Search Results (144)

With the rapid advancement of digitalization and intelligence in power systems, SF₆ high-voltage circuit breakers, as the core switching devices in power grid protection systems, have become critical components in high-voltage networks of 110 kV and above due to their superior insulation performance and exceptional arc-quenching capability. Their operational status directly impacts the reliability of power system protection. Therefore, real-time condition monitoring and accurate assessment of SF₆ circuit breakers along with science-based maintenance strategies derived from evaluation results hold significant engineering value for ensuring secure and stable grid operation and preventing major failures. In recent years, the frequency of extreme weather events has been increasing, necessitating a comprehensive consideration of both internal and external factors in the operational status prediction of SF₆ high-voltage circuit breakers. To address this, we propose an operational status assessment model for SF₆ high-voltage circuit breakers based on an Integrated Attribute-Weighted Risk Model Based on the Branch–Trunk Rule (IAR-BTR), which integrates internal and environmental influences. Firstly, to tackle the issues of incomplete data and feature imbalance caused by irrelevant attributes, this study employs missing value elimination (Drop method) on the fault record database. The selected dataset is then normalized according to the input feature matrix. Secondly, conventional risk factors are extracted using traditional association rule mining techniques. To improve the accuracy of these rules, the filtering thresholds and association metrics are refined based on seasonal distribution and the importance of time periods. This allows for the identification of spatiotemporally non-stationary factors that are strongly correlated with circuit breaker failures in low-probability seasonal conditions. Finally, a quantitative weighting method is developed for analyzing branch-trunk rules to accurately assess the impact of various factors on the overall stability of the circuit breaker. The DFP-Growth algorithm is applied to enhance the computational efficiency of the model. The case study results demonstrate that the proposed method achieves exceptional accuracy (95.78%) and precision (97.22%) and significantly improves the predictive performance of SF₆ high-voltage circuit breaker operational condition assessments. Full article

Wire Arc Additive Manufacturing (WAAM), a specific type of Directed Energy Deposition (DED) additive manufacturing, has recently gained widespread attention for manufacturing industrial components. WAAM has many advantages compared to other metal AM processes such as powder bed fusion. It is not only cost-efficient and easily accessible, but also capable of manufacturing large-scale industrial components in a short period of time. However, due to the inherent layered nature of the process and significant heat accumulation, parts can experience severe warping, often leading to part rejection. Predicting these anomalies prior to manufacturing would allow for process parameter adjustments to reduce or eliminate residual stresses and large deformations. In this study, we develop a simulation-based model capable of accurately predicting final deformations and unintended warpages. A Johnson–Cook plasticity model with isotropic hardening is implemented through a UMAT user subroutine in Abaqus. The proposed model is then utilized to predict the residual stresses and deformations in WAAM-fabricated parts. Simple wall geometries with 4, 8, and 20 layers deposited on build plates of varying thicknesses, are tested to assess the performance of the model. Combined Johnson–Cook plasticity and isotropic hardening for the WAAM process were implemented for the first time in this study, and the model was validated against experimental data, showing a maximum deviation of 4%. Thermal analysis of a four-layer-high wall took 12 min, while structural analysis using the proposed model took 1 h and 40 min. In comparison, thermo-mechanical analysis of the same geometry reported in the literature takes 14 h. The results demonstrate that the proposed model is not only highly accurate in predicting warpage but also significantly faster than other methodologies reported in the literature. Full article

This paper presents a wideband circularly polarized (CP) substrate-integrated waveguide (SIW) cavity-backed slot antenna array arranged in a 2 × 2 configuration with differential feeding structures. The design features arc-shaped microstrips within the SIW cavity to excite the ${\mathrm{TE}}_{011}^x$/${\mathrm{TE}}_{101}^y$ and ${\mathrm{TE}}_{211}^y$/${\mathrm{TE}}_{121}^x$ modes. By overlapping the center frequencies of the two modes, wideband CP radiation is achieved. The introduction of four modified ring couplers composes a simple but efficient differential feeding network, eliminating the need for balanced resistors like baluns, making it more suitable for millimeter wave or even higher frequency applications. Experimental results show that the antenna array achieves a −10 dB impedance bandwidth of 32.6% (from 17.28 to 24.00 GHz), a 3 dB axial ratio (AR) bandwidth of 13.8% (from 17.05 to 19.57 GHz), a 3 dB gain bandwidth of 41.8% (from 15.39 to 23.51 GHz) and a peak gain of 10.6 dBi, with results closely matching simulation data. This study enhances the development of differential CP SIW cavity-backed slot antenna arrays, offering a potential solution for creating compact integrated front-end circuits in the millimeter wave or Terahertz frequency range. Full article

