To address the issue of low diagnostic accuracy caused by distribution differences between the source and target domains in rolling bearing fault diagnosis, this study proposes a method combining balanced distribution adaptation (BDA) and support vector machines (SVMs). The approach utilizes BDA to simultaneously minimize discrepancies in both the marginal and conditional distributions between domains, enabling effective feature alignment and enhancing the model's cross-domain generalization in small-sample scenarios. After extracting time-and frequency-domain features, BDA adaptively adjusts the feature distributions, and SVMs are employed for fault classification. Experimental results demonstrate that the BDA-SVM method achieves over 94 % diagnostic accuracy, showcasing strong performance and robustness in bearing fault diagnosis. Compared with traditional SVMs and other methods without transfer learning, the proposed approach shows a significant improvement in diagnostic accuracy under cross-domain conditions.
With the continuous improvement of intelligent manufacturing and robot perception capabilities, traditional robotic arm grasping methods still face problems such as inaccurate posture prediction and poor task adaptability in dealing with dynamic scenes, complex objects, and functional action execution. Therefore, the research develops an optimized contact grasping network model that integrates scene constraints and task constraints. It combines UR5 six degree of freedom robotic arm, visual input, and Contact-GraspNet architecture based on point cloud, and introduces PointNet++ local feature enhancement mechanism and lightweight encoder design to effectively improve the spatial perception and action planning capabilities of grasping points. Experimental results show that on the GraspNet and YCB Dataset, the model achieves F1 scores of 92.54% and 91.82% respectively, with average execution time reduced to 0.61 seconds. In functional operation scenarios involving door handles, kettle handles, and drawer pulls, grasping accuracy remained above 0.89, with task completion rates significantly outperforming mainstream baseline models. Under visual interference conditions with up to 75% occlusion rate, the average inference latency was controlled within 0.82 seconds. Under varying light intensities, the pose angle error remained within the range of 1.21° to 1.87°. Therefore, this model exhibits comprehensive advantages in grasping precision, latency control, and deployment efficiency, and has the potential to be largely applied in industrial, service, and special task environments.
The alkali recovery boiler is an important piece of equipment in chemical pulp production. It uses papermaking black liquor as fuel. Due to the large number of impurities, the heating surface is prone to severe ash deposition. To improve the heat transfer coefficient, the traditional method is to carry out timed soot blowing, which has problems such as untimely ash cleaning or excessive steam consumption caused by overly frequent soot blowing. In this paper, an experimental device for the relationship between the heat transfer coefficient and the weight of ash deposition was developed. The functional relationship between the two was obtained. There is an inflection point when the amount of ash deposition reaches 294.77 g. A control strategy of soot blowing at the inflection point was further proposed. A load-strain experimental testing device was developed. Experiments show that when the weight of ash deposition reaches 3503 N, the deformation of the suspender is 9 με, and starting the soot blowing device is the most efficient when the heat transfer coefficient is 725.15 W/(m²·K). Therefore, the degree of decline of the heat transfer coefficient can be indirectly reflected by measuring the strain. A method of soot blowing by detecting the degree of suspender strain was further proposed. This method is more scientific than the original timed soot blowing method and provides a technical reference for the energy-saving and consumption-reduction theories and engineering applications of alkali recovery boilers.
This study investigates the impact of incorporating clay nanoplatelets and waste eggshell particles into polymethyl methacrylate (PMMA) to develop hybrid nanocomposites with improved mechanical and structural properties. Waste eggshells, rich in biogenic calcium carbonate, were utilized as a sustainable, low-cost filler, while clay nanoplatelets provided nanoscale reinforcement and improved interfacial bonding. Hybrid nanocomposites were prepared with 5 wt. % of filler contents using the solution casting method. Scanning electron microscopy (SEM) was employed to examine the dispersion and morphology of the fillers within the structure of the PMMA matrix. At the same time, Fourier-transform infrared spectroscopy (FTIR) was utilized to assess the powder chemical interactions and potential bonding between the fillers (clay nanoplatelets and eggshell particles). Mechanical behavior was also evaluated through tensile testing of PMMA and its produced hybrid nanocomposites. The results indicate a synergistic enhancement due to the combination of organic biowaste and inorganic nanoclay, offering a promising route for the development of sustainable, high-performance polymer nanocomposites.
