Tunisia: The Need for a New Development Model

The Tunisian revolution took everyone by surprise. What were the immediate causes of this historic event? What are the economic and financial challenges facing the country? How can they be addressed? The Tunisian revolution has proven the failure of the development model that has been in force since the seventies. The country is, today, facing major economic and social challenges, mainly recession, unemployment, regional disparity, a growing budget and current account deficit, a high inflation rate in addition to a heavy external public debt. The low level of national savings makes external financing the greatest challenge in the short and medium term. What development strategy should be followed? The objective of this article is to search for an appropriate development model that is capable of achieving the country’s economic and social objectives; the determination of adequate and coherent policies for its operation; and finally to provide the decision makers with practical recommendations to be implemented

Monitoring of pesticides in water media of Northeast Portugal

Mestrado de dupla diplomação com a Université Libre de TunisIn this work, an analytical methodology was developed for the monitoring of five emerging pollutants, namely, alachlor, metolachlor, heptachlor, dimethoate, and terbuthylazine. These compounds are among the most used pesticides in the northeast region of Portugal and Tunisia. A complete experimental methodology was optimized based on the simultaneous extraction and concentration of all five pesticides from aqueous matrices, by means of solid-phase micro-extraction (SPME) followed by detection and quantification using gas chromatography coupled to mass spectrometry (GC-MS). The optimization of the extraction step was performed using a polydimethylsiloxane–divinylbenzene (PDMS-DVB) coated SPME fiber by direct immersion (DI-SPME) in the aqueous sample. Experimental conditions, such as extraction temperature and time, pH value, salt concentration, and desorption time and temperature in the GC injector port were studied. The optimum value for each one of these parameters was selected based on the maximum total area value obtained in MS detector, using Full Scan Mode, for the mixture of the five pesticides. The extraction optimized conditions were achieved by immersion of a PDMS-DVB fiber in the sample mixture with 10% NaCl, a pH value of 2, at 60ºC for 80 min. Desorption of the compounds from the fiber is done in the GC port at 250ºC during 4 min. The GC-MS operating conditions were also studied and the main separation and detection parameters were selected. Samples were analyzed using the following oven temperature program: initial temperature of 120°C (held for 2 min), increased by 15°C min-1 to 190°C (held for 4 min) and, finally, increased by 10°C min-1 to 227°C held for 1min. The MS instrument operated in the Electron ionization mode (EI) was used for a full scan. The acquisition was performed in the range of 35–450 (m/z). The ion source temperature was 200 °C and the interface temperature was 270 °C. The identification and quantification were carried out using calibration curves obtained from the extraction of a standard mixture of the five selected pesticides for at least six concentrations levels, in the same experimental conditions used for the real samples. Detection limits ranged from 4.2 to 6.6 g/L. For pesticides with low values of KOW, like dimethoate, the use of a fiber of relatively non-polar nature would be favorable. The developed experimental methodology was implemented by the analysis of different samples collected from the surface water of three rivers from Bragança, namely, Fervença, Sabor and Onor. All three rivers showed different types and levels of contamination.Neste trabalho, apresenta-se o desenvolvimento de uma metodologia analítica para a monitorização de cinco poluentes emergentes, nomeadamente, alacloro, metolacloro, heptacloro, dimetoato e terbutilazina. Estes compostos estão entre os pesticidas mais utilizados na região nordeste de Portugal e da Tunísia. A metodologia experimental é baseada na extração e concentração simultânea de todos os 5 pesticidas presentes em matrizes aquosas, utilizando a micro-extração em fase sólida (SPME) seguida de deteção e quantificação utilizando um sistema de cromatografia gasosa acoplado com espectrometria de massas. (GC-MS). A otimização da etapa de extração é realizada com uma fibra de SPME com um revestimento de polidimetilsiloxano-divinilbenzeno (PDMS-DVB) e por imersão direta nas amostras aquosas (DI-SPME). As condições experimentais da extração, como sejam, o tempo e a temperatura de extração, o valor de pH, a adição de sal, e o tempo e a temperatura de dessorção na porta do injetor do GC, são estudadas. O valor ótimo para cada um destes parâmetros é selecionado baseado na