Prevision des ventes et efficacite des chaines logistiques - Essai de modelisation -

Le but de ce travail est un essai d’analyse du rôle effectif de certaines méthodes de prévision des ventes  dans la gestion d’une fonction très importante de l’entreprise, représentée par la gestion des chaines logistiques. Il s’agit aussi de clarifier le mode d’utilisation des données de prévision, dans la modélisation mathématique des  chaines logistiques, qui se distinguent par la multiplicité des objectifs. L’application de ces méthodes se fera dans une entreprise algérienne (la laiterie de RIO) spécialisée dans la production du yaourt. On étudiera les caractéristiques de la production et on estimera les ventes hebdomadaires en utilisant la méthode de Box et Jenkins. La modélisation des chaines logistiques se fera grâce à la méthode du «compromise programming». Ces méthodes et les résultats obtenus seront proposés aux responsables de la laiterie Rio pour les aider dans  la gestion stratégique de l’entreprise et plus précisément la chaine logistique des produits.LES MOTS CLES : Prévision, ventes, chaines logistiques, modélisation mathématique,méthodes multicritères

The relationship of job satisfaction to some organizational variables (A field study on postal workers in Oran)

هدفت هذه الدراسة إلى التعرف على مدى مساهمة بعض المتغيرات التنظيمية في تحقيق الرضا الوظيفي لدى عينة من عمال البريد بمدينة وهران. وذلك انطلاقا من إشكالية مفادها: هل تساهم المتغيرات التنظيمية (الأجر، نمط الإشراف، العلاقة مع الزملاء، الظروف الفيزيقية) في تحقيق الرضا الوظيفي لدى عمال البريد بمدينة وهران؟ واعتمد في هذه الدراسة على المنهج الوصفي الذي يلاءم موضوع البحث، أما أداة جمع المعلومات فكانت الاستبيان الذي صمم خصيصا لغرض الدراسة، وبعد التأكد من صدقه وثباته، تم تطبيقه على عينة قوامها 49 فردا من عمال البريد بمدينة وهران. وقد توصلت الدراسة إلى النتائج التالية: يساهم كل من متغير: نمط الإشراف، العلاقة مع الزملاء، الظروف الفيزيقية في تحقيق الرضا الوظيفي لدى عمال البريد بمدينة وهران. بينما لا يساهم متغير الاجر في تحقيق الرضا الوظيفي لديهم.This study aimed at identifying the extent to which some organizational variables contributed to achieving job satisfaction among a sample of postal workers in Oran. The study relied on the descriptive approach to the subject matter, and the information-gathering tool was the questionnaire designed specifically for the purpose of the study, after verifying its authenticity, the questionnaire was applied to a sample of 49 postal workers in Oran City. The study found the following findings: Each variable: pattern of supervision, relationship with colleagues, and physical conditions contribute to achieving in functional satisfaction with the postal workers in Oran city. The "remuneration" variable does not contribute to their job satisfaction

Hemicelluloses based fillers for papermaking industry

Résumé confidentielRésumé confidentie

Financial development, trade openness and economic growth in MENA countries: TYDL panel causality approach

This paper examines the causal relationship between financial development (measured as Kaopen index and Line and Milesi-Ferreti index), trade openness and economic growth for 16 MENA countries within the panel co-integration techniques, panel VAR model and TYDL (Toda, Yamamoto, Dolado and Lutkepohl) Granger causality (1996), the empirical results show that both of finance-led growth and trade-led growth hypothesis seem to be rejected for the group as a whole. The results imply that financial development and trade liberalization do not seem to have made a significant impulse on economic growth for the period 1980-2014

Vínculos de volatilidad entre precios de productos agrícolas, precios del petróleo y tipo de cambio del dólar estadounidense

URL del artículo en la web de la Revista: https://www.upo.es/revistas/index.php/RevMetCuant/article/view/2700This study examines the dynamic nexus betwixt oil prices, twenty-two world agricultural commodity prices and given the evolution of the relative strength of the US dollar in a panel setting. We use panel cointegration and Panel Granger causality methods for a panel of twenty-two agricultural products based on annual observations ranging from 1980 to 2015. The empirical results provide a strong evidence of long-term relationship between Agricultural Commodity Prices, Oil Prices and Real USD Exchange Rate. Contrary to the findings of many studies in the literature that report neutrality of agricultural prices to oil price changes, we find strong support of bi-directional causal linkages among Agricultural Commodity Prices, Oil Prices and Real USD Exchange Rate. The long-run causality analysis thereby implies that the oil prices and the dollar have a predictive power to forecast the agricultural prices, which could be a good tool to prioritize the allocation of resources across industries to ensure agricultural scenario in general and economic outcomes.Este estudio examina la relación dinámica entre los precios del petróleo del mundo y veintidós precios de las materias primas agrícolas del mundo que explican cambios en la fuerza relativa del dólar estadounidense en un panel. Empleamos los métodos del cointegración de panel y de la causalidad de Granger para un panel de veintidós productos agrícolas basados en las observaciones anuales que se extienden de 1980 a 2015. Los resultados empíricos proporcionan una prueba evidente de la relación a largo plazo entre los precios de las materias primas agrícolas, los precios del petróleo y el tipo de cambio real del dólar estadounidense. Al contrario de los hallazgos en muchos estudios en la literatura que exponen la neutralidad de los precios agrícolas frente a los cambios en el precio del petróleo, nosotros encontramos un fuerte respaldo a la existencia de acoplamientos causales bidireccionales entre precios de las materias primas agrícolas, precios del petróleo y el tipo de cambio real del dólar estadounidense. El análisis a largo plazo de la causalidad, de este modo, implica que los precios del petróleo y del dólar tienen un poder profético para prever los precios agrícolas, que podrían ser una buena herramienta para priorizar la asignación de recursos a través de industrias para asegurar el escenario agrícola en general y los resultados económicosUniversidad Pablo de Olavid

