No abstract

This study presents an analytical model for describing propagation of Rayleigh waves along the impermeable surface of an unsaturated poroelastic half-space. This model is based on the existence of the three modes of dilatational waves which employ the poroelastic equations developed for a porous medium containing two immiscible viscous compressible fluids (Lo, Sposito and Majer,[13]). In a twofluid saturated medium, the three Rayleigh waves induced by the three dilatational waves can be expressed as R1, R2, and R3 waves in descending order of phase speed magnitude. As the excitation frequency and water saturation are given, the dispersion equation of a cubic polynomial can be solved numerically to obtain the phase speeds and attenuation coefficients of the R1, R2, and R3 waves. The numerical results show the phase speed of the R1 wave is frequency independent (non-dispersive). Comparatively, the R1 wave speed is 93 ~ 95 of the shear wave speed, and 28 to 49 of the first dilatational wave speed for selected frequencies between 50Hz & 200Hz and relative water saturation ranging from 0.01 to 0.99. However, the R2 and R3 waves are dispersive at the frequencies examined. The ratios of R2 and R3 wave phase speeds to the second and third dilatational wave speeds fall between 56 and 90. The R1 wave attenuates the least while the R3 wave has the highest attenuation coefficient. Furthermore, the phase speed of the R1 wave under an impermeable surface approaches 1.01 ~ 1.37 times of the R1 wave under a permeable boundary. Impermeability has significant influence on the phase speeds and attenuation coefficients of the R1 and R2 waves at high water saturation due to the existence of confined fluids.

In order to effectively pump liquid in a fluidic chip, the PDMS or SU8 channels were frequently modified by surface treatments to obtain the hydrophilic surface but encountered the problem of the hydrophobic recovery. In this article, long-term highly hydrophilic fluidic chips were demonstrated using rapid fabrication of low-power CO 2 laser ablation and low-temperature glass bonding with an interlayer of liquid crystal polymer (LCP). The intrinsic hydrophilic materials of glass and LCP were beneficial for self-driven flow in the long-term fluidic chip by surfacetension force with no extra fluidic pumps. The higher viscosity fluid could increase the difficulty of self-driven capability. The stability of contact angle and flow test of the chip after 2 months is similar to that at beginning. The high-viscosity human whole blood was successfully driven at an average moving velocity of about 1.89 mm/s for the beginning and at 2.04 mm/s after 2 months. Our fluidic chip simplifies the traditional complex fabrication procedure of glass chips and conquers the problem of traditional hydrophobic recovery.

Four geosynthetic-reinforced model walls backfilled with an idealised two-dimensional uniform medium were built and brought to failure using surcharging and toe cutting to simulate the behaviour of waterfront structures subjected to potential slope toe scouring. External stability analyses – base sliding, overturning, and bearing capacity failure – were performed in order to examine their relevance to the displacement, and ultimate failure state, of the walls. It was shown that a well-designed geosynthetic-reinforced wall can sustain a surcharge and a uniform toe cut up to an equivalent wall height (He) equal to 1.4 times the total wall height (Ht) with negligible horizontal and vertical wall displacement. This can be attributed to the effective mobilisation of tensile force in the reinforcement layers. Safety factors for base sliding and overturning vary within small and acceptable ranges during this stage. However, a drastic increase in wall displacement occurred during ground cutting adjacent to the toe of the tested wall, owing to insufficient bearing capacity beneath the wall. This increase was associated with a rapid decrease in the safety factor against bearing capacity failure beneath the wall. Detailed internal and external stability analyses for the wall behaviour observed here are reported in a companion paper.

<div>With the rapid development of intelligent vehicles technology, it is extremely urgent to solve environmental pollution and energy crisis. The electric intelligent vehicles technology can accelerate the world to move towards low carbonization and intelligence. In this article, one automatic steering system and its controller are designed with this electric vehicle as the verification platform. First, based on the digital mock-up (DMU) module of the CATIA digital prototype, the motion simulation of the automatic steering system is carried out. Then, the transient dynamics and fatigue analysis module from ANSYS Workbench 16.0 software is used to simulate and analyze the transmission mechanism. After verifying the reasonable strength of the real vehicle parts, the original platform steering system is reformed. Our intelligent vehicle uses a monocular charge-coupled device (CCD) to detect road marking lines and then employs a linear two degrees of freedom (2-DOF) vehicle model to establish a preview deviation model based on the visual navigation lane lines. A vehicle lateral control method combining fuzzy logic rules, adaptive proportional-integral-derivative (PID) control strategy, and preview deviation is designed. A lateral controller is built using Simulink software for lane tracking simulation, and a good tracking effect is obtained. Finally, the results of low-speed real vehicle tests show that the vehicle can stably track the target lane line at low-speed conditions.</div>