The problems with elastic wave reflection at the interface between the water/patchy saturated porous media and the underlying solid matrix are considered. When porous media is saturated by biphasic ...fluids, the patchy saturation theory can explain the wave dispersion and attenuation better than the classical Biot theory at mesoscopic scales. Based on patchy saturation theory, this paper focuses on the reflection of elastic waves by patchy saturated porous media inclusion in layered media. Using numerical calculation, the reflection coefficients with different excitation frequencies, water saturations, and porous media depths are discussed. The results show that the differences between two kinds of patchy saturated porous media cases in the oil-water model are lower than those between the same two cases in the gas-water model. Low water saturation and high water saturation have significant effects on the reflection coefficient
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Stoneley wave in a fluid-filled pressurized borehole surrounded by a transversely isotropic elastic solid with nine independent third-order elastic constants in presence of biaxial stresses are ...studied. A simplified acoustoelastic formulation of Stoneley wave is presented for the parallelism of the borehole axis and the formation axis of symmetry. Sensitivity coefficients and velocity dispersions for Stoneley wave due to the presence of stresses are numerically investigated, respectively. The acoustoelastic formulation explicitly shows that the velocity dispersions of Stoneley wave depend on seven independent third-order elastic constants in presence of biaxial stresses and on six independent third-order elastic constants in the presence of borehole pressurization alone. Numerical results of both sensitivity coefficients and velocity dispersions of Stoneley wave show that at low frequency the velocity change of Stoneley wave is sensitive to c111 and c112. Stoneley wave velocity at low frequencies can be simplified by 3 independent third order elastic constants (c111, c112 and c123) instead of nine constants. In presence of biaxial stresses, at low frequencies the speed of the Stoneley wave is similar to White’s formula.
This paper is aimed to analyze Whiteleg shrimp's (Penaeus vannamei's) acoustic behavior collected in a farming pond. According to artificial feeding events, the chewing sound from shrimps is obtained ...by a passive acoustic recorder. The sound pressure level of the 1-minute segments between the two feedings is lower than that of after feeding, but higher than that of before feeding. There are two changing parts in the spectrum of several segments, in which one type has a low-frequency energy mainly in 2kHz, and the other has a high frequency energy in 4-15kHz. It is related to shrimps chewing behavior with a large number of 'click' signals. By analyzing the chewing sound from individual shrimp, time length of the signal is around 0.01s and the frequency range is about 4-15kHz. The behavior corresponding to the sound pressure level of 2kHz mentioned above has not been determined. In addition, from no-feeding data at night, there are also short-time 'click' signals, which are notably different from daytime's data, and sometimes is concentrated on the low-frequency (about 4kHz) from the energy of the signal. Further research is needed to determine whether there is a relationship between the two low-frequency signals.
The span-depth ratios of coupling beams to interconnect shear walls are generally small, so that brittle shear failure may occur and lead to reduced ductility. In order to improve the ductility of ...coupling beams for earthquake loading, a new type of ductile coupling beam is proposed in this paper. Along the middle depth of this beam, a slit through the entire thickness (a narrow hole) near each end and two lateral keyways along the remaining middle part of the span are made. The reductions of the stiffness under service load and the ultimate carrying capacity of the beam due to the weakening mentioned above are small and the ductility is greatly increased. Tests of 4-storey walls interconnected by coupling beams in three different constructions (monolithic beams, beams with a through-slit and new-type beams) indicated that shear walls with the new coupling beams possess the best aseismic behaviours under cyclic loading. The proposed new coupling beam has been used in a high-rise building.PUBLICATION ABSTRACT
We numerically calculate the Stoneley and flexural mode dispersion curves in a fluid‐filled borehole with borehole pressurization and uniaxially stressed solid formation. From the computational ...results of sensitivity coefficients and velocity‐stress coefficients, we show that the sensitivity coefficient without the third‐order elastic constant is larger than the other sensitivity coefficients , but the velocity‐stress coefficient corresponding to it is less than the other velocity‐stress coefficients with the third‐order elastic constants. Therefore, the fractional changes in the phase velocity hardly relate to the sensitivity coefficient without the third‐order elastic constant. In addition, computational results show that the point of dispersion curve crossover is affected by the borehole pressurization because of the change of velocity dispersion by borehole pressurization increasing with frequency, and as the borehole pressurization increases the velocity of the crossover point increases while the frequency of the point is unchanged.
In order thoroughly to improve the brittle failure characteristics of conventional lowrise shearwalls, this paper puts forward a new type of ductile lowrise shearwall scheme with friction damping ...control devices and carries out an experimental study on one piece of conventional framed lowrise shearwall and two pieces of the new type of lowrise shearwall under cyclic reversed loads. Moreover, from the basic assumption, after analysing the edge frame, wall panel and controlling forces, calculation formulae have been derived for the new type of lowrise shearwall. The calculated values given by the formulae show good agreement with the test values.
