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The titanium alloy blade is a key part of an aero-engine, but its high surface efficiency and precision machining present technical problems. Belt grinding can effectively prolong the fatigue life of the blade and enhance the service performance of the aero-engine. However, the residual stress of the workpiece after belt grinding directly affects its service performance and life. The traditional single particle abrasive model simulation is limited in exploring the influence of grinding process parameters on surface residual stress. In this study, an ABAQUS simulation model of multi-particle belt grinding is established for titanium alloy material, a finite element (FE) simulation is conducted with different technological parameters, and the results are analysed. The critical belt grinding experiment is conducted on thin-walled titanium alloy parts, and the distribution characteristics of surface residual stress after grinding are studied to understand the influence of grinding parameters on the formation of surface residual stress. Comparing the results of the FE simulation and the grinding experiment, the common law of stress change and the prediction model are obtained. The results show that the multi-particle belt grinding simulation is consistent with the belt grinding experiment in terms of the influence of grinding parameters on residual stress. The simulation can serve as a guide in actual belt grinding to some extent. Directions for improving the multi-particle abrasive simulation model are discussed.

Ion exchange of organic-inorganic hybrid perovskite plays a significant role in controlling the performance of materials ant its devices. In this study, an interesting phenomenon was observed that the precipitate in suspension (CH3NH3PbI3−xBrx in γ-butyrolactone) brought out different colors at high and room temperature. The mechanism study appears that the phenomenon is controlled by temperature sensitive and reversible halide ion exchange in organic-inorganic hybrid CH3NH3PbI3−xBrx mixed-halide perovskite. The results of structure phase, element composition morphology and band gap illustrate that high temperature 55 °C is beneficial to the increasing of I content in MAPbI3−xBrx and room temperature or lower is advantageous to increasing of Br content in MAPbI3−xBrx. Compared with MAPbI0.76Br2.24 precipitate acquired at room temperature, MAPbI1.17Br1.83 precipitate got at high temperature illustrate wider lattice spacing, better crystallinity, better morphology and narrower band gap. The results and findings in this study will prompt the interest of readers or experts in the field of organic-inorganic hybrid perovskite materials and related optoelectronic applications.

Online diagnosis of slight interturn short-circuit fault (ISCF) has always been difficult in low-speed permanent magnet synchronous motors (PMSMs). It is found that the residual zero-sequence voltage exists in healthy PMSMs due to the inherent unbalance of a low-speed motor. This article proposes a new ISCF diagnosis method based on zero-sequence voltage vector decomposition to solve this problem. The voltage vector whose phase angle is closest to the ISCF phase angle is extracted from the zero-sequence voltage vector, which improves the sensitivity of fault phase identification. Furthermore, the method of extracting phase voltage from PWM duty-cycle control voltage is proposed, which can reduce the error caused by measuring zero-sequence voltage with three-phase balanced resistance. Experiments demonstrate that the online detection limit of ISCF is reduced from 5% to 1% (short-circuit ratio) for a low-speed PMSM.

The structure, mobility and memristor properties of tetragonal CH3NH3PbBr3 single crystals (T-MAPbBr3 SC) are rarely reported. In this study, we synthesized T-MAPbBr3 SC with the P4/mmm (123) space group by the growing, dropping and growing (GDG) crystal seed method. A CH3NH3+ cation is a disordered state in T-MAPbBr3 SC. The mobility values of T-MAPbBr3 SC under light and dark conditions are 464.28 and −1685.3 cm2 V−1 s−1, respectively. The carrier types under light and dark conditions are holes and electrons, respectively. The memristor based on T-MAPbBr3 SC has a wide and low operating voltage window (0–0.9 V). The high and low resistances of the memristor based on T-MAPbBr3 SC achieve values of 41 and 0.35 GΩ, respectively. The values of high and low resistances are relatively stable for 100 cycles. Thus, the memristor device based on T-MAPbBr3 SC has good applications in the field of memristors.

Tubular permanent magnet motor (TPMM) can offer great thrust force density and high efficiency. To enhance its robustness against disturbances and solve the contradiction between response time and overshoot, a novel sliding mode control strategy based on disturbance observer (DOB-SMC) was proposed for a TPMM velocity drive system. The novelty of the proposed velocity control strategy lies in the incorporation of the mismatch disturbance observer in the sliding surface and the sliding mode control (SMC) law, and the introduction of internal model control (IMC) into the SMC law. The velocity control system is transformed to a first-order inertia model by IMC, thus the dynamic response performance is improved. The mismatched disturbances are estimated and the equivalent control voltage is employed, and then the effect of mismatched and matched disturbances can be restrained with little chattering. The simulated and experimental results are presented as validation for the proposed strategy.

