Analysis of the linewidth of a grating-feedback GaAlAs laser

Effects of external optical feedback from a reflection grating on the linewidth of a GaAlAs semiconductor laser operating at 780 nm are investigated. Accurate linewidth measurements as a function of the laser frequency tuning have been performed by applying the self-homodyne technique with a short delay line. A realistic coupled-cavity model, which incorporates the frequency-dependent reflection from the grating, is used to explain the measured data. The agreement between the theoretical and experimental results was found to be good     

Experiencing CSCL: from motivation to the embodied experience and beyond

International Journal of Computer-Supported Collaborative Learning -     

Reflections and looking ahead for CSCL: digital infrastructures,digital tools,and collaborative learning

International Journal of Computer-Supported Collaborative Learning -     

Information‐driven robotic sampling in the coastal ocean

Efficient sampling of coastal ocean processes, especially mechanisms such as upwelling and internal waves and their influence on primary production, is critical for understanding our changing oceans. Coupling robotic sampling with ocean models provides an effective approach to adaptively sample such features. We present methods that capitalize on information from ocean models and in situ measurements, using Gaussian process modeling and objective functions, allowing sampling efforts to be concentrated to regions with high scientific interest. We demonstrate how to combine and correlate marine data from autonomous underwater vehicles, model forecasts, remote sensing satellite, buoy, and ship‐based measurements, as a means to cross‐validate and improve ocean model accuracy, in addition to resolving upper water‐column interactions. Our work is focused on the west coast of Mid‐Norway where significant influx of Atlantic Water produces a rich and complex physical–biological coupling, which is hard to measure and characterize due to the harsh environmental conditions. Results from both simulation and full‐scale sea trials are presented.     

Improved frequency stability of an external cavity diode laser by eliminating temperature and pressure effects

The construction of a passively stabilized external cavity diode laser operating at 780 nm is reported. The sensitivity of laser frequency to changes in air pressure was studied and subsequently eliminated. The relative frequency stability obtained was 4 × 10(-9) for an integration time of 4000 s.     

VSS-version of energy-based control for swinging up a pendulum

A new algorithm ensuring global attractivity of the upright (unstable) equilibrium of a pendulum, based on the variable structure system-version of the energy-speed-gradient method, is proposed. It is shown that global attractivity cannot be obtained with continuous static state feedback. A detailed global analysis of the transient behavior of the closed loop system is presented. In addition, it is shown that the global attractivity of the upright equilibrium can be achieved by applying a control of arbitrarily small magnitude.