Dr.K.R.Salini[1] and Dr.S.Bamini[2]
[1] Guest Lecturer, PG & Department of Mathematics, Government Arts & Science College, Kariyampatti, Tirupattur, Tamilnadu, India.
Email: shalinimanoj1985@gmail.com
[2] Research Coordinator, Assistant Professor, PG & Research Department of Mathematics, Marudhar Kesari Jain College For Women, Vaniyambadi, Tamilnadu, India.
Email: saransham07@gmail.com
Abstract
We determine the numerical solution of the specific nonlinear Voltera-Fredholm Integro-Differential Equation is proposed. The method is based on new vector forms for representation of triangular functions and its operational matrix.
Introduction
A set of basic functions and an appropriate projection method or a direct method. These methods often transform an integro-differential equation to a linear or nonlinear system of algebraic equations which can be solved by direct or iterative methods.
Consider a Volterra-Fredhlom Integro-differential equations of the form ๐ฅโฒ(๐ )+๐(๐ )๐ฅ(๐ )+๐1โซ๐1(๐ ,๐ก)๐น(๐ฅ(๐ก))๐๐ก10+๐2โซ๐2(๐ ,๐ก)๐บ(๐ฅ(๐ก))๐๐ก10=๐ฆ(๐ )
๐ฅ(0)=๐ฅ0
Where the functions ๐น(๐ฅ(๐ก)) and ๐บ(๐ฅ(๐ก)) are polynomials of ๐ฅ(๐ก) with constant coefficients.
For convenience, we put ๐น(๐ฅ(๐ก))=[๐ฅ(๐ก)]๐1 and ๐บ(๐ฅ(๐ก))=[๐ฅ(๐ก)]๐2, where ๐1 & ๐2 are positive integers.
For ๐1,๐2=1, equation (1.1) is a linear integro- differential equation.
We present new vector forms of triangular functions (TFs), operational matrix of integration, expansion of functions of one and two variables with respect to TFs and other TFs properties.
By using new representations, a nonlinear integro-differential equation can be easily reduced to a nonlinear system of algebraic equations.
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Triangular Functions
Definition
Two ๐-sets of triangular functions are defined over the intercal [0,๐ก) as ๐1๐(๐ก)={1โ๐กโ๐โโ๐โโค๐ก<(๐+1)โ0๐๐กโ๐๐๐ค๐๐ ๐ ๐2๐(๐ก)={๐กโ๐โโ๐โโค๐ก<(๐+1)โ0๐๐กโ๐๐๐ค๐๐ ๐
Where ๐=0,1,2โฆ๐โ1 with a positive integer value for m.
Also consider โ=๐/๐, and ๐1๐ as the ๐๐กโ left-handed triangular function and ๐2๐ as
the ๐๐กโ right-handed triangular function.
It is assumed that ๐=1, so TFs are defined over [0,1) and โ=1/๐.
From the definition of TFs, it is clear that triangular functions are disjoint, orthogonal
and complete.
We can write โซ๐1๐10(๐ก)๐1๐(๐ก)๐๐ก=โซ๐2๐10(๐ก)๐2๐(๐ก)๐๐ก={โ3๐=๐0๐โ ๐
Also, โ ๐(๐ก)=๐1๐(๐ก)+๐2๐,๐=0,1,โฆ๐โ1
Where โ ๐(๐ก) is the ๐th block-pulse function defined as โ ๐(๐ก)={1๐โโค๐ก<(๐+1)โ0๐๐กโ๐๐๐ค๐๐ ๐
Where ๐=0,1,โฆ๐โ1.
Vector Forms
Consider the first ๐ terms of the left-handed triangular functions and the first ๐ terms of the right- handed triangular functions and write them concisely as ๐-vectors. ๐1(๐ก)=[๐10(๐ก),๐11(๐ก),โฆ๐1๐โ1(๐ก)]๐
๐2(๐ก)=[๐20(๐ก),๐21(๐ก),โฆ๐2๐โ1(๐ก)]๐
Where ๐1(๐ก) and ๐2(๐ก) are called left-handed triangular functions (LHTF) and right-handed triangular functions (RHTF) vector, respectively.