Hybrid electrocatalysts derived from surface self-reconstruction during reaction processes can facilitate charge transfer between different phases and nanostructures by their unique interfaces. Herein, amorphous/crystalline hybrid iron disulfide obtained by self-reconstruction is developed for the first time for the oxygen evolution reaction (OER). The amorphous/crystalline hybrid FeS2 catalyst exhibited a high OER activity with an overpotential of only 189.5 mV (IR-corrected) to deliver 10 mA cm-2 in 1.0 M KOH, which was superior to that of the commercial RuO2. Notably, in the two-electrode system with the amorphous/crystalline hybrid FeS2 as the anode electrocatalyst and Pt/C as the cathode, the catalytic activity towards the overall water splitting was enhanced with a voltage of only 1.43 V at 10 mA cm-2. The phase, composition and surface structure were changed greatly before and after the reaction. All these surface reconstructions after the OER reaction may play significant roles in the high electronic catalytic efficiency. Therefore, the study of the surface reconstruction of catalysts during the reaction process is very important for the structure-performance relationship and the design of efficient hybrid electrocatalysts.

Vanadium carbide embedded in mesoporous carbon (VC–MC) is prepared using an in-situ synthesis method as hybrid electrode for supercapacitor. The electrochemical performance of the VC and VC–MC electrodes are analyzed and compared through a combination of cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy measurements in 1 M H2SO4 aqueous electrolyte. The introduced mesoporous structure of the hybrid electrode provides optimized conducting pathways for electrons and protons, thus improving the capacitive performance of VC–MC electrode compared to pristine VC electrode. The synthesized VC–MC electrode achieves a specific capacitance up to 191.2 F g−1, which is significantly higher than the pristine VC electrode (95.6 F g−1). Moreover, the VC–MC hybrid electrode exhibits an excellent cycle performance with 89.5% capacitance retention after 10,000 charge–discharge cycles, considerably higher than the pristine VC electrode. Apparently, the VC–MC hybrid electrode which shows desirable capacitive performance, excellent stability and enhanced electrochemical properties can be attributable to the combination of the advantages possessed by MC and VC. Moreover, VC–MC was applied as counter electrode in flexible dye-sensitized solar cell which generate power conversion efficiencies of 6.50%, much higher than those of the devices using VC and MC counter electrodes (4.14% and 5.28%).

A five-phase fault-tolerant permanent-magnet (FTPM) motor can offer high torque density, low torque ripple, and good fault-tolerance. To improve operational performance under open-circuit fault condition, this article proposes a novel direct torque control (DTC) based on virtual stator flux strategy for an FTPM motor drive. The novelty of the proposed strategy is the development of virtual stator flux, which is used to achieve circular trajectories of current and rotating magneto-motive force vectors, and to derive feedforward voltage. Additionally, optimal fault-tolerant current references get derived based on maximum torque criterion, and then combined with reduced-order orthogonal decomposition matrices deduced from them, the feedforward voltage is used to eliminate asymmetrical motor behavior under the fault condition. Hence, the DTC becomes applicable to the FTPM motor drive under open-circuit fault condition. This control strategy not only enhances the torque performance with smooth torque and high dynamic response but also allows minimal reconfiguration of the control structure from healthy operation to fault-tolerant operation. The simulation and experimental results are given to verify the feasibility of the proposed strategy.

Under the assumption of invariant ray path in a weakly dissipative (high quality factor Q) subsurface medium, a tomographic inversion approach composed of two cascading applications of first arrival traveltime and Q tomography is proposed for compensating amplitude loss caused by near-surface anomalies, such as unconsolidated soils or the overburden gas cloud. To improve the computational efficiency, these two related tomography methods were adopted with an adjoint-state technique. First, arrival traveltime tomography will be performed to provide an inverted velocity model as one of the inputs for the following first arrival Q tomography. Then, the synthetic first break generated by the inverted velocity model will be used as a stable guidance of accessing the scopes of first arrival waveforms in the time domain where the potential attenuated time information is contained. The attenuated time will be estimated through a logarithmic spectral ratio linear regression corresponding to frequency-dependent propagation responses of different wave types. All these estimated attenuated times will be applied with reference signals to generate synthetic attenuated seismic data in the time domain, and their discrepancies with real data will be evaluated using similarity coefficients. The ones with larger values will be selected as optimal attenuated time inputs for the following Q tomographic inversion. Examples of both synthetic and field data reveal the feasibility and potential of this method.

