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Showing papers by "Instituto Politécnico Nacional published in 1994"


Book
01 Jan 1994
TL;DR: The connection between two level adaptive control and bilinear programming problem and two level hierarchical system of learning automata using a projectional stochastic approximation algorithm is studied.
Abstract: Preface. Contents. Notations. Introduction. Basic notations and definitions. Introduction. Contolled finite system. Control strategies. Dynamic characteristics of controlled finite systems and their structures. Adaptive strategies and learning automata. Classification of problems of adaptive control of finite systems. Reinforcement schemes for average loss function minimization. Introduction. Adaptive control and static systems and linear programming problem. Reinforcement schemes. Properties of reinforcement schemes Behaviour of learning automata for different Reinforcement Schemes. Introduction Reinforcement scheme of Narendra-Shapiro. Reinforcement scheme of Luce and Varshavskii-Verontsova. Bush-Mosteller reinforcement scheme. Projectional stochastic approximation algorithm. Conclusion. Multilevel systems for Automata. Introduction Hierarchical system .The connection between two level adaptive control and bilinear programming problem. Two-level hierarchical system of learning automata using a projectional stochastic approximation algorithm. Two level hierarchical system with transmission of current information to the lower level. Multilevel hierarchical learning system. Conclusion. Multimodal function optimization using learning automata. Introduction. Optimization using single learning automata. Optimization using a two level hierarchical system of learning automata. Conclusion. Application of Learning Automata. Introduction. Practical aspects. Multilevel learning control of a drying furnace. Hierarchical learning control of absorption column. Learning control of an evaporator. Adaptive choice of cyclic code in communications systems. Optimization of multimodal functions ( without constraints). Optimization in presence of constraints. Application of learning automaton to neural network synthesis. Conclusion. Nomenclature. References. Appendix. Index

249 citations


Journal ArticleDOI
TL;DR: Grove and Searle as discussed by the authors determined precisely which smooth closed manifolds admit a positively curved metric with maximal symmetry-rank, which is defined as the rank of the isometry group of a riemannian manifold.

144 citations


Journal ArticleDOI
TL;DR: It is shown that Kerr-lens mode locking of a Ti:sapphire laser, with no intracavity elements except the laser rod and the dispersion-compensating prisms, can be made to be completely self-starting.
Abstract: It is shown that Kerr-lens mode locking of a Ti:sapphire laser, with no intracavity elements except the laser rod and the dispersion-compensating prisms, can be made to be completely self-starting. We achieve this result by carefully designing the resonator to maximize the nonlinear mode variations and dynamic loss modulation.

134 citations


Journal ArticleDOI
TL;DR: In this paper, the conceptual requirements of a management control system based on accounting information for monitoring the environmental performance of an industrial firm (completeness, long term orientation, external orientation, measurability and cost) are described.
Abstract: It is now widely acknowledged that environmental issues will increasingly affect the performance of firms in western countries, both in the short and in the long run. Environmental issues can act on revenues and on costs. They can influence revenues when a firm follows a ‘green strategy’, i.e. it enhances the characteristics of environmental compatibility of its products or it promotes a credible image of a ‘green company’, that employs only clean technologies. They can influence costs as, on the one hand, more limiting environmental standards can result in higher manufacturing and non manufacturing costs and, on the other hand, programmes focused on improving environmental performances can result in less spoils and wastes, hence in lower costs. Hence, environmental performance should be a structured part of the management control system of an industrial firm. Unfortunately, it is not completely clear how accounting information can be structured in order to obtain this result. This paper is aimed at developing a set of information that can be used for a managerial control focused on the environmental performance of an industrial firm. This paper is organized in three main sections. Section I describes the conceptual requirements of a management control system based on accounting information for monitoring the environmental performance of an industrial firm (completeness, long term orientation, external orientation, measurability and cost). Section II analyses different classes of Environmental Performance Indicators (EPI) used in practice. Both accounting measures (prevention costs and investments; operating environmental costs; contingent environmental liabilities) and non financial measures (physical indicators; compliance) are considered. Section III suggests an integrated approach to the design of a management control system focused on environmental issues, where different classes of indicators are used jointly. More specifically, two integrated systems, one mostly based on physical measures and aimed at external communication, the other focused on accounting measures and supporting managerial decision making, are suggested.