Although radiographic inspection is one of the oldest techniques for non-destructive testing, it is still considered vital in many industrial fields to ensure the quality of welds and meet the demands of work conditions and design, as well as safety and reliability requirements. This paper presents an algorithm that identifies and categorizes welding defects in radiographic images using machine learning techniques. For this aim, two supervised classifiers are proposed and performed, which are 1) K-nearest Neighbour (KNN), which is a nonparametric classifier, and 2) a multiclass classifier based on Support Vector Machine (SVM) as an intensive learning-based classifier (enthusiastically learns). SVM is commonly used in binary classification, but it can be adapted for multi-classification using various common methods, such as one-versus-one and one-versus-all. The texture features are adopted in this paper as inputs to the classifiers, where two groups of them are used: the feature of the Local Binary Pattern (LBP) and the grey-level co-occurrence extraction matrix (GLCM), to obtain the feature vector. To avoid the risk of overfitting, four k-fold cross-validations are applied. The experimental results are reported for two different classifiers, achieving an accuracy of 91.66% when combining GLCM and SVM.
This paper investigates changes in the modal parameters of a composite beam resulting from damage introduced to the bottom flange of a steel I-beam. Variations in the modal damping ratio and energy transfer ratio (ETR) are analysed. The results of experimental tests and numerical analyses are presented. The beam was modelled using the rigid finite elements (RFEs) method. The introduced damage caused small changes in the damping ratio. In contrast, the ETR was found to be more sensitive to damage than the damping ratio in the experimental results, exhibiting variations on the order of several tens of percent. In the numerical simulation results, changes in the ETR were smaller, reaching a few percent.
This study systematically evaluates optimal heat sink geometry for enhanced thermal performance in electronic cooling applications. ANSYS-Icepak and COMSOL Multiphysics software assessed four distinct fin geometries (square, rectangular, circular, and conical), all uniformly sized for accurate comparison. Vital performance parameters were analyzed, including maximum temperature reduction, pressure drop, and airflow velocity. These indicators provide a holistic assessment of cooling efficacy and aerodynamic characteristics. Findings highlight the effectiveness of rectangular fins, which significantly reduce maximum temperatures due to their efficient balance of conductive and convective heat transfer. While conical fins display lower pressure drops and circular fins achieve higher airflow velocities, these attributes do not consistently enhance cooling capabilities. The importance of this study resides in its provision of definitive guidance for selecting fin geometry in designing efficient heat sinks, crucial for electronic devices. This knowledge is particularly vital for developing advanced cooling systems in compact, high-power electronics, underscoring the significant impact of fin geometry on overall thermal management efficiency. Quantitative data supporting these findings is available in the full study.
Based on the principles of geometrical optics, an analytical description of caustics generated in a spherical mirror is presented. The formation of caustics in a wave field is studied using acoustic and electromagnetic waves as an example. Symmetry of equations describing energy relations in acoustics and electromagnetism is shown. The presence of caustics in natural phenomena is demonstrated, as well as their manifestation in architectural acoustics and astronomy. It is explained why in the sound field in existing halls, rather than the entire caustics, only their cusp is observed, which is perceived as a blurred area with an increased sound level accompanied by unusual values of acoustic room parameters. The influence of caustics on the efficiency of spherical and parabolic antennas used in radio astronomy is discussed.
Carbon fiber-reinforced thermoplastic composites are widely utilized in 3D printing via the fused filament fabrication (FFF) process. However, defects within printed components can compromise their performance. This study investigates the application of ultrasonic non-destructive testing (NDT) techniques for structures manufactured through FFF. Common printing defects, such as weak interlayer bonding, surface imperfections, and internal cracks, are simulated using a finite element (FE) model. The model analyzes how guided ultrasonic waves interact with these defects. The proposed methodology incorporates digital transducer control and evaluates the energy distribution across incident, reflected, and transmitted wave modes. Three representative defect types are modeled, and the approach is applied to two structural geometries: plates and pipes. The study investigates the correlation between defect size and the behavior of energy reflection and transmission. A signal processing approach is applied, using transducers positioned symmetrically along the wave propagation axis to detect mode conversion and analyze wave reflections and transmissions. The phenomenon of mode conversion is analyzed in detail, and the results are validated by ensuring energy balance consistency.
The chemical, food processing, hydropower, thermal power, and oil industries are among the sectors that frequently face the problems of erosion, abrasion, and corrosion. Pipelines, elbows, reducers, separators, tees, and seals are among the hydraulic devices and pipeline components that are impacted by these difficulties. Silt erosion in turbines and related parts is a major issue in hydropower plants, particularly in Indian hydropower plants where rivers contain hard elements like feldspar, quartz, and other minerals. Remarkably, more than half of the quartz in the silt causes problems in turbines, including sediment erosion, leaks, and secondary flow disturbances. Hydropower plants' total efficiency is ultimately jeopardized by these issues. This paper aims to support scholars and researchers by highlighting the following topics: (i) component failures in impulse and response turbines used in hydropower projects; (ii) different turbine materials and their properties; and (iii) a comparison of several thermal spraying techniques for turbine materials along with numerous numerical models of erosion and abrasion informed by silt characteristics, material properties, and flow phenomena in different hydro-turbines. The study also discusses modeling, pilot plant loops, wear mechanisms, and protective techniques aimed at mitigating wear and safeguarding hydro turbines.
