Workload balancing in distributed virtual reality environments

Virtual Reality (VR) has grown to become state-of-theart technology in many business- and consumer oriented E-Commerce applications. One of the major design challenges of VR environments is the placement of the rendering process. The rendering process converts the abstract description of a scene as contained in an object database to an image. This process is usually done at the client side like in VRML [1] a technology that requires the client���s computational power for smooth rendering. The vision of VR is also strongly connected to the issue of Quality of Service (QoS) as the perceived realism is subject to an interactive frame rate ranging from 10 to 30 frames-per-second (fps), real-time feedback mechanisms and realistic image quality. These requirements overwhelm traditional home computers or even high sophisticated graphical workstations over their limits. Our work therefore introduces an approach for a distributed rendering architecture that gracefully balances the workload between the client and a clusterbased server. We believe that a distributed rendering approach as described in this paper has three major benefits: It reduces the clients workload, it decreases the network traffic and it allows to re-use already rendered scenes.

A realidade virtual como factor de atrac����o para a engenharia

O objectivo da Realidade Virtual �� simples de entender mas muito dif��cil de implementar: criar ambientes completamente indiferenci��veis do mundo real com os quais se possa interagir de um modo natural. Desde a cria����o do Sensorama por Morton Heiling em 1962, passando pela difus��o do conceito pelo p��blico geral na d��cada de 90 at�� os dias de hoje, a evolu����o da Realidade Virtual tem sido constante. Este conjunto de tecnologias tem estado envolvido por uma certa descren��a por parte da sociedade, motivada pelas grandes expectativas que lhe foram atribu��das e pelo estado de desenvolvimento do hardware aquando do seu auge. No entanto, actualmente assiste-se a um ressurgimento do seu interesse no p��blico geral com a introdu����o de imagem estereosc��pica no cinema ou o sucesso dos controladores da consola Nintendo Wii. Hoje em dia as suas aplica����es s��o muito variadas: desde o treino de pilotos de avi��o ao tratamento de fobias, passando pela industria do entretenimento e a visita virtual de locais com interesse hist��rico ou tur��stico. O objectivo desta tese de mestrado �� explorar uma ��rea que ainda n��o tem sido muito abrangida pela Realidade Virtual e que cobre tamb��m aspectos educacionais e l��dicos de modo a ser um factor de atrac����o para os estudantes do ensino secund��rio: a simula����o de instrumentos musicais. Para tal foi implementado um sistema capaz de simular instrumentos musicais de percuss��o (uma bateria) utilizando imagem estereosc��pica, som posicional e interfaces com o utilizador realistas. Os resultados obtidos nas sess��es de avalia����o efectuadas por alunos recentemente ingressados no ensino superior demonstram que o sistema desenvolvido, bem como a inova����o em interfaces do utilizador com os dispositivos electr��nicos de uma forma geral, constituem um meio efectivo na sua motiva����o para a escolha de um curso na ��rea da engenharia.

Taxonomy of broker's functions in virtual enterprises

Not just with the emergence but also with the growing of the electronic market, that is, the growth of online suppliers of services and products and Internet users (potential consumers), the necessary conditions to the affirmation of the agile/virtual enterprises (A/VE) as a present and future enterprise organizational model are created. In this context, it is our understanding that the broker may have an important role in its development, namely, if the broker performs functions for the A/VE with better efficacy and efficiency. In this article, we will present first a revision of the broker���s models in a structured form. We present a taxonomy of possible broker���s functions for the broker���s actuation near the A/VE and then the classification of the literature broker���s models. This classification will permit an analysis of a broker���s model and establish a mainframe for our broker���s model according to the BM_Virtual Enterprise Architecture Reference Model (BM_VEARM).

Simulador em Realidade Virtual para Aprendizagem da F��sica

A forma como aprendemos depende do contexto tecnol��gico e sociocultural que nos rodeia, actualmente a inclus��o de tecnologia recente na sala de aula n��o �� mais considerada opcional, mas sim uma necessidade pois a forma como o aluno aprende est�� em constante evolu����o. Tendo em aten����o esta necessidade, foi desenvolvido no decorrer desta tese um simulador em realidade virtual que utiliza comandos/interfaces h��pticos. O objectivo deste simulador �� ensinar conceitos de f��sica de forma interactiva. Os dispositivos h��pticos permitem adicionar o sentido t��ctil ou de toque �� interac����o entre homem e m��quina, permitindo assim aceder a novas sensa����es relativas ao seu uso nomeadamente com objectivos de aprendizagem. O simulador desenvolvido designado por ���Forces of Physics��� aborda tr��s tipos de for��as da f��sica: for��as de atrito, for��as gravitacionais e for��as aerodin��micas. Cada tipo de for��a corresponde a um m��dulo do simulador contendo uma simula����o individual em que s��o explicados conceitos espec��ficos dessa for��a num ambiente visual estimulante e com uma interac����o mais realista devido �� inclus��o do dispositivo h��ptico Novint Falcon. O simulador foi apresentado a v��rios utilizadores bem como �� comunidade cient��fica atrav��s de apresenta����es em confer��ncias. A avalia����o foi realizada com recurso a um question��rio com dez perguntas, cinco de sobre aprendizagem e cinco sobre a utiliza����o, tendo sido preenchido por 14 utilizadores. O simulador obteve uma boa recep����o por parte dos utilizadores, tendo v��rios utilizadores expressado as suas opini��es sobre estado actual do simulador, do futuro do mesmo e da respectiva validade para uso na sala de aula.

