Search

ZnFe2O4 (ZFO) nanospheres with complex structures have been synthesized by a one-step simple solvothermal method using two different types of precursors—metal chlorides and nitrates —and were fully characterized by XRD, SEM, XPS, and EDS. The ZFO nanospheres synthesized from chloride salts (ZFO_C) were loose with a size range of 100–200 nm, while the ZFO nanospheres synthesized from nitrate salts (ZFO_N) were dense with a size range of 300–500 nm but consisted of smaller nanoplates. The different morphologies may be caused by the different hydrolysis rates and different stabilizing effects of chloride and nitrate ions interacting with the facets of forming nanoparticles. Electrochemical tests of nitrate-based ZFO nanospheres as anode materials for lithium-ion batteries demonstrated their higher cyclic stability. The ZFO_C and ZFO_N samples have initial specific discharge/charge capacities of 1354/1020 and 1357/954 mAh∙g−1, respectively, with coulombic efficiencies of 75% and 71%. By the 100th cycle, ZFO_N has a capacity of 276 mAh∙g−1, and for ZFO_C, only 210 mAh∙g−1 remains after 100 cycles. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) and, in particular, Zn//MnO2 rechargeable batteries have attracted great attention due to the abundant natural resources of zinc and manganese, low cost, environmental friendliness, and high operating voltage. Among the various ways to improve the electrochemical performance of MnO2-based cathodes, the development of MnO2 cathodes doped with metal ions or composites of MnO2 with conducting polymers has shown such advantages as increasing the specific capacity and cycling stability. This mini-review focuses on the strategies to improve the electrochemical performance of manganese-based cathodes of AZIBs. [ABSTRACT FROM AUTHOR]

In the present paper, we investigate a problem, describing the deformations process for the Stieltjes strings system located along a geometric star - shaped graph under the influence of an external force. The case when the force can be concentrated at separate points, including a node of the graph, is considered. The non-linear condition arises due to the presence of a limiter on the strings displacement in the node. Using variational methods, the necessary and sufficient conditions for the extremum of an energy functional are established; existence and uniqueness theorems for the solution are proved; an explicit formula for the solution is obtained; and the dependence solution on the length of the limiter is studied. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) are being intensively developed as potential alternative electrochemical power sources, due to their advantages such as low cost, high safety, abundance of natural zinc resources and appropriate energy density. Among currently investigated prospective cathode materials for AZIBs, vanadium oxide-based composites with intrinsically conducting polymers have shown many advantages, such as high capacity, high power density and long battery life. This review gives a focused view of the design for the boosting of zinc ion storage performance using intrinsically conducting polymers in vanadium oxide-based composites and the mechanism of intercalation processes. The main challenges in interfacial engineering of vanadium oxide-conducting polymers composite structures and the prospects for further development of such cathode materials are summarized and discussed. The review would give rise to a broad interest focusing on the advantageous strategy of the development of vanadium oxide composite cathodes with intrinsically conducting polymers (polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene)) for AZIBs with improved energy density, high-rate capability and stability. [ABSTRACT FROM AUTHOR]

In this work the nanocomposite of vanadium oxide with conducting polymer poly(3,4-ethylenedioxythiophene) (VO@PEDOT) was obtained by microwave-assisted hydrothermal synthesis. The detailed study of its structural and electrochemical properties as cathode of aqueous zinc-ion battery was performed by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The initial VO@PEDOT composite has layered nanosheets structure with thickness of about 30–80 nm, which are assembled into wavy agglomerated thicker layers of up to 0.3–0.6 μm. The phase composition of the samples was determined by XRD analysis which confirmed lamellar structure of vanadium oxide V10O24∙12H2O with interlayer distance of about 13.6 Å. The VO@PEDOT composite demonstrates excellent electrochemical performance, reaching specific capacities of up to 390 mA∙h∙g−1 at 0.3 A∙g−1. Moreover, the electrodes retain specific capacity of 100 mA∙h∙g−1 at a high current density of 20 A∙g−1. The phase transformations of VO@PEDOT electrodes during the cycling were studied at different degrees of charge/discharge by using ex situ XRD measurements. The results of ex situ XRD allow us to conclude that the reversible zinc ion intercalation occurs in stable zinc pyrovanadate structures formed during discharge. [ABSTRACT FROM AUTHOR]

In this paper, we study a model of deformations of a beam with elastic supports and nonlinear boundary conditions under the influence of an external force. The case when the force can be concentrated at separate points is considered. The minimization problem of the potential energy functional with a constraint on the displacement of the beam end is investigated. The correctness of the model is established, and the necessary and sufficient conditions for the minimum of the potential energy functional are proved. [ABSTRACT FROM AUTHOR]

