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Fault diagnosis plays a crucial role in maintaining the operational safety of mechanical systems. As intelligent data-driven approaches evolve, deep learning (DL) has emerged as a pivotal technique in fault diagnosis research. However, the collected vibrational signals from mechanical systems are usually corrupted by unrelated noises due to complicated transfer path modulations and component coupling. To solve the above problems, this paper proposed the dynamic temporal denoise neural network with multi-head attention (DTDNet). Firstly, this model transforms one-dimensional signals into two-dimensional tensors based on the periodic self-similarity of signals, employing multi-scale two-dimensional convolution kernels to extract signal features both within and across periods. Secondly, for the problem of lacking denoising structure in traditional convolutional neural networks, a temporal variable denoise (TVD) module with dynamic nonlinear processing is proposed to filter the noises. Lastly, a multi-head attention fusion (MAF) module is used to weight the denoted features of signals with different periods. Evaluation on two datasets, Case Western Reserve University bearing dataset (single sensor) and Real aircraft sensor dataset (multiple sensors), demonstrates that the DTDNet can reduce the useless noises in signals and achieve a remarkable improvement in classification performance compared with the state-of-the-art method. DTDNet provides a high-performance solution for potential noise that may occur in actual fault diagnosis tasks, which has important application value. [ABSTRACT FROM AUTHOR]

Chrysanthemum, an agricultural economic crop with ornamental, medicinal, and edible values, faces the problem of continuous cropping obstacles in its cultivation. As a potential soil conditioner used to address continuous cropping obstacles (CCOs), the applicability of biochar in chrysanthemum cultivation has become a research hotspot. This study explored the effects of three different types of biochar (rice straw biochar = RB, pig manure biochar = PB, and sludge biochar = SB) on soil for chrysanthemum that had been continuously cultivated for eight years through pot experiments. The results indicate that the addition of biochar significantly reduced soil water loss. Compared with CK, the water retention rates of the SB and PB treatments increased by 25.4% and 18.4%, respectively. In the PB treatment, the contents of available phosphorus (AP) and available potassium (AK) increased by 85% and 164%, respectively. The available nitrogen (AN) content showed the highest increase under the SB treatment. All three types of biochar could improve the pH value of chrysanthemum soil with CCOs (increased by 0.4–5.4%). The results of microbial community diversity showed that, compared with CK, PB and RB slightly reduced the diversity of bacterial communities in chrysanthemum soil with CCOs (by 1.50% and 0.41%, respectively). However, the SB treatment increased the diversity of bacterial communities in chrysanthemum soil with CCOs (by 0.41%). At the same time, SB and PB significantly inhibited the diversity of fungal communities (reduced by 15.15% and 6.67%, respectively), while RB promoted the diversity of fungal communities (increased by 5.45%). Furthermore, the analysis results of bacterial phyla and genera indicated that PB and SB had enhancing effects on the beneficial bacterial phylum Actinobacteriota (8.66% and 4.64%) and the beneficial bacterial genus Nocardioides (23.29% and 9.69%). Additionally, the PB treatment enhanced the beneficial bacterial phylum Firmicutes (7.03%). The analysis results of fungal genera and phyla indicated that PB contributed to an increase in the beneficial fungal phylum Ascomycota (1.51%). RB significantly enhanced the beneficial fungal genus Chaetomium (56.34%). Additionally, all three types of biochar effectively reduced the abundance of the harmful fungal phylum Basidiomycota (30.37–73.03%). In the PB and SB treatments, the harmful fungal phylum Mucoromycota was significantly decreased (by 36.22% and 62.60%, respectively). Finally, all three types of biochar reduced the abundance of harmful fungal genera Acremonium (1.15–35.19%) and Phoma (97.1–98.7%). In this study, we investigated the effect of three kinds of biochar (RB, PB, and SB) on the soil of chrysanthemum continuous cropping through potting experiments and found that they could significantly reduce water loss, enhance water retention, increase the soil nutrient content, improve the pH value, regulate microbial communities, increase beneficial microorganisms, and reduce harmful microorganisms. These results provide a scientific basis for addressing barriers to continuous cropping (CC) while supporting the sustainability of agriculture and the development of agroecology. [ABSTRACT FROM AUTHOR]

The transverse leakage of leaky surface acoustic waves (LSAWs) occurs on 42°YX-lithium tantalate substrates (42LT), which increases the insertion loss, narrows the bandwidth and flattens the roll-off of band 40/41 SAW filters and duplexers. In this work, LSAW characteristics with different metal materials and thicknesses are calculated by the finite element method (FEM), which determines the IDT material and thickness used for band 40/41 SAW filter design. To deeply understand transverse leakage and suppress it, the effects of different gap and dummy lengths on transverse leakage are simulated and discussed. Then, a new technique of using a wider dummy without any additional lithographic or depositing processes is proposed to suppress the leakage. Its effectiveness is validated by both simulations and experiments. Then, the technique is extended to applications of band 40 and 41 SAW filters. The experimental results show that with the wider dummy structure, the band 40 and 41 SAW filters achieve a more than 0.2 dB improvement in the insertion loss, a wider bandwidth and a steeper roll-off characteristic. This technique may also be extended to the other band SAW filter applications. [ABSTRACT FROM AUTHOR]

