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Most of the frame structures in mechanical equipment are connected by bolts, and the non-uniform pretension among the bolts will have an obvious impact on the vibration characteristic parameters of the frame structure. In this paper, semi-analytical modeling and vibration analysis of a frame structure considering non-uniform pretension of bolts are carried out based on the Timoshenko beam theory and Rayleigh-Ritz method. Specifically, a method is proposed to decompose the frame structure into several substructures and model them respectively, and further the coupling springs are applied among the substructures. Through the vibration test of a beam lap structure with a bolted joint, the analytical expressions between bolt pretension and bolted joint stiffness and damping parameters are obtained. Moreover, the method of simulating the non-uniform pretension among each bolted joint is proposed. Considering the external factors such as reinforcing rib structures and flexible rod exciter, and a complete semi-analytical dynamic model of the bolted frame structure introducing the non-uniform pretension is further established. A case study is carried out on a frame structure that contains four connecting bolts with non-uniform pretension. The natural characteristics of the frame structure are solved by using the developed modeling method, and the rationality of the analysis results is verified by experiments. Based on this, the increasing trends of the resonant frequencies and the resonant response of the frame structure under different pretension conditions are analyzed from two aspects of experiment and simulation. [ABSTRACT FROM AUTHOR]

High‐temperature resistant solar‐blind optoelectronic synapse has a significant demand such as aerospace and fire warning, which integrates sensing and processing functions to realize complex functions like learning, recognition, and memory. However, developing such device remains a tremendous challenge. Herein, a two‐terminal GaOX solar‐blind optoelectronic synapse with high‐temperature working ability is proposed, and it is applied to neuromorphic computing and cryptography. Benefiting from the high internal gain, the device can detect the light intensity of nW cm−2, displaying one of the best figures‐of‐merit in solar‐blind photodetectors. Furthermore, the device possesses remarkable image sensing and memorization ability because of its ultrasensitive light detection ability and prominent synapse performance resulting from large charge trapping states density. Simultaneously, the device shows undamped photodetection and synaptic performances even at 610 K, reflecting a high‐temperature endurance and a desired property for practical applications under harsh environment. Moreover, by constructing an artificial neural network, high‐precision recognition of handwritten digits are realized under 610 K. A photosynaptic array with 12 × 12 pixels is constructed, and it is applied in cryptography that enables simultaneous sensing and encryption in the same devices. This work is expected to drive the progress of Ga2O3 in harsh environment. [ABSTRACT FROM AUTHOR]

The assembly of MXene materials into microcapsules has drawn great attentions due to their unique properties. However, rational design and synthesis of MXene-based microcapsules with specific nanostructures at the molecular scale remains challenging. Herein, we report a strategy to synthesize N/P co-doped MXene hollow flower-like microcapsules with adjustable permeability via dual surfactants assisted hydrothermal-freeze drying method. In contrast to anionic surfactants, cationic surfactants exhibited effective electrostatic interactions with MXene nanosheets during the hydrothermal process. Manipulation of dual surfactants in hydrothermal process realized N and P co-doping of MXene to improve flexibility and promoted the generation of abundant internal cavities in flower-like microcapsules. Based on the unique microstructure, the prepared hollow flower-like microcapsules showed excellent performance, stability and reusability in size-selective release of small organic molecules. Moreover, the release rate can be controlled by turning the oxidation state and type of MXene. The strategy delineates promising prospects for the design of MXene-based microcapsules with specific structures. [ABSTRACT FROM AUTHOR]

Mg-ion batteries (MIBs) possess promising advantages over monovalent Li-ion battery. However, the exploitation of desirable cathode materials encounters the dilemma of sluggish reaction kinetics caused by strong coulomb interaction between Mg2+ and cathode. Reasonable electrode structure design is of great importance for achieving fast Mg2+ intercalation kinetics. Herein, a novel configuration composed of sub-5 nm amorphous V2O5 quantum dots and nitrogen-doping carbon nanofibers (a-V2O5-QDs@NCNFs) was elaborately designed and fabricated. Sub-5 nm QDs provide shorter diffusion path and more storage sites for Mg2+. Simultaneously, a large range of disorder states in amorphous structure can provide more open diffusion channels for Mg2+ transport. In addition, NCNFs play a crucial part in relieving the volumetric strains of V2O5 and maintaining the structural integrity during Mg2+ insertion/extraction. Reflecting in MIBs, a-V2O5-QDs@NCNFs deliver ultra-long cycling life (5000 cycles at 5 A g−1) and outstanding rate performance (52 mAh g−1 at 20 A g−1). This design conception opens up a new route for exploiting high-performance cathode for MIBs. [ABSTRACT FROM AUTHOR]

