Complex dynamics of modified Hastings-Powell （HP） model （phytoplankton-zoo- plankton-fish） with Holling type IV functional response and density-dependent morta- lity （closure terms） for top predator species is i...Complex dynamics of modified Hastings-Powell （HP） model （phytoplankton-zoo- plankton-fish） with Holling type IV functional response and density-dependent morta- lity （closure terms） for top predator species is investigated in this paper. Closure terms describe the mortality of top predator in plankton food chain models. Modified HP model with Holling type IV functional response gives rise to similar type of chaotic dynamics （inverted ＂teacup attractor＂） as observed in original HP model with Holling type II functional response. It is observed that introduction of nonlinear closure terms eliminate chaos and system dynamics becomes stable. Observation of this paper support the ＂Steele-Henderson conjecture＂ that, nonlinear closure terms eliminate or reduces limit cycles and chaos in plankton food chain models. Chaotic or stable dynamics are numerically verified by Lyapunov exponents （LE） method and Sil＇nikov eigenvalue anal- ysis and also illustrated graphically by plotting bifurcation diagrams. It is assumed that mortality of fish population, caused by higher-order predators （which are not explicitly included in the model） is not constant, rather it exhibits random variation through- out the year. To incorporate the effect of random mortality of fish population, white noise term is introduced into the original deterministic model. It is observed that the corresponding stochastic model is stable in mean square when the intensity of noise is small. Keywords： Holling type IV; chaos; closure term; white noise; mean square stability展开更多
The advantages of multivalued logic in optical parallel computation need no introduction. There are lots of proposals, already reported, where tristate, quarternary state logic operations can be performed with optics....The advantages of multivalued logic in optical parallel computation need no introduction. There are lots of proposals, already reported, where tristate, quarternary state logic operations can be performed with optics. Here we report a new approach to implement tristate logic based all optical flip-flop using optical nonlinear material. The concept and the principle of operation of this type of flip-flop are different from that of the conventional binary one.展开更多
文摘Complex dynamics of modified Hastings-Powell （HP） model （phytoplankton-zoo- plankton-fish） with Holling type IV functional response and density-dependent morta- lity （closure terms） for top predator species is investigated in this paper. Closure terms describe the mortality of top predator in plankton food chain models. Modified HP model with Holling type IV functional response gives rise to similar type of chaotic dynamics （inverted ＂teacup attractor＂） as observed in original HP model with Holling type II functional response. It is observed that introduction of nonlinear closure terms eliminate chaos and system dynamics becomes stable. Observation of this paper support the ＂Steele-Henderson conjecture＂ that, nonlinear closure terms eliminate or reduces limit cycles and chaos in plankton food chain models. Chaotic or stable dynamics are numerically verified by Lyapunov exponents （LE） method and Sil＇nikov eigenvalue anal- ysis and also illustrated graphically by plotting bifurcation diagrams. It is assumed that mortality of fish population, caused by higher-order predators （which are not explicitly included in the model） is not constant, rather it exhibits random variation through- out the year. To incorporate the effect of random mortality of fish population, white noise term is introduced into the original deterministic model. It is observed that the corresponding stochastic model is stable in mean square when the intensity of noise is small. Keywords： Holling type IV; chaos; closure term; white noise; mean square stability
文摘The advantages of multivalued logic in optical parallel computation need no introduction. There are lots of proposals, already reported, where tristate, quarternary state logic operations can be performed with optics. Here we report a new approach to implement tristate logic based all optical flip-flop using optical nonlinear material. The concept and the principle of operation of this type of flip-flop are different from that of the conventional binary one.
