Showing papers by "Polytechnic University of Catalonia published in 1992"
TL;DR: In this article, a new definition of a probabilistic normed space is given, which is based on a characterization of normed spaces by means of a betweenness relation, including the earlier definition of A. N. Serstnev as a special case.
Abstract: In this paper we give a new definition of a probabilistic normed space. This definition, which is based on a characterization of normed spaces by means of a betweenness relation, includes the earlier definition of A. N. Serstnev as a special case and leads naturally to the definition of the principal class of probabilistic normed spaces, the Menger spaces.
163 citations
TL;DR: In this article, the authors considered a system x = (A + eQ(t))x in Rd is considered, where A is a constant matrix and Q a quasiperiodic analytic matrix with r basic frequencies.
161 citations
TL;DR: A versatile point process is proposed as model for a large class of variable bit rate sources and their superpositions and its use leads to computationally tractable and accurate solutions for various performance measures of the related statistical multiplexer.
145 citations
TL;DR: In this paper, an adaptive impulse correlated filter (AICF) was proposed to estimate the deterministic component of the signal and remove the noise uncorrelated with the stimulus even if this noise is colored, as in the case of evoked potentials.
Abstract: An adaptive impulse correlated filter (AICF) for event-related signals that are time-locked to a stimulus is presented. This filter estimates the deterministic component of the signal and removes the noise uncorrelated with the stimulus, even if this noise is colored, as in the case of evoked potentials. The filter needs two inputs: the signal (primary input) and an impulse correlated with the deterministic component (reference input). The LMS algorithm is used to adjust the weights in the adaptive process. It is shown that the AICF is equivalent to exponentially weighted averaging (FWA) when using the LMS algorithm. A quantitative analysis of the signal-to-noise ratio improvement, convergence, and misadjustment error is presented. A comparison of the AICF with ensemble averaging (EA) and moving window averaging (MWA) techniques is also presented. The adaptive filter is applied to real high-resolution ECG signals and time-varying somatosensory evoked potentials. >
144 citations
TL;DR: In this paper, the functions of the Peclet number that appear in the intrinsic time of the streamline upwind/Petrov-Galerkin (SUPG) formulation are analyzed for quadratic elements.
Abstract: In this paper the functions of the Peclet number that appear in the intrinsic time of the streamline upwind/Petrov-Galerkin (SUPG) formulation are analyzed for quadratic elements. Some related issues such as the computation of the characteristic element length and the introduction of source terms in the one-dimensional model problem are also addressed.
111 citations
TL;DR: In this article, stable spatial patterns are shown to appear in a 2D coupled map lattice (CML) approach, which is constructed from a two-dimensional nonlinear map based on the dynamics of interacting populations.
100 citations
11 Oct 1992
TL;DR: The authors present a cascade adaptive filter that can remove baseline wander in real time without needing to calculate the isoelectric levels, while preserving the low-frequency ECG clinical information.
Abstract: Baseline wandering is a classical problem in electrocardiogram (ECG) records that generally produces artifactual data when measuring ECG parameters. The authors present a cascade adaptive filter for removing the baseline wander and preserving the low-frequency components of the ECG. This cascade adaptive filter works in two stages. The first stage is an adaptive notch filter at zero frequency. The second stage is an adaptive impulse correlated filter that, using a QRS detector, estimates the ECG signal correlated with the QRS occurrence. In this way, all the signal components correlated with the QRS complex are preserved. The authors analyze the frequency response of the filter, showing that the filter can be seen as a comb filter without the DC lobe. The method was applied to ECG signals from the MIT-BIH database and its performance was compared with the cubic spline approach. The method can remove baseline wander in real time without needing to calculate the isoelectric levels, while preserving the low-frequency ECG clinical information. >
99 citations
TL;DR: The formulation of the microplane model has been modified to rationalise the structure of the basic hypotheses, simplify the equations and generalise the concepts whenever possible, resulting in a new formulation which gives a much better numerical efficiency for code implementation while keeping the same desirable features and accuracy in experimental data fitting.
