Introduction to Fractional Calculus Amna Al - Amri Project October 2010

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  • 8/8/2019 Introduction to Fractional Calculus Amna Al - Amri Project October 2010

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    Introduction to Fractional Calculus

    A Project

    Submitted to the University of Nizwa in Partial Fulfillment of the

    Requirements for the Degree of Bachelor of Education in Mathematics

    By

    AMNA ABDULSALAM YOUNIS AL-AMRY

    Supervised by

    Professor Dr. Ahmed S. El-Karamany

    2010

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    Supervisor Certification

    We certify that this thesis entitled" Introduction of Fractional

    Calculus" have been made by the Bachelor student

    AMNA ABDULSALAM YOUNIS AL-AMRYunder my supervision at the

    University of Nizwa as Partial Fulfillment of the Requirements for the

    Degree of Bachelor of Education in Mathematics.

    Signature

    Professor Dr. Ahmed Sadek El-Karamany

    In view of the available of the recommendations I forwarded this

    thesis for debate the examining committee.

    Signature

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    Committee Certification

    We certify that, we have read this project entitled" Introduction of Fractional

    Calculus " and examining committee examined the student AMNA

    ABDULSALAM YOUNIS AL-AMRY in its contents and what it connected with it,

    and that our opinion it meets the standard of project for degree bachelor of Education

    in Mathematics.

    1) Signature

    Name: Professor Dr. Ahmed S. El-Karamany

    Chairman and Supervisor. Date: 27/5/2010

    2) Signature

    Name: Professor Dr. Mohammad Elatrash

    Member Date: 27/5/2010

    3) Signature

    Name: Dr. Mahmood Khalid Jasim

    Associate Professor

    Member Date: 27/5/2010

    Approved by:

    Professor Dr. Ahmed S. El-Karamany

    Head of Department of Mathematical and Physical Sciences.

    Date: 27/5/2010

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    Abstract

    i

    AAbbssttrraacctt

    This work is devoted to exploreFractional Calculus whichhas been used

    successfully to modify many existing models of Physical processes.

    The Work consists of 5 chapters. In chapter 1; the introduction, some historical notes

    and an approach to fractional calculus using generalization of Cauchy formula for

    n folde integral. Laplace transform of the convolution and its properties are given.

    Integrals and derivatives of fractional order are defined in chapter 2. In this Chapter

    integrals and derivatives of fractional order of power and exponential functions are

    calculated. Semi-integrals and semi-derivatives of power function, exponential function,

    sine and cosine functions are given in chapter 3. In chapter 4 some illustrating solved

    problems are given. The Tautochrone problemisdiscussed in chapter 5 as an applicationof semi-derivatives in solving Abels integral equation. A list of references is given at the

    end of this project.

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    ACKNOWLEDGEMENT

    Thanks firstly and finally to God who deserves all thanks.

    I would like to express my deep appreciation to my supervisor

    Professor Dr. Ahmed Sadek El-Karamany the Head of department of

    Mathematical and Physical Sciences for his encouragement, Support,

    guidance and valuable suggestions. His enthusiasm and interest for

    science are contagious.

    I was also lucky to be able to associate myself with the talented

    and hard working members of the DMPS.

    My special thanks are due to the University of Nizwa, College

    of Arts & Sciences and to all staff members for their assistance and

    support during my study.

    My thanks also go to my friends and colleagues for their support

    and help.

    AMNA ABDULSALAM YOUNIS AL-AMRY

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    1

    Chapter 1

    Introduction1.1 Introduction

    Fractional calculus is three centuries old as the conventional calculus, but not very

    popular among science and/or engineering community. The beauty of this subject

    is that fractional derivatives (and integrals) are not a local (or point) property (or

    quantity). Thereby this considers the history and non-local distributed effects. In

    other words, perhaps this subject translates the reality of nature better! Therefore

    to make this subject available as popular subject to science and engineering community,

    it adds another dimension to understand or describe basic nature in a better

    way. Perhaps fractional calculus is what nature understands, and to talk with nature

    in this language is therefore efficient. For the past three centuries, this subject was with

    mathematicians, and only in last few years, this was pulled to several (applied) fields

    of engineering , science and economics. However, recent attempt is on to have

    the definition of fractional derivative as local operator specifically to fractal science

    theory. Next decade will see several applications based on this 300 years (old) new

    subject, which can be thought of as superset of fractional differintegral calculus, the

    conventional integer order calculus being a part of it. Differintegration is an operator

    doing differentiation and sometimes integrations, in a general sense. In this project,

    fractional order is limited to only real numbers; the complex order differentigrations

    are not touched. Also the applications and discussions are limited to fixed fractional

    order differintegrals, and the variable order of differintegation is kept as a future

    research subject. Perhaps the fractional calculus will be the calculus of twenty-first

    century. In this project, attempt is made to make this topic application oriented forregular science and engineering applications. Therefore, rigorous mathematics is

    kept minimal. In this introductory chapter.

