Search Results (56)

Aging or damaged electrical connectors always suffer intermittent failures (IFs) during operation. Because there are few quantitative studies on electrical connector intermittent failure mechanisms, the intermittent failures of electrical connectors are difficult to isolate. Therefore, the mechanism and dynamic characteristics of intermittent failure is studied in this paper. Firstly, the degradation process of an electrical connector is analyzed. Secondly, according to electrical contact model, the intermittent failure mechanism caused by vibration is studied. Thirdly, to make a profound study on dynamic behavior of intermittent failure, an intermittent failure dynamic model is proposed, and the behaviors of intermittent failure are analyzed. Finally, a simulation case is conducted to verify the correctness of the intermittent failure mechanism and the effectiveness of the intermittent failure dynamic model. Full article

Thermal conductivity is the key property of SiC-TRISO composite fuel. This study investigated the relationship between SiC phase transition, thermal conductivity, and microstructure across different temperatures. The physical phase, morphology, and microstructure of SiC and SiC-TRISO composite fuels were characterized by XRD and SEM. Meanwhile, EDS was employed to determine the chemical composition within SiC grains. The results showed the transformation of the β-SiC phase to α-SiC in the matrix with increasing sintering temperature, while Al, Y, and Ca concentrations within the SiC grains decreased. The highest λ value of SiC was achieved at a sintering temperature of 1750 °C, measuring 75.51 ${\displaystyle \frac{W}{m·K}}$ at room temperature and 43.36 ${\displaystyle \frac{W}{m·K}}$ at 500 °C. The incorporation of TRISO fuel lowered the $\lambda$ value of SiC-TRISO composite fuel, yielding 57.96 and 34.51 ${\displaystyle \frac{W}{m·K}}$ at room temperature and 500 °C, respectively. The outermost carbon layer of TRISO fuel interacts with the silicon carbide matrix and liquid phase, facilitating the phase transition from 3C-SiC to 6H-SiC and, subsequently, to 4H-SiC. This process accelerates the depletion of Al, Y, and Ca within the silicon carbide grains, encourages grain growth, and raises the free-carbon content, thereby decreasing the λ of the composite fuel. Full article

Upconversion luminescent materials (UCLMs) have garnered significant attention due to their broad potential applications in fields such as display technology, biological imaging, and optical sensing. However, optimizing crystal phase and morphology remains a challenge. This study systematically investigates the effects of phase transformation and morphology control on the upconversion luminescent properties of K₃GaF₆:Er³⁺. By comparing different synthesis methods, we found that the hydrothermal method effectively facilitated the transformation of the Na_xK_3-xGaF₆ crystal phase from cubic to monoclinic, with Na⁺/K⁺ ions playing a key role in the preparation process. Furthermore, the hydrothermal method significantly optimized the particle morphology, resulting in the formation of uniform octahedral structures. The 657 nm red emission intensity of the monoclinic phase sample doped with Er³⁺ was enhanced by 30 times compared to that of the cubic phase, clearly demonstrating the crucial role of phase transformation in luminescent performance. This study emphasizes the synergistic optimization of crystal phase and morphology through phase engineering, which substantially improves the upconversion luminescence efficiency of K₃GaF₆:Er³⁺, paving the way for further advancements in the design of efficient upconversion materials. Full article

Bacterial infections are one of the major problems affecting human health, which is exacerbated by increasing antibiotic resistance. Antimicrobial peptides (AMPs) are an ideal alternative to antibiotics, but their instability and toxicity to mammalian cells need to be addressed. Here, black phosphorus nanosheets (BPs) were successfully decorated with melittin (Mel), a kind of AMP, through electrostatic interaction. The size impacts of BPs on the antibacterial ability and biocompatibility of BPs/Mel nanocomposites were studied systematically. Results showed that the nanocomposites made from middle-sized BPs (BPs/Mel-7) have strong antibacterial ability as well as good biocompatibility. Moreover, BPs/Mel-7 could accelerate skin wound healing infected by Staphylococcus aureus. This study provides a facile strategy to expand the application of AMPs. Full article

In this paper, we focus on eddy current array (ECA) technology for defect detection in finely grooved structures of spinning cylinders, which are significantly affected by surface texture interference, lift-off distance, and mechanical dither. Unlike a single eddy current coil, an ECA, which arranges multiple eddy current coils in a specific configuration, offers not only higher accuracy and efficiency for defect detection but also the inherent properties of space and time for signal acquisition. To efficiently detect defects in finely grooved structures, we introduce a spatiotemporal self-attention mechanism to ECA testing, enabling the detection of defects of various sizes. We propose a Multi-scale SpatioTemporal Self-Attention Network for defect detection, called MSTSA-Net. In our framework, Temporal Attention (TA) and Spatial Attention (SA) blocks are incorporated to capture the spatiotemporal features of defects. Depth-wise and point-wise convolutions are utilized to compute channel weights and spatial weights for self-attention, respectively. Multi-scale features of space and time are extracted separately in a pyramid manner and then fused to regress the bounding boxes and confidence levels of defects. Experimental results show that the proposed method significantly outperforms not only traditional image processing methods but also state-of-the-art models, such as YOLOv3-SPP and Faster R-CNN, with fewer parameters and lower FLOPs in terms of Recall and F1 score. Full article

