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Conference Paper
Amorim, M., A. Mar, F. Monteiro, S. Sylaiou, P. Pereira, and J. Martins, "Smart Tourism Routes Based on Real Time Data and Evolutionary Algorithms", Digital Heritage. Progress in Cultural Heritage: Documentation, Preservation, and Protection, Cham, Springer International Publishing, pp. 417–426, 2018. Abstract

Tourism is an industry that has been growing rapidly in the last few years and it is expected that it will continue to grow. Due to the evolution of technology, mobile applications are being increasingly used in all kinds of industries, being one of them tourism. Presently there are already a few mobile applications used to increase the experience of the user when visiting a place, but these mobile applications lack some important features. This paper describes the development of a mobile application with integrated routing algorithms used to increase the experience of the tourists when visiting the city of Avila, Spain. The tourist will have at their disposal real time information about all the monuments available for visit, a full set of predefined circuits with different visit times and degrees of difficulty and also the possibility to create an optimized or personalized circuit combining the user preferences such as visiting time and number of monuments to visit.

Ramos, N. R., P. Pereira, and J. F. Martins, "Smart-meter in power quality", 2017 International Young Engineers Forum (YEF-ECE), pp. 42-46, 5 May, 2017. Abstract

In this paper, an innovative approach for monitoring home electric power quality indicators is presented. Using an electric power analysis device (for this work purpose it will be a smart-meter) and a personal computer it is proved that it is possible to monitor and register electric power quality anomalies, such as long interruptions, voltage dips/swells and frequency oscillations. Through an application developed in Java, a user can view real-time electric parameters, check for electric power quality anomalies and assess load diagram of previous days. Experimental results regarding the application performance are also presented with the respective conclusions.

Inacio, D., J. Murta Pina, P. Pereira, A. Pronto, M. Ventim Neves, and A. Alvarez, "Study of an axial flux disc motor with superconductor rotor", Compatibility and Power Electronics (CPE), 2015 9th International Conference on, Costa de Caparica, Portugal , pp. 488-493, June, 2015. Abstract

The integration of high temperature superconductors (HTS) in electrical machines potentially allows reduction in devices dimensions or performance improvement for the same active volume, when compared with their conventional ones. The use of polycrystalline HTS samples allows big bulk samples. An axial disc motor with HTS material or conventional aluminium in the rotor and conventional armature has been designed and developed. This paper describes simulations and laboratory experiments performed at liquid nitrogen temperature (77 K) in order to analyze the motor's behaviour and its electromechanical characteristics and to define an electric equivalent circuit that allows describing its operation. In order to evaluate the superconducting quality of the bulks and flux pinning phenomena, Hall probe mapping system was performed in order to define the field profiles at 77 K for different polar configurations. The analysis of the obtained results allows confirm the flux pinning phenomena, being the entire rotor magnetized and conclude that the motor with the HTS rotor behaves as a conventional hysteresis motor even though with a different nature, while the motor with aluminium rotor behaves as a conventional induction motor. In asynchronous regime, the HTS motor exhibits a constant torque, higher than the conventional aluminium one. For both cases, the developed torque is proportional to the poles pairs.

Pereira, P., and J. Martins, "Sustainable Heritage Management Towards Mass Tourism Impact: the HERIT-DATA project", 9th International Conference on Intelligent Systems IS’18, Madeira - PT, IEEE, 25-27 Sep., 2018. Abstract

Although tourism is a major engine of economic growth, it also creates a burden hard to manage, and has a great impact on the conservation of the heritage. The HERIT-DATA project aims to reduce the impact of human activities, related to tourism, on cultural heritage, with a special focus on two kind of cultural destinations that can benefit from and be affected by mass tourism: Old towns and places of specific cultural heritage or archaeological interest for visitors, including UNESCO World Heritage Sites. In that framework, HERIT-DATA plans to develop of a sustainable and responsible tourism management towards cultural heritage in MED regions, in particular by taking advantage of technology and innovation in management tools (Smart Cities), as well as other policy and social measures.

