Complex Dynamics and Synchronization of Delayed-Feedback Nonlinear Oscillators

We describe a flexible and modular delayed-feedback nonlinear oscillator that is capable of generating a wide range of dynamical behaviours, from periodic oscillations to high-dimensional chaos. The oscillator uses electrooptic modulation and fibre-optic transmission, with feedback and filtering implemented through real-time digital-signal processing. We consider two such oscillators that are coupled to one another, and we identify the conditions under which they will synchronize. By examining the rates of divergence or convergence between two coupled oscillators, we quantify the maximum Lyapunov exponents or transverse Lyapunov exponents of the system, and we present an experimental method to determine these rates that does not require a mathematical model of the system. Finally, we demonstrate a new adaptive control method that keeps two oscillators synchronized even when the coupling between them is changing unpredictably.Comment: 24 pages, 13 figures. To appear in Phil. Trans. R. Soc. A (special theme issue to accompany 2009 International Workshop on Delayed Complex Systems

Using Synchronization for Prediction of High-Dimensional Chaotic Dynamics

We experimentally observe the nonlinear dynamics of an optoelectronic time-delayed feedback loop designed for chaotic communication using commercial fiber optic links, and we simulate the system using delay differential equations. We show that synchronization of a numerical model to experimental measurements provides a new way to assimilate data and forecast the future of this time-delayed high-dimensional system. For this system, which has a feedback time delay of 22 ns, we show that one can predict the time series for up to several delay periods, when the dynamics is about 15 dimensional.Comment: 10 pages, 4 figure

Student’s perceptions and feedback about teaching-learning pharmacology in Nepalgunj Medical College of Chisapani, Nepal

Background: Pharmacology, being both basic and applied science, forms the backbone of rational therapeutics in medical field. Understanding of current perceptions and opinions of medical students is important for the betterment of teaching-learning methodologies in pharmacology subject. This study done with the objective to determine the perception and feedback of teaching learning pharmacology.Methods: Descriptive cross sectional questionnaire based study was conducted in Nepalgunj Medical College Chisapani, Banke Nepal, among second year MBBS students in September 2017. A questionnaire distributed in class and then collected. Data was analysed using the Statistical Package for Social Sciences (SPSS).Results: Total 119 students, 78 male and 41 females participated in this study. The percentage average of agreed responses for 15 questions (58.92±19.53) was significant (p <0.05) when compared with the percentage average of the disagreed (5.42± 5.17). Seventy three (61.3%) students agreed that pharmacology is a favourite subject but the preferences for pharmacology as a subject in post-graduation was low (18.5%). High proportion of students wanted the faculty members to make more use of Audio-Visual aids 93.3%, case based learning 96.6%, more clinical pharmacology, 97.5%, group discussions, 88.2%, integration to clinical sciences 92.4% and 82.4% prefer MCQs to be introduced in the curriculum for effective learning.Conclusions: Introduction of integrated teaching, MCQs, case based, and group based discussion with clinical pharmacology and audio-visual aids was favoured by majority of the students. Regular reviewing perception and feedback of the students help teachers to plan the curriculum and improve the teaching methodologies

Indices of equatorial electrojet and counter-electrojet in the Indian region: evolution of the indices and their authenticity

Indices of the equatorial electrojet and counter-electrojet in the Indian region have been evolved based on certain reasonable assumptions, by a criterion depending on the difference in the horizontal field strength between a station under the electrojet axis (Trivandrum) and a station outside the jet influence (Alibag). The indices enable one to characterize each day of the year by an appropriate index. Distribution, in the months, seasons and over the years, of the electrojet and counter-electrojet frequencies at Trivandrum during a 20-year period, 1959-78, is examined. The salient features of the distributions are: (i) Strong electrojets (range 50 nT) and the afternoon counter-electrojets occur, on an average, on about 50% of the days in the year; (ii) For the counter-electrojet, the monthly frequencies show an annual variation with a summer maximum, and for the strong electrojet, a semi-annual variation with maxima in the equinoxes; (iii) A secondary maximum is noted in January in the occurrence frequency of both counter-electrojet and strong electrojet events; (iv) Intense electrojets occur with greater frequency in September

The impact of health on professionally active people's incomes in Poland. Microeconometric analysis

The outcome of the research confirms the occurrence of positive interaction between professionally active people's incomes and the self-assessed state of health. People declaring a bad state of health have incomes by 20% on average lower than people who enjoy good health (assuming that the remaining characteristics of the surveyed person are the same). In case of men, the impact of health state on incomes is slightly greater than in case of women.Wyniki badań potwierdzają istnienie pozytywnej zależności dochodów osób aktywnych zawodowo od stanu zdrowia mierzonego jego samooceną. Osoby deklarujące zły stan zdrowia osiągają dochody przeciętnie o 20% niższe niż osoby, które cieszą się dobrym stanem zdrowia (przy założeniu, że pozostałe charakterystyki badanej osoby są takie same). W przypadku mężczyzn zależność dochodów od stanu zdrowia jest nieznacznie silniejsza niż w przypadku kobiet