Bevel gears are a kind of gears that transmit power between two intersecting shafts. Bevel gears with Octidal and spherical involute profiles are the most common types of bevel gears. The profile of spherical involute teeth is a three-dimensional complex surface, requiring an accurate geometric definition calculation. Due to this complex geometry, modeling, stress-strain analysis, and mesh stiffness calculation are very difficult. In this study by extracting Napier’s Equations from the tooth profile geometry, geometric parameters of the spherical involute curve have been calculated. The results show that the pitch cone angle has an important effect on the shape of the spherical involute curve, so choosing the correct angle is particularly important. A significant increase in the azimuthal angle is observed by increasing the polar angle. In addition, increasing the angle of the pitch cone reduces the curvature of the side surfaces of the teeth and facilitates the manufacturing process. On the other hand, reducing the pressure angle will result in flat lateral surfaces and a tooth shape similar to the octoidal tooth. The sphere radius variations do not affect the shape of the tooth and only change the size of the tooth. Finally, a gear system comprising a pinion and gear was made from Polylactic Acid (PLA) utilizing the calculated angles to verify the accuracy of computed angles. Also, experimental and finite element methods determined the pinion and gear contact pattern. There was a good agreement between the finite element simulation and the experimental observation.

This paper presents GVDET-Net, an innovative signal detection framework designed to enhance the detection accuracy and operational efficiency of NOMA systems utilizing non-orthogonal time-frequency resources. The proposed model integrates VGG19-based CNN layers with GRU layers to jointly extract spatial and temporal dependencies from input data. By sequentially processing hierarchical features, GVDET-Net achieves superior NOMA channel signal detection compared to ML, LS, and MMSE approaches across SNRs from 4 dB to 28 dB. Simulation results demonstrate its effectiveness under realistic NOMA conditions, outperforming SIC-LS and SIC-MMSE under multiple test scenarios with 64 and 16 pilot configurations for dual-user cases. GVDET-Net achieves a minimum Symbol Error Rate (SER) of approximately 10⁻³ at high SNR levels, delivering significant performance gains. Additionally, the model attains 96.4% classification accuracy, 3.1 ms inference latency for standard packet sizes, and an AUC score of 0.968, validating its robustness and real-time applicability. This work introduces advanced detection techniques for NOMA systems, paving the way for optimized wireless networks and supporting next-generation communication standards.

Riedel shears, formed under the action of shear stresses in rocks, are an important element in studying the nature of tectonic deformations. This work investigates their formation using acoustic emission (AE) during triaxial compression experiments. We identify four fracture stages: Stage 1: Dispersed microcracks at 40–80% peak stress. Stage 2: Localized macrofracture nucleation at 0.99σ (tensile strength), with AE activity surge (300–500% increase). Stage 3: Shear deformation along faults. Analyzing the mechanisms of formation of such fracture systems allows identifying patterns of rock failures, which in turn enables predicting the nature of geodynamic processes. This study examines the relationship between local geomechanical processes of Riedel shear formation and global tectonic faults. To address this issue, theoretical and experimental modeling of stress distribution in rock samples under triaxial compression was conducted, along with the analysis of geophysical data confirming the patterns of formation of en echelon fracture systems in natural conditions. As a result of the study, the features of Riedel shear development in idealized (modeled) and real geological environments were determined, and key factors indicating the connection between fracturing and shear deformation zones were identified. The obtained results can be used for interpreting tectonic structures and predicting geomechanical events. A new approach to the interpretation of acoustic emission for predicting shear deformations on the scale of a rock massif has been developed. A novel AE interpretation methodology links hypocenter concentration to shear zones, validated against the 2020 Bystrinskoe earthquake precursors. Results enable predicting geomechanical events and hydrocarbon migration paths.

This study examines the effect of nozzle count, nozzle diameter, and inlet pressure on the cooling and heating efficiency of double-circuit vortex tubes (DCVTs). Vortex tubes, simple devices without moving parts, are widely used but face challenges in optimizing cooling and heating efficiency. To address this issue, 15 different configurations with nozzle counts ranging from 2 to 5 and diameters of 1.5, 2, and 2.5 mm were tested under inlet pressures of 8, 9, and 10 bar, while maintaining the secondary circuit pressure at 1.5 bar. Additionally, three-dimensional numerical simulations using the k-ε turbulence model were performed to validate the experimental results. The findings revealed that increasing the nozzle count and diameter leads to a reduction in cooling and heating efficiency due to greater energy dissipation. The optimal performance was achieved with two nozzles of 1.5 mm diameter at an inlet pressure of 9 bar, resulting in a 2.41% improvement in cooling efficiency and an 3.10% increase in heating efficiency and a 18.39% improvement in cooling performance coefficient compared to other configurations. Conversely, increasing the inlet pressure to 10 bar caused a 1.38% decrease in cooling efficiency and a 2.58% reduction in heating efficiency and a 8.17% reduction in cooling performance coefficient. This study shows that optimal design enhances energy efficiency and reduces consumption in precise temperature control applications.

