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To analyze the kinetic characteristics of a debris flow that occurred on 9 April 2000 in Tibet, China, a meshfree numerical method named smoothed particle hydrodynamics (SPH) is introduced, and two-dimensional and three-dimensional models are established in this work. Based on the numerical simulation, the motion process of this debris flow is reproduced, and the kinetic characteristics are analyzed combining with the field investigation data. In the kinetic analysis, the flow velocity, runout distance, deposition, and energy features are discussed. Simulation results show that the debris flow mass undergoes an acceleration stage after failure, then the kinetic energy gradually dissipates due to the friction and collision during debris flow propagation. Finally, the debris flow mass blocks the Yigong river and forms a huge dam and an extensive barrier lake. The peak velocity is calculated to be about 100 m/s, and the runout distance is approximately 8000 m. The simulation results basically match the data measured in field, thus verifying the good performance of the presented SPH model. This approach can predict hazardous areas and estimate the hazard intensity of catastrophic debris flow.

Two groups of unsteady flows over a stationary SD7003 airfoil are studied with the large eddy simulation method. In the first group, the angle of attack (AoA) is fixed, while the freestream velocity magnitude varies harmonically with various frequencies and amplitudes. In the second group, the freestream velocity magnitude is fixed but its direction, therefore the AoA varies harmonically. Over the range of parameters considered in this study the mean lift and drag coefficients of the unsteady flows with oscillating freestream velocity magnitude are found to be nearly the same as those calculated for steady flows. However, there are significant phase shifts between the aerodynamic forces and the unsteady freestream velocity. The phase shift for drag force is larger than that for lift force, even though both increase as the frequency of freestream velocity oscillations increases. Furthermore, the computed lift amplitudes are found to be noticeably higher than those predicted by Greenberg's inviscid theory, while the lift phase shifts are in better agreement with the theory. For flows with oscillating freestream AoA, there is little change in the mean lift, while the mean drag is reduced by oscillations in AoA due to Katzmayr effect. As the frequency of oscillations in AoA increases, the phase shift for lift increases while that for drag decreases. Our results also indicate that the mean separation point moves downstream and the mean reattachment point moves upstream when the freestream velocity magnitude or the freestream flow direction oscillates with respect to the airfoil.

This study has developed a versatile nano-system with the combined advantages of photothermal effect, active tumor-targeting, temperature-sensitive drug release, and photoacoustic imaging. The nano-system consists of the core of the phase change material (PCM), the outer polypyrrole (PPY) shell and the hyaluronic acid (HA) modified in the PPY shell. The obtained composite nanoparticles (denoted as DTX/PPN@PPY@HA) were spherical with a mean diameter of about 232.7 nm. In vivo and in vitro photoacoustic imaging experiments show that DTX/PPN@PPY@HA is an effective photoacoustic contrast agent, which can be used for accurate localization of tumor region and real-time guidance of photothermal chemotherapy. DTX/PPN@PPY@HA shows good photothermal effects and temperature-sensitive drug release. In addition, cellular experiments showed that DTX/PPN@PPY@HA could be efficiently internalized into tumor cells and produce significant cytotoxicity with the help of near-infrared (NIR) laser. Furthermore, the remarkable inhibition of DTX/PPN@PPY@HA against tumor growth was achieved in 4T1 tumor-bearing mice model.

In this study, a numerical approach—the discontinuous Meshless Local Petrov-Galerkin-Eshelby Method (MLPGEM)—was adopted to simulate and measure material plasticity in an Al 7075-T651 plate. The plate was modeled in two dimensions by assemblies of small particles that interact with each other through bonding stiffness. The material plasticity of the model loaded to produce different levels of strain is evaluated with the Lamb waves of S0 mode. A tone burst at the center frequency of 200 kHz was used as excitation. Second-order nonlinear wave was extracted from the spectrogram of a signal receiving point. Tensile-driven plastic deformation and cumulative second harmonic generation of S0 mode were observed in the simulation. Simulated measurement of the acoustic nonlinearity increased monotonically with the level of tensile-driven plastic strain captured by MLPGEM, whereas achieving this state by other numerical methods is comparatively more difficult. This result indicates that the second harmonics of S0 mode can be employed to monitor and evaluate the material or structural early-stage damage induced by plasticity.