Virtual Reality (VR) video is emerging as a new art form. Viewing VR video requires wearing the VR headset to fully experience the immersive surrounding of the content. However, the novel viewing experience of VR video creates new challenges and requirements for conventional video authoring tools, which were designed mainly for working with normal video on a desktop display. Designing effective authoring tools for VR video requires intuitive video interfaces specific to VR. This dissertation develops new workflows and systems that enable filmmakers to create and improve VR video while fully immersed in a VR headset. We introduce a series of authoring tools that enables filmmakers to work with video in VR: 1) Vremiere, an in-headset video editing application that enables editors to edit VR video entirely in the headset, 2) CollaVR, a networked system that enables multiple users to collaborate and review video together in VR, and 3) a set of techniques to assist filmmakers in managing and accessing interfaces in stereoscopic VR video without suffering depth conflicts. The design of these applications is grounded in existing practices and principles learned in interviews with VR professionals. A series of studies is conducted to evaluate these systems, which demonstrate the potential of in-headset video authoring.

Virtual team leaders in health care must have the right resources available to help them effectively perform their jobs. Better performance from the leader may lead to greater employee satisfaction. The problem addressed by this study was the impact of leadership style on employee satisfaction of virtual nurses. The purpose of this quantitative correlational study was to investigate the relationship between the leadership styles of virtual nursing environment leaders as perceived by virtual employee nurses and the nurses' satisfaction as measured by the Multifactor Leadership Questionnaire-short form. Building on the theoretical foundation of Bass's 1990 work, this study examined the relationship between full range leadership and three measures linked to team success, work effort, perceived leader effectiveness, and employee satisfaction, for virtual teams. Populations came from national organizations that hire registered nurses to work remotely. The sampling strategy was a nonprobability convenience sample of 131 registered nurses. Data analysis included both descriptive and inferential statistics. Correlations were used to predict the relationship of the dependent and independent variables. There were strong positive correlations with transformational leadership and transactional leadership contingent reward with employee satisfaction, while passive/avoidant leadership correlations were negative with employee satisfaction. The potential significance of this study is a better understanding of how leadership in a virtual nursing environment can affect employee satisfaction, which can have a positive effect on job performance and employee retention, potentially leading to improved health care services and reduced health care costs.

Syftet med uppsatsen är att bidra med kunskap om virtuella team, genom att undersöka medarbetares och ledares upplevelser av att arbeta inom sådana team. Uppsatsens resultat förväntas kunna bidra till en ökad kunskap om virtuella team som verkar inom samma tidszon samt hur tillit och kommunikation förhåller sig inom virtuella team. Uppsatsen innefattar nio semistrukturerade intervjuer som genomförts med både ledare och medarbetare för att besvara frågeställningarna och genom det uppnå syftet. Att skapa en stark tillit mellan individerna i ett virtuellt team är det som anses svårast. Resultatet visade dock att virtuella team i dagens arbetsmiljö inte har samma problematik som de tidigare haft. Slutsatsen som drogs var att under premissen att virtuella team arbetar inom samma tidszon så påverkas arbetet inte i någon större utsträckning. / The aim of the study is to contribute with knowledge about virtual teams by investigating co-workers and leaders’ perception of working in such teams. Nine semi-structured interviews with co-workers and leaders were made in this qualitative case study. In line with previous studies, the result reveals that creating trust is considered the most difficult for the individuals within virtual teams. Virtual teams in today's working environment do not have the same problems as they used to have. It was concluded that if virtual teams work within the same time zone, the work is not affected to a great extent.

This paper presents designs for Multistable Shape-Shifting Surfaces (MSSS) by introducing bistability into the Shape-Shifting Surface (SSS). SSSs are defined as surfaces that retain their effectiveness as a physical barrier while undergoing changes in shape. The addition of bistability to the SSS gives the surface multiple distinct positions in which it remains when shifted to, i.e. by designing bistability into a single SSS link, the SSS unit cell can change into multiple shapes, and stabilize within the resulting shape, while maintaining integrity against various forms of external assaults normal to its surface. Planar stable configurations of the unit cell include, expanded, compressed, sheared, half-compressed, and partially-compressed, resulting in the planar shapes of a large square, small square, rhombus, rectangle, and trapezoid respectively. Tiling methods were introduced which gave the ability to produce out-of-plane assemblies using planar MSSS unit cells. A five-walled rigid storage container prototype was produced that allowed for numerous stable positions and volumes. Applications for MSSSs can include size-changing vehicle beds, expandable laptop screens, deformable walls, and volume-changing rigid-storage containers. Analysis of the MSSS was done using pseudo-rigid-Body Models (PRBMs) and Finite Element Analysis (FEA) which ensured bistable characteristics before prototypes were fabricated.

