Browsing by resource type "review article"
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- Adiabatic radial perturbations of relativistic stars: Analytic solutions to an old problemPublication . Luz, Paulo; Carloni, SanteWe present a new system of equations that fully characterizes adiabatic, radial perturbations of perfect fluid stars within the theory of general relativity. The properties of the system are discussed, and, provided that the equilibrium spacetime verifies some general regularity conditions, analytical solutions for the perturbation variables are found. As illustrative examples, the results are applied to study perturbations of selected classical exact spacetimes, and the first oscillation eigenfrequencies are computed. Exploiting the new formalism, we derive an upper bound for the maximum compactness of stable, perfect fluid stars, which is equation-of-state agnostic and significantly smaller than the Buchdahl bound.
- Are the physical activity habits of healthcare professionals associated with their physical activity promotion and counselling?: A systematic reviewPublication . Borges, Margarida D.; Ribeiro, Tiago; Peralta, Miguel; Gouveia, Bruna; Marques, AdilsonObjective: Healthcare professionals (HCPs) play an important role in conducting brief physical activity counselling during consultations, representing one of the population's most cost-effective interventions for its promotion. Despite this, their clinical practice often falls short in addressing physical activity with the necessary depth and frequency. This study aimed to synthesise the literature concerning the association between the physical activity habits of HCPs and their attitudes toward physical activity promotion and counselling. Methods: The systematic review followed PRISMA (Preferred Reporting Items for Systematic Reviews and MetaAnalyses) guidelines. Its protocol was registered in PROSPERO under ID: CRD42023408302. In March 2023, a comprehensive search was conducted using key terms related to physical activity levels and HCPs counselling practices across the Web of Science, Scopus, PubMed, SPORTDiscus, APA PsycInfo, and CINAHL databases. Registered HCPs classified under the International Standard Classification of Occupations (ISCO) were included. The Newcastle-Ottawa Scale was used for assessing articles quality. Results: The search yielded 6618 articles, with 51 meeting the inclusion criteria after filtering and crossreferencing. Predominantly cross-sectional studies were included, mainly involving HCPs responding to questionnaires regarding their physical activity habits and promotion and counselling practices. Heterogeneous results were found. Conclusion: High-quality studies mainly concluded that higher physical activity levels among HCPs were associated with more physical activity promotion and counselling practices. These findings are an important contribution to the relevance of the physical activity practice by HCPs and highlighting the importance of promoting its counselling in clinical practice.
- Cape Verde: Islands of Vulnerability or Resilience? A Transition from a MIRAB Model into a TOURAB One?Publication . Sarmento, Eduardo Moraes; Silva, Ana Lorga daSmall island developing states (SIDSs) traditionally face a set of challenges like the weak and highly fragile economic configuration, environmental issues, and a traditional dependence on a few economic activities forcing them to open the economy to the exterior. Therefore, their development model, like in Cape Verde, depends on migration, remittances, dependence on aid, tourism, and state employment. The current research offers an insight into the nature of Cape Verde’s economy as a SIDS economy and the degree to which the country has been relying on tourism receipts, external remittances from migrations, aid programs, and government services. Understanding Cape Verde’s development model is important to clarify the challenges the country faces and its development needs to gather a long-term resilience and to understand if it is changing from a MIRAB (Migrations, Remittances, Aid, and Bureaucracy) model into another one.
- Emerging Technologies to Promote Fans Interaction in Football Events: A Systematic ReviewPublication . Martins, Francisco; França, Cíntia; Paixão, Pedro; Martinho, Diogo V.; Campos, Pedro; Gouveia, Bruna R.; Lopes, Hélder; Ihle, Andreas; Marques, Eduardo; Gouveia, Élvio Rúbio; Gouveia, BrunaAs the digital revolution continues to take hold in contemporary society, new technology and communications networks have provided football with new possibilities and prospects for expansion. This study provides an assessment of the published research regarding innovative digital tools designed to increase the interactivity of fans when watching a football match, regardless of whether they do it at home or at the stadium. A systematic review of the literature was performed, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. The search was conducted in the PubMed, Web of Science, and Scopus databases. The final sample included eleven studies for analysis. Overall, the investigations that structure this review seem to be in the early stages of their development, with eight of them making tests with the target audience and the other three still in protocol development processes. Six studies concluded that fans had positive and exciting experiences using mobile applications or interactive systems. Two studies showed promising results in the area of football fans’ health, and only one study showed some difficulties for fans using an ad hoc network in the stadium. Adding personal information, fan interaction systems, specific information about the players and the teams’ tactical strategies, and interactive fan voting seem to be important elements for designing a successful interactive tool that contributes to increasing fans’ enthusiasm during football matches.
