Social-Aware Forwarding Improves Routing Performance in Pocket Switched Networks

Several social-aware forwarding strategies have been recently introduced in opportunistic networks, and proved effective in considerably in- creasing routing performance through extensive simulation studies based on real-world data. However, this performance improvement comes at the expense of storing a considerable amount of state information (e.g, history of past encounters) at the nodes. Hence, whether the benefits on routing performance comes directly from the social-aware forwarding mechanism, or indirectly by the fact state information is exploited is not clear. Thus, the question of whether social-aware forwarding by itself is effective in improving opportunistic network routing performance remained unaddressed so far. In this paper, we give a first, positive answer to the above question, by investigating the expected message delivery time as the size of the net- work grows larger

On Leveraging Partial Paths in Partially-Connected Networks

Mobile wireless network research focuses on scenarios at the extremes of the network connectivity continuum where the probability of all nodes being connected is either close to unity, assuming connected paths between all nodes (mobile ad hoc networks), or it is close to zero, assuming no multi-hop paths exist at all (delay-tolerant networks). In this paper, we argue that a sizable fraction of networks lies between these extremes and is characterized by the existence of partial paths, i.e. multi-hop path segments that allow forwarding data closer to the destination even when no end-to-end path is available. A fundamental issue in such networks is dealing with disruptions of end-to-end paths. Under a stochastic model, we compare the performance of the established end-to-end retransmission (ignoring partial paths), against a forwarding mechanism that leverages partial paths to forward data closer to the destination even during disruption periods. Perhaps surprisingly, the alternative mechanism is not necessarily superior. However, under a stochastic monotonicity condition between current v.s. future path length, which we demonstrate to hold in typical network models, we manage to prove superiority of the alternative mechanism in stochastic dominance terms. We believe that this study could serve as a foundation to design more efficient data transfer protocols for partially-connected networks, which could potentially help reducing the gap between applications that can be supported over disconnected networks and those requiring full connectivity.Comment: Extended version of paper appearing at IEEE INFOCOM 2009, April 20-25, Rio de Janeiro, Brazi

Motivated prediction of future feelings: The effects of mood and mood focus on affective forecasts

People often predict they will experience more positive or more negative emotional reactions to upcoming pleasant and unpleasant events respectively, than they actually do. Although researchers have identified several cognitive processes underlying this bias in affective forecasting, the present research examined the role of motivational factors. We proposed that people sometimes generate relatively positive affective forecasts to fixture positive events (or less negative affective forecasts to future negative events) as a mood regulation strategy. That is, they may attempt to cope with threatening negative feelings by anticipating pleasant emotions in the future. More specific hypotheses were derived from recent research examining the impact of negative mood and mood focus on various self-enhancing cognitions. We hypothesised that people would predict more positive feelings to upcoming positive events and less negative feelings when predicting for upcoming negative events when they adopt a reflective focus on their current negative moods (wherein they acknowledge their negative feelings and interpret them as a signal for mood-regulation efforts) rather than a ruminative focus (wherein they dwell passively on their feelings). Results from two studies were generally consistent with this hypothesis. Participants who focussed on their current feelings in a reflective manner predicted more positive future feelings (across predictions for both positive and negative future events) in the negative mood condition than in the neutral mood condition. Those who ruminated on their current feelings showed the opposite pattern

The experience of money and the domestic moral economy of a group of young adults in Khayelitsha and their transition to adulthood

