22,981 research outputs found
Cryptanalyzing a discrete-time chaos synchronization secure communication system
This paper describes the security weakness of a recently proposed secure
communication method based on discrete-time chaos synchronization. We show that
the security is compromised even without precise knowledge of the chaotic
system used. We also make many suggestions to improve its security in future
versions.Comment: 11 pages, 3 figures, latex forma
The weight of matter
Einstein's traceless 1919 gravitational theory is analyzed from a variational
viewpoint. It is shown to be equivalent to a transverse (invariant only under
diffeomorphisms that preserve the Lebesgue measure) theory, with an additional
Weyl symmetry, in which the gauge is partially fixed so that the metric becomes
unimodular. In spite of the fact that this symmetry forbids direct coupling of
the potential energy with the gravitational sector, the equivalence principle
is recovered in the unimodular gauge owing to Bianchi's identities.Comment: LaTeX, 11 page
Isoperimetric inequalities in Riemann surfaces of infinite type
75 pages, 1 figure.-- MSC2000 code: 30F45.MR#: MR1715412 (2000j:30075)Zbl#: Zbl 0935.30028Research partially supported by a grant from Dirección General de Enseñanza Superior (Ministerio de Educación y Ciencia), Spain.Publicad
Energy performance forecasting of residential buildings using fuzzy approaches
The energy consumption used for domestic purposes in Europe is, to a considerable extent, due to heating and cooling. This energy is produced mostly by burning fossil fuels, which has a high negative environmental impact. The characteristics of a building are an important factor to determine the necessities of heating and cooling loads. Therefore, the study of the relevant characteristics of the buildings, regarding the heating and cooling needed to maintain comfortable indoor air conditions, could be very useful in order to design and construct energy-efficient buildings. In previous studies, different machine-learning approaches have been used to predict heating and cooling loads from the set of variables: relative compactness, surface area, wall area, roof area, overall height, orientation, glazing area and glazing area distribution. However, none of these methods are based on fuzzy logic. In this research, we study two fuzzy logic approaches, i.e., fuzzy inductive reasoning (FIR) and adaptive neuro fuzzy inference system (ANFIS), to deal with the same problem. Fuzzy approaches obtain very good results, outperforming all the methods described in previous studies except one. In this work, we also study the feature selection process of FIR methodology as a pre-processing tool to select the more relevant variables before the use of any predictive modelling methodology. It is proven that FIR feature selection provides interesting insights into the main building variables causally related to heating and cooling loads. This allows better decision making and design strategies, since accurate cooling and heating load estimations and correct identification of parameters that affect building energy demands are of high importance to optimize building designs and equipment specifications.Peer ReviewedPostprint (published version
Direct test of time reversal invariance violation in B mesons
In this letter we reinterpret and reanalyze the available data of the B meson
factories showing the existence of direct experimental evidence of time
reversal invariance violation in B mesons. This reinterpretation consists of
using the available observables to define a new observable which, in a model
independent way and without assuming CPT invariance, compares a transition
between a and a here-defined -state, with its time reversed
transition. The observable then offers a direct way to probe time reversal
invariance and it is therefore independent of any conclusion obtained from
current experimental information on CP violation and CPT invariance. As far as
the authors are concerned, this is the first direct evidence of time reversal
invariance violation in B mesons and also the first one obtained from decaying
particles whose mean life time difference is negligible.Comment: 9 pages, no figures. Refined version matching published article in
Modern Physics Letters
Breaking projective chaos synchronization secure communication using filtering and generalized synchronization
This paper describes the security weaknesses of a recently proposed secure
communication method based on chaotic masking using projective synchronization
of two chaotic systems. We show that the system is insecure and how to break it
in two different ways, by high-pass filtering and by generalized
synchronization.Comment: 14 pages, 6 figures, latex forma
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