Search Results (33)

This work focuses on the hydrothermal aging of two-dimensional layered Ti₃C₂T_x (MXene)/epoxy (EP) nanocomposites. MXene/EP composites were successfully prepared by homogeneously dispersing multilayer MXene (m-MXene) and few-layer MXene (f-MXene) into the curing agent, methyl nadic anhydride (MNA). Considering the application, the MXene loading was designed to be 0.1 wt.%. Characterization included the characteristics of MXene, the water absorption behavior of the resin and composite samples, the glass transition temperatures (T_g) in various states, and the tensile strength evolution during aging. The curing behavior of the MXene composites was also discussed to facilitate an understanding of the processability. The results showed that MNA can chemically bond with MXene to obtain a stable suspension. The addition of MXene increased the curing characteristic temperature of the system, but the change in the activation energy of the curing reaction was minimal. The addition of MXene decreased the crosslink density of the epoxy resin, leading to a decrease in the T_g value of the initial samples. After hydrothermal aging, the T_g of pure EP decreased by 46.9 °C, and re-drying the samples did not fully restore the T_g. However, the T_g of the MXene/EP system decreased by only 8.9 °C (m-MXene) and 9.5 °C (f-MXene), respectively, and the T_g values of the samples were fully restored to their pre-aging levels via re-drying. Experiments with immersion at 25 °C and 100 °C showed that the difference in water absorption behavior between the MXene/EP and pure EP systems was minimal. Tensile tests showed that the addition of MXene increased the initial strength of the resin system by 14.7% (m-MXene) and 20.9% (f-MXene). After 400 h of hydrothermal aging, the tensile strength retention of the pure EP samples was 69.1%, while the strength retention of the MXene/EP samples was 85.3% (m-MXene) and 83.0% (f-MXene). The combined results demonstrate that the addition of MXene with a low loading of only 0.1% can effectively improve the hydrothermal resistance of epoxy resins. Full article

The explosive development of artificial intelligence technology is profoundly affecting the strategic landscape of cyberspace security, demonstrating enormous potential in the field of intrusion detection. Recent research has found that machine learning models have serious vulnerabilities, and adversarial samples derived from this vulnerability can significantly reduce the accuracy of model detection by adding slight perturbations to the original samples. In our article, we propose a novel method called adversarial sample generation based on model simulation that quickly generates adversarial samples in a short period of time and improves the model’s generalization and robustness after adversarial training. Extensive experiments on the CICIDS-2017 dataset demonstrated that the method consistently outperforms other current research methods. Full article

Photodetectors have a wide range of applications across various fields. Self-powered photodetectors that do not require external energy have garnered significant attention. The photoelectrochemical type of photodetector is a self-powered device that is both simple to fabricate and offers high performance. However, developing photoelectrochemical photodetectors with superior quality and performance remains a significant challenge. The electrolyte, which is a key component in these detectors, must maintain extensive contact with the semiconductor without degrading its material quality and efficiently catalyze the redox reactions of photogenerated electrons and holes, while also facilitating rapid charge carrier transport. In this study, $\alpha$-Ga₂O₃ nanorod arrays were synthesized via a cost-effective hydrothermal method to achieve a self-powered solar-blind photodetector. The impacts of different electrolytes—Na₂SO₄, NaOH, and Na₂CO₃—on the photodetector was investigated. Ultimately, a self-powered photodetector with Na₂SO₄ as the electrolyte demonstrated a stable photoresponse, with the maximum responsivity of 0.2 mA/W at 262 nm with the light intensity of 3.0 mW/cm², and it exhibited rise and decay times of 0.16 s and 0.10 s, respectively. The $\alpha$-Ga₂O₃ nanorod arrays and Na₂SO₄ electrolyte provided a rapid pathway for the transport of photogenerated carriers and the built-in electric field at the semiconductor–liquid heterojunction interface, which was largely responsible for the effective separation of photogenerated electron–hole pairs that provided the outstanding performance of our photodetector. Full article

