The lidar technique is an efficient tool for remote monitoring of the distribution of a number of atmospheric species. We
study measurements of sulphur dioxide emitted from the Italian volcano Mt. Etna. This study is focused on the treatment of
data and on the procedure to evaluate range-resolved concentrations. In order to make an in-depth analysis, the lidar system
was prepared to store measurements of individual backscattered laser pulses. Utilizing these repeated measurements a comparison
of three different methods to average the returned signals is made. In the evaluation process we use local polynomial regression
to estimate the range-resolved concentrations. Here we calculate optimal bandwidths based on the empirical-bias bandwidth
selector. We also compare two different variance estimators for the path-integrated curves: local polynomial variance estimation
and variance estimation based on Taylor approximations. Results show that the method performs well. An advantage compared
to previous methods for evaluation of lidar measurements is that an estimate of the mean squared error of the estimated concentration
can be calculated.
Received: 9 July 2001 / Revised version: 15 November 2001 / Published online: 17 January 2002 相似文献
Atomic oxygen has been detected in a lean acetylene/oxygen flame using the 2p43P2-2p33p3P two-photon transition at 226 nm and fluorescence detection at 845 nm. 相似文献
A new model for the location and distribution of carbonate ions in carbonated apatite was used to assign the IR spectra of A- and AB-carbonated apatites. The percentage of total carbonate as measured by the mass loss in the TGA of these compounds is in good agreement with the percentage obtained by combustion analysis. The decomposition of pure A-type carbonate appears at temperatures of 985–1123 °C, whereas the decomposition of AB-type carbonated apatites occurs in the range of 600–800 °C. This difference is attributed to changes in the environment of channel carbonate brought about by B-type substitution of carbonate for phosphate. In the presence of sodium ions, the channel is changed by substitution of sodium for calcium in order to accommodate the difference between the charge of the carbonate and phosphate ions. A thermodynamic cycle is introduced to rationalize the differences in decomposition temperatures of A- and B-type carbonate. Preferential loss of B-type carbonate upon heating to 600 °C also suggests the migration of B-type carbonate to A-sites.
2 flux measurements from a pulp and paper mill is presented, which shows a very good correlation with in situ measurements
taken at the source.
Received: 21 April 1997/Revised version: 28 July 1997 相似文献
Differential absorption lidar (DIAL) measurements are usually made on single compounds by alternately switching the wavelength between on and off a resonance line. The selection of more than two wavelengths is a mathematical necessity for simultaneous measurement of multiple species or for resolving interference effects between a compound of interest and a background gas such as water vapour or carbon dioxide. This is especially true in the mid-IR region, where many hydrocarbon compounds have important spectral features. We present a method for remote measurement of gas mixtures in the mid-IR region based on a newly developed fast-switching, frequency-agile optical parametric oscillator lidar transmitter. A multivariate statistical procedure has also been applied for this system, which combines a genetic algorithm for wavelength selection with a partial least squares method for identifying individual compounds from their combined absorption spectrum. A calibration transfer is performed for compounds of interest using reference spectra from an absorption spectra database. Both indoor absorption cell measurements and outdoor remote range resolved measurements of hydrocarbon mixtures were performed to explore the performance of the method. PACS 42.62 Fi; 42.79 Qx; 02.50 Sk 相似文献
Extensive fluorescence multispectral imaging of the cathedral and baptistery of Parma, Italy, is reported and discussed. In
particular, the first fluorescence imaging data from protection-treated stony materials were recorded. Fluorescence spectra
were taken with a mobile lidar system scanning the monument surfaces with a frequency-tripled Nd:YAG laser beam from a distance
of about 80 m. For each pixel of the area investigated, a high-spectral-resolution spectrum in the full visible range was
acquired. The principal-component analysis technique was used to obtain thematic maps that outlined areas subject to protective
treatment and biological growth, and other features, such as different types of stones and decoration pigments.
Received: 24 July 2002 / Revised version: 16 January 2003 / Published online: 3 April 2003
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ID="*"Corresponding author. Fax: +39-055/410-893, E-mail: g.cecchi@ifac.cnr.it 相似文献