Unanswered Questions

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

Hi, 

I'm currently studying the Rossler Attractor, which is the following system:

diff(x(t), t) = -y(t)-z(t)

 diff(y(t), t) = x(t)+a*y(t)

diff(z(t), t) = b+x(t)*z(t)-c*z(t).

I have found the points of equilibrium of the system.

But now I need to draw bifurcation diagrams: one for varying a, one for varying b, and one for varying c.

 

Can someone please help me with a procedure of how to do this?

Thanks in advance.

 

I have a relatively complicated ODE that i am plotting. One of the variables in particular (B[2211], purple line in the graph) should under go an exponential-like decay to zero, but instead flies off into negative territory  (see graph below) despite having a very simple equation:

problem variable rate of change= -problem variable*constant +linear combination of variables that  are always posotive.

 

My intuition is that this is because i have somehow used the odeplot tool wrong - possibly due to a problem with stepsizes.

Here is a MWE i've made:

aa_problem_MWE.mw

 

Maple 2018.

I am surprised Maple pdsolve can't solve this basic heat PDE. it is heat PDE on bar, with left end boundary condition being time dependent is only difference from basic heat PDE's on a bar.

May be a Maple expert can find a work around? I tried all the HINTS I know about.

restart;
#infolevel[pdsolve] := 3:
pde:=diff(u(x,t),t)=diff(u(x,t),x$2);
bc:=u(0,t)=t,u(Pi,t)=0:
ic:=u(x,0)=0:
sol:=pdsolve([pde,bc,ic],u(x,t)) assuming t>0 and x>0;

 

I also hope this question of mine do not get deleted as well, like the question I posted last night asking why pdsolve ignores assumptions that showed number of examples, was deleted few hrs after I posted it. 

If this question gets deleted, I will get the message that posts showing any problem in Maple software are not welcome here by Maplesoft and I will stop coming here.

 

Hi, I've been doing a few small explore plots where the ranges for the parameters are something like [-1,1], but 0 is a special value which will often need to be set.  The slider, gauge components, ... are a bit fiddly to set with exactly zero using a mouse to drag the value.  Thought about a few different ways to do this

* Right click and set value from the component properties option - a bit fiddly for the user and the graph doesn't immediately update when OK'ed.

* Extra control with a tick to set a zero value (fiddly programming and possible confusing interpretation)

* Slider component and snaptoticks=true

Last option seems to be the easiest all round, but I was wondering why it is only the slider component that has a snaptoticks property - none of the other components seem to support it and a gauge would probably be a more natural component to use.

Thanks in advance

Hi!

Consider, fixed an integer m>1, the mapping given by the following procedure:

 

G := proc (t) local k, C; C := NULL; C := t; for k from 2 to d do C := C, 1/2-(1/2)*cos(Pi*m^(k-1)*t) end do; return [C] end proc

Then, it can be proved that given x in the cube [0,1]^{d} there is t in [0,1] such that the norm of x-G(t) is less, or equal, than sqrt(d-1)/m. Indeed, dividing the cube [0,1]^{d} into m^{d-1} subcubes of side-length 1/m x ... x 1/m x 1, the point x belongs to some of these subcubes, say J. As, by the properties of the cosines function, the curve G(t) lies in J whenever t in certain subinterval of [0,1], the result follows.

In other words, computing all the solutions of the equation

1/2*(1-cos(Pi*m^(d-1)*t)) = x[d], (j-1)/m <= t and t <= j/m

for some of these solutions the desired t is obtained, where j is such that x1 in [(j-1)/m,j/m] (x1 is the first coordinate of the point x). However, for large values of m and d, the above equation have many solutions, I have tried find all of them and the process is extremely slow....Other way to find such a t can be the following: find a t satisfying the following system of inequalities

EQ := abs(t-x[1]) <= 1/m; for k from 2 to d do EQ := EQ, abs(1/2*(1-cos(Pi*m^(k-1)*t))-x[k]) <= 1/m end do

 

and then, a solution of this system is a such t. I do not know how to find, efficiently, a t such that of x-G(t) is less, or equal, than sqrt(d-1)/m   :(

Some idea?

Many thanks for your comments in advance.

 

 

I do not know how I can solve this equation, you can help me 

I am having trouble getting Maple 2017.3 with latest Physics update to give solution to Burger's PDE for viscous fluid flow with the following initial condition. May be I am not doing something right. I tried different HINTS, but no luck.

Maple can solve the PDE without the initial conditions.

May be a Maple expert can find work around or show what I might be doing wrong.

restart;
pde := diff(u(x, t), t) + u(x, t)*diff(u(x, t), x) = mu*diff(u(x,t),x$2);
ic  := u(x,0) = PIECEWISE([0,x>=0],[1,x<0]);
sol := pdsolve({pde,ic}, u(x, t)) assuming mu>0;

Maple returns () as solution.