Marine sand, in addition to oil and gas resources, is the second-largest marine mineral resource. The rational development and utilization of marine sand resources are conducive to the growth of the marine economy. In the process of marketing marine sand in China, local authorities are required to delineate auctioned sand mining areas after a general survey, commonly referred to as preliminary exploration. Marine sand can be categorized into surface marine sand and buried marine sand. Buried marine sand deposits are buried beneath the sea floor, making it challenging to locate them due to their thin thickness. Consequently, there exist numerous technical difficulties associated with marine sand exploration. We conducted the preliminary research work in the waters off Guangdong Province of the South China Sea, employing a reduced drilling and identifying a potentially extensive deposit of marine sand ore. In this study, various geophysical methods such as sub-bottom profile survey, single-channel seismic survey, and drilling engineering were employed in the northern offshore waters of the South China Sea. As a result, two distinct marine sand bodies were delineated within the study area. Additionally, five reflective interfaces (R₁, R₂, R₃, R₄, and R₅) were identified from top to bottom. These interfaces can be divided into five seismic sequences: A₁, B₁, C₁, D₁, and E₁, respectively. Three sets of strata were recognized: the Holocene Marine facies sediment layer (Q₄^m), the Pleistocene alluvial and pluvial facies sediment layer (Q₃^al+pl), as well as the Pleistocene Marine facies sedimentary layer (Q₃^m). In total, two placers containing marine sand have been discovered during this study. We estimated the volume of marine sand and achieved highly favorable results of the concept that we are proposing a geologic exploration approach that does not involve any previous outcropping analogue study. Full article

Laser drilling is widely used for fabricating holes in the semiconductor industry due to high throughput and a small heat-affected zone. However, it produces varying depths owing to uncertain external conditions and requires live control at the rate of a few tens of kHz to handle the fast material removal rate. Optical coherent tomography is capable of in situ acquiring a raw interferogram at a high rate (>80 kHz), but the depth extraction is slow due to the involved heavy Fast Fourier Transform (FFT). To address this, an efficient depth-tracking algorithm is proposed to save the FFT. It searches the depth in the raw interferogram locally with a known last depth given the two truths that only one depth exists and the adjacent depths do not change significantly. The proposed algorithm was proven to expedite the measuring rate six times with sub-pixel tracking precision. To further secure the rate against the interrupting of the system, the tracking process is parallelly implemented in a field-programmable gate array. The closed-loop control tests were conducted on probe cards with depth variations introduced by offsetting laser focus. The proposed method maintained a uniform depth, with variations reduced by 80% compared to traditional methods. Full article

This study investigates the structure of soil bacterial communities in the brown mountain soils beneath the deciduous broadleaf forests of Dongling Mountain and their response to soil physicochemical properties. Aiming to provide a scientific basis for soil conservation and sustainable forest development under deciduous broadleaf forests, this research utilized high-throughput sequencing technology to examine the diversity and community structure of bacteria in soil under different tree species, alongside assessing soil physicochemical properties. The results revealed significant differences in nutrient content between the 0–20 cm and 20–40 cm soil layers. Additionally, the N:P in the brown mountain soils of Dongling Mountain was found to be below the national average, indicating potential nitrogen limitation. Dominant bacterial phylum included Actinobacteria, Proteobacteria, and Acidobacteria. The study also found that soil bacterial community structure was similar under different tree species at the same depth but varied significantly with soil depth. Furthermore, redundancy analysis (RDA) showed that the available potassium (AK), total nitrogen (TN), and ammonium nitrogen (NH₄⁺-N) significantly influenced the structural changes in the soil bacterial community. This research highlights the characteristics of soil bacterial community structure beneath deciduous broadleaf forests and its relationship with soil physicochemical properties, offering valuable insights for regional soil ecosystem conservation and forest management. Full article

