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Copyright of Journal of Computational Applied Mechanics is the property of University of Tehran and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we propose the subtrigonometric series solution for the equation of the scaling-law wave motion to describe the special vibrating string associated with the Mandelbrot scaling law. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive examination of fractal diffusion in an isotropic medium. This process has a fascinating temporal memory and an extremely high initial response, which are unquestionably characterized by the Caputo fractional derivative. Its spatio-symmetric property is described by the Riesz fractional derivative. To illustrate the diffusion mechanism, we present an example of a toxic gas leak in a subway station. The numerical results are extremely promising and challenging. They clearly indicate that a MEMS-based gas sensor can track a toxic gas leak immediately due to its extremely fast diffusion at the initial time. This is of great importance for public safety. Furthermore, the diffusion process is primarily contingent upon the density of the air, which we can easily control. The diffusion pattern in an isotropic medium exhibits fractal behavior, which is extremely helpful for designing an emergency system for evacuating people from the center of toxic gas leaks by changing air density or temperature. This paper presents a rigorous mathematical concept for monitoring systems and early warning systems for toxic gas leaks. [ABSTRACT FROM AUTHOR]

Electrospinning is an amazing process that enables the production of primarily nanofiber membranes. Nevertheless, the mechanism underlying the formation of two-dimensional (2D) nonwoven structure remains a fascinating enigma. This paper presents a novel morphology of nanofiber membranes with a cluster structure that bears resemblance to the solar nebula. The mechanism of nanofiber cluster structures in the electrospinning process is elucidated through the geometric potential theory, which begins with a zero-dimensional receptor, progresses to a one-dimensional (1D) receptor, a 2D receptor, and ultimately culminates in a fractal-like lattice receptor. Moreover, a three-dimensional (3D) printing-like novel approach is presented for the manipulation of nanofiber membrane's shape through the use of a lattice-structured receptor. The fabrication process of the cluster structure nanofiber membranes by electrospinning is presented, and their remarkable potential applications are discussed. [ABSTRACT FROM AUTHOR]

Physical systems frequently exhibit nonlinear behavior that remains unresolved in the majority of cases. In this study, we employ the Aboodh transform-based variational iteration method (ATVIM) to resolve the nonlinear model of a tapered beam. In order to solve the governing equation, the periodic motion is sought, and the explicit relationship between frequency and amplitude is revealed. The outcomes of the ATVIM approach are compared with those of other prevalent techniques, and a satisfactory concordance is observed between them. This study also provides an analytical approximation of the tapered beam for a detailed understanding of the effects of factors on the nonlinear frequency, which can be beneficial to researchers and engineers working on the analysis and design of structural projects [ABSTRACT FROM AUTHOR]

How can we explain the thermal phenomenon by a fractal metasurface? This has been puzzling scientists and engineers for at least ten years, and so far no answer has been found. Now, modern mathematics offers a completely new window to physically understand the magical phenomenon that lies far beyond the Fourier law for heat conduction. A fractal-fractional modification of the Fourier law is elucidated, and its extremely high thermal conductivity is mathematically revealed. This article shows that thermal science is the key to nanotechnology. [ABSTRACT FROM AUTHOR]

5G communication technology has been skyrocketing, and has changed everything in our daily lives, and its applications in various fields are also promising. However, the thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming more and more prominent, and thermodynamics offers a solution, and fractal meta-surfaces provides an extremely efficient approach to transfer the generated waste heat, which can be used for thermal energy harvesting, and a fractal thermodynamic model is developed for thermal management. [ABSTRACT FROM AUTHOR]

The Fourier law and its various modifications have been widely used to study various thermal problems with great success, but many thermal phenomena cannot yet be explained, for example, the effect of pore size and distribution on the heat transfer of a porous medium, the extremely high thermal conductivity of metasurfaces, and the moisture transfer through a fabric. This short article shows the current state of thermal science for modern science and technology, and its challenge in the future. [ABSTRACT FROM AUTHOR]