121 citations


Journal ArticleDOI
TL;DR: In this paper, an irreversible simplified model for the air standard Otto thermal cycle is proposed, which takes into account the finite-time evolution of the cycle's compression and power strokes and considers global losses lumped in a friction-like term.
Abstract: We propose an irreversible simplified model for the air standard Otto thermal cycle. This model takes into account the finite-time evolution of the cycle's compression and power strokes and it considers global losses lumped in a friction like term. The proposed model permits the maximization of quantities such as the power output and the efficiency in terms of the compression ratio r. The optimum r values obtained compare well with standard r values for real Otto engines. Our model leads to loop-shaped power-versus-efficiency curves as is common to almost all real heat engines.

113 citations


Proceedings ArticleDOI
01 Aug 1994

99 citations


Journal ArticleDOI
TL;DR: Pulses with energies as high as 150 microJ and durations as low as 60 f(s) were generated by a traveling-wave parametric converter pumped by femtosecond pulses of a Ti:sapphire laser with chirped-pulse amplification.
Abstract: Pulses with energies as high as 150 microJ and durations as low as 60 f(s) were generated from 1.1 to 2.6 microm by a traveling-wave parametric converter pumped by femtosecond pulses of a Ti:sapphire laser with chirped-pulse amplification.

99 citations


Journal ArticleDOI
TL;DR: With a suitable resonator configuration, self-starting of the Kerr-lens mode-locking regime has been achieved and an effective resonator design and reliable guidelines for the final experimental optimization are offered.
Abstract: Resonators for Kerr-lens mode-locked lasers are studied with the help of an analytical model, and a new design procedure is presented. The experiments performed with a femtosecond Ti:sapphire laser demonstrate that this model permits an effective resonator design and offers reliable guidelines for the final experimental optimization. With a suitable resonator configuration, self-starting of the Kerr-lens mode-locking regime has been achieved.

93 citations


Journal ArticleDOI
TL;DR: Preliminary results indicated that hypnosis affects heart rate variability, shifting the balance of the sympatho-vagal interaction toward an enhanced parasympathetic activity, concomitant with a reduction of the sympathetic tone.
Abstract: Spectral analysis of beat-to-beat variability in electrocardiography is a simple, noninvasive method to analyze sympatho-vagal interaction. The electrocardiogram is analyzed by means of an automatic, autoregressive modeling algorithm that provides a quantitative estimate of R-R interval variability by the computation of power spectral density. Two major peaks are recognizable in this specter: a low-frequency peak (LF, -0.1 Hz), related to the overall autonomic activity (ortho + parasympathetic) and a high-frequency peak (HF, -0.25 Hz), representative of the vagal activity. The LF/HF ratio is an index of the sympatho-vagal interaction. This technique was applied, using a computer-assisted electrocardiograph, to 10 healthy volunteers (6 high and 4 low hypnotizable subjects as determined by the Stanford Hypnotic Susceptibility Scale, Form C) in randomized awake and neutral hypnosis conditions. Preliminary results indicated thathypnosis affects heart rate variability, shifting the balance of the symp...

89 citations


Journal ArticleDOI
TL;DR: In this article, the authors derive compatibility coefficients attempting to optimize the performance of the relaxation algorithm over a sample of training data; no statistical interpretation is given: compatibility coefficients are simply interpreted as real numbers, for which performance is optimal.
Abstract: Relaxation labeling processes have been widely used in many different domains including image processing, pattern recognition, and artificial intelligence. They are iterative procedures that aim at reducing local ambiguities and achieving global consistency through a parallel exploitation of contextual information, which is quantitatively expressed in terms of a set of "compatibility coefficients." The problem of determining compatibility coefficients has received a considerable attention in the past and many heuristic, statistical-based methods have been suggested. In this paper, the authors propose a rather different viewpoint to solve this problem: they derive them attempting to optimize the performance of the relaxation algorithm over a sample of training data; no statistical interpretation is given: compatibility coefficients are simply interpreted as real numbers, for which performance is optimal. Experimental results over a novel application of relaxation are given, which prove the effectiveness of the proposed approach. >

