1,721,044 research outputs found
A Virtual Element Method coupled with a Boundary Integral Non Reflecting condition for 2D exterior Helmholtz problems
Full text linkWe present a new numerical approach to solve 2D exterior Helmholtz problems defined in unbounded domains. This consists in reducing the infinite region to a finite computational one Omega, by the introduction of an artificial boundary B, and by applying in Omega a Virtual Element Method (VEM). The latter is coupled with a Boundary Integral Non Reflecting Condition defined on B (in short BI-NRBC), discretized by a standard collocation Boundary Element Method (BEM). We show that, by choosing the same approximation order of the VEM and of the BI-NRBC discretization spaces, the corresponding method allows to obtain the optimal order of convergence. We test the efficiency and accuracy of the proposed approach on various numerical examples, arising both from literature and real life application problems. (C) 2021 Elsevier Ltd. All rights reserved
The recovery of the buhayra of the Favara in the Conca d'oro of Palermo and the vegetation in the area of Zeus's temple in the Valley of the Temples in Agrigento
No full textDistribution of the genus Gagea (Liliaceae) in Sicily
No full textAn updated geographical distribution of the genus Gagea in Sicily with a grid map for each taxon is given. This study is based on literature, herbarium and field investigations. The examined species are G. bohemica (Zauschn.) Schult. & Schult. f., G. chrysantha Schult. & Schult.
f. sensu stricto, G. dubia A. Terracc., G. foliosa (C. Presl) Schult. & Schult. f., G. fragifera (Vill.) E. Bayer & G. L.pez Gonz.lez, G. granatelli (Parl.) Parl., G. lacaitae A. Terracc., G. lojaconoi Peruzzi, G. sicula Lojac., G. trinervia (Viv.) Greuter. The occurrence in Sicily of the phytogeographically interesting G. mauritanica Durieu is here confirmed in three localities. Besides, the actual presence in Sicily of historically occurring G. lutea (L.) Ker Gawl., G. pratensis (Pers.) Dumort. and G. villosa (M. Bieb.) Sweet is not confirmed. Finally, an analytical key for the identification of the studied species is presented
Two FEM-BEM methods for the numerical solution of 2D transient elastodynamics problems in unbounded domains
Full text linkWe consider wave propagation problems in 2D unbounded isotropic homogeneous elastic media, with rigid boundary conditions. For their solution, we propose and compare two alternative numerical approaches, both obtained by coupling the differential equation with the associated space-time boundary integral equation. The latter is defined on an artificial boundary, chosen to surround the (bounded) exterior computational domain of interest. The integral equation defines a boundary condition which is non-reflecting for incoming and also for outgoing waves. In both approaches, the differential equations are discretized by applying a finite element method combined with the Crank Nicolson time marching scheme, while the discretization of the integral equation is obtained by coupling a time convolution quadrature with a space collocation boundary element method. The construction of the two approaches is described and discussed. Some numerical tests are also presented
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
Variations 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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Long-term follow-up of adult patient with neurofibromatosis type 1 with retinal astrocytic hamartoma using spectral domain optical coherence tomography: a review of the literature and a report of a case
No full textBackground: Retinal astrocytic hamartoma (RAH) is a tumor that can be sporadic or in the context of tuberous sclerosis complex (TSC) and has been reported to be associated with neurofibromatosis type 1 (NF1) in a few cases. Patient and methods: A 65-year-old male patient with NF1 was referred for ophthalmological evaluation. Comprehensive examination, near-infrared reflectance (NIR), spectral-domain optical coherence tomography (SDOCT), fluorescein angiography (FFA), and indocyanine green angiography (ICGA) were carried out. The follow-up of the patient was at 4 and 7 years. Results: Best-corrected visual acuity (BCVA) was 20/20 in both eyes. Anterior segment examination revealed bilateral Lisch nodules. Fundus examination was unremarkable but at NIR and SDOCT the patient presented choroidal hamartoma, microvascular retinal alterations, and enlarged choroidal vessels in both eyes. NIR also revealed an unusual area of peripapillary hyporeflectivity in the right eye. On SDOCT, this corresponded to an elevated peripapillary mass characterized by intralesional optically empty cavities in the retinal nerve fiber layer (RNFL) and ganglion cell layer-inner plexiform layer (GCL-IPL), diagnosed as a RAH. Four years later, BCVA was 20/25 with a retinal schisis departing from the lesion to the macula. At 7 years, BCVA was stable at 20/25, the lesion was smaller, and there was a slight reduction of the schisis. Conclusion: RAH is a rare finding in NF1 and the translucent type has not been previously reported. RAH in NF1 has a peripapillary location and demonstrates clinically unpredictable behavior; thus, close monitoring with multimodal imaging is advisable
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