Abstract
Optical fiber Mach-Zehnder interferometers were fabricated by combining two TiO2 coated LPFGs fabricated through femtosecond laser direct writing. Results of its refractometric characterization are presented and compared with the single LPFGs sensors. Wavelength sensitivity of 1175 nm/RIU at 1.38 and spectral resolution of 2.2×10-5 were achieved. © 2021 The Author(s).

Abstract
In this chapter, the authors examine whether an individual’s wellbeing is enhanced by the level of innovation in the country in which they live. The study is based on quantitative analysis of cross-country data from the World Values Survey. The authors use the Global Innovation Index (GII) and the number of recorded patents as proxies for country-level innovation and find that innovation is positively associated with subjective wellbeing.

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Abstract
In recent years robots have been used as a tool for teaching purposes, motivating the development of fully virtual environments for combined real/simulated robotics teaching. The AlphaBot2 Raspberry Pi (RPi), a robot used for education, has no currently available simulator. A Gazebo simulator was produced and a ROS framework was implemented for hardware abstraction and control of low-level modules facilitating students control of the robot's physical behaviours in the real and simulated robot, simultaneously. For the demonstration of the basic model operation, an algorithm for detection of obstacles and lines was implemented for the IR sensors, however, some discrepancies in a line track timed test were detected justifying the need for further work in modelling and performance assessment. Despite that, the implemented ROS structure was verified to be functional in the simulation and the real AlphaBot2 for its motion control, through the input sensors and camera.

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This paper explores the connections between the classical maximum clique problem and its edge-weighted generalization, the maximum edge weight clique (MEWC) problem. As a result, a new analytic upper bound on the clique number of a graph is obtained and an exact algorithm for solving the MEWC problem is developed. The bound on the clique number is derived using a Lagrangian relaxation of an integer (linear) programming formulation of the MEWC problem. Furthermore, coloring-based bounds on the clique number are used in a novel upper-bounding scheme for the MEWC problem. This scheme is employed within a combinatorial branch-and-bound framework, yielding an exact algorithm for the MEWC problem. Results of computational experiments demonstrate a superior performance of the proposed algorithm compared with existing approaches.

Abstract
Portugal is a country in which the tourism sector assumes great importance, contributing around 15% of the national GDP and with more than 1 million jobs. In this sense, COVID-19 is expected to have a dramatic impact on the Portuguese economy aggravated by the existence of a reduced internal market with low purchasing power and in which there is a high dependence on the external market. This perspective study explores the challenges and opportunities that Portuguese companies in the field of tourism are facing due to the emergence of this pandemic. The challenges faced by companies are both short-term and long-term. In the short term, it is essential to ensure sufficient liquidity to reopen activities and in the long term, it is necessary to be prepared and reactive to disruptive movements that may arise in tourist demand. However, it is also important to recognize that some opportunities can be exploited, such as the quality of the health response, the exploitation of a less mass tourism supply based on the components of social and environmental sustainability, the increase of tourism among the elderly population from countries with greater purchasing power and the acceleration of the digitalization of tourism operations.