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By
Noriega, Pablo; Sierra, Carles
17 Citations
We present a formalism for the specification of agents within a multiagent system in which we characterize agents through a layered architecture with bridge rules between formal theories, and multiagent systems through dialogical frameworks. Concurrent Descriptive Dynamic Logic (an extension of Peleg's Concurrent Dynamic Logic) is introduced as the specification language to account for the computational interpretation of such multiagent systems.
We illustrate our proposal through the description and implementation of a multiagent environment: the downwardbidding fish market.
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By
Osorio, Mauricio; Jayaraman, Bharat
3 Citations
Setgrouping and aggregation are powerful nonmonotonic operations of practical interest in database query languages. We consider the problem of expressing aggregation via negation as failure (NF). We study this problem in the framework of partialorder clauses introduced in [JOM95]. We show a translation of partialorder programs to normal programs that is very natural: Any costmonotonic partialorder program P becomes a stratified normal program transl(P) such that the declarative semantics of P is equivalent to the stratified semantics of transl(P). The ability to effect such a translation is significant because the resulting normal programs do not make any explicit use of the aggregation capability, yet they are concise and intuitive. The success of this translation is due to the fact that the translated program is a stratified normal program. That would not be the case for other more general classes of programs than costmonotonic partialorder programs. We therefore investigate a second (and more natural) translation that does not require the translated programs to be stratified, but requires the use of a suitable NF strategy. The class of normal programs originating from this translation is itself interesting. Every program in this class has a clear intended total model, although these programs are in general not stratified and not even callconsistent and do not have a stable model. The partial model given by the wellfounded semantics is consistent with the intended total model and the extended well founded semantics WFS^{+} indeed defines the intended model. Since there is a welldefined and efficient operational semantics for partialorder programs [JOM95, JM95] we conclude that the gap between expression of a problem and computing its solution can be reduced with the right level of notation.
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By
TapiaRecillas, H.; Vega, G.; Daltabuit, E.
Several results about regular mappings are presented in connection with the associated substitution Sbox. A characterization of regular mappings is given and an upper bound for the ∈robustness of the Sbox against differential cryptanalysis is provided.
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By
Jesús HoyosRivera, Guillermo; Germán SánchezArias, Víctor
In the work presented we propose the definition, design of a Cooperative Work Model (CWM) [1] and a Cooperative Work Language (CWL) [2], and the implementation of an interface to support Cooperative Work in a Distributed Systems environment, called ICW^{1}, inspired upon the definition of CSP [3], and the basic notions of processes and pipes used in Unix [4].
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By
Hahn, Federico; Mota, Rafael
Jalapeno chili is grown extensively in Mexico, as it is one of the main vegetables consumed by the population, having also a high demand for exportation. Chili classification is fundamental before arriving to the processing plants, grocery stores and supermarkets. A CCD camera imaged the product which travelled through the conveyor belt, but it was very slow, so a laser scanning system was used to obtain the chili length in order to sort it by sizes. A brief study of the main chili features was carried out, before training a random backpropagation neural network classifier. It was noted that the best topology required to know only the chili width and length sorting up to five different sizes with accuracies over 94%.
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By
Rodriguez, Andrés F.; Vadera, Sunil; Sucar, L. Enrique
3 Citations
An exemplarbased model with foundations in Bayesian networks is described. The proposed model utilises two Bayesian networks: one for indexing of categories, and another for identifying exemplars within categories. Learning is incrementally conducted each time a new case is classified. The representation structure dynamically changes each time a new case is classified and a coverage function is used as a basis for selecting suitable exemplars. Finally, a simple example is given to illustrate the concepts in the model.
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By
Coolen, A. C. C.; Viana, L.
We use replica theory to analyse layered networks of binary neurons, with lateral Hebbiantype synapses within individual layers, in combination with strictly feedforward Hebbiantype synapses between successive layers. The competition between two qualitatively different modes of operation, feedforward versus lateral, induces interesting transitions, and allows for the identification of an optimal value for the balance between the two synapse types.
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By
Lano, K.; Sanchez, A.
1 Citations
This paper explores the combination of formal methods with techniques taken from control engineering for specifying, designing and verifying reactive systems.
