9,262 research outputs found

    Local Volume Effects in the Generalized Pseudopotential Theory

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    The generalized pseudopotential theory (GPT) is a powerful method for deriving real-space transferable interatomic potentials. Using a coarse-grained electronic structure, one can explicitly calculate the pair ion-ion and multi-ion interactions in simple and transition metals. Whilst successful in determining bulk properties, in central force metals the GPT fails to describe crystal defects for which there is a significant local volume change. A previous paper [PhysRevLett.66.3036 (1991)] found that by allowing the GPT total energy to depend upon some spatially-averaged local electron density, the energetics of vacancies and surfaces could be calculated within experimental ranges. In this paper, we develop the formalism further by explicitly calculating the forces and stress tensor associated with this total energy. We call this scheme the adaptive GPT (aGPT) and it is capable of both molecular dynamics and molecular statics. We apply the aGPT to vacancy formation and divacancy binding in hcp Mg and also calculate the local electron density corrections to the bulk elastic constants and phonon dispersion for which there is refinement over the baseline GPT treatment.Comment: 11 pages, 6 figure

    Where do uncertainties reside within environmental risk assessments? Expert opinion on uncertainty distributions for pesticide risks to surface water organisms

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    A reliable characterisation of uncertainties can aid uncertainty identification during environmental risk assessments (ERAs). However, typologies can be implemented inconsistently, causing uncertainties to go unidentified. We present an approach based on nine structured elicitations, in which subject-matter experts, for pesticide risks to surface water organisms, validate and assess three dimensions of uncertainty: its level (the severity of uncertainty, ranging from determinism to ignorance); nature (whether the uncertainty is epistemic or aleatory); and location (the data source or area in which the uncertainty arises). Risk characterisation contains the highest median levels of uncertainty, associated with estimating, aggregating and evaluating the magnitude of risks. Regarding the locations in which uncertainty is manifest, data uncertainty is dominant in problem formulation, exposure assessment and effects assessment. The comprehensive description of uncertainty described will enable risk analysts to prioritise the required phases, groups of tasks, or individual tasks within a risk analysis according to the highest levels of uncertainty, the potential for uncertainty to be reduced or quantified, or the types of location-based uncertainty, thus aiding uncertainty prioritisation during environmental risk assessments. In turn, it is expected to inform investment in uncertainty reduction or targeted risk management action

    Towards a theoretical framework on sensorial place brand identity

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    Purpose: This paper proposes a new framework on sensorial place brand identity. Design/Methodology/Approach: This conceptual paper draws from sensory marketing and brand identity theories to propose an integrative model to develop sensorial place brand identity. Findings: By relying on a broad spectrum of literature the study supports the notion that sensorial place brand identity is a bottom-up approach to branding that involves several enactment stakeholders and key influences as co-creators in the process of delivering sensory place branding messages based on a strong and unique place brand identity. This leads to the presentation of a provisional framework linking sensorial place identity, experiencescapes and multisensory place brand image. Originality/Value: This novel approach to place brand identity follows a holistic approach by considering several enactment stakeholders and key influencers as co-creators in the process of branding a place through the senses

    The problem of shot selection in basketball

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    In basketball, every time the offense produces a shot opportunity the player with the ball must decide whether the shot is worth taking. In this paper, I explore the question of when a team should shoot and when they should pass up the shot by considering a simple theoretical model of the shot selection process, in which the quality of shot opportunities generated by the offense is assumed to fall randomly within a uniform distribution. I derive an answer to the question "how likely must the shot be to go in before the player should take it?", and show that this "lower cutoff" for shot quality ff depends crucially on the number nn of shot opportunities remaining (say, before the shot clock expires), with larger nn demanding that only higher-quality shots should be taken. The function f(n)f(n) is also derived in the presence of a finite turnover rate and used to predict the shooting rate of an optimal-shooting team as a function of time. This prediction is compared to observed shooting rates from the National Basketball Association (NBA), and the comparison suggests that NBA players tend to wait too long before shooting and undervalue the probability of committing a turnover.Comment: 7 pages, 2 figures; comparison to NBA data adde

    The New Zealand Strong Motion Earthquake Recorder Network

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    The network of strong-motion earthquake recorders, maintained throughout New Zealand by the Engineering Seismology Section of the Department of Scientific and Industrial Research, is described. The instruments are either deployed as ground instruments to measure potential earthquake attack on structures, or in structures, e.g. buildings, dams and industrial installations, to record structural response. Details are given of installation of instruments , maintenance, laboratory work, record retrieval and digitisation, costs and staffing for the network. Future developments mooted include an improved digitising system, the introduction of an improved version of the existing mechanical-optical instrument in 1979, and, in the long term, the introduction of an entirely new digital recorder, having an electrical output from its accelerometers, which will make possible the transmission of data by telephone or radio link

    The Price of Pay to Play in Securities Class Actions

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    This paper studies the effect of campaign contributions to lead plaintiffs — “pay to play’’ — on the level of attorneys’ fees in securities class actions. We find that state pension funds generally pay lower attorneys’ fees when they serve as lead plaintiffs in securities class actions than do individual investors serving in that capacity. This differential disappears, however, when we control for campaign contributions made to officials with influence over state pension funds. Thus, pay to play appears to increase agency costs borne by shareholders in securities class actions

    On a weighted embedding for pontograms

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    AbstractA generalized pontogram {Kn(t): 0 ⩽ t ⩽ 1} corresponding pointwise to a renewal counting process {N(x): 0 ⩽ x < ∞} via Kn(t) = n−12(N(nt)−tN(n)) is investigated in this paper. A weighted embedding for the process {Kn(t): 0 ⩽ t ⩽ 1} is studied. After proper normalization, weak convergence results for the processes {Kn(t): 0 ⩽ t ⩽ 1} are derived both in sup-norm as well as in Lp-norm
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