Variational methods are used to study a model of the deformation of a discontinuous Stieltjes string (a chain of strings held together by springs) located along the segment [0; l]. The model is described by the integro-differential equation pu0 m - (x)+ pu0 m - (0)+ R x 0 ud[Q] = F(x)F(0) with derivatives with respect to the measure m generated by a given strictly increasing function m(x) on the segment [0; l], where the function u(x) determines the deformation of the string, p(x) characterizes the elasticity of the string, the functions Q(x) and F(x) describe the elastic response of the external environment and the external load, respectively. The integral R x 0 ud[Q] is understood in the generalized sense according to Stieltjes. We are looking for solutions u(x) in the class of m-absolutely continuous functions on [0; l], whose derivatives have bounded variation on [0; l]. We assume that one of the boundary conditions is nonlinear and has the form p(l 0)u0 m (l 0)gu(l) 2 N[k;k]u(l); where N[k;k]u(l) denotes the outward normal cone at the point u(l) to the segment [k;k]. This condition arises due to the presence of the limiter [k;k] on the motion of the elastically fixed right end of the string (by a spring with elasticity g) so that ju(l)j = k. In this paper, necessary and sufficient conditions for the minimization of the energy functional of the Stieltjes string system are established, the critical loads at which the contact of the end of the string with the boundary points of the limiter occurs are determined, and the dependence of the solution on the length of the limiter is studied. [ABSTRACT FROM AUTHOR]

We consider a Caratheodory differential equation with a state-dependent convex constraint that changes BV-continuously in time (a perturbed BV-continuous state-dependent sweeping process). By setting up an appropriate catching-up algorithm we prove solvability of the initial value problem. Then, for sweeping processes with T-periodic right-hand sides, we prove the existence of at least one T-periodic solution. Finally, we investigate a T-periodic sweeping process which is close to an autonomous sweeping process with a constant constraint and prove the existence of a T-periodic solution specifically located near the boundary switched equilibrium of the autonomous sweeping process. [ABSTRACT FROM AUTHOR]

We provide a new result of existence of equilibria of a single-valued Lipschitz function on a compact set of which is locally the epigraph of a Lipschitz functions (such a set is called epilipschitz set). Equivalently this provides existence of fixed points of the map . The main point of our result lies in the fact that we do not impose that is an "inward vector" for all point of the boundary of . Some extensions of the existence of equilibria result are also discussed for continuous functions and set-valued maps.

In this paper, a model of deformations of a Stieltjes string with localized interactions with the environment (elastic supports and forces are concentrated at no more than countable set of points) is studied via variational methods. One of the boundary conditions is nonlinear and occurs due to a sleeve, which limits the movement of the right end of the string. The necessary and sufficient conditions for the extremum of the energy functional are established; the critical loads at which the contact of the end of the string with the sleeve occurs are determined; the dependence of the solution on the sleeve length is studied. [ABSTRACT FROM AUTHOR]

In the present paper, we investigate the initial boundary value problem describing oscillation process on a geometric graph with hysteresis type boundary conditions. The analogue of the d'Alembert formula is obtained. [ABSTRACT FROM AUTHOR]

We develop a theory which allows making qualitative conclusions about the dynamics of both monotone and non-monotone Moreau sweeping processes. Specifically, we first prove that any sweeping processes with almost periodic monotone right-hand-sides admits a globally exponentially stable almost periodic solution. And then we describe the extent to which such a globally stable solution persists under non-monotone perturbations. [ABSTRACT FROM AUTHOR]

In the present paper we investigate the initial - boundary value problems describing oscillation processes with boundary conditions of hysteresis type. Analogues of the d’Alembert formula are obtained. Some control problems are analysed and explicit forms of control functions are presented. [ABSTRACT FROM AUTHOR]

In the present paper, we show that the solution set of a fractional order semilinear differential inclusion in a Banach space has the topological structure of an Rδ-set. This result allows to apply a fixed point result for condensing multimaps to the translation multioperator along the trajectories of such inclusion and to prove the existence of solutions satisfying periodic and anti-periodic boundary value conditions. An example concerning with a fractional order feedback control system is presented. [ABSTRACT FROM AUTHOR]

We apply the topological degree theory for condensing maps to study approximation of solutions to a fractional-order semilinear differential equation in a Banach space. We assume that the linear part of the equation is a closed unbounded generator of a $C_{0}$ -semigroup. We also suppose that the nonlinearity satisfies a regularity condition expressed in terms of the Hausdorff measure of noncompactness. We justify the scheme of semidiscretization of the Cauchy problem for a differential equation of a given type and evaluate the topological index of the solution set. This makes it possible to obtain a result on the approximation of solutions to the problem. [ABSTRACT FROM AUTHOR]

We are considering the Cauchy problem for a semilinear fractional differential inclusion in a Banach space. By using the fixed point theory for condensing multivalued maps, we prove the local and global theorems of the existence of mild solutions to this problem. We verify the compactness of the solutions set and its continuous dependence on parameters and initial data. We demonstrate also the application of the averaging principle to the investigation of the continuous dependence of the solutions set on a parameter in the case when the right-hand side of the inclusion is rapidly oscillating. [ABSTRACT FROM AUTHOR]

