Dissertations / Theses on the topic 'Enhanced emission'
To see the other types of publications on this topic, follow the link: Enhanced emission.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Enhanced emission.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Liu, Tsung-li. "Plasmonic Cavities for Enhanced Spotaneous Emission." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10868.
Abstract:
The modification of spontaneous emission, i.e. the Purcell effect, with optical cavities has been highly studied over the past 20 years as one of the most important goals for cavity quantum electrodynamics (cQED). The recent development of using surface plasmon resonances to concentrate optical field into sub-wavelength scale further extended cQED research of into a new regime. However, although metallic reflectors are used in some of the earliest demonstrations of cQED, the use of metals is not preferable in high Q optical cavities due to the lossy nature of metals. The presence of metals near an optical emitter also strongly alters its radiation dynamics. As a result, the development of plasmonic cavities brings not only new opportunities but also new problems and challenges. In this thesis we describe four different plasmonic cavity designs along with optical simulations and measurements on them to demonstrate: large spontaneous emission enhancement, controlled mode tuning, and control of the plasmonic band-gap and resonances of high-Q plasmonic cavities for coupling to specific emitters. We hope that our work can guide and inspire researchers who are moving from traditional cavity designs to novel plasmonic devices, helping them to establish design concepts, fabrication criteria, and baselines for characterizing these devices.Engineering and Applied Sciences
2
Day, Christopher M. "Field enhanced thermionic emission from oxide coated carbon nanotubes." Virtual Press, 2006. http://liblink.bsu.edu/uhtbin/catkey/1348860.
Abstract:
A cathode structure was demonstrated that utilizes aligned carbon nanotubes (CNTs) to improve the thermionic electron emission by increasing the field enhancement of the cathode surface. Aligned CNTs were grown on the surface of a tungsten substrate by plasma enhanced chemical vapor deposition. The tungsten-CNT structure was further coated with a thin film of low work function emissive materials by magnetron sputtering. Numerous cathodes with varying CNT morphology and oxide layer thickness were created. The field and thermionic emission of the cathodes were tested in order to study the effects of the surface properties on the emission characteristics. It was observed that the introduction of CNTs into an oxide cathode structure improves both the thermionic and field emission, even in cathodes with relatively low field enhancement factors. Because of the high field enhancement factors that are available for CNTs, there remains a potential for dramatically improved electron emission.Department of Physics and Astronomy
3
Graham, Luke Alan. "Observation of enhanced spontaneous emission in dielectrically apertured microcavities /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
4
Wang, Tong. "Enhanced Field Emission Studies on Nioboim Surfaces Relevant to High Field Superconducting Radio-Frequency Devices." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/29284.
Abstract:
Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling.
The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE.
To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance.
EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m.
To address concerns on the effect of natural air drying process on EFE, a comparative study was conducted on Nb and the results showed insignificant difference under the experimental conditions.
Nb thin films deposited on Cu present a possible alternative to bulk Nb in superconducting cavities. The EFE performance of a preliminary energetically deposited Nb thin film sample are presented.Ph. D.
5
Dimaria, Jeffrey V. "Plasmonic control of light emission for enhanced efficiency and beam shaping." Thesis, Boston University, 2014. https://hdl.handle.net/2144/10981.
Abstract:
Thesis (Ph.D.)--Boston UniversityInGaN alloys and related quantum structures are of great technological importance for the development of visible light emitting devices, motivated by a wide range of applications, particularly solid-state lighting. The InxGa1-xN material system provides continuous emission tuning from the ultraviolet across the visible spectrum by changing the In content. InGaN/GaN quantum wells (QW) also provide an efficient medium for electroluminescence for use as light emitting diodes. It is well known, however, that increasing the In content degrades the internal quantum efficiency of these devices, particularly in the green region of the spectrum. These limitations must be overcome before efficient all-solid-state lighting can be developed beyond the blue-green region using this material system. Recently, the application of plasmonic excitations supported by metallic nanostructures has emerged as a promising approach to address this issue. In this work, metallic nanoparticles (NPs) and nanostructures that support plasmonic modes are engineered to increase the local density of states of the electromagnetic field that overlaps the QW region. This leads to an enhancement of the spontaneous emission rate of the QW region mediated by direct coupling into the plasmonic modes of the nanostructure. Energy stored in these modes can then scatter efficiently into free-space radiation, thereby enhancing the light output intensity. The first section of this thesis concerns the enhancement of InGaN/GaN QW light emission by utilizing localized surface plasmon resonances (LSPRs) and lattice surface modes of metal NP arrays. This work comprises a detailed study of the effect of geometry variations of Ag NPs on the LSPR wavelength, and the subsequent demonstration of photoluminescence intensity enhancement by Ag NPs in the vicinity of InGaN multiple QWs. The second section of this thesis concerns the far-field control of QW emission utilizing metallic nanostructures that support plasmonic excitations. This includes a study of the dispersion and competing effects of a metallic NP-film system, and the demonstration of beam collimation and unidirectional diffraction utilizing a similar geometry. These results may find novel applications in the emerging field of solid-state smart lighting.
6
Unitt, David Christopher. "Enhanced single photon emission from a quantum dot in a semiconductor microcavity." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613784.
7
Bagge-Hansen, Michael. "Enhanced Field Emission from Vertically Oriented Graphene by Thin Solid Film Coatings." W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539623349.
Abstract:
Recent progress and a coordinated national research program have brought considerable effort to bear on the synthesis and application of carbon nanostructures for field emission. at the College of William and Mary, we have developed field emission arrays of vertically oriented graphene (carbon nanosheets, CNS) that have demonstrated promising cathode performance, delivering emission current densities up to 2 mA/mm2 and cathode lifetime >800 hours. The work function (&phis;) of CNS and other carbonaceous cathode materials has been reported to be &phis;∼4.5-5.1 eV. The application of low work function thin films can achieve several orders of magnitude enhancement of field emission.;Initially, the intrinsic CNS field emission was studied. The mean height of the CNS was observed to decrease as a function of operating time at a rate of ∼0.05 nm/h (I 1∼40 muA/mm2). The erosion mechanism was studied using a unique UHV diode design which allowed line-of-site assessment from the field emission region in the diode to the ion source of a mass spectrometer. The erosion of CNS was found to occur by impingement of hyperthermal H and O neutrals and ions generated at the surface oxide complex of the Cu anode by electron stimulated desorption. Techniques for minimizing this erosion are presented.;The Mo2C (&phis;∼3.7 eV) beading on CNS at previously reported carbide formation temperatures of ∼800??C was circumvented by physical vapor deposition of Mo and vacuum annealing at ∼300??C which resulted in a conformal Mo2C coating and stable field emission of 1∼50 muA/mm2. For a given applied field, the emission current was >102 greater than uncoated CNS.;ThO2 thin film coatings were presumed to be even more promising because of a reported work function of &phis; ∼2.6 eV. The fundamental behavior of the initial oxidation of polycrystalline Th was studied in UHV (p<1x10-11 Torr), followed by studies of thin film coatings on Ir and thermionic emission characteristics. Although a work function of 3.3 eV was determined by a RichardDushman plot, activation of the thin film was not achieved at T<1700??C. Rather, the deposited ThO2 film decomposed, surface diffused and aggregated into stable ThO2(111) crystallites.;Thin film ThO2 coatings deposited on CNS initially demonstrated excellent field emission (up to ∼2 muA/mm2) and apparently activated spontaneously without significant thermal energy. Fowler-Nordheim plots suggested a work function of &phis; ∼2.6 eV. Undesired beading and ThO2 surface diffusion away from active emission sites resulted in rapidly deteriorating performance at higher field emission currents. Techniques that should provide a more stable ThO2/CNS conformal coating are presented.;The impact of thin films of Mo2C and ThO2on the magnitude of field emission from carbon nanosheets (CNS) was substantial. For a given field emission current density, J ∼2 muA/mm 2, the necessary applied field for uncoated CNS was ∼12 V/mum, but only ∼8 V/mum when coated with Mo2C (&phis;∼3.7 eV) and ∼5 V/mum when coated with ThO2 (&phis;∼2,6 eV). The mechanism for enhanced emission and the stability of the coatings are discussed, with special focus on the activation of ThO2 thin films. The major limitation observed in these studies has been the difference in surface energy of the graphene and the coatings which resulted in a tendency for the films to bead and separate from active emission sites at elevated currents. Suggested techniques to prevent this unwanted surface diffusion are presented.
8
Gill, Simaranjit Singh. "Controlling diesel NO_x & PM emissions using fuel components and enhanced aftertreatment techniques : developing the next generation emission control system." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3643/.