    1.2 Birth of Fractional Calculus

    In a letter dated 30th September 1695, LHopital wrote to Leibniz asking him a

    particular notation that he had used in his publication for the nth derivative of a

    function

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    2

    n

    n

    D f

    Dx

    i.e., what would the result be ifn = 1/2. Leibnizs response an apparent paradox

    from which one day useful consequences will be drawn. (Debnath 2004) In these

    words, fractional calculus was born. Studies over the intervening 300 years have proved

    at least half right. It is clear that within the twentieth century especially numerous

    applications have been found. However, these applications and mathematical background

    surrounding fractional calculus are far from paradoxical. While the physical meaning is

    difficult to grasp, the definitions are no more rigorous than integer order counterpart.

    1.3 Fractional Calculus as Generalization of Integer Order Calculus

    Let us consider n an integer and when we sayxn we quickly visualizex multiply n

    times will give the result. Now we still get a result ifn is not an integer but fail to

    visualize how. Like to visualize 2is hard to visualize, but it exists.

    An approach to fractional calculus may be given using the generalization of Cauchy

    formula for n folder integral , the Laplace Transform of the convolution and its

    properties (Gorenflo and Mainardi 1997).

    The Laplace Transform of the function ( )f t is defined by

    0

    { ( )} ( ) ( )stL f t e f t dt F s

    = = (1.1)

    The convolution of two functions ( )f t and ( )g t is denoted by ( )( ) f g t and is

    defined by the relation

    0 0

    ( )( ) ( ) ( ) ( ) ( )

    t t

    f g t f t x g x dx f t y g y dy = = (1.2)

    It is easy to prove that

    0 0

    ( )( ) ( ) ( ) ( )( ) ( ) ( )

    t t

    f g t f t x g x dx g f t g t x f x dx = = = (1.3)

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    3

    We prove the following theorem

    Theorem 1.1:

    {( )} { ( )} { ( )} ( ) ( )L f g L f t L g t F s G s = = (1.4)

    where

    ( ) { ( )}, ( ) { ( )}F s L f t G s L g t = = (1.5)

    Proof: From the definitions of Laplace transform and the convolution we get

    0 0 0 0

    { } ( ( ) ( ) ) ( ) ( )

    t t

    st st L f g e f y g t y dy dt e f y g t y dydt

    = = (1.6)

    The region of integration is a simple vertically region in the tOy plane where Oy is the

    vertical axis and Otis the horizontal axis.

    It is the triangle in the first coordinate quarter whose base in the infinity and whose sides

    are the axis Ot and the line y t= : {( , ) : 0 0 }V R t y t y t = < .

    Reversing the order of integration we convert the region to simple horizontally:

    {( , ) : 0 }h R t y y t y= < < and the integral (1.6) takes the form

    0 0 0

    0

    { } ( ) ( ) ( ) ( )

    ( )( ( ) )

    tst st

    y

    st

    y

    L f g e f y g t y dydt e f y g t y dtdy

    f y e g t y dt dy

    = =

    =

    Substituting t y x = into the internal integral, where y is kept fixed, we get

    ( )

    0 0 0

    0 0

    { } ( )( ( ) ) ( )( ( ) )

    ( ( ) )( ( ) ) ( ) ( )

    st s x y

    y t y y x

    sy sx

    L f g f y e g t y dt dy f y e g x dx dy

    e f y dy e g x dx F s G s

    +

    = = = =

    == =

    = =

    This proves the theorem. As a consequence we have

    1

    0

    { ( ) ( )} ( ) ( ) ( )

    t

    L F s G s f g f t x g x dx = = (1.7)

