Short-Circuit Protection Schemes for LVDC Microgrids Based on the Combination of Hybrid Circuit Breakers and Mechanical Breakers

In recent years, low-voltage direct current (LVDC) microgrids are becoming more attractive because they represent a solution to integrate renewable sources, storage, and electronic loads bringing some advantages in comparison with traditional AC grids. However, the protection of such a network involves many challenges, especially in the case of LVDC microgrids with more than one feeder and multiple energy sources. Indeed, the traditional protection breakers used for an AC grid cannot isolate the faults and protect the components of a DC grid, while the use of solid-state circuit breakers increases energy losses. This paper deals with the analysis and design of the protection schemes for LVDC microgrids through the combination of mechanical circuit breakers and hybrid circuit breakers. This solution has the advantage of energy loss reduction but introduces further issues due to the slow transition times of the mechanical circuit breakers. Thus, a completely decentralized control system capable of overcoming the fast fault-clearing time, cost-effectiveness, and selectivity issues is designed to protect from pole-to-pole faults. The proposed control strategy is compared with a centralized protection scheme available in the literature through numerical simulation. The two algorithms show similar performances, with a mean voltage dip duration of less than 30 ms and a maximum voltage dip duration of about 100 ms in the most severe fault condition, but the proposed solution is more reliable and flexible since it does not depend on the communication system

In situ GISAXS study of the growth of Pd on MgO(001)

The morphology of growing Pd nano-particles on MgO(001) surfaces have been investigated in situ, during growth, by grazing incidence small angle x-ray scattering, for different substrate temperatures. The 2D patterns obtained are quantitatively analyzed, and the average morphological parameters (shape, size) deduced. Above 650 K, the aggregates adopt their equilibrium shape of truncated octahedron, and the interfacial energy is deduced.Comment: 10 pages, 1 Table, 2 Figure

Stochastic 0-dimensional Biogeochemical Flux Model: Effect of temperature fluctuations on the dynamics of the biogeochemical properties in a marine ecosystem

We present a new stochastic model, based on a 0-dimensional version of the well known biogeochemical flux model (BFM), which allows to take into account the temperature random fluctuations present in natural systems and therefore to describe more realistically the dynamics of real marine ecosystems. The study presents a detailed analysis of the effects of randomly varying temperature on the lower trophic levels of the food web and ocean biogeochemical processes. More in detail, the temperature is described as a stochastic process driven by an additive self-correlated Gaussian noise. Varying both correlation time and intensity of the noise source, the predominance of different plankton populations is observed, with regimes shifted towards the coexistence or the exclusion of some populations. Finally a Fourier analysis carried out on the time series of the plankton populations shows how the ecosystem responds to the seasonal driving for different values of the noise intensit

Single Nucleotide Polymorphism discovery and genotyping within the chicken Tapasin gene

Tapasin is one of the specific accessory molecules for the assembly of MHC class I molecules inside the Endoplasmic Reticulum (ER) (Antoniou et al., 2003). Mammalian tapasin is a 48 kDa transmembrane chaperone-protein (Sadasivan et al., 1996), and is member of the immunoglobulin superfamily (Ortmann et al., 1997)

Simulation of light‐weight membrane structures by wrinkling model

The computational challenge in dealing with membrane systems is closely connected to the lack of bending stiffness that constitutes the main feature of this category of structures. This manifests numerically in badly conditioned or singular systems requiring the use of stabilized solution procedures, in our case of a ‘pseudo‐dynamic’ approach. The absence of the flexural stiffness makes the membrane very prone to local instabilities which manifest physically in the formation of little ‘waves’ in ‘compressed’ areas. Current work presents an efficient, sub‐iteration free ‘explicit’, penalty material based, wrinkling simulation procedure suitable for the solution of ‘static’ problems. The procedure is stabilized by taking full advantage of the pseudo‐dynamic solution strategy, which allows to retain the elemental quadratic convergence properties inside the single solution step. Results are validated by comparison with published results and by setting up ‘numerical experiments’ based on the solution of test cases using dense meshes. Copyright © 2005 John Wiley & Sons, Ltd.&nbsp

Plasmonics of supported nanoparticles reveals adhesion at the nanoscale: implications for metals on dielectrics

