461 research outputs found
How perceived scarcity predicted cooperation during early pandemic lockdown.
Both material resources (jobs, healthcare), and socio-psychological resources (social contact) decreased during the COVID-19 pandemic. We investigated whether individual differences in perceived material and socio-psychological scarcity experienced during the pandemic predicted preference for cooperation, measured using two Public Good Games (PGGs), where participants contributed money or time (i.e., hours indoors contributed to shorten the lockdown). Material scarcity had no relationship with cooperation. Increased perceived scarcity of socio-psychological wellbeing (e.g., connecting with family) predicted increased preference for cooperation, suggesting that missing social contact fosters prosociality, whilst perceived scarcity of freedom (e.g., limited movement) predicted decreased willingness to spend time indoors to shorten the lockdown. The importance of considering individual differences in scarcity perception to best promote norm compliance is discussed
Generating and absorbing boundary conditions for combined wave-current simulations
The CFD simulation tool ComFLOW is extended to investigate the characteristics of wave motions in the presence of steady uniform currents. Initially, the inflow boundary is the superposition of waves and current. Effect of the latter on the former is resolved by solving Navier-Stokes equations within the domain as a next step. A Generating and Absorbing Boundary Condition (GABC) with currents is introduced that allows the simulation of a combined wave-current environment in truncated domain. This GABC is characterized by a rational function approximation of dispersion relation, based on Sommerfeld condition and irrotational wave model. The artificial boundaries where GABC with current is applied are transparent to incoming and outgoing waves and currents simultaneously. The absorption properties of the GABC for various waves and currents are analysed. The temporal and spatial differences of free surface elevation between the small domain and large domain turn out to be small, i.e. the GABC prevents the reflection from the boundaries well. The large domain here is arranged in such a way that the reflected waves and currents will not reach the outflow boundary of the small domain within the simulation time. The behaviour of GABC in 3D domain is also investigated, where waves and currents are traveling under an angle of incidence colinearly
Neurocognitive mechanisms of reactions to second- and third-party justice violations.
The aim of the current study was threefold: (i) understand people's willingness to engage in either punishment of the perpetrator or compensation of the victim in order to counteract injustice; (ii) look into the differences between victims of and witnesses to injustice; (iii) investigate the different role played by social preference and affective experience in determining these choices. The sample tested here showed an equal preference for punishment and compensation; neuroimaging findings suggested that compensation, as opposed to punishment, was related to Theory of Mind. Partially supporting previous literature, choosing how to react to an injustice as victims, rather than witnesses, triggered a stronger affective response (striatal and prefrontal activation). Moreover, results supported the idea that deciding whether or not to react to an injustice and then how severely to react are two distinct decisional stages underpinned by different neurocognitive mechanisms, i.e., sensitivity to unfairness (anterior insula) and negative affectivity (amygdala). These findings provide a fine-grained description of the psychological mechanisms underlying important aspects of social norm compliance
Enhanced Preconditioner for JOREK MHD Solver
The JOREK extended magneto-hydrodynamic (MHD) code is a widely used
simulation code for studying the non-linear dynamics of large-scale
instabilities in divertor tokamak plasmas. Due to the large scale-separation
intrinsic to these phenomena both in space and time, the computational costs
for simulations in realistic geometry and with realistic parameters can be very
high, motivating the investment of considerable effort for optimization. In
this article, a set of developments regarding the JOREK solver and
preconditioner is described, which lead to overall significant benefits for
large production simulations. This comprises in particular enhanced convergence
in highly non-linear scenarios and a general reduction of memory consumption
and computational costs. The developments include faster construction of
preconditioner matrices, a domain decomposition of preconditioning matrices for
solver libraries that can handle distributed matrices, interfaces for
additional solver libraries, an option to use matrix compression methods, and
the implementation of a complex solver interface for the preconditioner. The
most significant development presented consists in a generalization of the
physics based preconditioner to "mode groups", which allows to account for the
dominant interactions between toroidal Fourier modes in highly non-linear
simulations. At the cost of a moderate increase of memory consumption, the
technique can strongly enhance convergence in suitable cases allowing to use
significantly larger time steps. For all developments, benchmarks based on
typical simulation cases demonstrate the resulting improvements
Understanding the effect resonant magnetic perturbations have on ELMs
All current estimations of the energy released by type I ELMs indicate that,
in order to ensure an adequate lifetime of the divertor targets on ITER, a
mechanism is required to decrease the amount of energy released by an ELM, or
to eliminate ELMs altogether. One such amelioration mechanism relies on
perturbing the magnetic field in the edge plasma region, either leading to more
frequent, smaller ELMs (ELM mitigation) or ELM suppression. This technique of
Resonant Magnetic Perturbations (RMPs) has been employed to suppress type I
ELMs at high collisionality/density on DIII-D, ASDEX Upgrade, KSTAR and JET and
at low collisionality on DIII-D. At ITER-like collisionality the RMPs enhance
the transport of particles or energy and keep the edge pressure gradient below
the 2D linear ideal MHD critical value that would trigger an ELM, whereas at
high collisionality/density the type I ELMs are replaced by small type II ELMs.
