L'objet de cette thèse est de proposer une étude numérique, fondée sur l'application de résultats de la théorie du contrôle optimal géométrique, des trajectoires spatiales du système Terre-Lune dans un contexte de poussée faible. Le mouvement du satellite est décrit par les équations du problème restreint des trois corps controlé. Nous nous concentrons sur la minimisation de la consommation énergétique et du temps de transfert. Les trajectoires optimales sont recherchées parmi les projections des courbes extrémales solutions du principe du maximum de Pontryagin et peuvent être calculées grâce à une méthode de tir. Ce procédé fait intervenir l'algorithme de Newton dont la convergence nécessite une initialisation précise. Nous surmontons cette difficulté au moyen de techniques homotopiques ou d'études géométriques du système de contrôle linéarisé. L'optimalité locale des trajectoires extrémales est ensuite vérifée en utilisant les conditions du second ordre liées au concept de point conjugué. Dans le cas du problème de minimisation de l'énergie, une technique de "recollement" de trajectoires optimales kepleriennes autour de la Terre et La Lune et d'une solution optimale de l'équation du mouvement linéarisée au voisinage du point d'équilibre L1 est également proposée pour approximer les transferts Terre-Lune à énergie minimale. / This PhD thesis provides a numerical study of space trajectories in the Earth-Moon system when low-thrust is applied. Our computations are based on fundamental results from geometric control theory. The spacecraft's motion is modelled by the equations of the controlled restricted three-body problem. We focus on minimizing energy cost and transfer time. Optimal trajectories are found among a set of extremal curves, solutions of the Pontryagin's maximum principle, which can be computed solving a shooting equation thanks to a Newton algorithm. In this framework, initial conditions are found using homotopic methods or studying the linearized control system. We check local optimality of the trajectories using the second order optimality conditions related to the concept of conjugate points. In the case of the energy minimization problem, we also describe the principle of approximating Earth-Moon optimal transfers by concatening optimal keplerian trajectories around The Earth and the Moon and an energy-minimal solution of the linearized system in the neighbourhood of the equilibrium point L1.

許多研究證實企業落實企業社會責任（CSR），有助增進與利害關係人關係。然而，不同利害關係人對不同面向之CSR的態度因重視程度高低而有差異，若企業能以特定利害關係人所注重之CSR面向進行溝通，溝通效果將事半功倍。「天下企業公民獎」是國內CSR獎項的先行者，透過將CSR分為「公司治理」、「企業承諾」、「社會參與」與「環境保護」，邀請專家學者對參獎企業進行各構面的評比。此獎深耕台灣，許多企業視此獎為自身CSR的年度總體檢。 本研究以民眾角度，探討天下企業公民獎四大構面是否為衡量CSR的顯著指標，及各構面之衡量題項是否能真實反應該構面意涵。其次，探討四大構面在消費者心中的相對重要性，並進行跨產業比較：探討是否因產業不同，使民眾對四大構面的重要性排序發生改變。最後透過重要性－績效分析法，找出各產業之代表企業（玉山金控、華碩電腦與中華電信）在民眾心中仍可加強的CSR構面。本研究之有效網路問卷共344份（金融業115份、製造業117份、服務業112份），透過LISREL進行二階驗證式因素分析。研究結果歸納如下： 一、四大構面皆為衡量企業社會責任的顯著指標。 二、「環境保護」、「社會參與」、「公司治理」之題項皆為衡量構面的顯著指標。「企業承諾」構面下則有兩題項對該構面的解釋能力不足。 三、民眾對於企業社會責任之四大構面的重要性排序為「企業承諾」＞「公司治理」＞「環境保護」＞「社會參與」。 四、「企業承諾」在民眾心中屬於相對重要性高的構面。若企業透過企業承諾構面的CSR作為與民眾溝通，推測能夠有達到較佳的溝通效果。 五、對於三間代表企業而言，「企業承諾」皆為民眾較重視的構面，但玉山金控與華碩電腦在民眾心中的表現績效偏低，建議可列為優先改善重點。 六、企業的「社會參與」績效佳，但民眾認為重要性低，故可將資源重分配。 / Companies nowadays face an ever more difficult environment and more demanding stakeholders. This means corporate social responsibility has become a new area offering opportunity for reducing risks and developing new competitive advantages. Previous research has shown that corporate social responsibility helps companies better communicate with stakeholders and increase brand value as well as reputation. “CommonWealth Magazine Corporate Citizen Award” is the pioneer in domestic corporate social responsibility awards. Its corporate social responsibility (CSR) framework takes four dimensions into account, including Corporate Governance, Corporate Commitment, Community Involvement, and Environmental Protection. Annually, experts and scholars are invited to grade on these four dimensions, and awards are given out to the top 100 corporate citizens. The award is in its 11th consecutive year. With its long tradition and reputation, many companies regard this award as the annual examination for their corporate social responsibility practices. From the customers’ perspective, this study examines whether the four dimensions given by CommonWealth Magazine Corporate Citizen Award can be significant indicators for corporate social responsibility, and whether the measuring questions truly reflect each dimension. Next, it moves on to examine the relative importance for consumers of the four dimensions, including cross-industry comparison. By including the financial industry, the manufacturing industry and the service industry, it examines whether people would rank the four dimensions in a different order according to different industries. Finally, by applying Importance-Performance Analysis (IPA), it analyses the dimensions for three representative corporations in each industry (E. Sun Financial Holdings Company, ASUSTEK Computer Inc, and Chunghwa Telecom Co., Ltd.) Based on these findings, suggestions for improvement are made. With 344 valid online questionnaires (115 in the financial industry, 117 in the manufacturing industry, 112 in the service industy) and using second-order CFA in LISREL, the research findings are summarized as below: 1. All four dimensions are significant indicators for measuring corporate social responsibility. 2. The measuring questions for “Environmental Protection”, “Social Involvement” and “Corporate Governance” dimensions are all significant indicators for their respective dimensions. However, two measuring questions in “Corporate Commitment” do not provide sufficient explanation of this dimension. 3. People rank in the order of importance the four dimensions of corporate social responsibility as follows: Corporate Commitment, Corporate Governance, Environmental Protection, and Community Involvement. 4. In the cross-industry comparison, “Corporate Commitment” ranks the most or second most important dimension for consumers. Companies are advised to communicate with consumers through activities in this dimension. 5. Consumers place great value on “Corporate Commitment”, while E. Sun Financial Holdings Company and ASUSTEK Computer Inc perform poorly in this dimension. Suggestions are given as to better prioritize the practice of this dimension. 6. “Community Involvement” shows high performance, while consumers actually do not place that much importance on it. Thus, it is recommended that resources should be reorganized.

