497 research outputs found

    Short-term power generation scheduling rules for cascade hydropower stations based on hybrid algorithm

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    AbstractPower generation dispatching is a large complex system problem with multi-dimensional and nonlinear characteristics. A mathematical model was established based on the principle of reservoir operation. A large quantity of optimal scheduling processes were obtained by calculating the daily runoff process within three typical years, and a large number of simulated daily runoff processes were obtained using the progressive optimality algorithm (POA) in combination with the genetic algorithm (GA). After analyzing the optimal scheduling processes, the corresponding scheduling rules were determined, and the practical formulas were obtained. These rules can make full use of the rolling runoff forecast and carry out the rolling scheduling. Compared with the optimized results, the maximum relative difference of the annual power generation obtained by the scheduling rules is no more than 1%. The effectiveness and practical applicability of the scheduling rules are demonstrated by a case study. This study provides a new perspective for formulating the rules of power generation dispatching

    Bulk locality from the celestial amplitude

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    In this paper, we study the implications of bulk locality on the celestial amplitude. In the context of the four-point amplitude, the fact that the bulk S-matrix factorizes locally in poles of Mandelstam variables is reflected in the imaginary part of the celestial amplitude. In particular, on the real axis in the complex plane of the boost weight, the imaginary part of the celestial amplitude can be given as a positive expansion on the Poincar\'e partial waves, which are nothing but the projection of flat-space spinning polynomials onto the celestial sphere. Furthermore, we derive the celestial dispersion relation, which relates the imaginary part to the residue of the celestial amplitude for negative even integer boost weight. The latter is precisely the projection of low energy EFT coefficients onto the celestial sphere. We demonstrate these properties explicitly on the open and closed string celestial amplitudes. Finally, we give an explicit expansion of the Poincar\'e partial waves in terms of 2D conformal partial waves.Comment: 43 pages, 10 figures. v2: typos corrected, minor clarifications added, SciPost published versio

    Planets Across Space and Time (PAST) IV: The Occurrence and Architecture of Kepler Planetary Systems as a Function of Kinematic Age Revealed by the LAMOST-Gaia-Kepler Sample

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    One of the fundamental questions in astronomy is how planetary systems form and evolve. Measuring the planetary occurrence and architecture as a function of time directly addresses this question. In the fourth paper of the Planets Across Space and Time (PAST) series, we investigate the occurrence and architecture of Kepler planetary systems as a function of kinematic age by using the LAMOST-Gaia-Kepler sample. To isolate the age effect, other stellar properties (e.g., metallicity) have been controlled. We find the following results. (1) The fraction of stars with Kepler-like planets (FKepF_{\text{Kep}}) is about 50% for all stars; no significant trend is found between FKepF_{\text{Kep}} and age. (2) The average planet multiplicity (Nˉp\bar{N}_p) exhibits a decreasing trend (~2σ\sigma significance) with age. It decreases from Nˉp\bar{N}_p~3 for stars younger than 1 Gyr to Nˉp\bar{N}_p~1.8 for stars about 8 Gyr. (3) The number of planets per star (η=FKep×Nˉp\eta=F_{\text{Kep}}\times\bar{N}_p) also shows a decreasing trend (~2-3σ\sigma significance). It decreases from η\eta~1.6-1.7 for young stars to η\eta~1.0 for old stars. (4) The mutual orbital inclination of the planets (σi,k\sigma_{i,k}) increases from 1.20.5+1.41.2^{+1.4}_{-0.5} to 3.52.3+8.13.5^{+8.1}_{-2.3} as stars aging from 0.5 to 8 Gyr with a best fit of logσi,k=0.2+0.4×logAge1Gyr\log{\sigma_{i,k}}=0.2+0.4\times\log{\frac{\text{Age}}{\text{1Gyr}}}. Interestingly, the Solar System also fits such a trend. The nearly independence of FKepF_{\text{Kep}}~50% on age implies that planet formation is robust and stable across the Galaxy history. The age dependence of Nˉp\bar{N}_p and σi,k\sigma_{i,k} demonstrates planetary architecture is evolving, and planetary systems generally become dynamically hotter with fewer planets as they age.Comment: 27 pages, 20 figures, 4tables, accepted for publication in A

    Planets Across Space and Time (PAST). III. Morphology of the Planetary Radius Valley as a Function of Stellar Age and Metallicity in the Galactic Context Revealed by the LAMOST-Gaia-Kepler Sample

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    The radius valley, a dip in the radius distribution of exoplanets at ~1.9 Earth radii separates compact rocky Super-Earths and Sub-Neptunes with lower density. Various hypotheses have been put forward to explain the radius valley. Characterizing the radius valley morphology and its correlation to stellar properties will provide crucial observation constraints on its origin mechanism and deepen the understanding of planet formation and evolution. In this paper, the third part of the Planets Across the Space and Time (PAST) series, using the LAMOST-Gaia-Kepler catalog, we perform a systematical investigation into how the radius valley morphology varies in the Galactic context, i.e., thin/thick galactic disks, stellar age and metallicity abundance ([Fe/H] and [alpha/Fe]). We find that (1) The valley becomes more prominent with the increase of both age and [Fe/H]. (2) The number ratio of super-Earths to sub-Neptunes monotonically increases with age but decreases with [Fe/H] and [alpha/Fe]. (3) The average radius of planets above the valley (2.1-6 Earth radii) decreases with age but increases with [Fe/H]. (4) In contrast, the average radius of planets below the valley (R < 1.7 Earth radii) is broadly independent on age and metallicity. Our results demonstrate that the valley morphology as well as the whole planetary radius distribution evolves on a long timescale of giga-years, and metallicities (not only Fe but also other metal elements, e.g., Mg, Si, Ca, Ti) play important roles in planet formation and in the long term planetary evolution.Comment: Accepted for pubilication in AJ, 20 Pages, 10 figures, 2 Tables (Appendix: 13 Figures

    Moral perfectionism and moral values, virtues, and judgments: A preliminary investigation

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    Moral perfectionism has a long tradition in philosophical inquiry, but so far has been ignored in psychological research. This article presents a first psychological investigation of moral perfectionism exploring its relationships with moral values, virtues, and judgments. In three studies, 539 university students responded to items of the Frost Multidimensional Perfectionism Scale (Frost, Marten, Lahart, & Rosenblate, 1990) adapted to measure personal moral standards (PMS) and concern over moral mistakes (CMM) and completed measures of moral values, virtues, and forgiveness, gratitude, and wrong behavior judgments. When partial correlations were computed controlling for the overlap between PMS and CMM, PMS showed positive correlations with moral values, virtues, reciprocal helping, forgiveness, and condemnation of wrong behaviors. In contrast, CMM showed a positive correlation only with indebtedness and a negative correlation with self-reliance. The present findings, while preliminary, suggest that moral perfectionism is a personality characteristic that may help explain individual differences in moral values, virtues, and judgments
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