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    4

    Below is the Laplace transforms and inverse Laplace transforms of some functions that

    play an essential role in the generalization we are going to present

    The Laplace transform and the inverse Laplace transform of some functions:

    Laplace Transform The Inverse Laplace Transform

    11 ( 1)!{ }n

    n

    nL t

    s

    =1

    1 1{ }( )

    n

    n

    tL

    ns

    =

    2

    0

    ( ){ ( ) }

    tF s

    L f x dxs

    =1

    0

    ( ){ } ( )

    tF s

    L f x dxs

    =

    3

    2

    0 0

    ( ){ ( ) }

    t t

    F s L f x dxdxs

    = 1

    2

    0 0

    ( ){ } ( )

    t t

    F s L f x dxdxs

    =

    4

    0 0

    ( ){ ( ) }

    t t t

    n

    o

    n

    F s L f x dxdx dx

    s=

    1

    0 0 0

    ( ){ } ( )

    ( )

    t t t

    nn

    n

    n

    F s L f x dxdx dx

    s

    D f t

    =

    =

    Where

    21 2 1

    0 0

    ( ) 2 p x p x p x e dx x e dx

    = = (1.8)

    Using the convolution theorem with

    11( ) , ( )

    ( )

    n

    n

    tG s g t

    ns

    = =

    we obtain

    11 1 1

    0 0

    ( ) 1 1{ } ( )( ) ( )( ) ( )

    ( ) ( ) ( )

    t tnn n

    n

    F s t L f t f x t x dx x f t x dx

    n n ns

    = = =

    Therefore, we get from the last row

    1 1

    0 0

    1 1( ) ( ) ( ) ( )

    ( ) ( )

    t t

    n n n D f t t x f x dx x f t x dx

    n n

    = = (1.9)

    Here we have used that if two continuous functions have the same Laplace transform they

    are identical (Learch Theorem). This means that we restrict our derivation to include only

    continuous functions

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    6

    Chapter 2

    Fractional integrals and derivatives

    Definition (1):Let 0 > and let be continuous on (0, ) and integrable on any

    finite subinterval[ , ]a b . Then we shall say

    that is an element in the class C, and for 0t > , we call

    1

    0

    1( ) ( )

    ( )

    t

    D f t x f x dx

    =

    (2.1a)

    the Riemann-Liouville fractional integral of ( )t of order 0 > .The symbol

    ( )J f is also used for the expression (2.1) . We can add to the definition (1) that

    0 0( ) ( ) ( )J f t D f t f t = = , 1 1

    0

    ( ) ( ) ( )t

    J f t D f t f t dt = = (2.1b)

    Using the linearity property of the definite integral we obtain

    11 2 1 2

    0

    1[ ( ) ( )] ( ) [ ( ) ( )]

    ( )

    t

    D C f t C g t t x C f x C g x dx

    = (2.2)

    1 11 2

    1 20 0

    ( ) ( ) ( ) ( ) ( ) ( )( ) ( )

    t tC C

    t x f x dx t x g x dx C D f t C D g t

    = =

    Where 1C and 2C are constants.

    Because we now have a well-defined class of functions to which our definition of

    the fractional integral applies, it is worthwhile to see the fractional integrals of

    the power function . The fractional integration of even the simplest functions can lead

    to complicated higher transcendental functions.

    Example (1): The fractional integral of the power function.

    Let ( ) , 1 f t t = > . Then,

    1

    0

    1( ) ( )

    ( )

    t

    D t t x x dx

    = (2.3)

    Substituting x t u= into Eq. (2.3) we get

    1

    1

    0

    ( ) ( 1)( ) (1 ) ( , 1)

    ( ) ( ) ( 1)

    t t t D t u u du B

    + + + += = + =

    + +

    (2.4)

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    7

    Example (2): The fractional integral of the constant function

    Let ( ) f t C = . Then, using the preceding expression (2.4) and the linearity

    property (2.2) one obtains

    ( )D C =

    0 0

    ( 1)lim[ ( )] lim( 1) ( 1)

    Ct C t D Ct

    +

    += =

    + + + (2.5)

    As special case we get the fraction integral of ( ) 1f t =

    (1) 0( 1)

    tD

    = >+

    (2.6)

    Example (3): The fractional integral of the exponential function

    ( ) , 0.tt e =

    1 ( ) 1

    0 0

    1( )

