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Investigating the evolution of laser induced plasmas by complementary optical and spectroscopic methods
Buday, Jakub ; Novotný, Karel (referee) ; Pouzar, Miroslav (referee) ; Kaiser, Jozef (advisor)
Laser-Induced Breakdown Spectroscopy (LIBS) is a method of analytical chemistry that provides a qualitative and quantitative sample analysis. As this method has been implemented in more and more applications, certain limitations and drawbacks have been raised from this progress. Some of these limitations are connected to the fact, that the ablation process of a~sample is fast and dynamic and the changes of the plasma plume in time and space are a question of a few microseconds. As this can cause certain limitations in the analysis process, there has been a question of how to minimize or eliminate these problems. For this purpose, supplementary methods have been more and more implemented in the LIBS experiments. The goal is simple, acquire more information from the complex process of the ablation and improve the analytical performance of LIBS, be it in the scope of qualitative or quantitative analysis. Here lies the main motivation of this dissertation thesis. Goal of this thesis was to research, implement and utilize supplementary methods, that could be used in combination with the existing LIBS experimental setup. As a result, direct plasma imaging, shadowgraphy and sound analysis systems have been implemented and streamlined into the typical analytical process. Each of these methods brings certain additional information. For direct plasma imaging, it can be the spacious-temporal morphology of the plasma plume, or the distribution of individual elements within its volume. The Shadowgraphy method can be used to calculate the energy spent on the ablation itself, pointing at the thermal properties of the analyzed sample. Lastly, the sound information from the generated shock wave is connected to the amount of ablated mass. Within this thesis, all of the mentioned supplementary methods were examined, and utilized. Insight into these methods together with the LIBS analysis was done individually for each method as well as from the point of their mutual combination. The theoretical information as well as their background is described and discussed. Moreover, the technical information is discussed and analyzed, be it the implementation of the LIBS experiment, or the actual data analysis process. This work will serve as a foundation for further research in this area, where a selection of these methods will be used in several applications that are already using LIBS but suffer from certain limitations. These methods will be used to mitigate the limitation and to elevate the potential use of the LIBS in certain areas and applications.
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Laser induced breakdown spectroscopy as a technique for elemental analysis of soft biological tissues
Fedra, Vojtěch ; Holub, Daniel (referee) ; Kozáková, Zdenka (advisor)
This bachelor's thesis deals with the optimization of selected measurement parameters for soft tissue analysis using the laser-induced breakdown spectroscopy (LIBS) method. The SNR values (signal-to-noise ratio for spectral ion line Ca II 393,37 nm) were investigated by the LIBS technique for a combination of settings. For the analyses, a laser with a wavelength of 266 nm and a laser with a wavelength of 1064 nm, different values of laser pulse energy, gate delay and for different atmosphere in the ablation chamber (without and with argon purge) were selected. The best results were obtained by using a 1064 nm laser and with argon purge, which led to a significant improvement in SNR. The results of the work are useful for further analysis of soft tissues using the LIBS method.
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Automatic classification of geological samples using Laser-Induced Breakdown Spectroscopy and machine learning
Stříbrná, Klára ; Hrdlička, Aleš (referee) ; Prochazka, David (advisor)
This thesis focuses on creating a database of LIBS spectra from geological samples. These spectra are then used to train a Convolutional Neural Network (CNN)-based classification model for the automatic classification of the samples. The trained models are validated on unknown data and compared in terms of accuracy and training time. The aim of the thesis is to evaluate the potential of combining LIBS with Machine Learning for the automatic classification of geological samples. Current methods are often time-consuming and expensive. LIBS allows for fast chemical mapping and, compared to other methods of chemical analysis used in geology, is relatively inexpensive. Additionally, LIBS can detect light elements (such as Li and Be) that are undetectable by other methods.
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VUV spectrometer for vacuum interaction chamber
Drobil, Tomáš ; Šerý, Mojmír (referee) ; Novotný, Jan (advisor)
This thesis deals with the design of a VUV spectrometer for the Laser-induced breakdown spectroscopy (LIBS) method. A prototype using commercially available components was designed and tested. In addition to the actual development of the optical and mechanical design and the selection of the detector, a thorough research of elements emitting in the VUV region was carried out.
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Enhancement of detection limits in Laser-Induced Breakdown Spectroscopy (LIBS) using nanoparticles
Képeš, Erik ; Prochazka, David (referee) ; Sládková, Lucia (advisor)
This bachelor's thesis describes the options of ehnancing the detection limits of laser-induced breakdown spectroscopy (LIBS). It summarizes different modifications of the classical LIBS apparatus, which are used by methods double-pulsed LIBS (DPLIBS), Townsend effect plasma sectroscopy (TEPS), resonance enhanced LIBS (RELIBS), spark discharge LIBS (SDLIBS), flame-enhanced LIBS (FELIBS), and new ways of sample preparation, such as are used in the method nanoparticle enhanced LIBS (NELIBS). It briefly describes the mechanisms, which are used by each method to reduce the detection limit and it contains an overview of obtained enhancements against the classical method LIBS. It deals with the method nanoparticle enhanced LIBS in more detail and experimentally verifies and studies the effects of nanoparticles of different types and sizes on the emission spectrum of the method LIBS.
