http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
YoungJong Kim,JinKyung Park,WonSub Kang,SuKang Kim,Changsu Han,HaeRi Na,HaeJeong Park,JongWoo Kim,YoungYoul Kim,MoonHo Park,JongWoo Paik 대한신경정신의학회 2017 PSYCHIATRY INVESTIGATION Vol.14 No.1
Objective-Mitochondrial dysfunction is a prominent and early feature of Alzheimer’s disease (AD). The morphologic changes observed in the AD brain could be caused by a failure of mitochondrial fusion mechanisms. The aim of this study was to investigate whether genetic polymorphisms of two genes involved in mitochondrial fusion mechanisms, optic atrophy 1 (OPA1) and mitofusin 2 (MFN2), were associated with AD in the Korean population by analyzing genotypes and allele frequencies. Methods-One coding single nucleotide polymorphism (SNP) in the MFN2, rs1042837, and two coding SNPs in the OPA1, rs7624750 and rs9851685, were compared between 165 patients with AD (83 men and 82 women, mean age 72.3±4.41) and 186 healthy control subjects (82 men and 104 women, mean age 76.5±5.98). Results-Among these three SNPs, rs1042837 showed statistically significant differences in allele frequency, and genotype frequency in the co-dominant 1 model and in the dominant model. Conclusion-These results suggest that the rs1042837 polymorphism in MFN2 may be involved in the pathogenesis of AD.
Digital Current Mode PFC LED Driver with High Flicker Immunity against Line Distortion
Youngjong Kim(김영종),HyunChul Eom(엄현철),Seunguk Yang(양승욱),Dongjin Park(박동진) 전력전자학회 2013 전력전자학술대회 논문집 Vol.2013 No.7
In the conventional single-stage PFC LED driver with slow feedback response, LED current is easily unstable with visible flicker by randomly distorted line voltage. The proposed single-stage LED driver implements robust LED current regulation against the mains input voltage distortion. Internally generated sine reference by digital mapping significantly stabilizes LED current in the buck-boost topology. Power compensation at load voltage drop is also discussed. The high flicker immunity at the line distortion has been experimentally verified in 7.8 W PFC LED lighting system.
Active thermal control for reliability improvement in photovoltaic single‑phase T‑type NPC inverters
Youngjong Ko,Taerim Ryu,Ui‑Min Choi 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.5
Single-phase T-type neutral point clamped (NPC) inverters have been extensively employed in small scale photovoltaic (PV) systems due to their outstanding power conversion efficiency. However, it is still necessary to further reduce PV energy costs to successfully replace fossil fuels. To do so, the reliability of inverters needs to be improved, which will result in both operation and maintenance cost reductions and the energy production improvement. On the other hand, the T-type NPC inverter suffers from unevenly distributed power losses among power semiconductor devices, which implies that the devices generating the highest losses are quickly aged and fail sooner than other devices. In this context, it is recommended to reduce the thermal stresses of the highest stressed devices. This work proposes a thermally compensated modulation strategy that enables thermal stress reduction. The capability of the proposed method for controlling power losses is theoretically analyzed, and its impact on lifetime is evaluated. Finally, the feasibility of the proposed method is experimentally validated.
Youngjong Ko,Kiwoo Park,Kyo-Beum Lee,Frede Blaabjerg 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In a grid connected power conversion system, the phase angle information of a grid voltage is very essential for supplying power to the grid since it is used for active and reactive power control. A Phase Locked Loop (PLL) system is used and should be robust because often the actual grid voltages are usually distorted by unexpected harmonics. However, conventional PLL systems have steady state errors when distorted voltages are used as a PLL input. Furthermore, using this distorted phase angle in the power control could reduce the output power quality. In this paper, the grid voltages are separated into fundamental and harmonic components and a virtual phase voltage is generated from the fundamental component using a Full Order Observer (FOO). Two virtual voltages are used as an input for the PLL system so the phase angle errors can be reduced and the output power quality can be improved. The dynamic characteristics of the PLL system are designed using the modeling method to improve the dynamic response and stability of the whole system. The performance of the proposed method has been verified by a comparative analysis to the conventional PLL system. It is concluded the proposed method works well.
Broad-wavelength-range chemically tunable block-copolymer photonic gels
Kang, Youngjong,Walish, Joseph J.,Gorishnyy, Taras,Thomas, Edwin L. Nature Publishing Group 2007 NATURE MATERIALS Vol.6 No.12
Responsive photonic crystals have been developed for chemical sensing using the variation of optical properties due to interaction with their environment. Photonic crystals with tunability in the visible or near-infrared region are of interest for controlling and processing light for active components of display, sensory or telecommunication devices. Here, we report a hydrophobic block–hydrophilic polyelectrolyte block polymer that forms a simple one-dimensional periodic lamellar structure. This results in a responsive photonic crystal that can be tuned via swelling of the hydrophilic layers by contact with a fluid reservoir. The glassy hydrophobic layer forces expansion of the hydrophilic layer along the layer normal, yielding extremely large optical tunability through changes in both layer thickness and index of refraction. Polyelectrolyte polymers are known to be highly responsive to a range of stimuli. We show very large reversible optical changes due to variation of the salt concentration of a water reservoir. These one-dimensional Bragg stacks reflect incident light from the ultraviolet–visible region to the near-infrared region (λpeak=350–1,600 nm) with over a 575% change in the position of the stop band. Our work demonstrates the extremely high responsivity possible for polyelectrolyte-based photonic materials.