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Investigation on Oil-paper Degradation Subjected to Partial Discharge Using Chaos Theory
Gao, Jun,Wang, Youyuan,Liao, Ruijin,Wang, Ke,Yuan, Lei,Zhang, Yiyi The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
In this paper, oil-paper samples composed of transformer windings were used to investigate the insulation degradation process subjected to partial discharge (PD), with artificial defects inside to simulate the PD induced insulation degradation. To determine appropriate test voltages, the breakdown time obtained through a group of accelerated electrical degradation tests under high voltages was firstly fitted by two-parameter Weibull model to acquire the average breakdown time, which was then applied to establish the inverse power law life model to choose advisable test voltages. During the electrical degradation process, PD signals were synchronously detected by an ultra-high frequency (UHF) sensor from inception to breakdown. For PD analysis, the whole degradation process was divided into ten stages, and chaos theory was introduced to analyze the variation of three chaotic parameters with the development of electrical degradation, namely the largest Lyapunov exponent, correlation dimension and Komogorov entropy of PD amplitude time series. It is shown that deterministic chaos of PD is confirmed during the oil-paper degradation process, and the obtained results provide a new effective tool for the diagnosis of degradation of oil-paper insulation subjected to PD.
Environmental fatigue correction factor model for domestic nuclear-grade low-alloy steel
Gao, Jun,Liu, Chang,Tan, Jibo,Zhang, Ziyu,Wu, Xinqiang,Han, En-Hou,Shen, Rui,Wang, Bingxi,Ke, Wei Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8
Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (F<sub>en</sub>) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.
Gaojun Meng,Ye Yuan,Yukun Sun,Haitao Liu,Zhiying Zhu 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.2
The primary linear fl ux-switching permanent magnet (LFSPM) motor has the merits of high speed, high response, and direct drive. However, the presence of the cogging force in LFSPM motors compromises position and speed control accuracy, which can be particularly troublesome at low speeds. A novel approach of suppressing the slot eff ect cogging force for LFSPM is proposed according to repetitive control of time-varying periodic signals. The time-varying periodic thrust disturbance in t-domain is transformed to the signals defi ned in the x-domain, and a repetitive controller is designed. Furthermore, a series of specifi c harmonic currents are added into q-axis reference current, resulting in additional force components to counteract the end eff ect cogging force. Finally, experimental evaluations of the control strategy are performed on an AD5435-controlled LFSPM drive platform. The simulations and experiments verify that the proposed method can suppress the thrust ripple eff ectively.
Gaojun Meng,Haitao Yu,MinQiang Hu,Lei Huang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
An estimation method of initial rotor position is a difficult research branch in permanent magnet synchronous motors(PMSM), it is also an important research branch in sensorless technique. In PMSM with a saliency pole structured rotor, influenced by saliency effects, the self-inductance and mutual-inductance present periodicity variation, Starting from this feature,Firstly, the method of injecting high frequency low voltage pulses is utilized for identifying the line inductance and then the influence of winding current to line inductance are thorough analyzed by Fourier series decomposition. Secondly, using the rotational coordinate transformation, the fundamental harmonic and third harmonic can be eliminated to some extent, and then the inductance can be presented by a sine function, then the position vs. inductance characteristics are modeled for estimating the rotor position. The experimental results show that the proposed method estimates the initial rotor position reliably and efficiently.
Effect of Low Temperature Microwave Drying on Properties of Dyed Cashmere Fibers
Liuxiang Zhan,Wan Li,Gaojun Wang,Xianli Zhao,Yuling Li,Ni Wang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.3
A novel method of drying dyed cashmere fiber by low temperature microwave was proposed and investigated inthis paper, the effect of low temperature microwave drying on the properties of dyed cashmere fiber was characterized anddiscussed in details. The results showed that the mechanical properties of cashmere after vacuum microwave drying wereimproved, and the highest rise of elongation at break was more than 6 %. The directional friction effect was weakened, andthe maximum DFE loss was more than 40 % compared with that of steam-dried cashmere. The scales were damaged, whilemolecular structure and chemical bonds of cashmere fibers have not changed. Vacuum and microwave combined dryingmethod can dry dyed cashmere at low temperature quickly, which has considerable advantages compared with traditionaldrying, and shows great potential for eco-friendly production of cashmere.
Zou Bowen,Wang Wenlin,Liu Jian,Yan Zhenyu,Liu Gaojun,Wang Jun,Wei Guanxiang 한국원자력학회 2020 Nuclear Engineering and Technology Vol.52 No.8
A physical protection system (PPS) is used for the protection of critical facilities. This paper proposes a structure analytic hierarchy approach (SAHA) for the hierarchical evaluation of the PPS effectiveness in critical infrastructure. SAHA is based on the traditional analysis methods “estimate of adversary sequence interruption, EASI”. A community algorithm is used in the building of the SAHA model. SAHA is applied to cluster the associated protection elements for the topological design of complicated PPS with graphical vertexes equivalent to protection elements.
Xia Yu,Conggui Chen,Kezhou Cai,Cunliu Zhou,Daorong Mao,Gaojun Sun 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.4
The effects of blood plasma (BP, 0-2.5%), agar (0-1.0%), and microbial transglutaminase (MTG, 0-0.5%)on water-binding capacity, color (L*, a*, and b* values)and textural properties of pork muscle gels (PMG) were investigated with response surface methodology. The potential interaction among these ingredients was evaluated by DSC, SEM, and FT-IR. The results shown that the addition of BP into PMG could result in decreased cooking loss (CL) and L* (p<0.01), as well as increased a*, springiness,and chewiness of the gels (p<0.05), while the treatment with MTG led to increased CL (p<0.01). Agar could obviously improve CL of PMG, but lead to inferior springiness and cohesiveness (p<0.05). Moreover, the synergism among muscle proteins, BP, MTG, and agar implied that there were some kinds of interactions among these ingredients, thus influencing the properties of PMG.