Power systems stabilization with feedback linearization

Input-state feedback linearization is discussed in this paper as a method for power system control. This method linearizes for a range of operating points and is more appropriate than the conventional methods since the operating point can change frequently in power systems. A single generator, infinite bus model is used to illustrate the design

Are Foraging Patterns in Humans Related to Working Memory and Inhibitory Control?

In previous studies we have shown that human foraging patterns appear to be constrained by attention. However, we also noted clear individual differences in foraging ability, where some individuals can apparently keep more than one target template in mind during foraging. Here, we examine whether such individual differences relate to more general working memory capacity and/or the ability to inhibit a primed, or prepotent response. We had three main goals. First, to replicate general patterns of attention-constrained foraging. Second, to verify that some individuals appear immune to such constraints. Third, to investigate a possible link between individual foraging style and working memory abilities measured on a digit-span task and inhibitory control measured with a Stroop task. In sum, we replicated the finding that foraging differs greatly by whether foraging targets are defined by a single feature or a conjunction of features, but also again found that some observers show little differences in foraging between the two conditions, seemingly shifting with ease between search templates. In contrast, neither working memory nor Stroop performance were reliable predictors of these individual differences in foraging pattern. We discuss the implications of the findings for theories of visual attention.Peer Reviewe

Common attentional constraints in visual foraging

Predators are known to select food of the same type in non-random sequences or “runs” that are longer than would be expected by chance. If prey are conspicuous, predators will switch between available sources, interleaving runs of different prey types. However, when prey are cryptic, predators tend to focus on one food type at a time, effectively ignoring equally available sources. This latter finding is regarded as a key indicator that animal foraging is strongly constrained by attention. It is unknown whether human foraging is equally constrained. Here, using a novel iPad task, we demonstrate for the first time that it is. Participants were required to locate and touch 40 targets from 2 different categories embedded within a dense field of distractors. When individual target items “popped-out” search was organized into multiple runs, with frequent switching between target categories. In contrast, as soon as focused attention was required to identify individual targets, participants typically exhausted one entire category before beginning to search for the other. This commonality in animal and human foraging is compelling given the additional cognitive tools available to humans, and suggests that attention constrains search behavior in a similar way across a broad range of species.peer-reviewe

Correlation functions in a c=1 boundary conformal field theory

We obtain exact results for correlation functions of primary operators in the two-dimensional conformal field theory of a scalar field interacting with a critical periodic boundary potential. Amplitudes involving arbitrary bulk discrete primary fields are given in terms of SU(2) rotation coefficients while boundary amplitudes involving discrete boundary fields are independent of the boundary interaction. Mixed amplitudes involving both bulk and boundary discrete fields can also be obtained explicitly. Two- and three-point boundary amplitudes involving fields at generic momentum are determined, up to multiplicative constants, by the band spectrum in the open-string sector of the theory.Comment: 33 pages, 6 figure

Visual foraging with fingers and eye gaze

A popular model of the function of selective visual attention involves search where a single target is to be found among distractors. For many scenarios, a more realistic model involves search for multiple targets of various types, since natural tasks typically do not involve a single target. Here we present results from a novel multiple-target foraging paradigm. We compare finger foraging where observers cancel a set of predesignated targets by tapping them, to gaze foraging where observers cancel items by fixating them for 100 ms. During finger foraging, for most observers, there was a large difference between foraging based on a single feature, where observers switch easily between target types, and foraging based on a conjunction of features where observers tended to stick to one target type. The pattern was notably different during gaze foraging where these condition differences were smaller. Two conclusions follow: (a) The fact that a sizeable number of observers (in particular during gaze foraging) had little trouble switching between different target types raises challenges for many prominent theoretical accounts of visual attention and working memory. (b) While caveats must be noted for the comparison of gaze and finger foraging, the results suggest that selection mechanisms for gaze and pointing have different operational constraints.peer-reviewe

When is a randomised controlled trial health equity relevant? Development and validation of a conceptual framework

Background Randomised controlled trials can provide evidence relevant to assessing the equity impact of an intervention, but such information is often poorly reported. We describe a conceptual framework to identify health equity-relevant randomised trials with the aim of improving the design and reporting of such trials. Methods An interdisciplinary and international research team engaged in an iterative consensus building process to develop and refine the conceptual framework via face-to-face meetings, teleconferences and email correspondence, including findings from a validation exercise whereby two independent reviewers used the emerging framework to classify a sample of randomised trials. Results A randomised trial can usefully be classified as ‘health equity relevant’ if it assesses the effects of an intervention on the health or its determinants of either individuals or a population who experience ill health due to disadvantage defined across one or more social determinants of health. Health equity-relevant randomised trials can either exclusively focus on a single population or collect data potentially useful for assessing differential effects of the intervention across multiple populations experiencing different levels or types of social disadvantage. Trials that are not classified as ‘health equity relevant’ may nevertheless provide information that is indirectly relevant to assessing equity impact, including information about individual level variation unrelated to social disadvantage and potentially useful in secondary modelling studies. Conclusion The conceptual framework may be used to design and report randomised trials. The framework could also be used for other study designs to contribute to the evidence base for improved health equity

Cirrus Cloud Seeding has Potential to Cool Climate

Cirrus clouds, thin ice clouds in the upper troposphere, have a net warming effect on Earth s climate. Consequently, a reduction in cirrus cloud amount or optical thickness would cool the climate. Recent research indicates that by seeding cirrus clouds with particles that promote ice nucleation, their lifetimes and coverage could be reduced. We have tested this hypothesis in a global climate model with a state-of-the-art representation of cirrus clouds and find that cirrus cloud seeding has the potential to cancel the entire warming caused by human activity from pre-industrial times to present day. However, the desired effect is only obtained for seeding particle concentrations that lie within an optimal range. With lower than optimal particle concentrations, a seeding exercise would have no effect. Moreover, a higher than optimal concentration results in an over-seeding that could have the deleterious effect of prolonging cirrus lifetime and contributing to global warming

Social Support and Perceptions of COVID-19-Related Emotional Impact on Mental Health Among Early Adolescents in Appalachia

Background: Young people who experience higher levels of social support from their schools and families have been shown to be less likely to develop symptoms of negative mental health outcomes such as depression and anxiety.1–4 This raises questions concerning how young people\u27s stress and psychological changes due to the COVID-19 pandemic as well as social support during this time have affected their overall mental health. The aim of this study was to assess the association between sources of parental- and school-level social support and youth perceptions of COVID-19-related emotional impact on mental health among early adolescent girls and boys in Appalachia. Methods: Using linear regression, we analyzed the first and third wave of survey data from the larger parent study (Young Mountaineer Health Study) cohort, collected in 20 middle schools throughout West Virginia in the fall of 2020 and fall of 2021 (N = 1349, mean age: 11.5, response rate: 80.7%). Results: Approximately half of participants reported knowing someone that had been sick with COVID-19. Those experiencing higher levels of perceived COVID-19-related emotional impact reported greater levels of depression, anxiety, and anger. Both parental and school-level social support were associated with better mental health outcomes. Conclusions: Early adolescent perceptions of COVID-19-related emotional impact were associated with depression, anxiety, and anger and moderated by social support at home and in school among 11-12-year-old youth in Appalachia