## Solving piecewise set of 4th order homogeneous ODE...

Hi Maplers,

I'm struggling to write the correct code for this structural problem below.

The goal is to find the piecewise code for the horizontal deflection of a vertical beam (representing a offshore wind turbine) consisting of 5 segments. Below the EoM for the 5 segments, where segment 1 is in the soil hence the ksoil*u1(z) part.

sysODE := {
EI2*diff(u2(z), z, z, z, z) + m2*g*diff(u2(z), z, z) = 0,
EI3*diff(u3(z), z, z, z, z) + m3*g*diff(u3(z), z, z) = 0,
EI4*diff(u4(z), z, z, z, z) + m4*g*diff(u4(z), z, z) = 0,
EI5*diff(u5(z), z, z, z, z) + m5*g*diff(u5(z), z, z) = 0,
EI1*diff(u1(z), z, z, z, z) + m1*g*diff(u1(z), z, z) + ksoil*u1(z) = 0}

To find the general solution the dsolve function is used. This gives 5 eqs describing u1(z).. u5(z), with in total 20 unknown constants depicted as: _C1.._C20.

Now I have 20 BCs, shown below:

bcs := {
eval(subs(z = z2, EI2*diff(u2, z, z, z)) + Fwave = subs(z = z2, EI3*diff(u3, z, z, z))),
eval(subs(z = z5, EI5*diff(u5, z, z, z)) + Fwind = 0),
eval(subs(z = 0, EI1*diff(u1, z, z)) = 0),
eval(subs(z = 0, EI1*diff(u1, z, z, z)) = 0),
eval(subs(z = z1, u1) = subs(z = z1, u2)),
eval(subs(z = z1, diff(u1, z)) = subs(z = z2, diff(u2, z))),
eval(subs(z = z1, diff(u1, z, z)) = subs(z = z2, diff(u2, z, z))),
eval(subs(z = z1, diff(u1, z, z, z)) = subs(z = z1, diff(u1, z, z, z))),
eval(subs(z = z2, u2) = subs(z = z3, u3)),
eval(subs(z = z2, diff(u2, z)) = subs(z = z2, diff(u3, z))),
eval(subs(z = z3, u3) = subs(z = z3, u4)),
eval(subs(z = z3, diff(u3, z)) = subs(z = z3, diff(u4, z))),
eval(subs(z = z3, diff(u3, z, z)) = subs(z = z3, diff(u4, z, z))),
eval(subs(z = z3, diff(u3, z, z, z)) = subs(z = z3, diff(u4, z, z, z))),
eval(subs(z = z4, u4) = subs(z = z5, u5)),
eval(subs(z = z4, diff(u4, z)) = subs(z = z4, diff(u5, z))),
eval(subs(z = z4, diff(u4, z, z)) = subs(z = z4, diff(u5, z, z))),
eval(subs(z = z4, diff(u4, z, z, z)) = subs(z = z4, diff(u5, z, z, z))),
eval(subs(z = z5, EI5*diff(u5, z, z)) = 0)};

How do I write the correct Maple-code to find C1..C20.

krgs,

Floris

## Windows Maple 2023 crashes if Maplets will be used...

Hi,

i use an OpenMaple environment for my academic activity. Especially for plotting of results outside of Maple GUI. Until version 2023 everything was nice and working. But in 2023 calling of Maplets kills Maple 2023 and of course my jobs. Example to try:

#include <stdio.h>
#include <stdlib.h>

#include "maplec.h"

/* callback used for directing result output */
static void M_DECL textCallBack(void *data, int tag, const char *output)
{
printf("%s\n", output);
}

int main(int argc, char *argv[])
{
char err[2048];  /* command input and error string buffers */
MKernelVector kv;  /* Maple kernel handle */
MCallBackVectorDesc cb ={textCallBack,
0,   /* errorCallBack not used */
0,   /* statusCallBack not used */
0,   /* readLineCallBack not used */
0,   /* redirectCallBack not used */
0,   /* streamCallBack not used */
0,   /* queryInterrupt not used */
0    /* callBackCallBack not used */
};
ALGEB r, l;  /* Maple data-structures */

