1,721,022 research outputs found
Reconstruction of a general mass density in a rectangular membrane from finite eigenvalue data
No full textThis paper is concerned with the estimation of the mass density in a rectangular taut membrane from finite eigenvalue data of the small undamped transverse vibration. It is known that the first lower eigenvalues of the membrane supported at the boundary may allow the reconstruction of small perturbations of the uniform density, provided that the mass density is symmetric with respect to both the midlines of the domain. Here we show how the addition of suitable sets of eigenvalues corresponding to different boundary conditions can be useful for the determination of mass densities either with one symmetry axis only or without symmetry. The reconstruction procedure is based on a sequence of linearizations of the inverse problem in a neighborhood of the uniform membrane, under the assumption that the eigenvalues of the initial membrane used in identification are all simple. An extended series of numerical simulations performed for various mass densities allowed to test the effectiveness of the reconstruction, and also to highlight some indeterminacy inherent in this inverse eigenvalue problem with finite data
The role of boundary conditions in resonator-based mass identification in nanorods
No full textThe identification of distributed mass added to a nanosensor requires the adoption of suitable inverse techniques that must be sufficiently precise to identify the analyte. In previous research, we developed a method based on the first eigenfrequencies of the free axial vibration of a nanorod under a specific set of boundary conditions. Here, we extend and complete the previous analysis by considering a wider set of sensor’s end conditions and examining their influence on identification. Our results can guide the design of nanoresonators to have not only a higher sensitivity, but also to improve the implementation of reconstruction techniques
Eco-localization of a prey in a spider orb web
No full textOrb web spiders locate the position of a perturbation in the web because of a prey impact through highly sensitive slit sensilla at the tip of their legs. Thus, the web serves as a self-made extension of its sensory space which transmits vibrations from the perturbation point to the spider location. These vibrations may contain the information required by the spider to rapidly identify the position where the prey has impacted and approach to it before it flies away. For axially symmetric orb webs supported at the boundary and for a spider which stays at the center of the web, it was shown that the knowledge of the transverse deflection time history at the eight spider legs, for a sufficiently large interval of time, contains enough information to localize the position of the prey. In this article, we address the same inverse problem of localization of the prey, but we suppose that the spider knows only a small number of selected information of the transverse displacement, such as, for example, the maxima of the response of the time history at the eight control points. We show how this reduced information still allows the spider to obtain a fairly accurate angular localization of the prey, for different prey and orb web characteristics
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Inverse load identification in vibrating nanoplates
Get PDFIn this paper, we consider the uniqueness issue for the inverse problem of load identification in a nanoplate by dynamic measurements. Working in the framework of the strain gradient linear elasticity theory, we first deduce a Kirchhoff-Love nanoplate model, and we analyze the well-posedness of the equilibrium problem, clarifying the correct Neumann conditions on curved portions of the boundary. Our uniqueness result states that, given a transverse dynamic load (Formula presented.), where (Formula presented.) and (Formula presented.) are known time-dependent functions, if the transverse displacement of the nanoplate is known in an open subset of its domain for any interval of time, then the spatial components (Formula presented.) can be determined uniquely from the data. The proof is based on the spherical means method. The uniqueness result suggests a reconstruction technique to approximate the loads, as confirmed by a series of numerical simulations performed on a rectangular clamped nanoplate
Variations on the Author
Get PDF“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
Resonator-based detection in nanorods
Get PDFIn this paper the axial vibrational behaviour of nanorods with an
attached point-mass is studied, using the modified strain energy
theory. The natural frequencies of the nanorod with the
concentrated mass are obtained for different boundary conditions.
The effects of the concentrated mass intensity, mass location, as
well as the value of scale parameters have been analysed. For the
case of small intensity of the concentrated mass, the natural
frequencies of the nanorod can be estimated using a first order
perturbative solution. These approximate results are compared with
those corresponding to the exact solution. For this case, from
the properties of the eigenvalue perturbative theory, the
identification of single point mass in uniform nanorods (mass
intensity and position) is addressed. The results obtained
encourage the use of axial vibrations of nanorods as a very
precise sensing technique
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dynamic identification of pretensile forces in a spider orb-web
Get PDFIn this paper we propose a constructive procedure to determine the radial pretension in an axially-symmetric orb-web, on the basis of one eigenfrequency and its corresponding vibration mode. The method can be applied both to axisymmetric modes, corresponding to the solution of a regular Sturm–Liouville problem, and to non-axisymmetric modes, corresponding to the solution of a singular Sturm–Liouville problem. In the absence of measurement errors of the eigenfunction, the identification of the pretension field is almost perfect. On the contrary, if the measurement presents some noise, then identification is imprecise. In this case, a regularization technique applied to the measurement of the eigenfunction, or to its derivative, is proposed, as well as a filtering process, which significantly improves the reconstruction of the pretension field. The fundamental mode of vibration, sampled with a suitable number of points, is the one that provides the lowest identification error
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