Individual DC Voltage Balancing Method at Zero Current Mode for Cascaded H-bridge Based Static Synchronous Compensator

Zezhou Yang,Jianjun Sun,Shangsheng Li,Zhiqiang Liao,Xiaoming Zha 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

Individual DC voltage balance problem is an inherent issue for cascaded H-bridge (CHB) based converter. When the CHB-based static synchronous compensator (STATCOM) is operating at zero current mode, the software-based individual DC voltage balancing control techniques may not work because of the infinitesimal output current. However, the different power losses of each cell would lead to the individual DC voltages unbalance. The uneven power losses on the local supplied cell-controllers (including the control circuit and drive circuit) would especially cause the divergence of individual DC voltages, due to their characteristic as constant power loads. To solve this problem, this paper proposes an adaptive voltage balancing module which is designed in the cell-controller board with small size and low cost circuits. It is controlled to make the power loss of the cell a constant resistance load, thus the DC voltages are balanced in zero current mode. Field test in a 10㎸ STATCOM confirms the performance of the proposed method.

Individual DC Voltage Balancing Method at Zero Current Mode for Cascaded H-bridge Based Static Synchronous Compensator

Yang, Zezhou,Sun, Jianjun,Li, Shangsheng,Liao, Zhiqiang,Zha, Xiaoming The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.1

Individual DC voltage balance problem is an inherent issue for cascaded H-bridge (CHB) based converter. When the CHB-based static synchronous compensator (STATCOM) is operating at zero current mode, the software-based individual DC voltage balancing control techniques may not work because of the infinitesimal output current. However, the different power losses of each cell would lead to the individual DC voltages unbalance. The uneven power losses on the local supplied cell-controllers (including the control circuit and drive circuit) would especially cause the divergence of individual DC voltages, due to their characteristic as constant power loads. To solve this problem, this paper proposes an adaptive voltage balancing module which is designed in the cell-controller board with small size and low cost circuits. It is controlled to make the power loss of the cell a constant resistance load, thus the DC voltages are balanced in zero current mode. Field test in a 10kV STATCOM confirms the performance of the proposed method.

Preparation and photoluminescence properties of the Eu2+, Sm3+ co-doped Li2SrSiO4 phosphors

Lijuan Liu,Panli You,Guangfu Yin,Xiaoming Liao,Zhongbing Huang,Xianchun Chen,Yadong Yao 한국물리학회 2012 Current Applied Physics Vol.12 No.4

A series of Eu2+ and Sm3+ co-doped Li2SrSiO4 phosphors are prepared by the high temperature solidstate reaction. The morphology, structure and spectroscopic properties of the prepared samples are characterized by scanning electron microscopy, X-ray diffraction, diffuse reflection spectra, photoluminescence spectra and electron paramagnetic resonance spectra, respectively. The effect of Sm3þdoping concentration on the photoluminescence intensity of the prepared samples is also investigated. The results indicate that the crystal structure of Li2SrSiO4 is not changed with the Eu2+, Sm3+ co-doping. The spherical-like particle size of the obtained product is about 20-30 nm in diameter. When the Sm3+ concentration is 0.3 mol% and the Eu2+ concentration is 0.7 mol%, the phosphors show the maximum emission intensity, which is 50% higher than that of Eu2+ doped Li2SrSiO4. Excited at 420 nm, the phosphor presents a single broad emission band peaking at 558 nm, which is ascribed to the 4f65d1 / 4f7 transitions of Eu2+ and 4G5/2 / 6H5/2 and 4G5/2 / 6H7/2 transitions of Sm3+. The Commission International de I0Eclairage chromaticity coordinates of Li2SrSiO4:0.7 mol% Eu2+, 0.3 mol%Sm3+ are x = 0.28, y = 0.28. A series of Eu2+ and Sm3+ co-doped Li2SrSiO4 phosphors are prepared by the high temperature solidstate reaction. The morphology, structure and spectroscopic properties of the prepared samples are characterized by scanning electron microscopy, X-ray diffraction, diffuse reflection spectra, photoluminescence spectra and electron paramagnetic resonance spectra, respectively. The effect of Sm3þdoping concentration on the photoluminescence intensity of the prepared samples is also investigated. The results indicate that the crystal structure of Li2SrSiO4 is not changed with the Eu2+, Sm3+ co-doping. The spherical-like particle size of the obtained product is about 20-30 nm in diameter. When the Sm3+ concentration is 0.3 mol% and the Eu2+ concentration is 0.7 mol%, the phosphors show the maximum emission intensity, which is 50% higher than that of Eu2+ doped Li2SrSiO4. Excited at 420 nm, the phosphor presents a single broad emission band peaking at 558 nm, which is ascribed to the 4f65d1 / 4f7 transitions of Eu2+ and 4G5/2 / 6H5/2 and 4G5/2 / 6H7/2 transitions of Sm3+. The Commission International de I0Eclairage chromaticity coordinates of Li2SrSiO4:0.7 mol% Eu2+, 0.3 mol%Sm3+ are x = 0.28, y = 0.28.