Concrete thermal parameters in a natural pouring environment are essential inputs for simulating the temperature field of a concrete dam. This paper proposes a two-stage thermal parameters inversion method for a concrete dam based on optimal temperature measuring point selection to improve the accuracy of parameters. Firstly, a selection method of optimal measuring point for thermal parameters inversion is presented and the temperature response sensitivity of measuring points when the parameters disturb is taken as the critical evaluation index. And then, an inversion model is established based on support vector regression (SVR) and particle swarm optimization (PSO). Finally, the proposed method is applied to the thermal parameter inversion of a concrete dam. The results show that the proposed method is effective for improving the inversion accuracy and obtaining accurate parameters. The average error of the inversion results based on the SVR-PSO model is 28.54% lower than that of the genetic algorithm optimization using a back propagation neural network (BPNN-GA). Besides that, the average error of the inversion results based on the optimal measurement points is 35.57% lower than that of the nonoptimized ones.

The A15 structure of superconductors is a prototypical type-II superconductor that has generated considerable interest since the early history of superconducting materials. This paper discusses the superconducting properties of previously unreported V3−x Co x Si (0 ⩽ x ⩽ 0.30) alloys. It is found that the lattice parameter decreases with increasing cobalt-doped content and leads to an decreased residual resistivity ratio value of the V3−x Co x Si system. Meanwhile, the superconducting transition temperature (Tc ) also decreases with increasing cobalt-doped content. Furthermore, the fitted data show that the increase of cobalt-doped content also reduces the lower/upper critical fields of the V3−x Co x Si system. Type-II superconductivity is demonstrated in all V3−x Co x Si samples. With higher Co-doped content, V3−x Co x Si (0.15 ⩽ x ⩽ 0.30) alloys may have superconducting and structural phase transitions in low-temperature regions. As the electron/atom ratio increases, the Tc variation trend of V3Si is as pronounced as in crystalline alloys and monotonically follows the trend observed for amorphous superconductors.

Perovskite solar cells have become the current research focus because of their high conversion efficiency and other advantages; however, the toxicity of lead used in them has raised environmental concerns. Tin-based perovskite materials have become the most promising alternative materials for perovskite solar cells because of their relatively low toxicity, suitable band gap and relatively higher energy conversion efficiency than perovskite materials based on other elements. In this article, the status of this rapidly growing field, authors’ output and cooperation, hot research topics, important references and the development trends of tin-based perovskite solar cells are identified and visualized using CiteSpace software. The main research fields are found to be optical properties, 3D–2D perovskite and perovskite solar cell conduction band materials. The mixed organic metal halide perovskite solar cell and the CsSnI3 semiconductor are identified as emerging trends for tin-based perovskite solar cells. Such contents in this article highlight the key points in the wide field of literature so it can be understood efficiently.

Seafloor acoustic reflectivity is fundamental for both underwater detection and ocean acoustic field prediction, especially in shallow-water offshore regions. This paper presents a procedure to estimate the seafloor reflectivity in shallow water based on the direct wave and seafloor reflection data from single-channel seismic records of sparker sources. We apply the procedure to a seismic line acquired in the western part of the Taiwan Strait. To resolve the uncertainty in the inversion results, we implement strict quality control on the data obtained from seismic records and utilized for the inversion calculation. According to the preprocessing results, it is recommended to exclude the bubble pulses and their surface reflections, which are unstable and act as noise, from the estimated source wavelet applied to the inversion calculation. The calculation results show a significant level of directional variation in the acoustic energy radiated from the sparker source, and this variation should be considered in the calculation of seafloor reflectivity. In this work, the seafloor reflectivity is calibrated with relatively stable calculated values that correspond to known types of sediment, and the directivity constant of a sparker source is estimated (≈ 0.2), which is defined as the amplitude ratio between horizontally propagating seismic waves and vertically propagating seismic waves. The resulting relationship between the seafloor reflectivity and the sediment type is consistent with those of previous research, indicating the feasibility of our procedure.

While the CuBi2O4-based photocathode has emerged as an ideal candidate for photoelectrochemical water splitting, it is still far from its theoretical values due to poor charge carrier transport, poor electron–hole separation, and instability caused by self-photoelectric-corrosion with electrolytes. Establishing synthesis methods to produce a CuBi2O4 photocathode with sufficient cocatalyst sites would be highly beneficial for water splitting. Here, the platinum-enriched porous CuBi2O4 nanofiber (CuBi2O4/Pt) with uniform coverage and high surface area was prepared as a photocathode through an electrospinning and electrodeposition process for water splitting. The prepared photocathode material was composed of a CuBi2O4 nanofiber array, which has a freestanding porous structure, and the Pt nanoparticle is firmly embedded on the rough surface. The highly porous nanofiber structures allow the cocatalyst (Pt) better alignment on the surface of CuBi2O4, which can effectively suppress the electron–hole recombination at the electrolyte interface. The as-fabricated CuBi2O4 nanofiber has a tetragonal crystal structure, and its band gap was determined to be 1.8 eV. The self-supporting porous structure and electrocatalytic activity of Pt can effectively promote the separation of electron–hole pairs, thus obtaining high photocurrent density (0.21 mA/cm2 at 0.6 V vs. RHE) and incident photon-to-current conversion efficiency (IPCE, 4% at 380 nm). This work shows a new view for integrating an amount of Pt nanoparticles with CuBi2O4 nanofibers and demonstrates the synergistic effect of cocatalysts for future solar water splitting.

