781 |
Mid-IR Absorption Cross-Section Measurements of HydrocarbonsAlrefae, Majed Abdullah 05 1900 (has links)
Laser diagnostics are fast-response, non-intrusive and species-specific tools perfectly applicable for studying combustion processes. Quantitative measurements of species concentration and temperature require spectroscopic data to be well-known at combustion-relevant conditions. Absorption cross-section is an important spectroscopic quantity and has direct relation to the species concentration. In this work, the absorption cross-sections of basic hydrocarbons are measured using Fourier Transform Infrared (FTIR) spectrometer, tunable Difference Frequency Generation laser and fixed wavelength helium-neon laser. The studied species are methane, methanol, acetylene, ethylene, ethane, ethanol, propylene, propane, 1-butene, n-butane, n-pentane, n-hexane, and n-heptane.
The Fourier Transform Infrared (FTIR) spectrometer is used for the measurements of the absorption cross-sections and the integrated band intensities of the 13 hydrocarbons. The spectral region of the spectra is 2800 – 3400 cm-1 (2.9 – 3.6 μm) and the temperature range is 673 – 1100 K. These valuable data provide huge opportunities to select interference-free wavelengths for measuring time-histories of a specific species in a shock tube or other combustion systems. Such measurements can allow
developing/improving chemical kinetics mechanisms by experimentally determining reaction rates.
The Difference Frequency Generation (DFG) laser is a narrow line-width, tunable laser in the 3.35 – 3.53 μm wavelength region which contains strong absorption features for most hydrocarbons due to the fundamental C-H vibrating stretch. The absorption cross-sections of propylene are measured at seven different wavelengths using the DFG laser. The temperature range is 296 – 460 K which is reached using a Reflex Cell. The DFG laser is very attractive for kinetic studies in the shock tube because of its fast time response and the potential possibility of making species-specific measurements.
The Fixed wavelength helium-neon (HeNe) laser at 3.39 μm is used to measure the absorption cross-section of the fuels mentioned above. The dependence on temperature, pressure and bath gas (helium, argon and nitrogen) is also examined. The temperature and pressure ranges of this study are 296 – 800 K and 250 – 1000 Torr, respectively. These are the first measured cross-sections at HeNe laser wavelength that are applicable at combustion-relevant conditions.
|
782 |
Microplastics in the Gulf of Bothnia, SwedenA comparison between Österfjärden and Örefjärden.Overgaard, Emma January 2021 (has links)
Microplastics are emerging pollutants in the marine environment, including a range of polymers modified by varying quantities of additives and sorbed pollutants, differing in size, colour, and shape. This study focuses on characterization and quantification through visual characterization of microplastics >300 μm in surface water and at 5-meter depth in the Gulf of Bothnia. A comparison between a reference area and an urban impact area was made to estimate if the water is more polluted near rural or industrial areas. The visual characterization was based on general guidelines provided by GESAMP to minimize the risks of identifying false positives. The concentrations of microplastics were found to be similar in the current study in comparison to other studies in the Baltic Sea. There was insufficient evidence to conclude a difference between the reference area and the urban impact area. A key finding in this study was that fragments, i.e. irregular shaped hard particles having appearance of being broken down from a larger piece of litter were the most abundant type of microplastics particles found. The vast majority of the identified polymers by ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy) consisted of Polyethylene (PE) and Polystyrene (PS)
|
783 |
Sensitive Mid-IR Laser Sensor Development and Mass Spectrometric Measurements in Shock Tube and FlamesAlquaity, Awad 01 November 2016 (has links)
With global emission regulations becoming stringent, development of new combustion technologies that meet future emission regulations is essential. In this vein, this dissertation presents the application of sensitive diagnostic tools to validate and improve chemical kinetic mechanisms that play a fundamental role in the design of new combustion technologies.
First, a novel high sensitivity laser-based sensor with a wide frequency tuning range (900 – 1000 cm-1) was developed utilizing pulsed cavity ringdown spectroscopy (CRDS) technique. The novel laser-based sensor was illustrated by measuring trace amounts of multiple combustion intermediates, namely ethylene, propene, allene, and 1-butene in a static cell at ambient conditions. Subsequently, pulsed CRDS technique was utilized to develop an ultra-fast, high sensitivity diagnostic to monitor trace concentrations of ethylene in shock tube pyrolysis experiments. This diagnostic represented the first ever successful application of CRDS technique to transient species measurements in a shock tube. The high sensitivity and fast time response (10μs) diagnostic may be utilized for measuring other key neutrals and radicals which are crucial in the oxidation chemistry of practical fuels.
Secondly, a quadrupole mass spectrometer (QMS) was employed to measure relative cation mole fractions in atmospheric and low-pressure (30 Torr) flames of methane/oxygen diluted in argon. Lean, stoichiometric and rich flames were 4 examined to evaluate the dependence of ion chemistry on flame stoichiometry. Spatial distribution of cations was compared with predictions of an existing ion chemistry model. Based on the extensive measurements carried out in this work, modifications were suggested to improve the ion chemistry model to enhance the fidelity of such mechanisms. In-depth understanding of flame ion chemistry is vital to model the interaction of flames with electric fields and thereby pave the way to enable active combustion control for increased efficiency and reduced emissions.
