• Title/Summary/Keyword: sequential mixing model

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Numerical Simulation of Steel Mixing during Sequential Casting of Dissimilar Grades in the Continuous Caster (연속주조시 강종 혼합에 관한 수치해석적 연구)

  • Cho, M.J.;Kim, I.C.;Kim, S.J.;Park, H.;Lee, S.S.
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.436-443
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    • 2001
  • In order to investigate the mixing of dissimilar grades during the arbitrary grade transition in bloom caster, a computational model has been developed. The model is fully transient and consists of two sub models, which account for mixing in the bloom tundish, mixing in the strand. The developed model was verified using concentration histories measured on 1 : 1 scale bloom tundish water model. The result of numerical model showed good agreement with the experimental results of water model. By using this numerical model, the mixing of dissimilar grades in bloom caster has been simulated. As that result, the characteristics of the steel mixing in the bloom tundish and strand was showed and the amount of the intermixed grade bloom was predicted.

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Development of Sequential Mixing Model for Analysis of Shear Flow Dispersion (전단류 분산 해석을 위한 순차혼합모형의 개발)

  • Seo, Il Won;Son, Eun Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4B
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    • pp.335-344
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    • 2006
  • In this study, sequential mixing model (SMM) was proposed based on the Taylor's theory which can be summarized as the fact that longitudinal advection and transverse diffusion occur independently and then the balance between the longitudinal shear and transverse mixing maintains. The numerical simulation of the model were performed for cases of different mixing time and transverse velocity distribution, and the results were compared with the solutions of 1-D longitudinal dispersion model (1-D LDM) and 2-D advection-dispersion model (2-D ADM). As a result it was confirmed that SMM embodies the Taylor's theory well. By the comparison between SMM and 2-D ADM, the relationship between the mixing time and the transverse diffusion coefficient was evaluated, and thus SMM can integrate 2-D ADM model as well as 1-D LDM model and be an explanatory model which can represents the shear flow dispersion in a visible way. In this study, the predicting equation of the longitudinal dispersion coefficient was developed by fitting the simulation results of SMM to the solution of 1-D LDM. The verification of the proposed equation was performed by the application to the 38 sets of field data. The proposed equation can predict the longitudinal dispersion coefficient within reliable accuracy, especially for the river with small width-to-depth ratio.

Optimum Design of a Y-channel Microcmixer for Enhanced Mixing (혼합 개선을 위한 Y-채널 마이크로 믹서의 최적설계)

  • Shin Yong-Su;Choi Hyung-Il;Lee Dong-Ho;Lee Do-Hyung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.3 s.246
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    • pp.302-309
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    • 2006
  • Effective mixing plays a crucial role in microfluidics for biochemical applications. Owing to the small device scale and its entailing the low Reynolds number, the mixing in microchannels proceeds very slowly. In this work, we optimize the configuration of obstacles in the Y-channel mixer in order to attain maximum mixing efficiency. Before the optimum design, mixing characteristics are investigated using unstructured grid CFD method. Then, the analysis method is employed to construct the approximate analysis model to be used in the optimization procedure. The main optimization tool in the present work is sequential quadratic programming method. Using this approximate optimization procedure, we may obtain the optimum layout of obstacles in the Y-channel mixer in an efficient manner, which gives the maximum mixing efficiency.

Desorption Kinetics and Removal Characteristics of Pb-Contaminated Soil by the Soil Washing Method: Mixing Ratios and Particle Sizes

  • Lee, Yun-Hee;Oa, Seong-Wook
    • Environmental Engineering Research
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    • v.17 no.3
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    • pp.145-150
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    • 2012
  • Pb-contaminated soil at a clay shooting range was analyzed by the sequential extraction method to identify metal binding properties in terms of detrital and non-detrital forms of the soil. Most of the metals in the soils existed as non-detrital forms, exchangeable and carbonate-bound forms, which could be easily released from the soil by a washing method. Therefore, the characteristics of Pb desorption for remediation of the Pb-contaminated soil were evaluated using hydrochloric acid (HCl) by a washing method. Batch experiments were performed to identify the factors influencing extraction efficiency. The effects of the solid to liquid (S/L) ratio (1:2, 1:3, and 1:4), soil particle size, and extraction time on the removal capacity of Pb by HCl were evaluated. Soil samples were collected from two different areas: a slope area (SA) and a land area (LA) at the field. As results, the optimal conditions at 2.8 to 0.075 mm of particle size were 1:3 of the S/L ratio and 10 min of extraction time for SA, and 1:4 of the S/L ratio and 5 min of extraction time for LA. The characteristics of Pb desorption were adequately described by two-reaction kinetic models.

