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The paper deals with the dynamics of a resistance spot welding system. At the core of this system is a transformer, which is powered on the primary side by a pulse-width modulated inverter and has a full-wave output rectifier on the secondary side that provides a direct welding current. The entire system is nonlinear, due to magnetic hysteresis and electronics. The electronics prevent the current from flowing in all parts of the welding transformer at separate time intervals during the voltage supply period; therefore, not all the parameters affect the dynamic of currents and voltages all the time so the system is also time-variant. To design a high-performance welding system and to predict the maximum possible welding current at a specific load, it is necessary to know the welding and primary currents. The leakage inductances of the system can reduce the maximum welding current significantly at higher frequencies and the same load. There are several methods to determine these currents, each with its drawbacks. Measurements are time-consuming, using professional software is expensive and requires time to learn and free open-source software has many limitations and does not guarantee the correctness of the results. The article presents a new, fourth option—a theoretical derivation of analytical expressions that facilitate straightforward and rapid calculation of the welding and primary currents of the resistance spot welding system with symmetrical secondary branches. The derivation of the mathematical expressions is based on the equivalent circuits that describe the system in different operating states. The results of the numerical simulations confirmed the derived expressions completely. [ABSTRACT FROM AUTHOR]

Information technology applications are crucial to the proper utilization of manufacturing equipment in the new industrial age, i.e., Industry 4.0. There are certain fundamental conditions that users must meet to adapt the manufacturing processes to Industry 4.0. For this, as in the past, there is a major need for modeling and simulation tools in this industrial age. In the creation of industry-driven predictive models for machining processes, substantial progress has recently been made. This paper includes a comprehensive review of predictive performance models for machining (particularly analytical models), as well as a list of existing models' strengths and drawbacks. It contains a review of available modeling tools, as well as their usability and/or limits in the monitoring of industrial machining operations. The goal of process models is to forecast principal variables such as stress, strain, force, and temperature. These factors, however, should be connected to performance outcomes, i.e., product quality and manufacturing efficiency, to be valuable to the industry (dimensional accuracy, surface quality, surface integrity, tool life, energy consumption, etc.). Industry adoption of cutting models depends on a model's ability to make this connection and predict the performance of process outputs. Therefore, this review article organizes and summarizes a variety of critical research themes connected to well-established analytical models for machining processes. [ABSTRACT FROM AUTHOR]

Handoff mechanisms are very important in fifth-generation (5G) mobile networks because of the cellular architecture employed to maximize spectrum utilization. Together with call admission control (CAC) mechanisms, they enable better optimization of bandwidth use. The primary objective of the research presented in this article is to analyze traffic levels, aiming to optimize traffic management and handling. This article considers the two most popular CAC mechanisms: the resource reservation mechanism and the threshold mechanism. It presents an analytical approach to occupancy distribution and blocking probability calculation in 5G mobile networks, incorporating connection handoff and CAC mechanisms for managing multiple traffic streams generated by multi-service sources. Due to the fact that the developed analytical model is an approximate model, its accuracy was also examined. For this purpose, the results of analytical calculations of the blocking probability in a group of 5G cells are compared with the simulation data. This paper is an extended version of our paper published in 17th ConTEL 2023. [ABSTRACT FROM AUTHOR]

The difficulties in establishing an analytical model for plain woven fabric composites (PWFC) and its implementation are well-accepted due to the complexity of yarn architecture, approximations assumed, and lack of experimental validations. In this paper, a practical engineering approach is proposed to predict the tensile properties of PWFC. The approach assumes PWFC as cross-ply, the undulation angle an elliptical shape. The approach tremendously simplifies the calculation keeping a close agreement with the tensile experimental results of PWFC. The approach is remarkably compatible with other theoretical models and experiments that existed in the literature. [ABSTRACT FROM AUTHOR]

