Pervasive computing envisions an environment in which we are surrounded by many embedded computer devices. The existence of those networked devices provides us with a mobile, spontaneous and dynamic way to access various resources provided by different (security policy) domains. In recent years, we have witnessed the evolutionary development of numerous multiple domain applications. One of the richest examples is pervasive environments. Typi- cally, the conventional approach to secure access over multiple domains is to implement a unique trusted infrastructure, extending local identity or capa- bility based security systems and combining them with cross-domain authen- tication mechanisms. However, this does not adequately meet the security requirements of communicating with unknown players in pervasive environ- ments. Moreover, it is infeasible to define a global trust infrastructure and a set of assumptions that every player will trust in the multiple domain context. A powerful design technique to address those new security challenges posed by pervasive environments is to understand them from a domain perspective. This thesis presents Localisation of Trust (LoT), an architectural frame- work designed to address the security need of how to talk to correct strangers in pervasive environments. Based on the localising trust security principle, LoT provides a generic platform for building access control over multiple do- mains from two ends: authentication and authorisation. Firstly, LoT proposes a two-channel authentication protocol to replace traditional (strong) identity- based authentication protocols by exploring desirable contextual information for different pervasive applications. Then, delegation and localised authenti- cation are deployed to achieve authorisation in pervasive environments. The heart of this different semantic is to let the right domain get involved with its local players’ interactions by helping them to convert a “token” to a usable 2 access capability, whilst keeping revocation in mind. This is done by introduc- ing a domain-oriented Encryption-Based Access Control method, using ideas borrowed for Identity-based Encryption. The second part of this thesis describes several specific mechanisms and protocols including a Dual Capabilities Model to achieve the required anti- properties for LoT. Although novel, they are intended primarily as an existence proof rather than being claimed to be ideal. Depending upon the precise application and context, other mechanisms may be better. Most importantly, the architecture-focused LoT provides such a flexibility by introducing multiple domains as a primary concern but leaving untouched the security protocols underlying each single domain and system implementation. Finally, a single domain scenario, guest access, is examined with the light of LoT. The purpose of doing so is to enhance the understanding of domain and other concepts described in LoT and demonstrate the effectiveness and efficiency of LoT for the scenarios chosen.

MultiDetector-row Computed Tomography (MDCT) or MultiSlice Computed Tomography (MSCT) has undergone remarkable progress since its first introduction at the end of the 1990s. Given that CT examinations are generally recognized as a relatively high-dose procedure, concern has been expressed at the associated increase in doses. The International Committee on Radiation Protection (ICRP) noted in their report No.87 that absorbed doses in tissues from CT are among the highest observed in diagnostic radiology (i.e. 10–100 mGy). Therefore, the purpose of this thesis is to calculate the dosimetric quantities for brain, chest, and abdomen-pelvis examinations that were carried out using Philips Brilliance 16 and Brilliance 64 CT Scanners of the University General Hospital “Attikon”, as well as to perform their intercomparison. For brain examinations, axial technique was utilized. However, for chest and abdomen-pelvis examinations, spiral technique was applied. The effect of overranging (or overscanning) is connected with spiral mode and its contribution to patient dose is really important in case of MSCT scanners. Therefore, the contribution of the overrange effect for body examinations carried out was calculated. In the framework of this thesis, the contribution of overrange to the effective dose received by patients submitted to the forementioned examinations is calculated. Additionally, dose measurements were carried out in order to estimate the radiation burden to the eye lenses and the thyroid during the typical brain examination, both when eye lenses are inside and outside the irradiation field. / Οι Υπολογιστικοί Τομογράφοι (ΥΤ) πολλαπλών τομών έχουν σημειώσει μεγάλη πρόοδο από την κλινική εφαρμογή τους στις αρχές του 1990. Λαμβάνοντας υπ’ όψιν ότι οι εξετάσεις ΥΤ συνεπάγονται υψηλή ακτινική επιβάρυνση του ασθενή, η μελέτη τους έχει συγκεντρώσει το ερευνητικό ενδιαφέρον της επιστημονικής κοινότητας. Η Διεθνής Επιτροπή Ακτινοπροστασίας (ICRP) επισημαίνει στην αναφορά Νο 87 ότι η απορροφούμενη δόση στους ιστούς από εξετάσεις ΥΤ είναι από τις υψηλότερες στη διαγνωστική ακτινολογία (10-100 mGy). Συνεπώς, σκοπός της παρούσας διπλωματικής εργασίας είναι ο υπολογισμός των δοσιμετρικών μεγεθών για τις συνήθεις εξετάσεις εγκεφάλου, θώρακος και άνω-κάτω κοιλίας, οι οποίες πραγματοποιούνται με τους ΥΤ πολλαπλών τομών Brilliance 16 και Βrilliance 64 της Philips στο Π.