A concurrent precursor inflow method for Large Eddy Simulations and applications to finite length wind farms

In order to enable simulations of developing wind turbine array boundary layers with highly realistic inflow conditions a concurrent precursor method for Large Eddy Simulations is proposed. In this method we consider two domains simultaneously, i.e. in one domain a turbulent Atmospheric Boundary Layer (ABL) without wind turbines is simulated in order to generate the turbulent inflow conditions for a second domain in which the wind turbines are placed. The benefit of this approach is that a) it avoids the need for large databases in which the turbulent inflow conditions are stored and the correspondingly slow I/O operations and b) we are sure that the simulations are not negatively affected by statically swept fixed inflow fields or synthetic fields lacking the proper ABL coherent structures. Sample applications are presented, in which, in agreement with field data a strong decrease of the power output of downstream wind-turbines with respect to the first row of wind-turbines is observed for perfectly aligned inflow.Comment: 13 pages, 5 figure

A flat trend of star-formation rate with X-ray luminosity of galaxies hosting AGN in the SCUBA-2 Cosmology Legacy Survey

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.Feedback processes from active galactic nuclei (AGN) are thought to play a crucial role in regulating star formation in massive galaxies. Previous studies using Herschel have resulted in conflicting conclusions as to whether star formation is quenched, enhanced, or not affected by AGN feedback. We use new deep 850 μm observations from the SCUBA-2 Cosmology Legacy Survey (S2CLS) to investigate star formation in a sample of X-ray selected AGN, probing galaxies up to L 0.5-7keV = 10 46 erg s -1. Here, we present the results of our analysis on a sample of 1957 galaxies at 1 < z < 3, using both S2CLS and ancilliary data at seven additional wavelengths (24-500 μm) from Herschel and Spitzer. We perform a stacking analysis, binning our sample by redshift and X-ray luminosity. By fitting analytical spectral energy distributions (SEDs) to decompose contributions from cold and warm dust, we estimate star formation rates (SFRs) for each 'average' source. We find that the average AGN in our sample resides in a star-forming host galaxy, with SFRs ranging from 80 to 600 M ⊙ yr -1. Within each redshift bin, we see no trend of SFR with X-ray luminosity, instead finding a flat distribution of SFR across ∼3 orders of magnitude of AGN luminosity. By studying instantaneous X-ray luminosities and SFRs, we find no evidence that AGN activity affects star formation in host galaxies.Peer reviewedFinal Accepted Versio

What’s Wrong with Restitution

The law of restitution has developed out of the law of quasi-contract and the law of constructive trust. Inadequate attention to the logic and coherence of doctrines in the law of restitution, however, renders this new law as opaque and confused as its predecessor. This is largely due to the remedial mentality of the common law. The remedy to the remedial mentality is to concentrate future efforts in stating doctrine on defining rights, not remedies. The precedent for this type of change in method is the transformation that occurred in contract and tort over the past 100 years, inspired, in part, by civilian theories of private law. The right that generates the remedy restitution is the cause of action in unjust enrichment. It arises where there has been a non-consensual receipt and retention of value, that is, a receipt and retention of value that occurs without juristic reason. Nonconsensual means by mistake, by theft or by finding. There are a number of problems in the method of the common law tradition which stand in the way of recognizing this simple formulation: (a) The inherent expansiveness of restitution and unjust enrichment if these terms are not rigorously defined; (b) The lack of serious competition for the expansive versions of the subject, on a number of fronts; (c) The lack of a clear direction in the efforts to reform the law of quasi-contract and constructive trust; (d) The deeply embedded nature of the quasi-contract thinking; (e) Poor analysis in some areas of the law of contract and (f) Tort; and (g) The lack of an explicit agency of reform in the tradition

Enhancing the Fuel Value of Wood Pellets with the Addition of Lignin

Because of the increased cost of petroleum-based energy production, there is renewed interest in the use of wood for energy. In particular, residential heating using wood pellets has experienced a large increase during the last decade. Manufacturers of wood pellets are interested in producing high-quality, high fuel-value pellets. In this study, lignin was explored as an additive to wood to enhance pellet fuel value. Two types of lignin were examined in the production of wood pellets, Kraft black liquor and Indulin AT (IAT). Lignin was added to a softwood furnish and pellets were prepared on a commercial California Pellet Mill. The pellets were analyzed for fuel value, moisture content, and quality. Those prepared with IAT produced better quality pellets and had a higher fuel value than with Kraft black liquor. The Kraft black liquor pellets were soft and spongy and easily fell apart. A cost analysis indicates that lignin preparation will have a major impact on the feasibility of adding lignin to wood pellets to enhance fuel value

Does the basis regression overstate the predictive value of the futures price?

The spread between the current spot and futures prices (the basis) is one of the most popular predictors of movement in the future spot price. This paper demonstrates that the use of a popular regression technique to evaluate the ability of the futures price to predict movement in the spot price results in a test statistic with a non-standard distribution. A small Monte-Carlo experiment reveals that standard procedures may result in a high probability of type one error

Evidence that the AGN dominates the radio emission in z ~ 1 radio-quiet quasars

This document is the Accepted Manuscript version of the following article: Sarah V. White, Matt J. Jarvis, Eleni Kalfoutnzou, Martin J. Hardcastle, Aprajita Verma, Mose M. Cao Orjales, and Jason Stevens, 'Evidence that the AGN dominates the radio emission in z ~ 1 radio quiet quasars', Monthly Notices of the Royal Astronomical Society, first published online 3 February 2017, DOI: https://doi.org/10.1093/mnras/stx284 Key results are presented in Table 4 and Figure 7, which illustrates where the RQQs lie in relation to the far-infrared--radio correlation © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.In order to understand the role of radio-quiet quasars (RQQs) in galaxy evolution, we must determine the relative levels of accretion and star-formation activity within these objects. Previous work at low radio flux-densities has shown that accretion makes a significant contribution to the total radio emission, in contrast with other quasar studies that suggest star formation dominates. To investigate, we use 70 RQQs from the Spitzer-Herschel Active Galaxy Survey. These quasars are all at $z$ ~ 1, thereby minimising evolutionary effects, and have been selected to span a factor of ~100 in optical luminosity, so that the luminosity dependence of their properties can be studied. We have imaged the sample using the Karl G. Jansky Very Large Array (JVLA), whose high sensitivity results in 35 RQQs being detected above 2 $\sigma$. This radio dataset is combined with far-infrared luminosities derived from grey-body fitting to Herschel photometry. By exploiting the far-infrared--radio correlation observed for star-forming galaxies, and comparing two independent estimates of the star-formation rate, we show that star formation alone is not sufficient to explain the total radio emission. Considering RQQs above a 2-$\sigma$ detection level in both the radio and the far-infrared, 92 per cent are accretion-dominated, and the accretion process accounts for 80 per cent of the radio luminosity when summed across the objects. The radio emission connected with accretion appears to be correlated with the optical luminosity of the RQQ, whilst a weaker luminosity-dependence is evident for the radio emission connected with star formation.Peer reviewedFinal Accepted Versio