Complementarity or substitutability between private and public investment in R&D: An empirical study

In this paper, we investigate the relationship between private and public investment in R&D. Various models proposed in the literature to take account for several instruments policies as: (subsidies, taxes…) are estimated to verify if private and public R&D spending are complement or substitute. Our empirical study is based on a dynamic panel model for a sample of (23) countries over the period 1992-2004. This research is dealing with the relationship between private and public investment in R&D. Results based on the GMM method of Arellano and Bond (1991) and the tests of causality and unit root applied to the panel data show a positive and significant relation between private and public R&D.R&D; Complementarity; Substituability; GMM; Dynamic Panel Data

Complementarity between private and public investment in R&D: A Dynamic Panel Data analysis

This paper investigates the relationship between private and public investment in R&D, while taking into account the effect of several instruments policies such as subsidies and taxes. We design a new look of knowledge spillovers and R&D cooperation to explain the contribution of public and private R&D on growth. We propose a heterogeneous dynamic panel data model to consider the endogenous effect of R&D investment. We also distinguish between the estimated long and short run results. Our results based on a sample of 23 countries over the period 1992-2004 indicate that both public and private investments in R&D are complementary. By establishing an endogenous growth model, the estimates indicate that public and private R&D depends on the host country's human capital investment. Results indicate that foreign direct investment is a more significant spillover channel than imports.R&D investment; Technology Spillovers; Complementarities; Economic growth; Dynamic Panel Data; Cointegration; Unit root test; Private investment; Public investment; R&D cooperation

Etude comparative de la dureté (hardness) des détecteurs p+ n- n+ et n+ p- p+ au Silicium

Dans ce travail, l’effet des radiations sur une diode au silicium utilisée comme détecteur de particule est simulé numériquement. Ces radiations créent des défauts qui ont des effets indésirables et donc on peuvent dégrader les performances des détecteurs. L’étude est une comparaison de la dureté des détecteurs ayant différentes structures : p+ n- n+ et n+ p- p+. La dureté est caractérisée par les taux d’introduction des défauts (α) et (β). En partant des valeurs expérimentales de α et β, la tension de déplétion (Vdep) est évaluée à partir des caractéristiques capacité-tension en polarisation inverse pour différentes fluences d’irradiations (Φ) pour les deux structures. La densité des défauts crée par l’irradiation est proportionnelle à la fluence. La comparaison entre les deux structures (à régions actives de types n et p) est résumée dans les points suivants : -Dans la structure p+ n- n+, la région active de type n se convertie au type p mais la région active p du détecteur n+ p- p+ devient fortement de type p avec l’augmentation de la densité du piége accepteur. Au contraire avec l’augmentation de la densité du piége donneur où le type n devient fortement de type n mais le type p se convertie au type n. -la variation de la tension de déplétion du détecteur p+ n- n+ est plus important que celle du détecteur n+ p- p+. Donc, le détecteur n+ p- p+ est plus robuste vis-à-vis des radiations. Donc, il plus dure et peut avoir une durée de vie plus longue. -L’effet des centres de recombinaison devient important lorsque les piéges accepteurs sont plus éloigné de la bande de valence tandis que les piéges donneurs sont plus éloigné de la bande de conduction

Complementarity between private and public investment in R&D: A Dynamic Panel Data analysis

This paper investigates the relationship between private and public investment in R&D, while taking into account the effect of several instruments policies such as subsidies and taxes. We design a new look of knowledge spillovers and R&D cooperation to explain the contribution of public and private R&D on growth. We propose a heterogeneous dynamic panel data model to consider the endogenous effect of R&D investment. We also distinguish between the estimated long and short run results. Our results based on a sample of 23 countries over the period 1992-2004 indicate that both public and private investments in R&D are complementary. By establishing an endogenous growth model, the estimates indicate that public and private R&D depends on the host country's human capital investment. Results indicate that foreign direct investment is a more significant spillover channel than imports

R&D Cooperation and economic growth: A dynamic panel data analysis

Dans ce papier, on se propose d’étudier la relation entre la coopération en R&D et la croissance économique. Nous essayerons d’apporter quelques éclairages théoriques sur les relations de coopération technologique en s’intéressant à l’émergence de la coopération entant que nouveau mode de coordination des activités économiques. Notre étude empirique se base sur différentes méthodes d’estimations développées récemment dans le cadre des panels dynamiques pour un échantillon de 23 pays sur la période 1992-2004. Nous utiliserons la méthode des GMM d’Arellano et Bond (1992), les tests de causalité et de racine unitaire appliqués sur donnée de panel. Les conclusions totales suggèrent une relation positive et significative.Coopération en R&D; Croissance économique; Données de panel dynamique; Externalités technologiques

Texture classification of fabric defects using machine learning

In this paper, a novel algorithm for automatic fabric defect classification was proposed, based on the combination of a texture analysis method and a support vector machine SVM. Three texture methods were used and compared, GLCM, LBP, and LPQ. They were combined with SVM’s classifier. The system has been tested using TILDA database. A comparative study of the performance and the running time of the three methods was carried out. The obtained results are interesting and show that LBP is the best method for recognition and classification and it proves that the SVM is a suitable classifier for such problems. We demonstrate that some defects are easier to classify than others

Fonctionnement hydrodynamique et écologique du Lac Nord de Tunis par modélisation numérique

