Could anyone help me with the following task?

The simplest case is, for example, 

    If y=y(x). Denote y'(x)=D_x(y). Then we make a change of veriables :

    x=φ(z,w), y=ψ(z,w), where z independent and w=w(z),

    Now the ODE: y'(x)=1 turns to:

    D_z(y)/D_z(x)=1,  i.e. ψ_z+w'(z)ψ_w=φ_z+w'(z)φ_w.

    So we have the relation: D_z=(φ_z+w'(z)φ_w)D_x.

    The task is how to define the operators (D_x, D_z) to transform more complecated ODE of (x,y) (e.g. (D_x+F(x,y))⁵(y)=0,   

     F arbitrary) to its counterpart of (z,w)?

Thank you in advance!

Help me to solve this problem with pdsolve

I am trying to recreate an example,  See attached worksheet below.  I can't figure out what I am doing wrong here.  I have tried using the command StepProperties on other discrete transfer functions, without any problems.  Having a function that plots the Step Response of a system, Continuous or Discrete, should be built in.

 

Trying to recreate step response of discrete time system as in this example below:   https://www.mathworks.com/help/control/examples/creating-discrete-time-models.html   >  restart:with(DynamicSystems):interface(version); (1) >    >  sysz:=TransferFunction((z-1)/(z^2-1.85*z+0.9),discrete,sampletime=0.1); (2) >  propz:=StepProperties(sysz); (3) >    >

 

Download DiscreteStepResponseError.mw

Regards,

Georgios

Hello,

I am Seonhwa Kim, a mathematical researcher in Korea. Recently, I have extensively used Maple to compute character varieties of 3-manifolds. Several months ago, I obtained some strange results in Maple which implies a contradiction in theory.  I have been struggling with these issues since it is usually about enormous polynomial systems.  Eventually, I could figure out that the issues are caused by a defect in Maple and were able to construct a minimal working example to produce wrong computations in Maple.  I am writing this post to report them.

 

This is mainly about the PolynomialIdeal package.  Along with the documentation in Maple, If an ideal J is radical, PrimeDecomposition and PrimaryDecomposition should have the same result.  But, as we see the following, the result of PrimeDecomposition and PrimaryDecomposition are different although J is a radical ideal.

The problem seems to be that the PrimaryDecomposition command in Maple sometimes produces incorrect results.

We can compute the primary decomposition of J by hand.  It should be <x> and  <y, x-1>.

I double-checked this by the other software;Macauley2, Singular, and Magma, for example, you can see it as follows.

 

 

 

Secondly, not only for PrimaryDecomposition but also PrimeDecomposition may produce an incorrect result.

Here is a minimal working example.

Maple tells us a compatible result of prime and primary decomposition of a radical ideal J.

But the first component of J,  < b-1, c-a+1 >, contains the third component < a, b-1, c+1 >.

It contradicts with the definition of Primary decomposition. So the correct answer should be  < b - 1, c - a +1 >, <a,b,c>.

 

I also checked that  Macaluey2, Singular and Magma. They all say that my hand computation is correct. as follows.

 

I have used Maple 2017 by the license of my institute (Korea Institute for Advanced Study).

When I noticed these defects, I thought it would be fixed in the newest Maple version.

So, I have tried my examples by Maple2019  free trial, but It also has the same problem. 

I guess this problem is not reported or recognized yet. 

 

I hope this problem will be fixed as soon as possible.

Thank you for attention.

 

Sincerely,

Seonhwa

Hello every one
I have a question!
My code starts with assuming the time variable (t) to be specified in a an interval for each time that the for loop executes as follows:

discontinuity := [0.403e-8, 0.45e-8, 0.478e-8, 0.55e-8];
 for j from 1 to 3 do
assume(discontinuity[j]<=t,t<discontinuity[j+1]);

After that the code runs and calculate every thing. For the second time, I mean for J=2, it does not work properly.
T[1] is the result of its first running (for j=1):
T[1]:=3.000023586*10^(-6)*exp(-4977.085344*t~)-1.325122648*10^(-6)*exp(-4.015800624*10^9*t~)
When it wants to evaluate this expression at specific time such as discontinuity[2] it cannot evaluate it. I tried to use unapply command to consider it as a function of t but it did not work. Here is the results:
AA:=simplify(eval(T[1], t = discontinuity[1]));
This is its result:        AA:=3.000023586*10^(-6)*exp(-4977.085344*t~)-1.325122648*10^(-6)*exp(-4.015800624*10^9*t~)
Without unapply command:    AA:=T[1]
Please answer my question.
Thank you so much
 

Hello,

I want to sort the formulae to Psi and Beta, but I don't know how it works. I have tried it with sort, simplify, isolate, but that isn't what I'm searching.

