“Syndromes” of mobility limitations in older adults

Yunhwan Lee 대한골다공증학회 2016 Osteoporosis and Sarcopenia Vol.2 No.4

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Call Center Call Count Prediction Model by Machine Learning

Yunhwan Keon,Hyuna Kim,Jin Young Choi,김동호,Su Young Kim,Seonho Kim 한국정보기술학회 2018 JOURNAL OF ADVANCED INFORMATION TECHNOLOGY AND CON Vol.8 No.1

This paper is to introduce efficient human resource management in call center industry by coming up with a model that predicts how much the staffing is most appropriate at such a call center for a given hour period. The project aims to understand the characteristics of call center data through exploratory data analysis, and to test the effectiveness of call center staffing by formulating the rule based on a machine learning model. We initially conducted exploratory data analysis to find insights and implemented a machine learning model to predict the value of the target variable which consequently translated into the number of human receptionists preferred. From our intensive experiments, we found that Random Forest gave the best performance for call center data analysis.

Correlation between the Korean pork grade system and the amount of pork primal cut estimated with AutoFom III

( Yunhwan Park ),( Eunyoung Ko ),( Kwangwook Park ),( Changhyun Woo ),( Jaeyoung Kim ),( Sanghun Lee ),( Sanghun Park ),( Yun-a Kim ),( Gyutae Park ),( Jungseok Choi ) 한국축산학회 2022 한국축산학회지 Vol.64 No.1

It is impossible to know the amount of pork primal cut by pig carcass grade which is determined only by carcass weight and backfat thickness in the Korean Pig Carcass System. The aim of this study was to investigate the correlation between the pig carcass grade and the amount of pork primal cut estimated with AutoFom III. A total of 419,321 Landrace, Yorkshire, and Duroc (LYD) pigs were graded with the Korean Pig Carcass Grade System. Amounts of belly, neck, loin, tenderloin, spare ribs, shoulder, and ham were estimated with AutoFom III. Regression equations for seven primal cuts according to each grade were derived. There were significant differences among the three carcass grades due to heteroscedasticity variance (p < 0.0001). Three regression equations were derived from AutoFom III estimation of primal cuts according to carcass grades. The coefficient of determination of the regression equation was 0.941 for grade 1⁺, 0.982 for grade 1, and 0.993 for grade 2. Regression equations obtained from this study are suitable for AutoFom III software, a useful tool for the analysis of each pig carcass grade in the Korean Pig Carcass Grade System. The high reliability of predicting the amount of primal cut with AutoFom III is advantageous for the management of slaughterhouses to optimize their product sorting in Korea.

Proposal of conditional random inter-stimulus interval method for unconstrained enclosure based GPIAS measurement systems

Yunhwan Choe,Ilyong Park 대한의용생체공학회 2019 Biomedical Engineering Letters (BMEL) Vol.9 No.3

Gap prepulse inhibition of acoustic startle (GPIAS) method has been used eff ectively for the objective assessment of tinnitusin animals. Among two types of enclosures for the GPIAS, the unconstrained type carries less risk of animal death due tothe absence of binding stress in the enclosure, and lack of need for alteration to animal size variation as it grows. However,animals’ voluntary movements, which have no relation to the startles evoked by acoustic stimuli, are problematic, as theycannot be excluded in the case of the unconstrained enclosure based GPIAS measurement system. In order to discountvoluntary movements which are not associated with external acoustic stimuli, we propose the conditional random interstimulusinterval (CR ISI) method for unconstrained enclosure based GPIAS measurement. With the proposed ISI method,the unconstrained enclosure based acoustic startle response measurement system has been implemented in this paper. Asa result, the eff ectiveness of the proposed CR ISI method has been verifi ed and compared with those of conventional ISImethods through animal experiments using SD-rats. The experimental results showed that abnormal startle responses andinvalid GPIAS values caused by motion were prevented when our proposed CR ISI method was applied to our implementedsystem. It was also verifi ed that our proposed CR ISI method is advantageous in reducing the total experimental time foracquiring normal startle responses and valid GPIAS values, compared to conventional ISI methods, since our proposed CRISI can begin the acoustic stimulation only when the animal gets stable and motionless.

