Nouveau concept simplifié d’antennes reconfigurables utilisant les couplages interéléments : Mise en œuvre d’un réseau hybride

The work of this thesis aims to investigate a new concept of reconfigurable antenna allowing a good trade-off between performances, complexity and cost. This concept is called ‘hybrid’ because it is based on the capabilities of thinned arrays and parasitic element antennas. It is an alternative to classical antenna arrays and their complexity. The proposed concept has a modular architecture, and a good versatility for reconfigurable beams. The main advantage of this hybrid antenna is the simplicity of its beam formation network (BFN) which requires only a few number of excited elements. The antenna uses parasitic elements to manage the effects of couplings between the electromagnetic access. The problematic of active VSWR is also solved at the antenna level, avoiding the use of additional components in the BFN. This work details the principle of the reconfigurable hybrid antenna concept. The potentialities are evaluated. The elements required to realize a proof of concept are then defined, using a dedicated experimental setup. A prototype is manufactured and the performances have been checked to validate this innovative concept.Les travaux de cette thèse s’intéressent à un nouveau concept d’antenne reconfigurable offrant un bon compromis entre performances, complexité et coût. Ce concept, qualifié d’hybride, vise à combiner les avantages des réseaux d’antennes lacunaires et des antennes à éléments parasites. Cette hybridation est une alternative à la complexité des réseaux d’antennes conventionnels pour répondre aux exigences d’une architecture modulaire, générique et reconfigurable. L’intérêt majeur de ce concept est de proposer une architecture d’antenne permettant de réduire la complexité du circuit de formation des faisceaux (par la réduction du nombre d’éléments rayonnants à alimenter) tout en adressant les problématiques d’adaptation (TOS actif) des éléments excités. Ceci est permis grâce à la présence d’éléments parasites qui permettent de gérer la diffusion des couplages sur l’antenne. Cette thèse décrit le principe du concept hybride et propose une évaluation de ses potentialités. Par la suite, une définition des éléments à mettre en œuvre pour réaliser une preuve de concept est effectuée, en mettant l’accent sur l’importance de la caractérisation expérimentale. Les performances d’un prototype d’antenne hybride reconfigurable sont ensuite présentées afin de valider les développements et conclure sur cette solution innovante

Distribution of HLA-DRB1/DQB1 alleles and DRB1-DQB1 haplotypes among Tunisian patients with autoimmune hepatitis

Background: Autoimmune hepatitis (AIH) is a chronic inflammatory disease characterized by necrotic inflammation leading to hepatocyte destruction. The association of human leukocyte antigens (HLA) with AIH development and onset is not fully elucidated especially in the Tunisian population.Objectives: The aim of this study was to determine the association of HLA class II alleles and DRB1-DQB1 haplotypes with AIH in Tunisian population.Patients and Methods: A total of 30 AIH patients and 60 healthy controls were included in the study. HLA class II typing was performed by Single-specific-primer polymerase chain reaction (PCR-SSP) technique.Results: Among 13 DRB1 and 5 DQB1 alleles resolved, our results show a positive association of HLADRB1 ⁄03 (38.3% vs. 21.6%, OR = 2.24, P = 0.028) and negative association of HLA-DRB1⁄11 (3.3% vs. 16.7%, P = 0.019). The analysis of DRB1-DQB1 haplotypes in cases and controls revealed 11-shared haplotypes with a frequency exceeding 1%. HLA-DRB1⁄11-DQB1⁄03 haplotype showed a decreased frequency in AIH patients (1.6% vs. 15.8%, P = 0.009) and may be considered as an haplotype of resistance to AIH.Conclusions: To our Knowledge, this is the first study performed to detect the HLA-DRB1 and DQB1 alleles associated with predisposition to AIH in Tunisian patients. The search for HLA predisposing genes to AIH may permit an earlier diagnosis allowing a better management and treatment of the disease in order to avoid liver transplantation

Contribution of virtual water to improving water security in Tunisia: a case study of wheat and olive growing farms in Zaghouan region

