1,996 research outputs found

    An insight into some innovative cycles for aircraft propulsion

    Get PDF
    Emissions are important drivers in the design and use of aero-engines. This paper presents a part of the work carried out in the VITAL (EnVIronmenTALly aero-engine) project; it consists of a parameter study on the application of three innovative thermodynamic cycles to aircraft propulsion, looking for benefits on fuel consumption, carbon dioxide, nitrogen oxides, and noise. These cycles are intercooler-regenerative, the wave rotor topping, and the constant volume combustor cycles. The work, starting from a next-generation ultra-high bypass ratio turbofan, the baseline, and considering two possible design conditions, presents the influence of the application of these new cycles or design changes to the baseline on emissions and on the required technological level, represented by the turbine entry temperature (TET). VITAL is a project supported by the Sixth Framework Programme of the European Communities. The results showthat some significant benefits on emissions can be achieved although they are linked to significant technology improvements and in-depth studies of the new components involved in cycle implementation

    Trait self-control and beliefs about the utility of emotions for initiatory and inhibitory self-control

    Get PDF
    How do people with high trait self-control achieve their success? This research aimed to provide evidence for beliefs about emotion utility as a potential mechanism. Specifically, because beliefs about the utility of emotions predict emotion regulation and successful performance, we investigate the hypothesis that trait self-control influences beliefs about the utility of emotions for self-control. Two preregistered studies examined whether beliefs about the utility of emotions in everyday self-control situations varied depending on the person (trait self-control) and the situation (initiatory or inhibitory self-control). Our key finding was that people considered positive emotions more useful for self-control than negative emotions. This effect was also moderated by situational and individual factors, such that positive emotions were considered especially useful by participants with high trait self-control and in situations requiring initiatory self-control (with the opposite effect for negative emotions). This research suggests a potential role for instrumental emotion regulation in self-control success

    The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abundance

    Full text link
    The current uncertainty in Newton's constant, G_N, is of the order of 0.15%. For values of the baryon to photon ratio consistent with both cosmic microwave background observations and the primordial deuterium abundance, this uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the effect from the current uncertainty in the neutron lifetime, which is often treated as the dominant uncertainty in calculations of Y_P. Recent measurements of G_N seem to be converging within a smaller range; a reduction in the estimated error on G_N by a factor of 10 would essentially eliminate it as a source of uncertainty in the calculation of the primordial 4He abundance.Comment: 3 pages, no figures, fixed typos, to appear in Phys. Rev.

    The RR Lyrae Star Period - K-band Luminosity Relation of the Globular Cluster M3

    Full text link
    That the RR Lyrae star period -- K-band luminosity relation is a promising tool as a distance indicator in the Milky Way and Local Group of Galaxies is apparent on observational and theoretical grounds in the literature. Less clear is the sensitivity of the relation, and consequently the physics of horizontal branch stars, to differences in stellar environment. In this paper, the first measurement of the (fundamental) period -- K-band luminosity relation for the central region of a globular cluster is presented. It is based on a sample of seven RR Lyrae stars imaged with adaptive optics. In addition, the relation for the outer region has been reanalyzed, and is found to be in good agreement with both the previous estimate by Longmore et al. (1990), and with the inner region relation, especially when irregular and double-mode RR Lyrae stars are excluded. Importantly, there is no difference between the slope of the inner and outer region relation within measurement uncertainties, suggesting no difference in evolutionary state (luminosity). Taking the M3 distance modulus as 15.0 +/- 0.07mag, the period -- absolute K-band magnitude relation derived by linear least squares fitting is: M_K = -0.96 (+/- 0.10) - 2.42 (+/- 0.16)Log Po for the inner region. Excluding irregular variable stars, the outer region relation is: M_K = -1.07 (+/- 0.10) - 2.38 (+/- 0.15)Log Po. This good agreement provides further strong support for the near-IR period-luminosity relation as a distance indicator.Comment: Accepted for publication in Astronomy & Astrophysics, 10 pages, 5 figure

    Mapping Oil and Gas Development Potential in the US Intermountain West and Estimating Impacts to Species

    Get PDF
    Many studies have quantified the indirect effect of hydrocarbon-based economies on climate change and biodiversity, concluding that a significant proportion of species will be threatened with extinction. However, few studies have measured the direct effect of new energy production infrastructure on species persistence. in the western US and translate the build-out scenarios into estimated impacts on sage-grouse. We project that future oil and gas development will cause a 7–19 percent decline from 2007 sage-grouse lek population counts and impact 3.7 million ha of sagebrush shrublands and 1.1 million ha of grasslands in the study area.Maps of where oil and gas development is anticipated in the US Intermountain West can be used by decision-makers intent on minimizing impacts to sage-grouse. This analysis also provides a general framework for using predictive models and build-out scenarios to anticipate impacts to species. These predictive models and build-out scenarios allow tradeoffs to be considered between species conservation and energy development prior to implementation

    Near-Infrared Observations of RR Lyrae variables in Galactic Globular Clusters: I. The case of M92