    ( ) ( )

    t ttt t x xe D e x e dx x e dx

    = =

    Substitution x u = leads to:

    1

    0

    ( ) ( , ) ( , )( ) ( )

    tt tt u

    t

    e e D e u e du t E

    = = = (2.7)

    Where: the incomplete gamma function ( , )x is defined by the relation:

    1

    0

    ( , )

    x

    t x t e dt = (2.8)

    and the Et- function ( , )tE is defined by the relation:

    ( , )( , )

    ( )

    t

    t

    e tE

    = (2.9)

    Definition (2):: The fractional derivative of ( )t of order 0> (if exists) can be

    defined in terms of fractional integral ( )D f t as:

    ( )( ) ( )m mD f t D D f t = (2.10)

    Where m is an integer [ ] , and [ ] , [ , 1)x n x n n= + is the ceiling function

    (the greatest integer that equal or less thanx ).

    Example (4): The fractional derivative of the power function

    ( ) , 1t t

    = >

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    8

    Applying the definition (2.10) Using Eq. (2.4) with m = we get

    ( ) ( 1)( ) [ ( )]

    (1 )

    mm m m t

    D t D D t D

    m

    + += =

    + +

    (2.11)

    Sincem is integer, Eq. (2.11) yields

    [ ( 1)][( )( 1) ( 1)]( )

    (1 )

    m m tD t

    m

    + + + +=

    + +

    (2.12)

    From the properties of the Gamma function we have

    ( 1 ) ( )( 1) ( 1) ( 1)m m m + + = + + + + (2.13)

    Substituting from (2.13) into Eq. (2.12) we get

    ( 1)( ) ( )

    ( 1 ) D t t

    +=+

    (2.14)

    For integer m and n we have

    ( 1)( ) ( ),

    ( 1)

    n m m nm D t t m n

    m n

    += > +

    (2.15)

    Example (5):The fractional derivative of a constant function

    Eq. (2.14) when 0 yields

    (1) ,(1 )

    tD

    =

    ( is a noninteger ) (2.16)

    Before proving some properties of the fractional derivatives we introduce the Leibniz

    rule for the fractional derivative of product of two functions.

    Leibniz rule: For integer n the Leibniz rule for the product of two n times

    differentiable functions can be written in the form

    ( ) ( ) ( ) ( )

    0

    1 2 2

    ( 1)[ ( ) ( )] ( ) ( )

    ( 1) ( 1 )

    ( 1)( ) ( ) ( ) ( ) ( ) ( ) ( ) ( )

    2

    k n

    n n k k

    k

    n n n n

    nD f t g t D f t D g t

    k n k

    n nD f t g t n D f t Dg t D f t D g t f t D g t

    =

    =

    += + +

    = + + + +

    0

    ( 1)( ) ( )

    ( 1) ( 1 )

    k nk n k

    k

    nD f t D g t

    k n k

    =

    =

    +=

    + + (2.17)

    The analogy between the two expressions (2.14) and (2.15) suggests to generalize

    (2.17) for the fractional derivative of order 0 > as follows

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    9

    ( ) ( ) ( )0

    1

    ( 1)[ ( ) ( )] ( ) ( )

    ( 1) ( 1 )

    ( ) ( ) ( ) ( ) ( ) ( )

    k k

    k

    D f t g t D f t D g t k k

    D f t g t D f t Dg t f t D g t

    =

    +=

    + +

    = + + + +

    0

    ( 1) ( ) ( )( 1) ( 1 )

    k k

    k

    D f t D g t k k

    =

    += + + (2.18)

    Since is not integer the upper limit of the sum in (2.18) is infinite.

    Now, we are able to prove the following properties of the fractional derivative.

    Property (1):Let ( )g t C= is the constant function, then

    [ ( )] [ ( )]D Cf t CD f t = (2.19)

    Proof:since 0 ,D C C = and 0, 1,2,m D C m= = we get upon substituting

    ( )g t C= into (2.18):

    ( ) ( )0

    ( 1)[ ( ) ] ( ) ( ) ( )

    ( 1) ( 1 )

    k k

    k

    D f t C D f t D C D f t C C D f t k k

    =

    += = =

    + +

    Property (2):

    ( ) ( )[ ( ) ( )] ( ) ( )D f t h t D f t D h t + = + (2.20)

