208 research outputs found
On the optimal vorticity function of vortex rings
No full textWe present here an original approach to reconstruct the vorticity distribution inside an axisymmetric vortex ring from some incomplete and possibly noisy measurements of the corresponding velocity field. The idea is to formulate an inverse problem for identifying the structure of the vorticity distribution and solve this problem by a suitable numerical optimization algorithm. The novelty of the present study is that the vorticity function is reconstructed in a very general form with no assumptions other than smoothness and the behaviour at the endpoints of its domain of definition. This is fundamentally different from classical approaches reducing the reconstruction problem to fitting a small number of variables parameterizing the vorticity distribution of a given vortex-ring model
A mathematical model for mechanically-induced deterioration of the binder in lithium-ion electrodes
No full textThis study is concerned with modeling detrimental deformations of the binder phase within lithium-ion batteries that occur during cell assembly and usage. A two-dimensional poro- viscoelastic model for the mechanical behavior of porous electrodes is formulated and posed on a geometry corresponding to a thin rectangular electrode, with a regular square array of microscopic circular electrode particles, stuck to a rigid base formed by the current collector. Deformation is forced both by (i) electrolyte absorption driven binder swelling, and; (ii) cyclic growth and shrinkage of electrode particles as the battery is charged and discharged. In order to deal with the complex- ity of the geometry the governing equations are upscaled to obtain macroscopic effective-medium equations. A solution to these equations is obtained, in the asymptotic limit that the height of the rectangular electrode is much smaller than its width, that shows the macroscopic deformation is one-dimensional, with growth confined to the vertical direction. The confinement of macroscopic deformations to one dimension is used to obtain boundary conditions on the microscopic problem for the deformations in a ’unit cell’ centered on a single electrode particle. The resulting microscale problem is solved using numerical (finite element) techniques. The two different forcing mechanisms are found to cause distinctly different patterns of deformation within the microstructure. Swelling of the binder induces stresses that tend to lead to binder delamination from the electrode particle surfaces in a direction parallel to the current collector, whilst cycling causes stresses that tend to lead to delamination orthogonal to that caused by swelling. The differences between the cycling-induced damage in both: (i) anodes and cathodes, and; (ii) fast and slow cycling are discussed. Finally, the model predictions are compared to microscopy images of nickel manganese cobalt oxide cathodes and a qualitative agreement is found
Ianthinite et wyartite
No full textL'étude de la ianthinite, hydrate uranoso-uranique de formule UO₂.5 UO₃. 10,56 H₂O a permis de montrer l'existence d'une autre espèce : la wyartite, carbonate uranoso-uranique hydraté de calcium. Orthorhombique, a = 11,25 ; b = 7,08 ; c = 20,98 Â ; Z = 2, de formule UO₂.6 UO₃.2 CO₃.3 CaO. 12-14 H₂O.
Ce minéral a été trouvé sur de l'uraninite à Shinkolobwé (Katanga) .Guillemin Claude, Protas Jean. Ianthinite et wyartite. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 82, 1-3, 1959. pp. 80-86
Binder migration during drying of lithium-ion battery electrodes: modelling and comparison to experiment
No full textThe drying process is a crucial step in electrode manufacture that may lead to spatial inhomogeneities in the distribution of the electrode components resulting in impaired cell performance. Binder migration during the drying process, and the ensuing poor binder coverage in certain regions of the electrode, can lead to capacity fade and mechanical failure (e.g. electrode delamination from the current collector). A mathematical model of electrode drying is presented which tracks the evolution of the binder distribution, and is applicable in the relatively high drying rates encountered in industrial electrode manufacture. The model predicts that constant low drying rates lead to a favourable homogeneous binder profiles, whereas constant high drying rates are unfavourable and result in accumulation of binder near the evaporation surface and depletion near the current collector. These results show strong qualitative agreement with experimental observations and provide a cogent explanation for why fast drying conditions result in poorly performing electrodes. Finally, a scheme is detailed for optimisation of a time-varying drying procedure that allows for short drying times whilst simultaneously ensuring a close to homogeneous binder distribution throughout the electrode
