Unanswered Questions

This page lists MaplePrimes questions that have not yet received an answer

hello , there , i want ask a Question ,

i have a vector result n hier , and there is a long part with ^1/2 (like unter) , which is not defined before , just from compute ,i want to replace this part with A, and have tried to use subs , but it didnt work . 

And i have tried to define it before compute, and then use subs , aber it also didnt work .

so how can i replace or define this part in the result?

thanks

 

Good day!

I am working to solve a double series (LP  minimization) problem of the form 

z = add(add(x[i,j]*y[i,j]*z[j], j=1..6), i=1..3).

However, this returns a set [ ]. 

Since LPSolve does not operate on a set (removing the brackets manually will enable LPSolve to obtain the solution), can anyone suggest what is wrong with the structure of this z-equation? x, y are matrices and z is a column vector.

 

Thanks!

Hello everyone!

 

Total beginner here. So far I am just using the right click options in Maple,  and worked wonderfully until now.

 

Two questions for some charitable sould out there:

1) I have a system of inequalities that I need to solve. I am interested in the *conditions between the variables under which a given inequality is satisfied*.

Using the "solve" command I only get a few of these. Do you know any script that can obtain more solutions? 

 

2) I have some (long) equations and want to be able to visualize them in different ways to make sense of it. So far I have only been using "simplify" and "combine", but it keeps on returning the same result even if I can see there are other possible ways of factoring the equation. How can I tell Maple to give me "different optiosn" as to visualize the equation?

 

Thank you all!!

 

 

 

 

 

 

Is there a way in Maple to evaluate the following integral - where the "w" are set to go to zero to avoid singularities? B.t.w. Maple just returns the integral unevaluated with or without the "w" with the simple "int" command. 

int(ln(((p1-p3)^2+w^2)/(p1+p3)^(w^2+2))*ln(((p1-p4)^2+w^2)/((p1+p4)^2+w^2))*sin(p1)/(p1*p3*p4), p1 = 0 .. infinity);

or even

int(ln(((p1-p3)^2+w^2)/(p1+p3)^(w^2+2))*ln(((p1-p4)^2+w^2)/((p1+p4)^2+w^2))*sin(p1)/(p1*p3*p4), p1 = 0 .. 100, numeric);

 

Here's something neat to be done in Maple. 
This anaglyph or stereo image uses the red green glasses to make the model appear more 3 dimensional.  The static-non-stereo image of the animated plot below is done in maple by plot3d(sin(x*y)^2,x=-2..2,y=-2..2,scaling=constrained)

Anyone?

 

hi

how i can pdsolve these partial differentialequations?

thanks

10.mw
 

restart; R := 1; UB := 1; lambda := 1; pe1 := 1; pe2 := 1; L := 1; Gr := 1; Br := 1; p := 1; LinearAlgebra:-HermitianTranspose(L) := 1; Nb := 1; Nt := 1; a := lambda*pe1*u(r, z)*(diff(sigma(r, z), z))-(diff(r*(diff(sigma(r, z), r)), r))/r-lambda^2*(diff(sigma(r, z), z, z))-Nt*((diff(r*(diff(theta(r, z), r)), r))/r+lambda^2*(diff(theta(r, z), z, z)))/Nb

u(r, z)*(diff(sigma(r, z), z))-(diff(sigma(r, z), r)+r*(diff(diff(sigma(r, z), r), r)))/r-(diff(diff(sigma(r, z), z), z))-(diff(theta(r, z), r)+r*(diff(diff(theta(r, z), r), r)))/r-(diff(diff(theta(r, z), z), z))

(1)

b := lambda*pe2*u(r, z)*(diff(theta(r, z), z))-(diff(r*(diff(theta(r, z), r)), r))/r-lambda^2*(diff(theta(r, z), z, z))-Nb*((diff(sigma(r, z), r))*(diff(theta(r, z), r))+(diff(sigma(r, z), z))*(diff(theta(r, z), z))*lambda^2)-Nt*((diff(theta(r, z), r))^2+lambda^2*(diff(theta(r, z), z))^2)

u(r, z)*(diff(theta(r, z), z))-(diff(theta(r, z), r)+r*(diff(diff(theta(r, z), r), r)))/r-(diff(diff(theta(r, z), z), z))-(diff(sigma(r, z), r))*(diff(theta(r, z), r))-(diff(sigma(r, z), z))*(diff(theta(r, z), z))-(diff(theta(r, z), r))^2-(diff(theta(r, z), z))^2