Γ.Ν “ΑΤΤΙΚΟΝ ”,καθώς επίσης και η σύγκριση των αντίστοιχων δόσεων μεταξύ των συγκεκριμένων ΥΤ. Οι ασθενείς που υποβάλλονται σε εξετάσεις θώρακος και άνω-κάτω κοιλίας που πραγματοποιούνται με ελικοειδή τεχνική λαμβάνουν επιπλέον δόση (overscan) που οφείλεται στην τεχνική αυτή. Η συνεισφορά του “overscan” είναι ιδιαίτερα σημαντική στους ΥΤ πολλαπλών τομών, οπότε επιπλέον στόχος αυτής της διπλωματικής είναι ο υπολογισμός της. Τέλος, πραγματοποιήθηκαν μετρήσεις της δόσης του θυρεοειδή και των φακών των οφθαλμών κατά την υποβολή ασθενών στη συνήθη εξέταση εγκεφάλου, τόσο στην περίπτωση παρουσίας των οφθαλμών εντός όσο και εκτός πεδίου ακτινοβόλησης.

La compétitivité toujours plus importante et la mondialisation ont mis l'industrie manufacturière au défi de rationaliser les différentes façons de mettre sur le marché de nouveaux produits dans un délai court, avec des prix compétitifs tout en assurant des niveaux de qualité élevés. Le PDP moderne exige simultanément la collaboration de plusieurs groupes de travail qui assurent la création et l’échange d’information avec des points de vue multiples dans et à travers les frontières institutionnelles. Dans ce contexte, des problèmes d’interopérabilité sémantique ont été identifiés en raison de l'hétérogénéité des informations liées à des points de vue différents et leurs relations pour le développement de produits. Le travail présenté dans ce mémoire propose un cadre conceptuel d’interopération pour la conception et la fabrication de produits. Ce cadre est basé sur un ensemble d’ontologies clés, de base d’ingénierie et sur des approches de cartographie sémantique. Le cadre soutient les mécanismes qui permettent la conciliation sémantique en termes de partage, conversion et traduction, tout en améliorant la capacité de partage des connaissances entre les domaines hétérogènes qui doivent interopérer. La recherche a particulièrement porté sur la conception et la fabrication de produits tournants en plastique et explore les points particuliers de la malléabilité - la conception et la fabrication de moules. Un système expérimental a été proposé à l’aide de l'outil Protégé pour modéliser des ontologies de base et d’une plateforme Java intégrée à Jena pour développer l'interface avec l'utilisateur. Le concept et la mise en œuvre de cette recherche ont été testés par des expériences en utilisant des produits tournants en plastiques. Les résultats ont montré que l'information et ses relations rigoureusement définies peuvent assurer l'efficacité de la conception et la fabrication du produit dans un processus de développement de produits moderne et collaboratif / Global competitiveness has challenged manufacturing industry to rationalise different ways of bringing to the market new products in a short lead-time with competitive prices while ensuring higher quality levels. Modern PDP has required simultaneously collaborations of multiple groups, producing and exchanging information from multi-perspectives within and across institutional boundaries. However, it has been identified semantic interoperability issues in view of the information heterogeneity from multiple perspectives and their relationships across product development. This research proposes a conceptual framework of an Interoperable Product Design and Manufacturing based on a set of core ontological foundations and semantic mapping approaches. This framework has been particularly instantiated for the design and manufacturing of plastic injection moulded rotational products and has explored the particular viewpoints of moldability, mould design and manufacturing. The research approach explored particular information structures to support Design and Manufacture application. Subsequently, the relationships between these information structures have been investigated and the semantics reconciliation has been designed through mechanisms to convert, share and translate information from the multi-perspectives. An experimental system has been performed using the Protégé tool to model the core ontologies and the Java platform integrated with the Jena to develop the interface with the user. The conceptual framework proposed in this research has been tested through experiments using rotational plastic products. Therefore, this research has shown that information rigorously-defined and their well-defined relationships can ensure the effectiveness of product design and manufacturing in a modern and collaborative PDP

