Projections for infinitary rewriting

Proof terms in term rewriting are a representation means for reduction sequences, and more in general for contraction activity, allowing to distinguish e.g simultaneous from sequential reduction. Proof terms for finitary, first-order, left-linear term rewriting are described in the Terese book, chapter 8. In a previous work, we defined an extension of the finitary proof-term formalism, that allows to describe contractions in infinitary first-order term rewriting, and gave a characterisation of permutation equivalence. In this work, we discuss how projections of possibly infinite rewrite sequences can be modeled using proof terms. Again, the foundation is a characterisation of projections for finitary rewriting described in Terese, Section 8.7. We extend this characterisation to infinitary rewriting and also refine it, by describing precisely the role that structural equivalence plays in the development of the notion of projection. The characterisation we propose yields a definite expression, i.e. a proof term, that describes the projection of an infinitary reduction over another. To illustrate the working of projections, we show how a common reduct of a (possibly infinite) reduction and a single step that makes part of it can be obtained via their respective projections. We show, by means of several examples, that the proposed definition yields the expected behavior also in cases beyond those covered by this result. Finally, we discuss how the notion of limit is used in our definition of projection for infinite reduction

Ideas acerca de una teoría de la demostración para una reconstrucción de razonamientos revocables

David Poole presentó, en (Poole 88). una fonna de reconstruir algunos razonamientos revocables, en particular aquellos que incluyen la aplicación de enunciados de normalidad o defaults del tipo "normalmente, las aves vuelan" o "por lo general, los oficinistas son gente sedentaria". Poole caracteriza a su propuesta como un "marco lógico". En vez de construir una nueva lógica y definir una relación de consecuencia o un concepto de demostración en los que se refleje la relación entre premisas y conclusión de los razonamientos revocables, opta por definir nuevos tipos de relaciones entre fórmulas, fragmentando al conjunto de premisas de acuerdo al aporte que puede hacer cada una en el razonamiento.1 Describiré brevemente la versión simplificada que aparece en (Poole 88)

La regulación del nombre comercial

El nombre comercial es una institución jurídica perteneciente al derecho marcario que, en la práctica, genera confusiones pues se le confunde con la razón social y la denominación social. Al ser institución jurídica, su regulación jurídica se ha ido cimentando en la práctica y con la jurisprudencia, la cual se analiza en el presente artículo

Schmidt's Conjecture and Star Formation in Molecular Clouds

We investigate Schmidt's conjecture (i.e., that the star formation rate scales in a power-law fashion with the gas density) for four well-studied local molecular clouds (GMCs). Using the Bayesian methodology we show that a local Schmidt scaling relation of the form Sigma*(A_K) = kappa x (A_K)^{beta} (protostars pc^{-2}) exists within (but not between) GMCs. Further we find that the Schmidt scaling law, by itself, does not provide an adequate description of star formation activity in GMCs. Because the total number of protostars produced by a cloud is given by the product of Sigma*(A_K) and S'(> A_K), the differential surface area distribution function, integrated over the entire cloud, the cloud's structure plays a fundamental role in setting the level of its star formation activity. For clouds with similar functional forms of Sigma*(A_K), observed differences in their total SFRs are primarily due to the differences in S'(> A_K) between the clouds. The coupling of Sigma*(A_K) with the measured S'(> A_K) in these clouds also produces a steep jump in the SFR and protostellar production above A_K ~ 0.8 magnitudes. Finally, we show that there is no global Schmidt law that relates the star formation rate and gas mass surface densities between GMCs. Consequently, the observed Kennicutt-Schmidt scaling relation for disk galaxies is likely an artifact of unresolved measurements of GMCs and not a result of any underlying physical law of star formation characterizing the molecular gas.Comment: 34 pages, 8 figures, and 2 tables; accepted for publication in ApJ on Sept 23, 201

Choosing the extent of private partipation in public services: a computable general equilibrium perspective

