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223 results on '"Wang, Junnian"'

2. Cold quark matter in a quasiparticle model: thermodynamic consistency and stellar properties

Author

Ma, Zhi-Jun, Lu, Zhen-Yan, Xu, Jian-Feng, Peng, Guang-Xiong, Fu, Xiangyun, and Wang, Junnian

Subjects
High Energy Physics - Phenomenology, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Theory
Abstract

The strong coupling in the effective quark mass was usually taken as a constant in a quasiparticle model while it is, in fact, running with an energy scale. With a running coupling, however, the thermodynamic inconsistency problem appears in the conventional treatment. We show that the renormalization subtraction point should be taken as a function of the summation of the biquadratic chemical potentials if the quark's current masses vanish, in order to ensure full thermodynamic consistency. Taking the simplest form, we study the properties of up-down ($ud$) quark matter, and confirm that the revised quasiparticle model fulfills the quantitative criteria for thermodynamic consistency. Moreover, we find that the maximum mass of an $ud$ quark star can be larger than two times the solar mass, reaching up to $2.31M_{\odot}$, for reasonable model parameters. However, to further satisfy the upper limit of tidal deformability $\tilde{\Lambda}_{1.4}\leq 580$ observed in the event GW170817, the maximum mass of an $ud$ quark star can only be as large as $2.08M_{\odot}$, namely $M_{\text{max}}\lesssim2.08M_{\odot}$. In other words, our results indicate that the measured tidal deformability for event GW170817 places an upper bound on the maximum mass of $ud$ quark stars, but which does not rule out the possibility of the existence of quark stars composed of $ud$ quark matter, with a mass of about two times the solar mass., Comment: 10 pages, 8 figures

Published
2023
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7. Research on the Roller Contact Load Algorithm of Rolling Bearings Based on the Equivalent Substitution

Author

Li Pengfei, Wang Jingyue, Zheng Junwen, Han Yuntong, Lei Hu, and Wang Junnian

Subjects
Cylindrical roller bearing, Contact load, Contact deformation, Mechanical engineering and machinery, TJ1-1570
Abstract

The traditional calculation of roller contact load and contact deformation includes a number of calculation, which is prone to system collapse. In this research, three equivalent mathematical models are established by using the equivalent substitution method, the deformation of rollers is solved by using the Newton iterative principle, and then the contact deformation and contact load of different rollers under the three mathematical models are obtained. According to the number arrangement from small to large, the change range of contact deformation and contact load of any roller at different times is obtained. Compared with the traditional calculation method, the program generated in this study is fast, not prone to system collapse, and the calculation results meet the numerical value of the traditional method.

Published
2023
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31. Dynamic Analysis of DFIG Fault Detection and Its Suppression Using Sliding Mode Control

Author

Zhou Zuanbo, Jiang Dan, Wang Junnian, Zhong Guoliang, and Yu Wenxin

Subjects
Lyapunov function, Vector control, Rotor (electric), Computer science, Induction generator, Chaotic, Energy Engineering and Power Technology, Fault (power engineering), Sliding mode control, Fault detection and isolation, law.invention, symbols.namesake, Control theory, law, symbols, Electrical and Electronic Engineering
Abstract

In this paper, a fault detection method based on chaos is proposed for doubly-fed induction generator (DFIG). Firstly, the nonlinear differential equation of the DFIG is established by the stator flux-oriented vector control method, and then the motion state of the DFIG is proved by the 0-1 test algorithm. Secondly, the motion state of the DFIG is analyzed under normal and fault conditions. Due to some failures that may occur in the normal operation of the DFIG, the motion state of the DFIG system may enter chaos from the cycle, which is mainly manifested by the violent oscillation of the rotor current and speed. At this time, the system is in an extremely unstable operating condition. Thereby, a new sliding mode control rate is mentioned to suppress chaotic behavior. Its stability is analyzed by constructing the Lyapunov function to ensure that the system state can quickly and stably converge to the given value. After that, the simulation model of the system is built. The simulation results show that sliding mode control can make the DFIG get out of the chaotic state quickly. And, the sliding mode control has the characteristics of fast fault elimination and high control accuracy. In addition, the traditional sliding mode approach rate is compared with the proposed new sliding mode approach rate. It proves that the proposed new approach rate can achieve better control effect.

Published
2023

38. Dynamic analysis of seven-dimensional fractional-order chaotic system and its application in encrypted communication

Author

Peng, ZhiWei, Yu, WenXin, Wang, JunNian, Wang, Jing, Chen, Yu, He, XianKe, and Jiang, Dan

Abstract

This paper proposes a novel seven-dimensional fractional-order chaotic system applied to secure communication. First, a seven-dimensional fractional order system is constructed by selecting an arbitrary fractional order q. Then, the chaotic and non-chaotic dynamic behaviors of the system are analyzed by 0–1 Test, and the correctness is verified by phase diagram comparison and complexity analysis. Then, the corresponding fractional-order chaotic circuit is designed, and the phase image which is basically consistent with the experimental simulation results is obtained. Finally, the seven-dimensional fractional-order chaotic system is used to complete the signal encryption and decryption test to achieve secure communication. This indicates that the seven-dimensional fractional-order chaotic system proposed to this paper has more complex dynamic characteristics and can be used for secure communication.

Published
2024
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41. Practical active traction control for independent‐wheel‐drive electric vehicle based on slip‐ratio threshold determination.

Author

Wang, Junnian, Gao, Shoulin, Lv, Siwen, Sun, Jie, Sun, Wen, and Yang, Zhihua

Subjects
ELECTRIC vehicles, THRESHOLD logic, ANTILOCK brake systems in automobiles, HYDRAULIC brakes, ELECTRIC torque motors, AXLES
Abstract

The traditional traction control system (TCS) based on hydraulic braking only works when the wheels are slipping, which will cause the problem of slow response to extreme slip. In addition, the TCS of four‐wheel‐independent‐drive electric vehicle (4WIDEV) is often based on road adhesion characteristics identification or optimal slip ratio identification to implement active control, which is difficult to achieve in engineering. Aiming at this problem, a practical active TCS is proposed in this paper. Firstly, according to the wheel slip state of the front and rear axles, the dynamic transfer of torque between axles is realized to maintain the vehicle propulsion power. Second, the adhesion conditions between road and tire are classified, and two sets of target slip ratio thresholds are formulated for high and low adhesion pavement, respectively. Then the current road adhesion coefficient is estimated by using the advantage that the in‐wheel motor torque can be obtained in real‐time. Thirdly, the overall framework of the control strategy is established, the logic threshold control algorithm is adopted for tracking the wheel target slip ratio. Finally, the simulation results show that the proposed active TCS can improve the vehicle power and avoid excessive wheel slipping. [ABSTRACT FROM AUTHOR]

Published
2023
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