- Enhanced AutomaticWildfire Detection System Using Big Data and EfficientNetsPublication . Fernandes, Armando; Utkin, Andrei; Chaves, PauloPrevious works have shown the effectiveness of EfficientNet—a convolutional neural network built upon the concept of compound scaling—in automatically detecting smoke plumes at a distance of several kilometres in visible camera images. Building on these results, we have created enhanced EfficientNet models capable of precisely identifying the smoke location due to the introduction of a mosaic-like output and achieving extremely reduced false positive percentages due to using partial AUROC and applying class imbalance. Our EfficientNets beat InceptionV3 and MobileNetV2 in the same dataset and achieved a true detection percentage of 89.2% and a false positive percentage of only 0.306% across a test set with 17,023 images. The complete dataset used in this study contains 26,204 smoke and 51,075 non-smoke images. This makes it one of the largest, if not the most extensive, datasets reported in the scientific literature for smoke plume imagery. So, the achieved percentages are not only among the best reported for this application but are also among the most reliable due to the extent and representativeness of the dataset.
- The EU Emission Trading System Tax Regime and the Issue of Unfair Maritime CompetitionPublication . Faria, Duarte Lyncehis article starts by providing an updated literature review and the EU legislative framework concerning reducing carbon emissions in the maritime industry as part of the European Green Deal (EGD). It specifically examines the EU Emission Trading System (ETS) tax regime. This document then analyses the current factors influencing ships’ decisions to avoid stopping at hub ports and going to neighbouring Mediterranean countries, such as North Africa and Turkey. In the discussion section, this study presents various suggestions for updating EU laws or expediting the collection and analysis of data to prompt the Commission to take appropriate actions to prevent unfair competition between EU and non-EU ports. This study focuses on identifying the most effective solutions within the EU legislative framework to address the need for the Commission to take legitimate action to prevent ships from bypassing EU hub ports. These solutions can be further developed alongside initiatives at the International Maritime Organization (IMO), and certain provisions can be adjusted at the EU level. The IMO’s call for a carbon fee on bunkering exacerbates the existing challenges. Preventive measures must be implemented to control the diversion of shipping traffic from EU hub ports, ensure fair treatment of EU ports involved in transhipment, and prevent carbon leakage. Moreover, the recent Houthi attacks in the Red Sea have significantly increased shipping costs on the route around the Cape of Good Hope to Europe, necessitating increased allowances for traffic to and from Europe.
- Fault Diagnosis of Maritime Equipment Using an Intelligent Fuzzy FrameworkPublication . Mendonça, L. F.; Sousa, J. M. C.; Vieira, S. M.The task of automatically and intelligently diagnosing faults in marine equipment is of great significance due to the numerous duties that shipboard professionals must handle. Incorporating automated and intelligent systems on ships allows for more efficient equipment monitoring and better decision-making. This approach has attracted considerable interest in both academia and industry because of its potential for economic savings and improved safety. Several fault diagnosis methods are documented in the literature, often involving mathematical and control theory models. However, due to the inherent complexity of some processes, not all characteristics are precisely known, making mathematical modeling highly challenging. As a result, fault diagnosis often depends on data or heuristic information. Fuzzy logic theory is particularly well suited for processing this type of information. Therefore, this paper employs fuzzy models to diagnose faults in a marine pneumatic servo-actuated valve. The fuzzy models used in fault diagnosis are obtained from the data. These fuzzy models are identified for the normal operation of the marine pneumatic servo-actuated valve, and for each fault, predicting the system’s outputs from the inputs and outputs of the process. The proposed fault diagnosis framework analyzes the discrepancy signals between the outputs of the fuzzy models and the actual process outputs. These discrepancies, known as residuals, help in detecting and isolating equipment faults. The fault isolation process uses an intelligent decision-making approach to determine the specific fault in the system. This method is applied to diagnose abrupt faults in a marine pneumatic servo-actuated valve. The approach presented was used to detect and diagnose three very important faults in the operation of a marine pneumatic servo-actuated valve. The three faults were correctly detected and isolated, and no errors were detected in this detection and isolation process.
