1,030 research outputs found
Infrared and Raman studies of thin polymer films
No full text[Keywords:- Waveguide; Raman; Attenuated Total Reflection; Infrared; Polymer Films; Barrier Films; Epoxy; Diffusion; Isocyanate; Crosslinking Agents; Cure Time; Kinetics; Urethane; Film Quality]This thesis describes the experimental work carried out between October l(^st), 1990 and 30th September, 1993, in the Chemistry Department of the University of Durham, in association with Courtaulds Coatings plc, m partial fulfilment of the requirements for the degree of Doctor of Philosophy. The thesis is divided into three sections, namely Theoretical Considerations (three Chapters), Experimental Results (three Chapters) and Discussion of Results (one Chapter). There are also three appendices. The theoretical section presents a working description of Paint Chemistry, Vibrational spectroscopy, Waveguide Raman Spectroscopy, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Diffusion Processes. The experimental section is divided into three chapters. The first describes methods of film preparation and characterisation and includes methods of film thickness determination and the development of an off-line waveguiding rig at the University of Durham. Raman spectroscopic results are detailed in the second chapter, and include waveguide experiments on both single polymer films and laminate systems, some of which are reported for the first time, along with some FT-Raman results, also reported for the first time. The FT-IR ATR spectroscopic results are presented in the third chapter and include some barrier film studies on polymeric laminate systems, plus the study of certain diffusion processes, along with an estimation of the associated diffusion coefficients and some kinetic parameters, occurring in epoxy resins, which are reported for the first time. The discussion section concentrates on a full elucidation of the results, and conclusions that may be drawn from them, and ends with suggestions for future work. Refractive indices quoted, unless otherwise stated, refer to indices measured usmg 632.8 nm radiation, and have been estimated either using previous literature, or with the off-line rig. It is accepted that electric field calculations performed with these values will be slightly different to the actual fields observed in the Raman experiments, due to slightly different refractive indices at 514.5 nm. T in tables, unless otherwise stated, refers to band intensities in absorbance units. Finally, the attention of the reader is drawn to the fact that some of the materials used in the course of this project have no precise structure given. This is due to the fact that some of the substances used are of either a highly complicated and/or confidential nature
Further development and application of laser Raman scattering for the investigation of industrial premixed flames in a high-pressure combustion chamber
No full textDiese Dissertation beschreibt die Anpassung der 1D-Laser-Raman-Spektroskopie an einen Hochdruckbrennkammerprüfstand und die damit ermöglichte Untersuchung industrieller Gasturbinenflammen. Die Durchführung von Hochdruckexperimenten erforderte die Entwicklung einer Brennkammer mit großen optischen Zugängen, den erstmaligen Einsatz eines mobilen Raman-Messsystems am Prüfstand, den Aufbau einer zweidimensional beweglichen Fokussier- und Detektionsvorrichtung sowie die Anpassung des Kalibrierverfahrens an das Druckmodul. Die Weiterentwicklung des Auswerteverfahrens beinhaltete automatische Korrekturen von mechanisch bedingten Dejustagen und von Fehlern im Rohsignal, die durch die Trübung der Brennkammerfenster im Flammenbetrieb verursacht wurden. Bevor das 1D-Raman-Messsystem zum Einsatz kam, wurden die Erdgas-Luft-Flammen eines industriellen Gasturbinenbrenners mit ergänzenden Messtechniken untersucht. Dazu gehörten Strömungsfeldmessungen mit Particle Image Velocimetry (PIV), Untersuchungen der Flammenstruktur anhand der Chemolumineszenz elektronisch angeregter OH-Radikale und der planaren laserinduzierten Fluoreszenz (PLIF) von OH. Der Parameterbereich umfasste Drücke bis 6 bar, thermische Leistungen bis 1 MW und Reynolds-Zahlen bis 1,2·10^5 bei Luft-Äquivalenzverhältnissen zwischen 1,5 und 2,0. Die Ergebnisse der Geschwindigkeitsmessungen zeigen eine große innere Rezirkulationszone, starke turbulente Fluktuationen in den Scherschichten und Hinweise auf einen schnell rotierenden Axialwirbel. Mit den Chemolumineszenzaufnahmen ließ sich analysieren, wie die räumliche Verteilung der Flammenzone auf Variationen der Betriebsparameter reagiert. Die PLIF-Einzelaufnahmen zeigen stark