Magister Scientiae - MSc / To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80°C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM); Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker. / South Africa

Over the last four decades, relational database systems, with their mathematical basis in first-order logic, have provided a congenial and efficient environment to handle enterprise data during its entire life cycle of generation, storage, maintenance and processing. An organic reason for their pervasive popularity is intrinsic support for declarative user queries, wherein the user only specifies the end objectives, and the system takes on the responsibility of identifying the most efficient means, called “plans”, to achieve these objectives. A crucial input to generating efficient query execution plans are the compile-time estimates of the data volumes that are output by the operators implementing the algebraic predicates present in the query. These volume estimates are typically computed using the “selectivities” of the predicates. Unfortunately, a pervasive problem encountered in practice is that these selectivities often differ significantly from the values actually encountered during query execution, leading to poor plan choices and grossly inflated response times. While the database research community has spent considerable efforts to address the above challenge, the prior techniques all suffer from a systemic limitation - the inability to provide any guarantees on the execution performance. In this thesis, we materially address this long-standing open problem by developing a radically different query processing strategy that lends itself to attractive guarantees on run-time performance. Specifically, in our approach, the compile-time estimation process is completely eschewed for error-prone selectivities. Instead, from the set of optimal plans in the query’s selectivity error space, a limited subset called the “plan bouquet”, is selected such that at least one of the bouquet plans is 2-optimal at each location in the space. Then, at run time, an exploratory sequence of cost-budgeted executions from the plan bouquet is carried out, eventually finding a plan that executes to completion within its assigned budget. The duration and switching of these executions is controlled by a graded progression of isosurfaces projected onto the optimal performance profile. We prove that this construction provides viable guarantees on the worst-case performance relative to an oracular system that magically possesses accurate apriori knowledge of all selectivities. Moreover, it ensures repeatable execution strategies across different invocations of a query, an extremely desirable feature in industrial settings. Our second contribution is a suite of techniques that substantively improve on the performance guarantees offered by the basic bouquet algorithm. First, we present an algorithm that skips carefully chosen executions from the basic plan bouquet sequence, leveraging the observation that an expensive execution may provide better coverage as compared to a series of cheaper siblings, thereby reducing the aggregate exploratory overheads. Next, we explore randomized variants with regard to both the sequence of plan executions and the constitution of the plan bouquet, and show that the resulting guarantees are markedly superior, in expectation, to the corresponding worst case values. From a deployment perspective, the above techniques are appealing since they are completely “black-box”, that is, non-invasive with regard to the database engine, implementable using only API features that are commonly available in modern systems. As a proof of concept, the bouquet approach has been fully prototyped in QUEST, a Java-based tool that provides a visual and interactive demonstration of the bouquet identification and execution phases. In similar spirit, we propose an efficient isosurface identification algorithm that avoids exploration of large portions of the error space and drastically reduces the effort involved in bouquet construction. The plan bouquet approach is ideally suited for “canned” query environments, where the computational investment in bouquet identification is amortized over multiple query invocations. The final contribution of this thesis is extending the advantage of compile-time sub-optimality guarantees to ad hoc query environments where the overheads of the off-line bouquet identification may turn out to be impractical. Specifically, we propose a completely revamped bouquet algorithm that constructs the cost-budgeted execution sequence in an “on-the-fly” manner. This is achieved through a “white-box” interaction style with the engine, whereby the plan output cardinalities exposed by the engine are used to compute lower bounds on the error-prone selectivities during plan executions. For this algorithm, the sub-optimality guarantees are in the form of a low order polynomial of the number of error-prone selectivities in the query. The plan bouquet approach has been empirically evaluated on both PostgreSQL and a commercial engine ComOpt, over the TPC-H and TPC-DS benchmark environments. Our experimental results indicate that it delivers orders of magnitude improvements in the worst-case behavior, without impairing the average-case performance, as compared to the native optimizers of these systems. In absolute terms, the worst case sub-optimality is upper bounded by 20 across the suite of queries, and the average performance is empirically found to be within a factor of 4 wrt the optimal. Even with the on-the-fly bouquet algorithm, the guarantees are found to be within a factor of 3 as compared to those achievable in the corresponding canned query environment. Overall, the plan bouquet approach provides novel performance guarantees that open up exciting possibilities for robust query processing.