Soil bacterial and fungal community communities play significant ecological functions in mountain ecosystems. However, it is not clear how topographic factors and soil physicochemical properties influence changes in microbial community structure and diversity. This study aims to investigate how altitude and slope orientation affect soil physicochemical properties, soil microbial communities, and their contributing factors. The assessment was conducted using Illumina MiSeq sequencing in various altitude gradients and on slopes with different aspects (shady slopes and sunny slopes) in the subalpine meadow of Dongling Mountain, Beijing. Topographical factors had a significant effect on soil physicochemical properties: the primary factors determining the structure of microbial communities are total potassium (TK), ammonium nitrogen (NH₄⁺-N), and soil organic carbon (SOC). There was no significant change in the diversity of the bacterial community, whereas the diversity of the fungal community displayed a single-peaked trend. The effect of slope orientation on microbial communities was not as significant as the effect of elevation on them. The number of bacterial communities with significant differences showed a unimodal trend, while the number of fungal communities showed a decreasing trend. The co-occurrence network of fungal communities exhibits greater intricacy than that of bacterial communities, and bacterial communities are more complex in soils with sunny slopes compared to soils with shady slopes, and the opposite is true for fungal communities. The identification of the main factors that control soil microbial diversity and composition in this study, provided the groundwork for investigating the soil microbial response and adaptation to environmental changes in subalpine meadows. Full article

Metal–organic frameworks (MOFs) have broad potential applications in electrochemical glucose detection. Herein, a green ultrasonic synthesis process is presented for preparing two-dimensional (2D) copper–nickel metal–organic framework nanosheets (CuNi-MOFNs) for glucose detection. The synthesized CuNi-MOFNs were characterized using scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), X-ray diffractometer (XRD), and X-ray photoelectron spectrometer (XPS). The CuNi-MOFN nanocomposites were used to cover the glassy carbon electrode (GCE) and the CuNi-MOFNs-modified electrode was studied in alkaline media. Cyclic voltammetry (CV) and amperometric i–t curves indicated that the CuNi-MOFNs-modified electrode revealed great electrochemical performances towards glucose oxidation. Due to the ease of access to active metal sites in large specific surface of nanosheets, the CuNi-MOFNs-modified electrode can effectively improve the electronic transfer rate and enhance electrocatalytic activity of the CuNi-MOFNs-modified electrode. The CuNi-MOFNs-modified electrode showed electrochemical performances for glucose detection with a linear range from 0.01 mM to 4 mM, sensitivity of 702 μAmM⁻¹cm⁻², and detection limit of 3.33 μΜ (S/N = 3). The CuNi-MOFNs-modified electrode exhibited excellent anti-interference ability and high selectivity in glucose measurements. Hence, the CuNi-MOFNs-modified electrode has good, promising prospects in non-enzymatic electrochemical glucose detection. Full article

Landslides, the second largest geological hazard after earthquakes, result in significant loss of life and property. Extracting landslide information quickly and accurately is the basis of landslide disaster prevention. Fengjie County, Chongqing, China, is a typical landslide-prone area in the Three Gorges Reservoir Area. In this study, we newly integrate Shapley Additive Explanation (SHAP) and Optuna (OPT) hyperparameter tuning into four basic machine learning algorithms: Gradient Boosting Decision Tree (GBDT), Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), and Additive Boosting (AdaBoost). We construct four new models (SHAP-OPT-GBDT, SHAP-OPT-XGBoost, SHAP-OPT-LightGBM, and SHAP-OPT-AdaBoost) and apply the four new models to landslide extraction for the first time. Firstly, high-resolution remote sensing images were preprocessed, landslide and non-landslide samples were constructed, and an initial feature set with 48 features was built. Secondly, SHAP was used to select features with significant contributions, and the important features were selected. Finally, Optuna, the Bayesian optimization technique, was utilized to automatically select the basic models’ best hyperparameters. The experimental results show that the accuracy (ACC) of these four SHAP-OPT models was above 92% and the training time was less than 1.3 s using mediocre computational hardware. Furthermore, SHAP-OPT-XGBoost achieved the highest accuracy (96.26%). Landslide distribution information in Fengjie County from 2013 to 2020 can be extracted by SHAP-OPT-XGBoost accurately and quickly. Full article

Purple scapolite is a precious gemstone. In this paper, we compared the crystal structure and spectral characteristics of purple scapolite before and after heat treatment with conventional gemological tests, EPMA, XRF, LA-ICP-MS, infrared spectroscopy, Raman spectroscopy, UV–vis spectrophotometer, EPR, and other tests. The XRD results showed that the structure of purple scapolite fits perfectly with that of marialite. Compositional analyses indicate that purple scapolite has an average Me value of 16.85 and belongs to the subspecies marialite, and thus its specific gravity and refractive index are low. The absorption peak at 1045 cm⁻¹ in the infrared spectra has a direct relationship with the Me value, which is blue-shifted with increasing Me value. After heating at 400 °C for 2 h, the purple scapolite changed to colorless, and no phase transformation or significant structural changes occurred during this process. But this process is accompanied by the disappearance of the signal at g = 2.011 in the EPR spectra, which indicates the presence of oxygen hole centers, thus proving that the color of purple scapolite is caused by oxygen hole centers rather than Fe³⁺. The chlorine in the marialite structure occupies the structural center, which provides for the appearance of oxygen hole centers, and thus purple scapolite always has a high marialite content. This further leads to the refractive index and specific gravity always being lower. That is a new explanation for the relationship between scapolite coloration mechanism, specific gravity, and refractive index. Full article