Polycarboxylate superplasticizers BMC-L and BMC-S were utilized as modifiers in the formulation of novel cement-based grouting materials. Indoor tests were conducted on 32 groups of cement slurries, varying by water–cement ratio (0.5:1 and 0.6:1) and modifier content (0, 2‰, 4‰, 6‰, 8‰, 10‰, 12‰, and 14‰), to test their density, funnel viscosity, water separation rate, and stone rate. Four groups of slurry modified with BMC-L were selected as the preferred slurry, and the apparent viscosity test, uniaxial, and triaxial compression test of the slurry stone body were conducted. The study investigated the influence of BMC-L on various properties of the slurry, including its apparent viscosity, uniaxial compressive strength, stress–strain relationships, shear strength parameters, and elastic modulus. Ultimately, the pore structure and phase composition of the slurry stone body were detected by Nuclear Magnetic Resonance (NMR) and X-ray Diffraction (XRD), and the impact of BMC-L on slurry performance was examined from a microstructural perspective. Results indicate that the two polycarboxylate superplasticizers exert minimal influence on the density and water separation rate of the slurry. Within the effective incorporation range of the polycarboxylate superplasticizer, increasing the dosage correlates with a decrease in both the stone rate and viscosity of the slurry. BMC-L significantly enhances the mechanical properties of the slurry stone body by promoting more complete cement hydration and reducing porosity. The uniaxial compressive strength of slurry stone body with a 6 ‰ BMC-L dosage reached 29.7 MPa after 7 days and 38.5 MPa after 28 days of curing, representing increases of 118.4% and 64%, respectively, compared to masonry with 0 BMC-L dosage. The shear strength parameters and elastic modulus of the slurry stone body also showed corresponding increases. Full article

For noise reduction at a low-to-moderate Reynolds number, airfoil trailing-edge tonal noise has multiple prominent tones. Among these tones, secondary tones are greatly influenced by external disturbances such as oscillations commonly in the environment. In previous experiments, the spatial movement of sources was found to be related to an inherent high-frequency oscillation. Therefore, the spatial influence of external low-frequency oscillations was investigated in this study. By using tripping tapes to construct different symmetry source regions on the pressure side with side secondary tones, a transient spatial analysis of an NACA0012 airfoil at 2 degrees was performed by microphone arrays when a 10 Hz pressure oscillation was significant at 24 m/s. Temporally, this 10 Hz periodic strength change became more intense at a broader frequency bandwidth for a longer source region. Furthermore, a substantial time delay, significantly larger than the sound propagating time difference between microphones, was observed exclusively along the spanwise direction. This delay led to a periodic directivity pattern, particularly when two 0.2 m source regions were separated by a 0.2 m or 0.4 m tripping region. This low-frequency oscillation introduces an asymmetric transient switching pattern for symmetric spanwise source regions. Consequently, the response of airfoils to external oscillations in field tests should be considered. Full article

A novel pretreatment strategy utilizing a combination of NaOH and 1-Butyl-3-methylimidazolium chloride ([Bmim]Cl) was proposed to enhance the enzymatic hydrolysis of abandoned Medium-density fiberboard (MDF). The synergistic effect of NaOH and [Bmim]Cl pretreatment significantly improved the glucose yield, reaching 445.8 mg/g within 72 h, which was 5.04 times higher than that of the untreated samples. The working mechanism was elucidated according to chemical composition, as well as FTIR, ¹³C NMR, XRD, and SEM analyses. The combined effects of NaOH and [Bmim]Cl led to lignin degradation, hemicellulose removal, the destruction and erosion of crystalline regions, pores, and an irregular microscopic morphology. In addition, by comparing the enzymatic hydrolysis sugar yield and elemental nitrogen content of untreated MDF samples, eucalyptus, and hot mill fibers (HMF), it was demonstrated that the presence of adhesives and additives in waste MDF significantly influences its hydrolysis process. The sugar yield of untreated MDF samples (88.5 mg/g) was compared with those subjected to hydrothermal pretreatment (183.2 mg/g), Ionic liquid (IL) pretreatment (406.1 mg/g), and microwave-assisted ionic liquid pretreatment (MWI) (281.3 mg/g). A long water bath pretreatment can reduce the effect of adhesives and additives on the enzymatic hydrolysis of waste MDF. The sugar yield produced by the combined pretreatment proposed in this study and the removal ability of adhesives and additives highlight the great potential of our pretreatment technology in the recycling of waste fiberboard. Full article

