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축자속 영구자석 전동기의 인쇄회로 고정자 권선 형태 분석 및 비교
김준식(Junsik Kim),노명규(Myounggyu Noh),박영우(Young-Woo Park) 대한기계학회 2019 大韓機械學會論文集A Vol.43 No.10
인쇄회로 기판 고정자 권선을 사용하는 축자속 영구자석 전동기는 소형화가 용이하며 코깅 토크가 없고 높은 파워 밀도를 가진다. 권선의 형태로 가장 많이 사용되는 패턴은 사다리꼴과 마름모꼴이다. 인쇄회로 기판은 면적이 제한적이고 제작상의 제약으로 도선 간의 분리가 필수여서 전자기 토크와 면적이용률 관점에서 권선 패턴을 평가하는 것이 중요하다. 본 논문에서는 권선 패턴에 따라 발생하는 전자기 토크에 대한 수학적 모델을 수립하고, 단위 저항당 토크인 비토크를 통해 패턴을 정량적으로 비교한다. 사다리꼴 패턴은 마름모꼴에 비해 더 큰 토크를 만들지만 마름모꼴 패턴은 도선의 길이가 짧아 동손이 줄어든다. 토크 관점에서는 사다리꼴 패턴이 마름모꼴 패턴에 비해 81%의 토크를 더 만들어낼 수 있지만, 비토크 관점에서는 그 차이가 13%로 줄어든다. Printed-circuit stator windings allow low-profile construction, zero cogging torque, and high power density when used for axial flux permanent magnet machines. Trapezoidal and rhomboidal windings are the two most popular printing patterns. Since the area of printed-circuit boards is limited and the separation between conductor traces is inevitable owing to manufacturing requirements, it is critical to assess winding patterns in terms of their torque-producing capability and board-area utilization. In this paper, we present a detailed analysis of winding patterns and derive a mathematical model that predicts the coil resistance and torque produced by winding patterns. It was found that the trapezoidal pattern produces much larger torque, but the rhomboidal pattern has lower copper losses. The torque produced by the trapezoidal pattern is 81 % larger than that of the rhomboidal torque. However, if the torque is normalized by coil resistance, the trapezoidal pattern is 13 % better than the rhomboidal pattern with the same geometry.
National Follow-up Survey of Preventable Trauma Death Rate in Korea
Kwon Junsik,Lee Myeonggyun,Moon Jonghwan,Huh Yo,Song Seoyoung,Kim Sora,Lee Seung Joon,Lim Borami,Kim Hyo Jin,Kim Yoon,il Kim Hyung,Yun Jung-Ho,Yu Byungchul,Lee Gil Jae,Kim Jae Hun,Kim Oh Hyun,Choi Woo 대한의학회 2022 Journal of Korean medical science Vol.37 No.50
Background: The preventable trauma death rate survey is a basic tool for the quality management of trauma treatment because it is a method that can intuitively evaluate the level of national trauma treatment. We conducted this study as a national biennial follow-up survey project and report the results of the review of the 2019 trauma death data in Korea. Methods: From January 1, 2019 to December 31, 2019, of a total of 8,482 trauma deaths throughout the country, 1,692 were sampled from 279 emergency medical institutions in Korea. All cases were evaluated for preventability of death and opportunities for improvement using a multidisciplinary panel review approach. Results: The preventable trauma death rate was estimated to be 15.7%. Of these, 3.1% were judged definitive preventable deaths, and 12.7% were potentially preventable deaths. The odds ratio for preventable traumatic death was 2.56 times higher in transferred patients compared to that of patients who visited the final hospital directly. The group that died 1 hour after the accident had a statistically significantly higher probability of preventable death than that of the group that died within 1 hour after the accident. Conclusion: The preventable trauma death rate for trauma deaths in 2019 was 15.7%, which was 4.2%p lower than that in 2017. To improve the quality of trauma treatment, the transfer of severe trauma patients to trauma centers should be more focused.
