Large amplitude dynamics of micro/nanomechanical resonators actuated with electrostatic pulses

International audienceIn the field of resonant NEMS design, it is a common misconception that large-amplitude motion, and thus large signal-to-noise ratio, can only be achieved at the risk of oscillator instability. In the present paper, we show that very simple closed-loop control schemes can be used to achieve stable largeamplitude motion of a resonant structure, even when jump resonance (caused by electrostatic softening or Duffing hardening) is present in its frequency response. We focus on the case of a resonant accelerometer sensing cell, consisting in a nonlinear clamped-clamped beam with electrostatic actuation and detection, maintained in an oscillation state with pulses of electrostatic force that are delivered whenever the detected signal (the position of the beam) crosses zero. We show that the proposed feedback scheme ensures the stability of the motion of the beam much beyond the critical Duffing amplitude and that, if the parameters of the beam are correctly chosen, one can achieve almost full-gap travel range without incurring electrostatic pull-in. These results are illustrated and validated with transient simulations of the nonlinear closed-loop system

SEU Impact in Processor's Control-Unit: Preliminary Results Obtained for LEON3 Soft-Core

International audienceThe miniaturization issues from the advanced integrated circuit manufacturing technologies lead to increase the probabilities of single node upset and multiple upsets errors of neighbor nodes. The study of such conjecture is mandatory to specify the protection requirements. This paper deals with the study of such single and multiple errors due to the impact of a single particle in the control unit of complex devices such as processors. Because the layout of the studied device cannot be anticipated, the node’s neighborhood is thus unknown. To deal with this issue, this work presents the results of both exhaustive and random fault-injection experiments performed at register transfer level (RTL) and targeting the control bits of LEON3 processor. Fault injection is achieved by means an automatic netlist fault injection tool called NETFI-2

SEU Impact in Processor's Control-Unit: Preliminary Results Obtained for LEON3 Soft-Core

International audienceThe miniaturization issues from the advanced integrated circuit manufacturing technologies lead to increase the probabilities of single node upset and multiple upsets errors of neighbor nodes. The study of such conjecture is mandatory to specify the protection requirements. This paper deals with the study of such single and multiple errors due to the impact of a single particle in the control unit of complex devices such as processors. Because the layout of the studied device cannot be anticipated, the node’s neighborhood is thus unknown. To deal with this issue, this work presents the results of both exhaustive and random fault-injection experiments performed at register transfer level (RTL) and targeting the control bits of LEON3 processor. Fault injection is achieved by means an automatic netlist fault injection tool called NETFI-2

Field evolution of magnetic correlations in ϵ-Co nanoparticle assemblies

Small-angle neutron scattering measurements of Co nanoparticle assemblies reveal three characteristic length scales associated with the interparticle and intraparticle magnetic orders. The first length scale stemming from particle size and separation does not vary with applied field. In contrast, the magnetic correlation length increases from 71±9nm in zero field at 5K to greater than 1000nm in fields larger than 0.2T. The random-field length scale decreases from 37±8nm when H=0to9.1±0.3nm in H=0.2T, and the contribution of this term is less significant in large fields