Control Method for Grid-Connected/Islanding Switching of Hybrid AC/DC Microgrid

Qu Zheng-Wei,Chong Zhen-Xiao,Wang Yun-Jing,Shi Zhe,Yao Yun-Xiao 대한전기학회 2023 Vol.18 No.1

For hybrid AC/DC microgrid (HMG) under master–slave control strategy, DGs usually adopt constant power control (P control) in gird-connected mode and at least one DG adopts constant voltage control (V control) in islanding mode. However, when unplanned islanding happens, the voltage and current of the HMG will experience remarkable fl uctuations, which aff ects the system’s stability. This paper presents a control method to achieve smooth switching from grid-connected to islanding mode by introducing state tracking control between P control and V control. The state tracking control can make the current reference signal of the V control track that of the P control in grid-connected mode. When unplanned islanding happens, the mutation of the current reference signal can be tuned into a smooth transition by the voltage loop’s PI controller, and the transient oscillations can be eliminated to realize smooth switching. The eff ectiveness of the proposed control method is verifi ed by simulation results using MATLAB/Simulink.

Control Method for Grid-Connected/Islanding Switching of Hybrid AC/DC Microgrid

Qu Zheng-Wei,Chong Zhen-Xiao,Wang Yun-Jing,Shi Zhe,Yao Yun-Xiao 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.1

For hybrid AC/DC microgrid (HMG) under master–slave control strategy, DGs usually adopt constant power control (P control) in gird-connected mode and at least one DG adopts constant voltage control (V control) in islanding mode. However, when unplanned islanding happens, the voltage and current of the HMG will experience remarkable fluctuations, which affects the system’s stability. This paper presents a control method to achieve smooth switching from grid-connected to islanding mode by introducing state tracking control between P control and V control. The state tracking control can make the current reference signal of the V control track that of the P control in grid-connected mode. When unplanned islanding happens, the mutation of the current reference signal can be tuned into a smooth transition by the voltage loop’s PI controller, and the transient oscillations can be eliminated to realize smooth switching. The effectiveness of the proposed control method is verified by simulation results using MATLAB/Simulink.

Analysis of the Relationship between Breaking Stress and Whiteness in a New Hair Bleaching Method

Wei Wang,Qing-hui Mao,Yu Zhang,Jian-gang Qu,Zhi-jie Liang,Jia Yu,Lin-juan Zheng,Li Zhang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.12

In order to investigate the relationship between breaking stress and whiteness in a bleaching treatment withlaccase, hair samples from three biogeographically distinct populations were characterized by various chemical and physicaltechniques. Factors affecting whiteness and breaking stress were investigated by attenuated total reflection infraredspectroscopy, atomic absorption spectroscopy, X-ray diffraction and scanning electron microscopy. The results reveal thatwhiteness and breaking stress after bleaching are primarily influenced by the diversity of concentration of metal ions andfunctional groups in the hair. The hair samples with lower content of metal ions obtain better whiteness and higher stressretention. The presence of OH functional group increases the final whiteness of the hair sample, while lack of that not onlydecreases the whiteness but also leads to more stress loss. In addition, the presence of the C=C functional group alsodecreases the whiteness.

Investigation on characteristics of pressure fluctuation in a centrifugal pump with clearance flow

Lulu Zheng,Xiaoping Chen,Wei Zhang,Zu-chao Zhu,Jinglei Qu,Mengmeng Wang,Xiaojie Ma,Xueli Cheng 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.9

Clearance flow has great impact on pressure fluctuation of centrifugal pumps. Numerical calculations are performed to study the pressure fluctuation characteristics of centrifugal pump with wear ring clearance, especially in the regions of interaction between main flow and clearance flow (IMC) and clearance. The accuracy of numerical calculations is illustrated by comparing the experiments of performance and pressure fluctuation. Results show that, in clearance region the pressure fluctuation is still governed by blade passing frequency (f BPF ). Its amplitude of dominate frequency of pressure fluctuation becomes larger as the probe approaches the impeller exit. In IMC region, the pressure fluctuation at impeller outlet is dominated by f BPF . However, the dominate frequency at the entrance of impeller is less than f BPF . In addition, as the flow rate increased, the amplitude of dominate frequency of pressure fluctuation increases at impeller entrance, whereas an inverse trend is observed at wear ring clearance region.