Abstract:
The following research thesis focuses on methods of controlling nitrogen oxides (NO_x) and particulate matter (PM) emissions emitted from a low temperature diesel exhaust. This involves studying the influence of hydrogen (H₂) on various aftertreatment devices such as hydrocarbon selective catalytic reduction (HC-SCR) over silver-alumina (Ag-Al₂O₃) catalysts for lean NO_x reduction, platinum diesel oxidation catalysts (DOC) for nitrogen dioxide (NO₂) production and passive regeneration methods for the diesel particulate filter (DPF). H₂ was implemented on-board either through diesel exhaust gas fuel reforming or via the simulation of ammonia (NH₃) dissociation. Both methods showed to be very effective in enhancing the activity of a silver HC-SCR catalyst for the reduction of NO_x with conversions reaching 90% with the aid of an upstream DPF. A combined DOC and catalysed DPF (cDPF) configuration proved promising for passive regeneration in the presence of reformed exhaust gas recirculation (REGR). The addition of H₂ over the DOC led to an improved catalyst light-off temperature and increased rate of oxidation for NO₂ production. Implementing filtered EGR (FEGR) removes the hydrocarbon (HC) and soot recirculation penalty, thus minimising particulate growth which results in a significantly reduced engine-out soot emission during exhaust gas recirculation (EGR) and hence, an improved NO_x/soot ratio. Introducing fuel components which enhance the cetane number and oxygenate the diesel fuel allow better control of the NO_x/soot trade-off with improved soot oxidation properties.
9
Nur, Salahuddin. "Towards enhanced radiative emission for optical read-out of donor spins in silicon." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10055928/.
Abstract:
Silicon has several features that make it an attractive platform for implementing quantum information processing (QIP). The unique combination of a mature fabrication technology, extraordinarily long coherence times and high control fidelities of donor spins in isotopically purified silicon have made them good candidates for realising spin based quantum bits. Increased spin-photon coupling has the potential to add additional benefits including efficient optical readout of individual donor spins and even a route to generating entanglement. Efficient optical detection of the donor spin state could provide the missing piece of puzzle to realise long-range qubit couplings and construct quantum networks, however, achieving this in silicon is challenging due to its indirect bandgap. Photonic structures such as solid immersion lenses (SILs), circular Bragg resonators (CBRs), photonic crystal (PhC) cavities etc. can enhance radiative emission and/or its collection up to several orders of magnitude, potentially allowing it to compete with non-radiative processes such as Auger recombination. In this thesis, we report our first steps towards fabricating and characterizing such photonic structures, designed to enhance radiative emission and optical collection from 31P donor bound excitons (D0Xs) in silicon. We have fabricated silicon SILs using a neon focussed ion beam milling system. A bilayer resist based fabrication recipe has also been optimised using relatively inexpensive process materials, which efficiently produces CBRs and PhC cavities with desired optical properties on undoped silicon-on-insulator wafers. The optical properties of the fabricated devices are investigated using cavity reflection measurements. We have measured an absorption limited cavity quality factor (Q) of ∼ 5,000 around 31P D0X emission wavelengths (∼ 1078 nm) for silicon PhC cavities at room temperature. Silicon PhC cavities with such a quality factor (∼ 5,000) and enhanced collection can permit for optically accessing spins at a single or at least few donors level.
10
Liu, Quan. "Enhanced Emission of a Single Quantum Emitter Coupled to a Microcavity and a Nanocavity." Thesis, Troyes, 2021. http://www.theses.fr/2021TROY0029.
Abstract:
Le développement de techniques basées sur une seule molécule au cours des dernières décennies a permis de sélectionner, de suivre et de mesurer directement une molécule individuelle. Dans cette thèse, la dynamique structurelle d'un seul émetteur quantique, servi par l'hypéricine, est caractérisée. En utilisant la microscopie à balayage confocale combinée à des modes laser polarisés radialement / azimutalement, une réorientation tridimensionnelle du moment dipolaire de transition d'une seule molécule est observée. Pour quantifier les propriétés temporelles de la tautomérie, la fonction d'autocorrélation des photons est utilisée pour extraire les fluctuations d'intensité. Les résultats montrent l'influence distincte de l'environnement local, comme la matrice PVA et l'effet de deutération. L'environnement photonique local d'une molécule est modifié par la microcavité / nanocavité. Un changement significatif du taux d'émission radiatif et des spectres de fluorescence est discuté. Il nous permet de mesurer le rendement quantique absolu en utilisant une microcavité accordable. Les résultats montrent la possibilité de contrôler la tautomérisation en modifiant l'environnement photonique. Par la suite, la dissociation moléculaire est discutée par des spectres Raman améliorés en surface à molécule unique bénéficiant de l'amélioration en champ proche de la nanocavité. Une stratégie d'optimisation expérimentale rapide vers une amélioration optimale de la fluorescence est décriteThe development of single molecule-based techniques in the last decades has enabled directly selecting, tracking, and measuring an individual molecule. In this thesis, the structural dynamics of a single quantum emitter, served by hypericin, is characterized. By using confocal scanning microscopy combined with radially/azimuthally polarized laser modes, three-dimensional reorientation of the transition dipole moment of a single molecule is observed. To quantify the temporal properties of the tautomerism, photon autocorrelation function is used to extract the intensity fluctuations. The results show the distinct influence of the local environment, such as PVA matrix and deuteration effect. The local photonic environment of a molecule is modified by the microcavity/nanocavity. A significant change of the radiative emission rate and of the fluorescence spectra is discussed. It allows us to measure the absolute quantum yield by using a tunable microcavity. The results show the possibility of controlling tautomerization by changing the photonic environment. Subsequently, molecular dissociation is discussed by single molecule surface-enhanced Raman spectra profiting from near field enhancement of nanocavity. A fast experimental optimization strategy towards optimal fluorescence enhancement is outlined
11
Pliutau, Dzianis V. "LIBS and LITE Emission Based Laser Remote Sensing of Chemical Species and Enhanced Modeling of Atmospheric Absorption." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3531.
Abstract:
Laser-Induced Breakdown spectroscopy (LIBS) and Laser-Induced Thermal Emission (LITE) emission based laser remote sensing were investigated with the application to the remote measurements of trace chemical species. In particular, UVvisible LIBS and Mid-IR LITE systems were developed and measurements of remote targets and chemical surfaces were studied. The propagation through the atmosphere of the multi-wavelength backscattered LIBS and LITE optical spectrum with atmospheric absorption effects on the returned lidar signal was investigated. An enhanced model of the atmospheric effects on emission-based laser-remote sensing was developed and found to be consistent and in agreement with our experimental results.
LITE measurements were performed which involved heating a remote hard target and recording the vibrational band emission spectra produced. Sample heating was carried out using a 1.5W cw-CO2 10.6 μm wavelength laser, and a 9W cw-diode laser operating at 809nm. The emission spectra over the wavelength range of 8 to 14 μm was observed which can be potentially used to detect and identify chemical composition of the target. LITE spectra of DMMP and DIMP (chemical agent simulants), paints, and energetic materials on various substrates were measured for the first time.
A LIBS study was carried out with a 1.064 μm Nd:YAG laser (10 ns pulses, 50mJ per pulse) and remote LIBS measurements were performed for aluminum, copper, steel and plastics over the spectral range of 200 – 1000nm. LIBS measurements as a function of range were studied, and compared to a modified lidar equation suitable for emission based lidar remote sensing.
A computer simulation model was developed for emission-based LIDAR remote sensing such as LIBS and LITE. This involved the development and modification of atmospheric transmission modeling programs which use the HITRAN, PNNL and other atmospheric spectral databases to model the transmission of the atmosphere over a wide range of wavelengths from the deep-UV near 200 nm to the mid-IR near 14 microns. A comparison of HITRAN simulations with the PNNL database calculated spectra was carried out and used for the first time for improvements of the HITRAN database line intensities. In addition, a Principal Component Analysis (PCA) of the LIBS and LITE lidar return signal as a function of range was performed. This PCA analysis showed, for the first time, the degradation of the chemical selectivity (i.e. identification capability) of the emission lidar system as the range was increased and the effect of atmospheric absorption spectral lines on the propagated LIBS and LITE lidar multi-wavelength spectral signal.
12
Neupane, Suman. "Synthesis and Electron Emission Properties of Aligned Carbon Nanotube Arrays." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1168.
Abstract:
Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs.
In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time, the catalyst activity terminated and the plasma started etching CNTs destructively. CNTs with uniform diameter and length were synthesized on SS substrates subjected to chemical etching for a period of 40 minutes before the growth. The direct contact of CNTs with stainless steel allowed for the better field emission performance of CNTs synthesized on pristine SS as compared to the CNTs synthesized on Ni/Cr coated SS.
Finally, fabrication of large arrays of free-standing vertically aligned CNT/SnO2 core-shell structures was explored by using a simple wet-chemical route. The structure of the SnO2 nanoparticles was studied by X-ray diffraction and electron microscopy. Transmission electron microscopy reveals that a uniform layer of SnO2 is conformally coated on every tapered CNT. The strong adhesion of CNTs with SS guaranteed the formation of the core-shell structures of CNTs with SnO2 or other metal oxides, which are expected to have applications in chemical sensors and lithium ion batteries.
13
Orozco, Nieto Pedro Francisco. "Manufacturing strategy for high current cold field emission cathodes : floating catalyst chemical vapour deposition grown carbon nanotube fibres and films enhanced by laser patterning and laser purification process." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/278104.