The performance of lead halogen perovskite is often closely related to its crystal structure. However, the chemical and optoelectronic properties of tetragonal phase single crystal MAPbCl3 (SC T-MAPbCl3) are rarely reported. In this study, we synthesized SC T-MAPbCl3 with the P4/mcc (124) space group by a modified inverse temperature crystallization (M-ITC) method. The twist angle of the Cl anion on the equatorial plane of the PbCl64- octahedron around the c-axis is 8.4°. The resistance (62 MΩ) of SC T-MAPbCl3 obviously decreased to 3 MΩ under 395 and 404 nm ultraviolet light. The photodetector based on SC T-MAPbCl3 under 3 V bias voltage exhibits high sensitivity (2.60 μA cm-2 under 1 W m-2 light intensity). The high selectivity of the device is in the ultraviolet region, rather than the visible region.

Multi-phase permanent-magnet (PM) motor is a competitive candidate for application where uninterrupted operation is demanded under fault condition. However, double-phase open-circuit or short-circuit faults result in serious problems, such as high fluctuating-torque, deteriorated dynamic performance, even breakdown. This paper proposes a novel unified decoupling vector control strategy to restrain torque fluctuations and improve dynamic performance for a five-phase PM motor with arbitrary double-phase failures. The novelty of the proposed strategy is the development of reduced-order orthogonal transformation matrices and remedies voltages, and then the smooth operation with vector control strategy can be achieved under double-phase open-circuit or short-circuit fault condition. The decoupled motor model in the synchronous rotating frame is achieved by the combination of the reduced-order orthogonal transformation matrices deduced from the optimal fault-tolerant currents and the remedy voltages. The torque fluctuations cancellation is achieved by the remedy voltages. This control strategy exhibits the improved dynamic performance with smooth torque of the faulty PM motor. The experimental results are presented to verify the feasibility of the proposed strategy.

The control of surface elements and nanostructures is one of the effective ways to design and synthesize high performance catalysts. Herein, we, for the first time, prepare FeS2 crystal lattices on WS2 nanosheets (FeS2 CL@WS2 NS) by solvothermal methods for the oxygen evolution reaction (OER). The FeS2 CLs effectively prevent the oxidation and aggregation of WS2 nanosheets and increase the electrochemically active surface area. The abundant surface defect in the FeS2 CL@WS2 NS electrocatalyst reduces the stress between the crystal lattices of FeS2 and that of WS2. The overpotential (260 mV) of the FeS2 CL@WS2 NS electrocatalyst for the OER at a current density of 10 mA cm-2 is superior to those of WS2 NS/Ni foam (310 mV) and IrO2/Ni foam (300 mV) in 1.0 M KOH solution. An electrochemical-kinetic study shows that the Tafel slope of 54 mV per decade for the FeS2 CL@WS2 NS electrocatalyst is lower than those of WS2 NS (102 mV per decade) and IrO2/Ni foam (77 mV per decade). In addition, the charge transport resistor (2.3 Ω) of the FeS2 CL@WS2 NS electrocatalyst for the OER is smaller than that of WS2 NS. These faster kinetic properties, in turn, explain the high catalytic activity of the FeS2 CL@WS2 NS electrocatalyst for the OER. The XPS and HRTEM results of the post stability sample confirm that Fe2+ and W4+ are oxidized after durability measurement. Thus, we think that the FeS2 CL@WS2 NS electrocatalyst is a promising candidate for efficient, low-cost, and stable non-noble-metal-based OER electrocatalysts.

Photodetectors play a key role in the military, aerospace, communications, bio-imaging, etc. In this study, we fabricate photodetector devices based on (CH3NH3)2FeCuI4Cl2 (MA2FeCuI4Cl2) and (CH3NH3)2InCuI6 (MA2InCuI6) for the first time. We find that the device based on MA2InCuI6 is highly selective for ultraviolet light (880 nA mW-1) and shows high anti-interference for visible-light (20-50 nA mW-1). The electrochemical impedance results indicate that the value (480 ± 10 Ω) of the resistance based on the MA2InCuI6 photodetector device is much smaller than that (1 ± 0.001 MΩ) based on the MA2FeCuI4Cl2 photodetector device, which in turn proves the difference in photoelectric response.