86 citations


Journal ArticleDOI
TL;DR: This paper gives a sufficient condition for an envelope point to be contained in the Nyquist plot of a Kharitonov plant and uses this condition to generate large and critical portions of the Nyqv envelope as well as to create a framework for developing new extreme point results for interval feedback systems.
Abstract: In this note, we study the envelope of the Nyquist plots generated by an interval plant family and show that this boundary is not always contained in the Nyquist plots of the Kharitonov plants. With this motivation in mind, we give a sufficient condition for an envelope point to be contained in the Nyquist plot of a Kharitonov plant and use it to generate large and critical portions of the Nyquist envelope; e.g., we show that the outer Nyquist envelope of a stable interval plant is generated by the Nyquist plots of the Kharitonov plants. Another by-product of this sufficient condition is a framework for developing new extreme point results for interval feedback systems. This framework is useful in computing the phase margin and the maximal peaking in the sensitivity and complementary sensitivity functions and in stating a robust version of the circle criterion. We also use this framework to easily explain existing extreme point results for the gain margin, the H/sub /spl infin// norm and the positive realness of interval plants. One conclusion which emerges is this: Seemingly, all important properties of an interval feedback system are deducible from the Kharitonov plants. >

Journal ArticleDOI
TL;DR: In this article, the authors consider the problem of the intersection of two equal and opposite oblique shocks and introduce a curvature-corrected symmetry technique to obtain the boundary conditions.
Abstract: We consider the implementation of boundary conditions at solid walls in inviscid Euler solutions by upwind, finite-volume methods. We review some current methods for the implementation of surface boundary conditions and examine their behavior for the problem of an oblique shock reflecting off a planar surface. We show the importance of characteristic boundary conditions for this problem and introduce a method of applying the classical flux-difference splitting of Roe as a characteristic boundary condition. Consideration of the equivalent problem of the intersection of two (equal and opposite) oblique shocks was very illuminating on the role of surface boundary conditions for an inviscid flow and led to the introduction of two new boundary-condition procedures, denoted as the symmetry technique and the curvature-corrected symmetry technique. Examples of the effects of the various surface boundary conditions considered are presented for the supersonic blunt body problem and the subcritical compressible flow over a circular cylinder. Dramatic advantages of the curvature-corrected symmetry technique over the other methods are shown, with regard to numerical entropy generation, total pressure loss, drag and grid convergence.

Journal ArticleDOI
TL;DR: It is suggested that activation of the glutamatergic subthalamonigral pathway enhances dendritic DA release by activating NMDA receptors present on dopaminergic dendrites.

Journal ArticleDOI
TL;DR: In this paper, the sputtering power, argon pressure and bias voltage applied to substrates of sputter-deposited thin films were investigated. And the properties of these films were discussed and compared.


Journal ArticleDOI
TL;DR: In this article, β-perfluoroalkyl-β-dicarbonyls with hydrazonyl halides and halooximes were obtained in the presence of bases.

Journal ArticleDOI
TL;DR: In this article, a detailed time domain model for the eddy current losses in the windings of a transformer is presented, where the basic elements for the derivation of the model are the turns which may be combined into sections.
Abstract: A detailed time domain model for the eddy current losses in the windings of a transformer is presented. The basic elements for the derivation of the model are the turns which may be combined into sections. The model is expressed as an R-matrix. Its diagonal elements were fitted using a series Foster circuit while for the off-diagonal elements the authors used the basis functions of the Foster circuits to derive the time domain model in the form of state equations. For validation, the losses computed with the detailed model are compared with those obtained by considering full windings. The frequency response of the transformer model is compared with test results. Simulations are presented for illustration and further validation. >

Journal ArticleDOI
TL;DR: In this article, the authors used active entrapment in K-carrageenan to immobilize Spirulina maxima for tertiary treatment of diluted aeration-stabilized swine waste.

