Nonlinear Parameters Research Articles

Linear and nonlinear ultrasound parameters attributed to anisotropy in granite

The anisotropic nature of granite, a key factor affecting its mechanical properties, is inherently governed by its mineral alignment and the presence of orthogonal cleavage planes: rift, grain, and hardway. This study examines how these cleavage planes influence anisotropy, particularly in the context of microcracking formation and acoustic properties. A new measurement procedure for the acoustic nonlinearity parameter (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\beta\\:$$\\end{document}) is developed to address the well-known limitations of conventional linear ultrasound methods, including wave velocity and attenuation coefficient, in detecting microstructural changes induced by existing cleavage planes. Unlike other parameters, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\beta\\:$$\\end{document} exhibits remarkable changes depending on the plane type, highlighting its high sensitivity to the mineral distribution in each cleavage plane and to the microcracks. A correlation between the linear and nonlinear parameters provides further evidence of the superiority of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\beta\\:$$\\end{document} in detecting inherent microscale defects that develop in each plane and affect the anisotropic characteristics of granite. The findings of this study confirm that nonlinear ultrasound is capable of elucidating the mechanisms underlying the origin of anisotropy in granite due to microcracks, with broader implications for understanding unidentified chemical and mechanical phenomena in geological materials.

Design and matching control strategy of electro-hydraulic load-sensitive hydraulic power unit for legged robots

A hydraulic power unit is the core energy source of hydraulic legged robots, ensuring the robot's maneuverability and carrying capacity in complex terrains. However, its pressure and flow output are usually set to a fixed level under all working conditions, which leads to mismatched pressure and flow requirements of hydraulic drive units. This mismatch reduces the stability and control accuracy of the hydraulic drive units and results in significant energy waste. To address these issues, this paper proposes an electro-hydraulic load-sensitive hydraulic power unit and a matching control strategy to better align outputs with requirements, thereby enhancing energy efficiency. Firstly, with the variable speed servo motor driving axial piston pump as the core, the closed system working principle of an electro-hydraulic load-sensitive hydraulic power unit is proposed, and the mathematical model of key components exhibiting strong nonlinearity and time-varying parameters is derived. After that, a matching control strategy based on flow feedforward and pressure difference compensation feedback is proposed. Finally, simulations and experiments are conducted to verify the feasibility of the unit and its matching control strategy. This paper provides a new solution for the design and control of hydraulic power units, laying the groundwork for achieving high-performance hydraulic systems.

Synthesis, characterization, and study of linear and non-linear optical properties of some newly thieno[2,3-b]thiophene analogs

Abstract Newly 3,4-Diaminothieno[2,3-b]thiophene derivatives were synthesized by attaching with different aromatic have rich electron. The resulted compounds have been investigated by FT-IR, NMR, elemental analysis, and optical absorption spectra. Comparison between these resulted compounds revealed oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene has the highest absorption peak intensity at ~ 696nm, thin films have been prepared by thermal evaporation technique and characterized by UV-Visible-NIR spectroscopy as well as the allied absorption, dielectric and dispersion parameters have been investigated and compared with other reported results. Obtained results indicated diethyl 3,4-bis(((E)-2-oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene-2,5-dicarboxylate and 3,4-bis(((E)-2-oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene-2,5-dicarbonitrile have manifested small band energy gap energy 1.95, 1.66 eV; respectively as a result of increasing conjugation and high absorption coefficient, make these compounds ideal for use in solar cell. The high nonlinear parameters such as refractive index and third-order nonlinear susceptibility of these organic compound thin films are significantly asymptotic compared with chalcogenide and oxide materials, making them suitable for nonlinear optical devices.

Nonlinear system optimization of cutting tools with dynamic vibration absorbers in deep hole boring: A stability analysis

Deep hole boring vibrations pose challenges due to low stiffness of long cantilever bars, impacting accuracy and standards. Nonlinear modeling provides deeper insights into chatter. Integrating dynamic vibration absorbers enhances boring bar stability. In this study, a nonlinear model is developed to investigate the vibration stability of the boring process, with the model's dimensionless parameters analyzed and solved using the Runge-Kutta method. The impact of nonlinear parameters associated with the damping and stiffness of the absorbers on the vibration characteristics of boring bars is thoroughly examined. The findings reveal that there exists an optimal range for the damping and stiffness of the absorbers, where vibration amplitude is significantly reduced, especially under conditions of high excitation force. Moreover, it is demonstrated that the introduction of cubic stiffness elements can further diminish vibration amplitude. These results offer valuable guidance for the design and optimization of DVA in deep hole boring, contributing to improved machining performance and accuracy.

