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Metal halide perovskites are archetypal ionic‐electronic materials with great prospects for optoelectronic applications. Among the rich variety of physics exhibited by ionic‐electronic conduction, here, those most relevant to optoelectronic devices in which ionic mechanisms introduce a kinetic delay in the electronic phenomena are analyzed. The attention is focused on the inductive loop features and a dynamical model is developed to describe the corresponding complex multiscale dynamics in the time domain under experimental conditions, finally explaining the fundamental structure of the current transient responses in halide perovskite semiconductors. Based on complex capacitive and inductive patterns extensively studied in impedance measurements, an adequate interpretation of time domain methods capable of monitoring charge‐carrier dynamics is produced. Therefore, this methodology identifies the characteristic parameters of all types of transient dynamics in metal halide perovskites, providing a suitable connection of correlated techniques, including impedance and chronoamperometric experiments, toward a robust interpretation of the device response. The scope of the method is fairly general, since these counterintuitive transient effects are observable not only in metal halide perovskites, but also in multiple materials and processes, mainly in different research fields pertaining to electrochemistry and electronics. [ABSTRACT FROM AUTHOR]

The circuit simplification and simple structure of piezoelectric motor have become a major trend at present. Therefore, a novel, miniaturized, single-phase driven piezoelectric motor is proposed. The suggested piezoelectric motor employs a bending vibration mode of the first order, which is inspired by the motion patterns of fish tail fins. First, the motor's operational principle and structure are explained. By analyzing the relationship between the working frequency and amplitude of the motor and the output power, the key parameters of the motor are determined, and the structure size of the motor is calculated. Next, the FEM model of the stator is utilized to conduct transient analysis in order to examine the movement path of the driving foot. Symmetrical right-diagonal or left-diagonal motions are formed by the driving foot during the first bending vibration, creating oblique elliptical movements. Finally, a prototype is made and its vibration and mechanical characteristics are tested. At a frequency of 15.6 kHz, the motor's highest speed without any load is measured at 31.2 mm/s. Both forward and backward performance is identical. When the motor is supplied with a voltage of 140 Vpp and a preload of 2 N, it achieves a moving speed of 4.2 mm/s at 15.6 kHz, with an output thrust of around 0.9 N. [ABSTRACT FROM AUTHOR]

In this paper, a composite excitation method is used to optimize the design of an existing cantilevered cylindrical ultrasonic motor to avoid vibration interference. Modal and transient simulation analysis of the stator structure was carried out by the finite element method. Optimized stator structure is simpler than the original motor. Simulation analysis results show that the circumferential amplitude is increased by more than 35% with 55.7% reduction in ceramic usage. [ABSTRACT FROM AUTHOR]

Sommerfeld effect is a nonlinear jump phenomenon which occurs in unbalanced rotor–motor system, and its characteristics provide an idea of power required to operate the system in the post-resonance region. In this article, the steady-state and full transient characterization of Sommerfeld effect in an unbalanced rotor–motor active magnetic bearing system is studied by considering the nonlinear bearing force of the active magnetic bearing (AMB) in the system equation. The homotopy perturbation method (HPM) is used to solve the nonlinear coupled second-order differential equations of the 16-pole leg AMB system analytically, and the steady-state vibration amplitude of the rotor dynamic system is calculated using the same method. The numerical power balance technique is used to study the steady-state Sommerfeld effect in the system, and its characterization provided the range of unachievable speed range for the rotor dynamic system. The full transient analysis of the rotor–motor AMB system is done analytically, and the exact voltage requires to pass through the resonance, while the system accelerated by the motor is obtained. From the steady-state analysis, it is observed that as the bias current is increased from 0 to 20 A, the jump voltage required to escape resonance has been decreased from 94.7 to 71.5 V. From frequency response curve, it is also observed that as the bias current is increased, it decreases the steady-state vibration amplitude up to 13.8% and a peculiar phenomenon like shifting of resonance is also occurred. It is also observed that percentage of reduction in the jump voltage required for passage through resonance are obtained as 4.5%, 17%, and 24% as the bias current supply to the AMB is increased from 0 to 5, 15 A, and 20 A, respectively, for transient analysis. Both the steady-state and transient responses were attained by increasing the bias current supply to the AMB system, and it is observed that the system vibration amplitude is reduced significantly at the resonance while increasing the bias current. The Sommerfeld effect characterization with respect to bias current supply to the AMB system is provided a vital idea of major reduction in the required jump voltage for passage through the resonance and achievable rotor speeds to operate the system in the post-resonance region. [ABSTRACT FROM AUTHOR]

This research presents a detailed transient experimental and computational study of heat transfer and airflow in a scaled room linked with a double-duct vertical roof solar chimney (SC). The analysis was made in the coupled system, varying the heat flux supplied to the roof SC absorber during the day. Experimental temperature profiles were obtained at six different depths and heights, the empirical heat transfer coefficient was computed for the SC absorber, and the variation of air changes per hour was determined. A good agreement between experimental and numerical temperature profiles and average Nusselt number (Nut) is shown in the latter of average difference of 3.41%. The validated computational model was used to analyze the effect of the transient heating of the SC on temperature fields and flow patterns in the thermal system. Almost symmetrical temperature and y-velocity profiles are formed in the ducts at different hours of the day, with thermal boundary layers of about 4 mm. Correlations of the Nusselt number and air changes per hour (ACH) are provided as a function of the modified Rayleigh number. [ABSTRACT FROM AUTHOR]

The present paper investigates the von-Karman geometrically nonlinear structural responses of ceramic-metal functionally graded shell panels under the effect of the cases of mechanical and thermal shocks on their ceramic-rich surface. The constituents in the FGM are temperature-dependent and are graded as per the recently proposed four-parameter power laws while their effective properties in the shells are obtained using the Mori-Tanaka homogenization scheme. The transient thermoelastic problem is solved by importing the temporally varying temperature distribution from the nonlinear 1D heat equation as thermal loads into the FE code developed for thin and moderately thick shells based on higher-order shear deformation theory. The nonlinearity in the heat equation is linearized using Picard method in each Crank-Nicholson time-step while the linearization step in the geometric nonlinear problem uses Newton-Raphson method in each Newmark time-step. The new results presented in the manuscript study the effect of geometric nonlinearity on the responses of FG shell panels and the effect of different parameters of four-parameter FG laws. It was observed that including geometric nonlinearity significantly affects the responses of the shell panel structures when the loading direction, either mechanical or thermal, along with the gradation direction is reversed. [ABSTRACT FROM AUTHOR]

