Stability analysis of periodic orbits in a class of duffing-like piecewise linear vibrators

In this paper, we study the dynamical behavior of a Duffing-like piecewise linear (PWL) springmass-damper system for vibration-based energy harvesting applications. First, we present a continuous time single degree of freedom PWL dynamical model of the system. From this PWL model, numerical simulations are carried out by computing frequency response and bifurcation diagram under a deterministic harmonic excitation for different sets of system parameter values. Stability analysis is performed using Floquet theory combined with Fillipov method.Postprint (published version

Coatings in Photovoltaic Solar Energy Worldwide Research

This paper describes the characteristics of contributions that were made by researchers worldwide in the field of Solar Coating in the period 1957–2019. Scopus is used as a database and the results are processed while using bibliometric and analytical techniques. All of the documents registered in Scopus, a total of 6440 documents, have been analyzed and distributed according to thematic subcategories. Publications are analyzed from the type of publication, field of use, language, subcategory, type of newspaper, and the frequency of the keyword perspectives. English (96.8%) is the language that is most used for publications, followed by Chinese (2.6%), and the rest of the languages have a less than < 1% representation. Publications are studied by authors, affiliations, countries of origin of the authors, and H-index, which it stands out that the authors of China contribute with 3345 researchers, closely followed by the United States with 2634 and Germany with 1156. The Asian continent contributes the most, with 65% of the top 20 affiliations, and Taiwan having the most authors publishing in this subject, closely followed by Switzerland. It can be stated that research in this area is still evolving with a great international scientific contribution in improving the efficiency of solar cells

The Evolution of Secularization: Cultural Transmission, Religion and Fertility Theory, Simulations and Evidence

This study presents an evolutionary process of secularization that integrates a theoretical model, simulations, and an empirical estimation that employs data from 32 countries (included in the International Social Survey Program: Religion II – ISSP, 1998). Following Bisin and Verdier (2000, 2001a), it is assumed that cultural/social norms are transmitted from one generation to the next one via two venues: (i) direct socialization – across generations, by parents; and (ii) oblique socialization – within generations, by the community and cultural environment. This paper focuses on the transmission of religious norms and in particular on the 'religious taste for children'. The theoretical framework describes the setting and the process leading to secularization of the population; the simulations give more insight into the process; and 'secularization regressions' estimate the effects of the various explanatory variables on secularization (that is measured by rare mass-attendance and by rare-prayer), lending support to corollaries derived from the theory and simulations. The main conclusions/findings are that (i) direct religious socialization efforts of one generation have a negative effect on secularization within the next generation; (ii) oblique socialization by the community has a parabolic effect on secularization; and (iii) the two types of socialization are complements in 'producing' religiosity of the next generation.cultural transmission, religion, fertility, secularization, ISSP

The Evolution of Secularization: Cultural Transmission, Religion and Fertility Theory, Simulations and Evidence

This study presents an evolutionary process of secularization that integrates a theoretical model, simulations, and an empirical estimation that employs data from 32 countries (included in the International Social Survey Program: Religion II – ISSP, 1998). Following Bisin and Verdier (2000, 2001a), it is assumed that cultural/social norms are transmitted from one generation to the next one via two venues: (i) direct socialization – across generations, by parents; and (ii) oblique socialization – within generations, by the community and cultural environment. This paper focuses on the transmission of religious norms and in particular on the 'religious taste for children'. The theoretical framework describes the setting and the process leading to secularization of the population; the simulations give more insight into the process; and 'secularization regressions' estimate the effects of the various explanatory variables on secularization (that is measured by rare mass-attendance and by rare-prayer), lending support to corollaries derived from the theory and simulations. The main conclusions/findings are that (i) direct religious socialization efforts of one generation have a negative effect on secularization within the next generation; (ii) oblique socialization by the community has a parabolic effect on secularization; and (iii) the two types of socialization are complements in 'producing' religiosity of the next generation.cultural transmission, religion, fertility, secularization, ISSP

Electron refraction at lateral atomic interfaces

We present theoretical simulations of electron refraction at the lateral atomic interface between a “homogeneous” Cu(111) surface and the “nanostructured” one-monolayer (ML) Ag/Cu(111) dislocation lattice. Calculations are performed for electron binding energies barely below the 1 ML Ag/ Cu(111) M-point gap (binding energy EB ¼53 meV, below the Fermi level) and slightly above its C -point energy (EB ¼160 meV), both characterized by isotropic/circular constant energy surfaces. Using plane-wave-expansion and boundary-element methods, we show that electron refraction occurs at the interface, the Snell law is obeyed, and a total internal reflection occurs beyond the critical angle. Additionally, a weak negative refraction is observed for EB ¼53 meV electron energy at beam incidence higher than the critical angle. Such an interesting observation stems from the interface phase-matching and momentum conservation with the umklapp bands at the second Brillouin zone of the dislocation lattice. The present analysis is not restricted to our Cu-Ag/Cu model system but can be readily extended to technologically relevant interfaces with spinpolarized, highly featured, and anisotropic constant energy contours, such as those characteristic for Rashba systems and topological insulators. Published by AIP Publishing.Peer ReviewedPostprint (published version