Journal ArticleDOI
TL;DR: A computational improvement for the shortest paths ranking algorithm due to some of the authors entails a very significant reduction in its execution time and an even larger reduction in the required computer memory space.

Journal ArticleDOI
TL;DR: In this paper, a β-ketoesterate complex of iron (III), nickel (II), or cobalt (II) was used in the presence of a branched aldehyde and molecular oxygen (or air) at room temperature and atmospheric pressure.

Journal ArticleDOI
TL;DR: In this paper, a model of the SCR monolith reactor has been extended to include the treatment of the undesired SO 2 oxidation reaction, and a redox rate expression has been fitted to data, which accounts for the variable order of SO 2, the asymptotic zeroth order behavior with respect to O 2, inhibiting effects of water and ammonia and the slight promoting effect of NO.

Journal ArticleDOI
TL;DR: Passive mode locking of a cw lamp-pumped Nd:YLF laser with the nonlinear mirror technique with nearly transform-limited pulses of 13-ps duration and 1.5-W average power at 1.047 microm is reported.
Abstract: Passive mode locking of a cw lamp-pumped Nd:YLF laser with the nonlinear mirror technique is reported. Nearly transform-limited pulses of 13-ps duration and 1.5-W average power at 1.047 μm have been obtained. The nonlinear mirror consists of a lithium triborate frequency-doubling crystal and a dichroic mirror with high reflectivity for the second harmonic and lower reflectivity for the fundamental frequency. The mode-locking process is self-starting, with pulse duration and stability strongly dependent on the cavity parameters.

Journal ArticleDOI
TL;DR: Perfluoro cis-2,3-dialkyloxaziridine as discussed by the authors was shown to perform the oxyfunctionalization of silanes under very mild conditions to give silanols and silanediols in high chemical yields and complete enantioselectivity.

Journal ArticleDOI
TL;DR: The facile oxidation of alkenes, aldehydes, cyclic ketones, alkanes, sulfides and alcohols was achieved by a polymerizable β-ketoesterato complex under Mukaiyama's conditions as mentioned in this paper.

Journal ArticleDOI
TL;DR: This model of liver injury seems to be useful for testing hepatoprotective drugs that do not act as free‐radical scavengers, and administration of colchiceine or vitamin E prevented lipoperoxidation but not liver damage, confirming that lip operoxidation does not play an important role in liver damage induced by biliary obstruction.
Abstract: There is poor evidence about the participation of lipoperoxidative processes in liver damage induced by biliary obstruction, thus the aim of this work was to study the role of lipid peroxidation in this model of liver injury. Biliary obstruction was induced in male Wistar rats by ligation of the common bile duct; control animals were sham operated. Rats were sacrificed at different times after surgery. Liver sections were used for glycogen and lipoperoxidation quantification. Markers of liver damage were determined in serum. All serum markers of liver damage increased after 1 day of biliary obstruction. Liver glycogen content decreased 1 day after surgery. On the other hand, lipoperoxidation increased later than markers of liver damage, suggesting that it is a consequence rather than the cause of liver injury. Moreover, administration of colchiceine (a good free-radical scavenger) or vitamin E prevented lipoperoxidation but not liver damage, confirming that lipoperoxidation does not play an important role in liver damage induced by biliary obstruction. This model of liver injury seems to be useful for testing hepatoprotective drugs that do not act as free-radical scavengers.

