| 1. |
- Bargigia, Ilaria, et al.
(författare)
-
Diffuse optical techniques applied to wood characterisation
- 2013
-
Ingår i: Journal of Near Infrared Spectroscopy. - : SAGE Publications. - 0967-0335 .- 1751-6552. ; 21:4, s. 259-268
-
Tidskriftsartikel (refereegranskat)abstract
- We propose an optical method for non-invasive characterisation of wood samples based on two optical techniques: time-resolved diffuse optical spectroscopy and gas in scattering media absorption spectroscopy. While the latter is sensitive to gases present inside wood pores, the former extracts information on the bulk material regarding light scattering and absorption. Measurements on spruce samples, cut along different wood fibre directions, are presented to show an example of the advantages of this combined approach: by applying these two non-destructive techniques together, in fact, relevant information on wood such as porosity, permeability and moisture content can be assessed. Furthermore, the chemical composition, internal structure and the anisotropy due to the wood fibres can be investigated.
|
|
| 2. |
- Barup, Kerstin, et al.
(författare)
-
Multi-disciplinary lidar applications
- 2010
-
Ingår i: Laser Applications to Chemical, Security and Environmental Analysis, LACSEA 2010. - 2162-2701. - 9781557528803
-
Konferensbidrag (refereegranskat)abstract
- Lidar is a powerful technique normally associated with atmospheric monitoring. However, lidar techniques, also of the laser-induced fluorescence and laser-induced breakdown spectroscopy varieties, provide many new possibilities in unconventional fields including cultural heritage and ecological applications.
|
|
| 3. |
- Guan, Zuguang, et al.
(författare)
-
Vertical lidar sounding of atomic mercury and nitric oxide in a major Chinese city
- 2010
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 101:1-2, s. 465-470
-
Tidskriftsartikel (refereegranskat)abstract
- Vertical range-resolved measurements of atmospheric pollutants were performed in a major city in southern China, employing a lidar system operating with an optical parametric oscillator transmitter. Recordings of atomic mercury (Hg) and nitric oxide (NO) absorbing in the deep-UV region were taken, yielding concentration profiles only attainable with lidar techniques. In particular, the potential influence of molecular oxygen in low-concentration mercury monitoring was elucidated. Diurnal observations are discussed and presented together with weather parameters.
|
|
| 4. |
- Lou, Xiutao, et al.
(författare)
-
Detection of elemental mercury by multimode diode laser correlation spectroscopy
- 2012
-
Ingår i: Optics Express. - 1094-4087. ; 20:5, s. 4927-4938
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a method for elemental mercury detection based on correlation spectroscopy employing UV laser radiation generated by sum-frequency mixing of two visible multimode diode lasers. Resonance matching of the multimode UV laser is achieved in a wide wavelength range and with good tolerance for various operating conditions. Large mode-hops provide an off-resonance baseline, eliminating interferences from other gas species with broadband absorption. A sensitivity of 1 mu g/m(3) is obtained for a 1-m path length and 30-s integration time. The performance of the system shows promise for mercury monitoring in industrial applications.
|
|
| 5. |
- Lou, Xiutao, et al.
(författare)
-
Multimode diode laser correlation spectroscopy using gas-filled porous materials for pathlength enhancement
- 2012
-
Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 109:3, s. 453-460
-
Tidskriftsartikel (refereegranskat)abstract
- A novel pathlength enhancement approach has been applied in multimode diode laser correlation spectroscopy measurements of gas concentrations. Reference and sample gas cells made of porous polystyrene foam and alumina ceramic, respectively, were employed in proof-of-principle measurements of molecular oxygen. Equivalent pathlengths of 164 and 52 cm were obtained for the reference and sample cells with physical pathlengths of 4 and 1 cm, respectively. With a measurement time of 60 s, a physical-pathlength-integrated sensitivity of 15 ppma <...m was achieved with an enhancement of more than one order of magnitude compared with an open-air setup. Practical application aspects were investigated including gas cell size and light alignment tolerance. This generic approach for pathlength enhancement provides advantages in terms of compactness and robustness.
|
|
| 6. |
- Lou, X. T., et al.
