GLORIA - A globally representative hyperspectral \u3ci\u3ein situ\u3c/i\u3e dataset for optical sensing of water quality

The development of algorithms for remote sensing of water quality (RSWQ) requires a large amount of in situ data to account for the bio-geo-optical diversity of inland and coastal waters. The GLObal Reflectance community dataset for Imaging and optical sensing of Aquatic environments (GLORIA) includes 7,572 curated hyperspectral remote sensing reflectance measurements at 1nm intervals within the 350 to 900nm wavelength range. In addition, at least one co-located water quality measurement of chlorophyll α, total suspended solids, absorption by dissolved substances, and Secchi depth, is provided. The data were contributed by researchers affiliated with 59 institutions worldwide and come from 450 different water bodies, making GLORIA the de-facto state of knowledge of in situ coastal and inland aquatic optical diversity. Each measurement is documented with comprehensive methodological details, allowing users to evaluate fitness-for-purpose, and providing a reference for practitioners planning similar measurements. We provide open and free access to this dataset with the goal of enabling scientific and technological advancement towards operational regional and global RSWQ monitoring

Analytic Solution to the Piecewise Linear Interface Construction Problem and its Application in Curvature Calculation for Volume-of-Fluid Simulation Codes

The plane-cube intersection problem has been around in literature since 1984 and iterative solutions to it have been used as part of piecewise linear interface construction (PLIC) in computational fluid dynamics simulation codes ever since. In many cases, PLIC is the bottleneck of these simulations regarding compute time, so a faster, analytic solution to the plane-cube intersection would greatly reduce compute time for such simulations. We derive an analytic solution for all intersection cases and compare it to the one previous solution from Scardovelli and Zaleski (Ruben Scardovelli and Stephane Zaleski. "Analytical relations connecting linear interfaces and volume fractions in rectangular grids". In: Journal of Computational Physics 164.1 (2000), pp. 228-237.), which we further improve to include edge cases and micro-optimize to reduce arithmetic operations and branching. We then extend our comparison regarding compute time and accuracy to include two different iterative solutions as well. We find that the best choice depends on the employed hardware platform: on the CPU, Newton-Raphson is fastest with vectorization while analytic solutions perform better without. The reason for this is that vectorization instruction sets do not include trigonometric functions as used in the analytic solutions. On the GPU, the fastest method is our optimized version of the analytic SZ solution. We finally provide details on one of the applications of PLIC: curvature calculation for the Volume-of-Fluid model used for free surface fluid simulations in combination with the lattice Boltzmann method.Comment: 18 pages, 6 figure

Multi-inlet migration modeling for navigation channel management in Tabusintac Bay, Eastern Canada

In New Brunswick, Atlantic Canada, Tabusintac Bay’s multiple tidal inlets meander through narrow barrier islands and are prone to large storm-induced shifts, making navigation hazardous. A multi-evidence assessment comprised of air-photo analysis, field observations and modeling was undertaken to understand the system and recommend sustainable dredging strategies and/or engineering alternatives. The modeling relied on a combination of simple analytical methods for tidal inlet stability, and complex morphological modeling to project the evolution of the nearshore bathymetry. The study recommended reassigning dredging efforts to a new inlet projected to grow and have better stability. Observations two years after the initial modeling effort indicate that the morphological evolution is consistent with the simulation results, and allowed lowered maintenance dredging requirements. This study illustrates how such a multi-evidence assessment of complex coastal dynamics can concretely guide efforts to reduce maintenance dredging and improve safety at sea

Author Correction: GLORIA - A globally representative hyperspectral in situ dataset for optical sensing of water quality

Correction to: Scientific Data https://doi.org/10.1038/s41597-023-01973-y, published online 16 February 2023. An author of the paper was omitted in the original version (Ted Conroy, University of Waikato, New Zealand). This has been corrected in the pdf and HTML versions of the paper, and the associated metadata

Clear Shores: Enhancing Water Quality Monitoring

Mission goal: Improve monitoring of the quality of water in and around Aotearoa New Zealand for researchers, decision makers and the public at large through innovative space technolog

Comparison of Commonly Used Cooling Concepts for Electrical Machines in Automotive Applications

The thermal design of electrical machines has numerous influencing factors. This paper compares different cooling methods, their volume flow rates and other machine parameters with regard to the continuous power of a PMSM. Understanding the characteristics of different heat sinks depending on their operating point is important for an expedient design in order to avoid derating due to overtemperatures. As a design guideline, this contribution shows the influence of stator cooling jackets, rotor shaft cooling and direct end winding cooling for different machine lengths and volume flow rates. Both water and oil are investigated as coolants. With increasing machine dimensions, end winding cooling becomes less effective for heat sources in the center of the machine while the heat transferred in the cooling jacket increases. A sensitivity study of other machine parameters, such as the maximum allowed magnet temperature or the coolant inlet temperature, improves the understanding of the reader as to how the continuous power of a PMSM can be increased when the rotor temperature limits the performance

Groundwater-surface water interaction - A Lake-Modeller's conceptual view

This article explores the groundwater-surface water interaction from a conceptual point of view

Ejection of marine microplastics by raindrops : a computational and experimental study

Abstract Raindrops impacting water surfaces such as lakes or oceans produce myriads of tiny droplets which are ejected into the atmosphere at very high speeds. Here we combine computer simulations and experimental measurements to investigate whether these droplets can serve as transport vehicles for the transition of microplastic particles with diameters of a few tens of μm from ocean water to the atmosphere. Using the Volume-of-Fluid lattice Boltzmann method, extended by the immersed-boundary method, we performed more than 1600 raindrop impact simulations and provide a detailed statistical analysis on the ejected droplets. Using typical sizes and velocities of real-world raindrops – parameter ranges that are very challenging for 3D simulations – we simulate straight impacts with various raindrop diameters as well as oblique impacts. We find that a 4mm diameter raindrop impact on average ejects more than 167 droplets. We show that these droplets indeed contain microplastic concentrations similar to the ocean water within a few millimeters below the surface. To further assess the plausibility of our simulation results, we conduct a series of laboratory experiments, where we find that microplastic particles are indeed contained in the spray. Based on our results and known data – assuming an average microplastic particle concentration of 2.9 particles per liter at the ocean surface – we estimate that, during rainfall, about 4800 microplastic particles transition into the atmosphere per square kilometer per hour for a typical rain rate of 10 mm h $10 \frac {\text {mm}}{\mathrm {h}}$ and vertical updraft velocity of 0.5 m s $0.5 \frac {\mathrm {m}}{\mathrm {s}}$