This thesis is a qualitative study of patterns of earning, sharing and spending among a cohort of young South African men and women, aged 25 to 35, in Khayelitsha, a mainly poor, Black African residential area of Cape Town. As less skilled ‘youth,' they are rarely able to sustain regular employment and therefore remain intermittently dependent on household income and resident in or near their parents' homes; they may have children but are not married. This thesis interprets how their low wage irregular employment and spending patterns affect relationships of mutuality and the dynamics of redistribution in their households. The thesis then considers how these phenomena change with their transition to ‘adulthood,' which occurred in the context of the COVID19 pandemic. The young adults experience a state of ‘locked in' material and existential depletion while balancing their aspirations, reflected in urgent and often conspicuous consumption, with their obligations in a context of chronic economic stress. As older adults, they progress from an economically dependent status to a mainly precarious adult status in their household where the matrix of domestic obligations and entitlements overwhelm youthful, aspirational spending. The thesis advances our understanding of the lived experience of money of ‘township youth' – as young adults – and then, as they progress into adulthood, of adult decision-making, in their domestic domain. The thesis unpacks and explains this experience in relation to the notion of a ‘domestic moral economy' produced at the nexus of economic and social cultural factors. Here responses of young adults to labour market conditions and consumerism impact on and are in turn impacted by social relations in the household. These responses introduced and embedded in both domestic relations and their social lives among peers and friends, demonstrate the inseparability of external capitalist relation of production from historically instituted social relations in the wider South African moral economy

Integration of SysML with Trade-off Analysis Tools

Changes in technology, economy and society create challenges that force us to rethink the way we develop systems. Model-Based Systems Engineering is an approach that can prove catalytic in this new era of systems development. In this work we introduce the concept of the modeling "hub" in order to realize the vision of Model-Based Systems Engineering and especially we focus on the trade-off analysis and design space exploration part of this "hub". For that purpose the capabilities of SysML are extended by integrating it with the trade-off analysis tool Consol-Optcad. The integration framework, the implementation details as well as the tools that were used for this work are described throughout this thesis. The implemented integration is then applied to analyze a very interesting multi-criteria optimization problem concerning power allocation and scheduling of a microgrid

Modelling near-bank flow hydraulics

River bank erosion models are a fundamental requirement for understanding the migration and evolution of river meanders, estimating the potential for land-loss and threat to floodplain infrastructure, and predicting the delivery of contaminated floodplain sediments to aquatic ecosystems. While progress has recently been made in understanding and modelling processes controlling large-scale mass failure, less attention has been paid to the role that fluvial erosion plays in bank retreat. This project aims to address this gap by developing a new fluvial erosion model. Recent developments in bank erosion monitoring technology, and in the quantification of the bank erodibility parameters using jet-testing devices, offer the means of determining fluvial erosion rates and bank erodibility. However, the missing link remains the need to obtain highresolution, spatially distributed, flow data to characterize the near-bank fluid shear stresses that drive bank erosion. One possible solution is to use Computational Fluid Dynamics (CFD) models as a substitute for empirical data.Herein I evaluate a series of three-dimensional CFD simulations for a meander loop on the River Asker at Bridport in southern England. CFD models under specific steady peak flow conditions were developed using Fluent 6.2, with peak flow discharge estimates obtained from an adjacent gauging station. All the models obtained from the three examined flow events were successfully verified and validated using clearly defined and structured procedures. The modelling results indicated that the main qualitative features of the flow remain even as flow discharge varies. However, notable differences were observed between the examined flow events, such as, a general increasing of velocity and shear stress throughout the reach as flow stage is gradually increased, a slight reduction in the size and extent of separation zones at bank full stage, a movement of impingement points further downstream, and a continuation of the secondary flow within the fast streamtube further towards the bends exits. Bed/bank shear stress is mostly seen to decrease at shallow riffles as discharge approaches bankfull, while pools experience an increase in bed/bank shear stress with increase in discharge. Zones of higher bed/bank shear stress extend and combine, while marginal recirculation zones and areas of relatively low bed/bank shear stress generally reduce in area to form discrete locations for erosion and deposition phenomena. At bank full stage, the magnitudes of velocity and simulated shear stresses within the inner bank separation zones are found to be higher than those observed under low flow conditions and they may be sufficient to result in the removal of accumulated sediments into the main downstream flow. The presence of regions of high velocity in the form of a streamtube, especially along the outer banks, creates high shear stresses within these areas. As a result, outer bank migration rates are likely to be relatively high in bends with inner bank separation zones