2,962 research outputs found
Characterizing Strategic Cascades on Networks
Transmission of disease, spread of information and rumors, adoption of new
products, and many other network phenomena can be fruitfully modeled as
cascading processes, where actions chosen by nodes influence the subsequent
behavior of neighbors in the network graph. Current literature on cascades
tends to assume nodes choose myopically based on the state of choices already
taken by other nodes. We examine the possibility of strategic choice, where
agents representing nodes anticipate the choices of others who have not yet
decided, and take into account their own influence on such choices. Our study
employs the framework of Chierichetti et al. [2012], who (under assumption of
myopic node behavior) investigate the scheduling of node decisions to promote
cascades of product adoptions preferred by the scheduler. We show that when
nodes behave strategically, outcomes can be extremely different. We exhibit
cases where in the strategic setting 100% of agents adopt, but in the myopic
setting only an arbitrarily small epsilon % do. Conversely, we present cases
where in the strategic setting 0% of agents adopt, but in the myopic setting
(100-epsilon)% do, for any constant epsilon > 0. Additionally, we prove some
properties of cascade processes with strategic agents, both in general and for
particular classes of graphs.Comment: To appear in EC 201
Parameterisation effect on the behaviour of a head-dependent hydro chain using a nonlinear model
This paper is on the problem of short-term hydro scheduling (STHS), particularly concerning a head-dependent hydro chain. We use a method based on nonlinear programming (NLP), namely quadratic programming, to consider hydroelectric power generation a function of water discharge and of the head. The method has been applied successfully to solve a test case based on a realistic cascaded hydro system with a negligible computational time requirement and is also applied to show that the role played by reservoirs in the hydro chain do not depend only on their relative position. As a new contribution to earlier studies, which presented reservoir operation rules mainly for medium and long-term planning procedures, we show that the physical data defining hydro chain parameters used in the nonlinear model have an effect on the STHS, implying different optimal storage trajectories for the reservoirs accordingly not only with their position in the hydro chain but also with the new parameterisation defining the data for the hydro system. Moreover, considering head dependency in the hydroelectric power generation, usually neglected for hydro plants with a large storage capacity, provides a better short-term management of the conversion of the potential energy available in the reservoirs into electric energy, which represents a major advantage for the hydroelectric utilities in a competitive electricity market
Information Cascades on Arbitrary Topologies
In this paper, we study information cascades on graphs. In this setting, each
node in the graph represents a person. One after another, each person has to
take a decision based on a private signal as well as the decisions made by
earlier neighboring nodes. Such information cascades commonly occur in practice
and have been studied in complete graphs where everyone can overhear the
decisions of every other player. It is known that information cascades can be
fragile and based on very little information, and that they have a high
likelihood of being wrong.
Generalizing the problem to arbitrary graphs reveals interesting insights. In
particular, we show that in a random graph , for the right value of
, the number of nodes making a wrong decision is logarithmic in . That
is, in the limit for large , the fraction of players that make a wrong
decision tends to zero. This is intriguing because it contrasts to the two
natural corner cases: empty graph (everyone decides independently based on his
private signal) and complete graph (all decisions are heard by all nodes). In
both of these cases a constant fraction of nodes make a wrong decision in
expectation. Thus, our result shows that while both too little and too much
information sharing causes nodes to take wrong decisions, for exactly the right
amount of information sharing, asymptotically everyone can be right. We further
show that this result in random graphs is asymptotically optimal for any
topology, even if nodes follow a globally optimal algorithmic strategy. Based
on the analysis of random graphs, we explore how topology impacts global
performance and construct an optimal deterministic topology among layer graphs
Nerve growth factor, brain-derived neurotrophic factor, and the chronobiology of mood: a new insight into the "neurotrophic hypothesis"
The light information pathways and their relationship with the body rhythms have generated a new insight into the neurobiology and the neurobehavioral sciences, as well as into the clinical approaches to human diseases associated with disruption of circadian cycles. Light-based strategies and/or drugs acting on the circadian rhythms have widely been used in psychiatric patients characterized by mood-related disorders, but the timing and dosage use of the various treatments, although based on international guidelines, are mainly dependent on the psychiatric experiences. Further, many efforts have been made to identify biomarkers able to disclose the circadian-related aspect of diseases, and therefore serve as diagnostic, prognostic, and therapeutic tools in clinic to assess the different mood-related symptoms, including pain, fatigue, sleep disturbance, loss of interest or pleasure, appetite, psychomotor changes, and cognitive impairments. Among the endogenous factors suggested to be involved in mood regulation, the neurotrophins, nerve growth factor, and brain-derived neurotrophic factor show anatomical and functional link with the circadian system and mediate some of light-induced effects in brain. In addition, in humans, both nerve growth factor and brain-derived neurotrophic factor have showed a daily rhythm, which correlate with the morningness–eveningness dimensions, and are influenced by light, suggesting their potential role as biomarkers for chronotypes and/or chronotherapy. The evidences of the relationship between the diverse mood-related disorders, with a specific focus on depression, and neurotrophins are reviewed and discussed herein in terms of their circadian significance, and potential translation into clinical practice
Circadian regulation of glucose, lipid, and energy metabolism in humans.
