Search Results (364)

Given the issues in natural orchard environments, such as large-scale variations of defective citrus fruits, weak texture boundaries, strong illumination changes, branch and leaf occlusion, and significant background interference, this paper constructs a lightweight detection model, RT-DETR-DCEA, based on RT-DETR-R18. This model is improved through four aspects: “fine-grained defective feature extraction—multi-scale feature fusion—up-sampling detail recovery—global feature interaction for noise suppression”. First, a Dynamic Hybrid Convolution Module (DIMB) is introduced into the backbone network, drawing on the ideas of Inception-style multi-branch depthwise convolution and MetaFormer residual mixing. It extracts local textures of various forms through square convolution, horizontal strip convolution, and vertical strip convolution, and utilizes dynamic branch weights to enhance the model’s adaptability to irregular defects such as lesions, mildew, and external damage. Second, a Content-Guided Attention Feature Fusion Network (CGAFN) is designed in the neck network, which achieves adaptive fusion of low-level detail features and high-level semantic features through channel attention, spatial attention, and pixel-level fusion weights. Next, a lightweight upsampling enhancement module called EUCB-SC is constructed, which introduces channel rearrangement and Shift spatial offset into the efficient upsampling convolutional structure to enhance the local spatial interaction capability of upsampled features with low parameter overhead. Finally, adaptive sparse self-attention is introduced into the AIFI module to form AIFI-ASSA, which suppresses irrelevant background interactions through a sparse attention branch and retains necessary contextual information through a dense attention branch. The experimental results demonstrate that on a dataset containing four categories of citrus images—healthy, diseased, moldy, and severely externally damaged—RT-DETR-DCEA achieves 92.1% Precision, 86.1% Recall, and 91.8% mAP@50, with a parameter count of 1.477 × 10⁷ and an inference speed of 81 FPS. Compared with the original RT-DETR-R18 and various YOLO series models, this method strikes a favorable balance among detection accuracy, recall capability, and model lightweightness. This paper also discusses limitations such as data scale, ratio of private data, single training result, and insufficient validation on edge devices, providing a basis for subsequent cross-regional data validation and real-world deployment testing. Full article

Fabricated reinforced concrete columns are important components of reinforced concrete structures. During the design reference period, columns are prone to degradation in mechanical and deformation properties, which affects the normal service of the structure. Based on compressive tests of fabricated reinforced concrete columns, this paper uses ABAQUS 2021 finite element analysis software to explore how factors such as column damage and CFRP sheet layout affect the compressive performance of fabricated concrete columns under eccentric compression in order to investigate their mechanical properties and the confinement effect of CFRP sheets on such columns. The results indicate that the change trend of the bearing capacity of the finite element model is largely in agreement with that of the test specimens, and the ultimate bearing capacity error is below 3%, thereby confirming the validity of the finite element model. Compared with strip confinement, full-wrap confinement achieves a greater improvement in ultimate bearing capacity, and two to three layers are recommended as the ideal number of CFRP sheets for strengthening. The maximum increase in ultimate bearing capacity can reach 19.18%. When the strip width is constant, the smaller the spacing, the smaller the concrete strain in the compression zone. When the net spacing is constant, reducing the strip width increases the number of cracks and decreases crack width, but reduces the ultimate bearing capacity of the column accordingly. Strengthening with CFRP sheets can enhance the ultimate bearing capacity, deformability, and ductility of columns with initial damage under both small and large eccentric compression. The maximum increase in ultimate bearing capacity can reach 8.31%. The results obtained in this paper are conducive to promoting the reinforcement and reconstruction of fabricated reinforced concrete columns and reinforced concrete structures. Full article

