Hello everyone,

I am trying to solve a system of 4 ODEs that describe a physical system, however, I get the message:

Error, (in dsolve/numeric/bvp) matrix is singular

Any help is much appreciated. The initial conditions are such that to find solution in steady state, that means, v(0)=v(period) and so on with all variables.

Download LLCcircuit_SteadyState_numerical.mw

Good day. 

I have been looking into the time series features in Maple and was eager to apply the models to one specific example containing 47 data points (attached).

When I run the ESM routine, Maple provides a forecast based on a (A,N,N) configuration. You will notice that the forecast for the following 12 data points is a constant value. I have also noticed this for several other data set examples and I would have expected the predictions to vary across the next 12 data points.

Does the (A,N,N) configuration in Maple automatically provide an optimal forecast and can anyone advise me on how to specify all possible combinations of (error, trend, season) models?

Thanks you for reading.

MaplePrimes_TS_Example.mw

solve((∂(-    ∇(f) ))/(∂ t)+((DotProduct(v[0],∇f))*(1-e(DotProduct(B,Omega)))+(c[s0]^(2)*rho[1])/(rho[0])(1-e(DotProduct(B,Omega)))+e(CrossProduct(∇ f,B))*Omega-e((DotProduct(-∇f,Omega))*(DotProduct(B,∇)))*(-∇f)+e(E)*(1-(DotProduct(B,Omega)))+e^(2)(DotProduct(E,B))*Omega-e*((CrossProduct(E,Omega))*(∇(-∇f)),rho[1]);

Hi,

Since a couple of years ago,  SQLite has been enriched with a bunch of new math functions not existing in previous versions: acos, asin, atan, atn2, atan2, acosh, asinh, atanh, difference, degrees, radians, cos, sin, tan, cot, cosh, sinh, tanh, coth, exp, log, log10, power, sign, sqrt, square, ceil, floor, pi. 

Examples: In SQLite version 3.39.4 2022-09-29 15:55:41 we can invoke:

sqlite> select pi();
3.14159265358979

sqlite> select power(2, 3);
8.0

sqlite> select floor(2.35);
2.0

Package Database[SQLite] in Maple 2022.2 does not recognize these functions.

In oldest versions of Sqlite3 we were able to add these functions after loading an external extension with sqlite3 api function load_extension() (see  https://sqlite.org/contrib/download/extension-functions.c), but his option is blocked in Maple:

dbName := "d:/sq3_maple/etc.db":
sq3Extension := "d:/sq3_maple/extensions.sq3":

with(Database[SQLite]);
[Attach, Bind, ClearBindings, Close, ColumnCount, ColumnNames, 
  Execute, Fetch, FetchAll, FetchRow, Finalize, Open, Opened, 
  Prepare, RESULT_BUSY, RESULT_DONE, RESULT_ROW, Reset, Step]

conn := Open(dbName):
Execute(conn, sprintf("SELECT load_extension('%s')", sq3Extension));
Error, (in Database:-SQLite:-Execute) not authorized

Am I missing something? Any way to add these functions to SQLite in current version of Maple?

Thanks in advance.

César Lozada

PS: SQLite is updated in Mathematica 13.1

Dear all

I construct by hand the two matrices L and U so that A= LU ( LU-factorization) 
I would like to find the number of arithmetic operations required to obtain the matrices 𝐿 and 𝑈

Number_arithmetic_operation.mw

Thank you

Hello, 

does the update of MapleSim 2022.2 have a bug when loading the own libraries? 
After installing the MapleSim 2022.2 update, my libraries have disappeared. I am unable to load them again. The libraries are still in the same folder as before, but when I try to load them, I get the error message

However, the library NoiseX is not listed in the left bar. Even when I try to create a new library, it is not shown in the left bar. On the other hand, there are no problems with the imported libraries. Many thanks in advance for any advice. 

Best wishes,

Clemens 

Anybody find Import CAD closes MapleSim 2022.2 when just opening file chooser when attempting to import CAD file?