Exploration of cost-efficient and high-performance photocatalyst for H2 evolution by using a facile approach is of great importance. In this manuscript, a facile one-pot method was employed to fabricate MoS2/CdS heterostructures with MoS2 intimately grown on the surface of CdS resulting in the formation of well-defined heterostructures. Screen experiment reveals the optimized photocatalytic H2 evolution performance of MoS2/CdS is far exceeding that of pristine CdS by a factor of more than 162. The outstanding performance can be ascribed to the formation of heterostructures which accelerate charge transportation and separation, and the MoS2 serving as a cocatalyst for the decrease of H2 overpotential. Moreover, the photocatalytic mechanism of the MoS2/CdS was carefully investigated, which contributes to the deep understanding of the photocatalytic process and the designation of other low-cost and high-efficient photocatalyst.

MoO 2 and MoO 3 with specific morphologies are synthesized on flexible carbon cloth through a facile hydrothermal method as supercapacitor electrodes. The prepared prismatic MoO 3 shows a specific capacitance of 54.7 F g −1 in 1 M LiOH electrolyte. Moreover, the prepared MoO 2 presents a spherical profile with hierarchical porous structure. Each MoO 2 sphere is stacked with several layers of MoO 2 “spindle” which is further built by amounts of MoO 2 nanoparticles. A high specific capacitance of 381.0 F g −1 is achieved for the MoO 2 sphere electrode, 7 times higher than that of MoO 3 .

The semi-transparent solar cells are promising to be applied in building integrated photovoltaic (BIPV) and tandem solar cells. In this study, we fabricate semi-transparent and stable solar cells for BIPV by utilizing a poly (ethylene oxide) electrolyte and controlling the size of TiO2 nanoparticles and the thickness of the TiO2 film. The power conversion efficiency of the semi-transparent (over 50% transmittance at 620-750 nm) and quasi-solid solar cells is 5.78% under standard AM1.5G, 100 mW cm-2. The higher conductivity and smaller diffusion resistance of the quasi-solid electrolyte inside the mesoporous TiO2 film indicate the confinement effects of the polymer electrolyte inside a mesoporous TiO2 film. The unsealed semi-transparent and quasi-solid solar cell retains its initial efficiency during 1000 h irradiation in humid air.

Ocean-Bottom Node (OBN) acquisitions provide both non-converted and converted reflection energy. There is a clear advantage to independently imaging both P- and S-waves, as they provide more information collectively than either does alone. In many conventional converted-wave pre-stack migration algorithms, density is treated as a constant, which is not the real-life case on earth. S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of pore-filling fluids. In this paper, we focused on the effect of density on imaging, and developed a method of reverse-time migration (RTM) on converted s-waves of varying densities (VD-RTMCS). Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources. Synthetic data examples showed that when density variations were included, image profiles showed advantages in signal-to-noise ratio, vertical resolution and imaging of complex structures.

A novel kind of hollow carbon spheres with artificial surface openings is fabricated as highly effective supercapacitor electrode. This kind of carbon sphere possesses typical hierarchical mesoporous structure with surface area of 670.0 m2 g−1, much higher than that of the conventional hollow carbon spheres and solid carbon spheres. The electrochemical performance of the prepared hollow carbon spheres with surface openings, hollow carbon spheres and solid carbon spheres electrode are evaluated in acidic aqueous electrolyte. The hollow carbon sphere with surface openings electrode shows the optimal capacitive performance due to the specific surface openings and hierarchical mesoporous structure which can provide a large ion-accessible surface area and a loose channel for the electrolyte ions to diffuse into the internal of the spheres, making the internal charge storage sites work more effectively. The hollow carbon spheres with surface openings electrode achieves a remarkable specific capacitance of 272.2 F g−1, much higher than that of the hollow carbon spheres and solid carbon spheres. Besides, the hollow carbon spheres with surface openings preserves 96.9% of its initial capacitance after 10000 charge-discharge cycles, suggesting a perfect cycle life.

