Hello,

I have problem with usage of diff function. I need to compute partial derivative over   in that equation.

T__ln := (1/2)*(diff(varphi__l(t), t))^2+((1/2*(m))*v__l+(1/2*(I))*(diff(varphi__l(t), t))^2)+((1/2*(m))*v+(1/2*(I))*(diff(varphi__l(t), t))^2)

If I am trying to use:

diff(T__ln, diff(varphi__l(t), t))

I get the error:

Error, invalid input: diff received diff(varphi__l(t), t), which is not valid for its 2nd argument
 

Hi all, this is my first post here, I'm finding Maple super interesting so far.

I had a little problem with plots, whenever I update my underlying function and re-run my cells it won't update the curve at all whether automatically or after selecting the entry and pressing `execute ! `.

I'd have the select and delete the plot and then re-plot again.

Is this how it is or there is something I'm missing?

LeadingTerm(y^2-x^2/y, plex(x, y));
 

(in Groebner:-LeadingTerm) the input is not polynomial in, {x, y}

how to do when fraction in it ?

it return error

plot(x mod 3, x=-5..5);

plots exactly the same as

plot(x, x=-5..5);

and

plot(floor(x) mod 3, x=-5..5);

The mod function is doing nothing, why?

If I do 5 mod 4 I get 1, as expected.

n := 0
u[0] := x^3+(1/2)*A*x^2
for k from 0 to n do
A[k] := sum((Diff(u[i], x))*(Diff(u[k-i], x)), i = 0 .. k);
A[k] := sum((diff(u[i], x))*(diff(u[k-i], x)), i = 0 .. k)
end do;
 

it gives A[0]:=0 which is incorrect. why? and how it will give correct answer?

Need the code of the following:

h is the step size could be 0.1 or 0.01 etc

Dear experts

I am trying to study linear version of the Navier-Stokes (NS) equation. I define NS equations in a way suggested in this page

restart;

with(PDEtools): with(Student[VectorCalculus]):

SetCoordinates(cartesian[x,y,z]):

V:= VectorField(< v[1](x,z,t),0,v[3](x,z,t)>);

NavierStokes:= diff(V,t) - nu*Laplacian(V) +1/rho* Gradient(p(x,z,t)) - VectorField(< 0,0,-g>)=0;

the velocity components are intriduced as following

v[1]:=(x,z,t)->diff(f(z),z)*exp(I*k*x+(-1)*I*omega*t);

v[2]:=(x,z,t)->0;

v[3]:=(x,z,t)->(-1)*I*k*f(z)*exp(I*k*x+(-1)*I*omega*t);

So the problem is 2D model so that v[1] and v[3] satisfy incompresibility condition. It is clear that substituting velocity components into NS leads to differential equations for f(z). The general form of f(z) is

f(z) = a1*cosh(k*z)+a2*sinh(k*z)+a3*cosh(kappa*z)+a4*sinh(kappa*z).

my problems are

1) apply v[1], v[3] and find f(z) with Maple. then apply boundary conditions to find coeffs a[i] with Maple

2) In addition, Substituting the f(z) into BCs leads to a linear homogeneous system of equations for the coefficients. The vanishing of the determinant of this system which is the condition for the existence of a nontrivial solution is interested. How can I do that?

3) f(z) is for the case that the bottom is z=0 and surface is z=h. in my case bottom is z=-h and surface is z=0. how to do this in the solution. I dont know how to apply it.

4) calculate pressure

this file is what I did.

NSE.mw

The function evalf(  ) will encounter a critical bug when doing the following evaluation:

restart;
P1 := 1007;
P2 := 1014;
P3 := 1014.1;
evalf(P2 - P1, 2);
evalf(P3 - P1, 2);

The first evalf( ) returns a correct value, while the second one returns a wrong value.
This is really unbelievable!

Here is a little animation to wish all of you a Merry Christmas

FireWorks.mw

hello,

How I can remove this error for dsolve equation.

Thanks

2023.mw

Download 2023.mw

pointset := [A, [0,0], B, [0,v_B], C, [u_C, v_C], D, [x_D, y_D], O, [x_O, y_O]];
for i from 1 to nops(pointset)/2 do
print(i, i+1);
pointset[i] := pointset[i+1];
od:
how to Make A := [0,0] instead of pointset[1] 

Hi, 

In help page DocumentTools:-Layout:-Font, there is an example which shows how to inser a hyperlink in a Layout.