/* initialize Maple */
if((kv=StartMaple(argc, argv, &cb, NULL, NULL, err))==NULL) {
printf("Fatal error, %s\n", err);
return(1);
}
r=EvalMapleStatement(kv, "with(Maplets[Elements]): SimpleMaplet:=Maplet([Button('Close', Shutdown())]): Maplets[Display](SimpleMaplet):");
StopMaple(kv);

return(0);
}

Working in Maple 2020-2022, crashes in 2023

After a long investigation i found that the problem focuses in maple.dll.

It is only for me, or it is a general bug?

## Is there any bug in the new Quantifier Elimination...

The QuantifierElimination package has been added in Maple 2023.
However, in the following example, the old (yet not obsolete) RegularChains:-SemiAlgebraicSetTools:-QuantifierElimination command can solve the problem, but strangely, the new QuantifierElimination:-QuantifierEliminate command simply returns an error.

Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/QE_bug.mw .

So, is there any bug in Maple's QuantifierElimination package?

QuantifierElimination[QuantifierEliminate](forall([x, y, t], Implies(And(x^3 + y^2 - x = t, And(t^2 = 4/27, t < 0)), x^2 + y^2 >= rho)));

(By the way, it appears that  doesn't work....)

## FHow can I set the attribute "Parameters" in a use...

Here is a notional example of a user defined  Probability Distribution:

• One of the "attribute" or "property" (sorry but I don't know the correct word to use) in any known distribution (that is already implemented in Maple) is Parameters: an example is  provided for a Gaussian RV.

• In a first stage I define a simple Distribution named MyDist and declare X as a random variable of distribution MyDist.

• Then I decide to complete the definition of MyDist by adding the "property" Parameters.
I get an error I don't know how to get rid of.

Does anyone has any idea to fix that ?

PS: I browse the Statistics library to try and understand how this "property" is defined for a known distribution but I couldn't find any clue.

 > restart
 > with(Statistics):
 > G := RandomVariable(Normal(a, b)): attributes(G)[3]: exports(%); (attributes(G)[3]):-Parameters;
 (1)
 > MyDist := (mu, Sigma) -> Distribution(Mean=mu, Variance=Sigma): X := RandomVariable(MyDist(m, V)); (Mean, Variance)(X);
 (2)
 > MyDist := (mu, Sigma) -> Distribution(Mean=mu, Variance=Sigma, Parameters=[mu, Sigma]): Y := RandomVariable(MyDist(m, V));
 (3)
 >

## How do I solve this ODE?...

I need help to solve this ODE,

I didn't get series values F(k+3),Theta(k+2),phi(k+2),error comes in summation values.and

How to find the unknown parameters A,B,C.

## I need help to solve ODE using forward-backward sw...

Maple code for solving system of ODE using forward-backward sweep method.

## Maple 2023 workbook error...

While working a test workbook in Maple 2023 - added a file went away for a while and came back and started adding code to the workbook when I suppose it did an autosave and this error came up 4x in a row.

## Difficulty with pdsolve and electromagnetics...

perturb_mag_current_density_2.mw

I am trying to calculate the electric field E induced in a vibrating cantilever of conductive material, oscillating in the field of a permanent magnet.  However, I am having some difficulty getting pdsolve to work the way I want it to.  I'm also not sure if the partial differential eqations I derived from Maxwell's equations are correct, or if the boundary conditions for the electric field in the cantilever are correct.  Currently pdsolve gives me no solutions, which makes me think that either my PDEs or my BCs are not correct.  It may be that I need to try some sort of numerical method as well.  I am assuming that the z component of the electric field is just 0.  My third PDE comes from setting the divergence of the electric field to 0.  My first two PDEs come from the vector laplacian and its relation to the divergence and curl:

Laplacian * E = Div(E) -Curl(Curl(E))

The x and y components of this should be my first and second PDE, respectively.  Note that in this equation the divergence of E is 0, and the curl of E is -dB/dt, where B is the magnetic field.

