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Jeong, Yu Ra,Kim, Jeonghyun,Xie, Zhaoqian,Xue, Yeguang,Won, Sang Min,Lee, Geumbee,Jin, Sang Woo,Hong, Soo Yeong,Feng, Xue,Huang, Yonggang,Rogers, John A,Ha, Jeong Sook Nature Publishing Group 2017 NPG Asia Materials Vol.9 No.10
<P>This paper introduces a liquid-metal integrated system that combines soft electronics materials and engineering designs with advanced near-field-communication (NFC) functionality for human motion sensing. All of the active components, that is, strain sensor, antenna and interconnections, in this device are made of liquid metal, and the device has unique gel-like characteristics and stretchability. Patterning procedures based on selective wetting properties of the reduced GaInSn enable a skin-attachable, miniaturized layout, in which the diameter of the device is less than 2 cm. Electromechanical characterization of the strain sensor and antenna reveals their behaviors under large uniaxial tensile and compressive strains, as well as more complex modes of deformation. Demonstrations of these devices involve their use in monitoring various human motions in a purely wireless fashion; examples include wrist flexion, movements of the vocal cord and finger motion. This simple platform has potential for use in human-machine interfaces for prosthetic control and other applications.</P>
Dynamic Modeling and Parameter Identification of Magnetorheological Shock Absorber
Yang Yonggang,Yu Peng,Zhu Shixing,Kong Xiangfen 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.9
By dynamic analysis, the dynamic modeling of designed magnetorheological(MR) shock absorber with metering pin is established, and using the experimental data. The relation of kinematic viscosity and current, and shear stress and current are respectively identified, and the parameters of dynamic model are identified by the least square identification method. The experiment results show that the identified model has high accuracy, and can be used for the performance analysis and control system design of the shock absorber.
Xiuli Wang,Yonggang Lu,Rongsheng Zhu,Qiang Fu,Haoqian Yu,Yiming Chen 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.7
The AP1000 reactor coolant pump is a vertical shielded-mixed flow pump, is the most important coolant power supply and energy exchange equipment in nuclear reactor primary circuit system, whose steady-state and transient performance affect the safety of the whole nuclear island. Moreover, safety demonstration of reactor coolant pump is the most important step to judge whether it can be practiced, among which software simulation is the first step of theoretical verification. This paper mainly introduces the fluid-solid coupling simulation method applied to reactor coolant pump, studying the feasibility of simulation results based on workbench fluid-solid coupling technology. The study found that: for the unsteady calculations of the pure liquid media, the average head of the reactor coolant pump with bidirectional fluid-solid coupling decreases to a certain extent. And the coupling result is closer to the real experimental value. The large stress and deformation of rotor under different flow conditions are mainly distributed on impeller and idler, and the stress concentration mainly occurs at the junction of front cover plate and blade outlet. Among the factors that affect the dynamic stress change of rotor, the pressure load takes a dominant position.
Flow structure of conical distributed multiple gas jets injected into a water chamber
Jiajun Zhao,Yonggang Yu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
Based on an underwater gun firing project, a mock bullet with several holes on the head was designed and experimented to observe the combustion gas injected into a cylindrical water chamber through this mock bullet. The combustion gas jets contain one vertical central jet and 4 to 8 slant lateral jets. A high speed camera system was used to record the expansion of gas jets in the experimental study. In numerical simulations, the Euler two-fluid model and volume of fluid method were adopted to describe the gas-liquid flow. The results show the backflow zone in lateral jet is the main factor influencing the gas-liquid turbulent mixing in downstream. On cross sections, the gas volume fraction increased with time but the growth rate decreased. With a change of nozzle structure, the gas fraction was more affected than the shock structure.
CFD-DEM simulation on the complex gas-solid flow in a closed chamber with particle groups
An Chen,Yonggang Yu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11
There is a complex gas-solid flow in the cylindrical closed chamber during the interior ballistic process in a modular-charge gun launch. The motion and the distribution of particles in the flow have significant effects on the combustion stability in the interior ballistic process. Therefore, the solid particle-scale details of the gas-solid flow in the closed chamber with hollow-cylindrical particle groups were numerically simulated by using the computational fluid dynamics combined with the discrete element method (CFD-DEM). The results show that the particle final distribution is composed of a gentle-slope accumulation, a horizontal accumulation, and a steep-slope accumulation. Thereinto, the voidage of the steep-slope accumulation is decreased with the axial position far away from modules. With the increase of the initial spacing between two particle groups, the axial length of the steep-slope accumulation is increased exponentially, whereas the tangent value of the inclined angle is decreased exponentially.
Enhancing the penetration stability of plasma jet in liquid by improving the chamber structure
Yi Liu,Yonggang Yu,Shanshan Mang 한국물리학회 2019 Current Applied Physics Vol.19 No.9
Two kinds of chamber structures were designed to improve the penetration stability of plasma jet in the working fluid. They are the cone-truncated chamber with an inclined wall structure and the stepped-wall chamber with an abrupt expanding structure. Based on the experiment, the penetration characteristics of plasma jet in liquid were investigated by the numerical calculation, especially the multiphase flow field structure and the jet penetration stability. In the cone-truncated chamber, the arc-like pressure wave does not evolve into the plane wave like the wave evolution rule in the traditional cylindrical chamber, and an alternating structure of arc-like wave and the plane wave is formed in the stepped-wall chamber. The stability control of stepped wall is more significant than that of inclined wall because the low-pressure vortex formed at the corner of step enhances the radial induction effect. Besides, the stepped-wall structure can restrain the moving randomness of the big vortex's core. The axial expansion speed of plasma jet in the ambient fluid is decreased exponentially and the speed estimation formula was obtained in this work.
Numerical investigation on the multiphase flow field at various muzzle velocities
Jinghui Zhang,Yonggang Yu,Xinwei Zhang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8
To predict the multiphase flow field during the underwater launch, a twodimensional (2D) transient model and a visual experiment platform were employed. The simulated graphs were compared to the experimental photos, and the results indicate the reasonableness of the model. Furthermore, the effects of muzzle velocity on the flow field were investigated. The results demonstrate that a partially formed bottle-shaped shock wave is generated when t = 0.4 ms for various velocities, and a greater muzzle velocity can accelerate its expansion process. Additionally, the maximum displacement of the Mach disk fulfills the binomial law with the muzzle velocity. The maximum peak pressure of oscillations increases with the greater muzzle velocity, but the duration of pressure oscillations decreases.
Microflame diffusion properties of AP/HTPB propellant under binder width effects
Kaixuan Chen,Xiaochun Xue,Yonggang Yu,Zhenwei Ye 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.2
The present study proposes a method to estimate the microflame properties of ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant at different binder widths. A 3D random particle packing is generated by the Monte Carlo method. A transformation from Miller packing to sandwich model is used by the dual slicing technique. The gassolid coupling model and the two-step BDP flame model in the combustion field are established to study the influence of kinetic chemical and fluid diffusion process on the micrflame properties. Finally, the mathematical relationships of the burning rate br and the final flame height H 3on the HTPB thickness D are obtained by analyzing and fitting combustion processes of multiple AP/HTPB propellants, namely, b+1.22D 2 -13.07D+67.73.