gefaltete Flammenfronten. Anhand der OH-Radikal-Verteilung wurden auch Hinweise darauf gefunden, dass Selbstzündung, lokale Verlöschung und Effekte der Zündverzugszeit eine Rolle bei der Flammenstabilisierung spielen. Nach diesen Voruntersuchungen wurde das 1D-Raman-Experiment aufgebaut und durchgeführt. Im Rahmen dieser Dissertation erfolgten zum ersten Mal quantitative Raman-Messungen an Hochdruckflammen unter anwendungsnahen Bedingungen. Diese lieferten Informationen über die Stoffmengenanteile der Hauptspezies, den Mischungsbruch, die Temperatur und den Reaktionsfortschritt. Zu den Ergebnissen zählen zweidimensionale räumliche Mittelwertverteilungen, einzelschussbasierte statistische Verteilungen und 8 mm lange Einzelschussprofile. Raman-Messungen im Bereich der Brennstoff-Luft-Vormischung erlaubten eine quantitative Analyse der Homogenität der Mischung. Innerhalb der Flammenzone wurde ein hoher Anteil intermediärer thermochemischer Zustände gefunden, deren Temperaturen und chemische Zusammensetzungen zwischen denen von Frischgas und Abgas liegen. Darüber hinaus war es möglich, den Einfluss von Betriebsparametern auf die räumliche Verteilung des Reaktionsfortschritts zu ermitteln. Die gewonnenen Messergebnisse eignen sich zur Validierung numerischer Simulationen.This thesis describes the adaptation of the 1D laser Raman spectroscopy to a high pressure combustor test rig and the investigation of industrial gas turbine flames by the application of this technique. The realization of high pressure experiments required the development of a combustion chamber with large optical accesses, the build-up of a two-dimensionally moveable device for focusing and detection as well as the adaption of the calibration procedure to the pressurized test rig. The further development of the raw data analysis procedure included automatic corrections of mechanically caused misalignments and of raw signal errors that were due to a reduction of the window transparency during flame operation. Before the 1D Raman measurement system was applied, the swirling natural gas / air flames of an industrial gas turbine burner were studied with complementary measurement techniques. These included flow field measurements by Particle Image Velocimetry (PIV), investigations of the flame structure by observation of the chemiluminescence of electronically excited OH radicals and the planar laser-induced fluorescence (PLIF) of OH. The parameter range covered pressures up to 6 bar, thermal powers up to 1 MW and Reynolds numbers up to 1.2·10^5 at air equivalence ratios between 1.5 and 2.0. The results of the velocity measurements show a large inner recirculation zone, strong turbulent fluctuations in the shear layers and indications of a fast rotating axial swirl. The chemiluminescence enabled the analysis of the influence of operating parameter variations on the flame zone’s spatial distribution. The PLIF single exposures showed strongly corrugated flame fronts. Observations of the OH radical distribution corroborated the hypothesis of auto-ignition, local extinction and ignition delay effects playing a role in the flame stabilization. After these investigations, the 1D Raman experiment was built up and conducted. Quantitative Raman measurements at high pressure flames under gas-turbine-relevant conditions were carried out for the first time. They provided information about the mole fractions of the major species, the mixture fraction, the temperature and the reaction progress. All these quantities were obtained simultaneously from single shot measurements. The results include two-dimensional spatial mean value distributions, single-shot-based statistical distributions and 8 mm long single shot profiles. The analysis of premixing of fuel and air revealed the temporal and spatial variations of the mixture fraction present in technically premixed combustors. Inside of the flame zone, a high fraction of intermediate thermochemical states were found. These states exhibit temperatures and chemical compositions that lie between the states of unburned fuel/air mixture and exhaust gas. Furthermore, it was possible to evaluate the influence of the operating parameters on the spatial distribution of the reaction progress. The measurement results can be used for the validation of numerical simulations
ULB17-VT
No full textThis dataset includes Thermal-Visual images with the same aligned geometry taking by FLIR-E60 camera. Images are of size (320 x 240) pixel resolution with 0.05◦C thermal sensitivity and −20◦C to 650◦C. Thermal images were extracted in their raw format and logged in 16-bit float per-pixel in one channel.
