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[Display omitted] • A new and efficient fractional model is explored for the investigation of COVID-19 dynamics. • The associated dynamical behaviors are discussed in terms of equilibrium points, invariant region, etc. • To implement the proposed model numerically, an efficient approximation scheme is also employed. • Simulation results are compared with a real case of COVID-19 pandemic in Italy. • As a result, the new fractional model simulates the reality more precisely than the other classical frameworks. Mathematical modelling is a rapidly expanding field that offers new and interesting opportunities for both mathematicians and biologists. Concerning COVID-19, this powerful tool may help humans to prevent the spread of this disease, which has affected the livelihood of all people badly. The main objective of this research is to explore an efficient mathematical model for the investigation of COVID-19 dynamics in a generalized fractional framework. The new model in this paper is formulated in the Caputo sense, employs a nonlinear time-varying transmission rate, and consists of ten population classes including susceptible, infected, diagnosed, ailing, recognized, infected real, threatened, diagnosed recovered, healed, and extinct people. The existence of a unique solution is explored for the new model, and the associated dynamical behaviours are discussed in terms of equilibrium points, invariant region, local and global stability, and basic reproduction number. To implement the proposed model numerically, an efficient approximation scheme is employed by the combination of Laplace transform and a successive substitution approach; besides, the corresponding convergence analysis is also investigated. Numerical simulations are reported for various fractional orders, and simulation results are compared with a real case of COVID-19 pandemic in Italy. By using these comparisons between the simulated and measured data, we find the best value of the fractional order with minimum absolute and relative errors. Also, the impact of different parameters on the spread of viral infection is analyzed and studied. According to the comparative results with real data, we justify the use of fractional concepts in the mathematical modelling, for the new non-integer formalism simulates the reality more precisely than the classical framework. [ABSTRACT FROM AUTHOR]

Legendre polynomials' first derivatives have been used as the basis function via the pseudo-Galerkin spectral method. Operational matrices for derivatives have been used and extended to deal with the system of ordinary differential-algebraic equations. An algorithm via those matrices has been designed. The accuracy and efficiency of the proposed algorithm had been shown by two techniques, theoretically, via the boundedness of the approximated expansion and numerically through numerical examples. [ABSTRACT FROM AUTHOR]

In this paper, we explore the existence and uniqueness theorem for a problem of the fractional Cauchy form, with dependence on the generalized proportional Caputo derivative. Furthermore, a new numerical technique is presented based on a decomposition formula for the generalized proportional Caputo derivative. Convergence analysis of the proposed technique is proved. Finally, numerical results are obtained to confirm the validity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we study a coupled system of generalized Sturm–Liouville problems and Langevin fractional differential equations described by Atangana–Baleanu–Caputo (ABC for short) derivatives whose formulations are based on the notable Mittag-Leffler kernel. Prior to the main results, the equivalence of the coupled system to a nonlinear system of integral equations is proved. Once that has been done, we show in detail the existence–uniqueness and Ulam stability by the aid of fixed point theorems. Further, the continuous dependence of the solutions is extensively discussed. Some examples are given to illustrate the obtained results. [ABSTRACT FROM AUTHOR]

In this article, we construct approximate solution to multi-dimensional Fredholm integral equations of second kind using n -dimensional Legendre scaling functions. Error analysis of the problem is provided in the L 2 sense. It is shown that our numerical method is numerically stable. Some examples are discussed based on proposed method to show the importance and accuracy of the proposed numerical method. [ABSTRACT FROM AUTHOR]

In this article, we introduce a numerical technique for solving a class of multi-term variable-order fractional differential equation. The method depends on establishing a shifted Jacobi operational matrix (SJOM) of fractional variable-order derivatives. By using the constructed (SJOM) in combination with the collocation technique, the main problem is reduced to an algebraic system of equations that can be solved numerically. The bound of the error estimate for the suggested method is investigated. Numerical examples are introduced to illustrate the applicability, generality, and accuracy of the proposed technique. Moreover, many physical applications problems that have the multi-term variable-order fractional differential equation formulae such as the damped mechanical oscillator problem and Bagley-Torvik equation can be solved via the presented method. Furthermore, the proposed method will be considered as a generalization of many numerical techniques. [ABSTRACT FROM AUTHOR]

