Search Results (197)

This study evaluates the capabilities of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Hyperion remote sensing sensors for mapping ophiolitic sequences and identifying manganese mineralization in the Bela Ophiolite region, located along the axial fold–thrust belt northwest of Karachi, Pakistan. The study area comprises tholeiitic basalts, gabbros, mafic and ultramafic rocks, and sedimentary formations where manganese occurrences are associated with jasperitic chert and shale. To delineate lithological units and Mn mineralization, advanced image processing techniques were applied, including band ratio (BR), Principal Component Analysis (PCA), and Spectral Angle Mapper (SAM) on visible and near-infrared (VNIR) and shortwave infrared (SWIR) bands of ASTER. Using these methods, gabbros, basalts, and mafic-ultramafic rocks were effectively mapped, and previously unrecognized basaltic outcrops and gabbroic outcrops were also discovered. The ENVI Spectral Hourglass Wizard was used to analyze the hyperspectral data, integrating the Minimum Noise Fraction (MNF), Pixel Purity Index (PPI), and N-Dimensional Visualizer to extract the spectra of end-members associated with Mn-bearing host rocks. In addition, the Hyperspectral Material Identification (HMI) tool was tested to recognize Mn minerals. The remote sensing results were validated by petrographic analysis and ground-truth data, confirming the effectiveness of these techniques in ophiolite mapping and mineral exploration. This study shows that ASTER band combinations (3-6-7, 3-7-9) and band ratios (1/4, 4/9, 9/1 and 3/4, 4/9, 9/1) provide optimal results for lithological discrimination. The results show that remote sensing-based image processing is a powerful tool for mapping ophiolites on a regional scale and can help geologists identify potential mineralization zones in ophiolitic sequences. Full article

An unsupervised anomaly-detection framework is proposed and field validated for thrust-bearing monitoring in the impulse turbine of a shoreline oscillating water-column (OWC) wave energy converter (WEC) off Jeju Island, Korea. Operational monitoring is constrained by nonstationary sea states, scarce fault labels, and low-rate supervisory logging at 20 Hz. To address these conditions, a 24 h period of normal operation was median-filtered to suppress outliers, and six physically motivated time-domain features were computed from triaxial vibration at 10 s intervals: absolute mean; standard deviation (STD); root mean square (RMS); skewness; shape factor (SF); and crest factor (CF, peak divided by RMS). A feature-based autoencoder was trained to reconstruct the feature vectors, and reconstruction error was evaluated with an adaptive threshold derived from the moving mean and moving standard deviation to accommodate baseline drift. Performance was assessed on a 2 h test segment that includes a 40 min simulated fault window created by doubling the triaxial vibration amplitudes prior to preprocessing and feature extraction. The detector achieved accuracy of 0.99, precision of 1.00, recall of 0.98, and F1 score of 0.99, with no false positives and five false negatives. These results indicate dependable detection at low sampling rates with modest computational cost. The chosen feature set provides physical interpretability under the 20 Hz constraint, and denoising stabilizes indicators against marine transients, supporting applicability in operational settings. Limitations associated with simulated faults are acknowledged. Future work will incorporate long-term field observations with verified fault progressions, cross-site validation, and integration with digital-twin-enabled maintenance. Full article

Aerostatic bearings were proven to be an optimal choice in situations where low friction, cleanliness, and high motion accuracy are required. Their functionality relies heavily on flow restrictors, which are responsible for regulating and controlling the supply flow, and consequently, the thickness and stiffness of the fluid film. A diverse range of restrictors with varying characteristics is used, among which are the porous restrictors. The current work introduces a novel solution involving a porous, highly compressible restrictor, whose element of novelty compared to its predecessors consists of its variable thickness and corresponding permeability, regulated by the load on the bearing. The gas is supplied through an annular, elastic, deformable, porous disc, which is compressed by a metal plate, subjected to compression by the recess pressure on one side and by the supply pressure on the other side. One or more springs are used in parallel with the porous disc to obtain the optimum elastic response. The objective of this study is to evaluate the performance characteristics and compare them to a conventional restrictor. A parametric analysis is performed to define the size and properties of the porous restrictor. Full article

