Search Results (1,015)

In this paper, the evaluation of the mechanical performance of novel, designed topologically optimized shin pads with advanced materials will be conducted with the aid of Finite Element Analysis (FEA) to assess the endurance of the final structure on impact phenomena extracted from actual real-life data acquired from contact sports. The main focus of the developed prototype is to have high-enough energy absorption capabilities and vibration isolation properties, crucial for the development of trustworthy protective equipment. The insertion of advanced materials with controlled weight fractions and lattice geometries aims to strategically improve those properties and provide tailored characteristics similar to the actual human skeleton. The final design is expected to be used as standalone protective equipment for athletes or as a protective shield for the development of human lower limb prosthetics. In this context, computational investigation of the dynamic mechanical response was conducted by replicating a real-life phenomenon of the impact during a contact sport in a median condition of a stud kick impact and an extreme case scenario to assess the dynamic response under shock-absorption conditions and the final design’s structural integrity by taking into consideration the injury prevention capabilities. The results demonstrate that the proposed lattice geometries positively influence the injury prevention capabilities by converting a severe injury to light one, especially in the gyroid structure where the prototype presented a unified pattern of stress distribution and a higher reduction in the transmitted force. The incorporation of the PA-12 matrix reinforced with the reused ground tire rubber results in a structure with high enough overall strength and crucial modifications on the absorption and damping capabilities vital for the integrity under dynamic conditions. Full article

In this study, we report the synthesis, characterization, and performance evaluation of a series of bimetallic Pt_xRh_y/C electrocatalysts with systematically varied Rh content for glycerol electrooxidation in acidic and alkaline media. The catalysts were prepared via a polyol reduction method using ethylene glycol as both a solvent and reducing agent, with prior functionalization of Vulcan XC-72 carbon to enhance nanoparticles (NPs) dispersion. High-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses indicated the spatial co-location of Rh atoms alongside Pt atoms. Electrochemical studies revealed strong composition-dependent behavior, with Pt₉₅Rh₅/C exhibiting the highest activity toward glycerol oxidation. To elucidate the origin of raised results, density functional tight binding (DFTB) simulations were conducted to model atomic distributions and evaluate energetic parameters. The results showed that Rh atoms preferentially segregate to the surface at higher concentrations due to their lower surface energy, while at low concentrations, they remain confined within the Pt lattice. Among the series, Pt₉₅Rh₅/C exhibited a distinctively higher excess energy and less favorable binding energy, rationalizing its lower thermodynamic stability. These findings reveal a clear trade-off between catalytic activity and structural durability, highlighting the critical role of the composition and nanoscale architecture in optimizing Pt-based electrocatalysts for alcohol oxidation reactions. Full article

Internet of Vehicles (IoV) serves as the data support for intelligent transportation systems, and the information security of the IoV is of paramount importance. In view of the problems of centralized processing, easy information leakage, and weak anti-interference ability in traditional vehicle networking systems, this paper proposes a blockchain architecture suitable for IoV forensics scenario. By leveraging the decentralized, distributed storage and tamper-proof capabilities of blockchain, it solves the privacy protection and data security issues of the system. Considering the threat of quantum computing to the encryption technology in traditional blockchain, this paper integrates lattice cryptography and ring signatures into digital signature technology, achieving privacy protection and traceability of the signer’s identity. To enhance the efficiency of lattice-based cryptographic algorithms, the DualRing technology is introduced, which reduces the computational time and storage consumption of ring signatures. Theoretical analysis has proved the correctness, anonymity, unlinkability, and traceability of the proposed scheme, which is applicable to the IoV forensics system. Simulation comparisons demonstrated that the proposed scheme significantly improves computational efficiency and reduces storage overhead. When the number of ring members is 256, the signature and verification times require only 65.76 ms and 21.46 ms, respectively. Full article