Additive manufacturing (AM) stands out for its variable applications in terms of material, quality, and geometry. Wire Arc Additive Manufacturing (WAAM) is remarkable for producing large parts in reduced times when compared to other AM methods. The possibility of producing a part with a near-net shape not only enhances productivity but also reduces resources usage. However, parts produced by WAAM may need post-processing by machining to achieve functional surface requirements. Therefore, it is important that machining, even if minimized, does not lead to a significant environmental impact. In this sense, this work evaluates the effect of using compressed air, dry cut, and synthetic biodegradable cutting fluid at varying nozzle positions and flow rates on the surface quality of ER70S-6 steel produced by WAAM, after milling with TiAlN-coated carbide tools. To analyze the surface roughness, parameters Ra, Rq, and Rz were measured and microscopy was used to further evaluate the surfaces. The surface hardness was also evaluated. The results showed that a flow rate of 10 L/min promotes better surface quality, which can be further improved using compressed air, leading to a surface quality 50% better when compared to dry cutting. Dry cut was not suitable for machining ER70S-6 WAAM material as it resulted in rough surface texture with an Rz = 4.02 µm. Compressed air was the best overall condition evaluated, achieving a 36% Ra reduction compared to dry cutting, the second-lowest hardness deviation at 6.51%, and improved sustainability by eliminating the need for cutting fluid. Full article

Metal additive manufacturing (AM) techniques such Direct Energy Deposition (DED), Powder Bed Fusion (PBF), and Wire Arc Additive Manufacturing (WAAM) enable the production of complex metal components built at rapid rates. Because of the complexity of the process, including high thermal gradients, residual stress, and parameter optimization, these techniques pose significant challenges necessitating the need for advanced computational modeling. A powerful technique to reduce or, in some cases, eliminate these challenges at a much lower cost compared to trial-and-error experiments, is Finite Element Analysis (FEA). This study provides a comprehensive review of the FEA techniques being used and developed to model metal AM processes focusing on the thermal, mechanical, and coupled thermo-mechanical models in DED, PBF, and WAAM. Key topics include heat transfer, residual stress and distortion prediction, microstructure evolution and parameter optimization. Recent advancements in FEA have improved the accuracy of AM process simulations, reducing the need for costly experimental testing, though there is still room for improvement and further development of FEA in metal AM. This review serves as a foundation for future work in the metal AM modeling field, enabling the development of optimized process parameters, defect reduction strategies and improved computational methodologies for high-fidelity simulations. Full article

Drilling long horizontal wells in naturally cracked/fractured unconventional shale gas/oil formations presents a huge challenge to the energy industry because of wellbore clogging complications that cause pipe sticking problems. This work proposes to use smooth catenary well trajectories to reduce drilling friction to mitigate these problems. A mathematical model was developed in this study for designing well trajectory profiles with a smooth transition from the kick-out point (KOP) to the catenary section. This model consists of closed-form equations for the radius of curvature and inclination angle in the catenary section. Using the radius of curvature at the top point of the catenary section to design the arc section below the KOP eliminates the trial-and-error procedure required for achieving the smooth transition between the two sections. The result of a field case study with Tuscaloosa Marine Shale (TMS) data shows that the drilling drag (hook load) can be reduced by 15% to 30% with the use of smooth catenary well trajectories to replace the conventional arc-type well trajectories. Model-calculated reduction in the hook load drops linearly with the horizontal borehole friction coefficient (clog indicator). The reduction increases non-linearly from 15% to 30% with drill collar weight increasing from 20 lb/ft to 92 lb/ft. Full article

