I'm working with some sum values, but for some reason that I can't figure out, this sum always returns 1.
Have I made some mistake in the way it's supposed to be typed in or why does it return 1? Below the sum I've filled out the spots manually to show how I want them to be.

Download Sum_fejl.mw

The issue concerns calculation of 2nd derivative of the numerical solution of 2nd order BVP for an ordinal DE.

Lets consider a test problem:

-y’’(t)+y(t)=t*sin(5*t)

y(0)=0.2, y(1)=1

 Numerical solution was obtained by

dsolve([-diff(F(x), x$2)+F(x)= x*sin(5*x), F(0)=0.2, F(1)=1], [F(x)], type = numeric, 'output' = Array([seq(k/5, k=0..5)]));

dsolve returns the values of the solution and its 1st derivative (for the test example, a solution can be obtained analytically, but for general case I require numerical solution)..

It is needed to calculate the 2nd derivative of the solution.

I tried to use the Bessel method, when the solution’s 2nd derivative is calculated as the 2nd derivative of 5th degree polynomial having in consequent points t₁, t₂, t₃ the values y(t₁), y(t₂), y(t₃) and 1st derivatives y’(t₁), y’(t₂), y’(t₃), all obtained from the numerical solution. Later I use Hermit piecewise-polynomial interpolation, based on values of the solution and its 1st and 2nd derivatives (polynomial of 5th degree).

Unfortunately, 2nd derivative of such interpolation has a large non-smoothness.

Here, we see the solution. It is smooth.

Here, 1st derivative. Still smooth enough.

Here, 2nd derivative. Typical view with large and sharp teeth.

Maybe, there exists a simple method for calculation of more smooth 2nd derivative?

Also. it is desirable that it would be embedded in Maple.

How I can solve these time delay  differential equations?

please see attatched files.

Best

Doc191.pdf

ny.mw

Download ny.mw

Hi guys and girls, 

The new Maple 2018 have a feature in the buttom called editable. If you remove that mark in the buttom of the screen, then maple doc can't be edited. I teach students who have english as a second language and some remove the mark in the editable box by mistake. Such that they can't do there hand-ins etc. 

So is there anyway to disable the editable box in the buttom of the screen? 

thanks in advance.

Fred

 Is it possible to write the equation in Maple and produce the Latex code of it? Thanks in advance!

with(plots); R1 := .1; R0 := .1; m := .1; a := .1; Ha := .1; Nt := .1; Nb := .1; Pr := 6.2; Le := .6; Bi := 1; Ec := .1; k := 1; r := .1; A := 1; fcns := {C(y), T(y), U(y), W(y)}; sys := diff(U(y), `$`(y, 2))+(R1*(diff(U(y), y))-2*R0*W(y))*exp(a*T(y))-a*(diff(U(y), y))*(diff(T(y), y))-Ha*(U(y)+m*W(y))*exp(a*T(y))/(m^2+1)-U(y)/k+A*exp(a*T(y)) = 0, diff(W(y), `$`(y, 2))+(R1*(diff(W(y), y))+2*R0*U(y))*exp(a*T(y))-a*(diff(W(y), y))*(diff(T(y), y))-Ha*(W(y)-m*U(y))*exp(a*T(y))/(m^2+1)-W(y)/k = 0, diff(T(y), `$`(y, 2))+R1*Pr*(diff(T(y), y))+Pr*Ec*exp(-a*T(y))*((diff(U(y), y))*(diff(U(y), y))+(diff(W(y), y))*(diff(W(y), y)))+Nt*(diff(T(y), y))*(diff(T(y), y))+Pr*Ec*(U(y)*U(y)+W(y)*W(y))*exp(-a*T(y))/k = 0, diff(C(y), `$`(y, 2))+Pr*Le*R1*(diff(C(y), y))+Nt*(diff(C(y), `$`(y, 2)))/Nb-r*C(y) = 0; bc := U(0) = 0, W(0) = 0, C(0) = 0, (D(T))(0) = Bi*(T(0)-1), U(1) = 0, W(1) = 0, C(1) = 1, T(1) = 0; L := [.5, 1.0, 1.5, 2.0]; AP := NULL; for k to 4 do R := dsolve(eval({bc, sys}, Ha = L[k]), fcns, type = numeric, method = bvp[midrich], AP); AP := approxsoln = R; p1u[k] := odeplot(R, [y, U(y)], 0 .. 1, numpoints = 100, labels = ["y", "U"], linestyle = dash, color = black) end do; display({p1u[1], p1u[2], p1u[3], p1u[4]})

for small value of k no change show in plot... the resulted value is so small and the system consider it zero and show no change in plot.. then how to get the change in plot to change in k... ??? plz suggest 