The product of two TFs vectors are
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๐1(๐ก)๐1๐(๐ก)โ ( ๐10(๐ก)0โฏโฏโฏ00๐11(๐ก)โฏโฏโฏ0โฎโฎ0โฎโฎ0โฎโฎโฏโฎโฎโฏโฎโฎโฏโฎโฎ๐1๐โ1(๐ก))
๐2(๐ก)๐2๐(๐ก)โ ( ๐20(๐ก)0โฏโฏโฏ00๐21(๐ก)โฏโฏโฏ0โฎโฎ0โฎโฎ0โฎโฎโฏโฎโฎโฏโฎโฎโฏโฎโฎ๐2๐โ1(๐ก)) ๐1(๐ก)๐2๐(๐ก)=0
๐2(๐ก)๐1๐(๐ก)=0
Where 0 is the ๐ง๐๐๐ ๐ร๐ matrix.
Also โซ๐110(๐ก)๐1๐(๐ก)๐๐ก=โซ๐2(๐ก)๐1๐(๐ก)๐๐ก10โ โ3๐ผ
โซ๐110(๐ก)๐2๐(๐ก)๐๐ก=โซ๐2(๐ก)๐1๐(๐ก)๐๐ก10โ โ6๐ผ
In which ๐ผ is an ๐ร๐ identity matrix.
TFs Expansion
The expansion of a function ๐(๐ก) over [0,1) with respect to TFs written as ๐(๐ก)โ ฮฃ๐๐๐โ1๐=0๐1๐(๐ก)+ฮฃ๐๐๐โ1๐=0๐2๐(๐ก) ๐(๐ก)=๐๐๐1(๐ก)+๐๐๐2(๐ก)
Where we may put ๐๐=๐(๐โ) and ๐๐=๐((๐+๐)โ) for ๐=0,1,2,..๐โ1.
Operational Matrix of Integration
Expressing โซ๐1(๐)๐๐โ ๐1๐1(๐ )+๐2๐2(๐ )๐ 0
โซ๐2(๐)๐๐โ ๐1๐1(๐ )+๐2๐2(๐ )๐ 0
Where ๐1๐ร๐ and ๐2๐ร๐ are called operational matrices of integration in TFs domain and represented as follows ๐1=โ2( 011โฏ1001โฏ10โฎ00โฎ00โฎ0โฏโฑโฏ1โฎ0)
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๐2=โ2( 111โฏ1011โฏ10โฎ00โฎ00โฎ0โฏโฑโฏ1โฎ1)
So the integral of any function ๐(๐ก) can be approximated as โซ๐(๐)๐๐โ ๐๐๐1(๐ )+๐๐๐2(๐ )๐๐๐ 0 โซ๐(๐)๐๐โ (๐+๐)๐๐1๐1(๐ )+(๐+๐)๐๐2๐2(๐ )๐ 0
New Representation of TFs Vector Forms and Other Properties
We define a new representation of TFs vector forms. Then, some characteristics of TFs are presented using the new definition.
Definition and Expansion
Let ๐(๐ก) be a 2๐-vector defined as ๐(๐ก)=(๐1(๐ก)๐2(๐ก)),0<๐ก<1
Where ๐1(๐ก) and ๐2(๐ก) have been defined in (1.2).
Now, the expansion of ๐(๐ก) with respect to TFs can be written as ๐(๐ก)โ ๐น1๐๐1(๐ก)+๐น2๐๐2(๐ก)
โ ๐น๐๐(๐ก)
Where ๐น1 &๐น2 are TFs co-efficients with
๐น1๐=๐(๐โ)& ๐น2๐=๐((๐+1)โ),
For ๐=0,1,โฆ๐โ1.
Also, 2๐-vector ๐น is defined as ๐น=(๐น1๐น2)
Now, assume that ๐(๐ ,๐ก) is a function of two variables. It can be expanded with respect to TFs as follows
๐(๐ ,๐ก)โ ๐๐(๐ )๐พ๐(๐ก)
Where ๐(๐ )& ๐(๐ก) are 2๐1&2๐2 dimensional triangular functions and ๐พ is a
2๐1ร2๐2 TFs coefficient matrix.