In this article, the mechanism of relaxation polarization currents occurring at a constant temperature (isothermal process) in crystals with ionic-molecular chemical bonds (CIMBs) in an alternating electric field was investigated. Methods of the quasi-classical kinetic theory of dielectric relaxation, based on solutions of the nonlinear system of Fokker–Planck and Poisson equations (for the blocking electrode model) and perturbation theory (by expanding into an infinite series in powers of a dimensionless small parameter) were used. Generalized nonlinear mathematical expressions for calculating the complex amplitudes of relaxation modes of the volume-charge distribution of the main charge carriers (ions, protons, water molecules, etc.) were obtained. On this basis, formulas for the current density of relaxation polarization (for transient processes in a dielectric) in the k-th approximation of perturbation theory were constructed. The isothermal polarization currents are investigated in detail in the first four approximations (k = 1, 2, 3, 4) of perturbation theory. These expressions will be applied in the future to compare the results of theory and experiment, in analytical studies of the kinetics of isothermal ion-relaxation (in crystals with hydrogen bonds (HBC), proton-relaxation) polarization and in calculating the parameters of relaxers (molecular characteristics of charge carriers and crystal lattice parameters) in a wide range of field parameters (0.1–1000 MV/m) and temperatures (1–1550 K). Asymptotic (far from transient processes) recurrent formulas are constructed for complex amplitudes of relaxation modes and for the polarization current density in an arbitrary approximation k of perturbation theory with a multiplicity r by the polarizing field (a multiple of the fundamental frequency of the field). The high degree of reliability of the theoretical results obtained is justified by the complete agreement of the equations of the mathematical model for transient and stationary processes in the system with a harmonic external disturbance. This work is of a theoretical nature and is focused on the construction and analysis of nonlinear properties of a physical and mathematical model of isothermal ion-relaxation polarization in CIMB crystals under various parameters of electrical and temperature effects. The theoretical foundations for research (construction of equations and working formulas, algorithms, and computer programs for numerical calculations) of nonlinear kinetic phenomena during thermally stimulated relaxation polarization have been laid. This allows, with a higher degree of resolution of measuring instruments, to reveal the physical mechanisms of dielectric relaxation and conductivity and to calculate the parameters of a wide class of relaxators in dielectrics in a wide experimental temperature range (25–550 K). Full article

This study examines the effects of partial wakes caused by upstream turbine yaw control on the trailing-edge noise of a downstream turbine under stable and neutral atmospheric conditions. Using a combined model coupling the unsteady vortex lattice method (UVLM) with the Curl wake model, calibrated with large eddy simulation data, wake behavior and noise characteristics were analyzed for yaw angles from −30° to +30°. Results show that partial wakes slightly raise overall noise levels and lateral asymmetry of trailing-edge noise, while amplitude modulation (AM) strength is more strongly influenced by yaw control. AM varies linearly with wake deflection at moderate yaw angles but behaves nonlinearly beyond a threshold due to large wake deflection and deformation. Findings reveal that yaw control can significantly increase the lateral asymmetry in the AM strength directivity pattern of the downstream turbine, and that AM characteristics depend on the complex interplay between inflow distribution and convective amplification effects, highlighting the importance of accurate wake prediction, along with appropriate consideration of observer point location and blade rotation, for evaluating AM characteristics of a wind turbine influenced by a partial wake. Full article

Aluminum metal matrix composites (AMMCs) were obtained using the stir-casting method, adding 0.15, 0.25, and 0.50 in vol.% of ZrO₂. Microstructural observations made using scanning electron microscopy (SEM) indicated that oxide addition modified grain size. X-ray diffraction analyses revealed that mainly ZrAl₃ and Al₂O₃ phases had formed. Hardness evaluation indicated a maximum value of 63 HV for the zirconia-reinforced samples, representing an increase of approximately 70% compared with pure aluminum. This hardness increase was mainly attributed to the zirconia distribution in the aluminum matrix promoting lattice distortion, which promoted the inhibition of dislocation mobility. Wear tests indicated that the samples with 0.50 vol.% of ZrO₂ added presented the lowest wear rate because of the hardness they acquired. The results are discussed considering composite strengthening due to ZrO₂ addition and the thermal treatment applied (cooling rate). Full article