<i>Orobanche cernua</i> Loefling Attenuates Ultraviolet B-mediated Photoaging in Human Dermal Fibroblasts

Gao, Wei,Wang, Yu-shuai,Qu, Zheng-yi,Hwang, Eunson,Ngo, Hien T. T.,Wang, Ying-ping,Bae, Jahyun,Yi, Tae-hoo Wiley (Blackwell Publishing) 2018 Photochemistry and photobiology Vol.94 No.4

<P>UV radiation is the primary cause of skin photoaging, which results in an increase in matrix metalloproteinases and degradation of collagen. Developing new natural antioxidant as photoprotective agents has become a popular area of research. Orobanche cernua Loefling is a parasitic plant that is rich in phenylethanoid glycosides (PhGs). This study investigated the photoprotective effects of the ethanolic extract of Orobanche cernua Loefling (OC) and its principal component acteoside on UVB-induced photoaging as well as their underlying molecular mechanisms in normal human dermal fibroblasts (NHDFs). Biological testing demonstrated that OC and acteoside possessed significant photoprotective activities, reducing MMP and IL-6 levels while improving type-I procollagen synthesis in UVB-irradiated NHDFs. Further study showed that the protective mechanisms were the improvement of transcription factor Nrf2-mediated antioxidant defensive system, suppression of MAPK/AP-1 and activation of the TGF-/Smad pathway. Together, our results suggested that OC might be a promising antiphotoaging agent against UV radiation-induced skin damage.</P>

Facile synthesis of Nafion-supported Pt nanoparticles with ultra-low loading as a high-performance electrocatalyst for hydrogen evolution reaction

Yu, Jianguo,Wei, Dan,Zheng, Zhe,Yu, Wenjie,Shen, Honghui,Qu, Yuning,Wen, Shuya,Kwon, Young-Uk,Zhao, Yongnan Elsevier 2020 JOURNAL OF COLLOID AND INTERFACE SCIENCE - Vol.566 No.-

<P><B>Abstract</B></P> <P>x%Pt-Naf-CV (Pt-Nafion-Cyclic Voltammetry) catalysts with homogeneously distributed platinum nanoparticles and ultra-low Pt loading are successfully synthesized by using a facile potential cycling approach. The as-synthesized 0.8%Pt-Naf-CV catalyst exhibits an enhanced electrocatalytic activity for hydrogen evolution reaction (HER) in 0.5 M H<SUB>2</SUB>SO<SUB>4</SUB> solution, which obtains a low overpotential of 34 mV at 10 mA cm<SUP>−2</SUP>. The linear sweep voltammetry (LSV) curve of 0.8%Pt-Naf-CV catalyst is almost consistent with that of commercial Pt/C. However, the 0.8%Pt-Naf-CV catalyst displays a more excellent stability and durability in comparison with commercial Pt/C. Besides, the Pt loading of Pt/C (Pt–10 wt%) is about 10 times that of 0.8%Pt-Naf-CV catalyst. The improved electrocatalytic performances are derived from the synergistic effects of Pt and Nafion. The Nafion plays a significant role as a dispersant, carrier and structure directing agent on the morphology and size of the Pt catalyst. This result contributes a promising method to enhance the catalytic activity and reduce the amount of Pt.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Peroxisome Proliferator-Activated Receptor α Facilitates Osteogenic Differentiation in MC3T3-E1 Cells via the Sirtuin 1-Dependent Signaling Pathway

Gong, Kai,Qu, Bo,Wang, Cairu,Zhou, Jingsong,Liao, Dongfa,Zheng, Wei,Pan, Xianming Korean Society for Molecular and Cellular Biology 2017 Molecules and cells Vol.40 No.6

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease characterized by lack of insulin and high glucose levels. T2DM can cause bone loss and fracture, thus leading to diabetic osteoporosis. Promoting osteogenic differentiation of osteoblasts may effectively treat diabetic osteoporosis. We previously reported that Sirtuin 1 (Sirt1), a $NAD^+$-dependent deacetylase, promotes osteogenic differentiation through downregulation of peroxisome proliferator-activated receptor (PPAR) ${\gamma}$. We also found that miR-132 regulates osteogenic differentiation by downregulating Sirt1 in a $PPAR{\beta}/{\delta}$-dependent manner. The ligand-activated transcription factor, $PPAR{\alpha}$, is another isotype of the peroxisome proliferator-activated receptor family that helps maintain bone homeostasis and promot bone formation. Whether the regulatory role of $PPAR{\alpha}$ in osteogenic differentiation is mediated via Sirt1 remains unclear. In the present study, we aimed to determine this role and the underlying mechanism by using high glucose (HG) and free fatty acids (FFA) to mimic T2DM in MC3T3-E1 cells. The results showed that HG-FFA significantly inhibited expression of $PPAR{\alpha}$, Sirt1 and osteogenic differentiation, but these effects were markedly reversed by $PPAR{\alpha}$ overexpression. Moreover, siSirt1 attenuated the positive effects of $PPAR{\alpha}$ on osteogenic differentiation, suggesting that $PPAR{\alpha}$ promotes osteogenic differentiation in a Sirt1-dependent manner. Luciferase activity assay confirmed interactions between $PPAR{\alpha}$ and Sirt1. These findings indicate that $PPAR{\alpha}$ promotes osteogenic differentiation via the Sirt1-dependent signaling pathway.