Abstract:
The aim of this work is to produce a manufacturing strategy for high current (>10 mA) field emission (FE) devices for military (microwave generation) and civilian (particle accelerator electron beam) applications using carbon nanotubes (CNT) as base material. With a particular focus on the relationship of the laser time pulse duration used for cutting CNTs and how this affects the field emission performance. Material selection for this work was narrowed to CNT as they possess unique characteristics such as: high aspect ratio; high thermal conductivity; high chemical stability and high current carrying capacities up to a theoretical limit of 1,200 MA∙cm-1 making them an ideal material for FE. The CNT material studied in this work is produced in two distinct forms, fibres (∅~7-10 μm) and films (h~30 μm), using a floating catalyst chemical vapour deposition process which produces high quantities of CNT material with mixed mechanical and electrical properties. The material is difficult to handle because of its dimensions and is susceptible to environmental changes i.e. electrostatic forces. In order to reduce the variability in electrical properties, a laser purification process was developed. The process consists of locally irradiating an infra-red (IR) laser several microseconds directly at the material. A percentage is vaporised (mainly non-conductive or defective material) and the remaining CNT material shows very high crystallinity with an increase of up to ten times (G/D ratio > 100) compared to the original material and electron mean free path is increased by an order of magnitude. The production strategy is based on directly coating the CNT material with copper using an electroplating process. This allowed for CNT fibre and film to be easily handled and improved the overall electrical contact. Emitter geometry was customised by a laser cutting process to achieve increased enhancement factor geometries, in this case, triangles with 29 tips whilst reducing FE variability. FE performance was quantified by testing the devices in a continuous DC mode with a sweep up to 1,000 V until the material suffered catastrophic failure. The gap distance between the tip of the triangles and the anode was varied to increase the electric field until failure. FE results using the production strategy improved more than 400% compared to untreated material. Applications for these devices are intended to be in the creation of high energy electron beam lines and generation of high powered directed microwaves.
14
Picardi, Gennaro. "Raman spectroscopy and light emission at metal surfaces enhanced by the optical near field of a scanning tunneling tip." [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/191/index.html.
15
Ren, Zhengen. "Enhanced modelling of indoor air flows, temperatures, pollutant emission and dispersion by nesting sub-zones within a multizone model." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269182.
16
Tai, Chia-Hui. "Trace Elemental Analysis of Ashes in the Combustion of the Binder Enhanced d-RDF by Inductively Coupled Plasma Atomic Emission Spectroscopy." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc501168/.
Abstract:
Incineration is an attractive solution to the problems of disposing of municipal solid wastes and supplying energy. Because up to 25 percent of the waste in refuse-derived-fuel systems is ash, the physical and chemical characteristics of ash become more and more important for its potential impacts and methods suitable for their disposal. Trace elements concentration in ash is of great interest because of its relationship to regulatory criteria under the Resource Conservation and Recovery Act (RCRA) regarding toxicity and hazards. The applications of a microwave oven sample dissolution method has been tested on a variety of standard reference materials, with reproducible and accurate results. Fourteen trace elements, As, Ba, Be, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se, Tl, V, and Zn, from the dissolved ash samples were determined by inductively coupled plasma atomic emission spectrometry.
17
Merritt, Travis Robert. "Optoperforation of Intact Plant Cells, Spectral Characterization of Alloy Disorder in InAsP Alloy Disorder in InAsP Alloys, and Bimetallic Concentric Surfaces for Metal-Enhanced Fluorescence in Upconverting Nanocrystals." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25148.
Abstract:
The techniques of optoperforation, spectral characterization of alloy disorder, and metal-enhanced fluorescence were applied to previously unconsidered or disregarded systems in order to demonstrate that such applications are both feasible and consequential. These applications were the subject of three disparate works and, as such, are independently discussed.
Despite being ostensibly restricted to mammalian cells, optoperforation was demonstrated in intact plant cells by means of successful femtosecond-laser-mediated infiltration of a membrane impermeable dextran-conjugated dye into cells of vital Arabidopsis seedling stems. By monitoring the rate of dye uptake, and the reaction of both CFP-expressing vacuoles and nanocellulose substrates, the intensity and exposure time of the perforating laser were adjusted to values that both preserved cell vitality and permitted the laser-assisted uptake of the fluorophore. By using these calibrated laser parameters, dye was injected and later observed in targeted cells after 72 hours, all without deleteriously affecting the vital functions of those cells.
In the context of alloy disorder, photoluminescence of excitonic transitions in two InAsxP1-x alloys were studied through temperature and magnetic field strength dependencies, as well as compositionally-dependent time-resolved behavior. The spectral shape, behavior of the linewidths at high magnetic fields, and the divergence of the peak positions from band gap behavior at low temperatures indicated that alloy disorder exists in the x=0.40 composition while showing no considerable presence in the x=0.13 composition. The time-resolved photoluminescence spectrum for both compositions feature a fast and slow decay, with the slow decay lifetime in x=0.40 being longer than that of x=0.13, which may be due to carrier migration between localized exciton states in x=0.40.
In order to achieve broadband metal-enhanced fluorescence in upconverting NaYF4:Yb,Er nanocrystals, two nanocomposite architectures were proposed that retrofit metallic nanoshells to these lanthanide-doped nanocrystals. The typical monometallic construction was rejected in favor of architectures featuring Au-Ag bimetallic concentric surfaces, a decision supported by the considerable overlap of the calculated plasmon modes of the metallic structures with the emission and absorption spectrum of the nanocrystals. Furthermore, precursors of these nanocomposites were synthesized and photoluminescence measurements were carried out, ultimately verifying that these precursors produce the requisite upconversion emissions.Ph. D.
18
Masuda, Daisuke. "Enhanced external counterpulsation improved myocardial perfusion and coronary flow reserve in patients with chronic stable angina : Evaluation by 13N-ammonia positoron emission tomography." Kyoto University, 2001. http://hdl.handle.net/2433/150573.
19
Hudák, Igor. "Charakteristické parametry procesu spalování při využití vzduchu s obsahem kyslíku vyšším než 21 %." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230473.
Abstract:
Diplomová práce se zabývá spalováním zemního plynu při využití vzduchu s vyšším obsahem kyslíku (21–46 % kyslíku ve spalovacím vzduchu), tzv. kyslíkem obohaceným spalováním (OEC). Technologie OEC nalezla uplatnění v průmyslu, kde se jsou nároky na zvýšenou produktivitu, dosažení vyšší tepelné účinnosti, zlepšení vlastností plamene, snížení náklady, či zlepšení kvality výsledného produktu. Ačkoliv OEC přináší řadu výhod, je nutné zmínit i nevýhody jako: poškození zařízení, nestejnoměrné zahřívání, narušení plamene, zvýšené emise anebo zpětný zášleh plamene. Zkoušky proběhly na zkušebně hořáků, která umožňuje testovat hořáky nejen na plynná a kapalná paliva, ale i hořáky navržené pro kombinované spalování při maximálním výkonu hořáku 1 800 kW. Při zkouškách byl použit plynový „low-NOx“ hořák se stupňovitým přívodem paliva. V diplomové práci je popsán vliv obsahu kyslíku ve spalovacím vzduchu na emise oxidů dusíku (NOx), teplotu plamene, přenos tepla ze spalin do stěn spalovací komory, a také vlastnosti plamene, zvláště pak jeho stabilitu, tvar a rozměry. Zkoušky proběhly při výkonech 300 kW, 500 kW a 750 kW, přičemž pro výkon 750 kW proběhly testy jak při jednostupňové, tak dvoustupňové konfiguraci.
20
Hedman, Karolina. "Differences in tumor volume for treated glioblastoma patients examined with 18F-fluorothymidine PET and contrast-enhanced MRI." Thesis, Umeå universitet, Institutionen för fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-173693.
Abstract:
Background: Glioblastoma (GBM) is the most common and malignant primary brain tumor. It is a rapidly progressing tumor that infiltrates the adjacent healthy brain tissue and is difficult to treat. Despite modern treatment including surgical resection followed by radiochemotherapy and adjuvant chemotherapy, the outcome remains poor. The median overall survival is 10-12 months. Neuroimaging is the most important diagnostic tool in the assessment of GBMs and the current imaging standard is contrast-enhanced magnetic resonance imaging (MRI). Positron emission tomography (PET) has been recommended as a complementary imaging modality. PET provides additional information to MRI, in biological behavior and aggressiveness of the tumor. This study aims to investigate if the combination of PET and MRI can improve the diagnostic assessment of these tumors. Patients and methods: In this study, 22 patients fulfilled the inclusion criteria, diagnosed with GBM, and participated in all four 18F-fluorothymidine (FLT)-PET/MR examinations. FLT-PET/MR examinations were performed preoperative (baseline), before the start of the oncological therapy, at two and six weeks into therapy. Optimization of an adaptive thresholding algorithm, a batch processing pipeline, and image feature extraction algorithms were developed and implemented in MATLAB and the analyzing tool imlook4d. Results: There was a significant difference in radiochemotherapy treatment response between long-term and short-term survivors’ tumor volume in MRI (p<0.05), and marginally significant (p<0.10) for maximum standard uptake value (SUVmax), PET tumor volume, and total lesion activity (TLA). Preoperative short-term survivors had on average larger tumor volume, higher SUV, and total lesion activity (TLA). The overall trend seen was that long-term survivors had a better treatment response in both MRI and PET than short-term survivors. During radiochemotherapy, long-term survivors displayed shrinking MR tumor volume after two weeks, and almost no remaining tumor volume was left after six weeks; the short-term survivors display marginal tumor volume reduction during radiochemotherapy. In PET, long-term survivors mean tumor volumes start to decrease two weeks into radiochemotherapy. Short-term survivors do not show any PET volume reduction two and six weeks into radiochemotherapy. For patients with more or less than 200 days progression-free survival, PET volume and TLA were significantly different, and MR volume only marginally significant, suggesting that PET possibly could have added value. Conclusion: The combination of PET and MRI can be used to predict radiochemotherapy response between two and six weeks, predicting overall survival and progression-free survival using MR and PET volume, SUVmax, and TLA. This study is limited by small sample size and further research with greater number of participants is recommended.
