Journal of Computational and Nonlinear Dynamics

Nonlinear and Noise-Resilient Signal Processing for Enhanced Performance in Autonomous Systems and Underwater Acoustics

2026-08-23T07:50:41Z

Nonlinear and Noise-Resilient Signal Processing for Enhanced Performance in Autonomous Systems and Underwater Acoustics Radhakrishnan, Abilash; Neelam, Mounika; Railis, Dani Jermisha; R. S., Dinesh; Kanase, Digvijay B. Abstract. The increasing complexity of autonomous systems and underwater acoustics technologies necessitates the development of progressive signal dispensation methods that can handle nonlinear dynamics and mitigate the effects of noise. The problem lies in improving signal dispersion methods for autonomous systems and underwater acoustics to enhance accuracy, robustness, and overall system performance in complex environments. The objectives are to develop advanced nonlinear and noise-resilient signal processing techniques, enhance system performance, improve data accuracy, and ensure robust communication and navigation in autonomous systems and underwater acoustic environments. Adaptive bilateral kernel filtering (ABKF) enhances data preprocessing by effectively reducing noise, smoothing, and preserving edge details in nonlinear signal environments. Nonlinear iterative partial least squares (NIPALS) efficiently model complex relationships in data, improving signal extraction and reducing noise in autonomous systems and underwater acoustics. Reweighted sparse signal decomposition (RSSD) enhances noise resilience by effectively separating signals from noise, improving data quality in submerged audibility and autonomous systems. Hypergraph partitioning algorithm (HGPA) improves signal processing by efficiently partitioning complex data, enhancing performance, and reducing noise in autonomous systems and underwater acoustics. These systems can process real-time data with greater precision. The findings show that energy consumption varies with node count (6–20) across methods ABKF, NIPALS, RSSD, and HGPA. Energy starts near zero at six nodes, peaking around 350 units for ABKF, implemented in python software. Future scope focuses on real-time optimization, dynamic environment adaptability, and enhanced integration for autonomous navigation and underwater communication systems.

Computing Natural Frequencies and Mode Shapes of a Reddy Beam

2026-08-23T07:50:39Z

Computing Natural Frequencies and Mode Shapes of a Reddy Beam Sinha, Alok Abstract. This paper presents an algorithm to find natural frequencies and mode shapes of a uniform Reddy beam. In this method, spatial state equations are developed and the spatial state transition matrix is computed, which is independent of the boundary conditions of the beam. Then, natural frequencies and mode shape equations are easily derived for any boundary conditions in terms of elements of the state transition matrix evaluated at the right end of the beam. As examples, these equations are derived for pinned–pinned and clamped–clamped beams. Numerical difficulties in implementing this method are recognized, and a reduced-order spatial state space model is developed by analyzing the nature of roots of the sixth-order characteristic equation. Numerical results are presented for rectangular beams and compared to those for Timoshenko beams.

A Fractional-Derivative Interpretation of Viscoelastic Rubbers—Part II: Application to Filled and Vulcanized Rubbers Under Large Compression

2026-08-23T07:50:37Z

A Fractional-Derivative Interpretation of Viscoelastic Rubbers—Part II: Application to Filled and Vulcanized Rubbers Under Large Compression Fukunaga, Masataka; Fujikawa, Masaki; Shimizu, Nobuyuki; Ikeda, Kosuke; Inoue, Takumi Abstract. This paper explains the stress behavior of filled and vulcanized rubbers subject to large deformations by using the fractional derivatives proposed in a paper in this series (Fukunaga et al., 2025, “A Fractional Derivative Interpretation of Viscoelastic Rubbers. I. Thermodynamically Consistent Fractional-Derivative Models for Finite Strain,” ASME J. Comput. Nonlinear Dyn., 20(11), p. 111009, Paper I). The proposed rubber model consists of two fractional-derivative terms and one elastic term arranged in parallel. The orders of two fractional derivatives are α≃0.5 and β<α. Of the two fractional-derivative terms, the contribution from the term of order α (the α term) is small for low strain rates. Aside from the α term, the basic parameters are the order, β, the coefficient of the β term, and the shear modulus of the elastic term. Because the number parameters of fractional-derivative model is small, a deviation from the response of the fractional derivative can be directly interpreted as the effects of the ingredients or a change in state during the course of deformation. At large deformations, the influences of filler and vulcanization are represented by one parameter called the effective thickness, which is a measure of the effective volume fraction of the matrix. A method for decomposing these parameters is presented. The fractional-derivative model also suggests differences in the state of rubbers between the loading and unloading phases. The fractional-derivative term weakens or vanishes in the unloading phase. A model with β<0.2 is consistent with the stress data considered in this paper both in the loading and unloading phases.

Nonlinear Finite Element Model for Base-Isolated Tank-Block Systems Implementing Lead Rubber Bearing Isolator Controlling the Nonlinear Dynamic Responses

2026-08-23T07:50:29Z

Nonlinear Finite Element Model for Base-Isolated Tank-Block Systems Implementing Lead Rubber Bearing Isolator Controlling the Nonlinear Dynamic Responses Barik, Jyoti Ranjan; Biswal, Kishore Chandra Abstract. Liquid storage tanks are vital infrastructural applications that seek special attention to maintain their efficient functionality. Sometimes, an inappropriate assessment of excessive hydrodynamic force developed by strong seismic motions can induce severe structural damage. Emphasizing this fact, the present research extensively examines the inherent nonlinear sloshing effects of liquid inside a base-isolated container with a submerged block using a lead rubber bearing under different types of earthquakes categorized based on the frequency content. The study emphasizes the impact of different concentric and eccentric configurations of the block on the overall seismic performance of the structure. A mixed Eulerian–Lagrangian method is used to derive the nonlinear finite element model. The developed model is authenticated with the available results. Nonlinear slosh amplitudes are significantly greater than linear amplitudes, highlighting their importance in determining the appropriate freeboard clearance. The impulsive and total pressure components along the tank wall are significantly reduced, while an increase is observed over the block wall as the block height increases in both types of tanks. It is noticed that such components are drastically reduced due to base isolation. Moreover, the impulsive and total base shear is decreased significantly, regardless of the frequency content of the earthquakes. In contrast, the convective base shear exhibits an opposite phenomenon in some of the selected earthquakes. Overall, the contribution of the impulsive component is significant over the convective one in the ground-supported tank, whereas the base-isolated tank shows the reverse tendency.