Adaptive synchronization of chaotic Colpitts circuits against parameter mismatches and channel distortions

In this work, synchronization of chaotic Colpitts circuits, using adaptive controllers to combat circuit parameter mismatches and channel distortions, is studied by numerical simulations. Synchronization errors caused by different main circuit components are compared, and compensation for time-constant and time-varying circuit parameter mismatches is demonstrated. Different kinds of channel distortions, including time-constant and time-varying channel attenuation, Additive White Gaussian Noise (AWGN) are all investigated by numerical simulations and discussed. Simulation results indicated that the synchronization performance of chaotic Colpitts circuits can be greatly improved by applying adaptive controllers when parameter mismatches and channel attenuation are considered as time-constant or time-varying, but have no obvious enhancements regarding the effect on AWGN channel.     

Simple model for gas holdup and liquid velocity of annular photocatalytic external-loop airlift reactor under both bubble and developing slug flow

Based on the momentum conservation approach, a theoretical model was developed to predict the superficial liquid velocity, and a correlation equation was established to calculate the gas holdup of an annular external- loop airlift reactor(AELAR)in the bubble flow and developing slug flow pattern. Experiments were performed by using tap-water and silicone oil with the viscosity of 2.0 mm²/s(2cs-SiO)and 5.0 mm²/s(5cs-SiO)as liquid phases. The effects of liquid viscosity and flow pattern on the AELAR performance were investigated. The predictions of the proposed model were in good agreement with the experimental results of the AELAR. In addition, the comparison of the experimental results shows that the proposed model has good accuracy and could be used to predict the gas holdup and liquid velocity of an AELAR operating in bubble and developing flow pattern.     

Bakhtin's theory of dialogue: A construct for pedagogy, methodology and analysis

This article describes the application of Bakhtin's (1981, 1986a,b) theorisation of language as dialogue to the study of young students' struggle with discourses of ethnicity within the context of a Studies of Asia curriculum project (Hamston 2003). Bakhtin's rich conceptualisation of the productive and ethical nature of dialogue has operated at all levels in this study as a theoretical, pedagogical, methodological and analytic research construct.     

Nobel Prize in Physics 2006

The discovery of the cosmic microwave background radiation in 1965 was a defining moment in the history of cosmology — the science that deals with the universe as a whole, its origin, evolution and future. This discovery was recognized with Nobel Prizes to Penzias and Wilson in 1978. The Nobel Prize in Physics for 2006 further acknowledged the importance of the study of this background radiation. The precise measurement of the spectrum of this radiation and its variation across the sky have helped our understanding of the evolution of structures in the universe. This article explains these discoveries and their importance. T Padmanabhan is a professor at IUCAA, Pune. He is interested in all aspects of theoretical physics, and especially in those in which gravity plays a role.     

Mathematical Flexibility: Aspects of a Continuum and the Role of Prior Knowledge

Abstract

Psychologists and mathematics educators have long viewed flexibility as critical to students’ mathematical development. In this paper, we focused on the multidimensional nature of flexibility to better understand how preference, knowledge, and use of effective methods for solving algebra problems are related. In Study 1, we identified research-based aspects of flexibility with algebra and assessed students on them following a two-step equations unit. Results indicated that certain aspects of flexibility develop prior to others and that prior knowledge of algebra plays a significant role in that development. Study 2 confirmed and elaborated on these results using a larger sample size. Implications for theory and for supporting flexibility in classrooms are discussed.     

Noise assisted directed motion at the molecular level — 2

The term noise is used to describe fluctuations about the mean deterministic stationary value of a physical quantity. It is now being increasingly realised that noise is an important ingredient to bring order in dynamical processes. Though it appears counterintuitive, noise seems to help in directing transport processes in biological systems at the molecular level. In Part 2 of the article, we discuss some more examples of noise assisted directed motion.     

The Journey Toward Transformational Learning in a Statewide Doctoral Program

This article describes strategies for redesigning the University of Missouri's Statewide Cooperative Ed.D. Cohort Program in educational leadership. Results had suggested a need to redesign aspects of the program in order to achieve higher levels of cognitive learning outcomes inclusive of transformational learning. To help meet this objective, the areas targeted for redesign were the curriculum as it relates to issues of diversity and ethics, instruction as it relates to group dynamics and cohort models, and increased time and a forum for students to reflect on their leadership practices. This forum also allowed faculty to monitor and assess the transformational learning outcomes of their students. This article is meant to assist others who are interested in fostering higher levels of transformational learning outcomes within their programs. Meredith L. Mountford holds a Bachelor of Science degree from Illinois State University, a Master of Science degree in educational administration from Northern Illinois University and a Philosophy of Science degree in educational administration from the University of Wisconsin—Madison. She is an Assistant Professor and has served as Director for the Statewide Cooperative Ed.D. Cohort Program in educational leadership at the University of Missouri—Columbia.