Results 1 - 10 of 11
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[en] An update of the status of geothermal energy is given. The article presents a case for an increase in the use of environmentally-friendly geothermal energy for generation of electric power: at present, less than 0.25% of the world potential is used. In addition, there is potential for direct use of geothermal fluids. The article explains what is meant by 'geothermal energy,' utilization and production, environmental considerations, and the worldwide potential for geothermal energy
[en] A picture is drawn of the evolution undergone by the researchers' interests since the first 'Round Table on Water Column Separation' of 1971. Some hypothesis are put forward concerning the different roads to the future evolution and activity of the International Working Group. Among these, mention is made of possible extensions to nearby subjects (such as e.g. 'hot transients' in nuclear circuits etc.). Last, some 'free-reins' considerations are advanced concerning the conceptual possibility of an on-line safety control against transient dangers to the circuit
[en] Some general mathematical formulations of the dynamics of gas and vapour bubbles are examined giving particular attention to the cases of spherical symmetry and of uniform field within the bubbles. Together with the basic equations for the velocity, pressure, temperature, gas concentration, in the surounding liquid, the formulation of initial and boundary conditions at the bubble liquid interface and at a large distance from it are carefully taken into consideration. The analysis is particularly useful for the development of specialized numerical methods for a quantitative study of the phenomena of bubble dynamics. Numerical applications deal with the processes of growth and collapse by mass diffusion of gaseous bubbles in liquid gas solutions. The numerical methods here developed are intended for solution of the complete system of equations of bubble dynamics, under general initial and boundary conditions
[en] At the beginning of the 1980s the installed geothermal electric capacity in the world was 1960 MW, rising to 3698.5 MW in 1985, and 5835 MW in 1990. At the beginning of 1993 the installed capacity had reached 5915 MW, an increase of 202% with respect to 1980. The percentage increase in installed capacity worldwide per annum in that same period, however, dropped from 13.5 in the 1980--1984 period to 9.6 in the period 1985--1989 and 0.5 in the 1990--92. Geothermal development has recently assumed a downward trend. There is evidence, however, to believe that the situation will improve in the near future. Based on data from reliable sources, approximately 10,200 MW will be installed throughout the world by the year 2000, increasing 72% with respect to 1993 figures. The greatest increase (167%) is expected in Asia. The percentage increase per annum in the world in the period 1993--2000 should rise to 8.1. Between now and the end of this century one can therefore look forward to a period of recovery in the geothermal industry and a substantial increase in installed electric power
[en] At the beginning of the 1980s the installed geothermal electric capacity in the world was 1960 MW, rising to 3698.5 MW in 1985, and 5835.5. MW in 1990. At the beginning of 1993 the installed capacity had reached 5915 MW, an increase of 202% with respect to 1980. The percentage increase in installed capacity worldwide per annum in that same period, however, dropped from 13.5 in the 1980-1984 period to 9.6 in the period 1985-1989 and 0.5 in 1990-1992. Geothermal development has recently assumed a downward trend. There is evidence, however, to show that the situation will improve in the near future. Based on data from reliable sources, approximately 10,200 MW will be installed throughout the world by the year 2000, increasing 72% with respect to 1993 figures. The greatest increase (167%) is expected in Asia. The percentage increase per annum in the world in the period 1993-2000 should rise to 8.1. (author)
[en] Between 1985 and 1990 the International School of Geothermics of Pisa has held 5 long-term courses, attended by 93 trainees. This paper reports that since 1970, when it began its activity, the Italian geothermal training center has prepared a total of 293 goethermists from 64 countries. Under its present structure the International School of Geothermics organizes short courses and seminars, along with the long-term courses directed mainly at geothermal exploration
[en] We compute the properties of a sample of 221 local, early-type galaxies with a spectral energy distribution (SED) modeling software, CIGALEMC. Concentrating on the star-forming (SF) activity and dust contents, we derive parameters such as the specific star formation rate (sSFR), the dust luminosity, dust mass, and temperature. In our sample, 52% is composed of elliptical (E) galaxies and 48% of lenticular (S0) galaxies. We find a larger proportion of S0 galaxies among galaxies with a large sSFR and large specific dust emission. The stronger activity of S0 galaxies is confirmed by larger dust masses. We investigate the relative proportion of active galactic nuclei (AGNs) and SF galaxies in our sample using spectroscopic Sloan Digital Sky Survey data and near-infrared selection techniques, and find a larger proportion of AGN-dominated galaxies in the S0 sample than the E one. This could corroborate a scenario where blue galaxies evolve into red ellipticals by passing through an S0 AGN active period while quenching its star formation. Finally, we find a good agreement comparing our estimates with color indicators.
[en] We describe the properties of a sample of extremely isolated early-type galaxies (IEGs) selected from the spectroscopic Sloan Digital Sky Survey. Sample galaxies are isolated from nearest neighbors more luminous than MV = –16.5 by a minimum distance corresponding to 2.5 Mpc and 350 km s–1 in redshift space. The candidate IEGs exhibit a number of unusual features as compared to bulge-dominated galaxies in cluster and group environments, including fainter luminosities, blue colors suggesting possible recent star formation, and smaller physical sizes. The paper is the first in a series analyzing this isolated galaxy sample.
[en] We explore the properties of early-type galaxies (ETGs), including ellipticals (E) and lenticulars (S0), in rich environments, such as clusters of galaxies (Virgo and Coma). The L24/LK distribution of ETGs in both Virgo and Coma clusters shows that some S0s have a much larger L24/LK ratio (0.5 to ∼2 dex) than the bulk of the ETG population. This could be interpreted as an enhanced star formation rate in these lenticulars. We compare the optical colors of galaxies in these two clusters and investigate the nature of these sources with a large L24/LK ratio by looking at their spatial distribution within the cluster, analyzing their optical spectra, and looking at their optical colors compared to late-types. We obtain 10 Coma and 3 Virgo early-type sources with larger L24/LK ratios than the bulk of their population. We call these sources mid-infrared enhanced galaxies (MIEGs). In Coma, they are mostly located in the southwest part of the cluster where a substructure is falling onto the main cluster. MIEGs present a lower color than the rest of the ETG sample because of a blue continuum. We interpret the excess L24/LK ratio as evidence for enhanced star formation induced as a consequence of their infall into the main cluster.