Online Local Volatility Calibration by Convex Regularization with Morozov's Principle and Convergence Rates

We address the inverse problem of local volatility surface calibration from market given option prices. We integrate the ever-increasing flow of option price information into the well-accepted local volatility model of Dupire. This leads to considering both the local volatility surfaces and their corresponding prices as indexed by the observed underlying stock price as time goes by in appropriate function spaces. The resulting parameter to data map is defined in appropriate Bochner-Sobolev spaces. Under this framework, we prove key regularity properties. This enable us to build a calibration technique that combines online methods with convex Tikhonov regularization tools. Such procedure is used to solve the inverse problem of local volatility identification. As a result, we prove convergence rates with respect to noise and a corresponding discrepancy-based choice for the regularization parameter. We conclude by illustrating the theoretical results by means of numerical tests.Comment: 23 pages, 5 figure

Field coverage and weed mapping by UAV swarms

The demands from precision agriculture (PA) for high-quality information at the individual plant level require to re-think the approaches exploited to date for remote sensing as performed by unmanned aerial vehicles (UAVs). A swarm of collaborating UAVs may prove more efficient and economically viable compared to other solutions. To identify the merits and limitations of a swarm intelligence approach to remote sensing, we propose here a decentralised multi-agent system for a field coverage and weed mapping problem, which is efficient, intrinsically robust and scalable to different group sizes. The proposed solution is based on a reinforced random walk with inhibition of return, where the information available from other agents (UAVs) is exploited to bias the individual motion pattern. Experiments are performed to demonstrate the efficiency and scalability of the proposed approach under a variety of experimental conditions, accounting also for limited communication range and different routing protocols. © 2017 IEEE

Homogenization of Plasmonic Nanocluster Metamaterials

Metamaterials and plasmonics based on micro- and nanostructured metallic-dielectric composites are bringing an important revolution to the microwave and optics fields due to their potential for enabling the realization of novel physical properties unattainable from natural materials, such as isotropic negative refraction, slow light, near-field enhancement, as well as EM focusing and energy transfer beyond the diffraction limit. Such artificial composite structures owe their peculiar properties both to the constituent materials which comprise their elementary building blocks and to their specific spatial arrangement. The use of homogenization methods can provide a convenient characterization of EM-wave-matter interaction by describing metamaterials as bulk homogeneous materials with effective parameters that take into account their inherent qualities and complex nature. While the concept of homogenization theory is easily applied to the long-wavelength limit, e.g. the microwave regime where true sub-wavelength structures can be fabricated, the optical regime challenges the underlying hypothesis of a true subwavelength unit cell. Indeed, for artificial materials the size of the lattice constant is typically only moderately smaller than the wavelength of light. As a consequence, metamaterials can be characterized by nonnegligible spatial dispersion effects. © 2013 IEEE

The impact of the English national health inequalities strategy on inequalities in mortality at age 65: a time-trend analysis

\ua9 The Author(s) 2024. Published by Oxford University Press on behalf of the European Public Health Association. Background: During the 1997–2010 Labour government, several policies were implemented to narrow health inequalities as part of a national health inequalities strategy. Many of these policies are likely to have had a disproportionately large impact on people aged 65 and over. We aimed to understand the association between the health inequalities strategy period and inequalities in mortality at age 65–69. Methods: We use population at risk and mortality data covering 1991–2019 to calculate mortality rate at age 65–69 at the Local Authority level. We use the 2019 Index of Multiple Deprivation to examine geographical inequalities. We employ segmented linear regression models with marginal spline terms for the strategy period and interact these with an indicator of deprivation to understand how inequalities changed before, during and after the strategy. The reporting of this study adheres to STROBE guidelines. Results: Mortality rates in each deprivation quintile improved continuously throughout the period of study. Prior to the programme (1991–9) there was no significant change in absolute inequalities. However, during the strategy (2000–10) there was a significant decrease in absolute inequalities of −9.66 (−17.48 to −1.84). The period following the strategy (2011–19) was associated with a significant increase in absolute inequalities of 12.84 (6.60 to 19.08). Our results were robust to a range of sensitivity tests. Conclusion: The English health inequalities strategy was associated with a significant reduction in absolute inequality in mortality age 65–69. Future strategies to address inequalities in ageing populations may benefit from adopting a similar approach

Holocene regional gradients of dust provenance and flux between Talos Dome and Dome C, East Antarctica.

Aeolian sequences from Central East Antarctic ice cores provide climate and environmental information of hemispheric significance. Close to the margins of the ice sheet, high-elevation ice-free terrains protruding above the ice sheet surface can provide an additional input of fine dust particles to the atmosphere, making peripheral locations particularly interesting for the study of the regional climate evolution. In the Talos Dome area of East Antarctica, entrainment and transport of local mineral particles is merely influenced by local wind direction and strength, which in turn is tuned by regional climate changes. We investigate the spatial variability of modern and Holocene dust flux, grain size and isotopic (Sr-Nd) composition along a hypothetic transect from Talos Dome all through the interior of the ice sheet (Dome C/Vostok area), and compare the geochemical fingerprint of dust extracted from firn and ice cores to the equivalent size fraction of regolith and glacial deposits from high altitude Victoria Land sources. This study aims to better understand the environmental gradients of dust flux and provenance from the marginal Talos Dome site to the higher Dome C drainage area, with implications for the regional atmospheric circulation, while documenting the isotopic composition of local exposed sediments