Hi

https://www.energymatters.com.au/solar-calculators/solar-battery-calculator.php?utm_source=NewsletterMailingList&utm_medium=email&utm_campaign=EM171101CN

I am trying to find how it calculates how much solar will be exported back to the grid. I thought this could only be estimated  empirically, but apparently not.

Anyway, it depends on three factors, power consumption, power installed, and average hours of sun per day, or hours per day as a function of time of year. For C=4.5kWh/day and S=5kW and H=4 sun hrs per day, means 90% will be exported back to the grid Y. So Y(C,S,H)= a closed form expression.

How to guess the fuction? I tried array interpolation for a numeric solution, but it complains: independent coordinates must be sorted in increasing order

law.mw

I have the following inequality system : 

              [ U_1,2 + U_1,3 -1 = 0,

U_2,3 - U_1,2 = 0, 

-U_1,3 -U_2,3+1 = 0,

0 <=U_1,2,

0 <= U_1,3,

0 <= U_2,3]

I want to solve it using LinearMultivariateSystem, namely I excuted a command : 

Then the following is return : 

Error, (in Utilities:-SimpleAnd) invalid input: a string/name list is expected for sort method `lexorder`

 I tried that

My question is that how do you use LinearMultivariateSystem for varibles indexed by two params.

Thank you.

Hiya

from this

>with(combinat):
>A:=choose([CPC__h, SIZE__h,CPC__m, SIZE__m,CPC__l, SIZE__l],2): 

where h denotes high, m=medium, l=low

I want to select CPC and SIZE all the combinations w.r.t h, m and l

[[CPC__h, SIZE__h], [CPC__h, SIZE__l], [CPC__h, SIZE__m], [CPC__l, SIZE__h], [CPC__l, SIZE__l], [CPC__l, SIZE__m], [CPC__m, SIZE__h], [CPC__m, SIZE__l], [CPC__m, SIZE__m]]

>nops(A)-3

9

I want to apply the methodology to 
choose([CPC__h, SIZE__h, SH__h,CPC__m, SIZE__m, SH__m,CPC__l, SIZE__l, SH__l],3)
 

convert(...,Int) in Maple 2018.2 works for fourier, invfourier, laplace, but does not work for invlaplace.  

Why is that? Is there a workaround?

expr:=fourier(f(x), x, w):
convert(expr,Int);

expr:=invfourier(f(w), w, x):
convert(expr,Int);

expr:=laplace(f(s),s,t):
convert(expr,Int)

expr:=invlaplace(f(s),s,t):
convert(expr,Int)

Was expecting to see the Mellin's inverse formula.

Maple 2018.2 on windows 10

Hi I am trying to solve the following system of equation. I could solve it for approximate value of s(0)=0.9999 using middefer method of bvp, but as soon as I give the b.c. as s(0)=1, Maple gives me an error that there is an numeric exception. Can someone explain it what is going wrong with s(0)=1? Any sugesstion to solve the equation?
error.mw

b := 1;
r := .1;
l := 3;
a := 10; p := 1.5; ds := 100; dk := 1;

sol3 := dsolve({ds*(diff(i(x), x)) = exp(eta(x)), s(x)^3*i(x)*b*r+(1-s(x))^3*a*l*(diff(s(x), x))/s(x)^1.5 = (1-s(x))^3, diff(eta(x), x) = dk*(i(x)-1)/s(x)^p, i(0) = 0, i(1) = 1, s(0) = 1}, {eta(x), i(x), s(x)}, approxsoln = [eta(x) = .5, i(x) = .5, s(x) = 1], initmesh = 100000, type = numeric, maxmesh = 100000, range = 0 .. 1, output = listprocedure, method = bvp[middefer], abserr = 0.1e-3, adaptive = true);

Error, (in dsolve/numeric/bvp) numeric exception: division by zero

plots[odeplot](sol3, [[x, s(x)]], 0 .. 1, color = ["Green"]);

Thanks and regards,
 

Using Latest Physics updates (I am not sure when this started), pdsolve gives Error, (in PDEtools/eval/2) numeric exception: division by zero on the following problem from a HW from text book.

restart;
PackageTools:-IsPackageInstalled("Physics Updates");
                             "220"


pde:=diff(w(x,t),t)+3*t*diff(w(x,t),x)=w(x,t);
ic:=w(x,0)=f(x);
sol:=pdsolve([pde,ic],w(x,t));

Error, (in PDEtools/eval/2) numeric exception: division by zero
 

Mathematica answer btw is 

pde = D[w[x, t], t] + 3 t D[w[x, t], x] == w[x, t];
ic = w[x, 0] == f[x];
sol = Simplify[DSolve[{pde, ic}, w[x, t], {x, t}]]

This is on Maple 2018.2 on windows 10 64 bit.