Traps are central to petroleum exploration, where hydrocarbons accumulate during migration. Reservoirs are likewise an essential petroleum system element and serve as the primary medium for hydrocarbon storage. The buried hill is a geological formation highly favorable for reservoir development. However, the factors influencing hydrocarbon accumulation in buried hill reservoirs are highly diverse, especially in areas with complex, active fault systems. Fault systems play a dual role, both in the formation of reservoirs and in the migration of hydrocarbons. Therefore, understanding the impact of complex fault systems helps enhance the exploration success rate of buried hill traps and guide drilling deployment. In the Beibuwan Basin in the South China Sea, buried hill traps are key targets for deep-buried hydrocarbon exploration in this faulted basin. The low level of exploration and research in buried hills globally limits the understanding of hydrocarbon accumulation conditions, thereby hindering large-scale hydrocarbon exploration. By using drilling data, logging data, and seismic data, stress fields and tectonic faults were restored. There are two types of buried hills developed in the Beibuwan Basin, which were formed during the Late Ordovician-Silurian period and Permian-Triassic period, respectively. The tectonic genesis of the Late Ordovician-Silurian period buried hills belongs to magma diapirism activity, while the tectonic genesis of the Permian-Triassic period buried hills belongs to reverse thrust activity. The fault systems formed by two periods of tectonic activity were respectively altered into basement buried hills and limestone buried hills. The negative structural inversion controls the distribution and interior stratigraphic framework of the deformed Carboniferous strata in the limestone buried hill. The faults and derived fractures of the Late Ordovician-Silurian period and Permian-Triassic period promoted the diagenesis and erosion of these buried hills. The faults formed after the Permian-Triassic period are not conducive to calcite cementation, thus facilitating the preservation of the reservoir space formed earlier. The control of hydrocarbon accumulation by the fault system is reflected in two aspects: on the one hand, the early to mid-Eocene extensional faulting activity directly controlled the depositional process of lacustrine source rocks; on the other hand, the Late Eocene-Oligocene, which is closest to the hydrocarbon expulsion period, is the most effective fault activity period for connecting Eocene source rocks and buried hill reservoirs. This study contributes to understanding of the role of complex fault activity in the formation of buried hill traps within hydrocarbon-bearing basins. Full article

Solid propellant grain, as a typical polymer, are the thrust generation devices and core load-bearing components of solid rocket motor (SRM) and are also known as SRM grain. They are constantly exposed to extreme service environments such as high temperatures, high pressures, and dynamic shocks, and have a relatively high failure rate in the field use of SRM. Its life and reliability are the shortcomings that restrict the improvement of weapons and equipment capability in China at present. This paper summarizes the typical fault types of SRM grain at present, and compares and analyzes the research progress of reliability design and analysis technology, reliability optimization technology, life test technology and reliability evaluation technology of SRM grain at home and abroad; This paper analyzes the deficiencies and reasons in the research and application of SRM grain reliability technology in China, and points out the technical difficulties and challenges faced by the integrated design of performance and reliability of SRM independent innovation design according to the needs of the forward research and development system of SRM. Based on the existing design level and industrial foundation in China, the basic research suggestions that should be carried out to consolidate the design ability of SRM grain in China are given. Full article

As the core component of ultra-precision machine tools, the manufacturing errors of aerostatic spindles are inevitable due to the limitations of machining and assembly processes, and these errors significantly affect the spindle’s static and dynamic performance. To address this issue, a force model of the unbalanced air film, considering the straightness errors of the rotor’s radial and thrust surfaces, was constructed. Unlike conventional studies that rely solely on idealized error assumptions, this research integrates actual straightness measurement data into the simulation process, enabling a more realistic and precise prediction of bearing performance. Rotors with different tolerance specifications were fabricated, and static performance simulations were carried out based on the measured geometry data. An experimental setup was built to evaluate the performance of the aerostatic spindle assembled with these rotors. The experimental results were compared with the simulation outcomes, confirming the validity of the proposed model. To further quantify the influence of straightness errors on the static characteristics of aerostatic spindles, ideal functions were used to define representative manufacturing error profiles. The results show that a barrel-shaped error on the radial bearing surface can cause a load capacity variation of up to 46.6%, and its positive effect on air film load capacity is more significant than that of taper or drum shapes. For the thrust bearing surface, a concave-shaped error can lead to a load capacity variation of up to 13.4%, and its enhancement effect is superior to those of the two taper and convex-shaped errors. The results demonstrate that the straightness errors on the radial and thrust bearing surfaces are key factors affecting the radial and axial load capacities of the spindle. Full article

A modified static characteristic model for the multi-layer foil thrust bearing (MLFTB) is established. In this model, the finite difference method and the thick plate element are implemented, the compressible Reynolds equation is linearized by the Newton–Raphson method, and the evolution law of the static characteristics with the geometric and operational parameters is derived by iterative solution. The results indicate that the bearing capacity could be generally decreased by around 3.15% when considering the slip boundary condition, which should not be neglected. Also, when under the rigorous wedge effect, the pressure peak near the mini clearance exhibits an obvious double peak shape. The bearing capacity can be slightly enhanced by an increase in the tilt angle of the thrust disk. In comparison to data in the literature, the current model shows satisfactory precision for the multi-layer foil thrust bearing. It aims to provide effective predictive means and theoretical reference for MLFTB. Full article