This study is set in the broad context of the changing world of work that is characterised by the dissolution of full-time stable employment and the emergence of precarious, insecure forms of work (see e.g. Gorz, 1999, Hardt and Negri, 2005, Huws, 2016, Lorey, 2015, Ross, 2003, Ross, 2009, Smith, 2001, Standing, 2011). As a response to these labour market uncertainties a growing number of individuals are managing multiple areas of the self as part of their work or occupation. This trend has been termed 'the new worker-subjectivity' or 'the entrepreneurial self' that is formed through practices of self-management (Bührmann, 2005, Lorey, 2009). Despite increasing awareness of the emergence of the entrepreneurial worker-subjectivity, research into practices of self-management has only focused on occupational groups in formal work. Knowledge about the trend in the context of virtual workers who operate outside of conventional working relations and have no publicly recognised work identity is largely missing. In order to address this gap, this study explores how entrepreneurial worker-subjectivities manifest in professional online poker players as an emerging online occupation. It investigates how these workers manage themselves in the absence of formal organisational control and socially recognised occupational norms, and asks what are the effects of this self-management on the quality of their working lives? The study is based on 39 in-depth interviews with people involved in online poker or other similar activities such as online gaming or trading. The interviews were conducted either face-to-face in Estonia, Bulgaria, Romania and UK or over Skype between December 2012 and May 2014. The study develops an analytical framework for researching entrepreneurial worker-subjectivities in the context of an emerging occupation and a three-stage-model of the trajectory that provides a basis for exploring the career paths of professional online poker players. Using these framework, the study finds that professional online poker players manage various areas of the self by following informal occupational rules and that their sense of professionalism is largely derived from various practices of self-management that help them distinguish from recreational players. The study also discovers conflicting relations of autonomy and control among the workers and a range of negative effects that self-management practices have on professional online poker players. It concludes that professional online poker is not a sustainable long-term career option. These findings contribute to a better understanding of virtual work, the emergence of online poker playing as a form of work and the development of the entrepreneurial worker-subjectivity.

Estruturas Mistas de Aço-Concreto têm sido usadas extensivamente na construção de pontes e viadutos urbanos, especialmente a partir da segunda metade do século XX. A popularidade desse tipo de solução, com seções caixão, cresceu devido a sua alta capacidade à flexão, rigidez à torção e uma seção transversal fechada que reduz a superfície exposta a corrosão. Este trabalho discorre sobre o comportamento estrutural, procedimentos de análise e verificação em Estado Limite Último (ELU) de pontes mistas de seção caixão com aplicação de protensão externa. Em vista da escassez de literatura sobre o assunto e inexistência de norma brasileira, o trabalho objetiva produzir um roteiro de análise para a determinação da capacidade à flexão em ELU de estruturas mistas de seção caixão protendidas. Embasado na norma americana AASHTO-LRFD:2012 e na revisão bibliográfica, propôs-se um estudo de caso para verificação/dimensionamento analíticos da estrutura, tratando de Momentos Fletores Resistentes (positivos e negativos), Esforço Cortante Resistente e conectores de cisalhamento. Após esta etapa inicial, aplicou-se protensão à estrutura e, por meio de métodos analíticos, e auxílio do método dos trabalhos virtuais, obtiveram-se as perdas de protensão e a relação entre a deformação adicional do cabo de protensão em função do momento externo aplicado à estrutura. Deste modo pôde-se fazer o equilíbrio de forças horizontais, através do método da Bissecção, e obter-se o valor de incremento de Momentos Fletores Positivos e Negativos Resistentes da estrutura. Observou-se, com a protensão, um aumento de resistência importante na região de Momentos Fletores Negativos em ELU (~40%); para a região de flexão positiva esse incremento foi pouco superior a 7%, em relação à estrutura nãoprotendida. Por fim, modelou-se a estrutura em elementos finitos de casca com o software SAP2000, a fim de confrontar a análise inicial, feita em modelo de barras de pórtico espacial, preconizada pela norma AASHTO-LRFD:2012. Os resultados mostram que o modelo em barras de pórtico espacial, em termos de deslocamentos e tensões, é adequado à análise deste tipo de estrutura. / Steel-Concrete Composite Strutures have been used extensively in the construction of bridges and urban viaducts, especially from the second half of the twentieth century. The popularity of this type of