Summaries in English and Afrikaans / Text in Afrikaans / Key terms in English and Afrikaans / Verskeie tekortkomings is in die bestaande konseptuele model en kwantitatiewe navorsingsliteratuur oor skofwerk geidentifiseer. Ontevredenheid met die oorvereenvoudigde oorsaak-gevolg-verklarings vir getroude vroue se skofwerkervaring het in die studie gelei tot die ontwikkeling van 'n ekologiese model van vroueskofwerk. Hierdie nuwe konseptuele model weerspieel 'n altematiewe benadering waar erkenning gegee word aan die bestaan van meervoudige realiteite wat mense in konsensus deur taal konstrueer. Die oogmerk met die ekologiese model is om, met inagneming van vroueskofwerkers se wyer konteks, patrone te ondersoek van hoe die verskillende beskrywings van getroude vroue se ervaring van skofwerk bymekaar pas. Daarmee kan 'n meer sistemiese begrip verkry word wat die kompleksiteit van menslike interaksie respekteer. Die ekologiese model van vroueskofwerk is ontwikkel as 'n hulpmiddel vir die waamemer om ryk, beskrywende ekologiese verhale te kan konstrueer van hoe getroude vroue se belewing van skofwerk tot sistemiese ontwrigting of behoud kan lei. / Several shortcomings have been identified in the existing conceptual model and quantitative research literature regarding shiftwork. Dissatisfaction with the oversimplified cause-effect-explanations for married women's shiftwork experience has led to the development of an ecological model of women shiftwork in this study. This new conceptual model reflects an alternative approach where recognition is given to the existence of multiple realities which are consensually created by people through language. The aim with the ecological model, by taking into account the broader context of women shiftworkers, is to search for patterns of how the different descriptions of women's experience of shiftwork fit together. This offers a more systemic view that respects the complexity of human interaction. The ecological model for women shiftwork is developed as an aid to the observer to construct rich, descriptive ecological stories about how married women's experience of shiftwork can lead to systemic disruption or conservation. / Psychology / M.A. (Clinical Psychology)

Summaries in English and Afrikaans / Text in Afrikaans / Key terms in English and Afrikaans / Verskeie tekortkomings is in die bestaande konseptuele model en kwantitatiewe navorsingsliteratuur oor skofwerk geidentifiseer. Ontevredenheid met die oorvereenvoudigde oorsaak-gevolg-verklarings vir getroude vroue se skofwerkervaring het in die studie gelei tot die ontwikkeling van 'n ekologiese model van vroueskofwerk. Hierdie nuwe konseptuele model weerspieel 'n altematiewe benadering waar erkenning gegee word aan die bestaan van meervoudige realiteite wat mense in konsensus deur taal konstrueer. Die oogmerk met die ekologiese model is om, met inagneming van vroueskofwerkers se wyer konteks, patrone te ondersoek van hoe die verskillende beskrywings van getroude vroue se ervaring van skofwerk bymekaar pas. Daarmee kan 'n meer sistemiese begrip verkry word wat die kompleksiteit van menslike interaksie respekteer. Die ekologiese model van vroueskofwerk is ontwikkel as 'n hulpmiddel vir die waamemer om ryk, beskrywende ekologiese verhale te kan konstrueer van hoe getroude vroue se belewing van skofwerk tot sistemiese ontwrigting of behoud kan lei. / Several shortcomings have been identified in the existing conceptual model and quantitative research literature regarding shiftwork. Dissatisfaction with the oversimplified cause-effect-explanations for married women's shiftwork experience has led to the development of an ecological model of women shiftwork in this study. This new conceptual model reflects an alternative approach where recognition is given to the existence of multiple realities which are consensually created by people through language. The aim with the ecological model, by taking into account the broader context of women shiftworkers, is to search for patterns of how the different descriptions of women's experience of shiftwork fit together. This offers a more systemic view that respects the complexity of human interaction. The ecological model for women shiftwork is developed as an aid to the observer to construct rich, descriptive ecological stories about how married women's experience of shiftwork can lead to systemic disruption or conservation. / Psychology / M.A. (Clinical Psychology)