This paper presents a detailed case study of a semi-top-down excavation carried out for the Haowang Tower project in Shaoxing, China, where thick soft clay deposits dominate the subsurface profile. The excavation, covering approximately 10,000 m² in plan area and reaching a depth of 12.35 m, posed significant challenges due to the presence of sensitive adjacent utilities and roads. In response, an integrated design–construction strategy was adopted, combining soldier pile retaining walls with a permanent first-floor slab serving as horizontal bracing. Several innovative structural features—including load-transfer beams, stress-reinforced strips, and soil molds—were introduced to address the specific demands of the semi-top-down method in soft ground. A multi-stage numerical analysis framework was implemented, employing the Hardening-Soil (HS) model within 2D and 3D finite element analyses (PLAXIS), alongside the subgrade reaction method (FRWS2006). Predicted wall deflections, ground settlements, and structural forces were systematically compared with field measurements. The 3D analysis showed good agreement for wall deflections (within 5% of the maximum measured value), validating the approach’s effectiveness. However, the analysis over-predicted ground settlements (e.g., sewage pipe settlement was over-predicted by 60%), indicating a need for more refined settlement prediction models or parameter calibration. Based on this finding, a correction factor of 0.6–0.7 is proposed for settlement prediction when using HS parameters derived from standard drained tests. The results also highlight the importance of spatial effects and the critical role of construction sequencing. This study offers both practical insights and validated numerical tools for similar deep excavations in urban soft clay environments. Full article

This paper presents research on reinforced concrete beams strengthened with non-pretensioned and pretensioned near-surface-mounted (NSM) carbon fibre-reinforced polymer (CFRP) strips under self-weight and external preloading. The first part of this paper briefly describes and discusses the results of experimental tests performed on six beams with different reinforcing steel ratios, preloading levels, and strengthening-system configurations. Next, three-dimensional (3D) numerical models of the tested specimens were developed. The models consider the nonlinear behavior of concrete (both in tension and compression), steel bars, and the interface between concrete and CFRP laminates. For these models, the material parameters were established based on experiments and recommendations from the literature. Furthermore, a sensitivity analysis was conducted with respect to the material parameters of the model that were not directly obtained from experimental measurements. The analyses validated the applicability of the numerical model in predicting the flexural behavior of reinforced concrete (RC) members strengthened with near-surface-mounted (NSM) CFRP materials over the full loading range. Furthermore, the developed models were employed to assess the effectiveness of active strengthening relative to passive strengthening methods (i.e., without pretensioning of the laminate). A comparison study of actively and passively strengthened elements indicates that prestressing does not affect the ultimate limit state but enhances serviceability limit states. The presented computational model, together with the adopted computational strategy, demonstrates its effectiveness for analyzing realistic scenarios involving RC beams that are damaged and subjected to loading during the strengthening process. Full article

Lithium-ion batteries have been widely used as energy storage and power batteries due to their unique advantages. However, with increasing demands for battery performance and application scenarios, battery safety has become a significant obstacle to their application. To address this issue, this paper proposes and fabricates an advanced polyimide (PI) separator material with high porosity and excellent thermal stability. By introducing sodium chloride (NaCl) as a pore-forming template into a polyamic acid (PAA) precursor, a PI-based separator with a uniformly interpenetrating sponge-like pore structure was successfully constructed. The obtained PI-NaCl separator exhibits outstanding thermal structural stability, maintaining dimensional integrity without significant thermal shrinkage even when tested at temperatures as high as 250 °C. Furthermore, the porous structure of the PI-NaCl separator demonstrates excellent electrolyte wettability, as the electrolyte rapidly spreads upon contact (contact angle approaching 0°), which is significantly superior to commercial separators. In lithium symmetric cell tests, this separator achieves long-term stable stripping/plating cycling by virtue of its outstanding ionic conductivity, effectively mitigating interfacial side reactions with lithium metal. In LiFePO₄||C full-cell applications, the PI-NaCl-based battery exhibits good rate capability and cycling stability. Additionally, in an open-circuit voltage (OCV) monitoring experiment at a high temperature of 80 °C, the voltage of the PI-NaCl-based battery remained stable continuously for 8 h in comparison to that of the commercial separator-based battery. Full article

