• Title/Summary/Keyword: Optimal power generation ratio

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Study of Reduction of Mismatch Loss of a Thermoelectric Generator (열전발전 시스템의 부정합손실 저감방안 연구)

  • Choi, Taeho;Kim, Tae Young
    • Journal of Convergence for Information Technology
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    • v.12 no.3
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    • pp.294-301
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    • 2022
  • In this study, a multi-layer cascade (MLC) electrical array configuration method for thermoelectric generator consisting of plural number of thermoelectric modules (TEMs) was proposed to reduce mismatch loss caused by temperature maldistribution on the surfaces of the TEMs. To validate the effect of MLC on the mismatch loss reduction, a numerical model capable of reflecting multi-physics phenomena occuring in the TEMs was developed. MLC can be employed by placing a group of TEMs experiencing relatively low temperature differences in an electric layer with more electrical branches while locating a group of TEMs experiencing relatively high temperature differences in an electric layer with less electrical branches. The TEMs were classified using the temperature distribution obtained by the numerical model. A MLC with an optimal electrical branch ratio showed a 96.5% of electric power generation compared to an ideal case.

An optimized microwave-assisted extraction method for increasing yields of rare ginsenosides from Panax quinquefolius L.

  • Yao, Hua;Li, Xuwen;Liu, Ying;Wu, Qian;Jin, Yongri
    • Journal of Ginseng Research
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    • v.40 no.4
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    • pp.415-422
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    • 2016
  • Background: Rare ginsenosides in Panax quinquefolius L. have strong bioactivities. The fact that it is hard to obtain large amounts of rare ginsenosides seriously restricts further research on these compounds. An easy, fast, and efficient method to obtain different kinds of rare ginsenosides simultaneously and to quantify each one precisely is urgently needed. Methods: Microwave-assisted extraction (MAE) was used to extract nine kinds of rare ginsenosides from P. quinquefolius L. In this article, rare ginsenosides [20(S)-Rh1, 20(R)-Rh1, Rg6, F4, Rk3, 20(S)-Rg3, 20(R)-Rg3, Rk1, and Rg5] were identified by high performance liquid chromatography (HPLC)-electrospray ionization-mass spectrometry. The quantity information of rare ginsenosides was analyzed by HPLC-UV at 203 nm. Results: The optimal conditions for MAE were using water as solvent with the material ratio of 1:40 (w/v) at a temperature of $145^{\circ}C$, and extracting for 15 min under microwave power of 1,600 W. Seven kinds of rare ginsenosides [20(S)-Rh1, 20(R)-Rh1, Rg6, F4, Rk3, Rk1, and Rg5] had high extraction yields, but those of 20(S)-Rg3 and 20(R)-Rg3 were lower. Compared with the conventional method, the extraction yields of the nine rare ginsenosides were significantly increased. Conclusion: The results indicate that rare ginsenosides can be extracted effectively by MAE from P. quinquefolius L. in a short time. Microwave radiation plays an important role in MAE. The probable generation process of rare ginsenosides is also discussed in the article. It will be meaningful for further investigation or application of rare ginsenosides.

Engineering Characteristics of CLSM with Regard to the Particle Size of Bottom Ash (저회의 입도변화에 따른 CLSM의 공학적특성)

  • Lee, Yongsoo;Kim, Taeyeon;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
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    • v.21 no.10
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    • pp.5-10
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    • 2020
  • As the demand for the recycling of industrial by-products increases due to various environmental restrictions including the prohibition of ocean disposal, various studies regarding the recycling of industrial by-products are currently being carried out. One of the industrial by-product, coal ash is produced from thermal power generation; studies on the recycling of fly ash have been actively carried out and it is currently recycled in various fields. In the case of bottom ash, however, only a portion of the total amount generated is primarily processed into a particle size of 2~4mm or less than 2mm to be used for gardening purpose and light weight aggregate and so on. The remaining amount is buried at ash disposal sites. Therefore, various studies are needed to develop measures to use bottom ash. This study aimed at identifying the optimal particle size and mixing ratio of bottom ash to be used as CLSM aggregate. To this end, it evaluated the usability of bottom ash as CLSM aggregate, by investigating the flowability and strength change characteristics of CLSM produced with regard to the mixing ratio of weathered granite soil and bottom ash, particle size of bottom ash to be mixed and soil binder addition rate and conducting a heavy metal leaching test.

