The enthalpies of absorption and solubility at T=298.15 K of carbon dioxide in aqueous solutions of bis-(3-dimethylaminopropyl)amine (CAS RN: [6711-48-4]) are reported in
this paper. It was observed that the saturation loading of the CO2 is α=2.9 mol CO2/mol TMBPA, which is close to the theoretical value, α0=3 mol CO2/mol TMBPA. The molar heat of absorption of CO2 is independent of the polyamine concentration of the solutions and the amount of CO2 absorbed and was calculated to be ΔabsHm=–44 (2) kJ mol–1 CO2.
Biogas generally contains significant quantities of carbon dioxide in addition to methane. A bubbling column reactor operating
at atmospheric pressure is proposed for cheap separation and a Mettler RC1 reaction calorimeter was used to build a simplified
empirical model for measuring the molar heat of solubility of CO2 in aqueous solutions of monoethanolamine (MEA). Determinations were performed in 12 mass% MEA solutions regenerated at atmospheric
pressure and reflux temperature for 3 h. Flows of CO2 from 174 to 917 mL min−1 were used at a reactor temperature of 283 to 353 K.
Geometric progression fitting method has been used to compute energy absorption build-up factor of teeth [enamel outer surface,
enamel middle, enamel dentin junction towards enamel, enamel dentin junction towards dentin, dentin middle and dentin inner
surface] for wide energy range (0.015–15 MeV) up to the penetration depth of 40 mean free path. The dependence of energy absorption
build-up factor on incident photon energy, penetration depth, electron density and effective atomic number has also been studied.
The energy absorption build-up factors increases with the penetration depth and electron density of teeth. So that the degree
of violation of Lambert–Beer (I = I0e−μt) law is less for least penetration depth and electron density. The energy absorption build-up factors for different regions
of teeth are not same hence the energy absorbed by the different regions of teeth is not uniform which depends on the composition
of the medium. The relative dose of gamma in different regions of teeth is also estimated. Dosimetric implication of energy
absorption build-up factor in teeth has also been discussed. The estimated absorption build up factors in different regions
of teeth may be useful in the electron spin resonance dosimetry.
The operation of neutron generating tubes is presented. The real system is described. Some aspects of reversible absorption of hydrogen isotope by metals are analyzed. A model describing decisive phenomena and letting us to avoid undesirable situations is proposed. Analogies with other chemical systems are pointed out.
A method to obtain mass absorption coefficients of -articles in multielement substances is described. This method is based on a theoretical formula of the mass absorption coefficient. Mass absorption coefficient of compounds calculated by this method are in good agreement with earlier measurements and methods of computation.
A preliminary pulse radiolytic study is reported on transient optical absorption spectra in solid amino acids. Spectra have been obtained by improved Cherenkov Light Self-absorption Method applied during 5.5 s pulses of 10 or 13 MeV linac electrons. Amino acids exhibit a very different type of behaviour: from lack of absorption signal (at the present sensitivity of the system) to strong absorptions in the visible part of the spectrum and the near UV. The absorption may be due to the electron trapped in lattice imperfections or to the formed free radical. Comparison of spectra in a variety of preparations (hydrochlorides, salts of amino acids and sets of related compounds) suggests a free radical origin of spectra. All transient absorption disappear within a fraction of a second. Free radicals turn by deamination and/or decarboxylation into more stable species detected by ESR.
As part of an extended study of the absorption of uranium in life structures,some experiments on the uranium absorption in cultures of Saccharomices cerevisiaewere carried out. Using the wet ashing Arsenazo III method the absorbed weightof uranium in dregs dry cells was determined.
A statistical interpretation of the transmission vs. thickness curves indicates that the traditional mass absorption coefficient consists of two terms: one is the mass attenuation coefficient (MAC), the second depends on the central moments of the MAC. A theory of the mass attenuation coefficient is proposed. The theoretical results are in agreement with experiments. Comments on the shell effect have been presented.
We have investigated the effects of scattering and absorption in neutron beam activation analysis experiments, both by direct measurement and by Monte Carlo simulation. Significant sensitivity enhancements occur for thin disks placed at 45° to the beam but very much smaller effects occur for spheres. The agreement between measurement and calculation is generally good.
Authors:N. Ben Ezzine, M. Barhoumi, K. Mejbri, and A. Bellagi
Summary This paper deals with the modeling, thermodynamic analysis and comparison of irreversibility in two configurations of the double generator absorption chiller. First a computer simulation model is developed for each configuration on the basis of mass and energy balances. Simulation results were then used to analyse the entropy generation and irreversibility (or exergy destruction) of each component. It is found that the parallel flow configuration is more powerful than the serie flow configuration. Exergy losses in the parallel flow configuration are lower than that of the serie flow. The results indicate that the absorber and the solution heat exchangers have the most potential to improve the chiller energy efficiency. Also they indicate that focusing on irreversibility is more direct way of analysing the potential for improving the efficiency of ammonia-water absorption chiller.