V2O3@activated carbon (V2O3@C) composite catalysts with different mass ratios have successfully been fabricated using a facile one-step the reduction of ammonium vanadate (NH4VO3) with AC in a high-temperature solid-state reaction. V2O3@C composites were further served as catalytic materials for counter electrodes (CEs) in encapsulation of dye sensitized solar cells (DSSCs). The morphology and microstructure of each V2O3@C composite were determined by scanning electron microscopy and X-ray diffraction. Cyclic voltammetry studies revealed that the V2O3@C composites showed a higher electrocatalytic activity than AC and V2O3 for the reduction of triiodide ions. Electrochemical impedance spectroscopy and Tafel analysis data for the symmetrical cells indicated a lower charge transfer resistance and higher exchange current density for V2O3@C composite than AC and V2O3. The experimental results showed that power conversion efficiencies (PCE) of 4.94, 5.55 and 5.32% were obtained for AC:NH4VO3 mass ratios of 1:3, 2:3 and 4:3 as counter electrode toward the reduction of I3−/I− ions respectively, which were superior to higher than that of AC (2.10%) and V2O3 (3.33%) electrode under the same conditions. The enhanced electrode performance can be ascribed to the combined effects of the relatively larger surface area and higher conductivity of V2O3@C composite catalysts.

The structure, mobility and memristor properties of tetragonal CH3NH3PbBr3 single crystals (T-MAPbBr3 SC) are rarely reported. In this study, we synthesized T-MAPbBr3 SC with the P4/mmm (123) space group by the growing, dropping and growing (GDG) crystal seed method. A CH3NH3+ cation is a disordered state in T-MAPbBr3 SC. The mobility values of T-MAPbBr3 SC under light and dark conditions are 464.28 and -1685.3 cm2 V-1 s-1, respectively. The carrier types under light and dark conditions are holes and electrons, respectively. The memristor based on T-MAPbBr3 SC has a wide and low operating voltage window (0-0.9 V). The high and low resistances of the memristor based on T-MAPbBr3 SC achieve values of 41 and 0.35 GΩ, respectively. The values of high and low resistances are relatively stable for 100 cycles. Thus, the memristor device based on T-MAPbBr3 SC has good applications in the field of memristors.

Linear-rotary permanent magnet (PM) actuator is a type of multi degree of freedom actuators, which can be widely applied in many fields such as car driving, drilling process. This paper proposes a novel linear-rotary fault-tolerant consequent-pole (CP) PM actuator for an integrated electromagnetic suspension and steering system. The key of the proposed actuator is the special stator and CP rotor. Combined the alternating arrangement structure of armature teeth and fault-tolerant teeth, two sets of orthogonal fractional-slot concentrated-windings embedded in the adjacent slot of armature teeth are employed to achieve linear and rotary motion and their decoupling control, and enhance fault-tolerant capability. By employing CP and flux-modulation structures, not only the airgap flux density can be enhanced along circumferential direction but also higher torque performance with lower PM consumption can be achieved. The relevant electromagnetic performance is predicted by using the finite-element method.

In this study, for the first time, self-driven photodetector based on cubic CH3NH3PbI3 large single crystal (C-MAPbI3 LSC) with adjustable positive-negative signal is fabricated. The preparation of MAPbI3 large single crystal (MAPbI3 LSC) is realized by the method of growth-drop-growth (GDG). The band gap of MAPbI3 single crystals with Pm-3m (221) space group (6.134×6.134×6.134 Å, 90.00 x 90.00 x 90.00) is 1.58 eV. CH3NH3+ cation is orientation-disorder within the perovskite cubo-octahedral cavity. The photocurrent density at 803 nm of the C-MAPbI3 LSC photodetector under different bias voltages is the highest under different wavelength. The responsivities (R), response time, external quantum efficiencies (EQE) and the detectivity (D) for C-MAPbI3 LSC photodetector at 803 nm wavelength with 1 W m-2, respectively, is 508.7 µA/mW, 0.1338 ms, 79.6% and 8.64*1011 Jones. Notably, the C-MAPbI3 LSC photodetector can be self-driven under 0 V bias voltage, in particular, the positive and negative values of the photocurrent can be adjusted. The proposed mechanism of poling inducing built-in potential is explained adjustable positive-negative signal in self-driven photodetector based on cubic CH3NH3PbI3 large single crystal.

Ion exchange of organic-inorganic hybrid perovskite plays an important role in controlling the performance of materials ant its devices. In this study, we found an interesting phenomenon that the precipitate in the in suspension (CH3NH3PbI3-xBrx in γ – butyrolactone) presented different colors at high and room temperature. The mechanism study shows that the phenomenon is controlled by temperature sensitive and reversible halide ion exchange in organic-inorganic hybrid CH3NH3PbI3-xBrx mixed-halide perovskite. The results of structure phase, element composition morphology and band gap indicate that high temperature 55 °C is beneficial to the increasing of I content in MAPbI3-xBrx and room temperature or lower is beneficial to increasing of Br content in MAPbI3-xBrx.measurement were carried out. Compared with MAPbI0.76Br2.24 precipitate obtained at room temperature, MAPbI1.17Br1.83 precipitate obtained at high temperature exhibit wider lattice spacing, better crystallinity, better morphology and narrower band gap. The results and findings in this study will arouse the interest of readers or experts in the field of organic-inorganic hybrid perovskite materials and related optoelectronic applications.

