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In this paper, the optical and static permittivities of CaCu3Ti4O12 supercells are calculated based on the Skanavi model by decomposing the electric field of molecules into the electric field of ions. The results show that the Skanavi model's theoretical predictions are significantly more accurate than those of the Clausius–Mossotti equation and Born model and are in good agreement with the experimental data. In addition, the absence of ferroelectricity in CaCu3Ti4O12 is also revealed by investigating the changes in the structural coefficients of the effective electric field caused by the displacement of Ti4+ along the z-axis. Finally, by analyzing the contribution of TiO6 octahedra or CuO4 planar squares to the static permittivity, the main polarization unit in the structure of CaCu3Ti4O12 has been discovered. This study not only makes up for the insufficient research on the polarization mechanism of CaCu3Ti4O12 but also provides a new tool to explore the polarization mechanism of other materials. [ABSTRACT FROM AUTHOR]

Herein, the energy-storage performance of NaNbO3-based lead-free ceramics has been successfully reinforced by introducing Bi(Mg0.5Zr0.5)O3 to improve the breakdown strength (BDS) and suppress the remnant polarization (Pr). A superior discharge energy density (Wd) of 3.01 J cm−3 and an outstanding energy efficiency (η) of 90.2%, accompanied with high thermal stability of energy-storage performance ranging from 30 °C to 150 °C, have been concurrently recorded in 0.88NaNbO3-0.12Bi(Mg0.5Zr0.5)O3 ceramic at 320 kV cm−1. The results show that the introduction of Bi(Mg0.5Zr0.5)O3 can enhance BDS due to its considerable insulation, which is confirmed by the calculation of the band structure and the projected density of states. In addition, the remarkable current density (CD) of 644.51 A cm−2, preeminent power density (PD) of 38.68 MW·cm−3 and transient energy release times (t0.9) of 41.2 ns were also obtained in 0.88NaNbO3-0.12Bi(Mg0.5Zr0.5)O3 ceramic. Therefore, this study can significantly contribute to the application of NaNbO3-based ferroelectrics in advanced pulsed power systems. [ABSTRACT FROM AUTHOR]

The detection of masks is of great significance to the prevention of occupational diseases such as infectious diseases and dust diseases. For the problems of small target size, large number of targets, and mutual occlusion in mask-wearing detection, a mask-wearing detection algorithm based on improved YOLOv5s is proposed in this paper. First, the ultralightweight attention mechanism module ECA is embedded in the neck layer to improve the accuracy of the model. Second, the influence of different loss functions (GIoU, CIoU, and DIoU) on the improved model is explored, and CIoU is determined as the loss function of the improved model. Besides, the improved model adopted the label smoothing method, which effectively improved the generalization ability of the model and reduced the risk of overfitting. Finally, the influence of data augmentation methods (Mosaic and Mixup) on model performance is discussed, and the optimal weight of data augmentation is determined. The proposed model is tested on the verification set, and the mean average precision (mAP), precision, and recall are 92.1%, 90.3%, and 87.4%, respectively. The mAP of the improved algorithm is 4.4% higher than that of the original algorithm. [ABSTRACT FROM AUTHOR]

Piezocatalysis has attracted unprecedented research interest as a newly emerging catalysis technology. However, the inherent insulating property of ferroelectric materials ultimately leads to the poor vibration–electricity conversion ability. Herein, this work reports the (K0.52Na0.48)NbO3 ferroelectric ceramics (KNNFCx), for which the FeCo modification strategy is proposed. The substitution of the moderate amount of FeCo (x = 0.015) at Nb site not only optimizes ferroelectricity but also produces beneficial defects, notably increasing Rhodamine B water purification efficiency to 95%. The pinning effect of monovalent oxygen vacancies on ferroelectric domains is responsible for the excellent ferroelectric polarization of KNNFC0.015 through the generation of an internal field to promote charge carriers separation and reduce non-radiative recombination. Importantly, the accompanying electron carriers can easily move to the material surface and participate in redox reactions because they have low activation energy. Therefore, ferroelectric polarization and defects play synergetic roles in enhancing piezocatalytic performance. [ABSTRACT FROM AUTHOR]