F := Font( "Some text", size=16, color=blue, style=:-Hyperlink ):
InsertContent(Worksheet(Group(Input(Textfield( F ))))):
 

When this id done, how can we activate this hyperlink ?
5I'm presently working with Maple 2015.2 under Mac OS Mojave)

Thanks in advance

how I can gain a function that it is fitting in these data in x and y and z?

please see the following figure.

this curve is a 3D diagram in three coordinates x,y and z.

Thanks

PLOTfitting.xls

Let A be an nrxnr binary matrix. Suppose that the nxn binary matrix B is obtained from the matrix A using the following code:

n := upperbound(A)[1]/r; 
B := Matrix(n, n, 0); 
for i to n do
 for j to n do 
  B[i, j] := SubMatrix(A, [(i-1)*r+1 .. i*r], [(j-1)*r+1 .. j*r])
 end do;
end do;

In other words, the matrix B is a decomposition of matrix A by rxr binary matrices. In the rest, we want to compute all determinants of the submatrices of B in module 2 as follows: 

u := 1; 
for k to n do
 P := choose(n, k); 
 for i to nops(P) do
  for j to nops(P) do
   W := []; 
   for ii in P[i] do 
    for jj in P[j] do
     W := [op(W), B[ii, jj]] 
    end do 
   end do;
   x := `mod`(Det(convert(blockmatrix(k, k, W), Matrix)), 2); 
  if x = 0 then 
    u := 0;
    i := nops(P)+1;
    j := nops(P)+1;
    k := n+1 
   end if 
  end do 
 end do; 
 unassign('i, j, ii, jj, W, x, P') 
end do

In the last step, we check that if the value of all sub determinants of B in module 2, are non zero, then we announce that the block matrix B is an MDS matrix

if u = 1 then print(MDS) else print(NoMDS) end if

Based on the above description I wrote the following procedure:

restart

with(LinearAlgebra); 
with(linalg, blockmatrix);
with(combinat)

MDS:=proc(A::Matrix,r::integer) 
   local n,B,i,j,u,ii,jj,k,P,W,x; 
   n:=upperbound(A)[1]/r;
   B:=Matrix(n,n,0); 
   for i to n do 
       for j to n do 
	        B[i,j]:=LinearAlgebra:-SubMatrix(A,[(i - 1)*r+1..i*r],[(j - 1)*r+1..j*r]) 
		end do 
	end do; 
	unassign('i,j');
	u:=1; 
	for k to n do
    	P:=combinat:-choose(n,k); 
		for i to nops(P) do
     		for j to nops(P) do
    			W:=[]; 
				for ii in P[i] do
    				for jj in P[j] do 
					    W:=[op(W),B[ii,jj]] 
					end do 
				end do; 
				x:=mod(Det(convert(linalg:-blockmatrix(k,k,W),Matrix)),2);
				if x=0 then 
				   u:=0;
				   i:=nops(P)+1;
				   j:=nops(P)+1;
				   k:=n+1
				end if 
			end do 
		end do; 
		unassign('i,j,ii,jj,W,x,P') 
	end do; 
	if u=1 then print(MDS) else print(NoMDS) end if 
end proc

My problem is that if A is a 64x64 binary matrix and also r=8, then the procedure MDS(A,8) takes 453 seconds to run in my computer (Maple 15 on windows 7 32bit with 4G RAM).

Is it possible to optimize the procedure such that MDS(A,8) takes less than 1 minutes.

Thanks for any help

Here we simulate the motion of a container with a flat bottom that can slide on a horizontal surface subject to dry friction (Coulomb friction).  Installed inside the container is an ordinary mass/spring/damper system where the mass slides horizontally.  We impart an initial velocity to the container.  That sets the mass into motion which then affects the container's motion.  Under certain conditions the container will undergo a stick-slip motion which is evident in the simulation.

This simulation very roughly approximates the motion of a partially filled bucket of water that slides on the floor when kicked.  The idea arose in a discussoin with Carl Love and mmcdara:
https://www.mapleprimes.com/posts/211677-Mass-Spring-Conveyor-Belt-And-Dry-Friction

In the animation below, the container is shown in dark color when it slides against the floor, and light color when it sticks.

Worksheet: slosh.mw