The surface treatment method has a great influence on the structure and properties of applied materials for interface catalysis. In this study, we prepare Ni(OH)2·NiO/FeOOH by surface treatment in acid solution using oxidation-corrosion equilibrium (OCE). For comparison, we also treat Ni foam with the same process in alkaline solution. Ni(OH)2·NiO/FeOOH can arrive steady-morphology and metallization by oxidation-corrosion equilibrium and exhibits superior catalytic activity as water oxidation catalyst. Ni(OH)2·NiO/FeOOH(OCE) needs only 232 mV to reach a current density of 10 mA cm-2, while it is 254 mV for a reference IrO2/Ni foam. The mechanism study shows that the small charge transfer resistance (2.04 Ωcm2) is favorable for the rapid interface electron exchange between Ni(OH)2·NiO/FeOOH(OCE) and reactive species in water oxidation. In addition, the results of X-ray photoelectron spectroscopy and series impedance show that the catalyst is metallic property in virtue of exposed mental Ni in Ni(OH)2·NiO/FeOOH(OCE). The volume ratio of hydrogen to oxygen (about 2:1) indicates overall water splitting by the double electrode system. When the volume ratio of hydrogen to oxygen is 2:1, the Faraday efficiency of H2 or O2 is close to 100%. Ni(OH)2·NiO/FeOOH(OCE) exhibits good stability for one month. The research results provide a feasible approach for finding low cost metallized catalysts to replace noble metal as water oxidation catalysts and improving the efficiency of water splitting.

The free-surface related multiples of submarine seismic data are very serious. At present, the method to deal with such multiples is to combine the pressure component and vertical velocity component first and then use the conventional multiple suppression technology applied to tow-streamer data. In this paper, a multiple separation method for submarine seismic data on both sides is developed, that is, multiples on detection side are separated by P Z summation and then multiples waves on source side are separated by deconvolution of up-going wave and down-going wave. This method is fully data-driven and has the advantages of fast operation and high computational efficiency. Theoretical models verify the method and satisfactory separation effect is obtained.

Ship parametric roll is one of the main reasons for marine accidents and is introduced into the second-generation intact stability criteria by the International Maritime Organization (IMO) recently. In this paper, a 6-DOF three-dimensional time-domain model based on the IRF (Impulse Response Function) method is constructed to predict large-amplitude ship motions and investigate the phenomenon of parametric roll in head waves as well as major factors. The F-K forces and the restoring forces are calculated on the instantaneous wet surface while the radiation and diffraction forces are kept linear and transformed from frequency-domain results calculated with the three-dimensional Havelock form translating-pulsating source green function method. The proposed weakly nonlinear time-domain model is used to simulate motions of the C11 containership, which predicts the occurrence of the parametric roll successfully and shows a good agreement with the experimental data in amplitude. The inner mechanism of parametric roll is revealed by investigating the time-history and resonance frequencies of restoring forces and coefficients numerically.

The control of surface elements and nanostructures is one of the effective ways to design and synthesize high performance catalysts. Herein, we, for the first time, prepare FeS2 crystal lattices on WS2 nanosheets (FeS2 CL@WS2 NS) by solvothermal methods for the oxygen evolution reaction (OER). The FeS2 CLs effectively prevent the oxidation and aggregation of WS2 nanosheets and increase the electrochemically active surface area. The abundant surface defect in the FeS2 CL@WS2 NS electrocatalyst reduces the stress between the crystal lattices of FeS2 and that of WS2. The overpotential (260 mV) of the FeS2 CL@WS2 NS electrocatalyst for the OER at a current density of 10 mA cm-2 is superior to those of WS2 NS/Ni foam (310 mV) and IrO2/Ni foam (300 mV) in 1.0 M KOH solution. An electrochemical-kinetic study shows that the Tafel slope of 54 mV per decade for the FeS2 CL@WS2 NS electrocatalyst is lower than those of WS2 NS (102 mV per decade) and IrO2/Ni foam (77 mV per decade). In addition, the charge transport resistor (2.3 Ω) of the FeS2 CL@WS2 NS electrocatalyst for the OER is smaller than that of WS2 NS. These faster kinetic properties, in turn, explain the high catalytic activity of the FeS2 CL@WS2 NS electrocatalyst for the OER. The XPS and HRTEM results of the post stability sample confirm that Fe2+ and W4+ are oxidized after durability measurement. Thus, we think that the FeS2 CL@WS2 NS electrocatalyst is a promising candidate for efficient, low-cost, and stable non-noble-metal-based OER electrocatalysts.