The regular detection of weld seams in large-scale special equipment is crucial for improving safety and efficiency, and this can be achieved effectively through the use of weld seam tracking and detection robots. In this study, a wall-climbing robot with integrated seam tracking and detection was designed, and the wall climbing function was realized via a permanent magnet array and a Mecanum wheel. The function of weld seam tracking and detection was realized using a DeepLabv3+ semantic segmentation model. Several optimizations were implemented to enhance the deployment of the DeepLabv3+ semantic segmentation model on embedded devices. Mobilenetv2 was used to replace the feature extraction network of the original model, and the convolutional block attention module attention mechanism was introduced into the encoder module. All traditional 3×3 convolutions were substituted with depthwise separable dilated convolutions. Subsequently, the welding path was fitted using the least squares method based on the segmentation results. The experimental results showed that the volume of the improved model was reduced by 92.9%, only being 21.8 Mb. The average precision reached 98.5%, surpassing the original model by 1.4%. The reasoning speed was accelerated to 21 frames/s, satisfying the real-time requirements of industrial detection. The detection robot successfully realizes the autonomous identification and tracking of weld seams. This study remarkably contributes to the development of automatic and intelligent weld seam detection technologies. [ABSTRACT FROM AUTHOR]

Supported nanostructured photocatalysis is considered to be a sustainable and promising method for water pollution photodegradation applications due to its fascinating features, including a high surface area, stability against aggregation, and easy handling and recovery. However, the preparation and morphological control of the supported nanostructured photocatalyst remains a challenge. Herein, a one-step hydrothermal method is proposed to fabricate the supported vertically aligned ZnO nanosheet arrays based on aluminum foil. The morphologically controlled growth of the supported ZnO nanosheet arrays on a large scale was achieved, and the effects of hydrothermal temperature on morphologic, structural, optical, and photocatalytic properties were observed. The results reveal that the surface area and thickness of the nanosheet increase simultaneously with the increase in the hydrothermal temperature. The increase in the surface area enhances the photocatalytic activity by providing more active sites, while the increase in the thickness reduces the charge transfer and thus decreases the photocatalytic activity. The influence competition between the area increasing and thickness increasing of the ZnO nanosheet results in the nonlinear dependence between photocatalytic activity and hydrothermal temperature. By optimizing the hydrothermal growth temperature, as fabricated and supported ZnO nanosheet arrays grown at 110 °C have struck a balance between the increase in surface area and thickness, it exhibits efficient photodegradation, facile fabrication, high recyclability, and improved durability. The RhB photodegradation efficiency of optimized and grown ZnO nanosheet arrays increased by more than four times that of the unoptimized structure. With 10 cm2 of as-fabricated ZnO nanosheet arrays, the degradation ratio of 10 mg/L MO, MB, OFL, and NOR was 85%, 51%, 58%, and 71% under UV irradiation (365 nm, 20 mW/cm2) for 60 min. All the target pollutant solutions were almost completely degraded under UV irradiation for 180 min. This work offers a facile way for the fabrication and morphological control of the supported nanostructured photocatalyst with excellent photodegradation properties and has significant implications in the practical application of the supported nanostructured photocatalyst for water pollution photodegradation. [ABSTRACT FROM AUTHOR]

