Towards autonomous distributed coordination of fast power flow controllers

The liberalization of the power market, an overall increase in power demand and the integration of high capacity unpredictable renewable resources (e.g. wind power) pose a challenge to transmission network operators that have to guarantee a stable and efficient operating of the grid. A way to improve the stability and efficiency of the existing network – aside from expensive reconstruction – is the integration of fast power flow controllers in order to dynamically redirect power flows away from critically loaded resources that may be threatened by an overload. In this paper we outline our current work in progress on developing a multi-agent model that allows for an autonomous distributed coordination of fast power flow controllers without the need for global information

Electromagnetic Polarizabilities of Nucleons bound in 40^{40}Ca, 16^{16}O and 4^4He

Differential cross sections for elastic scattering of photons have been measured for $^{40}$Ca at energies of 58 and 74 MeV and for $^{16}$O and $^4$He at 61 MeV, in the angular range from 45$^o$ to 150$^o$. Evidence is obtained that there are no significant in-medium modifications of the electromagnetic polarizabilities except for those originating from meson exchange currents.Comment: 20 pages including 5 Figure

Zircon M127 - A Homogeneous Reference Material for SIMS U-Pb Geochronology Combined with Hafnium, Oxygen and, Potentially, Lithium Isotope Analysis

In this article, we document a detailed analytical characterisation of zircon M127, a homogeneous 12.7 carat gemstone from Ratnapura, Sri Lanka. Zircon M127 has TIMS-determined mean U-Pb radiogenic isotopic ratios of 0.084743 ± 0.000027 for 206Pb/238U and 0.67676 ± 0.00023 for 207Pb/235U (weighted means, 2s uncertainties). Its 206Pb/238U age of 524.36 ± 0.16 Ma (95% confidence uncertainty) is concordant within the uncertainties of decay constants. The d18O value (determined by laser fluorination) is 8.26 ± 0.06‰ VSMOW (2s), and the mean 176Hf/177Hf ratio (determined by solution ICP-MS) is 0.282396 ± 0.000004 (2s). The SIMS-determined d7Li value is -0.6 ± 0.9‰ (2s), with a mean mass fraction of 1.0 ± 0.1 µg g-1 Li (2s). Zircon M127 contains ~ 923 µg g-1 U. The moderate degree of radiation damage corresponds well with the time-integrated self-irradiation dose of 1.82 × 1018 alpha events per gram. This observation, and the (U-Th)/He age of 426 ± 7 Ma (2s), which is typical of unheated Sri Lankan zircon, enable us to exclude any thermal treatment. Zircon M127 is proposed as a reference material for the determination of zircon U-Pb ages by means of SIMS in combination with hafnium and stable isotope (oxygen and potentially also lithium) determination

Compton Scattering from the Deuteron and Extracted Neutron Polarizabilities

Differential cross sections for Compton scattering from the deuteron were measured at MAX-lab for incident photon energies of 55 MeV and 66 MeV at nominal laboratory angles of $45^\circ$, $125^\circ$, and $135^\circ$. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and difference of the isospin-averaged nucleon polarizabilities, $\alpha_N + \beta_N = 17.4 \pm 3.7$ and $\alpha_N - \beta_N = 6.4 \pm 2.4$ (in units of $10^{-4}$ fm$^3$), have been determined. By combining the latter with the global-averaged value for $\alpha_p - \beta_p$ and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of $\alpha_n= 8.8 \pm 2.4$(total) $\pm 3.0$(model) and $\beta_n = 6.5 \mp 2.4$(total) $\mp 3.0$(model), respectively.Comment: 4 pages, 2 figures, revtex. The text is substantially revised. The cross sections are slightly different due to improvements in the analysi

Phylogenetic Distribution of Intron Positions in Alpha-Amylase Genes of Bilateria Suggests Numerous Gains and Losses

