Production of light particles by very strong and slowly varying magnetic fields

The possibility that around some astrophysical objects there are non-static magnetic fields of enormous intensity suggests that in these situations real particles may be produced. The slowness of the variation is compensated by the huge intensity. The main issue is the production of e+,e- pairs annihilating into photons and the direct production of photons, as one of the concurrent process in the GRB (gamma ray bursts). Then some simple effects due to the presence of the intense gravity are studied and finally a look is given to the production of other kinds of particles.Comment: 3 pages ISMD (2006) Conference - Paraty, R.J. Brazi

OPTIMAL DESIGN OF ENERGY COMMUNITIES Multi-objective design of multi-vector energy hubs integrated with electric mobility charging systems and acting as an energy community

The present thesis has the aim to develop a tool based on prescriptive analytics to perform the optimal design of several multi-vector energy hubs, integrated with electric mobility charging infrastructures, jointly acting as a local energy community through a posteriori multi-objective function. In Chapter 1 after having introduced the scope of the study, the justification of its relevance, and the main objectives, a brief summary of the publications of the author and his main activities during the PhD program course is reported. In Chapter 2 the energy transition is introduced, underlining the EU environmental targets by 2030 and the main energy trends which the energy sector is facing. Then the main incentive policies which are used to reach the environmental targets are reported and briefly analysed. The focus is moved on the newly introduced concepts of energy communities and collective self-consumers at the EU and at the State Member level. The preliminary implementation of the EU directives in Italy and Spain are evaluated and commented. Finally, the concept of microgrid and nanogrid is reported, as an actual and real representation of integrated energy systems characterized by multiple energy demands and different technologies. Chapter 3 recalls the concept of traditional design and compare it with optimal design. After a brief introduction on the different analytics techniques (descriptive, predictive, prescriptive) the focus is moved to the MILP (Mixed-Integer Linear Programming) problem as a tool of prescriptive analytics which can be used to perform the optimal design. Finally, a review of the state of the art of optimal design algorithms and case studies are reported and the main contributions of the present work are underlined. Chapter 4 introduces the first step towards this thesis objective. At first a deterministic mathematical model capable of performing the optimal design of a single-vector (electricity) energy hub integrated with EVs (Electric Vehicles) infrastructure is reported and applied to the case of a single-family dwelling. The considered technologies are photovoltaic, electric storage systems and charging infrastructures. Later the complexity of the model is increased, by proposing a stochastic mathematical model capable of performing the optimal design of a single-vector energy hub integrated with EVs infrastructure. The model is applied to the Mensa building of the Savona Campus of the University of Genova. Several objective functions are considered and the results are reported and commented. Chapter 5 increases the complexity of the study by introducing a deterministic mathematical model to perform the optimal design of a multi-vector energy hub. Several energy demands are considered (electricity, space heating and cooling, domestic hot water) and the portfolio of technologies is significantly expanded involving electric and thermal RES (Renewable Energy Sources), micro cogeneration units, trigeneration units, conversion units (reversible heat pumps), electric and thermal storage systems and EVs charging infrastructures. A multi-objective function is implemented. The model is applied to the entirety of the Savona Campus of the University of Genova. Chapter 6 reports the final and complete version of the developed mathematical model. This model is able to perform the optimal design of several multi-vector energy hubs, integrated with EVs charging stations, jointly acting as an energy community. The model is then applied to the Opera Pia Engineering compound of the University of Genova through the analysis of two different cases. At first a purely virtual relationship between several hubs is considered similarly to the Italian implementation of the renewable energy community concept. Later, a physical relationship between hubs is investigated similarly to the Spanish implementation of the renewable energy community configuration. Finally, Chapter 7 reports the conclusions and possible future research activities

Detrending and the Distributional Properties of U.S. Output Time Series

We study the impact of alternative detrending techniques on the distributional properties of U.S. output time series. We detrend GDP and industrial production time series employing first-differencing, Hodrick-Prescott and bandpass filters. We show that the resulting distributions can be approximated by symmetric Exponential-Power densities, with tails fatter than those of a Gaussian. We also employ frequency-band decomposition procedures finding that fat tails occur more likely at high and medium business-cycle frequencies. These results confirm the robustness of the fat-tail property of detrended output time-series distributions and suggest that business-cycle models should take into account this empirical regularity.Statistical Distributions, Detrending, HP Filter, Bandpass Filter, Normality, Fat Tails, Time Series, Exponential-Power Density, Business Cycles Dynamics

Detrending and the Distributional Properties of U.S. Output Time Series

We study the impact of alternative detrending techniques on the distributional properties of U.S. output time series. We detrend GDP and industrial production time series employing first-differencing, Hodrick-Prescott and bandpass filters. We show that the resulting distributions can be approximated by symmetric Exponential-Power densities, with tails fatter than those of a Gaussian. We also employ frequency-band decomposition procedures finding that fat tails occur more likely at high and medium business-cycle frequencies. These results confirm the robustness of the fat-tail property of detrended output time-series distributions and suggest that business-cycle models should take into account this empirical regularity.statistical distributions, detrending, HP filter, bandpass filter, normality, fat tails, time series, Exponential-Power density, business cycles dynamics.

