Preparation and characterization of a poly(vinylbenzyl sulfonic acid)-grafted FEP membrane

Fei, Geng,Shin, Junhwa,Kang, Sung-A,Ko, Beom-Seok,Kang, Phil-Hyun,Lee, Youn-Sik,Nho, Young Chang Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of polymer science Part A, Polymer chemist Vol.48 No.3

<P>In this study, a novel polymer electrolyte membrane, poly(vinylbenzyl sulfonic acid)-grafted poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP-g-PVBSA), has been successfully prepared by simultaneous irradiation grafting of vinylbenzyl chloride (VBC) monomer onto a FEP film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. The chemical reactions for the sulfonation were carried out via the formation of thiouronium salt with thiourea, base-catalyzed hydrolysis for the formation of thiol, and oxidation with hydrogen peroxide. Each chemical conversion process was confirmed by FTIR, elemental analysis, and SEM-EDX. A chemical stability study performed with Fenton's reagent (3% H<SUB>2</SUB>O<SUB>2</SUB> solution containing 4 ppm of Fe<SUP>2+</SUP>) at 70 °C revealed that FEP-g-PVBSA has a higher chemical stability than the poly(styrene sulfonic acid)-grafted membranes (FEP-g-PSSA). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 563–569, 2010</P> <B>Graphic Abstract</B> <P>A novel polymer electrolyte membrane, FEP-g-PVBSA, has been successfully prepared by using a simultaneous irradiation grafting of vinylbenzyl chloride monomer onto a poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film and taking subsequent chemical modification steps to modify the benzyl chloride moiety to the benzyl sulfonic acid moiety. <img src='wiley_img/0887624X-2010-48-3-POLA23762-gra001.gif' alt='wiley_img/0887624X-2010-48-3-POLA23762-gra001'> </P>

동시조사방법을 이용한 폴리염화비닐벤질이 그라프트된 PFA 필름의 제조

Fei, Geng,신준화,이연식,노영창 한국방사선산업학회 2009 방사선산업학회지 Vol.3 No.3

An Improved Active Damping Method with Capacitor Current Feedback

Geng, Yi-Wen,Qi, Ya-Wen,Liu, Hai-Wei,Guo, Fei,Zheng, Peng-Fei,Li, Yong-Gang,Dong, Wen-Ming The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2

Proportional capacitor current feedback active damping (CCFAD) has a limited valid damping region in the discrete time domain as (0, $f_s/6$. However, the resonance frequency ($f_r$) of an LCL-type filter is usually designed to be less than half the sampling frequency ($f_s$) with the symmetry regular sampling method. Therefore, ($f_s/6$, $f_s/2$) becomes an invalid damping region. This paper proposes an improved CCFAD method to extend the valid damping region from (0, $f_s/6$ to (0, $f_s/2$), which covers all of the possible resonance frequencies in the design procedure. The full-valid damping region is obtained and the stability margin of the system is analyzed in the discrete time domain with the Nyquist criterion. Results show that the system can operate stably with the proposed CCFAD method when the resonance frequency is in the region (0, $f_s/2$). The performances at the steady and dynamic state are enhanced by the selected feedback coefficient H and controller gain $K_p$. Finally, the feasibility and effectiveness of the proposed CCFAD method are verified by simulation and experimental results.

A study on the characterization of FEP-<i>g</i>-PVBSA membranes as polymer electrolytes for direct methanol fuel cells

Fei, Geng,Hwang, Mi-Lim,Shin, Junhwa SAGE Publications 2011 HIGH PERFORMANCE POLYMERS Vol.23 No.7

방사선 그래프팅에 의한 염화비닐벤질 고분자가 그래프트된 불소필름의 제조

경비(Fei Geng),손준용(Joon Yong Sohn),이연식(Youn Sik Lee),노영창(Young Chang Nho),신준화(Jun Hwa Shin) 한국고분자학회 2010 폴리머 Vol.34 No.5

본 연구에서 염화비닐벤질(vinylbenzyl chloride) 단량체는 동시조사방법을 이용하여 poly(tetrafluoro-ethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-co-perfluoropropylvinyl ether) (PFA), poly(ethylene-co-tetrafluoroethylene) (ETFE) 불소고분자 필름에 성공적으로 그래프트되었다. 실험 결과 같은 조사조건을 적용할 경우 다른 불소고분자 필름보다 ETFE 불소필름에 PVBC 고분자가 쉽게 그래프트됨을 확인하였다. 그래프트된 필름들은 FTIR, TGA, SEM-EDS 기기들을 사용하여 분석하였다. 그래프트된 필름의 파단신장률은 그래프트률이 증가할수록 감소되는 것을 확인하였으며 ETFE에 그래프트된 필름은 다른 불소고분자에 그래프트된 필름들과 비교하여 더 좋은 기계특성을 가지고 있음을 확인하였다. In this study, a vinylbenzyl chloride (VBC) monomer was successfully grafted onto the several fluoropolymer films including poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(tetrafluoro-ethylene-co-perfluoropropylvinyl ether) (PFA), and poly (ethylene-co-tetrafluoroethylene) (ETFE) films by using a simultaneous irradiation method, The results indicated that PVBC graft polymer can be easily grafted onto the ETFE film than other fluorinated films under the same irradiation condition. The grafted Films were characterized by using FT1R, TGA, and SEM-EDS instruments. The elongation at the breaking of the grafted films was found to decrease with an increase of degree of grafting (DOG). The PVBC-grafted ETFE films were found to have better mechanical properties than other PVI3C-grafted fluorinated films.