Against the backdrop of global warming, extreme precipitation events have become more frequent. In complex terrain regions, due to the vulnerability of their ecosystems, extreme precipitation events can lead to significant secondary disasters. Utilizing daily rainfall data from the National Meteorological Information Center of China and statistical analysis, this study explores the spatial and temporal distribution of extreme precipitation in the Central Southwest China (CSC) region. The temporal pattern of extreme precipitation in CSC shows a consistent trend, while the spatial distribution reveals an opposite phase between the northern and southern parts of CSC. Based on this, we propose a new method for constructing extreme precipitation prediction models for complex terrain regions based on physical mechanisms, and take CSC area as a study case. Instead of anonymous feature selection, this method improves the accuracy and stability of the model by studying the impact of sea–air interactions on extreme precipitation and then introducing it into deep learning. It was found that the sea surface temperature (SST) anomaly in the South Indian Ocean affects extreme precipitation in the CSC by influencing uplift, atmospheric instability, and moisture. The SST anomaly also affects the intensity of cross-equatorial airflow, which changes the trajectory of the Pacific–Japan teleconnection wave and impacts extreme precipitation. These findings provide a comprehensive and reliable approach for forecasting extreme precipitation in CSC and are further integrated into the extreme precipitation prediction models. Full article

Accurate identification of individual cattle is of paramount importance in precision livestock farming, enabling the monitoring of cattle behavior, disease prevention, and enhanced animal welfare. Unlike human faces, the faces of most Hanwoo cattle, a native breed of Korea, exhibit significant similarities and have the same body color, posing a substantial challenge in accurately distinguishing between individual cattle. In this study, we sought to extend the closed-set scope (only including identifying known individuals) to a more-adaptable open-set recognition scenario (identifying both known and unknown individuals) termed Cattle’s Face Open-Set Recognition (CFOSR). By integrating open-set techniques to enhance the closed-set accuracy, the proposed method simultaneously addresses the open-set scenario. In CFOSR, the objective is to develop a trained model capable of accurately identifying known individuals, while effectively handling unknown or novel individuals, even in cases where the model has been trained solely on known individuals. To address this challenge, we propose a novel approach that integrates Adversarial Reciprocal Points Learning (ARPL), a state-of-the-art open-set recognition method, with the effectiveness of Additive Margin Softmax loss (AM-Softmax). ARPL was leveraged to mitigate the overlap between spaces of known and unknown or unregistered cattle. At the same time, AM-Softmax was chosen over the conventional Cross-Entropy loss (CE) to classify known individuals. The empirical results obtained from a real-world dataset demonstrated the effectiveness of the ARPL and AM-Softmax techniques in achieving both intra-class compactness and inter-class separability. Notably, the results of the open-set recognition and closed-set recognition validated the superior performance of our proposed method compared to existing algorithms. To be more precise, our method achieved an AUROC of 91.84 and an OSCR of 87.85 in the context of open-set recognition on a complex dataset. Simultaneously, it demonstrated an accuracy of 94.46 for closed-set recognition. We believe that our study provides a novel vision to improve the classification accuracy of the closed set. Simultaneously, it holds the potential to significantly contribute to herd monitoring and inventory management, especially in scenarios involving the presence of unknown or novel cattle. Full article

Massive emissions of carbon dioxide (CO₂) have caused environmental issues like global warming, which needs to be addressed. Researchers have developed numerous methods to reduce CO₂ emissions. Among these, photoelectrochemical (PEC) CO₂ reduction is a promising method for mitigating CO₂ emissions. Recently, Cu₂ZnSnS₄ (CZTS) has been recognized as good photocathode candidate in PEC systems for CO₂ reduction due to its earth abundance and non-toxicity, as well as its favourable optical/electrical properties. The performance of PEC CO₂ reduction can be evaluated based on its efficiency, selectivity, and stability, which are significantly influenced by the photocathode materials. As a result, researchers have applied various strategies to improve the performance of CZTS photocathodes, including band structure engineering and surface catalytic site engineering. This review provides an overview of advanced methods to enhance the PEC systems for CO₂ reduction, focusing on CZTS. Full article

