Scholte Wave Dispersion Modeling and Subsequent Application in Seabed Shear-Wave Velocity Profile Inversion

Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs the dispersion property of broadband Scholte-type surface wave signals, which propagate along the interface between the sea water and seafloor. It is of critical importance to establish the theoretical Scholte wave dispersion curve computation model. In this typical study, the stiffness matrix method is introduced to compute the phase speed of the Scholte wave in a layered ocean environment with an elastic bottom. By computing the phase velocity in environments with a typical complexly varying seabed, it is observed that the coupling phenomenon occurs among Scholte waves corresponding to the fundamental mode and the first higher-order mode for the model with a low shear-velocity layer. Afterwards, few differences are highlighted, which should be taken into consideration while applying the MASW method in the seabed. Finally, based on the ingeniously developed nonlinear Bayesian inversion theory, the seafloor shear wave velocity profile in the southern Yellow Sea of China is inverted by employing multi-order Scholte wave dispersion curves. These inversion results illustrate that the shear wave speed is below 700 m/s in the upper layers of bottom sediments. Due to the alternation of argillaceous layers and sandy layers in the experimental area, there are several low-shear-wave-velocity layers in the inversion profile.

Functionalization of the Fine Al2O3 Abrasive by the Polyacrylamide Deposition

In order to enhance the dispersion stability of ultra-fine Al2O3 powder in aqueous media, the alumina particles were modified with silane coupling agent KH570 at first, and then 2,2'-Azobis(2-amidinopropane) dihydrochloride (AIBA) was anchored onto the modified Al2O3 to initiate the graft polymerization of acrylamide monomer (AM), and PAM/Al2O3 composite particles were obtained finally. The structure and dispersion property of Al2O3 composite particles were characterized by XPS, FTIR, laser particle size analyzer, micro electrophoresis apparatus, SEM and spectrophotometer. The results indicated that the attained composite abrasive when water-soluble azo initiator was added at 40 ℃ showed good dispersion stability in aqueous media with PAM as shell and Al2O3 as core. Compared with unmodified Al2O3, the reunion phenomenon of grafting polymerization modified Al2O3 powder was improved by AM, the D50 of the modified particles reduced. The isoelectric point (IEP) of the grafting modified particles migrated, and the zeta potential of the modified particles reached to the maximum value when the pH was 9. After PAM/Al2O3 abrasive polished, the surface roughness of NiP/Al hard disk surface was obviously reduced.

Fabrication of Biodegradable Poly(caprolactone) Spherical-Microcarriers for Arterial Embolization

This study aimed to develop emulsification assisted with ultrasonic atomization (EUA) to make embolic biodegradable poly(caprolactone) (PCL) spherical-microcarriers with uniform particle size for mass production which was used to cure hepatocellular carcinoma, because this kind of embolic drugs is expensive at the current market due to their complex manufacturing process. The embolic spherical-microcarriers with sustained-releasing therapeutic agents can shrink an unresectable tumor into a respectable size. Through high frequency vibrating surface on the ultrasonic atomizer nozzle, the thin liquid film for PCL oil-phase solution was broken into the uniform PCL microdroplets (particle sizes are from 20 to 55 μm) with less medicine loss. To determine the optimal parameters to make PCL microcarriers, the ultrasonic module parameters including the concentration of PCL solution, vibrating amplitude of atomizer, feeding rate of PCL oil-phase solution and collection distance on the particle size of microdroplets were analyzed. Besides, a vertical circulation flow field of aqueous-phase poly(vinyl alcohol) (PVA) solution was created to enhance the separation of the microdroplets and increase the production of the PCL microcarriers, and about 8~11 wt% of PVA solution with high stable dispersion property was used to effectively improve the yield rate of PCL spherical-microcarriers (89.8~98.2 wt%). The final particle size of PCL microcarriers was ca. 5–18 μm, indicating an about 25–50% volume shrinkage from microdroplets to solid spherical-microcarriers.

Numerical Analysis of the Characteristics of Glass Photonic Crystal Fibers Infiltrated with Alcoholic Liquids

The characteristics of PCF with various air hole diameters infiltrated with alcoholic liquids such as ethanol, methanol, propanol and butanol are numerically investigated. Based on the numerical results, we have analyzed and compare in detail the characteristics of these fibers including effective refractive index, effective mode area, dispersion and confinement loss for two case: the diameters and lattices constant of air holes are equal 1 µm and 5µm, 1.42µm and 3.26µm, respectively. The PCF infiltrated with ethanol and butanol showed better near zero flattened dispersion property at 1.42µm and 1µm wavelength respectively. With diameters and lattices constant of air holes equal 1.42μm and 3.26μm, the smallest dispersion of PCF filled with ethanol of 5.91075308 (ps.(nm.km)-1) and methanol of 19.3592474 (ps.(nm.km)-1). The highest ZDW of the PCF infiltrated with ethanol and methanol is 1.24604224µm and 1.22405714µm, respectively. Specially, the value of effective refractive index, effective mode area, dispersion and confinement loss decrease in an orderly manner from butanol, propanol, ethanol to methanol and all the alcoholic liquids’s cuvers of dispersion are flat and are very close to each other and near the zero dispersion curve in case the diameters and lattices constant of air holes are equal 1µm and 5µm. The proposed PCF shows a promising prospect in technology applications such as supercontinuum generation.

Surface Wave Dispersion in a Layered Medium for Varying Subsurface Scenarios

Surface wave techniques are widely used to characterize a site based on shear wave velocity (Vs) or stiffness variation with depth. It utilizes the dispersion property of Rayleigh wave in a heterogeneous media. Dispersion curve is obtained from analyzing collected field test data and the final Vs profile is extracted from the inversion of the generated dispersion curve. The varying subsoil structures influence whether one or more Rayleigh modes will participate in the resulting wave propagation phenomenon. So, neglecting the higher mode participation may sometimes results in a completely different velocity profile than the actual existing one. In this paper, a detailed and comprehensive numerical study has been performed using finite element method for different types of soil profiles with different half-space impedances to assess how it affects the surface wave dispersion phenomenon. In addition to that, the effect of different data acquisition parameters on surface wave dispersion has also been studied.