Strengthening existing structures and bridges allows us to continue using them, increase their reliability, resistance, durability and extend their service life instead of demolishing them and replacing them with new ones. This helps to reduce CO₂ (decarbonization). The use of prestressed CFRP strips represents the use of new modern materials and new technology for strengthening existing bridges. The paper is focused on the use of prestressed CFRP strips for strengthening a concrete bridge made of precast prestressed box girders as the most suitable strengthening alternative in a given case. This is a technology that is more commonly used for strengthening structures, but it is not common to use this technology for strengthening bridges. There are relatively few examples of using this technology for strengthening bridges, also because these are dynamically loaded structures. The paper firstly presents the diagnostics and calculation of the load-carrying capacity of the railway bridge on a narrow-gauge railway line in Štrbské Pleso, Slovakia, and then the strengthening of the given bridge. The bridge is located in the mountains of the High Tatras in the northern part of Slovakia and bypasses two local roads. The bridge was made from the precast prestressed post-tensioned box girders of six single spans. The visual inspection, diagnostics, and verification of real dimensions and material characteristics were requested. The non-destructive and semi-destructive methods of testing were used to determine the geometrical and materials’ properties. After that, the calculation of the load-carrying capacity was done. For this purpose, a numerical 3D FEM model was created. For determining the load-carrying capacity, the standard approach, given in Eurocodes, was used according to provisions, which take into account the modified (lower) reliability levels and their adequate partial safety factors. From the calculation, it follows that the bridge should be strengthened. The strengthening of the superstructure was done using prestressed CFRP strips in the lower part of the box girders. This is one of the first applications of this modern method of strengthening, not only in Slovakia but in Central Europe as well. Full article

High friction composite brake shoes containing reinforced steel fibers are now widely used in freight train tread braking systems. With the demand for higher transportation efficiency on railway lines with long steep slopes, it is necessary to explore the braking capabilities of existing general freight train high friction composite brake shoes under continuous braking conditions. In this paper, continuous braking tests at different speed levels were conducted using a friction and wear test rig. Through material characterization and interface damage analysis, it was found that reinforced steel fibers can exist as a contact platform at the brake shoe friction interface. Due to the strip-like morphology and high strength features of steel fibers, even after the steel fiber layer is fragmented, it can still promote the formation of a continuous contact platform with complex material composition on the surface, maintaining the progress of the braking process. For existing general freight train high friction composite brake shoes, at speeds up to 80 km/h, although the friction coefficient decreases to some extent, the wear rate maintains a relatively low range. When the speed increases to 100 km/h, the friction coefficient of the braking interface deteriorates severely, and the wear rate of the brake shoe increases sharply, seriously endangering braking safety. The research results reveal the evolution of wear behavior of high friction composite brake shoes containing reinforced steel fibers at different speed levels, providing theoretical support for exploring the braking capabilities and design optimization of brake shoes. Full article

Crop disease diagnosis can be degraded by structured cast shadows, including panel-like strip shadows that motivate applications in agrivoltaic-style farming. This paper presents ShadowFormer-AV, a transformer-based framework that adapts general shadow-robust visual learning to crop disease classification by separating disease evidence from illumination interference. The proposed approach combines a soft shadow-prior extractor, an illumination-decoupled dual-stream token encoder, lesion-preserving adaptive attention, and a cross-view consistency objective between original and shadow-perturbed images. The method uses only standard RGB inputs and does not require shadow-free reference images, multispectral sensing, or pixel-level shadow annotation. We evaluated the framework on publicly available plant disease datasets using calibrated panel-like synthetic shadows and a naturally shadowed PlantDoc subset. Because no on-site agrivoltaic disease dataset was used, the conclusions were limited to shadow robustness under these simulated and naturally shadowed test conditions rather than verified performance under real photovoltaic-panel shadows. Within this validation boundary, ShadowFormer-AV improved accuracy, Macro-F1, and calibration over representative convolutional and transformer baselines, suggesting that illumination-aware token learning is useful for crop disease recognition under structured shadow interference. Full article

