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Search Results: 1 - 10 of 2521 matches for " Marcel Celaya "
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On the span of lattice points in a parallelepiped
Marcel Celaya
Mathematics , 2015,
Abstract: We find a good characterization for the following problem: Given an integral row vector $c=(c_{1}\ldots,c_{n})$ where each $c_{i}\in\{-1,0,1\}$ and a lattice $\Lambda\subset\mathbf{R}^{n}$ which contains the integer lattice $\mathbf{Z}^{n}$, do all lattice points of $\Lambda$ in the half-open unit cube $[0,1)^{n}$ lie on the hyperplane $\{x:cx=0\}$? The result is a direct generalization of the well-known Terminal Lemma of Reid, which in turn is based upon earlier work of Morrison and Stevens on the classification of terminal quotient singularities.
Morphic Words and Nested Recurrence Relations
Marcel Celaya,Frank Ruskey
Mathematics , 2013,
Abstract: We explore a family of nested recurrence relations with arbitrary levels of nesting, which have an interpretation in terms of fixed points of morphisms over a countably infinite alphabet. Recurrences in this family are related to a number of well-known sequences, including Hofstadter's G sequence and the Conolly and Tanny sequences. For a recurrence a(n) in this family with only finitely terms, we provide necessary and sufficient conditions for the limit a(n)/n to exist.
An Undecidable Nested Recurrence Relation
Marcel Celaya,Frank Ruskey
Computer Science , 2012,
Abstract: Roughly speaking, a recurrence relation is nested if it contains a subexpression of the form ... A(...A(...)...). Many nested recurrence relations occur in the literature, and determining their behavior seems to be quite difficult and highly dependent on their initial conditions. A nested recurrence relation A(n) is said to be undecidable if the following problem is undecidable: given a finite set of initial conditions for A(n), is the recurrence relation calculable? Here calculable means that for every n >= 0, either A(n) is an initial condition or the calculation of A(n) involves only invocations of A on arguments in {0,1,...,n-1}. We show that the recurrence relation A(n) = A(n-4-A(A(n-4)))+4A(A(n-4)) +A(2A(n-4-A(n-2))+A(n-2)). is undecidable by showing how it can be used, together with carefully chosen initial conditions, to simulate Post 2-tag systems, a known Turing complete problem.
La cesión de un derecho de la Real Hacienda: la administración del impuesto de la alcabala novohispana en el siglo XVII. Tres estudios de caso
Celaya Nández, Yovana;
América Latina en la historia económica , 2010,
Abstract: this article examines the transfer of rights of recovery which the royal treasury deposited in cabildos, consulados and individuals. for the beneficiaries, the assignment became the control over the collection of the levy of alcabala, and such control resulted in a configuration of a management system covered by the terms negotiated in the contract. the source which allowed the analysis was exactly the contracts established between the royal treasury and others to raise the alcabala. contracts are a window to the exercise of political power and economic stakeholders, which in such contracts were in play at the time of receiving such assignment. from the process of collecting the alcabala, it concerned to expand the dimensions of analysis on the tax and lease contracts which are other ways around this important study colonial taxation.
La cesión de un derecho de la Real Hacienda: la administración del impuesto de la alcabala novohispana en el siglo XVII. Tres estudios de caso
Yovana Celaya Nández
América Latina en la historia económica , 2010,
Abstract: El artículo analiza la cesión de derechos de recaudación que la Hacienda real depositó tanto en corporaciones políticas y económicas como en particulares. La cesión representó para los beneficiarios el control sobre la recaudación del gravamen de la alcabala, control que se tradujo en la configuración de un sistema de administración amparado por las cláusulas negociadas en la firma del contrato. La fuente que permitió el análisis fueron precisamente los contratos que se establecieron entre la Real Hacienda y terceros para recaudar la alcabala. Los contratos constituyen una ventana al ejercicio del poder político y económico que los interesados en dichos contratos ponían en juego al momento de recibir una cesión de tal naturaleza. Desde el proceso de recaudación de la alcabala interesó ampliar las dimensiones de análisis sobre este impuesto y los contratos de arrendamiento muestran otras posibilidades de estudio en torno a este importante gravamen colonial. This article examines the transfer of rights of recovery which the Royal Treasury deposited in cabildos, consulados and individuals. For the beneficiaries, the assignment became the control over the collection of the levy of alcabala, and such control resulted in a configuration of a management system covered by the terms negotiated in the contract. The source which allowed the analysis was exactly the contracts established between the Royal Treasury and others to raise the alcabala. Contracts are a window to the exercise of political power and economic stakeholders, which in such contracts were in play at the time of receiving such assignment. From the process of collecting the alcabala, it concerned to expand the dimensions of analysis on the tax and lease contracts which are other ways around this important study colonial taxation.
