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Amorphous aerogels with the microscopic nanoscale three-dimensional meshes provide superb platforms for investigating unique physicochemical properties. In order to enhance the physical, thermal and mechanical performances, one efficient and common approach is integrating diverse functional materials. Herein, we report a simple strategy to fabricate the amorphous silicon doped Y2O3 aerogels with the post-gelation method under the N2/EtOH supercritical atmosphere. The impact of Si concentration on the nonlinear optical properties is investigated for the first time. The maximum modulation depth is 1.65 % with a saturation intensity of 0.78 MW cm−2 with the 1-ps laser excitation at 1590 nm. Finally, we incorporated the silicon-doped Y2O3 aerogel based saturable absorber (SA) into an erbium-doped fiber laser (EDFL) and achieved various mode-locking operations at different wavelengths in the super C band, in terms of the conventional soliton, harmonic soliton molecules pulses, and dual-wavelength soliton mode-locking. Overall, this work confirms that amorphous silicon-doped Y2O3 aerogels are good nonlinear optical materials and pave a way for the ultrafast photonic and nonlinear optical applications with amorphous materials in near future.

Ultralow-density (35–60 mg·cm–3) Yb2O3 nanofibrous membranes (YbFMs) with a multilayer structure were successfully prepared for the first time using Yb-acetylacetone coordination polymer as a precursor. Thanks to the high ceramic yield (62.1%) and excellent spinnability of the precursor, the YbFMs exhibited outstanding flexibility, which does not cause damage even when bent or knotted. The tensile strength of the YbFMs was 1.69 MPa, and the maximum elongation could reach 33%. Notably, the YbFMs exhibited robust fatigue resistance, retaining 87.2% of the initial stress even after 500 buckling cycles and preserving 84.75% of the initial stress in compression resilience. Moreover, the YbFMs exhibited flexibility and compressive performance in the temperature range of −196–1350 °C. The thermal conductivity of the YbFMs was 28.9–34.6 mW·m–1·K–1. At a hot surface temperature of 1350 °C, the 6 mm thick YbFMs could reduce the back temperature by about 1070 °C. Thus, YbFMs are expected to be a flexible insulation material at extremely high temperatures. [ABSTRACT FROM AUTHOR]

Amorphous aerogels with the microscopic nanoscale three-dimensional meshes provide superb platforms for investigating unique physicochemical properties. In order to enhance the physical, thermal and mechanical performances, one efficient and common approach is integrating diverse functional materials. Herein, we report a simple strategy to fabricate the amorphous silicon doped Y2O3 aerogels with the post-gelation method under the N2/EtOH supercritical atmosphere. The impact of Si concentration on the nonlinear optical properties is investigated for the first time. The maximum modulation depth is 1.65 % with a saturation intensity of 0.78 MW cm−2 with the 1-ps laser excitation at 1590 nm. Finally, we incorporated the silicon-doped Y2O3 aerogel based saturable absorber (SA) into an erbium-doped fiber laser (EDFL) and achieved various mode-locking operations at different wavelengths in the super C band, in terms of the conventional soliton, harmonic soliton molecules pulses, and dual-wavelength soliton mode-locking. Overall, this work confirms that amorphous silicon-doped Y2O3 aerogels are good nonlinear optical materials and pave a way for the ultrafast photonic and nonlinear optical applications with amorphous materials in near future. [ABSTRACT FROM AUTHOR]

Cigarette defect detection is important in industrial production. Existing methods extract features for defect detection manually or using deep learning. However, due to the small size of cigarette defects, these methods are unable to effectively extract discriminative features, limiting detection performance. Hence, a deep learning‐based method called significant feature‐guided cigarette defect detection (SFGCD) is proposed, which combines saliency feature extraction methods with deep learning to enhance feature representation and improve detection. First, edge saliency features are extracted using the proposed target gradient saliency feature extraction (GSFE) strategy. Then, a dense multi‐level feature fusion network is designed to combine the original features with the saliency features obtained from the target gradient saliency feature extraction strategy. This network enriches feature representation and improves detection by fusing original and saliency features at different levels and scales. Experimental results demonstrate that the proposed method achieves a higher accuracy of 0.02 mean average precision (MAP) value and a detection speed of 5 frames per second (FPS) on the authors' own labeled cigarette defect dataset compared to existing state‐of‐the‐art methods. [ABSTRACT FROM AUTHOR]

