What drives diesel fuel prices?

Historically, gasoline has commanded a premium over diesel, but that changed in mid-to-late 2007, when diesel rose above gasoline. In 2007 and 2008, however, gasoline traded higher than diesel only 21.1 percent of the time. This deviation from historic norms raises an interesting question--what drives diesel prices? As with virtually all petroleum-derived products, the story begins with oil prices. Seasonal patterns also play a significant role. Demand for a range of oil-based products changes with the weather, and prices fluctuate as refiners adjust their output mix. Government regulations are another source of price variability. Earlier this decade, new standards aimed at reducing diesel fuel's sulfur content required further processing that increased refinery costs and prices for consumers. Finally, short-term changes in supply and demand--including imports--factor into pricing on a day-to-day basis. Our model suggests that spot diesel should rise 25 cents a gallon over the next six months and 41 cents a gallon over the next 18 months.Petroleum products - Prices ; Petroleum industry and trade ; Energy consumption ; Econometric models

A natural formation scenario for misaligned and short-period eccentric extrasolar planets

Recent discoveries of strongly misaligned transiting exoplanets pose a challenge to the established planet formation theory which assumes planetary systems to form and evolve in isolation. However, the fact that the majority of stars actually do form in star clusters raises the question how isolated forming planetary systems really are. Besides radiative and tidal forces the presence of dense gas aggregates in star-forming regions are potential sources for perturbations to protoplanetary discs or systems. Here we show that subsequent capture of gas from large extended accretion envelopes onto a passing star with a typical circumstellar disc can tilt the disc plane to retrograde orientation, naturally explaining the formation of strongly inclined planetary systems. Furthermore, the inner disc regions may become denser, and thus more prone to speedy coagulation and planet formation. Pre-existing planetary systems are compressed by gas inflows leading to a natural occurrence of close-in misaligned hot Jupiters and short-period eccentric planets. The likelihood of such events mainly depends on the gas content of the cluster and is thus expected to be highest in the youngest star clusters.Comment: 7 pages, 4 figures. Accepted for publication in MNRAS. Updated to match published versio

Multi-objective optimization of the operation and maintenance assets of an offshore wind farm using genetic algorithms

The first author was funded by the Marie Curie Actions of the European Union’s Seventh Framework Programme FP7/2007- 2013/ under REA grant agreement number 607656 (OceaNet project) and by the industrial partner James Fisher Marine Services Ltd. Mojo Maritime (JFMS group) have provided access to Mermaid to support, and for integration with, this research. This work is also funded by the EPSRC (UK) grant for the SuperGen United Kingdom Centre for Marine Energy Research (UKCMER) [grant number: EP/P008682/1]This is the author accepted manuscriptThis paper explores the use of genetic algorithms to optimize the operation and maintenance (O&M) assets of an offshore wind farm. Three different methods are implemented in order to demonstrate the approach. The optimization problem simultaneously considers both the reliability characteristics of the offshore wind turbines and the composition of the maintenance fleet, seeking to identify the optimal configurations for the strategic assets. These are evaluated in order to minimize the operating costs of the offshore farm while maximizing both its reliability and availability. The considerations used for the application of genetic algorithms as an effective way to support the assets management are described, and a case study to show the applicability of the approach is presented. The variation of the economic performance indicators as a consequence of the optimization procedure are discussed, and the implementation of this method in a wider computational framework for the O&M assets improvement introduced.European CommissionMojo Ocean Dynamics Ltd. T/A Mojo Maritime LtdEPSRC (UK) grant for the SuperGen United Kingdom Centre for Marine Energy Research (UKCMER

A discontinuity in the low-mass initial mass function

The origin of brown dwarfs (BDs) is still an unsolved mystery. While the standard model describes the formation of BDs and stars in a similar way recent data on the multiplicity properties of stars and BDs show them to have different binary distribution functions. Here we show that proper treatment of these uncovers a discontinuity of the multiplicity-corrected mass distribution in the very-low-mass star (VLMS) and BD mass regime. A continuous IMF can be discarded with extremely high confidence. This suggests that VLMSs and BDs on the one hand, and stars on the other, are two correlated but disjoint populations with different dynamical histories. The analysis presented here suggests that about one BD forms per five stars and that the BD-star binary fraction is about 2%-3% among stellar systems.Comment: 14 pages, 11 figures, uses emulateapj.cls. Minor corrections and 1 reference added after being accepted by the Ap