Journal ArticleDOI
U Meza1, Guillermo Avila1, Ricardo Felix1, J C Gomora1, G Cota1 
TL;DR: The results suggest that the control of prolactin production by the factors tested involves regulation of the surface density of functional Ca channels in the plasma membrane.
Abstract: In rat pituitary GH3 cells, epidermal growth factor (EGF) and insulin stimulate prolactin production, whereas glucocorticoids exert the opposite effect. In the present study, GH3 cells were subjected to whole-cell patch clamp to assess the chronic actions of such regulatory factors on voltage-dependent calcium currents. Before the electrical recording, cells were grown 5-6 d either under standard conditions or in the presence of 5 nM EGF, 100 nM insulin, 1 microM dexamethasone or 5 microM cortisol. EGF induced a twofold selective increase in high-threshold calcium current density. Insulin and glucocorticoids, on the other hand, specifically regulated low-threshold Ca channels. Current density through these channels increased by 70% in insulin-treated cells, and decreased by 50% in cells exposed to dexamethasone or cortisol. Other Ca channel properties investigated (conductance-voltage curves, deactivation rates, time course and voltage dependence of low-threshold current inactivation) were unaffected by the chemical messengers. The alterations in current density persisted for many hours after removing the regulatory factors from the culture medium. In fact, the stimulatory action of EGF on high-threshold current lasted > 3 d. The results suggest that the control of prolactin production by the factors tested involves regulation of the surface density of functional Ca channels in the plasma membrane.

Journal ArticleDOI
TL;DR: A parallel implementation of an algorithm based on Shifted-Picard dynamic iterations is presented, which proposes that a set of nonlinear Differential Algebraic Equations (DAEs), which describes the system, can be solved by the iterative solution of a linear set of DAEs.
Abstract: The most time consuming computer simulation in power system studies is the transient stability analysis. Parallel processing has been applied for time domain simulations of power system transient behavior. In this paper, a parallel implementation of an algorithm based on Shifted-Picard dynamic iterations is presented. The main idea is that a set of nonlinear Differential Algebraic Equations (DAEs), which describes the system, can be solved by the iterative solution of a linear set of DAEs. The time behavior of the linear set of differential equations can be obtained by the evaluation of the convolution integral. In the parallel-in-time implementation of the proposed algorithm, each processor is devoted to the evaluation of the complete set of variables relative to each time step. The quadrature formula, adopted for the integral evaluation, can be easily parallelized by using a number of processors equal to the number of time steps. The algorithm, implemented on a transputer network with 32 Inmos T800/20 adopting a uni-directional ring topology, has been tested on standard power systems. >

01 Jan 1994
TL;DR: In this paper, the convergence of the value iteration (or successive approximations) algorithm for average cost (AC) Markov control processes on Borel spaces, with possibly unbounded cost, under appropriate hypotheses on weighted norms for the cost function and the transition law, was shown.
Abstract: This paper shows the convergence of the value iteration (or successive approximations) algorithm for average cost (AC) Markov control processes on Borel spaces, with possibly unbounded cost, under appropriate hypotheses on weighted norms for the cost function and the transition law. It is also shown that the aforementioned convergence implies strong forms of AC-optimality and the existence of forecast horizons.

Journal ArticleDOI
TL;DR: In this paper, the normality-inertia parameter P ni was used to interpret the electrokinetic behavior and related structures of thin films of interest for possible electronic applications, such as magnetic heads, Co alloys for magnetic recording and Cu Sb as a possible underlayer for electric contacts.

Posted Content
TL;DR: In this article, the authors introduce the notion of relative convolution operators induced by a Lie algebra and show that relative convolutions provide a base for systematical applications of harmonic analysis to PDO theory, complex and hypercomplex analysis, coherent states, wavelet transform and quantum theory.
Abstract: To study operator algebras with symmetries in a wide sense we introduce a notion of {\em relative convolution operators} induced by a Lie algebra. Relative convolutions recover many important classes of operators, which have been already studied (operators of multiplication, usual group convolutions, two-sided convolution etc.) and their different combinations. Basic properties of relative convolutions are given and a connection with usual convolutions is established. Presented examples show that relative convolutions provide us with a base for systematical applications of harmonic analysis to PDO theory, complex and hypercomplex analysis, coherent states, wavelet transform and quantum theory. KEYWORDS: Lie groups and algebras, convolution operator, representation theory, Heisenberg group, integral representations, Hardy space, Szeg\"o projector, Toeplitz operators, Fock space, Segal--Bargmann space, Bargmann projector, Dirac equation, Clifford analysis, coherent states, wavelet transform, quantization.