Thomas Richard

Mr. Thomas Richard

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11 years, 177 days
Maplesoft Europe GmbH
Technical professional in industry or government
Aachen, North Rhine-Westphalia, Germany

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These are answers submitted by Thomas Richard

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Your expectation is not unreasonable; in fact, pdsolve is trying a factorization (albeit unsuccessfully), as can be seen from the diagnostic output. Other methods (separation ansatz) are successful, but return a very long solution which can be simplified somewhat:

restart:
eq1:=E*D(II)(x)*D[1](psi)(x,t)+E*II(x)*(D[1]@@2)(psi)(x,t)-G*A(x)*psi(x,t)+G*A(x)*D[1](v)(x,t):
eq1:=convert(eq1,diff);
eq2:=-(G*D[1](A)(x)*psi(x,t)+G*A(x)*D[1](psi)(x,t))+(G*D[1](A)(x)*v(x,t))+G*A(x)*(D[1]@@2)(v)(x,t)-m(x)/G*D[2](v)(x,t):
eq2:=convert(eq2,diff);
sys:=[eq1,eq2]:
infolevel[pdsolve]:=5:
sol:=pdsolve(sys,[psi(x,t),v(x,t)]);
length~(sol);
ot:=odetest(sol,sys);
ssol:=simplify~(sol): length~(ssol);

I've let this run over the lunch break, and saw the results afterwards.

Probably you have already found our FAQ page which confirms your observation. No need to delete any files if you are unsure, but modifying their date should be harmless. Please try that first.

This problem only affects time-limited licenses. The expiry date can be found in your license.dat file.

By the way, it's good that you made the SN field (activation code) unreadable before uploading the screenshot!

ExpandSteps is designed for products (or fractions) of polynomials - please see its help page. It gets confused by the presence of trig expressions. The error message could be better, but even then it won't solve the problem.

What you can do is: replace sin(theta) by s and cos(theta) by c, then ExpandSteps will succeed quickly - but also produce a lot of output! Backsubstitution will make it even (a bit) worse.

The activation code (aka Purchase Code) needs to be entered into the activation tool, which is typically launched at the end of the installation process for most of our products. If you get stuck, please send an e-mail with that code and error message (or other symptoms, if any) to custservice@maplesoft.com. See https://www.maplesoft.com/support/ for more options.

Do not post your code on MaplePrimes nor on any other public web sites.

This is a very common problem, and the background of the error message is explained on the help page that opens when entering

?cannotdetermineifthisexpression

(Clicking on the error message does not bring you there, unfortunately.)

The best solution for your code example is #2, i.e. to use the operator form when plotting:

plot(funktion, r1 .. r2);

This will ensure that evaluation of x is deferred so that the conditional statement (if...then...end if) inside the function definition can be executed.

Notice that both the argument to funktion and the left hand side of the equation that specifies the range have been omitted. So you even save a few keystrokes. :-)

The output of a Maple command can be suppressed by terminating it with a colon. Didn't that work for what you tried?

What did you enter in Maple?

Perhaps post one or two examples of your PDEs. You may also include a download link to your text file.

Please send your Maple worksheet (mw file) to support@maplesoft.com, or upload it via https://www.maplesoft.com/contact/webforms/support.aspx. You may also attach your PDF file, but the worksheet is needed to reproduce the problem.

Since you are evaluating Maple, I suppose you have the current version 2021.1 - otherwise please specify. Your platform (OS version) may also be relevant.

Please see the Parameters section of both help pages: Jacobian expects a list (or Vector) of algebraic expressions, whereas Hessian expects a single algebraic expression. So if you remove the square brackets from [Targetfunction] in the latter call, it will work.

The button was introduced in Maple 2020 to simplify reactivating an expired license. The most common scenario is this: When a Maple Student Edition is purchased from our webstore, the customer is given a temporary license (Purchase Code) so that he/she can start using Maple right away. Our customer service is then validating the certificate of enrolment or student ID, without any time pressure. Once that is completed, the Purchase Code is switched to permanent, and the customer has to reactivate.

For permanent licenses like yours, the button is not needed. Nothing to worry about. ;-)

This combine call requires the 'symbolic' option - and then it produces a simpler result than the old one from 1997.

This is simple:

sol := solve(identity(eq,x));

please see ?solve,identity for more information.

The backslash is the escape symbol in Maple, so problems are expected, depending on where you copy and paste the string. Please see ?backslash for more details.

Better use a file for data exchange:

ExportGraph(g, "check.g6", 'graph6');

 

We can help odetest in a trivial way:

simplify(eval(eval(the_diff_1,x=0),ic));

Likewise for the explicit solution.

Of course, odetest should do this automatically.

You can enter the fractional ODE as

fde := diff(g(t),t$alpha) = r*g(t)*t^(1-alpha)/GAMMA(2-alpha);

but dsolve does not handle ODEs of unspecified differential order.

For alpha=1, it's trivial, of course.

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