328 research outputs found
Power Modelling and Optimisation of a Communication bus for Small Satellite Missions
No full textAerospace EngineeringSpace Engineerin
Paradigm Lost: On the Value of Lost Causes in Transforming Cities and Water Systems’ Development Pathways
No full textIn the last decades, thousands of socio-environmental conflicts have spawned, especially at the sub-national scale. Among these, water conflicts are especially complex and multifaceted, since most are driven by a combination of socio-economic dynamics that increase pressure on natural resources, more extreme hydro-climatic trends, outdated or biased legal frameworks, large power asymmetries between actors, and the dominance of sociotechnical paradigms that reduce the decision space of water policies. Although water conflicts often receive a lot of attention, public scrutiny, and media exposure, this has not necessarily transcended into improving our understanding of their relation to the coupled human-water systems in which they are embedded, and even less of their transformative potential to open the decision space on the development pathways of cities and water systems. Furthermore, if a conflict drags on, it creates the notion of conflict impasse, of a static nature and confined to a narrowed space. This can further obstruct our understanding of what the conflict is really about, what are its root causes, what are the motivations of key actors, how do actors mobilize different capitals to achieve their goals and coalesce in networks, and what are the best ways to move forward and find transformative alternatives. This PhD thesis aims to reveal that water conflicts are highly dynamic and the result of a complex web of events influenced by social and natural long-term dynamics, knowledge controversies, and actors and network dynamics that widen the perception of the boundaries of water conflicts. To map out and navigate these turbulent waters of water conflicts, new transdisciplinary methods and action research are necessary. The realization that conflicts are complex and dynamic, and that transdisciplinary and action methods are needed to transform them has many implications. First, given the longterm dynamics that determine a conflict, it is necessary to analyze its history beyond the “official” start of the conflict, even before the involvement of the main actors in the conflict. Therefore, a water conflict involves much more than only just a dispute between parties, but also wider and more transcendent discussions of sustainability of cities and water systems and fairness of socio-political systems. Second, these long-term dynamics are both social and natural, thus, water conflicts need to be analyzed in an interdisciplinary manner to better deal with controversies composed of different kinds of uncertainties and ambiguity in the coupled human-water systems. The development of new hybrid disciplines like socio-hydrology and hydrosocial studies are a step forward, but they keep being dominated by either a natural sciences or social sciences epistemology. Third, further analyzing the conflict in a transdisciplinary and longitudinal manner, by involving actors in knowledge co-production, can improve our understanding of knowledge controversies, which in turn increases the reflectivity of the role of science and scientists in these conflicts.Water Resource
Observation of the Bc+→J/ψπ+π0 decay
No full textThe first observation of the Bc+→J/ψπ+π0 decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the Bc+→J/ψπ+ channel is measured to be (Formula presented.) where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and Bc+→J/ψπ+ decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation
Measurement of the branching fraction of B0→ J/ψπ0 decays
No full textThe ratio of branching fractions between B0 → J/ψπ0 and B+ → J/ψK*+ decays is measured with proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. The measured value is (Formula presented.) where the first uncertainty is statistical and the second is systematic. The branching fraction for B0 → J/ψπ0 decays is determined using the branching fraction of the normalisation channel, resulting in (Formula presented.) where the last uncertainty corresponds to that of the external input. This result is consistent with the current world average value and competitive with the most precise single measurement to date
Measurement of associated J/ψ-ψ(2S) production cross-section in pp collisions at √s = 13TeV
No full textThe cross-section of associated J/ψ-ψ(2S) production in proton-proton collisions at a centre-of-mass energy of √s = 13TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb−1, collected by the LHCb experiment. The measurement is performed for both J/ψ and ψ(2S) mesons having transverse momentum pT< 14 GeV/c and rapidity 2.0 < y < 4.5, assuming negligible polarisation of the J/ψ and ψ(2S) mesons. The production cross-section is measured to be 4.5 ± 0.7 ± 0.3 nb, where the first uncertainty is statistical and the second systematic. The differential cross-sections are measured as functions of several kinematic variables of the J/ψ-ψ(2S) candidates. The results are combined with a measurement of J/ψ-J/ψ production, giving a cross-section ratio between J/ψ-ψ(2S) and J/ψ-J/ψ production of 0.274 ± 0.044 ± 0.008, where the first uncertainty is statistical and the second systematic
