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Lazy Evaluation of Negative Preconditions in Planning Domains (Extended Abstract)
Get PDFAI planning technology faces performance issues with large-scale problems with negative preconditions. In this extended abstract, we show how to leverage the power of the Finite Domain Representation (FDR) used by the popular Fast Downward planner for such domains. FDR improves scalability thanks to its use of multi-valued state variables. However, it scales poorly when dealing with negative preconditions. We propose an alternative hybrid approach that evaluates negative preconditions on the fly during search but only when strictly needed. This is compared to the traditional use of PDDL bookmark predicates, which increases memory usage
Volcanic and Tectonic Constraints on the Evolution of Venus
Get PDFSurface geologic features form a detailed record of Venus’ evolution. Venus displays a profusion of volcanic and tectonics features, including both familiar and exotic forms. One challenge to assessing the role of these features in Venus’ evolution is that there are too few impact craters to permit age dates for specific features or regions. Similarly, without surface water, erosion is limited and cannot be used to evaluate age. These same observations indicate Venus has, on average, a very young surface (150–1000 Ma), with the most recent surface deformation and volcanism largely preserved on the surface except where covered by limited impact ejecta. In contrast, most geologic activity on Mars, the Moon, and Mercury occurred in the 1st billion years. Earth’s geologic processes are almost all a result of plate tectonics. Venus’ lacks such a network of connected, large scale plates, leaving the nature of Venus’ dominant geodynamic process up for debate. In this review article, we describe Venus’ key volcanic and tectonic features, models for their origin, and possible links to evolution. We also present current knowledge of the composition and thickness of the crust, lithospheric thickness, and heat flow given their critical role in shaping surface geology and interior evolution. Given Venus’ hot lithosphere, abundant activity and potential analogues of continents, roll-back subduction, and microplates, it may provide insights into early Earth, prior to the onset of true plate tectonics. We explore similarities and differences between Venus and the Proterozoic or Archean Earth. Finally, we describe the future measurements needed to advance our understanding of volcanism, tectonism, and the evolution of Venus
UK and global food security in the era of ‘permacrisis’
Get PDFThe UK’s food security is currently dependent on complex international supply chains that are under threat from climate change, conflicts, and geopolitical stressors; at the same time, climate change and the repercussions of Brexit challenge the UK's ability to increase self-reliance and internal resilience. Jennifer Cole and Ivica Petrikova examine the key drivers and pressures on global food security currently and how this is likely to be impacted in the near- and mid-term future, including by shifting geopolitical alliances
An Ecosystem Approach To Iot Adoption In Agriculture:A Multiple-Case Study
Get PDFIn this TREO paper, we present preliminary findings from our ongoing research on the adoption of the Internet of Things (IoT) technologies within the agricultural sector. The study is based on multiple exploratory case studies in four countries (Greece, Italy, Serbia, and Türkiye). These cases show how the diffusion of IoT innovations unfolds within diverse geographical, socio-economic, and legal contexts. Our preliminary findings underscore the early stage of the innovation ecosystem formation within the IoT market for agriculture, which is often fragmented, loosely coupled, and ephemeral. This necessitates that companies strategise effectively, aligning their approaches with the evolving and, in some cases, yet-to-emerge IoT ecosystem to ensure the success of their IoT-driven agricultural ventures
Truthful Interval Covering
Get PDFWe initiate the study of a novel problem in mechanism design without money, which we term Truthful Interval Covering (TIC). An instance of TIC consists of a set of agents each associated with an individual interval on a line, and the objective is to decide where to place a covering interval to minimize the total social or egalitarian cost of the agents, which is determined by the intersection of this interval with their individual ones. This fundamental problem can model situations of provisioning a public good, such as the use of power generators to prevent or mitigate load shedding in developing countries. In the strategic version of the problem, the agents wish to minimize their individual costs, and might misreport the position and/or length of their intervals to achieve that. Our goal is to design truthful mechanisms to prevent such strategic misreports and achieve good approximations to the best possible social or egalitarian cost. We consider the fundamental setting of known intervals with equal lengths and provide tight bounds on the approximation ratios achieved by truthful deterministic mechanisms. For the social cost, we also design a randomized truthful mechanism that outperforms all possible deterministic ones. Finally, we highlight a plethora of natural extensions of our model for future work, as well as some natural limitations of those settings
