118,112 research outputs found
Nanostructured graphene for energy harvesting
No full textEngineered nonlinearities have been shown to play an important role in increasing the efficiency of energy
harvesting devices. Macroscopic prototypes using this approach have been demonstrated recently [F. Cottone,
H. Vocca, and L. Gammaitoni, Phys. Rev. Lett. 102, 080601 (2009).] Here, in order to implement such a scheme
at the nanoscale, we propose a simple device which is based on strained nanostructured graphene and discuss
how it can respond to many energy sources that, although having a low intensity, are freely available, such as
ambient vibrations or thermal noise. We discuss in some detail the case of thermal fluctuations harvesting in the
steady-state nonequilibrium regime and of ambient vibrations
Esperienze di rigenerazione di shrinking cities nella Germania orientale / Urban regeneration experiences in shrinking cities of eastern Germany
No full textL’articolo presenta due due casi di intervento di pianificazione urbana in città e territorio caratterizzati dal fenomeno dello shrinkage: la città di Lipsia e la regione della Sassonia-Anhalt, in cui una varietà di interventi (tattiche, politiche urbane, rigenerazione fisica) è messa in campo con la volontà di rinascita delle città, in una ambivalenza tra costruire sul costruito e ulteriore crescita. I casi sono preceduti da una restituzione del contesto geo-politico dell’ex Germania est che ha vissuto continui repentini cambiamenti nel ’900 e della dove è presente una dualità territoriale tra grandi città e piccoli centri urbani rurali
STOCHASTIC RESONANCE WITHOUT SYMMETRY-BREAKING
No full textStochastic resonance in a bistable potential is characterized as a resonant synchronization effect of the random hopping mechanism. Most notably, synchronization may occur even in the absence of a coherent drive
DAMPING IN LOW-FREQUENCY MECHANICAL PENDULUMS
No full textA phenomenological equation of motion is proposed to account for two distinctive features of low-frequency inverted pendulums: frequency independent internal losses and instability at resonance frequencies below a critical threshold. The comparison with recent experimental data is discussed in detail. A new characterization of the background loss for a mass suspended as a pendulum by wires is also derived
Using a Mathematical Model to Evaluate the Efficacy of TB Control Measures
No full textWe evaluated the efficacy of recommended tuberculosis (TB) infection control measures by using a deterministic mathematical model for airborne contagion. We examined the percentage of purified protein derivative conversions under various exposure conditions, environmental control strategies, and respiratory protective devices. We conclude that environmental control cannot eliminate the risk for TB transmission during high-risk procedures; respiratory protective devices, and particularly high-efficiency particulate air masks, may provide nearly complete protection if used with air filtration or ultraviolet irradiation. Nevertheless, the efficiency of these control measures decreases as the infectivity of the source case increases. Therefore, administrative control measures (e.g., indentifying and isolating patients with infectious TB) are the most effective because they substantially reduce the rate of infection
PERIODICALLY TIME-MODULATED BISTABLE SYSTEMS - NONSTATIONARY STATISTICAL PROPERTIES
No full textThe relaxation properties of a one-dimensional overdamped system modulated by an external periodic force are studied analytically by means of a perturbation approach. The validity of the ap- proximations introduced is discussed in detail. The nonstationary nature of the process is illustrat- ed by evaluating explicitly the autocorrelation function for the relaxation in a bistable potential. The predictions thus obtained are shown to compare favorably with the results of analogue simula- tion for the case of a quartic double-well potential. The stochastic resonance mechanism is proven to set in only when the periodic perturbation breaks the symmetry of the bistable potential
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