Estratifica����o da intera����o com o utilizador em ambientes de Realidade Virtual

A evolu����o tecnol��gica tem sido de tal ordem que a realidade virtual deixou de ser um mero conceito que apenas �� poss��vel de implementar recorrendo a m��quinas com um poder de processamento muito elevado. Tendo em conta o potencial da realidade virtual e a n��o exist��ncia de boas pr��ticas na cria����o da interface de um sistema que use este conceito, pretende-se, nesta disserta����o, fazer um estudo sobre como pode ser analisada e estruturada a componente de intera����o atrav��s da estratifica����o de n��veis de intera����o para as diferentes opera����es do sistema pretendido. Por forma a ser poss��vel, posteriormente, comparar cada um dos sistemas relativamente �� intera����o, foram estipulados um conjunto de a����es/opera����es que teriam de ser pass��veis de executar em cada um, bem como, um tema base, uma aplica����o de realidade virtual de simula����o de espa��o aplicada ao sector mobili��rio. Depois de implementados os sistemas, estes foram apresentados a um conjunto de pessoas que foram inquiridas sobre os mesmos, por forma a avaliar a intera����o com cada um. Atrav��s dos resultados obtidos da avalia����o dos inqu��ritos entregues, foi poss��vel concluir que, para uma grande parte das opera����es implementadas, existe uma prefer��ncia para que a realiza����o da opera����o seja o mais similar �� sua execu����o num contexto real.

Effects of emotional valence and three-dimensionality of visual stimuli on brain activation: an fMRI study

BACKGROUND: Examining changes in brain activation linked with emotion-inducing stimuli is essential to the study of emotions. Due to the ecological potential of techniques such as virtual reality (VR), inspection of whether brain activation in response to emotional stimuli can be modulated by the three-dimensional (3D) properties of the images is important. OBJECTIVE: The current study sought to test whether the activation of brain areas involved in the emotional processing of scenarios of different valences can be modulated by 3D. Therefore, the focus was made on the interaction effect between emotion-inducing stimuli of different emotional valences (pleasant, unpleasant and neutral valences) and visualization types (2D, 3D). However, main effects were also analyzed.METHODS: The effect of emotional valence and visualization types and their interaction were analyzed through a 3x2 repeated measures ANOVA. Post-hoc t-tests were performed under a ROI-analysis approach. RESULTS: The results show increased brain activation for the 3D affective-inducing stimuli in comparison with the same stimuli in 2D scenarios, mostly in cortical and subcortical regions that are related to emotional processing, in addition to visual processing regions. CONCLUSIONS: This study has the potential of clarify brain mechanisms involved in the processing of emotional stimuli (scenarios��� valence) and their interaction with three-dimensionality.

Amygdala activation in response to 2D and 3D emotion-inducing stimuli

Studying changes in brain activation according to the valence of emotion-inducing stimuli is essential in the research on emotions. Due to the ecological potential of virtual reality, it is also important to examine whether brain activation in response to emotional stimuli can be modulated by the three-dimensional (3D) properties of the images. This study uses functional Magnetic Resonance Imaging to compare differences between 3D and standard (2D) visual stimuli in the activation of emotion-related brain areas. The stimuli were organized in three virtual-reality scenarios, each with a different emotional valence (pleasant, unpleasant and neutral). The scenarios were presented in a pseudo-randomized order in the two visualization modes to twelve healthy males. Data were analyzed through a GLM-based fixed effects procedure. Unpleasant and neutral stimuli activated the right amygdala more strongly when presented in 3D than in 2D. These results suggest that 3D stimuli, when used as ���building blocks��� for virtual environments, can induce increased emotional loading, as shown here through neuroimaging.

Electricity Markets Simulation: MASCEM Contributions to the Challenging Reality

Electricity Markets are not only a new reality but an evolving one as the involved players and rules change at a relatively high rate. Multi-agent simulation combined with Artificial Intelligence techniques may result in sophisticated tools very helpful under this context. Some simulation tools have already been developed, some of them very interesting. However, at the present state it is important to go a step forward in Electricity Markets simulators as this is crucial for facing changes in Power Systems. This paper explains the context and needs of electricity market simulation, describing the most important characteristics of available simulators. We present our work concerning MASCEM simulator, presenting its features as well as the improvements being made to accomplish the change and challenging reality of Electricity Markets.

