Abstract in English:

Abstract In this study, we developed a Radio Frequency Identification (RFID) sensor to monitor respiratory rates. The sensor utilizes a passive RFID tag enhanced with a metamaterial-inspired structure to boost its maximum gain value. This gain increased from -0.39 dBi to 0.57 dBi. Monitoring of the respiratory rate was conducted by analyzing variations in the Received Signal Strength Indicator (RSSI), which were influenced by respiratory movements. The RSSI data collected from the RFID tag readings were processed using the Daubechies wavelet of order 5 (db5) with three levels of signal decomposition, resulting in signals with reduced noise. These measurements were particularly effective when the participant was at rest, with the RFID tag positioned over the abdomen. The maximum reading range obtained was 1.04 m. The respiratory rates derived from the RSSI variations were validated against a vital signals monitor, confirming that they fell within the expected frequency variation range of the multiparameter monitor.

Abstract in English:

Abstract In this paper, it is presented a general optimization methodology for improving empirical models predicting Okumura-Hata, Cost-231, ECC-33, and Egli using Genetic and Differential Evolution Algorithms. The methodology was tested using georeferenced signal power samples from Uberlândia, Brazil, for a television channel operating at 569.142857 MHz. Each parameter of the model formulas was adjusted with a variable optimized by the algorithms. A significant innovation was the inclusion of an altitude parameter weighted by an optimized coefficient, which notably enhanced the prediction accuracy. The primary contribution of this work is the development of a set of analytical equations derived from the proposed methodology, eliminating the need for computational power to estimate path loss for the evaluated models in the area in question. The performance of these equations was assessed using the Mean Squared Error (MSE) metric, demonstrating improvements of up to 92.03% over standard models, contingent on the empirical model and optimization algorithm applied.

Abstract in English:

Abstract In this paper, we present a novel numerical model for simulating partial discharges (PDs) transient currents excited by high-voltage DC (HVDC) systems. The model is based on the telegraph equations, which are solved in the time domain via the finite-difference method (FDM). With the proposed model, one can simulate air ionization through its distinct phases based on the electric field’s magnitude. This study specifically provides effective electrical conductivity of ionized air over time and space, calculated in the discharge channel also as a function of voltage and gap distance in a needle-plate setup. Validation is performed against experimental results from our laboratory experiments, demonstrating agreement despite the model’s one-dimensional nature. The simplicity of the model leads to much smaller simulation times (up to two minutes) compared to more complex three-dimensional models (typically requiring hours to complete), highlighting its potential for efficient PD analysis and future developments of general PD models based on effective plasma conductivity.

Abstract in English:

Abstract This study investigates the effectiveness of employing Planar Transmission Lines (PTL) with stubs to determine the water content in transformer oils. The research aims to elucidate how transmission responses along the line can provide valuable patterns for oil characterization. Notable results were achieved, particularly in identifying representative frequencies for each range of S21 scattering parameters, enabling the derivation of well-fitted linear expressions for the data. These findings suggest promising potential for the practical application of this approach. This study contributes not only to the understanding of the proposed technique but also to the stimulation of subsequent research aiming to enhance and consolidate this analytical methodology.

Abstract in English:

Abstract Space-fed array comprising of E-shape or U-slot cut rectangular microstrip antennas using the modified feed designs are proposed for higher gain and wider bandwidth. Modified feed optimally illuminates the edge space-fed elements to achieve a maximum gain. Amongst the two space-fed array variations, 7 x 7 E-shape space-fed array, excited using the feed comprising of gap-coupled and stacked E-shape patches provides bandwidth and gain of 2.085 GHz (48.97%) and 18.5 dBi, respectively. The antenna exhibits broadside radiation pattern across the complete bandwidth. An experimental validation has been carried out for the simulated results that show a close agreement.

Abstract in English:

Abstract In our study, we conducted a thorough analysis of the spectral characteristics of a D-shaped surface plasmon resonance (SPR) photonic crystal fiber (PCF) refractive index sensor, incorporating a full width at half maximum (FWHM) analysis. We explored four distinct plasmonic materials-silver (Ag), gold (Au), Ga-doped zinc oxide (GZO), and an Ag-nanowire metamaterial-to understand their impact on sensor performance. Our investigation encompassed a comprehensive theoretical modeling and analysis, aiming to unravel the intricate relationship between material composition, sensor geometry, and spectral response. By scrutinizing the sensing properties offered by each material, we laid the groundwork for designing multiplasmonic resonance sensors. Our findings provide valuable insights into how different materials can be harnessed to tailor SPR sensing platforms for diverse applications and environmental conditions, fostering the development of advanced and adaptable detection systems. This research not only advances our understanding of the fundamental principles governing SPR sensor performance but also underscores the potential for leveraging varied plasmonic materials to engineer bespoke sensing solutions optimized for specific requirements and performance metrics.