21
Garcia, Wagner de Oliveira [Verfasser]. "Assessment of enhanced silicate rock weathering feasibility as a soil ameliorant and its influence on other terrestrial negative emission technologies : Bewertung der Machbarkeit einer verbesserten Verwitterung von Silikatgesteinen als Bodenverbesserungsmittel und seines Einflusses auf andere terrestrische Technologien für negative Emissionen / Wagner de Oliveira Garcia." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/1221276433/34.
22
BALDONI, NORA. "Innovations to enhance ecosystem services in mediterranean forage-cereal system." Doctoral thesis, Università Politecnica delle Marche, 2021. http://hdl.handle.net/11566/290869.
Abstract:
Nelle aree del Centro Italia una rotazione colturale convenzionale prevede un prato di lunga durata interrotto da 2-3 anni di colture cerealicole. La decisione di interrompere il prato e, iniziare la coltivazione dei cereali, influenza i servizi ecosistemici (ES) forniti da questo sistema foraggero. La presente ricerca ha voluto indagare quali pratiche possono essere adottate per gestire questa transizione da un punto di vista della mitigazione del cambiamento climatico e di altri ES.
A tal fine sono state effettuate tre sperimentazioni sul campo:
Il 1° esperimento ha voluto valutare se l'interruzione dei prati di erba medica in un clima mediterraneo sia conveniente rispetto al suo prolungamento oltre il 6° anno in termini di ES. I suoi benefici ES possono essere sostituiti dall'aggiunta di un alta dose di biochar prima della crescita di 2 colture di grano successive?
Sono stati esaminati dodici servizi di ES. Il prolungamento dell'erba medica sembra essere la scelta migliore per fornire il maggior numero di ES. L'aggiunta di biochar dopo l'interruzione dell'erba medica non ha mostrato alcun aumento significativo dell'ES, né sulla biodiversità vegetale, la quale è sempre risultata più elevata nelle colture di erba medica.
Il secondo esperimento ha confrontato l'emissione di N2O nel suolo al termine dell'erba medica da parte della lavorazione, seguita dalla crescita del grano, con la continuazione di erba medica a lungo termine.
I risultati hanno indicato che la lavorazione del terreno ha provocato una maggiore emissione di N2O (0,37 g N-N2O ha-1h-1) rispetto a quella dell'erba medica indisturbata (0,14 g N-N2O ha-1h-1). Questa maggiore emissione non è però durata a lungo; dopo un anno le emissioni delle 2 opzioni sono state simili. In conclusione, per ridurre le emissioni di GHG legate al termine dell'erba medica si raccomanda di ritardare la lavorazione sotto luna copertura di erba medica in autunno, poco prima della semina del grano.
Il 3° esperimento è stato effettuato per determinare se l'aggiunta di biochar può ridurre gli effetti dannosi della terminazione dell'erba medica, legati sia all'emissione di GHG che alle proprietà pedologiche. A tal fine ho studiato come un' alta dose di biochar (60 Mg ha-1) influenzi le caratteristiche del suolo e il comportamento di 12 enzimi del suolo legati ai principali cicli degli elementi. Il confronto è stato effettuato nelle 2 colture di frumento che sono state coltivate successivamente dopo l'interruzione dell'erba medica.
I risultati hanno mostrato una leggera tendenza del biochar a promuovere la stabilità degli aggregati del suolo e un aumento della materia organica del suolo. L'incorporazione di biochar, a breve termine, non ha avuto alcun effetto sul pH del suolo, sull' N totale, sul P disponibile e sulle rese di frumento. Il Biochar non ha influenzato gli enzimi, forse a causa della sua alcalinità. Al contrario, la lavorazione per la semina del grano e l'incorporazione di biochar hanno determinato un aumento dell'attività enzimatica, principalmente di quelle legate al ciclo del carbonio.
In conclusione, i risultati confermano gli effetti vantaggiosi del prato di erba medica, che è apparso il raccolto migliore anche se mantenuto per più di 6 anni. La produzione di foraggio potrebbe diminuire, ma i ES che esso fornisce sono sempre superiori a quelli di un sistema cerealicolo.
Per interrompere l'erba medica (a causa di una drastica riduzione della resa della quantità di foraggio), è meglio ritardare l'aratura del grano a fine stagione, per ridurre l'emissione di N2O. L'aggiunta di biochar potrebbe sostituire alcuni dei benefici dell'erba medica, ma questa sperimentazione non ha rivelato alcun effetto significativo del biochar sulla dinamica degli enzimi, probabilmente perché era un biochar legnoso, alcalino, ad alta temperatura distribuito su un terreno alcalino. Il biochar ha invece mostrato un'influenza su alcune caratteristiche chimico fisiche del suolo (stabilità degli aggregati e accumulo di sostanza organica del suolo) che, se confermate a lungo termine, possono essere di fondamentale importanza sulle colline dell'area mediterranea.In rainfed areas of Central Italy a conventional crop rotation includes a long-lasting meadow interrupted by 2-3 years of cereal crops. The decision when to interrupt the meadow and to start the cereal cropping influences the ecosystem services (ES) that are provided by this forage-crop system. The present research wanted to investigate which practices can be adopted to manage this transition from a point of view of climate change mitigation and other ES. Three field experiments were carried out with this scope: The 1st experiment wanted to evaluate whether alfalfa meadow interruption in Mediterranean climate is convenient compared to its prolongation over the 6th year in terms of ES. I wanted to find out if its ES benefits can be replaced by the addition of a high rate of biochar addition before the growing of 2 successive wheat crops. Twelve ES services were examined. Alfalfa prolongation appeared to be the best choice to provide the highest number of ES. Biochar addition after alfalfa interruption didn’t show any significant increase of the ES, nor on plant biodiversity, which always resulted higher in alfalfa crop. The 2nd experiment compared N2O soil emission at the end of alfalfa by tillage followed by wheat growing with the continuation of a long-term alfalfa. The results indicated that tillage provoked a greater N2O emission (0.37 g N-N2O ha-1h-1) than that from undisturbed alfalfa (0.14 g N-N2O ha-1h-1). But this greater emission didn’t last long; after one year the emissions of the 2 options were similar. In conclusion, to reduce the GHGs emission linked to alfalfa termination it is recommended to delay the tillage under of alfalfa vegetation in the autumn, soon before wheat sowing. The 3rd experiment was carried out to determine if biochar addition can reduce the detrimental effects of alfalfa termination linked both to GHG emission and to pedological properties. For this scope I studied how a high rate of biochar (60 Mg ha-1) influences the soil characteristics and the behavior of 12 soil enzymes linked to the main element cycles in the soil. The comparison was made in the 2 wheat crops which were grown subsequently after alfalfa interruption. The results showed a slight tendency of biochar to promote soil aggregate stability and an increase of soil organic matter. Biochar incorporation, in the short term, had no effect on soil pH, Total N, available P and wheat yields. Biochar didn’t influence the enzymes, perhaps because of its alkalinity. Conversely tillage for wheat sowing and biochar incorporation resulted in an increased enzyme activity, mainly of those linked to carbon cycle. As a conclusion, the results confirm the beneficial effects of rainfed alfalfa meadow, which appeared the best crop even if it is kept for more than 6 years. The forage production might decrease, but the ES that it provides, are always higher than those of a cereal-based system. To terminate alfalfa (because of a drastic yield reduction of forage quantity), it’s better to delay the ploughing for wheat late in the season, to reduce the N2O emission. Biochar addition might replace some of the benefits of alfalfa, but this research, didn’t reveal any significant effect of biochar on the enzyme dynamic, probably because it was a woody, alkaline, high temperature biochar spread on an alkaline soil. Instead, it showed an influence on some physical chemical soil characteristics (aggregate stability and soil organic matter build up) that, if confirmed in the long term, can be of paramount importance on the hills of Mediterranean area.