Virtual water represents all freshwater used in the process of producing a commodity. In the case of agricultural products, many studies have focused on quantifying virtual water flows through international trade products. The concept of virtual water commercialization should be carefully studied as a potential solution for water scarcity, especially in countries facing risks of water shortage in a few years such as in Tunisia. The main idea of this paper is to optimize water use, by the mean of estimation of virtual water in exported crops which have high water consumption. We also analyze the crops that are imported and therefore, might contribute to save water. Commonly exported and imported crops are widely cultivated in the region of Zaghouan characterized by diversity of agricultural products. That’s why it could represent a good case study from Tunisia. In this study we especially focus on olive oil which is one of the most strategic exported products in Tunisia and on wheat as main imported product. We attempt to create technical and economic data sheets through monitoring about 40 farmers in this region. These sheets are not only to estimate the gross margin but also to calculate water demand for each crop allowing the estimation of virtual water. We found out that Tunisia may saves 1.13 m3 of water per kilogram of wheat if we import it instead of producing it domestically. In the case of olive trees, for an average yield of 2339 kg per hectare we exports 2.10 m3 of virtual water for every kilogram of exported olive. Results presented in this study are of essential implications for policy making regarding water use optimization and water security enhancementPublishe

Contraintes et Défis de la Transition Agroécologique Comme Perçus par les Agriculteurs en Tunisie

Global food systems are moving away from the goals of sustainable development. In addition to the problems of undernourishment and inequity, these systems contribute to the degradation of natural resources, environmental pollution, and the loss of biodiversity. In this context, several initiatives are being launched by international bodies such as the Food and Agriculture Organisation (FAO) and the Consultative Group for International Agricultural Research (CGIAR) in order to establish more equitable and ecologically, socially, and economically sustainable systems. The agro-ecological transition is seen to change towards sustainable and resilient agricultural systems. However, this transition faces many institutional, social, technical, economic, and environmental obstacles and challenges. The main objective of this study is to determine and understand these obstacles and to identify the factors that inhibit this agro-ecological transition in the Tunisian context. The study is based on the convictions of farmers, who represent not only the first link in the production chain but also the weakest link. The research methodology is based on a participatory approach and qualitative analysis. Focus groups, workshops and an open-ended survey were conducted with farmers in the north-eastern region of Tunisia, where the mixed crop-livestock system is omnipresent. A literature review preceded and accompanied the field study and the analysis of the results. This work was carried out within the framework of the "Agroecology" initiative launched by the CGIAR and implemented in Tunisia by the International Center for Agricultural Research in the Dry Areas (ICARDA). The results of this study reveal many constraints perceived by farmers, mainly related to the climatic conditions, the institutional framework (notably the lack of incentive policies), the lack of financing mechanisms and the complexity of the acceptance and adoption of technical innovations at the farm level (lack of information, failure of extension services, etc.). The results also reveal the importance of using socio-technical systems analysis to better understand and address the root causes behind the issues blocking agro-ecological transitions in Tunisia. This diagnosis contributes to the identification of required actions and to generate the necessary recommendations for decision-makers to stimulate the agro-ecological transition. This communication occurred during the 20th International Scientific Day of INRGREF in Tunis, Tunisia “Sustainable Ecosystem Management for Agroecological Transition and Food Security” (10-11 October 2023)

Scoping study report on potential existing value chains in the North-West region of Tunisia

The objective of this report is to select the main value chains with potential to integrate the agroecological principles in the Northwest of Tunisia. A descriptive analysis on the two governorates chosen was first made, then 4 focus group discussions were organized with local farmers associations. The VC assessment according to agroecological principles conducted with the main actors places the olive oil VC as the major value chain with agroecological character

Value chain analysis and actors mapping: Case of Tunisia

The objective of this report is to analyze, mapping and select the main value chains with potential to integrate the agroecological principles in Tunisia. Based on the secondary data, rapid value chain analysis, focus group discussions at the living labs and participatory approach with the main stakeholders, three value chains were identified in Siliana and Kef governorates: olive oil, sheep meat and honey. The VC assessment according to agroecological principles conducted with the main actors places the olive oil VC as the major value chain with agroecological character. In this sense, an olive oil business model was proposed to encourage the olive producers of SMSA to produce a labeled olive oil to improve their revenues, enhance livelihoods and create a system of values that includes land (terroir)