Francisco, R., P. Pereira, and J. Martins, "Sustainable Housing Techno-Economic Feasibility Application", Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2011, vol. 349, Costa de Caparica - Portugal, Springer Boston, pp. 445-454, 2011. Abstract

The high prices currently achieved in the acquisition of non-renewable energy for electricity production and the low levels of energy efficiency in the housing sector are the national situation, which leads the Portuguese government to encourage the acquisition, the installation and the use of technologies which exploit indigenous and renewable energy. This study presents an application that was developed in order to help the citizen in his decision to invest in renewable technologies in their homes. The application is able to elaborate an economic analysis based on the selected type of renewable technology, providing the user with the knowledge of benefits and the annual costs involved in the system that he selected. This tool aims at facilitating the interaction of any user with such technologies and it can be used as a helpful tool to support the decision of investment in such systems.

Delgado-Gomes, V., J. A. Oliveira-Lima, J. F. Martins, C. Lima, and P. Pereira, "Towards to a Web Service alert software system for standard electrical protective devices", Intelligent Engineering Systems (INES), 2012 IEEE 16th International Conference on, Lisbon, Portugal, pp. 197 -201, june, 2012. Abstract

Electrical Protective Devices are key elements in the electrical network. Their purpose is to perform fault detection in electric power systems, by analysing power system voltages and currents. In order to achieve a more centralized control, protective devices can be connected using Web Services through a Service-Oriented Architecture (SOA) approach. This work targets planning and specification of a mapping between Abstract Communication Service Interface (ACSI) Reporting and Device Profile for Web Services (DPWS) Eventing to achieve a better protective electrical devices control, obtaining an event based alert software system, replacing conventional polling-based systems.

Pereira, P., M. H. Fino, and F. V. Coito, "Using discrete-variable optimization for CMOS spiral inductor design", Proc. Int Microelectronics (ICM) Conf, pp. 324–327, 2009. Abstract

In this paper a discrete-variable optimization methodology for the automatic design of CMOS integrated spiral inductors is introduced. The use of discrete variable optimization procedure offers the designer the possibility for exploring the design space exclusively in those points available for the technology under use. Further user-defined constraints between layout parameters may also be incorporated as a way of taking into account design heuristics. A comparison between using discrete-variable optimization and a continuous optimization procedure followed by a discretization of the results is presented, where the benefits of the proposed methodology are presented. An application using the proposed methodology was developed in Matlab and the optimization toolbox is used. For the sake of simplicity the pi-model has been used for characterizing the inductor. The validity of the design results is checked against circuit simulation with ASITIC.

Almeida, P., P. Pereira, and H. Fino, "Using Variable Width RF Integrated Inductors for Quality Factor Optimization", Technological Innovation for the Internet of Things, vol. 394: Springer Berlin Heidelberg, pp. 619-627, 2013. Abstract

The advancement of CMOS technology led to the integration of more complex functions. In the particular of wireless transceivers, integrated LC tanks are becoming popular both for VCOs and integrated filters [1]. For RF applications the main challenge is still the design of integrated inductors with the maximum quality factor. For that purpose, tapered, i.e., variable width inductors have been proposed in the literature. In this paper, analytical expressions for the determination the pi-model parameters, for the characterization of variable width integrated inductors are proposed. The expressions rely exclusively on geometrical and technological parameters, thus granting the rapid adaptation of the model to different technologies. The results obtained with the model are compared against simulation with ASITIC, showing errors below 10%. The model is then integrated into an optimization procedure where inductors with a quality factor improvement in the order of 20-30% are obtained, when compared with fixed width inductors.

Pereira, P., and H. Fino, "VCOSYM -an application for the automatic design of ring VCOS", Proc. 12th IEEE Int. Conf. Electronics, Circuits and Systems ICECS 2005, pp. 1–4, 2005. Abstract

This paper presents an application for the automatic design of ring VCOs. In this application a VCO model based on the Npower transistor model is considered as a away of granting the accuracy of results for submicron technologies. In order to easily integrate any VCO previously designed into a PLL automatic design tool, a corresponding linear model of the VCO is automatically generated, yielding a simple and precise characterization for higher level system design. The design of a 150 MHz VCO using a seven stage ring topology is presented. The validity of the design obtained is checked against Hspice simulation of the circuit.

Afonso, M., P. Pereira, and J. Martins, "Weather Monitoring System for Renewable Energy Power Production Correlation", Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2011, vol. 349, Costa de Caparica - Portugal, Springer Boston, pp. 481-490, 2011. Abstract

This work describes the development of a system designed for renewable power generation integration. It continuously acquires wind, solar and temperature data, which is automatically correlated with energy parameters, obtained from renewable energy systems. The developed system was installed in an urban building equipped with photovoltaic cells and wind renewable generation. To validate the developed application, it was analyzed data of a wind generator and a set of photovoltaic panels, installed near to the weather station. The developed application allows, in addition to the acquisition of weather and energy data, their continuous monitoring and correlation through a graphical user interface, providing a friendly interactivity with the user.

