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In this study, a dense WS2coating was deposited via high-power impulse magnetron sputtering (HiPIMS) after solving the glow discharge problem, and it was compared with WS2coating deposited via radio frequency (RF) sputtering. The latter showed a columnar growth, with a loose and porous microstructure. The columnar crystal growth of the former was inhibited, resulting in a more compact coating structure and a more uniform, flatter and smoother surface. Therefore, the structure and tribological properties of WS2coating prepared via HiPIMS were investigated under different loads and frictional frequencies. Under low loads (up to 15 N), the coefficient of friction (COF) decreased with polishing wear mechanism. Under a high load of 20 N, the COF rapidly increased, the wear rate was the highest, and the wear mechanism changed from polishing to abrasive wear. At low frequencies (5 and 10 Hz), the coating had a low and stable COF, good wear resistance and the wear mechanism was abrasive wear. At high frequencies (≥15 Hz), the COF and wear rates rapidly increased and the wear mechanism changed from abrasive to adhesive wear and plastic fracture. However, the friction and wear rates were similar across different wear mechanisms.

Herein, the functional poly(vinylidene fluoride) (PVDF) film that has a superior UV-blocking performance was made through the surface-initiated activators regenerated by electron transfer atom-transfer radical polymerization (SI-AGET ATRP). The colorless polydopamine (PDA) initiator layer was adhered to the alkaline-pretreated PVDF film through the copolymerization of dopamine (DOPA) and initiator-bearing DOPA (DOPA-BIBB). Then the reactive organic UV absorbent [3-(4-benzoyl-3-hydroxyphenoxy)-2-hydroxypropyl] 2-methylprop-2-enoate (BPMA) was incorporated to the initiator layer by the SI-AGET ATRP method, resulting in the formation of a PBPMA-chain-grafted PVDF film (PVDF-g-PBPMA). Furthermore, the effects of the experimental conditions such as the BPMA concentration and reaction time on the performance of as-prepared modified films were investigated. The characterization results indicated the formation of the PBPMA film on the PVDF film surface and the outstanding UV-blocking performance of the modified films. The PVDF-g-PBPMA film fabricated under the optimum conditions could completely block the UV light in the range of 200–370 nm.

3D controlled-source audio frequency magnetotelluric (CSAMT) responses can be distorted strongly by topography and should be accounted for in data inversion and interpretation. In this paper we present a scheme to incorporate topographic distortions into the inversion instead of correcting them. This approach has been verified by comparing the modelling results with 2D FEM CSAMT solutions and synthetic inversion examples. Compared with the responses generated from a half-space model with flat surface, it is found that not only the topography in the survey area but also that at the source position may strongly distort the CSAMT responses. The field example indicates that results with topography are much better than those without considering topography to map the distribution of coal seam underground, which also illustrates the effectiveness of our approach.

The controlled-source audio-frequency magnetotelluric (CSAMT) method has become an important method in geophysical electromagnetic exploration. However, traditional CSAMT only gathers a single set of orthogonal electric and magnetic data, which cannot describe the whole subsurface geological structure. Due to increasingly complex geological targets, the drawbacks of traditional CSAMT have gradually become more significant, promoting the need for tensor CSAMT. Tensor CSAMT can gather richer information, but the 3D forward and inversion models of this method have developed slowly since it was first proposed. The common method for inverting the data of the tensor CSAMT is still magnetotelluric (MT). This paper adopts a staggered-grid finite difference method to realise the 3D forward modelling of the tensor CSAMT. On this basis, we adopt a limited-memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) method to implement a 3D inversion with full impedance data. Through inverting synthetic and real data, we prove that: (1) directly using an MT method to invert the data of the tensor CSAMT will obtain an incorrect result, (2) the inversion result of tensor CSAMT is more reliable than that of the traditional CSAMT, and (3) LBFGS is more efficient than the nonlinear conjugate gradient (NLCG) for tensor CSAMT. Our research shows that 3D tensor CSAMT inversion with LBFGS is very useful and practical for electromagnetic exploration.

The eastern terminations of the Himalayan orogeny, named Namche Barwa, are considered a vital natural laboratory in the Tibetan plateau for geodynamics due to its distinctive geological and geomorphological characteristics. Magnetotelluric (MT) data measured at 83 sites around the Namche Barwa are imaged by three‐dimensional (3‐D) inversion to better reveal the crustal structure of the eastern Himalaya. The results show a complex and heterogeneous electrical structure beneath the Namche Barwa. The electrical conductors distributed in the middle and lower crust around the Namche Barwa provide additional evidence for the “crustal flow” model if they are considered as some parts of the flow in a relatively large‐scale region. The near‐surface resistivity model beneath the inner part of Namche Barwa conforms with the locations of hot spring and fluid inclusions, the brittle‐ductile transition, and the 300°C–400°C isotherm from previous hydrothermal studies. Relatively resistive upper crust (>800 Ωm) is underlain by a more conductive middle to lower crust (<80 Ωm). The electrical characteristics of the thermal structure at shallow depth indicate an accumulation of hydrous melting, a localized conductive steep dipping zone for decompression melting consistent with the “tectonic aneurysm” model for explaining the exhumation mechanism of metamorphic rocks at Namche Barwa. The results also imply that both surface processes and local tectonic responses play a vital role in the evolution of Namche Barwa. An alternative hypothesis that the primary sustained heat source accounts for the local thermal‐rheological structure beneath Namche Barwa is also discussed. We present new reticular MT data and 3‐D inversion results of Namche BarwaOur results at Namche Barwa provide additional evidence to the crustal flow modelOur results on the inner part of the Namche Barwa support the “tectonic aneurysm” model

