Search Results (9,955)

In order to explore the influence of different layer treatment methods on the macro- and meso-mechanical properties of cemented sand and gravel (CSG), in this paper, the shear behavior of CSG material was simulated by a three-dimensional particle flow program (PFC3D) based on the results of direct shear test in the laboratory. In shear tests, untreated CSG samples with interface coating mortar and chiseling were used, and granular discrete element software (PDC3D 7.0) was used to establish mesoscopic numerical models of CSG samples with the above three interface treatment methods, in order to reveal the effects of interface treatment methods on the interface strength and damage mechanism of CSG samples. The results show that, with the increase in normal stress, the amount of aggregate falling off the shear failure surface increases, the bump and undulation are more obvious, and the failure mode of the test block is inferred to be extrusion friction failure. The shear strength of the mortar interface is 40% higher than that of the untreated interface, and the failure surface is smooth and flat under different normal stresses. The shear strength of the chiseled interface is 10% higher than that of the untreated interface, and the failure surface fluctuates significantly under different normal stresses. Through the analysis of the fracture evolution process in the numerical simulation, it is found that the fracture of the sample at the mortar interface mainly expands along the mortar–aggregate interface and the damage mode is shear slip. However, the cracks of the samples at the gouged interface are concentrated on the upper and lower sides of the interface, and the damage mode is tension–shear. The failure mode of the samples without surface treatment is mainly tensile and shear failure, and the failure mode gradually changes to extrusion friction failure. Full article

Current designs of sealing systems for non-adhesive flexible pipe end-fittings primarily address short-term loading conditions, often overlooking the creep behavior of polyvinylidene fluoride (PVDF) and the material used in the sealing layer. Over time, the creep of PVDF, particularly at elevated temperatures, can lead to excessive reduction in the sealing layer’s thickness, thereby compromising the sealing performance of the end-fittings. In this study, to address the creep-related issues in the sealing layer, the compression and compression creep tests of PVDF were conducted at different temperatures to establish the material’s elastic-plastic constitutive relationship and develop a creep constitutive model based on the time hardening model. Using the pressure penetration method within ABAQUS software, a two-dimensional axisymmetric finite element model of the end-fitting sealing system was constructed, incorporating the effects of internal fluid pressure. This model was employed to analyze the sealing performance while accounting for the materials’ creep behavior across varying temperature conditions. The results demonstrate that creep in the sealing layer occurs predominantly in the early stages post-installation. Furthermore, the API 17J standard, which stipulates that reduction in sealing layer thickness should not exceed 30%, is found to be conservative at high temperatures. In these conditions, although the thickness reduction exceeds 30% before the maximum contact pressure drops below the fluid pressure, no fluid leakage is observed. Thus, in the initial phase following installation, especially at elevated temperatures, monitoring for potential leakage is critical. This research is the first to quantify the long-term impact of PVDF creep behavior on the sealing performance of flexible pipe end-fittings through comprehensive experiments and simulation analysis. The findings provide both a theoretical foundation and practical guidance for enhancing the long-term sealing performance of flexible pipe end-fittings. Full article

Masked jet electrolytic machining has the advantages of high machining efficiency and good surface morphology, giving it important applications in fields such as bionic marine animal manufacturing. The factors affecting the electrolytic machining speed are deduced; a modeling simulation is carried out by COMSOL software; the electrolyte potential map and current density line map inside the microgroove are analyzed; and measurements of the actual machined microgroove are made by a scanning microscope to carry out the experiments of electrolytic characteristics and morphology of the microgroove under different pulse voltages, machining gaps, and machining times. Experiments show that the pulse voltage plays a dominant role in processing, and when the pulse voltage is increased from 50 V to 125 V, the microgroove width increases by an average of 7.7%, and the depth increases by an average of 28.8%, which significantly improves the surface microstructure of the bionic marine animal. Full article

