Maritime pine (Pinus pinaster Ait.) is one of the most important timber species in Asturias and more generally in northwest Spain. A dynamic growth model has recently been developed for this species and region, allowing computation of the merchantable volume by two alternative methods: a disaggregation system and a stand volume ratio function. The model enables optimization of the management schedule for the species by modifying the rotation age and the number, intensity, and timing of thinning operations. The two methods of volume estimation were compared in optimization by using the depth-first search (DFS) method, and both were found to provide similar results. Because the stand volume ratio function is computationally much more efficient, it was used in the next step, in which five direct search methods were tested: Hooke and Jeeves method (HJ); differential evolution (DE); particle swarm optimization (PS); evolution strategy (ES); Nelder and Mead method (NM); the last four are population-based methods. The HJ and DE methods yielded the highest values of the objective function, slightly outperforming the results of DFS in most cases, which proved to be about 100 times slower than HJ and 30 times slower than DE. DE was more stable than HJ (standard deviation was €30.6·ha −1 for HJ and €8.8·ha −1 for DE) and was therefore used for subsequent evaluation of the effects of site quality, stem density, and discount rate on the optimal management schedule. Rotation age and timing of thinnings both decreased as site quality and discount rate increased. The optimal management schedules often included three heavy thinning operations. The pseudo-code of the optimization methods tested is provided in an Appendix.Résumé : Le pin maritime (Pinus pinaster Ait.) est une des plus importantes espèces forestières des Asturies et, plus généralement, du nord-ouest de l'Espagne. Un modèle de croissance dynamique, récemment mis au point pour cette espèce dans cette région, permet de calculer le volume marchand de deux façons : à l'aide d'un système de désagrégation ou d'une fonction du rapport de volume d'un peuplement. Le modèle permet d'optimiser le calendrier d'aménagement des espèces en modifiant l'âge de rotation ainsi que le nombre, l'intensité et le calendrier des opérations d'éclaircie. Les deux méthodes d'estimation du volume ont été comparées après optimisation en utilisant la recherche priorisant la profondeur (RPP) et elles ont produit des résultats semblables. Parce que la fonction du rapport de volume d'un peuplement est associée à des calculs beaucoup plus efficaces, elle a été utilisée à l'étape suivante qui consistait à tester cinq méthodes de recherche directe (la méthode de Hooke et Jeeves, HJ; l'évolution différentielle, ED; l'optimisation par essaim de particules, EP; la stratégie d'évolution, SE; et la méthode de Nelder et Mead, NM; les quatre dernières méthodes sont fondées sur les populations). Les méthodes de Hooke et Jeeves et d'évolution différentielle ont produit les plus grandes valeurs de la fonction ob...
Mild traumatic brain injury (MTBI) is a common cause of short-term cognitive disturbances in children that rarely are related to objective neurophysiological markers. With the aim of correlating cognitive processing with event-related brain potential variation, visual Continuous Performance Tests (CPT) were administered to 15 children with MTBI and a matched control group. All the patients had suffered post-traumatic loss of consciousness lasting less than 15 minutes, and they were evaluated within 5-to-15 days post-trauma. A few additional neuropsychological tests were also administered to both groups. Behavioral results showed that the injured children achieved poorer scores for phonological and verbal fluency tasks and no interference effect in a computerized version of the Stroop test. They had fewer correct responses on CPT-AX, where a warning signal preceded targets. The N90, P240 and P390 ERP components varied significantly between groups while performing CPT-AX. Present findings could be interpreted as reflecting disturbances that impede injured children from using contextual information efficiently. The higher amplitude of the slow late positivity observed in the control group might reflect updating memory preparatory processes that could increase subsequent cognitive operational competence. The ERP assessment could be helpful to demonstrate early neurophysiological disturbances subsequent to a MTBI in children.
Background Forest management planning involves deciding which silvicultural treatment should be applied to each stand and at what time to best meet the objectives established for the forest. For this, many mathematical formulations have been proposed, both within the linear and non-linear programming frameworks, in the latter case generally considering integer variables in a combinatorial manner. We present a novel approach for planning the management of forests comprising single-species, even-aged stands, using a continuous, multi-objective formulation (considering economic and even flow) which can be solved with gradient-type methods. Results The continuous formulation has proved robust in forest with different structures and different number of stands. The results obtained show a clear advantage of the gradient-type methods over heuristics to solve the problems, both in terms of computational time (efficiency) and in the solution obtained (effectiveness). Their improvement increases drastically with the dimension of the problem (number of stands). Conclusions It is advisable to rigorously analyze the mathematical properties of the objective functions involved in forest management planning models. The continuous bi-objective model proposed in this paper works with smooth enough functions and can be efficiently solved by using gradient-type techniques. The advantages of the new methodology are summarized as: it does not require to set management prescriptions in advance, it avoids the division of the planning horizon into periods, and it provides better solutions than the traditional combinatorial formulations. Additionally, the graphical display of trade-off information allows an a posteriori articulation of preferences in an intuitive way, therefore being a very interesting tool for the decision-making process in forest planning.
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