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Dual SRF based Torque Ripple Mitigation Strategy for a Fault Tolerant PMSM Drive System
Byeng-joo Byen,Seunghoon Baek,Younghoon Cho,Gyu-Ha Choe 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper presents a torque ripple mitigation strategy for the fault tolerant permanent magnet synchronous motor (PMSM) drive system, in which an auxiliary phase is employed. It is shown that the torque ripple whose frequency is twice the fundamental frequency is induced in the PMSM undergoing an open circuit fault on a certain phase. In order to compensate the torque ripple, current controllers are implemented in the dual synchronous reference frame (SRF), in which the rotating frequencies of the two SRF are different. In more detail, one of the SRFs rotates in two times of the fundamental frequency to actively compensate the torque ripple in the steady state while another one is synchronized to the fundamental component. Compared to traditional methods, the proposed algorithm effectively extends the operating speed of the PMSM where the torque ripple can be compensated. Both the simulations and the experimental results confirm the usefulness of the proposed torque ripple mitigation strategy.
Go, Younghoon,Jeong, Ji Yun,Jeoung, Nam Ho,Jeon, Jae-Han,Park, Bo-Yoon,Kang, Hyeon-Ji,Ha, Chae-Myeong,Choi, Young-Keun,Lee, Sun Joo,Ham, Hye Jin,Kim, Byung-Gyu,Park, Keun-Gyu,Park, So Young,Lee, Chul- American Diabetes Association 2016 Diabetes Vol.65 No.10
<P>Hepatic steatosis is associated with increased insulin resistance and tricarboxylic acid (TCA) cycle flux, but decreased ketogenesis and pyruvate dehydrogenase complex (PDC) flux. This study examined whether hepatic PDC activation by inhibition of pyruvate dehydrogenase kinase 2 (PDK2) ameliorates these metabolic abnormalities. Wildtype mice fed a high-fat diet exhibited hepatic steatosis, insulin resistance, and increased levels of pyruvate, TCA cycle intermediates, and malonyl-CoA but reduced ketogenesis and PDC activity due to PDK2 induction. Hepatic PDC activation by PDK2 inhibition attenuated hepatic steatosis, improved hepatic insulin sensitivity, reduced hepatic glucose production, increased capacity for beta-oxidation and ketogenesis, and decreased the capacity for lipogenesis. These results were attributed to altered enzymatic capacities and a reduction in TCA anaplerosis that limited the availability of oxaloacetate for the TCA cycle, which promoted ketogenesis. The current study reports that increasing hepatic PDC activity by inhibition of PDK2 ameliorates hepatic steatosis and insulin sensitivity by regulating TCA cycle anaplerosis and ketogenesis. The findings suggest PDK2 is a potential therapeutic target for nonalcoholic fatty liver disease.</P>
Byeng-Joo Byen,Kyung-Pil Kang,Younghoon Cho,Anno Yoo 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a variable modulation strategy for a dual-active-bridge (DAB) converter with a wide operating range to achieve high efficiency. In the propose method, four voltage modulation strategies are automatically changed for efficiency optimization under the operating voltage and the output power. To do this, the boundary conditions of each modulation region are derived to minimize the power loss, and a seamless mode transition algorithm between each modulation strategy is introduced. A 3kW DAB converter whose primary voltage is 380V and the secondary voltage ranges from 100V to 500V has been built. The experimental results show that the DAB converter with the proposed modulation strategy achieves peak 98.9% peak efficiency under 400V output voltage condition.