A characteristic feature of the six-parameter theories of bars is a coupled form of the constitutive equations; in particular the equations linking transverse forces with transverse shear deformations cannot be, in general, decoupled, keeping a separated form of the remaining constitutive equations. The mentioned feature of the constitutive equations implies that within the six-parameter theories of straight elastic prismatic bars there do not exist, in general, plane states of bend-ing/shearing deformations. Thus, any vertical load causes lateral deflections, the only exception being the pure bending problem. The present paper delivers analytical solutions: the closed formulae for shape functions, i.e. deformation states associated with kinematic loads at the ends, and solutions to selected static problems corresponding to the transverse span load. Although elementary, the presented solutions seem to be derived for the first time. In particular, the hitherto published shape functions concerned the theories of moderately thick bars in which all the constitutive equations are decoupled.
Examining torsion in functionally graded materials (FGMs) is crucial because their properties vary spatially. FGMs with continuously graded architectures provide a robust basis for investigating mechanical behavior. Current understanding of torsional response draws on analytical, numerical, and experimental approaches. This review synthesizes how material gradation influences stress distribution, stiffness, and failure modes, and compares advances in FGM torsion across diverse models and geometries. The theoretical background is framed by classical torsion theories, including Saint-Venant, Prandtl’s membrane analogy, and Vlasov formulations. We further discuss modeling with isoparametric finite elements and summarize established homogenization schemes for FGMs. A tabulated overview of torsion-related results is also provided. The novelty of this review lies in its exclusive focus on torsion in FGMs, the systematic tabulation of prior contributions, and a coherent exposition of homogenization models and torsion theories tailored to FGM structures. To our knowledge, this is among the first reviews to focus specifically on torsion of FGM structures, distinguishing it from prior overviews that address torsion only briefly. Methodologically, we conduct a structured scoping review that screens peer-reviewed sources, classifies studies by geometry, torsion theory, homogenization scheme, and numerical strategy, and synthesizes observed trends. Finally, we present concise conclusions and future research directions. This review covers analytical, numerical, and experimental studies of torsion in FGMs, identified via a structured Google Scholar search and prioritized by citation impact and relevance.
Graphical methods remain an important tool in the theory of mechanisms due to their ability to visually convey fundamental kinematic principles. They are particularly useful in the early design stages and in educational contexts, where intuitive understanding is essential. Among the applications of graphical synthesis methods, mechanisms that require a link to momentarily stop at specific angular positions-commonly referred to as angular reversal positions-are of particular interest. While various analytical and numerical methods exist for designing such mechanisms, they typically focus on dwell positions of rotational or translational links and rely on optimization techniques, often at the cost of geometric transparency. This paper presents a graphical synthesis method for a four-bar linkage designed to achieve two prescribed positions at which the coupler reverses its direction of rotation. This specific problem has not been previously addressed in the literature. It arises in mechanisms used for emptying containers, where the coupler carries the container and must instantaneously pause at two distinct angular positions to ensure stable discharge. Unlike many graphical methods, which may involve ambiguity due to trial-and-error selection of geometric parameters, the proposed technique ensures a unique and geometrically consistent solution while also allowing the Grashof conditions to be satisfied. This contrasts with many numerical methods, where constraint verification is often deferred until the final stages. The construction proposed here is both practically relevant and introduces a novel graphical approach, broadening the scope of synthesis methods to encompass mechanisms exhibiting link dwells in planar motion and reaffirming the relevance of graphical approaches.
Self-supporting arch halls are increasingly used in the construction of buildings with a significant impact on public safety. Unfortunately, no specific design methodology has yet been established. Even more concerning is the growing emergence of new design challenges, including local structural modifications and unconventional loading conditions. This study reviews methods applied in engineering practice as well as those proposed in research studies. A comparative analysis of results obtained using various methods is presented for selected structures subjected to loads according to applicable standards.
This work concerns a global elastic buckling problem of a thin-walled T-frame with consideration of the shear effect. A novel approach was used to account for this effect, namely, the non-linear shear deformation theory, which gives as a result the shear deformation function describing the behaviour of the beam cross section. This thin-walled T-frame consists of a horizontal beam and a vertical column made of the same standard H-beams. The shape of this standard H-beam and the dimensionless deformation function of the plane cross section, being the result of the shear effect, are analytically described. The buckling problem of the frame is analytically formulated and solved. The critical loads of exemplary beams are analytically determined. Moreover, a numerical model, based on the finite element method (FEM), of the frame is elaborated and the critical loads of exemplary frames are determined. Consequently, the research results obtained by both methods are compared, and the advantages of the proposed approach are discussed.
