Cables and fire hazards

Besides describing the experiments conducted to develop a nonflammable cable, this article discusses several considerations regarding other hazards which might result from cable fires, particularly the toxicity and opacity of the fumes emitted by the burning cable. In addition, this article examines the effects of using the Oxygen Index as a gauge of quality control during manufacture

Design-driven Uniaxial and Biaxial Tensile Testing of Knitted Fabrics Applied to Construction

Knitted fabrics are rarely subjected to tensile stress tests in the field of architectural construction materials, mostly due to their common use as drapery. However, recent non-standard applications of tensioned knitted textiles to hybrid lightweight constructions call for the assessment of their mechanical behavior. In the light of the absence of specific testing methodologies regarding knitted fabrics in the field of construction, this study aims at investigating customized testing techniques that target design requisites, as well as extending previous groundwork on plain weftknitted textiles to tuck-loop knit structures. Fabrics with a piquet Lacoste loop structure are tested uniaxially and biaxially in order to estimate the feasibility of a relatively large-scale project. The challenging task consists of stretching the limited production width in weft direction to the extended dimensions of the tensile architectural project. Hence the study focuses on elongation limits and especially on the maximum elongation that allows elastic deformation. Extracted empirical data are expressed in the form of stress/strain curves that enable an appropriate understanding of the textiles’ mechanical behavior. This inquiry points out the extent to which knit pattern favors directional elongation in warp as opposed to weft or vice-versa. In addition, it addresses the mechanical performance of knitted textiles by means of a strategic customization of tensile tests that can make them better at informing the design process and feasibility assessment

Couplings between Chern-Simons gravities and 2p-branes

The interaction between Chern-Simons (CS) theories and localized external sources (2p-branes) is analyzed. This interaction generalizes the minimal coupling between a point charge (0-brane) and a gauge connection. The external currents that define the 2p-branes are covariantly constant (D-2p-1)-forms coupled to (2p-1) CS forms. The general expression for the sources --charged with respect to the corresponding gauge algebra-- is presented, focusing on two special cases: 0-branes and (D-3)-branes. In any dimension, 0-branes are constructed as topological defects produced by a surface deficit of (D-2)-sphere in AdS space, and they are not constant curvature spaces for D>3. They correspond to dimensionally continued black holes with negative mass. On the other hand, in the case of CS (super) gravities, the (D-3)-branes are naked conical singularities (topological defects) obtained by identification of points with a Killing vector. In 2+1 dimensions, extremal spinning branes of this type are BPS states. Stable (D-3)-branes are shown to exist also in higher dimensions, as well. Classical field equations are also discussed and in the presence of sources there is a large number of inequivalent and disconnected sectors in solution space.Comment: 29 pages, no figures; version accepted in PRD; extended introduction and several references added; some sections have been reorganized and several minor corrections mad

Deposits, composition and technological behavior of fluxes for ceramic tiles

The ceramic tile industry is a big consumer of feldspathic rocks and further raw materials able to act as flux during firing. This demand is currently fed with the recourse to a wide range of sources of igneous, sedimentary, metamorphic and metasomatic origin. The main geological features of flux deposits actually exploited by the ceramic industry are reviewed. The chemical and mineralogical composition is described to have a general picture of raw fluxes as well as average data and compositional perimeter for deposits of different origin. Overall beneficiation routes are drawn to trace the compositional path from deposit to commercial flux. The technological behavior in tile-making is shortly overviewed and new experimental data are provided on flux fusibility (by hot-stage microscopy). A chart is proposed to discriminate fluxes according to different fusibility

Black Hole Entropy and the Dimensional Continuation of the Gauss-Bonnet Theorem

The Euclidean black hole has topology $\Re^2 \times {\cal S}^{d-2}$. It is shown that -in Einstein's theory- the deficit angle of a cusp at any point in $\Re^2$ and the area of the ${\cal S}^{d-2}$ are canonical conjugates. The black hole entropy emerges as the Euler class of a small disk centered at the horizon multiplied by the area of the ${\cal S}^{d-2}$ there.These results are obtained through dimensional continuation of the Gauss-Bonnet theorem. The extension to the most general action yielding second order field equations for the metric in any spacetime dimension is given.Comment: 7 pages, RevTe

Effect of waste glass (TV/PC cathodic tube and screen) on technological properties and sintering behaviour of porcelain stoneware tiles

In the present work, the effects of TV and PC cathodic tube and screen glasses additions (5 and 10 wt.%) to a porcelain stoneware body, in replacement of feldspar, were evaluated simulating the tilemaking process. The presence of glass allows to preserve good technological and mechanical properties, complying with the latest requirements of the industrial practice. The sintering pattern of the glass-added bodies, evaluated by hot stage microscopy, is modified according to the different glass amount and typology; in particular, cathodic tube glass when present at 5 wt.% brings about a lowering of the maximum densification temperature and of the activation energy

Conformal couplings of a scalar field to higher curvature terms

We present a simple way of constructing conformal couplings of a scalar field to higher order Euler densities. This is done by constructing a four-rank tensor involving the curvature and derivatives of the field, which transforms covariantly under local Weyl rescalings. The equation of motion for the field, as well as its energy momentum tensor are shown to be of second order. The field equations for the spherically symmetric ansatz are integrated, and for generic non-homogeneous couplings, the solution is given in terms of a polynomial equation, in close analogy with Lovelock theories.Comment: 9 pages, no figures. Based on a talk given by one of the authors at Centro de Estudios Cientificos, Valdivia, Chile, on June 22, 2011. V2: 11 pages, no figures. Typos fixed, appendices and references added. v3: to appear in CQ

A fixed-time second order sliding mode observer for a class of nonlinear systems

This paper presents a second order fixed time sliding mode observer based on an extension of the super-twisting algorithm. This observer can be applied to a class of nonlinear system with a block-wise representation. The block structure provides a straightforward form to the application of the proposed second order sliding mode algorithm, yielding to finite-time convergence with a settling time independent to the system initial conditions. Finally, as numerical simulation example, the case of a linear induction motor is studied, exposing the efficiency and feasibility of the proposal