In the lidar-dial method, the amount of the water vapor present in the smoke of the vegetable fuel is detected to reduce the number of false alarms. We report the measurements of the smoke backscattering coefficients for the CO2 laser lines 10R20 and 10R18 as determined in an absorption cell for two different vegetable fuels (eucalyptus and conifer). These experimental backscattering coefficients enable us to determine the error to be associated to the water vapor measurements when the traditional first-order approximation is assumed. We find that this first-order approximation is valid for combustion rates as low as 100 g/s.
Forest fires can be the cause of environmental catastrophe, with the natural outcomes of serious ecological and
economic damages, together with the possibility to endanger human safety. At the aim to reduce this catastrophe
several author have been shown that the Laser light scattering can be uses to reveals the particulate emitted in the
smoke. Infact experimental and theoretical investigations have shown that lidar is a powerful tool to detect the tenuous
smoke plumes produced by forest fires at an early stage. In early 90's Arbolino and Andreucci have shown the
theoretical possibility to detect the particulate emitted in atmosphere from smoke forest fire. Vilar at all have shown
experimentally the possibility to measure the density variation in atmosphere due to plume emitted in forest fire event.
Gaudio at all. have already shown that it is possible to evaluate water vapor emitted in smoke of vegetable fuel using a
CO2 dial system.
In this paper a theoretical model to evaluate the capabilities of a lidar system in fire surveillance of wooded areas will
be presented. In particular we intend propose a technique to minimizing the false alarm in the detection of forest fire by
lidar based on a measurement of second components emitted in a combustion process. Usually to detect a fire alarm a
rapid increase of aerosol amount is measured. If the backscattering signal report a peak, the presences of a forest fire
will be probable. Our idea to confirm this hypothesis is measure the second components emitted in a forest fire at the
aim to minimize the false alarm. The simulated measurements of the humidity amount within the smoke plume will be
carried out by means of Raman analysis. Fixing the burning rate of the vegetable-fuels, the maximum range of
detection will be evaluated.
Detection of smoke from forest fire is one of the practical applications of lidar. As it is well known, smoke contains a
large number of small particles of ash or soot, leading to a large backscattering efficiency and consequently favourable
conditions for lidar application.
We have developed a compact mobile lidar system based on Nd:YAG Q-Switched laser source, operating at three
wavelengths: 1064 nm, 532 nm and 355 nm, with emission rate of 10 Hz and pulse duration equal to 5 ns when the laser
operate at the fundamental harmonic and 4 ns for the second and the third ones.
The system has been tested by experimental measurements of the smoke backscattering coefficients carried out in an ad
hoc cell. Since the spatial resolution of laser pulse is smaller than the cell length it has been possible to evaluate the
profile of the smoke backscattering coefficients inside the cell itself. Moreover it has been developed a computational
model for simulating the temporal and spatial evolution of smoke within the cell. These experimental and theoretical data
have been used to optimize the theoretical already developed to study the smoke evolution into the atmosphere.
In this paper measurements of smoke backscattering coefficients into a cell and simulations of smoke evolution will be
presented.
In the present paper feasibility and potential advantages of using diode laser for surgical treatment of cerebral ischemia
and intracranial aneurysms will be evaluated.
At this purpose non linear mathematical model was developed and experimentally validated to investigate the effects of
the changes in tissue physical properties, in terms of operating time, tensile strength and tissue damage during medical
laser application.
The numerical simulations have been carried on by a finite-elements based software package (FEMLAB). In vitro results of human saphenous veins of inferior limbs (n=55) after 799 nm diode laser soldering, combined with an indocyanine green-enhanced, will be presented.
The simulations results and their comparison with experimental measurements will be reported.
Forest fires can be the cause of serious environmental and economic damages. For this reason a considerable effort has been directed toward the forest protection and fire fighting. In the early forest fire detection, Lidar technique present considerable advantages compared to the passive detection methods based on infrared cameras currently in common use, due its higher sensitivity and ability to accurately locate the fire. The combustion phase of the vegetable matter causes a great amount of water vapour emission, thus the water molecule behaviour will be studied to obtain a fire detection system ready and efficient also before the flame propagation. A first evaluation of increment of the water vapour concentration compared to standard one will be estimated by a numerical simulation. These results will be compared with the experimental measurements carried out into a cell with a CO2 Dial system, burning different kinds of vegetable fuel. Our results and their comparison will be reported in this paper.
The DIAL system and the HYPACT model are two useful means to study plume evolution and dispersion. We developed a mobile DIAL system, mounted onto a truck. The DIAL is based on a single TEA CO2 laser source, able to switch between the 'on' and 'off' lines. This set-up allows rapid tuning of the two lines and keeps the misalignment within a range of 0.1 mrad, moderately below the beam divergence. The receiving system is a Newtonian telescope. All the instrumentation and the telescope are located inside the van. A large size scanning mirror, installed on the roof, sends the laser radiation into the atmosphere and, at the same time, it collects the backscattered light. To test all instrumentation, preliminary measurements have been completed to monitor a water vapor plume of a cement factory. The measurements are qualitatively compared against a dispersion plume model run initially from climatological fields.
In this paper we discuss the evolution of water vapor profiles over a complex valley located in Calabria Peninsula, in souther of Italy. This evolution is studied by means of water vapor profiles measurements, based on a CO2 LIDAR/DIAl station and by numerical simulations of the water vapor atmospheric content. The simulations have been performed by the CSU-RAMS mesoscale model. As shown in a previous study, the water vapor profiles evolution over Calabria are strongly affected by the main topographic features even in calm large scale condition, when the interaction between the orography and the large scale winds weakens. Indeed, in calm or nearly calm synoptic scale conditions, a strong sea-breeze and intense mountain valley flow develop over this peninsula determining convergence and updraft over the mountain peaks. In this paper we discuss interesting features in three days of July 2000. These days were characterized by both light winds, fair weather conditions and stronger wind, sky covered conditions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.