(Polarity and acid-base equilibrium of the A-site ions in organic-inorganic hybrid perovskites are the major origins of structure instability that limits the efficiency of perovskite solar cells (PSCs). It is effective to stabilize the structure of perovskite by partial replacement of A-site ions with larger radius and non-polar ions. Here, we fabricate tetramethylammonium ions N(CH3)4+(TMA+) substituting perovskite, MA1-xTMAxPbI3, by partially replacing MA+in MAPbI3with large and rigid TMA+. Theoretical and experimental study demonstrates that the introduction of TMA+cation in MA1-xTMAxPbI3perovskite leads to a more stable crystal structure and reduces the defects state density in perovskite films. The PSCs based on MA1-xTMAxPbI3(x = 0.15) films demonstrate a champion efficiency of 22.23% and an improved stability against air environment. This work highlights the significance of A-site ionic characteristics of perovskite structure and provides a new strategy in constructing high efficiency and stable hybrid PSCs.)

Abstract: We implement a parallel algorithm with the advantage of MPI (Message Passing Interface) to speed up the rapid relaxation inversion for 3D magnetotelluric data. We test the parallel rapid relaxation algorithm with synthetic and real data. The execution efficiency of the algorithm for several different situations is also compared. The results indicate that the parallel rapid relaxation algorithm for 3D magnetotelluric inversion is effective. This parallel algorithm implemented on a common PC promotes the practical application of 3D magnetotelluric inversion and can be suitable for the other geophysical 3D modeling and inversion.

Abstract: Based on the analysis of the conjugate gradient algorithm, we implement a threedimensional (3D) conjugate gradient inversion algorithm with magnetotelluric impedance data. During the inversion process, the 3D conjugate gradient inversion algorithm doesn’ t need to compute and store the Jacobian matrix but directly updates the model from the computation of the Jacobian matrix. Requiring only one forward and four pseudo-forward modeling applications per frequency to produce the model update at each iteration, this algorithm efficiently reduces the computation of the inversion. From a trial inversion with synthetic magnetotelluric data, the validity and stability of the 3D conjugate gradient inversion algorithm is verified.

Electrical anisotropy is increasingly recognized as an important aspect of the resistivity models required to explain magnetotelluric (MT) observations. However, a limited number of practical MT inversion algorithms that can consider anisotropy have been published to date. To address this problem, we have developed a three‐dimensional (3‐D) MT inversion algorithm that recovers a 3‐D resistivity model that considers arbitrary electrical anisotropy. The inversion uses the same inversion algorithm as the widely used ModEM inversion algorithm, and a novel forward modeling algorithm to consider the anisotropic Earth. The algorithm was tested on both synthetic and field MT data. Inversions considered both a completely general anisotropy tensor with six components and approximations with less parameters. Synthetic inversions show that the two horizontal components of resistivity and the anisotropy strike can be well recovered, while the vertical component of resistivity is poorly resolved, primarily because current flow in MTs is dominantly horizontal. The synthetic examples confirm the limitation of the axial anisotropic inversion technique when applied to MT data produced by a resistivity model with arbitrary anisotropy. The synthetic inversions also showed that inversion of data from an isotropic model will not result in an artificially anisotropic model. Compared to the isotropic inversion model of the real MT data, the anisotropic model clearly shows some features that are consistent with the mapped geology. As expected, the results showed that a given data set can be fit by a range of models, with an inherent trade‐off from 3‐D heterogeneity to 3‐D anisotropy. This uncertainty can be reduced with the use of prior information in the inversion. The resistivity model of real Earth generally contains anisotropic features. Field magnetotelluric (MT) data may be significantly influenced by these features. To interpret such data, inversion algorithms which can consider electrical anisotropy are highly demanded. However, a limited number of practical MT inversion algorithms that can consider anisotropy have been published to date. To address this problem, we have developed a three‐dimensional (3‐D) MT inversion algorithm that recovers a 3‐D resistivity model that considers arbitrary electrical anisotropy. The algorithm was tested to be effective on both synthetic and field MT data. Compared to the isotropic inversion models of the tested MT data, the resolved anisotropic models are more reliable. A three‐dimensional non‐linear conjugate gradient inversion algorithm is implemented for the inversion of magnetotelluric (MT) data to produce an electrical resistivity model with arbitrary anisotropyInversion examples of synthetic and real MT data validate the usefulness of the algorithmReal MT data inversion obtains an anisotropic model which is more consistent with the mapped geology than the corresponding isotropic model A three‐dimensional non‐linear conjugate gradient inversion algorithm is implemented for the inversion of magnetotelluric (MT) data to produce an electrical resistivity model with arbitrary anisotropy Inversion examples of synthetic and real MT data validate the usefulness of the algorithm Real MT data inversion obtains an anisotropic model which is more consistent with the mapped geology than the corresponding isotropic model