(2)

c := -p+(diff(r*(diff(u(r, z), r)), r))/r-L^2*(diff(r*(diff((diff(r*(diff(u(r, z), r)), r))/r, r)), r))/r+Gr*theta(r, z)+Br*sigma(r, z)

-1+(diff(u(r, z), r)+r*(diff(diff(u(r, z), r), r)))/r-(-(diff(u(r, z), r)+r*(diff(diff(u(r, z), r), r)))/r^2+(2*(diff(diff(u(r, z), r), r))+r*(diff(diff(diff(u(r, z), r), r), r)))/r+r*(2*(diff(u(r, z), r)+r*(diff(diff(u(r, z), r), r)))/r^3-2*(2*(diff(diff(u(r, z), r), r))+r*(diff(diff(diff(u(r, z), r), r), r)))/r^2+(3*(diff(diff(diff(u(r, z), r), r), r))+r*(diff(diff(diff(diff(u(r, z), r), r), r), r)))/r))/r+theta(r, z)+sigma(r, z)

(3)

bc := {sigma(R, z) = 0, sigma(r, 0) = 1, theta(R, z) = 0, theta(r, 0) = 1, u(R, z) = UB, (D[1](sigma))(0, z) = 0, (D[1](sigma))(r, LinearAlgebra:-HermitianTranspose(L)) = 0, (D[1](theta))(0, z) = 0, (D[1](theta))(r, LinearAlgebra:-HermitianTranspose(L)) = 0, (D[1](u))(0, z) = 0, (D[2](u))(R, z) = 0}

{sigma(1, z) = 0, sigma(r, 0) = 1, theta(1, z) = 0, theta(r, 0) = 1, u(1, z) = 1, (D[1](sigma))(0, z) = 0, (D[1](sigma))(r, 1) = 0, (D[1](theta))(0, z) = 0, (D[1](theta))(r, 1) = 0, (D[1](u))(0, z) = 0, (D[2](u))(1, z) = 0}

(4)

``


 

Download 10.mw

 

Dear Maple  users,

I am facing the memory allocation problem while calculating the inverse Laplace transformation of a big expression. I have many such terms (401) and I am importing them from a text file.

For an individual term itself, Maple consumes huge memory but at the end, it is able to calculate it in about an hour. I want to automate the process of reading and writing the terms one by one from the different text files. While doing so, maple eats a lot of memory and I see the error msg

"Error, (in expand/bigprod) Maple was unable to allocate enough memory to complete this computation.
Please see ?alloc "

Is there a way to do so? The maple file is attached.

InvLaplace_ex.mw

Thanks,

I´m new to Maple and I´m trying to find the minimum distance of an ECC from its parity check matrix or the generator matrix. Is this possible?

A fact that seems to be not documented. Probably it should be obvious.

 

Digits := d0
evalf[d](expr);

 

The toplevel float sub-expressions in expr  are computed with Digits=d0 but in procedures Digits is set to d.
Notice that the actual float parameters of the toplevel procedures are evalf-ed with Digits=d0.

 

restart;

g:=proc() convert(1/3., string) end:
h:=proc() 1/3. end:

Digits:=3;
evalf[10]([
  1/3. = h(),
  convert(1/3.,string) = g(),  
  fsolve(3*x=1) = add([1/3]),
  fsolve(x/3=1/9.) # 1/9. being at top level is evalf-ed with Digits=3
])

3

 

[.333 = .3333333333, ".333" = ".3333333333", .3333333333 = .3333333333, .3330000000]

(1)

 

k:=proc(x) convert(x,string) end:

kernelopts(floatPi);

true

(2)

4.+Pi;

7.14

(3)

evalf(k(1/3.+Pi));
# floatPi seems to be ignored inside actual parameters

".333+Pi"

(4)

evalf(k(4+evalf(Pi)));

"7.14"

(5)

evalf(k(4+Pi));
# 4 not being float (or "infected" by a float) is not evalf-ed

"4+Pi"

(6)

 

### (this is documented)

`evalf/h` := proc() 7.777 end:

evalf(h(1/3));

.333

(7)

evalf('h'(1/3));

7.777

(8)

 

 

Download digits.mw

(edited)

collect((sqrt(x)+y)^2, [x, y], distributed);
                                       (sqrt(x)+y)^2

I think this is wrong. Documentation says that collect supports fractional powers of the variables, so in this case collect should return x+2*sqrt(x)*y+y^2.