[Display omitted] • A high-performance amorphous FeOOH-based anode is developed for Li-ion batteries. • One-step atmospheric plasma-assisted synthesis of FeOOH composite with graphite. • A capacity of ∼ 750 mAh g−1 is sustained after 500 cycles at 0.3 A g−1. • A capacity of ∼ 550 mAh g−1 is sustained after 2000 cycles at 1.2 A g−1. Iron oxide derivatives are promising materials for large-scale use as anode materials, owing to their natural abundance, inexpensiveness, and high theoretical capacity. Here, we synthesized amorphous urchin-like FeOOH nanoparticles and their graphite composite (FeOOH/Gr) in a one-step atmospheric plasma-assisted procedure and employed it in anode materials for Li-ion batteries. The obtained FeOOH nanoparticles are up to 300 nm in diameter with a needle thickness of about (3–10) nm, while FeOOH/Gr composite consists of graphite sheets covered with FeOOH needles. The FeOOH and FeOOH/Gr materials show excellent electrochemical performance as anode materials, with 633 mAh g−1 and 740 mAh g−1 at 0.3 A g−1 after 500 cycles, 353 mAh g−1 and 542 mAh g−1 at 1.2 A g−1 after 2000 cycles, respectively. By analyzing the state of the material at various stages of their life, we identify electrochemical milling as the performance-boosting process responsible for the 277% specific capacity increase during charge-discharge cycling after 50 cycles. [ABSTRACT FROM AUTHOR]

In this paper we study the existence of a mild solution of a periodic boundary value problem for fractional quasilinear differential equations in a Hilbert spaces. We assume that a linear part in equations is a self-adjoint positive operator with dense domain in Hilbert space and a nonlinear part is a map obeying Carathéodory type conditions. We find the mild solution of this problem in the form of a series in a Hilbert space. In the space of continuous functions, we construct the corresponding resolving operator, and for it, by using Schauder theorem, we prove the existence of a fixed point. At the end of the paper, we give an example for a boundary value problem for a diffusion type equation. [ABSTRACT FROM AUTHOR]

In this paper we consider an infinite dimensional bifurcation equation depending on a parameter ε > 0. By means of the theory of condensing operators, we prove the existence of a branch of solutions, parametrized by ε, bifurcating from a curve of solutions of the bifurcation equation obtained for ε = 0. We apply this result to a specific problem, namely to the existence of periodic solutions bifurcating from the limit cycle of an autonomous functional differential equation of neutral type when it is periodically perturbed by a nonlinear perturbation term of small amplitude. [ABSTRACT FROM AUTHOR]

We consider a neutral type operator differential inclusion and apply the topological degree theory for condensing multivalued maps to justify the question of existence of its periodic solution. By using the averaging method, we apply the abstract result to an inclusion with a small parameter. As example, we consider a delay control system with the distributed control. [ABSTRACT FROM AUTHOR]

This paper proposes an approach to investigate bifurcation of periodic solutions to functional-differential equations of neutral type with a small delay and a small periodic perturbation from the limit cycle under the assumption that there exists adjoint Floquet solutions to the linearized equation. [ABSTRACT FROM AUTHOR]

Abstract: In this Note, we obtain two new results for existence of periodic solutions for differential equations perturbed by a small parameter. The first one is based on a new fixed point theorem previously obtained by the authors. The second one is based on study of suitable linearized equations. Our approach deals with degree theory and nonsmooth analysis. To cite this article: A. Gudovich et al., C. R. Acad. Sci. Paris, Ser. I 347 (2009). [Copyright &y& Elsevier]

We obtained results on the existence and uniqueness of a mild solution for a fractional-order semi-linear differential inclusion in a Hilbert space whose right-hand side contains an unbounded linear monotone operator and a Carathéodory-type multivalued nonlinearity satisfying some monotonicity condition in the phase variables. We used the Yosida approximations of the linear part of the inclusion, the method of a priori estimates of solutions, and the topological degree method for condensing vector fields. As an example, we considered the existence and uniqueness of a solution to the Cauchy problem for a system governed by a perturbed subdifferential inclusion of a fractional diffusion type. [ABSTRACT FROM AUTHOR]

The electrodes of lithium-ion batteries (LIBs) are multicomponent systems and their electrochemical properties are influenced by each component, therefore the composition of electrodes should be properly balanced. At the beginning of lithium-ion battery research, most attention was paid to the nature, size, and morphology peculiarities of inorganic active components as the main components which determine the functional properties of electrode materials. Over the past decade, considerable attention has been paid to development of new binders, as the binders have shown great effect on the electrochemical performance of electrodes in LIBs. The study of new conductive binders, in particular water-based binders with enhanced electronic and ionic conductivity, has become a trend in the development of new electrode materials, especially the conversion/alloying-type anodes. This mini-review provides a summary on the progress of current research of the effects of binders on the electrochemical properties of intercalation electrodes, with particular attention to the mechanisms of binder effects. The comparative analysis of effects of three different binders (PEDOT:PSS/CMC, CMC, and PVDF) for a number of oxide-based and phosphate-based positive and negative electrodes for lithium-ion batteries was performed based on literature and our own published research data. It reveals that the combined PEDOT:PSS/CMC binder can be considered as a versatile component of lithium-ion battery electrode materials (for both positive and negative electrodes), effective in the wide range of electrode potentials. [ABSTRACT FROM AUTHOR]