Peroxisome Proliferator-Activated Receptor α Facilitates Osteogenic Differentiation in MC3T3-E1 Cells via the Sirtuin 1-Dependent Signaling Pathway

Kai Gong,Bo Qu,Cairu Wang,Jingsong Zhou,Dongfa Liao,Wei Zheng,Xianming Pan 한국분자세포생물학회 2017 Molecules and cells Vol.40 No.6

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease characterized by lack of insulin and high glucose levels. T2DM can cause bone loss and fracture, thus leading to diabetic osteoporosis. Promoting osteogenic differentiation of osteoblasts may effectively treat diabetic osteoporosis. We previously reported that Sirtuin 1 (Sirt1), a NAD+-dependent deacetylase, promotes osteogenic differentiation through downregulation of peroxisome proliferator-activated receptor (PPAR) γ. We also found that miR-132 regulates osteogenic differentiation by downregulating Sirt1 in a PPAR /δ-dependent manner. The ligand-activated transcription factor, PPAR , is another isotype of the peroxisome proliferator-activated receptor family that helps maintain bone homeostasis and promot bone formation. Whether the regulatory role of PPAR in osteogenic differentiation is mediated via Sirt1 remains unclear. In the present study, we aimed to de-termine this role and the underlying mechanism by using high glucose (HG) and free fatty acids (FFA) to mimic T2DM in MC3T3-E1 cells. The results showed that HG-FFA significantly inhibited expression of PPAR , Sirt1 and osteogenic differentiation, but these effects were markedly reversed by PPAR overexpression. Moreover, siSirt1 attenuated the positive effects of PPAR on osteogenic differentiation, suggesting that PPAR promotes osteogenic differentiation in a Sirt1-dependent manner. Luciferase activity assay confirmed interactions between PPAR and Sirt1. These findings indicate that PPAR promotes osteogenic differentiation via the Sirt1-dependent signaling pathway.

Comparison of Liver Transplantation and Liver Resection for Hepatocellular Carcinoma Patients with Portal Vein Tumor Thrombus Type I and Type II

Jia-Yu Lv,Ning-Ning Zhang,Ya-Wei Du,Ying Wu,Tian-Qiang Song,Ya-Min Zhang,Yan Qu,Yu-Xin Liu,Jie Gu,Ze-Yu Wang,Yi-Bo Qiu,Bing Yang,Da-Zhi Tian,Qing-Jun Guo,Li Zhang,Ji-San Sun,Yan Xie,Zheng-Lu Wang,Xin 연세대학교의과대학 2021 Yonsei medical journal Vol.62 No.1

Purpose: The aim of this study was to compare the efficacy of liver transplantation (LT) and liver resection (LR) for hepatocellularcarcinoma (HCC) patients with portal vein tumor thrombus (PVTT) and to investigate risk factors affecting prognosis. Materials and Methods: A total of 94 HCC patients with PVTT type I (segmental PVTT) and PVTT type II (lobar PVTT) were involvedand divided into LR (n=47) and LT groups (n=47). Recurrence-free survival (RFS) and overall survival (OS) were comparedbefore and after inverse probability of treatment weighting (IPTW). Prognostic factors for RFS and OS were explored. Results: Two treatment groups were well-balanced using IPTW. In the entire cohort, LT provided a better prognosis than LR. Among patients with PVTT type I, RFS was better with LT (p=0.039); OS was not different significantly between LT and LR(p=0.093). In subgroup analysis of PVTT type I patients with α-fetoprotein (AFP) levels >200 ng/mL, LT elicited significantly longermedian RFS (18.0 months vs. 2.1 months, p=0.022) and relatively longer median OS time (23.6 months vs. 9.8 months, p=0.065). Among patients with PVTT type II, no significant differences in RFS and OS were found between LT and LR (p=0.115 and 0.335,respectively). Multivariate analyses showed treatment allocation (LR), tumor size (>5 cm), AFP and aspartate aminotransferase(AST) levels to be risk factors of RFS and treatment allocation (LR), AFP and AST as risk factors for OS. Conclusion: LT appeared to afford a better prognosis for HCC with PVTT type I than LR, especially in patients with AFP levels>200 ng/mL.