Recent content by ManuelF

I have not understood the figure ... The mass is attached to the spring and the dashpot? For the system in figure (I've attached), the equation of motion is: m\ddot{x}+c\dot{x}+kx=0

How can I construct the phase portrait(with Mathematica) of the following system? \dot{x}(t)=y(t) \dot{y}(t)=-x^3(t)+4x(t)y(t)

Thank you very much!

That is a necessary condition, but I do not think is enough! Are you sure? Thank you.

Hello! I have to solve a system of PDEs with Comsol and do not know where to start ... This is the system: &u_{,x}+v_{,y}=k y+h x\ \ \ &in\ \mathcal{A} v_{,x}-u_{,y}=k x-h y\ \ \ &in\ \mathcal{A} u n_x+v n_y=0\ \ \ &on\ \partial\mathcal{A} \mathcal{A}\ in\...

Hello! Can you tell me the sufficient condition for the existence of the vector potential? Thank you very much!