Long Noncoding RNA NEAT1 Aggravates Aβ-Induced Neuronal Damage by Targeting miR-107 in Alzheimer’s Disease

Sha Ke,Zhaohui Yang,Fei Yang,Xiaoming Wang,Juan Tan,Bo Liao 연세대학교의과대학 2019 Yonsei medical journal Vol.60 No.7

Purpose: Alzheimer’s disease (AD) is the most common neurodegenerative disease, with a rising prevalence worldwide. Longnoncoding RNAs (lncRNAs) have been found to play important roles in the development and treatment of AD. However, the exactrole of lncRNA nuclear enriched abundant transcript 1 (NEAT1) in neuronal damage in AD is largely unknown. Materials and Methods: The AD model was established in SH-SY5Y and SK-N-SH cells via treatment with amyloid β1-42 (Aβ). Theexpression of NEAT1 and microRNA-107 (miR-107) was measured by quantitative real-time polymerase chain reaction. Cell viabilityand apoptosis were detected by MTT assay, immunocytochemistry, and flow cytometry. The expression of phosphorylated tauprotein (p-Tau) was measured by Western blot. The interaction between NEAT1 and miR-107 was explored by bioinformaticsanalysis, luciferase activity, and RNA immunoprecipitation assays. Results: NEAT1 expression was enhanced in Aβ-treated SH-SY5Y and SK-N-SH cells, and its knockdown attenuated Aβ-inducedinhibition of viability and promotion of apoptosis and p-Tau levels. NEAT1 was indicated as a decoy of miR-107. miR-107 abundancewas reduced in Aβ-treated cells, and its overexpression reversed Aβ-induced injury. Moreover, interference of miR-107 abatedsilencing of NEAT1-mediated inhibition of neuronal damage in Aβ-treated SH-SY5Y and SK-N-SH cells. Conclusion: LncRNA NEAT1 aggravated Aβ-induced neuronal damage by sponging miR-107, indicating a novel avenue for treatmentof AD.

Preparation and properties of the green-emitting phosphors NaCa0.98-xMgxPO4:

Bo Yue,Juan Gu,Guangfu Yin,Zhongbing Huang,Xiaoming Liao,Yadong Yao,Yunqing Kang,Panli You 한국물리학회 2010 Current Applied Physics Vol.10 No.4

In this study, a series of the green-emitting phosphors NaCa0.98-xMgxPO4:Eu2þ 0:02 was prepared through high temperature solid-state reaction. The structure and spectroscopic properties of these samples were characterized by XRD, FT-IR, reflectance spectra and photoluminescence (PL) spectra, respectively. The effect of Mg2+ co-doping concentration on the PL intensity of as-prepared samples was also investigated. The enhanced intensities of excitation and emission band of Eu2+ and a slight red-shift of the emission peak were observed due to Mg2+ co-doping. When the x value is 0.08, the phosphors possessed the maximum emission intensity monitored at 360 nm and the emission spectrum shows a single band centered at about 500 nm. The obtained phosphors had strong absorption in near-UV zone (350–400 nm), which can match the emission of near-UV light-emitting diodes. The prepared material is potential green phosphors for white LEDs.

The precipitation of three Ca-P phase whiskers from an acid solution through hydrolysis of urea

Yunqing Kang,Yunshan Liu,Zhongbing Huang,Yadong Yao,Xiaoming Liao,Li Liao,Guangfu Yin 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2

Hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP) and dicalcium phosphate (DCP) whiskers with high aspect ratio and good crystallinity were successfully prepared by hydrolysis of urea in acid solutions at 90oC for 96 h. The precipitated whiskers were characterized by XRD, SEM and TEM. The lengths and aspect ratios of whiskers could be controlled by the precipitation agent, urea, with a proper incubation time. Results revealed good morphology and crystallinity of the precipitated whiskers without any impurities. TEM indicated single crystal diffraction patterns of HA and β-TCP were clearly identified. The high aspect ratio of whiskers could be potentially used as the scaffold in tissue engineering or filler in composite biomaterials to enhance mechanical properties. Hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP) and dicalcium phosphate (DCP) whiskers with high aspect ratio and good crystallinity were successfully prepared by hydrolysis of urea in acid solutions at 90oC for 96 h. The precipitated whiskers were characterized by XRD, SEM and TEM. The lengths and aspect ratios of whiskers could be controlled by the precipitation agent, urea, with a proper incubation time. Results revealed good morphology and crystallinity of the precipitated whiskers without any impurities. TEM indicated single crystal diffraction patterns of HA and β-TCP were clearly identified. The high aspect ratio of whiskers could be potentially used as the scaffold in tissue engineering or filler in composite biomaterials to enhance mechanical properties.