531 almostperiodicfunctions chaoticbehaviorinsystems chemistry differentialequations duffingequations dynamischessystem electric electricity electrodynamics electromagneticfields electromagneticwaves engineering engineeringmathematics mathematicalmodels mathematicalphysics mathematics mechanical mechanics motion nichtlineareschwingung nichtlinearewelle nonlinearoscillations nonlineartheories oscillationsnonlinéaires oscillationtheory oscillators physicalandtheoreticalchemistry physicalorganicchemistry physics plasma(ionizedgases) radiation science solarradiation solidstatephysics stars systemanalysis systèmesdynamiques technology theoryof vibration wave-motion wavemechanics waves