Wick polynomials and time-evolution of cumulants

We show how Wick polynomials of random variables can be defined combinatorially as the unique choice which removes all "internal contractions" from the related cumulant expansions, also in a non-Gaussian case. We discuss how an expansion in terms of the Wick polynomials can be used for derivation of a hierarchy of equations for the time-evolution of cumulants. These methods are then applied to simplify the formal derivation of the Boltzmann-Peierls equation in the kinetic scaling limit of the discrete nonlinear Schr\"{o}dinger equation (DNLS) with suitable random initial data. We also present a reformulation of the standard perturbation expansion using cumulants which could simplify the problem of a rigorous derivation of the Boltzmann-Peierls equation by separating the analysis of the solutions to the Boltzmann-Peierls equation from the analysis of the corrections. This latter scheme is general and not tied to the DNLS evolution equations

Derivation of the linear Landau equation and linear Boltzmann equation from the Lorentz model with magnetic field

We consider a test particle moving in a random distribution of obstacles in the plane, under the action of a uniform magnetic field, orthogonal to the plane. We show that, in a weak coupling limit, the particle distribution behaves according to the linear Landau equation with a magnetic transport term. Moreover, we show that, in a low density regime, when each obstacle generates an inverse power law potential, the particle distribution behaves according to the linear Boltzmann equation with a magnetic transport term. We provide an explicit control of the error in the kinetic limit by estimating the contributions of the configurations which prevent the Markovianity. We compare these results with those ones obtained for a system of hard disks in \cite{BMHH}, which show instead that the memory effects are not negligible in the Boltzmann-Grad limit.Comment: 22 pages, 4 figures in Journal of Statistical Physics 201

A Symbolic Execution Algorithm for Constraint-Based Testing of Database Programs

In so-called constraint-based testing, symbolic execution is a common technique used as a part of the process to generate test data for imperative programs. Databases are ubiquitous in software and testing of programs manipulating databases is thus essential to enhance the reliability of software. This work proposes and evaluates experimentally a symbolic ex- ecution algorithm for constraint-based testing of database programs. First, we describe SimpleDB, a formal language which offers a minimal and well-defined syntax and seman- tics, to model common interaction scenarios between pro- grams and databases. Secondly, we detail the proposed al- gorithm for symbolic execution of SimpleDB models. This algorithm considers a SimpleDB program as a sequence of operations over a set of relational variables, modeling both the database tables and the program variables. By inte- grating this relational model of the program with classical static symbolic execution, the algorithm can generate a set of path constraints for any finite path to test in the control- flow graph of the program. Solutions of these constraints are test inputs for the program, including an initial content for the database. When the program is executed with respect to these inputs, it is guaranteed to follow the path with re- spect to which the constraints were generated. Finally, the algorithm is evaluated experimentally using representative SimpleDB models.Comment: 12 pages - preliminary wor

Making the Rerum vulgarium fragmenta

The collection of lyric poems that Petrarch worked on for nearly forty years reflects, through successive stages of composition, his evolving poetic and philosophical values. The genesis of the collection, the stratification of its many forms and stages, and its gradually emerging status as Petrarch's crowning achievement have all been studied since the sixteenth century and retraced by many modern scholars, especially after the fundamental reconstruction of the internal history of the text by Ernest Hatch Wilkins and its refinement by Marco Santagata, H. Wayne Storey, and Arnaldo Soldani. In addition to drawing on information from Petrarch's biography and other works, scholars have also made use of the direct testimony of the author, including statements in his letters to Ludwig van Kempen in 1351 (Fam. I.1) and to Pandolfo Malatesta in 1373 (Sen. XIII.11), drafts and marginal notes, and erasures in the final version of the work, which is the basis of what we read today. Petrarch's RVF, along with its contemporary, Boccaccio's Decameron, is the first classical work of Italian literature whose diffusion originates with an autograph; that is, a copy, or rather a series of copies, written in the hand of the author himself. This copy is known as the Vat. Lat. 3195 codex. It is a parchment volume measuring 27 × 20.3 cm, comprising seventy-three pages, and written in semi-gothic script, in part by Petrarch and mainly by his trusted copyist Giovanni Malpaghini, who was in his service from 1364 to April 1367. According to most authorities, the manuscript was completed by Petrarch himself shortly before his death. Besides its philological and linguistic features, it is particularly important due to its status as an “authorial book”; that is to say, Petrarch himself saw to the disposition of the single poems and to the ordering and formatting of the collection. Among the most important paratextual features are the title, “Francisci Petrarche laureati poete Rerum vulgarium fragmenta,” written in Malpaghini's hand in a rubric on f. 1r; the white pages separating the first and the second parts of the collection; and the initial letters of the first sonnet and of canzone 264, “I’ vo’ pensando” (“I go thinking”), painted in red on a golden background with floral ornamentation

