Magnetic gear dynamics for servo control

This paper considers the analysis and application of magnetic gearbox and magnetic coupling technologies and issues surrounding their use for motion control servo systems. Analysis of a prototype magnetic gear is used as a basis for demonstrating the underlying nonlinear torque transfer characteristic, nonlinear damping, and `pole-slipping' when subject to over-torque (overload) conditions. It is also shown how `pole-slipping' results in consequential loss of control. A theoretical investigation into the suppression of mechanical torsional resonances in transmission systems encompassing these highly-compliant magnetically-coupled components is included, along with experimental results, from a demonstrator drive-train. The automatic detection of pole-slipping, and recovery scenarios, is also presented

Cavity Protection Techniques for Red-cockaded Woodpeckers

Population growth of red-cockaded woodpeckers (Picoides borealis) is often limited by the availability of suitable cavities. Structural damage to natural and artificial cavities intended for use by P. borealis is common. Roost and nest cavities of P. borealis often become occupied by other cavity-dependent species. Techniques for preventing damage to artificial cavities and for deterring southern flying squirrel (Glaucomys volans) use of otherwise serviceable cavities are described. Such cavity protection techniques may be necessary to prevent extirpation of small, isolated populations of P. borealis

Electromechanical Simulation of Actively Controlled Rotordynamic Systems with Piezoelectric Actuators

Theories and tests for incorporating piezoelectric pushers as actuator devices for active vibration control are discussed. It started from a simple model with the assumption of ideal pusher characteristics and progressed to electromechanical models with nonideal pushers. Effects on system stability due to the nonideal characteristics of piezoelectric pushers and other elements in the control loop were investigated

Some considerations on coastal processes relevant to sea level rise

The effects of potential sea level rise on the shoreline and shore environment have been briefly examined by considering the interactions between sea level rise and relevant coastal processes. These interactions have been reviewed beginning with a discussion of the need to reanalyze previous estimates of eustatic sea level rise and compaction effects in water level measurement. This is followed by considerations on sea level effects on coastal and estuarine tidal ranges, storm surge and water level response, and interaction with natural and constructed shoreline features. The desirability to reevaluate the well known Bruun Rule for estimating shoreline recession has been noted. The mechanics of ground and surface water intrusion with reference to sea level rise are then reviewed. This is followed by sedimentary processes in the estuaries including wetland response. Finally comments are included on some probable effects of sea level rise on coastal ecosystems. These interactions are complex and lead to shoreline evolution (under a sea level rise) which is highly site-specific. Models which determine shoreline change on the basis of inundation of terrestrial topography without considering relevant coastal processes are likely to lead to erroneous shoreline scenarios, particularly where the shoreline is composed of erodible sedimentary material. With some exceptions, present day knowledge of shoreline response to hydrodynamic forcing is inadequate for long-term quantitative predictions. A series of interrelated basic and applied research issues must be addressed in the coming decades to determine shoreline response to sea level change with an acceptable degree of confidence. (PDF contains 189 pages.

Past and Present Distribution of the Red-Cockaded Woodpecker Picoides borealis and its Habitat in the Ouachita Mountains, Arkansas

Within the past 15 years, at least 41 and probably more active cavity tree clusters (or colonies) of Red cockaded Woodpeckers (Picoides borealis) have existed in remnant, mature shortleaf pine (Pinus echinata) woodlands in the Ouachita Mountains of Arkansas. These clusters were located on both private timberlands and in the Ouachita National Forest. Fewer than half of this number were still active in early 1991, and none remained on private timberlands. The species is presently restricted to the xeric, western margins of the Ouachitas in Scott and Polk counties within the confines of the Ouachita National Forest where it receives protection of the Endangered Species Act. The decline of P. borealis in the Ouachitas resulted from intense logging of old growth pine forests during the timber boom period, ca. 1910-1950, and from the suppression of natural fires, which subsequently allowed hardwoods to invade former pine woodlands

Short-term mindfulness practice attenuates reward prediction errors signals in the brain

Activity changes in dopaminergic neurons encode the ongoing discrepancy between expected and actual value of a stimulus, providing a teaching signal for a reward prediction process. Previous work comparing a cohort of long-term Zen meditators to controls demonstrated an attenuation of reward prediction signals to appetitive reward in the striatum. Using a cross-commodity design encompassing primary- and secondary-reward conditioning experiments, the present study asks the question of whether reward prediction signals are causally altered by mindfulness training in naive subjects. Volunteers were randomly assigned to 8 weeks of mindfulness training (MT), active control training (CT), or a one-time mindfulness induction group (MI). We observed a decreased response to positive prediction errors in the putamen in the MT group compared to CT using both a primary and a secondary-reward experiment. Furthermore, the posterior insula showed greater activation to primary rewards, independently of their predictability, in the MT group, relative to CT and MI group. These results support the notion that increased attention to the present moment and its interoceptive features - a core component of mindfulness practice - may reduce predictability effects in reward processing, without dampening (in fact, enhancing) the response to the actual delivery of the stimulus