Volatility Linkages between Agricultural Commodity Prices, Oil Prices and Real USD Exchange Rate || Vínculos de volatilidad entre precios de productos agrícolas, precios del petróleo y tipo de cambio del dólar estadounidense

This study examines the dynamic nexus betwixt oil prices, twenty-two world agricultural commodity prices and given the evolution of the relative strength of the US dollar in a panel setting. We use panel cointegration and Panel Granger causality methods for a panel of twenty-two agricultural products based on annual observations ranging from 1980 to 2015. The empirical results provide a strong evidence of long-term relationship between Agricultural Commodity Prices, Oil Prices and Real USD Exchange Rate. Contrary to the findings of many studies in the literature that report neutrality of agricultural prices to oil price changes, we find strong support of bi-directional causal linkages among Agricultural Commodity Prices, Oil Prices and Real USD Exchange Rate. The long-run causality analysis thereby implies that the oil prices and the dollar have a predictive power to forecast the agricultural prices, which could be a good tool to prioritize the allocation of resources across industries to ensure agricultural scenario in general and economic outcomes. || Este estudio examina la relación dinámica entre los precios del petróleo del mundo y veintidós precios de las materias primas agrícolas del mundo que explican cambios en la fuerza relativa del dólar estadounidense en un panel. Empleamos los métodos de cointegración de panel y de la causalidad de Granger para un panel de veintidós productos agrícolas basados en las observaciones anuales que se extienden de 1980 a 2015. Los resultados empíricos proporcionan una prueba evidente de la relación a largo plazo entre los precios de las materias primas agrícolas, los precios del petróleo y el tipo de cambio real del dólar estadounidense. Al contrario de los hallazgos en muchos estudios en la literatura que exponen la neutralidad de los precios agrícolas frente a los cambios en el precio del petróleo, nosotros encontramos un fuerte respaldo a la existencia de acoplamientos causales bidireccionales entre precios de las materias primas agrícolas, precios del petróleo y el tipo de cambio real del dólar estadounidense. El análisis a largo plazo de la causalidad, de este modo, implica que los precios del petróleo y del dólar tienen un poder profético para prever los precios agrícolas, que podrían ser una buena herramienta para priorizar la asignación de recursos a través de industrias para asegurar el escenario agrícola en general y los resultados económicos

Green synthesis of xylan hemicellulose esters

BIOVERT+FZB:CPIThe esterification of xylan type hemicelluloses, isolated from birchwood, was carried out firstly in homogeneous conditions using N,N-dimethylformamide (DMF) and lithium chloride (LiCl) in the presence of 4-dimethylaminipyridine (DMAP). The degree of substitution (DS) of xylan acetates ranged between 0.9 and 2.0 as a function of experimental conditions. Due to the problems of toxicity and recycling of DMF, an alternative method of esterification is reported in the second part of this work, performing in the absence of organic solvent and using DMAP or methanesulfonic acid (MSA) as catalysts. Acetylation reaction catalyzed by MSA was developed through an experimental design in order to achieve the highest DS under the mildest conditions. The significant factors and their interactions were identified. The optimization of reaction parameters allowed to obtain a high DS (1.6) and maximal yield (85%). Moreover, the reactivity of propionic and hexanoic anhydrides was evaluated and hydrophobic xylan esters with low degrees of substitution were obtained. (C) 2011 Elsevier Ltd. All rights reserved

Novel nucleophilic/basic and acidic organocatalysts for reaction between poorly reactive diisocyanate and diols

International audienceOriginal basic or acidic organic compounds derived from guanidine or phenyl phosphonic acid were specifically designed and tested as new catalysts for the bulk synthesis of polyurethane prepolymers from a precursor system with particularly low reactivity (secondary alcohol + aliphatic isocyanate at low temperature). Both families showed interesting catalytic activities at 60-80 degrees C, but must nevertheless be used in much higher amounts (1mol%, i.e. between 0.15 and 0.50wt%) than traditional metal-based catalysts. The efficiency of guanidine derivatives seems to be related to their nucleophilicity, whereas that of phosphonic acid derivatives depends on their acidity. However, the solubility of the considered species in the reactive medium also plays a major role. The water/alcohol selectivity of the catalysts, especially at room temperature, was then examined as an additional criterion. Guanidines are not selective and favor the reaction of isocyanate groups with water as much as that with alcohols. Phenyl phosphonic acid derivatives are more selective, and particularly pentafluorophenyl phosphonic acid displays a remarkable catalytic activity together with an acceptable selectivity and could represent an interesting and safer alternative to toxic tin and mercury derivatives for many industrial polyurethanes