In this paper, a meshless method for analyzing the elastodynamic behavior of two-dimensional problems is introduced. The nonsingular method of fundamental solutions (NMFS) is combined with the method of particular solutions. To overcome singularities arising from point-shaped sources, a technique known as the boundary distributed source (BDS) method is used, which involves distributing sources across disks centered on the boundary. The NMFS is regarded as a mesh-free boundary method due to source point independence to the neighboring source details. The dual reciprocity method (DRM) with a suitable approximation is used to obtain the particular solution corresponding to the nonhomogeneous inertial term; moreover, added benefits of eliminating domain integration and readiness for computer algorithms anchor desirability. Cautious investigation of solutions to various numerical examples using DRM reinforces reliability and accuracy. Finally, the study comprehensively examines factors such as the number of collocation points, internal points, the radius of the circular disk, and the time-step size to assess their impact on achieving convergence. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure discharges generated in air are expected to be electronegative, but experiments that examine negative ion densities are limited to date. In this work, we measured the temporal variation of the negative ion density in a streamer discharge generated in air. We adopted cavity ringdown spectroscopy, where negative ions were detected via weak optical absorption caused by laser photodetachment. The temporal variation of the absolute negative ion density was deduced by the transient analysis of the ringdown curve. Negative ions were detected after the disappearance of the discharge voltage and current. The negative ion density started the increase at 0.4 µ s after the initiation of the discharge. The increase means the enhancement of the electron attachment frequency in the late phase of the secondary streamer with electron cooling. The survival of electrons until 0.4 µ s is understood by the steep decrease in the cross section of dissociative recombination with the electron energy. The maximum negative ion density was observed at 1 µ s, and it was around the noise level at 1.5 µ s. The rapid decay is consistent with the destruction of negative ions by mutual neutralization with positive ions. [ABSTRACT FROM AUTHOR]

The transient lubrication conditions of rolling bearings are different in gearboxes and bearing testers. It has been observed that samples of qualified rolling bearings tested in rolling bearing testers often fail and do not meet lifespan requirements when employed in other lubrication conditions. This may be caused by different factors affecting the bearing in testing and applying lubrication. Needle roller bearings were selected for this study to investigate the causes of this phenomenon in terms of lubrication. Based on the computational fluid dynamics (CFD) method, fluid domain models for the same type of rolling bearings with different lubrication conditions were established. The transient flow fields of rolling bearings with oil jet lubrication in a tester and splash lubrication in a planetary gearbox were simulated. The air–oil transient distribution of rolling bearings in two kinds of lubrication was analyzed. The results indicate that the rotational speed significantly affected the oil jet lubrication of the needle roller bearing. The average oil volume fraction rose by 0.2 with the increase in the bearing speed from 1200 r/min to 6000 r/min and by 0.06 with the increase in the oil jet velocity from 8 m/s to 16 m/s. The splash lubrication of the bearings in the planetary gearbox was directly related to the immersion depth of the rolling bearings in the initial position. Meanwhile, the splash lubrication of the bearings was also affected by other factors, including the initial layout of the planetary gears. The increase in speed from 1200 r/min to 6000 r/min made the average oil volume fraction of splash lubrication decrease by 4.4%. The average oil volume fraction of the bearings with splash lubrication was better than that with oil jet lubrication by an average of 41.9% when the bearing speed was in the low-speed stage, ranging from 1200 r/min to 3600 r/min. On the contrary, the bearings with oil jet lubrication were better than those with splash lubrication by an average of 31.8% when the bearing speed was in the high-speed stage, ranging from 4800 r/min to 6000 r/min. [ABSTRACT FROM AUTHOR]

Despite the significant development and wide application of 3D printing technology, there are rarely reports on the influence of the build plate temperature upon the manufactured products. By conducting transient thermal analysis and 3D printing experiments, researchers optimized the build plate temperature for reducing defects in printed samples formed through material extrusion (MEX). The temperature distribution near the bottom interface was analyzed using ANSYS parametric design language (APDL) numerical calculation, and the temperature variation at the key monitoring node was examined for different build plate temperatures. Standard samples were then prepared to study warping and tensile properties. The results indicated that sagging would occur when the key monitoring node's temperature exceeded the glass state temperature of the PLA filament, particularly at build plate temperatures of 55 and 60°C. This conclusion was verified through MEX experiments. Ultimately, without sagging, an optimal build plate temperature of 50°C was determined based on APDL calculations, warping measurements (0.42 mm), and tensile yield strength (39.63 MPa). Thus, research on this parameter of temperature field distribution will contribute to the realization of high‐quality and high‐precision 3D printing. Highlights: Optimized the build plate temperature to reduce defects of MEX.The temperature distribution of the interface near the bottom was analyzed by APDL and monitored.Optimal temperature was discussed by combining the results of APDL and experiment data. [ABSTRACT FROM AUTHOR]

Fused-Deposition Modeling (FDM) is a commonly used 3D printing method for rapid prototyping and the fabrication of plastic components. The history of temperature variation during the FDM process plays a crucial role in the degree of bonding between layers. This study presents research on the thermal analysis of the 3D printing process using a developed simulation code. The code employs numerical discretization methods with an implicit scheme and an effective heat transfer coefficient for cooling. The computational model is validated by comparing the results with analytical solutions, demonstrating an agreement of more than 99%. The code is then utilized to perform thermal analyses for the 3D printing process. Interlayer and intralayer reheating effects, sensitivity to printing parameters, and realistic printing patterns are investigated. It is shown that concentric and zigzag paths yield similar peaks at different time intervals. Nodal temperatures can fall below the glass transition temperature (Tg) during the printing process, especially at the outer nodes of the domain and under conditions where the cooling period is longer and the printed volume per unit time is smaller. The article suggests future work to calculate welding time at different conditions and locations for the estimation of the degree of bonding. [ABSTRACT FROM AUTHOR]

Understanding the transient properties of cementitious pastes is crucial for construction materials engineering. Computational modeling, particularly through Computational Fluid Dynamics (CFD), offers a promising avenue to enhance our understanding of these properties. However, there are several numerical uncertainties that affect the accuracy of the simulations using CFD. This study focuses on evaluating the accuracy of CFD simulations in replicating slump flow tests for cementitious pastes by determining the impact of the numerical setup on the simulation accuracy and evaluates the transient, viscosity-dependent flows for different viscous pastes. Rheological input parameters were sourced from rheometric tests and Herschel–Bulkley regression of flow curves. We assessed spatial and temporal convergence and compared two regularization methods for the rheological model. Our findings reveal that temporal and spatial refinements significantly affected the final test results. Adjustments in simulation setups effectively reduced computational errors to less than four percent compared to experimental outcomes. The Papanastasiou regularization was found to be more accurate than the bi-viscosity model. Employing a slice geometry, rather than a full three-dimensional cone mesh, led to accurate results with decreased computational costs. The analysis of transient flow properties revealed the effect of the paste viscosity on the time- and shear-dependent flow progress. The study provides an enhanced understanding of transient flow patterns in cementitious pastes and presents a refined CFD model for simulating slump flow tests. These advancements contribute to improving the accuracy and efficiency of computational analyses in the field of cement and concrete flow, offering a benchmark for prospective analysis of transient flow cases. [ABSTRACT FROM AUTHOR]

