Search results for "EVAPORATION"
showing 10 items of 175 documents
Multiphase chemistry in a microphysical radiation fog model—A numerical study
1993
A microphysical radiation fog model is coupled with a detailed chemistry module to simulate chemical reactions in the gas phase and in fog water during a radiation fog event. In the chemical part of the model the microphysical particle spectrum is subdivided into three size classes corresponding to non-activated aerosol particles, small and large fog droplets. Chemical reactions in the liquid phase are separately calculated in the small and in the large droplet size class. The impact of the chemical constitution of activated aerosols on fogwater chemistry is considered in the model simulations. The mass transfer of chemical species between the gas phase and the two liquid phases is treated …
DSC study on hyaluronan drying and hydration
2011
Abstract The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning calorimetry. In the first approach the isoconversional Kissinger–Akahita–Sunose (KAS) method was applied in order to determine actual activation energies of evaporation of pure water and water from concentrated HYA solutions. Since the evaporation is a single-step process, the activation energies for pure water provided results consistent with tabulated values of evaporation enthalpies. In the course of water evaporation from hyaluronan solution a break in increasing enthalpy followed by a decrease below 0.34 g of water per 1 g of HYA was observed. This result confirmed earlier observati…
Physicochemical Investigation of Lightfast AgCl and AgBr Nanoparticles Synthesized by a Novel Solid−Solid Reaction
2003
Small size AgX (X = Br, Cl) nanoparticles have been synthesized by a novel solid−solid reaction performed by mixing two dry dispersions of AgNO3 and KX nanoparticles in AOT/n-heptane solutions. UV−vis investigation ascertained that formation of nanosized particles taking place after the mixing process is fast and complete. Microcalorimetric measurements of the thermal effect coupled with the mixing process suggest the occurrence of confinement effects and adsorption of the surfactant molecules at the nanoparticle surface, hinting at formation of charged nonstoichiometric surfactant-coated nanoparticles. The analysis of SAXS spectra shows that salt-containing AOT reversed micelles are slight…
Heterogeneous nucleation at a wall near a wetting transition: a Monte Carlo test of the classical theory
2009
While for a slightly supersaturated vapor the free energy barrier ΔF(hom)(*), which needs to be overcome in a homogeneous nucleation event, may be extremely large, nucleation is typically much easier at the walls of the container in which the vapor is located. While no nucleation barrier exists if the walls are wet, for incomplete wetting of the walls, described via a nonzero contact angle Θ, classical theory predicts that nucleation happens through sphere-cap-shaped droplets attracted to the wall, and their formation energy is ΔF(het)(*) = ΔF(hom)(*)f(Θ), with f(Θ) = (1-cosΘ)(2)(2+cosΘ)/4. This prediction is tested through simulations for the simple cubic lattice gas model with nearest-nei…
Unprecedented evidence for deep convection hydrating the tropical stratosphere
2008
[1] We report on in situ and remote sensing measurements of ice particles in the tropical stratosphere found during the Geophysica campaigns TROCCINOX and SCOUT-O3. We show that the deep convective systems penetrated the stratosphere and deposited ice particles at altitudes reaching 420 K potential temperature. These convective events had a hydrating effect on the lower tropical stratosphere due to evaporation of the ice particles. In contrast, there were no signs of convectively induced dehydration in the stratosphere.
Sintering of copper nanopowders under hydrogen: an in situ X-ray diffraction analysis.
2003
Abstract The reduction by hydrogen gas of the cuprite layer on copper nanocrystals and the subsequent sintering of the nano-particles were studied using in-situ X-ray diffraction and dilatometry. Spherical nanocrystals produced by evaporation and condensation have an average size of 35 nm, exhibiting a large surface curvature. Each nanoparticle is coated with a 3.5 nm layer of Cu 2 O, which is rough and disordered, as revealed by high-resolution electron microscopy. Reduction by hydrogen of this curved cuprite layer occurs at 363 K, which is ≈65 K lower than is observed on a layer supported by micrometer-sized or bulk copper with a flat surface. The reduction process and its effect on the s…
Exergy analysis and thermoeconomic cost accounting of a CHP steam cycle integrated with MED-TVC desalination
2016
In this paper exergy analysis and thermoeconomic cost accounting of a CHP steam cycle integrated with MED-TVC plant is performed; the purpose is to show how this methodology provides a rational criterion to allocate production costs on electricity and freshwater. After a brief overview on methodology and a description of reference plant, exergy analysis is carried out in order to calculate exergy flows and plant exergetic performance. A detailed description of the adopted thermoeconomic model is given. Cost accounting is performed considering two scenarios: in the first, the concentrated brine is disposed back to sea, thus being its exergy content definitively wasted; in the second, convers…
A cost-effective method for estimating di(2-ethylhexyl)phthalate in coastal sediments.
2013
This study describes the development of a new method for the analysis of di(2-ethylhexyl)phthalate (DEHP) using 0.1-0.3 g of sediment sample, based on matrix solid phase dispersion (MSPD) using C18 as dispersant phase (0.4 g) and acetonitrile-water as eluting solvent (3.4 mL 1:3.25, v/v). No evaporation step is required. 3 mL of extracts were processed on-line by in-tube solid phase microextraction (IT-SPME) coupled to capillary liquid chromatography (CapLC) and diode array detector (DAD). A short analytical column Zorbax SB C18 (35×0.5 mm, 5 μm) provided suitable results. FTIR-ATR was employed for characterizing sediment samples and MSPD procedure. The total analysis time was less than 20 …
Soil Water Content Assessment: Critical Issues Concerning the Operational Application of the Triangle Method
2015
Knowledge of soil water content plays a key role in water management efforts to improve irrigation efficiency. Among the indirect estimation methods of soil water content via Earth Observation data is the triangle method, used to analyze optical and thermal features because these are primarily controlled by water content within the near-surface evaporation layer and root zone in bare and vegetated soils. Although the soil-vegetation-atmosphere transfer theory describes the ongoing processes, theoretical models reveal limits for operational use. When applying simplified empirical formulations, meteorological forcing could be replaced with alternative variables when the above-canopy temperatu…
Towards saturation of the electron-capture delayed fission probability: The new isotopes $^{240}Es$ and $^{236}Bk$
2016
Abstract The new neutron-deficient nuclei 240 Es and 236 Bk were synthesised at the gas-filled recoil separator RITU. They were identified by their radioactive decay chains starting from 240 Es produced in the fusion–evaporation reaction 209 Bi( 34 S,3n) 240 Es. Half-lives of 6 ( 2 ) s and 22 − 6 + 13 s were obtained for 240 Es and 236 Bk, respectively. Two groups of α particles with energies E α = 8.19 ( 3 ) MeV and 8.09 ( 3 ) MeV were unambiguously assigned to 240 Es. Electron-capture delayed fission branches with probabilities of 0.16 ( 6 ) and 0.04 ( 2 ) were measured for 240 Es and 236 Bk, respectively. These new data show a continuation of the exponential increase of ECDF probabilitie…