Reliable information on the chemical and physical makeup of mine tailings is critical in meeting environmental and regulatory requirements, as well as identifying whether contained elements, including critical minerals, might be economically recovered in future to meet growing demands. Detailed mineralogical characterization, supported by chemical assays and automated mineralogy (MLA) data on different size fractions, underpins a case study of flotation tailings from the processing plant at the Carrapateena mine, South Australia. The study provides valuable insights into the deportment of minor and critical elements, including rare earth elements (REEs), along with uranium (U). REE-minerals are represented by major phosphates (monazite and florencite) and subordinate REE-fluorocarbonates (bastnäsite and synchysite). More than half the REE-minerals are concentrated in the finest size fraction (−10 μm). REEs in coarser fractions are largely locked in gangue, such that economic recovery is unlikely to be viable. MLA data shows that the main REE-minerals all display specific associations with gangue, which change with particle size. Quartz and hematite are the most common associations, followed by sericite. Synchysite shows a strong affiliation to carbonates. The contents of other critical elements (e.g., tungsten, molybdenum, cobalt) are low and for the most part occur within other common minerals as submicron-sized inclusions or in the lattice, rather than discrete minerals. Nevertheless, analysis of mine tailings from a large mining–processing operation provides an opportunity to observe intergrowth and replacement relationships in a composite sample representing different ore types from across the deposit. U-bearing species are brannerite (associated with rutile and chlorite), coffinite (in quartz), and uraninite (in hematite). Understanding the ore mineralogy of the Carrapateena deposit and how the ore has evolved in response to overprinting events is advanced by observation of ore textures, including between hematite and rutile, rutile and brannerite, zircon and xenotime, and the U-carbonate minerals rutherfordine and wyartite, the latter two replacing pre-existing U-minerals (uraninite, coffinite, and brannerite). The results of this study are fundamental inputs into future studies evaluating the technical and economic viability of potentially recovering value metals at Carrapateena. They can also guide efforts in understanding the distributions of valuable metals in analogous tailings from elsewhere. Lastly, the study demonstrates the utility of geometallurgical data on process materials to assist in geological interpretation. Full article

This study presents a flutter answer analysis of the Romanian IAR-99 HAWK advanced trainer aircraft equipped with multiple external store configurations. A high-fidelity finite element model (FEM) of the complete aircraft, including pylons and external stores, was coupled with a Doublet Lattice Method (DLM) aerodynamic model. The aeroelastic framework was validated against Ground Vibration Test (GVT) data to ensure structural accuracy. Four representative configurations were assessed: (A) RS-250 drop tanks on inboard pylons and PRN 16 × 57 unguided rocket launchers on outboard pylons; (B) four B-250 bombs; (C) eight B-100 bombs mounted on twin racks; and (D) a hybrid layout with B-100 bombs inboard and PRN 32 × 42 launchers outboard. Results show that spanwise distribution governs aeroelastic stability more strongly than total carried mass. Distributed stores lower wing-bending frequencies and densify the modal spectrum, producing critical pairs and subsonic crossings near M ≈ 0.82 at sea level, whereas compact heavy loads remain subsonic-stable. A launcher-specific modal family around ≈29.8 Hz is also identified in the hybrid layout. The validated FEM–DLM framework captures store-driven mode families (≈4–7 Hz) and provides actionable guidance for payload placement, certification, and modernization of the IAR-99 and similar platforms. Full article

The fast and accurate calculation of the internal temperature rise in the oil-immersed transformer is the premise to realize the thermal health management and load energy evaluation of the in-service transformer. In view of the influence of nanofluids on the heat transfer process of transformer, a numerical simulation algorithm based on lattice Boltzmann method (LBM) and finite difference method (FDM) is proposed to study the heat and mass transfer process inside nano-modified oil-immersed transformer. Firstly, the D2Q9 lattice model is used to solve the fluid and thermal lattice Boltzmann equations inside the oil-immersed transformer at the mesoscopic scale, and the temperature field and velocity field are obtained by macroscopic transformation. Secondly, the electric field distribution inside the oil-immersed transformer is calculated by FDM. The viscous resistance in LBM analysis and the electric field force in FDM analysis, as well as the gravity and buoyancy of particles, are used to explore the motion characteristics of nanoparticles and metal particles. Finally, compared with the thermal ring method and the finite volume method (FVM), the relative error is less than 5%, which verifies the effectiveness of the numerical model and provides a method for studying the internal electrothermal convection of nano-modified oil-immersed transformers. Full article

