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Performance assessment of network system network comprising four subsystems via multi failure and multi repair methodology
Get PDFA multi-dimensional repair approach is the most effective policy for restoring repairable systems. This research study analyzes a complex repairable system that consists of four subsystems with different configurations. The system consists of four subsystems: Subsystem 1 contains a single unit, Subsystem 2 includes n identical units operating under a k-out-of-n: G policy, Subsystem 3 features two identical load balancers responsible for distributing the load (with at least one required for operation), and Subsystem 4 consists of four identical units functioning under a 3-out-of-4: G policy. It is assumed that all subsystems have constant failure rates that are distributed exponentially. General repair, which is utilized while the system continues to function in accordance with the established operating policy, and copula-based repair, which is employed when the system stops completely, are the two types of repair techniques that are put into practice. A supplementary variable approach is incorporated to analyses system performance. Various reliability measures are computed using Maple 18, software, and future behaviour of system have been predicted in long run operation. By means of illustrations in the tables and graph it clearly shown how the copula repair is beneficial over ordinary repair
Rocking responses of free-standing rigid blocks on flexible foundation with a slope under earthquakes: structure-foundation interaction effects
Get PDFTo simulate the dynamic rocking responses of free-standing rigid blocks on a flexible foundation with a slope, a modified concentrated spring model (CSM) is proposed. The shaking table model test of a rigid steel frame structure was conducted, and the test results indicated that the rocking response of the structure can be effectively predicted by the proposed model. Utilizing the modified CSM, the interaction effects between the structure and foundation on the rocking of the free-standing rigid blocks on a flexible foundation with a slope were investigated. The influences of spring stiffness, viscous damping, and the frictional coefficient on the rocking of the rigid blocks under pulse-type ground motions were analyzed numerically. The results indicated that decreasing the spring stiffness and increasing the viscous damping coefficient of the modified CSM can reduce the number of impacts and rocking duration, while the friction coefficient has a significantly non-linear effect on the rocking response
Aeroelastic stability analysis and optimal PID control strategy simulation for large-scale HAWT blades
Get PDFAiming at the classical flutter problem of wind turbine blades, a wind turbine blade aeroelastic model is constructed based on the typical leaf cross-section model of spring-mass-damper and the classical flutter aerodynamic model. The stability analysis of the wind turbine aeroelastic model is carried out using the Liapunov indirect method, and the effects of different parameters on stability are compared. Combining the aeroelastic model with the second-order model of pitch exciter, the pitch aeroelastic equation of the system is given, and the system controllability is analyzed. The optimal PID pitch control is designed, and the Simulink simulation is performed to explore the optimal combination under different combinations by selecting the torsion angle and waving displacement as the error signals, and different combinations of the torsion angle, waving displacement, and pitch angle as the optimal control objectives, respectively. The simulation results show that when the torsional angle is used as the error feedback signal and the torsional angle is set as the optimal control objective, it is the only scenario without overshoot. The overshoot in other cases ranges from 30 % to 500 %. In terms of adjustment time, this scenario also demonstrates good performance. Although it is not the fastest, the gap from the fastest is no more than 20 %. Therefore, using the torsional angle as the error feedback signal and the torsional angle as the optimal control objective is the best choice
Enhancing loess deformation resistance using waste tire rubber particles
Get PDFLoess, characterized by its large pore structure and vertical joints, is prone to collapsible deformation upon moisture infiltration and significant settlement under load, threatening the stability of buildings and infrastructure. This study systematically investigates the effects of rubber particle size (10, 20, 40, and 100 mesh), content (0 %, 5 %, 10 %, 15 %, and 20 % by volume), moisture content, and freeze-thaw cycles on the deformation properties of loess. This systematic investigation distinguishes itself by using waste tire rubber particles as the sole amendment to elucidate both the individual and coupled effects of these factors. Results demonstrate that incorporating rubber particles significantly reduces the compression coefficient of loess, with optimal compressibility achieved at a 5 % rubber particle content and 40 mesh particle size. The collapsibility coefficient is minimized at a 20 mesh particle size with