Branch-and-lift algorithm for deterministic global optimization in nonlinear optimal control

This paper presents a branch-and-lift algorithm for solving optimal control problems with smooth nonlinear dynamics and potentially nonconvex objective and constraint functionals to guaranteed global optimality. This algorithm features a direct sequential method and builds upon a generic, spatial branch-and-bound algorithm. A new operation, called lifting, is introduced, which refines the control parameterization via a Gram-Schmidt orthogonalization process, while simultaneously eliminating control subregions that are either infeasible or that provably cannot contain any global optima. Conditions are given under which the image of the control parameterization error in the state space contracts exponentially as the parameterization order is increased, thereby making the lifting operation efficient. A computational technique based on ellipsoidal calculus is also developed that satisfies these conditions. The practical applicability of branch-and-lift is illustrated in a numerical example. © 2013 Springer Science+Business Media New York

Instrumentation and Measurement Strategy for the NOAA SENEX Aircraft Campaign as Part of the Southeast Atmosphere Study 2013

Natural emissions of ozone-and-aerosol-precursor gases such as isoprene and monoterpenes are high in the southeast of the US. In addition, anthropogenic emissions are significant in the Southeast US and summertime photochemistry is rapid. The NOAA-led SENEX (Southeast Nexus) aircraft campaign was one of the major components of the Southeast Atmosphere Study (SAS) and was focused on studying the interactions between biogenic and anthropogenic emissions to form secondary pollutants. During SENEX, the NOAA WP-3D aircraft conducted 20 research flights between 27 May and 10 July 2013 based out of Smyrna, TN. Here we describe the experimental approach, the science goals and early results of the NOAA SENEX campaign. The aircraft, its capabilities and standard measurements are described. The instrument payload is summarized including detection limits, accuracy, precision and time resolutions for all gas-and-aerosol phase instruments. The inter-comparisons of compounds measured with multiple instruments on the NOAA WP-3D are presented and were all within the stated uncertainties, except two of the three NO2 measurements. The SENEX flights included day- and nighttime flights in the Southeast as well as flights over areas with intense shale gas extraction (Marcellus, Fayetteville and Haynesville shale). We present one example flight on 16 June 2013, which was a daytime flight over the Atlanta region, where several crosswind transects of plumes from the city and nearby point sources, such as power plants, paper mills and landfills, were flown. The area around Atlanta has large biogenic isoprene emissions, which provided an excellent case for studying the interactions between biogenic and anthropogenic emissions. In this example flight, chemistry in and outside the Atlanta plumes was observed for several hours after emission. The analysis of this flight showcases the strategies implemented to answer some of the main SENEX science questions

Coaches' learning and sustainability in high performance sport

In undertaking their complicated and multi-faceted work, high performance coaches have previously been shown to be influential in the performance of athletes. It has also been noted that high performance coaches are learners by necessity. However, what remains unclear is how coaches' learning influences their engagement in sustainable practice. This study draws on three cohorts of full-time high performance coaches employed in Olympic and professional sports throughout Australia. Semi-structured interviews were conducted face-to-face and were inductively analysed. The results revealed that the coaches were presented with a variety of opportunities to learn, with the most valued sources being 'learning on the job', 'discussions with others' and 'experience as athletes'. These unmediated learning opportunities are critiqued along with other mediated opportunities in relation to notions of sustainability. The dominance of unmediated sources of learning meant that sustainable practice was present but was not assured. Sustainable practice is also discussed in relation to the dominant models of high performance athlete development and the demands of coaching work

The nature and distribution of flowing features in a weakly karstified porous limestone aquifer

The nature and distribution of flowing features in boreholes in an area of approximately 400 km2 in a weakly karstic porous limestone aquifer (the Chalk) was investigated using single borehole dilution tests (SBDTs) and borehole imaging. One-hundred and twenty flowing features identified from SBDTs in 24 boreholes have densities which decrease from ∼0.3 m−1 near the water table to ∼0.07 m−1 at depths of more than 40 m below the water table; the average density is 0.20 m−1. There is some evidence of regional lithological control and borehole imaging of three boreholes indicated that most flowing features are associated with marls, hardgrounds and flints that may be developed at a more local scale. Borehole imaging also demonstrated that many flowing features are solutionally enlarged fractures, suggesting that even in carbonate aquifers where surface karst is developed on only a small scale, groundwater flow is still strongly influenced by dissolution. Fully connected solutional pathways can occur over 100s, sometimes 1000s of metres. However, conduits, tubules and fissures may not always be individually persistent along a flowpath, instead being connected together and also connected to unmodified fractures to create a relatively dense network of voids with variable apertures (15 cm). Groundwater therefore moves along flowpaths made up of voids with varying shape and character. Local solutional development of fractures at significant depths below the surface suggests that mixing corrosion and in situ sources of acidity may contribute to solutional enhancement of fractures. The study demonstrates that single borehole dilution testing is a useful method of obtaining a large dataset of flowing features at catchment-regional scales. The Chalk is a carbonate aquifer with small-scale surface karst development and this study raises the question of whether other carbonate aquifers with small-scale surface karst have similar characteristics, and what hydrological role small-scale dissolutional features play in highly karstic aquifers