hi i did this in maple and i get an error when i try to solve the system of equation  :

restart;
with(Student[VectorCalculus]);
with(PDEtools);with(plots);

h_f := 300;
h_a := 1000;
T_f := 1500 + 273;
T_a := 30 + 273;
k_r := 15;
k_s := 70;
Ra := 5;
Rf := 6.05;
Rc := 6;

Hello. I'm plotting in polar coordinates. I use to build an expression

polarplot(MF(t), t = 0 .. 2*Pi, color = black, linestyle = 1, thickness = 3, coordinateview = [0 .. 11, 0 .. Pi], axesfont = ["TIMES", "ROMAN", 20], scaling = CONSTRAINED)

At the top there is a lot of empty space. Are there any settings that will allow you to remove the empty space and build only the part of the grid where the graph is located?

I like using Record in Maple. It allows me to collect related variables to pass around inside one object. (Like with Pascal or Ada records or C struct).

But I find myself copying the record definition over and over everywhere I want to use the same specific record layout.

Is there a way to define specific record layout somewhere, may be as a type and give it a name, and then in each proc I want to make a variable of this record type, just tell Maple that this variable is a record of that type so I do not have to explicity define the record there each time? 

Here is a simple example to make it more clear

foo:=proc() #some proc that uses same Record layout
   local S;
   S:=Record('name','age');   
   S:-name:="joe doe 1";
   S:-age:=99;
   return S;
end proc:

boo:=proc() #another proc that wants to use same Record layout
   local S;
   S:=Record('name','age');   
   S:-name:="joe doe 2";
   S:-age:=80;
   return S;
end proc:

S1:=foo();
S2:=boo();

These proc's can be anywhere, such as inside package or module, either local or exported.

I just want to avoid having to type   S:=Record('name','age');   Each time. I want to tell Maple that a local variable is of this specific Record layout, without having to type the layout explicitly.

This way, when I add new field to this Record,  I just have to do it in one place and not in 10 places in the code. 

I think I need to add a new type? But do not know how to do this.  I hope the question is clear. If not, will add more information.

How can I fix the error of ChangeOfVariables: Error, (in Student:-MultivariateCalculus:-ChangeOfVariables) unable to solve the change-of-variables equations for the original variables ?

Thanks!

I am preparing a document where in I want to show half circle inide the drawing. I can plot a half circle, but can not bring it inside the drawing canvass. Is there a way to show smooth curves inside the drawing. Pencil tool helps to show my curve, but not a smooth one! In any picture tool, bring forward, sent backward options will be there. Are there such tools in maple?
Thanks for answers.

Cheers.

Ramakrishnan V
 

Download drawing_semicircle.mw

Hello everyone

I have the solution of diffusion equation from Help of maple website. I put the code here

*****************************

restart: with(plots):
 

unprotect(D);
 

alias(c[0]=c0, c[1]=c1, c[2]=c2);
PDE:=diff(C(x,t),t)=D*diff(C(x,t),x,x);
IBC:={C(x,0)=cx0, C(0,t)=ct0, D[1](C)(10,t)=0};
ct0:=1;
cx0:=0;
D:=1;
pds:=pdsolve(PDE,IBC,numeric);
L1:=[0.01, 0.1, 1, 5, 10];
L2:=[red, green, yellow, blue, magenta, black];
for i from 1 to 5 do
 pn[i] := pds:-plot(t=L1[i], color=L2[i]):
end do:
display({seq(pn[i], i=1..5)}, title=`Numerical solution at t=0.01, 0.1, 1, 5, 10`);

****************************

the code is working perfectly. But, My question is how can I found the diffusion constant (D) if I have the solution ( C(x,t) ).  Probably it should be an algorithm which use least square method to find (D) based on the data C(x,t).

I am looking for a fast and efficient algorithm if there is any.

thank you so much for your kind attentions in advance

Sincerely yours,

Amir

This ODE turns out to be a simple separable ODE. With one solution, if the ODE is rewritten.

But in its original form, Maple dsolve gives 6 complicated looking solutions with complex numbers in some of them. Even though all 6 solutions are valid.

Any one knows why Maple did that and not give the one simple solution instead? 

I used isolate to solve for y' from the original ODE. Verfiied that only one solution exist.  The ODE then became y'(x)= 3*y(x)/(2*x). Which by uniqueness theorem, should have one unique solution in some region in the RHS or in some region in the LHS that does not inculde x=0 ?

Just wondering what is going on, and why Maple did not give same simpler solution, so I can learn something new. That is all.