Does physical activity moderate the association between depressive symptoms and disability in older adults?

Lee, Yunhwan,Park, Kyunghye John Wiley Sons, Ltd. 2008 International journal of geriatric psychiatry Vol.23 No.3

<B>Objective</B><P>Depressive symptoms and disability are closely associated and known to have reciprocal relationships. This study examines whether physical activity moderates the association between depressive symptoms and disability in community-dwelling older adults.</P><B>Methods</B><P>Baseline and 1-year follow-up data of 645 persons aged 65 years or older from the Suwon Longitudinal Aging Study were analyzed. A 15-item Geriatric Depression Scale, Physical Functioning scale, and physical performance tests were used to assess the individual's depressive symptoms and functional disability. Physical activity was defined as the recommended level of exercise based on its frequency and intensity. Multiple regression analysis with generalized estimating equations was conducted to examine the physical activity's role as an effect modifier in the association between depressive symptoms and disability.</P><B>Results</B><P>Physical activity was a significant effect modifier in the ‘depressive symptoms–disability’ association, controlling for sociodemographic characteristics and health-related covariates. Moderate-intensity activity was as effective as vigorous activity in moderating the relationship. The moderating effect was notable among those displaying severe depressive symptoms and functional disability. Over time the strength of the association between depressive symptoms and disability tended to diminish for those engaging in physical activity.</P><B>Conclusion</B><P>The association between depressive symptoms and disability is moderated by physical activity in older persons. The findings suggest that healthcare professionals need to promote moderate amount of physical activity as a potential intervention tool in attenuating the depression–disability connection in later life, especially among those with high levels of physical and mental impairments. Copyright © 2007 John Wiley & Sons, Ltd.</P>

플라즈마 반응기를 이용한 LPG 개질에서의 화학반응 특성

박윤환(Yunhwan Park),이대훈(Deahoon Lee),김창업(Changup Kim),강건용(Kernyoung Kang),조용석(Yongseok Cho) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

In this study, characteristics of reforming process of automotive LPG fuel using plasma reactor are investigated. Plasma reformer technology has advantages of a fast start-up and wide fuel/oxidizer ratio of operation and reactor size is small and simpler than typical combustor and catalytic reactor. For these reasons, plasma reforming is suitable for a on-board vehicle reformer. To evaluate the characteristics of the reforming process, parametric effect of O₂/C ratio, reactant flow rate and plasma power on the process were investigated. In C₄H10 plasma reforming process, SED values and O₂ /C ratios are the main factors. SED effect or plasma chemistry is effective in the earlier steps of the reaction and O₂/C ratio or thermal activation affects throughout over the whole reaction. The result can give essential information for optimization of a reforming process.

LPG 연료의 플라즈마 개질 특성연구

박윤환(Yunhwan Park),이대훈(Deahoon Lee),김창업(Changup Kim),강건용(Kernyoung Kang),조용석(Yongseok Cho) 한국자동차공학회 2012 한국자동차공학회 부문종합 학술대회 Vol.2012 No.5

In this study, characteristics of reforming process of LPG using plasma reactor is investigated. Plasma reformer has advantages of a fast start-up and wide fuel/oxidizer ratio of operation. Volume of reactor is small and simple compared to typical combustor and catalytic reactor. Because of these merits, plasma reforming is prominent for the use of on-board reformer. To evaluate the characteristics of the reforming process, parametric effect of O₂/C ratio and reactant flow rate on the process was investigated. In the test of varying O₂/C ratio from partial oxidation stoichiometry to combustion stoichiometry, conversion of LPG was increased but selectivity of H₂ decreased. The optimum condition of O₂/C ratio for the highest H₂ selectivity was determined to be 0.91 and 0.89 for 20 lpm and 30 lpm respectively. The result can be a guide to map optimal condition of reforming process.