solution, with box sections, has increased due to its high flexural capacity and torsion stiffness combined with a closed cross section that reduces the exposed surface to corrosion. This paper discusses the structural behavior, analysis and verification procedures in the Ultimate Limite State (ULS) of Composite Box Girder Bridges with application of external prestressing. In view of the paucity of literature on the subject and the absence of Brazilian standard, this work aims to produce a analysis script to determine the flexural capacity of prestressed composite box girder structures in ULS. Grounded in the American Standard AASHTO-LRFD:2012 and the literature review, we propose a case study for analytical verification/dimensioning of the structure, concerning positive and negative bending moments, shear and shear connectors. After this initial stage, prestressing was applied to the structure, and with de aid of analytical methods, and the virtual work method, the prestress losses and the relation between the additional strain of the tendons and the external applied moment were obtained. Thus, it was possible to make the horizontal forces balance through the Bisection Method and obtain the increment of positive and negative flexion strength. It was observed, with prestressing, an important increase of capacity in the negative bending region for ULS (~40%); for the positive bending region, the increase was somewhat higher than 7%, compared with the non-prestressed structure. Finally, a finite element model with shell elements was held with aid of the software SAP2000 to confront the initial analysis, made in space frame bars model, recommended by AASHTO-LRFD:2012 standard. The results show that the space frame bars model, in terms of displacements and stresses, is appropriate to analyze this type of structure.

Estruturas Mistas de Aço-Concreto têm sido usadas extensivamente na construção de pontes e viadutos urbanos, especialmente a partir da segunda metade do século XX. A popularidade desse tipo de solução, com seções caixão, cresceu devido a sua alta capacidade à flexão, rigidez à torção e uma seção transversal fechada que reduz a superfície exposta a corrosão. Este trabalho discorre sobre o comportamento estrutural, procedimentos de análise e verificação em Estado Limite Último (ELU) de pontes mistas de seção caixão com aplicação de protensão externa. Em vista da escassez de literatura sobre o assunto e inexistência de norma brasileira, o trabalho objetiva produzir um roteiro de análise para a determinação da capacidade à flexão em ELU de estruturas mistas de seção caixão protendidas. Embasado na norma americana AASHTO-LRFD:2012 e na revisão bibliográfica, propôs-se um estudo de caso para verificação/dimensionamento analíticos da estrutura, tratando de Momentos Fletores Resistentes (positivos e negativos), Esforço Cortante Resistente e conectores de cisalhamento. Após esta etapa inicial, aplicou-se protensão à estrutura e, por meio de métodos analíticos, e auxílio do método dos trabalhos virtuais, obtiveram-se as perdas de protensão e a relação entre a deformação adicional do cabo de protensão em função do momento externo aplicado à estrutura. Deste modo pôde-se fazer o equilíbrio de forças horizontais, através do método da Bissecção, e obter-se o valor de incremento de Momentos Fletores Positivos e Negativos Resistentes da estrutura. Observou-se, com a protensão, um aumento de resistência importante na região de Momentos Fletores Negativos em ELU (~40%); para a região de flexão positiva esse incremento foi pouco superior a 7%, em relação à estrutura nãoprotendida. Por fim, modelou-se a estrutura em elementos finitos de casca com o software SAP2000, a fim de confrontar a análise inicial, feita em modelo de barras de pórtico espacial, preconizada pela norma AASHTO-LRFD:2012. Os resultados mostram que o modelo em barras de pórtico espacial, em termos de deslocamentos e tensões, é adequado à análise deste tipo de estrutura. / Steel-Concrete Composite Strutures have been used extensively in the construction of bridges and urban viaducts, especially from the second half of the twentieth century. The popularity of this type of solution, with box sections, has increased due to its high flexural capacity and torsion stiffness combined with a closed cross section that reduces the exposed surface to corrosion. This paper discusses the structural behavior, analysis and verification procedures in the Ultimate Limite State (ULS) of Composite Box Girder Bridges with application of external prestressing. In view of the paucity of literature on the subject and the absence of Brazilian standard, this work aims to produce a analysis script to determine the flexural capacity of prestressed composite box girder structures in ULS. Grounded in the American Standard AASHTO-LRFD:2012 and the literature review, we propose a case study for analytical verification/dimensioning of the structure, concerning positive and negative bending moments, shear and shear connectors. After this initial stage, prestressing was applied to the structure, and with de