Reinforcement Learning for Agents with Many Sensors and Actuators Acting in Categorizable Environments
E. Celaya,J. M. Porta
Computer Science , 2011, DOI: 10.1613/jair.1437
Abstract: In this paper, we confront the problem of applying reinforcement learning to agents that perceive the environment through many sensors and that can perform parallel actions using many actuators as is the case in complex autonomous robots. We argue that reinforcement learning can only be successfully applied to this case if strong assumptions are made on the characteristics of the environment in which the learning is performed, so that the relevant sensor readings and motor commands can be readily identified. The introduction of such assumptions leads to strongly-biased learning systems that can eventually lose the generality of traditional reinforcement-learning algorithms. In this line, we observe that, in realistic situations, the reward received by the robot depends only on a reduced subset of all the executed actions and that only a reduced subset of the sensor inputs (possibly different in each situation and for each action) are relevant to predict the reward. We formalize this property in the so called 'categorizability assumption' and we present an algorithm that takes advantage of the categorizability of the environment, allowing a decrease in the learning time with respect to existing reinforcement-learning algorithms. Results of the application of the algorithm to a couple of simulated realistic-robotic problems (landmark-based navigation and the six-legged robot gait generation) are reported to validate our approach and to compare it to existing flat and generalization-based reinforcement-learning approaches.
Making Sense of Environmental Complexity in a Reform Context: The Case of Megaproject Alpha  [PDF]
Marcel Veenswijk
American Journal of Industrial and Business Management (AJIBM) , 2012, DOI: 10.4236/ajibm.2012.24015
Abstract: In this paper, new concepts on environmental complexity and sense making are developed and explored and analysed. The article based on a case study regarding a public-private collaboration in a Dutch infrastructural mega project. It is argued that the ability to influence the direction of the change process of the mega project “Alpha” depends on the way actors are able to influence the so aleed “cultural interfaces” into the power arena by means of a specific group of organizational stakeholders. After a short theoretical introduction, we describe the case in terms of two dominant cultural stages and their specific interface dynamics. The paper concludes with a general reflection on the central concepts.
AGE-RELATED DIFFERENCES IN THE DEVELOPMENT OF WRITTEN PRODUCTION. AN EMPIRICAL STUDY OF EFL SCHOOL LEARNERS'
Maria Rosa Torras,Maria Luz Celaya
International Journal of English Studies (IJES) , 2001, DOI: 10.6018/ijes.1.2.48211
Abstract: The aim of this paper is to analyse the development of the written production of two groups of EFL leamers (N = 63) in a school context. The two groups started instruction at different ages (8 and 11, respectively). Their written production was measured afier 200 and 416 hours of instruction. and analysed longitudinally. Both intragroup and intergroup analyses were carried out a) to analyse the development of the participants' written production as measured by three indicators of writing proficiency (fluency, complexity and accuracy); and b) to ascertain whether the differences observed (both in terms of attainment and rate of development) could be attributed to the age at which the groups of participants initiated their contact with the L2. Results show that not all the areas of writing proficiency (fluency, complexity and accuracy) develop in parallel and that an earlier start does not seem to show clear advantages in the development of EFL written production.
Una estrategia para favorecer la comprensión y el aprendizaje en las Ciencias Morfológicas: Presentaciones en PowerPoint. [ A strategy to improve the comprehension and learning in morphological science: powerpoint presentation ]
Carranza, Miriam L. y Celaya, Gabriela
Revista Electrónica de Investigación y Evaluación Educativa , 2003,
Abstract: In this paper, a hypertext to the Morphological Sciences in biological area was developed and evaluated. The application with format of digital atlas approaches Anatomical, Histological and Functional concepts about the man and animals in integrated form. PowerPoint presentation was developed to operators which experience in the handling of software are limited. This digital resource was qualified as a good complement of other didactic materials. In this knowledge area offers opportunity to develop significant knowledge to improve the understanding and learning through an interactive methodology
Narrating National Geo Information Infrastructures: Balancing Infrastructure and Innovation  [PDF]
Henk Koerten, Marcel Veenswijk
Journal of Service Science and Management (JSSM) , 2009, DOI: 10.4236/jssm.2009.24040
Abstract: This paper examines narratives relating to the development of National Geo Information Infrastructures (NGII) in ethnographic research on a Dutch NGII project which was monitored throughout its course. We used an approach which focuses on narratives concerning the environment, groups and practice to elicit sense-making processes. We assert that narratives are relatively fixed and that they only change under specific circumstances. Moreover, the fixing of or change in narratives takes place in practice, so our research approach aimed at analysing narratives of practice, which we label ‘storyboards’. For this purpose, project meetings and conferences were observed, key persons both within and outside the project environment were interviewed, and an analysis of relevant documents and video footage was undertaken. Storyboards are created by actors as a result of day-to-day challenges related to project goals, technology and infrastructure. In our research we found that these storyboards occur as vicious circles from which actors cannot escape. In the specific case analysed, our interpretation of the narrative storyboards suggested that these vicious circles are caused by the inability of project participants to distinguish between infrastructure and innovation requirements in their daily work.
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