Conference Proceedings
, "Emerging Trends in Technological Innovation: First IFIP WG 5.5/SOCOLNET Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2010, Costa de Caparica, Portugal, February 22", Doctoral Conference on Computing, Electrical and Industrial Systems, DoCEIS 2010, vol. 314, Costa de Caparica - Portugal, Springer-Verlag New York Inc, 2010.
Paiva, L., P. Pereira, B. Almeida, P. Maló, J. Hyvärinen, K. Klobut, V. Dimitriou, and T. Hassan, "Interoperability: A Data Conversion Framework to Support Energy Simulation", Sustainable Places 2017, vol. 1, no. 7, 2017. Abstract

In this paper an interoperability solution is proposed, aiming to go from (building) construction models to energy simulation. Moreover, the energy simulation results will feed the KPI’s analysis of a designed building. The proposed solution will be used to translate different data formats allowing the communication between different systems in an automated environment. The solution presented in this paper exploits the concept of Plug’n’Interoperate (PnI), that is supported by the principle of self-configuration as to automate, as much as possible, the configuration and participation of systems into a shared interoperability environment. In order to validate this approach two different scenarios were taken into account, translating from a CAD (Computer- Aided Design) model data format to an energy simulation data format.

Noack, F., P. Katranuschkov, R. Scherer, V. Dimitriou, S. K. Firth, T. M. Hassan, N. Ramos, P. Pereira, P. Maló, and T. Fernando, "Technical challenges and approaches to transfer building information models to building energy", Proceedings of ECPPM 2016: CRC Press, pp. 355-362, 2016/08/15. Abstract

The complex data exchange between architectural design and building energy simulation constitutes the main challenge in the use of energy performance analyses in the early design stage. The enhancement of BIM model data with additional specific energy-related information and the subsequent mapping to the input of an energy analysis or simulation tool is yet an open issue. This paper examines three approaches for the data transfer from 3D CAD applications to building performance simulations using BIM as central data repository and points out their current and envisaged use in practice. The first approach addresses design scenarios. It focuses on the supporting tools needed to achieve interoperability given a 74 wide-spread commercial BIM model (Autodesk Revit) and a dedicated pre-processing tool (DesignBuilder) for EnergyPlus. The second approach is similar but addresses retrofitting scenarios. In both workflows gbXML is used as the transformation format. In the third approach a standard BIM model, IFC is used as basis for the transfer process for any relevant lifecycle phase.

Journal Article
Sallem, A., P. Pereira, H. M. Fino, and M. Fakhfakh, "A hybrid approach for the sensitivity analysis of integrated inductors", Integration, the \{VLSI\} Journal, pp. 1-6, 2015. AbstractWebsite

Abstract This paper proposes a hybrid methodology for the evaluation of integrated inductors sensitivity against technological/geometrical parameters variation. The obtained results are used in an optimization-based design environment for integrated inductors, as a way of guaranteeing that obtained solutions are robust against parameter variation. For the inductor characterization, a lumped element model is used, where each element value is evaluated through physics based equations. The sensitivity of the inductor characterization to parameter variations is evaluated at two levels. At the physical level, the sensitivity of the model element values to technological/geometrical parameters variations is computed through an equation-based strategy. Then, the sensitivity of the inductor characterization to the model parameter variations is obtained through a simulation-based approach, where the Richardson extrapolation technique is used for the calculation of the partial derivatives. Several examples considering the evaluation of sensitivity of both inductance and quality factor of two inductors in \{UMC130\} technology are presented. Obtained results are compared against Monte-Carlo simulations.

Pina, J. M., P. Pereira, A. Pronto, P. Arsénio, and T. Silva, "Modelling and Simulation of Inductive Fault Current Limiters", Physics Procedia, vol. 36, pp. 1248 - 1253, 2012. AbstractWebsite

Inductive superconducting fault current limiters have already demonstrated their technical viability in electrical networks. Its architecture and robustness make them potentially adequate for distribution networks, and this type of devices is considered as an enabling technology for the advent of embedded generation with renewable energy sources. In order to promote the growth and maturity of these superconducting technologies, fast design tools must be developed, allowing simulating devices with different materials in grids with diverse characteristics. This work presents advances in the development of such tool, which, at present stage, is an effective alternative to software simulations by finite elements methods, reducing dramatically computation time. The algorithms are now compared with experimental results from a laboratory scale prototype, showing the need to refine them.

