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A4-format til udskrift. - Aarhus Universitet

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3. GENERELLE METODER 161<br />

y ′<br />

Fasediagram<br />

y ′ = F(y)<br />

3.27. Logistisk stabilitet ☞ [LA] 18 Stabilitet<br />

Eksempel 1<br />

Den logistiske ligning<br />

har ligevægts løsninger<br />

og<br />

F ′ (0) = k > 0: 0 Ustabil ligevœgt.<br />

F ′ (K) = −k: K Stabil ligevœgt.<br />

dP<br />

dt<br />

= kP(1 − P<br />

K )<br />

P(t) = 0, P(t) = K<br />

F ′ (P) = − 2k<br />

P + k<br />

K<br />

3.28. Logistisk stabilitet ☞ [LA] 18 Stabilitet<br />

Eksempel 1 - figur<br />

P ′<br />

Fasediagram<br />

P ′ = kP(1 − P<br />

K )<br />

3.29. Lotka-Volterra stabilitet ☞ [LA] 18 Stabilitet<br />

Eksempel 2<br />

For Lotka-Volterra systemet,<br />

a,b,k,r > 0,<br />

dR<br />

= kR − aRW<br />

dt<br />

dW<br />

= −rW + bRW<br />

dt<br />

y<br />

P

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