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High‐precision P‐wave and S‐wave velocity models are very important for seabed exploration. Elastic full‐waveform inversion is an effective way to obtain the velocity models. Full‐waveform inversion is strongly dependent on source wavelet, and inaccurate wavelet estimation will severely affect the inversion results. Furthermore, elastic full‐waveform inversion is a highly non‐linear problem and has larger calculation and memory cost. Based on the deconvolution method, we develop a multi‐scale source‐independent elastic full‐waveform inversion method in a hybrid domain to alleviate the non‐linearity, to improve computation efficiency and decrease memory cost and to reduce the influence of source wavelet. We reconstruct the deconvoluted objective function and further derive the adjoint source and gradient formulas for elastic full‐waveform inversion with the adjoint‐state method. We can obtain good inversion results by using this objective function, adjoint source and gradient even if the source wavelet is unknown. In order to illustrate the influence of different reference traces on the objective function, we provide the theoretical formula of the objective function changing with the variation of reference traces. Experiments show that the deconvolution objective function cannot completely eliminate the influence of inaccurate source wavelet on the inversion, and the inversion effect depends on the selection of reference trace. Different inversion results of the Marmousi2 model indicate that the minimum offset trace is the best reference trace. Comparison of the inverted Marmousi2 model by the proposed method and the conventional elastic full‐waveform inversion method using correct wavelet shows that the two inversion results are very close, which proves the effectiveness of the proposed method and indicates a potential application of the method in seabed exploration. [ABSTRACT FROM AUTHOR]

Due to the limitations of the actual acquisition environment in the field, especially in ocean bottom seismometer (OBS) acquisition, the acquired seismic data are often irregular and incomplete, which affects the subsequent data imaging, interpretation and hydrocarbon‐bearing reservoir prediction. The interpolation reconstruction algorithm based on the compressive sensing theory can reconstruct the data without the limitation of Nyquist sampling interval. However, the reconstruction accuracy and effect are different for different sparse representations of the data. On the basis of compressed sensing theory, we propose a Bregman iterative seismic data reconstruction method based on the sparse decomposition of discrete orthonormal Coiflets and Symlets wavelet transforms. First, the discrete orthonormal matrix is constructed by using the above two wavelet functions to make the original seismic data sparse, then the Bregman iterative algorithm is used to reconstruct the sparse coefficients in the discrete wavelet domain, and finally the recovery matrix is used to reconstruct the seismic data. The discrete orthonormal Coiflets and Symlets wavelet transforms have good sparse representation ability and can compensate for the problem that discrete Fourier transform cannot well sparse representation of the data. After numerical experiments on horizontal‐layered model, Marmousi2 model and actual data, it is verified that the proposed method can reconstruct the missing seismic data under the regular observation system and under the irregular observation system with non‐uniform OBS distribution. Furthermore, this method can hardly bring the interference of random noise, and the reconstruction result is of high accuracy. [ABSTRACT FROM AUTHOR]

C‐vinyl glycosides are an important class of carbohydrates and pose a unique synthetic challenge. A new strategy has been developed for stereoselective synthesis of C‐vinyl glycosides via Pd‐catalyzed directed C−H glycosylation of alkenes with glycosyl chloride donors using an easily removable bidentate auxiliary. Both the γ C−H bond of allylamines and the δ C−H bond of homoallyl amine substrates can be glycosylated in high efficiency and with excellent regio‐ and stereoselectivity. The resulting C‐vinyl glycosides can be further converted to a variety of C‐alkyl glycosides with high stereospecificity. These reactions offer a broadly applicable method to streamline the synthesis of complex C‐vinyl glycosides from easily accessible starting materials. [ABSTRACT FROM AUTHOR]

A key route to advancing power plant efficiency is to enhance current steam operating parameters, namely, increase in steam temperature and pressure from the current levels of 540°C and 180 bar to the proposed 700°C (EU) and 300 bar. Conventional ferritic–martensitic steels, while having good mechanical properties and fatigue resistance, do not possess the high‐temperature corrosion resistance for long‐term use, with a temperature limit of ~620°C. Adding aluminide coatings to the surfaces of the steels can improve the oxidation resistance of this class of material through the growth of an Al2O3 scale. One of the major concerns in using coating is the potential deleterious effects on the mechanical properties of the substrate, either through the precipitation of brittle phases or through cracks in the coating. This study compares the microstructural features of slurry aluminide coatings applied to Grade 91 and the change in mechanical performance. The tensile, thermomechanical fatigue and creep test results showed that while the coated samples entered the tertiary creep zone earlier than the uncoated ones, cracking of the coating remained confined to the surface of the specimen. Nanoindentation mapping showed a hardness increase in the coating and within the aluminium diffusion zone, which is related to the exposure time. [ABSTRACT FROM AUTHOR]

The hydrophobic properties of methyl poly siloxane ( MK) were pushed into the 'hydrophilic' range by cross-linking it with (3-aminopropyl)triethoxysilane ( APTES) and subsequent pyrolysis to enable water-based freeze casting. Filler properties are investigated by varying the ratios of MK to APTES (1:1, 1:2, 1:3, 1:4, 1:5), and pyrolysis temperatures (400°C, 500°C, 600°C) for the purpose of determining an optimal set of characteristics for freeze casting. Additionally, filler selection for this purpose is facilitated by analysis of zeta potential values and vapor adsorption. It was found that water-based freeze casting with hybrid fillers, followed by a pyrolysis step (600°C-700°C), leads to a Si OC ceramic monolith with a lamellar pore morphology and a hierarchically ordered micro/meso/macropore structure. Samples pyrolyzed at 1000°C contain mesopores, having a SSA as high as 51.6 m2/g. The hierarchically porous structure is very promising for applications involving gas or liquid transportation. [ABSTRACT FROM AUTHOR]

We study the existence and concentration of positive solutions for the coupled nonlinear Schrödinger system [ABSTRACT FROM AUTHOR]

SiC coatings in tri-structural isotropic-coated ( TRISO) particles were thermally treated at 2000°C for 1 h in argon atmosphere. The fracture strength of the SiC decreased while change in the Weibull modulus of the failure strength is more complex after the thermal treatment. The variation in both fracture strength and Weibull modulus can be explained by the formation of the pores in SiC due to thermal treatments, as annihilation of the stacking faults and diffusion of intrinsic defects lead to the pore formation. [ABSTRACT FROM AUTHOR]

In this paper, we consider the following perturbed nonlinear Schrödinger system with electromagnetic fields [ABSTRACT FROM AUTHOR]

In this study, the microstructure and Vickers indentation fracture toughness ( VIF fracture toughness) of three different types of silicon carbide ( SiC) coatings (stoichiometric SiC, SiC with excess silicon and SiC with excess carbon) were investigated. SiC coatings were produced on tri-isotropic fuel particles by fluidized bed chemical vapor deposition ( FBCVD). The microstructure was investigated using a scanning electron microscope ( SEM) and X-ray diffraction, while a transmission electron microscope was used for the analysis of defects and micro-cracks. The VIF fracture toughness was measured using Vickers indentation. The fracture beneath the indenter consists of Palmqvist cracks as observed using SEM. Based on this crack mode, VIF fracture toughness values of 3.51, 4.03, and 4.93 MPa·m1/2 for stoichiometric, extra- C and extra- Si SiC coatings were obtained, respectively. It was found that stress-induced micro-cracks seem to be a mechanism for the fracture behavior, which gave SiC coatings with high VIF fracture toughness. The difference in the VIF fracture toughness of FBCVD SiC coatings is discussed in terms of defects and grain morphology. [ABSTRACT FROM AUTHOR]