The rapid development of shrimp aquaculture has resulted in numerous ecological problems, thereby necessitating the assessment of its sustainable ecological development. This study employed the ecological footprint method to conduct a quantitative analysis of the environmental ramifications of two culture modes (pond and factory) of Penaeus vannamei. The analysis includes a horizontal comparison between two different modes and a vertical comparison among different aquaculture links of the same mode, with the objective of identifying the weak link in the aquaculture process. The results show that the ecological footprint per unit of profit of the factory culture mode was lower than that of the pond mode, while the ecological footprint per unit of output was higher in the former. Water resource consumption was identified as the primary component of the ecological footprint in both modes, accounting for over 70% of the total, followed by feed consumption. The higher energy consumption in the factory culture mode is ascribed to the operation of mass-production facilities. The feed conversion ratio in shrimp aquaculture requires improvement, as evidenced by a ratio of 1.05 in the pond mode and a higher ratio of 1.82 in the factory culture mode, indicating suboptimal feed utilization efficiency. In light of these conclusions, various measures and suggestions are put forth, including improving shrimp feed composition, implementing energy-saving measures, weighing production planning across different culture modes, and optimizing water resource utilization. Full article

As a widely used material in underground engineering, clay–cement slurry grouting is known for its initial poor anti-seepage and filtration capacity, the low strength of the resulting stone body, and its tendency towards brittle failure. To explore efficient and environmentally friendly grouting materials, industrial-grade graphene oxide (GO) was incorporated into a clay–cement slurry to create a new type of slurry called a GO composite. These GO composites were then utilized to reinforce fractured formations. Uniaxial compression tests, shear strength tests, permeability tests, and electron microscopy scans were conducted to investigate the strength, permeability, and microscopic features of the GO composite-reinforced fractured formations. Furthermore, the optimization effect and application prospects of graphene oxide on clay–cement slurry materials were evaluated. The experimental results demonstrated that the modified slurry effectively improved the compressive strength (increased by 7.2% to 32.5%) and shear strength (increased by 28.6% to 105.3%) of consolidated fractured gravel. By conducting orthogonal experiments with range analysis, variance analysis, and multiple regression analysis, it was shown that there was a strong correlation between the consolidated body and three factors influencing the permeability coefficient. Among these factors, the OPC content had the most significant impact on the permeability coefficient, followed by the GO content. Graphene oxide was found to promote cement hydration reactions, guide the growth of hydration products on the surface of graphene oxide nanosheets, optimize the pore structure in grouting materials, and reduce microcracks between the slurry and the fractured gravel interface. Electron microscopy characterization and fractal analysis revealed that the addition of graphene oxide effectively reduced the degree of microdamage during the sample’s failure process. This ensured the integrity of the sample during the unstable failure process, enhanced the material’s toughness, and improved its ability to resist loads. Full article

Cattle behavior recognition is essential for monitoring their health and welfare. Existing techniques for behavior recognition in closed barns typically rely on direct observation to detect changes using wearable devices or surveillance cameras. While promising progress has been made in this field, monitoring individual cattle, especially those with similar visual characteristics, remains challenging due to numerous factors such as occlusion, scale variations, and pose changes. Accurate and consistent individual identification over time is therefore essential to overcome these challenges. To address this issue, this paper introduces an approach for multiview monitoring of individual cattle behavior based on action recognition using video data. The proposed system takes an image sequence as input and utilizes a detector to identify hierarchical actions categorized as part and individual actions. These regions of interest are then inputted into a tracking and identification mechanism, enabling the system to continuously track each individual in the scene and assign them a unique identification number. By implementing this approach, cattle behavior is continuously monitored, and statistical analysis is conducted to assess changes in behavior in the time domain. The effectiveness of the proposed framework is demonstrated through quantitative and qualitative experimental results obtained from our Hanwoo cattle video database. Overall, this study tackles the challenges encountered in real farm indoor scenarios, capturing spatiotemporal information and enabling automatic recognition of cattle behavior for precision livestock farming. Full article