Ultraviolet position‐sensitive detectors (PSDs) are expected to undergo harsh environments, such as high temperatures, for a wide variety of applications in military, civilian, and aerospace. However, no report on relevant PSDs operating at high temperatures can be found up to now. Herein, we design a new 2D/3D graphitic carbon nitride (g‐C3N4)/gallium nitride (GaN) hybrid heterojunction to construct the ultraviolet high‐temperature‐resistant PSD. The g‐C3N4/GaN PSD exhibits a high position sensitivity of 355 mV mm−1, a rise/fall response time of 1.7/2.3 ms, and a nonlinearity of 0.5% at room temperature. The ultralow formation energy of −0.917 eV atom−1 has been obtained via the thermodynamic phase stability calculations, which endows g‐C3N4 with robust stability against heat. By merits of the strong built‐in electric field of the 2D/3D hybrid heterojunction and robust thermo‐stability of g‐C3N4, the g‐C3N4/GaN PSD delivers an excellent position sensitivity and angle detection nonlinearity of 315 mV mm−1 and 1.4%, respectively, with high repeatability at a high temperature up to 700 K, outperforming most of the other counterparts and even commercial silicon‐based devices. This work unveils the high‐temperature PSD, and pioneers a new path to constructing g‐C3N4‐based harsh‐environment‐tolerant optoelectronic devices. [ABSTRACT FROM AUTHOR]

X-ray detectors have numerous applications in medical imaging, industrial inspection, and crystal structure analysis. Gallium oxide (Ga2O3) shows potential as a material for high-performance X-ray detectors due to its wide bandgap, relatively high mass attenuation coefficient, and resistance to radiation damage. In this study, we present Sn-doped Ga2O3 microwire detectors for solar-blind and X-ray detection. The developed detectors exhibit a switching ratio of 1.66 × 102 under X-ray irradiation and can operate stably from room temperature to 623 K, which is one of the highest reported operating temperatures for Ga2O3 X-ray detectors to date. These findings offer a promising new direction for the design of Ga2O3-based X-ray detectors. [ABSTRACT FROM AUTHOR]

Flexible photodetectors (PDs) are indispensable components for next-generation wearable electronics. Recently, two-dimensional (2D) materials have been implemented as functional flexible optoelectronic devices due to their characteristics of atomically thin layers, excellent flexibility, and strain sensitivity. In this work, we developed a flexible photodetector based on MoS2/NiO heterojunction, and Fabry-Perot (F-P) and piezo-phototronic effect have been employed to enhance the responsivity (R) and external quantum efficiency (EQE) of the devices. The F-P effect is utilized to improve the optical absorption of the MoS2, resulting in an enhancement in the photoluminescence (PL) of monolayer MoS2 and the EQE of the photodetector by 30 and 130 times, respectively. The flexible photodetector exhibits an ultrahigh detectivity (D*) of 2.6 × 1,014 Jones, which is the highest value ever reported for flexible MoS2 PDs. The piezo-potential of monolayer MoS2 decreases the valence band offset at the interface of MoS2/NiO, which increases the transfer efficiency of the photon-generated carriers significantly. Under 1.17% tensile strain, the R of the flexible photodetector can be enhanced by 271%. This research may provide a universal strategy for the design and performance optimization of 2D materials heterostructures for flexible optoelectronics. [ABSTRACT FROM AUTHOR]

The quest for solar-blind photodetectors with outstanding optoelectronic properties and weak signals detection capability is essential for their applications in the field of imaging, communication, warning, etc. To date, Ga2O3 has demonstrated potential for high-performance solar-blind photodetectors. However, the performance usually decays superlinearly at low light intensities due to carrier-trapping effect, which limits the weak signal detection capability of Ga2O3 photodetectors. Herein, a Ga2O3 solar-blind photodetector with ultra-thin absorbing medium has been designed to restrain trapping of photo-generated carriers during the transporting process by shortening the carrier transport distance. Meanwhile, multiple-beam interference is employed to enhance the absorption efficiency of the Ga2O3 layer using an Al/Al2O3/Ga2O3 structure. Based on the ultra-thin absorbing medium with enhanced absorption efficiency, a 7 × 7 flexible photodetector array is developed, and the detectivity can reach 1.7 × 1015 Jones, which is among the best values ever reported for Ga2O3 photodetectors. Notably, the performance of the photodetector decays little as the illumination intensity is as weak as 5 nW/cm2, revealing the capacity to detect ultra-weak signals. In addition, the flexible photodetector array can execute the functions of imaging, spatial distribution of light source intensity, real-time light trajectory detection, etc. Our results may provide a route to high-performance solar-blind photodetectors for ultra-weak light detection. [ABSTRACT FROM AUTHOR]