Phase transition in the 3-D massive Gross-Neveu model

We consider the 3-dimensional massive Gross-Neveu model at finite temperature as an effective theory for strong interactions. Using the Matsubara imaginary time formalism, we derive a closed form for the renormalized $T$-dependent four-point function. This gives a singularity, suggesting a phase transition. Considering the free energy we obtain the $T$-dependent mass, which goes to zero for some temperature. These results lead us to the conclusion that there is a second-order phase transition.Comment: 06 pages, 02 figures, LATE

Installation Innovation for floating offshore wind

This is the author accepted manuscript.Floating offshore wind turbines are an emerging technology with notable prototype and demonstration projects being installed in recent years. Future floating wind farms enable the access to significant new wind resources in expanses of water too deep for conventional, bottom-fixed farms. Spar, barge, TLP and semisubmersible types have been deployed as demonstration units. Pre commercial units have been installed off the coasts of Portugal and the East Coast of Scotland. This paper discusses naval architecture requirements for the temporary conditions of construction, ocean transport and installation. The requirements of Marine Warranty Surveyor guidelines for temporary conditions and the Classification Society requirements during the temporary phase are also taken into account. It is expected that major offshore maintenance will be carried out on floating offshore wind turbines by towing them back to more sheltered port locations. This paper is a literature and guideline review with additional information on intact stability during the tow to the offshore location. Thus, marine operations play a pivotal role throughout all phases of a floating wind farm’s life cycle. In particular, uncertainties associated with offshore installation work can extend construction schedules and increase the capital expenditure required for the project. This paper will be of interest to researchers and practitioners in the floating wind sector, considering innovative installation methods as a means to reduce overall project lifecycle cost.Engineering and Physical Sciences Research Council (EPSRC

Recent advances on IMF research

Here I discuss recent work on brown dwarfs, massive stars and the IMF in general. The stellar IMF can be well described by an invariant two-part power law in present-day star-formation events within the Local Group of galaxies. It is nearly identical in shape to the pre-stellar core mass function. The majority of brown dwarfs follow a separate IMF. Evidence from globular clusters and ultra-compact dwarf galaxies has emerged that IMFs may have been top heavy depending on the star-formation rate density. The IGIMF then ranges from bottom heavy at low galaxy-wide star formation rates to being top-heavy in galaxy-scale star bursts.Comment: 6 pages, LaTeX, to appear in The Labyrinth of Star Formation, 18-22 June 2012, Crete, (eds.) D. Stamatellos, S. Goodwin, and D. Ward-Thompson, Springer, in press; replaced version: very minor corrections plus the addition of reference Smith & Lucey (2013) on the bottom-heavy IMF in elliptical galaxie

2D Coupled CFD model of and Oscillating Water Column using PROTEUS

This is the author accepted manuscript. The final version is available from ASRANet via the link in this recordFloating Oscillating Water Columns (OWC) are one of many potential Renewable Energy Devices under consideration as part of the global drive towards clean energy sources. In order to reach deployment, these devices first exist in the form of computational models. These models allow the devices to be tested under a range of conditions and mooring configurations. However, the design of systems often fails to account for the moorings at an early stage, which can result in disappointing performance at later stages of design and deployment. In this study, Proteus is used to produce a 2D model of an OWC that demonstrates its effectiveness as a tool for modelling floating marine structures. The model solves the Reynolds Averaged Navier Stokes equations in the fluid domain, using a Volume of Fluid-Level Set approach for defining the air-water interface. Proteus is coupled with the Chrono library to solve the rigid body motions, and the response of the mooring lines. The model is validated against both experimental and other computational models. The effect of a mooring system is shown on the water column response. This study provides a launch pad for more complex studies. Proteus has 3D modelling capabilities, and as a result, 3D OWC, other wave energy devices and floating wind turbines are all potential devices that Proteus has the capability to recreate in high fidelity models.ERDCHR WallingfordEnergy Technologies Institute (ETI)Engineering and Physical Sciences Research Council (EPSRC