The limited surface coverage and activity of active hydrides on oxide surfaces pose challenges for efficient hydrogenation reactions. Herein, we quantitatively distinguish the long-puzzling homolytic dissociation of hydrogen from the heterolytic pathway on Ga2O3, that is useful for enhancing hydrogenation ability of oxides. By combining transient kinetic analysis with infrared and mass spectroscopies, we identify the catalytic role of coordinatively unsaturated Ga3+ in homolytic H2 dissociation, which is formed in-situ during the initial heterolytic dissociation. This site facilitates easy hydrogen dissociation at low temperatures, resulting in a high hydride coverage on Ga2O3 (H/surface Ga3+ ratio of 1.6 and H/OH ratio of 5.6). The effectiveness of homolytic dissociation is governed by the Ga-Ga distance, which is strongly influenced by the initial coordination of Ga3+. Consequently, by tuning the coordination of active Ga3+ species as well as the coverage and activity of hydrides, we achieve enhanced hydrogenation of CO2 to CO, methanol or light olefins by 4-6 times. Zhu et al. report a quantitative and time-resolved analysis of hydrogen activation on Ga2O3, specifically shedding light on the long-standing puzzle of homolytic dissociation as opposed to the heterolytic pathway on oxides. [ABSTRACT FROM AUTHOR]

The analysis of electrical machine faults during start-up, and variable speed and load conditions offers numerous advantages for fault detection and diagnosis. In this context, diagnosing localized bearing faults through vibration signals remains challenging, particularly in developing physically meaningful, simple, and resampling-free techniques to monitor fault characteristic components throughout machine start-up. This study introduces a straightforward method for qualitatively identifying the time-frequency evolutions of localized bearing faults during the start-up of an inverter-fed machine. The proposed technique utilizes the time-frequency representation of the envelope spectrum, effectively highlighting characteristic fault frequencies during transient operation. The method is tested in an open-source dataset including transient vibration signals. In addition, the work studies the method limitations induced by the mechanical transfer path, when the bearing surroundings are not directly accessible for vibration acquisition. The proposed methodology efficiently identifies incipient localized bearing faults during inverter-fed machine start-up when the fault signature is not highly attenuated. [ABSTRACT FROM AUTHOR]

Vortex breakdown occurs in highly swirling flows in various engineering applications, such as hydraulic turbines working in either high-load or part-load conditions, leading to pressure pulsations and performance degradation. In the present study, the formation of a helical vortex breakdown having rotational and plunging components (axial oscillation) in a straight diffuser is investigated with transient simulation from its columnar state to a helical vortex breakdown state. It is similar to the helical precessing vortex rope occurring in hydraulic turbines operating at part-load condition. In addition, considering vortex breakdown as a global instability, a linear global stability analysis of the time-averaged turbulent flow field is conducted for different flow states. The main objective is to understand the role of plunging mode in vortex rope formation in straight draft tubes and identify its differences with the one observed in hydraulic turbines with elbow draft tubes operating at part-load condition. Results showed that in contrast to the elbow draft tubes where the plunging mode appears earlier than the rotating mode, the transient simulation showed that the plunging mode appears after several vortex rope rotations in the straight draft tube. This is confirmed by the stability analysis showing that the flow is unstable to the asymmetrical disturbances with a frequency close to the rotating frequency not the plunging ones. Finally, the stability analysis showed a higher critical flow rate than the one obtained from the contour of local swirl number and time history of pressure and velocity. [ABSTRACT FROM AUTHOR]

The use of simple bar elements in nonlinear structural finite element formulations has the academic advantage of uncoupling element technology issues from the structural phenomena to be observed. In this work, we present a finite element setting for the formulation of different nonlinear material models applied to the transient analysis of trusses. While nonlinear elasticity is considered by studying a Hooke-like linear relationship between different pairs of nonlinear measures of stress and strain, hyperelasticity is formulated using Ogden's model. Viscoelasticity is introduced using a generalized Kelvin rheological model to account for strain rate effects. The finite kinematics is set in a corotational total Lagrangian description where the virtual work is described using the Second Piola-Kirchhoff and the Green Lagrange measures. Although the derivation is omitted, the consistent tangent moduli are given for all these cases. Numerical problems involving simultaneously different truss models are studied and made available as benchmarks since little comparative data is found in literature. [ABSTRACT FROM AUTHOR]

This work describes the implementation of a novel dynamic Arbitrary LagrangianEulerian (ALE) formulation for the simulation of pavement structures loaded by rolling tires in a finite element framework. The proposed formulation enables the simulation of dynamic effects like acceleration, deceleration and variation of the wheel load on the pavement. The ALE scheme is described for a hyperelastic St. Venant-Kirchhoff material capable of finite deformations. With the adoption of this dynamic ALE formulation, a significant improvement in terms of speed and efficiency of the simulation is achieved in comparison to a classical transient Lagrangian formulation. This is primarily because only the relevant portion of the mesh around the applied load needs to be discretized and simulated. Another benefit is that a cumbersome moving load formulation does not need to be implemented. The results show satisfactory agreement with a conventional Lagrangian simulation with a moving load. [ABSTRACT FROM AUTHOR]

• Propose a transient mathematic model to predict the temperature of rotary compressors during startup process. • Discuss the instantaneous heat transfer law of the compression unit of the rotary compressor. • Put forward methods to improve the efficiency of compressor. The transient temperature distribution and heat transfer characteristics of the rotary compressor are crucial to its reliability and efficiency of the compressor. In this paper, a transient mathematical model on predicting the temperature in the compressor during startup is proposed. Control volumes are divided including the fluid and solid domains. The convective heat transfer coefficient of each surface is discussed. A coupled solution method and its Fortran calculation program are developed. This mathematical model is experimentally validated by comparing the measured and calculated temperatures of the compressor. The results shows that calculated temperatures are consistent with the measured results during the startup process. The maximum error of the steady-state temperature is within 2 °C. The refrigerant in the compression unit mainly absorbs heat from the refrigerant in the lower chamber. Measures should be taken to reduce the heating of the upper bearing surface by the refrigerant in the lower chamber to improve the volume and indicated efficiencies. [ABSTRACT FROM AUTHOR]