An Application of Design of Experiments for Optimization of MOF-235 Synthesis for Acetylene Adsorption Process (아세틸렌 흡착공정용 MOF-235 합성 최적화를 위한 실험 계획법 적용)

  • Cho, Hyungmin;Yoo, Kye Sang
    • Applied Chemistry for Engineering
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    • v.31 no.4
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    • pp.377-382
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    • 2020
  • A sequential design of experiments was employed to optimize MOF-235 synthesis for acetylene adsorption process. Two experimental designs were applied: a two-level factorial design for screening and a central composite design, one of response surface methodologies (RSM). In this study, 23 factorial design of experiment was used to evaluate the effect of parameters of synthesis temperature and time, and also mixing speed on crystallinity of MOF-235. Experiments were conducted 16 times follwing MINITAB 19 design software for MOF-235 synthesis. Half-normal, pareto, residual, main and interaction effects were drawn based on the XRD results. The analysis of variance (ANOVA) of test results depicts that the synthesis temperature and time have significant effects on the crystallinity of MOF-235 (response variable). After screening, a central composite design was performed to optimize the acetylene adsorption capacity of MOF-235 based on synthesis conditions. From nine runs designed by MINITAB 19, the result was calculated using the second order model equation. It was estimated that the maximum adsorption capacity (18.7 mmol/g) was observed for MOF-235 synthesized at optimum conditions of 86.3 ℃ and 28.7 h.

A Study on the Reduction Mechanism of Tungsten and Copper Oxide Composite Powders (W-Cu산화물 복합분말의 환원 기구에 관한 연구)

  • Lee, Seong;Hong, Moon-Hee;Kim, Eun-Pyo;Lee, Sung-Ho;Noh, Joon-Woong
    • Journal of Powder Materials
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    • v.10 no.6
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    • pp.422-429
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    • 2003
  • The reduction mechanism of the composite powders mixed with $WO_3$ and CuO has been studied by using thermogravimetry (TG), X-ray diffraction, and microstructure analyses. The composite powders were made by simple Turbula mixing, spray drying, and ball-milling in a stainless steel jar with the ball to powder ratio of 32 to 1 at 80 rpm for 1 h without process controlling agents. It is observed that all the oxide composite powders are converted to W-coated Cu composite powder after reducing treatment under hydrogen atmosphere. For the formation mechanism of W-coated Cu composite powder, the sequential reduction steps are proposed as follows: CuO contained in the ball-milled composite powder is initially reduced to Cu at the temperature range from 20$0^{\circ}C$ to 30$0^{\circ}C$. Then, $WO_3$ powder is reduced to W $O_2$ via W $O_{2.9}$ and W $O_{2.72}$ at higher temperature region. Finally, the gaseous phase of $WO_3(OH)_2$ formed by reaction of $WO_2$ with water vapour migrates to previously reduced Cu and deposits on it as W reduced by hydrogen. The proposed mechanism has been proved through the model experiment which was performed by using Cu plate and $WO_3$ powder.

Analysis of Shear Flow Dispersion Using Sequential Mixing Model (순차혼합모형에 의한 전단류 분산 해석)

  • Seo, Il-Won;Son, Eun-Woo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2005.05b
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    • pp.991-995
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    • 2005
  • 본 연구에서는 1차원 이송-분산 과정을 연구하고 전단류 흐름 및 분산거동에 있어 Taylor 이론의 핵심이라 할 수 있는 '종방향 이송과 횡방향 확산의 균형'을 기본 개념으로 하여, 이송과 확산을 분리하여 이 두 과정이 순차적으로 발생한다는 가정에 의거한 순차혼합모형을 제시하였다. 본 모형에서는 가상의 하천을 여러 개의 행과 종방향 거리를 길이가 일정한 구획으로 나누어 연속적인 분산과정을 이산적인 형태로 나타낼 수 있게 하고, 횡방향 유속분포에 따라 각 행에 각기 다른 유속을 할당한다. 오염물질은 하폭방향 선오염원으로 원점에 순간주입되며, 주어진 혼합시간 $t_m$ 동안 각 행의 오염물질들이 각자에 할당된 유속을 따라 진행하고 진행이 끝난 후 횡방향 확산이 순간적으로 이루어진다. 횡방향 확산은 횡방향으로 완전하게 일어남을 가정하여, 횡방향 확산이 끝나면 각 열에서의 농도 평균값이 할당된다. 이러한 혼합시간 $t_m$ 동안의 순차적인 이송-확산 과정이 반복되면서 오염물질의 분산이 일어나며, 농도 분포 그래프를 그릴 수 있게 된다. 순차혼합모형을 가상의 직선하천에 적용하여 종분산계수를 유도하였는데, 본 연구에서 유도된 종분산계순식은 Fischer.가 제안한 식과 유사한 형태로 나타남을 알 수 있었다. 본 모형에서 계산된 농도분포 곡선을 해석해와 비교한 결과,두 곡선이 적절히 일치함을 확인할 수 있었으며 해석해와의 비교를 통해 종분산계수 K가 혼합시간 $t_m$과 선형관계임을 확인할 수 있었다. 수심대하폭비에 따라 각기 다른 유속분포에 적용하여 종분산계수 K가 유속편차강도의 제곱에 비례관계에 있음이 밝힐 수 있었다. 수압은 $4.69kg/cm^2$으로 나타났다. 밸브 개폐도가 $100\%$일 때가 밸브를 $60\%$$80\%$ 개폐시켰을 때보다 $0.3kg/cm^2,\;0.29kg/cm^2$ 낮게 나타나 밸브를 전체 개방 했을 때 관로내의 수압이 상수설계기준에 적합한 수압을 유지함을 알 수 있다. 상수관로 설계 기준에서는 관로내 수압을 $1.5\~4.0kg/cm^2$으로 나타내고 있는데 $6kg/cm^2$보다 과수압을 나타내는 경우가 $100\%$로 밸브를 개방하였을 때보다 $60\%,\;80\%$ 개방하였을 때가 더 빈번히 발생하고 있으므로 대상지역의 밸브 개폐는 $100\%$ 개방하는 것이 선계기준에 적합한 것으로 나타났다. 밸브 개폐에 따른 수압 변화를 모의한 결과 밸브 개폐도를 적절히 유지하여 필요수량의 확보 및 누수방지대책에 활용할 수 있을 것으로 판단된다.8R(mm)(r^2=0.84)$로 지수적으로 증가하는 경향을 나타내었다. 유거수량은 토성별로 양토를 1.0으로 기준할 때 사양토가 0.86으로 가장 작았고, 식양토 1.09, 식토 1.15로 평가되어 침투수에 비해 토성별 차이가 크게 나타났다. 이는 토성이 세립질일 수록 유거수의 저항이 작기 때문으로 생각된다. 경사에 따라서는 경사도가 증가할수록 증가하였으며 $10\% 경사일 때를 기준으로 $Ro(mm)=Ro_{10}{\times}0.797{\times}e^{-0.021s(\%)}$

