Il ruolo del “magico numero sette” nella canzone d’autore italiana

peer reviewedCon il presente articolo si vogliono indagare le possibili correlazioni fra la regola milleriana del “Magical Number Seven” e le modalità di produzione e fruizione della canzone d’autore italiana. I dati qui presentati (in accordo con la legge di Miller) permettono di verificare che, in assenza di vincoli metrici autoimposti, le canzoni d’autore mostrano una generalizzata (e dunque cognitiva?) tendenza ad organizzare le sillabe, i versi e le strofe in gruppi delimitati, composti approssimativamente da sette più o meno due elementi

Separation of hydrogen isotopes by cryogenic distillation

The hydrogen element exists naturally in the form of three isotopes, sharing the same number of proton and electron, which is equal to one, but not that of neutrons, which ranges from zero to two. In order, these isotopes are: protium, commonly said light hydrogen and indicated with (_1^1)H or simply H; deuterium, commonly heavy hydrogen indicated with (_1^2)H or D; and tritium, (_1^3)H or T. Naturally, deuterium abundance is 0.0115 per cent, while tritium is rare and radioactively unstable. Protium, deuterium and tritium form diatomic molecules bonding together, which can be homonuclear, H_2, D_2 and T_2, or heteronuclear, HD, HT and DT. Homonuclear molecules can exists in either a ortho modification, oH_2, oD_2, oT_2, or a para modification, pH_2, pD_2, pT_2. Hydrogen has the largest isotope effects principally due to the largest differences in the relative mass of its isotopes. Isotope effects are differences in chemical and physical properties arising from differences in the nuclear mass. In particular, lighter hydrogen molecules are characterized by higher vapour pressures than heavier ones; in other words, lighter molecules are more volatile. Among the isotope separation techniques, distillation is adopted in industrial applications because of the advantages of achieving high separation degrees and of processing large quantities of fluids. Distillation is based on the different vapour pressures of the components to be separate and, hence, it requires the coexistence of liquid and vapour phases. Coexistence occurs in the cryogenic range 10-40 K for molecular hydrogen. The number of cryogenic distillation plants constructed for deuterium and tritium separation is small due to their limited market. One example is the deuterium plant built in Germany in the late 1960s, and another the tritium plant in Canada in late 1980s. Both plants proved the possibility to achieve high purities, exceeding 99.8 per cent, as well as high separation factors. Today, deuterium is employed mostly as constituent of heavy water as neutron moderator for a number of nuclear fission reactors; it is also utilized for the preparation of nuclear weapons or as a non-radioactive tracer in chemical and metabolic reactions. Tritium is used instead as a radioactive tracer in chemistry and biology. Both deuterium and tritium are adopted for the research on the physics of matter and, notably, they have been selected for the future ITER nuclear fusion reactor

Chemical Absorption by Aqueous Solution of Ammonia

Carbon capture is proposed as a viable way of exploiting the fossil resources for power plants and industrial processes. The post-combustion capture by chemical absorption in amine aqueous solutions has been in use in chemical and petrochemical areas for decades. As an alternative, the absorption in aqueous ammonia has received great attention recently. The carbon capture by aqueous ammonia is based on the conventional absorption-regeneration scheme applied to the ternary system CO2–NH3–H2O. It can be implemented in a chilled and a cooled process, depending upon the temperatures in the absorber and, hence, the precipitation of salts. The process simulation can be conducted in two manners: the equilibrium and the rate-based approaches. The specific heat duty is as low as 3.0, for the cooled process, and 2.2 MJ/kgCO2, for the chilled one. Moreover, the index SPECCA is as low as 2.6, for the cooled, and 2.9 MJ/kgCO2, for the chilled one. The overall energy performances from the simulations in the rate-based approach, compared against those in the equilibrium approach, result only slightly penalized. From an economic perspective, the carbon capture via chemical absorption by aqueous ammonia is a feasible retrofitting solution, yielding a cost of electricity of 82.4 €/MWhe and of avoided CO2 of 38.6 €/tCO2 for the chilled process

Experimental investigation on materials and lubricants for sliding-vane air compressors

