APPLICATION OF ADJOINT CMAQ CHEMICAL TRANSPORT MODEL IN THE ATHENS GREATER AREA: SENSITIVITIES STUDY ON OZONE CONCENTRATIONS

An operational meteorology and air quality forecasting system is currently under development by the Environmental Research Laboratory of NCSR “Demokritos”. The system is based on the meteorological model MM5, the in-house EMISLAB emissions processing system and the chemical transport model CMAQ. It is configured to apply on the Greater Athens Area with a 4-domains nested configuration focusing on a high spatial resolution (1x1 km2) inner domain. The system produces meteorological and air quality predictions for a 72-hours time horizon with 1 hour time step. This paper uses the output of the operational system to apply the CMAQ adjoint for ozone sensitivity calculations, focusing for the two days of 18 and 19 July 2005. In the current study, the calculated ground level ozone concentrations at certain defined locations and times are considered as the “response functional”. Sensitivities of the response functional with respect to the state variables (species concentrations on the grid points and species emissions, e.g., NOX, CO, VOCs) are calculated by running the adjoint model backwards in time (reverse mode). The distribution of the sensitivities in the computational domain, obtained for different times, provides essential information for the analysis: isosurfaces of sensitivities delineate influence regions, i.e., areas where perturbations in some concentrations will result in significant changes in the ozone concentrations in the area of interest at the final time

History effects on nonwetting fluid residuals during desaturation flow through disordered porous media

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Dielectric and thermal response of TiO2 and SiC natural ester based nanofluids for use in power transformers

Summarization: The improvement of dielectric and thermal properties of insulating oils used in High Voltage (HV) equipment has been a key part of research over the last three decades. In this study, a natural ester oil is used as matrix oil and dispersions of two semi-conducting nanoparticles (NPs), titanium oxide (TiO 2 ) and silicon carbide (SiC), are prepared in 0.004 weight percentage ratio (0.004% w/w). In terms of thermal features, thermal diffusivity and thermal conductivity are measured over a large temperature range between 25 and 90 oC . By means of the dielectric properties, the Lightning Impulse Breakdown Voltage (LI BDV) of nanofluids (NFs) is measured and compared to the corresponding ones of the matrix. Moreover, the dielectric constant and dielectric dissipation factor (DDF) are determined for the NF and matrix samples in the frequency range of 1 to 10 6 Hz. The obtained results show that the NF containing SiC NPs is characterized from the greatest increase in thermal conductivity, by 58% with respect to natural ester oil’s, as well as the lowest dielectric constant in both 25 and 90 oC , most likely due to their higher permittivity and thermal conductivity. Lastly, the LI BDV of the same NF is the most enhanced, by 10% relatively to the matrix, while a numerical model in COMSOL Multiphysics is developed and is found to successfully verify the LI BDV results.Presented on: IEEE Acces