For convenience, we put ๐1=๐2=๐. So matrix ๐พ can be written as
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๐พ=((๐พ11)๐ร๐(๐พ12)๐ร๐(๐พ21)๐ร๐(๐พ22)๐ร๐)
Where ๐พ11,๐พ12,๐พ21,๐พ22 can be compted by sampling the function ๐(๐ ,๐ก) at points ๐ ๐ & ๐ก๐ such that ๐ ๐=๐โ & ๐ก๐=๐โ, for ๐,๐=0,1,โฆ๐. (๐พ11)๐๐=๐(๐ ๐,๐ก๐),๐=0,1,โฆ๐โ1,๐=0,1,โฆ๐โ1 (๐พ12)๐๐=๐(๐ ๐,๐ก๐),๐=0,1,โฆ๐โ1,๐=0,1,โฆ๐ (๐พ21)๐๐=๐(๐ ๐,๐ก๐),๐=0,1,โฆ๐,๐=0,1,โฆ๐โ1 (๐พ22)๐๐=๐(๐ ๐,๐ก๐),๐=0,1,โฆ๐,๐=0,1,โฆ๐
Product Properties
Let ๐ be an 2๐-vertor which can be written as ๐๐=(๐1๐ ๐2๐) such that ๐1 & ๐2 are ๐-vectors.
It can be concluded from (1.3) & (1.4) that ๐(๐ก)๐๐(๐ก)๐=(๐1(๐ก)๐2(๐ก))(๐๐(๐ก)๐2๐(๐ก))(๐1๐2)
โ (๐๐๐(๐1(๐ก))๐๐ร๐๐๐ร๐๐๐๐(๐2(๐ก)))(๐1๐2)
=๐๐๐ (๐(๐ก))๐
=๐๐๐(๐)๐(๐ก)
Therefore,
๐(๐ก)๐๐(๐ก)๐โ ๐ฬ ๐(๐ก)
Where ๐ฬ =๐๐๐(๐) is an 2๐ร2๐ diagonal matrix.
Let ๐ต be a 2๐ร2๐ matrix as ๐ต=((๐ต11)๐ร๐(๐ต12)๐ร๐(๐ต21)๐ร๐(๐ต22)๐ร๐)
So, it can be similarly concluded from equations (1.3) and (1.4) that ๐(๐ก)๐ต๐(๐ก)=๐1๐(๐ก)๐2๐(๐ก)(๐ต11๐ต12๐ต21๐ต22)(๐1(๐ก)๐2(๐ก)) โ ๐1๐(๐ก)๐ต11๐1(๐ก)+๐2๐(๐ก)๐ต22๐2(๐ก) โ ๐ตฬ11๐๐1(๐ก)+๐ตฬ22๐๐2(๐ก)
Where ๐ตฬ11 and ๐ตฬ22 are ๐โvectors with elements equal to the diagonal entries of matrices ๐ต11 and ๐ต22 respectively.
Therefore,
๐๐(๐ก)๐ต๐(๐ก)โ ๐ตฬ ๐๐(๐ก)
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In which ๐ตฬ is a 2๐- vector with elements equal to the diagonal entries of matrix ๐ต.
It is immediately concluded from equation (1.5) that โซ๐10(๐ก)๐๐(๐ก)๐๐ก=โซ(๐1(๐ก)๐2(๐ก))๐1๐(๐ก)๐2๐(๐ก)๐๐ก10
=โซ(๐1(๐ก)๐1๐(๐ก)๐1(๐ก)๐2๐(๐ก)๐2(๐ก)๐1๐(๐ก)๐2(๐ก)๐2๐(๐ก))๐๐ก10
โ (โ3๐ผ๐ร๐โ6๐ผ๐ร๐โ6๐ผ๐ร๐โ3๐ผ๐ร๐)
Therefore,
โซ๐10(๐ก)๐๐(๐ก)๐๐กโ ๐ท
Where ๐ท is the following 2๐ร2๐ matrix. ๐ท=โ3( 10โฏ012โ0โฏ001โฏ0012โโฏ0โฎ012โ0โฎ0โฎ0012โโฎ0โฑโฏโฏโฏโฑโฏโฎ100โฎ12โโฎ010โฎ0โฎ001โฎ0โฑโฆโฏโฏโฑโฏโฎ12โ00โฎ1)
Operational Matrix
Expressing โซ๐(๐)๐๐๐ 0 in terms of ๐(๐ ), we can write โซ๐(๐)๐๐๐ 0=โซ(๐1(๐)๐2(๐))๐๐๐ 0