    Proof: Let0

    ( ) 1g t t= = then, ( )0

    [ ( ) ( )] [ ( ) ( ) ]D f t h t D t f t h t

    + = + and

    ( )

    ( ) ( )

    0 0

    0

    0

    0

    ( 1)[ ( ) ( ) ] ( )

    ( 1) ( 1 )

    ( 1)( ) ( ) ( )

    ( 1) ( 1 )

    k k

    k

    k k

    k

    D t f t h t D f t D t k k

    D h t D t D f t D g t k k

    =

    =

    ++ =

    + +

    ++ = +

    + +

    Combining properties (1) and (2) we obtain the following linearity property of the

    fractional derivative

    ( ) ( )1 2 1 2[ ( ) ( )] ( ) ( )D C f t C h t C D f t C D h t + = + (2.21)

    Where 1C and 2C are constants.

    Theorem (1): The Index law for fractional integrals

    (i)( )

    ( ( )) ( )D D f t D f t += (2.25a)

    (ii) ( ( )) ( ( ))D D f t D D f t = (2.25b)

    For C

    , 0 1< the substitution 2x u = leads to:

    1 22

    0

    2( )( ) erf ( )

    tt tt ue e D e e du t

    = = (3.5)

    Where2

    0

    2erf ( )

    t

    xt e dx

    = is the error function.

    Setting lna = where 0, 1a a> in Eq. (3.5)we get

    12 ( ) erf ( ln )

    ln

    tt a

    D a t a

    a

    = (3.6)

    The semi- derivative of the exponential function can be obtained from (3.5) using the

    definition (3.2):

    12

    1( ) erf ( )t t D e e t

    t

    = + (3.7)

    Where used the Leibnizs formula

    ( )

    ( )

    ( ) ( ( )). ( ( )).

    v t

    u t

    d dv duf x dx f v t f u t

    dt dt dt =

    (3.8)

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    15

    From Eqs. (3.3b) , (3.5) and (3.7) we get:1 12 2

    1( ) ( 1)t t D e D e

    = ,

    4): The functionssint andcost :

    12

    0

    1 sin( ) 2(sin ) [sin ( ) cos ( )]

    t

    t x dx D t t C t t S t x

    = = (3.9)

    12

    2(cos ) [cos ( ) sin ( )] D t t C t t S t

    = + (3.10)

    Where ( )C t and ( )S t are the Fresnel integrals defined by the relations

    2 2

    0 0

    ( ) cos( ) , ( ) sin( ) ,

    t t

    C t y dy S t y dy= = and therefore, we have

    2 2

    0 0

    ( ) cos( ) , ( ) sin( ) ,

    t t

    C t y dy S t y dy= = (3.11)

    The semi -derivatives can be obtained from the definition (3.2) using Leibniz formula

    (3.8) as:

    1 12 2

    2(sin ) { (sin )} { [sin ( ) cos ( )]}

    dD t D D t t C t t S t

    dt

    = =

    2 1[cos ( ) sin ( )] [sin cos cos sin ]t C t t S t t t t t

    t = + + . Therefore,

    12

    2(sin ) [cos ( ) sin ( )] D t t C t t S t

    = + (3.12)

    Taking into consideration Eq. (3.10) we get

    1 12 2(sin ) (cos ) D t D t

    = (3.13)

    Similarly, we get1 12 2

    1(cos ) (sin ) D t D t

    t

    = (3.14)

    Taking into consideration Eq. (3.3a) the preceding equation can be written in the

    form:

    1 12 2(sin ) (1 cos ) D t D t

    = (3.15)

    AMNA ABDULSALAM YOUNIS AL-AMRY

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    16

    Chapter 4

    Examples

    (Semi- Integrals and Semi-Derivatives of Some Algebraic Functions)

    ( )f x 1/ 2

    0 0

    1 ( ) 1 ( )( )

    t t f x dx f t x dx

    D f xt x x

    = =

    1/2

    1/2

    ( )

    [ ( )]

    D f x

    D D f x

    =

    1 1( )

    x

    0

    1x

    y x z

    dy x dz

    dy

    y x y

    =

    =

    1

    1/ 2 1/ 2

    0

    1(1 )