aid of analytical methods, and the virtual work method, the prestress losses and the relation between the additional strain of the tendons and the external applied moment were obtained. Thus, it was possible to make the horizontal forces balance through the Bisection Method and obtain the increment of positive and negative flexion strength. It was observed, with prestressing, an important increase of capacity in the negative bending region for ULS (~40%); for the positive bending region, the increase was somewhat higher than 7%, compared with the non-prestressed structure. Finally, a finite element model with shell elements was held with aid of the software SAP2000 to confront the initial analysis, made in space frame bars model, recommended by AASHTO-LRFD:2012 standard. The results show that the space frame bars model, in terms of displacements and stresses, is appropriate to analyze this type of structure.

Estruturas Mistas de Aço-Concreto têm sido usadas extensivamente na construção de pontes e viadutos urbanos, especialmente a partir da segunda metade do século XX. A popularidade desse tipo de solução, com seções caixão, cresceu devido a sua alta capacidade à flexão, rigidez à torção e uma seção transversal fechada que reduz a superfície exposta a corrosão. Este trabalho discorre sobre o comportamento estrutural, procedimentos de análise e verificação em Estado Limite Último (ELU) de pontes mistas de seção caixão com aplicação de protensão externa. Em vista da escassez de literatura sobre o assunto e inexistência de norma brasileira, o trabalho objetiva produzir um roteiro de análise para a determinação da capacidade à flexão em ELU de estruturas mistas de seção caixão protendidas. Embasado na norma americana AASHTO-LRFD:2012 e na revisão bibliográfica, propôs-se um estudo de caso para verificação/dimensionamento analíticos da estrutura, tratando de Momentos Fletores Resistentes (positivos e negativos), Esforço Cortante Resistente e conectores de cisalhamento. Após esta etapa inicial, aplicou-se protensão à estrutura e, por meio de métodos analíticos, e auxílio do método dos trabalhos virtuais, obtiveram-se as perdas de protensão e a relação entre a deformação adicional do cabo de protensão em função do momento externo aplicado à estrutura. Deste modo pôde-se fazer o equilíbrio de forças horizontais, através do método da Bissecção, e obter-se o valor de incremento de Momentos Fletores Positivos e Negativos Resistentes da estrutura. Observou-se, com a protensão, um aumento de resistência importante na região de Momentos Fletores Negativos em ELU (~40%); para a região de flexão positiva esse incremento foi pouco superior a 7%, em relação à estrutura nãoprotendida. Por fim, modelou-se a estrutura em elementos finitos de casca com o software SAP2000, a fim de confrontar a análise inicial, feita em modelo de barras de pórtico espacial, preconizada pela norma AASHTO-LRFD:2012. Os resultados mostram que o modelo em barras de pórtico espacial, em termos de deslocamentos e tensões, é adequado à análise deste tipo de estrutura. / Steel-Concrete Composite Strutures have been used extensively in the construction of bridges and urban viaducts, especially from the second half of the twentieth century. The popularity of this type of solution, with box sections, has increased due to its high flexural capacity and torsion stiffness combined with a closed cross section that reduces the exposed surface to corrosion. This paper discusses the structural behavior, analysis and verification procedures in the Ultimate Limite State (ULS) of Composite Box Girder Bridges with application of external prestressing. In view of the paucity of literature on the subject and the absence of Brazilian standard, this work aims to produce a analysis script to determine the flexural capacity of prestressed composite box girder structures in ULS. Grounded in the American Standard AASHTO-LRFD:2012 and the literature review, we propose a case study for analytical verification/dimensioning of the structure, concerning positive and negative bending moments, shear and shear connectors. After this initial stage, prestressing was applied to the structure, and with de aid of analytical methods, and the virtual work method, the prestress losses and the relation between the additional strain of the tendons and the external applied moment were obtained. Thus, it was possible to make the horizontal forces balance through the Bisection Method and obtain the increment of positive and negative flexion strength. It was observed, with prestressing, an important increase of capacity in the negative bending region for ULS (~40%); for the positive bending region, the increase was somewhat higher than 7%, compared with the non-prestressed structure. Finally, a finite element model with shell elements was held with aid of the software SAP2000 to confront the initial analysis, made in space frame bars model, recommended by AASHTO-LRFD:2012 standard. The results show that the space frame bars model, in terms of displacements and stresses, is appropriate to analyze this type of structure.