The mixture powders were designed by adding 0 wt.%~1.0 wt.% CeO₂ into the 2205 duplex stainless steel (DSS) powders. The 2205 DSS cladding layer was prepared on the surface of Q345 steel by plasma arc cladding technology. The effects of different CeO₂ contents on the macro-morphology, microstructure composition, and corrosion resistance of the cladding layer were studied. The action mechanism of CeO₂ in the cladding layer was also discussed. The results showed that the addition of CeO₂ modified the appearance and decreased the defect of the cladding layer. Also, the austenite grains were refined, and the austenite proportion was increased under the action of CeO₂. When the CeO₂ content was 0.5 wt.%, the appearance of the cladding layer was optimum; the austenite proportion in the upper cladding layer and the lower cladding layer reached up to 52.6% and 55.5%, respectively, and the crystal changed from columnar to equiaxed. CeO₂ decomposes into Ce element and O element under the action of the plasma arc, after which Ce element is easily absorbed at the grain boundary to reduce the surface tension and improve the fluidity of the liquid metal so as to modify the appearance of the cladding layer. Meanwhile, Ce element primarily reacts with O, S, Al, and Si elements to form low-melting-point oxygen sulfides and are then removed, which eliminates the defect of the cladding layer. Moreover, the high melting point of CeO₂ acts as heterogeneous nucleation sites during solidification, thus improving the value of nucleation rate/growth rate of the grain and promoting the transformation from ferrite to austenite. According to the electrochemical corrosion testing result, Ce element inhibited the enrichment of Cr element at grain boundaries and promoted the formation of Cr₂O₃, which improved the corrosion resistance of the 2205 DSS cladding layer. It was optimum with the CeO₂ content of 0.5 wt.%. Full article

Kidney-paired donation programs assist patients in need of a kidney to swap their incompatible donor with another incompatible patient–donor pair for a suitable kidney in return. The kidney exchange problem (KEP) is a mathematical optimization problem that consists of finding the maximum set of matches in a directed graph representing the pool of incompatible pairs. Depending on the specific framework, these matches can come in the form of (bounded) directed cycles or directed paths. This gives rise to a family of KEP models that have been studied over the past few years. Several of these models require an exponential number of constraints to eliminate cycles and chains that exceed a given length. In this paper, we present enhancements to a subset of existing models that exploit the connectivity properties of the underlying graphs, thereby rendering more compact and tractable models in both cycle-only and cycle-and-chain versions. In addition, an efficient algorithm is developed for detecting violated constraints and solving the problem. To assess the value of our enhanced models and algorithm, an extensive computational study was carried out comparing with existing formulations. The results demonstrated the effectiveness of the proposed approach. For example, among the main findings for edge-based cycle-only models, the proposed (*PRE(i)) model uses a new set of constraints and a small subset of the full set of length-k paths that are included in the edge formulation. The proposed model was observed to achieve a more than 98% reduction in the number of such paths among all tested instances. With respect to cycle-and-chain formulations, the proposed (*ReSPLIT) model outperformed Anderson’s arc-based (AA) formulation and the path constrained-TSP formulation on all instances that we tested. In particular, when tested on a difficult sets of instances from the literature, the proposed (*ReSPLIT) model provided the best results compared to the AA and PC-based models. Full article

Recently, integral electric hot incremental forming technology has been proposed to form hard-to-form sheet metals and to eliminate some defects obtained through the local heating method via current, such as inhomogeneous temperature distribution, arc burns for the sheet and the tool, unsuitability for multistage forming, etc. However, the simulation of integral electric hot incremental forming involves coupled electro-thermal-mechanical analysis, which is difficult through existing simulation software. Meanwhile, the effect of the electrode structure on temperature distribution is not clear; therefore, a preheating flux model for Joule heat was proposed to simulate the temperature distribution of Ti-6Al-4V titanium alloy sheet in this work, which could simplify the coupled electro-thermal-mechanical analysis to the coupled thermal–mechanical simulation. Meanwhile, the effect of the electrode section and length on the temperature distribution was analyzed in detail, and then a design criterion for the electrode length was obtained during integral electric hot incremental forming. Full article