The variational theory is an inextricable part of both continuum mechanics and physics, and plays an important role in mathematics and nonlinear science, however it is difficult to find a variational formulation for a nonlinear system, and it is more difficult for a fractional differential system. This paper is to search for a variational formulation for the Schrödinger-KdV system with M-fractional derivatives. The fractional complex transformation is used to convert the system into a traditional differential system, and the semi-inverse method is further applied to establish a needed variational principle. [ABSTRACT FROM AUTHOR]

An accurate frequency of the Helmholtz–Duffing oscillator is obtained by a sophisticated modification of He's frequency formulation. The pull-down instability existing in the symmetric breaking phenomenon is a newly discovered dynamic motion for oscillators with even nonlinearities. A criterion for predicting the asymmetrical amplitude motion and the pull-down instability is built by measuring the amplitude change. The good matching performance between the analytic results and numerical ones indicates that the criterion offers a starting point for future research into the pull-down phenomenon, and opens a new path for studying more complex nonlinear oscillators with even nonlinearities. [ABSTRACT FROM AUTHOR]

Laplace and Fourier transforms are widely used independently in engineering for linear differential equations including fractional differential equations. Here we introduce a generalized integral transform, which is a generalization of the Fourier transform, Laplace transform, and other transforms, e.g., Sumudu transform, Aboodh transform, Pourreza transform, and Mohand transform, making the new transform much attractive and promising. Its basic properties are elucidated, and its applications to initial value problems and integral equations are illustrated, when coupled with the homotopy perturbation, it can be used for various non-linear problems, opening a new window for non-linear science. [ABSTRACT FROM AUTHOR]

A nonlinear vibration system, over a span of convincing periodic motion, might break out abruptly a catastrophic instability, but the lack of a theoretical tool has obscured the prediction of the outbreak. This paper deploys the amplitude-frequency formulation for nonlinear oscillators to reveal the critically important mechanism of the pseudo-periodic motion, and finds the quadratic nonlinear force contributes to the pull-down phenomenon in each cycle of the periodic motion, when the force reaches a threshold value, the pull-down instability occurs. A criterion for prediction of the pull-down instability is proposed and verified numerically. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the competition of two species for a single essential growth-limiting nutriment with viral infection that affects only the first species. Although the classical models without viral infection suggest competitive exclusion, this model exhibits the stable coexistence of both species. We reduce the fourth-dimension proposed model to a three-dimension one. Thus, the coexistence of the two competing species is demonstrated using the theory of uniform persistence applied to the three-variable reduced system. We prove that there is no coexistence of both species without the presence of the virus and the satisfaction of some assumptions on the growth rates of species. Finally, we give some numerical simulations to confirm the obtained theoretical findings. [ABSTRACT FROM AUTHOR]

In the paper, we consider some fractional integral formulas in terms of the Riemann–Liouville, Erdélyi–Kober type, and Weyl fractional integral operators and present the general fractional kinetic model involving the hypergeometric superhyperbolic sine function via the Gauss hypergeometric series. [ABSTRACT FROM AUTHOR]

In this article we consider an even entire function of order one as the solution of the classical wave equation in one-dimensional space. We suggest a conjecture that this function has only purely real zeros in the entire complex plane. This is given as a new prospective on a nice connection with number theory and wave equation. [ABSTRACT FROM AUTHOR]

This article addresses a novel anomalous relaxation model with the new general fractional derivative of the Sonine kernel. This operator is considered in the sense of general fractional derivative proposed in the work [Yang et al., General fractional derivatives with applications in viscoelasticity, Academic Press, New York, USA, 2020]. The solution of the mathematical model is obtained with the aid of Laplace transform. The comparison among the classical and anomalous relaxation models is discussed in detail. This result is proposed as a mathematical tool to model the anomalous relaxation behavior of the complex materials. [ABSTRACT FROM AUTHOR]