Micro-hole aerostatic bearings have emerged as critical components in ultra-precision machining systems, offering a superior load capacity, stiffness, and stability compared to traditional orifice-based designs. These enhancements are primarily attributed to the high-density configurations of micro-holes and the reduction in hole diameter. However, research on the design and analysis of micro-hole aerostatic bearings for high-rotational-speed applications remains limited. In this study, the finite element method (FEM) was employed to solve the Reynolds equation, thereby conducting a systematic evaluation of the static and high-speed performance characteristics of micro-hole aerostatic thrust bearings. The effects of restrictor types, micro-hole layouts, structural parameters, and centrifugal deformation under high-rotational-speed conditions on bearing performance have been comprehensively examined. The objective of this study is to provide a basis for the design of micro-hole high-speed aerostatic spindles. Full article

Vanes are critical components of a rotary-vane compressor. If the vanes do not achieve sufficient contact with the inner wall of the cylinder, the compression chambers do not form completely. However, excessive contact between the vane and the cylinder wall can produce wear on both, also decreasing the lifespan of the compressor. We applied the Poisson equation and the Reynolds equation to calculate the gas force and fluid-reaction force acting on the vane. We solved the equations for the motion of the rigid vane in six degrees of freedom to determine the dynamic motion of the vane. We operated the rotary-vane compressor for 800 h under the same simulation conditions and measured the wear patterns of the vane, the bottom thrust bearing, and the cylinder wall. Finally, we validated the proposed method by confirming that the simulated contact force matches well with the measured wear patterns on the vane and the inner wall of the cylinder. The proposed method overcomes the limitations of the previous three-degrees-of-freedom analyses of the vane and will contribute to developing a robust and efficient rotary-vane compressor. Full article

In many applications, it is necessary to optimise the performance of hydrodynamic (HD) bearings. Many studies have proposed different strategies, but there remains a lack of conclusive research on the suitability of various optimisation methods. This study evaluates the most commonly used algorithms, including the genetic (GA), particle swarm (PSWM), pattern search (PSCH) and surrogate (SURG) algorithms. The effectiveness of each algorithm in finding the global minimum is analysed, with attention to the parameter settings of each algorithm. The algorithms are assessed on HD journal and thrust bearings, using analytical and numerical solutions for friction moment, bearing load-carrying capacity and outlet lubricant flow rate under multiple operating conditions. The results indicate that the PSCH algorithm was the most efficient in all cases, excelling in both finding the global minimum and speed. While the PSWM algorithm also reliably found the global minimum, it exhibited lower speed in the defined problems. In contrast, genetic algorithms and the surrogate algorithm demonstrated significantly lower efficiency in the tested problems. Although the PSCH algorithm proved to be the most efficient, the PSWM algorithm is recommended as the best default choice due to its ease of use and minimal sensitivity to parameter settings. Full article

Firstly, the Reynolds equation considering gas inertia force is theoretically deduced in the cylindrical coordinate system, and then a mathematical model of aerostatic thrust bearing with three degrees of freedom (3-DOF) is constructed. Secondly, the Reynolds equation and velocity control equation are solved by the finite difference method (FDM), and the characteristics of gas pressure and velocity distribution in the gas film under steady-state conditions are revealed. On this basis, in the single-factor analysis, the bearing capacity error and recovery torque error caused by the inertia force term are quantitatively analyzed. It is found that the bearing rotating speed has a significant influence on the inertial force error, and the bearing radius also has a certain influence on the inertial force error, while the initial clearance, gas supply pressure, and torsion angle have relatively little influence on the inertial force error. Finally, in the multi-factor analysis, the sample regression equation of relative error of bearing capacity and relative error of restoring torque is established by using the multiple regression analysis method. By comparing the estimated values with the simulation results, the validity of the constructed regression equation is verified. Full article

In this paper, the calculation model and method of the lubrication performance of the thrust bearing, which considers the thermal bomb deformation, are constructed based on the working characteristics of the main pump thrust of the nuclear power plant. The key design parameters of the tile package Angle θ are analyzed by taking the design parameters of the thrust-bearing tile as the variable. The circumferential fulcrum coefficient of tile, the influence of tile thickness B, and tile elastic modulus E on the lubrication performance of thrust bearing are analyzed to obtain improved design parameters. The lubrication performance of the thrust bearing includes the minimum oil film thickness h_min, the maximum temperature of oil film T_max, total flow Q_x, total power consumption W, maximum thermal deformation of axial bush δT_max, and the maximum elastic deformation of the axial bush δF_max. The scale test of the designed thrust bearing is carried out. The take-off speed of the bearing is tested and compared with the results of the theoretical analysis. The study results show that the influence is becoming more obvious from θo to h_min. Moreover, the impact becomes more obvious from T_max to Q_x, B to hmin, and Q_x to δT_max and δF_max. Lastly, the impact is also obvious from E to Q_x and δF_max. Full article