The pantograph–catenary system is a crucial component of rail transit vehicles, performing the vital function of electric energy transmission. During train operation, the current-carrying components continuously emit particulate matter into the surrounding environment due to friction, and these particulate emissions have a significant impact on human health. However, research on the correlation between the current-carrying friction of carbon contact strips and particulate matter emission characteristics is rarely reported. Based on a semi-enclosed pin-on-disc current-carrying friction and wear test rig, this paper investigates the effects of varying current intensity under different contact load conditions on the friction and wear performance of carbon/copper pairs, as well as the associated particulate matter emission behavior. It reveals the damage characteristics of carbon contact strips, the particulate matter emission characteristics, and the relationship between them under different service conditions. The results indicate that the wear mechanism and particulate matter emission behavior of carbon contact strips are jointly influenced by current magnitude and contact load. In the absence of current, increasing the load exacerbates the mechanical wear on the carbon friction pair surface, while elevating the emission concentration of particles of various sizes and stabilizing the particle size distribution. Under current-carrying conditions, a higher contact load effectively reduces the frequency of arc discharges between the friction pair. Meanwhile, the degree of arc erosion on the contact surface worsens with increasing current intensity. Arc discharges instantaneously lead to a sharp increase in particulate emissions, and the higher the discharge intensity or the greater the number of discharges, the higher the particulate concentration around the contact pair. Full article

To address the problem of insufficient shear bearing capacity of highway reinforced concrete (RC) T-beams, this paper systematically conducts a comparative study on the shear performance of RC T-beams strengthened with UHPC-CFP toughened composite plates of different configurations, and proposes a shear strengthening method using UHPC-CFP toughened composite plates. Comparative tests on different strengthening configurations are carried out. Meanwhile, a finite element numerical model is established to compare with the experimental results, analyze the influences of different strengthening schemes on the shear bearing capacity and mechanical properties of the beams, reveal the shear strengthening mechanism, and put forward a recommended formula for calculating the shear bearing capacity. The results show that after the diagonal cracks appeared in Beam T-0, they propagated rapidly from the support to the loading point. Beam T-1 had more diagonal cracks in the concrete between the UHPC-CFP toughened composite strips, while Beam T-2 had fewer. Fine cracks occurred in the UHPC-CFP toughened composite strips of Beams T-1 and T-2, whereas no cracking was observed in the UHPC composite rectangular plate of Beam T-3. The shear capacity of all strengthened beams was improved, with increases of 27.0%, 40.5%, and 43.2% for Beams T-1, T-2, and T-3, respectively. Beam T-3 exhibited the maximum deflection, and the strengthening configuration of Beam T-2 was determined to be the optimal. The carbon fiber strips embedded in UHPC effectively delayed the propagation of cracks in the UHPC plate and played the role of “reinforcement”. The truss–arch model theory is also applicable to the shear mechanism of concrete T-beams strengthened with UHPC-CFP toughened composite plates. Verification of Beams T-2 and T-3 using the proposed formula for shear design of strengthened beams showed that the average ratio of the calculated shear capacity to the experimental value was 0.87, indicating the reliability of the calculation results. Full article

Paper-based rapid tests are widely used in point-of-care diagnostics due to their simplicity and low cost. However, their application in quantitative analysis remains limited. In this work, a nucleic acid lateral flow assay (NALFA) was integrated with an automated image acquisition system built on a Raspberry Pi platform for the quantitative detection of SARS-CoV-2 virus, increasing the accuracy of the test compared to subjective visual interpretation. The assay employed blue polystyrene microspheres as reporters, while automated image capturing, image processing and quantification were performed using custom Python software (version 3.12). Signal quantification was achieved by comparing the grayscale intensity of the test line with that of a simultaneously captured negative control strip, allowing correction for illumination and background variability. Calibration curves were used for the training of the algorithm. The system was applied for the analysis of a series of samples with varying DNA concentrations, yielding recoveries between 84 and 108%. The proposed approach integrates a simple biosensor with an accessible computational platform to achieve full low-cost automation. This work introduces the first Raspberry Pi-driven image processing approach for accurate quantification of NALFAs and establishes a foundation for future low-cost, portable diagnostic systems targeting diverse nucleic acids, proteins, and biomarkers. Full article