In particular, it is shown how to use techniques for specification and verification in VDM^{++} in combination with the synthesis of procedural controllers, a mathematical abstraction of the logic controlling an eventdriven sequential operation. The procedural controller is used as a provably correct specification of an eventdriven operation to be implemented using VDM^{++}. The resulting method enables a systematic approach for creating formalized designs of controllers for this type of operations, and proof obligations for the correctness of the designs against specifications to be generated. The approach is illustrated using an example.
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By
ColladoVides, Julio; Huerta, Araceli M.; Klose, Kathleen
We have initiated the construction of a database on the regulation of transcription initiation in E. coli. In this chapter we discuss three alternative designs of this database. The first model is based on considering promoters, and binding sites for regulators, as objects, and the regulatory interaction as a function linking essentially three objects: the regulatory protein, the site, and the regulated promoter. The second model is based on considering the notions of promoters, sites and genes, as functional properties mapped on specific sequences. Their associated physical sequences are no more considered DNA sequences with inherent properties. Finally, the third model emphasizes the different levels of representation that can be used to describe gene regulation. The selection of a representation among several alternatives is found when designing a database as well as when building grammatical models. Taking this notational problem seriously may help to a better biological insight of the process being modelled.
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By
Negrete, A.
Time and budget constraints are often limiting factors in resource management projects, especially in third world countries. Therefore the development of cheaper and faster alternative computational tools should be promoted. “Gridmapper” is a geographical information system (GIS) capable of working with inexpensive hardware. It is easy to understand, offering a user friendly interface in Windows. By using small quantities of information, this system can generate usefull maps and carry out basic statistical analyses. It has been tested successfully in environmental projects, in educational programs, and in the field for previewing and analyzing spatial data on portable computers.
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By
Morales, Eduardo F.
10 Citations
It has been argued that much of human intelligence can be viewed as the process of matching stored patterns. In particular, it is believed that chess masters use a pattern–based knowledge to analyze a position, followed by a pattern–based controlled search to verify or correct the analysis. In this paper, a first–order system, called PAL, that can learn patterns in the form of Horn clauses from simple example descriptions and general purpose knowledge is described. The learning model is based on (i) a constrained least general generalization algorithm to structure the hypothesis space and guide the learning process, and (ii) a pattern–based representation knowledge to constrain the construction of hypothesis. It is shown how PAL can learn chess patterns which are beyond the learning capabilities of current inductive systems. The same pattern–based approach is used to learn qualitative models of simple dynamic systems and counterpoint rules for two–voice musical pieces. Limitations of PAL in particular, and first–order systems in general, are exposed in domains where a large number of background definitions may be required for induction. Conclusions and future research directions are given.
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By
MartínezContreras, Jorge; GutiérrezLombardo, Raúl; LombardoOtero, Marcela
This contribution is divided in three parts. The first draws attention to the problem of the new global order and the complex realities lived in the many diverse countries of Latin America. The second part analyzes the problem of identities and culture. We try to answer two fundamental questions: 1) How the question of cultural identity and problems concerning resistance and integration in Latin America arise in the framework of the neoliberal model? 2) What is the role of the media in the current redefining of new identities and new cultural borders? The third part of the paper refers to the problems of globalization and sustainable growth in the modernitypostmodernity debate in Latin America. In particular, we analyze the preservation and/or conservation ecological question.
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By
Coello Coello, C. A.; Christiansen, A. D.; Hernández, F. Santos
52 Citations
We present an optimization model for the design of rectangular reinforced concrete beams subject to a specified set of constraints. Our model is more realistic than previously published models because it minimizes the cost of the beam on strength design procedures, while also considering the costs of concrete, steel and shuttering. Thus our method leads to very practical designs. As there is an infinite number of possible beam dimensions and reinforcement ratios that yield the same moment of resistance, an efficient search technique is preferred over the more traditional iterative methods. We employ a simple genetic algorithm as the search engine, and we compare our results with those obtained via geometric programming. Since the adjustment of parameters in a genetic algorithm (e.g., population size, crossover and mutation rates, and maximum number of generations) is a significant problem for any application, we present our own methodology to deal with this problem. A prototype of this system is currently being tested in México, in order to evaluate its potential as a reliable design tool for real world applications.
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By
Giddings, L. E.; Chiappy, C.; Soto, M.; Gama, L.
