Optics and Photonics Society of Iran

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Several characteristic emission lines due to the metal target (Cu) were investigated in the presence of radon trace in the atmospheric air using Q-SW Nd:YAG laser induced plasma within the irradiation control chamber. Regarding the previous experiments the emission lines of metal species in (Rn+air) are noticeably enhanced respect to those in the synthetic air, while those peak intensities instantaneously decreases due to radon decay, such that the radon's half-life can be determined by an optical method too. Here we made an attempt to utilize optical methods in order to determine nuclear characteristics accordingly.

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In this paper, a new method for studying of aluminum thick plasma in LTE condition is introduced. The presented method calculates very simple and accurate the plasma parameters such as temperature, particle densities, shock wave expansion and instrumental function of system from the data of the spectral self absorbed lines. The LIBS experiment is done on aluminum sample at atmospheric air by combination of two techniques of spectroscopy and shadowgraphy. It should be mentioned that in this calculation, the plasma parameters can be evaluated exactly when electron density, plasma length and three intensities of spectral lines from specific element were obtained from experiment.

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In this research the results of the analysis of organic gases of acetone, ethanol, methanol, cyclohexane and nonane by using LIBS technique are presented. By focusing a Q-switched Nd:YAG laser at wavelength of 1064 nm on gas inside of a glass chamber containing organic gas and air at atmospheric pressure, plasma radiation is generated. Then, the spectrum of the plasma radiation is analyized by time resolved method in ICCD camera with a delay time of 1 μs. In this paper, the effects ignition and vapor pressure on the spectrum obtained from laser induced plasma of organic gases has been studied.

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Simultaneous LIF and LIBS spectroscopic techniques with acoustic response can be applied to have early and rapid identification of malignant tissues. This capability is due to distinct differences between collected spectra of normal and malignant tissues. For malignant tissue, red shift due to fluorescence peak wavelength in LIF spectroscopy and increase in characteristic emission intensity of Ca and Na and In LIBS technique, has been shown. Moreover an increase has been observed in acoustic impedance of malignant tissue which was in accordance with the former results.

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In this study the design and fabrication of stand-off laser-induced breakdown spectroscopy (LIBS) system in open-path configuration is discussed. The transmitter and the receiver systems in experimental setup are in non-collinear form and so, all optical aberrations are tried to be optimized as much as possible. Laser pulse is focused on the target by an adjustable Keplerian telescope and plasma light of the target is collected by a Newtonian telescope. Laser pulses with temporal length of 10 ns and energies of 80 to 180 mJ are applied for elemental analysis of materials from 20 to 35m distances. The acquired spectra of different samples by our designed system have acceptable signal to noise ratios and show the performance of this system for remote detection of materials.

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In this study, laser induced breakdown spectroscopy is used to investigate the possibility of discrimination of healthy and carious teeth. This feasibility is examined using multivariate statistical analysis called partial least square discriminant analysis (PLS-DA). It is based on atomic and ionic emission lines of LIBS spectra of teeth belonging to P, Ca, Mg, Zn, K, Sr, C, Na, H, O elements. Our results show well discrimination and also prediction of unknown tooth tissues. So, it shows the ability of LIBS in classification of healthy and carious teeth using PLS-DA method and its feasibility in future clinical applications.

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In this work, elements identification in the structure of a typical solid composite propellant and aging effect determination was performed by laser induced breakdown spectroscopy. The presence of all elements of propellant was confirmed by line spectrum identification. Spectrum peaks of CN bounds were observed too. Also, by spectrum recorded comparison on the samples it was found that with aging increasing due to time and temperature increasing, the spectrum peak intensity of CN is decreased.

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In this study, elements in the hair of 25 Isfahanian and Tehranian women was determined by laser induced breakdown spectroscopy to investigate the reason of high velocity growth, trichoptilosis and the effect of dye colors on the hair. Results showed that Nitrogen, Hydrogen and Oxygen levels of colored hairs are more than natural hairs. In addition, direct relations between Calcium level and hair velocity growth and also Sodium level with the trichoptilosis were observed.

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The available elements in the input and output water from household water purifier device were identified by Laser Induced Breakdown Spectroscopy (LIBS) method. The relative intensity of Ca and Mg spectral lines as the main factors of water hardness, decreased in output water compared to input water. Fibers and carbon block filters, which have the most important role in elimination of mineral of water, were studied in both new and used types. Comparison between the new and used filters spectra indicated an increasing in relative intensity in used filters. The results of this research, indicate that with absorption of Ca and Mg by filters, the concentration of these elements in water (water hardness) are reduced after passing through the purifier device.