Simultaneous Effect of Temperature and Irradiance on Growth and Okadaic Acid Production from the Marine Dinoflagellate Prorocentrum belizeanum

Benthic marine dioflagellate microalgae belonging to the genus Prorocentrum are a major source of okadaic acid (OA), OA analogues and polyketides. However, dinoflagellates produce these valuable toxins and bioactives in tiny quantities, and they grow slowly compared to other commercially used microalgae. This hinders evaluation in possible large-scale applications. The careful selection of producer species is therefore crucial for success in a hypothetical scale-up of culture, as are appropriate environmental conditions for optimal growth. A clone of the marine toxic dinoflagellate P. belizeanum was studied in vitro to evaluate its capacities to grow and produce OA as an indicator of general polyketide toxin production under the simultaneous influence of temperature (T) and irradiance (I0). Three temperatures and four irradiance levels were tested (18, 25 and 28 °C; 20, 40, 80 and 120 µE·m−2·s−1), and the response variables measured were concentration of cells, maximum photochemical yield of photosystem II (PSII), pigments and OA. Experiments were conducted in T-flasks, since their parallelepipedal geometry proved ideal to ensure optically thin cultures, which are essential for reliable modeling of growth-irradiance curves. The net maximum specific growth rate (µm) was 0.204 day−1 at 25 °C and 40 µE·m−2·s−1. Photo-inhibition was observed at I0 > 40 μEm−2s−1, leading to culture death at 120 µE·m−2·s−1 and 28 °C. Cells at I0 ≥ 80 µE·m−2·s−1 were photoinhibited irrespective of the temperature assayed. A mechanistic model for µm-I0 curves and another empirical model for relating µm-T satisfactorily interpreted the growth kinetics obtained. ANOVA for responses of PSII maximum photochemical yield and pigment profile has demonstrated that P. belizeanum is extremely light sensitive. The pool of photoprotective pigments (diadinoxanthin and dinoxanthin) and peridinin was not able to regulate the excessive light-absorption at high I0-T. OA synthesis in cells was decoupled from optimal growth conditions, as OA overproduction was observed at high temperatures and when both temperature and irradiance were low. T-flask culture observations were consistent with preliminary assays outdoors

Nonlinear self-collimated sound beams in sonic crystals

We report the propagation of high-intensity sound beams in a sonic crystal, under self-collimation or reduced-divergence conditions. The medium is a fluid with elastic quadratic nonlinearity, where the dominating nonlinear effect is harmonic generation. The conditions for the efficient generation of narrow, non-diverging beam of second harmonic are discussed. Numerical simulations are in agreement with the analytical predictions made, based on the linear dispersion characteristics in modulated media and the nonlinear interaction in a quadratic medium under phase matching conditions.Comment: Sent to PR

Chaos controller for switching regulators aiming enhanced design-space towards miniaturization

This paper tackles the control of fast-scale instabilities in a buck switching power converter aiming to expand its design-space towards miniaturization. After briefly revisiting the working principle of existing chaos controllers, the paper explores an alternative approach based on amplifying the harmonic at the switching frequency. Numerical simulations show that the proposed controller can concurrently improve both fast-scale and slow-scale stability margins. Finally, the paper proposes a chaos controller combined with an output ripple reduction network and studies their interaction with the aim of achieving both low-ripple and improved stability.Preprin

A mobile terminal leaky-wave antenna for efficient 5G communication

The millimeter-wave 37 –43.5GHz band is proposed to provide the requested multigigabit-per-second (Gb/s) data rates for future 5G cellular communications. As a total wireless-link gain of 37 dBi may be required, the mobile terminal antennas should provide 12 dBi gain –being the remaining 25 dBi for the base station antennas. This high gain is linked to the synthesis of narrow directive radiated beam, which must somehow be scanned into space over a wide field of view (FoV), and thus satisfy the mobility and coverage conditions. Such high-gain beam-scanning antenna design is very challenging, taking into account that high radiation efficiency, compact size/volume, and low-cost are key features for mass-market mm-wave applications. In this sense, most of the proposed 5G mobile-antenna solutions are based on phased arrays, which rely on active scanning/beam-forming networks which might be impractical due to an increase cost and manufacturing complexity. However, owning to their characteristics of high-gain, simple-feeding, planar structure, and inherent frequency-beam-scanning behavior, leaky-wave antennas (LWAs) might offer an interesting solution for high-gain low-cost scanning

A Monte Carlo study of old, new and tadpole improved actions

Scaling of mass ratios in intermediate volumes, obtained with improved SU(2) lattice actions is tested against analytic results for the Wilson and continuum action. A new improved action is introduced by adding a 2X2 plaquette to the Symanzik action. Completing a square leads to a covariant propagator that simplifies perturbative calculations. Data is presented on lattices of size 4**3X128, with lattice spacings of approximately 0.02 and 0.12 fermi. For the latter case no further improvement as compared to the tree-level action was observed when including the Lepage-Mackenzie tadpole correction to the one-loop improved Luscher-Weisz Symanzik action.Comment: 12 pages, including 2 tables and 2 figures, late