Établissement de la stratégie et du modèle d'affaire de la Junior Entreprise de la Haute École de Gestion et Tourisme de Sierre pour entrer sur le marché valaisan

En juillet 2015, la Junior Entreprise de la Haute École de Gestion et Tourisme de Sierre a été créée dans le but d'apporter une possibilité aux étudiants de pouvoir acquérir une expérience professionnelle durant et en relation avec leur formation. Pour ce faire, elle offre aux entreprises des prestations en relation avec les domaines d'économie d'entreprise, informatique de gestion et tourisme. Le présent travail a pour principal objectif d'étudier la stratégie d'implantation idéale pour une telle organisation à but non lucratif en Valais. En tant que première association de ce type dans le canton, elle a besoin de mener une étude sur son environnement afin d'avoir un business model adéquat lui permettant de développer son activité dans le futur

Mezclas asfálticas semicalientes elaboradas con aditivos tensoactivos: estudios comparativos del comportamiento mecánico respecto a las mezclas en caliente convencionales

Considerando las implicancias ambientales en la fabricación de mezclas asfálticas en caliente se han desarrollado tecnologías para reducir las temperaturas de trabajo de manera de generar significativos ahorros de energía, menores emisiones y mayor nivel de seguridad en obra. Las mezclas que utilizan asfaltos modificados con polímeros o asfaltos especiales como ligantes hacen posible la reducción de las temperaturas de trabajo sin afectar significativamente las propiedades mecánicas y de adherencia. Sin embargo, cuando se fabrican mezclas con asfaltos convencionales la reducción de las temperaturas de trabajo implican directamente un importante desmedro de la calidad, aún cuando sea posible obtener las densidades de diseño. El presente estudio se enfoca en dos aditivos del tipo tensoactivos que fueron incorporados en diferentes tipos de cemento asfáltico para fabricar mezclas semicalientes (WMA), trabajando con sustanciales reducciones de temperatura, de 35 a 55ºC. Los resultados muestran que en todos los casos se presenta una merma en las prestaciones de la mezcla respecto de la mezcla de referencia, asimismo algunos ensayos evidencian más fehacientemente el efecto de la disminución de las temperaturas de fabricación, tales como los ensayos de daño por humedad. Se concluye que, para este fin, los ensayos de daño inducido por humedad son indudablemente métodos muy adecuados para definir rangos aceptables de reducción de las temperaturas para la fabricación de mezclas semicalientes.Considering the environmental implications in the use of HMA (hot mix asphalt), new technologies have been developed in order to reduce the mixing and compaction temperatures and consequently to save energy, to cut emissions and to improve safety during the construction tasks. Polymer modified and non-conventional asphalt binders make it possible to reduce laying and compaction temperatures down to a limit which does not necessarily affect the performance of the hot mixtures. Nevertheless, when it comes to conventional asphalt binders a reduction in temperature –i. e., temperatures below the usual ones- result in an apparent reduction in quality, even when the design densities was reached. This research focuses on two surfactant additives which were incorporated into different types of cement ashpalts in order to manufacture warm mix-asphalts (WMA). In our research we have worked with substantial reductions in temperature, from 35 to 55ºC. The results show, without exception, a decrease in the performance of the mixture when compared with the HMA (T1) control specimens, besides, some tests are more suitable tools to prove the effect of temperature reduction, as it happens with moistureinduced damage tests. We may conclude, along this line of thought, that moisture-induce damage tests are undoubtedly a suitable method to define the acceptable range in temperature reduction for warm mixtures design

Nuevas mezclas asfálticas tibias con reciclado: un enfoque sustentable dentro del medio vial

Debido a las implicancias ambientales en la fabricación de mezclas asfálticas en caliente (HMA en inglés) se han desarrollado tecnologías con la finalidad de reducir las temperaturas de producción y pavimentación que permiten disminuir la cantidad de energía requerida respecto a las mezclas asfálticas en caliente (HMA), reducir las emisiones de CO2 y olores durante la elaboración, menores gastos de combustible, mejorar las condiciones de seguridad para los obreros en la planta y en obra y mantener un nivel aceptable de desempeño durante la vida útil del pavimento. Sin embargo esta reducción de temperaturas no debe traer aparejado problemas durante la elaboración así como en el desempeño final de la mezcla. Otro aspecto favorable para con el medio ambiente y el ahorro de materiales vírgenes es la utilización dentro de mezclas nuevas de reciclados de pavimentos conocidos como RAP. El objeto del presente trabajo es compartir los resultados obtenidos en la búsqueda de mezclas asfálticas que combinen las técnicas enunciadas precedentemente y que permitan la fabricación de pavimentos flexibles de alta calidad aunando las ventajas de reciclabilidad y de trabajabilidad, mejorando la huella de carbono de todo el proceso, debido al menor consumo energético y el menor tenor de emisiones al ambiente