It should looks like the simplier formula in the picture.

 

ab := (diff(Psii(t), t, t))*J-l[f]*(F[s, f, l]+F[s, f, r])+l[r]*(F[s, r, l]+F[s, r, r])-(1/2)*b[r]*(-F[s, r, l]*delta[l]+F[s, r, r]*delta[r]) = 0;
  / d  / d         \\                                   
  |--- |--- Psii(t)|| J - l[f] (F[s, f, l] + F[s, f, r])
  \ dt \ dt        //                                   

     + l[r] (F[s, r, l] + F[s, r, r])

       1                                                      
     - - b[r] (-F[s, r, l] delta[l] + F[s, r, r] delta[r]) = 0
       2                                                      
bc := (diff(betaa(t), t, t))*m*v*betaa(t)+F[s, r, l]*delta[l]+F[s, r, r]*delta[r]-(diff(Psii(t), t)) = 0;
    / d  / d          \\                                   
    |--- |--- betaa(t)|| m v betaa(t) + F[s, r, l] delta[l]
    \ dt \ dt         //                                   

                               / d         \    
       + F[s, r, r] delta[r] - |--- Psii(t)| = 0
                               \ dt        /    
cd := (diff(betaa(t), t))*m*v+F[s, r, l]+F[s, r, r]+F[s, f, l]+F[s, f, r]-(diff(Psii(t), t)) = 0;
   / d          \                                           
   |--- betaa(t)| m v + F[s, r, l] + F[s, r, r] + F[s, f, l]
   \ dt         /                                           

                     / d         \    
      + F[s, f, r] - |--- Psii(t)| = 0
                     \ dt        /    
F[s, f, l] := c[fl]*alpha[fl];
                        c[fl] alpha[fl]
F[s, f, r] := c[fr]*alpha[fr];
                        c[fr] alpha[fr]
F[s, r, l] := c[rl]*alpha[rl];
                        c[rl] alpha[rl]
F[s, r, r] := c[rr]*alpha[rr];
                        c[rr] alpha[rr]
alpha[fl] := (-v*betaa-l[f]*(diff(Psii(t), t)))/(-v+(1/2)*b[f]*(diff(Psii(t), t)));
                                 / d         \
                 -v betaa - l[f] |--- Psii(t)|
                                 \ dt        /
                 -----------------------------
                        1      / d         \  
                   -v + - b[f] |--- Psii(t)|  
                        2      \ dt        /  
alpha[fr] := (-v*betaa-l[f]*(diff(Psii(t), t)))/(v-(1/2)*b[f]*(diff(Psii(t), t)));
                                 / d         \
                 -v betaa - l[f] |--- Psii(t)|
                                 \ dt        /
                 -----------------------------
                       1      / d         \   
                   v - - b[f] |--- Psii(t)|   
                       2      \ dt        /   
alpha[rl] := delta[l]+(-v*betaa+l[r]*(diff(Psii(t), t)))/(-v+(1/2)*b[r]*(diff(Psii(t), t)));
                                       / d         \
                       -v betaa + l[r] |--- Psii(t)|
                                       \ dt        /
            delta[l] + -----------------------------
                              1      / d         \  
                         -v + - b[r] |--- Psii(t)|  
                              2      \ dt        /  
alpha[rr] := delta[r]+(-v*betaa+l[r]*(diff(Psii(t), t)))/(-v-(1/2)*b[r]*(diff(Psii(t), t)));
                                       / d         \
                       -v betaa + l[r] |--- Psii(t)|
                                       \ dt        /
            delta[r] + -----------------------------
                              1      / d         \  
                         -v - - b[r] |--- Psii(t)|  
                              2      \ dt        /  

ab;
                             /
                             |
/ d  / d         \\          |
|--- |--- Psii(t)|| J - l[f] |
\ dt \ dt        //          |
                             |
                             \

        /                / d         \\
  c[fl] |-v betaa - l[f] |--- Psii(t)||
        \                \ dt        //
  -------------------------------------
             1      / d         \      
        -v + - b[f] |--- Psii(t)|      
             2      \ dt        /      