This paper describes the composites of silane cross-linked polyethylene (PEXb) mixed with four different fillers dedicated to improving thermal conductivity, such as multi-walled carbon nanotubes, graphite, boron nitride, and mineral filler. Using the mathematical modeling, the concentration of each filler was estimated to reach the value of 0.675 W m−1 K−1 suitable for the usage PEXb in the production of geothermal pipes. From tested fillers, all improve the thermal conductivity of pure PEXb; however, above the required value, only 28 mass% of boron nitride (0.937 W m−1 K−1). It was associated with its perfect dispersion and the highest gel content achieved, also resulting in the highest flexural modulus. Graphite at 5 mass% and mineral filler at 35 mass% allowed the thermal conductivity to equal 0.622 W m−1 K−1 and 0.624 W m−1 K−1, respectively, with a simultaneous medium effect on the mechanical properties. Carbon nanotubes increased PEX's conductivity to a small extent, due to their occurrence as agglomerates. [ABSTRACT FROM AUTHOR]

AbstractThe increasing interest in adhesives, such as pressure-sensitive adhesives (PSAs), is often held back by uncertainties regarding their long-term behavior, which includes creep behavior. However, little information exists in the literature regarding creep behavior of PSAs. In this paper, a unified phenomenological creep model for PSAs is applied in SLJs for static and cyclic creep, seeking to develop a tool to predict creep behavior of PSAs. The model was validated by comparing the predicted creep curves with experimental data. It captured the three creep phases and predicted the creep curves for different stresses and temperatures, which is uncommon in literature. [ABSTRACT FROM AUTHOR]

This paper studies the mechanical properties of the 2-D tri-axial braided composite. A volume element is established, so that the classical laminate plate theory and the series-parallel model can be adopted to study a bi-directional stress--strain response. Failure criteria are given and the failure strength is determined. The finite element simulation is used to verify the reliability of the present theoretical model. [ABSTRACT FROM AUTHOR]

Adequate mathematical description of magnetization curves is indispensable in engineering. The accuracy of the description has a significant impact on the design of electric machines and devices. The aim of this paper was to analyze the capability of Bézier curves systematically, to describe the nonlinear static magnetic properties of non-oriented electrical steels, and to compare this approach versus the established mathematical descriptions. First, analytic functions versus measurements were analyzed. The Bézier curves were then compared systematically with the most adequate analytic functions. Next, the most suitable orders of Bézier curves were determined for the approximation of nonlinear magnetic properties, where the influence of the range of the input measurement dataset on the approximation process was analyzed. Last, the extrapolation capabilities of the Bézier curves and analytic functions were evaluated. The general conclusion is that Bézier curves have adequate flexibility and significant potential for the approximation and extrapolation of nonlinear properties of non-oriented electrical steels. [ABSTRACT FROM AUTHOR]

Coreless fault current limiter with variable series reactor is an emerging technology for limiting the amplitude and shortening the fault duration in the power network with simple and reversible operation. The device includes two coaxial, coreless reactors with axial mobility to vary and increase the effective inductance of the network during the short circuit fault. The reactors are automatically returned back to their initial position after the fault is cleared, with minimal net inductance. This paper aims to analytically describe the electromagnetic theory and validate the functionality of the device. For this purpose, the resistance and inductance of the device are first computed at normal condition via the basic theory of engineering electromagnetics. Next, the respective electromechanical performance characteristics such as force, positional displacement of the reactors, and the effective inductance are calculated at the faulty condition. For verification purposes, analytical results are compared against the finite element model. [ABSTRACT FROM AUTHOR]

