Formal verification of distributed deadlock detection algorithms

The problem of distributed deadlock detection has undergone extensive study. Formal verification of deadlock detection algorithms in distributed systems is an area of research that has largely been ignored. Instead, most proposed distributed deadlock detection algorithms have used informal or intuitive arguments, simulation or just neglect the entire aspect of verification of correctness; As a consequence, many of these algorithms have been shown incorrect. This research will abstract the notion of deadlock in terms of a temporal logic of actions and discuss the invariant and eventuality properties. The contributions of this research are the development of a distributed deadlock detection algorithm and the formal verification of this algorithm

Critiquing commodification in environmental governance :examples of urban waste governance in Cape Town, Rotterdam, and Bristol

Is the governance of waste in cities being encroached by logics of commodification? This question is posed to analyse a capitalistic turn in environmental governance. Encroachment of such logics is hypothesised to occur by innovation- and discourse-based means. But, alongside changes in how urban waste governance systems are contested, there are changes in how they are maintained and reinforced, e.g., through information technologies. Therefore, this thesis aims to better understand the commodification of waste – including relevant ideas with political traction – which is shaping and shaped by institutionalisation in urban waste governance. Three objectives follow this aim. The first is to identify and critically analyse institutions sharing explicit alignment with either or both circular economy or food-energy-water nexus ideas, and relationships between these institutions in Rotterdam, Cape Town, and Bristol. The second is to investigate and critically analyse the role of ideational power in processes of institutionalisation, or institutional change, within urban waste governance systems. And third, to synthesise and simulate factors affecting the outcomes of institutionalisation or institutional change aligned with circular economy or foodenergy-water nexus discourse in different urban waste governance systems. An innovative mixed method methodology which includes social network analysis, qualitative analysis, and agentbased modelling has been developed and applied to achieve these research objectives. Methods were selected and integrated with reference to an interdisciplinary theoretical framework including environmental governance and critical institutionalism, a systems-thinking analytical framing, and a conceptual frame that foregrounds context in the interaction between research and government policy. Results suggest that the way critique is mobilised and affects institutional networks through which waste governance occurs in cities is becoming increasingly complex and nuanced. Whilst this may mean that contestation is increasingly open to influence or disruption, caution is warranted in such interpretations. A shallow process of institutional diversification may obscure deeper rigidity of established power hierarchies in urban environmental governance. How such systemic asymmetries or inequities might be addressed by innovative forms of critique is an open question, but a systems-thinking analytical approach which is sensitive to contextual factors determining how and whether critical engagement affects policy, and its outcomes, is instructive. The commodification of waste and of competing ideas interacting with waste governance systems calls for holistic analysis of urban waste governance networks. Mixed methods that appraise and integrate computer based- and empirical forms of social data enable holistic-critical analysis of the governance networks wherein hegemony or domination is difficult to pinpoint and destabilise. Such exercises of holistically analysing and critically engaging with diffuse / fluid domination in urban waste governance networks give impetus to unorthodox alternatives to commodification – both in terms of governance processes and outcomes that we might reasonably expect from those

Beyond Power over Ethernet : the development of Digital Energy Networks for buildings

Alternating current power distribution using analogue control and safety devices has been the dominant process of power distribution within our buildings since the electricity industry began in the late 19th century. However, with advances in digital technology, the seeds of change have been growing over the last decade. Now, with the simultaneous dramatic fall in power requirements of digital devices and corresponding rise in capability of Power over Ethernet, an entire desktop environment can be powered by a single direct current (dc) Ethernet cable. Going beyond this, it will soon be possible to power entire office buildings using dc networks. This means the logic of “one-size fits all” from the existing ac system is no longer relevant and instead there is an opportunity to redesign the power topology to be appropriate for different applications, devices and end-users throughout the building. This paper proposes a 3-tier classification system for the topology of direct current microgrids in commercial buildings – called a Digital Energy Network or DEN. The first tier is power distribution at a full building level (otherwise known as the microgrid); the second tier is power distribution at a room level (the nanogrid); and the third tier is power distribution at a desktop or appliance level (the picogrid). An important aspect of this classification system is how the design focus changes for each grid. For example; a key driver of the picogrid is the usability of the network – high data rates, and low power requirements; however, in the microgrid, the main driver is high power and efficiency at low cost

The evolving relation between star-formation rate and stellar mass in the VIDEO Survey since z=3z=3

We investigate the star-formation rate (SFR) and stellar mass ($M_*$) relation of a star-forming (SF) galaxy sample in the XMM-LSS field to $z\sim 3.0$ using the near-infrared data from the VISTA Deep Extragalactic Observations (VIDEO) survey. Combining VIDEO with broad-band photometry, we use the SED fitting algorithm CIGALE to derive SFRs and $M_*$ and have adapted it to account for the full photometric redshift PDF uncertainty. Applying a SF selection using the D4000 index, we find evidence for strong evolution in the normalisation of the SFR-$M_*$ relation out to $z\sim 3$ and a roughly constant slope of (SFR $\propto M_*^{\alpha}$) $\alpha=0.69\pm0.02$ to $z\sim 1.7$. We find this increases close to unity toward $z\sim2.65$. Alternatively, if we apply a colour selection, we find a distinct turnover in the SFR-$M_*$ relation between $0.7\lesssim z\lesssim2.0$ at the high mass end, and suggest that this is due to an increased contamination from passive galaxies. We find evolution of the specific SFR $\propto(1+z)^{2.60}$ at $\log(M_*)\sim$10.5, out to $z\lesssim2.4$ with an observed flattening beyond $z\sim$ 2 with increased stellar mass. Comparing to a range of simulations we find the analytical scaling relation approaches, that invoke an equilibrium model, a good fit to our data, suggesting that a continual smooth accretion regulated by continual outflows may be a key driver in the overall growth of SFGs.Comment: 19 pages, 18 figures, accepted for publication in MNRA

A Turn to Reception

At the turn of the millennium, powered by emerging canons, a narrative of discovery and art-historical contextualisation, the photobook became a central object of interest for photographers, scholars and collectors. As a product of this situation a community coalesced, constructing photobook-specific events, platforms and publications that gave space to deep-dive the processes and products of book making. Now, the photobook enters a new moment. As large institutions embrace photography on the page more readily and the frenzy of the photobook phenomenon is tempered, an emerging critical movement seeks to address the sustainability, reception and legacy of the post-millennium medium. This article argues that key to such discussions will be the previously sidelined matter of reading and what it can contribute to a prevailing, production-oriented discourse. By reviewing what literature exists around the subject and its periphery, combining with reflections on the author’s own activities and drawing from a number of contemporary photobook initiatives it is posited that there are three substantial challenges that can arrest visibility and comprehension of photobook reading. From the difficulty faced when speaking about books to an absence of space held to accommodate reading and the subdued level of interest in this elusive activity, each theme is outlined and expanded in turn before being located as pivotal in constructing a more inclusive and meaningful future for the photobook

Understanding environmental injustice : the case of Imizamo Yethu and the poverty-population-environment nexus

No abstractMini Dissertation (MA)--University of Pretoria, 2018.Geography, Geoinformatics and MeteorologyMAUnrestricte