Stability of Cauchy horizon in Einstein–Power–Maxwell–de Sitter black holes

We investigated the Strong Cosmic Censorship (SCC) conjecture in Einstein–Power–Maxwell–de Sitter (EPMdS) black holes by analyzing the quasinormal modes (QNMs) of a massless neutral scalar field perturbation. Using the pseudospectral method, we calculated the QNM frequencies across various cosmological constants and nonlinear electromagnetic parameters. Our results show that for black holes far from extremality, the lowest QNM frequency -Im(ω)/κ-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\ ext {Im} (\\omega )/\\kappa _-$$\\end{document} remains below 1/2. However, as the black holes approach extremality, the lowest mode’s -Im(ω)/κ-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\ ext {Im} (\\omega )/\\kappa _-$$\\end{document} consistently exceeds 1/2, leading to a violation of SCC. Moreover, with a fixed cosmological constant, as the nonlinearity parameter α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} increases, the interval of SCC violation under the charge extremality ratio narrows. Considering that k=1/2+1/α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k = 1/2 + 1/\\alpha $$\\end{document} is inversely proportional to α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}, our results indicate that increasing the order k of the non-linear electromagnetic field can effectively mitigate SCC violations.

Comparative of light propagation in Born-Infeld, Euler-Heisenberg and ModMax nonlinear electrodynamics

We compare light propagation through an intense electromagnetic background as described by three different nonlinear electrodynamics: Born-Infeld (BI), Euler-Heisenberg (EH), and Modified Maxwell (MM). We use the concept of effective metric to determine the phase velocities of a propagating wave from the BI and EH nonlinear electrodynamics and use them to set constraints on the MM nonlinear parameter. In a second part of the paper, we consider the black hole solutions of the nonlinear electrodynamics coupled with General Relativity and determine the shadows cast by the static black holes. Confronting the observations of the shadows of M87* and Sagittarius A* with our theoretical results allows us to set restrictions on the nonlinear parameters.

Stochastic Nonlinear Model Updating in Structural Dynamics Using a Novel Likelihood Function within the Bayesian-MCMC Framework

The study presents a novel approach for stochastic nonlinear model updating in structural dynamics, employing a Bayesian framework integrated with Markov Chain Monte Carlo (MCMC) sampling for parameter estimation by using an approximated likelihood function. The proposed methodology is applied to both numerical and experimental cases. The paper commences by introducing Bayesian inference and its constituents: the likelihood function, prior distribution, and posterior distribution. The resonant decay method is employed to extract backbone curves, which capture the non-linear behaviour of the system. A mathematical model based on a single degree of freedom (SDOF) system is formulated, and backbone curves are obtained from time response data. Subsequently, MCMC sampling is employed to estimate the parameters using both numerical and experimental data. The obtained results demonstrate the convergence of the Markov chain, present parameter trace plots, and provide estimates of posterior distributions of updated parameters along with their uncertainties. Experimental validation is performed on a cantilever beam system equipped with permanent magnets and electromagnets. The proposed methodology demonstrates promising results in estimating parameters of stochastic non-linear dynamical systems. Through the use of the proposed likelihood functions using backbone curves, the probability distributions of both linear and non-linear parameters are simultaneously identified. Based on this view, the necessity to segregate stochastic linear and non-linear model updating is eliminated.

Measurement Technique for the Absolute Acoustic Nonlinearity Parameter Employing Only a Narrowband Pulser

In the nonlinear ultrasonic technique, the measurement of the absolute acoustic nonlinearity parameter is employed to obtain quantitative material nonlinearity. In the piezoelectric method, this measurement involves two processes: calibration and harmonic measurements. In the calibration process, a transfer function is obtained, and distortion of the propagating wave is measured in the harmonic measurement. In the conventional method for this measurement, a narrowband pulser is typically used for the harmonic measurement, while a broadband pulser is used for the calibration measurement. In this study, we propose a technique that utilizes a narrowband pulser for both harmonic and calibration measurements. First, we introduced the proposed method to measure the transfer function in the calibration measurement employing the narrowband pulser. Then, we compared the results of the transfer functions and the absolute acoustic nonlinearity parameters obtained using both a narrowband and broadband pulser in the calibration. Based on the experimental results, we found that the results obtained using both the proposed and conventional methods are highly similar, confirming the validity of the proposed measurement technique. In conclusion, even though we exclusively employ the narrowband pulser, we can accurately measure the absolute nonlinearity parameter, leading to a reduction in the required measurement equipment.