Taking the high⁃voltage disconnector of the GW46 type as research object, this research first use Solidworks to build its three-dimensional simplified model, then use ABAQUS to simulate the mechanical characteristics of the disconnector over a wide temperature range, analyzing the influence of the clamping force between the dynamic and static contacts on temperature, the contact pressure between the dynamic and static contacts of the high⁃voltage disconnector of the GW46 type increases with the ambient temperature, and the contact pressure becomes smaller. Compared simulation results with experimental data, the error is less than 5%. Analysis shows that using the ABAQUS to simulation analysis of temperature rise of the high⁃voltage disconnector of the GW46 type, it can be determined that the contact pressure between the dynamic and static contacts changes with temperature. It avoids the complexity of the traditional theoretical calculation of query parameters and tedious calculations, and provides strong reference evidence for improving the reliability of the high⁃voltage disconnector of the GW46 type.

In order to solve the problem of self-energy supply of vehicle-mounted micro-sensors, bridge detection and some other low-power electronic devices in their working state, a vortex-induced flutter composite nonlinear piezoelectric energy harvester (VFPEH) with symmetrical airfoils on both sides of a cylindrical bluff body is designed. The VFPEH consists of a cantilever beam, a cylindrical bluff body connected to the free end of the cantilever beam, and two airfoil components symmetrically fixed at both ends of the shaft, which enables coupling between vortex-induced vibration and flutter. The airfoil symmetrically arranged on both sides of the cylindrical bluff body induces the cantilever beam to produce bending and torsional composite vibrations at high wind velocities, realizing energy harvest in the two degrees of freedom motion direction, which can effectively improve the output power of the energy harvester. Based on a wind tunnel experimental platform, the effect of key parameters matching impedance and the diameter of the cylindrical bluff body on the output performance of the VFPEH is investigated, together with the output performance of the classical vortex-induced energy harvester (VEH), the flutter energy harvester (FEH) and the VFPEH. The experimental results show that for the VFPEH under a combination of vortex-induced vibrations and flutter vibrations has a better output performance than the VEH and the FEH when using the same size. The coupling of vortex-induced vibration and flutter can reduce the start-up wind velocity of the VFPEH and expand the wind velocity range of the high output power of the VFPEH. The VFPEH has a better output performance at the cylindrical bluff body diameter of 30 mm and a load resistance of 140 kΩ. When the wind velocity range is 2 m/s–15 m/s, the maximum output power of the VFPEH is 6.47 mW, which is 129.4 times and 24.9 times of the maximum output power of the VEH (0.05 mW) and FEH (0.26 mW), respectively. [ABSTRACT FROM AUTHOR]

In order to solve the demand for low-power microcomputers and micro-electro-mechanical system components for continuous energy supply, a magnetic coupling piezoelectric–electromagnetic composite galloping energy harvester (MPEGEH) is proposed. It is composed of a piezoelectric energy harvester (PEH) and an electromagnetic energy harvester (EEH) coupled by magnetic force. The bistable nonlinear magnetic coupling structure improves the output power of the MPEGEH. The advantages and output performance of the MPEGEH are analyzed. The prototype of the energy harvester is made, and the nonlinear output characteristics under different load resistances are analyzed. Through the experiment on the key parameters of the composite energy harvester, it is found that the higher the coupling degree of the two parts of the MPEGEH, the stronger the nonlinear characteristics and the better the output characteristics. The results show that the onset wind velocity and output power of the MPEGEH are better than the classic galloping piezoelectric energy harvester (CGPEH). At the same wind speed, with the increase in the distance d0 between magnets A and B, the output power of both the PEH and the EEH decreases. When d0 is 37 mm, the output power of the EEH is the largest. The distance s0 between magnets B and C has little influence on the output power of the PEH but has a great influence on the EEH. When s0 is 23 mm, the EEH has the best output characteristics. Compared with the CGPEH, the onset wind velocity is reduced by 28%, and the output power is increased by 136% when the wind speed is 11 m/s. [ABSTRACT FROM AUTHOR]