CeO and FeO co-modified titanate nanosheet (FeO/CeO@TNS) was prepared by one-pot hydrothermal method; the photocatalyst exhibited large surface area with CeO and FeO particles well dispersed on the surface. The results of XRD, BET, and Raman proved that the CeO and FeO introduced in the TNS influenced its structure evolution from 3D to 2D. The modification resulted in a shift of the absorption edge toward a longer wavelength and the band gap reduced to 2.87 eV. The three-component systems performed excellent photocatalytic activity and cycle stability on phenol and methyl blue (MB) solution under sunlight; nearly total phenol and MB were degraded in dozens of minutes. And the reaction rate constant ( K) of FeO/CeO@TNS on phenol degradation was 1.77, 3.25, 4.88, and 13-fold of FeO@TNS, CeO@TNS, bare TNS, and P25, respectively. The enhanced photocatalytic activity could be ascribed to the efficient separation of photogenerated pairs through the formation of tandem n-n-n heterojunction among the three-component systems. This work will be useful for the design of other tandem n-n-n heterojunction photocatalytic systems for application in energy conversion and environmental remediation. [ABSTRACT FROM AUTHOR]

A surfactant-free and facile one-pot synthetic route in the alkaline glycol system has been developed for the fabrication of Pt/metal oxide nanocomposites. The structure and chemical composition of the as-prepared products were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively coupled plasma-mass spectrometry (ICP-MS). It is found that the corresponding precursors have been completely converted into the Pt/metal oxide nanocomposites. As for Pt/ZnO nanocomposites, the Pt loading amount can be controlled by the different molar ratios of Pt and Zinc precursor, while Pt nanoparticle sizes can be adjusted through the different mass of NaHCO3added. In addition, the catalytic activities of Pt/metal oxide nanocomposites for glycerol hydrogenation were also studied. When the amount of platinum metal was kept constant, different metal oxide supporters demonstrated different levels of catalytic activation. The diverse reason of the catalytic activation for the different Pt/metal oxide nanocomposites was also speculated. [ABSTRACT FROM AUTHOR]

A series of holmium-doped TiO2-based nanosheet (Ho-TNS) photocatalysts with different Ho/Ti molar ratios were prepared via a simple hydrothermal method. The photocatalysts were characterized by field-emission scanning electron microscope, high-resolution transmission electron microscope, X-ray diffraction (XRD), Raman Spectroscopy, X-ray photoemission spectroscopy, nitrogen adsorption-desorption isotherm measurement, ultraviolet-visible light diffuse reflectance spectra (DRS), and fluorescence spectra (FL). The TEM images of Ho-TNS exhibit clearly sheet-like structures and existence of the (201) plane of H2Ti3O7. The increased (101) peak intensity in XRD spectrum and the enhanced Eg mode (141 cm-1) in Raman spectrum indicate that Ho doping has obvious influence on the formation and structure of Ho-TNS, which can be explained by the formation of Ho-O-Ti bonds. With the doping ratio (Ho/Ti molar ratio) increasing from 0 to 2.0 %, the absorption edge shifts to a longer wavelength, and the band-gap of photocatalysts reduces from 3.18 to 3.07 eV. The decline of FL intensity implies that the photocatalysts with higher Ho content have higher electron-hole separation efficiency. However, after Ho doping, the surface structure of specimens is significantly altered, which will lead to the specific surface areas and adsorption capacity decrease. Under the combined effect of the variables, the photocatalyst with a doping ratio of 1.0 % reaches the best photoactivity, which is 1.90-fold and 12.38-fold higher compared with undoped TNS and P25 under visible light, respectively. The high photoactivity of the prepared Ho-TNS indicates that it may be useful for dealing with wastewater. [ABSTRACT FROM AUTHOR]

Self-supporting nanoporous InP membranes are prepared by electrochemical etching, and are then first transferred to highly reflective (> 96%) mesoporous GaN (MP-GaN) distributed Bragg reflector (DBR) or quartz substrate. By the modulation of bandgap, the nanoporous InP samples show a strong photoluminescence (PL) peak at 541.2 nm due to the quantum size effect of the nanoporous InP structure. Compared to the nanoporous InP membrane with quartz substrate, the nanoporous membrane transferred to DBR shows a twofold enhancement in PL intensity owing to the high light reflection effect of bottom DBR. [ABSTRACT FROM AUTHOR]