After waiting about six hours for the worksheet to be executed, I finally lost hope and stopped it. (My CPU usage was stuck on 100% the whole time and I almost ran out of memory) Is this evaluation time normal and should I have waited longer, or is there a problem with my worksheet? (I'm uploading it here) Or is it possible that the equation cannot be solved by Maple at all?

parasitic.mw

help me on thispde_solutionalpha.mw
 

restart

M := 1; S := .78; K := .5; Sh := .2; alpha := .7; R := .3; N := .6; k := .5

pde1 := diff(u(y, t), t)+S.(diff(u(y, t), y))-2*k^2*u(y, t) = diff(u(y, t), y, y)+theta(y, t)+N.C(y, t)+M.u(y, t)+u(y, t)/K

                pde2 := theta(y, t)+t*(diff(theta(y, t), t))+S*(diff(theta(y, t), y)) = (diff(theta(y, t), y, y))/Pr-alpha.theta(y, t)

pde3 := C(y, t)+t*(diff(C(y, t), t))+S*(diff(C(y, t), y)) = (diff(C(y, t), y, y))/Sh-R.C(y, t)

PDE := unapply({pde || (1 .. 3)}, Pr)

proc (Pr) options operator, arrow; {C(y, t)+t*(diff(C(y, t), t))+.78*(diff(C(y, t), y)) = 5.000000000*(diff(diff(C(y, t), y), y))-.3*C(y, t), diff(u(y, t), t)+.78*(diff(u(y, t), y))-.50*u(y, t) = diff(diff(u(y, t), y), y)+theta(y, t)+.6*C(y, t)+3.000000000*u(y, t), theta(y, t)+t*(diff(theta(y, t), t))+.78*(diff(theta(y, t), y)) = (diff(diff(theta(y, t), y), y))/Pr-.7*theta(y, t)} end proc

(1)

IBC := {C(0, t) = 1, C(1, t) = 0, C(y, 0) = 0, theta(0, t) = 1, theta(1, t) = 0, theta(y, 0) = 0, u(0, t) = 0, u(1, t) = 0, u(y, 0) = 0}

``

PrList := [.71, 7, 10, 100]; Colours := table(`~`[`=`](PrList, ["blue", "red", "green", "cyan"])); for Pr in PrList do pds := pdsolve(PDE(Pr), IBC, numeric); Plots[Pr] := pds:-plot[display](u(y, t), t = .5, linestyle = "solid", colour = Colours[Pr], legend = sprintf("Pr=%2.2f", Pr), title = "Velocity Profile", labels = ["y", "theta"]) end do; plots:-display([seq(Plots[Pr], `in`(Pr, PrList))])

 

NULL


 

Download pde_solutionalpha.mw

 

Exporting one plot in program works well:

       MapleEngine.EvalMapleStatement(kv, "Export(\"D:\\\\MyGraph.jpeg\",plot(sin(x)*cos(2*x)));");

But if I'm trying to export two plots, program stops working and prints no exception:
        MapleEngine.EvalMapleStatement(kv, "Export(\"D:\\\\MyGraph.jpeg\",plot(sin(x)*cos(2*x)));");
        MapleEngine.EvalMapleStatement(kv, "Export(\"D:\\\\MyGraph2.jpeg\",plot(sin(x)*cos(2*x)));");

What is the cause?

f := (s) -> -HankelH1(1, s)-2*I/Pi*BesselK(1, s);

evalf(Int(f(s), s = 0 .. 1));
                 -0.2348023134 + 0.3562894462 I

evalf(Int(Re(f(1.*s)), s = 0 .. 1)+I*Int(Im(f(1.*s)), s = 0 .. 1));
                 -0.2348023134 + 0.3562894462 I

evalf(Int(f(1.*s), s = 0 .. 1));
               -0.2094198744 + Float(infinity) I

I don't know if the third one is really an issue, but given that the first two work fine, looks suspicious.

First 152 153 154 155 156 157 158 Last Page 154 of 362