Abstract
Over the years, methods and algorithms have been extensively studied to solve variations of the rectangular twodimensional strip packing problem (2D-SPP), in which small rectangles must be packed inside a larger object denominated as a strip, while minimizing the space necessary to pack all rectangles. In the rectangular 2D-SPP, constraints are used to restrict the packing process, satisfying physical and real-life practical conditions that can impact the material cutting. The objective of this paper is to present an extensive literature review covering scientific publications about the rectangular 2D-SPP constraints in order to provide a useful foundation to support new research works. A systematic literature review was conducted, and 223 articles were selected and analyzed. Real-life practical constraints concerning the rectangular 2D-SPP were classified into seven different groups. In addition, a bibliometric analysis of the rectangular 2D-SPP academic literature was developed. The most relevant authors, articles, and journals were discussed, and an analysis made concerning the basic constraints (orientation and guillotine cutting) and the main solving methods for the rectangular 2D-SPP. Overall, the present paper indicates opportunities to address real-life practical constraints.

Abstract
Comparing companies solely based on tax incentives for R&D activities can be misleading. Hence, this research aims to assess how Portuguese companies that make use of tax incentives for R&D activities on an ongoing basis behave in terms of promoting and appropriating value through innovation. From an initial population of 3,156 companies, a final database with 339 Portuguese companies that made use of fiscal credits from 2013 to 2016 was analyzed. The tax incentive program targeted was the Fiscal Incentive System supporting R&D in Enterprises (SIFIDE). Using the analysis of variance (one-way ANOVA), the main results suggest that, considering the internal resources, there are no statistically significant differences between the promotion and appropriation of value through innovation according to the size and age of companies. The data indicate that good management regarding the generation and implementation of innovations may occur independently of size and age of firms, in the Portuguese case. Albeit the averages of the indicators of value appropriation of the intangible (e.g. patents, trademarks, and new processes), and the efficiencies of assets and liabilities for the promotion of the intangible are different according to the level of technological intensity. These results point to the need to reevaluate the tax incentives for R&D activities, since its generic nature may not meet the different innovation needs arising from the distinctive characteristics of these enterprises and their technological dynamics. Implications and future research directions are provided.

Abstract
Today's power grid is in a transitional stage to cater to the needs of energy efficiency, climate change, and environmental targets. In the process of designing the future power grid, one of the most fundamental models to be utilized is AC optimal power flow (AC-OPF). Since the feasible space of AC-OPF is non-convex, the optimization models developed using it often result in multiple local minima. To avoid such computational challenges in solving optimization models, various relaxation methods have been developed in the past. In the literature, these relaxation methods are mainly tested on specific networks. However, the scalability of relaxation techniques on branch-flow-based AC-OPF is yet to be explored. In this context, this paper compares the performance of different relaxation methods with the well-established MATPOWER AC-OPF solver in terms of the mean square error (MSE), maximum squared error, minimum and maximum values of voltage magnitude, and the average simulation time. In addition, the scalability of these models is tested on various radial and mesh networks with nodes ranging from 33 to 6655 nodes and 9 to 6515 nodes, respectively. In this manner, the trade-off between computational complexity and solution accuracy is demonstrated and analyzed in depth. This provides an enhanced understanding of the suitability and efficiency of the compared relaxation methods, helping, in turn, the efficiency of optimization models for varying sizes and types (i.e., radial or meshed) of networks.

Abstract
Purpose There is a scarcity of empirical evidence in the literature on the chain of causality involving tax incentives for Research and Development (R&D) activities and their subsequent transformation into innovation. This study aims to assess the influence of R&D tax incentives on the organizational attributes of Portuguese firms to identify how they are converted into innovation. Design/methodology/approach A structural research model consisting of 339 companies that benefited from the Fiscal Incentive System supporting R&D in Enterprises, during the period from 2013 to 2016, was developed. This was done to assess the role of R&D tax incentives on the organizational attributes that form the innovation capacity. The model was validated using the multivariate statistical technique of structural equation modeling with partial least squares estimation (partial least squares structural equation modeling - PLS-SEM). Findings The results found suggest that although it is not possible to unequivocally identify the mechanisms used to convert tax incentives into innovation, it is possible to conclude that they play an important spillover effect for the construction and strengthening of organizational attributes. These form the basis of innovation capacity, to the extent that they positively influence the firms' total assets, equity, liabilities, number of employees and sales. Hence, contributions are brought to both the literature on tax incentives and the general literature on innovation. Originality/value For policymakers, the evidence points to the fact that in addition to the incentives provided, novel mechanisms need to be established to help firms develop their absorptive capacity. The objective is to effectively convert the incentives received into innovation through the organizational attributes analyzed. From the firms' point of view, the results found suggest that tax incentives act as a catalyst for making R&D investments. Additionally, there is an influence on employability, which effectively enhances the chances of innovation in the long run. Tax incentives received by Portuguese firms also have the effect of promoting economic dynamism - by enhancing the following: investments in infrastructure, the hiring of employees and the increasing of sales, generating positive externalities for both firms and society.

Abstract
This paper deals with an optimal operation of a microgrid in the electricity market and presents the communication between the distribution market operator and microgrid operator. The distribution market operator controls and manages the electricity market established in the distribution level, determining the amount of both electricity price and power exchange between market participants. The microgrid operator is able to purchase active and reactive power from the local distribution market. An effective short-term scheduling of the microgrid is implemented to ensure optimal operation. A risk based stochastic model is used to model the prevailing uncertainties such as loads, wind generation, and main-grid availability in a market-based operation framework. Moreover, in this model, a linearized AC power flow is added to the mathematical formulations to offer a comprehensive solution to the security-constraint operation of the microgrid. The stochastic operation strategy is formulated as a mixed integer linear programming problem. Regarding the uncertainty modeling, the substation equipment failure is modeled with Monte-Carlo algorithm. The effectiveness of the risk-based stochastic method is demonstrated using a microgrid test bed in the presence of demand response resources, dispatchable and wind generation units as well as energy storage system. The results demonstrate demand response program can significantly reduce the operation cost in worst scenarios. Also, it is indicated that the risk averse decisions reduce the risk of experiencing costly scenario. The proposed framework incorporating the distribution market constraints reduces the uncertainty in real-time operation as it can specified the required energy before running the problem. The deviations from assigned energy to the microgrid are penalized through the distribution market operator.

Abstract
Engineering aims to improve the quality of daily life on a planet with limited resources. This chapter describes how the European Project Semester offered by the School of Engineering of the Porto Polytechnic contributes to make engineering undergraduates conscious of their environmental and societal impact. The program is a project-based active learning framework where problem-solving is supported by intercultural communication and creativity, ethical and sustainable reasoning, and global contextual analysis. This analysis shows that it fosters scientific, technical, and interpersonal competencies, emphasizing ethical and sustainable design as recommended by several reference institutions through the testimonials left on the project reports and the evolution perceived by the participants during the semester. These findings are supported by a sample of 45 projects conducted by 228 students from 23 countries and 65 degrees. All projects aimed to have a lasting impact on the future engineering practice of participants and, somehow, transform the world positively.