My boundary conditions are simply that the components of the electric field at the surface of the cantilever is always tangent to the surface.

I have tried various simplifications, such as setting the right hand side of the PDEs to 0, and still I don't get any solution.

My question:  Are my PDEs and BCs sensible?  And if so, what do I need to do with pdsolve to get a proper solution?

## How can I implement a simple code to obtain the di...

Let us consider the following assumptions:

Any set of binomials $B \in R=K[x_1, \cdots, x_n]$ induces an equivalence relation on the set of monomials in $R$ under which $m_1∼m_2$ if and only if $m_1−tm_2\in \langle B \rangle$ for some non-zero $t\in K$. As a k-vector space, the quotient ring $R/B$ s spanned by the equivalence classes of monomials. Now let $f =x^2−y^2$ be a binomial in $K[x, y]$. Among monomials of total degree three, $x^3$ and $xy^2$, as well as $x^2y$ and $y^3$ become equal in $K[x, y] / \langle f\rangle$.

Why the degree three part in the quotient is two-dimensional with one basis vector per equivalence class?

Also, why does the polynomial $f=x^3+xy^2+y^3$ map to a binomial with a coefficient matrix [2, 1]? I think this matrix arises from the matrix [1, 1, 1, 0] by summing the columns corresponding to $x^3$ and $xy^2$ and those for $x^2y$ and $y^3$.

How can I implement a simple code to obtain these results in {\tt Maple}?

I am looking forward to hearing any help and guidance.

## Create excel file with sheets of independent varia...

Given a excel sheet with data for regression as input column Y will be a dependent variable

Say a maximum of 120 independent variables are their

A function that takes excel as input with headers as in the excel file

Do pick all possible subsets of maximum size 5 that is sizes 2,3,4,5 only

Pick each and eleminate not to store them all together as otherwise storage will be a problem if more data

Copy only those subsets of independent variables to seperate seperate sheet

Only those subsets

where the variables are independent pairwise between them

Step 2 function

Then need to run a multiple linear regression on these subsets like training and test

And choose the best models I each of cases of number of variable

That is best with 2 variables

Again with 3 variables

Similarly 4 and 5

Atleast if possible upto 2 to 3 variables it will be good kind help with your guidance and what is possible

If you are not able give the program of train test regression with charts no issues

Kind help with atleast storing the independent pairwise subsets of size 2 and 3 into seperate sheets in a Excel file atleast

I will do the regression at my end

## Taking an excel sheet perform operation create new...

I will have excel sheet with minium 500 coulmns and 1000 rows say

For sample to explain my question I attach a demo excel

I am looking to find all 2 way multiplication and add them as columns to my excel sheet and return it as a new excel sheet say

The column names for the new 2 way column should be like the

header name of column you are multiply * the name of the other columsn

Now in sample file if i multiple column with name A with column with name B I get a new column with header A*B the header name should be inserted and

Below that all the elements of that A column multiplied  with that of B should come

I am looking to form columns for all possible2  way multiplication for the excel I will give.

As you can see the demo file

Excel_to_explain.xlsx

## Global setting of character size in maple 2022...

Hello!

I have changed the the global character size from 12 to 14 but it is not stable. Suddenly size 12 is coming up when a try to copy a row to a another row in the same worksheet.

It is very annoying!!

Any tips????

Regards

Kjell

## limit at infinity ...

Dear all

I have an equation obtained from partial derivable of some functions, I would like to compute the limit when my variable named Pe goes to infinity.

I hope to get a more appreciate presentation of my code to obtain the limit (  Pe -> + infty)

limit_infinity.mw

All derivative are well compute, but How can I add the limit as Pe goes to infinity

Thank you

## Maple on-line help...

Could someone explain to me why the Maple online help pages (see here) are still apparently matching the Maple 2021 release for the past few years? Does this mean that all the information on the Maple online help pages is out of date, or just this one specific page is terribly out of date?