Evaluations of UAV-enabled FSO Communications in the Arctic

This paper investigates the feasibility of using free space optics (FSO) for communication between multiple hovering unmanned aerial vehicles (UAVs) and a detection unit (DU) in the Arctic. The uniqueness that sets apart UAV-based FSO systems from conventional FSO systems is the dynamics of the system since location and inclination of the UAV changes over time due to wind load and UAV oscillations. The envisioned scenario consists of UAVs equipped with laser diodes and a DU mounted on top of a ship. We propose an application scenario of search and rescue (SAR) operations in the High North. In the system design, the SAR team establishes communication with UAVs using radio frequency multiple-access links while DU demodulates the information from the incoming FSO fronthaul signals. Furthermore, statistical models for the FSO channel, random position and orientation fluctuations, snow, and fog have been derived. This work amplifies the need and possibility of enabling enhanced accessibility and connectivity in the Arctic utilizing UAVs and FSO

Learning from problem-based projects in cross-diciplinary student teams.

This paper explores how Engineering students and Work and Welfare students reflect upon their own engagement in a one-week cross-disciplinary project. To develop a better understanding of what unfolds during these activities we collected data through anonymous surveys two consecutive years. Data from these 141 respondents were analysed using a learning history approach and are presented as narratives. Results show major disruptions and conflicts driving the student projects, exposing inviting confrontations, social identity threats, managing diversity, and friction of ideas. Whereas this in many cases led to new and better project solutions, these real-world experiences raise awareness of the need for tools and methods for training students. The aim of the paper is to learn from students’ experiences through narrative distance, and fill a gap in the literature between problem-based learning (PBL) and the learning history method. Discussing different experiences of cross-disciplinary teamwork through the explanations of these theories, we also lay out potential questions for future research on the topic.publishedVersio

TRACKING VOLUME CHANGE OF THE BULK COMMODITIES WITH INTERFEROMETRIC SAR

Source at https://ieeexplore.ieee.org/xpl/conhome/1000307/all-proceedings.Bulk commodities are crucial to global economy and modern society. Some commodities, such as grain, are normally stored in cylindrical tanks. The height of the tank’s roof may be correlated to the substance quantity inside the tank, indicating that roof displacement may be associated with the volume of the bulk commodities. Here we analyzed the displacements derived from C-band Sentinel-1 data with the vessel tracking Automatic Identification System (AIS) data from a major grain export port - Chornomorsk port in Ukraine. Our results show that displacements of silos’ roof derived from satellite observation are consistent with the discharge quantities estimated from AIS and other data sources. This preliminary investigation suggests the feasibility of integrating InSAR measurements and AIS data to improve the efficiency and accuracy of commodity cargoflow tracking and resource management for the global commodity and shipping industry

Conformal Transformation Analysis of Capacitive Wireless Charging

This paper studies the capacitive coupling in a capacitive power transfer (CPT) system designed for charging applications. It proposes mathematical models using the conformal transformation for calculating air-gapped and underwater capacitance and verifies the proposed models using COMSOL multiphysics and measurements. The measured results show that we can achieve nano-farad capacitance ranges if we submerge the capacitor in seawater. The seawater’s capacitance slightly changes when we increase the gap distance or the operating frequency. As the under seawater CPT system can be an attractive option for loosely-coupled charging applications, we further examine the system by focusing on the crosscoupling effects. The results show that the cross-coupling between the plate degrades the system’s power transfer capability and efficiency. With negligible cross-coupling effects, the system gives 129 W output power at an efficiency of 81.2%

A new spectral harmonization algorithm for Landsat-8 and Sentinel-2 remote sensing reflectance products using machine learning: a case study for the Barents Sea (European Arctic)

The synergistic use of Landsat-8 operational land imager (OLI) and Sentinel-2 multispectral instrument (MSI) data products provides an excellent opportunity to monitor the dynamics of aquatic ecosystems. However, the merging of data products from multisensors is often adversely affected by the difference in their spectral characteristics. In addition, the errors in the atmospheric correction (AC) methods further increase the inconsistencies in downstream products. This work proposes an improved spectral harmonization method for OLI and MSI-derived remote sensing reflectance ( Rrs ) products, which significantly reduces uncertainties compared to those in the literature. We compared Rrs retrieved via state-of-the-art AC processors, i.e., Acolite, C2RCC, and Polymer, against ship-based in situ Rrs observations obtained from the Barents Sea waters, including a wide range of optical properties. Results suggest that the Acolite-derived Rrs has a minimum bias for our study area with median absolute percentage difference (MAPD) varying from 9% to 25% in the blue–green bands. To spectrally merge OLI and MSI, we develop and apply a new machine learning-based bandpass adjustment (BA) model to near-simultaneous OLI and MSI images acquired in the years from 2018 to 2020. Compared to a conventional linear adjustment, we demonstrate that the spectral difference is significantly reduced from ∼6 % to 12% to ∼2 % to Rrs products for water quality monitoring applications. The proposed method has the potential to be applied to other waters

