Complex Dynamical Phenomena Research Articles

Compound cavity modes in semiconductor lasers with asymmetric optical feedback

We describe a static model for determining the oscillating modes of an external cavity semiconductor laser with asymmetric feedback induced by external mirror misalignment. The most significant prediction of this model, the existence of double loss minima leading to compound cavity mode splitting, has been confirmed directly by spectral measurements. This result is important for analyzing complex dynamical phenomena in semiconductor lasers with optical feedback.

Modular Modelling Applied to a Benson® Boiler

A comprehensive nonlinear model for a once-through steam generator (OTSG) of BENSON design is presented. A modular “first-principles” modelling technique is applied and the basic equations describing the boiler, combustion chamber and flue gas system as well as the turbine are stated. The emphasis is placed on consistent modelling, i.e. developing a model consistent with the intended application.The implicit numerical scheme employed to solve the extremely stiff system of equations is briefly outlined. Superheater temperature control and decoupling boiler control is discussed. Compari son of actual and simulated data shows good agreement supporting the validity of the model. Two special dynamic events, the rupture of a fccdwater pipe and the loss of a coal mill are analyzed in details. It is concluded that first-principles modelling can provide detailed physical insight into complex dynamical phenomena thus enabling improved boiler design.

Grazing of ciliates on blue–green algae: Effects of ciliate encystment and related phenomena

AbstractGrazing of the ciliate Colpoda steinii on the blue–green alga Anacystis nidulans has been studied in batch and chemostat type laboratory cultures. Growth of the populations, grazing of the ciliates on the algae, hydrodynamic washout of the populations (in chemostat cultures), encystment of Colpoda, and transfer of cysts from the liquid culture to the vessel wall and their attachment thereto were all found to have significant effects on the dynamics of this system. In addition, reinoculation of the liquid with ciliates excysted from the wall and with algae detached from the wall may be important. The interaction of all of these processes produces quite complex dynamical phenomena which at present cannot be predicted by a model. The results obtained differ from those found earlier for feeding of ciliates or slime mold amoebas on bacteria in that steady states of coexistence, rather than sustained oscillations, were exhibited by the present system.