โ (๐1๐1(๐ )+๐2๐2(๐ )๐1๐1(๐ )+๐2๐2(๐ ))
=(๐1๐2๐1๐2)(๐1(๐ )๐2(๐ ))
So, โซ๐(๐)๐๐๐ 0โ ๐๐(๐ )
Where ๐2๐ร2๐, operational matrix of ๐(๐ ) is
๐=(๐1๐2๐1๐2) (
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Where ๐1 & ๐2 are given by
The integral of any function ๐(๐ก) can be approximated as โซ๐(๐)๐๐๐ 0โ โซ๐น๐๐(๐)๐๐๐ 0
โ ๐น๐๐๐(๐ )
Solving Nonlinear Integro-Differential Equation
Consider the following nonlinear Volterra-Fredhlom integro-differential equation
{๐ฅโฒ(๐ )+๐(๐ )๐ฅ(๐ )+๐1โซ๐1(๐ ,๐ก)[๐ฅ(๐ก)]๐1๐๐ก+๐ 0๐2โซ๐2(๐ ,๐ก)[๐ฅ(๐ก)]๐2๐๐ก=๐ฆ(๐ )๐ 0๐ฅ(0)=๐ฅ0, 0โค๐ <1,๐1,๐2โฅ1
Where the parameters ๐1 and ๐2 and โ2 functions ๐(๐ ),๐ฆ(๐ ),๐1(๐ ,๐ก),๐2(๐ ,๐ก) are known but ๐ฅ(๐ ) is not.
The appearance of initial condition equation. This is necessary to ensure the existence of a solution.
Approximating functions
๐ฅ(๐ ),๐ฅโฒ(๐ ),๐(๐ ),๐ฆ(๐ ),[๐ฅ(๐ก)]๐1,[๐ฅ(๐ก)]๐2,๐1(๐ ,๐ก),๐2(๐ ,๐ก)
with respect to TFs, ๐ฅ(๐ )โ ๐ฅ๐(๐ )๐ ๐ฅโฒ(๐ )โ ๐โฒ๐๐(๐ )=๐๐๐โฒ
๐(๐ )โ ๐๐๐(๐ )=๐๐(๐ )๐
๐ฆ(๐ )โ ๐๐๐(๐ )=๐๐(๐ )๐ [๐ฅ(๐ก)]๐1โ ๐๐1๐๐(๐ )=๐๐(๐ )๐๐1 [๐ฅ(๐ก)]๐2โ ๐๐2๐๐(๐ )=๐๐(๐ )๐๐2 ๐1(๐ ,๐ก)โ ๐๐๐พ1๐(๐ก)
๐2(๐ ,๐ก)โ ๐๐๐พ2๐(๐ก)
Where 2๐-vectors ๐,๐โฒ,๐,๐,๐๐1,๐๐2 and 2๐ร2๐ matrices ๐พ1 & ๐พ2 are TFs coefficients of
๐ฅ(๐ ),๐ฅโฒ(๐ ),๐(๐ ),๐ฆ(๐ ),[๐ฅ(๐ก)]๐1,[๐ฅ(๐ก)]๐2,๐1(๐ ,๐ก),๐2(๐ ,๐ก) respectively.
Lemma
Let 2๐-vectors ๐ and ๐๐ be TFs coefficients of ๐ฅ(๐ ) and [๐ฅ(๐ )]๐ respectively. If
๐=(๐1๐๐2๐)๐=(๐10,๐11,โฆ,๐1๐โ1,๐20,๐21โฆ๐2๐โ1)๐, then
๐๐=(๐10,๐11,โฆ,๐1๐โ1,๐20,๐21โฆ๐2๐โ1)๐
Where ๐โฅ1 is a positive integer.
Proof:
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When ๐=1, , follows at once from [๐ฅ(๐ )]๐=๐ฅ(๐ ).
Suppose that (4.16), holds for ๐, we shall deduce it for ๐+1.
Since [๐ฅ(๐ )]๐+1โ (๐๐๐(๐ )).(๐1๐๐(๐ ))
=๐๐๐(๐ )๐๐(๐ )๐๐ =๐๐๐๐ฬ๐(๐ )
we obtain ๐๐๐๐ฬ=(๐10๐+1,๐11๐+1,โฆโฆ,๐1๐โ1๐+1,๐20๐+1,๐21๐+1,โฆโฆ,๐2๐โ1๐+1)๐
Equation holds for ๐+1.