High CO2 concentration in atmosphere causes serious environmental issues, and carbon capture and storage technologies have attracted attention as a means to reduce the atmospheric CO2 concentration. Metal-organic frameworks (MOFs) can potentially be used for CO2 adsorption, but their poor stability and microporosity limit their applications. Herein, a novel strategy was proposed to combine a cellulose aerogel and hierarchically-porous MOFs (HP-MOFs) with larger pores. According to this strategy, a series of microcrystalline cellulose/HP-UIO-66-NH2 hybrid aerogels (MC-HUN-X) was constructed by adding a modulator (monocarboxylic acid, MA), followed by the in-situ growth of HP-UIO-66-NH2 on a cellulose aerogel. By adjusting the chain length of MA, the structure–function relationship between pore size and the CO2 adsorption capacity of MC-HUN-X was explored. The results showed that the CO2 adsorption capacity increased first and then decreased upon increasing the MOFs pore size, while the adsorption selectivity of CO2 continuously increased. Among all samples, MC-HUN-4 with a moderate pore size had the highest CO2 adsorption capacity (1.90 mmol/g at 298 K and 1 bar) and adsorption selectivity (13.02 and 2.40 for CO2/N2 and CO2/CH4). The combination with a cellulose aerogel endowed MC-HUN-X with excellent mechanical stability and reusability. Cellulose/HP-UIO-66-NH2 hybrid aerogel with larger aperture sizes of MOF showed excellent adsorption capacity and selectivity for CO2, and the combination with aerogel could effectively improve the mechanical stability and reusability. [ABSTRACT FROM AUTHOR]

To widen the operation wind speed bandwidth of a classic vortex shedding induced vibration piezoelectric energy harvester, a piezoelectric-electromagnetic hybrid energy harvester based on vortex shedding induced vibration is designed. The hybrid vortex shedding induced vibration energy harvester (HVSIVEH) includes a vortex shedding induced vibration piezoelectric energy harvester (VSIVPEH) and an electromagnetic vibration energy harvester (EVEH). The electromechanical coupled vibration model of the hybrid structure was established. By comparing the variations of the output power as a function of the wind speed of the HVSIVEH and the classic VSIVPEH, it is found that the power response curve of the HVSIVEH has two peaks. The hybrid structure can broaden the working wind speed range. The lower the requirement on the output power level, the more obvious the effect of widening the wind speed range. By the solution and analysis of the electromechanical coupled model, better values of related parameters of the HVSIVEH are obtained. The first and second peaks of the output power of the HVSIVEH show better values of 1.9 and 2.2 mW, respectively, under these parameters. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable photocatalysts is an effective method to achieve CO2 photocatalytic reduction. Herein, PI/WO3 aerogel photocatalyst was prepared by chemical amide reaction coupled with an ethanol supercritical drying technique. The novel aerogel photocatalysts exhibit excellent photocatalytic performance for reducing CO2 into CO. In particular, PI/WO3-10 aerogel photocatalyst shows the highest yield of CO (5.72 μmol g–1 h–1), which is ca 11-fold higher than that of the pristine PI aerogel. The high CO2 reduction activity can be attributed to the Z-scheme structure, which enhances the separation of photo-generated electron – holes, and induces H2O oxidation on WO3 nanosheets and CO2 reduction on PI aerogel. The photocatalytic reaction mechanism of CO2 when using PI/WO3 aerogel photocatalyst is proposed. [ABSTRACT FROM AUTHOR]