In this paper, we present a new fractional-order mathematical model for a tumor-immune surveillance mechanism. We analyze the interactions between various tumor cell populations and immune system via a system of fractional differential equations (FDEs). An efficient numerical procedure is suggested to solve these FDEs by considering singular and nonsingular derivative operators. An optimal control strategy for investigating the effect of chemotherapy treatment on the proposed fractional model is also provided. Simulation results show that the new presented model based on the fractional operator with Mittag–Leffler kernel represents various asymptomatic behaviors that tracks the real data more accurately than the other fractional- and integer-order models. Numerical simulations also verify the efficiency of the proposed optimal control strategy and show that the growth of the naive tumor cell population is successfully declined. [ABSTRACT FROM AUTHOR]

We have perused about the existence of a solution toward hybrid initial value problem (HIVP) featuring fractional q-derivative ... in which D948q denotes the Riemann-Liouville fractional q-derivative in the order of δ. In Banach algebra, by making use of a fixed point theorem based Dhage along with mixed Lipschitz and Caratheodory condition, a way of solving the above fractional Hybrid initial value problem (FHIVP) featuring q-derivatives verified, in this study. [ABSTRACT FROM AUTHOR]

The manuscript is primarily concerned with the new existence results for fractional neutral integro-differential equation (FNIDE) with nonlocal conditions (NLCs) in Banach spaces. Based on the Banach contraction principle and Krasnoselskii fixed point theorem (FPT) joined with resolvent operators, we develop the main results. Ultimately, an representation is also offered to demonstrate the accomplished theorem. [ABSTRACT FROM AUTHOR]

This article aims to discuss a class of quaternion Fourier integral operators on certain set of generalized functions, leading to a method of discussing various integral operators on various spaces of generalized functions. By employing a quaternion Fourier integral operator on points closed to the origin, we introduce convolutions and approximating identities associated with the Fourier convolution product and derive classical and generalized convolution theorems. Working on such identities, we establish quaternion and ultraquaternion spaces of generalized functions, known as Boehmians, which are more general than those existed on literature. Further, we obtain some characteristics of the quaternion Fourier integral in a quaternion sense. Moreover, we derive continuous embeddings between the classical and generalized quaternion spaces and discuss some inversion formula as well. [ABSTRACT FROM AUTHOR]

This article aims to discuss a class of quaternion Fourier integral operators on certain set of generalized functions, leading to a method of discussing various integral operators on various spaces of generalized functions. By employing a quaternion Fourier integral operator on points closed to the origin, we introduce convolutions and approximating identities associated with the Fourier convolution product and derive classical and generalized convolution theorems. Working on such identities, we establish quaternion and ultraquaternion spaces of generalized functions, known as Boehmians, which are more general than those existed on literature. Further, we obtain some characteristics of the quaternion Fourier integral in a quaternion sense. Moreover, we derive continuous embeddings between the classical and generalized quaternion spaces and discuss some inversion formula as well. [ABSTRACT FROM AUTHOR]

In this paper, we investigate numerical solution of the variable-order fractional Galilei advection-diffusion equation with a nonlinear source term. The suggested method is based on the shifted Legendre collocation procedure and a matrix form representation of variable-order Caputo fractional derivative. The main advantage of the proposed method is investigating a global approximation for the spatial and temporal discretizations. This method reduces the problem to a system of algebraic equations, which is easier to solve. The validity and effectiveness of the method are illustrated by an easy-to-follow example. [ABSTRACT FROM AUTHOR]

Many numerical methods have been developed for nonlinear fractional integro-differential Volterra's population model (FVPG). In these methods, to approximate a function on a particular interval, only a restricted number of points have been employed. In this research, we show that it is possible to use the fuzzy transform method (F-transform) to tackle with FVPG. It makes the F-transform preferable to other methods since it can make full use of all points on this interval. We also make a comparison showing that this method is less computational and is more convenient to be utilized for coping with nonlinear integro-differential equation (IDEs), fractional nonlinear integro-differential equation (FIDEs), and fractional ordinary differential equations (FODEs). [ABSTRACT FROM AUTHOR]

