 업무는 지속적으로 발생하고 있으며, 담당자의 경험적인 역량으로 해결해 왔다. 본 논문에서는 증편되는 화물열차의 운행 가능성을 판단하고, 증편요청열차들이 기존 열차의 운행시간 지연을 최소로 하면서 가급적 많은 추가 스케줄을 생성할 수 있는 모형을 제시한다. 제시된 모형은 시공간 네트워크로 문제를 표현하고 다중상품 흐름문제로 모델링하여 열생성 기법으로 해를 구하였다. 제시된 모형으로 3가지 실험을 수행하였으며, 복잡한 문제의 경우에도 계산시간상 실용적임을 확인하였다.

• 한국응용과학기술학회지
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• 제9권2호
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• pp.157-163
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• 1992

A microorganism, isolated from soil and designated Pseudomonas sp13, produced two kinds of rhamnolipid in the medium containing glucose as carbon source. There were both rhamnolipid contain L-rhamnose and ${\beta}$-hydroxydecanoic acid. Coumpound A and B elucted chloroform-methanol mixed solution of silicic acid column chromatography and recrystallized from a mixture of ether and n-hexane. Studies on the structure of these products reveled that compound A is L-rhamnopyranosyl-${\beta}$-hydroxydecanoyl-${\beta}$-hydroxydecanoic acid and compound B is L-rhamnopyranosyl-L-rhamnopyranosyl-${\beta}$-hydroxydecanoyl-${\beta}$-hydroxydecanoic acid.