The derivation of performance expressions for communication protocols from timed Petri net models

Petri Net models have been extended in a variety of ways and have been used to prove the correctness and evaluate the performance of communication protocols. Several extensions have been proposed to model time. This work uses a form of Timed Petri Nets and presents a technique for symbolically deriving expressions which describe system performance. Unlike past work on performance evaluation of Petri Nets which assumes a priori knowledge of specific time delays, the technique presented here applies to a wide range of time delays so long as the delays satisfy a set of timing constraints. The technique is demonstrated using a simple communication protocol

Yield gaps and nutrients use efficiency of apple tree (golden delicious/MM106) in the middle Atlas Mountains of Morocco

The main objective of this work was to evaluate use efficiency of nitrogen, phosphorus, potassium, calcium and magnesium in adult apple orchards in the Middle Atlas of Morocco and to establish preliminary reference norms for fertilizing this crop under local conditions. The study was based on soil and leaf analysis and data with regard to farming practices and yield on forty apple orchards (cv. Golden delecious/MM106) where nineteen are growing on silty-clay soil and twenty-one on sandy-loam soil. The results showed significant correlations between leaf content for each nutrient and yield level following polynomial equations, thereby indicating local reference norms for apple leaf analysis. Moreover, correlations were significant between leaf and soil contents that permitted to determine apple needs in nitrogen fertilizer and references norms for soil richness in phosphorus, potassium, calcium and magnesium to obtain yield potential in the study region. However, the found norms are less than International standards because of feebleness of yield level in the study region, largely related to deficient cultural practices adopted by farmers. In addition, investigation of leaf nutrients ratios N/K, N/Ca, K/Ca, K/Mg and Ca/Mg showed that there was disharmony in uptake of these nutrients originating particularly from high soil richness in Ca and Mg. Taking into account these considerations, the found references norms can be applied only under the adopted farming practices. Nevertheless, by improving local practices, reference values may change

Structural, magnetic and magnetocaloric study of Ni0.5Zn0.5Fe2O4 spinel

International audienc

Structural, magnetic and magnetocaloric study of Ni0.5Zn0.5Fe2O4 spinel

International audienc

Evaluation de la variabilité spatiotemporelle dans un verger d’olivier à travers des images multispectrales prises par un drone

Precision Agriculture (PA) is a management strategy based on Information and Communication Technologies (ICT) used to assist management decisions with the aim to increase productivity, to reduce labor time and inputs needed, to improve benefits and to protect the environment. Techniques related to PA were initially used to monitor status of annual crops and they were recently adopted on fruit trees. Nevertheless, PA is still in its initiation phase in Morocco. Given the importance of olive in the national and international levels, applying this concept in the intensive and hyper-intensive production systems would be a reliable and cost-effective approach for the assessment of orchards health and nutritional status and then make reliable decisions. With the aim to assess the potential of multi-spectral images to inform on temporal and spatial variability characterizing an olive orchard, this study was carried out in an orchard of 22 ha, in Meknes region, Morocco, planted principally with “Picholine marocaine” variety. Four Unmanned Aerial Vehicle (UAV) flights, from June to November 2020, were performed and three vegetation indices (VIs) were computed: NDVI, GNDVI and NDRE. Spatial variability was assessed using variogram, a geostatistical tool, and temporal variability was evaluated using Spearman rank correlation and relative difference methods. The three VIs showed a weak temporal and spatial stability of trees which indicate an overall unstable canopy condition related to tree physiological behavior and environmental conditions (temperature and rainfall). Additionally, the observation of a potential stress was recorded firstly by NDRE, followed by NDVI and GNDVI. Results show promising perspectives of using remote sensing techniques to assess olive trees status and therefore support farmers in orchards management. Such challenge requires more in-depth work to develop in house models correlating VIs to agronomical parameters.L’agriculture de précision (AP) est un concept, basé sur les technologies de l’information et de communication (TIC), qui conjugue à la fois des objectifs agronomiques (amélioration du rendement et de la qualité des produits), économiques (minimisation des coûts de production) et environnementaux (meilleure utilisation des intrants). Les techniques relevant de l’AP ont été utilisées au premier abord sur les grandes cultures, mais ont été vite adoptées en arboriculture fruitière. Au Maroc, le recours à ce nouveau concept reste limité et encore moins au niveau de l’olivier. Etant donné l’importance de cette culture, tant à l’échelle nationale qu’internationale, le recours à l’AP comme moyen d’aide à la décision pour une gestion raisonnée et efficiente des vergers d’olivier; conduits en intensif et semi intensif; présente une approche prometteuse pour l’oléiculture marocaine. Le présent travail consiste à étudier le potentiel des images multispectrales pour déceler la variabilité spatiotemporelle pouvant caractériser un verger d’olivier. L’étude a été menée dans une oliveraie de 22 ha dans la région de Meknès, plantée par la variété « Picholine marocaine ». A partir des images multispectrales, prises sur 4 survols de drone (de juin à novembre), trois indices de végétation (IV) : NDVI, GNDVI et NDRE ont été dérivés. La variabilité spatiale a été évaluée à l'aide du variogramme, un outil géostatistique, alors que la variabilité temporelle a été évaluée à l'aide des méthodes de corrélation de Spearman Rank et des différences relatives. Les trois IVs ont montré une faible stabilité temporelle et spatiale au niveau du verger; une instabilité liée au comportement physiologique des arbres (la canopée particulièrement) et aux conditions environnementales (température et précipitations). En plus, la présence d’un stress potentiel a été enregistrée d'abord par le NDRE, puis par le NDVI et le GNDVI. Les résultats montrent des perspectives prometteuses d'utilisation des images multispectrales dans le cas des oliviers et invitent à un travail plus approfondi pour développer des modèles corrélant les IVs aux paramètres agronomiques qu’il serait utile de suivre