In this study, we consider the motion of a bead sliding on a wire which is bent into a parabola form. We first introduce the classical Lagrangian from the system model under consideration and obtain the classical Euler-Lagrange equation of motion. As the second step, we generalize the classical Lagrangian to the fractional form and derive the fractional Euler-Lagrange equation in terms of the Caputo fractional derivatives. Finally, we provide numerical solution of the latter equation for some fractional orders and initial conditions. The method we used is based on a discretization scheme using a Grünwald-Letnikov approximation for the fractional derivatives. Numerical simulations verify that the proposed approach is efficient and easy to implement. [ABSTRACT FROM AUTHOR]

According to semigroup theories, fractional calculus, Banach contraction principle and Schaefer's fixed point theorem, this paper is fundamentally involved with the existence of mild solutions for an impulsive fractional neutral differential systems (abbreviated, IFNDS) with nonlocal conditions (abbreviated, NLC) in Banach space X. At last, an illustration is also presented to exhibit the use of our theoretical results. [ABSTRACT FROM AUTHOR]

We investigate the fractional harmonic oscillator on a moving platform. We obtained the fractional Euler-Lagrange equation from the derived fractional Lagrangian of the system which contains left Caputo fractional derivative. We transform the obtained differential equation of motion into a corresponding integral one and then we solve it numerically. Finally, we present many numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we have generalized theFα-calculus by suggesting Fourier and Laplace transformations of the function with support of the fractals set which are the subset of the real line. Using this generalization, we have found the diffraction fringes from the fractal grating Cantor sets. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to compute two unified fractional integrals involving the product of twoH-functions, a general class of polynomials and Appell function. These integrals are further applied in proving two theorems on Saigo–Maeda fractional integral operators. Some consequent results and special cases are also pointed out in the concluding section. [ABSTRACT FROM AUTHOR]

We propose a simple and accurate numerical scheme for solving the time fractional telegraph (TFT) equation within Caputo type fractional derivative. A fictitious coordinate ϑ is imposed onto the problem in order to transform the dependent variable u ( x , t ) into a new variable with an extra dimension. In the new space with the added fictitious dimension, a combination of method of line and group preserving scheme (GPS) is proposed to find the approximate solutions. This method preserves the geometric structure of the problem. Power and accuracy of this method has been illustrated through some examples of TFT equation. [ABSTRACT FROM AUTHOR]

In this manuscript, we have a tendency to execute Banach contraction xed point theorem combined with resolvent operator to analyze the exact controllability results for fractional neutral integro-differential systems (FNIDS) with state-dependent delay (SDD) in Banach spaces. An illustration is additionally offered to exhibit the achieved hypotheses. [ABSTRACT FROM AUTHOR]

Using Saigo's fractional integral operators, we establish a generalized version of the Grüss type integral inequality related to the bounded integrable functions, whose bounds are integrable functions. Some special cases of our results are also considered. [ABSTRACT FROM AUTHOR]

Using Saigo's fractional integral operators, we establish a generalized version of the Grüss type integral inequality related to the bounded integrable functions, whose bounds are integrable functions. Some special cases of our results are also considered. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to provide an efficient numerical approach for the fractional differential equations (FDEs) on the half line with constant coefficients using a generalized Laguerre tau (GLT) method. The fractional derivatives are described in the Caputo sense. We state and prove a new formula expressing explicitly the derivatives of generalized Laguerre polynomials of any degree and for any fractional order in terms of generalized Laguerre polynomials themselves. We develop also a direct solution technique for solving the linear multi-order FDEs with constant coefficients using a spectral tau method. The spatial approximation with its fractional-order derivatives described in the Caputo sense are based on generalized Laguerre polynomials Li(α)(x) with x∈Λ=(∞) and i denoting the polynomial degree. [ABSTRACT FROM PUBLISHER]

A new Legendre rational pseudospectral scheme is proposed and developed for solving numerically systems of linear and nonlinear multipantograph equations on a semi-infinite interval. A Legendre rational collocation method based on Legendre rational-Gauss quadrature points is utilized to reduce the solution of such systems to systems of linear and nonlinear algebraic equations. In addition, accurate approximations are achieved by selecting few Legendre rational-Gauss collocation points. The numerical results obtained by this method have been compared with various exact solutions in order to demonstrate the accuracy and efficiency of the proposed method. Indeed, for relatively limited nodes used, the absolute error in our numerical solutions is sufficiently small. [ABSTRACT FROM AUTHOR]