23
Andreiuk, Bohdan. "Self-assembly of ionic fluorescent dyes inside polymer nanoparticles : engineering bright fluorescence and switching." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF027/document.
Abstract:
L’encapsulation dans des nanomatériaux de polymères de colorants ioniques à l’aide de contre-ions hydrophobes volumineux apparaît être une méthode très efficace pour générer des nanoparticules (NPs) fluorescentes ultra-brillantes pour la bioimagerie. Nous avons d’abord étendu cette approche par contre-ions aux colorants cyanine opérant dans la gamme du bleu au proche infra-rouge. A partir de NPs chargés en cyanines, une methode de code-barre multicolore pour le traçage cellulaire à long terme a été développé. Ensuite, le rôle des contre-ions hydrophobes volumineux dans l’auto-assemblage des colorants cationiques à l’intérieur des NPs de polymères a été étudié en testant une large collection d’anions. Nous avons montré qu’une forte hydrophobicité du contre-ion augmente l’encapsulation du colorant, régule son clustering et empêche l’agrégation de nanoparticules, alors qu’une grande taille empêche l’auto-inhibition de fluorescence. Enfin, nous avons introduit les contre-ions à base d’aluminates et de barbiturates, qui sur-performent les tetraphénylborates fluorés. Ce travail procure une base solide au concept d’émission et d’encapsulation augmentées par contre-ions pour la préparation de NPs chargés en colorants fluorescentsEncapsulation of ionic dyes with help of bulky hydrophobic counterions into polymer nanomaterials emerged as powerful method for generating ultrabright fluorescent nanoparticles (NPs) for bioimaging. Here, this counterion-based approach is extended to cyanine dyes, operating from blue to near-infrared range. Based on cyanine-loaded NPs, a multicolour cell barcoding method for long-term cell tracking is developed. Second, the role of bulky hydrophobic counterion in self-assembly of cationic dyes inside polymeric NPs is studied by testing a large library of anions. We show that high hydrophobicity of a counterion enhances dye encapsulation, prevents particle aggregation and tunes dye clustering, while large size prevents dyes from self-quenching. Third, counterions based on aluminates and barbiturates are shown to outperform fluorinated tetraphenylborates. This work provides a solid basis for counterion-enhanced encapsulation and emission concept in preparation of dye-loaded fluorescent NPs
24
Dřímal, Jiří. "Parametry procesu spalování při využití vzduchu s obsahem kyslíku vyšším než 21 %." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231276.
Abstract:
The thesis is focused on the experimental investigation of the oxygen enhanced combustion technology (OEC), which uses the combustion air with higher concentration of oxygen, i.e. more than 21 %. The OEC technology is used in those industrial applications, which requires higher thermal efficiency, increased productivity, improved character of the flame, reduced equipment cost, lower volume of exhaust gases and improved product quality. Although this technology involves a number of advantages, it is appropriate to mention some of its disadvantages such as refractory damage, inconsistent heating, increased pollutant emission or flame disturbance and/or flashback. The combustion tests of OEC were carried out at the burners testing facility that enables to test many types of burners (gaseous, liquid, or combined). The two-staged low-NOx burner fired by natural gas was used during the tests. The observed parameters include the effect of oxygen concentration in the combustion air on the NOx emissions, heat flux into the wall of the combustion chamber, in-flame temperature distribution in the horizontal symmetry plane of the combustion chamber and also the shape and dimensions of the flame. The combustion tests of the air-enrichment, air-oxy/fuel and O 2 lancing OEC methods were carried out at the burner thermal input of 750 kW and air excess of 1,1 for two combustion regimes, namely one-staged and two-staged fuel supply.
25
Morton, Jonathan Andrew Scott. "2D photonic crystals to enhance up-conversion emission for silicon photovoltaics." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3110.
Abstract:
This thesis investigates the application of 2D photonic crystals to enhance the emission of up-conversion layers to improve the efficiency of silicon photovoltaics. Two up-conversion material compositions are of particular interest in this work: erbium doped titanium dioxide (TiO2:Er) and erbium doped yttrium fluoride (YF3:Er). The 2D photonic crystals under investigation are composed of TiO2:Er and air; and YF3:Er and silicon. These nano-structures are investigated using both simulation and experimental methods. Further work in this thesis analyses the properties of the highly conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) for use as a transparent electrode and thin film electrically conductive adhesive for the application of silicon photovoltaics. The design and geometrical parameters for the 2D photonic crystals were optimised through simulations (plane wave expansion and finite-difference time-domain), before the structures were experimentally fabricated and optically characterised. The novel analysis of the refractive index of the prepared up-conversion materials using ellipsometry was a key step in the design of the photonic crystal structures. A maximum photoluminescence enhancement of 3.79 times was observed for the 980 nm emission profile, however this could not be successfully attributed to a photonic crystal effect. The optical, mechanical and electronic properties of PEDOT:PSS were characterised for thin film samples, using novel ellipsometry analysis.
26
Ganesan, Parameshwari. "Investigation of Luminescent Properties in Rare-Earth free Metallophosphonate Hybrid Materials : structural Insights in photophysical studies." Electronic Thesis or Diss., Normandie, 2023. http://www.theses.fr/2023NORMC266.
Abstract:
Durant ce travail de thèse, les propriétés structurelles et photoniques des metallophosphonates luminescents hybrides ont été étudiées en abordant le rôle de leur structure dans les propriétés luminescentes. Les métallophosphonates possèdent différentes coordinations chimiques montrant leurs capacités à former plusieurs centres métalliques ainsi qu’une forte liaison chimique de type P-O-M. L’objective de ce travail est l’étude des matériaux hybrides organiques-inorganiques luminescents dont le composant organique offre une plateforme solide facilement amovible avec divers groupes fonctionnels. Cette étude s’articule sur différents metallophosphonates hybrides synthétisés par voie hydrothermale à l’aide de ligands organiques tels que le fluorène, le thianthrène et l’acide phosphonique avec des éléments alcalino-terreux (Mg, Ca, Sr, Ba) et des métaux de transitions (Mn, Co, Cu, Zn). Ces derniers ont été obtenus en manipulant la nature de la molécule, le nombre de groupes fonctionnels et les propriétés cationiques au sein de la structure. Grace à leurs caractéristiques liés à leurs différents arrangements structurels, les matériaux synthétisés montrent diverses propriétés, notamment la rigidité et la stabilité thermique. De plus, ces matériaux montrent des propriétés de luminescences intéressantes tel que la fluorescence, phosphorescence à température ambiante (PTA), les déplacements bathochrome et hypsochrome, l’émission de type excimère ainsi que l’apparition de nouvelles bandes de luminescence rouge et verte pour certains cations spécifiques. Enfin, la variation des propriétés de composés hybrides en fonction de la structure est discutée, en tenant compte le phénomène d’émission induite par Agrégation (AIE) et d’émission améliorée par agrégation (AEE)This thesis work systematically investigates the structural and photophysical properties of rare-earth-free metallophosphonate hybrid luminescent materials, emphasizing the role of structure in luminescent properties. Metallophosphonates demonstrate exceptional versatility with their coordination chemistry, highlighted by their ability to interact with multiple metal centers and form robust P-O-M metal bonds. We aim to study crystalline organic-inorganic hybrid luminescent materials in which the organic part provides a rigid platform which is easily modifiable with various functional groups. we present various metallophosphonate hybrids synthesized through the hydrothermal route using functionalized organic ligands such as Fluorene, Thianthrene, and Tetraphenylethylene (TPE) phosphonic acid with different alkaline-earth elements (Mg, Ca, Sr, Ba) and transition elements (Mn, Co, Cu, Zn). Different metallophosphonate materials are obtained by manipulating the nature of molecules, the number of functional groups, and the characteristics of cations in the structure. Due to that, the synthesized metallophosphonate hybrid materials exhibit diverse structural properties, including rigidity, thermal stability, and different arrangements like face-to-face or edge-to-face and herringbone stacking patterns. Furthermore, these materials display intriguing luminescent properties, such as Fluorescence, Room Temperature Phosphorescence (RTP), Bathochromic and Hypsochromic shift (red and blue shift), Excimer emission, and other novel green and red luminescence bands, particularly in the presence of specific cations. Lastly, we discuss and explore the interconnection between structural and physical properties including the phenomena of Aggregation Induced Emission (AIE) and Aggregation Enhanced Emission (AEE) for hybrid compounds
27
Adams, Thomas John. "Atmospheric measurements of biogenic and anthropogenic emissions by broadband cavity enhanced absorption spectroscopy." Thesis, University of Leicester, 2016. http://hdl.handle.net/2381/37611.