In order to study the influence of vehicle body vibration caused by road excitation on the output performance of a vehicle piezoelectric electromagnetic hybrid energy harvester, the theoretical analysis of the energy harvester is carried out, and a corresponding electromechanical coupling model is established. The hybrid energy harvester includes a flutter piezoelectric energy harvester (FPEH) and an electromagnetic vibration energy harvester (EVEH). Sweep frequency experiments and wind tunnel experiments were carried out to verify the correctness of the coupling model. By establishing the road-vehicle coupling differential equations solving module, the vehicle body vibration under different road surfaces was simulated, and the influence of different roads on output performance is analyzed. The results show that when vehicle body vibration is not considered, the cut-in speed of the harvester is 32 km h−1. When the vehicle speed is higher than 32 km h−1, vehicle body vibration caused by road roughness will suppress the overall output performance. When the vehicle speed is less than 32 km h−1, the vibration of the vehicle body will cause the energy harvester to have no obvious cut-in wind speed. And the higher the road level, the stronger the body vibration, and the better the output performance when the vehicle speed is less than 32 km h−1. Under E-class road with vehicle body vibration considered, it has already power output at a vehicle speed of 20 km h−1. When the vehicle speed reaches 57 km h−1, the output power of hybrid FPEH and EVEH reach 1.74 and 2.51 mW under E-class road (2.88 and 3.25 mW under A-class road), respectively. [ABSTRACT FROM AUTHOR]

In order to study the influence of structural parameters of longitudinal vibration ultrasonic transducer on the viscoelastic heat generation of polymers during the ultrasonic plasticization process, the composition of ultrasonic viscoelastic heat generation system was determined, and then the structure of longitudinal vibration ultrasonic transducer was designed. The ultrasonic viscoelastic heat generation process and the corresponding mechanisms were analyzed. A single variable method was adopted to investigate the influence of structural parameters of the transducer on the longitudinal vibration frequency and maximum amplitude of the particle at the front end of tool head. Finally, the longitudinal vibration excitation of the transducer was loaded on the molten polymers to study the effect of structural parameters on the ultrasonic viscoelastic heating process of the polymer and the time required for reaching its glass transition temperature. The results indicated that the polymer temperature increases nonlinearly with an increase of longitudinal vibration excitation time. The amplification ratio generated the much greater influence on the variation of polymer temperature than on the front cover thickness and tool head length, but there was the least influence on the horn length. [ABSTRACT FROM AUTHOR]

High‐strength zirconia (ZrO2) continuous fibers, which are potential candidates as ultra‐high temperature thermal insulators and reinforced materials, are typically fabricated by dry spinning an organozirconium precursor. However, the uncontrolled decomposition of organozirconium precursor usually occurs upon heat treatment that breaks the continuous fibers into pieces, resulting in the loss of tensile strength. Herein, in this contribution, we aimed to maintain the integrity of ZrO2 precursor fibers during heat treatment. For this purpose, novel high‐pressure vapor (HPV) pretreatment of ZrO2 precursor fiber was introduced. The HPV pretreatment is considered to be efficient for the removal of the organics in precursor, promoting the formation of amorphous structures of Zr(OH)4 and Zr(OH)3HCO3. Combining the studies of microstructures and tensile strengths, it was found that the amorphous structures played roles of cross‐linking points, keeping the fibers integrity during the followed heat treatment. After HPV pretreatment, the high‐strength ZrO2 continuous fibers would be obtained by direct sintering in air without any atmosphere which substantially lowered the cost. The tensile strengths of sintered ZrO2 continuous fibers pretreated by an optimized HPV procedure could reach up to as high as 1.299 GPa. The HPV pretreatment method provides a high‐efficiency, low‐cost technique for preparing high‐quality ceramic fibers. [ABSTRACT FROM AUTHOR]

