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Kwon Seonghyeon,Lee Yesung,서은혜,Kim Dae Hoon,Lee Jaehong,Jeong Youshik,Kim Jihoon,정진숙,Lee Woncheol 대한직업환경의학회 2023 대한직업환경의학회지 Vol.35 No.1
Background: Shift work has been reported to have several harmful effects on the human body. However, a small number of studies have evaluated the association between shift work and adverse effects on the thyroid. In our longitudinal study, we examined the causal association between shift work and the risk of hypothyroidism. Methods: A Kangbuk Samsung Cohort Study was conducted on 112,648 men without thyroid disease at baseline who were followed up at least once between 2012 and 2019. Shift work status and shift schedule types were categorized using standardized questionnaires. Hypothyroidism was defined using the reference ranges of serum thyroid-stimulating hormones and free thyroxine levels. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident hypothyroidism were estimated using Cox proportional hazards regression analyses with the daytime work group as the reference. Results: During the 501,237 person-years of follow-up, there were 6,306 incident cases of hypothyroidism (incidence density, 1.26 per 100 person-years). The multivariable-adjusted HR of incident hypothyroidism for the shift work total group that included all shifts compared with the daytime work group was 1.27 (95% CI: 1.15–1.40). For the fixed evening, fixed night, rotating shift, and other shift workers, the multivariable-adjusted HRs (95% CI) were 1.11 (0.76–1.61), 2.18 (1.20–3.93), 1.39 (1.23–1.56), and 1.00 (0.82–1.22), respectively. In subgroup analyses by age, the association between shift work and hypothyroidism was more pronounced in younger participants (< 40 years; HR: 1.31; 95% CI: 1.16–1.47). Conclusions: Our large-scale cohort study showed an association between shift work and the incidence of hypothyroidism, especially in younger workers with night shifts.
Composite Momentum-based Observers for the Estimation of External Force on Robot Manipulators
Wookyong Kwon,Seonghyeon Jo,Jeyoun Dong,Dongyeop Kang,Sang Jun Lee 제어로봇시스템학회 2021 제어로봇시스템학회 국제학술대회 논문집 Vol.2021 No.10
This paper investigates the estimation of external force on robot manipulators. The issue is of great importance for the safety of human-robot collaborative tasks and for the human-robot interactive tasks. However, the estimation of external force using model-based approach suffers from model uncertainties and disturbances. It also requires a quick estimate when detecting a collision. To satisfy both fast convergence and robustness, composite observers are newly proposed, which is composed of sliding mode observers and polynomial observers based on momentum state. Through their complementary roles, a composite observer achieves improved performance in safety and estimation. The simulation results show the effectiveness and validity of the proposed composite momentum-based observers.
Obeen Kwon,Junghyun Park,Gyutae Park,Seonghyeon Yang,Taehyun Park 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.2
Fuel cells are promising electrochemical energy conversion devices with eco-friendliness and sustainability, while challenges have remained depending on their components. Meanwhile, researchers have paid significant attention to carbon nanotubes (CNTs) due to their excellent mechanical, thermal, electrical, morphological, and chemical properties. To meet this demand, suitable synthesis methods for CNTs have been naturally developed for large-scale production and proper application for devices. Also, numerous research efforts have been made to apply CNTs to ultimately improve fuel cell performance and durability. This review summarizes the brilliant strategies of CNTs that have been applied to pivotal components in fuel cells, such as catalysts, polymer electrolyte membranes (PEMs), gas diffusion layers (GDLs), and bipolar plates (BPs). Plus, this review provides a summary of methods that have been introduced for the synthesis and mass production of CNTs, like arc discharge, chemical vapor deposition (CVD), and laser ablation. Based on these proposed approaches in the literature, laid issues that need to be overcome for each component and what remarkable contribution occurred due to the application of CNTs in fuel cells are examined and discussed. In consequence, the application of CNTs in fuel cells still holds great potential for outstanding improvements in electrochemical performance and durability.