the same 5 % content. Moisture content significantly influences deformation behavior, with both high and low levels increasing the compression and collapsibility coefficients. The study also reveals that rubber particle-loess mixtures exhibit superior freeze-thaw resistance, with smaller increases in deformation coefficients after multiple freeze-thaw cycles compared to remolded loess. The particle size and content of rubber particles are identified as the most important factors influencing the compressibility and collapsibility of loess. This research provides specific guidelines for optimizing rubber particle size and content, controlling moisture levels, and evaluating freeze-thaw impacts to enhance the engineering performance of loess. The findings offer a scientific basis for sustainable waste tire management and advance the application of rubber particles in geotechnical engineering
Structure design and sensitivity analysis of flexible ultrasonic transducer array
Get PDFTo investigate the influence of element parameters on the performance and acoustic field of flexible ultrasonic transducer arrays, this study employs finite element multiphysics simulation software to analyze various parameters of flexible ultrasonic transducers within a multiphysics coupled field. The analysis begins with simulating the width and thickness of piezoelectric materials in a single-element ultrasonic transducer structure. Simulation results indicate that the electromechanical coupling coefficient of the ultrasonic transducer exhibits a quasi-sinusoidal relationship with width. When the piezoelectric material width is 1.8 mm, the electromechanical coupling coefficient reaches its maximum at a thickness of 0.4 mm. Subsequently, simulations were conducted on various parameters of the flexible ultrasonic transducer array. Key investigations included the effects of piezoelectric unit count, inter-unit spacing, and frequency on the ultrasonic focusing performance of linear phased array transducers. Findings indicate that the focusing capability of flexible ultrasonic transducer arrays improves with reduced spacing and increased unit count. However, due to varying practical application requirements and manufacturing precision constraints, array parameters should be selected by comprehensively considering real-world factors. Overall, this study employs multiphysics coupling simulation to visually demonstrate how array element parameters influence the performance of flexible ultrasonic transducers. It provides valuable reference for advancing flexible ultrasonic technology from laboratory research toward commercial application
Magnetoelastic oscillation of current-carrying plates in an alternating magnetic field
Get PDFModern technological advancements, particularly in micro- and nanoelectronics, aerospace engineering, sensor systems, and robotics, necessitate a deeper understanding of how structural elements behave under various physical influences. One significant and relevant phenomenon is magnetoelastic interaction, which involves how the mechanical behavior of current-carrying elastic bodies is affected not only by external loads but also by internal electromagnetic processes. Current-carrying plates, commonly utilized in micro- and nanoelectronics, respond to external fields by altering their stress-strain states. To accurately model these processes, an integrated approach is required that considers mechanical, electromagnetic, and thermal effects caused by electrical currents. This paper focuses on the mathematical modeling and numerical study of transverse magnetoelastic oscillations in thin current-carrying plates subjected to an alternating magnetic field. The problem is formulated considering electromagnetic interactions, geometric nonlinearity, and external alternating currents. A comprehensive system of equations is developed that includes the equations of motion, Maxwell's equations, and the heat equation with Joule heating sources. For the numerical solution, the finite difference method using the Newmark scheme and discrete orthogonalization techniques are applied. Graphs illustrating stress and strain distributions are presented, and the effects of magnetic field frequency and external current on the system’s behavior are analyzed. This research is vital for designing reliable components in micro- and nano-electronics and aviation
Digital solutions for the transition to a sustainable public transport system in Tashkent
Get PDFThe purpose of this study is to analyze the prospects for transitioning the city from automobile-dominated mobility to a public transport-oriented system. The methodological framework is based on the analysis of transport infrastructure. The research is conducted on the example of Tashkent – the capital of Uzbekistan – characterized by a high level of motorization and significant commuter migration. The study concludes that a successful transition to public transport requires a phased implementation, involving infrastructure modernization, digitalization, regulation of motorization, and transformation of citizens’ mobility behavior. The novelty of this study lies in developing a digital transition model for Tashkent that integrates international best practices (Berlin, London, Singapore) with the local transport and socio-economic conditions