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Sentiment Analysis of Movie Review Using Integrated CNN-LSTM Mode (CNN-LSTM 조합모델을 이용한 영화리뷰 감성분석)

  • Park, Ho-yeon;Kim, Kyoung-jae
    • Journal of Intelligence and Information Systems
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    • v.25 no.4
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    • pp.141-154
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    • 2019
  • Rapid growth of internet technology and social media is progressing. Data mining technology has evolved to enable unstructured document representations in a variety of applications. Sentiment analysis is an important technology that can distinguish poor or high-quality content through text data of products, and it has proliferated during text mining. Sentiment analysis mainly analyzes people's opinions in text data by assigning predefined data categories as positive and negative. This has been studied in various directions in terms of accuracy from simple rule-based to dictionary-based approaches using predefined labels. In fact, sentiment analysis is one of the most active researches in natural language processing and is widely studied in text mining. When real online reviews aren't available for others, it's not only easy to openly collect information, but it also affects your business. In marketing, real-world information from customers is gathered on websites, not surveys. Depending on whether the website's posts are positive or negative, the customer response is reflected in the sales and tries to identify the information. However, many reviews on a website are not always good, and difficult to identify. The earlier studies in this research area used the reviews data of the Amazon.com shopping mal, but the research data used in the recent studies uses the data for stock market trends, blogs, news articles, weather forecasts, IMDB, and facebook etc. However, the lack of accuracy is recognized because sentiment calculations are changed according to the subject, paragraph, sentiment lexicon direction, and sentence strength. This study aims to classify the polarity analysis of sentiment analysis into positive and negative categories and increase the prediction accuracy of the polarity analysis using the pretrained IMDB review data set. First, the text classification algorithm related to sentiment analysis adopts the popular machine learning algorithms such as NB (naive bayes), SVM (support vector machines), XGboost, RF (random forests), and Gradient Boost as comparative models. Second, deep learning has demonstrated discriminative features that can extract complex features of data. Representative algorithms are CNN (convolution neural networks), RNN (recurrent neural networks), LSTM (long-short term memory). CNN can be used similarly to BoW when processing a sentence in vector format, but does not consider sequential data attributes. RNN can handle well in order because it takes into account the time information of the data, but there is a long-term dependency on memory. To solve the problem of long-term dependence, LSTM is used. For the comparison, CNN and LSTM were chosen as simple deep learning models. In addition to classical machine learning algorithms, CNN, LSTM, and the integrated models were analyzed. Although there are many parameters for the algorithms, we examined the relationship between numerical value and precision to find the optimal combination. And, we tried to figure out how the models work well for sentiment analysis and how these models work. This study proposes integrated CNN and LSTM algorithms to extract the positive and negative features of text analysis. The reasons for mixing these two algorithms are as follows. CNN can extract features for the classification automatically by applying convolution layer and massively parallel processing. LSTM is not capable of highly parallel processing. Like faucets, the LSTM has input, output, and forget gates that can be moved and controlled at a desired time. These gates have the advantage of placing memory blocks on hidden nodes. The memory block of the LSTM may not store all the data, but it can solve the CNN's long-term dependency problem. Furthermore, when LSTM is used in CNN's pooling layer, it has an end-to-end structure, so that spatial and temporal features can be designed simultaneously. In combination with CNN-LSTM, 90.33% accuracy was measured. This is slower than CNN, but faster than LSTM. The presented model was more accurate than other models. In addition, each word embedding layer can be improved when training the kernel step by step. CNN-LSTM can improve the weakness of each model, and there is an advantage of improving the learning by layer using the end-to-end structure of LSTM. Based on these reasons, this study tries to enhance the classification accuracy of movie reviews using the integrated CNN-LSTM model.