The acquisition was made in different scenes and different environments (indoor and outdoor, during winter and summer and with static and moving objects). Thermal and RGB images were manually extracted and annotated with a total of 570 pairs in the original paper.
Due to European regulations about data and privacy protection, Images shows identified faces were excluded from this published version. This published benchmark has 404 pair of images, divided into 280 training samples, 78 validation validation samples and 46 testing samples.
The file 'ULB17-VT.pkl' is saved in Pkl format, using python 3.5 and cPickle.HIGHEST_PROTOCOL and arranged in the following way:
[Train_RGBx, Train_HRx, Train_LRx], [Valid_RGBx, Valid_HRx, Valid_LRx], [Test_RGBx, Test_HRx, Test_LRx]
X_RGBx: Visual RGB image
X_HRx: High-Resolution Thermal image
X_LRx: Low-Resolution 'Gaussian Pyramid' down-sampled Thermal image
This dataset is first presented in the article below, Please cite this paper if the dataset is used in your publication.
@article{almasri2018multimodal,
title={Multimodal Sensor Fusion In Single Thermal image Super-Resolution},
author={Almasri, Feras and Debeir, Olivier},
journal={arXiv preprint arXiv:1812.09276},
year={2018}
}</pre
Eliminating VT uncertainties in modeling ferroresonance phenomena caused by single phase-to-ground faults in isolated neutral network
No full textIt is commonly recognized that correct transformer model (particularly topological one) is a key element for any ferroresonance simulations. This paper represents a line of reasoning by which a reliable model of a voltage transformer (VT) can be constructed given substantial uncertainties in its parameters and characteristics. Starting with catalog data for electric steels and typical leakage inductances of 6-kV VTs, a model of an isolated neutral network with three inductive VTs is initially fitted to reproduce in detail its ferroresonant behavior for a chosen network capacitance. Then, validity of the network model is verified by accurate predictions of ferroresonance processes for all other capacitance values available and thus different ferroresonance modes recorded during full-scale factory tests. Possibilities to simplify the VT model by neglecting dynamic, and then entire core losses and hysteresis are also shown
Single stage electrochemical exfoliation method for the production of few-layer graphene via intercalation of tetraalkylammonium cations
No full textWe present a non-oxidative production route to few layer graphene via the electrochemical intercalation of tetraalkylammonium cations into pristine graphite. Two forms of graphite have been studied as the source material with each yielding a slightly different result. Highly orientated pyrolytic graphite (HOPG) offers greater advantages in terms of the exfoliate size but the source electrode set up introduces difficulties to the procedure and requires the use of sonication. Using a graphite rod electrode, few layer graphene flakes (2 nm thickness) are formed directly although the flake diameters from this source are typically small (ca. 100–200 nm). Significantly, for a solvent based route, the graphite rod does not require ultrasonication or any secondary physical processing of the resulting dispersion. Flakes have been characterized using Raman spectroscopy, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS)
Combined use of Raman spectroscopy, cluster analysis, and SEM-EDS for the characterization of Roman bronze artifacts from Spoletino’s cistern (Civitella D’Agliano, VT)
No full textThis study focuses on chemical and microstructural results on four bronze artifacts, dating back to the 3rd–4th
centuries AD. These artifacts were unearthed in the archaeological site of the Roman Cistern at Spoletino
(Civitella D’Agliano, VT, Central Italy). They were studied using a Reflected Light Microscope, micro-Raman
spectroscopy, SEM-EDS analysis, and cluster analysis, providing reliable and complementary data on the samples.
