1,720,969 research outputs found
Chemical and isotopic analysis using diode laser spectroscopy: applications to volcanic gas monitoring
No full textSeasonal Variation of aerosols properties in South Italy: a study on aerosol optical depths, Angstrom turbidity parameters and aerosol size distributions
No full textDirect solar radiation measurements, carried out from June 2001 to October 2001 in a site in South Italy, have been analysed. This site is characteristic of a continental area but it can be affected by the intrusion of marine and dust particles. Solar irradiance was measured using a high-resolution spectroradiometer, working in the visible range (400–800 nm), collecting about 500 spectra under cloudless conditions. From the aerosol optical depths we estimated the Angström turbidity parameters, by means of a least-square fitting procedure. Finally, a Twomey modified inversion technique allowed us to estimate the aerosol size distribution, obtaining mostly two-modal functions. Integrating the second mode of the aerosol size distribution, it was surprising to find a high correlation with the β parameter only for data corresponding to low turbidity conditions
Seasonal variation of the correlation between round-based optical depth and TOMS Aerosol Index in South of Italy
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High precision measurements of CO2 concentration in air by means of diode-laser absorption spectroscopy near 2 μm
No full textIntercomparison between spectral databases using REFIR/BB and BOMEM MR100 down-welling spectra in the range 450-900 cm-1
No full textGround based Fourier Transform Spectrometer (FTS) observations from two field campaigns in the 2004 summer have been considered in this study and compared to calculations. Synthetic spectra radiance has been obtained using an up-to-date line-by-line radiative transfer model along with three different spectral databases: HITRAN2000, HITRAN2004 and GEISA2003. Observations
have been recorded with two FTS, which cover different spectral ranges. It has been found that synthetic radiance computations fit quite well to the data, even though the goodness of the fit depends on the spectral database. In particular, differences in the spectral residual behaviour appear in the short wave part of water vapour rotational band (450-600 cm-1). In this range GEISA2003 provides almost the same results as those of HITRAN2000, while HITRAN2004 shows a mixed behaviour: better than the first two in a large region of the spectral range, but worse at very few specific wave numbers. On overall, HITRAN2004 yields the highest consistency with the observations. Sensitive differences appear also between HITRAN (both) and GEISA for the CO2 Q-branches at 620 cm-1, 720 cm-1 and 792 cm-1
High-precision measurements of CO 2 concentration in air by means of diode-laser absorption spectroscopy near 2 μm
No full textA compact and portable laser-based sensor has been developed for absolute measurements of CO2 concentration with high precision and accuracy, in air samples at atmospheric pressure. A DFB diode laser, operating near 2 mum at room temperature, was used. It was tuned into resonance with the R(34) line of the nu (1)+nu (degrees)(2)+nu (3) combination band. The laser beam was fiber-coupled in order to allow remote operation. Severe tests of the spectrometer were done using certified air mixtures, with the aim to determine its performance. Applications to atmospheric monitoring were discussed. Particularly, the suitability of our spectrometer for measuring soil CO2 efflux was demonstrated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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