[연료 및 윤활유부문] 엔진 이상 소음의 발생 원인 및 기구 파악
서성현(Seonghyeon Seo),강경필(Jyungphil Kang),김원규(Won-Kyu Kim),오대윤(Dae-Yoon Oh),최재권(Jae-Kwon Choi) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
An internal combustion engine is highly susceptible to mechanical noises. They originate from combustion and mechanical motion of engine components, and cannot be avoided with an engine at a normal operation. However,<br/> abnormal engine noises at a specific period can occur due to various reasons. Here in this study, four cases of<br/> undesirable engine noises were investigated. To identity the mechanisms of engine noises, accelerations and movements of interested engine components were measured using accelerometers and gap sensors, respectively. Through the analysis of these experimental data, mechanisms for each case were found and provide the solutions for the reduction of the noises.<br/>
K-Means Clustering 알고리즘과 헤도닉 모형을 활용한 서울시 연립 · 다세대 군집분류 방법에 관한 연구
권순재(Soonjae Kwon),김성현(Seonghyeon Kim),탁온식(Onsik Tak),정현희(Hyeonhee Jeong) 한국지능정보시스템학회 2017 지능정보연구 Vol.23 No.3
Recent centrally the downtown area, the transaction between the row housing and multiplex housing is activated and platform services such as Zigbang and Dabang are growing. The row housing and multiplex housing is a blind spot for real estate information. Because there is a social problem, due to the change in market size and information asymmetry due to changes in demand. Also, the 5 or 25 districts used by the Seoul Metropolitan Government or the Korean Appraisal Board(hereafter, KAB) were established within the administrative boundaries and used in existing real estate studies. This is not a district classification for real estate researches because it is zoned urban planning. Based on the existing study, this study found that the city needs to reset the Seoul Metropolitan Governments spatial structure in estimating future housing prices. So, This study attempted to classify the area without spatial heterogeneity by the reflected the property price characteristics of row housing and Multiplex housing. In other words, There has been a problem that an inefficient side has arisen due to the simple division by the existing administrative district. Therefore, this study aims to cluster Seoul as a new area for more efficient real estate analysis. This study was applied to the hedonic model based on the real transactions price data of row housing and multiplex housing. And the K-Means Clustering algorithm was used to cluster the spatial structure of Seoul. In this study, data onto real transactions price of the Seoul Row housing and Multiplex Housing from January 2014 to December 2016, and the official land value of 2016 was used and it provided by Ministry of Land, Infrastructure and Transport(hereafter, MOLIT). Data preprocessing was followed by the following processing procedures: Removal of underground transaction, Price standardization per area, Removal of Real transaction case(above 5 and below -5). In this study, we analyzed data from 132,707 cases to 126,759 data through data preprocessing. The data analysis tool used the R program. After data preprocessing, data model was constructed. Priority, the K-means Clustering was performed. In addition, a regression analysis was conducted using Hedonic model and it was conducted a cosine similarity analysis. Based on the constructed data model, we clustered on the basis of the longitude and latitude of Seoul and conducted comparative analysis of existing area. The results of this study indicated that the goodness of fit of the model was above 75 % and the variables used for the Hedonic model were significant. In other words, 5 or 25 districts that is the area of the existing administrative area are divided into 16 districts. So, this study derived a clustering method of row housing and multiplex housing in Seoul using K-Means Clustering algorithm and hedonic model by the reflected the property price characteristics. Moreover, they presented academic and practical implications and presented the limitations of this study and the direction of future research. Academic implication has clustered by reflecting the property price characteristics in order to improve the problems of the areas used in the Seoul Metropolitan Government, KAB, and Existing Real Estate Research. Another academic implications are that apartments were the main study of existing real estate research, and has proposed a method of classifying area in Seoul using public information(i.e., real-data of MOLIT) of government 3.0. Practical implication is that it can be used as a basic data for real estate related research on row housing and multiplex housing. Another practical implications are that is expected the activation of row housing and multiplex housing research and, that is expected to increase the accuracy of the model of the actual transaction. The future research direction of this study involves conducting various analyses to overcome the limitations of the threshold and indicates the need for deeper researc
의료 관련 질의응답을 위한 BERT 기반 한국어 QA 모델
권세린(Serin Kwon),정성현(Seonghyeon Jeong),정아연(Ayeon Jeong),조영진(Yeongjin Jo),김지희(Jihie Kim),김광일(Kwangil Kim) 한국정보기술학회 2022 Proceedings of KIIT Conference Vol.2022 No.6
Question Answering(QA)는 자연어 처리 분야에서 활발하게 연구가 되고 있는 주제이다. 따라서 본 연구에서는 ‘질병과 건강’이라는 특정 도메인에 대한 질의에, 자동적으로 답안을 제시하는 한국어 QA 모델을 제시한다. QA 시스템에서는 기존의 KoBERT 시퀀스 모델을 활용했으며, fine-tuning을 위해 KorQuAD 데이터와 질병관리청에서 제공하는 데이터를 KorQuAD 형식으로 수기로 변환한 데이터를 사용했다. 본 연구에서 제안하는 모델은, 기존의 KoBERT 모델과 비교 했을 때, F1 score은 77.49 그리고 Exact Match는 75.00이라는 향상된 성능을 보였다. Question Answering (QA) is a topic that is being actively researched in the field of natural language processing. Therefore, in this study, we propose a Korean QA model that automatically provides answers to questions about a specific domain called ‘disease and health’. In the QA system, we use the existing KoBERT sequence model, and for fine-tuning, KorQuAD data and data provided by the Korea Centers for Disease Control and Prevention were manually converted into KorQuAD format. Compared with the existing KoBERT model, the model proposed in this study showed improved performance with an F1 score of 77.49 and an Exact Match of 75.00.