To improve the resistance of bitumen pavements to low-temperature cracking, this study proposes a composite-modified bitumen based on styrene-butadiene-styrene (SBS) copolymer and crumb rubber. This modified bitumen is also tested for its performance in a lowtemperature environment. The test results indicate that, after aging and freeze-thaw cycles (FTCs), the creep rates (CRs) of both SBS-modified bitumen and the SBS/crumb rubber composite-modified bitumen decreased. However, the CR of the SBS/crumb rubber compositemodified bitumen was constantly lower than that of the SBS-modified bitumen. For example, at -12 degrees C, the CRs of the aged SBS-modified bitumen and SBS/crumb rubber composite-modified bitumen were 0.44 and 0.37, respectively. When the bitumen mixtures underwent FTCs and aging, their fracture energy densities (FEDs) drastically decreased. Nevertheless, the FEDs of the SBS/crumb rubber composite-modified bitumen mixtures were higher than those of the SBS-modified bitumen mixtures. These results indicate that the composite-modified bitumen with SBS/crumb rubber has good rheological properties and freeze-thaw resistance, thereby effectively ensuring the low-temperature performance of bitumen pavements.
This work deals with the theoretical modeling of the vertical dynamics of a specialized vehicle featuring a dual suspension system. Vehicle ride quality is essential for ensuring the safety and comfort of passengers and the protection of sensitive or hazardous cargo. The study focuses on a two-axle vehicle model with a dual suspension system. The first-level comprises a traditional suspension with linear stiffness, while the second-level features nonlinear quasi-zero-stiffness (QZS) characteristics. The research employs a discrete nonlinear dynamic model that considers the vertical displacements and angular rotations of the vehicle masses. The nonlinear QZS response is modeled to optimize vibration isolation performance under varying load conditions, while damping effects are included via a Rayleigh dissipation function. The integral characteristics of the QZS element are also studied in detail using finite element (FE) computer simulations in a 3D setting. These simulations provide a comprehensive understanding of the mechanical response and stress-strain distribution within the QZS element, validating its performance under real-world conditions. The results demonstrate the influence of the nonlinear suspension characteristics on vibration isolation performance and load stability. The QZS-based suspension effectively reduces dynamic stresses, particularly under low-frequency excitations, while maintaining structural integrity and operational efficiency.
This manuscript proposes a multicriteria approach to the design optimization of adaptive pneumatic impact absorbers. The considered absorber consists of two sealed chambers separated by a piston with an internal valve. Proper valve control affects gas flow between the chambers and ensures a flat reaction force profile over a possibly long piston stroke. The design of such an absorber is defined by three parameters: initial gas pressure, diameter, and length. For a given range of impact conditions, the worst-case maximum deceleration and maximum mass flow rate are used as design criteria in a multicriterial minimization problem. Solutions to this problem provide an optimal balance between impact absorption performance and the technical requirements the valve must meet. An example is considered, which illustrates the Pareto-optimal solutions in the design space and the complex interdependency between initial pressure and absorber diameter at each absorber length. The results demonstrate that a proper choice of design parameters can result in significant performance improvements.
This paper presents the concept of a vision system designed to determine the position of a camera within a given coordinate system. The system focuses on identifying pulsating light markers in images recorded by the camera. These markers are characterized by specific colors, pulsation frequencies and known locations. Detection is achieved using a spatial-time-frequency processing method developed by the authors. The identified markers serve as input data for a mathematical model that determines the camera's position within the reference system. The article discusses the theoretical foundations of the proposed system design. The system was subjected to testing to verify its operational accuracy and precision in position determination. The results of these tests are presented. The article concludes with a summary of the work and a discussion of the system's further development and practical applications.
The switched reluctance motor (SRM), known for its robust and simple construction, is widely utilized in critical applications. This study investigates the impact of rotor dynamic eccentricity on the motor's current signal. Our research introduces a straightforward diagnostic method to detect and quantify dynamic eccentricity by analyzing the current signal spectrum. This approach specifically focuses on identifying amplitude increases in characteristic additional harmonics, leveraging fundamental electromagnetic transformations to eliminate the need for complex algorithms. Through coupled computer simulations, combining a finite element analysis model (FEMM, Finite Element Method Magnetics software) with dynamic equation solutions in Simulink, this study identifies specific eccentricity ranges and their corresponding characteristic current values, offering a reliable tool for SRM condition monitoring.