In this study, the JiaoGang Basin in the Yangtze River Delta plains of the river network area was the research object. A basin water level simulation model was constructed based on the physical mechanism model and Mike software, and the parameters were calibrated and validated. Based on the dataset produced by the physical model, three types of ML models, Support Vector Machine (SVM), random forest (RF), and gradient boosting decision tree (GBDT), were constructed, trained, validated, and compared with the physical model. The results showed that the physical mechanism model met the water level simulation accuracy requirements at most stations. In the training and validation periods, the RF water level simulation and GBDT water level simulation models had root mean square errors (RMSEs) of all stations less than 0.25 and the Nash–Sutcliffe coefficient (NSE) of all stations was greater than 0.7. The physical mechanism model and ML water level simulation models can simulate the water level in the JiaoGang Basin better. The RF and GBDT models considerably outperform the physical mechanism model in terms of the peak simulation errors and peak present time errors, and the fluctuations of the ML water level simulation models (RMSE and NSE) are minor compared to those of the physical mechanism model. Full article

As a non-invasive imaging method, electrical impedance tomography (EIT) technology has become a research focus for grounding grid corrosion diagnosis. However, the existing algorithms have not produced ideal image reconstruction results. This article proposes an electrical impedance imaging method based on sparse representation, which can improve the accuracy of reconstructed images obviously. First, the basic principles of EIT are outlined, and the limitations of existing reconstruction methods are analyzed. Then, an EIT reconstruction algorithm based on sparse representation is proposed to address these limitations. It constructs constraints using the sparsity of conductivity distribution under a certain sparse basis and utilizes the accelerated Fast Iterative Shrinkage Threshold Algorithm (FISTA) for iterative solutions, aiming to improve the imaging quality and reconstruction accuracy. Finally, the grounding grid model is established by COMSOL simulation software to obtain voltage data, and the reconstruction effects of the Tikhonov regularization algorithm, the total variation regularization algorithm (TV), the one-step Newton algorithm (NOSER), and the sparse reconstruction algorithm proposed in this article are compared in MATLAB. The voltage relative error is introduced to evaluate the reconstructed image. The results show that the reconstruction algorithm based on sparse representation is superior to other methods in terms of reconstruction error and image quality. The relative error of the grounding grid reconstructed image is reduced by an average of 12.54%. Full article

The knotter, as a core module for the knotting function of a rice electric binder, has structural parameters and spatial configurations that significantly impact the efficiency and quality of rice collection, making the in-depth analysis and optimization of these parameters, and their spatial relationships, crucial for enhancing the operational quality of the rice electric binder. At present, rice binders still face the issues of a low bundling efficiency and quality, which affect the progress of rice harvesting during the harvest season. Through theoretical analysis and calculation, this study determined the main parameters affecting the knotter’s knotting process and their value ranges. Based on the ADAMS software, a simulation model of the knotter operation was constructed. Using the Box–Behnken design (BBD) method and response surface analysis of variance, a regression prediction model for knotter operation evaluation indicators was established, and the multi-objective optimization of the knotter’s operation quality was performed. The prediction results showed that, under the optimal structural parameter combination of a 30.23° angle between the knotting pincer and rope guard axes, a −3.75 mm rope clamping board position, and a 40.75° inclination angle of the knotting pincer convex platform, the knotter’s knotting quality reached the best state, with an average knot end protrusion of 9.10 mm and a maximum tension of 134.25 N on the knotting rope. The field tests results showed an average knot end protrusion of 9.60 mm and a maximum tension of 127.87 N on the knotting rope, with average relative errors of 5.82% and 4.72% compared to the theoretical values, respectively. After optimizing the knotter, the average knot end protrusion increased by 14.48% and the maximum tension of the knot rope was reduced by 11.27%. Meanwhile, the knotter achieved an average bundling rate as high as 99.3%. The bundling success rate also increased by 2.7%. These results fully verify the reliability and accuracy of the regression model, and demonstrate the reasonableness of the knotter structural parameter optimization design, providing a theoretical basis and reference for improving the operational quality of the rice electric binder. Full article

