Cloud droplet formation at the base of tropical convective clouds: closure between modeling and measurement results of ACRIDICON–CHUVA

Aerosol–cloud interactions contribute to the large uncertainties in current estimates of climate forcing. We investigated the effect of aerosol particles on cloud droplet formation by model calculations and aircraft measurements over the Amazon and over the western tropical Atlantic during the ACRIDICON–CHUVA campaign in September 2014. On the HALO (High Altitude Long Range Research) research aircraft, cloud droplet number concentrations (Nd) were measured near the base of clean and polluted growing convective cumuli using a cloud combination probe (CCP) and a cloud and aerosol spectrometer (CAS-DPOL). An adiabatic parcel model was used to perform cloud droplet number closure studies for flights in differently polluted air masses. Model input parameters included aerosol size distributions measured with an ultra-high sensitive aerosol spectrometer (UHSAS), in combination with a condensation particle counter (CPC). Updraft velocities (w) were measured with a boom-mounted Rosemount probe. Over the continent, the aerosol size distributions were dominated by accumulation mode particles, and good agreement between measured and modeled Nd values was obtained (deviations ≲ 10 %) assuming an average hygroscopicity of κ∼0.1, which is consistent with Amazonian biomass burning and secondary organic aerosol. Above the ocean, fair agreement was obtained assuming an average hygroscopicity of κ∼0.2 (deviations ≲ 16 %) and further improvement was achieved assuming different hygroscopicities for Aitken and accumulation mode particles (κAit=0.8, κacc=0.2; deviations ≲ 10 %), which may reflect secondary marine sulfate particles. Our results indicate that Aitken mode particles and their hygroscopicity can be important for droplet formation at low pollution levels and high updraft velocities in tropical convective clouds.

Filtration Efficiency and Regeneration Behavior in a Catalytic Diesel Particulate Filter with the Use of Diesel/Polyoxymethylene Dimethyl Ether Mixture

Polyoxymethylene dimethyl ether (PODEn) is a promising diesel additive, especially in particulate matter reduction. However, how PODEn addition affects the filtration efficiency and regeneration process of a catalytic diesel particulate filter is still unknown. Therefore, this experimental work investigated the size-dependent particulate number removal efficiency under various engine loads and exhaust gas recirculation ratios when fueling with diesel and diesel/PODEn mixture. In addition, the regeneration behavior of the cDPF was studied by determining the break-even temperatures for both tested fuels. The results showed that the cDPF had lower removal efficiencies in nucleation mode particles but higher filtration efficiencies in accumulation mode particles. In addition, the overall filtration efficiency for P10 particles was higher than that for D100 particles. Positioning the upstream cDPF, increasing the EGR ratio slightly decreased the number concentration of nucleation mode particles but greatly increased that of accumulation mode particles. However, increasing the EGR ratio decreased the removal efficiency of nanoparticles, and this effect was more apparent for the P10 case. Under the same period of soot loading, the pressure drop of P10 fuel was significantly lower than that of diesel fuel. In addition, a significantly lower BET was observed for the P10 fuel, in comparison with D100 fuel. In conclusion, adopting cDPF is beneficial for fueling with P10 in terms of the overall filtration efficiency in the particulate number and the lower input energy requirement for active regeneration. However, with the addition of EGR, the lower filtration efficiencies of nanoparticles should be concerned, especially fueling with diesel/PODEn mixture.

Junctionless Accumulation Mode Ferroelectric FET (JAM-FE-FET) for High Frequency Digital and Analog applications

In this paper, a Junctionless Accumulation Mode Ferroelectric Field Effect Transistor (JAM-FE-FET) has been proposed and assessed in terms of RF/analog specifications for varied channel lengths through simulations using TCAD Silvaco ATLAS simulator, using the Shockley-Read-Hall (SRH) recombination, ferro, Lombardi CVT, fermi and LK models. Major analog metrics like transconductance (gm), intrinsic gain (AV), output conductance (gd), and early voltage (VEA) are obtained for the JAM-FE-FET arrangement. The proposed structure shows an improvement in parameters like gm, Ion/Ioff, Av, TGF by 6.82%, 27.95%, 5.2%, 38.83% respectively. Further, frequency analysis of the proposed device is performed and several critical RF parameters like fT, TFP, GFP, and GTFP have been observed to be enhanced by 6.89%, 11.38%, 13.65%, 12.01% respectively. Thus, the Junctionless accumulation mode ferroelectric FET (JAM-FE-FET) arrangement has been found to have superior analog and RF performance when compared to Junctionless ferroelectric FET(JL-FE-FET). As a result, the JAM-FE-FET device presented here can be contemplated a good contender for applications in high-frequency systems.