In this paper, both numerical and analytical method were developed for computing, in strip or plate rolling, the distribution of roll pressure, rolling force, and rolling torque (from which also rolling power can be estimated), assuming an homogeneous deformation of the rolled material. Unlike other similar models present in the literature, which solve the resulting rolling differential equation for the roll pressure, the model presented in this work solves the problem for the horizontal force. In this way, it is possible to avoid the calculation of the derivative of material flow stress curve, which is not always analytically easy and possible (i.e., point material flow stress data). The proposed numerical model is based on the friction law proposed by Chen and Kobayashi while the analytical one is based on the simple shear friction model and brings to useful analytical formulas for a quick calculation of rolling torque and force. Moreover, a relationship between the shear friction factor and Coulomb friction coefficient in rolling was found. The developed models show good agreement with experimental measures, in terms of rolling force and torque, found in literature. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on applying the two-scale asymptotic homogenization method to derive the effective properties of piezoelectric composite materials characterized by generalized periodicity in curvilinear coordinates. The methodology involves formulating the homogenization problem in a general curvilinear framework suitable for materials with complex geometric configurations. By systematically deriving the homogenized equations and effective coefficients, the paper provides a robust theoretical foundation for understanding the macroscopic behavior of piezoelectric composites under various loading conditions. The model's versatility is demonstrated through its application to specific curvilinear coordinate systems, including the helix coordinate system and cylindrical coordinates with wavy geometry. These examples highlight the potential of the proposed approach in analyzing and designing piezoelectric materials with intricate geometries. The state-of-the-art numerical homogenization methods have also validated the proposed homogenization method, ensuring its accuracy and robustness. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental and analytical behavior assessment of novel sandwich panels fabricated with recycled glass-fiber/polyester resin (GFRP) core and PVC face sheets. The originality of the present work is based on sustainable development and waste recovery to design lightweight and eco-friendly structures. In this respect, the panels cores were fabricated using fully recycling of fiber-glass waste issued form the boats building. Accordingly, a set of sandwich panels with various core configuration and fibers orientation were manufactured and tested up to failure under three-point bending to characterize flexural and shear properties. In addition, validated analytical equations were advocated to assess the bearing capacity of the studied panels. The obtained results in terms of mechanical, thermal and physical features are emphasized, discussed and confronted with a good agreement to literature ones. A principal component analysis was conducted to optimize the effect of the geometrical parameters on the panel failure mechanisms. As main outcomes, the work can provide environmental and economic solutions for the design of sandwich structures. • Lightweight and eco-friendly sandwich structures-based GFRP waste core were designed • Validated analytical equations were advocated to assess the bearing capacity of the studied panels under bending • A principal component analysis was conducted to optimize the geometric parameters of the panels • The paper results provide environmental and economic solutions for the design of sandwich structures [ABSTRACT FROM AUTHOR]

In this work, we present a comprehensive analytical model for the Spacer-Engineered Reconfigurable Silicon Nanowire Schottky Barrier Transistor (SE R–Si NW SBT) for biosensing applications. This device operates in both n-mode and p-mode configurations by incorporating dual gates located near the source and drain terminals. The electrostatic integrity of the device is enhanced by incorporating high-K spacers on both sides of the gate electrode, facilitating improved interaction between the gate and the Schottky barrier. The biomolecules present on the silicon dioxide layer within the underlap cavity at the channel center, significantly impact the electrostatic properties throughout the device channel, including channel surface potential, drain current, electric field, and threshold voltage. By utilizing the 2D Poisson equation, we effectively capture the behavior of these key electrostatic properties. The primary metrics for biomolecule detection in this device are the changes observed in the threshold voltage and drain current. Furthermore, the variations in threshold voltage are analyzed to evaluate the sensitivity of the proposed biosensor and compared with that of state-of-the-art FET-based biosensors. The reliability of our analytical approach is validated using a virtual model of the proposed biosensor and performing simulations using the Silvaco TCAD device simulation tool. Through a meticulous comparison of our analytical findings with the simulated results, we establish the accuracy and dependability of our model. • The paper introduces a novel physics-based analytical model for detecting charged and neutral biomolecules. • The model accurately estimates channel surface potential, drain current, electric field, and threshold voltage profiles. • The analytical model is calibrated with experimental results. • The paper benchmarks the performance of proposed biosensors against state-of-the-art FET-based biosensors. [ABSTRACT FROM AUTHOR]

Given the increasing penetration of converter-interfaced resources in power systems, properly estimating the short-circuit current (SCC) contribution in large networks has become a growing challenge and necessity to ensure the security and stability of the systems and assets. This paper presents two novel methods to estimate the SCC contribution of type IV wind turbines at both the transient and steady-state stages of unbalanced and balanced faults: (1) a machine learning-based method trained with electromagnetic transient (EMT) simulations and capable of estimating some of the initial peak and transient current magnitudes; (2) an analytical approach to estimate the steady-state SCC based on the voltage and grid code dependency of the converter during the fault. The methods are coupled into a single framework and compared to field-validated EMT models of a real turbine. The results show that the majority of the estimated currents in the transient stages present errors below 5%. In steady-state, the errors are not greater than 1.21%. Given the complexity of the problem, these margins may be deemed acceptable for short-circuit studies. [Display omitted] • Short-Circuit Current Contribution from IBRs is becoming increasingly important. • The novel framework has been verified against field-validated EMT Models. • For the steady-state stage, the power-flow-based algorithm shows high accuracy. • Due to the complexity of the transient stage, a Machine-Learning model is used. [ABSTRACT FROM AUTHOR]

