Using matrix norms to estimate the direction of arrival of planar waves on an ULA

SEAD method estimates the direction-of-arrival angles on an uniformly linear array based on the difference between the two largest singular values, what is called differential spectrum. Although it presented an outstanding performance, the ability to indicate the source positions was not elucidated yet. Inspired by the differential spectrum formulation we derived a total differential spectrum and found out that the matrix norm induced by the vector 2-norm of a modified spatial covariance matrix can be used to estimate the direction-of-arrival of multiple plane waves. Indeed we show that matrix norms are estimators and we propose their use instead of the singular value decomposition in SEAD-based methods. We present a general mathematical expression in order to explicit the operating principles of the proposed methods. Consequently, we were able to explain how the relation between the arriving and the search angles produces the larger peaks on the differential spectrum. To evaluate the important role played by matrix norms, a thousand experiments were carried out. They showed that the proposed approach proved to be as accurate as the previous SEAD-based methods, while providing a significant reduction on runtime. It also outperformed well-established methods like MODEX regarding the estimation error.     

Conceiving multiple markets through network analysis: evidence from the emergence of the World Music market

The idea of multiple markets, conceptualised as a variety of concrete market configurations, was fruitfully developed in the socio-material networks research programme. However, it has not yet been able to solve the following puzzle: the differentiation and specification of multiple markets that exist at the same time in the same place. In this paper, I argue that White’s model of ‘markets from networks’ can contribute to filling this gap, since it is centred on the specification of a market’s structural and cultural boundaries. His model allows for the analysis of concrete market practices intertwined with more abstract concepts of markets formed in discourses that move firms and markets across different levels – from local markets to market sectors. An in-depth analysis of the emergence of the World Music market demonstrates the advantages of employing this model in the analysis of multiple markets.     

When Things Go Wrong

In this project, we worked in partnership with school teachers who are frequent users of experimental kits available for loan to schools using the historical-investigative approach. The original kits bring a traditional approach to experimentation, without the presence of the history of science. We developed and implemented new guides to the kits, without changing their materials and instruments. Design-based research supports the development methodology; the school science topics covered in this paper are Joseph Black’s studies on latent and specific heat. Although some of the challenges faced in the implementation of historical-investigative approach are known and well-documented, the present article addresses teachers’ perspectives and some of the problems they faced in the implementation process, most of them related to school and teacher working conditions. Even though this is a case study with a small number of schools and teachers, it is possible to say that there is a huge gap to overcome before the historical-investigative approach can be implemented in large scale.

     

Overcompliance and reluctance to make decisions: Exploring warning systems in support of public managers

Post-scandal effects in public management point to the occurrence of overcompliance in the work of public managers, leading to reluctance and paralysis in decision-making. This article discusses the proposition of an artifact in the form of a warning system to aid the analysis process and issuing of opinions (APIO) by public managers, providing more information and, consequently, less risk and fear. The Design Science Research method was used to exapt a scientific artifact to the context of public management. The textual structure of 178 opinions issued by public agencies was analyzed, as was the perception of 17 public managers of the characteristics of the APIO. Exaptating the artifact from a technological perspective is simple and feasible, as it involves processes with strong functional similarities. The greatest challenges to operationalize the artifact broadly and without restrictions, as occurs in scientific academia, are associated with informational behaviors.     

Digital educational games and mathematics. Results of a case study in primary school settings

The study presents the results of a project in which a series of digital games were used for teaching Mathematics to first, fourth, and sixth-grade primary school students (ages 6–7, 8–9, and 11–12). Mathematics was selected as the teaching subject because of the difficulties students face in understanding basic math concepts. Although digital games are used quite extensively for educational purposes, they are scarcely used for teaching Mathematics. The games were developed by the classes' teachers using Microsoft's Kodu Game Lab. The learning outcomes were compared to two other groups of students. The first was taught using the model proposed by Driver and Oldham while the second was taught conventionally. Data was collected using questionnaires and evaluation sheets. A total of 201 students participated in the study coming from three schools in Athens, Greece. Results indicated that students in the games group outperformed, in most cases, students in the other groups. Students' views for the games were highly positive. The implications for software engineers and education administrators are also discussed.     

Who is tech savvy? Exploring the adoption of smartphones and tablets: An empirical investigation

The present analysis performs a Multinomial Probit Model in order to observe which mobile technology qualifies across individuals. The findings indicate that individuals in family businesses prefer to combine both tablets and smartphones in their purchases, rather than separately. Younger individuals report an adoption preference towards smartphones, while older individuals are inclined towards tablets. The theoretical contributions encompass both the technology acceptance model (TAM) and the social cognitive theory (SCT). Individuals working in a family business exhibit a curious behaviour and they are becoming early adopters. TAM helps explain this behaviour as they tend to try new novelties exploring the potential usefulness they might derive; these technological advancements allow them to connect with customers and partners. By contrast, SCT helps gain a better understanding on young and old individuals' behaviour. The younger generations seem to be easily influenced by their peers with a tendency to technologies which are fun and allow them to build connections. Older individuals are equally influenced by their peers, with the difference that their social circle being more mature (e.g., business owners, professionals). This combined with the complexity of the technology orients them into adopting tablets more easily than smartphones.