    Get PDF
    We present near-infrared J,H, and K-band time series observations of the Galactic Globular Cluster (GGC) M92. On the basis of these data, we derived well-sampled light curves for eleven out of the seventeen cluster RR Lyrae variables, and in turn, accurate mean near-infrared (NIR) magnitudes. The comparison between predicted and empirical slopes of NIR Period-Luminosity (PL) relations indicates a very good agreement. Cluster distance determinations based on independent theoretical NIR PLPL relations present uncertainties smaller than 5% and agree quite well with recent distance estimates based on different distance indicators. We also obtained accurate and deep NIR color-magnitude diagrams (CMDs) ranging from the tip of the Red Giant Branch (RGB) down to the Main Sequence Turn-Off. We detected the RGB bump and the NIR luminosities of this evolutionary feature are, within theoretical and empirical uncertainties, in good agreement with each other.Comment: 30 pages, 8 figures, accepted for pubblication on A

    Phase structures of strong coupling lattice QCD with finite baryon and isospin density

    Full text link
    Quantum chromodynamics (QCD) at finite temperature (T), baryon chemical potential (\muB) and isospin chemical potential (\muI) is studied in the strong coupling limit on a lattice with staggered fermions. With the use of large dimensional expansion and the mean field approximation, we derive an effective action written in terms of the chiral condensate and pion condensate as a function of T, \muB and \muI. The phase structure in the space of T and \muB is elucidated, and simple analytical formulas for the critical line of the chiral phase transition and the tricritical point are derived. The effects of a finite quark mass (m) and finite \muI on the phase diagram are discussed. We also investigate the phase structure in the space of T, \muI and m, and clarify the correspondence between color SU(3) QCD with finite isospin density and color SU(2) QCD with finite baryon density. Comparisons of our results with those from recent Monte Carlo lattice simulations on finite density QCD are given.Comment: 18 pages, 6 figures, revtex4; some discussions are clarified, version to appear in Phys. Rev.

    Childbirth experience questionnaire: validating its use in the United Kingdom

    Get PDF
    BACKGROUND: The Childbirth Experience Questionnaire (CEQ) was developed in Sweden in 2010 and validated in 920 primiparous women. It has not been validated in the United Kingdom (UK). Measuring the impact of an intervention on a woman's childbirth experience is arguably as important as measuring its impact on outcomes such as caesarean delivery and perinatal morbidity or mortality and yet surprisingly it is rarely done. The lack of a robust validated tool for evaluating labour experience in the UK is a topical issue in the UK at present. Indeed NICE say 'A standardised method to measure and quantify women's psychological and emotional wellbeing and their birth experiences is urgently required to support any study investigating the effectiveness of interventions, techniques or strategies during birth.' METHODS: The Childbirth Experience Questionnaire and part of the Care Quality Commission Maternity Survey (2010) was sent to 350 women at one month postnatal. The CEQ was sent again two weeks later. The CEQ was tested for face validity among 25 postnatal mothers. Demographic data and delivery data was used to establish construct validity of the CEQ using the method of known-groups validation. The results of the scored CEQ sent out twice were used to measure test-retest reliability of the CEQ by calculating the quadratic weighted index of agreement between the two scores. Criterion validity was measured by calculating the Pearson correlation coefficient for the CEQ and Maternity Survey scores. RESULTS: Face validity of the CEQ in a UK population was demonstrated with all respondents stating it was easy to understand and complete. A statistically significantly higher CEQ score for subgroups of women known to report a better birth outcome demonstrated construct validity of the CEQ. A weighted kappa of 0.68 demonstrated test-retest reliability of the CEQ. A Pearson correlation co-efficient of 0.73 demonstrated a strong correlation between the results of the CEQ and the results of the 'gold standard' assessment of childbirth experience in the UK: the Maternity Survey and hence criterion validity of the CEQ. CONCLUSIONS: The Childbirth Experience Questionnaire is a valid and reliable measure of childbirth experience in the UK population

    Are youth mentoring programs good value-for-money? An evaluation of the Big Brothers Big Sisters Melbourne Program

    Get PDF
    Background : The Big Brothers Big Sisters (BBBS) program matches vulnerable young people with a trained, supervised adult volunteer as mentor. The young people are typically seriously disadvantaged, with multiple psychosocial problems.Methods : Threshold analysis was undertaken to determine whether investment in the program was a worthwhile use of limited public funds. The potential cost savings were based on US estimates of life-time costs associated with high-risk youth who drop out-of-school and become adult criminals. The intervention was modelled for children aged 10&ndash;14 years residing in Melbourne in 2004.Results : If the program serviced 2,208 of the most vulnerable young people, it would cost AUD 39.5 M. Assuming 50% were high-risk, the associated costs of their adult criminality would be AUD 3.3 billion. To break even, the program would need to avert high-risk behaviours in only 1.3% (14/1,104) of participants.Conclusion : This indicative evaluation suggests that the BBBS program represents excellent \u27value for money\u27.<br /
    • …
    corecore