Lorsqu’ils travaillent en équipe, les humains ont rarement des comportements optimaux : ils peuvent faire des erreurs, manquer de motivation ou de compétence. Dans les domaines des environnements virtuels ou des systèmes multi-agents, de nombreux travaux ont cherché à reproduire les comportements d’équipes humaines : un agent représente alors un membre de l’équipe. Cependant, ces travaux ont très souvent pour objectif la performance de l’équipe, et non la fidélité des comportements produits. Pour former un apprenant en environnement virtuel à prêter attention et à s’adapter aux autres, nous avons cherché dans cette thèse à reproduire des comportements humains réalistes et non-optimaux de travail d’équipe. Plus particulièrement, nous nous sommes intéressés aux équipes auto-organisées, c’est-à-dire aux équipes dans lesquelles le pouvoir de décision est réparti entre les membres, et dans lesquelles l’organisation est implicite. Dans de telles équipes, l’organisation se fait non pas au travers des communications mais par l’observation et l’anticipation des comportements des autres. Pour s’organiser, chaque agent doit se demander ce qu’il est préférable de faire en fonction de ce que pourraient faire les autres, et donc se poser des questions telles que Ai-je confiance en la compétence de mon coéquipier pour faire cette tâche ? Les relations de confiance permettent donc à chacun de prendre en compte les autres. Pour générer de tels comportements, nous proposons un système permettant aux agents de raisonner d’une part sur un modèle de l’activité à effectuer et d’autre part sur les relations de confiance qui les lient aux autres agents de l’environnement. Dans ce cadre, notre première contribution porte sur l’augmentation du langage de description de l’activité Activity-DL de manière à permettre la description d’activités collectives. Nous proposons également des mécanismes de propagation de contraintes et d’informations qui faciliteront le raisonnement des agents. Ces contraintes et informations permettront par exemple aux agents de répondre à la question Avons-nous les compétences nécessaires pour faire la tâche qui permettra de réaliser notre but collectif ? Notre seconde contribution porte sur la proposition d’un modèle d’agent opérationnalisant le modèle de confiance de Mayer et al. (1995), sélectionné après une étude de la littérature en sciences humaines et sociales sur la confiance. La confiance d’un agent en un autre est décrite selon trois dimensions : l’intégrité, la bienveillance et les compétences. Chaque agent est donc défini par ces trois dimensions et a des croyances sur l’intégrité, la bienveillance et la compétence des autres agents. De plus chaque agent possède des buts qui lui sont personnels ainsi que des buts collectifs et devra donc choisir quel but privilégier. Finalement nous proposons un moteur décisionnel qui permet à chaque agent de calculer l’importance qu’il accorde à ses buts afin de sélectionner une tâche. Nous avons défini les mécanismes de calcul de l’importance des buts de manière à modéliser l’influence sur l’agent de ses croyances sur les autres, et pour sélectionner une tâche, l’agent raisonne à la fois sur les modèles d’activité et sur ses attentes à propos du comportement des autres, également générées à partir des croyances de l’agent sur les autres. Nous avons implémenté notre système et constaté qu’il répond à nos objectifs de génération de comportements d’équipe réalistes et non optimaux. Nous avons également conduit une évaluation perceptive préliminaire au cours de laquelle les participants ont notamment été capables de percevoir la confiance ou le manque de confiance d’un agent en un autre grâce à son comportement. / When working in teams, humans rarely display optimal behaviors: they sometimes make mistakes, lack motivation or competence. In virtual environments or in multi-agent systems, many studies have tried to reproduce human teamwork: each agent acts as a team member. However, the main objective in those studies is the performance of the team: each agent should display optimal behavior, and the realism of those simulated behaviors is not a concern. To train someone in a virtual environment to pay attention to and to adapt to their teammates, we built a decision-making system for agents to display realistic and non-optimal behaviors. More specifically, we are interested in self-organized teams (i.e. teams where the decision power is decentralized among its members) and in implicit organization (i.e. when team members do not interact through communications but rather through the observation of others’ behaviors). In such a team, each agent has to think about what it should do given what others could do. Agents then have to ask themselves questions such as Do I trust my teammate’s competence to perform