The Method Of Quasi-specular Elements To Reduce Stochastic Noise During Illuminance Simulation

When simulating the propagation of light, luminance/ radiance brought by a ray is calculated from the optical properties of the scene objects it interacts with. According to their optical properties, objects can be roughly divided into diffuse and specular. In Monte Carlo ray tracing luminance/radiance is calculated only for diffuse surfaces. When a ray hits a specular a surface, it is reflected (or refracted) until it reaches a diffuse surface, and only then the luminance/radiance is calculated. In the proposed approach, diffuse elements are further divided into genuine diffuse and quasi-specular elements. The most natural criterion for the latter is that it scatters light in a narrow cone about the specular direction. An element of the scene can also be a superposition of both types when its scattering function is a sum of the genuine diffuse and quasi-specular parts. This article shows how different components of illuminance/irradiance interact with quasi-specular objects and describe how this works in the bi-directional stochastic ray tracing. The proposed approach significantly reduces stochastic noise for multiple scenes. This method is also applicable for simulation of volume scattering, treating the phase function of the medium as quasi-specular. In this case, the choice of quasi-specular objects is not based on the nature of the bidirectional scattering distribution function (BSDF): the medium is treated as completely quasi-specular while the surfaces, even if their BSDFs are narrower, remain genuine diffuse. The article shows the advantage of this approach.

Influence of surface effects on neutron skin in atomic nuclei

The influence of the diffuse surface layer of a finite nucleus on the mean square radii and their isotopic shift is investigated. We present the calculations within the Gibbs - Tolman approach using the experimental values of the nucleon separation energies. Results are compared with that obtained by means of a direct variational method based on Fermi-like trial functions.

Understanding coastal wetland conditions and futures by closing their hydrologic balance: the case of the Gialova lagoon, Greece

Coastal wetlands and lagoons are under pressure due to competing demands for freshwater resources and climatic changes, which may increase salinity and cause a loss of ecological functions. These pressures are particularly high in Mediterranean regions with high evaporative demand compared to precipitation. To manage such wetlands and maximize their provision of ecosystem services, their hydrologic balance must be quantified. However, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components. To overcome this difficulty, we developed a mass balance approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova lagoon, southwestern Peloponnese, Greece. Our approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates over a study period of 2 years (2016–2017). While water exchanges were dominated by evaporation and saline water inputs from the sea during the summer, precipitation and freshwater inputs were more important during the winter. About 40 % and 60 % of the freshwater inputs were from precipitation and lateral freshwater flows, respectively. Approximately 70 % of the outputs was due to evaporation, with the remaining 30 % being water flow from the lagoon to the sea. Under future drier and warmer conditions, salinity in the lagoon is expected to increase, unless freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies. This restoration strategy would be fundamental to stabilizing the current wide seasonal fluctuations in salinity and maintain ecosystem functionality but could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon.

Understanding coastal wetland conditions and futures by closing their hydrologic balance: the case of Gialova lagoon, Greece

Coastal wetlands and lagoons are under pressure due to competing demands for freshwater resources and climatic changes, which may increase salinity and cause loss of ecological functions. These pressures are particularly high in Mediterranean regions with high evaporative demand compared to precipitation. To manage such wetlands and maximize their provision of ecosystem services, their hydrologic balance must be quantified. However, multiple channels, diffuse surface water exchanges, and diverse groundwater pathways complicate the quantification of different water balance components. To overcome this difficulty, we developed a mass balance approach based on coupled water and salt balance equations to estimate currently unknown water exchange fluxes through the Gialova lagoon, SW Peloponnese, Greece. Our approach facilitates quantification of both saline and freshwater exchange fluxes, using measured precipitation, water depth and salinity, and estimated evaporation rates over a study period of two years (2016–2017). While water exchanges were dominated by evaporation and saline water inputs from the sea during the summer, precipitation and freshwater inputs were more important during the winter. About 40 % and 60 % of the freshwater inputs were from precipitation and lateral freshwater flows, respectively. Approximately 70 % of the outputs was due to evaporation, with the remaining 30 % being water flow from the lagoon to the sea. Under future drier and warmer conditions, salinity in the lagoon is expected to increase, unless freshwater inputs are enhanced by restoring hydrologic connectivity between the lagoon and the surrounding freshwater bodies. This restoration strategy would be fundamental to stabilize the current wide seasonal fluctuations in salinity and maintain ecosystem functionality, but could be challenging to implement due to expected reductions in water availability in the freshwater bodies supporting the lagoon.