39,515 research outputs found
Design strategies for the creation of aperiodic nonchaotic attractors
Parametric modulation in nonlinear dynamical systems can give rise to
attractors on which the dynamics is aperiodic and nonchaotic, namely with
largest Lyapunov exponent being nonpositive. We describe a procedure for
creating such attractors by using random modulation or pseudo-random binary
sequences with arbitrarily long recurrence times. As a consequence the
attractors are geometrically fractal and the motion is aperiodic on
experimentally accessible timescales. A practical realization of such
attractors is demonstrated in an experiment using electronic circuits.Comment: 9 pages. CHAOS, In Press, (2009
High-Performance low-vcc in-order core
Power density grows in new technology nodes, thus requiring Vcc to scale especially in mobile platforms where energy is critical. This paper presents a novel approach to decrease Vcc while keeping operating frequency high. Our mechanism is referred to as immediate read after write (IRAW) avoidance. We propose an implementation of the mechanism for an Intel® SilverthorneTM in-order core. Furthermore, we show that our mechanism can be adapted dynamically to provide the highest performance and lowest energy-delay product (EDP) at each Vcc level. Results show that IRAW avoidance increases operating frequency by 57% at 500mV and 99% at 400mV with negligible area and power overhead (below 1%), which translates into large speedups (48% at 500mV and 90% at 400mV) and EDP reductions (0.61 EDP at 500mV and 0.33 at 400mV).Peer ReviewedPostprint (published version
Regime change thresholds in flute-like instruments: influence of the mouth pressure dynamics
Since they correspond to a jump from a given note to another one, the mouth
pressure thresholds leading to regime changes are particularly important
quantities in flute-like instruments. In this paper, a comparison of such
thresholds between an artificial mouth, an experienced flutist and a non player
is provided. It highlights the ability of the experienced player to
considerabily shift regime change thresholds, and thus to enlarge its control
in terms of nuances and spectrum. Based on recent works on other wind
instruments and on the theory of dynamic bifurcations, the hypothe- sis is
tested experimentally and numerically that the dynamics of the blowing pressure
influences regime change thresholds. The results highlight the strong influence
of this parameter on thresholds, suggesting its wide use by experienced
musicians. Starting from these observations and from an analysis of a physical
model of flute-like instruments, involving numerical continuation methods and
Floquet stability analysis, a phenomenological modelling of regime change is
proposed and validated. It allows to predict the regime change thresholds in
the dynamic case, in which time variations of the blowing pressure are taken
into account
Mariner Venus 67 guidance and control system
Subsystems of Mariner Venus 67 spacecraft guidance and control syste
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