A Study on the RDF Manufacturing of Coffee grounds by using Pilot scale Oil-drying Equipment (Pilot scale 유중건조 장비를 이용한 커피찌꺼기의 고형연료화 연구)

  • Kwon, Ik-Beom;Ha, Jin-Wook
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.2
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    • pp.443-450
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    • 2019
  • We studied to find the optimal manufacturing conditions of coffee grounds sludge RDF with oil drying method. We expanded the lab scale to pilot scale to compare the efficiency of the oil-drying equipment and The selection of the ratio of coffee grounds and oil, the setting temperature, and the temperature change and water content with time were measured. In order to analyze the characteristics of the research results, characteristics of solid fuels produced(Coffee grounds of oil-dried) by calorimeter, TGA, combustion equipment, and combustion gas measuring instrument were analyzed. As a result, the ratio of oil to coffee grounds was 4: 1, and when the setting temperature was set to $300^{\circ}C$, the water content reached 10wt.% or less within 20 minutes. ln addition, it showed high calorific value of 6,273kcal/kg. However, coffee grounds had a similar composition to wood and showed high luminance and produced a lot of CO in combustion gas. As a result, it is considered to be unsuitable for thermoelectric power plant and camping fuel, but the initial ignition speed is high and the heat generation is high, so it is considered that it can replace the fuels for current use.

Corporate Default Prediction Model Using Deep Learning Time Series Algorithm, RNN and LSTM (딥러닝 시계열 알고리즘 적용한 기업부도예측모형 유용성 검증)

  • Cha, Sungjae;Kang, Jungseok
    • Journal of Intelligence and Information Systems
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    • v.24 no.4
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    • pp.1-32
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    • 2018
  • In addition to stakeholders including managers, employees, creditors, and investors of bankrupt companies, corporate defaults have a ripple effect on the local and national economy. Before the Asian financial crisis, the Korean government only analyzed SMEs and tried to improve the forecasting power of a default prediction model, rather than developing various corporate default models. As a result, even large corporations called 'chaebol enterprises' become bankrupt. Even after that, the analysis of past corporate defaults has been focused on specific variables, and when the government restructured immediately after the global financial crisis, they only focused on certain main variables such as 'debt ratio'. A multifaceted study of corporate default prediction models is essential to ensure diverse interests, to avoid situations like the 'Lehman Brothers Case' of the global financial crisis, to avoid total collapse in a single moment. The key variables used in corporate defaults vary over time. This is confirmed by Beaver (1967, 1968) and Altman's (1968) analysis that Deakins'(1972) study shows that the major factors affecting corporate failure have changed. In Grice's (2001) study, the importance of predictive variables was also found through Zmijewski's (1984) and Ohlson's (1980) models. However, the studies that have been carried out in the past use static models. Most of them do not consider the changes that occur in the course of time. Therefore, in order to construct consistent prediction models, it is necessary to compensate the time-dependent bias by means of a time series analysis algorithm reflecting dynamic change. Based on the global financial crisis, which has had a significant impact on Korea, this study is conducted using 10 years of annual corporate data from 2000 to 2009. Data are divided into training data, validation data, and test data respectively, and are divided into 7, 2, and 1 years respectively. In order to construct a consistent bankruptcy model in the flow of time change, we first train a time series deep learning algorithm model using the data before the financial crisis (2000~2006). The parameter tuning of the existing model and the deep learning time series algorithm is conducted with validation data including the financial crisis period (2007~2008). As a result, we construct a model that shows similar pattern to the results of the learning data and shows excellent prediction power. After that, each bankruptcy prediction model is restructured by integrating the learning data and validation data again (2000 ~ 2008), applying the optimal parameters as in the previous validation. Finally, each corporate default prediction model is evaluated and compared using test data (2009) based on the trained models over nine years. Then, the usefulness of the corporate default prediction model based on the deep learning time series algorithm is proved. In addition, by adding the Lasso regression analysis to the existing methods (multiple discriminant analysis, logit model) which select the variables, it is proved that the deep learning time series algorithm model based on the three bundles of variables is useful for robust corporate default prediction. The definition of bankruptcy used is the same as that of Lee (2015). Independent variables include financial information such as financial ratios used in previous studies. Multivariate discriminant analysis, logit model, and Lasso regression model are used to select the optimal variable group. The influence of the Multivariate discriminant analysis model proposed by Altman (1968), the Logit model proposed by Ohlson (1980), the non-time series machine learning algorithms, and the deep learning time series algorithms are compared. In the case of corporate data, there are limitations of 'nonlinear variables', 'multi-collinearity' of variables, and 'lack of data'. While the logit model is nonlinear, the Lasso regression model solves the multi-collinearity problem, and the deep learning time series algorithm using the variable data generation method complements the lack of data. Big Data Technology, a leading technology in the future, is moving from simple human analysis, to automated AI analysis, and finally towards future intertwined AI applications. Although the study of the corporate default prediction model using the time series algorithm is still in its early stages, deep learning algorithm is much faster than regression analysis at corporate default prediction modeling. Also, it is more effective on prediction power. Through the Fourth Industrial Revolution, the current government and other overseas governments are working hard to integrate the system in everyday life of their nation and society. Yet the field of deep learning time series research for the financial industry is still insufficient. This is an initial study on deep learning time series algorithm analysis of corporate defaults. Therefore it is hoped that it will be used as a comparative analysis data for non-specialists who start a study combining financial data and deep learning time series algorithm.