Although ELM suppression only occurs within limitied operational ranges, ELM
mitigation is much more easily achieved. The exact parameters that determine
the onset of ELM suppression are unknown but in all cases the magnetic
perturbations produce 3D distortions to the plasma and enhanced particle
transport. The incorporation of these 3D effects in codes will be essential in
order to make quantitative predictions for future devices.Comment: 32 pages, 9 figure
Non-linear Simulations of MHD Instabilities in Tokamaks Including Eddy Current Effects and Perspectives for the Extension to Halo Currents
The dynamics of large scale plasma instabilities can strongly be influenced
by the mutual interaction with currents flowing in conducting vessel
structures. Especially eddy currents caused by time-varying magnetic
perturbations and halo currents flowing directly from the plasma into the walls
are important. The relevance of a resistive wall model is directly evident for
Resistive Wall Modes (RWMs) or Vertical Displacement Events (VDEs). However,
also the linear and non-linear properties of most other large-scale
instabilities may be influenced significantly by the interaction with currents
in conducting structures near the plasma. The understanding of halo currents
arising during disruptions and VDEs, which are a serious concern for ITER as
they may lead to strong asymmetric forces on vessel structures, could also
benefit strongly from these non-linear modeling capabilities. Modeling the
plasma dynamics and its interaction with wall currents requires solving the
magneto-hydrodynamic (MHD) equations in realistic toroidal X-point geometry
consistently coupled with a model for the vacuum region and the resistive
conducting structures. With this in mind, the non-linear finite element MHD
code JOREK has been coupled with the resistive wall code STARWALL, which allows
to include the effects of eddy currents in 3D conducting structures in
non-linear MHD simulations. This article summarizes the capabilities of the
coupled JOREK-STARWALL system and presents benchmark results as well as first
applications to non-linear simulations of RWMs, VDEs, disruptions triggered by
massive gas injection, and Quiescent H-Mode. As an outlook, the perspectives
for extending the model to halo currents are described.Comment: Proceeding paper for Theory of Fusion Plasmas (Joint Varenna-Lausanne
International Workshop), Varenna, Italy (September 1-5, 2014); accepted for
publication in: to Journal of Physics: Conference Serie
Recent progress in the quantitative validation of JOREK simulations of ELMs in JET
Future devices like JT-60SA, ITER and DEMO require quantitative predictions of pedestal
density and temperature levels, as well as inter-ELM and ELM divertor heat fluxes, in order
to improve global confinement capabilities while preventing divertor erosion/melting in the
planning of future experiments. Such predictions can be obtained from dedicated pedestal
models like EPED, and from non-linear MHD codes like JOREK, for which systematic
validation against current experiments is necessary. In this paper, we show progress in the
quantitative validation of the JOREK code using JET simulations. Results analyse the impact
of diamagnetic terms on the dynamics and size of the ELMs, and evidence is provided that
the onset of type-I ELMs is not governed by linear MHD stability alone, but that a nonlinear
threshold could be responsible for large MHD events at the plasma edgeEURATOM 633053RCUK Energy Programme EP/I501045Plasma HEC Consortium EPSRC EP/L000237/
A scarcity mindset alters neural processing underlying consumer decision making
Not having enough of what one needs has long been shown to have detrimental consequences for decision making. Recent work suggests that the experience of insufficient resources can create a "scarcity" mindset; increasing attention toward the scarce resource itself, but at the cost of attention for unrelated aspects. To investigate the effects of a scarcity mindset on consumer choice behavior, as well as its underlying neural mechanisms, we used an experimental manipulation to induce both a scarcity and an abundance mindset within participants and examined the effects of both mindsets on participants' willingness to pay for familiar food items while being scanned using fMRI. Results demonstrated that a scarcity mindset affects neural mechanisms related to consumer decision making. When in a scarcity mindset compared with an abundance mindset, participants had increased activity in the orbitofrontal cortex, a region often implicated in valuation processes. Moreover, again compared with abundance, a scarcity mindset decreased activity in dorsolateral prefrontal cortex, an area well known for its role in goal-directed choice. This effect was predominant in the group of participants who experienced scarcity following abundance, suggesting that the effects of scarcity are largest when they are compared with previous situations when resources were plentiful. More broadly, these data suggest a potential neural locus for a scarcity mindset and demonstrate how these changes in brain activity might underlie goal-directed decision making
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