Regards,
Bill

Hi.  I am using the linux version of Maple.  I seem to experience more bombs in Maple/Linux vs MathCad/Windows.  The program just froze as I was entering text.  Just text.  It is not a disaster since I make very frequent saves.  But it is very annoying.  I was a heavy user of MathCad from about 2005 to 2019.  In the early days, it bombed a lot.  But I do not recall that it ever bombed when I was entering text.  Any suggestions?  Would there be a limition on the number of text characters?  Is it Linux?  Other than this problem, it is a great program.

Hi! This is probably simple, but
I would like to know if there's an specific algorithm to do this:

let B =  in such a way that:

f( B ) = ; a_i in R; b_i in B; N>n.

so Linearcomb: f->V(R).

Linearcomb( f ) =

  + ... +.

with V(R) a vector space; R the Real numbers, and B the base. Neither the "factorize", nor the "simplify" are proving useful to this. Is there something i'm missng?

Does Maple Flow support the Maple Physics[Vectors] package? If so, how are vectors entered?

Let the square matrix A satisfy A^2023 = 0.

a. Prove: I-A is invertible.

b. If B is invertible, is B - A invertible?

This is not a Maple problem but it has something to do with math, specifically linear algebra, and I need help. Sorry if I bothered you. If possible please help me!

Download Unit_of_t.mw

The edge connectivity of a connected graph G  is the minimum number of edges whose deletion from the graph G disconnects G. Below we are concerned with a particular kind of edge-cut.

• For a connected graph G=(V ,E), an edge set S ⊂ E is a restricted-edge-cut, if G−S is disconnected and every connected component of  G−S has at least 2 vertices. 

Clearly, a restricted-edge-cut is an edge cut with a special requirement.

• The restricted-edge-connectivity of G, denoted by κres(G), is defined as the cardinality of a minimum restricted-edge-cut.

For example, a graph g is as follows.

Clearly, its edge-connectivity is 1 since (0,3) or (0,4) is a edge cut of g. But we can find that  if we remove the edge (0,3), then "3" is a isolated vertex. Similarly, "4" is a isolated vertex if we remove  (0,4). It is not difficult to find g has exactly the two cut-edges (0,3) and (0,4).

Based on the definition of the restricted-edge-cuts, neither {(0,3)} nor  {(0,4)} are restricted-edge-cuts.  A minimum restricted-edge-cut is {(0,1),(0,2)} since every connected component of G-{(0,1),(0,2)} has  (at least) 2 vertices.

So  κres(g) is 2.  My problem is:

Given a graph G, how to calculate the restricted-edge-connectivity of  G?  Moreover, how to find a minimum restricted-edge-cut? 

A specific graph that I want to test is as follows. (it has 16 vertices and 56 edges.) I would like to calculate its restricted-edge-connectivity and find a minimum restricted-edge-cut. 

g:=ConvertGraph("O~tIID@wL~j`PbOqgLJ@p");
DrawGraph(g, stylesheet=[vertexborder=false,vertexpadding=15,edgecolor = "Black",
     vertexcolor="Black",edgethickness=2])

EdgeConnectivity(g) 

6

One option I came up with is to find all 6-edge subsets first. Test if they satisfy  the restricted condition (one by one). Then continue to increase to 7 or more. But this violent calculation may get stuck in the first step. That is, test all the minimum edge cut sets (Note that we will consider 32468436 edge-subsets!) I was referring to the efficiency aspect.  

with(Iterator):
C:=Combination(58,6):
K:=Edges(g):
#sub:=seq( K[[seq(c[]+1)]], c=C); # do not run this code since it has 32468436 members.

Any language is acceptable.( C or C++, Python. )

PS: Some time ago, I also asked a related question (but with some differences) on mathematica stack （Find all the minimum edge cuts of a graph）. Although Bob Hanlon  gave a reply, the actual result is not good.

Edits: The following literature gives a polynomial algorithm for computing the restricted-edge-connectivity of a given  graph. The heart of it is to computing the least cardinality of some  edge-pairs's edge separator. I'm stuck here.

• Esfahanian A H, Hakimi S L. On computing a conditional edge-connectivity of a graph[J]. Information processing letters, 1988, 27(4): 195-199.

How to implement this algorithm is my current concern.

Hello:

I've changed my laptop this week and I'd like to know how to install Maple with my account in the new one.

Thanks in advance.

Sergio Sanz.

 Help in writing Maple code to transform differential equation with partial derivatives into ordinary differential equation