98 citations
TL;DR: In finite labelled transition systems the problems of deciding strong bisimilarity, observation equivalence and observation congruence areP-complete under many—oneNC-reducibility, so the design of anNC algorithm to solve any of these problems will require an algorithmic breakthrough, which is exceedingly hard to achieve.
Abstract: In finite labelled transition systems the problems of deciding strong bisimilarity, observation equivalence and observation congruence areP-complete under many--oneNC-reducibility. As a consequence, algorithms for automated analysis of finite state systems based on bisimulation seem to be inherently sequential in the following sense: the design of anNC algorithm to solve any of these problems will require an algorithmic breakthrough, which is exceedingly hard to achieve.
91 citations
TL;DR: It is shown that various decompositions can be achieved using a class of nonlinear filters known as rank order based filters, which includes, as a special case, classical rank order filters and a large number of morphological filters with flat structuring element.
77 citations
TL;DR: The spatiotemporal behaviour of a two-species competition coupled map lattice is explored and the coexistence of the two competitors is demonstrated although they have high interspecific competition coefficients.
26 Feb 1992
TL;DR: Equality constrained equations and clauses are defined and used to prove the completeness of what is called basic superposition: a restricted form of superposition in which only the subterms not created in previous inferences is superposed upon.
Abstract: We define equality constrained equations and clauses and use them to prove the completeness of what we have called basic superposition: a restricted form of superposition in which only the subterms not created in previous inferences is superposed upon. We first apply our results to the equational case and define an unfailing Knuth-Bendix completion procedure that uses basic superposition as inference rule. Second, we extend the techniques to completion of full first-order clauses with equality. Moreover, we prove the refutational completeness of a new simple inference system.
TL;DR: It is shown that the graph isomorphism problem, is low for PP and for C=P, i.e., it does not provide a PP or C= P computation with any additional power when used as an oracle.
Abstract: We show that the graph isomorphism problem, is low for PP and for C=P, i.e., it does not provide a PP or C=P computation with any additional power when used as an oracle. Furthermore, we show that graph isomorphism belongs to the class LWPP (see Fenner, Fortnow, Kurtz [12]). A similar result holds for the (apparently more difficult) problem Group Factorization. The problem of determining whether a given graph has a nontrivial automorphism, Graph Automorphism, is shown to be in SPP, and is therefore low for PP, C=P, and Mod
k
P,k≥2.
15 Jun 1992
TL;DR: In this work, clauses with ordering constraints are used to reduce the search space in ordered inference systems for clauses with or without equality, such as ordered resolution or superposition.
Abstract: We use clauses with ordering constraints to reduce the search space in ordered inference systems for clauses with or without equality, such as ordered resolution or superposition. In our completion procedure for ordering constrained clauses redundant inferences can be ignored and redundant clauses can be deleted without loosing refutational completeness. Two new results needed for fast ordering constraint solving and incrementality of the set of function symbols are given. We discuss the use of our methods for reasoning about infinite sets of clauses defined by a finite number of ordering constrained ones.
TL;DR: In this paper, the effect of temperature and concentration on the viscosity of clarified and depectinated peach juice is examined. And an equation describing the combined effect of the temperature and the concentration on their viscosities is given.
01 Apr 1992
TL;DR: Address transformation schemes, such as skewing and linear transformations, have been proposed to achieve conflict-free vector access for some strides in vector processors with multi-module memories and it is shown that the number of strides is even larger for the latter case.
Abstract: Address transformation schemes, such as skewing and linear transformations, have been proposed to achieve conflict-free vector access for some strides in vector processors with multi-module memories. In this paper, we extend these schemes to achieve this conflict-free access for a larger number of strides. The basic idea is to perform an out-of-order access to vectors of fixed length, equal to that of the vector registers of the processor. Both matched and unmatched memories are considered: we show that the number of strides is even larger for the latter case. The hardware for address calculations and access control is described and shown to be of similar complexity as that required for access in order.