Shrinking shrimp-shaped domains and multistability in the dissipative asymmetric kicked rotor map.

An interesting feature in dissipative nonlinear systems is the emergence of characteristic domains in parameter space that exhibit periodic temporal evolution, known as shrimp-shaped domains. We investigate the parameter space of the dissipative asymmetric kicked rotor map and show that, in the regime of strong dissipation, the shrimp-shaped domains repeat themselves as the nonlinearity parameter increases while maintaining the same period. We analyze the dependence of the length of each periodic domain with the nonlinearity parameter, revealing that it follows a power law with the same exponent regardless of the dissipation parameter. Additionally, we find that the distance between adjacent shrimp-shaped domains is scaling invariant with respect to the dissipation parameter. Furthermore, we show that for weaker dissipation, a multistable scenario emerges within the periodic domains. We find that as the dissipation gets weaker, the ratio of multistable parameters for each periodic domain increases, and the area of the periodic basin decreases as the nonlinearity parameter increases.

Relationship between rheological parameters and structure formation in high moisture extrusion of plant protein biopolymers

High moisture extrusion (HME) is widely employed to texturize plant-derived protein ingredients, but its development is still much based on trial and error. In this project, it was hypothesized that the rheological properties of plant-based mixtures analyzed when in the molten state and during their cooling can aid in understanding their structure formation. To test this hypothesis, biopolymer formulations containing pea protein isolate (PPI) were examined at different moisture and starch contents, and their rheological properties were analyzed using a closed cavity rheometer (CCR) at temperatures relevant to those applied during HME processing. The results obtained with the CCR were then contrasted with the mechanical properties of HME obtained using a lab scale extruder, measured using oscillatory rheology, large deformation, and dynamic mechanical analysis. Low moisture (55 %) HMEs were stiff and brittle, while high moisture (65 %) HMEs formed more flexible and anisotropic structures. Addition of starch created softer structures. The viscoelastic properties of the biopolymer mixes measured with the CCR were correlated with the mechanical parameters of the final extrudates. Strong correlations were found between small deformation rheological parameters measured in the CCR and the hardness values, while non-linear viscoelastic parameters were correlated with anisotropy indexes. Results demonstrated that the material properties measured at the early cooling stages strongly influence the structural heterogeneity in HMEs. This study highlights the potential to use the viscoelastic properties of the biopolymer mix measured with the CCR to predict their structural features when processed by extrusion.

Thermal analysis of nonlinear mixed convection effects within wavy enclosure

The analysis in this study focusses on the transfer of heat within a wavy cavity in the presence of nonlinear mixed convection and MHD. We conduct the investigation under conditions where the upper wall of the cavity remains cold, the lower wall receives heat, and the left and right wavy walls remain adiabatic. Using the PDE solver in COMSOL, the non-dimensional system is simplified, employing the finite element method. The study aims to explore the impact of parameters such as nanoparticle concentration, Hartmann number, Reynolds number, Richardson number, and nonlinear mixed convection parameters on fluid flow and heat transfer. An artificial neural network has been employed to examine the behaviour of the Nusselt number within a cavity. The isotherms reveal that the temperature is higher near the lower wall for all parameters due to the heated source. Analysis of the streamline plots indicates that heat increases as it moves towards the upper wall, influenced by the Hartman number and volume fraction parameter. The use of ANN in the study forecasts the accuracy, smoothness, and convergence of the data through plots of mean squared error (MSE), error histogram, regression analysis, and transition state plot. The authors believe that using artificial neural networks to explore the heat transfer rate under the assumptions of MHD and nonlinear mixed convection is a novel approach that has not been previously investigated. Additionally, researchers can utilise ANN concepts to predict intricate cavity formations through multiphysics. This approach will require less human effort and computing time to analyse the heat response of any dataset.

