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Jinwoo Ha,Seong-Ah Kim,Kyungjoon Lim,Sangah Shin 한국영양학회 2020 Nutrition Research and Practice Vol.14 No.1
BACKGROUND/OBJECTIVES: Osteoporosis is characterized by low bone mass and results in vulnerability to fracture. Calcium and vitamin D are known to play an important role in bone health. Recently, potassium has been identified as another important factor in skeletal health. We examined the link between potassium intake and bone health among the Korean older adult population. SUBJECTS/METHODS: This retrospective, cross-sectional study included 8,732 men and postmenopausal women over 50 years old who completed the Korean National Health and Nutrition Survey (KNHANES) between 2008 and 2011. Potassium consumption was evaluated using a 24-hour recall method. Bone mineral density (BMD) was measured at three sites (total hip, femur neck, and lumbar spine) by dual-energy X-ray absorptiometry (DEXA). Multinomial logistic regression was used to examine the link between potassium intake and prevalence of osteoporosis and osteopenia, after controlling for potential confounding variables. RESULTS: The BMD of the total femur and Ward’s triangle were significantly different according to the potassium intake among men (P = 0.031 and P = 0.010, respectively). Women in the top tertile for potassium intake showed higher BMD than those in the bottom tertile at all measurement sites (all P < 0.05). Daily potassium intake was significantly related to a decreased risk of osteoporosis at the lumbar spine in postmenopausal women (odds ratios: 0.68, 95% confidence interval: 0.48-0.96, P trend = 0.031). However, the dietary potassium level was not related to the risk of osteoporosis in men. CONCLUSION: Current findings indicate that higher dietary potassium levels have a favorable effect on bone health and preventing osteoporosis in older Korean women.
최적 노면 마찰력 기반 Anti-lock Braking System 제어
하진우(Jinwoo Ha),유세선(Sesun You),김원희(Wonhee Kim) 한국자동차공학회 2022 한국자동차공학회 부문종합 학술대회 Vol.2022 No.6
In this paper, we propose new anti-lock braking system(ABS) control technique using wheel cylinder pressure control. In the proposed control algorithm, the extended state observer estimates the longitudinal tire-road friction forces. Using these estimated value, the longitudinal tire-road friction forces are optimized by directly controlling wheel cylinder pressure based on the friction’s behavior. The performance of the proposed method is validated via hardware-in-the-loop simulation by using MATLAB/Simulink, Carsim and dSPACE vector tool for snow road. The proposed method presents a new method rather than slip ratio based control and can be further developed through various optimization algorithms.
분산 실시간 시스템의 설계 공간 탐색을 위한 최악 응답시간 분석 기법
하효진(Hyojin Ha),정연(Yan Zheng),김진우(Jinwoo Kim),하순희(Soonhoi Ha) 한국정보과학회 2013 정보과학회논문지 : 시스템 및 이론 Vol.40 No.3
분산 실시간 시스템에서 정확한 최악 응답시간을 분석하는 것은 시스템의 안정성 측면에서 매우 중요하다. 따라서 시스템의 설계 과정에서부터 최악 응답시간이 데드라인을 만족시키는 것을 검증하는 것이 바람직하다. 그러나 기존의 최악 응답시간 분석법들은 시간이 너무 오래 걸리거나 분석의 정확도가 떨어져 설계 공간 탐색시에 실제로 활용하기에는 무리가 있었다. 본 논문에서는 다목적 유전 알고리즘을 사용하는 최악 응답시간 분석법을 제안하고 그 성능을 실험을 통해 측정하였다. 그 결과 수행시간 대비높은 분석 정확도를 보이는 것을 확인하여 수행시간과 분석의 정확도 사이의 최적 트레이드-오프를 얻을 수 있었다. 그리고 비슷한 정확도를 갖는 기존의 분석법에 비하여 시간 복잡도 측면의 확장성이 좋은 것을 확인하였다. 또한 분석의 부산물로 준-최악 시나리오를 다양하게 제공하여 정확성, 확장성, 빠른 분석시간 외에도 설계 공간 탐색시에 유용하게 사용할 수 있는 특성을 가짐을 볼 수 있었다. Since worst-case response time (WCRT) is critical to the real-time system’s safety, it is important to analyze the exact WCRT before its implementation. So, the design space exploration for distributed real-time system should include WCRT analysis and verify whether it meets the deadline even in WCRT or not. But existing WCRT analysis is not proper for design space exploration because it takes too long or over-estimates the WCRT. This paper presents a WCRT analysis using multi-objective genetic algorithm and shows its performance and characteristics. As a result, this analysis technique showed highly accurate results in relatively short time and achieved the trade-off between accuracy of analysis and analyzing time in existing WCRT analysis. It also has good scalability, when compared with other highly accurate analysis techniques. In addition, the proposed WCRT analysis provides near-worst-case scenarios as a byproduct of the genetic algorithm, which will be useful in design space exploration.