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In this research, plasma spectrum of aluminized RDX explosives compositions were recorded using the laser induced breakdown spectroscopy (LIBS) method under an argon ambient atmosphere. The atomic lines of Al, C, H, N and O and molecular bands of AlO and CN were identified and relative intensities of Al/O were used to plot calibration curve versus stoichiometric ratios of Al/O. By investigation of the dependence of relative intensity of Al/O to detonation velocity and pressure and by plotting the calibration curve with very good regression coefficient, the capability of LIBS method for determining the explosives parameters of RDX/Al unknown samples are well demonstrated. Also, the results of this research indicate that the energy released in the laser induced plasma of aluminized RDX explosives compositions is related to the heat of explosion and percentage of aluminum.

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In this research, ability of laser induced breakdown spectroscopy (LIBS) with applying support vector machine (SVM) method was evaluated in order to separate Polyvinyl chloride (PVC) from other polymers in recycling process. Intensity ratio of C₂/C and N/C was selected as input variables for SVM and then Radial Basis and Polynomial kernel function and linear function in order to classify 150 data related to different kind of polymers were applied. With polynomial kernel function of degree 2 and 5, polymers were separated correctly with accuracy of 90.5%. The results of this research showed that LIBS method by application of SVM model in separating of PVC from other polymers is successful.

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In this research principal component analysis as one of statistical multivariate analysis methods with aim of reduction dimensions of data and also finding a pattern in laser induced breakdown spectroscopy data in order to classify of samples was applied.At first 5 polymer samples was prepared and then intensity corresponding to 17 wavelengths relating to atomic and ionic lines and molecular bands for each sample as input matrix in PCA method,was selected.The results show that with only 3 output variables from PCA method,analysis polymers can be recognized from each other and also dimensions of data ,was reduced.





 

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In this paper, bacterial samples were investigated using Laser Induced Breakdown Spectroscopy (LIBS). The bacteria studied include non-pathogenic Escherichia Coli and Bacillus Cereus. Bacterial samples were prepared on three form: tablet, powder and thin film on glass substrate. Bacteria samples spectrum were compared with glass substrate spectrum and elements of calcium, magnesium, , phosphorus, sulfur, chlorine, iron, manganese, copper, hydrogen, and CN molecular bonding were observed in the spectra of samples. The results of the spectroscopy investigation show that laser Induced Breakdown Spectroscopy is capable of identification and discrimination bacterial samples.

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In this research, the effect of the detection angle on polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) of Al alloy has been studied. The analysis revealed that there is no significant difference between the polarization degree of the continuum and discrete emission for all detection angles under-investigated. Also, no improvement in signal to background ratio (SBR) was found in PRLIBS compared to the laser-induced breakdown spectroscopy (LIBS).

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In this paper, constituent elements of Escherichia Coli bacterial were investigated and compared using Laser Induced Breakdown Spectroscopy (LIBS). The studied sample is non-pathogenic Specimen of Escherichia Coli that has been cultured in three time phases of growth phase with optical density 0.4, 0.8 and 1.2. Bacterial samples were prepared at each stage of the growth phase, after freezdry are transformed into tablets. Bacteria spectrum are obtained in all three stages of growth phase with standard layout and desktop LIBSCAN100.  Based on the results of spectroscopy under the same experimental conditions, and compared with glass substrate spectrum, elements of calcium, sodium, potassium and CN molecular bonds were observed in the spectra of samples and their relative intensities were compared with each other. The results of the spectroscopy investigation show that laser Induced Breakdown Spectroscopy is capable of identification and discrimination different phases of bacterial growth from each other.

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In this paper, concentration of constituent elements of seven standard aluminum’S alloys is predicted by using statistical methods of support vector regression model (SVR and KSVR) and the combinational method of principal component analysis with support vector regression model (PCA_SVR and PCA-KSVR) in laser induced breakdown laser spectroscopy technique. The results of the analyzes showed that the PCA_KSVR method reported the most accurate concentration with the least error for Fe element.

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Dimensional reduction is a technique used to increase the accuracy of the classification model. In this study, the effect of dimensional reduction by Principle Component Analysis(PCA) and Linear Discriminant Analysis(LDA) on the classification of laser-induced breakdown spectroscopy(LIBS) data of iron-chromiumnickel alloy samples was investigated using the Support Vector Machine(SVM) method with two linear and Radial Basis kernel(RBF) functions. For PCA method, classification results for SVM method with linear and radial kernels were %100 and %98, respectively, and for LDA method, these results were %100 and %68, respectively. The results showed that the PCA method was more effective than the LDA method in this field.