As a widely used material in underground engineering, clay-cement slurry grouting is characterized by poor initial anti-seepage and filtration capacity, low strength of the resulting stone body, and a tendency to brittle failure. In this study, a novel type of clay-cement slurry was developed by adding of graphene oxide (GO) as a modifier to ordinary clay-cement slurry. The rheological properties of the improved slurry were studied through laboratory tests, and the effects of varying amounts of GO on the slurry’s viscosity, stability, plastic strength, and stone body mechanical properties were analyzed. The results indicated that the viscosity of clay-cement slurry increases by a maximum of 163% with 0.05% GO, resulting in a decrease in the slurry’s fluidity. The stability and plastic strength of GO-modified clay-cement slurry were significantly enhanced, with the plastic strength increasing by a 5.62 time with 0.03% GO and a 7.11 time with 0.05% GO at the same curing time. The stone body of the slurry exhibited increased uniaxial compressive strength and shear strength, with maximum increases of 23.94% and 25.27% with 0.05% GO, respectively, indicating a significant optimization effect on the slurry’s durability. The micro-mechanism for the effect of GO on the properties of slurry was investigated using scanning electron microscopy (SEM) and a diffraction of X-rays (XRD) test. Moreover, a growth model of the stone body of GO-modified clay-cement slurry was proposed. The results showed that after the GO-modified clay-cement slurry was solidified, a clay-cement agglomerate space skeleton with GO monolayer as the core was formed inside the stone body, and with an increase in GO content from 0.03% to 0.05%, the number of clay particles increased. The clay particles filled the skeleton to form a slurry system architecture, which is the primary reason for the superior performance of GO-modified clay-cement slurry when compared with traditional clay-cement slurry. Full article

The tree-of-heaven trunk weevil, Eucryptorrhynchus brandti (Harold) (Coleoptera: Curculionidae), is one of the most harmful pests that damage the tree of heaven, Ailanthus altissima Swingle (Sapindales: Simaroubaceae). Aggregation behavior tests of E. brandti adults were conducted in laboratory conditions. The effects of temperature and light on the aggregation behavior of adults were tested, and the effect of sex and host was conducted with binomial choice experiments. The results showed that (1) the adults aggregate in both light and dark environments but preferred the dark environment, (2) temperature can drive the aggregation of E. brandti adults, (3) host plants could trigger E. brandti adults’ aggregation behavior, which is probably related to phytochemicals and insect feeding and localization, (4) there was mutual attraction of males and females and chemical attraction of crude intestinal extracts of males and females, and (5) aggregation behavior of E. brandti adults may also be related to the mediating of physical signals in insects. In this study, aggregation behavior can help us understand conspecific interactions and discover some strategies for effective control. Full article

Breaking the highly oil-dependent energy use structure in the transportation sector will be crucial for China to reduce its dependence on crude oil imports and ensure its energy security, and the development of new energy vehicles is helping to break this dilemma. A time series analysis summarizes the possible relationships between new energy vehicles and crude oil imports, i.e., new energy vehicles, as alternatives to fuel vehicles, will reduce the demand for oil in the transportation sector, which will in turn reduce crude oil imports, and crude oil prices and crude oil production will inhibit crude oil imports. In this empirical study, monthly data from 2015 to 2021 on crude oil imports, the market share of new energy vehicles, crude oil prices, and crude oil production are selected, time-series multiple regression modelling is adopted, and endogeneity is treated using a generalized method of moments (GMM). The regression results show that crude oil imports decrease by one unit for every 16.32% increase in crude oil prices, indicating that price factor is the most influential factor in China’s crude oil imports, while crude oil imports decrease by one unit for every 133.99% increase in crude oil production, indicating that an increase in crude oil production contributes less to the reduction of crude oil imports. One unit of crude oil imports is added for every 15.53% increase in the share of new energy vehicles, indicating that the effect of new energy vehicles on limiting crude oil imports has not yet emerged. Probably due to the fact that new energy vehicles have not yet had a significant impact on fuel vehicles, oil consumption will continue to increase in the short and medium term, with oil for the petrochemical industry becoming the primary driver of this increase. Finally, policy implications are provided from the perspective of crude oil demand, supply, and China’s oil price mechanism. Full article