Phonetic accommodation in non‑native directed speech supports L2 word learning and pronunciation

Published: 02 December 2023This study assessed whether Non-native Directed Speech (NNDS) facilitates second language (L2) learning, specifically L2 word learning and production. Spanish participants (N = 50) learned novel English words, presented either in NNDS or Native-Directed Speech (NDS), in two tasks: Recognition and Production. Recognition involved matching novel objects to their labels produced in NNDS or NDS. Production required participants to pronounce these objects’ labels. The novel words contained English vowel contrasts, which approximated Spanish vowel categories more (/i-ɪ/) or less (/ʌ-æ/). Participants in the NNDS group exhibited faster recognition of novel words, improved learning, and produced the /i-ɪ/ contrast with greater distinctiveness in comparison to the NDS group. Participants’ ability to discriminate the target vowel contrasts was also assessed before and after the tasks, with no improvement detected in the two groups. These findings support the didactic assumption of NNDS, indicating the relevance of the phonetic adaptations in this register for successful L2 acquisition.This research was supported by a Doctoral Fellowship (LCF/BQ/DI19/11730045) from “La Caixa” Foundation (ID 100010434) to G.P., and by the Spanish Ministry of Science and Innovation through the Ramon y Cajal Research Fellowship (RYC2018-024284-I) to M.K. This research was supported by the Basque Government through the BERC 2022-2025 program and by the Spanish State Research Agency through BCBL Severo Ochoa excellence accreditation CEX2020-001010-S. The research was also supported by the Spanish Ministry of Economy and Competitiveness (PID2020-113926GB-I00 to C.D.M.), and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 819093 to C.D.M.)

Acoustoelectric luminescence from a field-effect n-i-p lateral junction

A surface-acoustic-wave (SAW) driven light-emitting-diode structure that can implement a single-photon-source for quantum-cryptography applications is demonstrated. Our lateral n-i-p junction is realized starting from an undoped GaAs/AlGaAs quantum well by gating. It incorporates interdigitated transducers for SAW generation and lateral gates for current control. We demonstrate acoustoelectric transport and SAW-driven electroluminescence. The acoustoelectric current can be controlled down to complete pinch-off by means of the lateral gates

The Acoustic Features and Didactic Function of Foreigner-Directed Speech: A Scoping Review

Published online: Aug 1, 2022Purpose: This scoping review considers the acoustic features of a clear speech register directed to nonnative listeners known as foreigner-directed speech (FDS). We identify vowel hyperarticulation and low speech rate as the most representative acoustic features of FDS; other features, including wide pitch range and high intensity, are still under debate. We also discuss factors that may influence the outcomes and characteristics of FDS. We start by examining accommodation theories, outlining the reasons why FDS is likely to serve a didactic function by helping listeners acquire a second language (L2). We examine how this speech register adapts to listeners’ identities and linguistic needs, suggesting that FDS also takes listeners’ L2 proficiency into account. To confirm the didactic function of FDS, we compare it to other clear speech registers, specifically infant-directed speech and Lombard speech. Conclusions: Our review reveals that research has not yet established whether FDS succeeds as a didactic tool that supports L2 acquisition. Moreover, a complex set of factors determines specific realizations of FDS, which need further exploration. We conclude by summarizing open questions and indicating directions and recommendations for future research.This research was supported by a Doctoral Fellowship (LCF/BQ/DI19/11730045) from “La Caixa” Foundation (ID 100010434) awarded to Giorgio Piazza and by the Spanish Ministry of Science and Innovation through the Ramon y Cajal Research Fellowship (RYC2018-024284-I) awarded to Marina Kalashnikova. This research was supported by the Basque Government through the BERC 2022-2025 program and by the Spanish State Research Agency through BCBL Severo Ochoa excellence accreditation CEX2020-001010-S. This research was also supported by the Spanish Ministry of Economy and Competitiveness (PID2020-113926GB-I00 awarded to Clara D. Martin) and by the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement 819093 awarded to Clara D. Martin)

Surface-acoustic-wave driven planar light-emitting device

Electroluminescence emission controlled by means of surface acoustic waves (SAWs) in planar light-emitting diodes (pLEDs) is demonstrated. Interdigital transducers for SAW generation were integrated onto pLEDs fabricated following the scheme which we have recently developed. Current-voltage, light-voltage and photoluminescence characteristics are presented at cryogenic temperatures. We argue that this scheme represents a valuable building block for advanced optoelectronic architectures

Anti-bunched photons from a lateral light-emitting diode

We demonstrate anti-bunched emission from a lateral-light emitting diode. Sub-Poissonian emission statistic, with a g$^{(2)}$(0)=0.7, is achieved at cryogenic temperature in the pulsed low-current regime, by exploiting electron injection through shallow impurities located in the diode depletion region. Thanks to its simple fabrication scheme and to its modulation bandwidth in the GHz range, we believe our devices are an appealing substitute for highly-attenuated lasers in existing quantum-key-distribution systems. Our devices outperform strongly-attenuated lasers in terms of multi-photon emission events and can therefore lead to a significant security improvement in existing quantum key distribution systems