Cardinality versus q-Norm Constraints for Index Tracking

Index tracking aims at replicating a given benchmark with a smaller number of its constituents. Different quantitative models can be set up to determine the optimal index replicating portfolio. In this paper, we propose an alternative based on imposing a constraint on the q-norm, 0 < q < 1, of the replicating portfolios’ asset weights: the q-norm constraint regularises the problem and identifies a sparse model. Both approaches are challenging from an optimisation viewpoint due to either the presence of the cardinality constraint or a non-convex constraint on the q-norm. The problem can become even more complex when non-convex distance measures or other real-world constraints are considered. We employ a hybrid heuristic as a flexible tool to tackle both optimisation problems. The empirical analysis on real-world financial data allows to compare the two index tracking approaches. Moreover, we propose a strategy to determine the optimal number of constituents and the corresponding optimal portfolio asset weights

Where is the best site on Earth? Domes A, B, C and F, and Ridges A and B

The Antarctic plateau contains the best sites on earth for many forms of astronomy, but none of the existing bases was selected with astronomy as the primary motivation. In this article, we try to systematically compare the merits of potential observatory sites.We include South Pole, Domes A, C, and F, and also Ridge B (running northeast from Dome A), and what we call "Ridge A" (running southwest from Dome A). Our analysis combines satellite data, published results, and atmospheric models, to compare the boundary layer, weather, aurorae, airglow, precipitable water vapor, thermal sky emission, surface temperature, and the free atmosphere, at each site. We find that all Antarctic sites are likely to be compromised for optical work by airglow and aurorae. Of the sites with existing bases, Dome A is easily the best overall; but we find that Ridge A offers an even better site. We also find that Dome F is a remarkably good site. Dome C is less good as a thermal infrared or terahertz site, but would be able to take advantage of a predicted "OH hole" over Antarctica during spring.Comment: Revised version. 16 pages, 21 figures (22 in first version). Submitted to PASP 16/05/09, accepted 13/07/09; published 20/08/0

Studying Algebraic Structures Using Prover9 and Mace4

In this chapter we present a case study, drawn from our research work, on the application of a fully automated theorem prover together with an automatic counter-example generator in the investigation of a class of algebraic structures. We will see that these tools, when combined with human insight and traditional algebraic methods, help us to explore the problem space quickly and effectively. The counter-example generator rapidly rules out many false conjectures, while the theorem prover is often much more efficient than a human being at verifying algebraic identities. The specific tools in our case study are Prover9 and Mace4; the algebraic structures are generalisations of Heyting algebras known as hoops. We will see how this approach helped us to discover new theorems and to find new or improved proofs of known results. We also make some suggestions for how one might deploy these tools to supplement a more conventional approach to teaching algebra.Comment: 21 pages, to appear as Chapter 5 in "Proof Technology in Mathematics Research and Teaching", Mathematics Education in the Digital Era 14, edited by G. Hanna et al. (eds.), published by Springe

New approaches in glass investment casting: Creative practitioners researching and innovating in the field of digital fabrication

© 2014, BLOOMSBURY PUBLISHING PLC. This paper describes a research project aimed at delivering innovation in a combined sphere of digital fabrication and glass investment casting. The project has established an entirely new method for creating glass casting moulds directly from three-dimensional computer files without the need for a physical mould pattern, by using a moulding approach based on Additive Layer Manufacturing (ALM) technology. While the paper includes a narrative of the development of the moulding process, the central argument of the paper is rooted in the project’s research/innovation methodology. This argument concerns our profile as creative practitioners and the impact this position has on the research/ innovation scenario. Also central in this argument is the use of ‘emergent methodologies’ and ‘reflective practice’. A new type of rich media enabled research journal to aid the use of these methodologies was developed as a part of this project and is also presented in this paper

Simulation of Cloud-aerosol Lidar with Orthogonal Polarization (CALIOP) attenuated backscatter profiles using the Global Model of Aerosol Processes (GLOMAP)

To permit the calculation of the radiative effects of atmospheric aerosols, we have linked our aerosol-chemical transport model (CTMGLOMAP) to a new radiation module (UKCARADAER). In order to help assess and improve the accuracy of the radiation code, in particular the height dependence of the predicted scattering, we have developed a module that simulates attenuated backscatter (ABS) profiles that would be measured by the satellite-borne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) if it were to sample an atmosphere with the same aerosol loading as predicted by the CTM. Initial results of our comparisons of the predicted ABS profiles with actual CALIOP data are encouraging but some differences are noted, particularly in marine boundary layers where the scattering is currently under-predicted and in dust layers where it is often over-predicted. The sources of these differences are being investigated

Title: will be set by the publisher Editors: will be set by the publisher EAS Publications Series, Vol.?, 2009 THE BEST SITE ON EARTH?