SEM-EDS results indicated the use of different Cu alloys at the Roman site. Lead was added to improve the
fluidity of the molten bronze in the locked item, while scrap metal containing Zn and leaded bronze were mixed
to produce gunmetal and furniture accessories. A binary Cu-Sn alloy was employed for decorative and cosmetic objects. The corrosion products, identified by micro-Raman spectroscopy, are cuprite (Cu2O), malachite (Cu2(OH)2CO3), hydrocerussite (Pb3(CO3)2(OH)2), and libethenite (Cu2(OH)PO4), reflecting interactions with burial environments. Cluster analysis simplified the interpretation of complex Raman maps, especially in samples with multifaceted corrosion processes that involved overlapping phases. The data confirmed the absence of chloride ions on the patinas and extensive decuprification processes on the external surface, with the diffusion of environmental elements, such as phosphates, towards the bulk metal. A strong correlation was observed between fractured paths and corrosion patterns along artifact edges
Nondestructive ion-implant monitoring using laser Raman spectroscopy
No full text A new Raman technique for monitoring low-dose ion implants is described. The capability for detection of implants of 20– 50 keV B+ (or equivalent [Formula: see text] energies) at doses as low as ~1010 cm−2 is of particular interest. Currently, there are few other noncontact, nondestructive methods of evaluating implant doses below 1013 cm−2 (e.g., Vt-adjust, field, and p-well implants) in patterened production wafers. The feasibility of using the technique for monitoring Vt-adjust implants is demonstrated.Low-energy B+ and [Formula: see text] ion implants in silicon were studied to determine the detection limits of the technique. Samples were analyzed immediately after implantation, without annealing. Implant doses in the range from 3 × 1016 cm−2 to the detection limit of 3 × 1010 cm−2 were characterized in this way. The presence of a surface layer of SiO2 (≤ 100 nm thick) did not interfere with the measurements. A tunable laser was used to optimize the sensitivity to implants of different energies.Since the frequency spectrum of Raman scattering can also provide information on the structure of the damaged region or on the distribution of activated boron and residual ion damage after annealing, Raman spectroscopy shows promise in several applications for in situ process monitoring of ion implantation for very large scale integration technology. </jats:p
First intention epicardial VT ablation : what are the results?
No full textPublished on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2019. For permissions, please email: [email protected]: Ventricular tachycardia (VT) endocardial mapping and ablation may not be sufficient in several arrhythmogenic contexts, because ventricular myocardium may comprise intricate endocardial, intramural and epicardial substract. Thus, epicardial ablation has lately become a complementary and necessary tool to approach some VTs in different types of cardiomyopathies.info:eu-repo/semantics/publishedVersio
The performance enhancement of multibeam adaptive base-station antennas for cellular land mobile radio systems
No full textThe problem of meeting the proliferating demands for mobile telephony within the confinement of the limited radio spectrum allocated to these services is addressed. A multiple-beam adaptive base-station antenna is proposed as a major system component in an attempt to solve this problem. The approach is demonstrated by employing an antenna array capable of resolving the angular distribution of the mobile users as seen at the base-station site, and then using this information to direct beams toward either lone mobiles, or groupings of mobiles, for both transmit and receive modes of operation. The energy associated with each mobile is thus confined within the addressed volume, greatly reducing the amount of cochannel interference experienced from and by neighboring cochannel cells. To ascertain the benefits of such an antenna, the conventional and proposed antenna systems are modeled in a typical mobile radio environment. For a given performance criterion, the theoretical results indicate that a significant increase in the spectral efficiency, or capacity, of the network is obtainable with the proposed antenn
Enhancing flexibility and strength-to-weight ratio of polymeric stents: A new variable-thickness design approach
No full textThis paper presents a new design strategy to improve the flexibility and strength-to-weight ratio of polymeric stents. The proposed design introduces a variable-thickness (VT) stent that outperforms conventional polymeric stents with constant thickness (CT). While polymeric stents offer benefits like flexibility and bioabsorption, their mechanical strength is lower compared to metal stents. To address this limitation, thicker polymer stents are used, compromising flexibility and clinical performance. Leveraging advancements in 3D printing, a new design approach is introduced in this study and is manufactured by the Liquid Crystal Display (LCD) 3D printing method and PLA resin. The mechanical performance of CT and VT stents is compared using the Finite Element Method (FEM), validated by experimental tests. Results demonstrate that the VT stent offers significant improvements compared to a CT stent in bending stiffness (over 20%), reduced plastic strain distribution of expansion (over 26%), and increased radial strength (over 10%). This research showcases the potential of the VT stent design to enhance clinical outcomes and patient care.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and Environmen
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