Selective laser melting (SLM) enables the production of complexly shaped metals with programmable mechanical responses, yet most lattice studies still rely on a single unit cell and a simple columnar build, severely restricting performance improvements. Here, we examine how combining distinct unit cells and rearranging them within the build volume affects the compressive behavior of SLM Corrax maraging stainless steel lattice structures. Three designs are additively manufactured as follows: a columnar cubic-FCCZ lattice, an alternating cubic and FCCZ lattice, and a hybrid lattice (cubic+FCCZ unit cell). In situ 2D digital image correlation (DIC) and finite element analysis (FEA) are used to resolve full-field strain evolution and failure modes under quasi-static compression. The hybrid lattice achieves the highest first maximum compressive strength (418 ± 5.78 MPa) and energy absorption (128.5 ± 6.83 MJ/m³), with its specific energy absorption (44.2 ± 1.48 kJ/kg) outperforming that of the columnar cubic-FCCZ lattice and alternating cubic and FCCZ lattice by 21.76% and 8.07%, respectively. The enhanced performance is attributed to the more uniform stress distribution and delayed shear band localization afforded by the hybrid lattice. These findings show that simultaneously optimizing unit cell geometry and arrangement can significantly expand the design space of metal lattices and provide a practical approach to improving the compressive strength and energy absorption capacity of load-bearing SLM components. Full article

Distributed electric propulsion has emerged as a prominent research area in aerospace engineering. The capabilities of shorter takeoff distance and efficient cruise flight are the important advantages of a distributed propulsion UAV over a traditional fixed-wing UAV, and the composition of multiple motors can significantly improve the safety of the aircraft. This paper proposed an overall design method for the power system of the distributed propulsion UAV with the mission requirements as inputs, using the Actuator Disk Theory and Vortex Lattice Method to analyze the aerodynamic performance corresponding to different propeller numbers and layouts, and combining with the BP neural network to obtain the optimal propeller position. Meanwhile, the Linear Quadratic Regulator method was employed to analyze different configurations of UAVs, and the effects of the number of propellers and thrust redundancy on their safety were explored. The parametric study revealed that as the number of propellers increased, the optimal horizontal distance between the propeller and the leading edge of the wing gradually decreased (closer to the wing), and the vertical distance also gradually decreased (lower to the wing). The safety study revealed that when the number of propellers reached eight or more, the UAV could maintain stable flight with a probability exceeding 70% even when two or three propulsion components fail. The computational method and safety analysis for different propeller combinations studied in this paper feature high efficiency and low computational consumption, which can provide an effective reference for the overall design phase of distributed propulsion aircraft. Full article

Compared with a traditional distribution transformer with silicon steel sheet as the core material, the no-load loss of an amorphous alloy transformer is greatly reduced due to its core using iron-based amorphous metal material, which has been applied in many countries. However, due to the brittleness of its amorphous strip, an amorphous alloy transformer is prone to debris in the process of production, transportation and work. The charge and migration characteristics of these debris will reduce the insulation strength of the transformer oil and endanger the safe operation of the transformer. In this paper, a charge measurement platform of amorphous alloy debris is set up, and the charging characteristics of amorphous alloy core debris under different flow velocities, particle radius and plate electric field strength are obtained. The results show that with an increase in pipeline flow velocity, the charge-to-mass ratio of the debris increases first and then decreases. With an increase in electric field strength, the charge-to-mass ratio of the debris increases; with an increase in the number of debris, the charge-to-mass ratio of the debris decreases; with an increase in debris size, the charge-to-mass ratio of the debris increases. The debris with different charge-to-mass ratios and types obtained from the above experiments are added to the simulation model of an amorphous alloy transformer. The lattice Boltzmann method (LBM) coupled with the discrete element method (DEM) is used to simulate the migration process of metal particles in an amorphous alloy transformer under the combined action of gravity, buoyancy, electric field force and oil flow resistance under electrothermal excitation boundary. The results show that the trajectory of the debris is related to the initial position, electric field strength and oil flow velocity. The LBM–DEM calculation model and charge measurement platform proposed in this paper can provide a reference for studying the charge mechanism and migration characteristics of amorphous alloy core debris in insulating oil. Full article