In this paper, a new lossy capacitance multiplier (CM) circuit using a single current follower differential input transconductance amplifier (CFDITA), one resistor and one capacitor (virtually grounded) is presented. The proposed circuit does not require any passive component matching constraints and has independently controllable equivalent capacitance with a multiplication factor up to 7102. Both ideal and non‐ideal analyses of the proposed CM circuit are carried out and compared. The performance of the proposed CM circuit is validated using a CMOS CFDITA and its validity is supported by various analyses including frequency analysis, transient analysis, Monte‐Carlo analysis and temperature analysis. The workability of the proposed circuit is also tested using layout design, and its pre and post‐simulated results are appended. The results are further confirmed with experimental results using the AD844 and LM13700 ICs with CFDITA implementation. [ABSTRACT FROM AUTHOR]

Purpose: The response of the Pine Flat dam–water–foundation rock system is studied by a new described approach (i.e. FE-(FE-TE)-FE). The initial part of study is focused on the time harmonic analysis. In this part, it is possible to compare the transfer functions against corresponding responses obtained by the FE-(FE-HE)-FE approach (referred to as exact method which employs a rigorous fluid hyper-element). Subsequently, the transient analysis is carried out. In that part, it is only possible to compare the results for low and high normalized reservoir length cases. Therefore, the sensitivity of results is controlled due to normalized reservoir length values. Design/methodology/approach: In the present study, dynamic analysis of a typical concrete gravity dam–water–foundation rock system is formulated by the FE-(FE-TE)-FE approach. In this technique, dam and foundation rock are discretized by plane solid finite elements while, water domain near-field region is discretized by plane fluid finite elements. Moreover, the H-W (i.e. Hagstrom–Warburton) high-order condition is imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. Findings: High orders of H-W condition, such as O5-5 considered herein, generate highly accurate responses for both possible excitations under both types of full reflective and absorptive reservoir bottom conditions. It is such that transfer functions are hardly distinguishable from corresponding exact responses obtained through the FE-(FE-HE)-FE approach in time harmonic analyses. This is controlled for both low and high normalized reservoir length cases (L/H = 1 and 3). Moreover, it can be claimed that transient analysis leads practically to exact results (in numerical sense) when one is employing high order H-W truncation element. In other words, the results are not sensitive to reservoir normalized length under these circumstances. Originality/value: Dynamic analysis of concrete gravity dam–water–foundation rock systems is formulated by a new method. The salient aspect of the technique is that it utilizes H-W high-order condition at the truncation boundary. The method is discussed for all types of excitation and reservoir bottom conditions. [ABSTRACT FROM AUTHOR]

Summary: Distributed multitask learning over adaptive networks with non‐ideal links is studied in this paper. The performance of an adaptive multitask network with wireless communication links suffering from flat fading and additive white Gaussian noise is derived through simulation and theoretical analysis. The effect of the wireless link on the learning performance of a multitask network is analyzed. It is shown that this destroying effect is reduced by using local equalizers at each agent along with the intelligent cooperation policy based on the correntropy criterion. Stability condition, steady‐state and transient performances are studied theoretically. Finally, the theoretical results are validated by numerical simulations and computer experiments. [ABSTRACT FROM AUTHOR]

The 2-layer medium has a semitransparent diffuse interface and four black surfaces. The fully implicit finite difference method is used to discretize the 2-D transient differential heat transfer equation, in which a radiative source term is considered. The radiative source term is expressed by radiative transfer coefficients, which are solved by establishing functions to trace the reflection and transmission of radiative energy. By using the Patankar linearization method, additional source term method, and alternating direction implicit method, temperature distribution within the 2-layer medium is solved. The increase in the refractive indexes of the 2-layer medium makes the temperature distribution of the composite more uniform and the time to reach a steady state to be reduced. Compared with pure radiation, the participation of conduction makes the heat transfer ability of the 2-layer medium to be enhanced and the temperature distribution discontinuity at the interface disappears. [ABSTRACT FROM AUTHOR]

The transient anti‐plane problem of a functionally graded magneto‐electro‐elastic (FGMEE) rectangular plane weakened by several embedded and edge cracks under various boundary conditions is solved. First, the solutions to the dynamic magneto‐electro‐elastic dislocation in the finite rectangular domain are derived by employing Laplace and finite Fourier cosine transforms. The solutions can be utilized to construct the singular integral equations in Laplace transform domain for FGMEE rectangular plane with multiple embedded and edge cracks. The integral equations arising from dislocation solutions have Cauchy‐type singularities with unknown dislocation density functions. These unknown functions may be obtained by reducing the integral equations into a system of linear algebraic equations, hereby, the dynamic stress intensity factors (DSIFs) for several arbitrarily embedded and edge cracks are obtained. The overshoots of dynamic stress intensity factors are shown to be intensely affected by the rectangular plane dimensions, length and position of the cracks, loading parameter, and negative or positive gradient index. Highlights: The dynamic magneto‐electro‐elastic dislocation is solved in the rectangular plane.A cracked rectangular functionally graded magneto‐electro‐elastic plane is investigated.The analysis can be applied to any number of embedded and edge cracks.The effects of boundary conditions and geometry of the plane on DSIFs are studied. [ABSTRACT FROM AUTHOR]

Based on the large eddy simulation method, this study performed the threedimensional transient numerical analysis of the near-wall flow field of the spiral flow in a circular pipe and applied the sub-grid model of the kinetic energy transport. The low-speed bands, streamwise vortices and hairpin vortices of the spiral flow in the near-wall region of the circular pipe are determined using the Q criterion. The ejection and sweeping of coherent structures are identified using the velocity vector of the near-wall region; moreover, the two methods of creating the hairpin vortices are established by the image time series. The results demonstrate that the development directions of the near-wall bands, streamwise vortices and hairpin vortices of the spiral flow in the circular pipe develop along the path of the spiral line. The average spanwise period of the low-speed bands in the near-wall region is approximately 120 wall units, the length is more than 900 wall units and the height is not more than 40 wall units. The separation distance of the streamwise vortices is about 119 wall units. It has a certain angle with the wall (approximately 22°). The average burst period of a hairpin vortices is less than 0.015 s. [ABSTRACT FROM AUTHOR]