Any idea what is causing this and any workaround? Do others get the same exception?

For some reason the Maple software is not evaluating the last bounds for a triple integral.

But the evalf command works.

I have Maple through the school where I teach math, and the IT-guy gave us Maple 2018.1 to install. 

But after a while even though I have Maple 2018.1 installed on my computer Windows 10 pc, then Maple 2018.1 surgests that I upgrade to 2018.1?? Any idea why? 

Trying Maple on a textbook problem to verify my hand solution. 

But Maple pdsolve hangs with the mserver.exe tallomg almost 100% CPU and over 10 GB of RAM!

I waited for almost 20 minutes. Tried another time, same thing.

It is no problem if Maple can't solve this, but Maple seems to suffer from too many hangs when it is not able to solve a problem. I've had similar problems with dsolve also.

This is on windows 10, 64 bit with Maple 2018.2 With Physics updates version 218

restart;
PackageTools:-IsPackageInstalled("Physics Updates");

218

interface(showassumed=0);
infolevel[pdsolve]:=2;
pde :=  diff(u(x,t),t)=k*diff(u(x,t),x$2)+Q(x,t);
ic  :=  u(x,0)=f(x);
bc  :=  eval(diff(u(x,t),x),x=0)=A(t),eval(diff(u(x,t),x),x=1)=B(t);
sol:=pdsolve({pde,ic,bc},u(x,t)) assuming t>0,k>0;

then

* trying method "_Fn" for 2nd order PDEs
   -> trying "linear_in_xt"
   -> trying "BC_equal_0"
* trying method "_Cn_cn" for 2nd order PDEs
Trying travelling wave solutions as power series in tanh ...
Trying travelling wave solutions as power series in ln ...
Trying travelling wave solutions as power series in tanh ...
Trying travelling wave solutions as power series in ln ...
* trying method "Wave" for 2nd order PDEs
   -> trying "Cauchy"
   -> trying "SemiInfiniteDomain"
   -> trying "WithSourceTerm"
* trying method "Heat" for 2nd order PDEs
   -> trying "SemiInfiniteDomain"
   -> trying "WithSourceTerm"
* trying method "Series" for 2nd order PDEs
   -> trying "ThreeBCsincos"
   -> trying "FourBC"
   -> trying "ThreeBC"
   -> trying "ThreeBCPeriodic"
   -> trying "WithSourceTerm"
      * trying method "_Fn" for 2nd order PDEs
         -> trying "linear_in_xt"
         -> trying "BC_equal_0"
      * trying method "_Cn_cn" for 2nd order PDEs

And here is hangs. Notice that because both ends are Neumann, there is no unique solution to this problem.  So the solution will contain arbitrary constant. May be this is what made pdsolve hang? 

No it is not. Trying with only one end nonhomogeneous  Neumann, and the other end Dirichlet, it still hangs. The problem seems to be with one end is nonhomogeneous  Neumann, which is a function of time. So this hangs also (same place)

restart;
interface(showassumed=0);
infolevel[pdsolve]:=2;
pde :=  diff(u(x,t),t)=k*diff(u(x,t),x$2)+Q(x,t);
ic  :=  u(x,0)=f(x);
bc  :=  eval(diff(u(x,t),x),x=0)=A(t),eval(diff(u(x,t),x),x=1)=0;
sol:=pdsolve({pde,ic,bc},u(x,t)) assuming t>0,k>0;

And this also

restart;
interface(showassumed=0);
infolevel[pdsolve]:=2;
pde :=  diff(u(x,t),t)=k*diff(u(x,t),x$2)+Q(x,t);
ic  :=  u(x,0)=f(x);
bc  :=  eval(diff(u(x,t),x),x=0)=sin(t),eval(diff(u(x,t),x),x=1)=0;
sol:=pdsolve({pde,ic,bc},u(x,t)) assuming t>0,k>0;

But this does not hang

interface(showassumed=0);
infolevel[pdsolve]:=2;
pde :=  diff(u(x,t),t)=k*diff(u(x,t),x$2)+Q(x,t);
ic  :=  u(x,0)=f(x);
bc  :=  eval(diff(u(x,t),x),x=0)=1,eval(u(x,t),x=1)=0;
sol:=pdsolve({pde,ic,bc},u(x,t)) assuming t>0,k>0;

The issue seems to be when one end is nonhomogeneous  Neumann which is function of time. 

