Dear all 
I have a PDE, with unknown u(t,x,t) ,  zero boundary condition and initial condition given

I converted the equaiton using finite difference to get a system of algebraic equation 

The system is solved at each time step 
I think i have a problem to update the solution inside the loop. 

I hope find the problem or why the numerical solution is different to exact solution at last time 

System_finite_difference.mw

Thank you for your help 

Delay differential equations in Chebfun lists 15 examples "taken from the literature". Many of them can be (numerically) solved in Maple without difficulty, yet when I attempt to solve the  in the above link, Maple's internal solver `dsolve/numeric` just halts with an error. 

plots:-odeplot(dsolve({D(u)(t) + u(t)**2 + 2*u(1/2*t) = 1/2*exp(t), u(0) = u(1/3)}, type = numeric, range = 0 .. 1/3), size = ["default", "golden"]);
Error, (in dsolve/numeric) delay equations are not supported for bvp solvers

Even if I guess an initial (or final) value artificially, the solution is still less reliable (For instance, what is the approximate endpoint value? 0.26344 or 0.2668?): 

restart;
dde := D(u)(t) + u(t)**2 + u(t/2)*2 = exp(t)/2:
x__0 := 2668/10000:
sol0 := dsolve([dde, u(0) = x__0], type = numeric, 'delaymax' = 1/6, range = 0 .. 1/3):
plots['odeplot'](sol0, [[t, u(t)], [t, x__0]], 'size' = ["default", "golden"]);

x__1 := 26344/100000:
sol1 := dsolve([dde, u(1/3) = x__1], type = numeric, 'delaymax' = 1/6, range = 0 .. 1/3):
plots['odeplot'](sol1, [[t, u(t)], [t, x__1]], size = ["default", "golden"]);

Compare:  (Note that the reference numerical solution implies that its minimum should be no less than 0.258 (Is this incorrect?).).

And actually, the only known constraint is simply u(0)＝u(⅓) (so neither value is known beforehand). Can Maple process this boundary condition automatically (that is, without the need for manual preprocessing and in absence of any other prior information)?
I have read the help page How to | Numeric Delay Differential Equations and Numerical Solution of Difficult ODE Boundary Value Problems, but it appears that those techniques are more or less ineffective here. So, how do I solve such a "first order nonlinear 'BVP' with pantograph delay" in Maple?

restart;
Pr:=0.71: n:=-1:

eta0:=0.0699;

EQ1:=diff(H(x), x ) - x*diff(F(x), x ) ;
 

EQ2:=(1+x^2)*diff(F(x), x$2) + (3*x + x*F(x)-H(x))*diff(F(x), x) + F(x)^2 + G(x)^2 +2*P(x) + x*diff(P(x), x) ;

EQ3:=(1+x^2)*diff(G(x), x$2) + (3*x + x*F(x)-H(x))*diff(G(x), x) ;

EQ4:=(1+x^2)*diff(H(x), x$2) + (3*x + x*F(x)-H(x))*diff(H(x), x) + (1+F(x))*H(x)- diff(P(x), x);

EQ5:=(1+x^2)*diff(theta(x), x$2) + x*(1-2*n)*diff(theta(x), x) + n^2*theta(x) - Pr*( n*F(x)*theta(x) + ( H(x)-x*F(x) )*diff(theta(x), x)  ) ;

EQ:={EQ1=0, EQ2=0,EQ3=0,EQ4=0 ,EQ5=0}:

IC:={ F(0)=0, G(0)=12, H(0)=0, theta(0)= 1, F(eta0)=0, G(eta0)=12, H(eta0)=0, theta(eta0)= 0, P(0)=0};
 

sol:= dsolve(EQ union IC,numeric,output=Array([0,0.0699]));

ques.mw

dS/dt=qnv-alpha_1*S*H-mu_sh*S

dH/dt=lamda_h-alpha_1*S*H-mu_h*H

dI/dt=alpha_1*S*H-beta_1*I-mu_i*I

dS/dt=beta_1*I-delta_1*S-mu_s*S

DATA:

q=0.75; n=15;v=20; alpha_You1=0.001; S=2000; H=3000; mu_sh=0.000000000012; lambda=3000;mu_h=0.94; beta_1=0.125; I=0; mi_i=0.95; delta_1=0.0975; S=0; mu_s=0.029

Good day all,

please I am new Maple user, i used the same code to solve boundary layer flow. Itried to use the same code in solving nanofluid but the solution is not coverging at some point. But the author i want to compared my results with had solution at those points.

Is there any way i can get solution of this model at this with these values?. Please i need your help. Thank you in advance

secod_code.mw

Sometimes the canvas in the 2d-workspace of a subsystem (or component) is grayed out and the parameters in the parameter pane cannot be changed.

Example from the Model Gallery where the mass cannot be changed

Another example of a CAD geometry where I would like to change color and transparency:  seeshell.msim

How to unprotect the parameters?

I have observed that copy and pasting (Edit2: in a new document) and deleting the original component and copy/paste back into the original document and reconnection of the pasted  component works. Are there shorter ways to unprotect? 

And: How to do the reverse action (i.e. protecting a component)?

(I could not find a "when" and "why" for the protection in the documentation. Maybe I overlooked something)

Edit:

Other reasons why to unprotect are suppressions of components and highlight of multibody ports and axes.

Adding or reformating automatically generated ports (Edit3).

 

How to conver a patial differetial equation to ordinary differential equation with or without dchange?
 

Download pde_to_ode.mw

Dear Maple experts,

I am running a Maple code with several lines/ curves in a plot.

For two of the curves, I use style=pointline. But in the legend the symbols on the lines are not shown. Can you advise how we can make them appear?

I have attached the file. Thank you so much! 

Download LegendPlot.mw

When i try to log on to my maplesoft acount on Maple 2023 i get a messeage saying "Sign in Error: Please check your credentials and try again." i have done this multiple time double checked my password and everything, but it won't let me log on... what do i do?

Hi @Acer, and of course also hi to the whole mapleprimes comunnity.

I have a problem with the Phasors module. Very often I have to use the in calculations involving phasors. Sometimes it might make sense, since one of the involved variables are not defined as a phasor.

May I suggest that you upgrade the phasors module to a package Acer? I'd be honored to help in the testing.

Besides I have the same experience as mentioned in this question (bear over with me it's years since already): Maple 2020 Sheet now opening in 2021, 2022, and 2023 results in errors.

attached some examples:

Eksempel_8.2.mw

Example_12.3.mw

Eksempel_14.5.mw

Opgave_4_-_SHS_-_RA_ref-UL1.mw

Opgave_4_-_SHS_-_RA_ref-UL1_using_context_menu.mw

Hi,

I'm just working on som electricity tasks and have to calculate thre phase power in alternating current systems. I use the SI system and have checked that with UsingSystem() -> SI and GetUnits() -> voltampere[power], voltampere_reactive[power] among others, so everything should be alright, but why can't I then choose theese units from neither the Units Palette, the Context Panel or right click menu option Convert Output Units?

convert(expr, units, var) and convert(expr, units, VA) works but my students and colleagues won't be satisfied with that.

Thank you for any help.

Is there a way to delete frames arround the legend in a plot?

I have a calculation sheet that used to work in Maple 2020 and earlier, but with an upgrade to versions 2021 to 2023 the same errors are appearing. The sheet still functions fine in 2020 but unknown why these errors appear when using 2021 thru 2023.

Does anyone know what might have changed with the later versions to result in these types of errors?

Hi . My question is about writing a gravity equation, which I explained comprehensively I  explain in the PDF linked below, and I need the code for this equation in Maple.

My_Question2.pdf