           /                / d         \\\        /      /      
     c[fr] |-v betaa - l[f] |--- Psii(t)|||        |      |      
           \                \ dt        //|        |      |      
   + -------------------------------------| + l[r] |c[rl] |delta[
               1      / d         \       |        |      |      
           v - - b[f] |--- Psii(t)|       |        |      |      
               2      \ dt        /       /        \      \      

                       / d         \\
       -v betaa + l[r] |--- Psii(t)||
                       \ dt        /|
  l] + -----------------------------|
              1      / d         \  |
         -v + - b[r] |--- Psii(t)|  |
              2      \ dt        /  /

           /                           / d         \\\          /
           |           -v betaa + l[r] |--- Psii(t)|||          |
           |                           \ dt        /||   1      |
   + c[rr] |delta[r] + -----------------------------|| - - b[r] |
           |                  1      / d         \  ||   2      |
           |             -v - - b[r] |--- Psii(t)|  ||          |
           \                  2      \ dt        /  //          \
       /                           / d         \\         
       |           -v betaa + l[r] |--- Psii(t)||         
       |                           \ dt        /|         
-c[rl] |delta[l] + -----------------------------| delta[l]
       |                  1      / d         \  |         
       |             -v + - b[r] |--- Psii(t)|  |         
       \                  2      \ dt        /  /         

           /                           / d         \\         \   
           |           -v betaa + l[r] |--- Psii(t)||         |   
           |                           \ dt        /|         |   
   + c[rr] |delta[r] + -----------------------------| delta[r]| = 
           |                  1      / d         \  |         |   
           |             -v - - b[r] |--- Psii(t)|  |         |   
           \                  2      \ dt        /  /         /   

  0
bc;
 / d  / d          \\             
 |--- |--- betaa(t)|| m v betaa(t)
 \ dt \ dt         //             

            /                           / d         \\         
            |           -v betaa + l[r] |--- Psii(t)||         
            |                           \ dt        /|         
    + c[rl] |delta[l] + -----------------------------| delta[l]
            |                  1      / d         \  |         
            |             -v + - b[r] |--- Psii(t)|  |         
            \                  2      \ dt        /  /         

            /                           / d         \\         
            |           -v betaa + l[r] |--- Psii(t)||         
            |                           \ dt        /|         
    + c[rr] |delta[r] + -----------------------------| delta[r]
            |                  1      / d         \  |         
            |             -v - - b[r] |--- Psii(t)|  |         
            \                  2      \ dt        /  /         

      / d         \    
    - |--- Psii(t)| = 0
      \ dt        /    
cd;
 / d          \    
 |--- betaa(t)| m v
 \ dt         /    

            /                           / d         \\
            |           -v betaa + l[r] |--- Psii(t)||
            |                           \ dt        /|
    + c[rl] |delta[l] + -----------------------------|
            |                  1      / d         \  |
            |             -v + - b[r] |--- Psii(t)|  |
            \                  2      \ dt        /  /

            /                           / d         \\
            |           -v betaa + l[r] |--- Psii(t)||
            |                           \ dt        /|
    + c[rr] |delta[r] + -----------------------------|
            |                  1      / d         \  |
            |             -v - - b[r] |--- Psii(t)|  |
            \                  2      \ dt        /  /

            /                / d         \\
      c[fl] |-v betaa - l[f] |--- Psii(t)||
            \                \ dt        //
    + -------------------------------------
                 1      / d         \      
            -v + - b[f] |--- Psii(t)|      
                 2      \ dt        /      

            /                / d         \\                    
      c[fr] |-v betaa - l[f] |--- Psii(t)||                    
            \                \ dt        //   / d         \    
    + ------------------------------------- - |--- Psii(t)| = 0
                1      / d         \          \ dt        /    
            v - - b[f] |--- Psii(t)|                           
                2      \ dt        /                           
 

 

 

 

Hello, 

For a few days Maple crashs everytime i try to use the command "plot3d()". 

I had'nt this problem befor and I have no idea what the reason could be. It ist irrelevant what Funktion I try to visualize,  the window just get closed evertime.

I hope someone can help me.

Thank you!