Study of the rare decay J/ψ → μ+μ−μ+μ−
No full textThe rare electromagnetic J/ψ → μ+μ−μ+μ− decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016–2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb−1. The rate of this decay is measured relative to that of the J/ψ → μ+μ− mode. Using the QED model for the four-muon decay in the efficiency estimation, its branching fraction is determined to be (Formula presented.) where the uncertainties are statistical, systematic and due to the uncertainty on the branching fraction of the J/ψ → μ+μ− decay
Observation of the Bc+ → J/ψπ+π0 decay
No full textThe first observation of the Bc+→J/ψπ+π0 decay is reported with high significance using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV. The ratio of its branching fraction relative to the Bc+→J/ψπ+ channel is measured to beBBc+→J/ψπ+π0BBc+→J/ψπ+=2.80±0.15±0.11±0.16, where the first uncertainty is statistical, the second systematic and the third related to imprecise knowledge of the branching fractions for B+ → J/ψK*+ and Bc+→J/ψπ+ decays, which are used to determine the π0 detection efficiency. The π+π0 mass spectrum is found to be consistent with the dominance of an intermediate ρ+ contribution in accordance with a model based on QCD factorisation
Fraction of χc Decays in Prompt J/ψ Production Measured in pPb Collisions at √SNN=8.16 TeV
No full textThe fraction of χc1 and χc2 decays in the prompt J/ψ yield, Fχc→J/ψ=σχc→J/ψ/σJ/ψ, is measured by the LHCb detector in pPb collisions at sNN=8.16 TeV. The study covers the forward (1.5<4.0) and backward (-5.0<-2.5) rapidity regions, where y∗ is the J/ψ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6±0.3 and 20.8±0.5 nb-1, respectively. The result is presented as a function of the J/ψ transverse momentum pT,J/ψ in the range
Unraveling intractable water conflicts: The entanglement of science and politics in decision-making on large hydraulic infrastructure
No full textThe development of large infrastructure to address the water challenges of cities around the world can be a financial and social burden for many cities because of the hidden costs these works entail and social conflicts they often trigger. When conflicts erupt, science is often expected to play a key role in informing policymakers and social actors to clarify controversies surrounding policy responses to water scarcity. However, managing conflicts is a sociopolitical process, and often quantitative models are used as an attempt to depoliticize such processes, conveying the idea that optimal solutions can be objectively identified despite the many perspectives and interests at play. This raises the question as to whether science depoliticizes water conflicts or whether instead conflicts politicize science-policy processes. We use the Zapotillo dam and water transfer project in Mexico to analyze the role of science-policy processes in water conflicts. The Zapotillo project aims at augmenting urban water supply to Guadalajara and León, two large cities in western Mexico, but a social and legal conflict has stalled the project until today. To analyze the conflict and how stakeholders make sense of it, we interviewed the most relevant actors and studied the negotiations between different interest groups through participant observation. To examine the role of science-policy processes in the conflict, we mobilized concepts of epistemic uncertainty and ambiguity and analyzed the design and use of water resources models produced by key actors aiming to resolve the conflict. While the use of models is a proven method to construct future scenarios and test different strategies, the parameterization of scenarios and their results are influenced by the knowledge and/or interests of actors behind the model. We found that in the Zapotillo case, scenarios reflected the interests and strategies of actors on one side of the conflict, resulting in increased distrust of the opposing actors. We conclude that the dilemma of achieving urban water security through investing in either large infrastructure (supply augmentation) or alternative strategies (demand-side management) cannot be resolved if some key interested parties have not been involved in the scientific processes framing the problem and solution space.Water Resource
Search for Bc+→π+μ+μ- decays and measurement of the branching fraction ratio B(Bc+→ψ(2S)π+)/B(Bc+→J/ψπ+)
No full textThe first search for nonresonant Bc+→π+μ+μ- decays is reported. The analysis uses proton–proton collision data collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9fb-1. No evidence for an excess of signal events over background is observed and an upper limit is set on the branching fraction ratio B(Bc+→π+μ+μ-)/B(Bc+→J/ψπ+)<2.1×10-4 at 90% confidence level. Additionally, an updated measurement of the ratio of the Bc+→ψ(2S)π+ and Bc+→J/ψπ+ branching fractions is reported. The ratio B(Bc+→ψ(2S)π+)/B(Bc+→J/ψπ+) is measured to be 0.254±0.018±0.003±0.005, where the first uncertainty is statistical, the second systematic, and the third is due to the uncertainties on the branching fractions of the leptonic J/ψ and ψ(2S) decays. This measurement is the most precise to date and is consistent with previous LHCb results
- …
