Cross-Layer Admission Control to Enhance the Support of Real-Time Applications in WSN

Real-time monitoring applications may be used in a wireless sensor network (WSN) and may generate packet flows with strict quality of service requirements in terms of delay, jitter, or packet loss. When strict delays are imposed from source to destination, the packets must be delivered at the destination within an end-to-end delay (EED) hard limit in order to be considered useful. Since the WSN nodes are scarce both in processing and energy resources, it is desirable that they only transport useful data, as this contributes to enhance the overall network performance and to improve energy efficiency. In this paper, we propose a novel cross-layer admission control (CLAC) mechanism to enhance the network performance and increase energy efficiency of a WSN, by avoiding the transmission of potentially useless packets. The CLAC mechanism uses an estimation technique to preview packets EED, and decides to forward a packet only if it is expected to meet the EED deadline defined by the application, dropping it otherwise. The results obtained show that CLAC enhances the network performance by increasing the useful packet delivery ratio in high network loads and improves the energy efficiency in every network load.

Nova metodologia de execução do ensaio SCPTu com avaliação da influência da fonte sísmica quanto à sua dimensão e afastamento

O objectivo deste trabalho consiste na determinação das Ondas de Corte, onda S, através de uma nova metodologia de ensaio do piezocone sísmico, SCPTu. A nova metodologia adoptada de aquisição de dados, consiste na aquisição da onde de corte no movimento ascendente de remoção de varas, após execução do já conhecido ensaio CPTu, ao invés da tradicional aquisição, no movimento descendente, previamente ao acréscimo de nova vara. Além da introdução de uma nova metodologia de aquisição sísmica, tentou-se avaliar a influência da dimensão da fonte geradora da onda de corte e a influência do afastamento das mesmas ao ponto de cravação, do ensaio de penetração estática mencionado. Na avaliação das influências foram usadas três fontes de madeira de secção rectangular, com uma chapa de ferro a topo e diferenciadas entre si pelas dimensões de 1m, 2m e 3m e afastamentos até 4m.

Financing local development through crowdfunding: An empirical analysis of social projects in Portugal

Crowdfunding (CF) is an increasingly attractive source to fund social projects. However, to our best knowledge, the study of CF for social purposes has remained largely unexplored in the literature. This research envisages a detailed examination of the role of CF on the early-stage of the social projects at regional level. By comparing the characteristics of the projects available in the Portuguese Social Stock Exchange (PSSE) platform with others that did not use this source of financial support, we explore its role on regional development. The results we got show that, in most cases, both PSSE and Non-Governmental Organizations projects complemented the services offered by the State or by the private sector. Furthermore, about a quarter of the projects present in PSSE operated in areas that were not being addressed neither by the services offered by the State nor by the ones of the private sector. The results attained show that more recent social ventures have a greater propensity to use PSSE. The same is find in those organizations which work closely with the target audience. We also observed that the use of PSSE was correlated with the geographical scope of the Social Venture. The circumstance of having the social organization acting at a local or regional level seems to be strongly associated with the possibility of using social crowdfunding for financing social projects.