Extending MGCAMB tests of gravity to nonlinear scales

Modified Growth with CAMB (MGCAMB) is a patch for the Einstein-Boltzmann solver CAMB for cosmological tests of gravity. Until now, MGCAMB was limited to scales well-described by linear perturbation theory. In this work, we extend the framework with a phenomenological model that can capture nonlinear corrections in a broad range of modified gravity theories. The extension employs the publicly available halo model reaction code ReACT, developed for modeling the nonlinear corrections to cosmological observables in extensions of the ΛCDM model. The nonlinear extension makes it possible to use a wider range of data from large scale structure surveys, without applying a linear scale cut. We demonstrate that, with the 3×2pt Dark Energy Survey data, we achieve a stronger constraint on the linear phenomenological functions μ and Σ, after marginalzing over the additional nonlinear parameter p 1, compared to the case without the nonlinear extension and using a linear cut. The new version of MGCAMB is now forked with CAMB on GitHub allowing for compatibility with future upgrades.

Characteristics of Human Postactivation Effect of Skeletal Muscles Using Spectral and Non-Linear Parameters of the Surface Electromyogram

Postactivation effect (PAE, postactivation phenomenon) is a specific type of involuntary muscle tone (tonic automatism) which is generated in the “tonogenic” structures of the brain, presumably without the “sensory copy” and “motor command” mechanisms. In this regard, the electromyogram (EMG) signal of PAE may have a simpler temporal signal structure compared to PAE-inducing voluntary activity. The purpose of this work is to characterize the temporal structure and complexity of surface EMG (sEMG) of the human deltoid and biceps brachii muscles using fractal (D) and correlation dimensions (Dc). It was found that in deltoid muscles the value of D was 1.78–1.81 both during PAE and voluntary effort (p 0.05). Dc (approximately 4.0–4.2) also did not differ between PAE and voluntary effort, although the average frequency of the sEMG spectrum during PAE was 15–16 Hz (p 0.05) higher compared to voluntary effort. In biceps brachii muscles, the D value was 1.8 during PAE and 1.62 during voluntary effort (p 0.05). Dc values did not differ between PAE and voluntary contraction (4–4.8). Thus, despite the supposed difference in the central organization of PAE and voluntary effort, the temporal structure of their sEMG did not differ, indicating that isometric voluntary effort and involuntary tone in the form of PAE share a common principle of sEMG signal generation. At the same time, the differences in the frequency of the sEMG spectrum indicate that the organization of sEMG signal during PAE is specific on the level of the motoneuron pool.

Impact of non-linear radiation on magneto - Casson fluid suspended hybrid nanomaterials in sodium alginate: Smarter textiles

BackgroundThe combination of sodium alginate (SA) and nanoparticles in Casson nanofluids can have several advantages in textile applications such as to enhance the dye absorption and finishing properties and uniform and controlled coatings on complex shapes of the fabric and garments with intricate designs or three-dimensional textile structures etc. These fascinating properties attracted us to work on this article, a Casson hybrid nanoflow under the influence of magnetic effects past a curved stretching surface. Key terms & problem definitionThis study examines the heat transfer characteristics of Casson nanofluid flow over a stretching sheet with nonlinear thermal radiation and convective boundary conditions. A Casson fluid is a non-Newtonian fluid that exhibits a yield stress, meaning it behaves like a solid below a certain shear stress. Nonlinear thermal radiation accounts for the effects of temperature-dependent radiative heat transfer. Convective boundary conditions simulate the heat exchange between the fluid and a surrounding environment. The nanoflow has its base fluid as Sodium Alginate (SA) and a mixture of Silver (Ag) and Titanium oxide (TiO2) is suspended in the fluid. MethodologyThe nanoflow model is cracked numerically employing Runge-Kutta Fehlberg technique along with shooting method. Results of flow affecting parameters on the flow characteristic quantities and engineering quantities are portrayed and presented through graphs and tables. Key findingsHybrid Nanoflow momentum decreases with an increase in the Casson parameter due to the yield stress which quite helps in the controlled and complex shape printing on the garments. The temperature of the nanofluid increases with an increase in nonlinear radiation parameter. In the presence of Ag and TiO2 nanoparticles, the non-linear radiation parameter becomes essential for managing their intricate impact on heat transfer within the fabric. Practical relevanceImproved heat transfer can significantly reduce drying times, leading to increased productivity. More efficient heat transfer can reduce energy consumption. Reduced viscosity can allow for better penetration of fluids into fabrics, leading to more uniform dyeing and finishing. Casson hybrid nanofluids can accelerate the dyeing process and improve colour uniformity. Casson hybrid nanofluids can be used in finishing processes to enhance wrinkle resistance and improve fabric appearance.

