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

On the determination of constitutive parametersin a hyperelastic model for a soft tissue

The aim of this paper is to study a model of hyperelastic materials and itsapplications into soft tissue mechanics. In particular, we first determine an unbounded domain of the constitutive parameters of the model making our smoothstrain energy function to be polyconvex and hence satisfying the Legendre–Hadamard condition. Thus, physically reasonable material behaviour are described by our model with these parameters and a plently of tissues can betreated. Furthermore, we localize bounded subsets of constitutive parameters in fixed physical and very general bounds and then introduce a family of descrete stress–strain curves. Whence, various classes of tissues are characterized. Ourgeneral approach is based on a detailed analytical study of the first Piola–Kirchhoff stress tensor through its dependence on the invariants and on the constitutive parameters. The uniqueness of parameters for one tissue is discussed by introducing the notion of manifold of constitutive parameters, whichis locally represented by possibly different physical quantities. The advantage of our study is that we show a possible way to improve of the usual approachesshown in the literature which are mainly based on the minimization of a costfunction as the difference between experimental and model results

S(P)EEDKITS & smart packaging. Nuove applicazioni tessili per ridefinire la risposta alle emergenze

Il saggio traccia una visione d'insieme di S(P)EEDKITS, un progetto di ricerca co-finanziato dall'Unione Europea nell'ambito del Programma Quadro FP7 e, in particolare, si concentra sulle attività in corso da parte del Politecnico di Milano (POLIMI) sui due diversi fronti del Design Industriale e della Tecnologia dell'architettura. L'ambito della progettazione dei nuovi kit di pronto intervento e ricostruzione in situazioni di disastro delinea una nuova frontiera per la Tecnologia dell'architettura, che si trova a coniugare la tradizionale vocazione della progettazione di componenti con le ricerche innovative sui tessili tecnici e sulle costruzioni leggere

The Universe as a topological defect

Four-dimensional Einstein's General Relativity is shown to arise from a gauge theory for the conformal group, SO(4,2). The theory is constructed from a topological dimensional reduction of the six-dimensional Euler density integrated over a manifold with a four-dimensional topological defect. The resulting action is a four-dimensional theory defined by a gauged Wess-Zumino-Witten term. An ansatz is found which reduces the full set of field equations to those of Einstein's General Relativity. When the same ansatz is replaced in the action, the gauged WZW term reduces to the Einstein-Hilbert action. Furthermore, the unique coupling constant in the action can be shown to take integer values if the fields are allowed to be analytically continued to complex values.Comment: 18 pages, LaTex, 4 figures. Title of the published version changed to "Universe as a Topological defect" by the journa

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

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

Analysis of Deterioration in a Plasma Focus Device

Indexación: Scopus.The Plasma Focus (PF) is a kind of dense transient plasmas in with high-pulsed voltage. To produce devices for eld application it is necessary to obtain PF equipment able to operate for a long period of time. Thus, a reliability analysis is indispensable. In this work a reliability analysis program for plasma focus devices is presented. The program considers a criticality analysis using Failure Modes and Effects Criticality Analysis (FMECA) to identify the most important failure modes of the system. Said failure modes are studied operating the Plasma Focus for many cycles, obtaining from them the characteristic curves of V(t) and İ(t). Feature Extraction (FE) techniques are applied to obtain a list of parameters that correlate to the degrading process. Furthermore, Machine Learning tools are used to learn from the obtained data, linking the changes in these parameters during its life cycle to the decay of the system in hope for future implementation of a predictive maintenance system and a reference for data analysis and prediction in PFs. The study was applied to a portable plasma focus device operated at 2 joules of stored energy. © Published under licence by IOP Publishing Ltd.The work is supported by IAEA CRP contract 20370 and by grant ACT-1115, CONICYT, Chile.https://iopscience.iop.org/article/10.1088/1742-6596/1043/1/01204

de Sitter black hole with a conformally coupled scalar field in four dimensions

A four-dimensional black hole solution of the Einstein equations with a positive cosmological constant, coupled to a conformal scalar field, is given. There is a curvature singularity at the origin, and scalar field diverges inside the event horizon. The electrically charged solution, which has a fixed charge-to-mass ratio is also found. The quartic self-interacting coupling becomes bounded in terms of Newton's and the cosmological constants.Comment: 5 pages, no figures, CECS style, energy conditions are discussed and some references were added. To appear in Phys. Rev.

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