Convertible Codes: New Class of Codes for Efficient Conversion of Coded Data in Distributed Storage

Erasure codes are typically used in large-scale distributed storage systems to provide durability of data in the face of failures. In this setting, a set of k blocks to be stored is encoded using an [n, k] code to generate n blocks that are then stored on different storage nodes. A recent work by Kadekodi et al. [Kadekodi et al., 2019] shows that the failure rate of storage devices vary significantly over time, and that changing the rate of the code (via a change in the parameters n and k) in response to such variations provides significant reduction in storage space requirement. However, the resource overhead of realizing such a change in the code rate on already encoded data in traditional codes is prohibitively high. Motivated by this application, in this work we first present a new framework to formalize the notion of code conversion - the process of converting data encoded with an [n^I, k^I] code into data encoded with an [n^F, k^F] code while maintaining desired decodability properties, such as the maximum-distance-separable (MDS) property. We then introduce convertible codes, a new class of code pairs that allow for code conversions in a resource-efficient manner. For an important parameter regime (which we call the merge regime) along with the widely used linearity and MDS decodability constraint, we prove tight bounds on the number of nodes accessed during code conversion. In particular, our achievability result is an explicit construction of MDS convertible codes that are optimal for all parameter values in the merge regime albeit with a high field size. We then present explicit low-field-size constructions of optimal MDS convertible codes for a broad range of parameters in the merge regime. Our results thus show that it is indeed possible to achieve code conversions with significantly lesser resources as compared to the default approach of re-encoding

Quantitative Optimisation of Drilling for Brownfields Mineral Exploration

This research presents a novel optimisation framework for brownfields exploration drilling. The proposed optimisation methodology has been developed applying geostatistical methods and modern portfolio theory. The use of conditional simulations ensures that geological uncertainty is taken into account, and the application of Markowitz portfolio theory makes drilling funds allocation optimal. The proposed method closes the gap in current research by incorporating the inherent geological uncertainty of an exploration target and mineral economics

Le système des villes moyennes du sud du chili, vers la construction de nouveaux espaces de relations ?

La question des villes moyennes ou intermédiaires a été largement débattue, en raison de la difficulté à établir leur définition. Les différentes recherches sur les villes moyennes et intermédiaires montrent que le débat sur les concepts est très ouvert et très développé en géographie. Les appréciations des concepts varient selon les pays et selon le rôle que possède chaque ville moyenne à l’intérieur de l'armature urbaine. Il est possible en reliant le concept de ville intermédiaire aux « fo..

A hierarchical, fuzzy inference approach to data filtration and feature prioritization in the connected manufacturing enterprise

In manufacturing, the technology to capture and store large volumes of data developed earlier and faster than corresponding capabilities to analyze, interpret, and apply it. The result for many manufacturers is a collection of unanalyzed data and uncertainty with respect to where to begin. This paper examines big data as both an enabler and a challenge for the connected manufacturing enterprise and presents a framework that sequentially tests and selects independent variables for training applied machine learning models. Unsuitable features are discarded, and each remaining feature receives a crisp numeric output and a linguistic label, both of which are measures of the feature’s suitability. The framework is tested using three datasets employing time series, binary, and continuous input data. Results of filtered models are compared to results obtained by base, unfiltered sets of features using a proposed metric of performance-size ratio. Framework results outperform base feature sets in all tested cases, and the proposed future research will be to implement it in a case study in the electronic assembly manufacture

El estudio de sistemas de ciudades. Una aproximación desde métodos de análisis de redes sociales

Los métodos de análisis de redes sociales son potentes herramientas para la comprensión de elementos que están en relación, estos métodos han traspasado las personas como nodos de análisis y junto a la teoría de grafos, se aplican a otro tipo de actores como ciudades, países y organizaciones. Este artículo, trata a partir del caso del sistema de ciudades de la región de La Araucanía, las aplicaciones y potencialidades de un enfoque de red a los centros urbanos a través del software Pajek. En la primera parte, discutimos elementos relevantes sobre los métodos de análisis de redes sociales, teoría de grafos y ciertos elementos de los sistemas de ciudades. En una segunda parte, se analizan los métodos aplicados, así como sus potencialidades y debilidades. En una tercera parte, se presenta una caracterización del sistema de ciudades de La Araucanía, se discuten los índices de centralidad y de equivalencia estructural analizados. Finalmente, se discuten los aspectos metodológicos y resultados obtenidos a través del caso en análisis, con el objetivo de comprender un sistema de ciudades y de tal forma de poder contribuir la comprensión del grado de cohesión territorial de un territorio

Analysis of territorial patterns of age population structure at the subnational level in Chile

From the evidence obtained in the 2017 Chilean population census pyramid for the country scale, the question arises whether the population structure by age is replicated homogeneously at the subnational level or, on the contrary, it presents heterogeneous local characteristics based on age groups. For each of the third-level subnational units (n=346), the standard deviation of the different age classes was compared in relation to the national population pyramid. With these differences, the k-means method was used to identify eight groups of communes, and four demographic indicators were calculated. The results allow to affirm that the population structure by age and sex at the communal level presents heterogeneous characteristics. The analysis of territorial patterns identified groups of the aging population, households with active aging, transition to aging, adult population, men in terminal productive age, men in initial age, households with children under 15 years and households with children over 15 years