Le présent travail propose et développe une méthode originale de dimensionnement vis-à-vis de l'incendie de parois de bâtiments industriels, en s'intéressant plus spécifiquement au cas des panneaux en béton armé de grande hauteur. Soumis à un fort gradient thermique, ces derniers subissent en effet des déplacements hors plan importants qui, du fait de l'excentrement du poids propre qui en résulte, vont engendrer des efforts de flexion venant s'ajouter aux efforts de compression déjà existants. Un tel changement de géométrie, d'autant plus prononcé que le panneau est de grande hauteur, combiné à une dégradation simultanée des propriétés de résistance des matériaux sous l'effet de l'élévation de température, peut conduire à un effondrement de la structure sous poids propre, bien avant par exemple l'apparition d'une instabilité de type flambement. L'approche proposée repose très largement sur la théorie du Calcul à la Rupture, appliquée d'une part à la détermination d'un diagramme d'interaction au feu caractérisant la résistance du panneau en chacune de ses sections, d'autre part à l'analyse de la ruine globale du panneau dans sa configuration déformée. Cette démarche est d'abord mise en œuvre et complètement explicitée dans le cas où le panneau peut être modélisé comme une poutre unidimensionnelle, conduisant à la détermination exacte d'un facteur adimensionnel caractérisant la stabilité de ce dernier. La généralisation de la méthode de calcul à la configuration plus réaliste, mais plus complexe, d'un panneau schématisé comme une plaque rectangulaire, est ensuite développée. Elle aboutit à un certain nombre de résultats préliminaires qui devront être confortés et affinés dans un travail ultérieur. L'approche théorique ici présentée est par ailleurs complétée par un volet expérimental (essais de flexion quatre points de dalles dans un four à maquette) qui a permis de valider au moins partiellement les évaluations du diagramme d'interaction prédites par le calcul / In this contribution, an original and comprehensive method aimed at designing vertical concrete walls submitted to fire loadings, is proposed and developed, with a special emphasis on high rise panels used in industrial buildings. Indeed, when subjected to high thermal gradients, such slender structures exhibit quite significant out-of-plane movements, resulting in an eccentricity of the gravity loads and thus to bending moments in addition to the pre-existing compressive forces. It is such a change of geometry, which is all the more pronounced as the panel is tall, combined with a temperature-induced degradation of the constituent materials strength properties, which may explain why an overall collapse of the structure may occur, well prior to buckling instability. The proposed approach is fundamentally based on the theory of yield design. This theory is first applied to the determination of an interaction diagram, characterizing the fire resistance of a reinforced concrete panel cross-section. It is then implemented as a design method for analysing the stability of the panel in its previously calculated deformed configuration. The whole procedure is explained in full details in the simplified situation when the high rise panel can be modeled as a one-dimensional beam, leading to the exact determination of a dimensionless factor characterizing the stability of the panel. The method is then extended to deal with a more realistic, but somewhat more complex, configuration of a rectangular panel. Some preliminary results, which need to be further validated in a subsequent work, are finally produced. As a necessary complement to the mostly theoretical and computational approach presented in this work, a series of four-point bending tests has been performed on reduced scale slabs placed in a furnace. The results of these tests partially validate the predicted interaction diagram of a fire loaded panel section

L'objectif du travail est de mettre en place des méthodes d'évaluation des risques microbiologiques et des bénéfices nutritionnels lors de la transformation des légumes, en vue d'une analyse risque-bénéfice. Le risque (industriel) considéré est l'altération des conserves de haricots verts due à la bactérie thermophile Geobacillus stearothermophilus, et le bénéfice nutritionnel est la teneur en vitamine C des haricots verts appertisés. Des paramètres de référence ont d'abord été acquis, par une méta-analyse par approche bayésienne pour la partie risque. Les paramètres de résistance thermique D à 121.1°C et pH 7, zT et zpH de G.stearothermophilus ont ainsi été estimés respectivement à 3.3 min, 9.1°C et 4.3 unités pH en moyenne en milieu aqueux. Les modèles risque et bénéfice ont ensuite été analysés par la méthode de simulation de Monte Carlo à deux dimensions, permettant une propagation séparée de la