6,573 research outputs found
Memory in random bouncing ball dynamics
The bouncing of an inelastic ball on a vibrating plate is a popular model
used in various fields, from granular gases to nanometer-sized mechanical
contacts. For random plate motion, so far, the model has been studied using
Poincar{\'e} maps in which the excitation by the plate at successive bounces is
assumed to be a discrete Markovian (memoryless) process. Here, we investigate
numerically the behaviour of the model for continuous random excitations with
tunable correlation time. We show that the system dynamics are controlled by
the ratio of the Markovian mean flight time of the ball and the mean time
between successive peaks in the motion of the exciting plate. When this ratio,
which depends on the bandwidth of the excitation signal, exceeds a certain
value, the Markovian approach is appropriate; below, memory of preceding
excitations arises, leading to a significant decrease of the jump duration; at
the smallest values of the ratio, chattering occurs. Overall, our results open
the way for uses of the model in the low excitation regime, which is still
poorly understood.Comment: Final published version, 5 pages, 4 figure
The cognitive revolution in Europe: taking the developmental perspective seriously
We can do little but to share Miller’s view [1] that
cognitive psychology was born in the 1950s. However, his
article distorts the role of psychology in the birth of
cognitive science. On two occasions, Miller proposes that
psychology could not play a role in the cognitive revolution
because of its narrow focus on behaviorism
ACTIVITY SYSTEMS AND LIVELIHOODS IN EASTERN CAPE PROVINCE RURAL AREAS (TRANSKEI): HOUSEHOLD TYPOLOGIES AS SOCIO-ECONOMIC CONTRIBUTIONS TO A LANDCARE PROJECT
Consumer/Household Economics,
Design concepts and performance of NASA X-band (7162 MHz/8415 MHz) transponder for deep-space spacecraft applications
The design concepts and measured performance characteristics are summarized of an X band (7162 MHz/8415 MHz) breadboard deep space transponder (DSP) for future spacecraft applications, with the first use scheduled for the Comet Rendezvous Asteroid Flyby (CRAF) and Cassini missions in 1995 and 1996, respectively. The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X band (8415 MHz) exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X band (7162 MHz) uplink carrier signal. The exciter phase modulates the X band (8415 MHz) downlink signal with composite telemetry and ranging signals. The receiver measured tracking threshold, automatic gain control, static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB
A scala library for spatial sensitivity analysis
The sensitivity analysis and validation of simulation models require specific approaches in the case of spatial models. We describe the spatialdata scala library providing such tools, including synthetic generators for urban configurations at different scales, spatial networks, and spatial point processes. These can be used to parametrize geosimulation models on synthetic configurations, and evaluate the sensitivity of model outcomes to spatial configuration. The library also includes methods to perturb real data, and spatial statistics indicators, urban form indicators, and network indicators. It is embedded into the OpenMOLE platform for model exploration, fostering the application of such methods without technical constraints
Reconstitution des principaux stades glaciaires du Chablais : base scientifique pour la valorisation d'un patrimoine glaciaire régional
International audienc
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