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Hello!

I'm trying to solve a differential equation of the form y.y"+y'+y= { 1 for 0<x<1 and 0 for else } with conditions: y(0)=0 and y'(0)=1.

I wrote this:

f(x):=heaviside(0)-heaviside(1);

Eq := y(x)*(diff(y(x), x, x))+diff(y(x), x)+y(x)-f(x);

ans := dsolve({Eq, y(0) = 0, (D(y))(0) = 1},numeric);

But it gives an error.

I also tried ODE tools>assistants>analyzer

It says: the ODE system does not contain derivatives of the unknown function heaviside.

 

It's the first time I use Maple and I don't know what to do. Need your help urgently. Thanks in advance.

 

optimal control problem...

Yesterday at 5:49 PM aylin 20

Hi there,

Is there a way in which i can solve the following optimal control problem numerically with Maple?

 dH/dt=λ-µ H-(1-u1)β H V+δ I,

dI/dt=(1-u1)β H V-σ I,

‎dV/dt=(1-u2)k I-γ‎V,

dλ1/dt=-1+λ1µ+β‎‎V(1-u1)(λ1-λ2),‎

dλ2/dt=λ1δ+λ2σ-λ3(1-u2)k‎,‎

‎dλ3/dt=β H(λ1-λ2)(1-u1)‎‎+λ3γ.

where

u1=βHV(λ1-λ2)/A1,

u2=-λ3kI/A2,

σ = α + δ,

and

H(0)=1.7*10^8,    I(0)=0,    V(0)=400.

 

λ=5*10^5,    µ=0.003,     β=4*10^(-10),    α=0.043,    δ= 0.2                  k=6.24,       γ‎=0.65.

A1=900, A2=1000.

 

Answers and advice are very appreciated. 

Thank you all for reading.

Aylin

Hi all,

I am stuck with the following problem:

convert(cos(alpha), exp); works fine for me.

Once I have the trigonometric functions in a matrix, it does not work any more:

In the latter line, A keeps the trigonometric functions. Why is this the case? Is there any way to force maple to keep the complex exponentials instead of trigonometric functions?

 

I am using LinearAlgebra and VectorCalculus.

 

Best Regards

Wassja

Is there any command in maple that can show us an assigned varibale how much bytes occupied on memory ?

a:=["just a string", 3.14 , 123 , x/y]

d:=array( 1 .. 2, 1 .. 2, [( 1, 1 ) = ("just a string"), ( 1, 2 ) = (3.14), ( 2, 1 ) = (123), ( 2, 2 ) = (x/y)  ] )

c:=a x^2 + b x + c

b := Matrix(2, 2, {(1, 1) = "just a string", (1, 2) = 3.14, (2, 1) = 123, (2, 2) = x/y})

b := Matrix(2, 2, {(1, 1) = "just a string", (1, 2) = 3.14, (2, 1) = 123, (2, 2) = x/y})

(1)

``


It should be great for benchmarking !

I have an integral that maple can not solve but I can solve it by hand. How can I add this to maple integration database?

f:=int(r^2*BesselJ(0,a*r)*BesselI(1,b*r),r)

Please see the file below.

Integral.mw

 

Many many thanks! :)

How do i use d'Alembert formula to solve,plot and animate with Maple software

So for the part of the erdos gallai theorem that says:


\sum^{k}_{i=1}d_i\leq k(k-1)+ \sum^n_{i=k+1} \min(d_i,k)

 

how could I translate this into maple? I'm assuming I'll need to use nested for...dos

Here was my search strategy to find the answer:

keyboard shortcut execute worksheet on http://www.mapleprimes.com/search/?term=keyboard%20shortcut%20execute%20worksheet

only found one thing http://www.mapleprimes.com/users/erik10/answers

Googled it found 

http://www.maplesoft.com/support/help/maple/view.aspx?path=worksheet%2Freference%2Fhotwin

http://www.maplesoft.com/support/help/Maple/view.aspx?path=worksheet/expressions/executeworksheet

http://scipp.ucsc.edu/~haber/webpage/maple_cheatsheet.pdf

Don't see a keyboard shortcut. 

What is the keyboard shortcut to execute entire worksheet? Is there a name for this action of executing the whole worksheet? 

 

What did you search and click to find the answer? 

I am Maple 15 student edition user and the packages is not loaded when I use the execute all command from the GUI. I have to manually press the enter key to have by package loaded before I use a function defined in the package. How can I work around this issue?

Thanks

P.S: You can see the Maple document attached to this post.

