Dirichlet parabolicity and L1L^1-Liouville property under localized geometric conditions

We shed a new light on the $L^1$-Liouville property for positive, superharmonic functions by providing many evidences that its validity relies on geometric conditions localized on large enough portions of the space. We also present examples in any dimension showing that the $L^1$-Liouville property is strictly weaker than the stochastic completeness of the manifold. The main tool in our investigations is represented by the potential theory of a manifold with boundary subject to Dirichlet boundary conditions. The paper incorporates, under a unifying viewpoint, some old and new aspects of the theory, with a special emphasis on global maximum principles and on the role of the Dirichlet Green's kernel

Second-level NIST randomness tests for improving test reliability

Testing Random Number Generators (RNGs) is as important as designing them. Here we consider the NIST test suite SF 800-22 and we show that, as suggested by NIST itself, to reveal non-perfect generators a more in-depth analysis should be performed using the outcomes of the suite over many generated sequences. Testing these second-level statistics is not trivial and, relying on a proper model that takes into account the errors due to the approximations in the first level tests, we propose a tuning of the parameters in the simplest cases. The validity of our consideration is widely supported by experimental results on several RNG currently employed by major IT players, as well as a chaos-based RNG designed by authors

A 3 GHz spread spectrum clock generator for SATA applications using chaotic PAM modulation

This paper proposes a prototype of a Spread Spectrum Clock Generator which is the first known specifically meant for 3 GHz Serial ATA-II applications. The modulation is obtained from a fractional PLL which employs a Delta-Sigma modulator. A further innovative aspect of our work is that our prototype takes advantage of a chaotic PAM as driving signal, instead a triangular signal as in all spread spectrum generators proposed in literature for SATA-II. In this way we avoid the periodicity of the modulated clock, completely flattening the peaks in the power spectral density. The circuit prototype has been designed n 0.13 μm CMOS technology and achieves a peak reduction greater than 14 dB measured at RBW = 100 kHz. The chip active area is 0.27×0.78 mm2 and the power consumption is as low as 14.7 mW. © 2008 IEEE

Asymptotic expressions of mismatch variance in interdigitated geometries

Performance in analog integrated circuits strongly depends on the mismatch between nominally identical devices. In this work we derive closed-form asymptotic expressions describing mismatch variance in multifinger structures, under the assumption of Gaussian autocorrelation for the mismatch-generating stochastic process. The analysis is performed on interdigitated geometries, eventually modified to make them common-centroid. Comparison with the numerical results provided by an independent model validates the theoretical expressions presented here

Resonate and fire dynamics in Complex Oscillation Based Test of analog filters

Recently, proposals have been made for enhancing the Oscillation Based Test (OBT) methodology by using non-plain oscillation regimes, leading to so called Complex Oscillation Based Test (COBT). Here we focus on a recently illustrated strategy for the testing of analog 2nd order filters, showing that the COBT dynamics is quite similar to that expressed by Resonate & Fire (R+F) neuron models. In this interpretation, the testing approach can be related to firing-rate measures. A brief description is given of the mathematical models necessary to achieve a precise characterization of firing times, showing how it can be used for testing purposes. A practical example with simulation data is also provided. © 2011 IEEE

A Zero-Transient Dual-Frequency Control for Class-E Resonant DC-DC Converters

In this paper, a dual-frequency control method for regulating the output power in class-E resonant DC-DC converters has been introduced. As in the standard ON-OFF control or other recently proposed dual-frequency controls, the approach is based on the ability of the converter to alternately operate in a high- and a low-power state. The proposed solution has a twofold advantage: on the one hand, soft-switching capabilities (i.e., Zero-Voltage and Zero-Voltage-Derivative switching) are preserved in both operating states; on the other hand, it is possible to reduce to zero the transient time required to switch from one state to the other one. The most straightforward consequence is the possibility to increase to very large values the frequency at which the two operating states are switched, up to the same order of magnitude as the main switching frequency of the converter. In this way, the additional ripple introduced by the proposed dual-frequency control can be decreased to a negligible value. The approach has been validated by measurements on a prototype operating between 4 MHz and 8 MHz and in which it has been possible to increase the control frequency up to 500 kHz

Unlocking the gender diversity-group performance link: the moderating role of relative cultural distance

PurposeThis study aims to shed light on the relationship between gender diversity and group performance by considering the moderating role of relative cultural distance. Drawing from the categorization-elaboration model (CEM), the authors hypothesize that gender-diverse collaborative learning groups perform better when a low level of relative cultural distance in country-level individualism-collectivism or power distance exists among group members.Design/methodology/approachTo test this hypothesis, the authors conducted a study on 539 undergraduate students organized into 94 groups. The assessment of group performance was based on scores given by external raters.FindingsThe authors found that relative cultural distance significantly moderated the gender diversity-group performance relationship such that gender diversity was positively related to group performance when the collaborative learning group included members who similarly valued individualism-collectivism or power distance (i.e. relative cultural distance was low) and was negatively related to group performance when the collaborative learning group comprised members who differently valued individualism-collectivism or power distance (i.e. relative cultural distance was high).Originality/valueThis study contributes to understanding when gender diversity is positively associated with group performance by expanding the range of previously examined diversity dimensions to include relative cultural distance in country-level individualism-collectivism and power distance

Adapted Compressed Sensing: A Game Worth Playing

Despite the universal nature of the compressed sensing mechanism, additional information on the class of sparse signals to acquire allows adjustments that yield substantial improvements. In facts, proper exploitation of these priors allows to significantly increase compression for a given reconstruction quality. Since one of the most promising scopes of application of compressed sensing is that of IoT devices subject to extremely low resource constraint, adaptation is especially interesting when it can cope with hardware-related constraint allowing low complexity implementations. We here review and compare many algorithmic adaptation policies that focus either on the encoding part or on the recovery part of compressed sensing. We also review other more hardware-oriented adaptation techniques that are actually able to make the difference when coming to real-world implementations. In all cases, adaptation proves to be a tool that should be mastered in practical applications to unleash the full potential of compressed sensing

Managers' compassionate goals, innovation, and firm performance: an examination of mediating processes, and boundary conditions in small- and medium-sized enterprises

This study aims to examine the relationships of managers' compassionate goals with innovation and performance in small- and medium-sized enterprises (SMEs). By integrating social exchange theory with social information processing theory, we hypothesize a serial mediation model in which organizational cooperation and firm innovation sequentially mediate a positive relationship between managers' compassionate goals and firm performance. However, we predict that this positive indirect effect would occur only when managers have low self-image goals and there is a high innovation-supportive work environment. Based on survey data from a sample of 116 SMEs in France, our results provide support for our predictions. This study contributes to the literature by disclosing the mechanisms and boundary conditions of the relationship of managers' compassionate goals with SMEs' innovation and performance. Theoretical and managerial implications of this study are discussed

An architecture for ultra-low-voltage ultra-low-power compressed sensing-based acquisition systems

Compressed Sensing (CS) has been addressed as a paradigm capable of lowering energy requirements in acquisition systems. Furthermore, the capability of simultaneously acquiring and compressing an input signal makes this paradigm perfectly suitable for low-power devices. However, the need for analog hardware blocks makes the adoption of most of standard solutions proposed so far in the literature problematic when an aggressive voltage and energy scaling is considered, as in the case of ultra-low-power IoT devices that need to be battery-powered or energy harvesting-powered. Here, we investigate a recently proposed architecture that, due to the lack of any analog block (except for the comparator required in the following A/D stage) is compatible with the aggressive voltage scaling required by IoT devices. Feasibility and expected performance of this architecture are investigated according to the most recent state-of-the-art literature