Pereira, P., M. Helena Fino, and M. Ventim-Neves, "Optimal LC-VCO design through evolutionary algorithms", Analog Integrated Circuits and Signal Processing, vol. 78, issue 1: Springer US, pp. 99-109, 2014. AbstractWebsite

The need for implementing low cost, fully integrated RF wireless transceivers has motivated the widespread use CMOS technology. However, in the particular case for voltage-controlled oscillators (VCO) where ever more stringent specifications in terms of phase-noise must be attained, the design of the on-chip LC tank is a challenging task, where fully advantage of the actual technologies characteristics must be pushed to nearly its limits. To overcome phase-noise limitations arising from the low quality factor of integrated inductors, optimization design methodologies are usually used. In this paper a model-based optimization approach is proposed. In this work the characterization of the oscillator behaviour is guaranteed by a set of analytical models describing each circuit element performance. A set of working examples for UMC130 technology, aiming the minimization of both VCO phase noise and power consumption, is addressed. The results presented, illustrate the potential of a GA optimization procedure design methodology yielding accurate and timely efficient oscillator designs. The validity of the results is checked against HSPICE/RF simulations.

Pereira, P., S. Valtchev, J. Pina, A. Gonçalves, V. M. Neves, and A. L. Rodrigues, "Power electronics performance in cryogenic environment: evaluation for use in HTS power devices", Journal of Physics: Conference Series, vol. 97, no. 1, pp. 012219, 2008. AbstractWebsite

Power electronics (PE) plays a major role in electrical devices and systems, namely in electromechanical drives, in motor and generator controllers, and in power grids, including high-voltage DC (HVDC) power transmission. PE is also used in devices for the protection against grid disturbances, like voltage sags or power breakdowns. To cope with these disturbances, back-up energy storage devices are used, like uninterruptible power supplies (UPS) and flywheels. Some of these devices may use superconductivity. Commercial PE semiconductor devices (power diodes, power MOSFETs, IGBTs, power Darlington transistors and others) are rarely (or never) experimented for cryogenic temperatures, even when designed for military applications. This means that its integration with HTS power devices is usually done in the hot environment, raising several implementation restrictions. These reasons led to the natural desire of characterising PE under extreme conditions, e. g. at liquid nitrogen temperatures, for use in HTS devices. Some researchers expect that cryogenic temperatures may increase power electronics' performance when compared with room-temperature operation, namely reducing conduction losses and switching time. Also the overall system efficiency may increase due to improved properties of semiconductor materials at low temperatures, reduced losses, and removal of dissipation elements. In this work, steady state operation of commercial PE semiconductors and devices were investigated at liquid nitrogen and room temperatures. Performances in cryogenic and room temperatures are compared. Results help to decide which environment is to be used for different power HTS applications.

Pina, J. M., D. Inacio, G. Luis, J. M. Ceballos, P. Pereira, J. Martins, M. Ventim-Neves, A. Alvarez, and A. L. Rodrigues, "Research and Development of Alternative Concepts in HTS Machines", Applied Superconductivity, IEEE Transactions on, vol. 21, no. 3, pp. 1141 -1145, june, 2011. Abstract

High temperature superconducting (HTS) machines are recognized to offer several advantageous features when comparing to conventional ones. Amongst these, highlights the decrease in weight and volume of the machines, due to increased current density in conductors or the absence of iron slots' teeth; or the decrease in AC losses and consequent higher efficiency of the machines, even accounting for cryogenics. These concepts have been already demonstrated and some machines have even achieved commercial stage. In this paper, several alternative approaches are applied to electrical motors employing HTS materials. The first one is an all superconducting linear motor, where copper conductors and permanent magnets are replaced by Bi-2223 windings and trapped flux magnets, taking advantage of stable levitation due to flux pinning, higher current densities and higher excitation field. The second is an induction disk motor with Bi-2223 armature, where iron, ironless and hybrid approaches are compared. Finally, an innovative command strategy, consisting of an electronically variable pole pairs' number approach, is applied to a superconducting hysteresis disk motor. All these concepts are being investigated and simulation and experimental results are presented.