This PDE can be solved analytically. Here is Mathematica' solution

ClearAll[u,x,y,mu]
pde = D[u[x,t],{t}]+u[x,t]*D[u[x,t],{x}]==mu*D[u[x,t],{x,2}];
ic  = u[x,0]==Piecewise[{{1,x<0},{0,x>=1}}];
sol = DSolve[{pde,ic},u[x,t],{x,t},Assumptions->mu>0]

 

 

Is it possible to use Regex to generate a complete list of patterns?

for search pattern in a list of characters

Strange (inconsistent) behavior of eval in piecewise

 

restart;#####################

a:=2:

p:=piecewise(x<a, 1/(x-a), x=a, 22, 33);

p := piecewise(x < 2, 1/(-2+x), x = 2, 22, 33)

(1)

eval(p, x=a);

22

(2)

restart;#####################

a:=Pi:

p:=piecewise(x<a, 1/(x-a), x=a, 22, 33);

p := piecewise(x < Pi, 1/(-Pi+x), x = Pi, 22, 33)

(3)

eval(p, x=a);

Error, (in eval/piecewise) numeric exception: division by zero

 

restart;#####################

a:=Pi+ln(2):

p:=piecewise(x<a, 1/(x-a), x=a, 22, 33);

p := piecewise(x < Pi+ln(2), 1/(-Pi-ln(2)+x), x = Pi+ln(2), 22, 33)

(4)

eval(p, x=a);

22

(5)

restart;#####################

a:=Pi+1:

p:=piecewise(x<a, 1/(x-a), x=a, 22, 33);

p := piecewise(x < Pi+1, 1/(-Pi-1+x), x = Pi+1, 22, 33)

(6)

eval(p, x=a);

Error, (in eval/piecewise) numeric exception: division by zero

 

restart;#####################

a:=gamma:

p:=piecewise(x<a, 1/(x-a), x=a, 22, 33);

p := piecewise(x < gamma, 1/(-gamma+x), x = gamma, 22, 33)

(7)

eval(p, x=a);

Error, (in eval/piecewise) numeric exception: division by zero

 

#######################

f:=x->piecewise(x<Pi, 1/(x-Pi), x=Pi, 22, 33);

f := proc (x) options operator, arrow; piecewise(x < Pi, 1/(x-Pi), x = Pi, 22, 33) end proc

(8)

f(Pi);

22

(9)

 


Download piecewise-strange.mw

how do i solve the following expression in maple and how do i plot sigma wrt a?

sigma = 4*sigma[s](1/4-(int((BesselJ(1, y))^2/y(1+y(400*10^(-10)/a)^2+sqrt(1+y(400*10^(-10)/a)^2)), y = 0 .. 10^4)))

 

I really need help to understand this i know it is a non associative operation but i just cannot see how no operator is handled in the computation here


 

A := (rand(1 .. 100))():

8

 

8

 

9424

(1)

A := (rand(1 .. 100))():

33

 

33

 

33

(2)

``


 

Download please_HELP.mw

This will be my last question i promise then i will go to bed for a week.

(its what happens when the government decide after 20 years they are going to make it illegal for me taking stimulants therefore must purchase from non pharmacy sources and can barely afford 1 out of every 2 weeks supply, they charge $6 AUD per tablet on the street so, i was prescribed 8 per day, i earn $250 a week, so yes, that is more than all of my money)

Sorry, just want to repeat that as much as possible to embarass my government an infintesimal amount in public forums, never go to australia, my country is a piece of shit and the people here are on the most part uncivilized socially backward morons 

 

 

Edit: Here is a better worksheet for you comrades 
 

restart

X := proc (A, B) options operator, arrow; (`mod`((`mod`(A, n))*(`mod`(B, n)), n))((`mod`(A, n))*(`mod`(B, n))) end proc:

Y := proc (A, B) options operator, arrow; (`mod`((`mod`(A, n))*(`mod`(B, n)), n))*(`mod`(A, n))*(`mod`(B, n)) end proc:

is(X(A, B) <> Y(A, B))

false

(1)

is((`mod`((`mod`(A, n))*(`mod`(B, n)), n))((`mod`(A, n))*(`mod`(B, n))) <> (`mod`((`mod`(A, n))*(`mod`(B, n)), n))*(`mod`(A, n))*(`mod`(B, n)))

false

(2)

A := (rand(1 .. 100))():

is((`mod`((`mod`(A, n))*(`mod`(B, n)), n))((`mod`(A, n))*(`mod`(B, n))) <> (`mod`((`mod`(A, n))*(`mod`(B, n)), n))*(`mod`(A, n))*(`mod`(B, n)))

true

(3)

is(X(A, B) <> Y(A, B))

true

(4)

``


 

Download helpPlz.mw

 

Hi dears,

I hope that my request (question) is appropriate for Mapleprimes.

I know Gröbner bases and Buchberger's algorithm and I want to understand  the F4-algorithm. However, I know that  the corresponding paper can be found:

https://www.sciencedirect.com/science/article/pii/S0022404999000055 

Could you please state the sketch and main parts of the algorithm s.t. I can understand it?
Is there any primary Maple implementation of F4-algorithm?

Thanks in advance.

Hello All,

 

Please any sugestions on mathmateical projects. They assigned me to do a project for my math class for something I should be interested about. But since the deadline is one week and I don't have anything in mind right now. So I just need y'all help t suggest for me any ideas 

Hello All,

 

This is Alex, I'm doing a master degree in computer sience at UMICH. They assigned me to do a math project and deadlined by next week, and I need y'all help to suggest some ideas for me if you guys having any 

 

Thanks 

Ali

First 117 118 119 120 121 122 123 Last Page 119 of 334