We introduce confinement effect to overcome disadvantages of directly immobilizing Fe2O3 on the surface of TiO2 by encapsulating Fe2O3 in photocatalyst, which exhibits a higher photocatalytic ...activity.
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•Spatially confined Fe2O3 in hierarchical SiO2@TiO2 (SFT) photocatalyst was prepared.•A complete degradation of antibiotics was achieved under natural sunlight irradiation.•Transformation intermediates and pathways of antibiotics were presented.•This work provided a new insight for constructing other metal oxides confined photocatalysts.
Although TiO2-based photocatalysts have achieved great successes for the degradation of organic pollutants, the complete removal of antibiotics is hard to be realized because of its unique macromolecular ring structure under solar-light irradiation. Herein, this work demonstrates the rational design of the hierarchical hollow SiO2-Fe2O3@TiO2 (SFT) photocatalyst by introducing spatially confined Fe2O3 as a modifier of TiO2, in which inner SiO2 serves as a carrier to support and disperse Fe2O3 in order to obtain small size of Fe2O3 (2–6 nm), while outer TiO2 acts as a bounding wall to protect Fe2O3 from aggregation and abscission. The as-synthesized SFT photocatalyst not only can overcome easy corrosion, dissolution and deactivation of Fe2O3 during the photoreaction process, but also can substantially enhance the adsorption of antibiotics because of its hierarchical hollow structure, facilitating the separation of electron-hole pairs and prolonging the trapping of incident light. Therefore, the SFT photocatalyst manifests the complete removal of antibiotics under simulated solar light irradiation. The intermediates of antibiotics were analyzed by liquid chromatography-mass spectrometry (LC/MS) and the possible degradation pathway was proposed accordingly. Besides, SFT photocatalyst exhibits an excellent recyclability due to confinement effect. Especially, the as-synthesized SFT also achieves the 100% degradation rate of antibiotics under natural sunlight irradiation, efficiently overcoming the incomplete removal of antibiotics for many previous TiO2-based photocatalysts.
TiO2 has been widely used as a photocatalyst and an electrode material toward the photodegradation of organic pollutants and electrochemical applications, respectively. However, the properties of ...TiO2 are not enough up to meet practical needs because of its intrinsic disadvantages such as a wide bandgap and low conductivity. Incorporation of carbon into the TiO2 lattice is a promising tool to overcome these limitations because carbon has metal-like conductivity, high separation efficiency of photogenerated electron/hole pairs, and strong visible-light absorption. This review would describe and discuss a variety of strategies to develop carbon-doped TiO2 with enhanced photoelectrochemical performances in environmental, energy, and catalytic fields. Emphasis is given to highlight current techniques and recent progress in C-doped TiO2-based materials. Meanwhile, how to tackle the challenges we are currently facing is also discussed. This understanding will allow the process to continue to evolve and provide facile and feasible techniques for the design and development of carbon-doped TiO2 materials.
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•The p-n heterojunction Bi2O3/Ti3+-TiO2 photocatalyst was reported by a facile method.•The Bi2O3/Ti3+-TiO2 enabled the complete removal (100%) of tetracyclines under visible ...light.•The effect of environmental factors on the photodegradation of tetracyclines was detailed.•The mechanism onphotodegradation was analyzed through LC–MS spectrum.
The search for a highly active visible-light photocatalyst toward the complete degradation of antibiotic residuals remains a challenging task due to the fast emergence of antibiotic resistance. To address the problem, we explore a novel p-n heterojunction visible-light photocatalyst by coupling a p-type Bi2O3 with an n-type Ti3+self-doped TiO2 porous material. The as-synthesized photocatalyst exhibits a narrowed bandgap (~2.89 eV) and enhanced visible-light absorption, leading to the complete degradation (100%) of antibiotics under visible light irradiation (λ > 420 nm) and excellent recyclability (98%) because of the synergistic effect of Ti3+self-doping and p-n heterojunction. The results effectively work out the challenging task of the incomplete removal of tetracyclines over almost all of the reported visible-light photocatalysts. Additionally, the effects of antibiotics mixture, pH value, inorganic ions, water matrix, and outdoor light on the degradation of tetracyclines were also detailed. Especially, the transformation pathways and degradation mechanism of tetracycline were revealed in depth via trapping experiments and photoelectrochemical characterizations. Therefore, this work provides a new insight in exploring excellent photocatalysts to realize the complete removal of other refractory organic pollutants under visible light.
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