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Positioning unit for laser spectroscopy
Brada, Michal ; Mazůrek, Ivan (referee) ; Koutný, Daniel (advisor)
This diploma thesis deals with design of positioning unit for laser spectroscopy and its realization to shape of prototype. The design of positioning unit is based on the analysis of the current state of knowledge in the field of remote laser spectroscopy systems. Precise harmonic drive and worm drive with stepper motors are used to drive. The main parts of positioning unit are designed primarily from duraluminium. The positioning unit will be used for experimental measurements at the Institute of Physical Engineering Faculty of Mechanical Engineering Brno University of Technology. 3D digital prototype and technical drawings were created in Autodesk Inventor 2010.
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Detection of Braking Tracks using Laser-Induced Breakdown Spectroscopy (LIBS) and Laser-Induced Fluorescence Spectroscopy (LIBS + LIFS)
Prochazka, David ; Vémola, Aleš (referee) ; Pína,, Ladislav (referee) ; Kaiser, Jozef (advisor)
The aim of this work is to investigate the potential of Laser-Induced Breakdown Spectroscopy (LIBS) for identification of visually unrecognizable braking tracks. Identification of these tracks is based on different chemical composition of tire tread in comparison to road surface. The investigation was divided in several sequential steps – selection of suitable chemical element and its spectral line for break tracks identification; determination of the limits of detection and threshold intensity respectively for the selected chemical element; verification of LIBS ability to detect braking tracks on a real braking track. This testing braking track was prepared by exactly defined and described conditions. The detection was performed in two ways – laboratory analysis of tire treads particles collected via adhesive tape and in situ analysis via mobile apparatus. Results of both measurements showed that LIBS is able to detect visually unrecognizable braking tracks. Concepts of the devices capable of routine braking tracks identification for both possibilities were introduced.
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Optimization of the experimental parameters for laser induced breakdown spectroscopy (LIBS) of selected plant samples
Prochazka, David ; Novotný, Karel (referee) ; Kaiser, Jozef (advisor)
This diploma thesis describes optimization of the experimental parameters for Laser-induced breakdown spectroscopy of plant samples. First part deals with the theoretical method of LIBS and explains the principles and terms. In the next part there is described device which was used for measurements. Main part of diploma thesis describes creation of program for measurement-automation. Main task of program was to solve the connection of autofocus on the sample with the sample automatic movement. Furthermore are described and elaborated specific measurements for optimization of the experimental parameters for Laser-induced breakdown spectroscopy of plant samples.
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Identification of Relevant Tire Traces in Traffic Accident Place Based on their physical characteristics
Bilík, Martin ; Kovanda, Jan (referee) ; Kledus, Robert (referee) ; Bradáč, Albert (advisor)
The thesis deals with the possibilities of identifying the relevant tire traces at the place of a traffic accident based on their physical characteristics. Braking traces on the road are one of the most important objective elements for accident analysis, their easy and accurate detection is very important for accurate accident assessment. With the increasing technical equipment of vehicles, especially with the introduction of newer generations of braking assistance systems, traces left by the tires become almost invisible to the human eye. It is therefore highly desirable that their detection should be not only as accurate as possible but also as easy and fast as possible, not only for forensic experts, but especially for members of the traffic police departments. In line with the development and introduction of new safety and assistance systems for vehicles should also be the development of means and methods of providing the basis for technical analysis of traffic accidents. Reality shows that the procedures, even if still functional, are practically identical for several decades, are dependent on the subjective capabilities of the documenting person. An essential element of the work, compared to the previously described measurement procedures, is the use of modern methods and devices at the highest known level of knowledge. The aim is to find and verify a simple, accurate, subjectively least influenced detecting method for tire traces on the road. A series of measurements confirmed the possibility of using the thermal camera at the technical level usually available at the place of the accident, under limited atmospheric and time conditions. In addition, laser-induced plasma spectroscopy and rLIBS were used. This method of detecting spotless tire treads can be marked as a minimally feasible documentary and at the same time as fast enough, based on the measurements made and the intended removal of defects of the instrument in the development phase of the prototype.
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Automatic sample tilt compensation for chemical mapping by LIBS
Stříbrná, Klára ; Pořízka, Pavel (referee) ; Prochazka, David (advisor)
This thesis deals with designing an algorithm for slope compensation of a sample examined using the LIBS (Laser-induced breakdown spectroscopy) method. It mainly fucuses on the purpose of elemental mapping. The sample slope noticeably affects the result quality and therefore a demand for a simple and inexpensive solution to this problem appeared that would also be applicable for commercial uses of LIBS.
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