    1 1 1( , )2 2

    z z dz

    B

    =

    = =

    zero

    2( )x

    0

    1

    3 1( , ) ( )2 2 2 2

    x

    y x z

    dy x dz

    x y dy

    y

    x x xB

    =

    =

    = = =

    2

    3 1

    1 x+

    0

    2(1 )sin ,

    2(1 )sin cos

    1

    1

    x

    y x

    dy x d

    dy

    x y y

    = +

    = ++

    1tan

    1

    0

    2 (1 ) sin cos 2tan ( )

    (1 ) sin cos

    xx d

    xx

    += =

    +

    1

    (1 )x x+

    41 x+

    0

    2(1 )sin ,

    2(1 )sin cos

    11x

    y x

    dy x d

    x y dy

    y

    = +

    = +

    +

    1(1 )tan ( )

    x xx

    += +

    11 tan ( )x

    x

    +

    5

    3/ 2

    1

    (1 )x+

    3

    0

    2(1 )sin ,

    2(1 )sin cos

    1

    (1 )

    x

    y x

    dy x d

    dy

    x y y

    = +

    = ++

    2

    (1 )

    x

    x =

    +

    2

    1

    (1 )

    x

    x x

    +

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    17

    6 1

    1 x

    0

    2(1 )sinh

    2(1 )sinh cosh

    1

    1

    x

    y x

    dy x d

    dy

    x y y

    =

    = +

    12tanh ( )x

    =

    1

    (1 )x x

    71 x

    2(1 )sinh

    2(1 )sinh cosh

    0

    11x

    y x

    dy x d

    x y dy

    y

    =

    =

    +

    1(1 )tanh ( )

    x xx

    +

    1

    1[

    tanh ( )]

    x

    x

    8

    3/ 2

    1

    (1 )x

    2(1 )sinh

    2(1 )sinh cosh30

    1

    (1 )

    x

    y x

    dy x d dy

    x y y

    = =

    +

    2

    (1 )

    x

    x =

    21(1 )

    xx x

    +

    9 1( )1 x

    0

    2

    2

    (1 ) tan

    2(1 )tan sec

    1

    (1 )

    x

    y x

    dy x d

    dy

    x y y

    =

    = +

    12sin ( )

    (1 )

    x

    x

    =

    3/ 2

    1

    3/ 2

    1

    (1 )

    sin ( )

    (1 )

    x

    x x

    x x

    x x

    +

    10 1( )1 x+

    0

    2

    2

    (1 ) tanh

    2(1 )tanh sech

    1

    (1 )

    x

    y x

    dy x d

    dy

    x y y

    = +

    = ++

    12sinh ( )

    (1 )

    x

    x

    =+

    3 / 2

    1

    3 / 2

    1

    (1 )

    sinh ( )

    (1 )

    x

    x x

    x x

    x x

    +

    +

    +

    11

    (1 )

    x

    x+

    0

    2sin

    2 sin cos

    1

    (1 )

    x

    y x t

    dy x t tdt

    x y dy

    x y y

    =

    =

    +

    1 x

    =

    +

    3/ 22(1 )x

    +

    12 1

    (1 )x x+

    0

    2sin

    2 sin cos

    1

    (1 )

    x

    y x t

    dy x t tdt

    dy

    x y x y y

    =

    =+ 3/ 22(1 )x

    +

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    19

    Cha pte r 5

    Applications

    The Tautochrone Curve

    A tautochrone curve or isochrone curve is the curve for which the time taken by an object

    sliding without friction in uniform gravity to its lowest point independent of its starting

    point. Abel was interested in the tautochrone problem; that is, determining a curve in the

    ( ),x y plane such that the time required for a particle to slide down the curve to its

    lowest point is independent of its initial placement on the curve.

    Firstly, we shall consider the time required for descent as a function of initial height.

    Let us fix the lowest point of the curve at the origin and position the curve in the positive

    quadrant of the plane, denoting by ( )0 0, M x y the initial point and ( ),P x y any point

    on the curve between (0,0)O and ( )0 0,x y . We denote the curve by ( )S S y= ( at

    P )and then, (0) 0S = . we also have the following conditions: at point M we have

    00,t y y= = , 0v = ( the initial velocity) and at point O we have

    0( ), 0, 0t T y y S= = = . Assuming no frictional losses we may apply the

    conservation of energy law (the sum of kinetic energy and potential energy is constant) :

    2 20

    1 1

    2 2 M M p P E mv mgy E mv mgy= + = = + . Since 0Mv = we get:

    20

    1( ) ( )

    2

    dSm mg y y

    dt= (5.1)

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    20

    Since the distance S is decreasing as the time increases we have 0dS

    dt< .