Is there a workaround so it does not hang? The complaint is that Maple hangs, and not that Maple unable to solve the PDE.

Why  

eval(diff(u(x,t),x),x=0)=A(t)

gives

But

eval(diff(u(x,t),x),x=L)=A(t)

gives

I was expecting the same syntax in both cases. It seems for numbers Maple uses the first syntax and for symbols it uses the second syntax.

Does one need to worry about this difference?

Hi all,

I'm struggling with solving a delayed differential equation with time-dependent delay.

I have already use dde solver with matlab and find it cannot reaches my numerical accuracy. 

Does maple can solve this problem? I explore a little bit and don't find there is a document to guide how to tackle with this problem.

Constant delay cannot solve my problem.

Thank you very much,

Peter

Hi, 
So I am trying to use Maple to find the integer points in a region(s) bounded buy a set of inequalities. But for a specific set of inequalities, in four variables,
inequalities:= [-a1-a2+a3+a4 <= 2, a1+a2 <= 3, -2*a1 <= -1, -2*a2 <= -1, -2*a3 <= -1, -2*a4 <= -1, -a1+a2+a3-a4 <= 4, -a1+a2-a3+a4 <= 4, a1-a2+a3-a4 <= 4, a1-a2-a3+a4 <= 4]; in four variables, vars :=[a1,a2,a3,a4];

I am getting the following error
Error, (in solver) invalid input: LinearMultivariateSystemInternal expects its 1st argument, eqns, to be of type ({list, set})({`<`, `<=`, `=`}), but received {a1-a2 = 0, -11/2+a1 <> 0}

Also, upon checking the inequalities by hand, I am sure that the region mentioned in the error doesnt come up. as based on the inequalities, it is not possible to have -11/2+a1 > 0. But though I could be wrong about my manual inequality analysis, the error is still suprising and worrying. 
Another point to note is that if I do a variable change, as
t1 := a1-a2;
t2 := a1+a2;
r1 := a3-a4;
r2 := a3+a4;
Then with new variables the inequalities are solved without any errors.

I am working with Maple2018 for this problem. 

Any help or insight into the root of this problem would be a lot of help. 


 

I havev to calculate the intersection of three planes and need to plot them, when I try to plot them I get this error:

Error, (in plot3d) bad range arguments: (Vector(3, {(1) = -4*_t2[3], (2) = 3*_t2[3], (3) = _t2[3]})) = -8 .. 8, y = -20 .. 20

This is my code so far:

with(LinearAlgebra);
A := <1, 1, -2|3, 4, -7|-5, -8, 13>
b := <0,0,0>

x := LinearSolve(A, b)
P1 := x+3*y;
P2 := x+4*y;
P3 := -2*x-7*y;
plot3d([P1, P2, P3], x = -8 .. 8, y = -20 .. 20, plotlist = true, color = [blue, red, green]);
Error, (in plot3d) bad range arguments: (Vector(3, {(1) = -4*_t2[3], (2) = 3*_t2[3], (3) = _t2[3]})) = -8 .. 8, y = -20 .. 20

Hello,

I am currently doing this thing:

unapply(piecewise(x>37-0.25*t and x<37+0.25*t,-(11*sin(t/2+1.145)-10)*((x-37)^2)+(-3.5*sin(t)+ 1),10),x);

(It is used with "for t from 0 to 8 do *things* end do", hence why I use "t")

The problem I have is I don't want this (over) complicated function to go over y=10, but the conditions I tried were not working that well.

I saw on the Help page that it should be possible, but my attempts were unsuccessful...

Maple 2018.2 generates wrong latex in this example. In Latex a space in command name is important. So "\tau L" is not the same as "\tauL".  Since in the later case, Latex will complain that there is no command "\tauL"

Maple generates "\tauL" in the latex, when it should be "\tau L" in the following example, so the latex fails to compile because there is no command called "\tauL" in Latex.

Here is screen shot showing the problem and the Maple command to reproduce it

restart;
interface(showassumed=0);
pde :=  diff(u(x,t),t)=k*diff(u(x,t),x$2)+(exp(-c*t)*sin(2*Pi*x/L));
ic  :=  u(x,0)=f(x);
bc  :=  D[1](u)(0,t)=0, D[1](u)(L,t)=0;
sol:=pdsolve({pde,ic,bc},u(x,t)) assuming L>0,t>0,k>0;

latex(sol)

Any chance Maplesoft could fix this?

Possible workaround for now is to use something like "\newcommand{\tauL}{\tau L}" in preamble for this specific case.