Abstract. Positive-displacement compressors and, among them, sliding-vane rotary machines are widely used in the compressed air sector. As in many other industrial fields, the efficient utilization of energy has become a major goal also in this sector. The aim of the present activity is the experimental investigation on the influence of two vanes materials (cast iron and aluminium with anodized surface) and of four commercial lubricants (characterized by different formulations and additives concentrations) on the performance of a mid-capacity sliding-vane rotary compressor in a number of operating pressures. The performance is identified by both the volume flow rate and the absorbed mechanical power, evaluated according to the international standard ISO 5167 and ISO 1217. The campaign indicates that the considered lubricants do not affect appreciably the volumetric flow rate. On the other hand, the specific lubricants determine a variation of about 1% of the mechanical power for both materials, while the specific material a variation between 0.9% and 2.6%. The best performance is achieved by aluminium vanes and a synthetic poly-α-olefin lubricant

Modeling And Testing The Thermal Effect Of Lubricating Oil Sprayed In Sliding-Vane Air Compressors Using Pressure-Swirl Nozzles

Positive-displacement compressors and, among them, sliding-vane machines are widely used in the compressed air sector. As in many other industrial fields, the efficient utilization of energy has become a major goal also in this sector. The aim of the present activity is the numerical modeling and the experimental testing of the positive thermal effect due to spraying the lubricating oil inside sliding-vane air compressors using pressure-swirl nozzles. The benefits of proper oil atomization in positive-displacement compressors have been documented already by a number of investigations (Singh and Bowman, 1986; Stosic et al., 1988; Fujiwara and Osada, 1995; Valenti et al., 2013; Cipollone et al. 2014). The novelty of this work resides in the extension of a previous model to describe more accurately the quantity and the diameter distribution of the droplets generated by the nozzles and, consequently, to predict more precisely the heat transfer occurring between the liquid and the gas phase within a compression chamber. The model is applied to a pre-commercial mid-size compressor that is equipped with a number of pressure-swirl nozzles. The numerical data are validated successfully against the measurements of the pressure as a function of the angular position. The results indicate that the specific energy of compression is appreciable reduced with respect to the case of an adiabatic process. The model is applied here to a sliding-vane compressor, but it is general in nature and can be promptly modified for another kind of machine. It may be used also for optimizing type, number and position of the nozzles in order to further improve the performances of air compressors

Rate-based Approaches for the Carbon Capture with Aqueous Ammonia Without Salt Precipitation

The aim of this paper is the evaluation of the influence of the kinetic of the NH3-CO2-H2O reactions in the absorber with respect to the electric power losses due to the steam bleeding from the turbine for the regeneration of the solvent. The results exposed conclude that there are few works about the kinetic of the aqueous reaction of the system NH3-CO2-H2O and data from the literature are not in agreement among them probably due to a dependence of the kinetic constants on the ammonia concentration in the liquid. The kinetic parameters have a strong influence on the specific electric power losses

Modeling of ultra super critical power plants integrated with the chilled ammonia process

Abstract As carbon dioxide anthropogenic generation and climate change appear to be correlated, carbon capture becomes necessary, in particular if applied to coal-fired power plants. The Chilled Ammonia Process (CAP) is a promising technology to be proved for the purpose. This work investigates the integration of Ultra Super Critical (USC) power plants with CAP, conducting a parametric investigation on the design parameters to find the optimum and analyzing then on the details of the power block. The commercial code Aspen Plus and the in-house research code GS are employed. With respect to a reference plant, carbon capture reduces the net electrical power by 19% and the net electrical efficiency by 8.5 percent points. The performance index SPECCA is also utilized. The optimum SPECCA is 3.18 MJ/kg CO 2 , which is to be compared to 4.2 MJ/kg CO 2 for conventional amine

Energy and exergy analyses for the carbon capture with the Chilled Ammonia Process (CAP)

Abstract Post-combustion carbon capture in existing power plants is a strategic technology that can reduce emissions from power generation. The proven approach is scrubbing with amines. However, its drawbacks are energy requirement, 3 to 5 MJ per kg of captured CO 2 , as well as solution corrosion and solvent degradation. An alternative approach is scrubbing with chilled aqueous ammonia. This technology aims at mitigating energy usage and solving corrosion and degradation issues. Here an approximate model of the CO 2 - H 2 O- NH 3 system is coupled with a proposed process to evaluate mass, energy and entropy flows. For 1 kg of captured CO 2 , the simulation yields a steam extraction of 0.59 kg, equivalent to a heat duty exceeding slightly 1.5 MJ and a generation loss approaching closely 0.1 kWh, an auxiliary consumption of 0.1 kWh and a delta of almost 0.18 kWh with respect to the ideal case. Assuming a cost of electricity of 7c/kWh, the sole operation of the capture system totals 14C/ton_ CO 2

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