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- Activities of Daily Living and Environment Recognition Using Mobile DevicesPublication . Ferreira, José M.; Pires, Ivan; Marques, Gonçalo; Garcia, Nuno M.; Zdravevski, Eftim; Lameski, Petre; Flórez-Revuelta, Francisco; Spinsante, Susanna; Xu, LinaThe recognition of Activities of Daily Living (ADL) using the sensors available in off-the-shelf mobile devices with high accuracy is significant for the development of their framework. Previously, a framework that comprehends data acquisition, data processing, data cleaning, feature extraction, data fusion, and data classification was proposed. However, the results may be improved with the implementation of other methods. Similar to the initial proposal of the framework, this paper proposes the recognition of eight ADL, e.g., walking, running, standing, going upstairs, going downstairs, driving, sleeping, and watching television, and nine environments, e.g., bar, hall, kitchen, library, street, bedroom, living room, gym, and classroom, but using the Instance Based k-nearest neighbour (IBk) and AdaBoost methods as well. The primary purpose of this paper is to find the best machine learning method for ADL and environment recognition. The results obtained show that IBk and AdaBoost reported better results, with complex data than the deep neural network methods.
- Advancements in High-Frequency Antenna Design: Integrating Photonic Crystals for Next-Generation Communication TechnologiesPublication . Bagheri, Nila; Velez, Fernando J.; Peha, JonCentral to this study is the introduction of a pioneering photonic crystal-based microstrip patch antenna array with high gain. Engineered to meet the demands of evolving wireless communication technologies, this novel antenna system leverages Photonic Band Gap (PBG) structures. A fractal microstrip patch antenna, operating within the E-W-F band, is designed and simulated using the High-Frequency Structure Simulation (HFSS) software. With an operational frequency spanning 60.15 GHz to 120 GHz and a resonant band at 64.80 GHz, the antenna achieves a peak gain of 10.50 dBi within the obtained bandwidth. In this study, we selected Rogers RT/Duroid 5880 as the substrate material for our antenna, capitalizing on its unique properties to achieve superior functionality in high-frequency applications. One of the advantages of RT/Duroid 5880 is its exceptionally low dielectric constant (Ɛr = 2.2). This property is paramount for high-frequency antennas, as a lower dielectric constant facilitates improved signal propagation characteristics. The result is reduced signal loss and enhanced impedance matching, contributing to the overall efficiency of the antenna. The mechanical machinability of RT/Duroid substrates, including RT/Duroid 5880, adds another layer of advantage. The material can be easily cut, sheared, and machined to shape, streamlining the manufacturing process, and allowing for precise customization of the antenna design. In addition, by creating air hole in substrate reduce the dielectric constant, the introduction of air holes can decrease the effective dielectric constant of the material. As a lower dielectric constant results in a slower wave propagation speed, a reduction wavelength and a more compact antenna design may result. The presence of air holes or a photonic crystal structure can modify the electromagnetic properties of the substrate, potentially leading to enhanced bandwidth characteristics of broadband antennas.
- An Eco-Energetic Performance Comparison of Dehumidification Systems in High-Moisture Indoor EnvironmentsPublication . Santos, Alexandre Fernandes; Gaspar, Pedro Dinis; Souza, Heraldo; Caldeira, João M. L. P.; Soares, Vasco N. G. J.This study discusses the choice of dehumidification systems for high-moisture indoor environments, such as indoor swimming pools, supported by an eco-energetic performance comparison. Initially, the causes of the high relative humidity and condensation in these spaces are reported, as well as the available dehumidification technologies. Two different solutions are described: desiccant wheel dehumidification and re-cooling. The energy demand required by a refrigeration system is lower than the desiccant wheel; however, the former system requires less maintenance and does not require refrigerant fluid. An eco-energetic comparison is performed between the two systems in two countries with different energy matrices (Brazil and USA). In Brazil, the desiccant wheel is the best choice for the past 10 years, with a predicted 351,520 kgCO2 of CO2 emissions, which is 38% lower than the refrigeration system. In the USA, the best option is the refrigeration system (1,463,350 kgCO2), a 12% more efficient option than desiccant wheels. This model can be considered for energy and CO2 emissions assessment, predicting which system has better energy efficiency and lower environmental impact, depending on the refrigerant type, location and environmental conditions.