An Improved Active Damping Method with Capacitor Current Feedback

Yi-Wen Geng,Ya-Wen Qi,Hai-Wei Liu,Fei Guo,Peng-Fei Zheng,Yong-Gang Li,Wen-Ming Dong 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2

Proportional capacitor current feedback active damping (CCFAD) has a limited valid damping region in the discrete time domain as (0, fs/6). However, the resonance frequency (fr) of an LCL-type filter is usually designed to be less than half the sampling frequency (fs) with the symmetry regular sampling method. Therefore, (fs/6, fs/2) becomes an invalid damping region. This paper proposes an improved CCFAD method to extend the valid damping region from (0, fs/6) to (0, fs/2), which covers all of the possible resonance frequencies in the design procedure. The full-valid damping region is obtained and the stability margin of the system is analyzed in the discrete time domain with the Nyquist criterion. Results show that the system can operate stably with the proposed CCFAD method when the resonance frequency is in the region (0, fs/2). The performances at the steady and dynamic state are enhanced by the selected feedback coefficient H and controller gain Kp. Finally, the feasibility and effectiveness of the proposed CCFAD method are verified by simulation and experimental results.

Condition monitoring of inverter power devices based on electromagnetic acoustic emissions

Fei Liu,Chenghao Zeng,Liang Cheng,Yunze He,Yun Bai,Xuefeng Geng,Songyuan Liu,Dantong Ren,Lei Wang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.12

Unlike conventional voltage and current sensing, this paper studies the use of acoustic emission signals to detect the condition of the power device for a DC–AC inverter. As a relatively new method for monitoring power devices, there are some unknown phenomena in acoustic emissions (also called mechanical stress wave). Therefore, the authors present an experimental setup that is used to analyze acoustic emission signals. Based on experimental results, some interesting points have been found: (1) The generation of a mechanical stress wave is verified for the first time. (2) The time-domain peak value, energy, and rise time of the mechanical stress wave at the turn-on time of a power device are barely affected by the load. Meanwhile, these values decrease with an increase of the load at the turn-off time. (3) The frequency-domain peak value of the mechanical stress wave tends to decrease with an increase of the load, and the peak frequency is barely affected by the load. These mechanical stress analysis results can be utilized for condition monitoring in many applications.

Comparison of the mechanical performance between two-stage and flat-face cutter head for the rock tunnel boring machine (TBM)

Geng Qi,Wei Zhengying,He Fei,Meng Hao 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

To overcome the drawbacks of the large flat-face TBM cutter head (for example, enormous rock cutting forces and eccentric forcescause excessive deformation of the cutter head and damage to the main bearing), a two-stage cutter head is introduced. The two-stagecutter head was designed using grey relational analysis method according to the flat-face cutter head applied in the West Qinling Tunnel,China. The mechanical performance analysis models of the two cutter heads in the layered-banded rock (LBR) mixed ground were builtto calculate the cutter heads’ rock cutting thrust and torque, eccentric forces and overturning moments. The two cutter heads’ deformationand stress distribution were also compared. We concluded that with the same penetration, the thrust, torque, eccentric force, overturningmoment, deformation and maximum stress of the two-stage cutter head were smaller than those of the flat-face cutter head.

A Virtual RLC Active Damping Method for LCL-Type Grid-Connected Inverters

Geng, Yiwen,Qi, Yawen,Zheng, Pengfei,Guo, Fei,Gao, Xiang The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.5

Proportional capacitor-current-feedback active damping (AD) is a common damping method for the resonance of LCL-type grid-connected inverters. Proportional capacitor-current-feedback AD behaves as a virtual resistor in parallel with the capacitor. However, the existence of delay in the actual control system causes impedance in the virtual resistor. Impedance is manifested as negative resistance when the resonance frequency exceeds one-sixth of the sampling frequency ($f_s/6$). As a result, the damping effect disappears. To extend the system damping region, this study proposes a virtual resistor-inductor-capacitor (RLC) AD method. The method is implemented by feeding the filter capacitor current passing through a band-pass filter, which functions as a virtual RLC in parallel with the filter capacitor to achieve positive resistance in a wide resonance frequency range. A combination of Nyquist theory and system close-loop pole-zero diagrams is used for damping parameter design to obtain optimal damping parameters. An experiment is performed with a 10 kW grid-connected inverter. The effectiveness of the proposed AD method and the system's robustness against grid impedance variation are demonstrated.

Cloning and expression analysis of c-type and g-type lysozymes in yellow catfish (Pelteobagrus fulvidraco)

Fei Ke,Yun Wang,XiaoYao Cao,GaoWei Pan,Rui Geng 한국유전학회 2016 Genes & Genomics Vol.38 No.8

Lysozymes have important roles in innate immune system. Here, a c-type and a g-type lysozyme were identified from yellow catfish (Pelteobagrus fulvidraco). The deduced amino acid sequences of both lysozymes were conserved in catalytic sites and structural features as compared to their counterparts from other species. It was interesting that the g-type lysozyme possessed a signal peptide. The c-type and g-type lysozymes had the highest identity 89.4 and 76.2 % with that from channel catfish respectively. Phylogenetic analysis showed that the two lysozymes had a closely relationship with that from channel catfish and Astyanax mexicanus. Lysozymes from one order could form more than one clade in the phylogenetic tree, which indicated the gene duplications in evolution. Expression analysis with real time quantitative PCR revealed that the two lysozyme genes were constitutively expressed in all the tested tissues. The highest expression of c-type lysozyme was observed in liver, followed by spleen, head kidney, and trunk kidney, while the g-type lysozyme had highest expression in intestine, followed by spleen, head kidney, and trunk kidney. The mRNA levels of both genes were all up-regulated after challenging with Aeromonas hydrophila. However, there were differences in tissues and time points when the mRNA levels reached its peak between the two lysozymes. It indicated the diversity in regulation mechanisms and detailed functions among lysozymes. Taking together, these results will benefit the understanding of yellow catfish lysozymes.