1,355,062 research outputs found
On the quasistatic effective elastic moduli for elastic waves in three-dimensional phononic crystals
No full textEffective elastic moduli for 3D solid-solid phononic crystals of arbitrary anisotropy and oblique lattice structure are formulated analytically using the plane-wave expansion (PWE) method and the recently proposed monodromy-matrix (MM) method. The latter approach employs Fourier series in two dimensions with direct numerical integration along the third direction. As a result, the MM method converges much quicker to the exact moduli in comparison with the PWE as the number of Fourier coefficients increases. The MM method yields a more explicit formula than previous results, enabling a closed-form upper bound on the effective Christoffel tensor. The MM approach significantly improves the efficiency and accuracy of evaluating effective wave speeds for high-contrast composites and for configurations of closely spaced inclusions, as demonstrated by three-dimensional examples.Peer reviewe
Analytical formulation of 3D dynamic homogenization for periodic elastic systems
No full textHomogenization of the equations of motion for a three dimensional periodic elastic system is considered. Expressions are obtained for the fully dynamic effective material parameters governing the spatially averaged fields by using the plane wave expansion (PWE) method. The effective equations are of Willis form [1] with coupling between momentum and stress and tensorial inertia. The formulation demonstrates that the Willis equations of elastodynamics are closed under homogenization. The effective material parameters are obtained for arbitrary frequency and wavenumber combinations, including but not restricted to Bloch wave branches for wave propagation in the periodic medium. Numerical examples for a 1D system illustrate the frequency dependence of the parameters on Bloch wave branches and provide a comparison with an alternative dynamic effective medium theory [2] which also reduces to Willis form but with different effective moduli.Peer reviewedReceived by the journal publisher November 28, 2011; accepted January 13, 2012; published online April 25, 2012. Manuscript dated January 16, 2012
Effective Willis constitutive equations for periodically stratified anisotropic elastic media
No full textA method to derive homogeneous effective constitutive equations for periodically layered elastic media is proposed. The crucial and novel idea underlying the procedure is that the coefficients of the dynamic effective medium can be associated with the matrix logarithm of the propagator over a unit period. The effective homogeneous equations are shown to have the structure of a Willis material, characterized by anisotropic inertia and coupling between momentum and strain, in addition to effective elastic constants. Expressions are presented for the Willis material parameters which are formally valid at any frequency and horizontal wavenumber as long as the matrix logarithm is well defined. The general theory is exemplified for scalar SH motion. Low frequency, long wavelength expansions of the effective material parameters are also developed using a Magnus series and explicit estimates for the rate of convergence are derived.Peer reviewedReceived July 22, 2010; accepted December 15, 2010; published online April 21, 2011. Manuscript dated December 21, 2013
Effective shear speed in two-dimensional phononic crystals
No full textThe quasistatic limit of the antiplane shear-wave speed ('effective speed') c in 2D periodic lattices is studied. Two new closed-form estimates of c are derived by employing two different analytical approaches. The first proceeds from a standard background of the plane wave expansion (PWE). The second is a new approach, which resides in x-space and centers on the monodromy matrix (MM) introduced in the 2D case as the multiplicative integral, taken in one coordinate, of a matrix with components being the operators with respect to the other coordinate. On the numerical side, an efficient PWE-based scheme for computing c is proposed and implemented. The analytical and numerical findings are applied to several examples of 2D square lattices with two and three high contrast components, for which the new PWE and MM estimates are compared with the numerical data and with some known approximations. It is demonstrated that the PWE estimate is most efficient in the case of densely packed stiff inclusions, especially when they form a symmetric lattice, while in general it is the MM estimate that provides the best overall fitting accuracy.Peer reviewe
Spectral properties of a 2D scalar wave equation with 1D-periodic coefficients: application to SH elastic waves