TL;DR: In this article, a spatially extended model of density-dependent discrete maps is presented, based on the so-called coupled map lattice formalism and applied to two well-known discrete models of population biology.
TL;DR: A new design of a BIC sensor for current testing static CMOS circuits is proposed, based on a lateral BJT device which is easy to incorporate in any standard CMOS process.
Abstract: A new design of a BIC sensor for current testing static CMOS circuits is proposed. It is based on a lateral BJT device which is easy to incorporate in any standard CMOS process. The design diverts a fraction of the iDD current from the cell under test and a resistive component generates a voltage proportional to iDD Additional features are the possibility of continuous measure of iDD and increased speed of this sensor compared with sensors based on the current integration principle. The design does not have substrate currents due to the parasitic vertical BJTs. Experimental work on the sensor is reported.
TL;DR: In this article, the distribution of impregnated resins containing di-(2,2,4-trimethylpentyl)phosphinic acid (Cyanex 272) between the aqueous and resin phase was studied as a function of pH and loading of the organophosphorous extractant on the resin.
TL;DR: In this paper, three spectral approximations based on expansions by functions defined on the [0, ∞] interval are presented: a tau type method using Laguerre functions, a collocation method using laguero polynomials and a rational Chebyshev function.
Abstract: This paper deals with three spectral approximations based on expansions by functions defined on the [0, ∞) interval: a tau type method using Laguerre functions, a collocation method using Laguerre polynomials and a collocation method using rational Chebyshev functions. We apply them to several boundary value problems, comparing their applicability, their efficiency and their accuracy. The numerical examples considered include the boundary value problem describing the edge waves on a longshore shear flow and the ‘Charney’ stability problem of meteorology. We also consider some Laguerre type equations and the computation of the imaginary Bessel function K 1
01 Jan 1992
TL;DR: Carrrasco et al. as mentioned in this paper presented a new importance sampling scheme called failure biasing for the efficient simulation of Markovian models of repairable fault-tolerant systems.
Abstract: This paper presents a new importance sampling scheme called failure biasing for the efficient simulation of Markovian models of repairable fault-tolerant systems. The new scheme enriches the failure biasing scheme previously proposed by exploiting the concept of failure distance. This results in a much more efficient simulation with speedups over failure biasing of orders of magnitude in typical cases. The paper also discusses the efficient implementation of the new importance sampling scheme and presents a practical method for the optimization of the biasing parameters. NOTE FROM THE AUTHOR: The method proposed in the paper for the optimization of the biasing parameters introduces correlation, making the estimates invalid. A more recent paper, J. A. Carrasco, “Failure Transition Distance-Based Importance Sampling Schemes for the Simulation of Repairable Fault-Tolerant Computer Systems, IEEE Trans. on Reliability, vol. 55, no. 2, June 2006, pp. 207–236, minor corrections in IEEE Trans. on Reliability, vol. 56, no. 2, June 2007. p. 360, presents two slightly modified biasing schemes which can be proved to be more efficient for balanced systems than failure and balanced failure biasing, and describe a correct and efficient method for the optimization of the biasing parameters. The author apologizes for the error in this paper.
TL;DR: This work treats two different problems in the recognition of polychromatic images: (1) recognition of an object with a given shape and color combination; (2) recognitionof an object regardless of its color combination.
Abstract: We treat two different problems in the recognition of polychromatic images: (1) recognition of an object with a given shape and color combination; (2) recognition of an object regardless of its color combination. To solve each problem we propose different strategies. The number of filters and the objects to which the filters are matched vary with the strategy. Phase-only filters have been used to achieve recognition of both problems. Computer results are given for different targets and scenes to show the behavior of the proposed strategies.
TL;DR: A generalized coupled map lattice (CML) model of ecosystem dynamics is presented, which considers the spatiotemporal behavior of a prey-predator map, a model of host-parasitoid interactions, and two-species competition.