Pereira, P., M. Helena Fino, F. Coito, and M. Ventim-Neves, "RF integrated inductor modeling and its application to optimization-based design", Analog Integrated Circuits and Signal Processing, vol. 73, issue 1: Springer Netherlands, pp. 47-55, 2011. AbstractWebsite

In this paper an optimization-based approach for the design of RF integrated inductors is addressed. For the characterisation of the inductor behaviour the double pi-model is used. The use of this model is twofold. On one hand it enables the generation of the inductor characterisation in a few seconds. On the other hand its integration into the optimization procedure is straightforward. For the evaluation of the model element values analytical expressions based on technology parameters as well as on the device geometric characteristics are used. The use of a technology-based methodology for the evaluation of the model parameters grants the adaptability of the model to any technology. The inductor analytical characterization is integrated into an optimization-based tool for the automatic design of RF integrated inductors. This tool uses a modified genetic algorithm (MGA) optimization procedure, which has proved its validation in previous work. Due to the design parameter constraints nature as well as the topology constraints, discrete variables optimization techniques are used. The accuracy of the results is checked against a non-commercial software.

Pina, J. M., P. Pereira, D. Valadas, J. M. Ceballos, and A. Alvarez, "Sand Pile Modeling of Multiseeded HTS Bulk Superconductors: Current Densities Identification by Genetic Algorithms", IEEE Transactions on Applied Superconductivity, vol. 23, issue 3, pp. 8000804 - 8000804, June, 2013. AbstractWebsite

The sand pile model, in conjunction with Bean model, is often applied to describe single grain bulk superconductors. However, in several applications such as electric motors, multiseeded bulks are needed, due to the need to increase sample dimensions. In this paper, an extension of the sand pile model is presented in order to manage this type of materials. Multiseeded HTS bulk superconductors, produced, e.g., by the top-seeded melt growth process, are characterized by intra- and intergrain currents, and these are reflected in the model. However, identifying these currents from flux density measurements is not straightforward, when considering more than one grain. In fact, the number of currents increases with the number of grains, and these have to be identified from the measured field surface. A method to identify these currents based on genetic algorithms is validated with artificial data and then used in real measurements.

Kchaou, B. O., A. Garbaya, M. Kotti, P. Pereira, M. Fakhfakh, and H. M. Fino, "Sensitivity aware NSGA-II based Pareto front generation for the optimal sizing of analog circuits", Integration, the \{VLSI\} Journal, vol. 55, pp. 220 - 226, 2016. AbstractWebsite

Abstract This paper deals with multiobjective analog circuit optimization taking into consideration performance sensitivity vis-a-vis parameters' variations. It mainly considers improving computation time of the inloop optimization approaches by including sensitivity considerations in the Pareto front generation process, not as a constraint, but by involving it within the used metaheuristic evolution process. Different approaches are proposed and compared. NSGA-II metaheuristic is considered. The proposed sensitivity aware approaches are showcased via two analog circuits, namely, a second generation \{CMOS\} current conveyor and a \{CMOS\} voltage follower. We show that the proposed ideas considerably alleviate the long computation time of the process and improve the quality of the generated front, as well.

Pina, J., P. Pereira, S. Valtchev, A. Gonçalves, V. M. Neves, A. Alvarez, and L. Rodrigues, "A test rig for thrust force measurements of an all HTS linear synchronous motor", Journal of Physics: Conference Series, vol. 97, no. 1, pp. 012220, 2008. AbstractWebsite

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor's ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

Murta-Pina, J., P. Pereira, J. M. Ceballos, A. Alvarez, N. Amaro, A. Pronto, J. Silva, and P. Arsenio, "Validation and Application of Sand Pile Modeling of Multiseeded HTS Bulk Superconductors", Applied Superconductivity, IEEE Transactions on, vol. 25, no. 3, pp. 1-5, June, 2015. AbstractWebsite

Sand pile and Bean models have already been applied to describe single grain HTS bulks. An extension to that approach was used to model multiseed bulks, needed for several practical applications as electric motors or flywheels with superconducting bearings. The use of genetic algorithms was then proposed to determine intra- and intergrain current densities, and application to two and three seeds samples using trapped flux experimental measurements was exemplified. However, this model assumed some simplifications, as equal properties in grain boundaries between neighboring grains. In this paper an extension to this methodology is proposed and evaluated by analyzing measurements performed in plans at different distances from surfaces of samples with three seeds. Discussion of its influence on a practical application is also explored.