This paper presents an in-depth study of electrostatic actuators based on flexible side-electrodes focusing on the available electrostatic force and the derived useful force. A design tool is proposed considering technological aspects as aspect ratio, insulating layer material and voltage level. A space discretized mechanical approach based on Euler-Bernoulli beam theory is developed to model the bending deflection of the flexible movable electrode and "zipping" contact. Analytical developments and simplifications are achieved, rapidly and efficiently implemented in a proposed algorithm. ANSYS® simulations validate the procedure for updating the contact zone through the updating of the electrostatic pressure distribution. Optimum movable electrode width and appropriate "opposable" stiffness for guiding system are discussed. A "residual air thickness" parameter is introduced to address imperfect contact between the electrodes. characterization studies various prototypes with different structural parameters as thickness (50 µm and 200 µm), gaps (5 µm and 15 µm) and material for insulating layers (silicon oxide and parylene C). The metrology campaign highlights the impact of aspect ratio and oxidation/deoxidation on electrode sidewall quality and hence mechanical performance. A comparison with well-known comb-drive shows higher electrostatic force for flexible side-electrode actuators. As an example, for a 10 µm stroke, the available electrostatic force for flexible electrodes with irregular sidewalls (residual air thickness 0.6 µm) is 2.2 times greater and rises to 7.3 times greater for perfect sidewalls (no residual air). [Display omitted] • An analytical model and its algorithm are proposed for flexible side-electrodes electrostatic actuators. • Useful force is maximized according to an optimum electrode width and an appropriate "opposable" guiding stiffness. • Experimental characterization is conducted on set-ups including different aspect ratio and insulating layer material. • A relationship between performances and imperfection of the contact is established through a "residual air thickness". [ABSTRACT FROM AUTHOR]

Progressive collapse can be triggered by impact loading from vehicles or other objects and propagated by impact loading from falling debris. Therefore, the correct modeling of impact loading is necessary to assess the resistance of a structure against progressive collapse. As the number of timber buildings increases, the importance of adequate considerations of impact loading is growing. Previous research on impact loading of wood or timber was carried out on small clearwood specimens or on single boards. However, modern timber buildings use advanced wood-based composites, such as glued laminated timber and laminated veneer lumber. The characteristics of these materials are widely different from clearwood and single boards. In this paper, energy-based equations are derived for the peak impact force and the dynamic strength increase factor. These are quantified by pendulum impact hammer tests on 95 full-size glued laminated timber beams. The results are applied in a calculation example to demonstrate their potential use in practice. • Energy-based models for impact loading of timber beams are presented. • Results from 95 impact tests on full-size timber beams are discussed. • High-speed imagery reveals the impact process and five distinct failure modes. • The energy-release properties of timber beams are found to be strength class independent. • The dynamic increase or load duration factor is found for impact loading of timber beams. [ABSTRACT FROM AUTHOR]

• The creep in compaction was correlated with the recovery in the relaxation phase. • A unified viscoelastic-plastic model with one set of parameters was proposed. • Elevated temperature and in-plane tension intensify creep/recovery behavior. • Model captured temp. and time-related creep/recovery considering in-plane strain. In the manufacturing process of fiber-reinforced composite materials, the preforming of dry fiber fabrics is typically carried out under specific out-of-plane pressure, in-plane tension, and at designated temperatures. The fabric exhibits significant time and temperature-dependent permanent deformation as well as creep/recovery behavior. Gaining a better understanding of these phenomena and harnessing predictive capabilities will be instrumental in achieving more precise control over fiber volume fraction and material composition. In this paper, creep/recovery experiments and cyclic loading-unloading tests were conducted on CF3031 dry fiber preforms under various in-plane tensions and temperatures, measuring in-plane strains using Fiber Bragg Grating (FBG) sensors. Based on this data, a modified Burgers viscoelastic-plastic model has been proposed to describe the time-dependent creep/recovery behavior of dry fiber fabric preforming under the coupled effects of in-plane tension, out-of-plane pressure, and temperature variations. This model employs a single set of equations and parameters to represent the complete creep/recovery process of the material. The experimental results align well with the predicted outcomes across different compression scenarios. [ABSTRACT FROM AUTHOR]