variabilité et de l'incertitude. Les pertes en vitamine C prédites par le modèle entre la matière première et les légumes appertisés sont de 86% en moyenne, et le taux de non-stabilité à 55°C prédit est de 0.5% en moyenne, globalement en accord avec la réalité. Une analyse risque-bénéfice a ensuite visé à optimiser le bénéfice tout en gardant le risque à un niveau acceptable, par exploration de scénarios d'interventions possibles basés sur les résultats d'analyses de sensibilité. Enfin, un modèle d'évaluation des risques dus à la bactérie pathogène Bacillus cereus dans une purée de courgettes a été confronté à des données de contamination dans des produits incubés, par le biais d'une inférence bayésienne. / The aim of this work is to set up microbiological risk and nutritional benefit assessment methods in the transformation of vegetables, in view of a risk-benefit analysis. The considered (industrial) risk is the alteration of green bean cans due to thermophilic bacteria Geobacillus stearothermophilus, and the nutritional benefit is the vitamin C content in appertized green beans. Reference parameters have first been acquired, by a meta-analysis using Bayesian inference for the risk part. Thermal resistance parameters D at 121.1°C and pH 7, zT and zpH of G.stearothermophilus have been respectively estimated at 3.3 min, 9.1°C and 4.3 pH units on average in aqueous media. The risk and benefit models have then been analyzed by a two-dimensional Monte Carlo simulation method, allowing a separated propagation of uncertainty and variability. The vitamin C losses between fresh and appertized green beans predicted by the model are of 86% on average, and the predicted non-stability at 55°C rate is of 0.5% on average, in good accordance with reality. A risk-benefit analysis has then been carried out to optimize benefit while keeping risk at an acceptable level, by exploring possible intervention scenarios based on some sensibility analysis results. Finally, a risk analysis model involving pathogenic bacteria Bacillus cereus in a courgette puree has been confronted to incubated product contamination data, by means of a Bayesian inference.

La première partie de cette thèse (articles I et II) est consacrée à l'étude du comportement asymptotique des solutions d'un système dynamique du second ordre avec dissipation évanescente. Le système dynamique est étudié dans sa version continue et dans sa version discrète via un algorithme.La deuxième partie de cette thèse (articles III à VI) est consacrée à l'étude de plusieurs algorithmes de type proximal. Nous montrons que ces algorithmes convergent vers des solutions de certains problèmes de minimisation. Dans chaque cas, une application est donnée dans le cadre de la décomposition de domaine pour les EDP. / The first part of this thesis is devoted to the study of the asymptotic behavior of solutions of a second order dynamic system with vanishing dissipation. The dynamic system is studied in its continuous version and in its discrete version via an algorithm.The second part is about the study of several proximal-type algorithms. We show that these algorithms converge to solutions of some minimization problems. In each case, an application is given in the area of domain decomposition for PDE's.

Ce travail porte sur le développement de modèles micromécaniques pour le calcul de la réponse homogénéisée de matériaux architecturés, en particulier des matériaux se présentant sous forme de treillis répétitifs. Les matériaux architecturés et micro-architecturés couvrent un domaine très large de de propriétés mécaniques, selon la connectivité nodale, la disposition géométrique des éléments structuraux, leurs propriétés mécaniques, et l'existence d'une possible hiérarchie structurale. L'objectif principal de la thèse est la prise en compte des nonlinéarités géométriques résultant des évolutions importantes de la géométrie initiale du treillis, causée par une rigidité de flexion des éléments structuraux faible en regard de leur rigidité en extension. La méthode dite d'homogénéisation discrète est développée pour prendre en compte les non linéarités géométriques pour des treillis quais périodiques; des schémas incrémentaux sont construits qui reposent sur la résolution incrémentale et séquentielle des problèmes de localisation - homogénéisation posés sur une cellule de base identifiée, soumise à un chargement contrôlé en déformation. Le milieu continu effectif obtenu est en général un milieu micropolaire anisotrope, dont les propriétés effectives reflètent la disposition des éléments structuraux et leurs propriétés mécaniques. La réponse non affine des treillis conduit à des effets de taille qui sont pris en compte soit par un enrichissement de la cinématique par des variables de microrotation ou par la prise en compte des seconds gradients du