| 1. |
- Abrahao, FS, et al.
(författare)
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Emergence and algorithmic information dynamics of systems and observers
- 2022
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Ingår i: Philosophical transactions. Series A, Mathematical, physical, and engineering sciences. - : The Royal Society. - 1471-2962. ; 380:2227, s. 20200429-
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Tidskriftsartikel (refereegranskat)abstract
- One of the challenges of defining emergence is that one observer’s prior knowledge may cause a phenomenon to present itself as emergent that to another observer appears reducible. By formalizing the act of observing as mutual perturbations between dynamical systems, we demonstrate that the emergence of algorithmic information does depend on the observer’s formal knowledge, while being robust vis-a-vis other subjective factors, particularly: the choice of programming language and method of measurement; errors or distortions during the observation; and the informational cost of processing. This is called observer-dependent emergence (ODE). In addition, we demonstrate that the unbounded and rapid increase of emergent algorithmic information implies asymptotically observer-independent emergence (AOIE). Unlike ODE, AOIE is a type of emergence for which emergent phenomena will be considered emergent no matter what formal theory an observer might bring to bear. We demonstrate the existence of an evolutionary model that displays the diachronic variant of AOIE and a network model that displays the holistic variant of AOIE. Our results show that, restricted to the context of finite discrete deterministic dynamical systems, computable systems and irreducible information content measures, AOIE is the strongest form of emergence that formal theories can attain.This article is part of the theme issue ‘Emergent phenomena in complex physical and socio-technical systems: from cells to societies’.
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| 2. |
- Andrighetto, Giulia, et al.
(författare)
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A research agenda for the study of social norm change
- 2022
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Ingår i: Philosophical Transactions. Series A. - : ROYAL SOC. - 1364-503X .- 1471-2962. ; 380:2227
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Forskningsöversikt (refereegranskat)abstract
- Social norms have been investigated across many disciplines for many years, but until recently, studies mainly provided indirect, implicit and correlational support for the role of social norms in driving behaviour. To understand how social norms, and in particular social norm change, can generate a large-scale behavioural change to deal with some of the most pressing challenges of our current societies, such as climate change and vaccine hesitancy, we discuss and review several recent advances in social norm research that enable a more precise underpinning of the role of social norms: how to identify their existence, how to establish their causal effect on behaviour and when norm change may pass tipping points. We advocate future research on social norms to study norm change through a mechanism-based approach that integrates experimental and computational methods in theory-driven, empirically calibrated agent-based models. As such, social norm research may move beyond unequivocal praising of social norms as the missing link between self-interested behaviour and observed cooperation or as the explanation for (the lack of) social tipping. It provides the toolkit to understand explicitly where, when and how social norms can be a solution to solve large-scale problems, but also to recognize their limits.This article is part of the theme issue 'Emergent phenomena in complex physical and socio-technical systems: from cells to societies'.
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| 3. |
- Argatov, Ivan
(författare)
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Controlling the adhesive pull-off force via the change of contact geometry
- 2021
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 379:2203
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Tidskriftsartikel (refereegranskat)abstract
- A first-order asymptotic analysis of the Griffith energy balance in the Johnson-Kendall-Roberts model of adhesive contact under non-symmetric perturbation of the contact geometry is presented. The pull-off force is evaluated in explicit form. A particular case of adhesive contact between a relatively stiff sphere and an elastic half-space is considered under the assumption that the sphere geometry is changed by the application of an arbitrary lateral normal surface loading. The effect of the sphere Poisson's ratio on controlling the adhesive pull-off force is considered.This article is part of a discussion meeting issue 'A cracking approach to inventing new tough materials: fracture stranger than friction'.
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| 4. |
- Bhatnagar, Akshay, et al.
(författare)
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Rate of formation of caustics in heavy particles advected by turbulence
- 2022
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 380:2219
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Tidskriftsartikel (refereegranskat)abstract
- The rate of collision and the relative velocities of the colliding particles in turbulent flows are a crucial part of several natural phenomena, e.g. rain formation in warm clouds and planetesimal formation in protoplanetary discs. The particles are often modelled as passive, but heavy and inertial. Within this model, large relative velocities emerge due to formation of singularities (caustics) of the gradient matrix of the velocities of the particles. Using extensive direct numerical simulations of heavy particles in both two (direct and inverse cascade) and three-dimensional turbulent flows, we calculate the rate of formation of caustics, J as a function of the Stokes number (St). The best approximation to our data is J similar to exp(-C/St), in the limit St -> 0 where C is a non-universal constant. This article is part of the theme issue 'Scaling the turbulence edifice (part 2)'.
