1,721,108 research outputs found
Shape determination for real curves and surfaces
No full textIn this paper we describe algorithms to find the shape of a real algebraic curve in P2 and the topology of a real algebraic surface in P3. The algorithm runs as follows: choose a point O∈P2 outside the curve C and in general position with respect to C; consider the projection π from the curve to P1 with center 0; determine the critical points and the critical values of π, and the inverse image of the critical values. Investigating the mutual position of these points, we obtain two finite sequences of integers, from which we obtain explicitly the shape of C, as a finite set corresponding to the set of branches of C, and a partial order relation on this set, corresponding to the inclusion between branches. The algorithm for surfaces considers the variation of the shape of the curve in a pencil, to find the number of connected components and their rational homology; this describes completly the topology of the surface. We discuss some results on the explicit computer implementation of the algorithm for curves, which has proved to be rapid and reliable
The Effects of Phacoemulsification and Intraocular Lens Implantation on Anatomical and Functional Parameters in Patients with Primary Angle Closure: A Prospective Study. (An American Ophthalmological Society Thesis)
No full textTo investigate the clinical, anatomical, and patient-reported outcomes of phacoemulsification (PE) with intraocular lens implantation performed to treat primary angle closure (PAC) and primary angle-closure glaucoma (PACG)
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
Heterogeneous lattice metrics and the NTWO cryptosystem
No full textIn citegb-issac we have introduced a new cryptosystem; it was called GB-NTRU, since initially we used Grobner bases to make the computations, but since eventually everything was made through Lagrange interpolation the name was inappropriate, and we name it now NTWO. This cryptosystem, from the public point of view, looks like NTRU, citeNTRU, (except the non secondary detail that multivariate polynomial algebra is used, instead of univariate algebra), but is different in key creation and decryption. As a consequence, while the message attacks are shared with NTRU, the key attacks are different; it is still possible to define a lattice like the Coppersmith-Shamir lattice, citeCS,NTRU, and breaking the private key via a SVP (shortest vector problem) in this lattice, but the metric on this lattice is heterogeneous: in some components the distance is Euclidean, in some other components the distance is Hamming. We study the SVP in this metric, and reduce the approximate solution of this problem to the approximate solution of the same problem in a larger lattice. The increased complexity of this heterogeneous SVP should allow shorter keys, and allow better protection of the message through bigger randomizing polynomials. The decoding of NTWO requires moreover the solution of a CVP (closest vector problem) in a private lattice; this lattice has a special form, being the sum of a constant sublattice qZn and a sublattice of very low dimension; we expect that specialized algorithms might exist for this kind of lattices, that might be better formalized as low dimension subspaces of (Z/q)n with a Lee metric; this is however work in progress, for which we can only provide the study of a few special cases
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
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