What determines the propensity to reduce or widen the extent of public ownership? Why has there been a propensity to privatize and concede public utilities in the nineties? The answers to these questions depend both on macroeconomic and microeconomic considerations. And correct answers could also help to avoid or prevent inefficient reversals and frustrations that jeopardize reform processes. An alternative perspective, that combines micro and macro arguments, is given by general equilibrium models. The objective of this paper is to explore the rationality of the decision of choosing in an endogenous way the implicit “technologies” of private and state owned operators of utilities in an economy that has fiscal budget and trade balance in equilibrium. The simulations confirm that the choice of the technology to be used for servicing infrastructure depends on deep parameters of efficiency and costs. The model shows that there are plausible scenarios where the selection is not all-or-nothing and that they can coexist. ¿Qué determina la propensión a reducir o extender la propiedad pública? ¿Por qué esa propensión fue mayor en los años noventa? Las respuestas a estas preguntas dependen tanto de consideraciones macroeconómicas como microeconómicas. Respuestas correctas podrían ayudar también a evitar o prevenir reversiones ineficientes y frustraciones que pongan en peligro los procesos de reforma. Una perspectiva alternativa, que combina argumentos micro y macro, viene dada por los modelos de equilibrio general. El objetivo de este trabajo es explorar la racionalidad de la decisión de elegir de manera endógena entre las tecnologías de empresas de servicios públicos privadas y de propiedad estatal, en una economía en la que el presupuesto fiscal y el balance comercial deben estar en equilibrio. Las simulaciones confirman que la elección de la tecnología a ser usada en servicios de infraestructura depende de algunos parámetros profundos de eficiencia y costo. El modelo muestra que hay escenarios plausibles en los que la selección no es excluyente y que ambas tecnologías pueden coexistir

Normalisation for Dynamic Pattern Calculi

The Pure Pattern Calculus (PPC) extends the lambda-calculus, as well as the family of algebraic pattern calculi, with first-class patterns; that is, patterns can be passed as arguments, evaluated and returned as results. The notion of matching failure of the PPC not only provides a mechanism to define functions by pattern matching on cases but also supplies PPC with parallel-or-like, non-sequential behaviour. Therefore, devising normalising strategies for PPC to obtain well-behaved implementations turns out to be challenging. This paper focuses on normalising reduction strategies for PPC. We define a (multistep) strategy and show that it is normalising. The strategy generalises the leftmost-outermost strategy for lambda-calculus and is strictly finer than parallel-outermost. The normalisation proof is based on the notion of necessary set of redexes, a generalisation of the notion of needed redex encompassing non-sequential reduction systems

Comentarios al procedimiento acelerado de refinanciación concursal

Dentro del paquete de normas para hacer frente a la emergencia sanitaria ocasionada por la COVID-19, el Estado creó el Procedimiento acelerado de refinanciación concursal-PARC. Como ha ocurrido con momentos de inminente crisis económica, el Sistema concursal peruano, creado mediante Ley 27809, debe dar alternativas al sector empresarial para  reordenar su situación económico financiera y evitar que sus efectos generen un alto costo social. Este procedimiento llega también en un contexto de reducción considerable de los procesos concursales, derivado de varios factores que no son objeto de análisis del presente trabajo. Por el contrario, consideramos que este es el momento preciso para que el sistema se ponga a prueba y se resalte su verdadera naturaleza: ser instancia de diálogo entre acreedores y deudor. En las siguientes líneas analizaremos exclusivamente el PARC, tomando como base la norma concursal general y dentro de esta el procedimiento que lo inspiró: el procedimiento concursal preventivo. &nbsp

Corrosion resistance evaluation of precipitation hardening stainless steels with nb

Os aços inoxidáveis endurecíveis por precipitação foram desenvolvidos a partir de 1945, em decorrência das necessidades da indústria aeroespacial em termos da disponibilidade de aços com resistência mecânica e à corrosão, em temperaturas mais elevadas, superiores às dos aços inoxidáveis tradicionais, aliadas à facilidade de soldagem. Esses aços apresentam microestruturas martensíticas do tipo substitucional, endurecidas posteriormente por precipitados. Nesse trabalho, foram produzidos dois aços com composições alternativas usando o Nb como formador de precipitados, bem como um aço PH13-8Mo para efeito de comparação, em termos de resistências mecânica e à corrosão. O Aço 1 apresentou resistência à corrosão semelhante à do aço PH13-8Mo e o Aço 2 apresentou resistência mecânica próxima à do aço PH13-8Mo.Precipitate-hardened stainless steel was developed in 1945 as a consequence of the aerospace industry’s need for a high-strength steel that would be resistant to corrosion at high temperatures, and easily welded exceeding the properties of conventional stainless steel. This steel possesses substitutional martensitic microstructures that can afterwards be hardened by precipitation. For this research, two types of steel with alternative compositions were produced by using Nb as a precipitate producer, and PH13-8Mo steel for comparison purposes in terms of mechanical and corrosive resistance. Steel 1 showed corrosive resistance similar to PH13-8Mo and Steel 2 presented mechanical resistance close to that of PH13-8Mo.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP