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By
EstivillCastro, V.; Urrutia, J.
2 Citations
A floodlight of size α is a light source that projects light in a cone of size α. In this paper we study the problem of illuminating a convex polygon using floodlights. We give an O(n^{2}) time algorithm to find an optimal pair of floodlights to illuminate a convex polygon P with n vertices; that is a pair of floodlights to illuminate a convex polygon in such a way that the sum of their sizes is minimized. When our polygon is cocircular (i.e. all of the vertices of P lie on a circle) such a pair of floodlights can be found in linear time.
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By
Abello, James; EstivillCastro, Vladimir; Shermer, Thomas; Urrutia, Jorge
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1 Citations
We provide the first tight bound for covering a polygon with n vertices and h holes with vertex guards. In particular, we provide tight bounds for the number of floodlights, placed at vertices or on the boundary, sufficient to illuminate the interior or the exterior of an orthogonal polygon with holes. Our results lead directly to simple linear, and thus optimal, algorithms for computing a covering of an orthogonal polygon.
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By
Trejo, Luis A.; Sandoval, Carlos
2 Citations
A modified version of backpropagation learning algorithm is introduced. This new algorithm called epsilonbackpropagation allows a neural network to learn faster or al least as good as backpropagation. Experimental data is given in order to compare both methods.
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By
Even, Shimon; Itkis, Gene; Rajsbaum, Sergio
2 Citations
Vertex and edge connectivity are special cases of mixed connectivity, in which all edges and a specified set of vertices play a similar role. Certificates of kconnectivity for a graph are obtained by removing a subset of its edges, while preserving its connectivity up to k.
We unify the previous work on connectivity certificates and extend it to handle mixed connectivity and multigraphs. Our treatment contributes a new insight of the pertinent structures, yielding more general results and simpler proofs. Also, we present a communicationoptimal distributed algorithm for finding mixed connectivity certificates.
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By
Agustin, Rodolfo San
1 Citations
In this paper Cayley’s configurations in projective rlimensional space are redefined recursively using a combinatorial characterization of them and a recovery algorithm for a generating point set. Then, the loubletriple notation system characterization is justified also through an ad hoc algorithm.
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By
Viana, L.
A review of recent results on the performance of a string of n Hopfield subnetworks interconnected by means of strong unidirectional low density connections is presented. Such networks store p random unbiased patterns {ξ
_{i}^{u}
, composed by n subpatterns, each of them to be recalled sequentially, by one of the subnetworks.
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By
Weitzenfeld, Alfredo
1 Citations
NSL, Neural Simulation Language, is a general purpose simulation system providing a highlevel language with many constructs and libraries developed to ease the specification of large neural networks. NSL integrates objectoriented programming methodologies in its design and implementation, providing a simulation environment for users with little programming background, as well as those with more extensive programming expertise, who can use C++ as an extension to NSL's modeling language. NSL is widely used in research and teaching, having lead to many different neural network models, both in the artificial and biological domains. NSL enables the simulation of models with different levels of neural details, with special support for the leaky integrator.
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By
Alvarado, Matías; Núñez, Gustavo
ThreeValued Strong Kleene Logic [16], provides an adequate framework to deal with belief increasing. In this paper, undefined truthvalue is used to denote opinionless information. Through an informative refinement, such information could become to be true or false in a step by step way. Our approach is based upon model frames [9], that are sets of informatively ordered threevalued interpretations. A relation of compatibility among frames, being a partial informative order, is defined. Belief increasing is accomplished by using the compatibility relation that is based on concatenation operation over model frames. A correspondence between model frames and analytic tableaux is outlined. It provides to deal with model frames by using that powerful proof method [11].
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By
Hirose, Luis Montaño
1 Citations
This paper tackles the main changes that have taken place in the mechanical worldview of simple, selfregulating and intelligent machines, and studies their repercussions at the ethical and organisational level. These views of machines agree with the scientific, humanrelations and postmodern proposals in organisation theory, in that they are in fact reflections on human nature which depend on metaphorical devices within which the machine metaphor is central.
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By
Esteva, Luis
This is an abridged version of Ref. 1. It eliminates most of the references, as well as the discussion concerning the probabilistic modelling of seismic hazard and ground motion, and concentrates on the system reliability concepts.
By
Lazcano, Antonio
Although the origin of selfsustaining, autoreplicating systems capable of undergoing Darwinian evolution is still unknown, a research program based on the hypothesis of chemical and precellular evolution has provided a framework within which the abiotic synthesis of biochemical monomers and membrane components, the experimental study of replicative systems, and the interactions between different ribozymes and a potentially wide range of substrates including amino acids, can be incorporated into a coherent historical narrative of evolutionary events. The significance of mathematical models and computerbased simulations of autocatalytic cycles based on complexity theory to the study of the origin of life will be considerable enhanced when experimental evidence supporting them becomes available.
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By
Leal, Fernando
3 Citations
This paper first illustrates what kind of ethical issues arise from the new information, communication and automation technology. It then argues that we may embrace the popular idea that technology is ethically neutral or even ambivalent without having to close our eyes to those issues and in fact, that the ethical neutrality of technology makes them all the more urgent. Finally, it suggests that the widely ignored fact of normal responsible behaviour offers a new and fruitful starting point for any future thinking about such issues.
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By
García, R.; Motta, S.
Modern organizations of the so called ‘modernity’ era have been characterised by a high degree of Systematisation in their operations which involves a high degree of specialisation. This has resulted in an almost unbreakable hierarchical order and a strict control on the people who execute the task related operations, who, for this reason, turn out to resemble the pieces of a chess game. “The different pieces of chess are only defined by the functions given by the game rules...these can be substituted by any other without losing their identity. As long as these are moved according to the game rules...its properties have no effect on the system. (Llano, 1994:50)
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By
Russell, Jane M.
12 Citations
Increasing importance is being given to international scientific activities, especially with regard to developing countries. In the present paper, an analysis is made of the studies published by Mexican institutions in coauthorship with foreign colleagues between 1980 and 1990, as registered in mainstream journals. Different characteristics of the collaboration are described, such as research areas, countries and institutions involved, of interest to Mexican policy makers and scientists, as well as to foreign governments and international organizations sponsoring cooperative agreements with Mexico.
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By
Ramírez, Gabriel A.
The reduction of time elapsed between scientific innovation and using it successfully, constitutes one of the most important abilities that today’s companies must have to keep competitive in the international markets. The process of going from spotting an innovation to its application is determined by a large number of complex activities and situations taking place through the internal and external organizational environment. In managerial terms, that process corresponds to going from strategic awareness and reflection to action and results.
This paper deals with the problems of organizing the efforts to bridge the gap existing between strategic and operational Technology Management and with the definition of the information requirements that support this effort. The ideas are the result of applying theories of organizational viability and methods of systemic problem solving to Technology Management, in a large corporation that, as a result of its country’s integration to international markets, has to face increased foreign competition.
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By
Echevarria, J.; Tapia, M.; Bohigas, J.; Costero, R.; Lopez, J. A.; Alvarez, M.; Rodriguez, L. F.; Barral, J.; Lara, E.; Tovmassian, G.; Asatrian, N.; Shara, M.; Jones, D. H. P.; Wallis, R.; Roth, M.; Stover, R.; Martinez, C.; Garzon, F.; Gilmozzi, R.; Vogt, N.; Zsoldos, E.; Szkody, P.; Mattei, J.; Batteson, F.
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SU UMa — the prototype of a subgroup of dwarf novae, which displays superhumps in superoutbursts, has been observed1 during an international campaign dedicated to the observation of the first day of outburst of dwarf novae during February 1986. After the start of a brightening was reported, the star was monitored by IUE, groundbased photometry and spectrophotometry, IRphotometry and Radio observations by VLA. However, it did not undergo to a normal outburst or a superoutburst.
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By
NarvaezBerthelemot, N.
14 Citations
International collaboration is an important ingredient of presentday scientific research. Latin America, for instance, is increasing its production of internationally coauthored publications and, the number of national institutions involved in this activity. An index developed to measure international collaboration by taking into account individual institutional participation resulted in a positive average increase in the production of developing countries (DCs) research. Nonetheless, the degree of institutional participation varies between field and with respect to the country in question. Giving weight to individual institutional participation, could motivate DCs scientists to enhance their role in the international science of the region. Likewise, this index could be developed as “quality indicator” of national institutional performance.
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By
MaciasChapula, C. A.
2 Citations
This work reports the first results of a research in progress on the production, dissemination and impact of the literature on primary health care (PHC), as produced in Mexico during the period 1980–1992. The methodology used involved computerized searches in the MEDLINE, LILACS, and PERIODICA databases to identify the existing Mexican literature in the field. Results indicated a limited dissemination of the Mexican production through conventional databases. A total of 117 references were found in the field. Most of these references (72.65%) corresponded to journal articles. Over 55% of the documents were published by more than one author. Further research in the field as well as the implications of these results to PHC in Mexico are discussed by the author.
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By
Campos, R. G.
5 Citations
We present in this paper a quadrature formula for a certain FourierBessel transform and, closely related to this, for the Hankel transform of order ν>−1. Such formulas originate in the context of a Galerkintype projection of the weightedL_{2}(−∞, ∞; ω_{μ}) space (ω_{μ} is the weight function mentioned below) used to get a discrete representation of a certain physical problem in Quantum Mechanics. The generalized Hermitee polynomialsH_{0}^{μ}
(x),H_{1}^{μ}
(x),..., with weight function ω_{μ}(x), are used as the basis on which such a projection takes place. It is shown that theNdimensional vectors representing certain projected functions as well as the entries of theN×N matrix representing the kernel of that FourierBessel transform, approach the exact functional values at the zeros of theNth generalized Hermitee polynomial whenN→∞.
These properties lead to propose this matrix as a finite representation of the kernel of the FourierBessel transform involved in this problem and theN zeros of the generalized Hermitee polynomialH_{N}^{μ}
(x) as abscissas to yield certain quadrature formulae for this integral and for the related Hankel transform. The error function produced by this algorithm is estimated at theN nodes and its is shown to be of a smaller order than 1/N. This error estimate is valid for piecewise continuous functions satisfying certain integral conditions involving their absolute values. The algorithm is presented with some numerical examples.
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