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In-line valves are devices typically used for isolation or flow regulation in pipe systems, playing a key role in the operational management of transmission mains (TM). However, there is no fast and expeditious procedure available for checking the efficacy of the sealing mechanism, and its ability to prevent leakage, unwanted flow or partial blockages, which is a crucial action for any maintenance operation. Due to the different values of the conveyed discharge, the diameter changes along the TM at a series junctions which therefore makes diameter changes a very common singularity. This paper has two aims. The first one is to evaluate the feasibility of Inverse Transient Analysis (ITA) for checking the sealing of in-line valves. In particular, the primary objective of the numerical model is to identify the distinctive features of the measured pressure signals that correspond to the status of an in-line valve, discerning whether it is fully sealed or partially closed. The second objective is to use Direct Analysis (DA) of the pressure signals to appropriately capture the transient response of the series junctions. To address these issues, safe transients have been generated in a real TM by means of a Portable Pressure Wave Maker (PPWM) device, refined at the Water Engineering Laboratory (WEL) of the University of Perugia, Italy. The results of the field tests and numerical model point out that the positive pressure wave reflected by the in-line valve is smaller than the one expected if it were perfectly sealed. Moreover, the transient response of the series junction has been properly captured by the DA of the pressure signal. Accordingly, the proposed procedures have been demonstrated to be suitable tools for the management of long transmission pipelines. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study is to compare three endodontic files: ProTaper Universal (PTU), ProTaper Next (PTN), and ProTaper Gold (PTG) under bending forces using finite element analysis. Methods: This study utilizes finite element analysis conducted with ANSYS software. 3D models of the three endodontic files were prepared using ANSYS. A non-linear material model was applied, idealizing the stress-strain curve for Nickel-Titanium alloy (NiTi), the material of these endodontic files. Static and transient analyses were performed to identify three different material phases: austenitic phase, transition phase, and martensitic phase. Results: Finite element analysis reveals that the PTU file exhibited a maximum von Mises stress magnitude of 1249.7 MPa, PTN showed a maximum von Mises stress magnitude of 798.16 MPa, whereas the PTG file showed a minimum von Mises stress magnitude of 465.68 MPa. PTN showed more bending compared to the other file models for the same load magnitude. PTN remained in the austenitic phase until a tip displacement of 7.3657 mm, while PTU reached a maximum displacement of 4.5633 mm in the austenitic phase. Conclusion: The study concludes that the PTU file is the most rigid among the three file models. PTU generates higher stress magnitudes compared to the other files; thus, it is more likely to fracture under lesser bending forces. The study also concludes that PTG exhibits higher displacement with the lowest von-Mises stresses, making it the most flexible file among the three models. [ABSTRACT FROM AUTHOR]

The reliability of packaged laser diodes is heavily dependent on the quality of the die attach. Even a small void or delamination may result in a sudden increase in junction temperature, eventually leading to failure of the operation. The contact thermal resistance at the interface between the die attach and the heat sink plays a critical role in thermal management of high-power laser diode packages. This paper focuses on the investigation of interface contact thermal resistance of the die attach using thermal transient analysis. The structure function of the heat flow path in the T3ster thermal resistance testing experiment is utilized. By analyzing the structure function of the transient thermal characteristics, it was determined that interface thermal resistance between the chip and solder was 0.38 K/W, while the resistance between solder and heat sink was 0.36 K/W. The simulation and measurement results showed excellent agreement, indicating that it is possible to accurately predict the interface contact area of the die attach in the F-mount packaged single emitter laser diode. Additionally, the proportion of interface contact thermal resistance in the total package thermal resistance can be used to evaluate the quality of the die attach. [ABSTRACT FROM AUTHOR]

Transient response of the pinch point is crucial to the evaluations of the recuperator efficiency. A reheat and recompression cycle dynamic simulation system for supercritical CO2 is built, and a transient segmented model is developed to explore the dynamic characteristics of the recuperators. The operating conditions including inlet mass flowrate, temperature and pressure of the low temperature recuperator (LTR) change dramatically with the withdraw-mass variation, which causes different response characteristics of the pinch point. The pinch point gradually transfers from the cold end to the hot end of the LTR as the mass flowrate decreases. The higher pinch-point temperature difference leads to lower heat exchanger effectiveness, and the internal pinch point greatly weakens the recuperator performance. A new prediction model is proposed to quickly determine the pinch point location and analyze the operating conditions prone to cause internal pinch point. The range of split ratio in which the internal pinch point exists in the LTR is obtained. The lower-limit of split ratio variation is sensitive to the high- and low-pressures, the isentropic efficiency of the compressor, and the outlet temperature of the precooler, while the upper-limit of split ratio is only related to the pressures of the recuperator. [ABSTRACT FROM AUTHOR]

SCWR (supercritical water cooled reactor) is one of the Generation IV reactors. This review summarizes the results of SCWR design concept development through numerical simulations carried out by the author-led team at the University of Tokyo and Waseda University from 1989 to 2014. They are core design, subchannel analysis, statistical thermal design, fuel rod design, development of fuel integrity criteria, plant system and heat balance, plant dynamics analysis, plant control, startup system, stability analysis, safety principle, safety criteria, safety analysis, transient subchannel analysis and fast reactor SCWR. A brief summary of experimental results on thermal hydraulics, materials and water chemistry follows. Discussion includes SCPR study by Japanese BWR manufacturers, comments on the 2005 INEEL SCWR report, misconceptions about SCWR and commercialization challenges. The SCWR is an innovation in light water reactors based on supercritical coal-fired power plant technology that has been in use worldwide for over half a century. This review covers most of the SCWR design and analysis. For researchers, it is a good subject to understand the design and analysis of light water reactors. [ABSTRACT FROM AUTHOR]

For the tower crane, the luffing trolley and cargoes are equivalent to concentrated force. This study established a moving load model. The transient dynamic analysis method was used to carry out dynamic simulation, analyze and obtain the vibration characteristics of the boom under luffing and lifting, and calculate the fatigue life of the key components of the boom based on the S-N curve. The analysis results showed that the greater the luffing speed, the greater the arm end vibration amplitude. The lifting speed has influence on the amplitude and frequency of vibration. Under the worst working conditions, the minimum service life of the top chord 638 of the most dangerous component was 17.96 years, which can meet the requirements of the safety regulations for tower cranes. At the same time, the damage degree of the dangerous component during luffing was greater than that during lifting. [ABSTRACT FROM AUTHOR]