An analysis of the ultrasonic technology to stitch materials, and conceptualization and realization of a new sewing machine
Get PDFUltrasonic stitching is a thread-free and green technology for stitching fabrics, which uses the vibration energy of high frequency to transform it into heat at the joint to achieve local fusion. This paper provides the conceptual design and experimental validation of a roller-based ultrasonic sewing system for thermoplastic and composite textile. This work introduces a portable roller-type ultrasonic actuator coupled with a physics-based thermal model which allows the controlled and threadless joining of textiles, which is the main innovation of this paper. When operated at 27 kHz, 100 W and contact pressure of 5 MPa, the method gives maximum lap shear strengths of 86 N for polyester and 67 N for cotton + LDPE. The measured results define the process window and show the possibility of low-waste industrial utilization. Novelty: (I) a small size ultrasonic stitching unit based on the roller technology; (II) a closed-form thermal model for the relationship between energy input and joint strength; (III) validated process parameters towards a sustainable textile bonding application
Self-supervised CNN for user behavior analysis on smart meter data
Get PDFSmart meters generate extensive data on individual consumer electricity usage, providing valuable insights that can aid in identifying demographic information and advancing the development of smart grids. Current research has primarily focused on traditional machine learning approaches for this task, with relatively few studies exploring deep learning methods, despite their potential for more accurate and efficient analysis. To address this gap, this paper proposes a self-supervised deep learning approach based on Convolutional Neural Network (CNN) to identify demographic information from smart meter data. The model leverages the Fast Fourier Transform (FFT) to detect frequency cycles within the dataset, which are then used to optimize the sizes of convolutional kernels. This design enhances periodic stability during shallow feature extraction, improving the model’s ability to capture meaningful patterns in the data. Furthermore, the model incorporates a self-supervised pre-training strategy to predict temporal and spatial interactions in load signals, effectively enhancing representation learning without relying on extensive labeled data. This approach ensures the model’s robustness and adaptability to different datasets. Comprehensive experiments were conducted on a publicly available Irish dataset to evaluate the model’s performance. Results demonstrate that the proposed model surpasses a series of state-of-the-art (SOTA) methods, achieving superior performance in demographic information identification. These findings highlight the effectiveness of integrating FFT-based kernel design and self-supervised learning in improving feature extraction and representation learning for smart meter data
Study on vortex-induced vibration response of large-scale two-lay steel trusses bridge under large wind angle of attack
Get PDFWith the advancement of urbanization, two-lay trusses bridges are widely used because of their good traffic capacity and structural performance. However, the aerodynamic behavior of this beam type is still in the exploratory stage. The local microclimate characteristics at the bridge site in mountainous cities are obvious, and it is easy to form a large wind angle of attack, which has a significant impact on the vortex-induced vibration (VIV) performance of the bridge. Therefore, this study takes a long-span two-lay steel trusses bridge in a mountainous city as the engineering background, and uses wind tunnel test and numerical calculation methods to study the changes of the static three-component force coefficient and VIV response of the main beam in the construction and completion state under the action of high wind angle of attack. The results show that the three-component force coefficient curves under different wind speeds are close to each other, and the Reynolds number effect is not obvious. The vibration test shows that the vertical bending VIV first occurs at +3° and +5°, and then two torsional VIV with different amplitudes occur. Both vertical bending and torsional VIV are simple harmonic vibrations with a single frequency, and the vertical bending VIV frequency is locked at 2.227 Hz, and the torsional VIV frequency is locked at 4.289 Hz, which are close to the natural frequency of the test model. Compared with +3°, the maximum amplitude of vertical bending VIV under +5° increases by 30.0 %, while the maximum amplitude of torsional VIV under high and low wind speed increases by 16.6 % and 12.7 % respectively, and the locking range is longer. It can be seen that the wind angle of attack has a significant effect on the VIV response of the main beam in the completion state. Especially, the trusses beam at a large angle is more sensitive to VIV, and it is more prone to large-scale and large-amplitude VIV. The research results can provide a theoretical basis for the aerodynamic shape optimization and provide a reference for the design of related bridges