By making use of the fractional hypergeometric operators, we establish certain new fractional integral inequalities for synchronous functions which are related to the weighted version of the Chebyshev functional. Some consequent results and special cases of the main results are also pointed out. [ABSTRACT FROM AUTHOR]

The classical free Lagrangian admitting a constant of motion, in one- and two-dimensional space, is generalized using the Caputo derivative of fractional calculus. The corresponding metric is obtained and the fractional Christoffel symbols, Killing vectors, and Killing-Yano tensors are derived. Some exact solutions of these quantities are reported. [ABSTRACT FROM AUTHOR]

An efficient Legendre–Gauss–Lobatto collocation (L–GL–C) method is applied to solve the space-fractional advection diffusion equation with nonhomogeneous initial-boundary conditions. The Legendre–Gauss–Lobatto points are used as collocation nodes for spatial fractional derivatives as well as the Caputo fractional derivative. This approach is reducing the problem to the solution of a system of ordinary differential equations in time which can be solved by using any standard numerical techniques. The proposed numerical solutions when compared with the exact solutions reveal that the obtained solution produces highly accurate results. The results show that the proposed method has high accuracy and is efficient for solving the space-fractional advection diffusion equation. [ABSTRACT FROM AUTHOR]

A new operationalmatrix of fractional integration of arbitrary order for generalized Laguerre polynomials is derived. The fractional integration is described in the Riemann-Liouville sense. This operational matrix is applied together with generalized Laguerre tau method for solving general linear multitermfractional differential equations (FDEs). The method has the advantage of obtaining the solution in terms of the generalized Laguerre parameter. In addition, only a small dimension of generalized Laguerre operational matrix is needed to obtain a satisfactory result. Illustrative examples reveal that the proposedmethod is very effective and convenient for linear multiterm FDEs on a semi-infinite interval. [ABSTRACT FROM AUTHOR]

We solve three versions of nonlinear time-dependent Burgers-type equations. The Jacobi-Gauss-Lobatto points are used as collocation nodes for spatial derivatives. This approach has the advantage of obtaining the solution in terms of the Jacobi parameters α and β. In addition, the problem is reduced to the solution of the system of ordinary differential equations (SODEs) in time. This system may be solved by any standard numerical techniques. Numerical solutions obtained by this methodwhen compared with the exact solutions reveal that the obtained solutions produce high-accurate results. Numerical results show that the proposed method is of high accuracy and is efficient to solve the Burgers-type equation. Also the results demonstrate that the proposed method is a powerful algorithm to solve the nonlinear partial differential equations. [ABSTRACT FROM AUTHOR]

We present a direct solution technique for approximating linear multiterm fractional differential equations (FDEs) on semiinfinite interval, using generalized Laguerre polynomials. We derive the operational matrix of Caputo fractional derivative of the generalized Laguerre polynomials which is applied together with generalized Laguerre tau approximation for implementing a spectral solution of linear multitermFDEs on semi-infinite interval subject to initial conditions. The generalized Laguerre pseudospectral approximation based on the generalized Laguerre operational matrix is investigated to reduce the nonlinear multiterm FDEs and its initial conditions to nonlinear algebraic system, thus greatly simplifying the problem. Through several numerical examples, we confirm the accuracy and performance of the proposed spectral algorithms. Indeed, the methods yield accurate results, and the exact solutions are achieved for some tested problems. [ABSTRACT FROM AUTHOR]

This paper deals with modified generalized Laguerre spectral tau and collocation methods for solving linear and nonlinear multiterm fractional differential equations (FDEs) on the half line. A new formula expressing the Caputo fractional derivatives of modified generalized Laguerre polynomials of any degree and for any fractional order in terms of the modified generalized Laguerre polynomials themselves is derived. An efficient direct solver technique is proposed for solving the linear multiterm FDEs with constant coefficients on the half line using a modified generalized Laguerre tau method. The spatial approximation with its Caputo fractional derivatives is based on modified generalized Laguerre polynomials Li(α,β)(x) with x ∊ Λ = (0,∞), α > -1, and β > 0, and i is the polynomial degree. We implement and develop the modified generalized Laguerre collocation method based on the modified generalized Laguerre-Gauss points which is used as collocation nodes for solving nonlinear multiterm FDEs on the half line. [ABSTRACT FROM AUTHOR]