Download Crank_scheme_4.mw
 

Download Crank_scheme_4.mw

Dear all, I had a challenge of using maple to obtain numerical solution of a volterra-integral equation using the method of reproducing kernel space, however I converted the integral equation to an ode and try to solve it numerically but obtatined an error message. Please how do I overcome it? the problem is as follows:

dsn := dsolve({diff(u(x), x) = e^x*ln(e)+(2/9)*e^3-1/9+int(y*u(y)^3, y = 0 .. 1), u(0) = 1}, numeric)

Here in my code I am trying to differentiate a finite summation and the command Sum is giving me a simpler evaluation than the command sum.

But I have a problem, the command Sum doesn't work under signal processing tool. Is there away to make it work?

For some unknown reason, the code below does not work in Maple 2018.1, but works in Maple 2015 and Maple 2017 (the idea is taken from here) 

restart; 
with(plottools): with(plots):
V1,V2,V3,V4,V5,V6,V7,V8:=[0,-1,0],[0,0,0],[1,0,0],[1,-1,0],[0,-1,1],[0,0,1],[1,0,1],[1,-1,1]:  # The vertices of the cube
Faces:=[[V1,V4,V8,V5],[V5,V6,V7,V8],[V2,V3,V7,V6],[V1,V2,V3,V4],[V3,V4,V8,V7],[V1,V2,V6,V5]]: # The list of the faces
Colors:=[green, red,RGB(1, 0, 4),blue,grey,gold]: # The list of the colors
Cube[0]:=display([seq(polygon(Faces[i],color=Colors[i]),i=1..6)]):

for n from 1 to 7 do
F[n]:=t->rotate(Cube[n-1],t, [[0,n-1,0],[1,n-1,0]]):
Cube[n]:=rotate(Cube[n-1],-Pi/2, [[0,n-1,0],[1,n-1,0]]):
A[n]:=animate(display,[F[n](t)], t=0..-Pi/2,paraminfo=false);
od:

for m from 6 to 0 by -1 do
G[m]:=t->rotate(Cube[m+1],t, [[0,m,0],[1,m,0]]):
B[m]:=animate(display,[G[m](t)], t=0..Pi/2,paraminfo=false);
od:

C1:=display([seq(A[k], k=1..7)], insequence):
C2:=display([seq(B[k], k=6..0, -1)], insequence):
display([C1,C2], insequence, scaling=constrained, axes=normal);

I currently have a procedure that runs a fairly complicated formula involving non-commutative variables. The procedure is Vu(a, b, c) where a, b, and c are any integers. I have to run this formula whenever v_a^cu_b appears in my expression. I'm currently replacing each variable of this type with the procedure Vu(a, b, c). I'm wanted to automate that process if possible. One thought I had was to assign the value of Vu(a, b, c) to the variable v_a^cu_b for any value of a, b, and c from 1 to 5. Then use the eval command to replace the variables with the proper values. Is there any way to automate this process? Let me give you an example:

v₀u₀ = u₀v₀ + 2w₀

So u₀v₀u₀ = u₀(u₀v₀+2w₀) = u₀²v₀+2u₀w₀

I have a procedure to truncate algebraic equations. Found the basic answer hrere. I would like to make it handle equations and functions i.e f:=a x^2 +b y... and f(x,y):=c x y^2.... I can make it handle the first type but not the second.

Download Truncate.mw

Could anyone tell me why Maple changes the sign of some expressions? For example...

How to prevent this changes?

Thanks in advance,

Denis

How to linearize this complex dynamical system around x1(t)=0, x2(t)=0, x3(t)=0. Basically i want to keep nonlinear part up to fifth order on the right hand side and later want to drop it. How can i do it. The maplesheet Dyn_system.mw is attached.

Many thanks in advance.