In this paper, the temperature-dependent gate-induced drain leakage (GIDL) current model is proposed with the help of a lateral electric field (E L) across the inner and outer gate interfaces of the junctionless double-gate-all-around (JL-DGAA) field-effect transistor (FET). The E L at the interface is obtained from the surface potential equation after solving the 3D Poisson equation with appropriate boundary conditions. The derived model is validated using the well-calibrated TCAD simulator platform with experimental data. A higher GIDL current at the outer gate-channel interface is observed compared to the inner gate-channel interface in the OFF-state conditions due to the high E L between the channel and drain, which is reported for the first time here. The effect of temperature (from 200 K to 500 K) on the GIDL current is also observed, which increases linearly with increasing temperature. Further, the impact of induced mechanical stress (MS) is investigated on the GIDL current, where the GIDL current increases exponentially with increasing induced MS due to effective mass and band gap reduction. Finally, the dynamic performance is investigated in terms of the gate delay time as a function of channel length and temperature. The gate delay diminishes with decreasing channel length and increasing temperature, which shows the switching speed and ability of the device. [ABSTRACT FROM AUTHOR]

The concrete-cored cement mixing (CCM) pile composite foundation is a practical technology for soft soil ground treatment. This paper proposed a theoretical analysis model for the CCM pile composite foundation under embankment in undrained condition which comprehensively considered the interaction between the various components of the CCM pile composite foundation. The working behavior and influencing factors of CCM pile composite foundation under the embankment was also investigated based on the proposed analysis model. The research results showed that: the embankment load was transferred from the outer soil column to the inner soil column. The formation of soil arch effect promoted the concrete core pile to undertake the majority of embankment load, which improved the working behavior of the CCM pile composite foundation under flexible foundation. There was a neutral plane at a certain depth below the ground surface, and the pile shaft above the neutral plane was under negative skin friction, moreover, the vertical stresses of the concrete core pile, cement mixing pile and the soil around the pile all reached the maximum value at the neutral plane. [ABSTRACT FROM AUTHOR]

This research article focuses on using a junctionless-based dielectric modulated vertical Tunnel FET (VTFET-DM-JL) as a biosensor. The objective is to detect biomolecules without the need for labeling, using electrical signals by modulating the dielectric constant. The JLFET, which is a device without any doping gradient or junction, serves as the structural foundation for this research. To understand the behavior of the structure, a potential model is created in this research which involves solving the Poisson equations (PE) under various boundary conditions. In addition, the incorporation of a high- K gate oxide improves the reliability of the device, particularly in terms of low power consumption. The paper explores the impact of dielectric constant values ranges from 1 to 12 by calculating figure of merit (FOM) values, including linearity, sensitivity, and noise assessment. As an example, Gelatin with a dielectric constant value of 12 exhibits a drain current sensitivity of 6.7 × 108, which is 9 % higher than apomyoglobin (κ = 8.1), 12 % higher than Bacteriophage-T7 (κ = 6.4), and 46 % higher than APTES (κ = 3.57) sensitivity, at a cavity length of 30 nm. Additionally, various FOMs, including linearity, sensitivity, and noise characteristics, are computed for the device across the dielectric constant range of 1–12. The simulated results obtained using the widely available Silvaco TCAD tool is compared with the modeled outcomes. A comprehensive assessment of the FOM standards establishes the promising nature of the proposed VTFET-DM-JL structure in terms of linearity and sensitivity. • In this manuscript, the sensitivity, linearity, and noise evaluation attributes of the VTFET-DM-JL biosensor is explained in detail. • The VTFET-DM-JL device exhibits a comprehensive surface potential model, incorporating five separate regions, as its distinguishing feature. The regions included the depleted regions for the source and drain, along with depleted sections within the channel at the source and drain sides, as well as channel transport regions. • This novel model is specifically developed for low voltage applications. The analytical model utilizes a parabolic approximation to solve both the one-dimensional (1-D) and two-dimensional (2-D) Poisson's equations. It improves the effect of band bending and enables smoother electrons tunneling paths, thereby enhancing device performance. • The accuracy of the potential model is evaluated by comparing it with simulated results. The observation reveals a strong agreement between both sets of results, demonstrating the reliability of the potential model proposed in this study. [ABSTRACT FROM AUTHOR]