Nonlinear vibration analysis of multi-support oil-tank system in aero-engine based on asymptotic methods

This article is primarily focused on the complicated nonlinear vibration behavior of an aero-engine lubricating oil-tank system with multiple nonlinear pedestals. First, the rubber damping ring’s nonlinear factors are introduced into a cubic nonlinear dynamic model of lubricating oil-tank system. The nonlinear system parameters are identified by testing a simplified aero-engine lubricating oil-tank structure. Then, the nonlinear dynamic model is solved via asymptotic approach, and results are confirmed using Runge-Kutta numerical analysis approach. The system’s vibration responses and amplitude-frequency curves are also acquired, and influence of system parameters on nonlinearity is analyzed. Finally, an experimental investigation on the simplified oil-tank is performed. The nonlinear vibration characteristics of the rubber damping ring and its vibration reduction mechanism are verified using vibration transmissibility. The experimental results are consistent with numerical results. This paper’s recommended analysis approach has engineering significance for vibration and noise reduction design of aero-engine components.

Investigation on Effect of Nonlinear Parameters in torque accuracy of Permanent Magnet Synchronous Machines

EVs and PHEVs are mainly driven by inverter control topologies which will be driving permanent magnet synchronous machines. PMSM is widely used for high drive performance. However, due to parameter variations high torque accuracy is not achieved. The performance of the PMSM drives is widely affected which is caused mainly due to environmental factors and aging. This would include component tolerance, input signal tolerance, machine parameters, software algorithms, sensor accuracy and calibration. It is important to understand these factors and make the tuning throughout the lifecycle since it may show performance deviations over the time and may lead to field complaints. As a step-by-step procedure, the factors which affects the torque accuracy are identified as part of the literature review. This is given as input to a cause effect relationship model which could demonstrate the deviation points. Simulation is performed by varying the operating points at different regions in the e-drive system modeled in Matlab/Simulink. Simulation results are used with different operating points to find out the influential parameters contributing to the deviation. The outcomes derived from the simulations are analyzed and dominant factors are determined. It is observed that this behavior will vary according to the changes in speed and torque. Correlation coefficient is derived from the statistical analysis. The future scope will be applying the optimization techniques and verification of improvements.

Automatic calculation of the parasympathetic, sympathetic and Baevsky stress indexes provides a more comprehensive assessment of cardiac autonomic modulation

Abstract Background Cardiac autonomic modulation (CAM) is clinically evaluated by measuring the Heart Rate Variability (HRV) parameters, related to sympathetic and parasympathetic efferences to the heart, with linear (L), nonlinear (NL), and time-varying (TV) mathematical methods. Recently, automatic calculation of the parasympathetic (PNSi), sympathetic (SNSi), and Baevsky’s stress (BSTRi) indexes [1,2], integrating some L and NL parameters, has become available for more synthetic assessment of CAM. This study aimed to evaluate in healthy subjects (HS) the normal range of PNSi, SNSi, and BSTRi and their physiological variations during daily activity (ACT) and Non-REM sleep (NREM), taking also into account aging-related changes. Methods 24-hour (H24) Holter ECG recordings of 87 HS, divided into three (Age1, Age2 and Age3) groups (16-34, 35-52, and 53-84 years old, respectively), were retrospectively analyzed with the Kubios software (version 4.0), which automatically calculates the PNSi, SNSi, and BSTRi [1], and time domain (TD), frequency domain (FD), NL and TV HRV parameters. HRV was calculated from H24 and short-term (2 minutes) intervals, selected during ACT and NREM. All HRV calculations were done after "detrending" with the "smooth priors" function (lambda=500). Statistical analysis was performed with SPSS 21. Results Average values of the three indexes and several independent L and NL parameters are summarized in Table 1. Average BSTRi values of each age group were not different between ACT and NREM, whereas significant (p<0.05) increments between Age3 and Age1 (during ACT) and between Age3 and both Age1 and 2 (during NREM and H24) were found. Average SNSi values were slightly above the normality range [1] during ACT, or normal (during NREM and H24). Average PNSi values were within the suggested normality range [1] with minimal aging-related variations. Significant aging-related decrement of the selected TD and FD parameters was found in all analysed conditions. Among NL parameters, the correlation dimension (D2) values showed significant aging-related decrement (H24 and NREM), while H24 and ACT sample entropy (SampEn) was lower in Age1 and Age2, compared with Age3 (p<0.05). An example (H24 analysis of Age3 data) of significant (p<0.01) correlation among the three indexes and the selected independent linear and non-linear parameters is shown in Figure 1. Conclusions In this study, a significant aging-related increment of BSTRi was found in all investigated conditions. PNSi and SNSi were always within the suggested normality range [1]. In spite of the significant changes of linear parameters consistent with the well-known aging-related decrement of HRV, the higher SampEn (and BSTRi) found in Age3 HS suggests that an "healthy elderly", is characterized by a more complex adaptation of CAM, likely mediated also by the observed moderate (healthy?) increment of physiological stress. However further investigation on a broader population is warranted.Table 1Figure 1