this task? Trust relationships therefore allow agents to take others into account. We propose a system that allows agents to reason, on the first hand, on models of the activity they have to do, and on the other hand, on trust relationships they share with others. In that context, we first augmented the Activity-Description Language so that it supports the description of collective activities. We also defined mechanisms for constraint generation that facilitates agent reasoning, by giving them the answer to questions like Do we have the required abilities to perform the task which will achieve our goal? We then proposed an agent model based on the model of interpersonal trust of Mayer et al. (1995) that we selected after a study of trust in social science. This model describes trust relationship with three dimensions: the trustor trusts the trustee’s integrity, benevolence and abilities. An agent is therefore defined through those three dimensions, and has a mental model of each other agent; i.e. has trust beliefs about others’ integrity, benevolence and abilities. Moreover each agent has both personal and collective goals (i.e. goals that are shared with other members of the team), and thus will have to decide which goal to focus on. Finally we proposed a decision-making system that allows an agent to compute the importance it gives to its goals and then to select a task. When computing goal importance, the agent is influenced by its trust beliefs about others, and to select a task, it reasons on the activity models and on its expectations about what others could do. Those expectations are generated from the agents’ trust beliefs. We implemented our system and observed that it produces realistic and non-optimal behaviors. We also conducted a preliminary perceptive evaluation which showed that participants were able to recognize one agent’s trust or lack of trust in another through the behaviors of the first one.

This thesis presents the results of a research project to investigate the behaviour of the two components of a reverse channel connection to concrete filled tubular sections: the reverse channel and the steel tubular section, at both ambient and elevated temperatures. This research forms part of a European Union funded project on the robustness of joints to composite columns under fire conditions. The specific objectives of this research are to develop methods of quantifying the load-deformation behaviour at various temperatures of the two components. This research has been carried out through a combination of experiments, numerical simulations and analytical developments. Two series of tests have been carried out at different elevated temperatures, one for the reverse channels with lateral loads to the web applied as tensile loads through bolts and one for the concrete filled tubular sections under lateral loads applied through two steel plates (simulating the legs of a reverse channel) in the longitudinal direction of the section. These tests have been used to provide data for the validation of the numerical models based on using the general finite element package ABAQUS. The validated numerical models have been used to conduct a number of parametric studies to provide extensive data for the development of analytical methods to determine the load-deflection characteristics of the two components. For the reverse channel web, the load-deflection relationship consists of two parts and this research has developed analytical equations to predict initial stiffness, yield and ultimate resistance. The initial stiffness is based on extending and simplifying the Timoshenko solution for a plate under a block of lateral loads. The yield resistance is based on the yield line solution that the failure patterns were chosen based on the results attained from test and simulations. The ultimate resistance was calculated based on virtual work principle for the patterns considered in the yield resistance part. For the rectangular concrete filled tubular sections under lateral pulling forces applied through two plates, the load-deflection curve consists of two parts, depicting a linear phase followed by a nonlinear part. This research has developed expressions to calculate initial stiffness, yield resistance, and ultimate resistance. The initial stiffness is formulated according to the Timoshenko solution for a partially loaded plate. The yield resistance is determined by employing yield line solution for the yield patterns obtained from both the test and FE modelling. The ultimate resistance is evaluated by implementing the virtual work principle to the patterns considered in former part. The analytical load-deflection solutions have been compared with the numerical simulation and the experimental results and the agreement is generally satisfactory.