maximização do valor da área cromatográfica total obtido a partir da mistura dos 5 pesticidas, fornecida pelo detetor de massas. As condições ótimas para a extração são obtidas imergindo a fibra de PDMS-DVB na amostra da mistura, após a adição de 10% (m/m) de NaCl, ajuste do valor de pH para 2, a extração é realizada durante 80 min a 60ºC. A dessorção deve ser realizada na porta do GC a 250ºC durante 4 min. As condições operatórias do GC-MS foram também estudadas, tendo-se otimizado alguns dos parâmetros de separação e deteção. As amostras são analisadas utilizando o seguinte programa de temperaturas do forno do GC: temperatura inicial de 120ºC (2 min), uma rampa de 15°C.min-1 até 190°C (4 min) e, finalmente, nova rampa de 10 °C.min-1 até 227°C (1 min). O detetor de massas foi utilizado em modo de ionização de iões (EI) e em varrimento total de massas (FullScan). A aquisição de massas foi realizada entre 35-450 m/z. A temperatura da fonte de iões foi de 200ºC e a temperatura de interface foi de 270ºC. Os limites de deteção e de quantificação estimados através da determinação experimental das curvas de calibração obtidas após a extração de soluções padrão com os 5 pesticidas em estudo, utilizando pelo menos seis níveis de concentração diferentes, nas mesmas condições experimentais utilizadas para as amostras reais. Os limites de deteção obtidos, variam de 4,2 a 6,6 g/L. Para pesticidas com valores de KOW baixos, como por exemplo, o dimetoato, a utilização de um tipo de fibra de natureza relativamente não-polar pode ser favorável. O desenvolvimento da metodologia experimental foi seguida da sua implementação através da análise de diferentes amostras, recolhidas das águas superficiais de 3 rios de Bragança, especificamente, rio Fervença, Sabor e Onor. Todas as amostras analisadas revelaram diferentes tipos e graus de contaminação pelos pesticidas em estudo.Dans ce travail, une méthodologie analytique est développée pour la surveillance de cinq polluants émergents, à savoir l'alachlor, le métolachlore, l'heptachlore, le diméthoate et la terbuthylazine. Ces composés sont parmi les pesticides les plus utilisés dans la région nord-est du Portugal et de la Tunisie. Une méthodologie expérimentale complète est optimisée, basée sur l'extraction et la concentration simultanées des cinq pesticides à partir de matrices aqueuses, au moyen d'une micro-extraction en phase solide (SPME) suivie d'une détection et d'une quantification par chromatographie en phase gazeuse avec spectrométrie de masse (GC-MS). L'optimisation de l'étape d'extraction est réalisée à l'aide d'une fibre SPME revêtue de polydiméthylsiloxane – divinylbenzène (PDMS-DVB) par immersion directe (DI-SMPE) dans l'échantillon aqueux. Les conditions expérimentales, telles que la température et la durée d'extraction, la valeur du pH, l'addition de sel, la durée et la température de désorption dans l'orifice d'injection du CPG ont été étudiées. La valeur optimale pour chacun de ces paramètres a été choisie sur la base de la valeur de la surface totale maximale obtenue dans le détecteur MS, en utilisant le mode de balayage complet, pour le mélange des cinq pesticides. Les conditions d'extraction optimisées ont été obtenues par immersion d'une fibre de PDMS-DVB dans le mélange d'échantillon avec 10% de NaCl, une valeur de pH de 2, à 60°C pendant 80 min. La désorption des composés de la fibre est effectuée dans le port GC à 250ºC pendant 4 min. Les conditions de fonctionnement de la GC-MS ont également été étudiées et les principaux paramètres de séparation et de détection ont été sélectionnés. Les échantillons ont été analysés en utilisant le programme de température du four suivant : température initiale de 120°C (maintenue pendant 2 min), augmentée de 15°C min-1 à 190°C (maintenue pendant 4 min) et enfin augmentée de 10 °C min-1 à 227°C maintenu pendant 1 min. L'instrument MS fonctionnant en mode d'ionisation électronique (EI) a été utilisé pour une analyse complète. L'acquisition a été réalisée entre 35 et 450 (m / z). La température de la source d'ions était de 200°C et la température d'interface de 270°C. L'identification et la quantification ont été effectuées à l'aide de courbes d'étalonnage obtenues à partir de l'extraction d'un mélange standard des cinq pesticides sélectionnés pour au moins six concentrations, dans les mêmes conditions expérimentales que celles utilisées pour les échantillons réels. Les limites de détection allaient de 4,2 à 6,6 μg/L. Pour les pesticides à faible KOW, tels que le diméthoate, l'utilisation d'une fibre de nature relativement non polaire serait favorable. La méthodologie expérimentale développée a été mise en oeuvre par l'analyse de différents échantillons prélevés dans les eaux de surface de trois rivières de Bragança, à savoir Fervença, Sabor et Onor. Les trois rivières présentaient différents types et niveaux de contamination