déplacement. La construction de milieux effectifs du second gradient est faite dans un formalisme de petites perturbations. Il est montré que ces deux types de milieu effectif sont complémentaires en raison de l'analogie existant lors de la construction théorique des réponses homogénéisées, et par le fait qu'ils fournissent des longueurs internes en extension, flexion et torsion. Des applications à des structures tissées et des membranes biologiques décrites comme des réseaux de filaments quais-périodiques ont été faites. Les réponses homogénéisées obtenues sont validées par des comparaisons avec des simulations par éléments finis réalisées sur un volume élémentaire représentatif de la structure. Les schémas d'homogénéisation ont été implémentés dans un code de calcul dédié, alimenté par un fichier de données d'entrée de la géométrie du treillis et de ses propriétés mécaniques. Les modèles micromécaniques développés laissent envisager du fait de leur caractère prédictif la conception de nouveaux matériaux architecturés permettant d'élargir les frontières de l'espace 'matériaux-propriétés' / The present thesis deals with the development of micromechanical schemes for the computation of the homogenized response of architectured materials, focusing on periodical lattice materials. Architectured and micro-architectured materials cover a wide range of mechanical properties according to the nodal connectivity, geometrical arrangement of the structural elements, their moduli, and a possible structural hierarchy. The principal objective of the thesis is the consideration of geometrical nonlinearities accounting for the large changes of the initial lattice geometry, due to the small bending stiffness of the structural elements, in comparison to their tensile rigidity. The so-called discrete homogenization method is extended to the geometrically nonlinear setting for periodical lattices; incremental schemes are constructed based on a staggered localization-homogenization computation of the lattice response over a repetitive unit cell submitted to a controlled deformation loading. The obtained effective medium is a micropolar anisotropic continuum, the effective properties of which accounting for the geometrical arrangement of the structural elements within the lattice and their mechanical properties. The non affine response of the lattice leads to possible size effects which can be captured by an enrichment of the classical Cauchy continuum either by adding rotational degrees of freedom as for the micropolar effective continuum, or by considering second order gradients of the displacement field. Both strategies are followed in this work, the construction of second order grade continua by discrete homogenization being done in a small perturbations framework. We show that both strategies for the enrichment of the effective continuum are complementary due to the existing analogy in the construction of the micropolar and second order grade continua by homogenization. The combination of both schemes further delivers tension, bending and torsion internal lengths, which reflect the lattice topology and the mechanical properties of its structural elements. Applications to textiles and biological membranes described as quasi periodical networks of filaments are considered. The computed effective response is validated by comparison with FE simulations performed over a representative unit cell of the lattice. The homogenization schemes have been implemented in a dedicated code written in combined symbolic and numerical language, and using as an input the lattice geometry and microstructural mechanical properties. The developed predictive micromechanical schemes offer a design tool to conceive new architectured materials to expand the boundaries of the 'material-property' space

This research was conducted as part of the formative evaluation of a mother-child interaction intervention, which was incorporated into the Kgolo Mmogo pilot study at the Kalafong Hospital in Tshwane (South Africa). The purpose of the intervention was to encourage the development of parenting skills and to improve mother-child relationships within an HIV context over a six-month period. By promoting more effective interaction between mother and child, child resilience could be enhanced and children could learn the necessary coping skills that would help them deal with the challenges posed by HIV and other life events. The aim of the study was to generate a systemic understanding of families affected by HIV/AIDS. The study explored (1) the effect of HIV on family interaction and (2) the effect of the mother-child interaction intervention on family interaction from the perspective of HIV-infected mothers. The theoretical framework chosen for the study was of a systemic nature and the standpoints, as set out