The development of rotordynamic systems with reduced energy dissipation is a key challenge in modern applications, such as Flywheel Energy Storage Systems. This paper investigates a fully passive vertical rotor system supported by two passive magnetic bearings whose configuration provides radial stability while minimising power losses due to their thrust effect. A numerical model describes the forces and stiffness of the magnetic bearings, identifying the operational range of the thrust–radial support configuration. A test rig is developed for the experimental characterisation of the rotor and passive magnetic bearings in both static and dynamic conditions. Different magnetic thrust force levels are tested by varying the axial distance between the rotor and stator magnetic rings of the bearings. Static tests are performed to measure the weight force compensation corresponding to the different bearing configurations, validating the numerical model. Dynamic tests analyse the rotor power losses with a non-invasive approach via optical sensor measurements. Full article

Older individuals with hip osteoarthritis (OA) who have difficulty walking, climbing stairs, or performing daily tasks often find non-weight-bearing (NWB) exercises essential for rebuilding strength and preserving function without further stressing the joints. In addition, those with a higher body mass index (BMI) particularly benefit from NWB therapy, as it alleviates joint pressure while facilitating safe and effective rehabilitation. Thus, NWB interventions, such as manual therapy (MT) and aquatic therapy (AT), are especially critical for older adults aged 60 and above, offering pain relief and functional improvement by minimizing gravitational impact on the hip joint. This review examines the effectiveness of these approaches in managing hip OA symptoms and decreasing pain. The inclusion criteria for the study consisted of randomized controlled trials or controlled trials focused on adult patients with primary osteoarthritis of the hip joint, utilizing interventions such as MT (including thrust joint mobilizations, non-thrust/oscillatory mobilizations, and soft tissue mobilization) or AT (including hydrotherapy and water therapy), and assessing outcomes related to pain. We selected nine studies that included a total of n = 1037 individuals. It evaluated outcomes such as self-reported pain levels using measures like the Western Ontario and McMaster Universities Osteoarthritis (WOMAC), Numeric Rating Scale (NRS), and Visual Analog Scale (VAS). Beyond statistical differences, both therapies were evaluated for Minimal Clinically Important Difference (MCID). While MT studies indicated a decrease in pain according to pain index scores, they showed short-term effectiveness till five weeks but lacked sustained clinical efficacy beyond this period. AT showed positive results within a ten-week period, although its effectiveness seemed to level off beyond this duration, falling below the threshold of clinical efficiency. After 10 weeks of treatment, there is no discernible clinical benefit in terms of pain reduction. Both interventions without gravitational impact seem suitable for providing short-term pain relief for primary hip osteoarthritis patients, but long-term pain relief—meaning after ten weeks—should be maintained through therapeutic exercise and patient education. Full article

Permanent magnet thrust bearings have garnered significant attention due to their high rotational speeds, low noise levels, and excellent vibration-damping performance. However, existing designs of these bearings often suffer from low load-carrying capacity and are tailored to specific machines, which limits their broader applicability. To address these limitations, this paper proposes a novel modular multi-unit cell structure for permanent magnet thrust bearings. The load-carrying performance of this design is validated through theoretical analysis, simulation, and experimentation. The inspiration for this design comes from bionics and honeycomb structures, emphasizing modularization and the combination of multiple unit cells. The unit cell consists of four permanent magnets, and multiple unit cells can be connected to form a structure that replaces the traditional design of directly embedding a permanent magnet ring into the bearing structure. Moreover, the designed unit cell structure can expand in both axial and radial directions, allowing for the creation of various nested or cross structures tailored to specific usage requirements. With this modular approach, the theoretical model of the bearing structure can be extended from the traditional single-layer cross-nested structure to an arbitrary number of nested cross-nested configurations using the equivalent magnetic circuit method. The bearing’s performance is validated through finite element simulations and experimental testing. The results demonstrate that the bearing with a four-layer cross-nested structure achieves a maximum load capacity of 48.45 kN, with a deviation of 7.3% from the theoretical value and 4% from the simulation results. By leveraging the generalization of the unit cell, the maximum axial load capacity across various configurations ranges from 6.78 kN to 288.9 kN, significantly enhancing the bearing’s adaptability to diverse operational scenarios. Full article