Reliable and energy efficient routing for ad hoc networks

In Mobile Ad hoc NETworks (MANETs), where cooperative behaviour is mandatory, there is a high probability for some nodes to become overloaded with packet forwarding operations in order to support neighbor data exchange. This altruistic behaviour leads to an unbalanced load in the network in terms of traffic and energy consumption. In such scenarios, mobile nodes can benefit from the use of energy efficient and traffic fitting routing protocol that better suits the limited battery capacity and throughput limitation of the network. This PhD work focuses on proposing energy efficient and load balanced routing protocols for ad hoc networks. Where most of the existing routing protocols simply consider the path length metric when choosing the best route between a source and a destination node, in our proposed mechanism, nodes are able to find several routes for each pair of source and destination nodes and select the best route according to energy and traffic parameters, effectively extending the lifespan of the network. Our results show that by applying this novel mechanism, current flat ad hoc routing protocols can achieve higher energy efficiency and load balancing. Also, due to the broadcast nature of the wireless channels in ad hoc networks, other technique such as Network Coding (NC) looks promising for energy efficiency. NC can reduce the number of transmissions, number of re-transmissions, and increase the data transfer rate that directly translates to energy efficiency. However, due to the need to access foreign nodes for coding and forwarding packets, NC needs a mitigation technique against unauthorized accesses and packet corruption. Therefore, we proposed different mechanisms for handling these security attacks by, in particular by serially concatenating codes to support reliability in ad hoc network. As a solution to this problem, we explored a new security framework that proposes an additional degree of protection against eavesdropping attackers based on using concatenated encoding. Therefore, malicious intermediate nodes will find it computationally intractable to decode the transitive packets. We also adopted another code that uses Luby Transform (LT) as a pre-coding code for NC. Primarily being designed for security applications, this code enables the sink nodes to recover corrupted packets even in the presence of byzantine attacks.

The effects of chemicals in isopods : a multi-organizational evaluation

The global aim of this thesis was to evaluate and assess the effects of a pesticide (dimethoate) and a metal (nickel), as model chemicals, within different organization levels, starting at the detoxification pathways (enzymatic biomarkers) and energy costs associated (energy content quantification, energy consumption and CEA) along with the physiological alterations at the individual and population level (mortality), leading to a metabolomic analysis (using liquid 1H-NMR) and finally a gene expression analysis (transcriptome and RT-qPCR analysis). To better understand potential variations in response to stressors, abiotic factors were also assessed in terrestrial isopods such as temperature, soil moisture and UV radiation. The evaluation performed using biochemical biomarkers and energy related parameters showed that increases in temperature might negatively affect the organisms by generating oxidative stress. It also showed that this species is acclimated to environments with low soil moisture, and that in high moisture scenarios there was a short gap between the optimal and adverse conditions that led to increased mortality. As for UV-R, doses nowadays present have shown to induce significant negative impact on these organisms. The long-term exposure to dimethoate showed that besides the neurotoxicity resulting from acetylcholinesterase inhibition, this stressor also caused oxidative stress. This effect was observed for both concentrations used (recommended field dose application and a below EC50 value) and that its combination with different temperatures (20ºC and 25ºC) showed different response patterns. It was also observed that dimethoate’s degradation rate in soils was higher in the presence of isopods. In a similar study performed with nickel, oxidative stress was also observed. But, in the case of this stressor exposure, organisms showed a strategy where the energetic costs necessary for detoxification (biomarkers) seemed to be compensated by positive alterations in the energy related parameters. In this work we presented for the first time a metabolomic profile of terrestrial isopods exposed to stressors (dimethoate and niquel), since until the moment only a previous study was performed on a metabolomic evaluation in nonexposed isopods. In the first part of the study we identify 24 new metabolites that had not been described previously. On the second part of the study a metabolomic profile variation of abstract non-exposed organism throughout the exposure was presented and finally the metabolomic profile of organisms exposed to dimethoate and nickel. The exposure to nickel suggested alteration in growth, moult, haemocyanin and glutathione synthesis, energy pathways and in osmoregulation. As for the exposure to dimethoate alterations in osmoregulation, energy pathways, moult and neurotransmission were also suggested. In this work it was also presented the first full body transcriptome of a terrestrial isopod from the species Porcellionides pruinosus, which will complement the scarce information available for this group of organisms. This transcriptome also served as base for a RNA-Seq and a RT-qPCR analysis. The results of the RNA-Seq analysis performed in organisms exposed to nickel showed that this stressor negatively impacted at the genetic and epigenetic levels, in the trafficking, storage and elimination of metals, generates oxidative stress, inducing neurotoxicity and also affecting reproduction. These results were confirmed through RT-qPCR. As for the impact of dimethoate on these organisms it was only accessed through RT-qPCR and showed oxidative stress, an impact in neurotransmission, in epigenetic markers, DNA repair and cell cycle impairment. This study allowed the design of an Adverse Outcome Pathway draft that can be used further on for legislative purposes.

Desenvolvimento de um carro elétrico puro: instrumentação e registos energéticos

Desde meados do século XX os avanços na indústria automóvel trazem a associação da eletrónica sendo esta cada vez mais necessária. Com este trabalho pretende-se construir um computador de bordo de um veículo elétrico dando continuação a uma dissertação anterior, que consistiu em um Controlador de Motor de carro elétrico com capacidade de travagem regenerativa. Este Computador deve ser de baixo custo e é destinado à instrumentação, apresentação de balanços energéticos e funções básicas de diagnóstico do estado do veículo. Foi igualmente um objetivo desenvolver uma Interface a partir de um LCD para este Computador de Bordo. No modelo de Controlador de Motor disponível foram aplicadas alterações e adições na instrumentação de forma a conseguir um diagnóstico do veículo mais preciso e extenso. Para o computador ter conhecimento do consumo e outros parâmetros relacionados com o motor e respetivo Controlador, foi necessário estabelecer uma comunicação entre ambas unidades. Antes de se implementar um protocolo de comunicação realizou-se uma pesquisa por protocolos usados na indústria automóvel, com o intuito de saber qual o mais apropriado para o presente trabalho. A tarefa seguinte consistiu em uma pesquisa por hardware com o qual desenvolver o Computador e sua Interface. Os balanços energéticos implicaram o desenvolvimento de métodos de cálculo, efetuados com os parâmetros transmitidos pelo Controlador de Motor. No final da dissertação demonstra-se todas as funcionalidades do Computador de Bordo desenvolvido e como este é utilizado.