Contamination of depressional wetlands in the Mpumalanga Lake District of South Africa near a global emission hotspot
Get PDFThe Mpumalanga Lake District (MLD) of South Africa hosts a regionally unique cluster of water bodies of great importance for wetland biodiversity. It is also located close to a global hotspot for coal-fired power station emissions but the local impacts from these sources of pollution are poorly understood. Sediment cores from three contrasting wetlands were 210Pb dated and analysed for a range of contaminants linked to fossil fuel combustion, including trace elements, Hg, sulphur and spheroidal carbonaceous fly-ash particles (SCPs). At the two sites with pre-industrial (1900) baseline sediments, Pb, Zn and especially Cr concentrations and fluxes showed significant increases in the impact period (post-1975). Mercury showed the greatest proportional increase in flux (>4-fold) of all trace metals. Mercury and sulphur concentrations and fluxes showed highly significant correlations with emissions over the corresponding periods, while SCPs in sediments also closely tracked emissions. In a global context, levels of sediment contamination are relatively minor compared with other heavily industrialised regions, with only Cr exceeding the sediment Probable Effects Concentration for biological impact post-1975. Despite the relatively large increases in Hg, concentrations do not reach the Threshold Effects Concentration. The unexpectedly low levels of contamination may be due to i) low levels of many trace contaminants in South African coals compared to global averages, ii) prevailing recirculation patterns which transport pollution away from the study area during the wet season, minimising wet deposition, and iii) pollutant remobilisation through desiccation of wetlands or volatilization. The effects of hydrology and sediment accumulation rates lead to differential transport and preservation of organic-associated and more volatile contaminants (e.g. Hg, S) relative to non-volatile trace elements in wetlands of the MLD. The greatest fluxes of Hg and S are recorded in the site with the highest catchment: lake area ratio, lowest salinity and greatest sediment organic matter content
An investigation into the physical factors that control slow mass movements
Get PDFThe behavior of slow mass movements like soil creep is well known to be governed by soil composition, slope, and cycles in temperature and rainfall. However, their magnitude and importance vary dramatically in often unpredictable ways, with important consequences for creep rate and infrastructure damage prediction. Here, we present long-term (2015–2022) creep measurements for four regions of the UK characterized by intense mass movement activity but different bedrock lithologies. We also obtained co-located temperature and precipitation time series over this period, as well as local measurements of slope and soil thickness and composition. Our goal was to deconvolve the relative importance of each observable on creep behavior. Our results imply that parent lithology governs first-order creep rates indirectly via hillslope repose angles and soil thickness and composition. Rates of ground movement on peat and sandstone soils are dictated by annual fluctuations in precipitation and temperature, respectively. By employing a simple error-minimizing regression routine, we demonstrate how creep rates can be predicted in these settings as a function of climatological observables. Over thinner limestone and thicker clay soils, however, our model fails: in these settings, we suggest that creep behavior is instead dominated by variations in regolith thickness, and slope and clay mineral content, respectively
Bubble Economics
Get PDFThis article provides a self-contained overview of the theory of rational asset price bubbles. We cover topics from basic definitions, properties, and classical results to frontier research, with an emphasis on bubbles attached to real assets such as stocks, housing, and land. The main message is that bubbles attached to real assets are fundamentally nonstationary phenomena related to unbalanced growth. We present a bare-bones model and draw three new insights: (i) the emergence of asset price bubbles is a necessity, instead of a possibility; (ii) asset pricing implications are markedly different between balanced growth of stationary nature and unbalanced growth of nonstationary nature; and (iii) asset price bubbles occur within larger historical trends involving shifts in industrial structure driven by technological innovation, including the transition from the Malthusian economy to the modern economy
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