43 research outputs found

    Combined CI+MBPT calculations of energy levels and transition amplitudes in Be, Mg, Ca, and Sr

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    Configuration interaction (CI) calculations in atoms with two valence electrons, carried out in the V(N-2) Hartree-Fock potential of the core, are corrected for core-valence interactions using many-body perturbation theory (MBPT). Two variants of the mixed CI+MBPT theory are described and applied to obtain energy levels and transition amplitudes for Be, Mg, Ca, and Sr

    Machine learning for estimation of building energy consumption and performance:a review

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    Ever growing population and progressive municipal business demands for constructing new buildings are known as the foremost contributor to greenhouse gasses. Therefore, improvement of energy eciency of the building sector has become an essential target to reduce the amount of gas emission as well as fossil fuel consumption. One most eective approach to reducing CO2 emission and energy consumption with regards to new buildings is to consider energy eciency at a very early design stage. On the other hand, ecient energy management and smart refurbishments can enhance energy performance of the existing stock. All these solutions entail accurate energy prediction for optimal decision making. In recent years, articial intelligence (AI) in general and machine learning (ML) techniques in specic terms have been proposed for forecasting of building energy consumption and performance. This paperprovides a substantial review on the four main ML approaches including articial neural network, support vector machine, Gaussian-based regressions and clustering, which have commonly been applied in forecasting and improving building energy performance

    Revegetation dynamics after 15 years of rewetting in two extracted peatlands in Sweden

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    The restoration of extracted peatlands poses challenges with regard to their recolonisation by vegetation. The most significant problems are unstable water levels, destroyed propagule bank, and temperature fluctuations on bare peat surfaces. Rewetting is considered necessary for the re-establishment of peat-forming vegetation. Revegetation was investigated in a long-term field study at two rewetted extracted peatland sites in south-central Sweden, namely Västkärr (originally a lagg fen) and Porla (originally a bog). Both sites were expanses of bare peat before rewetting.Rewetting procedures were applied in 1999 and strongly promoted plant colonisation. At Västkärr, colonisation started in the first year after rewetting, mostly by species that were not found during repeat vegetation surveys 15 years later. By 2014, Västkärr was a shallow lake surrounded by mesotrophic and eutrophic vegetation with species such as Carex rostrata, Lemna minor, Typha latifolia, Phalaris arundinacea and Phragmites australis. Revegetation of the Porla site was slower and started with Eriophorum vaginatum and Polytrichum spp. Sphagnum mosses appeared after six years and had established quite well after 13 years. A residual Sphagnum peat layer, inflowing surface water and groundwater provided spatially variable nutrient conditions. Sphagnum species and E. vaginatum established in nutrient-poor areas, while C. rostrata, P. australis and Eriophorum angustifolium colonised more nutrient-rich locations
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