http://hdl.handle.net/10174/37664 2026-11-12T23:22:38Z http://hdl.handle.net/10174/42712 Title: Compound fire–meteorology extremes drove megacity air pollution during the 2024 South American fire season Authors: Duarte, de Souza Fernandes Duarte; Rémy, Samuel; Elias, Thierry; Costa, Maria João; de Arruda Moreira, Gregori; Guerrero-Rascado, Juan Luis; Bortoli, Daniele; Salgado, Rui; Hoelzemann, Judith Johanna Abstract: Extreme air pollution increasingly threatens major cities, yet the relative roles of urban emissions and biomass-burning smoke transported across multiple spatial scales remain difficult to quantify. Here, we investigate three multi-day pollution extremes that affected São Paulo State during the 2024 South American fire season, when daily fine particulate matter (PM2.5) reached 80–100 μg m−3 in the Metropolitan Area of São Paulo. We combined surface observations, aerosol optical thickness measurements, backward trajectories, and controlled global atmospheric simulations differing only in fire-emission representation to quantify the biomass-burning contribution. Simulations without fire emissions failed to reproduce the observed PM2.5 and carbon monoxide (CO) peaks, whereas fire-attributable PM2.5 increments reached 17–21 μg m−3 at the state scale and the ensemble-mean cumulative metropolitan fire-attributable burden reached ∼547 μg m−3 day across E1–E3 combined. The three events revealed contrasting source–receptor configurations: regional and longer-range transport combined with weak receptor ventilation during E1 (15–24 August), greater fire activity during E2 (29 August–5 September) produced a comparatively weaker receptor response under less persistent transport pathways, and E3 (7–15 September) occurred when intense fire activity across multiple spatial scales coincided with favourable transport configurations, anomalous heat and dryness, and weak ventilation. Fire-emission configurations producing larger aerosol enhancements generally showed better agreement with observations, although all inventories underestimated the most extreme episode. These results show that megacity pollution can arise from the combined effects of biomass-burning emissions, atmospheric transport, and adverse meteorological conditions, while highlighting substantial sensitivity to fire-emission representation in operational atmospheric-composition systems. 2026-10-06T23:00:00Z http://hdl.handle.net/10174/42699 Title: Brazilian heatwaves are shifting towards dry-hot thermodynamic regimes in transformed landscapes Authors: Duarte, de Souza Fernandes Duarte Abstract: Heatwaves are intensifying globally, but their impacts depend strongly on the atmospheric moisture conditions under which extreme heat occurs. We show that Brazilian heatwaves underwent preferential dry-hot amplification during 1990–2024. Hourly ERA5 reanalysis was converted into daily thermodynamic diagnostics to classify general, humid, dry-hot, and compound dry-hot/stagnant heatwaves. General heatwaves showed widespread increases in frequency, cumulative duration, and intensity, whereas humid-heatwave trends were weak and spatially fragmented. Dry-hot heatwaves intensified coherently across central and southeastern Brazil, including the Cerrado, MATOPIBA, the southern Amazon–Cerrado transition, Pantanal, and parts of the Caatinga/Semi-arid region. Using a common Tmax-only severity metric, dry-hot amplification exceeded humid amplification across much of Brazil, with a positive DHW − HHW contrast over 73.6% of the country. This pattern was spatially associated with increasing vapour-pressure deficit and declining relative humidity. Cumulative landscape state was more consistently associated with the DHW − HHW contrast than recent land-cover change, although landscape–atmosphere relationships were regionally heterogeneous. VPD decomposition showed that atmospheric drying reflected both warming-driven increases in saturation demand and regional changes in actual vapour pressure, rather than a uniform decline in atmospheric moisture. Spatially robust controlled models supported positive associations among transformed land, evaporative demand, and dry-hot amplification, while accounting for spatial dependence and without implying causality or mediation. The DHW − HHW contrast remained positive under alternative VPD and wet-bulb thresholds, although its magnitude was sensitive to minimum event duration. Temporal tests showed that recent extremes strengthened, but did not generate, the multi-decadal dry-hot signal. Brazilian heatwave trends therefore show preferential amplification under dry-hot conditions, with implications for vegetation water stress, agriculture, ecosystem vulnerability, and fire-conducive weather. 