Background: QRS complex detection is a key processing step of automated ECG analysis and determines its overall quality. The purpose of this paper is to study the detection performance of probably the most frequently implemented ready-to-use QRS detector in the presence of noise and with tightened temporal tolerance of detection points. Methods: We applied commonly used detection statistics (Detection Error Rate, Sensitivity, Positive Predictive Value, and F₁ score), but re-defined true positive detection based on variable time jitter between detected and reference points. We also applied a controlled level of mixed noise to assess the detector’s performance in true-to-life conditions. Results: We found the following: (1) the detector under test showed a considerable drop in quality when reducing the jitter between 97.23 ms (DER = 8.08%) and 86.12 ms (DER = 67.22%), which means that the detection points’ time series are not accurate enough to be directly used for ECG time analysis; (2) with jitter allowed to 163.90 ms and an increasing noise level (SNR from 20 dB to −7.96 dB), the detection quality drops (DER from 0.98% to 57.13% respectively); however, an analysis of individual files revealed records, where the algorithm performs better in the presence of noise; (3) with a step-by-step code execution analysis of ECG strips where better performance was the most prominent, the imprecise definition of the local maximum was the cause of DER errors. Conclusions: Our research clearly indicates that selecting a QRS-detection algorithm based solely on DER, Se, and PPV detection statistics may be incorrect. Two equally important detection quality parameters are the change in the DER error rate with tightened requirements of jitter and robustness of the detection statistics DER, Se, and PPV to noise level variations (algorithm’s detection points immunity to noise). Full article

Natural dyes have emerged as a promising alternative to synthetic dyes for industrial applications due to their advantages, namely, easy availability, low cost, and environmental friendliness. In this sense, natural dyes, due to their potential to react over the pH range, could offer an alternative to conventional pH measuring techniques for industrial products, such as potentiometers, sensors, or indicator drops. Therefore, this project aims to evaluate the potential of several natural organic dyes in response to changes in pH and develop an indicator for determining pH grades. We extracted and analyzed the pigments of forty natural vegetable species using two extraction methods with a mixture of solvents, specifically 70% MeOH/30% H₂O. The results find that pigments of cabbage, hibiscus flower, radish, and turmeric in their dry state exhibit the best reaction over a broad pH range, and color can be easily distinguished according to its level. These findings demonstrate the potential of natural dyes as a novel approach for pH verification, providing a sustainable and cost-effective alternative to conventional techniques. Full article

As the core observation instrument of the China Space Station Telescope (CSST), the Survey Camera (SC) generates microvibrations that significantly degrade the telescope’s imaging quality. Consequently, evaluating the microvibration response of the SC is of critical importance. However, for large-inertia, high-stiffness payloads like the SC with discrete interfaces, structural coupling between the payload and the test system leads to distortions in microvibration test results. Since the vibration transmission under structural coupling is not a simple series superposition, and the transfer functions of each link in the transmission path as well as the coupling correction matrices are difficult to obtain, this paper proposes a semi-physical simulation method for microvibration decoupling. The method first establishes a coupled finite element model of the SC and the test system. The model is iteratively modified based on the results of modal tests and transmissibility tests to ensure consistency with the dynamic characteristics of the actual coupled system. The model is validated through microvibration response tests, and the results show good agreement between the model and the actual system (the RMS deviation of force/torque is less than 5%). After stripping the test system from the modified coupled model, the intrinsic microvibration responses of the SC can be extracted, achieving the dynamic decoupling analysis of the complex coupled system. Full article

Bisphenol A (BPA) is widely used as a hardener in plastics production and its release and circulation in ecosystems lead to negatively impacts the human endocrine system. Therefore, there is a need for simple and efficient BPA monitoring tools. This paper presents a combination of two approaches for this purpose: the use of magnetic particles (MPs) as antibody carriers and immunochromatographic test strips based on quantum dots (QDs) for recording labeled immune complexes. Initially, free antigen binds to the MP-specific antibody conjugate, concentrating the sample to a final volume of 200 µL. A competitive interaction then occurs in the analytical zone of the test strip with immersion in a QDs solution. The visual detection limit of BPA was 2.7 μg/mL, the instrumental detection limit was 0.03 μg/mL, and the working range of quantification was 0.3–100 μg/mL (reproducibility was 7.7%, R² = 0.985). Concentration using MP reduces the detection limit by 100-fold (0.3 ng/mL). The developed test was used for qualitative control of the presence and quantitative determination of BPA content in samples of drinking and natural water (the detection rate is in the range of 94–110%). Full article