The shear-yielding bolt is a new type of anchoring structure, and its working mechanism in layered rocks is not yet well understood. To investigate its transverse shear characteristics, this paper takes the shear-yielding bolt as the research subject and uses different anchoring states of bolts as variables. A comparative study of shear-yielding bolts and traditional bolts is conducted using the Abaqus numerical simulation software and large-scale direct shear tests. The results show that (1) low-modulus material allows a slight displacement between the structural surface layers, which exerts the friction strength between rock mass layers and avoids stress concentration on the bolt. The shear-yielding bolts reach their peak shear stress in the case of greater displacement, averagely increased by 40% compared to traditional anchor bolts. (2) An increase in the moisture content has less influence on the shear-yielding bolt owing to the material properties. When the moisture content of the structural surface rises from 12% to 20%, for cases where the shear-yielding bolts are used, the peak shear stress decreases by 0.12 kPa, which only accounts for 12% of the original strength. (3) There is an optimum thickness of the low-modulus material in the shear-yielding bolt, considering its effect of releasing shear and the bonding effect between it and the bolt. According to the test results and numerical analysis, the optimum thickness is 15 mm. The results of this research provide a reference and basis for future study and engineering applications of shear-yielding bolts. Full article

Road paving costs have significantly increased in the last decades not only because of the increase in oil price globally, which has in turn increased the prices of bitumen, transportation, coarse aggregate and fine aggregate, but also due to the shortage of these virgin materials. Thus, it is essential to find more sustainable and cost-effective road paving solutions. This research focuses on the combination of recycled asphalt pavement (RAP) and crumb rubber extracted from end-life tires and new asphalt mixtures to assess the enhancement of asphalt performance and cost minimization. The optimal percentage of RAP mixed with new asphalt including crumb rubber with achieves the highest performance, stability, and durability of pavement, while considering the economic and environmental impacts was investigated. Experimental investigations, including a universal testing machine and the Marshall stability test, were implemented to evaluate different mixing percentages of RAP and the new asphalt including crumb rubber at different bitumen contents. Abaqus software was utilized to simulate a model with the new mixture to determine the stress and deformation characteristics under different loading conditions. The findings of the experimental study from testing more than 150 samples of asphalt with different percentages of mixing illustrated that a balanced mix of 50% RAP with 50% new rubberized asphalt with a 5% bitumen content achieved the optimal balance of stability, flow and density characteristics, which will offer a promising solution for more sustainable and cost-effective road-paving solutions. Full article

The cleanliness of lubricating oil plays a key role in determining the operational health of mechanical systems, serving as a critical metric that delineates the extent of equipment wear. In this study, we present a magnetic-core-type planar coil particle detection sensor. The detection accuracy and detection limit are improved by optimizing the magnetic field inside the sensor. The optimization of the magnetic field is achieved through the finite element simulation analysis of the coil and the magnetic core. First, the finite element simulation software COMSOL 6.0 is used to model the sensor in three dimensions (3D). Then, we study the distribution of the magnetic field under different coil radii, core conductivity levels, and other parameters. We obtain the sensor structure after optimizing the magnetic field. The sensor is made using experimental methods, and the iron particles and copper particles are detected. The results show that the lower limit of detection of iron particles can reach 46 μm, and the lower limit of detection of copper particles can reach 110 μm. Full article

The static aeroelastic characteristics of the distributed propulsion wing (DPW) were studied using the CFD/CSD loose coupling method in this study. The momentum source method of the Reynolds-averaged Navier–Stokes equation based on the k-ω SST turbulence model solution was used as the CFD solution module. The upper and lower surfaces of the DPW were established using the cubic B-spline basis function method, and the surfaces of the inlet and outlet were established using the fourth-order Bezier curve. Finally, a three-dimensional parametric model of the DPW was established. A structural finite-element model of the DPW was established, a multipoint array method program based on the three-dimensional radial basis function (RBF) was written as a data exchange module to realize the aerodynamic and structural data exchange of the DPW’s static aeroelastic analysis process, and, finally, an aeroelastic analysis of the DPW was achieved. The results show that the convergence rate of the CFD/CSD loosely coupled method is fast, and the structural static aeroelastic deformation is mainly manifested as bending deformation and positive torsion deformation, which are typical static aeroelastic phenomena of the straight wing. Under the influence of static aeroelastic deformation, the increase in the lift characteristics of the DPW is mainly caused by the slipstream region of the lower surface and the non-slipstream region of the upper and lower surface. Meanwhile, the increase in its nose-up moment and the increase in the longitudinal static stability margin may have an impact on the longitudinal stability of the UAV. To meet the requirements of engineering applications, a rapid simulation method of equivalent airfoil, which can be applied to commercial software for analysis, was developed, and the effectiveness of the method was verified via comparison with the CFD/CSD loose coupling method. On this basis, the static aeroelastic characteristics of the UAV with DPWs were studied. The research results reveal the static aeroelastic characteristics of the DPW, which hold some significance for engineering guidance for this kind of aircraft. Full article