Sur la Dumontite de Shinkolobwe (Katanga)
No full textL'analyse chimique d'un échantillon de dumontite montre que la formule de ce minéral rare est : Pb₂ (UO₂)₃ (PO₄)₂ (OH)₄. 3 H₂O ; densité : 5,65. La formule chimique et les propriétés optiques sont en bon accord avec celles du minéral initialement décrit. L'étude des diagrammes de Weissenberg (strates hko, hk1, hk2 ; hol, h1l, h2l) montre l'existence d'une macle suivant le plan (100). Les paramètres de la maille sont : a = 8,16 ± 0,03 À ; b = 16,73 ± 0,03 À ; c = 7,02 ± 0,03 À ; β = 110° ; Z = 2. Groupe spatial : P2₁ ou P2₁/m.Thoreau Jacques, Van Meerssche Maurice, Protas Jean. Sur la Dumontite de Shinkolobwe (Katanga). In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 81, 1-3, 1958. pp. 63-65
Causes of binder damage in porous battery electrodes and strategies to prevent it
No full textThe mechanisms for binder delamination from electrode particles in porous lithium-ion electrodes are considered. The problem is analysed using a model that makes use of a multiscale continuum description of the battery electrode and specifically accounts for the viscoelastic properties of the binder [9]. This model predicts the evolution of the stress fields in the binder in response to: (i) binder swelling due to electrolyte absorption during cell assembly, and; (ii) shrinkage and growth of the electrode particles during cell cycling. The model predictions provide a cogent explanation for morphological damage seen in microscopy images of real cathodes. The effects of altering electrode particle shape, binder rheology and cycling rates on binder delamination are all investigated and used to make suggestions on how electrode lifetimes could be extended
ANALYSIS OF METHODS FOR INCREASING THE EFFICIENCY OF DYNAMIC ROUTING PROTOCOLS IN TELECOMMUNICATION NETWORKS WITH THE POSSIBILITY OF SELF-ORGANIZATION
No full textSova O., Odarushchenko E., Protas N., Degtyareva L., Nalapko O., Shyshatskyi A. ANALYSIS OF METHODS FOR INCREASING THE EFFICIENCY OF DYNAMIC ROUTING PROTOCOLS IN TELECOMMUNICATION NETWORKS WITH THE POSSIBILITY OF SELF-ORGANIZATION. Theoretical and practical scientific achievements: research and results of their implementation: collection of scientific papers «SCIENTIA» with Proceedings of the II International Scientific and Theoretical Conference (Vol. 1), September 3, 2021. Pisa, Italian Republic: European Scientific Platform. P. 78-83
Grynojo proto problema šachmatuose
No full textŠiame straipsnyje filosofuojama apie grynojo proto problemą šachmatuose, svarstoma, ar žmogus šachmatininkas disponuoja grynuoju šachmatiniu protu, ar tai kompiuterinės programos privilegija. Atkreipiamas dėmesys, kad grynasis žmogaus šachmatininko protas yra fragmentuotas ir priklauso nuo baltųjų arba juodųjų figūrų vizualinės bei teorinės sistemos perspektyvos, o kompiuterinės šachmatų programos protas (arba tiesiog „mašinos“ protas) yra vientisas. Straipsnyje svarstoma, ar grynojo šachmatinio proto, neturinčio juodųjų ir baltųjų figūrų vizualinės perspektyvos bei psichologinio nuovargio, reiktų ieškoti ne žmoguje, o kompiuterinėje programoje. Reikšminiai žodžiai: Šachmatai; Grynasis protas; Šachmatininkas; Immanuel Kant (Imanuelis Kantas); Filosofija; Chess; Pure mind; Human chess; Immanuel Kant; PhilosophyThis article philosophizes about the problem of the pure mind in chess. The author considers whether only a human chess player possesses a pure chess mind or if it is the privilege of a computer program. It highlights that the pure human-chess mind is fragmented and depends on a visual perspective of white and black pieces as well as on the perspective of a theoretical system. On the other hand, the mind of a computer program (or simply the mind of a „machine“) is all-in-one. The article considers whether we should be looking for a pure chess mind not in a human being, but in a chess computer program, which has no visual perspective of black and white pieces and does not experience psychological fatigue
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