Business model identification in the selected value chains in the Northwest of Tunisia: Case of Kef and Siliana

The report describes the approach used to co-identify potential Business Models through the integration of HLPE’s agroecological principles in a variety of Value chains co-selected in the Agroecological Living Landscape ‘Kef-Siliana Transect’, Northwest Tunisia

Transition Pathway Toward Agroecology in Agroforestry Systems: Case of Kesra

The mountain of Kesra is located at an altitude of 1245 m with a very uneven relief. It belongs to the upper semi-arid bioclimatic stage. The range of soils is very diverse due to the extreme variability of substrates, climates, and plant species. Despite the richness of natural resources and heritage, and the ancestral know-how of local populations, the region of Kesra, continues to suffer from economic and social underdevelopment. Standard applications, which do not take into account the specificities of each area, often do not achieve the objectives of ecodevelopment and sustainability. The application of a holistic agroecological transition approach in this rural mountain area requires an inclusive co-design which takes into consideration the socio-ecological context (Natural resources use, agricultural practices, agroforestry, etc.). So, the main objective was to define and build context-specific agroecological transition pathways throw a solid methodology which combines literature review, consultation, and focus group discussions. The visioning approach was conducted with 12 farmers from the community to reflect on the state of agriculture in Kesra and to identify a desirable future of agriculture in 10 years (2022-2032) from their own perspective. This vision was discussed and debated referred to the 13 principals of agroecology. The AE transition pathway identified in Kesra suggests an emphasis on the diversification of local and natural based products to insure synergies between system components as a basis of a swift transition. The resulting impact pathway promotes increasing resilience to market and climate change, economic autonomy, diversifying market, and promotion of local products. Based on this approach and other research activities a set of actions will be executed during 2023 and 2024 to monitor the co-designed transition pathways and to scaling-up the agroecological transition in the mountainous areas like Kesra

New simplified concept of reconfigurable antennas using the inter-element couplings : Implementation of a hybrid network

Les travaux de cette thèse s’intéressent à un nouveau concept d’antenne reconfigurable offrant un bon compromis entre performances, complexité et coût. Ce concept, qualifié d’hybride, vise à combiner les avantages des réseaux d’antennes lacunaires et des antennes à éléments parasites. Cette hybridation est une alternative à la complexité des réseaux d’antennes conventionnels pour répondre aux exigences d’une architecture modulaire, générique et reconfigurable. L’intérêt majeur de ce concept est de proposer une architecture d’antenne permettant de réduire la complexité du circuit de formation des faisceaux (par la réduction du nombre d’éléments rayonnants à alimenter) tout en adressant les problématiques d’adaptation (TOS actif) des éléments excités. Ceci est permis grâce à la présence d’éléments parasites qui permettent de gérer la diffusion des couplages sur l’antenne. Cette thèse décrit le principe du concept hybride et propose une évaluation de ses potentialités. Par la suite, une définition des éléments à mettre en œuvre pour réaliser une preuve de concept est effectuée, en mettant l’accent sur l’importance de la caractérisation expérimentale. Les performances d’un prototype d’antenne hybride reconfigurable sont ensuite présentées afin de valider les développements et conclure sur cette solution innovante.The work of this thesis aims to investigate a new concept of reconfigurable antenna allowing a good trade-off between performances, complexity and cost. This concept is called ‘hybrid’ because it is based on the capabilities of thinned arrays and parasitic element antennas. It is an alternative to classical antenna arrays and their complexity. The proposed concept has a modular architecture, and a good versatility for reconfigurable beams. The main advantage of this hybrid antenna is the simplicity of its beam formation network (BFN) which requires only a few number of excited elements. The antenna uses parasitic elements to manage the effects of couplings between the electromagnetic access. The problematic of active VSWR is also solved at the antenna level, avoiding the use of additional components in the BFN. This work details the principle of the reconfigurable hybrid antenna concept. The potentialities are evaluated. The elements required to realize a proof of concept are then defined, using a dedicated experimental setup. A prototype is manufactured and the performances have been checked to validate this innovative concept

Potentialities of Hybrid Arrays with Parasitic Elements

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