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| 5. |
- Bostan, Lars, et al.
(författare)
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Upscaling of lignin precursor melt spinning by bicomponent spinning and its use for carbon fibre production
- 2021
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Ingår i: Philosophical Transactions. Series A. - : Royal Society Publishing. - 1364-503X .- 1471-2962. ; 379:2209
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Tidskriftsartikel (refereegranskat)abstract
- Upscaling lignin-based precursor fibre production is an essential step in developing bio-based carbon fibre from renewable feedstock. The main challenge in upscaling of lignin fibre production by melt spinning is its melt behaviour and rheological properties, which differ from common synthetic polymers used in melt spinning. Here, a new approach in melt spinning of lignin, using a spin carrier system for producing bicomponent fibres, has been introduced. An ethanol extracted lignin fraction from LignoBoost process of commercial softwood kraft black liquor was used as feedstock. After additional heat treatment, melt spinning was performed in a pilot-scale spinning unit. For the first time, biodegradable polyvinyl alcohol (PVA) was used as a spin carrier to enable the spinning of lignin by improving the required melt strength. PVA-sheath/lignin-core bicomponent fibres were manufactured. Afterwards, PVA was dissolved by washing with water. Pure lignin fibres were stabilized and carbonized, and tensile properties were measured. The measured properties, tensile modulus of 81.1 ± 3.1 GPa and tensile strength of 1039 ± 197 MPa, are higher than the majority of lignin-based carbon fibres reported in the literature. This new approach can significantly improve the melt spinning of lignin and solve problems related to poor spinnability of lignin and results in the production of high-quality lignin-based carbon fibres. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'. © 2021 The Author(s).
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| 6. |
- Chafik, Léon, 1985-, et al.
(författare)
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Observed mechanisms activating the recent subpolar North Atlantic Warming since 2016
- 2023
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Ingår i: Philosophical Transactions. Series A. - 1364-503X .- 1471-2962. ; 381:2262
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Tidskriftsartikel (refereegranskat)abstract
- The overturning circulation of the subpolar North Atlantic (SPNA) plays a fundamental role in Earth's climate variability and change. Here, we show from observations that the recent warming period since about 2016 in the eastern SPNA involves increased western boundary density at the intergyre boundary, likely due to enhanced buoyancy forcing as a response to the strong increase in the North Atlantic Oscillation since the early 2010s. As these deep positive density anomalies spread southward along the western boundary, they enhance the North Atlantic Current and associated meridional heat transport at the intergyre region, leading to increased influx of subtropical heat into the eastern SPNA. Based on the timing of this chain of events, we conclude that this recent warming phase since about 2016 is primarily associated with this observed mechanism of changes in deep western boundary density, an essential element in these interactions.This article is part of a discussion meeting issue 'Atlantic overturning: new observations and challenges'.
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| 7. |
- Field, A. R., et al.
(författare)
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Comparing pedestal structure in JET-ILW H-mode plasmas with a model for stiff ETG turbulent heat transport
- 2023
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 381:2242
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Tidskriftsartikel (refereegranskat)abstract
- A predictive model for the electron temperature profile of the H-mode pedestal is described, and its results are compared with the pedestal structure of JET-ILW plasmas. The model is based on a scaling for the gyro-Bohm normalized, turbulent electron heat flux qe/qe,gB resulting from electron temperature gradient (ETG) turbulence, derived from results of nonlinear gyrokinetic (GK) calculations for the steep gradient region. By using the local temperature gradient scale length L-Te in the normalization, the dependence of q(e)/q(e,g)B on the normalized gradients R/L-Te and R/(Lne) can be represented by a unified scaling with the parameter eta(e) = L-ne/L-Te, to which the linear stability of ETG turbulence is sensitive when the density gradient is sufficiently steep. For a prescribed density profile, the value of R/L-Te determined from this scaling, required to maintain a constant electron heat flux qe across the pedestal, is used to calculate the temperature profile. Reasonable agreement with measurements is found for different cases, the model providing an explanation of the relative widths and shifts of the T-e and n(e) profiles, as well as highlighting the importance of the separatrix boundary conditions. Other cases showing disagreement indicate conditions where other branches of turbulence might dominate.This article is part of a discussion meeting issue "H-mode transition and pedestal studies in fusion plasmas'.
