The main purpose of viability theory is to explain the evolution of the state of a control system, governed by nondeterministic dynamics and subjected to viability constraints, to reveal the concealed feedbacks which allow the system to be regulated and provide selection mechanisms for implementing them. It assumes implicitly an “opportunistic” and “conservative” behavior of the system: a behav...

The purposes of this study were to explore the effects and the validity of on-line peer assessment in high schools and to analyze effects of various types of peer feedback on students. The participating students, a total of 184 10th graders, developed their individual course projects by involving the on-line peer assessment learning activities in a computer course. The peer assessment activitie...

It is shown that under reasonable assumptions, conservation of angular momentum provides a strong constraint on gravity wave drag feedbacks to radiative perturbations in the middle atmosphere. In the time mean, radiatively induced temperature perturbations above a given altitude z cannot induce changes in zonal mean wind and temperature below z through feedbacks in gravity wave drag alone (assu...

Bioturbation—sediment mixing and ventilation by burrowing animals—provides one of the most prominent examples how animals shape their surroundings. A critical but longstanding question is when in Earth's history bioturbators began to similarly influence marine biogeochemistry. Recent work has proposed that even though development well-mixed sediments was a protracted process, initial rise led d...

Cutaneous sensory feedback can be used to provide additional sensory cues to a person performing a motor task where vision is a dominant feedback signal. A haptic joystick has been widely used to guide a user by providing force feedback. However, the benefit of providing force feedback is still debatable due to performance dependency on factors such as the user's skill-level, task difficulty. M...

The mechanisms of interdecadal changes of El NifioSouthern Oscillation (ENSO) modes are examined through an eigen analysis of a simple coupled ocean-atmosphere model. It is shown that the observed interdecadal climate shift can effectively modify the strength of two major coupled feedbacks for the ENSO mode, namely, the zonal advection and thermocline feedbacks. These modifications lead to quan...