Stability domains for time-delay feedback control with latency

We generalize a known analytical method for determining the stability of periodic orbits controlled by time-delay feedback methods when latencies associated with the generation and injection of the feedback signal cannot be ignored. We discuss the case of extended time-delay autosynchronization (ETDAS) and show that nontrivial qualitative features of the domain of control observed in experiments can be explained by taking into account the effects of both the unstable eigenmode and a single stable eigenmode in the Floquet theory.Comment: 9 pages, 6 figures; Submitted to Physical Review

Time--delay autosynchronization of the spatio-temporal dynamics in resonant tunneling diodes

The double barrier resonant tunneling diode exhibits complex spatio-temporal patterns including low-dimensional chaos when operated in an active external circuit. We demonstrate how autosynchronization by time--delayed feedback control can be used to select and stabilize specific current density patterns in a noninvasive way. We compare the efficiency of different control schemes involving feedback in either local spatial or global degrees of freedom. The numerically obtained Floquet exponents are explained by analytical results from linear stability analysis.Comment: 10 pages, 16 figure

Fejér Polynomials and Chaos

We show that given any μ \u3e 1, an equilibrium x of a dynamic system xn+1=f(xn) (1) can be robustly stabilized by a nonlinear control u=−∑j=1N−1εj(f(xn−j+1)−f(xn−j)), |εj| \u3c 1, j=1,…,N−1, (2) for f ′ (x) ∈ (−μ, 1). The magnitude of the minimal value N is of order √μ. The optimal explicit strength coefficients are found using extremal nonnegative Fejér polynomials. The case of a cycle as well as numeric examples and applications to mathematical biology are considered

Dimensions and predictors of literary response

To rest the validity of the Literary Response Questionnaire (LRQ, Miall & Kuiken, 1995b) and to assess its relationships with student, home-background, and school-related variables, the LRQ was administered to Dutch students in grades 7, 8, and 9. The seven first-order factors of the LRQ, as identified by Miall and Kuiken (1995b) were confirmed. One of the two second-order factors was not identified. However, a model with two different second-order factors fitted the data. Trance, the first factor, represents the degree to which a reader is absorbed in a story. Literary Interpretation, the second factor, represents the degree to which a reader likes or dislikes literary criticism and reflection on the meaning of what is read. Grade, gender, type of education, vocabulary size, reading behavior, and cultural level of the home environment were the best predictors of the literary response scores. Results are discussed in relation to response theories and research and to literary education

Riparian Deforestation Affects the Structural Dynamics of Headwater Streams in Southern Brazilian Amazonia

Comparative studies of streams with altered versus conserved riparian zones are important to evaluate the degree of alterations caused by inappropriate use of these streams’ vital buffer zones. The aim of this study was to determine the impact of riparian deforestation on the habitat structure of southern Brazilian Amazonian headwater streams, as well as to provide elements for impact assessment and the monitoring of these water bodies. We selected ten sites and two headwater streams at each site; one stream was located in an area with preserved riparian vegetation (pristine streams) and the other stream in a deforested riparian zone (altered streams). Stretches of these streams were analyzed across hydrological periods (dry period, beginning of the rainy period, and end of the rainy period) for hydro-morphological aspects, water physical-chemical variables, and habitat integrity (proportion of forestation in buffer zones and habitat integrity index). Compared to pristine streams in all the hydrological periods analyzed, altered streams presented lower oxygen concentration (~1.0 mg/L), an increase of 1 °C in water temperature, and less organic material availability. We found that riparian deforestation affects habitat structure variability among hydrological periods, making them more homogeneous. Therefore, beyond the necessary broadening of the spatial scale of studies in this region, monitoring these understudied headwater stream environments is also crucial for determining the magnitude of deforestation effects on these vulnerable aquatic ecosystems. © Monica Elisa Bleich, Amanda Frederico Mortati, Thiago André and Maria Teresa Fernandez Piedade