Is ruling out the possibility that one is dreaming a requirement for a knowledge claim? In “Philosophical Scepticism and Everyday Life” (1984), Barry Stroud defends that it is. In “Others Minds” (1970), John Austin says it is not. In his defense, Stroud appeals to a conception of objectivity deeply rooted in us and with which our concept of knowledge is intertwined. Austin appeals to a detailed account of our scientific and everyday practices of knowledge attribution. Stroud responds that what Austin says about those practices is correct in relation to the appropriateness of making knowledge claims, but that the skeptic is interested in the truth of those claims. In this paper, we argue that Stroud’s defense of the alleged requirement smuggles in a commitment to a kind of internalism, which asserts that the perceptual justification available to us can be characterized independently of the circumstances in which we find ourselves. In our reading of Austin, especially of Sense & Sensibilia, he rejects that kind of internalism by an implicit commitment to what is called today a “disjunctive” view of perception. Austin says that objectivity is an aspect of knowledge, and his disjunctivism is part of an explanation of why the alleged requirement is not necessary for a knowledge claim. Since both Stroud and Austin are committed to the objectivity of knowledge, Stroud may ask which view of perceptual knowledge is correct, whether the internalist or the disjunctive. We argue that by paying closer attention to what Austin says about our practices of knowledge attribution, one can see more clearly that it is grounded not only on a conception of objectivity, but also on a conception of ourselves as information agents, a conception that is as deeply rooted as that of the objectivity of knowledge. This gives us moral and practical reasons to favor the disjunctive view of perception.

Electrostatic harmonic Langmuir waves are virtual modes excited in weakly turbulent plasmas, first observed in early laboratory beam-plasma experiments as well as in rocket-borne active experiments in space. However, their unequivocal presence was confirmed through computer simulated experiments and subsequently theoretically explained. The peculiarity of harmonic Langmuir waves is that while their existence requires nonlinear response, their excitation mechanism and subsequent early time evolution are governed by essentially linear process. One of the unresolved theoretical issues regards the role of nonlinear wave-particle interaction process over longer evolution time period. Another outstanding issue is that existing theories for these modes are limited to one-dimensional space. The present paper carries out two dimensional theoretical analysis of fundamental and (first) harmonic Langmuir waves for the first time. The result shows that harmonic Langmuir wave is essentially governed by (quasi)linear process and that nonlinear wave-particle interaction plays no significant role in the time evolution of the wave spectrum. The numerical solutions of the two-dimensional wave spectra for fundamental and harmonic Langmuir waves are also found to be consistent with those obtained by direct particle-in-cell simulation method reported in the literature.

Este artigo apresenta um comentário aos versos 20-21 da chamada “Elegia do Selo” de Teógnis (os versos 19 a 26 da Teognideia), visando mostrar como a Teognideia alude a expedientes de uma poética própria às performances no simpósio grego arcaico.

Abstract Continuous process industries usually have hundreds to thousands of control loops, most of which are coupled, i.e. one control loop affects the behavior of another control loop. In order to properly design the controllers and reduce the interactions between loops it is necessary to consider the multivariable structure of the process. Usually {MIMO} (multiple-input, multiple-output) controllers are designed using {MIMO} models of the process, but obtaining these models is a task very demanding and time consuming. Virtual Reference Feedback Tuning ({VRFT}) is a data-driven technique to design controllers which do not use a model of the process; all the needed information is collected from input/output data from an experiment. The method is well established for {SISO} (single-input, single-output) systems and there are some extensions to {MIMO} process which assume that all the outputs should have the same closed-loop performance. In this paper we develop a complete framework to {MIMO} {VRFT} which provides unbiased estimates to the optimal {MIMO} controller (when it is possible) even when the closed-loop performances are distinct to each loop. When it is not possible to obtain the optimal controller because the controller class is too restrictive (for example {PID} controllers) then we propose the use of a filter to reduce the bias on the estimates. Also, when the data is corrupted by noise, the use of instrumental variables to eliminate the bias on the estimate should be considered. The article presents simulation examples and a practical experiment on a tree tank system where the goal is to control the level of two tanks.

O avanço na forma de coleta de dados populacionais a partir da geolocalização dos domicílios e a disseminação de dados em escalas cada vez maiores possibilitam a realização de análises espaciais e demográficas mais detalhadas e complexas. Ao mesmo tempo, à medida que aumenta a possibilidade de espacializar dados demográficos percebe-se uma atenção aos desafios da Big Data na demografia e as formas de visualização de dados começam a ganhar destaque. Este artigo visa refletir sobre as potencialidades de distintas formas de representar e de analisar espacialmente o fenômeno da migração/mobilidade com base em grandes volumes dedados, testando duas técnicas de análise e visualização de dados que vem sendo utilizadas em estudos de migração e mobilidade: diagrama de cordas (circos) e redes. Também realiza um levantamento de artigos publicados sobre migração nos últimos anos na Revista Brasileira de Estudos de População buscando analisara forma como as informações sobre os movimentos espaciais foram utilizados, avaliando o modo como as matrizes migratórias foram utilizadas.Argumenta-se que conforme se avança em direção ao Big Data, se avança na resolução espacial e, consequentemente, menos adequadas/eficientes fica a convencional matriz migratória e, até mesmo, os mapas.

O texto busca analisar as primeiras representações literárias da guerra na literatura ocidental. Concentra-se primeiramente na Ilíada de Homero, oferecendo um panorama do sistema de valores que a enforma e enfatizando o forte caráter imagético de suas descrições, que intentam delinear uma visão idealizada da guerra. Em seguida, considera exemplos da lírica grega arcaica, a fim de atestar que, embora situados em outro gênero, os expedientes utilizados na épica para representar a guerra também se encontram na poesia lírica, sobretudo a enargia.

This study examines quaternion Dirac solutions for an infinite square well. The quaternion result does not recover the complex result within a particular limit. This raises the possibility that quaternionic quantum mechanics may not be understood as a correction to complex quantum mechanics, but it may also be a structure that can be used to study phenomena that cannot be described through the framework of complex quantum mechanics.

Using the WKB approximation we analyse the tunnelling of a pulsating string in deformed Minkowski spacetime.