A new generalized KdV equation, describing the motions of long waves in shallow water under the gravity field, is considered in this paper. By adopting a series of well-organized methods, the Bäcklund transformation, the bilinear form and diverse wave structures of the governing model are formally extracted. The exact solutions listed in this paper are categorized as lump-type, complexiton, and soliton solutions. To exhibit the physical mechanism of the obtained solutions, several graphical illustrations are given for particular choices of the involved parameters. As a direct consequence, diverse wave structures given in this paper enrich the studies on the KdV-type equations. [ABSTRACT FROM AUTHOR]

We investigate the existence and multiplicity of positive solutions for the nonlinear fractional differential equation initial value problem D0ɑ+u(t) + D0+β+u(t) = f(t,u(t)), u(0) = 0, 0 < t < 1, where 0 < β < α < 1, D0+ɑ is the standard Riemann-Liouville differentiation and f : [0,1] x [0, ∞) → [0, ∞) is continuous. By using some fixed-point results on cones, some existence and multiplicity results of positive solutions are obtained. [ABSTRACT FROM AUTHOR]

In this paper for a given example we proved that the Riemann-Liouville fractional integral term appears naturally and relates the external force with acceleration within the fractional Newtonian equation. The consideration of some self-similar process that leads to the fractional integral as well as some possible generalizations of the proposed model was discussed. [ABSTRACT FROM AUTHOR]

Studies the front-form Harada gauged Floreanini-Jackiw action and its BRST and anti-BRST symmetry within Hamilton-Jacobi (HJ) formalism. Chiral Schwinger model in one-space and one-time dimension; HJ formalism requiring many Hamiltonians; Application of the HJ formalism to a BRST invariant theory; Investigation of the physical states with HJ formalism.

The presence of Killing-Yano tensors implies the existence of nongeneric supercharges in spinning point particle theories on curved backgrounds. Dual metrics are defined through their associated nondegenerate Killing tensors of valence two. Siklos spacetimes, which are the only nontrivial Einstein spaces conformal to nonflat pp-waves are investigated with regard to the existence of their corresponding Killing and Killing-Yano tensors. It is found that a class of Siklos space-times admit dual metrics and nongeneric supercharges. [ABSTRACT FROM AUTHOR]

Classical least-squares (CLS) and principal component regression (PCR) techniques were proposed for the simultaneous analysis of tablets containing acetaminophen and caffeine without using a chemical separation procedure. The chemometric calibrations were prepared by measuring the absorbances values at the 15 wavelengths in the spectral region 215–285 nm and by using a training set of the mixtures of both drugs in 0.1 M HCl. The obtained chemometric calibrations were used for the estimation of acetaminophen and caffeine in samples. The numerical calculations were performed with the ‘maple V’ software. By applying two techniques to synthetic mixtures, the mean recoveries and the relative standard deviations in the CLS and PCR techniques were found as 99.5 and 1.29, 99.7 and 1.00% for acetaminophen and 99.9 and 1.92, 100.0 and 1.178% for caffeine, respectively. Our results were compared with those obtained previously by one of us considering HPLC method as a reference method. These two methods were successfully applied to a pharmaceutical tablet formulation of two drugs. [Copyright &y& Elsevier]

The tensorial form of the Lax pair equations are given in a compact and geometrically transparent form in the presence of Cartan's torsion tensor. Three-dimensional space–times admitting Lax tensors are analyzed in detail. Solutions to Lax tensor equations include interesting examples as separable coordinates and the Toda lattice. [ABSTRACT FROM AUTHOR]

The existence of both subsonic (M < 1) and supersonic (M > 1) compressive (N > 1) solitons within a three-dimensional magnetized plasma model featuring thermal ions and electrons, incorporating electron inertia through the pseudopotential method is established. The study delves into ion-acoustic solitary waves, numerically exploring the dependency of the solitary wave profile on different plasma parameters. The findings suggest that, as the ion temperature (α) increases, both subsonic and supersonic potential profiles exhibit a decrease in amplitude and depth. Furthermore, the study investigates the influence of the Mach number on the potential profile. It reveals that as the Mach number increases in the direction of wave propagation, the amplitude and depth of the potential profile also increase. The findings not only enrich our understanding of the intricate dynamics of plasmas but also provide profound insights with broad applicability, encompassing natural and engineered plasma systems across diverse scientific and technological domains. [ABSTRACT FROM AUTHOR]