Abstract:
This thesis describes the quantification of biogenic and anthropogenic trace gases using the highly sensitive spectroscopic technique of broadband cavity enhanced absorption spectroscopy (BBCEAS). This technique uses a high finesse optical cavity to make absorption measurements over extended path lengths within a compact instrument and over wavelength ranges that are sufficiently broad to enable several overlapping absorbers to be quantified simultaneously. Here, BBCEAS was applied to measure I₂ emissions in coastal regions, NO₂ in urban ambient air, and VOC oxidation products during experiments in an atmospheric simulation chamber. Much of the work used a novel, mobile, battery-powered BBCEAS system to measure gas concentrations in very close proximity to their emission sources. The dominant emission source of iodine into the atmosphere in coastal regions comes from intertidal macroalgal beds. Gas-phase iodine chemistry perturbs the HOₓ and NOₓ radical cycles, provides additional sink reactions for tropospheric ozone, and initiates nucleation of new aerosol particles. Results are presented from an extensive laboratory study of I₂ emissions from five species of temperate seaweeds. Time- and species-dependent I₂ emission rates were quantified in studies mimicking the progressive exposure of seaweeds to air around low tide. Seasonal differences in I₂ emission rates were investigated. By deploying the BBCEAS instrument from a boat, I₂ concentrations were also measured directly above Laminaria digitata and Ascophyllum nodosum seaweeds growing in their natural habitat. NOₓ emissions affect urban air quality directly and indirectly (the latter via formation of tropospheric ozone and secondary aerosol). BBCEAS was applied to measure NO₂ and the optical extinction from aerosol particles at locations around the Leicester University campus. BBCEAS results were compared with commercial NOₓ (chemiluminescence) and aerosol instrumentation. The mobile BBCEAS instrument was also deployed to investigate the dispersion of NO₂ from the roadside.
28
Pekárek, Jan. "Katodové nanostruktury v MEMS aplikacích." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217244.
Abstract:
The main goal of this work is to introduce new carbon structures - carbon nanotubes. The main objective of this work is to take advantage of the unique characteristic of carbon nanotubes to emit electrons at very low supply voltage.
29
Preza, Fontes Giovani. "Managing cover crops and nitrogen fertilization to enhance sustainability of sorghum cropping systems in eastern Kansas." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35267.
Abstract:
Master of ScienceDepartment of Agronomy
Peter J. Tomlinson
Growing cover crops (CCs) in rotation with cash crops has become popular in recent years for their many agroecosystem benefits, such as influencing nutrient cycling and reducing nutrient losses. This study aimed to (i) determine the long-term effects of no-till with CCs and varying nitrogen (N) rates on subsequent sorghum [Sorghum bicolor (L.) Moench] yield and yield components, (ii) assess how CCs affect the N dynamic in the soil-crop relationship during the growing season and N use efficiency (NUE) of sorghum, and (iii) define and evaluate important periods of nitrous oxide (N₂O) losses throughout the cropping system. Field experiments were conducted during the 2014-15 and 2015-16 growing season in a three-year no-till winter wheat (Triticum aestivum L.) – sorghum – soybean [Glycine max (L.) Merr] rotation. Fallow management consisted of a chemical fallow (CF) control plus four CCs and a double-crop soybean (DSB) grown after wheat harvest. Nitrogen fertilizer was subsurface banded at five rates (0, 45, 90, 135, and 180 kg ha⁻¹) after sorghum planting. On average, DSB and late-maturing soybean (LMS) provided one-third and one-half of the N required for optimum economic grain yield (90 kg N ha⁻¹), respectively; resulting in increased grain yield when compared to the other CCs and CF with 0-N application. Crimson clover (Trifolium incarnatum L.) and daikon radish (Raphanus sativus L.) had no or negative effects on sorghum yield and N uptake relative to CF across all N rates. Sorghum-sudangrass (SS) (Sorghum bicolor var. sudanese) significantly reduced N uptake and grain yield, even at higher N rates. Sorghum following CF had the lowest NUE at optimum grain yield when compared to all CC treatments, suggesting that CCs have a tendency to improve NUE. Cover crops reduced N₂O emissions by 65% during the fallow period when compared to CF; however, DSB and SS increased emissions when N was applied during the sorghum phase, indicating that N fertilization might be the overriding factor. Moreover, about 50% of the total N₂O emissions occurred within 3 weeks after N application, regardless of the cover crop treatment, indicating the importance of implementing N management strategies to reduce N₂O emissions early in the growing season. Overall, these results show that CC selection and N fertilizer management can have significant impacts on sorghum productivity and N₂O emissions in no-till cropping systems.
30
Muller, Jesse Michael. "Improving fertiliser nitrogen recovery and mitigating nitrous oxide emissions from intensive vegetable cropping systems in South East Queensland." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/132721/1/Jesse_Muller_Thesis.pdf.
Abstract:
This thesis is a study into the efficacy of cropping methods Australian vegetable growers can adopt to increase nitrogen fertiliser efficiency, reduce nitrogen fertiliser application rates and reduce nitrous oxide emissions. The experiment, conducted in the Lockyer Valley (South East Queensland, Australia) investigated the utilization of the DMPP and Piadin nitrification inhibitors to achieve these research objectives. Outcomes from this research will help growers to reduce nitrogen fertiliser application rates and reduce greenhouse gas emissions without reducing yields.
31
Duhl, Tiffany Rae. "Advancing air quality modeling through improved urban vegetation characterization and an enhanced understanding of biogenic sesquiterpene emissions." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442951.
32
Jen, Jen-Fon. "Analysis of Acid Gas Emissions in the Combustion of the Binder Enhanced d-RDF by Ion Chromatography." Thesis, University of North Texas, 1988. https://digital.library.unt.edu/ark:/67531/metadc331848/.
Abstract:
Waste-to-energy has become an attractive alternative to landfills. One concern in this development is the release of pollutants in the combustion process. The binder enhanced d-RDF pellets satisfy the requirements of environmental acceptance, chemical/biological stability, and being storeable. The acid gas emissions of combusting d-RDF pellets with sulfur-rich coal were analyzed by ion chromatography and decreased when d-RDF pellets were utilized. The results imply the possibility of using d-RDF pellets to substitute for sulfur-rich coal as fuel, and also substantiate the effectiveness of a binder, calcium hydroxide, in decreasing emissions of SOx.
In order to perform the analysis of the combustion sample, sampling and sample pretreatment methods prior to the IC analysis and the first derivative detection mode in IC are investigated as well. At least two trapping reagents are necessary for collecting acid gases: one for hydrogen halides, and the other for NOx and SOx. Factors affecting the absorption of acid gases are studied, and the strength of an oxidizing agent is the main factor affecting the collection of NOx and SOx. The absorption preference series of acid gases are determined and the absorption models of acid gases in trapping reagents are derived from the analytical results. To prevent the back-flushing of trapping reagents between impingers when leak-checking, a design for the sampling train is suggested, which can be adopted in sample collections. Several reducing agents are studied for pretreating the sample collected in alkali-permanganate media. Besides the recommendation of the hydrogen peroxide solution in EPA method, methanol and formic acid are worth considering as alternate reducing agents in the pretreatment of alkaline-permanganate media prior to IC analysis. The first derivative conductivity detection mode is developed and used in IC system. It is efficient for the detection and quantification of overlapping peaks as well as being applicable for non-overlapping peaks.
33
Günther, Marcus. "Harte amorphe wasserstoffhaltige Kohlenstoffschichten mittels mittelfrequenzgepulster Plasmaentladungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-95197.
Abstract:
Harte amorphe wasserstoffhaltige Kohlenstoffschichten (a-C:H) haben in den letzten Jahrzehnten stark an Bedeutung gewonnen. Diese Art von Hartstoffschichten wird zunehmend für die Reduzierung von Reibung und Verschleiß in unterschiedlichen Bereichen eingesetzt. In der Forschung, aber auch für Kleinserien, werden a-C:H-Schichten üblicherweise mit Hochfrequenzplasmaentladungen abgeschieden. Eine Alternative ist die Plasmaaktivierung mit einer asymmetrisch bipolar gepulsten Spannung im Mittelfrequenzbereich. Auf diese Weise wird eine homogene Beschichtung großer Substratflächen mit qualitativ hochwertigen Schichten ermöglicht.
Die vorliegende Arbeit beschäftigt sich mit der plasmagestützten Abscheidung von harten a-C:H-Schichten mit mittelfrequenzgepulsten Entladungen. Zur Schichtabscheidung werden Ethin-Argon- und Isobuten-Argon-Gasgemische verwendet. Der Einfluss des Prozessdrucks auf den Abscheideprozess und die Schichteigenschaften wird untersucht. Dazu wurden Argonentladungen und Beschichtungsplasmen mittels optischer Emissionsspektroskopie charakterisiert. Zur Charakterisierung der Schichteigenschaften wurden unter anderem Nanoindentation-Messungen, elastische Rückstreudetektionsanalysen und thermische Desorptionsspektroskopie verwendet. Zur Untersuchung des Einflusses der Ionen auf das Schichtwachstum wird ein Modell zur Identifizierung von Ionenspezies in Beschichtungsplasmen vorgestellt. In Verbindung mit der Messung der Substratströme konnte der Ionenanteil am Schichtwachstum bestimmt werden.