Components of ๐ฟ๐ can be Computed in terms of Components of Unknown Vector ๐ฟ
We substitute (1.15) into (1.14), we have ๐๐๐(๐ )โ ๐โฒ๐๐(๐ )+๐๐๐(๐ )๐๐(๐ )๐+๐1๐๐(๐ )๐พ1โซ๐(๐ก)๐๐(๐ก)๐๐1๐๐ก+๐ 0๐2๐๐(๐ )๐พ2โซ๐(๐ก)๐๐(๐ก)๐๐2๐๐ก๐ 0
it follows that ๐๐๐(๐ )โ ๐โฒ๐๐(๐ )+(๐ฬ ๐(๐ ))๐๐+๐1๐๐(๐ )๐พ1๐ฬ๐1โซ๐(๐ก)๐๐ก+๐2๐๐(๐ )๐พ2๐ท๐๐2๐ 0
Using Operational matrix ๐,
๐๐๐(๐ )โ ๐โฒ๐๐(๐ )+๐๐๐ฬ ๐(๐ )+๐1๐๐(๐ )๐พ1๐ฬ๐1๐๐(๐ )+๐2(๐พ2๐ท๐๐2)๐๐(๐ )
In which ๐1๐พ1๐ฬ๐1๐ is a 2๐ร2๐ matrix
๐๐(๐ )๐1๐พ1๐ฬ๐1๐๐(๐ )โ ๐๐1๐ฬ๐(๐ )
Where ๐ฬ๐1 is an 2๐-vector with components equal to the diagonal entries of the matrix ๐1๐พ1๐ฬ๐1๐.
๐๐๐(๐ )โ ๐โฒ๐๐(๐ )+๐๐๐ฬ ๐(๐ )+๐๐1๐ฬ๐(๐ )+๐2(๐พ2๐ท๐๐2)๐๐(+๐ฬ ๐+๐๐1ฬ+ ๐2๐พ2๐ท๐๐2โ ๐
Where ๐ฬ is a diagonal matrix, so ๐ฬ ๐=๐ฬ.
๐โฒ must be computed in terms of ๐. ๐ฅ(๐ )โ๐ฅ(0)=โซ๐ฅโฒ(๐)๐๐๐ 0
โ โซ๐โฒ๐๐(๐)๐๐๐ 0 โ ๐โฒ๐๐๐(๐ ) ๐ฅ(๐ )โ ๐โฒ๐๐๐(๐ )+๐0๐๐(๐ )
Where ๐0 is the 2๐- vector of the form
Journal of the Maharaja Sayajirao University of Baroda ISSN: 0025-0422
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Volume-56, No.1 (IV) 2022
๐0=[๐ฅ0,๐ฅ0,โฆ๐ฅ0]๐
Consequently,
๐โ ๐๐๐โฒ+๐0
Now, combining (1.19) and (1.20) and replacing โ with =, it follows that
(๐ผ+๐๐๐ฬ)๐+๐๐๐๐1ฬ+๐2๐๐๐พ2๐ท๐๐2โ ๐๐๐+๐0
Equation is a nonlinear system of 2๐ algebraic equations for the 2๐ unknowns ๐10,๐11,โฆ๐1๐โ1,๐20,๐21,โฆ๐2๐โ1.
Components of ๐๐=(๐1๐ ๐2๐) can be obtainbed by an iterative method.
Hence, an approximate solution ๐ฅ(๐ )โ ๐๐๐(๐ )
๐ฅ(๐ )โ ๐1๐๐1(๐ )+๐2๐๐2(๐ )
Can be computed for equation (1.14) without using any projection method.
Conclusion
We investigated the numerical solution of nonlinear and singularly perturbed for Vulture integro-differential equations. Also, numerical solution of high-order and fractional nonlinear Volterra-Fredholm integro-differential equations and its error analysis are discussed. Finally, some numerical results of integro-differential equations are presented to illustrated the efficiency and accuracy of the proposed methods.
Reference
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2. H.Brunner, โCollection method for Volterra integral and Relation Functional Equationsโ, Cambridge University Press, Cambridge,2004.
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