Recent content by tcuay

ø is the magnetic flux. i have double checked for it, the deriving process should be right. and it seems reasonable if t approaches infinity Vs=Køω quite similar to Ea=Køω

Thanks for your reply. I did in the following steps: 1.J(ω/t)=KøIa; 2. and then substitute Ia from Vs=IaRa+Ea into 1; finally, i got: ω=Vs/(Kø+JRa/Køt) But it turns out the term ø cannot be eliminated and it is unknown. Where am i wrong?

Homework Statement I try to derive the expression of ω with respect to t, but the problem is the armature current Ia or the flux is unknown. I don't know how to solve it. Anyone could give me ideas? Thanks a lotHomework Equations τ=J(ω/t) Vs=IaRa+Ea T=KEøIa Ea=KEøω

Okay, thanks very much; And all answers are solved, thanks for your reminder;

Okay, you are right. Then i also want to ask, for Q2 part d, if i find a steepest descent directional vector at a point, i.e x*, is zero; can i say that the point is a local minimizer? can the directional vector be zero when the point is a saddle point or maximum point?

First of all, really thanks for your reply; These 2 questions both are required to find their global optima, it implies they should have a finite global optima; but what i am confused is how to determine whether those local optima are also global optima? And Even though i know the methods to...

no body can help?:cry::cry:

These 2 questions,I have attempted them for hours but still no outcome:confused: For the first question: part a) i take the ∇f(x) and set it to be zero; then find out(x1,x2)=(0,-1) or((-2a-1)/3,(-2a-4)/3); but then for part b), after using second-order necessary condition, i have no idea...