The article presents an analysis of electromagnetic transient processes in long ultra-high voltage transmission lines, taking into account shield wires. It was shown that EMTP and Matlab/Simulink software are currently widely used in the study of transient processes in power lines. The EMTP software package uses the finite element method when integrating the equation that mathematically models the distributed parameter transmission line. The Matlab/Simulink software uses the d'Alembert method. In both cases, it is not known how the boundary conditions for the partial differential equation that mathematically models the transmission line are determined. The power line is analyzed as a distributed parameter system, described by a second-order partial differential equation. The advantage of the proposed method of calculating the boundary conditions for the abovementioned equation is the use of boundary conditions of the second and third types of Neumann and Poincaré, which allowed us to take into account the mutual influence of shield wires and phase conductors of the line in one power system. On this basis, the methodology for obtaining time domain graphs, spatial distributions, and traveling wave distributions of voltages and currents for phase conductors and line shielding wires is presented. The results of a computer simulation of transient processes when switching on the power line, taking into account controlled phase commutation and under single-phase earth fault conditions, are presented. All calculation results of transient processes presented in the article were obtained exclusively using numerical methods. [ABSTRACT FROM AUTHOR]

This paper examines the use of manifold learning in the context of electric power system transient stability analysis. Since wide-area monitoring systems (WAMSs) introduced a big data paradigm into the power system operation, manifold learning can be seen as a means of condensing these high-dimensional data into an appropriate low-dimensional representation (i.e., embedding) which preserves as much information as possible. In this paper, we consider several embedding methods (principal component analysis (PCA) and its variants, singular value decomposition, isomap and spectral embedding, locally linear embedding (LLE) and its variants, multidimensional scaling (MDS), and others) and apply them to the dataset derived from the IEEE New England 39-bus power system transient simulations. We found that PCA with a radial basis function kernel is well suited to this type of power system data (where features are instances of three-phase phasor values). We also found that the LLE (including its variants) did not produce a good embedding with this particular kind of data. Furthermore, we found that a support vector machine, trained on top of the embedding produced by several different methods was able to detect power system disturbances from WAMS data. [ABSTRACT FROM AUTHOR]

When multiple Virtual Synchronous Generators (VSGs) operate in parallel in an islanded grid, power and frequency oscillations will occur when one VSG goes offline. However, the existing literature does not cover the related analysis and transient suppression schemes for this scenario. To analyze these complex high-order system dynamics, this paper first establishes an intuitive equivalent circuit model for multiple VSGs, and the frequency domain expressions of the multi-machine VSG system during the VSG offline transient simulation are then derived. Based on the multi-VSG model and its transient oscillations analysis, this paper further proposes a configuration scheme for the equivalent circuit parameters. Equivalently, the virtual inertia, damping coefficient and virtual impedance of the VSGs can be configured. With the proposed parameter configuration scheme, the power oscillation during the VSG offline transient can be eliminated, as verified by experiments with a microgrid lab platform using three VSGs. Compared with the existing multi-VSG studies, the proposed scheme is not only the first attempt to study the transient suppression when a VSG goes offline, but also is more intuitive in analysis and less complicated in the controller parameter tuning. [ABSTRACT FROM AUTHOR]

The main purpose of the current study is to design a control system for a sloshing system to suppress the vibration of functionally graded graphene platelet-reinforced composite (FG GPL-RC) on the top surface. A set of piezoelectric sensors and actuators are used for active control of fluid-structure coupling in transient seismic analysis of an inviscid liquid sloshing in a cylindrical tank. First, the top surface FG GPL-RC is optimized to satisfy maximum deformation, face failure, mid shear, and face wrinkling by changing the geometrical parameters and weight fraction distribution through the thickness. The nonlinear governing equations of nanocomposite panels with mechanical properties derived from the Halpin–Tsai model are solved by smoothed particle hydrodynamics (SPH) method. A parameter study counting the boundary condition effects, thickness-to-radius ratio, material distribution of the laminates, and dimensions of the sloshing tank on the FG GPL-RC natural frequencies are surveyed and explained in detail. Then, the frequency analysis of the plate with and without sloshing is performed while the inviscid fluid motion is modeled by SPH. The proposed method is validated with available data in the literature. Finally, the active control of the coupled system in response to the external disturbances is completed by a tuned proportional–integral–derivative (PID) controller which used the piezoelectric sheets on the top surface plate. The performance of the proposed control system is illustrated by a comparison of the controlled and uncontrolled transient responses of the coupled hydro-elastic system to the El-Centro seismic load. [ABSTRACT FROM AUTHOR]

A closed-loop integrated model including micro-vibration disturbance, dynamic characteristics of satellite, optical system of star sensor and attitude control algorithm is established. The control torque error caused by additional disturbance torque and the star sensor imaging error caused by structural resonance is fully integrated analyzed, which are firstly presented into the attitude control system (ACS). Steady-state and transient response analyses are completed to evaluate the impact of such two errors on performances of (ACS). Steady-state response results show that the effect of control torque error appears in lower frequency band with a peak of 6.784E-8″ at 53 Hz, while influence of star sensor imaging error on attitude determination mainly concentrates in high frequency band with maximum response of 0.4101″ at 315 Hz. Transient response results show that the two errors will not significantly affect control indicators such as rise time, overshoot and peak time. The results indicate that the influence of star sensor imaging error is non-negligible for satellite ACS which required milli-arc-second attitude control accuracy. According to the analytical results, traditional analysis only on payload optical axis cannot reveal the whole impact of micro vibration on LOS error, the two errors of micro-vibration introduced to ACS in this work must be considered for the development of spacecraft with 0.1″ pointing accuracy. • A closed-loop integrated model and attitude control algorithm is established. • ACS offset caused by control torque error and star sensor imaging error induced by micro vibration are presented. • The two errors significantly affect control indicators under steady-state response condition. • Control torque error appears in lower frequency band with small magnitude. • Star sensor imaging error mainly concentrates in high frequency band with considerable magnitude. [ABSTRACT FROM AUTHOR]

The propagations of acoustic waves in bubbly liquids have been extensively investigated through experimental and theoretical methods, a computational fluid dynamics (CFD) method was introduced to investigate the acoustic attenuation through bubbles in this study. Numerical 'measurements' of attenuation coefficient (α) and phase velocity (V) were conducted using a homogeneous cavitation model, which were modeled from experimental schemes and compared with the theoretical results. At extremely small bubble volume fraction (β around 10-11), new formulas of the theoretical α (αtheo) were proposed respectively for linear and transient oscillations, and a new formula of the numerical α (αnum) was proposed for transient oscillations. Results showed that αnum matched precisely with αtheo for linear, nonlinear and transient oscillations. At medium β (around 10-4), the relative difference of αnum between the VOF and present methods was less than 1.6%, while it reached 15.4% after replacing the bounded Keller-Miksis equation (KME) in the present method with the KME. However, the traditional theoretical α and V matched precisely with the predictions by the present method with the KME. Thus new theoretical α and V were proposed based on the bounded KME, and the relative differences between αtheo and αnum were less than 1%. It can be concluded that the bounded KME should be used in both numerical and theoretical predictions. [ABSTRACT FROM AUTHOR]