(författare)
-
Simultaneous detection of multiple-gas species by correlation spectroscopy using a multimode diode laser
- 2010
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 35:11, s. 1749-1751
-
Tidskriftsartikel (refereegranskat)abstract
- Simultaneous detection of multiple-gas species has for the first time (to our knowledge) been demonstrated by using a multimode diode-laser-based correlation spectroscopy (MDL-COSPEC) scheme. Concentration measurements of a mixture of CO2 and CO gas were performed by probing overlapping line spectra around 1.57 using an MDL. Species identification and corresponding quantitive analysis were implemented by correlating the recorded absorption signals of the sample gas mixtures with those of the reference gases of particular interest, attaining accuracies of 2% and 1%, respectively. MDL-COSPEC is a generic technique with potential application for simultaneous detection of multiple gases having resolvable narrow lines.
|
|
| 7. |
- Lou, Xiutao, et al.
(författare)
-
Temperature-Corrected Oxygen Detection Based on Multi-Mode Diode Laser Correlation Spectroscopy
- 2013
-
Ingår i: Journal of Spectroscopy. - : Hindawi Limited. - 2314-4920 .- 2314-4939. ; 2013, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- Temperature-corrected oxygen measurements were performed by using multi-mode diode laser correlation spectroscopy at temperatures ranging between 300 and 473 K. The experiments simulate in situ monitoring of oxygen in coal-combustion exhaust gases at the tail of the flue. A linear relationship with a correlation coefficient of -0.999 was found between the evaluated concentration and the gas temperature. Temperature effects were either auto-corrected by keeping the reference gas at the same conditions as the sample gas, or rectified by using a predetermined effective temperature-correction coefficient calibrated for a range of absorption wavelengths. Relative standard deviations of the temperature-correction coefficient calibrated for a range of absorption wavelengths. Relative standard deviations of the temperature-corrected oxygen concentrations obtained by different schemes and at various temperatures were estimated, yielding a measurement precision of 0.6%.
|
|
| 8. |
- Lundin, Patrik, et al.
(författare)
-
Gas Monitoring in Human Body Cavities Using Non-Intrusive Diode Laser Absorption Spectroscopy
- 2012
-
Ingår i: 2012 Asia Communications and Photonics Conference. - : IEEE. - 2162-108X. ; , s. 4-7
-
Konferensbidrag (refereegranskat)abstract
- Diode laser absorption spectroscopy was utilized for non-intrusive assessment of gas content in human body cavities, including intestines and lungs of a new-born, the mastoid bone, and sinus cavities for monitoring sinusitis recovery in adults.
|
|
| 9. |
- Lundin, Patrik, et al.
(författare)
-
Noninvasive monitoring of gas in the lungs and intestines of newborn infants using diode lasers: feasibility study.
- 2013
-
Ingår i: Journal of Biomedical Optics. - 1083-3668. ; 18:12
-
Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT. Preterm newborn infants have a high morbidity rate. The most frequently affected organs where free gas is involved are the lungs and intestines. In respiratory distress syndrome, both hyperexpanded and atelectatic (collapsed) areas occur, and in necrotizing enterocolitis, intramural gas may appear in the intestine. Today, these conditions are diagnosed with x-ray radiography. A bed-side, rapid, nonintrusive, and gas-specific technique for in vivo gas sensing would improve diagnosis. We report the use of noninvasive laser spectroscopy, for the first time, to assess gas content in the lungs and intestines of three full-term infants. Water vapor and oxygen were studied with two low-power diode lasers, illuminating the skin and detecting light a few centimeters away. Water vapor was easily detected in the intestines and was also observed in the lungs. The relatively thick chest walls of the infants prevented detection of the weaker oxygen signal in this study. However, results from a previous phantom study, together with scaling of the results presented here to the typical chest-wall thickness of preterm infants, suggest that oxygen also should be detectable in their lungs.
|
|
| 10. |
- Mei, L., et al.
(författare)
-
Agricultural pest monitoring using fluorescence lidar techniques Feasibility study
- 2012
-
Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 106:3, s. 733-740
-
Tidskriftsartikel (refereegranskat)abstract
- The fluorescence of different types of planthopper (Hemiptera) and moth (Lepidoptera), which constitute important Chinese agricultural pests, was investigated both in situ in a laboratory setting and remotely using a fluorescence light detection and ranging (lidar) system operating at a range of about 50 m. The natural autofluorescence of different species, as well as the fluorescence from insects that had been dusted with fluorescent dye powder for identification were studied. Autofluorescence spectra of both moths and planthoppers show a maximum intensity peak around 450 nm. Bleaching upon long-time laser illumination was modest and did not affect the shape of the spectrum. A single dyed rice planthopper, a few mm in size, could be detected at 50 m distance by using the fluorescence lidar system. By employing various marking dyes, different types of agricultural pest could be determined. We suggest that lidar may be used in studies of migration and movement of pest insects, including studies of their behavior in the vicinity of pheromone traps and in pheromone-treated fields.
|
|
