mehran rajabi

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6 years, 250 days

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These are replies submitted by mehran rajabi

@Kitonum 

tnx, can I solve this below equation with this method:

eq := diff(F1(zeta), zeta, zeta)-b^2*F1(zeta)+2*exp(-b*zeta)*G1(zeta)+(exp(2*b*zeta)-2*exp(b*zeta)+1)*exp(-2*b*zeta)*(exp(b*zeta)*exp(-2*b*zeta)/(3*b)-(2*(exp(b*zeta)-1))*exp(-2*b*zeta)/(3*b))/(3*b^3)-(exp(b*zeta)-1)^2*(exp(-2*b*zeta))^2/(9*b^4)+(1/3)*(exp(b*zeta)-1)*exp(-2*b*zeta) = 0, diff(G1(zeta), zeta, zeta)-b^2*G1(zeta)-(exp(2*b*zeta)-2*exp(b*zeta)+1)*exp(-2*b*zeta)*exp(-b*zeta)/(3*b^2)-(2*(exp(b*zeta)-1))*exp(-2*b*zeta)*exp(-b*zeta)/(3*b^2)+b^2*exp(-b*zeta) = 0, 2*F1(zeta)+diff(H1(zeta), zeta) = 0
ics := F1(0) = 0, G1(0) = 0, H1(0) = 0, F1(infinity) = 0, G1(infinity) = 0

@nm 

tnx for the answer, I got this answer but I won't that inform limit, my answers must be:

@tomleslie 

alpha=sqrt((G*A)/(E*MI))

@acer 

thank you for your answer, I answer your questions hereunder:

I want to look for all the solutions and solve the system with the numeric method but when I use the fsolve command don't have all the answers and when using the solve command it takes a long time. is there any code, for example, Newton method code for solving it or I have to use the solve or fsolve commands? if I want to supposed to implement numeric rooting from scratch how can I do it?

with regards...

@Kitonum 

thank you, but is there any other command except solve & fsolve? because when numbers of my equations are increasing the solve command very takes a long time.

tnx...

@tomleslie 

thank you so much, if I want to write t[1],t[2],... instead of the t1,t2,... in your code, how can I do it? 

with regards. 

 

@Carl Love 

thank you for your answer, my unknowns are x[0], x[1], y[0],  y[1] but I want to solve them numerically by Newton’s method in t=0.5 for example.

@Kitonum 

thank you for your answer, I have to use the Gauss–Legendre quadrature rule for EQ after transformation that you did, has the Maple command for this rule? 

@Kitonum 

tnx my friend, I followed this command(unapply). thank you. 

@Carl Love 

tnx for your answer, I know that but can you express f function in terms of zeta only? my goal is to express f function in terms of zeta only and no x in it. 

@Carl Love 

Thank you so much, but this equation has several roots, how can I get the other roots?

@tomleslie 

thank you for this point but that answer(

https://www.mapleprimes.com/questions/227667-Solve-PDE-With-RungeKutta-Method-And-Plot

) has been deleted!!!

@tomleslie 

I created the right PDE and attached again, and the boundary conditions are:

w(0,t)=0
wx(0,t)=0
wxx(L,t)=0
wxxx(L,t)=0

and the initial conditions are:

w(x,0)=0
wt(x,0)=0

PDE := 35139.16048*(diff(w(x, t), x, x, x, x))+98646.00937*(diff(w(x, t), t, t))-2771.636*(diff(w(x, t), x, x)) = 24883.20000

code.mw

@Carl Love 

nothing, there aren't points for those states, you are right, in partial derivatives we always assume that the other variables are constant, thank you, you solved my problem.

 

@Carl Love 

Diff(P,T)[V] is diff(P,T) when V is constant and Diff(P,V)[T] is diff(P,V) when T is constant, infact I want to obtain the diff(P,T) , diff(P,V) and diff(P,V,V) with this equation:

EQ := V^3-R*T*V^2/P-(B^2+P*B*R*T*sqrt(T)/(P-A))*V-A*B/(P*sqrt(T)) = 0;

 

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