The morphology and adhesion energy of nanosized metal particles supported on dielectrics are a puzzling issue since, due to the increasing contribution of surfaces and interfaces in their energetics, their equilibrium shape escapes the rules established for large objects. The evolution of wetting during Volmer–Weber growth of nanoparticles is herein studied by in situ ultraviolet/visible surface differential reflectivity spectroscopy (SDRS). The integrated s-polarized SDR signal is shown to be proportional to the oscillator strength of the optically excited plasmon resonances parallel to the surface. Dielectric modelings show that this quantity, which is marginally affected by the size and density of the objects, depends mainly on the aspect ratio of the particles from which adhesion energy can be derived. Applied to noble (Ag, Au) or transition metals (Cr, Ni) and Zn on weakly interacting dielectric (Al2O3, SiO2, KBr) and semiconducting (TiO2, ZnO) substrates, this plasmonic approach evidences a robust U-shaped variation of the aspect ratio with film thickness and therefore size. In line with the thorough study of the Ag/Al2O3(0001) growth and linear elasticity predictions of the equilibrium shape of strained epitaxial particles, the first branch of the “U” is assigned to a size-dependent equilibrium shape related to surface/interface stress effects. A significant decrease in adhesion energy parallels a rounding of the particles. The second branch partly stems from flattening due to incomplete coalescence. The common behavior of poorly wetting supported metal nanoparticles that is revealed herein, with strong changes in shape and adhesion as a function of particle size, had not been evidenced so far. Both the proposed optical methodology and the final findings about adhesion at the nanoscale are of interest in the wide field of application of supported metal nanoparticles that involves heterogeneous catalysis and thin film growth.We thank all reviewers for their very constructive comments. R.C., E.C., and Q.H. thank ANRT (Agence Nationale de la Recherche et de la Technologie), Arcelor-Mittal Maizières Research, and Saint-Gobain Recherche for the CIFRE funding of their thesis (grants 2013/0521 and 2016/0650). M.M. and E.M. acknowledge the support of the French state fund managed by the ANR (Agence Nationale de la Recherche) within the Investissements d’Avenir program under reference ANR-11-IDEX-0004-02 and more specifically within the framework of the Cluster of Excellence MATISSE. R.L., I.G., and Q.H. acknowledge the support of ANR (Industrial chair FRAXOS, reference ANR-15-CHIN-0003). The SDRS setup was designed by S. Chenot (INSP, Paris).Peer ReviewedPostprint (published version

Eficácia de Beauveria bassiana para o controle de Hedypathes betulinus em erva-mate, Ilex paraguariensis.

O controle das pragas da erva-mate, dentre as quais a broca-da-erva-mate, Hedypathes betulinus, é limitado principalmente a técnicas silviculturais e catação manual, pois não é permitida a aplicação de agroquímicos nessa cultura. A fim de contribuir com informações para o controle biológico de H. betulinus, o presente trabalho teve por objetivos determinar a eficácia e o número de aplicações anuais do micoinseticida à base do fungo entomopatogênico Beauveria bassiana para o controle dessa praga. Os experimentos foram conduzidos em uma área de erva-mate em monocultura, no município de Campo Alegre, SC, Brasil. O formulado foi pulverizado no tronco e na base das árvores, de acordo com um cronograma de duas ou três aplicações, em diferentes meses do ano. Constatou-se a eficácia com a utilização do formulado, sendo que os dados de captura das áreas tratadas diferiram estatisticamente da testemunha e do tratamento com catação manual. Contudo, não houve diferença estatística entre os tratamentos com duas e três aplicações, sendo capturados, respectivamente, 18,4% e 17,7% dos insetos marcados. Assim, apenas duas pulverizações com B. bassiana realizadas nos meses de novembro e fevereiro são eficientes para o controle de H. betulinus e manutenção do inóculo na área de erva-mate em monocultur

Tricorynus rudepunctatus (PIC) (Coleoptera: Anobiidae): Diagnosis and damage

The objective of this research was to identify and study a species of Anobiidae that causes great damage and is a cause of concern as an urban pest in Brazil. This species has been found infesting wood, furniture, doors, books, insect collections, tea, dried fruits, handcrafts, and many other commodities. Inspections were done in houses and storehouses in the city of Curitiba, PR, Brazil in order to collect objects and materials that present signs of anobiid attack. The only species identified was Tricorynus rudepunctatus (Coleoptera: Anobiidae). There is only one reference to this species in the central region of Brazil. Another anobiid, the book pest Tricorynus herbarius has been recorded attacking books and historical documents and Tricorynus sp. attacking forest trees, but it was not recorded in our survey. Usually, the damage caused by T. rudepunctatus is mistaken with damage by termites; and when the insect is collected it is frequently misidentified as T. herbarius or as the cigarette beetle, Lasioderma serricorne or even as Stegobium paniceum, the drugstore beetle. Some morphological characters useful to identify T. rudepunctatus are: oval body about 2.7 mm long; dark brown with smooth hairs all over the body; head concealed under the pronotum; 10-segmented antenna with the three apical segments forming a 3-segmented loose club; elytra with two grooves at the posterior edge; fore femur with a transversal line on its anterior face; pro and mesotibia with two distinct striae; metasternum longitudinally carinate in the middle. Adults and larvae bore inside the materials, forming galleries and producing a coarse powder. Keywords: Anobiids, Insect identification, Morphological characters, Urban pest

Age-related changes in the energy of human mesenchymal stem cells

Aging is a physiological process that leads to a higher risk for the most devastating diseases. There are a number of theories of human aging proposed, and many of them are directly or indirectly linked to mitochondria. Here, we used mesenchymal stem cells (MSCs) from young and older donors to study age-related changes in mitochondrial metabolism. We have found that aging in MSCs is associated with a decrease in mitochondrial membrane potential and lower NADH levels in mitochondria. Mitochondrial DNA content is higher in aged MSCs, but the overall mitochondrial mass is decreased due to increased rates of mitophagy. Despite the higher level of ATP in aged cells, a higher rate of ATP consumption renders them more vulnerable to energy deprivation compared to younger cells. Changes in mitochondrial metabolism in aged MSCs activate the overproduction of reactive oxygen species in mitochondria which is compensated by a higher level of the endogenous antioxidant glutathione. Thus, energy metabolism and redox state are the drivers for the aging of MSCs/mesenchymal stromal cells