Ein weiterer Teil der vorliegenden Arbeit untersucht ein Hybridverfahren, in dem die mittelfrequenzgepulste Entladung mit einer zusätzlichen ECR-Entladung kombiniert wird. Es wird gezeigt, dass durch dieses Hybridverfahren eine deutliche Steigerung der Abscheiderate harter a-C:H-Schichten erreicht werden kann. Die abgeschiedenen Schichten wurden zusätzlich bezüglich ihrer Oberflächenstruktur und ihrer Verschleißfestigkeit untersucht.
34
Hofgård, Daniel, and John Sundkvist. "Climate enhanced concrete in the civil engineering industry." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278216.
Abstract:
In 2017, the Swedish Parliament stated a new climate law with the goal that Sweden should be climate neutral by 2045. The concrete industry has developed a roadmap on how the goal for 2045 can be achieved, where one way to reduce the carbon emissions from concrete is by replacing a part of the cement clinker with alternative binders in the concrete mix. Ground granulated blast furnace slag (GGBS), fly ash, silica fume and trass are alternative binders that are possible to use in concrete mixes to reduce the amount of ordinary Portland cement (OPC). GGBS, fly ash and silica fume are by-products from other industries, while trass is volcanic ash that can be extracted. Besides the positive environmental impact that comes from using alternative binders and reducing the amount of cement clinker, the alternative binders have other properties, both positive and negative, that affect the concrete. The aim of this thesis was to investigate whether concrete with alternative binders does fulfill the regulations set by Swedish standards and how concrete with alternative binders does affect the material parameters. The concrete mixes were divided into three different types of concrete: concrete for bridges (w/c ratio 0.4), hydropower structures (w/c ratio 0.45) and wind powerplant foundations (w/c ratio 0.55). A total of seven concrete mixes were cast in a laboratory and the concrete mixes were investigated in the three hardening stages of concrete: fresh, young and hardened. The analyzed material parameters were compressive strength, shrinkage, frost resistance, workability, air voids and temperature development. Beyond the experimental testing, a global warming potential (GWP) comparison was made to compare the reduction of GWP for each concrete mix compared to a reference concrete for each usage area. The mix containing a CEM II/A-V fly ash cement and 15% GGBS showed great potential regarding the different material parameters. This mix, however, is according to Swedish standards not possible to certify for structures in exposure class XF4, such as bridges, but is possible to certify for structures in exposure class XF3, such as wind powerplant foundations. The mix containing 30% GGBS and 5% silica fume also showed beneficiary properties, but superplasticizers are required in this mix to ensure good workability. For hydropower structures, the mix containing 35% GGBS showed a great compressive strength but a high temperature development and low workability. The mix containing trass had a notably low temperature development, but with an increase in shrinkage and low workability. Moreover, all concrete mixes showed a frost resistance which, according to standard, is classified as “Very Good”.Sveriges regering antog 2017 ett nytt klimatpolitiskt ramverk med målet att Sverige ska ha noll nettoutsläpp av växthusgaser år 2045. Betongindustrin har tagit fram en färdplan för hur betong kan bli klimatneutralt, där ett sätt att reducera klimatpåverkan från betong är att byta ut en del av cementklinkern mot alternativa bindemedel. Mald granulerad masugnsslagg (GGBS), flygaska, silikastoft och trass är alternativa bindemedel som är möjliga att använda i betongblandningar för att reducera mängden Portlandcement. GGBS, flygaska och silikastoft är restprodukter från andra industrier medan trass är en vulkanisk aska som kan utvinnas. Utöver den positiva miljöeffekten som erhålls när alternativa bindemedel ersätter cementklinker, så har de alternativa bindemedlen andra egenskaper, både positiva och negativa, som påverkar betongen. Målet med denna studie var att undersöka och jämföra om betongblandningar där en del av cementklinkern har ersatts med alternativa bindemedel når upp till de krav som ställs i nuvarande regelverk. Utöver det så undersöktes även hur betongblandningarnas materialparametrar påverkades av alternativa bindemedel. Betongblandningarna delades in i tre olika typer av betong: betong för broar (vct 0.4), vattenbyggnader (vct 0.45) och vindkraftverksfundament (vct 0.55), där totalt sju betongblandningar tillverkades i ett laboratorium. Betongblandningarna undersöktes i de tre olika faserna för hårdnande av betong, vilka är färsk, ung och hårdnad betong. De materialparametrar som analyserades var tryckhållfasthet, krympning, frostresistens, arbetbarhet, luftporhalt och temperaturutveckling. Förutom de experimentella testerna gjordes en jämförelse kring hur mycket koldioxid som kan reduceras för varje betongblandning, jämfört med en referensbetong för varje användningsområde. Betongblandningen med ett CEM II/A-V flygaska-cement och 15% GGBS visade stor potential med avseende på de olika materialparametrarna. Denna blandning är dock enligt svensk standard inte möjlig att certifiera för betongbyggnad i exponeringsklass XF4, exempelvis broar, men kan certifieras för betongbyggnad i exponeringsklass XF3, exempelvis fundament för vindkraftverk. Blandningen med 30% GGBS och 5% silikastoft visade även positiva egenskaper, men flyttillsatsmedel måste användas i denna blandning för att erhålla en god arbetbarhet. För vattenbyggnadsbetong så visade blandningen med 35% GGBS en hög tryckhållfasthet, men samtidigt en hög temperaturutveckling och en låg arbetbarhet. Blandningen med trass hade en noterbart låg temperaturutveckling, men med ökad krympning samt låg arbetbarhet. Avslutningsvis så uppvisade alla blandningar en frostresistens som enligt standard klassificeras som ”Mycket bra”.
35
Schlosser, Joseph S., Rachel A. Braun, Trevor Bradley, Hossein Dadashazar, Alexander B. MacDonald, Abdulmonam A. Aldhaif, Mojtaba Azadi Aghdam, Ali Hossein Mardi, Peng Xian, and Armin Sorooshian. "Analysis of aerosol composition data for western United States wildfires between 2005 and 2015: Dust emissions, chloride depletion, and most enhanced aerosol constituents." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626273.
Abstract:
This study examines major wildfires in the western United States between 2005 and 2015 to determine which species exhibit the highest percent change in mass concentration on day of peak fire influence relative to preceding nonfire days. Forty-one fires were examined using the Environmental Protection Agency (EPA) Interagency Monitoring of Protected Visual Environments (IMPROVE) data set. Organic carbon (OC) and elemental carbon (EC) constituents exhibited the highest percent change increase. The sharpest enhancements were for the volatile (OC1) and semivolatile (OC2) OC fractions, suggestive of secondary organic aerosol formation during plume transport. Of the noncarbonaceous constituents, Cl, P, K, NO3-, and Zn levels exhibited the highest percent change. Dust was significantly enhanced in wildfire plumes, based on significant enhancements in fine soil components (i.e., Si, Ca, Al, Fe, and Ti) and PMcoarse (i.e., PM10-PM2.5). A case study emphasized how transport of wildfire plumes significantly impacted downwind states, with higher levels of fine soil and PMcoarse at the downwind state (Arizona) as compared to the source of the fires (California). A global model (Navy Aerosol Analysis and Prediction System, NAAPS) did not capture the dust influence over California or Arizona during this case event because it is not designed to resolve dust dynamics in fires, which motivates improved treatment of such processes. Significant chloride depletion was observed on the peak EC day for almost a half of the fires examined. Size-resolved measurements during two specific fires at a coastal California site revealed significant chloride reductions for particle aerodynamic diameters between 1 and 10 mu m.
36
Leix, Carmen [Verfasser], Jörg E. [Akademischer Betreuer] [Gutachter] Drewes, Susanne [Gutachter] Lackner, and Eberhard [Gutachter] Morgenroth. "Innovative strategies for enhanced deammonification performance and reduced nitrous oxide emissions / Carmen Leix ; Gutachter: Jörg E. Drewes, Susanne Lackner, Eberhard Morgenroth ; Betreuer: Jörg E. Drewes." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1141904667/34.
37
Min, Zhenhua. "Catalytic steam reforming of biomass tar using iron catalysts." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/184.
Abstract:
Biomass has become an increasingly important renewable source of energy forenhanced energy security and reduced CO[subscript]2 emissions. Gasification is at the core of many biomass utilisation technologies for such purposes as the generation of electricity and the production of hydrogen, liquid fuels and chemicals. However, gasification faces a number of technical challenges to become a commercially feasible renewable energy technology. The most important one is the presence of tar in the gasification product gas. The ultimate purpose of this thesis was to investigate the catalytic reforming of tar using cheap catalysts as an effective means of tar destruction.In this thesis, natural ilmenite ore and novel char-supported catalysts were studied as catalysts for the steam reforming of biomass tar derived from the pyrolysis of mallee biomass in situ in two-stage fluidised-bed/fixed-bed quartz reactors. In addition to the quantification of tar conversion, the residual tar samples were also characterised with UV-fluorescence spectroscopy. Both fresh and spent catalysts were characterised with X-ray diffraction spectroscopy, FT-Raman spectroscopy and thermogravimetric analysis.The results indicate that ilmenite has activity for the reforming of tar due to its highly dispersed iron-containing species. Both the externally added steam and low concentration oxygen affect the tar reforming on ilmenite significantly. The properties of biomass affect the chemical composition of its volatiles and therefore their reforming with the ilmenite catalyst. Compared with sintering, coke deposited on ilmenite is the predominant factor for its deactivation.During the steam reforming process, the char-supported iron/nickel catalysts exhibit very high activity for the reforming of tar. In addition, NO[subscript]x precursors could be decomposed effectively on the char-supported iron catalyst during the steam reforming process. The hydrolysis of HCN and the decomposition of NH[subscript]3 on the catalyst are the key reactions for the catalytic destruction of NO[subscript]x precursors.The kinetic compensation effects demonstrate that the reaction pathways on the char-supported catalysts are similar but different from those on ilmenite. The proprieties of catalyst support could play important roles for the activities of the catalysts and the reaction pathways on the catalysts. The char support as part of the char-supported catalysts can undergo significant structural changes during the catalytic reforming of biomass volatiles.