TiO2/SiO2-Based nanocomposites with highly porous structures have received increasing attention due to their excellent photocatalytic activity. In this work, a TiO2/SiO2/Ag ternary composite aerogel with enhanced visible-light photocatalytic activity has been successfully synthesized through a facile sol–gel method combined with a supercritical drying technique. The specific surface area and pore structure of TiO2/SiO2/Ag aerogel could be controlled by adjusting the Si content. The TiO2/SiO2/Ag aerogel with pore size of 9.2 nm achieved the maximum adsorption capacity of oxytetracycline. The presence of SiO2 in TiO2/SiO2/Ag improved the compression strength of the aerogel and thus achieved long-term stability in photocatalysis. Furthermore, the addition of Ag particles in TiO2/SiO2/Ag effectively decreased the recombination of photo-electrons and holes. The photocatalytic degradation rates of oxytetracycline over the TiO2/SiO2/Ag aerogel with a mole ratio of Ag : Si : Ti = 0.1 : 10 : 4 were 3.1 and 2.3 times those over P25 and a TiO2/SiO2 aerogel. The enhanced photocatalytic performance of the TiO2/SiO2/Ag aerogel is attributed to the large specific surface area, 3-D porous structure, high electrical conductivity and compression strength of this novel composite aerogel. [ABSTRACT FROM AUTHOR]

Polyaceticzirconium (PEZ) sol, which is the precursor of zirconia (ZrO 2 ) continuous fibers, has been synthesized by means of the reaction between zirconium oxychloride octahydrate (ZrOCl 2 ·8H 2 O) and potassium acetate (CH 3 COOK) in methanol. The polymeric structures and the rheological behaviors of the sols with different molar ratios of ZrOCl 2 ·8H 2 O/CH 3 COOK are different and would affect the spinnability and stability significantly. Herein, the polymeric structures and rheological behaviors of the PEZ sols with the molar ratios of 1:1, 1:1.5, 1:1.8 and 1:2 were investigated by Fourier transform infrared (FT-IR), 1 H nuclear magnetic resonance spectrum ( 1 H-NMR), thermogravimetry and differential thermal analysis (TG/DTA) and rheological measurements. The results showed the carboxyl group acted as a chelating ligand instead of bidentate ligand, and the water molecule coordinated to Zr 4+ was deprotoned gradually with the decrease of the molecular ratios. The different polymeric structures lead to a different rheological behaviors of the sols. It is divided into three types, the Newton fluid with a low viscosity produced by the charged linear polymeric structures, the shear thinning fluid with a high viscosity produced by the three-dimensional polymeric structures and the shear thinning fluids with a proper viscosity produced by the linear twining polymeric structures. Through the experimental guidance, we successfully synthesized a sol with suitable viscosity and stability, and used it to fabricate high quality ZrO 2 fibers. [ABSTRACT FROM AUTHOR]

In the study, cetyltrimethyl ammonium bromide (CTAB) has been found to have a significant effect on the grain size of zirconia (ZrO 2 ) polycrystalline fibers from a precursor of polyacetylacetonatozirconium (PAZ). A relation between the variation in the grain size of the fibers sintered at 1000 °C for 1 h and CTAB addition has been established by scanning electron microscopy (SEM) and matching the results by a Gaussian Function. The grain size increased firstly and then decreased at an elevated weight percent of CTAB with respect to PAZ. ZrO 2 nucleation at 500 °C and grain growth during thermal treatment between 500 and 1000 °C were investigated by thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The results indicate that the addition of CTAB accelerated the decomposition of PAZ. The enhanced decomposition promoted ZrO 2 nucleation and the removal of residual carbon. While excess CTAB resulted in the increase of residual carbon on grain surface. The general kinetics of the grain growth was evaluated by Arrhenius equation and the results did matched well with the variation in grain size. [ABSTRACT FROM AUTHOR]