Spare Parts And Maintenance Optimization In A Mobile Telephone Company

(WP12/02 Clave pdf) Telecommunication companies depend on high availability of equipment to maintain service quality. In cellular communications electronic cards maintenance is basically reduced to exchanging parts as they fail. These parts are geographically dispersed in unmanned locations. Spares and maintenance policies are thus interrelated and tend to follow multiechelon configurations, following the architecture of the physical network. We describe the optimization of spare parts and maintenance policies performed by the Venezuelan mobile phone operator Movilnet.Mobile phone, MRO, Multi-echelon inventory systems, Spare parts optimization

Logistics Strategies And Practices In Venezuela

(WP11/02 Clave pdf) This paper presents an empirical and statistical analysis identifies the key characteristics and opportunities of logistics in Venezuela. Among the key findings are conservative approaches to logistics in a protected market whose environment is changing faster than preferred by the responsible actors, limiting the application of modern logistics practices. This and other considerations, such as geographical location, production of commodities and the identification in the strategy of the firms of the need for better logistics practices indicate important opportunities for the application of modern logistics practices.Conservative approaches, Logistics in Venezuela, Modern logistics practices

Enterprise Systems Analysis and Modelling

In ES implementations, process modelling is a critical and often overlooked activity. This paper proposes a framework for process modelling of ES. The four steps method involves: Current Situation Analysis, Business Process Improvements and Requirements, Gap Analysis, and To-be process to develop. Outputs of the methodology are an interdependent set of organizational and system proposed changes, and feedback loops to the ES vendors and to the strategy of the firm. In-depth case studies and extensive literature review provides methodological support. For practitioners, this study provides useful insights into one of the reasons by which companies could be frustrated with ES implementation.E-business, ERP

Estudio comparativo del nivel de riesgo entre los cultivos de granos, frutales y hortalizas, 1980-2003

Este artículo presenta un estudio comparativo de la varianza del ingreso entre tres grupos de productos agrícolas, granos, frutales y hortalizas, a partir del empleo de la metodología de conformación de portafolios de inversión. Cada grupo de cultivos fue considerado como una cartera de inversión. Se observó que la variación del ingreso en frutales y hortalizas es mayor que la de granos para el periodo en estudio; por ejemplo, la varianza estimada para los cultivos de granos resultó de 0.1498, de 0.5374 en frutales y de 0.1604 en hortalizas. Por lo tanto, se sostiene que la inversión en la producción de frutales y hortalizas resulta más riesgosa en comparación con la realizada en granos.Este artículo presenta un estudio comparativo de la varianza del ingreso entre tres grupos de productos agrícolas, granos, frutales y hortalizas, a partir del empleo de la metodología de conformación de portafolios de inversión. Cada grupo de cultivos fue considerado como una cartera de inversión. Se observó que la variación del ingreso en frutales y hortalizas es mayor que la de granos para el periodo en estudio; por ejemplo, la varianza estimada para los cultivos de granos resultó de 0.1498, de 0.5374 en frutales y de 0.1604 en hortalizas. Por lo tanto, se sostiene que la inversión en la producción de frutales y hortalizas resulta más riesgosa en comparación con la realizada en granos

Scaling of distributions of sums of positions for chaotic dynamics at band-splitting points

The stationary distributions of sums of positions of trajectories generated by the logistic map have been found to follow a basic renormalization group (RG) structure: a nontrivial fixed-point multi-scale distribution at the period-doubling onset of chaos and a Gaussian trivial fixed-point distribution for all chaotic attractors. Here we describe in detail the crossover distributions that can be generated at chaotic band-splitting points that mediate between the aforementioned fixed-point distributions. Self affinity in the chaotic region imprints scaling features to the crossover distributions along the sequence of band splitting points. The trajectories that give rise to these distributions are governed first by the sequential formation of phase-space gaps when, initially uniformly-distributed, sets of trajectories evolve towards the chaotic band attractors. Subsequently, the summation of positions of trajectories already within the chaotic bands closes those gaps. The possible shapes of the resultant distributions depend crucially on the disposal of sets of early positions in the sums and the stoppage of the number of terms retained in them

De la recesión a la recuperación: Producción y empleo en México y el Estado de México

El objetivo de este documento es medir la magnitud y analizar las causas de la caída e incremento de la producción y del empleo sectoriales de México y del Estado de México durante el ciclo económico internacional en curso. Nuestros resultados principales son: 1) el comercio exterior ha desempeñado un papel central en la caída y recuperación del empleo y la producción a lo largo del ciclo completo, en tanto que la inversión extranjera directa y las remesas solamente han sido determinantes en la fase recesiva; 2) las fluctuaciones de la producción industrial y manufacturera son mayores que las del sector servicios y todas ellas superan a las del empleo; 3) ha habido una recomposición del empleo a favor del eventual, especialmente en el sector terciario, incluso durante la expansión

Prescriptive Analytics in Electricity Markets

Electricity markets are a clear example of a sector in which decision making plays a crucial role in its daily activity. Moreover, uncertainty is intrinsic to electricity markets and affects most of the tasks that agents operating in them must carry out. Many of these tasks involve decisions characterized by low risk and being addressed periodically. In this thesis, we refer to these tasks as iterative decisions. This thesis applies the aforementioned innovative frameworks for decision making under uncertainty using contextual information in iterative decision making tasks faced daily by electricity market agents.Decision making is critical for any business to survive in a market environment. Examples of decision making tasks are inventory management, resource allocation or portfolio selection. Optimization, understood as the scientific discipline that studies how to solve mathematical programming problems, can help make more efficient decisions in many of these situations. Particularly relevant, because of their frequency and difficulty, are those decisions affected by uncertainty, i.e., in which some of the parameters that precisely determine the optimization problem are unknown when the decision must be made. Fortunately, the development of information technologies has led to an explosion in the availability of data that can be used to assist decisions affected by uncertainty. However, most of the available historical data do not correspond to the unknown parameter of the problem but originate from other related sources. This subset of data, potentially valuable for obtaining better decisions, is called contextual information. This thesis is framed within a new scientific effort that seeks to exploit the potential of data and, in particular, of contextual information in decision making. To this end, in this thesis, we have developed mathematical frameworks and data-driven optimization models that exploit contextual information to make better decisions in problems characterized by the presence of uncertain parameters

Effects of the Great Recession on state output in Mexico

This paper investigates the effects of a battery of variables on total and sector output drops in the Mexican states during the Great Recession by estimating spatial and cross-section regression models. Our main results can be summarized as follows. First, there is evidence of spatial autocorrelation only in the case of total production and it seems to be negative, which does not support the hypothesis of in - terstate transmission of the recession. Second, total and sector production falls can be explained by the specialization in the production of tradable (mainly durable) goods. Third, exposure to external shocks plays an important role in the cases of industrial and services production, but not in total output. Fourth, there seems to be that federal fiscal policy has actually been pro-cyclical while state fiscal policies have contributed to mitigate the recession