Le Lac Nord de Tunis, dont la superficie est d’environ 24 km2 et la profondeur moyenne de 1,5 m, est lié à la mer par des écluses à marée appelées « Écluses de Khéréddine ». Nous avons étudié le fonctionnement hydrodynamique actuel de ce lac en utilisant un modèle bidimensionnel, intégré sur la hauteur d’eau. Le logiciel utilisé («Surfacewater Modeling System» ou SMS) ne simule pas le fonctionnement des écluses qui s’ouvrent et se ferment automatiquement en fonction du niveau de la marée en mer, comme c’est le cas dans le lac de Tunis. Pour cela, nous avons modifié son code source pour tenir compte du fonctionnement réel des écluses.Les paramètres du modèle sont calibrés en utilisant des mesures hydrauliques récentes, réalisées en décembre 2005. Le modèle a ensuite été utilisé pour simuler le fonctionnement hydrodynamique moyen actuel du lac. Les résultats de ces simulations montrent un bon fonctionnement hydraulique du lac : absence de zones de stagnation et renouvellement fréquent des eaux ne dépassant pas 21 jours.L’étape suivante a consisté en la mise au point d’un modèle écologique par zone (en divisant le lac en cinq zones supposées homogènes) couplé avec le modèle hydrodynamique. Il est basé sur les équations utilisées par HALCROW (en 1990) et calibré sur des mesures de l’année 2002. Ce modèle traite l’évolution des variables suivantes : la salinité, l’oxygène dissous, la chlorophylle a, les biomasses des macroalgues, du phytoplancton et du zooplancton, ainsi que les nutriments dans le compartiment détritique, dans la colonne d’eau et dans les sédiments.Les premiers résultats du modèle écologique sont encourageants. Cependant, des mesures complémentaires (des macroalgues, du phytoplancton et du zooplancton dans le lac, de l’azote et du phosphore dans les sédiments de surface) permettraient d’améliorer le calage et les résultats du modèle écologique.This work deals with the modelling of the hydrodynamic and ecological functioning of the Tunis North Lake. The Tunis North Lake is situated north-east of Tunisia, its surface is about 24 km2 and the average depth is 1.5 m. The lake is connected to the Gulf of Tunis by the Khereddine channel through ten sluices functioning under tide’s effect. In fact, five of these sluices are opened on flood tide and the others on ebb tide. These sluices were built with a separation dam, in the centre of the lake, during the period between 1985 and 1988, in order to improve the water circulation and the quality of the lake.We then studied the actual hydrodynamic functioning of the lake by using a 2D vertical-integrated model. The numerical software used is the «Surfacewater Modeling System» (SMS). The initial code, SMS, does not simulate the change of the boundary conditions through the time of simulation, as it really occurs on the Khereddine sluices, which open in an automatic way according to the tide: high tide (opened northern sluices and closed southern sluices) and low tide (closed northern sluices and opened southern sluices). Therefore, first of all, we modified the source code of software «SMS» to take into account this specification of the Tunis North Lake.After these modifications, we carried out the calibration of the model by basing outselves on recent hydraulic measurements performed in December 2005. The model’s calibration enabled us to simulate the average hydrodynamic functioning of the lake, by imposing average boundary conditions: An average tide of marling 20 cm at the Khereddine sluices and a constant flow on the power electric station of La Goulette. The results of these simulations showed «a correct» functioning of the Tunis North Lake through an exchanged flow with the sea of 66 m3/s, an exchanged daily volume of 1.65 Mm3/day, a velocity field that scanned all the surface of the lake and an average residence time of water in the lake of approximately 21 days which can reach 16 days with maximal tide and western wind of intensity 6 m/s.The following stage consisted in the development of a zonal ecological model taking into account specificities of the lake and the data which are available. This model was coupled with the hydrodynamic model that is presented in the preceding stage, in particular with regard to the exchanges between the zones (or sea) defined in the ecological model. The ecological model computes the evolution of the biomasses of the macroalgae, phytoplankton and zooplankton as well as nutrients in detritus, water column and sediments, the salinity, the dissolved oxygen and the chlorophyll-a concentrations. In this model, the growth of phytoplankton and macroalgae depends on the water temperature, light intensity and nutrient. Competition between phytoplankton and macroalgae for nutriments is simulated. The computation was carried out in two steps. The first step consists in the preliminary calibration of the model on the basis of measurements of water quality performed during the year 2002 and the parameter update used by HALCROW (Sir William Halcrow & Partners Ltd) (in 1990) which enabled us to bring closer the results of the model to the actual characteristics of the lake. The cyclical nature of the population density of macroalgae was reproduced, with a bloom throughout the spring especially in the southern part of the lake. In the second step, we carried out a five-year predictive simulation of the ecological functioning of the lake from the year 2002. The results of this simulation showed us that the lake presents good ecological conditions.The results of the present ecological model are the best results that we can obtain using the available data, but further measurements of phytoplankton, zooplankton, macroalgae and nutrients in the sediments can improve considerably the results of this model

Stock Market Indexes: A random walk test with ARCH (q) disturbances

We will here study the stock market indexes, in the context of a random walk test with ARCH (q) disturbances. This model based on these theoretical predictions has been valuated from the Tunis Stock market data. The coherence of the parameters signs and the statistical relevance of the estimations are validating the choice of the conditionally heteroskedastic random walk mode

Expense items: test on items generating inflation

This study aims to spot the inflation – generating expenses. The expenses items are represented by series of prices statistical indexes. We are going to determine the series of gaps on these prices indexes. We will afterwards study the data- generating process in the context of the ARCH model and the V-GARCH model. We will find out the following items (food, clothes and transports) as inflation- generating items