A novel long-lasting luminescent composite material based on the (Ca,Sr)-Al-O system was synthesized using a solution combustion method. (Ca,Sr)₃Al₂O₆ is the primary phase, with SrAl₂O₄ as a controllable secondary phase. Compared to conventional single-phase SrAl₂O₄ phosphors, the introduction of a calcium-rich hexaaluminate matrix creates additional defects and a specific trap distribution at the composite interface, significantly improving carrier storage and release efficiency. Eu²⁺ + Nd³⁺ synergistic doping enables precise control of the trap depth and number. Under 365 nm excitation, Eu²⁺ emission is located at ~515 nm, with Nd³⁺ acting as an effective trap center. Under optimal firing conditions at 700 °C (Eu²⁺ = 0.02, Nd³⁺ = 0.003), the afterglow lifetime exceeds 30 s. Furthermore, The (Ca,Sr)₃Al₂O₆ host stabilizes the lattice and optimizes defect states, while synergizing with the SrAl₂O₄ secondary phase to improve the afterglow performance. This composite phosphor exhibits excellent dual-mode anti-counterfeiting properties: long-lasting green emission under 365 nm excitation and transient blue-violet emission under 254 nm excitation. Based on this, a screen-printing ink was prepared using the phosphor and ethanol + PVB, enabling high-resolution QR code printing. Pattern recognition and code verification can be performed both in the UV on and off states, demonstrating its great potential in high-security anti-counterfeiting applications. Compared to traditional single-phase SrAl₂O₄ systems, this study for the first time constructed a composite trap engineering of the (Ca,Sr)₃Al₂O₆ primary phase and the SrAl₂O₄ secondary phase, achieving the integration of dual-mode anti-counterfeiting functionality with a high-resolution QR code fluorescent ink. Full article

Compact nuclear reactor systems usually use helium–xenon (He-Xe) mixtures as coolants. Tight-lattice rod-bundled channels, serving as primary core configurations in compact nuclear reactor designs, exhibit quasi-triangular cross-sections where fluid dynamics substantially deviate from circular tube behavior. This study evaluates the applicability of turbulence models and turbulent Prandtl number (Pr_t) models in quasi-triangular channels through systematic numerical simulations. The results demonstrate that the Transition SST model accurately resolves flow dynamics and turbulence development in helium–xenon mixtures, while implementing Pr_t models significantly enhances temperature prediction accuracy. Among the evaluated models, the Weigand model achieves optimal performance by dynamically adapting Pr_t values across flow regimes. Further refinements targeting parameters governing near-wall Pr_t distribution are identified as critical pathways for improving numerical simulation precision of low-Prandtl-number fluids in geometrically complex nuclear systems. Full article

Shale oil extraction efficiency hinges on the interfacial interactions between oil molecules and reservoir clay minerals, such as kaolinite, whose slit-like pores serve as primary storage spaces for alkanes. This study introduces a novel multi-dimensional quantification method using four angular parameters—elevation angle (θ), azimuth angle (φ), rotation angle (ω), and dihedral angle (τ)—to systematically investigate the adsorption configuration of n-octane in kaolinite slit pores ranging from 0.45 to 14.05 nm. Through molecular simulations and advanced trajectory analysis, we elucidate the impact of pore sizes on alkane adsorption density, layering, and molecular configurations. Results reveal that pore size regulates molecular behavior via steric hindrance and potential field superposition, while the four angular parameters can effectively capture subtle changes in. this molecular behavior: (1) the elevation angle (θ) around 0° indicates complete alignment parallel to surface, but is modulated at increasing distance from the surface into the pore-region highlighting a disordered state; (2) the azimuth angle (φ) is concentrated at 60° and 120° on the siloxane tetrahedral surface due to lattice regulation, but shows a disordered distribution on the hydroxyl octahedral surface; (3) the rotation angle (ω) is mainly concentrated at 0° and 90° indicating molecular plane being either parallel or perpendicular to the surface; (4) the dihedral angle (τ) remains at ~0°, indicating that the molecular chains are straight. In pores smaller than 4.26 nm, strong confinement yields ordered molecular arrangements (θ = 0°, φ at 60° or 120°, ω = 0°) with high adsorption density; for larger pores than 4.26 nm, disordered configurations and increased layering (up to eight layers) with stable density and adsorption capacity per unit area are observed. The proposed parameter system overcomes limitations of traditional qualitative approaches, offering a standardized, scalable tool for quantifying alkane-clay interactions. This framework enhances understanding of shale oil occurrence mechanisms and supports optimized extraction strategies, with broad applicability to other chain molecules and 2D materials in interface science. Full article