1,720,965 research outputs found
Active material utilization and capacity of fiber-based battery electrodes
Full text linkThis study presents a three-dimensional computational model to evaluate effective conductivity and capacity of fiber-based battery electrodes. We employ electrodes composed of conductive and active material nanofibers dispersed in an electrolyte matrix. The effective conductivity is calculated by means of an equivalent resistor network model, while capacity evaluation is based on the identification of active material fibers that are accessible to electrons (i.e., those connected with the electronically conductive network). When a constraint is applied to the total fiber content, an optimal active-conductive material ratio is determined that maximizes the active material utilization and the electrode capacity. We also study fiber orientation effects on the electrode electrochemical properties. It is found that fiber orientation has a strong impact on the percolation threshold, and this impact also reflects on the active material utilization: the more the fiber orientation deviates from the ideal isotropic distribution, the lower the utilization of active material fibers. This is of special interest for practical applications where geometrical constraints on fiber orientation arise, as in the case of electrospun fibers deposited on a substrate. The results of this study are therefore meant to give an insight into how a fibrous electrode architecture performs and suggest effective design solutions.Applied Mechanic
Tensorial effective transport properties of Li-ion battery separators elucidated by computational multiscale modeling
Full text linkExisting battery modeling works have limitations in addressing the dependence of transport properties on local field variations and characterizing the response of anisotropic media.
These limitations are tackled by means of a nested finite element (FE2) multiscale framework in which microscale simulations are employed to comprehensively characterize an anisotropic medium (macroscale).
The approach is applied to the numerical simulation of transport processes in lithium ion battery separators.
From the microscale solution, homogenized fluxes and their dependence on the downscaled macroscale variables are upscaled, thereby replacing otherwise assumed macroscale constitutive laws.
The tensorial nature of macroscale effective transport properties stems from the numerical treatment.
The proposed approach is verified against full-scale simulations. Several numerical examples are used to demonstrate the perils associated with accepted procedures, leading in some cases to severe discrepancies in the prediction of field quantities (from differences in the potential drop across the separator of about 27% for a fixed microstructure to more than 100% in the case of an evolving microstructure). Despite the use of simplified assumptions (e.g., synthetic microstructures), the numerical results demonstrate the importance of a tensorial description of transport properties in the modeling of battery processes
An efficient computational approach for three-dimensional modeling and simulation of fibrous battery electrodes
No full textFibrous electrodes are a promising alternative to conventional particle-based lithium-ion battery electrodes. In this contribution, we propose an efficient computational approach for the modeling and simulation of electrochemical phenomena taking place in fibrous electrodes during battery charge/discharge processes. Since each fiber is explicitly modeled by means of a dimensionally reduced embedded fiber model, the framework enables simulations in a three-dimensional setting with relatively modest discretization and computational requirements compared to simulations with fully resolved fiber discretizations. The approach is applied to electrodes with high volume fractions of high aspect ratio fibers. Various local and global quantities are analyzed and results are compared to those obtained with the standard finite element method and the pseudo-2D model
A coupled model of transport-reaction-mechanics with trapping. Part I – Small strain analysis
No full textA fully coupled model for mass and heat transport, mechanics, and chemical reactions with trapping is proposed. It is rooted in non-equilibrium rational thermodynamics and assumes that displacements and strains are small. Balance laws for mass, linear and angular momentum, energy, and entropy are stated. Thermodynamic restrictions are identified, based on an additive strain decomposition and on the definition of the Helmholtz free energy. Constitutive theory and chemical kinetics are studied in order to finally write the governing equations for the multi-physics problem. The field equations are solved numerically with the finite element method, stemming from a three-fields variational formulation. Three case-studies on vacancies redistribution in metals, hydrogen embrittlement, and the charge–discharge of active particles in Li-ion batteries demonstrate the features and the potential of the proposed model.Applied Mechanic
Molecular identification of Borrelia valaisiana and HGE-Ehrlichia in Ixodes ricinus tick sampled in North East Italy: first report in Veneto region
No full textPCR amplification was applied to screen the presence of both Borrelia burgdorferi s.l. and Ehrlichia species in pools of field-collected Ixodes ricinus ticks. The specimens so far analysed (n = 55), grouped in 11 pools, were sampled in Feltre area (Veneto region, NE Italy). Five pools proved positive for B. valaisiana (45%) and one of them (9%) was also positive for Ehrlichia, that was further characterised as a HGE-like Ehrlichia. This is the first report of the two bacteria in the Veneto region. The pool positive for both pathogens was used to adjust a multiplex PCR assay, which allowed the detection and identification of both parasites in a single experiment. The advantages offered by this assay, when standardised, will substantially broaden the perspectives of ecological and epidemiological investigations on animal/human Lyme disease and ehrlichiosis, greatly facilitating disease surveillance and control programs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Babesiosis in ticks and foresters of the Parco Nazionale delle Dolomiti Bellunesi (Feltre, Italy): preliminary results
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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