Studying both soil carbon (C) and nitrogen (N) storages in different climate zones and their relationship with climatic factors is of great significance for understanding soil fertility and predicting global climate change. Climate influences soil minerals, which are important for soil organic carbon (SOC) and N retention. However, there are few studies on SOC and soil total nitrogen (STN) storage in different climatic zones, and of the effects of soil oxidation minerals on SOC and STN storage. We measured the storage of SOC and STN and the content of oxidizable minerals in soils from different climatic regions, then obtained climate data from the China Meteorological Data Service Center, and finally investigated the effects of climate factors and soil oxides minerals on SOC and STN. The results showed that climatic factors (mean annual temperature—MAT, mean annual precipitation—MAP, and ≥10 °C mean annual cumulative temperature—MACT) had significant effects on SOC and STN content, and there was significant epistatic clustering of SOC and STN contents in different climatic zones. When MAT, MAP, and MACT increased, SOC and STN storage showed a trend of increasing and then decreasing, and both SOC and STN storages were largest in the middle temperate zone. The content of soil metal oxides (Al₂O₃, Fe₂O₃, Na₂O, MgO, CaO, K₂O, and TiO₂) showed significant positive correlation with climatic factors (MAT, MAP, and MACT). The contents of Al₂O₃, Fe₂O₃, CaO, K₂O, and TiO₂ showed significant negative correlation with SOC and STN contents. In summary, our results showed that, although soil metal oxides (SMO) have a protective effect on SOC and STN to some extent, they do not change the influence of climatic factors on SOC and STN storage. Full article

Agate attracts the attention of gem mineralogists because of its variable colors. The color of agate is closely related to its naming and classification, so it is necessary to study the color and mineral origin of agate. In this paper, the mineralogical characteristics and color origin of red, yellow and green Moqi agates from Inner Mongolia were systematically studied by means of Fourier transform infrared spectrometer, Raman spectrometer, X-ray powder diffractometer, electron probe microanalyzer and ultraviolet–visible spectrophotometer. It is found that the color of Moqi agate is related to the minerals and trace elements contained in it, and is associated with the electron transition or charge transfer of Fe ions in the contained minerals. Green agate has the highest Fe content, and its color is caused by celadonite inclusions. The red and yellow color in Moqi agate is mainly caused by hematite and goethite, while red agate contains more Fe than yellow agate. Raman spectroscopy and X-ray diffraction analysis show that the content of moganite in Moqi agate is 0–30%. It is calculated that the crystallinity of Moqi agate is 1.5–3.5. This work provides a theoretical basis for future research on the identification of Moqi agate. Full article

The pulse-jet cleaning process is a critical part of the bag filter workflow. The dust-cleaning effect has a significant impact on the operating stability of bag filters. Aiming at the multi-parameter optimization problem involved in the pulse-jet cleaning process of bag filters, the construction method of hybrid surrogate models based on second-order polynomial response surface models (PRSMs), radial basis functions (RBFs), and Kriging sub-surrogate models is investigated. With four sub-surrogate model hybrid modes, the corresponding hybrid surrogate models, namely PR-HSM, PK-HSM, RK-HSM, and PRK-HSM, are constructed for the multi-parameter optimization involved in the pulse-jet cleaning process of bag filters, and their objective function is the average pressure on the inner side wall of the filter bag at 1 m from the bag bottom. The genetic algorithm is applied to search for the optimal parameter combination of the pulse-jet cleaning process. The results of simulation experiments and optimization calculations show that compared with the sub-surrogate model PRSM, the evaluation indices RMSE, ${\mathrm{R}}^2$, and RAAE of the hybrid surrogate model RK-HSM are 9.91%, 4.41%, and 15.60% better, respectively, which greatly enhances the reliability and practicability of the hybrid surrogate model. After using the RK-HSM, the optimized average pressure F on the inner side wall of the filter bag at 1 m from the bag bottom is −1205.1605 Pa, which is 1321.4543 Pa higher than the average pressure value under the initial parameter condition set by experience, and 58.4012 Pa to 515.2836 Pa higher than using the three sub-surrogate models, verifying its usefulness. Full article