Transients in hydraulic systems are normally simulated by one-dimensional (1D) method of characteristics (MOC). When local three-dimensional (3D) flow patterns have crucial impacts on the hydraulic system characteristics, 3D computational fluid dynamics (CFD) simulation should be incorporated. Since simulating an entire long system by the 3D CFD method is unrealistic, we have proposed several 1D-3D coupled simulation methods. However, the coupled methods are difficult to apply and popularise because most CFD codes are inaccessible and implementation details are unclear. Consequently, we utilised the open source toolbox OpenFOAM to develop a 1D-3D coupled simulation method and proved its feasibility by applying it to analysing practical problems. This paper describes the implementations of water compressibility, 1D-3D coupling, gas-liquid flow simulation, and dynamic mesh; shows their verifications of accuracy by benchmark cases; demonstrates the simulations of the closing and opening processes of a 194 km long water conveyance system. The gas-liquid flow patterns in the gate chamber and the maximum/minimum water head envelopes along the tunnels, which support the design optimisation of the project, are presented. It is shown that the method is computationally efficient and accurate, and can be applied to hydraulic transient analyses for water conveyance systems, pumped-storage power stations, etc. [ABSTRACT FROM AUTHOR]

This study investigates the time dependent behaviour of the single server queue with differentiated working vacations. The model also takes into account the possibility of a disaster happening during busy periods and working vacations, with the repair procedure starting right away. The time-dependent probabilities of system size are described in terms of modified Bessel functions in the paper using explicit equations that were generated using generating functions. Numeric instances have been added to support the theoretical findings even more. [ABSTRACT FROM AUTHOR]

Nowadays, integration of large-scale wind farms (WFs) into power systems is experiencing rapid growth. As this rapid integration can affect transient stability significantly, employing doubly fed induction generator (DFIG)-based wind turbines, which have shown better behavior regarding system stability, has attracted much attention. This research contributes to the literature by investigating the transient stability of the power system with increasing penetration of DFIG-based WFs. In the proposed framework, the current-balance form is utilized for the network equations, and in this way, transient stability is performed using time-domain simulation. According to the simulation results, when the rate of wind power generation exceeds 0.7 per-unit, the increasing trend of the critical clearing time (CCT) is reversed and the CCT decreases greatly with the increased wind power penetration. In addition, the reactive power compensation by DFIG, the gearbox ratio, the power system strength, and DFIG parameters are comprehensively investigated as effective parameters on transient stability. Since the rated rotor speed of DFIG significantly impacts the electrical torque and machine currents, the reduction of the rated rotor speed due to the change of the gearbox ratio has been investigated as one of the effective factors to improve the transient stability. The simulation results demonstrate the effectiveness of the proposed approach in improving power system transient stability. [ABSTRACT FROM AUTHOR]

Molten Salt Reactors (MSRs) have recently gained resurged research and development interest in the advanced reactor community. Several computational tools are being developed to capture the strong neutronics/thermal-hydraulics coupling effect in this special reactor configuration. This paper presents a consistent one-dimensional (1D) multigroup neutron diffusion model for MSR analysis, with the primary aim for fast and accurate calculations for long transients, as well as sensitivity and uncertainty analysis of the reactor. A fictitious radial leakage cross section is introduced in the model to properly account for the radial leakage effects of the reactor. The leakage cross section and other consistent neutronics parameters are generated with the Monte Carlo code Serpent using high-fidelity three-dimensional (3D) models. The accuracy of the 1D consistent model is verified by the reference solution from the Monte Carlo model on the Molten Salt Reactor Experiment (MSRE) configuration. The 1D consistent model successfully reproduced the integrated flux from the 3D model and the reactor multiplication factor keff with the error in the range of 95 to 397 pcm (per cent mille), depending on discretized energy group structures. The developed model is also extended to estimate the reactivity loss due to fuel circulation in MSRE. The estimate of reactivity loss in dynamics analysis is in great agreement with the experimental data. This model functions as the first step in the development of a 1D fully neutronics/thermal-hydraulics coupled model for short- and long-term MSRE transient analysis. [ABSTRACT FROM AUTHOR]

Maintaining a stable voltage level at the DC bus is crucial to safeguard equipment, ensure a consistent power supply, and enhance system efficiency. A combination of battery storage and photovoltaic (PV) systems is often employed to maintain an equilibrium between energy supply and demand and keep the DC bus voltage within optimal levels. Nonetheless, frequent and rapid charging and discharging of battery storage in dynamic conditions can negatively impact its lifespan. To address this issue, this study utilizes the application of a frequency‐based current controller in battery storage that facilitates smooth charging and discharging operations in transient conditions. The study evaluates the performance of a grid‐tied PV‐based nanogrid (GT‐PVN) system with three distinct configurations: (a) PV system without storage, (b) PV system with battery storage, and (c) PV system with hybrid energy storage system (HESS) under varying dynamic load and irradiance conditions. The results show that the transient performance on DC bus voltage with battery integration is efficiently improved by 0.3%‐0.5% under dynamic irradiance conditions and 0.5%‐1.17% under dynamic load conditions. Further, with HESS installation, the DC bus voltage transients are improved by 0.85%‐1.25% under dynamic irradiance conditions and 0.5%‐1.5% under dynamic load conditions. Moreover, energy storage technology implementation has the potential to decrease energy procurement from the grid by up to 80%. These findings highlight the potential of energy storage technology in mitigating the intermittency and dynamic operational challenges faced by PV systems. [ABSTRACT FROM AUTHOR]

Feedwater leakages due to excessive loads and cracking caused by corrosion or fatigue failure can affect the reliability of the production facilities. In the present work, a numerical study of a small leakage accident type SB-LOCA on the feed water pipeline was investigated using Computational Fluid Dynamics (CFD) and Relap5 computer codes. The aim is to understand the behavior of the incompressible water flow and its effect on the relevant parameters at the leakage location vicinity, including the mass flow rate, velocity, pressure, and temperature. For this, a mathematical model was developed and validated to evaluate the release of water through the pipe, which is mainly based on the variables that may affect the leakage. The results of CFD show that the leakage has important effects on the distribution of main parameters of the water flow through the pipe, which has an identical outcome from the Relap5 code simulation. The change of fluid velocity only has a little impact on the flow behavior at the leakage region. [ABSTRACT FROM AUTHOR]