Numerical validation of the fire resistance of partition walls

Mestrado de dupla diplomação com a Université Libre de TunisThis work investigates the impact of fire in non-loadbearing Light Steel Frame (LSF) walls. Numerical validation and a set of parametric analyses are carried out using ANSYS Multiphysics software in order to show the impact of structural stud’s space, cavity thickness, the effect of the protective layer, and the effect of insulating material in the cavity. The results show that the cavity insulation has the greatest influence on fire resistance, followed by the increase of the number of gypsum plasterboards of the protection layer. Also the decreasing of the studs spacing has improved the time of the resistance of walls under fire.Ce travail étudie l'impact du feu dans les murs non porteurs à ossature légère en acier (LSF). Une validation numérique et un ensemble d'analyses paramétriques sont réalisés à l'aide du logiciel ANSYS®Multiphysics afin de montrer l'impact de l'espace du montant structurel, de l'épaisseur de la cavité, de l'effet de la couche protectrice et de l'effet du matériau isolant dans la cavité. Les résultats montrent que l'isolation de la cavité a la plus grande influence sur la résistance au feu, suivie par l'augmentation du nombre de plaques de plâtre de la couche de protection et aussi la diminution de l'espacement entre les montants a amélioré la durée de la résistance des murs sous le feu

Recursive Least-Squares Estimation for the Joint Input-State Estimation of Linear Discrete Time Systems with Unknown Input

This paper presents a recursive least-squares approach to estimate simultaneously the state and the unknown input of linear time varying discrete time systems with unknown input. The method is based on the assumption that no prior knowledge about the dynamical evolution of the input is available. The joint input and state estimation are obtained by recursive least-squares formulation by applying the inversion lemmas. The proposed filter is equivalent to recursive three step filter. To illustrate the performance of the proposed filter an example is given

Climbing depth-bounded adjacent discrepancy search for solving hybrid flow shop scheduling problems with multiprocessor tasks

This paper considers multiprocessor task scheduling in a multistage hybrid flow-shop environment. The problem even in its simplest form is NP-hard in the strong sense. The great deal of interest for this problem, besides its theoretical complexity, is animated by needs of various manufacturing and computing systems. We propose a new approach based on limited discrepancy search to solve the problem. Our method is tested with reference to a proposed lower bound as well as the best-known solutions in literature. Computational results show that the developed approach is efficient in particular for large-size problems

Solar Air-Conditioning Systems

The chapter presents the recent studies focusing on optimizing the efficiency of air-conditioning (AC) systems using solar energy. For this purpose, several advanced AC plants (absorption, adsorption, and desiccant) are designed. Their technology and components are described in this chapter. It also discusses the energy intake of the solar energy use in air-conditioning, especially in rural regions where the electricity shortage is frequent, as well as the reduction of the energy costs and the pollution rate. A comparison between solar AC systems and traditional AC systems at the level of the designs, costs, and effectiveness is made at the end of the chapter

Does firm political risk affect the relationship between corporate social responsibility and firm value?

This paper investigates whether firm-level (idiosyncratic) political risk (PR) affects the relationship between corporate social responsibility (CSR) and firm value using a sample of 16,518 firm-year observations which correspond to 2055 unique firms belonging to the Russell 3000 Index over the sample period 2010–2020. Our main findings are as follows: First, firm-level PR does not affect firm value. Second, CSR is positively related to firm value, which is mainly driven by the social component of CSR. Finally, PR has no effect on the CSR–firm value relationship, regardless of the PR type. Our evidence suggests that firm-level PR is not priced in the financial market and as such it does not affect the CSR–firm value relationship. This is consistent with portfolio theory which suggests that only systematic risk is priced.Publisher PDFPeer reviewe