Extended immersive learning environment: a hybrid remote/virtual laboratory

This paper presents a collaborative virtual learning environment, which includes technologies such as 3D virtual representations, learning and content management systems, remote experiments, and collaborative learning spaces, among others. It intends to facilitate the construction, management and sharing of knowledge among teachers and students, in a global perspective. The environment proposes the use of 3D social representations for accessing learning materials in a dynamic and interactive form, which is regarded to be closer to the physical reality experienced by teachers and students in a learning context. A first implementation of the proposed extended immersive learning environment, in the area of solid mechanics, is also described, including the access to theoretical contents and a remote experiment to determine the elastic modulus of a given object.These instructions give you basic guidelines for preparing camera-ready papers for conference proceedings. Use this document as a template if you are using Microsoft Word 6.0 or later. Otherwise, use this document as an instruction set. The electronic file of your paper will be formatted further. Define all symbols used in the abstract. Do not cite references in the abstract.

Virtual Power Players Internal Negotiation and Management in MASCEM

Electricity Markets are not only a new reality but an evolving one as the involved players and rules change at a relatively high rate. Multi-agent simulation combined with Artificial Intelligence techniques may result in very helpful sophisticated tools. This paper presents a new methodology for the management of coalitions in electricity markets. This approach is tested using the multi-agent market simulator MASCEM (Multi-Agent Simulator of Competitive Electricity Markets), taking advantage of its ability to provide the means to model and simulate Virtual Power Players (VPP). VPPs are represented as coalitions of agents, with the capability of negotiating both in the market and internally, with their members in order to combine and manage their individual specific characteristics and goals, with the strategy and objectives of the VPP itself. A case study using real data from the Iberian Electricity Market is performed to validate and illustrate the proposed approach.

Innovation through virtual communities of Practice: motivation and constraints in the knowledge-creation process

Communities of Practice are places which provide a sound basis for organizational learning, enabling knowledge creation and acquisition thus improving organizational performance, leveraging innovation and consequently increasing competitively. Virtual Communities of Practice (VCoP���s) can perform a central role in promoting communication and collaboration between members who are dispersed in both time and space. The ongoing case study, described here, aims to identify both the motivations and the constraints that members of an organization experience when taking part in the knowledge creating processes of the VCoP���s to which they belong. Based on a literature review, we have identified several factors that influence such processes; they will be used to analyse the results of interviews carried out with the leaders of VCoP���s in four multinationals. As future work, a questionnaire will be developed and administered to the other members of these VCoP���s

Virtual communities of practice: investigating motivations and constraints in the processes of knowledge creation and transfer

With accelerated market volatility, faster response times and increased globalization, business environments are going through a major transformation and firms have intensified their search for strategies which can give them competitive advantage. This requires that companies continuously innovate, to think of new ideas that can be transformed or implemented as products, processes or services, generating value for the firm. Innovative solutions and processes are usually developed by a group of people, working together. A grouping of people that share and create new knowledge can be considered as a Community of Practice (CoP). CoP���s are places which provide a sound basis for organizational learning and encourage knowledge creation and acquisition. Virtual Communities of Practice (VCoP's) can perform a central role in promoting communication and collaboration between members who are dispersed in both time and space. Nevertheless, it is known that not all CoP's and VCoP's share the same levels of performance or produce the same results. This means that there are factors that enable or constrain the process of knowledge creation. With this in mind, we developed a case study in order to identify both the motivations and the constraints that members of an organization experience when taking part in the knowledge creating processes of VCoP's. Results show that organizational culture and professional and personal development play an important role in these processes. No interviewee referred to direct financial rewards as a motivation factor for participation in VCoPs. Most identified the difficulty in aligning objectives established by the management with justification for the time spent in the VCoP. The interviewees also said that technology is not a constraint.

Virtual communities of practice: examining the motivations and constraints in their knowledge creation and knowledge transfer preocesses

Paper accepted for the OKLC 2009 - International Conference on Organizational Learning, Knowledge and Capabilities (26-28th, April 2009, Amsterdam, the Netherlands).

Virtual power producers integration into MASCEM

All over the world Distributed Generation is seen as a valuable help to get cleaner and more efficient electricity. Under this context distributed generators, owned by different decentralized players can provide a significant amount of the electricity generation. To get negotiation power and advantages of scale economy, these players can be aggregated giving place to a new concept: the Virtual Power Producer. Virtual Power Producers are multi-technology and multi-site heterogeneous entities. Virtual Power Producers should adopt organization and management methodologies so that they can make Distributed Generation a really profitable activity, able to participate in the market. In this paper we address the integration of Virtual Power Producers into an electricity market simulator ���MASCEM ��� as a coalition of distributed producers.

Virtual power players demand response programs management based on locational marginal prices

Power systems have been suffering huge changes mainly due to the substantial increase of distributed generation and to the operation in competitive environments. Virtual power players can aggregate a diversity of players, namely generators and consumers, and a diversity of energy resources, including electricity generation based on several technologies, storage and demand response. Resource management gains an increasing relevance in this competitive context, while demand side active role provides managers with increased demand elasticity. This makes demand response use more interesting and flexible, giving rise to a wide range of new opportunities.This paper proposes a methodology for managing demand response programs in the scope of virtual power players. The proposed method is based on the calculation of locational marginal prices (LMP). The evaluation of the impact of using demand response specific programs on the LMP value supports the manager decision concerning demand response use. The proposed method has been computationally implemented and its application is illustrated in this paper using a 32 bus network with intensive use of distributed generation.