Download strange_ode_answer.mw

Maple 2019.1

Physics 395

Hi, I am trying to plot the phase potrait for this as follow:

s0 := 3*10^5;
d := 10^(-3);
delta := 10^4;
b := 5*10^6;
lamda := 4.16;

DEplot([diff(I(t), t) = s0 + I(t)*(-d - delta*Q(t)/(b + Q(t))), diff(Q(t), t) = -lamda*Q(t)], [I(t), Q(t)], t = 0 .. 10, I = 0 .. 100, 0, Q = 0 .. 100, 0, dirfield = 400, arrows = smalltwo, number = 2, [[0, 4, 0.1], [0, 0.2, 4.1], [0, 7, 0.2], [0, 0.2, 7]], color = red, linecolor = blue, numsteps = 100)

But, there is an error saying "Error, (in DEtools/DEplot) vars must be declared as a list, e.g. [x(t),y(t),...]". However, I did the same for other problem and worked well tho. I have no idea what the problem is for above.

Please download 1.txt.

Integrand := parse(FileTools[Text][ReadFile]("1.txt")):

int(Integrand, [z = -R .. R, y = 0 .. R], numeric);

plots[implicitplot3d](Phi = phi, z = -R .. R, y = 0 .. R, Phi = 0 .. 0.1e-1, color = ColorTools[Gradient]("Red" .. "Blue", best)[4], grid = [50, 50, 20]);

Why the integrand has positive real amounts in the domain [z = -R .. R, y = 0 .. R] for R=0.5, but the integral value is negative?

Hi guys

I've created a joint display which plots a spacecurve and an arrow which represents the tangent to the curve:

I've written this in the animation format so I can move the tangent arrow along the curve, however when I replace

arrow(subs(s=0,p),subs(s=0,ptan),width=0.3,length=4)

with

arrow(subs(s=A,p),subs(s=A,ptan),width=0.3,length=4)

I get the error:

Error, (in Plot:-AnalyzeData:-StandardizeData) points cannot be converted to floating-point values

I have tried animating the arrow alone(see below) and this works fine, so the problem is coming from try to pass the animation parameter A into the display array of multiple plots.

DG.mw

Thanks

Hi

I have trouble with solving this ODE system using dsolve command:

and 

This system have following solutions:

where

and

C's and A are constants of integration.

They're equations from this paper https://arxiv.org/abs/1710.01910 (45 and 47). 
               

However, my solution differs from correct one - in output there are hypergeometric functions everywhere.

Is there any way to fix/convert this solution? Or to get rid of these functions (my f1 solution looks very close to original one but with coupled hypergeometric function). 
 

Download question.mw

When I apply the uses function with the Physics package in a procedure, the commands in this package are not restricted to the inside of the procedure, but are applied globally. See the example below:

gds := proc(LL, qi, t)

 local ta,i;  

uses Physics;

ta := sec(diff(diff(LL, diff(qi[i](t), t)), t), i = 1 .. nops(qi));

RETURN(ta) end:

sxy := diff(x(t), t)^2 + diff(y(t), t)^2:

gds(sxy, [x, y], t);

Error, (in Physics:-diff) name expected for external function
 

On the other hand, when I apply the uses function with the LinearAlgebra package in a procedure, the commands in this package are restricted to the inside of the procedure only.
dst:=proc(MM) 

local DA; 

uses LinearAlgebra;

DA:=Determinant(MM); 

RETURN(DA) end:

dst(<<1 | 2>, <3 | 4>>);

                  -2

Determinant(<<1 | 2>, <3 | 4>>);

                         Determinant(Matrix(2, 2, [[1, 2], [3, 4]]))

This could be a bug in Maple 2019?

Hello, I am wondering if Maple is capable of generating a subgraph for a directed, weighed graph with the GraphTheory package. The online resources I can find only include undirected, unweighed graphs. 

can you please include an example with commands that is able to perform the said task?

hi everyone:

how can I solve this below equation?

w:=(x)->sin(lambda*x)+b*cos(lambda*x)-sinh(lambda*x)-b*cosh(lambda*x);

b := -(sin(lambda*L)+sinh*lambda*L)/(cos(lambda*L)+cosh*lambda*L);

L:=10;

equation:=int(w(x)^2,x=0..L)=1;

lambda=????

tnx..

Hi everybody?

how can I solve this PDE with Runge-Kutta method and 2D plot in terms of w(x,t) , t and 3D plot in terms of t, x, w(x,t)?

code1.mw