Kim, Younghoon,Koo, Jaehyoung,Hwang, In-Chul,Mukhopadhyay, Rahul Dev,Hong, Soonsang,Yoo, Jejoong,Dar, Ajaz Ahmad,Kim, Ikjin,Moon, Dohyun,Shin, Tae Joo,Ko, Young Ho,Kim, Kimoon American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.44
<P>We report a new approach to building hierarchical superstructures using a shape-persistent porous organic cage, which acts as a premade secondary building unit, and coordination chemistry. To illustrate the principle, a zinc-metalated porphyrin box (<B>Zn-PB</B>), a corner-truncated cubic porous cage, was connected by suitable dipyridyl terminated bridging ligands to construct <B>PB</B>-based hierarchical superstructures (<B>PSS</B>s). The <B>PSS</B>s were stabilized not only by the coordination bonds between Zn ions and bipyridyl-terminated ligands but also by π-π interactions between the corners of the <B>Zn-PB</B> units. By varying the length of the linker, we identified an optimum range of the linker length for construction of <B>PSS</B>s. The <B>PSS</B>s have large void volumes and an extrinsic surface area compared to the parent PBs, which can be exploited for the selective encapsulation and interior functionalization of the <B>PSS</B>s for various applications, including catalysis. We observed that singlet oxygen induced synthesis of the natural product, juglone, is more efficiently catalyzed by <B>PSS-1</B> than its constituent component <B>Zn-PB</B>.</P> [FIG OMISSION]</BR>
Ham, Byung-Joo,Chey, Jeanyung,Yoon, Sujung J.,Sung, Younghoon,Jeong, Do-Un,Ju Kim, Seog,Sim, Minyoung E.,Choi, Namhee,Choi, Ihn-Geun,Renshaw, Perry F.,Lyoo, In Kyoon Published on behalf of the European Neuroscience A 2007 The European journal of neuroscience Vol.25 No.1
<P>Abstract</P><P>The purpose of this study was to investigate the concentration of <I>N</I>-acetyl-aspartate (NAA) in the brain and its relationship with clinical characteristics in patients with post-traumatic stress disorder (PTSD). Proton magnetic resonance spectroscopy was performed in order to measure NAA concentrations in the anterior cingulate cortex (ACC) and bilateral hippocampus in 26 subjects with fire-related PTSD, who were survivors of a subway fire in South Korea, and 25 age- and sex-matched healthy comparison subjects. There were decreased NAA levels in the ACC (<I>t</I> = −3.88, d.f. = 49, <I>P</I> < 0.001) and bilateral hippocampus (right, <I>t</I> = −3.88, d.f. = 49, <I>P</I> < 0.001; left, <I>t</I> = −3.62, d.f. = 49, <I>P</I> < 0.001) in the PTSD group relative to the healthy comparison group. Also, NAA levels of the ACC (<I>r = –</I>0.43, <I>n</I> = 26, <I>P</I> = 0.027) and bilateral hippocampus (right, <I>r = –</I>0.48, <I>n</I> = 26, <I>P</I> = 0.013; left, <I>r</I> = −0.40, <I>n</I> = 26, <I>P</I> = 0.04) were negatively correlated with re-experience symptom scores in subjects with PTSD. In conclusion, our findings suggest that subjects with PTSD had decreased neuronal viabilities in the ACC and bilateral hippocampus, and that these deficits may play an important role in the pathophysiology of PTSD, especially regarding the re-experiencing of traumatic events.</P>
Intelligent Digital Redesign of Uncertain Nonlinear Systems : Global approach
성화창(Hwachang Sung),주영훈(Younghoon Joo),박진배(Jinbae Park),김도완(Dowan Kim) 한국지능시스템학회 2005 한국지능시스템학회 학술발표 논문집 Vol.15 No.2
This paper presents intelligent digital redesign method of global approach for hybrid state space fuzzy-model-based controllers. For effectiveness and stabilization of continuous-time uncertain nonlinear systems under discrete-time controller, Takagi-Sugeno(TS) fuzzy model is used to represent the complex system. And global approach design problems viewed as a convex optimization problem that we minimize the error of the norm bounds between nonlinearly interpolated linear operators to be matched. Also by using the power series, we analyzed nonlinear system's uncertain parts more precisely. When a sampling period is sufficiently small, the conversion of a continuous-time structured uncertain nonlinear system to an equivalent discrete-time system have proper reason. Sufficiently conditions for the global state-matching of the digitally controlled system are formulated in terms of linear matrix inequalities (LMIs). Finally, we prove the effectiveness and stabilization of the proposed intelligent digital redesign method by applying the chaotic Lorentz system.
Facility characteristics as independent prognostic factors of nursing home-acquired pneumonia
( Che Wan Lim ),( Younghoon Choi ),( Chang Hyeok An ),( Sang Joon Park ),( Hee Jin Hwang ),( Jae Ho Chung ),( Joo Won Min ) 대한내과학회 2016 The Korean Journal of Internal Medicine Vol.31 No.2
Background/Aims: Recently, the incidence of nursing home-acquired pneumonia (NHAP) has been increasing and is now the leading cause of death among nursing home residents. This study was performed to identify risk factors associated with NHAP mortality, focusing on facility characteristics. Methods: Data on all patients ≥70 years of age admitted with newly diagnosed pneumonia were reviewed. To compare the quality of care in nursing facilities, the following three groups were defined: patients who acquired pneumonia in the community, care homes, and care hospitals. In these patients, 90-day mortality was compared. Results: Survival analyses were performed in 282 patients with pneumonia. In the analyses, 90-day mortality was higher in patients in care homes (12.2%, 40.3%, and 19.6% in community, care homes, and care hospitals, respectively). Among the 118 NHAP patients, residence in a care home, structural lung diseases, treatment with inappropriate antimicrobial agents for accompanying infections, and a high pneumonia severity index score were risk factors associated with higher 90-day mortality. However, infection by potentially drug-resistant pathogens was not important. Conclusions: Unfavorable institutional factors in care homes are important prognostic factors for NHAP.