253 research outputs found
Some remarks on the coincidence set for the Signorini problem
No full textWe study some properties of the coincidence set for the boundary Signorini problem, improving some results from previous works by the second author and collaborators. Among other new results, we show here that the convexity assumption on the domain made previously in the literature on the location of the coincidence set can be avoided under suitable alternative conditions on the data
Sul S. Pantaleo 8 della Biblioteca Nazionale Centrale di Roma: una miscellanea dantesca di metà Trecento
No full textThe article discusses the MS S. Pantaleo 8, a remarkable collection of Dante’s works now
kept at the Biblioteca Nazionale Centrale in Rome. By investigating how the manuscript
was prepared, and on the basis of the eight different writings of the scribes who copied
the texts, as well as of the work of the three illuminators involved in the decoration of the
book, the author suggests that the manuscript might have been copied around the mid-14th
century either in eastern Tuscany or in Umbria
Macromodeling of I/O Buffers via Compressed Tensor Representations and Rational Approximations
No full textThis paper addresses the generation of accurate and efficient macromodels of high-speed input/output buffers. The proposed modeling approach extends the state-of-the-art methods that are currently available, yielding to a modular and scalable tool for model generation. The modeling procedure applies to both single-ended and differential devices, possibly exhibiting a rich dynamical behavior due to large supply fluctuations or internal voltage regulators. The models are defined by the combination of static surfaces described via compact tensor approximations and linear dynamical state-space relations generated using a robust time-domain vector fitting algorithm. A simple and effective solution is adopted to account for the overclocking operation of output buffer models as well. The feasibility and strength of the proposed method are demonstrated using real devices and complex application test cases for signal and power integrity cosimulation
Enhanced Mpilog macromodels for Signal and Power Integrity Simulations
No full textDue to increasingly stringent low-cost and small form-factor design constraints, Signal and Power Integrity analyses (SI&PI) have gained a paramount importance in the definition and optimization of mobile platforms. Operating margins are dramatically reduced in order to meet all the required design targets and constraints (extensive re-use, time-to-market, etc.). In this scenario, transistor-level simulations for platform-level analyses are inefficient and often, impractical. I/O-buffer models become essential and their accuracy is crucial for the reliability of SI&PI studies. As data-rates increase, signaling swing reduces and power-supply voltage noise becomes inevitable, state-of-the-art legacy models are limited for SI&PI co-simulations. This work summarizes the recent enhancements of "Mpilog"-class macromodels for high-speed I/O-buffers. Mpilog macromodels reproduce voltage and currents at I/O and (multiple) supply ports as weighted combinations of pull-up/pull-down static and dynamic components. The static parts are extracted via nested DC sweeps simulations and reproduced by tensor representations obtained via high-order singular value decomposition (SVD) processes. The dynamic components are described by linear state-space models identified from device's transient responses to suitable stimuli. For transmitters, the weighting functions match the output-port transitions and the dynamic supply-current profiles, capturing also the dependency of switching delays upon supply-voltage fluctuations; this is a key feature that enables Mpilog macromodels to precisely reproduce simultaneous-switching-noise (SSN) effects in complex system-level SI&PI simulations. The macromodels can be readily synthesized as SPICE netlists (including resistors, capacitors and controlled-sources) or Verilog-A codes; this allows their use in any SPICE-type electrical solver. Several examples of realistic SI&PI simulations for single-ended and differential interfaces are presented. Transistor-level simulations are compared with the corresponding ones based on Mpilog-macromodels: the resulting accuracy and the speed-up factors are extensively discussed. Comparisons with state-of-the-art legacy models (IBIS) are also discusse
Behavioral macromodeling of high-speed drivers via compressed tensor representations
No full textThis paper addresses the behavioral modeling of digital drivers for Signal and Power Integrity co-simulations. State-of-the-art two-piece model representations are combined with a compact description of the device static characteristics. The latter are considered as multivariate mappings that are functions of the device electrical variables, and of additional parameters defining process corners and device settings. Overall model complexity is reduced through a compressed tensor representation obtained via a high-order singular value decomposition. Several application examples demonstrate the feasibility and the advantages of the proposed approac
Power and Signal Integrity co-simulation via compressed macromodels of high-speed transceivers
No full textThis paper presents innovative compressed macro-models of high-speed digital transceivers for system-level Signal and Power Integrity co-simulations. These simulations assume a paramount importance for the design of modern, low-cost and highly integrated systems. An excellent accuracy and an outstanding run-time speed-up are demonstrated by applying the macromodeling methodology to a state-of-the-art I/O buffer for a low-power memory interface. Supply voltage variations and related effects on output transitions are accurately reproduced, enabling precise estimates of critical system-level timing margin
Enhanced macromodels of high-speed low-power differential drivers
No full textHigh-speed differential interfaces implementing specific solutions for low-power consumption and low-EMI disturbances are vastly used in mobile platforms. In these devices, the slew rate is suitably controlled, the communication scheme alternates data-bursts followed by power-saving states, the voltage swing and the common-mode level are reduced. To achieve these targets, a key role in voltage-mode output drivers is played by an internal voltage-regulator. The latter exhibits a rich dynamic behavior, with non-negligible effects on the transmitter outputs, that need to be carefully characterized. In this paper, a modeling strategy based on a few key enhancements of state-of-the-art solutions is presented, leading to compact and accurate models. The feasibility and strengths of the proposed approach are verified on a low-power high-speed voltage-mode drive
The vision of dreams: from ontogeny to dream engineering in blindness
No full textThe mechanisms involved in dreams’ origin remain one of the great unknowns in science. In the twenty-first century, studies in the field have focused on three main topics: functional networks that underlie dreaming, neural correlates of dream contents, and signal propagation. We review neuroscientific studies about dreaming processes, focusing on their cortical correlations. The involvement of frontoparietal regions in the dream-retrieval process allows us to discuss it in light of the Global Workspace theory of consciousness. However, dreaming in distinct sleep stages maintains relevant differences suggesting that multiple generators are implicated. Then, given the strong influence of light perception on sleep regulation and the mostly visual content of dreams, we investigate the effect of blindness on dreams’ organization. Blind individuals represent a worthwhile population to clarify the role of perceptual systems in dreams’ generation, and to infer about their top-down and/or bottom-up origin. Indeed, congenitally blind people maintain the ability to produce visual dreams, suggesting that bottom-up mechanisms could be associated with innate body schemes or multisensory integration processes. Finally, we propose the new dream engineering technique as a tool to clarify the mechanisms of multisensory integration during sleep and related mental activity, presenting possible implications for rehabilitation in sensory-impaired individuals. Theory of Protoconsciousness suggests that the interaction of brain states underlying waking and dreaming ensures the optimal functioning of both. Therefore, understanding the dreams’ origin and capabilities of our brain during a dreamlike state, we could introduce it as a rehabilitative tool
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