by the Milan family therapy team, were implemented. Ten months after the intervention, four of the HIV-positive mothers who had participated in the intervention were interviewed and encouraged to share their experiences. Circular questions were employed in the interviews as a means of gathering data. A qualitative design was therefore the best option for this study. The research findings of this study coincide with previous literature and research findings; thus, the findings of this study have been consolidated. The current study findings support the importance of bridging the distance that is created by HIV in family relations, particularly between mother and child. Newly-diagnosed mothers often become stuck in their own processes and distance themselves from others in order to make sense of their situation. The broader social stigmas associated with HIV/AIDS contribute further to the sense of isolation that HIV-positive women experience. Often, women perceive HIV to be a disruptive force in their relationships with their partners and children, which creates tension, secrets and uncertainty within the family. HIV-infected mothers generally feel that keeping secrets from their children protects them from being traumatized by the social stigmas surrounding HIV/AIDS. Some HIV-positive mothers also feel that an emotional distance will shield their children from the pain of losing their mother. Because they are grappling with many negative feelings, such as anger and frustration, many HIV-positive mothers resort to strict disciplinary measures and avoid spending time with their children. The children misinterpret their mother’s behaviour and react in a manner that the mother perceives to be both disrespectful and disobedient, thus creating a recurring cycle in which both mothers and children become stuck. The participating mothers perceived the mother-child interaction intervention to focus on their emotional, physical, cognitive and behavioural needs as well as the needs of their children. The mothers experienced the intervention as having been particularly helpful to them and their children. They perceived themselves to be warmer, more supportive, more accepting and to have found meaning in their lives. In addition they felt that their children had begun to behave themselves and were also less avoidant of them. It enhanced their understanding of one another, and strengthened their bond so that they can depend on each other in times of difficulty. Copyright / Dissertation (MA)--University of Pretoria, 2009. / Psychology / unrestricted

Denna forskningsöversikt syftade till att undersöka vad som kan utgöra kognitiva hinder i lärandeprocessen under samhällskunskapsundervisning, med målet att finna implikationer för undervisning och examinationsformer som kan nå och engagera fler elever. Arbetet utgick ifrån ett teoretiskt ramverk för universellt utformade lärandesituationer, för att bidra till proaktiv och preventiv planering utifrån elevers funktionsvariation. Målet var att om möjligt reducera behovet av speciallösningar i efterhand, samt stödja samhällskunskapslärare i att möta eleverna såväl kollektivt som individuellt. Översikten inkluderar 48 peer-review-granskade artiklar publicerade i utvalda vetenskapliga tidskrifter, vilka bygger på antingen metaanalyser eller primärforskning som har utförts i skolmiljö med elever i årskurs 4 upp till och med gymnasiet. Särskild uppmärksamhet riktas mot de kognitiva krav som ställs när elever i takt med ökad ålder självständigt förväntas kunna bearbeta och skapa mening av samhällskunskapligt innehåll. Utifrån en kombinatorisk analys rekommenderar jag sammantaget mer explicit undervisning – i synnerhet litteracitetsutvecklande sådan sett till betydelsen av läs- och skrivförmåga för att lyckas inom samhällskunskapsämnet – samt mer kognitiv vägledning och modellering från samhällskunskapsläraren, dels för att utveckla elevens samhälleliga och akademiska litteracitet, dels för att på sikt möjliggöra självständig tillämpning av samhällskunskapliga tankeredskap. Vidare rekommenderas mer kognitiv validering av examinationer, för att synliggöra vilka kognitiva krav som bör ställas, vilka som faktiskt ställs och huruvida eleven använder sig av de förväntade kognitiva processerna. I ämnesdidaktisk forskning som hittills har genomförts i skandinavisk kontext framstår elevernas funktionsvariation som anmärkningsvärt osynliggjord, sett till den centrala roll som eleven spelar i många didaktiska modeller. När samhällkunskapsdidaktiken fokuserar på relationen mellan elev och innehåll är det utifrån en relativt homogen syn på gruppen nybörjare. Specialpedagogisk och språkvetenskaplig forskning däremot uppmärksammar i högre utsträckning “startsträckan” som elever har innan de når ämnesinnehållet och kan börja öva på ämnesspecifika förmågor.