With the advancement of electric vehicles, their low energy recovery efficiency has become the main obstacle to development. This study focuses on the problem of braking energy loss in electric vehicles during urban road driving and proposes an improved fuzzy control strategy to optimize the energy management of electric vehicles. The exploration first introduces fuzzy control logic to adjust and optimize the energy recovery system of electric vehicles and then introduces a sparrow search algorithm to optimize the adjustment parameters. Finally, using MATLAB R2022a simulation software environment, a comparative analysis is conducted on two driving cycles: urban dynamometer driving schedule and New York City conditions. Simulation results show that the improved fuzzy control strategy can recover 906.41 kJ of energy under urban driving cycle conditions, and the energy recovery rate reaches 49.00%, while the ADVISOR strategy is 507.47 kJ and 27.13%, respectively. The energy recovery rate of the research method is 21.87% higher than that of the comparison method. Improved energy recovery rate of 80.68%. In the driving cycle with New York City, the improved strategy recovered 294.45 kJ of energy, and the energy recovery rate was 48.54%. Compared with the ADVISOR strategy, the energy recovery rate increased by 100.20%, and the energy recovery rate increased by about 110.77%. The research results indicate that the improved fuzzy control strategy is significantly superior to the ADVISOR control strategy, effectively improving energy recovery efficiency and battery charge state maintenance ability under an urban dynamometer driving schedule, achieving more efficient energy management. Full article

The number of high-rise residential buildings in China has a large base and rapid growth, with huge energy-saving potential. Most of the existing research focuses on the use of renewable energy to reduce energy consumption and optimize energy systems. When optimizing the renewable energy system configuration of residential buildings for solar-air source heat pump systems, the optimization algorithm and the setting of parameter ranges will have an impact on the optimization results. Therefore, to make up for the shortcomings of a single optimization process, this study proposes a joint solution based on simulations and multi-stage multi-objective optimization to improve the energy efficiency of the system and maximize economic benefits. This method was applied to perform energy consumption and economic optimization analyses for typical high-rise residential buildings in four cities in China (Shanghai, Nanjing, Wuhan, Chongqing) characterized by hot summers and cold winters. First, DeST software is used to model and calculate the building load. Then, TRNSYS software is used to establish a system simulation model. Next, the GenOpt program and the Hooke–Jeeves algorithm are used to perform the first stage of optimization with the lowest annual cost value as the objective function. Finally, MATLAB software and the NSGA-II algorithm are used to perform the second stage of optimization with the lowest annual cost value and the highest system energy efficiency ratio as the objective function, respectively. Moreover, the TOPSIS method is used to evaluate and sort the Pareto optimal solution sets to obtain the optimal decision solution. Overall, the two-stage optimization of the solar-air source heat pump system brings multiple benefits and a more significant improvement in overall performance compared to a single-stage optimization. In terms of energy utilization efficiency, the tilt and azimuth adjustments in the first stage allow the collectors to be better oriented towards the sun and to absorb solar energy more fully. This helps to improve the energy utilization efficiency of the system. For the economy of the system, the increase in the collector area and the reduction in the heat production of the air source heat pump in the second stage, as well as the increase in the volume of the water tank, have combined to reduce the operating costs of the system and improve its economy. Results demonstrate that the proposed two-stage optimization significantly improves the overall performance of the solar-air source heat pump system across all four cities, providing a robust framework for sustainable urban residential energy systems. This is a positive aspect for sustainability and environmental friendliness. Taken together, the two-stage optimization improves the performance of the system in a more comprehensive manner compared to the single-stage optimization. Full article