- An Extensive Study on the Performance Evaluation and Scheduling of HeNBsPublication . Paulo, Rui R.; Velez, Fernando J.Since the dawn of mobile communication systems, reducing the cell size has been one option to increase the signal-to-interference-plus-noise ratio (SINR) in both links. The impact of this reduction can be perfectly understood by considering Shannon’s law. This work studies in detail the performance of Home eNBs (HeNBs), nodes with a smaller coverage area. After a detailed theoretical study of the SINR, a simulation approach is used to extract performance results in small cell indoor scenarios. Results corresponding to the goodput, delay and packet loss ratio are analyzed. Based on an improved version of LTE-Sim, the proportional fair, frame level scheduler (FLS) and exponential rule are tested in an indoor environment. With the saturation conditions taken into consideration, the FLS performs better than the other schedulers. This work shows that with the considered applications, it is possible to achieve a reduction in the transmitter power of HeNBs without compromising the small cell network performance.
- An Intelligent Sensor Array Distributed System for Vibration Analysis and Acoustic Noise Characterization of a Linear Switched Reluctance ActuatorPublication . Salvado, José; Espírito Santo, António; Calado, M. do RosárioThis paper proposes a distributed system for analysis and monitoring (DSAM) of vibrations and acoustic noise, which consists of an array of intelligent modules, sensor modules, communication bus and a host PC acting as data center. The main advantages of the DSAM are its modularity, scalability, and flexibility for use of different type of sensors/transducers, with analog or digital outputs, and for signals of different nature. Its final cost is also significantly lower than other available commercial solutions. The system is reconfigurable, can operate either with synchronous or asynchronous modes, with programmable sampling frequencies, 8-bit or 12-bit resolution and a memory buffer of 15 kbyte. It allows real-time data-acquisition for signals of different nature, in applications that require a large number of sensors, thus it is suited for monitoring of vibrations in Linear Switched Reluctance Actuators (LSRAs). The acquired data allows the full characterization of the LSRA in terms of its response to vibrations of structural origins, and the vibrations and acoustic noise emitted under normal operation. The DSAM can also be used for electrical machine condition monitoring, machine fault diagnosis, structural characterization and monitoring, among other applications.
- An Overview of Blockchain Integration with Robotics and Artificial IntelligencePublication . Lopes, Vasco; Alexandre, LuísBlockchain technology is growing everyday at a fast-passed rhythm and it's possible to integrate it with many systems, namely Robotics with AI services. However, this is still a recent field and there isn't yet a clear understanding of what it could potentially become. In this paper, we conduct an overview of many different methods and platforms that try to leverage the power of blockchain into robotic systems, to improve AI services or to solve problems that are present in the major blockchains, which can lead to the ability of creating robotic systems with increased capabilities and security. We present an overview, discuss the methods and conclude the paper with our view on the future of the integration of these technologies.
- An Overview of Blockchain Integration with Robotics and Artificial IntelligencePublication . Lopes, Vasco; Alexandre, LuísBlockchain technology is growing everyday at a fast-passed rhythm and it is possible to integrate it with many systems, namely Robotics with AI services. However, this is still a recent field and there is not yet a clear understanding of what it could potentially become. In this paper, we conduct an overview of many different methods and platforms that try to leverage the power of blockchain into robotic systems, to improve AI services, or to solve problems that are present in the major blockchains, which can lead to the ability of creating robotic systems with increased capabilities and security. We present an overview, discuss the methods, and conclude the paper with our view on the future of the integration of these technologies.