Common single-line 2D LiDAR sensors and cameras have become core components in the field of robotic perception due to their low cost, compact size, and practicality. However, during the data fusion process, the randomness and complexity of real industrial scenes pose challenges. Traditional calibration methods for LiDAR and cameras often rely on precise targets and can accumulate errors, leading to significant limitations. Additionally, the semantic fusion of LiDAR and camera data typically requires extensive projection calculations, complex clustering algorithms, or sophisticated data fusion techniques, resulting in low real-time performance when handling large volumes of data points in dynamic environments. To address these issues, this paper proposes a semantic fusion algorithm for LiDAR and camera data based on contour and inverse projection. The method has two remarkable features: (1) Combined with the ellipse extraction algorithm of the arc support line segment, a LiDAR and camera calibration algorithm based on various regular shapes of an environmental target is proposed, which improves the adaptability of the calibration algorithm to the environment. (2) This paper proposes a semantic segmentation algorithm based on the inverse projection of target contours. It is specifically designed to be versatile and applicable to both linear and arc features, significantly broadening the range of features that can be utilized in various tasks. This flexibility is a key advantage, as it allows the method to adapt to a wider variety of real-world scenarios where both types of features are commonly encountered. Compared with existing LiDAR point cloud semantic segmentation methods, this algorithm eliminates the need for complex clustering algorithms, data fusion techniques, and extensive laser point reprojection calculations. When handling a large number of laser points, the proposed method requires only one or two inverse projections of the contour to filter the range of laser points that intersect with specific targets. This approach enhances both the accuracy of point cloud searches and the speed of semantic processing. Finally, the validity of the semantic fusion algorithm is proven by field experiments. Full article

Real-time parametric interpolation plays a crucial role in achieving high-speed and high-precision multi-axis CNC machining. In the interpolation cycle, the position of the next interpolation point is required to be calculated in real-time to guide the action of the machining process. Due to the existence of the positioning error of the interpolation point, it is extremely difficult to eliminate the feedrate fluctuation, which may lead to dramatic decreases in machining quality and the driving capabilities’ saturation of each axis. A computationally efficient and precise feedrate fluctuation minimization method is proposed for the NURBS tool path interpolation in the CNC milling process. The model for the arc length and curvature, with respect to the parameter of the NURBS tool path, is established to reduce the calculation amount required by interpolation points determination. The deviation between the theoretical and actual interpolation step length is decreased by the proposed arc length compensation method to minimize the feedrate fluctuation. In addition, the interpolation points derived from the arc length compensation process are further corrected by performing the Newton iteration to restrict the feedrate fluctuation within the preset accuracy threshold. The effectiveness and superiorities of the proposed feedrate fluctuation minimization method are verified by simulation and milling experiments. Full article

Zinc-based oxides are the main products obtained after the Waelz process, a metallurgical method used industrially for the treatment of electric arc furnaces. These oxides have certain impurities in their composition, which can be a disadvantage. Carbochlorination reduction reactions have proven to be useful in eliminating certain impurities (especially Pb) through thermal treatments. In this work, a method for purifying Waelz oxide through carbochlorination reduction reactions is presented. Several experiments have been conducted with the aim of obtaining samples with potential end applications. A deep characterization of the purified oxides has been performed by means of X-ray microanalysis, X-ray diffraction, Raman spectroscopy, and cathodoluminescence. These measurements indicate the presence of ZnO and ZnFe₂O₄ in different proportions, depending on the different amounts of reducing and chlorinating agents used. Full article

