Sub-ppb level HCN photoacoustic sensor employing dual-tube resonator enhanced clamp-type tuning fork and U-net neural network noise filter.

Hydrogen cyanide (HCN) is a toxic industrial chemical, necessitating low-level detection capabilities for safety and environmental monitoring. This study introduces a novel approach for detecting hydrogen cyanide (HCN) using a clamp-type custom quartz tuning fork (QTF) integrated with a dual-tube acoustic micro-resonator (AmR) for enhanced photoacoustic gas sensing. The design and optimization of the AmR geometry were guided by theoretical simulation and experimental validation, resulting in a robust on-beam QEPAS (Quartz-Enhanced Photoacoustic Spectroscopy) configuration. To boost the QEPAS sensitivity, an Erbium-Doped Fiber Amplifier (EDFA) was incorporated, amplifying the laser power by approximately 286 times. Additionally, a transformer-based U-shaped neural network, a machine learning filter, was employed to refine the photoacoustic signal and reduce background noise effectively. This combination yielded a significantly low detection limit for HCN at 0.89 parts per billion (ppb) with a rapid response time of 1 second, marking a substantial advancement in optical gas sensing technologies. Key modifications to the QTF and innovative use of AmR lengths were validated under various experimental conditions, affirming the system's capabilities for real-time, high-sensitivity environmental monitoring and industrial safety applications. This work not only demonstrates significant enhancements in QEPAS but also highlights the potential for further technological advancements in portable gas detection systems.

Fabrication of a Fluorocarbon Low Surface Energy Coating for Anti-Stain Applications.

In the long-term working state, stains such as dust, oil, and charged particles in the environment are prone to deposit on the surface of the power equipment, which has great security risks. To achieve anti-stain performance, fluorocarbon composite coating with a low surface energy was prepared and studied. In this paper, SiO2 nanoparticles were used as inorganic fillers and fluorocarbon resin was used as the substrate to form anti-stain coatings. By adjusting and optimizing the ratio of fillers and organic resins, coatings with different static contact angles were constructed. The optimum composite coating has a contact angle of 151 ± 2° and a surface energy of 9.6 mJ/m2. After high-temperature treatment (up to 200 °C), immersion in corrosive solutions (pH 3-11), and sandpaper abrasion (after 5 abrasion cycles), the coating has been proven to show good thermal, chemical and mechanical stability. Our study provides significant research and market opportunities for the anti-stain application of the fluorocarbon composite coating on power equipment.

Design and Synthesis of Low Surface Energy Coating with Functionalized Al2O3 Nanoparticles.

In a high-moisture environment where dust and coastal saltwater are prevalent, the stability of power equipment can be adversely affected. This issue can result in equipment downtime, particularly for transformers, severely disrupting the continuous operation of DC transmission systems. To address this challenge, a superhydrophobic modified fluorosilicone coating was developed, incorporating anti-stain properties. To tackle this issue comprehensively, an orthogonal experiment was conducted, involving six factors and three levels. The study focused particularly on assessing the impact of water-repellent recovery agents, nanofillers, antistatic agents, anti-mold agents, leveling agents, as well as wetting and dispersing agents on the coating's surface tension. The results demonstrate that selecting an appropriate base resin and incorporating well-matched functional additives played a central role in effectively reducing the surface tension of the coating. Consequently, optimized coatings exhibited exceptional resistance to stains and displayed strong corrosion resistance.

Piezoelectric Nanogenerator Based on Electrospinning PVDF/Cellulose Acetate Composite Membranes for Energy Harvesting.