- Fuzzy-Set QCA on Performance and Sustainability Determinants of Ports Supporting Floating Offshore Wind FarmsPublication . Caldeirinha, V.; Felício, J. A.; Pinho, T.; Rodrigues, R.The present study explores the relationship between the characteristics, performance, and sustainability of ports that will, in the future, support the logistical chains of new floating offshore wind farms, considering the crucial advancement and expansion of the offshore wind energy sector for the transition to a low-carbon economy. Through a detailed analysis, which includes international case studies in America and Europe utilizing expert interviews and quantitative methods through surveys, the importance of the location, new types of infrastructure and superstructure, and new planning and governance models for the performance and sustainability of ports that will be involved in this new energy industry is highlighted. Also, the context in which ports associated with floating wind turbines are located influences the performance and sustainability. This research employs Fuzzy-Set Qualitative Comparative Analysis (fsQCA), based on a survey of 22 European sector company experts, to emphasize the critical port characteristics for the performance and sustainability. This study reveals the significant contribution of supporting ports for the future floating offshore wind sector for the gross added value and the expansion of regional employment, and the need for new planning, construction, operation, and management models for ports instead of the traditional models applied to simple cargo loading and unloading ports, offering valuable new insights for port managers, policymakers, and academics. However, a future research trajectory with a more geographically diverse sample is suggested to enhance the applicability and generalizability of the results.
- Gauge invariant perturbations of static spatially compact LRS II spacetimesPublication . Luz, Paulo; Carloni, SanteWe present a framework to describe completely general first-order perturbations of static, spatially compact, and locally rotationally symmetric class II spacetimes within the theory of general relativity. The perturbation variables are by construction covariant and identification gauge invariant and encompass the geometry and the thermodynamics of the fluid sources. The new equations are then applied to the study of isotropic, adiabatic perturbations. We discuss how the choice of frame in which perturbations are described can significantly simplify the mathematical analysis of the problem and show that it is possible to change frames directly from the linear level equations. We find explicitly that the case of isotropic, adiabatic perturbations can be reduced to a singular Sturm–Liouville eigenvalue problem, and lower bounds for the values of the eigenfrequencies can be derived. These results lay the theoretical groundwork to analytically describe linear, isotropic, and adiabatic perturbations of static, spherically symmetric spacetimes
- The Impact of Curing Temperature and UV Light Intensity on the Performance of Polymer-Dispersed Liquid Crystal Devices Exhibiting a Permanent Memory EffectPublication . Mouquinho, Ana; Sotomayor, JoãoPDLC films, synthesized via polymerization-induced phase separation (PIPS) utilizing both temperature and UV monochromatic radiation, were derived from a blend of E7 nematic liquid crystal (LC) and PolyEGDMA875 (polyethyleneglycoldimethacrylate) oligomers, serving as the precursor for the polymeric matrix. The influence of the curing temperature on thermal polymerization, UV light intensity on photochemical polymerization, and exposure time during these processes on the electro-optical characteristics of PDLC films was thoroughly examined. Observations revealed that employing thermal polymerization during device preparation notably enhanced the permanent memory effect of the PDLC films. Sustained high transparency (TOFF = 45%) over an extended duration at room temperature, even subsequent to voltage cessation, was achieved. This transition initiated from an opaque state (T0 = 0%) through to a transparent state (TMAX = 65%), resulting in a substantial 70% permanent memory effect.