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Conservation efforts in the state of Veracruz, Mexico, are supported by the geographical information system, BIOCLIMAS. In addition to its original use in study of climatic parameters as related to plant geography, it has recently been adapted to the semiautomatic determination of degree of conservation of natural areas, producing an “Ecological Landscape Modification Map” (“Mapa de Modificaciones EcoldgicoPaisajisticas”). The method, first applied to the state of Veracruz (73 000 km^{2}), is based on machine interpretation of information from available maps at 1:1,000,000 and produces an evaluation on a scale from 1 (very well conserved) to 8 (completely changed from natural state). The method is soon to be applied to a much larger area of the country, and eventually will be used for the whole country (2 000 000 km^{2}) A disadvantage of the method is its use of maps made in the past; it can only be as accurate as are its source maps, some of which in Mexico are a decade old. Aside from its general use in evaluating the conservation of large areas, it is being used to evaluate existing reserve areas and planning for new reserves.
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By
Poveda, A.; Allen, Christine; Herrera, M. A.
3 Citations
Utilizing the authors’ recent catalogue of wide double and multiple stars for the solar vicinity (Poveda et al. 1994) we investigate the distribution of separations of their components. We find that the distribution of separations, f(s), is well represented by Öpik’s relation f(s) ∝ s^{1} for separations smaller than 2,400 AU. We find an agedependent critical separation S_{c} which divides those binaries that have been affected by energy exchanges in encounters with perturbing objects from those whose separations are still unchanged from their primeval distribution. For the group of youngest systems from our catalogue S_{c}= 7, 800 AU, and for the oldest, S_{c} = 2, 400 AU. The velocity dispersions for the first group give a mean age of 2.5 × 10^{9} years, while those for the oldest systems yield 7 × 10^{9} years.
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By
Herrera, M. A.; Poveda, A.; Nigoche, A.; Segura, A.
Show all (4)
1 Citations
With the purpose of studying the time evolution of the distribution of separations of binary systems, a long term effort is being made to obtain homogeneous samples of binaries of different ages. In this work, the results of a search for binaries in the Hyades cluster are presented. The search was done by means of the nearest neighbor statistic, complemented with numerical simulations. The data base was Luyten’s list of 929 probable Hyades. A total of 53 probable binaries was detected; 22 of them are the 22 binaries in Luyten’s list that were previously known, and the other 31 are new probable identifications.
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By
Ferro, A. Arellano; Rosenzweig, Patricia; Arellano, E. Rojo
1 Citations
Secular period variations occurring in classical cepheids are of astrophysical importance since they are the result of structural changes in the star and a direct observational consequence of stellar evolution. During the preparation of a uvbyβ photometric catalogue of galactic cepheids (Arellano Ferro et al. 1997), important shifts were distinguished in the light and color curves maxima relative to standard ephemeris for the cepheids V572 Aql, AO Aur, AD Gem, DX Gem, AP Her, and BL Her. In this paper we report the new times of maximum, discuss the resulting OC diagrams, and calculate the present periods of these stars.
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By
Sucar, Luis Enrique; PérezBrito, Joaquín; RuizSuárez, J. Carlos; Morales, Eduardo
Show all (4)
16 Citations
In this paper we propose an algorithm for structure learning in predictive expert systems based on a probabilistic network representation. The idea is to have the “simplest” structure (minimum number of links) with acceptable predictive capability. The algorithm starts by building a tree structure based on measuring mutual information between pairs of variables, and then it adds links as necessary to obtain certain predictive performance. We have applied this method for ozone prediction in México City, where the ozone level is used as a global indicator for the air quality in different parts of the city. It is important to predict the ozone level a day, or at least several hours in advance, to reduce the health hazards and industrial losses that occur when the ozone reaches emergency levels. We obtained as a first approximation a treestructured dependency model for predicting ozone in one part of the city. We observe that even with only three parameters, its estimations are acceptable.
A causal network representation and the structure learning techniques produced some very interesting results for the ozone prediction problem. Firstly, we got some insight into the dependence structure of the phenomena. Secondly, we got an indication of which are the important and not so important variables for ozone forecasting. Taking this into account, the measurement and computational costs for ozone prediction could be reduced. And thirdly, we have obtained satisfactory short term ozone predictions based on a small set of the most important parameters.
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By
Tovmassian, G.; Greiner, J.; Zickgraf, F.J.; Kroll, P.; Krautter, J.; Thiering, I.; Serrano, A.
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A new cataclysmic variable is identified as the optical counterpart of the Xray source RX J0757.0+6306. The emission lines bear evidence of a strong disc with an Swave with period of 75±1.4 min, which we identify with the orbital period of the system. CCD photometry reveals an additional period of 8.45 min. which is stable over five nights. We assume it is the spin period of the accreting primary. We tentatively identify RX J0757.0+6306 as an intermediate polar.