NumericalSimulation.mw

A := Matrix(3, 4, {(1, 1) = 1, (1, 2) = 0, (1, 3) = 0, (1, 4) = 0, (2, 1) = 2, (2, 2) = 2, (2, 3) = 0, (2, 4) = 0, (3, 1) = 0, (3, 2) = 6, (3, 3) = 4, (3, 4) = 0});
print(`output redirected...`); # input placeholder
Matrix(%id = 4436610626)
RowSpace(A);
print(`output redirected...`); # input placeholder
RowSpace(Matrix(%id = 4436610626))

 Why is this failing to give the row space? I copied and pasted it from the tutorial on this and it seems to run in the tutorial but not when I copy and paste it outside the tutorial? 

tutorial http://www.maplesoft.com/support/help/maple/view.aspx?path=LinearAlgebra%2FRowSpace

See picture

http://i.imgur.com/eQtEJU4.png?1

 

In general what is the best way to share maple code with users on this forum ? The above copy and paste looks messy. 

 

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Dear all,

 

Let me first explain a problem I've encountered when working with Maple 18 64 bit in Linux (Ubuntu 12.04). I've tried some things to solve it, but unfortunately without succes

When working with the DifferentialAlgebra package I'm encountering a problem concerning memory. Without going into details, I'm using the RosenfeldGroebner function (DifferentialAlgebra/RosenfeldGroebner) . After about 10 minutes of calculation or so, the computation stops with the error message

>> Error, (in DifferentialAlgebra:-RosenfeldGroebner) out of memory error

This particular error does not have a *help*-file, so no help there.

Now, I'm pretty bumped out because of this error, because I'm working on 16 GB RAM computer which is imo quite a lot. Moreover, I have the feeling, that Maple is not using the full capacity of memory. This, is because I was monitoring the memory during the computation (via the System monitor). Before I start the calculation: the memory usage is about 3.6 GiB (=22.8%). During the calculation it slowly rises until about 8GiB (50%) at which the computation stops and the above-mentioned error message pops up. So it looks there's a big part (about 7.5-8 GiB) of memory still available, but isn't used.

So my question is: What are the possibilities to solve this problem. What can I try to do to have more memory available to be able to do the calculation.


Of course I was looking into the possibilities myself. In my experience I found the information found on this forum and on the Maple help files confusing or not very helpful. Probably, because I have little knowledge of programming or computer architecture. Nevertheless I would like to know some things about it. So, iI'll  present what I tried to do:

- The command kernelopts('datalimit') returns the total amout of heap memory in kibibtyes that Maple may consume   
  In my aplication this is set to infinity. So I presume that this could not explain why the program stops at only 50% Memory usage

- The command kernelopts('bytesalloc') returns the total amount of bytes allocated by Maple kernel. This value cannot be set.  Does this attribute pose a limit on calculations or is this  the amount of memory used by the Maple 'overhead'?   
In my application the value of this attribute is 8781824 bytes, so that's about 8 MB. I suppose it is not related to the problem I'm having, or is it? 

The command kernelopts('stacklimit') returns The total amount of stack space avilable. In my application this was initially set to 8160 kibityes. I've changed this to 8160000000, wel beyond the availble memory. I would think that this now would not anymore present a limit on the memory usage.

The command kernelopts('jvmheaplimit') returns the maximum amout of heap memory for the Java virtual machine. I presume this is the maximum amout of memory for the visiualisation part of Maple (is this correct) In my application this was initially set to 65536 kiB. I've changed this to 65536000000 kBib which is well above the available memroy. I would think that this now would not anymore present a limit on the memory usage

The command   kernelopts('cacheclearlimit'); returns the memory for maintaining temporary elements in cache. In my application this was initially 524288 kiB, but i changed this to 524288000000. I would think that, again, the limit on the memory usage would be gone.

I tried the calculation again with the mentioned changes in the memory attributes. Unfortunately, the error message *out of memory error* still popped up at about 50% memory usage.

Did I overlook something?? What can I do?? Is there actually that I can do? Where should I look?

Many thanks !!

how to save the session of maple worksheet so that no need to calculate again after restart computer

after calculated 70 million result for a long time, how to save the result and session so that no need to recalculate again?

Hello,

One again, I have a problem to solve some bifurcation problem using maple.

Discuss the existance of Equilibria and determine any possible bifurcation.

x'=r*x-ln(x+1);

where $r$ is a parameter.

many thinks for your help and suggestion.

 

 

 

I actually had the same problem on Maple 16. When i go to plot an equation (usually on implicit plots) it just repeats the equation in blue text rather than showing any sort of plot. Im sure i am just missing a simple option somewhere, but for the life of me I cant find it. Any and all help would be appreciated. 

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