Tom

Error, (in PDEtools/NumerDenom) invalid input: `PDEtools/NumerDenom` expects its 1st argument, ee, to be of type algebraic, but received {[(s_j*e^sigma*b^m*`σ_m`*y_i-s_j*e^sigma*beta*`σ_i`+s_j*e^sigma*b_ilo+(1/2)*b^(m+2)*`σ_j`*e^sigma*`σ_m`*y_i-b^2*`σ_j`*e^sigma*beta*`σ_i`+(1/2)*b^2*`σ_j`*e^sigma*b_ilo-(1/2)*b^(2*m)*`σ_m`^2*b_j*e^sigma*y_i+(1/2)*b^m*`σ_m`*b_j*e^sigma*beta*`σ_i`-(1/2)*b^m*`σ_m`*b_j*e^sigma*b_ilo+b_j*(s_ilo+(1/2)*(b^2*`σ_i`-b^m*`σ_m`*beta)*_lo)+b_j*(s_jlo+(1/2)*(b^2*`σ_j`-b^m*`σ_m`*beta)*_lo)+s_i*e^sigma*b^m*`σ_m`*y_j-s_i*e^sigma*be... when I use simplify I have this error. please guide me Saberali

Hi all,

I have a system of nonlinear equations with for equations, 4 variables I want to solve for, and 2 parameters. All of the variables and parameters must be non-negative.

The code I used to try to do this is:

Where eq_i (i = 1, ... , 4) are expression (not equations in themselves). For example, eq₁ is:

 

When I try to run this code I get the following error:

"Error, (in SolveTools:-Inequality:-Piecewise) piecewise takes at least 2 parameters"

 

Can anyone help me how I can make Maple do what I want here? :)

 

Thank you in advance,

JTamas

I'm plotting some simple plots such as

plot(frac(x^2/3)*3,x=-5..5, discont=true);

 

Some discontinuities are connected. Using numpoints, resolution, and Digits doesn't help. Sometimes it will produce a plot with no connections but then other times it does. I need a general solution that is simple. Is there any way to refine the quality of discont?

 

discont=[usefdiscont=[bins=35]],

 

I have tried that and it seems to work but I haven't put it through the ringer. Is that all I have?

 

Hello, I'm using free 15 day trial Maple 2019.2 on my Macbook (Macos 10.15.3).

I can't work Maple. I enter some inputs (2+3) and press enter. It works. But when I write plot, version(), f, sin.. or something else it didn't works. And no response. When I click enter, nothind happen. What is the problem? Please help me.. 

How do I simplify KdV equation in Maple by using =fxt))xx)?)

 

>     I am by using =2*difffxtxx)     My aim is to get the form     >  >  >  >  >  (1) >  (2) >  (3) >  (4) >  (5) >  >  >  >

 

Download KdV_simplify

Is there lifting function for polynomials or algebra use?

expect input a list univariate polynomial , then output a list of polynomials of two variables.

it should be the reverse operation of projection.

Which library has this function in maple 12 or maple 2015?

Hello All,

I have an autonomous system of ordinary nonlinear equations. In order to investigate it near the fixed points, I would like to reduce it to the normal or hyper-normal form. I see in the literature that some authors developed unique algorithms for the very specific differential systems (e.g., the systems with two/three eigenvalues), which is not my case.  

Maybe you know, if Maple has any specific commands that may conduct such type of reduction?

Thanks in advance,

Dmitry

 

 

 

I’m starting a large project in education for which I can see great potential in the use of the “MapleCloud”.  For many of the students, the ability to see information on their phone is a game-changer. Hence while my students do have access to Maple on their computers, they are more willing to check out a worksheet if they can view it in a browser.

Unfortunately, in the little time that I have started using MapleCloud, and sharing my work with others, numerous issues have arisen. Some examples:
  * the file system is too simplistic and can be overwhelmed easily as I add content;
  * the group sharing system is too limited – one must log on, which is not true for worksheets;
  * the display of the mathematics is sufficiently quirky that it is not easy to read;
  * the hiding of input mathematics appears not to work;
  * plots, animations and the output of the Explore function fails too frequently.

So, my questions:
  1) are you using MapleCloud, and
  2) if so, for what?
  3) And if you are using MapleCloud, do you have similar problems?
  4) Have you developed solutions that you would be willing to share.

If there is no interest, I’ll look in another direction. But if there is sufficient interest, I would hope Maplesoft notices and works to correct and improve. Some of it may be my own failing to understand Maple, but instead of overwhelming MaplePrimes with questions, I would rather converse with similar interested folks.