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| 8. |
- Flammini, Francesco, Senior Lecturer, 1978-
(författare)
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Digital twins as run-time predictive models for the resilience of cyber-physical systems : a conceptual framework
- 2021
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Ingår i: Philosophical Transactions. Series A. - : ROYAL SOC. - 1364-503X .- 1471-2962. ; 379:2207
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Tidskriftsartikel (refereegranskat)abstract
- Digital twins (DT) are emerging as an extremely promising paradigm for run-time modelling and performability prediction of cyber-physical systems (CPS) in various domains. Although several different definitions and industrial applications of DT exist, ranging from purely visual three-dimensional models to predictive maintenance tools, in this paper, we focus on data-driven evaluation and prediction of critical dependability attributes such as safety. To that end, we introduce a conceptual framework based on autonomic systems to host DT run-time models based on a structured and systematic approach. We argue that the convergence between DT and self-adaptation is the key to building smarter, resilient and trustworthy CPS that can self-monitor, self-diagnose and-ultimately-self-heal. The conceptual framework eases dependability assessment, which is essential for the certification of autonomous CPS operating with artificial intelligence and machine learning in critical applications. This article is part of the theme issue 'Towards symbiotic autonomous systems'.
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| 9. |
- Grennfelt, Peringe, et al.
(författare)
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A chronology of global air quality
- 2020
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962.
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Tidskriftsartikel (refereegranskat)abstract
- Air pollution has been recognized as a threat to human health since the time of Hippocrates, ca 400 BC. Successive written accounts of air pollution occur in different countries through the following two millennia until measurements, from the eighteenth century onwards, show the growing scale of poor air quality in urban centres and close to industry, and the chemical characteristics of the gases and particulate matter. The industrial revolution accelerated both the magnitude of emissions of the primary pollutants and the geographical spread of contributing countries as highly polluted cities became the defining issue, culminating with the great smog of London in 1952. Europe and North America dominated emissions and suffered the majority of adverse effects until the latter decades of the twentieth century, by which time the transboundary issues of acid rain, forest decline and ground-level ozone became the main environmental and political air quality issues. As controls on emissions of sulfur and nitrogen oxides (SO2 and NOx) began to take effect in Europe and North America, emissions in East and South Asia grew strongly and dominated global emissions by the early years of the twenty-first century. The effects of air quality on human health had also returned to the top of the priorities by 2000 as new epidemiological evidence emerged. By this time, extensive networks of surface measurements and satellite remote sensing provided global measurements of both primary and secondary pollutants. Global emissions of SO2 and NOx peaked, respectively, in ca 1990 and 2018 and have since declined to 2020 as a result of widespread emission controls. By contrast, with a lack of actions to abate ammonia, global emissions have continued to grow. This article is part of a discussion meeting issue ‘Air quality, past present and future’
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| 10. |
- Kaynak, O., et al.
(författare)
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Towards symbiotic autonomous systems
- 2021
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 379:2720
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Tidskriftsartikel (refereegranskat)abstract
- Starting in the second half of the last century, the widespread use of computers has significantly changed the lifestyles of humankind. Since then, with the explosive and perhaps disruptive developments in digital technology, the internet and Internet of Things and artificial intelligence have promoted a growing interaction among humans and machines, with technology capable of extending human capabilities (augmentation) and making devices seamlessly interact with humans. In the longer term, there is a growing consensus that this will create symbiotic autonomous systems (SASs). Although this is a trend that will see maturity possibly in the next decade, research and industry interest are already strong, resulting in several concrete results ready to hit the market. What matters most in the context of SASs is the varying degrees of autonomy they have, their capability to evolve (e.g. to learn and adapt), and their ability to interact with their environment, between themselves, and with humans. Hence, SAS is a class of advanced information and control technology that has gradually evolved, based on cybernetics, information theory, artificial intelligence, bionics, neurophysiology and computer science. At the same time, it has also promoted the joint development and mutual penetration of multiple fields such as microelectronics, life sciences and automation technology. In all future areas, SASs will become a seamless extension of our body and mind and an integral part of our life.
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