Observations of sunlit N2+ aurora at high altitudes during the RENU2 flight

We present measurements of sunlit aurora during the launch of the Rocket Experiment for Neutral Upwelling 2 (RENU2) on the 13 December 2015, 07:34 UTC. The in situ auroral conditions coincide with those of sunlit aurora and were characterised by the 391.4 and 427.8 nm N2 + emissions. A correlation between several auroral wavelengths, as measured by a meridian-scanning photometer, was used to detect sunlit aurora and indirectly neutral upwelling. These results, based on ground data, agree well with the RENU2 measurements recorded during its pass through the sunlit polar cusp. Using in situ data from RENU2 and the solar photon flux, it was estimated that the sunlit aurora was a major part (≈ 40 %) of the observed 427.8 nm emissio

Fast and optimal broad-band Stokes/Mueller polarimeter design by the use of a genetic algorithm

A fast multichannel Stokes/Mueller polarimeter with no mechanically moving parts has been designed to have close to optimal performance from 430-2000 nm by applying a genetic algorithm. Stokes (Mueller) polarimeters are characterized by their ability to analyze the full Stokes (Mueller) vector (matrix) of the incident light. This ability is characterized by the condition number, $\kappa$, which directly influences the measurement noise in polarimetric measurements. Due to the spectral dependence of the retardance in birefringent materials, it is not trivial to design a polarimeter using dispersive components. We present here both a method to do this optimization using a genetic algorithm, as well as simulation results. Our results include fast, broad-band polarimeter designs for spectrographic use, based on 2 and 3 Ferroelectric Liquid Crystals, whose material properties are taken from measured values. The results promise to reduce the measurement noise significantly over previous designs, up to a factor of 4.5 for a Mueller polarimeter, in addition to extending the spectral range.Comment: 10 pages, 6 figures, submitted to Optics Expres

Polarimetric and hyperspectral imaging methods for characterisation of bio- and nanomaterials

Presented here is the development of a time gated Raman spectrometer, a new method for designing polarimeters, testing of an overdetermined Mueller matrix imaging ellipsometer and Mueller matrix imaging of collagen fibre directions and silicon strain. In addition, a new method, spectral correlation, for analysing hyperspectral images, is developed, implemented and tested. The time gated Raman spectrometer is capable of gating away long lifetime luminescence (> 2 ns), by using a time gated ICCD and a 2 ns pulsed Nd:YAG laser. Furthermore, the system can be used to study UV resonance Raman effects, due to the third (355 nm) and fourth (266 nm) order harmonic excitations available. For optimising broadband polarimeters, genetic algorithms are employed. The resulting polarimeters are demonstrated to have a lower noise propagation and a broader spectral range, compared to previous commercial and patented designs. One of the designs is realised as a Mueller matrix liquid crystal variable retarder based ellipsometer. Its performance is in good agreement with computer optimised models. For calibrating the instrument, an extended version of the eigenvalue calibration method is employed. Mueller matrix imaging is used together with state of the art decomposition methods to image collagen fibre orientations in cartilage and tendon. 3D directional imaging of the collagen fibres is achieved by using different angles of incidence upon the sample and a new method for calculating the fibre direction from the linear retardance. The method uses an effective medium approach to justify that the slow axis is along the direction of the fibres. A similar approach is used to study strain in silicon wafers. Lastly, a spectral correlation method for analysing hyperspectral fluorescence images is developed and demonstrated to be good for analysing double stained amyloid plaques in mice. The resulting analysis allows for calculating the radius dependent mean and standard deviations for a set of plaques as a function of radius. By studying amyloid plaques from mice of different ages, it was found that there were significant changes with age in the structure of the plaques. Furthermore, the method was found to work well for analysing multi-component Raman spectra, where it detected small amounts of tetrahydrofuran in water