Abstract
This paper aims to develop a low-cost stroboscope, which consists of an optical equipment capable of generating flashes of light at different frequencies, allowing to measure the rotation velocity of machines and contributing to maintenance processes in the industry. This device is based on the stroboscopic effect, a visual event that occurs when a continuous movement is presented by a series of samples, generated by flashes of light. When the frequency of the rotation movement is the same frequency of light pulses, the process will appear stationary. Based on the high cost of the commercial stroboscopes, it was developed a stroboscope prototype based on the Arduino platform, LED technology and 3D printing with an open hardware and software. The final prototype went through calibration and validation processes, achieving a performance very similar to a commercial instrument. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021.

Abstract
Telecoms are companies that provide communication services. In 2020 a drop in Telecom's revenues is expected due to COVID and this impact will remain for future years, with higher drops in coming years. The adoption of Self-Service Technologies allows to solve the problem of selling and serve the customers on-line, increasing customer loyalty, reducing cost, fostering innovation and thus increasing revenues. The major research question for this work is: Which factors influence the adoption of online self-service technologies by Business-to-Business customers of a Telecom?. In order to derive a conceptual framework to answer this question several theories where used: The Technology Acceptance Model (TAM), The Innovation Diffusion Theory (IDT) and the SST attitude/intention model. A conceptual framework that drives the adoption of Self-service technologies in Telecom B2B segments was proposed and tested.

Abstract
Objective Artificial intelligence (AI) may reduce underdiagnosed or overlooked upper GI (UGI) neoplastic and preneoplastic conditions, due to subtle appearance and low disease prevalence. Only disease-specific AI performances have been reported, generating uncertainty on its clinical value. Design We searched PubMed, Embase and Scopus until July 2020, for studies on the diagnostic performance of AI in detection and characterisation of UGI lesions. Primary outcomes were pooled diagnostic accuracy, sensitivity and specificity of AI. Secondary outcomes were pooled positive (PPV) and negative (NPV) predictive values. We calculated pooled proportion rates (%), designed summary receiving operating characteristic curves with respective area under the curves (AUCs) and performed metaregression and sensitivity analysis. Results Overall, 19 studies on detection of oesophageal squamous cell neoplasia (ESCN) or Barrett's esophagus-related neoplasia (BERN) or gastric adenocarcinoma (GCA) were included with 218, 445, 453 patients and 7976, 2340, 13 562 images, respectively. AI-sensitivity/specificity/PPV/NPV/positive likelihood ratio/negative likelihood ratio for UGI neoplasia detection were 90% (CI 85% to 94%)/89% (CI 85% to 92%)/87% (CI 83% to 91%)/91% (CI 87% to 94%)/8.2 (CI 5.7 to 11.7)/0.111 (CI 0.071 to 0.175), respectively, with an overall AUC of 0.95 (CI 0.93 to 0.97). No difference in AI performance across ESCN, BERN and GCA was found, AUC being 0.94 (CI 0.52 to 0.99), 0.96 (CI 0.95 to 0.98), 0.93 (CI 0.83 to 0.99), respectively. Overall, study quality was low, with high risk of selection bias. No significant publication bias was found. Conclusion We found a high overall AI accuracy for the diagnosis of any neoplastic lesion of the UGI tract that was independent of the underlying condition. This may be expected to substantially reduce the miss rate of precancerous lesions and early cancer when implemented in clinical practice.

Abstract
The growth of undersea exploration is pushing both the length and the complexity of propeller-driven autonomous underwater vehicles (AUVs) missions, leading to more stringent energy requirements. One approach to decrease the energy consumption of a hovering capable AUV is to use variable buoyancy systems (VBS) as a complement to the propeller actuators. These devices only require energy consumption during limited periods of time, taking into advantage the fact that whenever buoyancy is different from zero, the vehicle will continuously ascend or descend. Nevertheless, literature is scarce regarding the choice of the type of the VBS and of its constitutive elements, and regarding their effects on the energy required for buoyancy changes. This work presents structured and detailed static models of electromechanical and electrohydraulic VBSs that allow the calculation of the power required to actuate them. Based on the VBS desired characteristics and on manufacturer's data, the power consumption in each element of the VBS can be pinpointed to determine critical elements. Furthermore, a direct energy comparison with propeller-based solutions can be performed, allowing an easy evaluation of the energy gains provided by the VBS in different scenarios. This work also presents the preliminary development of an electromechanical and electrohydraulic VBS for an existing AUV at the University of Porto, Porto, Portugal. Based on the developed VBS and the developed model, numerical examples are provided for typical mission profiles. It is shown that the use of a VBS in the case of the existing AUV at the University of Porto leads to considerable energetic improvements.

Abstract
The subprime crisis was a global financial crisis that affected a large number of countries and, in particular, the European economies. In this paper we considered fourteen variables associated to the public, private and financial sectors, in order to analyze the main vulnerabilities, differences and similarities observed in twenty-seven European countries. The statistical analysis was performed with the STATIS methodology, with data collected in the period 2002-2011, including some years before and some after the historical crisis of 2007-2008. The study led us to conclude that European countries are different in which concerns to investment, savings, sustainability of public accounts and public investment.

Abstract