    Therefore, Eq. (5.1) leads to 0( ) 2 ( )dS dS dy

    g y ydt dy dt

    = = . Thus, separating the

    variables one obtains

    0

    ( )

    2( )

    dSdy

    dyg dt

    y y=

    (5.2)

    Integrating from 0,t = to t T= which corresponds from 0y y= to 0y = we get

    0

    0

    00

    ( / )2

    ( )

    T

    y

    dS dyg dt dy

    y y=

    . Therefore,

    0

    0

    00

    ( / )2 ( )

    ( )

    ydS dy

    g T y dyy y

    = (5.3)

    Equation (5.3) can be written in the form

    0

    ( / )2 ( )

    ( )

    ydS dz

    g T y dzy z

    =

    (5.4)

    Equation (5.4) is the Abels integral equation. We shall use the fractional calculus to

    obtain the solution of this equation (Samko et all 1993). Recalling the definition of the

    semi integral:1/2

    0

    1 ( )( )

    yf z

    D f y dzy z

    = we get

    1/2 1/2 1/22 ( ) (( / )) ( ( )) ( ( ))gT y D dS dy D DS y D S y = = = . (5.5)

    Therefore, we get

    1/22( ) { ( )}g

    S y D T y

    = (5.6)

    Thus, we have obtained the solution of Abels integral equation in terms of the semi-

    integral of ( )T y .

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    21

    Now, to get the required curve we must set ( ) .T y T Const = = and use

    1/2

    { } 2y

    D C C

    = and Eq. (5.6) becomes

    2 22( ) 2 2 , 2 / y g

    S y T ay a gT

    = = = (5.7)

    Differentiating both sides with respect to y one obtains

    2( ) 1 ( )dS y dx a

    dy dy y= + = , from which

    2 21 ( ) ( ) 1dx a dx a

    dy y dy y+ = = (5.8)

    Let

    2sin ( / 2)y a = . (5.9)

    Then from (5.8) we get

    cot( / 2) tan( / 2)dx dy

    dy dx = = (5.10)

    From (5.9) and (5.10) we get sin( / 2)cos( / 2) tan( / 2)dy dadx dx

    = = which leads to

    2cos ( / 2)

    dxa

    d

    = , and we get (1 cos )

    2

    dx a

    d

    = +

    From the preceding equation we obtain ( sin )2

    ax C = + + . The curve is passing

    through the origin so, 0x = at 0y = and therefore, 0C = . Thus we obtain the

    parametric equations of the tautochrone curve (a cycloid)

    ( sin ) (1 cos )2 2

    a ax y = + = (5.11)

    AMNA ABDULSALAM YOUNIS AL-AMRY

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    22

    References

    [1] L. Debnath, (2004), A brief historical introduction to fractional calculus, INT. J.

    MATH. EDUC. SCI., TECHNOL., vol. 35, No 4, 487-501.

    [2] Gorenflo, R. and F. Mainardi (1997) , Fractional calculus : integral and differential

    equations of fractional order, in Fractals and Fractional Calculus in Continuum

    Mechanics (Ed. A. Carpinteri and F. Mainardi), Springer Verlag , Wien.

    [3] Oldham Keith B. and Spanier Jerome.( 2002), The fractional Calculus, 2nd

    Ed,

    Dover Publications , INC, Mineola, New York.

    [4] I. Padlubny (1999), Fractional Differential Equations, Academic Press, N.Y.

    [5] Samko S. G., Kilbas, A. A. and O. I. Marichev (1993), Fractional Integrals and

    Derivatives, Theory and Applications, Gordon and Breach, Amsterdam.

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    Learning Outcomes

    1. I knew about modern branches in Mathematics and theirapplications.

    2. I reviewed many subjects such as Laplace Transforms, Gammaand Beta functions, double integrals and techniques ofintegration. I learned how to use many mathematical skills.

    3. I learned new subjects like the error function, Fresnel integralsDawsons function, incomplete Gamma function .and Etfunction which were not taught in the undergraduate program.

    4. This Project helped me to gain much knowledge in physics andgeometry.

    5. Helped me in gaining critical thinking.

    AMNA ABDULSALAM YOUNIS AL-AMRY