- Análise de Sistemas de Comunicação LEO / MEO para Otimizar a Transmissão de Dados na AviaçãoPublication . Rodrigues, Tayná; Reis, António; Velez, Fernando J.Este trabalho consiste em estudar e analisar um conjunto de modelos de comunicação entre satélites e aviões, explorando novas tecnologias LEO (Low Earth Orbit)/ MEO (Medium Earth Orbit). Por muitas décadas, os aviões dependiam só de sistemas de comunicações no solo, como o NDB (Non-Directional Beacon), cujas estações terrestres transmitem numa só direcção, e o VOR (Very high frequency Omnidirectional radio Range), cujas estações transmitem em todas as direcções. Estes sistemas, operam na banda dos 118 MHz – 137 MHz, estão a ficar obsoletos e, sobretudo nos vôos transcontinentais, têm vindo a ser substituidos por comunicações via satélite. Estas comunicações já possibilitam que os passageiros possam utilizar telemóveis a bordo. A órbita terrestre é a rota de movimento dos satélites naturais ou artificiais em volta da Terra. Há quatro tipos de órbitas para satélites de comunicação que são: GEO (Geostationary Earth Orbit), com uma altitude de 36000 km da Terra, LEO, com uma altitude de 500km a 1500 km, MEO, com uma altitude de 10400 km e a HEO (Highly Elliptical Orbit), com uma altitude elíptica, entre 1000 km (próximo) e 39000 km. Esta investigação foca-se nas comunicações de satélites LEO / MEO, assim como na integração com as futuras redes 5G. Através de uma simulação com a ferramenta Ansys STK, cujo objectivo é analisar os parâmetros críticos da ligação ascendente (UL) e também ligação descendente (DL), num contexto de comunicação de satélite para avião e de avião para satélite, respetivamente, estudou-se como diferentes condições meteorológicas afetam a comunicação. Verificou-se que a degradação na qualidade da comunicação apenas ocorreu logo após o satélite começar a comunicação com o avião e imediatamente antes de ocorrer o handover. Foram sugeridas também técnicas de mitigação, como a utilização de satélites redundantes, técnicas de modulação adaptativa, diversidade de frequência.
- Analysis of the Influence of Different Topologies on a TLSRG Generation Performance for WECPublication . Mendes, R. P. G.; Calado, M. do Rosário; Mariano, S.In this work, 4 structural configurations are proposed, and analysed, to be used as a tubular linear switched reluctance generators with tubular topology (TLSRG). For the 4 models under assessment, inductance change with the mover part position is assessed to quantify the machine capabilities as generator for an wave energy converter (WEC), namely a point absorber device. This evaluation is supported by a 2D FEM analysis based software through which are determined the inductance values at different alignment conditions as well as the magnetic flux densities for the referred alignment conditions. An analytic design procedure is presented for one structural model and the same procedure is used to size the generator for given nominal power and based velocity, derived from an ocean wave energy assessment based on meteorological data.
- Android Library for Recognition of Activities of Daily Living: Implementation Considerations, Challenges, and SolutionsPublication . Pires, Ivan; Teixeira, Maria Cristina Canavarro; Pombo, Nuno; Garcia, Nuno M.; Flórez-Revuelta, Francisco; Spinsante, Susanna; Goleva, Rossitza; Zdravevski, EftimBackground: Off-the-shelf-mobile devices have several sensors available onboard that may be used for the recognition of Activities of Daily Living (ADL) and the environments where they are performed. This research is focused on the development of Ambient Assisted Living (AAL) systems, using mobile devices for the acquisition of the different types of data related to the physical and physiological conditions of the subjects and the environments. Mobile devices with the Android Operating Systems are the least expensive and exhibit the biggest market while providing a variety of models and onboard sensors. Objective: This paper describes the implementation considerations, challenges and solutions about a framework for the recognition of ADL and the environments, provided as an Android library. The framework is a function of the number of sensors available in different mobile devices and utilizes a variety of activity recognition algorithms to provide a rapid feedback to the user. Methods: The Android library includes data fusion, data processing, features engineering and classification methods. The sensors that may be used are the accelerometer, the gyroscope, the magnetometer, the Global Positioning System (GPS) receiver and the microphone. The data processing includes the application of data cleaning methods and the extraction of features, which are used with Deep Neural Networks (DNN) for the classification of ADL and environment. Throughout this work, the limitations of the mobile devices were explored and their effects have been minimized. Results: The implementation of the Android library reported an overall accuracy between 58.02% and 89.15%, depending on the number of sensors used and the number of ADL and environments recognized. Compared with the results available in the literature, the performance of the library reported a mean improvement of 2.93%, and they do not differ at the maximum found in prior work, that based on the Student’s t-test. Conclusion: This study proves that ADL like walking, going upstairs and downstairs, running, watching TV, driving, sleeping and standing activities, and the bedroom, cooking/kitchen, gym, classroom, hall, living room, bar, library and street environments may be recognized with the sensors available in off-the-shelf mobile devices. Finally, these results may act as a preliminary research for the development of a personal digital life coach with a multi-sensor mobile device commonly used daily.