A human being standing upright with his feet as the pivot is the most popular example of the stabilized inverted pendulum. Achieving stability of the inverted pendulum has become common challenge for engineers. In this paper, we consider an initial value discrete fractional Duffing equation with forcing term. We establish the existence, Hyers–Ulam stability, and Hyers–Ulam Mittag-Leffler stability of solutions for the equation. We consider the inverted pendulum modeled by Duffing equation as an example. The values are tabulated and simulated to show the consistency with theoretical findings. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to conduct a detailed study on a high-order nonlinear Schrödinger (HONLS) equation involving nonlinear dispersions and the Kerr effect. More precisely, after reducing the governing model describing ultra-short pulses in optical fibers in a one-dimensional domain, its optical solitons including the bright and dark solitons are derived through the modified Kudryashov (MK) method. The dynamical behavior of the bright and dark solitons is formally investigated for different sets of the involved parameters. It is shown that increasing and decreasing nonlinear dispersions lead to significant changes in the amplitude of the bright and dark solitons. [ABSTRACT FROM AUTHOR]

We investigate some new class of hybrid type fractional differential equations and inclusions via some nonlocal three-point boundary value conditions. Also, we provide some examples to illustrate our results. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel mathematical model of Corona virus with new hybrid fractional operator derivative are presented. • Three control variables are presented to minimize the number of infected population. • Necessary control conditions are derived. • Two numerical methods are constructed to study the behavior of the obtained fractional optimality system. • The stability of the proposed methods are proved. • Numerical simulations and comparative studies are given. Coronavirus COVID-19 pandemic is the defining global health crisis of our time and the greatest challenge we have faced since world war two. To describe this disease mathematically, we noted that COVID-19, due to uncertainties associated to the pandemic, ordinal derivatives and their associated integral operators show deficient. The fractional order differential equations models seem more consistent with this disease than the integer order models. This is due to the fact that fractional derivatives and integrals enable the description of the memory and hereditary properties inherent in various materials and processes. Hence there is a growing need to study and use the fractional order differential equations. Also, optimal control theory is very important topic to control the variables in mathematical models of infectious disease. Moreover, a hybrid fractional operator which may be expressed as a linear combination of the Caputo fractional derivative and the Riemann–Liouville fractional integral is recently introduced. This new operator is more general than the operator of Caputo's fractional derivative. Numerical techniques are very important tool in this area of research because most fractional order problems do not have exact analytic solutions. A novel fractional order Coronavirus (2019-nCov) mathematical model with modified parameters will be presented. Optimal control of the suggested model is the main objective of this work. Three control variables are presented in this model to minimize the number of infected populations. Necessary control conditions will be derived. The numerical methods used to study the fractional optimality system are the weighted average nonstandard finite difference method and the Grünwald-Letnikov nonstandard finite difference method. The proposed model with a new fractional operator is presented. We have successfully applied a kind of Pontryagin's maximum principle and were able to reduce the number of infected people using the proposed numerical methods. The weighted average nonstandard finite difference method with the new operator derivative has the best results than Grünwald-Letnikov nonstandard finite difference method with the same operator. Moreover, the proposed methods with the new operator have the best results than the proposed methods with Caputo operator. The combination of fractional order derivative and optimal control in the Coronavirus (2019-nCov) mathematical model improves the dynamics of the model. The new operator is more general and suitable to study the optimal control of the proposed model than the Caputo operator and could be more useful for the researchers and scientists. [ABSTRACT FROM AUTHOR]

Our aim in this research is to investigate the motion of a beam on an internally bent nanowire by using the fractional calculus theory. To this end, we first formulate the classical Lagrangian which is followed by the classical Euler--Lagrange equation. Then, after introducing the generalized fractional Lagrangian, the fractional Euler--Lagrange equation is provided for the motion of the considered beam on the nanowire. An efficient numerical scheme is introduced for implementation and the simulation results are reported for different fractional-order values and various initial settings. These results indicate that the fractional responses approach the classical ones as the fractional order goes to unity. In addition, the fractional Euler--Lagrange equation provides a flexible model possessing more information than the classical description -- the fact that leads to a considerably better evaluation of the hidden features of the real system under investigation. [ABSTRACT FROM AUTHOR]