The organic piezoelectric polymer polyvinylidene fluoride (PVDF) has attracted extensive research because of its excellent flexibility and mechanical energy-harvesting properties. Here, the electrospinning technique was taken to fabricate synthesized fiber membranes of a PVDF/cellulose acetate (CA) composite. The obtained PVDF/CA electrospun fiber membranes (EFMs) were employed to prepare a flexible nanogenerator. XRD and FTIR spectroscopy revealed the enhancement of piezoelectric behavior due to an increase in ß-phase in PVDF/CA EFMs compared with cast films. The PVDF/CA fibers (mass ratio of PVDF to CA = 9:1) showed an output voltage of 7.5 V and a short-circuit current of 2.1 µA under mechanical stress of 2 N and frequency of 1 Hz, which were 2.5 and two times greater than those of the pure PVDF fibers, respectively. By charging a 4.7 µF capacitor for 15 min with the voltage generated by the PVDF/CA EFMs, nine LED lamps could be lit. The work provides an effective approach to enhancing the piezoelectric effects of PVDF for low-power electronic loading of macromolecule polymers.

Single-frame-based column fixed-pattern noise correction in an uncooled infrared imaging system based on weighted least squares.

Uncooled infrared images typically suffer from column fixed-pattern noise (FPN), which is introduced by the non-uniformity of the column-parallel readout circuit. It is a challenging task to remove column FPN without introducing stripe artifacts near strong vertical edges. In this paper, we introduce a novel single-frame-based algorithm to accurately correct column FPN. The algorithm contains two 1D filters. First, a 1D weighted least-squares filter is applied to perform edge-preserving filtering in the horizontal direction to obtain a coarse estimation of the clear scene. Then, a local weighted ridge regression is performed between the horizontal smoothed image and the raw infrared image in vertical direction to refine this estimation. Through an analysis on the cause of stripe artifacts, the proposed non-uniformity correction (NUC) algorithm is proved to be effective in eliminating this problem. The performance of our proposed algorithm is thoroughly investigated and compared to four state-of-the-art single-frame-based destriping methods using both simulated and real experiments.

[Kinematics and workspace analysis of a spherical exoskeleton parallel mechanism].

Based on the biomechanical simulation curve of OpenSim, an open source software of biomechanical model, a spherical exoskeleton parallel mechanism with two degrees of freedom for hip joint is proposed in this paper for the rehabilitation therapy of patients with impaired leg motor function or elderly people with walking dysfunction. Firstly, the parallel mechanism is modeled and the position inverse solution of the parallel mechanism is obtained using inverse kinematics analysis. The velocity analysis expression of the mechanism is derived by deriving the inverse kinematics solution. The model is imported into the mechanical system dynamics analysis software ADAMS and matrix processing analysis software MATLAB to carry out simulation experiments. The correctness of the velocity analysis is verified by comparing the velocity simulation results of the two methods. Then, three singular types of the mechanism are analyzed according to the obtained Jacobian matrix. According to the inverse solution of the mechanism, the reachable workspace of the mechanism is obtained by programming in MATLAB with given mechanism parameters and restriction conditions. Finally, the prototype platform is built. The experimental results show that the exoskeleton hip joint using this parallel mechanism can satisfy the requirement of rotation angle of human hip joint movement, but also can be good to assist patients with leg flexion-extension movement and adduction-abduction movement, and it is helpful to carry out corresponding rehabilitation training. It also has theoretical significance and application value for the research work of human hip exoskeleton parallel mechanism.

N,N-Dimethylaminobenzoates enable highly enantioselective Sharpless dihydroxylations of 1,1-disubstituted alkenes.

A design scenario aimed at exploring beneficial catalyst-substrate π-π stacking electronic interactions in the classical Sharpless asymmetric dihydroxylations (SAD) leads to the identification of highly polarizable allylic N,N-dimethylaminobenzoate as a remarkably efficient auxiliary for inducing high levels of enantioselectivities (up to 99% ee) in the traditionally challenging substrate class of 1,1-disubstituted aliphatic alkenes.

New approach to oximes through reduction of nitro compounds enabled by visible light photoredox catalysis.

A range of nitro compounds are smoothly reduced to their corresponding oximes under the synergistic effects of visible light irradiation, the Ru(bpy)3Cl2 photocatalyst, Hünig's base, Mg(ClO4)2 activation, and MeCN solvent. This remarkably mild and environmentally benign protocol, when orchestrated with classical Beckmann rearrangement, enables such high-value industrial feedstock as caprolactam to be readily accessed from simple precursor nitrocyclohexane.