Homotopy perturbation method (HPM) is applied in this paper for the transient study of some queueing/inventory/healthcare models. Semi-analytic approximate transient probabilities are obtained as power series in the time variable. The numerical implementation of the method using a programming language like MATLAB, is easy. However, the number of terms that is required in the above power series, to get an accurate approximation, grows with time. This obstacle is overcame by adopting a step-by-step HPM method. Implementation of the method is discussed in the case of the classic M/M/1 queue, the (s, S) inventory model with random replenishment time but without backlogs, the (s, S) inventory model with positive service and replenishment times, allowing infinite backlogs, and the Markov chain model for the patient handoff process in emergency departments. Numerical experimentation has been carried out to evaluate the efficiency of the method and to understand the challenges involved in its implementation. [ABSTRACT FROM AUTHOR]

In this paper, a novel hybrid technique is proposed for transient stability analysis on grid connected Wind-Diesel-PV hybrid system. The proposed hybrid methodology is combination of the dwarf mongoose optimization algorithm (DMO) and the recalling enhanced recurrent neural network (RERNN) named DMO-RERNN. The main purpose of this work is to consider various elements on hybrid system for the analysis of transient stability according to different conditions. The voltage profile of hybrid system is enhanced using the proposed unified power flow controller (UPFC), which also has higher performance improving transient performance compared to the conventional ANN, PI and fuzzy-sliding mode controller. Considering the proposed technique, DMO is used to find the optimal global solution for the fault predicted by the RERNN approach. The proposed system is executed on MATLAB work platform; its performance with existing systems is analyzed. The result proves that the proposed hybrid technique based UPFC controller provides better results compared with other existing technique. The efficiency of the PI is 82.136, ANN is 77, Fuzzy Sliding Mode is 65.097% and proposed technique is 97.99038%. [ABSTRACT FROM AUTHOR]

Microgrids, with integrated PV systems and nonlinear loads, have grown significantly in popularity in recent years, making the evaluation of their transient behaviors in grid-connected and islanded operations paramount. This study examines a microgrid's low-voltage ride-through (LVRT) and high-voltage ride-through (HVRT) capabilities in these operational scenarios. The microgrid's behavior was analyzed using both electromagnetic transient (EMT) and RMS simulation methods. Two operational modes, grid-connected and islanded, were considered. A three-phase diesel generator acted as a reference machine in islanded mode. Findings highlighted distinct behaviors in the two operational modes. The EMT simulation revealed in-depth characteristics of electrical parameters, showing high-frequency oscillations more precisely than the RMS simulation. Additionally, the transient recovery times were longer in islanded mode compared to grid-connected mode. The EMT simulation offers a more detailed portrayal of transient behaviors than the RMS simulation, especially in capturing high-frequency disturbances. However, its completion time becomes significantly extended with longer simulation durations. Microgrids showcase distinct transient behaviors in grid-connected versus islanded modes, especially in LVRT and HVRT scenarios. These findings are critical for the design and operation of modern microgrids. [ABSTRACT FROM AUTHOR]

This paper presents a simplified method for launch vehicle coupled loads analysis (CLA) with spacecraft which is normally conducted in the process of the spacecraft development. The method allows spacecraft developers to calculate coupled vibration response of their own without performing transient analysis for the coupled whole system model. A new method, which allows us to obtain coupled vibration response by convolving non-loaded acceleration time history at the spacecraft boundary with corresponding impulse response of combined apparent mass matrices in frequency domain, has been proposed. The proposed method functions well in any CLA cases including lift-off forced events where loads accompany quasi-static component in nature. We propose a novel approach to escape the error caused in the process of convolution for the quasi-static event by making use of the method to convolve only dynamic acceleration response extracted from the original acceleration by inertia relief technique. Finally, we demonstrate the validity of the proposed method through the analysis using practical launch vehicle and spacecraft models.

Abstract This paper introduces a new approach for analyzing the dynamics of DC–DC converters. Currently, the primary widely accepted method for examining dynamic processes is the Small Signal Analysis technique. However, when applied to modern complex converters, this method poses additional challenges in formulating and solving systems of differential equations. The method proposed in this paper is based on its application to the analysis of dynamic modes of energy functions—Lagrangians. These functions make it possible to define simple criteria to describe the course of dynamic processes, and in the end define an equivalent (approximating) conventional converter identical to the original one with respect to the course of dynamics. If the magnetic and electrical energies in the Lagrangians of both the converters are equal, the outcome is practically identical transient processes. These findings were confirmed by both theoretical analysis and experimentally modelling the dynamics of the initial converter and an equivalent to it in the Matlab–Simscape program. An additional possibility of using the transfer functions of a conventional boost converter for the theoretical analysis of the converters of much greater orders is also discussed. The authors’ experiments confirm the correctness of their theoretical conclusions.

Scoliosis is a medical condition marked by an abnormal lateral curvature of the spine, typically forming a sideways “S” or “C” shape. Mechanically, it manifests as a three-dimensional deformation of the spine, potentially leading to diverse clinical issues such as pain, diminished lung capacity, and postural abnormalities. This research specifically concentrates on the Adolescent Idiopathic Scoliosis (AIS) population, as existing literature indicates a tendency for this type of scoliosis to deteriorate over time. The principal aim of this investigation is to pinpoint the biomechanical factors contributing to the progression of scoliosis by employing Finite Element Analysis (FEA) on computed tomography (CT) data collected from adolescent patients. By accurately modeling the spinal curvature and related deformities, the stresses and strains experienced by vertebral and intervertebral structures under diverse loading conditions can be simulated and quantified. The transient simulation incorporated damping and inertial terms, along with the static stiffness matrix, to enhance comprehension of the response. The findings of this study indicate a significant reduction in the Cobb angle, halving from its initial value, decreasing from 35° to 17°. In degenerative scoliosis, failure was predicted at 109 cycles, with the Polypropylene brace deforming by 10.34 mm, while the Nitinol brace exhibited significantly less deformation at 7.734 mm. This analysis contributes to a better understanding of the biomechanical mechanisms involved in scoliosis development and can assist in the formulation of more effective treatment strategies. The FEA simulation emerges as a valuable supplementary tool for exploring various hypothetical scenarios by applying diverse loads at different locations to enhance comprehension of the effectiveness of proposed interventions.