Monitoring the status of surge arrester has always been considered as an important operation in the power system. In this paper, a new method has been proposed to assess indexes of metal oxide surge arrester monitoring based on correlation coefficients with environmental conditions. In this regard, the surge arrester leakage current was experimentally measured under different humidity and pollution levels for fan-shaped (D) and longitudinal (Z) contaminations. The impact of light, medium, and heavy pollution on the leakage current was examined under humidity from 60 to 90%. New indexes have been proposed with the aim of assessing the surge arrester performance, which are based on the harmonic components of the leakage current and the phase angles of the applied voltage and leakage current. The effect of the humidity and pollution level on the new and conventional indexes has been analyzed with respect to the Pearson correlation under uniform and non-uniform pollution. The results show that the correlation between the proposed indexes and humidity, pollution type, and level is greater than that of the conventional indexes. Also, the index based on the phase difference has the best performance relative to the other indexes.

Geological risk assessment is crucial for ensuring construction safety in undersea tunnel projects, particularly when traversing structurally complex fault zones. This study quantifies the hydrogeological and geomechanical risks associated with the Qingdao Jiaozhou Bay Second Undersea Tunnel crossing of the Cangkou Fault Zone and develops targeted mitigation strategies based on empirical data. Comprehensive field investigations—including water pressure tests (maximum: 48.38 Lu), pumping tests (permeability coefficient K = 6.74–14.56 m/d), and hydraulic fracturing stress measurements (σHmax = 4.57 MPa, N67°E orientation)—revealed two primary challenges: high-permeability fracture networks and anisotropic in situ stress conditions (lateral stress coefficients λ = 1.2–1.8). The results indicate that conventional grouting techniques are inadequate under these conditions, prompting the implementation of an 8-m full-section grouting design. This method effectively penetrates fracture networks and reinforces the surrounding rock mass upon solidification. Key limitations include the localized nature of the drill core data (limited to five core samples) and the assumption of homogeneous fracture distribution beyond the sampled zones. These findings provide an actionable framework for fault-zone tunneling in similar coastal geological settings.

Grid-connected inverters connect distributed generation and renewable energy sources to the grid. Various filters, including inductor-capacitor-inductor (LCL) filter, are utilized to increase the quality of grid-injected power. In addition to the inherent resonance of the LCL filter, the weak network with variable network impedance leads to instability of the power transmission system. This paper aims to improve the injection power quality of the LCL filter-based grid-connected fuel cell with control based on the grid current feedback and capacitor current active damping. Although active damping can theoretically guarantee the grid-connected passive inverter behavior, the system performance is sensitive to both the current controller phase lag and the variations of the filter parameters. To control these two factors, a suitable phase compensator has been proposed to enhance the passive behavior. In this paper, the control of LCL based grid-tied fuel cell power conditioning system with control based on LCL filter-based utilizing the grid current feedback and capacitor current active damping scheme has been studied, and the passive and stable performance of this system has been evaluated considering the effect of the current regulator phase compensation. The process of systematic design of the control system parameters has been described with necessary details and the passive performance of the grid-connected system has been evaluated. The obtained results for the simulation of the grid-connected fuel cell power optimization system indicate the current injection with very high quality and the passive behavior of the system under variations in the impedance of the weak network.

The oil and gas industry uses austenite stainless steels because of their high strength, flexibility, and resistance to the impacts of the atmosphere, damp environment, acids, salts, and other harsh chemicals. Problems in machining of such steels are associated with the formation of drain chip, their adhesion to the edge of the tool with the formation of build-up and the emergence of vibrations, which complicates the machining process and reduces its quality. The complexity of machining places greater demands on the tool used, the rigidity of technological equipment mandates the use of coolant, and various ways of chip removal. The scientific novelty consists in the fact that development of a method matches local cryogenic treatment with mechanical processing, ensuring automatic chip breaking and increased productivity. The influence of the method of cryogenic treatment on the structure, properties and machinability of austenitic steels was evaluated on the most common steel grade 08Kh18N10T. The formation of a magnetic martensitic phase with increased hardness at the boundaries of austenitic grains, which causes a change in the mechanism and conditions of chip formation in the local zone, acts as a stress concentrator, resulting in drain chip segmentation and improved machinability. The main findings include an analysis of the method's impact on the dynamic stability of the mechanical processing technological system; reduction of surface roughness by 2 times during mechanical processing with local cryogenic treatment compared to conventional cutting; ensuring stable segmentation and uniform fragmentation of the chip.