VegMachine.net. Online land cover analysis for the rangelands

VegMachine.net is an online land cover monitoring tool unded by the Fitzroy Basin Association (FBA). The tool focuses primarily on Queensland, but has functionality for much of Australia’s rangelands. The website went live in July 2016 and recently logged the 1000th user session. Users can view seven different seasonal time series of cover products across the landscape and interactively interrogate and graph ground cover change in six different on-the-fly and email delivered reports. Results can then be exported for use in other software. To date, users have generated over 400 VegMachine® FORAGE ground cover reports which provide paddock-by-paddock, landtype-by-landtype analysis of ground cover change from 1990 to the present. Detailed help is available in multiple formats, including website popups and a dedicated YouTube channel. The web application was designed for two main user groups; technically equipped RD&E personnel including those servicing land manager clients, and a subset of the grazier community willing to operate the service themselves. Initial rollout of the application focused primarily on training events for government agency, private consultancy and natural resource management (NRM) staff in regional Queensland. These users form the core of the current user base. In this paper, we outline the development of VegMachine.net. We demonstrate the primary functionality of the website, provide an overview of user experience including a case study and discuss major learnings and future directions

Moiré flat bands in strongly coupled atomic arrays

Moiré effects arise from stacking periodic structures with a specific geometrical mismatch and promise unique possibilities. However, their full potential for photonic applications has yet to be explored. Here, we investigate the photonic band structure for an atomic stack of strongly coupled linear arrays in the dipolar regime. A moiré parameter θ is used to parameterize a relative lattice constant mismatch between the two arrays that plays the role of a 1D twist angle. The system’s interaction matrix is analytically diagonalized and reveals the presence of localized excitations which strongly enhance the density of optical states in spectral regions that can be controlled via the moiré parameter. We also confirm our findings by numerical simulations of finite systems. Our work provides a better understanding of photonic moiré effects and their potential use in photonic devices such as optical sensors and light traps

VegMachine.net. online land cover analysis for the Australian rangelands

This paper documents the development and use of the VegMachine.net land cover monitoring tool. From 2002 to 2015, VegMachine® software was used by government agencies, natural resource management (NRM) groups and individual pastoralists in northern Australia to assess and benchmark vegetation cover levels. In 2016 the VegMachine.net website was launched to build a wider user base and assure service continuity. Users can now graph historical (1990-) cover on one or more user defined areas of interest (AOI), produce comprehensive paddock-by-paddock property monitoring reports, and view a range of land cover raster images through the website map panel. In its first 32 months of operation 913 users logged 1604 sessions on the website and more than 1000 of the website's most comprehensive monitoring reports were distributed to users. Levels of use varied 26% of users (n = 237) have used the website more than once, and within this group a smaller set of regular users (n = 36) have used the site more than five times, in many cases to provide analyses to multiple clients. We outline four case studies that document the significant impact VegMachine.net has had on users including graziers, government agencies, NRM groups and researchers. We also discuss some possible paths forward that could widen the user base and improve retention of first time users. © 2019 The State of Queensland (through the Department of Agriculture and Fisheries) 2019 Open Access

Gradient-less Federated Gradient Boosting Trees with Learnable Learning Rates

The privacy-sensitive nature of decentralized datasets and the robustness of eXtreme Gradient Boosting (XGBoost) on tabular data raise the needs to train XGBoost in the context of federated learning (FL). Existing works on federated XGBoost in the horizontal setting rely on the sharing of gradients, which induce per-node level communication frequency and serious privacy concerns. To alleviate these problems, we develop an innovative framework for horizontal federated XGBoost which does not depend on the sharing of gradients and simultaneously boosts privacy and communication efficiency by making the learning rates of the aggregated tree ensembles learnable. We conduct extensive evaluations on various classification and regression datasets, showing our approach achieves performance comparable to the state-of-the-art method and effectively improves communication efficiency by lowering both communication rounds and communication overhead by factors ranging from 25x to 700x.Comment: Accepted at the 3rd ACM Workshop on Machine Learning and Systems (EuroMLSys), May 8th 2023, Rome, Ital

Inverse design of all-dielectric metasurfaces with accidental bound states in the continuum

Metasurfaces with bound states in the continuum (BICs) have proven to be a powerful platform for drastically enhancing light–matter interactions, improving biosensing, and precisely manipulating near- and far-fields. However, engineering metasurfaces to provide an on-demand spectral and angular position for a BIC remains a prime challenge. A conventional solution involves a fine adjustment of geometrical parameters, requiring multiple time-consuming calculations. In this work, to circumvent such tedious processes, we develop a physics-inspired, inverse design method on all-dielectric metasurfaces for an on-demand spectral and angular position of a BIC. Our suggested method predicts the core–shell particles that constitute the unit cell of the metasurface, while considering practical limitations on geometry and available materials. Our method is based on a smart combination of a semi-analytical solution, for predicting the required dipolar Mie coefficients of the meta-atom, and a machine learning algorithm, for finding a practical design of the meta-atom that provides these Mie coefficients. Although our approach is exemplified in designing a metasurface sustaining a BIC, it can, also, be applied to many more objective functions. With that, we pave the way toward a general framework for the inverse design of metasurfaces in specific and nanophotonic structures in general

Inverse Design of All-dielectric Metasurfaces with Bound States in the Continuum

Metasurfaces with bound states in the continuum (BICs) have proven to be a powerful platform for drastically enhancing light-matter interactions, improving biosensing, and precisely manipulating near- and far-fields. However, engineering metasurfaces to provide an on-demand spectral and angular position for a BIC remains a prime challenge. A conventional solution involves a fine adjustment of geometrical parameters, requiring multiple time-consuming calculations. In this work, to circumvent such tedious processes, we develop a physics-inspired, inverse design method on all-dielectric metasurfaces for an on-demand spectral and angular position of a BIC. Our suggested method predicts the core-shell particles that constitute the unit cell of the metasurface, while considering practical limitations on geometry and available materials. Our method is based on a smart combination of a semi-analytical solution, for predicting the required dipolar Mie coefficients of the meta-atom, and a machine learning algorithm, for finding a practical design of the meta-atom that provides these Mie coefficients. Although our approach is exemplified in designing a metasurface sustaining a BIC, it can, also, be applied to many more objective functions. With that, we pave the way toward a general framework for the inverse design of metasurfaces in specific and nanophotonic structures in general.Comment: 20 pages, 5 figures, Supplementary Materia