A core dielectric cylindrical rod wrapped in a dielectric circular pipe whose outer surface is enclosed by a helical conducting strip grating that is skewed along the axial direction is herein analyzed using the asymptotic strip boundary conditions along with classical vector potential analysis. Targeted for use as a cylindrical holographic antenna, the resultant field solutions facilitate the aperture integration of the equivalent cylindrical surface currents to obtain the radiated far fields. As each rod section of a certain skew angle exhibits a distinct modal attribute; this topology allows for the distribution of the cylindrical surface impedance via the effective refractive index to be modulated, as in gradient-index (GRIN) materials. Beam steering can also be achieved by altering the skew angle via mechanical sliding motion while leaving the cylindrical structure itself unchanged, as opposed to impractically reconfiguring the geometrical and material parameters of the latter to attain each new beam direction. The results computed by the program code based on the proposed technique in terms of the modal dispersion and radiation patterns are compared with simulations by a software solver. Manufactured prototypes are measured, and experimentally acquired dispersion diagrams and radiation patterns are favorably compared with theoretical predictions. Full article

The poor quality of natural pastures in the dry season does not make it possible to meet dairy cows’ requirements for milk production in Burkina Faso and in most West African countries. Therefore, it is urgent to find an alternative by developing a full diet from locally available ingredients. The objective was to determine a diet for dairy cattle based on locally available ingredients in the peri-urban area of Ouagadougou. A progressive methodology was used. Thus, a survey was conducted ontoonton 30 dairy farms. This survey was followed by chemical analysis, for which the most dominant forage and concentrate ingredients were selected. Secondly, the recording of milk and on-farm ingredient use was also carried out using Op-Ration software (Op-Ration version V3.4.5.0) in order to compare and determine the most suitable diets. The data from the survey were subjected to descriptive statistics using SPSS version 20. Those from chemical analysis, milk recording, and ingredient assessment on the farm were subjected to a statistical method using the software Minitab version.18.1.0.0 setup. The results showed two dominant forage species, Sorghum (84.85%) and Pennisetum pedicellatum (90.91%), and two dominant concentrates, corn bran (32%) and cottonseed meal (26%), used by dairy farmers. From these ingredients and simulating the requirements of 400 kgPV^0.75 of lactating cows, a diet assessment was carried out at early, middle, and end lactation. The results showed that at the beginning of lactation, the diet consisted of 6.73 kg of forage and 6.59 kg of concentrate for 13.5 L as the main objective of milk production. The diet for mid-lactation was 8 kg of forage and 6.5 kg of concentrate for 15.5 L per day and 5.7 kg of forage and 3.8 kg of concentrate for the end of lactation. The results of this study show that it is possible to manufacture a complete ration for dairy cows at different stages of lactation from locally available forages and concentrates in the peri-urban area of Ouagadougou. This type of method could be applied to other regions from local forages and concentrates for milk production. Full article

Antimony selenide (Sb₂Se₃) shows promise for photovoltaics due to its favorable properties and low toxicity. However, current Sb₂Se₃ solar cells exhibit efficiencies significantly below their theoretical limits, primarily due to interface recombination and non-optimal device architectures. This study presents a comprehensive numerical investigation of Sb₂Se₃ thin-film solar cells using SCAPS-1D simulation software, focusing on device architecture optimization and interface engineering. We systematically analyzed device configurations (substrate and superstrate), hole-transport layer (HTL) materials (including NiOx, CZTS, Cu₂O, CuO, CuI, CuSCN, CZ-TA, and Spiro-OMeTAD), layer thicknesses, carrier densities, and resistance effects. The substrate configuration with molybdenum back contact demonstrated superior performance compared with the superstrate design, primarily due to favorable energy band alignment at the Mo/Sb₂Se₃ interface. Among the investigated HTL materials, Cu₂O exhibited optimal performance with minimal valence-band offset, achieving maximum efficiency at 0.06 μm thickness. Device optimization revealed critical parameters: series resistance should be minimized to 0–5 Ω-cm² while maintaining shunt resistance above 2000 Ω-cm². The optimized Mo/Cu₂O(0.06 μm)/Sb₂Se₃/CdS/i-ZnO/ITO/Al structure achieved a remarkable power conversion efficiency (PCE) of 21.68%, representing a significant improvement from 14.23% in conventional cells without HTL. This study provides crucial insights for the practical development of high-efficiency Sb₂Se₃ solar cells, demonstrating the significant impact of device architecture optimization and interface engineering on overall performance. Full article