Ha, Jinjin,Lee, Jinwoo,Kim, Ji Hoon,Lee, Myoung-Gyu,Barlat, Fré,dé,ric Elsevier 2017 International journal of plasticity Vol.93 No.-
<P><B>Abstract</B></P> <P>Micromechanical-based finite element simulations were carried out to investigate the transient plastic strain rate evolutions of ferrite and martensite dual-phase steel during strain path changes. A representative volume element (RVE) was generated through a three-dimensional (3D) reconstruction of microstructure images which were acquired from sequential polishing of a small material volume. The 10 × 10 × 10 μm<SUP>3</SUP> 3D RVEs consisted of martensite islands embedded in a ferrite base matrix. Each phase was assumed to exhibit distinct mechanical properties but the grain and phase boundary effects were ignored in this work. The effective mechanical properties for the constituent phases were assumed to be well defined by the von Mises or Hill 1948 yield criteria, the associated flow rule, and an empirical isotropic hardening equation based on chemical composition. This model was applied to investigate the transient behavior of the r-value (Lankford coefficient) in uniaxial tension when the loading direction changed. In addition to monotonic tension, compression-tension, and tension-orthogonal tension, sequences were considered. The simulation results captured well in a qualitative manner the experimental r-value evolutions in terms of a temporary transition and asymptotic limit. The evolutions of stress states in ferrite and martensite were analyzed to explain the r-value behavior that resulted from three factors: (1) r-value differences between ferrite and martensite, (2) martensite configuration-induced stress state in phases, and (3) stress partitioning and its evolution during non-proportional loading. Finally, an analytical relationship between the stress evolution in the constituent phases and the relevant r-value changes is suggested.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A 3D representative volume element is generated from real microstructure of DP780. </LI> <LI> The plastic strain dependent r-value evolution of DP780 is investigated. </LI> <LI> The stress partitioning in ferrite and martensite are analyzed. </LI> <LI> The analysis shows a strong correlation with r-value transition and loading history. </LI> <LI> An analytical model for the stress redistribution and r-value change is proposed. </LI> </UL> </P>
Ordered mesoporous carbon nanochannel reactors for high-performance Fischer–Tropsch synthesis
Ha, Kyoung-Su,Kwak, Geunjae,Jun, Ki-Won,Hwang, Jongkook,Lee, Jinwoo The Royal Society of Chemistry 2013 Chemical communications Vol.49 No.45
<P>A hexagonally ordered mesoporous carbon, CMK-3, was utilized as a support for a Fischer–Tropsch catalyst. Each array of elongated pore structures with Co nanoparticles can be regarded as a nanochannel reactor. Due to the pore confinement and the hydrophobic nature of the support, this catalyst demonstrated excellent catalytic performance.</P> <P>Graphic Abstract</P><P>A CMK-3 supported cobalt catalyst demonstrated excellent catalytic performance due to the pore confinement and the hydrophobic nature of CMK-3. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cc00297g'> </P>
Meso-Scopic Analysis of Strain Path Change Effect on the Hardening Behavior of Dual-Phase Steel
Ha, Jinjin,Lee, Jinwoo,Kim, Ji Hoon,Barlat, Fré,dé,ric,Lee, Myoung-Gyu Wiley (John WileySons) 2014 STEEL RESEARCH INTERNATIONAL Vol.85 No.6
To study the anisotropic hardening behaviors of dual-phase steels under strain path changes, a meso-scale finite element analysis was considered with the representative volume elements. For the constitutive model, the Homogeneous yield function based on Anisotropic Hardening (HAH model) was used as a phenomenological constitutive equations to describe complex anisotropic material responses in an efficient way. For the martensite inclusions, three different configurations - elongated, large, and small spherical shapes - with two different volume fractions - 10 and 30% - were assumed. In order to represent strain path changes, two loading conditions were considered: tension-compression and tension-orthogonal tension. The simulation results for tension-compression test showed that the Bauschinger ratio increases as the volume fraction of martensite inclusion increases. For the tension-orthogonal tension test, the hard martensite attenuated the transient flow stress characteristics, which were observed in the single ferritic phase. The effect of hard phase inclusion was analytically explained using a simple one-dimensional analysis based on the elastic-linear plastic theory.