Abstract. We compare the merits of potential observatory sites on the Antarctic Plateau, in regard to the boundary layer, cloud cover, free atmosphere seeing, aurorae, airglow, and precipitable water vapour. We find that (a) all Antarctic sites are likely compromised for optical work by airglow and aurorae; (b) Dome A is the best existing site in almost all respects; (c) there is an even better site (‘Ridge A’) 150kms SW of Dome A; (d) Dome F is a remarkably good site except for aurorae; (e) Dome C probably has the least cloud cover of any of the sites, and might be able to use a predicted ‘OH hole ’ in the Spring. The Antarctic plateau probably contains the best astronomical sites on Earth, but none of the existing bases were situated with astronomy in mind. In Saunders et al.(2009), we use published data and models, and unpublished meteorological and other information, to try to compare the merits of the potential sites. Here, we summarise only the new findings and conclusions. We include boundary layer thickness, cloud cover, auroral emission, airglow, precipitable water vapour, an

Assessment of the CALIPSO Lidar 532 nm Attenuated Backscatter Calibration Using the NASA LaRC Airborne High Spectral Resolution Lidar

The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft has provided global, high-resolution vertical profiles of aerosols and clouds since it became operational on 13 June 2006. On 14 June 2006, the NASA Langley Research Center (LaRC) High Spectral Resolution Lidar (HSRL) was deployed aboard the NASA Langley B-200 aircraft for the first of a series of 86 underflights of the CALIPSO satellite to provide validation measurements for the CALIOP data products. To better assess the range of conditions under which CALIOP data products are produced, these validation flights were conducted under both daytime and nighttime lighting conditions, in multiple seasons, and over a large range of latitudes and aerosol and cloud conditions. This paper presents a quantitative assessment of the CALIOP 532 nm calibration (through the 532 nm total attenuated backscatter) using an internally calibrated airborne HSRL underflight data and is the most extensive study of CALIOP 532 nm calibration. Results show that average HSRL and CALIOP 532 nm total attenuated backscatter agree on average within 2.7% +/- 2.1% (CALIOP lower) at night and within 2.9 % +/- 3.9% (CALIOP lower) during the day., demonstrating the accuracy of the CALIOP 532 nm calibration algorithms. Additionally, comparisons with HSRL show consistency of the CALIOP calibration before and after the laser switch in 2009 as well as improvements in the daytime version 3 calibration scheme compared with the version 2 calibration scheme. Potential systematic uncertainties in the methodology relevant to validating satellite lidar measurements with an airborne lidar system are discussed and found to be less than 3.7% for this validation effort with HSRL. Results from this study are also compared to those from prior assessments of CALIOP calibration and attenuated backscatter

Pathways and Management of Phosphorus in urban areas

Due to the finite nature of mineral phosphorus reserves, effective management of anthropogenic phosphorus flows is currently under investigation by the international research community. This article emphasizes the importance of urban phosphorus flows, which are often marginalized due to the greater magnitude of agricultural phosphorus flows. A study on phosphorus flows in Gothenburg, Sweden, points out the potential role of solid waste in nutrient management, as the amounts of phosphorus in solid waste and in wastewater were found to be equal. Importation of food commodities accounts for 50% of the total inflow of phosphorus, and food waste is a major contributor of phosphorus to solid waste. The results suggest that solid waste incineration residues represent a large underestimated sink of phosphorus. Focusing on wastewater as the sole source of recovered phosphorus is not sufficient. The Swedish national goal on phosphorus recycling, which is limited to sewage sludge, targets only a part of the total phosphorus flow that can potentially be recovered. In contrast to previous studies, agricultural flows in Gothenburg were marginal compared to flows related to the urban waste management infrastructure. We emphasize the need for debate on preferable routes for disposal of waste with a high phosphorus content. Both recovery potential and usefulness of the recovered product for agricultural purposes have to be considered. Impacts of five waste management strategies on phosphorus flows were evaluated: incineration of all the waste, comprehensive food waste separation, installation of kitchen grinders, urine diversion, and separation of blackwater and food waste

A New Approach for Checking and Complementing CALIPSO Lidar Calibration

We have been studying the backscatter ratio of the two CALIPSO wavelengths for 3 different targets. We are showing the ratio of integrate attenuated backscatter coefficient for cirrus clouds, ocean surface and liquid. Water clouds for one month of nightime data (left:July,right:December), Only opaque cirrus classified as randomly oriented ice[1] are used. For ocean and water clouds, only the clearest shots, determined by a threshold on integrated attenuated backscatter are used. Two things can be immediately observed: 1. A similar trend (black dotted line) is visible using all targets, the color ratio shows a tendency to be higher north and lower south for those two months. 2. The water clouds average value is around 15% lower than ocean surface and cirrus clouds. This is due to the different multiple scattering at 532 nm and 1064 nm [2] which strongly impact the water cloud retrieval. Conclusion: Different targets can be used to improve CALIPSO 1064 nm calibration accuracy. All of them show the signature of an instrumental calibration shift. Multiple scattering introduce a bias in liquid water cloud signal but it still compares very well with all other methods and should not be overlooked. The effect of multiple scattering in liquid and ice clouds will be the subject of future research. If there really is a sampling issue. Combining all methods to increase the sampling, mapping the calibration coefficient or trying to reach an orbit per orbit calibration seems an appropriate way