No full textThe paper provides a rigorous analysis of the dispersion spectrum of SH (shear horizontal) elastic waves in periodically stratified solids. The problem consists of an ordinary differential wave equation with periodic coefficients, which involves two free parameters ω (the frequency) and k (the wavenumber in the direction orthogonal to the axis of periodicity). Solutions of this equation satisfy a quasi-periodic boundary condition which yields the Floquet parameter K. The resulting dispersion surface ω(K, k) may be characterized through its cuts at constant values of K, k and ω that define the passband (real K) and stopband areas, the Floquet branches and the isofre-quency curves, respectively. The paper combines complementary approaches based on eigenvalue problems and on the monodromy matrix M. The pivotal object is the Lyapunov function ∆ ω2, k2) ≡ 12 traceM = cosK which is generalized as a function of two variables. Its analytical properties, asymptotics and bounds are examined and an explicit form of its derivatives obtained. Attention is given to the special case of a zero-width stopband. These ingredients are used to analyze the cuts of the surface ω(K, k). The derivatives of the functions ω(k) at fixed K and ω(K) at fixed k and of the function K(k) at fixed ω are described in detail. The curves ω(k) at fixed K are shown to be monotonic for real K, while they may be looped for complex K (i.e. in the stopband areas). The convexity of the closed (first) real isofrequency curve K(k) is proved thus ruling out low-frequency caustics of group velocity. The results are rele-vant to the broad area of applicability of ordinary differential equation for scalar waves in 1D phononic (solid or fluid) and photonic crystals. 1 a
Study on propagation regularity of harmonic waves in periodic structures of beams
No full textThe wide application of elements with periodic configuration in dynamically loaded structures stimulates a study of the propagation phenomenon of harmonic waves in mechanical systems of a periodic structure. The absolute majority of investigations of the wave propagation phenomenon in periodic structures concern one-dimensional and quasi-one-dimensional systems. Therefore, it is of certain interest to study the regularities in the distribution of the "transparency windows" of a mechanical system of a periodic structure with continuously changing parameters, which can be obtained by passing through the limit from the corresponding system with the threshold-type irregularities. Besides, the non-homogeneity in these systems is of a discrete, i.e. threshold type. The article presents the research results of propagation of harmonic waves along unfixed beams of a periodic structure. In addition two beam configurations are considered: with a constant cross section in individual segments and a continuous change in the cross section along the beam axis. The solution of the two problems has been made on the basis of the Floquet theory. As a result of the solution of this problem, frequency bands of the waves for both types of beams were found, and a comparative analysis of their propagation was carried out
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Variations on the Author
No full text“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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Treatment of recurrent vulvovaginal candidiasis in women planning a pregnancy
No full textTreatment of recurrent vulvovaginal candidiasis in women planning a pregnancy
Borovikov I.O., Kutsenko I.I., Gerasimenko E.E.
Kuban State Medical University, Krasnodar
Aim: evaluation of treatment methods for recurrent vulvovaginal candidiasis (VVC) in patients planning pregnancy.
Patients and Methods: a comparative, open, randomized study of the results of treatment of 150 women with recurrent vulvovaginal candidiasis (RVVK) in which, after completing the course of the proposed therapy, fertilization took place within
6 months, followed by successful fetal bearing and childbirth: group I (n = 50) - intravaginal clotrimazole cream 2% application once a day for 6 days; II group (n = 50) - polyenic macrolide natamycin intravaginally at a dose of 100 mg once a day for
10 days; III group (n = 50) - orally fluconazole to reduce the recurrence rate of VVC 150 mg every 3 days (1st, 4th and 7th day). The direct microscopy method, measurement of the pH level of the vaginal environment and culture technique was used.
Results: it has been established that the intravaginal application of clotrimazole and fluconazole according to the clinical and microbiological efficacy of RVVK therapy is comparable and is 1.6 ± 0.2 times higher in clinical and 1.2 ± 0.15 times in microbiological efficacy than the intravaginal application of natamycin. The advantage of clotrimazole is a faster relief of candidiasis symptoms, a higher safety profile and microbiological sanation from the concomitant opportunistic pathogenic microflora.
Key words: recurrent vulvovaginal candidiasis, antimycotics, clotrimazole, natamycin, fluconazole, planning pregnancy.
For citation: Borovikov I.O., Kutsenko I.I., Gerasimenko E.E. Treatment of recurrent vulvovaginal candidiasis in women planning a pregnancy // RMJ. 2018. № 2(I). P. 13–18.<br
- …
