88,533 research outputs found
Classification of (1,2)-Grassmann secant defective threefolds
No full textWe classify all smooth threefolds X in P^N , for which the Grassmann secant variety G(1;2) (i.e. the closure of the set of lines contained in the span of 3 independent points of X) has not the expected dimension
A tropical interpretation of m-dissimilarity maps
No full textLet T be a weighted tree with n numbered leaves and let D = (D (i, j))i, j be its distance matrix, so D (i, j) is the distance between the leaves i and j. If m is an integer satisfying 2 ≤ m ≤ n, we prove a tropical formula to compute the m-dissimilarity map of T (i.e. the weights of the subtrees of T with m leaves), given D. For m = 3, we present a tropical description of the set of m-dissimilarity maps of trees. For m = 4, a partial result is given
Boron nitride housing cools transistors
No full textBoron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted
High-order quasi-curl conforming functions for multiplicative Calderón preconditioning of the EFIE
No full textMethod of moments (MoM)-based electric field integral equation (EFIE) solvers are widely used for analyzing time-harmonic electromagnetic scattering from perfect electrically conducting (PEC) surfaces. In the last decade, MoM-based EFIE solvers using high-order basis functions have been shown to be more accurate as well as CPU and memory efficient than their zeroth-order predecessors leveraging Rao-Wilton-Glisson (RWG) functions. Due to the spectral properties of the EFIE operator, and their effects on the MoM interaction matrices, the use of Calderon identities for preconditioning the EFIE has been studied extensively. In this context, Buffa-Christiansen (BC) basis functions recently have been shown to permit a robust discretization of the Calderon preconditioned EFIE. Unfortunately, the BC basis functions are zeroth-order in nature, and only can be used in conjunction with RWG basis functions. This limitation imposes a severe constraint on the accuracy and efficiency of present Calderon preconditioned EFIE solvers. In this paper, a new set of basis functions is presented, that extends the qualities of the (zeroth-order) BC functions to high-order
Nullspaces of MFIE and Calderon Preconditioned EFIE Operators Applied to Toroidal Surfaces
No full textMagnetic field integral equation (MFIE) and Calderon preconditioned electric field integral equation (EFIE) operators applied to toroidal surfaces have nontrivial nullspaces in the static limit. The nature of these nullspaces is elucidated and a technique for generating a basis for them presented. In addition, the effects of these nullspaces on the numerical solution of both frequency and time-domain MFIE and Calderon preconditioned EFIEs are investigated. The theoretical analysis is accompanied by corroborating numerical examples that show how these operators' nullspaces affect real-world problems
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
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