Unanswered Questions

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

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.

كيفية حل مشكلة فوات (إنفينتي)

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.

How can i export a plot using open maple in java?

engine.evaluate("Export(\"D:\\MyGraph.jpeg\", plot(sin(x)));");

and 

engine.evaluate("exportplot(\"D:\\MyGraph.jpeg\", plot(sin(x)));");

doesn't work,

exception - com.maplesoft.externalcall.MapleException: Error, (in Export) exported file D:MyGraph.jpeg could not be createdError, plotting was not implemented by the application

 

Thanks.

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