The development of 5G mobile communication imposes requirements of high frequency, miniaturization, and integration on surface acoustic wave devices. Compared with traditional piezoelectric bulk single crystal material, surface acoustic wave filters fabricated with silicon-based piezoelectric single crystal film materials exhibit advantages such as high frequency, low insertion loss, high temperature stability and so on, making silicon-based piezoelectric single crystal film material prime foundation material. Smart-Cut™ is the universal method for preparing silicon-based piezoelectric single crystal film materials, and bonding process is one of the most essential procedures. Bonding quality determines the quality of piezoelectric single crystal film and ultimately affects the performance of the devices. In this work, high-quality heterogeneous silicon-based LiTaO3 wafers with the bonding strength up to 1. 84 J/m² and bonding area over 99. 9% were achieved through optimizing low-temperature direct bonding process, which includes plasma activation, megasonic cleaning, pre-bonding, and thermal treatment. [ABSTRACT FROM AUTHOR]

Carbon dioxide is one of the greenhouse gases responsible for global warming, and how to reduce the amount of carbon dioxide in the air is a major issue. Scholars have found that herbaceous flowers can fix 12.16 g•m-2• D-1 carbon dioxide per unit leaf area in green space, which has a good ecological benefit of carbon sequestration. Therefore, how to further improve the ecological benefits of carbon sequestration has become a concern of landscape architecture industry. This paper summarizes seven kinds of garden green land carbon ecological concrete approaches to improve, including selecting high carbon sequestration ability of plant species, increase high carbon sequestration ability of plant population, rich garden plant hierarchy, increase use native plants, increasing the vertical greening, choose low maintenance plants landscape, choose the appropriate maintenance management way, In order to deal with global warming phenomenon on the full play of green landscape fixed carbon dioxide capacity.

SAW devices with a multi-layered piezoelectric substrate have excellent performance due to advantages such as a high quality factor, Q, low loss insertion, large bandwidth, etc. Prior to manufacturing, a comprehensive analysis and proper design are essential to evaluating the device's key performance indicators, including the Bode Q value, bandwidth, and transverse mode suppression. This study explored the performance of SAW resonators employing a 42°Y-X LiTaO3 (LT) thin-plate-based multi-layered piezoelectric substrate. The thicknesses for each layer of the 42°Y-X LT/SiO2/poly-Si/Si substrate were optimized according to the index of phase velocity, Bode Q value, and bandwidth. The effect of the device structure parameters on the dispersion curve and slowness curve was studied, and a flat slowness curve was found to be favorable for transverse mode suppression. In addition, the design of the dummy configuration was also optimized for the suppression of spurious waves. Based on the optimized design, a one-port resonator on the 42°Y-X LT/SiO2/poly-Si/Si substrate was fabricated. The simulation results and measurements are presented and compared, which provides guidelines for the design of new types of SAW devices configured with complex structures. [ABSTRACT FROM AUTHOR]

The Baeyer–Villiger oxidation (BVO) of ketone and aldehyde can produce ester and formate, which both have wide applications in many areas. In this work, a series of Sn-containing silicates were prepared through the sol-gel process by using structure-directing and crystallizing agents and post-synthetic coordinated modification of binaphthol. Characterizations revealed that loading of (L)-sodium lactate as the crystallizing agent decreased the crystal size of the synthesized catalyst, and there were SnO2 nanoparticles with sizes of 17–19 nm on the catalyst. Furthermore, quite differently from the 3D mesoporous structure of classical Sn-beta zeolites, the synthesized catalysts had a silt-like mesoporous structure. In the catalysis, when cyclic aliphatic ketones were used as the substrate, only BVO-type products and corresponding ring-opening products were obtained. BVO of aliphatic aldehyde produced both an aerobic oxidation product (carboxylic acid) and a BVO-type product. The presented transformation of aromatic aldehyde (benzaldehyde) only gave an aerobic oxidation product (benzoic acid). The post-synthetic coordinating attachment of (S)-binaphthol to the Sn-containing silicate backbone worsened the BVO of aliphatic ketones but improved the BVO of aliphatic aldehyde and the aerobic oxidation of aromatic aldehyde. In addition, this work also developed two new routes for the synthesis of high-value-added 6-hydroxyhexanoic acid and cyclohexylformate under catalytic BVO conditions. [ABSTRACT FROM AUTHOR]

The Baeyer-Villiger Oxidation (BVO) of ketones and aldehydes produce lactones and formates, while aerobic carboxylation of aldehydes manufactures carboxylic acids, both having high added value. This work prepared a series of Al-containing silicates modified with organic ligands and SnO2 nanoparticles, which were then employed as catalyst in BVO and carboxylation. Characterizations revealed the morphology of the synthesized catalyst was changed from micron-sized thin sheets to smaller blocks, and then to uniform nanoparticles (size of 50 nm) having the doped SnO2 nanoparticles with a size of 29 nm. All catalysts showed high BET surface areas featuring silt-like mesopores. In determining the priority of BVO and carboxylation, an influence evaluation of the parameters showed the order to be substrate > oxidant > solvent > catalyst. Cyclic aliphatic ketones were suitable for BVO, but linear aliphatic and aromatic aldehydes for carboxylation. Coordination of (S)-binaphthol or doping of Sn into catalyst showed little influence on BVO under m-CPBA, but the Sn-doped catalyst largely increased BVO under (NH4)2S2O8 and H2O2. Calculations revealed that the catalyst containing both Al and Sn could give BVO intermediates lower energies than the Sn-beta zeolite model. The present system exhibited merits including wider substrate scope, innocuous catalytic metal, greener oxidant, as well as lower catalyst cost. [ABSTRACT FROM AUTHOR]