Finally, a compact fast time-response time-of-flight mass spectrometer (TOFMS) was coupled to the shock tube through a pin-hole end-wall to enable timeresolved species concentration measurements. This diagnostic tool was demonstrated by investigating the decomposition of 1,3,5-trioxane over a wide range of shock conditions. Reaction rate coefficients were extracted by the best fit to the experimentally measured species time-histories. TOF-MS coupled to the shock tube is an ideal diagnostic tool for developing kinetic mechanisms for future fuels due to its ability to simultaneously measure several species during fuel pyrolysis/oxidation processes.
|
784 |
Bezdotykové měření povrchových teplot při obrábění / Contactless measurement of surface temperatures when machiningŠťáva, Radek January 2008 (has links)
Contactless measuring of surface temperature integration in the other measurement methods and their assimilation at evaluation of surface temperature of a semi-finished product bored by various tools is the target of the work. An impassable opening is being bored by these tools. The opening is close to a scanned wall. The semi-finished wall temperatures are being scanned by thermocamera and subsequently compared for every single used tool in this experiment.
|
785 |
Bezdotykové měření povrchových teplot ve strojírenství / Contactless measurement of surface temperatures in mechanical engineeringFrňka, Tomáš January 2009 (has links)
The subject of this thesis is the incorporation of the contactless temperature measurement of surface temperatures among other methods of temperature measurement with the analysis of (individual) advantages and disadvantages. The study is focused on the measurement and finding alternative protective clingfilms for thermo camera “Flir SC2000” and possible ways of their usage.
|
786 |
Bezdotykové měření povrchových teplot v průběhu frézování / Contactless measurement of surface temperatures during millingKmenta, Michal January 2011 (has links)
This Master's theses deals with the contactless measurement of surface temperatures and incorporates it among other methods of temperature measurement. For practical experiments were used infrared camera ThermaCAM SC 2000 from producer FLIR. The experiment was focused on the area of manufacturing technology – milling. Have been investigated effects of different cutting conditions on the surface temperature of the machined sample and the results are expressed mainly in the charts.
|
787 |
Dekódování binárního kódu do vyšší formy reprezentace / Binary-Code Decoding to a High-Level RepresentationMacko, Lukáš January 2015 (has links)
The thesis deals with reverse techniques in software engineering. It presents practical application of software reverse engineering, used tools and approaches. The topic of instruction decoding is discussed in detail. Two basic methods are presented-linear sweep and recursive descent. Their strengths and weaknesses are highlighted. Subsequently a decompiler developed by AVG Technologies is introduced. The decompiler is retargetable. This feature allows to decompile applications of multiple platforms into various target languages. The aim of the thesis is to design and implement algorithm for decoding binary files into high-level representation. The designed algorithm is based on modified recursive descent algorithm, which uses control flow information. In order to achieve more accurate decoding results, symbol table records and other additional information are used. The proposed algorithm was implemented for the AVG Technologies retargetable decompiler. The tests showed that the implemented algorithm improved the function detection in decoded programs. Furthermore, the implemented solution allows to decode files that could not be analysed using the previous version of the decompiler.
|
788 |
Obesity-related insulin resistance in adolescents: a systematic review and meta-analysis of observational studiesThota, P., Perez-Lopez, F. R., Benítes-Zapata, Vicente A., Pasupuleti, V., Hernandez, Adrian V. 19 January 2017 (has links)
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Insulin resistance is common among obese adolescents; however, the extent of this problem is not clear. We conducted a systematic review of PubMed-Medline, CINAHL, The Web of Science, EMBASE and Scopus for observational studies evaluating components defining insulin resistance (insulin, C-peptide and homeostatic model assessment-insulin resistance [HOMA-IR]) in obese adolescents (12–18 years) versus non-obese adolescents. Our systematic review and meta-analysis followed the PRISMA guidelines. Data were combined using a random-effects model and summary statistics were calculated using the mean differences (MDs). 31 studies were included (n = 8655). In 26 studies, fasting insulin levels were higher in obese adolescents when compared to non-obese adolescents (MD = 64.11 pmol/L, 95%CI 49.48–78.75, p < 0.00001). In three studies, fasting C-peptide levels were higher in obese adolescents when compared to non-obese adolescents (MD = 0.29 nmol/L, 95%CI 0.22–0.36, p < 0.00001). In 24 studies, HOMA-IR values were higher in obese adolescents when compared to non-obese adolescents (MD = 2.22, 95%CI 1.78–2.67, p < 0.00001). Heterogeneity of effects among studies was moderate to high. Subgroup analyses showed similar results to the main analyses. Circulating insulin and C-peptide levels and HOMA-IR values were significantly higher in obese adolescents compared to those non-obese. / Revisión por pares
|
789 |
Generický zpětný překlad programů v bajtkódu do vyšší formy reprezentace / Generic Decompilation of Bytecode into High-Level RepresentationMrázek, Petr January 2013 (has links)
The work describes methods and principles of decompilation, basic information about reverse engineering and its use in both software engineering and engineering in general. Furthermore, it introduces the decompiler developed within the Lissom project at BUT FIT. The goal of the work is to design and implement a retargetable decompiler for bytecode, which extends the original decompiler.
|
790 |
Rekonstrukce datových typů při zpětném překladu kódu / Reconstruction of Data Types for DecompilationMatula, Peter January 2013 (has links)
This document describes methods for a reconstruction of data types in the decompilation problem. It defines the concept of reverse engineering and introduces decompiler developed by the Lissom project. It presents existing methods of reconstruction of the simple and complex data types, and explains in detail approaches based on data-flow analysis and analysis of the memory operation offsets. The core of this thesis is the design of a new technique of reconstructing simple and complex data types, suitable for deployment in a retargetable decompiler environment of the Lissom project. Basic principles of the new technique, its implementation and related changes in decompiler and intermediate language are described. The solution is tested and the conclusion discusses the achievements, shortcomings and direction of the further work.
|
Page generated in 0.023 seconds