The performance of lead halogen perovskite is often closely related to its crystal structure. However, the chemical and optoelectronic properties of tetragonal phase single crystal MAPbCl3 (SC T-MAPbCl3) are rarely reported. In this study, we synthesized SC T-MAPbCl3 with the P4/mcc (124) space group by a modified inverse temperature crystallization (M-ITC) method. The twist angle of the Cl anion on the equatorial plane of the PbCl64- octahedron around the c-axis is 8.4°. The resistance (62 MΩ) of SC T-MAPbCl3 obviously decreased to 3 MΩ under 395 and 404 nm ultraviolet light. The photodetector based on SC T-MAPbCl3 under 3 V bias voltage exhibits high sensitivity (2.60 μA cm-2 under 1 W m-2 light intensity). The high selectivity of the device is in the ultraviolet region, rather than the visible region.

In recent years, permanent magnet vernier (PMV) machines have been attracting more and more attention due to the inherently exhibited advantages such as high torque density and simple mechanical structure. In this paper, a consequent pole (CP) PMV machine with single-layer concentrated winding is proposed. The novelty is that the asymmetric air-gap field distribution is introduced to improve its working harmonics and to reduce the PM consumption. By employing a CP structure, the flux density amplitude can be enhanced. Moreover, due to uneven distribution of modulator poles on the armature teeth and fault tolerant teeth, the number of periods of modulator poles is only half of that of the stator teeth. Then, significant improvement in flux density working harmonics can be achieved. Furthermore, the superior electromagnetic decoupling capability can be achieved by introducing the fault-tolerant teeth. The relevant electromagnetic performance such as flux density, back electromotive forces, cogging torque and on-load torque have been calculated by using finite-element analyses, which have also been validated by experiments.

While bismuth vanadate (BiVO4) has emerged as a promising photoanode in solar water splitting, it still suffers from poor electron-hole separation and electron transport properties. Therefore, the development of BiVO4 nanomaterials that enable performing high charge transfer rate at the interface and lowering charge recombination is urgent needed. Herein, cobalt borate (Co-B) nanoparticle arrays anchored on electrospun W-doped BiVO4 porous nanotubes (BiV0.97W0.03O4) was prepared for photoelectrochemical (PEC) water oxidation. One-dimensional, free-standing and porousBiV0.97W0.03O4/Co-B nanotubes was synthesized through electrospun and electrodeposition process. BiV0.97W0.03O4/Co-B arrays exhibit a unique self-supporting core-shell structure with rough porous surface, providing abundant conductive cofactor (W) and electrochemically active sites (Co) exposed to the electrolyte. When applied to PEC water oxidation. BiV0.97W0.03O4/Co-B modified FTO electrode displays high incident photon-to-current conversion efficiency (IPCE) of 33% at 405 nm (at 1.23 V vs. RHE) and its photocurrent density is about 4 times to the pristine nanotube. The higher PEC water oxidation properties of BiV0.97W0.03O4/Co-B porous nanotubes may be attributed to the effectively suppress the electron-hole recombination at electrolyte interface due to its self-supporting core-shell structure, the high electrocatalytic activity of Co and the good electrical conductivity of BiV0.97W0.03O4 arrays. This work offers a simple preparation strategy for the integrated Co-B nanoparticle with BiV0.97W0.03O4 nanotube, demonstrating the synergistic effect of co-catalysts for PEC water oxidation.

In this study, all-inorganic copper halide salt K2Cu2Cl6 single-crystal and thin films were prepared. The single-crystal diffraction data belonged to the monoclinic K2Cu2Cl6 (space group = P2(1)/C, unit cell parameters of a = 4.0340 A, b = 13.7987 A, c = 8.7445 A, α = 90.000, β = 97.123, and γ = 90.000). As far as we know, this is the first study of the copper halide salt K2Cu2Cl6 for optoelectronic applications. The band gap of K2Cu2Cl6 is calculated to be approximately 1.85 eV. A low-cost photodetector based on the K2Cu2Cl6 thin film was efficient under different monochromatic light from 330 to 390 nm with different chopping frequencies (1.33–30 Hz). Density functional theory (DFT) computational results indicate that the valence bands (VBs) and conduction bands (CBs) are shifted up in energy using the orbital-dependent correction to the DFT energy. Partial density of states reveals that the VBs and narrow CBs are derived from the hybrid orbitals of Cu2+ 3d and Cl– p, respectively.