Fatigue Strength Analysis of Rail Fastening Baseplate

Superstructural elements of a railway track experience dynamic loads varying over time. As a consequence, this is accompanied by the initiation and accumulation of fatigue damages. Defects in intermediate rail fastening are quite difficult to identify using flaw detection methods, and some can be destructed. In particular, rail fastening baseplates often fail due to insufficient fatigue strength.Purpose: To investigate the fatigue strength of rail fastening baseplate.Methodology: Development of the mathematical model of deformation based on the finite element method (FEM). Strength analysis of the baseplate using the model of a variable-thickness slab resting on a nonlinear elastic foundation. The latter is modeled by a set of rods with nonlinear deformation and parameters determined by compression tests of the baseplate. A mathematical model developed in COSMOS software for the FE analysis of the stress-strain state of the baseplate at a time-varying load from rolling equipment and assembly forces from attaching the baseplate to the sleeper and rail.Research findings: The cyclic loading parameters are obtained at dangerous points of the baseplate and its durability is analyzed at different loads with respect to unevenness of track settlement and failure of bolt connections of rail fasteners. The influence of these factors on actual loads on the rail fastener is determined. It is found that the service life of the baseplate mainly depends on the dynamic load.

Impact of Balanced Exploration and Exploitation on Highdimensional Feature Selection with Hierarchical Whale Optimisation Algorithm

High-dimensional datasets (HDDs) pose significant challenges in feature selection due to their complex nature. While metaheuristic algorithms like the Whale Optimisation Algorithm (WOA) have shown promise in addressing these challenges, stability issues are least addressed. Through an extensive literature review, it was identified that stability is manifested in the equilibrium of exploration and exploitation. Hence, this study introduced the Hierarchical Whale Optimisation Algorithm (HiWOA), an approach designed to enhance the WOA’s stability and performance in HDD feature selection tasks. The HiWOA incorporates a two-phase strategy comprising a nonlinear control parameter based on the arcsine function and a hierarchical position-update mechanism adapted from the Grey Wolf Optimiser. The proposed HiWOA was evaluated through 23 benchmark optimisation functions and feature selection experiments on 11 medical HDDs. The results indicate that the HiWOA outperformed the WOA and a modified variant (mWOA) in terms of a better fitness value, a more balanced exploration-exploitation ratio, and improved classification accuracy with fewer selected features. These findings demonstrate the HiWOA’s effectiveness in enhancing stability, making it a robust solution for high-dimensional optimisation and feature selection.

The impact of proton ion irradiation on Se70Te20In10 thin films: Linear and non-linear optical properties for photonic applications

The examination of the linear and non-linear optical features was conducted on amorphous ternary Se70Te20 In10 thin films, which were exposed to proton irradiation energy of 3 MeV at varying fluences of 5×1013, 5×1014, 5×1015 and 5×1016 ions/cm2. The bulk sample was produced using the melt quenching method, and subsequently, thin films were obtained through electron beam evaporation. Calculations of linear and non-linear optical parameters were carried out based on transmittance and reflectance data acquired from UV–Vis–NIR spectroscopy spanning 300–2500 nm. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) confirmed an amorphous phase in the films. The optical parameters showed strong dependency on the proton radiation fluence. In addition, the existence of minima or maxima for a number of parameters at a fluence of 5×1014 ions/cm2 showed that this was the optimum fluence. The linear and non-linear properties showed that the sample have potential applications in photonic devices.