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RISS 인기검색어
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- 저자 : Guoping Lei (검색결과 4 건)
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Lei Ling,Jinhui Li,Guoping Zhang,Rong Sun,Ching-Ping Wong 한국고분자학회 2018 Macromolecular Research Vol.26 No.4
Self-healing polymeric materials have attracted extensively interests due to the ability to heal the damage autonomously. The self-healing systems based on dynamic disulfide bonds have been the most promising due to the efficient healing capacity at a mild condition. However, it is still of great challenge for designing the polymer with excellent mechanical and self-healing property by a simple synthetic route. Herein, a novel series of self-healing linear polyurethanes with the disulfide linkage as the grafting point were developed. The synthetic polymers all exhibited excellent mechanical properties (breaking strength and elongation at break were as much as 31.91 MPa and 1156% for PU-A). Meanwhile, the effects of different ratios of soft/hard segments on the mechanical properties and healing efficiencies have been investigated by stress-strain tests. The results showed that with the increase of soft segments contents, the breaking strength and elongation at break of the polymer improved significantly, while the healing efficiency and Young’s modulus showed a declining trend. The self-healing polyurethane can quickly restore its over 90% of mechanical property after healing at moderate temperature for 10 min. The cyclic tensile tests also showed the dissipated efficiencies and self-recovery abilities of the polymers. Finally, the recovery capability tests verified the shape memory effect in the polymers, which can replace an external force to accelerate the healing process.
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Dynamic performance of a cable with an inspection robot – analysis, simulation, and experiments
Fengyu Xu,Lei Wang,Xingsong Wang,Guoping Jiang 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5
A special cable inspection robot is designed to inspect automatically the cables of a cable-stayed bridge. The free vibration equation of the cable-robot system is derived firstly to study the dynamic characteristics and safety performance of the system. Then, the effect of the robot on the cable natural frequency is discussed, and the dynamic response equation when a robot is climbing at a constant speed is deduced. Furthermore, the effect of the cable vibration on the robot’s climbing ability is studied. The natural frequency characteristics of the robot are analyzed and optimized to avoid the resonance between the cable and the robot, using a finite element model. Additionally,dynamic cable responses are simulated under different conditions wherein the robot mass are 10 and 200 kg, and the speeds are 0.2 and 0.3 m/s, respectively. At last, to demonstrate further the dynamic characteristics of the cable-robot system experimentally, cables are set up on the Junshan highway bridge over the Yangtze river. Similar experimental models of these cables are constructed, and vibration experiments are conducted to validate the theoretical calculation. The results show that a light robot has little effects on the cable vibration amplitude and vibration acceleration; this confirms the safety of the cable.
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New Results on Stability Analysis of Markovian Switching Singular Systems
Xiao, Xiaoqing,Park, Ju H.,Zhou, Lei,Lu, Guoping IEEE 2019 IEEE transactions on automatic control Vol.64 No.5
<P>This paper addresses the stability problem for linear continuous-time Markovian switching singular systems. Considering the inherent state jump behavior at the switching instants, a necessary and sufficient condition of exponential stability in the mean square sense for the Markovian switching singular system is established in terms of linear matrix inequalities by means of a stochastic Lyapunov approach. Based on the obtained stability result, sufficient conditions of exponential stability in the mean square sense for the Markovian switching singular system with uncertain and partly unknown transition probability are presented. Numerical examples are presented to illustrate the effectiveness of the proposed approach.</P>
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Haiting Ji,Hui Li,Yang Li,Li Yang,Guoping Lei,Hongwei Xiao,Jie Zhao,Lefeng Shi 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2
This paper presents a reliability assessment model for the power semiconductors used in wind turbine power converters. In this study, the thermal loadings at different timescales of wind speed are considered. First, in order to address the influence of long-term thermal cycling caused by variations in wind speed, the power converter operation state is partitioned into different phases in terms of average wind speed and wind turbulence. Therefore, the contributions can be considered separately. Then, in regards to the reliability assessment caused by short-term thermal cycling, the wind profile is converted to a wind speed distribution, and the contribution of different wind speeds to the final failure rate is accumulated. Finally, the reliability of an actual power converter semiconductor for a 2.5 MW wind turbine is assessed, and the failure rates induced by different timescale thermal behavior patterns are compared. The effects of various parameters such as cut-in, rated, cut-out wind speed on the failure rate of power devices are also analyzed based on the proposed model.
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