Most eukaryotes have at least some genes interrupted by introns. While it is well accepted that introns were already present at moderate density in the last eukaryote common ancestor, the conspicuous diversity of intron density among genomes suggests a complex evolutionary history, with marked differences between phyla. The question of the rates of intron gains and loss in the course of evolution and factors influencing them remains controversial. We have investigated a single gene family, alpha-amylase, in 55 species covering a variety of animal phyla. Comparison of intron positions across phyla suggests a complex history, with a likely ancestral intronless gene undergoing frequent intron loss and gain, leading to extant intron/exon structures that are highly variable, even among species from the same phylum. Because introns are known to play no regulatory role in this gene and there is no alternative splicing, the structural differences may be interpreted more easily: intron positions, sizes, losses or gains may be more likely related to factors linked to splicing mechanisms and requirements, and to recognition of introns and exons, or to more extrinsic factors, such as life cycle and population size. We have shown that intron losses outnumbered gains in recent periods, but that “resets” of intron positions occurred at the origin of several phyla, including vertebrates. Rates of gain and loss appear to be positively correlated. No phase preference was found. We also found evidence for parallel gains and for intron sliding. Presence of introns at given positions was correlated to a strong protosplice consensus sequence AG/G, which was much weaker in the absence of intron. In contrast, recent intron insertions were not associated with a specific sequence. In animal Amy genes, population size and generation time seem to have played only minor roles in shaping gene structures

Feature selection of autoregressive Neural Network inputs for trend Time Series Forecasting

The capability of artificial Neural Networks to forecast time series with trends has been a topic of dispute. While selected research following Zhang and Qi has indicated that prior removal of trends is required for a Multilayer Perceptron (MLP), others provide evidence that Neural Networks are capable of forecasting trends without data preprocessing, either by choosing input-nodes employing an adequate autoregressive lag-structure of lagged realisations or by adding explanatory variables with trends. This paper proposes a novel variable selection methodology of autoregressive lags for trended time series with and without seasonality, and assesses its efficacy using the dataset of the International Time Series Forecasting Competition conducted at WCCI 2016. Our experiments indicate that MLPs are capable of forecasting different trend forms, but that more than a single lag-structure is required to do so, making the use of multiple input-lag variants and a robust model selection strategy necessary to achieve robust forecast accuracy

Effective impact of DER on distribution system protection

Godkänd; 2007; Bibliografisk uppgift: 2 CD-ROM; 20071207 (matbol

Future development of the carbon cycle: the role of the biota/forests within the IPCC stabilization scenarios

For the analyzed period between 1980 and 1989 a terrestrial biospheric sink of the order of 1.7 to 1.8 Gt C per year is required to close the CO2 budget between atmospheric CO2 input, observed atmospheric CO2 increase, CO2 ocean uptake and CO2 release from deforestation. The reasons for the additional terrestrial sink are still not completely clarified, however, the fertilization through additional atmospheric CO2 and deposition of nitrogen compounds are believed to be of importance in addition to factors associated with climate change, age class distribution of forests as well as land management practices. The IPCC (Intergovernmental Panel on Climate Change) has generated a series of atmospheric CO2 profiles leading to stabilization levels in the range 350 to 1000 ppmV. These profiles correspond to developments with very strong efforts, intermediate efforts, or nearly absent (at least during the next 30 to 50 years) efforts to stabilize greenhouse gases. In the present study, we examine the CO2 exchange between the land biota and the atmosphere studying in particular the long term development of a potential CO2 related fertilization effect for the profiles stabilizing atmospheric CO2 at 450 (S450), 650 (S650) and 1000 (S1000) ppmV. Two different biosphere box models, an ultra-simple two-box model (USBM) and the Bern four-box biosphere model as well as the high-resolution Frankfurt Biosphere Model (FBM) were investigated to study the long-term response (up to the year 2300) of the biota and soils. We applied a linear pulse response function substitute model of the HILDA ocean model to calculate the oceanic CO2 uptake. Similar to the ocean behaviour the uptake of carbon by the biosphere follows the sigmoidal increase function of atmospheric CO2, both with the USBM, the Bern Biosphere Model as well as with the more detailed Frankfurt Biosphere Model. Biospheric carbon uptake is highest near the inflection point of the annual CO2 emissions into the atmosphere and then falls off at times beyond. We summarize in stating that a potential CO2 fertilization effect with respect to a biospheric carbon increase drops off during the first half of next century for the profiles S450 and S650 and somewhat later for the the S1000 scenario