2026-09-16T23:00:00Z http://hdl.handle.net/10174/42359 Title: Modeling and Simulation of GaSb/GaAs Quantum Dot Solar Cells in SILVACO TCAD Authors: Haque, Md Ekramul; Ahmed, Md Tofael; Tlemçani, Mouhaydine Abstract: GaSb/GaUtilizing type-II band alignment to increase sub -bandgap absorption and possibly exceed the Shockley–Queisser efficiency limit, quantum dot solar cells (QDSCs) offer an attractive solution for third - generation photovoltaics. In this work, a GaSb QD-embedded GaAs p-i-n solar cell structure is mathematically modeled using the SILVACO TCAD Atlas simulator. An effective medium approximation is used to describe the quantum dot area, and modified Shockley–Read–Hall recombination parameters are used to model intermediate band states. Under AM1.5G illumination, the effects of QD layer count, dot density, and doping concentration on J_SC, V_OC, fill factor, and total power conversion efficiency are carefully examined. Deltadoping and surface passivation have been suggested as mitigation techniques, and results confirm increased infrared photocurrent collection together with a V_OC deficit ascribed to interface recombination. Standard empirical models are used to incorporate temperature-dependent material properties to guarantee physical accuracy under all operating situations. For the experimental design of high-efficiency GaSb/GaAs QDSCs, the simulation framework provides a solid basis. 2026-07-07T23:00:00Z http://hdl.handle.net/10174/42358 Title: Review of different types of solar cooling system for photovoltaic panel Authors: Olarewaju, Taiwo Olatowale; Ahmed, Md Tofael; Tlemçani, Mouhaydine Abstract: Photovoltaic panels generate electrical energy from sunlight, but they lose efficiency as the temperature exceeds 25°C (STC). For each degree Celsius rise, they may lose efficiency by 0.4-0.5%. This paper reviews various solar cooling technologies used in photovoltaic panels, their models, impacts of temperature on them, and efficiency increases according to some studies done recently. The main purpose of this paper is to compile information that could be used to develop extensive research on solar cooling technologies for photovoltaic panels. Passive cooling does not use any additional energy and is economical and straightforward to deploy. Some examples are radiative cooling by using special paint that dissipates heat into space, evaporative cooling by using water evaporation (effective in arid areas), natural convection cooling using fin-based or heat sinkbased systems, and phase change material (PCM), which absorbs and releases heat to maintain temperature control. However, passive cooling technologies have fewer cooling capabilities under extremely high temperatures. The active cooling system works with the help of pumps or fans to improve the cooling process. The water-based PV/T (hybrid cooling) system utilizes the flow of water behind or at the back side of the panel in order to generate both electrical and hot water. This approach may lead to electrical efficiency of up to 10- 20% and thermal efficiency of up to 50-60%. Moreover, there are other active cooling methods including forced air flow, spraying/jetting impingement and nanoparticle-based fluid cooling (nanofluid, Al2O3 or CuO). The hybrid andadvanced cooling systems include thermoelectric, floating PV panels, microchannel or heat pipe methods. Higher temperatures cause lower voltage and power output of the PV modules. Several studies show that effective cooling helps to decrease the panel's temperature of 10-49°C, resulting in increasing electrical efficiency of 5-47%. Hybrid PV/T systems are widely used due to generating both electricity and heat with efficiency being more than 60%. Modeling of the system is typically carried out via application of energy balance equation, CFD analysis or with TRNSYS or MATLAB software programs. Important parameters are solar radiation, ambient temperature, flow rate and material properties. The cooling techniques can significantly improve the efficiency and life of solar PV panels. The passive cooling technique is appropriate for cheap cases whereas the active and hybrid types have higher efficiency. Further studies for obtaining low cost, durability, and efficiency in different climatic regions is also conducted. 2026-07-05T23:00:00Z