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By
Shapiro, Michael V.; Vasilevski, Nikolai L.
26 Citations
The hyperholomorphic Bergmann kernel function _{ψ}ß for a domain Ω is introduced as the special quaternionic “derivative” of the Green function for Ω. It is shown that _{ψ}ß is hyperholomorphic, Hermitian symmetric and reproduces hyperholomorphic functions.
We obtain an integral representation of _{ψ}ß as a sum of two integrals. One of them gives a smooth function, and the other describes the behaviour of _{ψ}ß near a boundary. To investigate the hyperholomorphic Bergmann function for some fixed class of hyperholomorphic functions we have to use not only the properties of just this class but also those of some other classes. The second fact is completely unpredictable from the complex analysis point of view.
The connection between the hyperholomorphic Bergmann projector (the integral operator with the kernel _{ψ}ß) and some classical multidimensional singular integral operators is established.
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By
HernándezLerma, Onésimo; Lasserre, Jean B.
13 Citations
This paper studies the policy iteration algorithm (PIA) for average cost Markov control processes on Borel spaces. Two classes of MCPs are considered. One of them allows some restrictedgrowth unbounded cost functions and compact control constraint sets; the other one requires strictly unbounded costs and the control constraint sets may be noncompact. For each of these classes, the PIA yields, under suitable assumptions, the optimal (minimum) cost, an optimal stationary control policy, and a solution to the average cost optimality equation.
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By
Morales, L. B.
2 Citations
HereR andN denote the real numbers and the nonnegative integers, respectively. Alsos(x)=x_{1}+···+x_{n} whenx=(x_{1}, …,x_{n}) inR^{n}. A mapf:R^{n} →R is call adiagonal function of dimensionn iffN^{n} is a bijection ontoN and, for allx, y inN^{n}, f(x)<f(y) whens(x)<s(y). Morales and Lew [6] constructed 2^{n−2} inequivalent diagonal polynomial functions of dimensionn for eachn>1. Here we use new combinatorial ideas to show that numberd_{n} of such functions is much greater than 2^{n−2} forn>3. These combinatorial ideas also give an inductive procedure to constructd_{n+1}diagonal orderings of {1, …,n}.
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By
Allen, Christine; Poveda, A.; Herrera, M. A.
4 Citations
Several recent observational determinations of the distribution of separations of wide binaries are critically reviewed and compared with the distributions inferred from observational work on premain sequence stars and from theoretical ideas on binary formation. It is concluded that it is not very fruitful to depict the whole distribution function of separations by one law, and that it is preferable to represent separately the two main mechanisms of binary formation, namely firstcollapse fragmentation (for s > 25 AU) and disk fragmentation (for s < 25 AU). It is also found that the best representation for the group of wide binaries (s > 25 AU) is given by Öpik’s law ρ(s) = ks^{2}, but that this distribution has a cutoff that is agedependent. This cutoff is interpreted in terms of the dynamical evolution of wide binaries.
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By
Baba, N.; Kuwamura, S.; Norimoto, Y.; Hirata, R.; Isobe, S.; Cuevas, S.; RuelasMayorga, A.
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Speckle spectroscopy is a method to obtain objective spectra of stellar objects with high spatial resolution. We conducted speckle spectroscopic observations of binary stars at the Okayama Astrophysical Observatory in Japan and at the San Pedro Mártir Observatory in Mexico. Spectra of primary and secondary stars are spatially separated and the spectral distribution around Ha line is examined. We report observational results for some Be and B binary stars.
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By
MacíasChapula, C. A.; RodeaCastro, I. P.
2 Citations
This work reports on the subject content analysis performed to 1323 records retrieved from international databases, related to the Mexican production on environmental health. The U.S. National Library of Medicine's Medical Subject Headings (MeSH) and BIREME's Health Sciences Descriptors (DeCS) were used as guiding tools to select the subject content of records. Overall, 97 descriptors were identified; 65 corresponded to MeSH terms and 32 were, generated by the authors. Results indicated that most of the production was related to environmental pollution studies focused on water and air pollution, and environmental monitoring. Through the development of hierarchical models, patterns of subjects covered and uncovered could be easily identified. Further lines of action and research are proposed by the authors.
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