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RISS 인기검색어
- 검색키워드
- 저자 : Guifeng Zhao (검색결과 5 건)
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Full Scale Experiment for Vibration Analysis of Ice-Coated Bundled-Conductor Transmission Lines
Guifeng Zhao,Zhongbin Lu,Xu Wang,Yongbo Peng,Shaojun Chang 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.1
Full scale experiment has received increasing attention in recent years for the reliability analysis of power supplies and power systems. In this paper, the vibration behaviours of conductors with and without D-section ice coatings are addressed by virtue of a field test platform consisting of the prototype of a transmission tower-line system. Utilizing fibre Bragg grating sensors, the vibration of conductors under artificial displacement and natural wind excitations are monitored, and their dynamic characteristics are assessed by the spectral analysis and the identification technique of Hilbert-Huang transform. It is revealed that the vibrations of ice-free and ice-coated multi-bundled conductors vary wildly despite under similar artificial displacements and natural wind excitations. The vibration of ice-coated conductors is mainly dominated by their low-order modes, especially in the frequency range of 0.24 − 2.0 Hz; while the vibration of ice-free conductors gains more benefits from their high-order modes. Compared to the ice-free conductors, the conductors with eccentric ice coating are prone to suffer from galloping under specified wind attack angle; although their vibrations are still controlled by the low-order modes, yet the frequency values of the dominant modes have changed from one wind attack angle case to another. This kind of frequency modulation phenomenon indicates that nonlinear vibration characteristics of ice-coated conductors might change under different wind conditions, which brings great challenges to the research of wind-induced vibration characteristics of ice-coated conductors.
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Photochemical synthesis of 2,3,9,10-tetrabromopentacene: its unusual photodimerization
Zhao, Yuewei,Cai, Xichen,Danilov, Eugene,Li, Guifeng,Neckers, Douglas C. Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.1
The photogeneration of 2,3,9,10-tetrabromopentacene from its precursor dione by photodecarbonylation was investigated. An unusual photodimer, 3,3',9,9',10,10'-hexabromo-2,2'-bipentacene, is produced.
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Study of structural-thermal characteristics of electrified conductors under aeolian vibration
Meng Zhang,Jian Zhou,Guifeng Zhao,Jiankun Xu,Chao Sun 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.2
High-voltage transmission lines are featured by electrical and structural properties. Current studies on aeolian vibration of transmission lines focus primarily on structural responses of unenergized conductors. However, moderate aeolian vibration can also enhance the convection heat transfer capability of a transmission line, which improves the steady current-carrying capacity. In this paper, a fluid-structure interaction (FSI) model is established to study the structural thermal characteristics of overhead electrified aluminum conductor steel-reinforced cable (ACSR) conductors. Moreover, the fatigue damage of the energized conductor is analyzed under operational conditions. Results show that there is considerable influence from aeolian vibration on the current-carrying capacity of energized conductors. Compared with the nonelectrical conductors, aeolian vibration can enhance the convective heat transfer effect of energized conductors. Additionally, fatigue life of electrified transmission lines is larger than that of nonelectrical conductors under aeolian vibration. The developed structure-fluid-thermal model can be used to aid design and operation optimization of transmission lines.
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Dynamic response of an overhead transmission tower–line system to high-speed train-induced wind
Meng Zhang,Ying Liu,Hao Liu,Guifeng Zhao 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.4
The current work numerically investigates the transient force and dynamic response of an overhead transmission tower–line structure caused by the passage of a high-speed train (HST). Taking the CRH2C HST and an overhead transmission tower–line structure as the research objects, both an HST–transmission line fluid numerical model and a transmission tower–line structure finite element model are established and validated through comparison with experimental and theoretical data. The transient force and typical dynamic response of the overhead transmission tower–line structure due to HST-induced wind are analyzed. The results show that when the train passes through the overhead transmission tower–line structure, the extreme force on the transmission line is related to the train speed with a significant quadratic function relationship. Once the relative distance from the track is more than 15 m, the train-induced force is small enough to be ignored. The extreme value of the mid-span dynamic response of the transmission line is related to the train speed and span length with a significant linear functional relationship.
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Jin Yuqin,Li Jialing,Ding Liang,Zhao Qing,Song Yuxian,Li Guifeng,Ji Jun,Ni Yanhong,Hu Qingang 대한독성 유전단백체 학회 2022 Molecular & cellular toxicology Vol.18 No.1
Background Oxidative stress is involved in the pathogenesis of various inflammatory diseases, such as periodontitis. When periodontitis occurs, reactive oxygen species (ROS) are overproduced and cannot be balanced by the antioxidant defense system, resulting in tissue damage. Madecassic acid (MA), an abundant triterpenoid in Centella asiatica (L.) Urban, has been used as a wound healing, antiinflammatory, and anticancer agent. Moreover, recent studies have shown that MA has an antioxidative effect, but the underlying mechanism remains unclear. Objective Here, we established an effective oxidative stress model induced by hydrogen peroxide (H 2 O 2 ) in human periodontal ligament fi broblasts (hPDLFs) to investigate the antioxidant and protective effects of MA against cell damage and its underlying mechanism of action. Results Pretreatment with MA inhibited cell apoptosis and promoted cell invasion and migration against oxidative injury induced by H 2 O 2 . In addition, MA was able to maintain mitochondrial membrane potential (ΔΨm) under oxidative stress. Notably, we found that MA restored redox balance by reducing intracellular ROS production. Furthermore, we investigated apoptosis-related proteins and found that the levels of anti-apoptosis markers Bcl-xL and Bcl-2 were remarkably upregulated, whereas that of the pro-apoptotic marker Bax was strikingly downregulated. Conclusions Collectively, these findings suggest that MA inhibits H 2 O 2 -induced oxidative stress and apoptosis of hPDLFs by reducing intracellular ROS production to maintain ΔΨm stability.
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