이준식(Junsik Lee),김건우(Keon-Woo Kim),박도형(Do-Hyung Park) 한국지능정보시스템학회 2018 지능정보연구 Vol.24 No.2
In this study, we conducted an empirical analysis of the factors that affect the change of Bitcoin Closing Price. Previous studies have focused on the security of the block chain system, the economic ripple effects caused by the cryptocurrency, legal implications and the acceptance to consumer about cryptocurrency. In various area, cryptocurrency was studied and many researcher and people including government, regardless of country, try to utilize cryptocurrency and applicate to its technology. Despite of rapid and dramatic change of cryptocurrencies’ price and growth of its effects, empirical study of the factors affecting the price change of cryptocurrency was lack. There were only a few limited studies, business reports and short working paper. Therefore, it is necessary to determine what factors effect on the change of closing Bitcoin price. For analysis, hypotheses were constructed from three dimensions of consumer, industry, and macroeconomics for analysis, and time series data were collected for variables of each dimension. Consumer variables consist of search traffic of Bitcoin, search traffic of bitcoin ban, search traffic of ransomware and search traffic of war. Industry variables were composed GPU vendors’ stock price and memory vendors’ stock price. Macro-economy variables were contemplated such as U.S. dollar index futures, FOMC policy interest rates, WTI crude oil price. Using above variables, we did times series regression analysis to find relationship between those variables and change of Bitcoin Closing Price. Before the regression analysis to confirm the relationship between change of Bitcoin Closing Price and the other variables, we performed the Unit-root test to verifying the stationary of time series data to avoid spurious regression. Then, using a stationary data, we did the regression analysis. As a result of the analysis, we found that the change of Bitcoin Closing Price has negative effects with search traffic of ‘Bitcoin Ban’ and US dollar index futures, while change of GPU vendors’ stock price and change of WTI crude oil price showed positive effects. In case of ‘Bitcoin Ban’, it is directly determining the maintenance or abolition of Bitcoin trade, that’s why consumer reacted sensitively and effected on change of Bitcoin Closing Price. GPU is raw material of Bitcoin mining. Generally, increasing of companies’ stock price means the growth of the sales of those companies’ products and services. GPU’s demands increases are indirectly reflected to the GPU vendors’ stock price. Making an interpretation, a rise in prices of GPU has put a crimp on the mining of Bitcoin. Consequently, GPU vendors’ stock price effects on change of Bitcoin Closing Price. And we confirmed U.S. dollar index futures moved in the opposite direction with change of Bitcoin Closing Price. It moved like Gold. Gold was considered as a safe asset to consumers and it means consumer think that Bitcoin is a safe asset. On the other hand, WTI oil price went Bitcoin Closing Price’s way. It implies that Bitcoin are regarded to investment asset like raw materials market’s product. The variables that were not significant in the analysis were search traffic of bitcoin, search traffic of ransomware, search traffic of war, memory vendor’s stock price, FOMC policy interest rates. In search traffic of bitcoin, we judged that interest in Bitcoin did not lead to purchase of Bitcoin. It means search traffic of Bitcoin didn’t reflect all of Bitcoin’s demand. So, it implies there are some factors that regulate and mediate the Bitcoin purchase. In search traffic of ransomware, it is hard to say concern of ransomware determined the whole Bitcoin demand. Because only a few people damaged by ransomware and the percentage of hackers requiring Bitcoins was low. Also, its information security problem is events not continuous issues. Search traffic of war was not significant. Like stock market, generally it has negative in relation to war, but exceptional case
( Sungwook Won ),( Junsik Bang ),( Sang-woo Park ),( Jungkyu Kim ),( Minjung Jung ),( Seungoh Jung ),( Heecheol Yun ),( Hwanmyeong Yeo ),( In-gyu Choi ),( Hyo Won Kwak ) 한국목재공학회 2024 목재공학 Vol.52 No.3
Lignin, a prominent constituent of woody biomass, is abundant in nature, cost-effective, and contains various functional groups, including hydroxyl groups. Owing to these characteristics, they have the potential to replace petroleum-based polyols in the polyurethane industry, offering a solution to environmental problems linked to resource depletion and CO<sub>2</sub> emissions. However, the structural complexity and low reactivity of lignin present challenges for its direct application in polyurethane materials. In this study, Kraft lignin (KL), a representative technical lignin, was fractionated with ethanol, an eco-friendly solvent, and mixed with conventional polyols in varying proportions to produce polyurethane films. The results of ethanol fractionation showed that the polydispersity of ethanol-soluble lignin (ESL) decreased from 3.71 to 2.72 and the hydroxyl content of ESL increased from 4.20 mmol/g to 5.49 mmol/g. Consequently, the polyurethane prepared by adding ESL was superior to the KL-based film, exhibiting improved miscibility with petrochemical-based polyols and reactivity with isocyanate groups. Consequently, the films using ESL as the polyol exhibited reduced shrinkage and a more uniform structure. Optical microscope and scanning electron microscope observations confirmed that lignin aggregation was lower in polyurethane with ESL than in that with KL. When the hydrophobicity of the samples was measured using the water contact angle, the addition of ESL resulted in higher hydrophobicity. In addition, as the amount of ESL added increased, an increase of 7.4% in the residual char was observed, and a 4.04% increase in Tmax the thermal stability of the produced polyurethane was effectively improved.
리그닌 아세틸화를 통한 고함량 리그닌 기반 PBAT 복합 필름 개발 및 특성 평가
김정규 ( Jungkyu Kim ),방준식 ( Junsik Bang ),박상우 ( Sang-woo Park ),김윤진 ( Yunjin Kim ),정민정 ( Minjung Jung ),정승오 ( Seungoh Jung ) 한국목재공학회 2022 한국목재공학회 학술발표논문집 Vol.2022 No.2
리그닌은 생산 비용이 낮을 뿐만 아니라 UV 차단성, 항산화성을 가지고 있어 PBAT의 생산 비용 절감을 위한 블렌드 물질로 적합하다고 평가된다. 그러나 압사출 및 고분자 가공 공정에서 리그닌의 응집이 발생하여 PBAT와의 상용성과 복합재의 기계적 물성을 감소시키기 때문에 리그닌의 전처리를 통해 자가응집을 방지하는 기술이 필요하다. 본 연구에서는 리그닌의 아세틸화를 통해 리그닌의 수산기를 개질하여 리그닌/PBAT 복합 필름 제조 시 자가 응집을 방지하였다.