conditions, which hinders the development of flexible electronics as an emerging technology. [6][7][8][9][10] Ideally, a flexible electrode should be provided reliable conductivity and mechanical flexibility at the same time. [11,12] Therefore, a key problem that should be solved at present to obtain a flexible electrode with these two properties simultaneously.Currently, flexible electrode with metal film based on a flexible substrate is widely utilized due to the inherent excellent flexibility, high conductivity, simple processing and low cost. [13][14][15][16][17] Hence, some investigators have fabricated metal films on flexible substrates (e.g., polydimethylsiloxane (PDMS), polyimide (PI) and polyethylene terephthalate (PET), etc.) to realize the use of flexible electrodes in flexible electrons. For example, Wu et al. reported a flexible PDMS-based three-electrode sensor, which was flexible without inducing irreversible deformation or fatigue after electrochemical testing with forced deformations. [18] Xie et al. manufactured a patterned microelectrode array on PI substrate by photolithography, stripping and sputtering deposition processes, forming a wireless cortical electroencephalogram (EEG) recording system with excellent biocompatibility and flexibility. [19] Liu et al. fabricated a three-layer dry electrode based on PI substrate for detecting electrophysiological signals utilizing sacrificial-layer assisted one-step transfer printing method, which exhibits excellent conformability and stretchability and low electrode-skin contact impedance. [20] Liu et al. designed and fabricated a flexible microthree-dimensional temperature sensor with excellent stability and reliability on PI film by a microfabrication process to achieve in situ real-time temperature measurements. [21] Nonetheless, metal film of most flexible electrodes with flexible substrates often produces microcracks due to complex deformation of substrate, which eventually leads to the surface fracture of the metal film and then affects the conductivity of the electrode. Emergence of the issue will seriously shorten the service life of flexible electrode in flexible electronic equipment. [22][23][24][25][26] Consequently, a key challenge for designing independent high-performance electronic equipment is developing stretchable electrodes that can maintain metal film structural integrity during repeated severe deformations.The negative Poisson's ratio (NPR) structure has been successfully employed in flexible electronic, biomedicine, sensor Recent advances in the development of flexible electronic devices have increased the demand for flexibility and conductivity. However, there is still a significant challenge to manufacture flexible electrodes featuring satisfactory mechanical and conductivity performance simultaneously. In this paper, based on synergistically combining theoretical structural design and screen printing, a new flexible electrode with butterfly-shaped honeycomb (BSH) negative Poisson's ratio (NPR) structure through combining honeyc...
A simulation model of overtaking maneuvers is established to research into the flow and vortex structures around two identical Ahmed vehicles. The simulation demonstrates how the flow and vortex structures generate and change, which influences the aerodynamical coefficients of the vehicles most. In this study, a transient solver is used on the platform of ANSYS/Fluent, and the sliding mesh method is adopted to simulate the motion of the overtaking vehicle, which realizes a more actual recovery of the road conditions. Based on the fact that the primary factor that influences the aerodynamical coefficients of a vehicle is the change in the outer flow around it, a research into the variation in the outer flow field is conducive to in-depth analysis of the aerodynamical characteristics of the vehicle. Most previous studies focused only on the lateral aerodynamical coefficients during overtaking maneuvers. This article establishes a comprehensive model that takes the lift force into consideration to more accurately simulate the aerodynamical characteristics. Moreover, it is aimed at figuring out the key factors that cause the change in the aerodynamical coefficients at vortex level in this study, not just at pressure level as most previous studies did.
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