Objectives: We aimed to develop a population pharmacokinetic (PopPK) model and evaluate dosing regimens for different renal clearances and continuous renal replacement therapy (CRRT) settings. Methods: Data were collected from four studies in intensive care unit (ICU) adult patients receiving 400–600 mg of ceftaroline every 8–12 h in a one-hour infusion. The PopPK model was developed according to non-linear mixed effects modeling implemented in Monolix 2024R1. To investigate dosing recommendations, Monte Carlo simulations and probability of target attainment (PTA) analysis were performed in Simulx 2024R1. Results: We collected 296 plasma concentrations from 29 non-CRRT patients and 24 pre-filter (systemic), 23 post-filter, and 23 effluent concentrations from four CRRT patients using WebPlotDigitizer (Version 4.7). A five-compartment model, with the first-order elimination from the central compartment and additional elimination with the effluent during CRRT, best described the ceftaroline concentrations. Creatinine clearance (Cl_Cr) was identified as a covariate on the clearance of elimination (Cl) and CRRT modality on the central and peripheral compartments’ volumes and intercompartmental clearance. The results of dosage simulations for different CRRT modalities and Cl_Cr, S. pneumoniae (MIC = 0.25 mg/L) and methicillin-resistant S. aureus (MRSA) (MIC = 1 mg/L) infections, and assumed 100%ƒT_>MIC target, revealed that registered ceftaroline dosages are sufficient to achieve assumed PTA, except MRSA infection in patients with augmented renal clearance (ARC). Conclusions: Our successfully developed model allows flexible PK simulations of ceftaroline, including real-time changes in settings and even temporary or permanent cessation of CRRT. However, the results of our study warrant clinical validation and should be used with caution primarily due to the limited CRRT patient number included in the analysis. Full article

Boron nitride (BN) ceramic is an important support material in aerospace, arc discharge devices, and vacuum electronics. The electron emission properties of BN surfaces are of significance among various space applications. In this work, by preparing BN thin films and microstructured BN bulks, we have investigated the influence of the surface physical properties on the electron emission coefficient (EEC). The results showed that the surfaces of BN films, which were prepared by magnetron sputtering, produced serious gas adsorption and organic contamination when they were left for 10 days, and these surface modifications made the EEC of BN film surface decrease to a certain extent. The argon ion cleaning experiments indicated that the process of ion cleaning was able to partly eliminate the surface adsorption and contamination for the BN film. The EEC of the cleaned BN film surface was significantly improved compared to that of the original polluted BN film surface, with an EEC peak value of about 3.2 instead of 3.0 for the original polluted surfaces. By contrast, the EEC curves of the BN bulk show some difference, with the peak values of the EEC curves being 2.62 for the untreated BN bulk. The results of laser etching on the BN bulk surface to form microarray structures show that the EEC of BN bulk decreases significantly with the increase of the average aspect ratio of the microstructures. The EEC peak values of the BN bulks decrease from 2.62 to 1.16 when the porosity of the BN bulk reaches 49.11% and the aspect ratio reaches 1.36, indicating that constructing a surface microstructure is an effective method to achieve EEC reduction. By employing the electron trajectory tracking algorithm and the phenomenological model of electron emission, the effect of microstructure on EEC for BN bulk was quantitatively explained. The results of the study are of engineering application significance for vacuum devices involving the electron emission process of BN ceramic. Full article

Although wire arc-directed energy deposition (WA-DED) technology demonstrates advancements in the rapid manufacturing of high-strength Al-Cu aluminum alloy components, coarse microstructures and pore defects inhibit its further development and application. In this study, friction stir processing (FSP) post-treatment was employed to improve the microstructure and mechanical properties of the 205A aluminum alloy component produced by WA-DED, and the effects of rotational rate on the microstructure and properties were also investigated. Key findings showed that the average grain size of the as-deposited sample was significantly refined from 22.8 μm to less than 5 μm after FSP post-treatment, and most of the pore defects were eliminated. Most of the α-Al + θ-Al₂Cu eutectic structures distributed on the grain boundaries were dissolved into the α-Al matrix after FSP post-treatment, and the element segregation phenomenon was effectively improved. The microhardness of the stirred zone significantly increased due to the microstructure refinement and pore elimination. The excellent elongation of the component was obtained after FSP post-treatment using a relatively low rotational rate of 800 min⁻¹. Comparatively, after improving the rotational rate to 1200 min⁻¹, the strength of the component slightly increased with the reduction in elongation. Compared to the as-deposited sample, the average yield strength, ultimate tensile strength, and elongation increased by 32.7%, 20.6% and 56.7%, respectively. Full article