플라즈마 개질기 형상변화에 따른 LPG연료의 개질특성연구

박윤환(Yunhwan Park),이대훈(Deahoon Lee),김창업(Changup Kim),강건용(Kernyoung Kang) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5

HLPG fuel research has been started recently, which is obtained by adding hydrogen to the LPG fuel. The characteristics of the fuel LPG is stored in two phases in the fuel tank. Therefore, on-board vehicle reforming is suitable for LPG vehicle. Suitable methods for on-board reforming vehicle, does not require supply of water, small size and rapid response is available plasma partial oxidation method. So, in this study the characteristics of LPG fuel reforming using a plasma reactor are investigated. When the total flow rate of reformer inlet at 20~50lpm and supplied power is 200W, parametric effect of O2/C ratio, geometric designs of plasma reformer on the process were investigated. As a result of the experiment, the optimum condition of O2/C ratio for the highest H2 yield and H2 selectivity were determined to be 0.8 to 0.9 and 1.0 to 1.4 for reformer 1 and reformer 2 respectively. Highest H2 yield of both reformer 1 and reformer 2 condition were 20lpm(reformer 1; 20%, reformer 2; 34%), and highest H2 yield decrease as th total flow rate is increased.

Emotional Stress Factors and Heart Rate Variability in Different Age Groups

서윤환(Yunhwan Seo),리자와티 살라후딘(Lizawati Salahuddin),박예슬(Yeseul Park),김대석(Desok Kim) 한국정보과학회 2007 한국정보과학회 학술발표논문집 Vol.34 No.2A

LPG 연료의 플라즈마 개질 특성연구

박윤환(Yunhwan Park),이대훈(Deahoon Lee),김창업(Changup Kim),강건용(Kernyoung Kang),조용석(Yongseok Cho) 한국가스학회 2012 한국가스학회지 Vol.16 No.6

본 연구에서는 플라즈마 반응기를 이용한 자동차용 LPG 연료의 개질 특성에 대해서 실험하였다. 실험에서 사용된 플라즈마 반응기술은 종전의 촉매반응기술에 비해서 빠른 기동시간 및 연소기 부하변동 응답성, 단순하고 소형화가 가능한 장점을 가지고 있어 차량의 온-보드형 개질에 적합하다. 본 개질 반응의 특성을 평가하기 위해 플라즈마 반응기로 공급되는 O₂/C 비와 공급되는 공기와 LPG의 총 유량 및 플라즈마 공급전력을 주요 변수로 실험하였다. 공급되는 전력이 일정할 때, O₂/C 비 변화 실험에서는 완전산화 조건으로 갈수록 LPG 전환율은 증가하지만 수소의 선택도는 감소되었다. 높은 수소 선택도와 수율을 동시에 만족시키는 O₂/C 비는 20~50lpm 조건에서 0.8~0.9 이었으며, 총 유량이 증가할수록 LPG 전환율과 수소 수율이 감소 하는 경향을 나타내었다. In this study, characteristics of reforming process of Automotive LPG fuel using plasma reactor are investigated. Because plasma reformer technology has advantages of a fast start-up and wide fuel/oxidizer ratio of operation, and reactor size is smaller and more simple compared to typical combustor and catalytic reactor, plasma reforming is suitable to the on-board vehicle reformer. To evaluate the characteristics of the reforming process, parametric effect of O₂/C ratio, reactant flow rate and plasma power on the process were investigated. In the test of varying O₂/C ratio from partial oxidation stoichiometry to combustion stoichiometry, conversion of LPG was increased but selectivity of H2 decreased. The optimum condition of O₂/C ratio for the highest H₂ yield was determined to be 0.8~0.9 for 20~50 lpm. The result can be a guide to map optimal condition of reforming process.