Abstract: A generalized coupled map lattice (CML) model of ecosystem dynamics is presented. We consider the spatiotemporal behavior of a prey-predator map, a model of host-parasitoid interactions, and two-species competition. The latter model can show phase separation of domains (Turing-like structures) even when chaos is present. We also use this CML model to explore the time evolution and structural properties of ecological networks built with a set of N competing species. The May-Wigner criterion is applied as a measure of stability, and some regularities in the stable networks observed are discussed.
TL;DR: An algorithm is developed to simulate a Gaussian stochastic process that is non-δ-correlated in both space and time coordinates and obeys a linear reaction-diffusion Langevin equation with Gaussian white noise.
Abstract: We develop an algorithm to simulate a Gaussian stochastic process that is non-\ensuremath{\delta}-correlated in both space and time coordinates. The colored noise obeys a linear reaction-diffusion Langevin equation with Gaussian white noise. This equation is exactly simulated in a discrete Fourier space.
TL;DR: In this article, a theoretical model for describing the reduction of a metal ion in the presence of a macromolecular ligand, including both the ligand adsorption and the induced adorption of the metal ion, was developed.
TL;DR: Using the Darmois junction conditions, the necessary and sufficient conditions for the matching of a general spherically symmetric metric to a Vaidya radiating solution are given.
Abstract: Using the Darmois junction conditions, we give the necessary and sufficient conditions for the matching of a general spherically symmetric metric to a Vaidya radiating solution. We present also these conditions in terms of the physical quantities of the corresponding energy-momentum tensors. The physical interpretation of the results and their possible applications are studied, and we also perform a detailed analysis of previous work on the subject by other authors.
TL;DR: Steregular polyamides containing two chiral backbone carbons in the repeating unit were prepared by polycondensation of bis(pentachlorophenyl) 2,3-O-methylene-L-tartrate with 1,9 and 1,12-alcanediamines activated as N,N′-bis(trimethylsilyl) derivatives as mentioned in this paper.
Abstract: Stereoregular polyamides containing two chiral backbone carbons in the repeating unit were prepared by polycondensation of bis(pentachlorophenyl) 2,3-O-methylene-L-tartrate with 1,9 and 1,12-alcanediamines activated as N,N′-bis(trimethylsilyl) derivatives. The polymers were characterized by elemental analysis, IR, and 1H-NMR spectroscopy, and differential scanning calorimetry. Both viscosimetry and GPC were used to estimate the molecular weights which ranged between 6000 and 44000. These polytartaramides were readily soluble in chloroform, displayed moderate optical activity in solution, and formed highly crystalline films.
TL;DR: In this article, a control design for absolute motion reduction of base-isolated structures subjected to earthquake excitation is presented, where predictive control theory is used for the control design.
Abstract: A control design for absolute motion reduction of base-isolated structures subjected to earthquake excitation is presented herein. The control objective is to provide a vibration-free environment for sensitive equipment protection. Predictive control theory is used for the control design. This theory allows the designer to handle time delays generated by the dynamics of actuators. The study reported herein demonstrates, by numerical simulation, the efficacy of this controller in reducing acceleration response in the superstructure in the presence of delays. Stability analysis, frequency response and response to ground motion excitation are developed to assess the characteristics of the controller.
TL;DR: A criterion for ensuring that a given design for conceptual model discrimination will indeed lead to data with sufficient discriminating capacity is proposed, based on finding the minimum distance between simulations of the experiment obtained with the alternative models.
TL;DR: In this article, the transition form factors for the {ital P}{gamma, ε, ϵ, and ε-prime vertices were compared with different models, such as vector-meson dominance, constituent-quark loops, and chiral perturbation theory.
Abstract: Recent measurements of the transition form factors for the {ital P}{gamma}{gamma}{sup *} vertices, with {ital P}={pi}{sup 0}, {eta}, and {eta}{prime}, are compared with different models. These include vector-meson dominance, constituent-quark loops, the QCD-inspired interpolation by Brodsky-Lepage, and chiral perturbation theory. General agreement is observed and differences--due to SU(3) breaking--are stressed and discussed.