The circadian system orchestrates metabolism in daily 24-hour cycles. Such rhythms organize metabolism by temporally separating opposing metabolic processes and by anticipating recurring feeding-fasting cycles to increase metabolic efficiency. Although animal studies demonstrate that the circadian system plays a pervasive role in regulating metabolism, it is unclear how, and to what degree, circadian research in rodents translates into humans. Here, we review evidence that the circadian system regulates glucose, lipid, and energy metabolism in humans. Using a range of experimental protocols, studies in humans report circadian rhythms in glucose, insulin, glucose tolerance, lipid levels, energy expenditure, and appetite. Several of these rhythms peak in the biological morning or around noon, implicating earlier in the daytime is optimal for food intake. Importantly, disruptions in these rhythms impair metabolism and influence the pathogenesis of metabolic diseases. We therefore also review evidence that circadian misalignment induced by mistimed light exposure, sleep, or food intake adversely affects metabolic health in humans. These interconnections among the circadian system, metabolism, and behavior underscore the importance of chronobiology for preventing and treating type 2 diabetes, obesity, and hyperlipidemia
Research Methods for Non-Representational Approaches of Organizational Complexity. The Dialogical and Mediated Inquiry
This paper explores the methodological implications of non-representational approaches of organizational complexity. Representational theories focus on the syntactic complexity of systems, whereas organizing processes are predominantly characterized by semantic and pragmatic forms of complexity. After underlining the contribution of non-representational approaches to the study of organizations, the paper warns against the risk of confining the critique of representational frameworks to paradoxical dichotomies like intuition versus reflexive thought or theorizing versus experimenting. To sort out this difficulty, it is suggested to use a triadic theory of interpretation, and more particularly the concepts of semiotic mediation, inquiry and dialogism. Semiotic mediation dynamically links situated experience and generic classes of meanings. Inquiry articulates logical thinking, narrative thinking and experimenting. Dialogism conceptualizes the production of meaning through the situated interactions of actors. A methodological approach based on those concepts, “the dialogical and mediated inquiry” (DMI), is proposed and experimented in a case study about work safety in the construction industry. This interpretive view requires complicating the inquiring process rather than the mirroring models of reality. In DMI, the inquiring process is complicated by establishing pluralist communities of inquiry in which different perspectives challenge each other. Finally the paper discusses the specific contribution of this approach compared with other qualitative methods and its present limits.Activity; Dialogism; Inquiry; Interpretation; Pragmatism; Research Methods; Semiotic Mediation; Work Safety
"She Said WHAT'' "He Did THAT'' Believing False Rumors
Why do false rumors spread? Why do otherwise sensible people believe them? Why are they sometimes impervious to correction? There are several answers with significant implications for freedom of speech and the marketplace of ideas, especially in the age of the Internet; they demonstrate that the exchange of information may not produce convergence on truth and that damaging false reports will often be widely credited. In some circumstances, a "chilling effect" on false rumors can be desirable; the goal should be to produce optimal chill, rather than no chill at all.
An evaluation of the total quality management implementation strategy for the advanced solid rocket motor project at NASA's Marshall Space Flight Center
An evaluation of the NASA's Marshall Space Flight Center (MSFC) strategy to implement Total Quality Management (TQM) in the Advanced Solid Rocket Motor (ASRM) Project is presented. The evaluation of the implementation strategy reflected the Civil Service personnel perspective at the project level. The external and internal environments at MSFC were analyzed for their effects on the ASRM TQM strategy. Organizational forms, cultures, management systems, problem solving techniques, and training were assessed for their influence on the implementation strategy. The influence of ASRM's effort was assessed relative to its impact on mature projects as well as future projects at MSFC
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