Análisis y optimización de nuevos sistemas determinísticos y estocásticos en gestión de stocks

En el Capítulo 1 se investiga un nuevo modelo EOQ con demanda dependiente del nivel de stock y coste de almacenamiento no lineal con respecto al tiempo de permanencia de los productos en el inventario y la cantidad de productos almacenados. En este contexto, los problemas de minimización de costes y de maximización de beneficios no necesariamente tienen la misma solución óptima. El problema se ha enfocado desde la perspectiva más completa de maximización de beneficios. En el Capítulo 2 se investiga una extensión del problema del newsboy con pedido de emergencia en el cual la fracción de demanda satisfecha con dicho pedido es una función no creciente con respecto al tamaño de la escasez. La función objetivo no es necesariamente convexa, pero se han demostrado resultados teóricos que ayudan a encontrar la solución del problema en casos concretos y a realizar un análisis de sensibilidad de la política óptima.Departamento de Estadística e Investigación Operativ

Antonio Machado y el psicoanálisis.

Sin resumen

Antonio Machado y el psicoanálisis.

Sin resumen

Nota Necrológica: Ronal Laing.

Sin resumen

Nota Necrológica: Ronal Laing.

Sin resumen

Physically and chemically modified starches as texturisers of low-fat milk gels

In reduced fat-milk gels lack of fat globules results in undesirable texture changes. This study evaluates application of chemically modified (E-1412,E-1414,E-1422,E-1442), pregelatinized, and both pregelatinized (PG) and chemically modified (PGE-1414) starches as fat replacers. Skimmed milk was substituted with 2% of each starch. The pH and rheological evolution during the acidification process, viscosity of the stirred gels, texture of the set gels and syneresis of all gels were measured. Skimmed and full-fat milk gels were included as controls. All starches had lower or higher pH values, than skimmed or full fat milk gels during acidification. Gelation time was reduced for all starches compared to the skimmed milk gel. For both stirred and set milk gels, with PG, PGE-1414, E-1422 and E-1442 had viscosity/texture values similar or higher to those found for full fat milk gel. For syneresis, E-1412 had drastically increased values when compared with both controls.  Spanish Ministry of Economy and Competitiveness (Project AGL2014-52928-C2)European Regional Development Fund (FEDER

Carbon content of forest floor and mineral soil in Mediterranean Pinus spp. and Oak stands in acid soils in Northern Spain

Aim of study: The aim of the study was to determine the baseline carbon stock in forest floor and mineral soils in pine and oak stands in acid soils in Northern Spain.Area of study: The study area is situated in northern Spain (42° N, 4° W) on “Paramos y Valles” region of PalenciaMaterial and methods: An extensive monitoring composed of 48 plots (31 in pine and 17 in oak stands) was carried out. Litter layers and mineral soil samples, at depths of 0-30 cm and 30-60 cm, were taken in each plot. An intensive monitoring was also performed by sampling 12 of these 48 plots selected taken in account species forest composition and their stand development stage. Microbial biomass C (CMB), C mineralization (CRB), and soil organic C balance at stand level were determined in surface soil samples of intensive monitoring.Main results: No differences in soil C content were detected in the two forest ecosystems up to 60 cm depth (53.0±25.8 Mg C ha-1 in Pinus spp. plantations and 60.3±43.8 Mg C ha-1 in oak stands). However, differences in total C (CT), CMB and CRB were found in the upper 10 cm of the soils depending on the stand development stage in each species forest composition (Pinus nigra, Pinus pinaster, Pinus sylvestris and Quercus pyrenaica). Plots with high development stage exhibited significant lower metabolic quotient (qCO2), so, meant more efficient utilization of C by the microbial community. The C content in the forest floor was higher in pine stands (13.7±0.9 Mg C ha-1) than in oak stands (5.4±0.7 Mg C ha-1). A greater turnover time was found in pine ecosystems vs. oak stands. In contrast, forest floor H layer was nonexistent in oak stands.Research highlights: Results about litterfall, forest floor and mineral soil dynamics in this paper can be used strategically to reach environmental goals in new afforestation programs and sustainable forest management approaches.Keywords: C stocks; pine; Quercus pyrenaica; litter; metabolic quotient (qCO2)

Multinomial logit estimation of a diameter growth matrix model of two Mediterranean pine species in Spain

Understanding diameter growth of the Mediterranean pine species is fundamental for evaluating and making appropriate strategic decisions in forest management. A matrix diameter growth model for two Mediterranean pine forest ecosystems in Spain has been developed. Methods Multinomial logistic (MNL) regression was employed to estimate the transition probabilities of a matrix growth model. The model combines individual tree and stand attributes and explores the effects of independent variables and their relationships with tree size and the probabilities of stand diameter growth. The aim was to predict growth of individual trees by diameter class for a 5-year period. Results MNL model results for diameter growth gave better predictions for Maritime pine (Pinus pinaster Aiton) than for Scots pine (Pinus sylvestris L.). Stand simulations showed that diameter growth probabilities depended on productivity and stand density. Stand simulations under fixed conditions showed that the probabilities of diameter growth increased as site productivity increased and decreased with increased stand density index. Conclusions This study demonstrates the usefulness of matrix growth models as tools to predict growth in Mediterranean pine forests. Stand density and site productivity are key factors in explaining Scots pine and Maritime pine forest growth in the study area.Instituto Universitario de Gestión Forestal Sostenibl