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Analysis of the thresholds of granular mixtures using the discrete element method
Jian, Gong,Jun, Liu Techno-Press 2017 Geomechanics & engineering Vol.12 No.4
The binary mixture consists of two types of granular media with different physical attributes and sizes, which can be characterized by the percentage of large granules by weight (P) and the particle size ratio (${\alpha}$). Researchers determine that two thresholds ($P_S$ and $P_L$) exist for the peak shear strength of binary mixtures, i.e., at $P{\leq}P_S$, the peak shear strength is controlled by the small granules; at $P{\leq}P_L$, the peak shear strength is controlled by the large granules; at $P_S{\leq}P{\leq}P_L$, the peak shear strength is governed by both the large and small granules. However, the thresholds of binary mixtures with different ${\alpha}$ values, and the explanation related to the inner details of binary mixtures to account for why these thresholds exist, require further confirmation. This paper considers the mechanical behavior of binary mixtures with DEM analysis. The thresholds of binary mixtures are found to be strongly related to their coordination numbers $Z_L$ for all values of ${\alpha}$, where $Z_L$ denotes the partial coordination number only between the large particles. The arrangement structure of the large particles is examined when P approaches the thresholds, and a similar arrangement structure of large particles is formed in both 2D and 3D particle systems.
Guided viscoelastic wave in circumferential direction of orthotropic cylindrical curved plates
Jiangong Yu,Zhijuan Ma 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.5
In this paper, guided circumferential wave propagating in an orthotropic viscoelastic cylindrical curved plate subjected to traction-free conditions is investigated in the frame of the Kelvin-Voight viscoelastic theory. The obtained three wave equations are decoupled into two groups, Lamb-like wave and SH wave. They are separately solved by the Legendre polynomial series approach. The availability of the method is confirmed through the comparison with the published data of the SH wave for a viscoelastic flat plate. The dispersion curves and attenuation curves for the carbon fiber and prepreg cylindrical plates are illustrated and the viscous effect on dispersion curves is shown. The influences of the ratio of radius to thickness are analyzed.
Research on High-Frequency Isolation Type of Dual-PWM Variable Frequency Speed Regulation
Liu Jiangong,Liu Wenzhuang,Wang Yiying,Zhang Guilin,Chen Longfei 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4
Frequency converters are widely used in power grids, motor speed regulation, and other fields. When the voltage level is above low voltage and the workspace is limited, traditional frequency converters mostly adopt the power frequency transformer to connect to the power grid. But the structure has the problems of bigger volume and complexity. To solve these problems, this paper proposes a three-stage topology structure of high-frequency isolation type of dual-PWM variable frequency speed regulation based on three-phase rectification, single active isolated DC/DC converter, and three-phase inverter, and analyzes its power transmission characteristics in detail. And a new method that combines high-frequency electrical isolation and frequency conversion is discussed. Then, the control strategies of the new method are also described. Lastly, simulation and experiment are constructed to verify the new design method is correct and feasible, and that the steady and dynamic characteristics of the three-stage high-frequency isolated frequency converter are better.
Guided viscoelastic wave in circumferential direction of orthotropic cylindrical curved plates
Yu, Jiangong,Ma, Zhijuan Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.5
In this paper, guided circumferential wave propagating in an orthotropic viscoelastic cylindrical curved plate subjected to traction-free conditions is investigated in the frame of the Kelvin-Voight viscoelastic theory. The obtained three wave equations are decoupled into two groups, Lamb-like wave and SH wave. They are separately solved by the Legendre polynomial series approach. The availability of the method is confirmed through the comparison with the published data of the SH wave for a viscoelastic flat plate. The dispersion curves and attenuation curves for the carbon fiber and prepreg cylindrical plates are illustrated and the viscous effect on dispersion curves is shown. The influences of the ratio of radius to thickness are analyzed.
Propagating and evanescent waves in a functionally graded nanoplate based on nonlocal theory
Cancan Liu,Jiangong Yu,Bo Zhang,Xiaoming Zhang,Xianhui Wang Techno-Press 2023 Advances in nano research Vol.14 No.5
The purpose of this paper is to present the analysis of propagating and evanescent waves in functionally graded (FG) nanoplates with the consideration of nonlocal effect. The analytical integration nonlocal stress expansion Legendre polynomial method is proposed to obtain complete dispersion curves in the complex domain. Unlike the traditional Legendre polynomial method that expanded the displacement, the presented polynomial method avoids employing the relationship between local stress and nonlocal stress to construct boundary conditions. In addition, the analytical expressions of numerical integrations are presented to improve the computational efficiency. The nonlocal effect, inhomogeneity of medium and their interactions on wave propagation are studied. It is found that the nonlocal effect and inhomogeneity of medium reduce the frequency bandwidth of complex evanescent Lamb waves, and make complex evanescent Lamb waves have a higher phase velocity at low attenuation. The occurrence of intersections of propagating Lamb wave in the nonlocal homogeneous plate needs to satisfy a smaller Poisson's ratio condition than that in the classical elastic theory. In addition, the inhomogeneity of medium enhances the nonlocal effect. The conclusions obtained can be applied to the design and dynamic response evaluation of composite nanostructures.
Space-Time Pattern of Ion Flow Under AC/DC Hybrid Overhead Lines and Its Application
Qiao, Ji,Zou, Jun,Zhang, Jiangong,Lu, Yao,Lee, Jaebok,Ju, Mun-No IEEE 2018 IEEE transactions on power delivery Vol.33 No.5
<P>Building HVdc and HVac transmission lines in the same corridor or even on the same tower is an attractive way to extend electricity transport capacity where getting the new right of way is difficult. The resulting hybrid lines produce a new corona performance, such as ground-level hybrid electric field and ion current density, which are quite different from those of pure ac or dc lines. In this paper, inherent space-time pattern and characteristics of the information propagation in Lagrangian description are presented for the ion transport problem, that is, the ion density at a certain point has a direct relationship with its drift time. Based on this, the theoretical explanation is provided for the decoupling algorithm, by which the ground-level dc component can be solved with the ac conductors assumed to be at zero potential and vice versa. The simulation results show that the sinusoidal ac field has negligible influence on the dc ion drift time from conductor surface to ground, whereas stationary electric field generated by the grounded ac lines has a dominant effect. Therefore, ac energization has a rather low impact on ground-level quantities and the simplification of grounded ac conductors is quite reasonable.</P>
Safe Arm Using Compliant Hybrid Joints for Mobile Manipulators in Human-Symbiotic Environments
Zhijun Li,Aiguo Ming,Ning Xi,Jiangong Gu,Makoto Shimojo 한국과학기술원 인간친화 복지 로봇 시스템 연구센터 2005 International Journal of Assistive Robotics and Me Vol.6 No.1
In this paper, a safe arm with compliant hybrid joints for human-friendly service robots is presented, which realizes human safety, absorbing impact force, and task fulfillment. The robot is composed of links covered with soft materials and hybrid joints, which can be put into active or passive mode as needed. In an unexpected or expected collision with human, the arising impulse force is attenuated effectively by the physical model, which is developed with hybrid joints and soft covering. Owing to the displacement of the links when the joint is passive, a recovery control algorithm has been developed for the end-effector to maintain its desired task position after the collision. The force attenuation property has been verified through collision experiments in that the capability of the proposed passive arm in overcoming the limitations of active compliance control has been demonstrated. Simulation results also showed that the proposed control method is useful for robot"s task fulfillment as well.