Marcos Fernández

Bio: Marcos Fernández is an academic researcher from University of Valencia. The author has contributed to research in topics: Augmented reality & Virtual reality. The author has an hindex of 17, co-authored 90 publications receiving 1042 citations. Previous affiliations of Marcos Fernández include University of Oviedo & University of Minho.

Virtual reality for driving simulation

Abstract: In this paper, the authors describe the data structure necessary to provide real time simulation and visualization of complex environments and situations. Through the SIRCA project, the development of driving oriented simulators, using Virtual Reality (VR) and evaluating it in comparison with convention technologies, has taken place. Focus is on some of the algorithms and data structure required to provide real time simulation of the complex urban environment and its visualization under the conditions of VR devices.

Improving the performance of distributed virtual environment systems

Abstract: The last years have witnessed a dramatic growth in the number as well as in the variety of distributed virtual environment systems. These systems allow multiple users, working on different client computers that are interconnected through different networks, to interact in a shared virtual world. One of the key issues in the design of scalable and cost-effective DVE systems is the partitioning problem. This problem consists of efficiently assigning the existing clients to the servers in the system and some techniques have been already proposed for solving it. This paper experimentally analyzes the correlation of the quality function proposed in the literature for solving the partitioning problem with the performance of DVE systems. Since the results show an absence of correlation, we also propose the experimental characterization of DVE systems. The results show that the reason for that absence of correlation is the nonlinear behavior of DVE systems with regard to the number of clients in the system. DVE systems reach saturation when any of the servers reaches 100 percent of CPU utilization. The system performance greatly decreases if this limit is exceeded in any server. Also, as a direct application of these results, we present a partitioning method that is targeted to keep all the servers in the system below a certain threshold value of CPU utilization, regardless of the amount of network traffic. Evaluation results show that the proposed partitioning method can improve DVE system performance, regardless of both the movement pattern of clients and the initial distribution of clients in the virtual world.

Augmented mirror: interactive augmented reality system based on kinect

Abstract: In this paper we present a virtual character controlled by an actor in real time, who talks with an audience through an augmented mirror. The application, which integrates video images, the avatar and other virtual objects within an Augmented Reality system, has been implemented using a mixture of technologies: two kinect systems for motion capture, depth map and real images, a gyroscope to detect head movements, and control algorithms to manage avatar emotions.

Protective Elements of Mental Health Status during the COVID-19 Outbreak in the Portuguese Population.

Abstract: The outbreak of COVID-19 might produce dramatic psychological effects on individuals' lives. In this study, we aimed to explore the elements that may reduce the negative effects on mental health of the quarantine period imposed by most governments during this worldwide crisis. We conducted an online survey to evaluate demographic, lifestyle and mental health variables in a sample of 1280 Portuguese individuals (79.8% females) with an average age of 37 years. We observed that factors related to living conditions, maintaining work either online or in the workplace, frequency of exercise and absence of previous psychological or physic disorders are protective features of psychological well-being (anxiety, depression, stress and obsessive-compulsive symptoms). Finally, the individuals previously receiving psychotherapeutic support exhibited better psychological indicators if they did not interrupt the process as a consequence of the outbreak. Our results indicate that the practice of physical exercise, reduced consumption of COVID-19 information and the implementation of remote mental healthcare measures might prevent larger impacts on mental health during the COVID-19 outbreak.

Tapped-Inductor Buck HB-LED AC–DC Driver Operating in Boundary Conduction Mode for Replacing Incandescent Bulb Lamps

Abstract: High-brightness light-emitting diodes (HB-LEDs) are recognized as being potential successors of incandescent bulb lamps due to their high luminous efficiency and long lifespan. To achieve these advantages, HB-LED ballast must be durable and efficient. Furthermore, for this specific application, ac-dc HB-LED ballast requires a high-step-down ratio, high power factor and low cost. This paper presents a tapped-inductor buck power factor corrector (PFC) operating in boundary conduction mode design for replacing incandescent bulb lamps. This low-cost solution presents a suitable high-step-down ratio without galvanic isolation in order to produce an output voltage of about 20 V from line voltage. In addition, the tapped-inductor buck PFC maintains high efficiency in comparison to other one stage solutions widely used to design low-cost ac-dc HB-LED drivers (e.g., flyback PFCs). Static analysis, input current distortion analysis, and an average small signal model of the tapped-inductor buck PFC have been implemented in this paper both to check the validity of the proposed solution and to provide a suitable design procedure of the ac-dc HB-LED driver. Finally, a 12-W experimental prototype was developed to validate the theoretical results presented.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.