Abstract in English:

Abstract The Internet of Things (IoT) encompasses a diverse array of solutions with applications ranging from smart cities to environmental monitoring and industrial processes. In this context, communication techniques that offer long-range coverage, cost-effectiveness, and minimal energy consumption are essential. Among such technologies, LoRaWAN stands out. However, deploying wireless networks, especially for LoRaWAN, requires meticulous planning, including link budget analysis based on appropriate wave propagation path loss models. This paper investigates the suitability of the ITU-R P.1812 recommendation model for LoRaWAN radio coverage planning. We explore two distinct approaches, focusing on the choice of terrain clutter heights. Approach 1 involves a detailed point-by-point evaluation, considering different clutter heights for each pixel in the area under analysis. In contrast, Approach 2 simplifies the process by selecting a single representative clutter height based on terrain morphology. Comparative analysis using data from Brazilian measurement campaigns reveals that Approach 2 may be more favorable for rural or open environments, while Approach 1 is better suited for complex scenarios. Our findings contribute to informed decision-making in LoRaWAN network design, emphasizing the importance of terrain-specific considerations.

Abstract in English:

Abstract This paper presents a reflectarray antenna with an innovative dielectric mirror in the form of a discretized concave reflector. The mirror, manufactured via 3D printing, combines dielectric and air layers, forming an Electromagnetic Band Gap (EBG) that reflects signals to the reflectarray feed antenna within its operating frequency band. A transmission line model was used for EBG parametric analysis, resulting in a simple, fast, and efficient design tool implemented in Octave. A design technique was developed to optimize the position and tilt of each mirror element, aligning reflected signal phases for constructive addition in the antenna's main beam direction. An Octave code implemented this design technique. Additionally, a Python program automated the generation of the dielectric reflector simulation model for Ansys HFSS. A reflectarray antenna is designed to operate in the 10.7 GHz to 12.7 GHz band, using a Yagi-Uda feed and a dielectric reflector made of PLA and air layers. The reflectarray antenna was manufactured and characterized, demonstrating a gain of 19.56 dBi and a half-power beam width of 8.04 degrees at 11.7 GHz at 〖θ〗_0=23° and 〖φ〗_0=0°. Good agreement was obtained between simulated and measured results, validating the design procedure.

Abstract in English:

Abstract Elastic optical networks (EONs) have characteristics that meet the growing demand for current and future bandwidth, such as 5G and Internet of Things. In EONs, connections must have a route and a spectrum slice available between the nodes to establish communication. The process associated with this task is named routing and spectrum allocation (RSA) problem. The RSA problem is NP-hard and several approaches have been proposed in the literature using computational intelligence (CI). This paper provides a systematic literature review (SLR) regarding applying CI to solve the RSA problem in EONs. We offer a research roadmap encouraging the community to address identified limitations and open questions requiring further investigation. This study selects 40 primary studies for analysis and data extraction out of the 659 initially obtained papers. The main conclusions indicate that the community still needs to explore the RSA problem with the freedom to solve it without considering a fixed order of the two subproblems: routing and spectrum allocation. The studies reveal that efficient solutions are achieved with the techniques used in the RSA problem, which made them excellent tools. Furthermore, this SLR presents a set of open questions, suggesting valuable topics for future research through a research guide.

Abstract in English:

Abstract In this study, we propose a novel biosensor based on a hexagonal-shaped microcavity with two slot waveguides within a two-dimensional photonic crystal. The biosensor aims to detect various blood components by utilizing a refractive index measurement. The device operates in the TM-polarized light wavelength range of 1150-1880 nm. It consists of two slot waveguides coupled with a hexagonal-shaped microcavity, formed by removing seven lattice holes. The microcavity is separated from the waveguides by two holes. When the analyte infiltrates the cavity, it induces a change in refractive index, leading to a wavelength shift at the output terminal. The proposed design achieves a high sensitivity of over 687.496 nm/RIU. The simulation of the proposed design is performed using both the Plane Wave Expansion (PWE) method and the Finite-Difference Time-Domain (FDTD) algorithm. The results demonstrate that the slot waveguide configuration provides excellent transmission.