38
Brändström, Urban. "The Auroral Large Imaging System : design, operation and scientific results." Doctoral thesis, Umeå University, Space Science, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-36.
Abstract:
The Auroral Large Imaging System (ALIS) was proposed in 1989 by Åke Steen as a joint Scandinavian ground-based nework of automated auroral imaging stations. The primary scientic objective was in the field of auroral physics, but it was soon realised that ALIS could be used in other fields, for example, studies of Polar Stratospheric Clouds (PSC), meteors, as well as other atmospheric phenomena.
This report describes the design, operation and scientic results from a Swedish prototype of ALIS consisting of six unmanned remote-controlled stations located in a grid of about 50 km in northern Sweden. Each station is equipped with a sensitive high-resolution (1024 x 1024 pixels) unintensified monochromatic CCDimager. A six-position filter-wheel for narrow-band interference filters facilitates absolute spectroscopic measurements of, for example, auroral and airglow emissions. Overlapping fields-of-view resulting from the station baseline of about 50 km combined with the station field-of-view of 50° to 60°, enable triangulation as well as tomographic methods to be employed for obtaining altitude information of the observed phenomena.
ALIS was probably one of the first instruments to take advantage of unintensi- fied (i.e. no image-intensifier) scientific-grade CCDs as detectors for spectroscopic imaging studies with multiple stations of faint phenomena such as aurora, airglow, etc. This makes absolute calibration a task that is as important as it is dificult.
Although ALIS was primarily designed for auroral studies, the majority of the scientific results so far have, quite unexpectedly, been obtained from observations of HF pump-enhanced airglow (recently renamed Radio-Induced Aurora). ALIS made the first unambiguous observation of this phenomena at high-latitudes and the first tomography-like inversion of height profiles of the airglow regions. The scientific results so far include tomographic estimates of the auroral electron spectra, coordinated observations with satellite and radar, as well as studies of polar stratospheric clouds. An ALIS imager also participated in a joint project that produced the first ground-based daytime auroral images. Recently ALIS made spectroscopic observations of a Leonid meteor-trail and preliminary analysis indicates the possible detection of water in the Leonid.
39
Yang, Chih-Min, and 楊智閔. "Ionic Luminogen with Aggregation-Enhanced Emission." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/13225030049700524989.
Abstract:
碩士國立中山大學
材料與光電科學學系研究所
101
Restricted intramolecular rotation (RIR) of the non-coplanar aromatic fluorophores has been proven in several instances as the operative mechanism leading to the aggregation-enhanced emission (AEE) property. Besides using the bulky substituent as structural moiety of AEE-active materials, ionic bond interaction is also considered to be effective in reinforcing RIR. In this study, ionic ammonium sulfonate bond was used to introduce long chain orientation order and thus to impose effective RIR to generate emission enhancement on AEE-active organic fluorophores. With this aspect, a surfactant (surf) molecule of weakly-luminescent dodecylbenzenesulfonic acid (DBSA) was used to complex to different amines of varied structures and certain diamines (piperazine (PZ) and poly(ethyleneimine (PEI)) with right geometry to generate orientated dodecyl chains in the ionic products result in the further emission intensifications of the complex systems. Additionally, long-chain dodecylamine (DA) was used to react with weakly-fluorescent biphenyldisulfonate (BPS) and poly(styrene sulfonate) (PSS) to generate AEE-active materials with required orientation order and strong fluorescence due to the active RIR effect. An interesting aggregation-enhanced excimer emission (AEEE) was observed specifically for PSS(DA)1 complex system. Several complex systems (such as DBSA(PZ)x, DBSA(PEI)X, BPS(DA)x and PSS(DA)x ) were found to self-assemble into well-ordered supramolecular lamellar structures with the preferable orientation orders among their long aliphatic chains. RIR in relation to orientation order is therefore the main focus of this research.
40
Chien, Wei-Lun, and 簡偉倫. "Anthracene-Based Luminogen with Aggregation-Enhanced Emission." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04019539460649668011.
Abstract:
碩士國立中山大學
材料與光電科學學系研究所
101
In regards to the role of H-bond interaction as restriction forces on molecular rotation, we thereby explore further possibilities of using this facile strategy to generate AEE-active fluorescence systems with enhanced emissions. We used typical Heck coupling reaction to synthesis two different systems based on the facile H-bond interaction between H-bond donating hydroxyl and H-bond accepting pyridine functions are illustrated in this research. In chapter 2, an AEE-active dipyridine fluorophore was used to H-bond to monomeric diphenol (bisphenol A, BPA) and poly(vinyl phenol) (PVPh) to generate pseudo-linear and crosslinked systems, respectively, with beneficial AEE-active strong fluorescence. Instead of diphenol fluorophore, AEE-active diphenol compound was used in Chapter 3 as the fluorescent component to react with poly(vinylpyrrolidone) to generate peudo-crosslinked network with strong fluorescence. Both systems described in Chapter 2 and 3 are all subjected to different instrumentation analyses to identify the restricted molecular rations and the related enhanced emissions.
41
Tsai, Yao-ching, and 蔡耀慶. "UV-enhanced field emission property of ZnO nanowires." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/57875598006660603718.
Abstract:
碩士國立臺南大學
電機工程研究所
98
In this study we investigate the influence of field emission properties of the ZnO nanowires after being illuminated by UV light. We also compared the effect of different illumination (1.9 mW/cm2 and 3.2 mW/cm2) and different wavelength (UV-A：320-400 nm, UV-B：280-320 nm, UV-C：200-280 nm) of UV light. We discovered that more illumination could enhance more emission current, and reduce the turn–on voltage. However, UV-A light had stronger ability to enhance emission current. Then we measured three kinds of UV light at different pressure. It is observed that emission current of UV-A light had less fluctuation among different pressure. The others would decay more when environmental elements were worse. We also investigated the recovery current of three kinds of UV light. All of them took much time (20 min) for emission current to fall to its original value. After measuring the current characteristics, the stability of field emission was also investigated.
42
Tsai, Chun-Ping, and 蔡俊平. "Photo-Enhanced Field Emission Organic Light Emitting Diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/69203989403199258823.
Abstract:
碩士義守大學
電子工程學系碩士班
99
This thesis presents a structure of photo-enhanced field emission organic light emitting diodes (PEFEOLEDs) to enhance the luminous efficiency of organic light emitting diode, (OLED) of 1.52 times in the same current density. The PEFEOLEDs is composed by three parts: OLED acts as the anode, a field emission template of CNTs acts as the cathode, and a LED acts a light source. FEOLEDs is a current driven device, electrons and holes are injected from anode and cathode, respectively. And they will recombination at emission layer. Then it uses the field emission template of CNTs to emit extra electrons, that are injected in cathode of OLED. This way could make the numbers balance, that electrons and holes in OLED’s emitting layer, and improve the luminous efficiency of OLED. In this thesis, we provide the property of field emission template of CNTs first. It improves the stability and enhances the emission currents of CNTs’ template by annealing process. Furthermore, we have coated the wide band gap material of Magnesium Oxide (MgO) and Cesium Iodide (CsI) onto CNTs to reduce the work function of CNTs and enhanced the field emission capability of CNTs. And the field emission current density of the CNTs templates is 48.87 mA/cm2 under the electrical field of 1.47 V/μm. Then we insert the LED light source under the CNTs template can further increase the field emission current density to 62.5 mA/cm2 under the same electrical field of 1.4 V/μm. In this thesis, the FEOLEDs can effectively enhance the luminance efficiency of OLED to 1.32 times, and the luminance of OLED from 8124 cd/m2 to 9751 cd/m2. Furthermore,we use a LED light source to enhance the luminance efficiency of OLED to 1.52 times, and the luminance of PEFEOLEDs 11937 cd/m2.
43
Lan, Yin-Feng, and 藍銀鋒. "Thermionic Emission Enhanced Sputter Deposition of PZT Thin Film." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/14537203969709951151.
Abstract:
碩士逢甲大學
材料科學所
92
In recent years, micro-electromechanical systems (MEMS) have been widely investigated in order to develop intelligent sensor or actuators. Lead zirconate titanate (PZT) films are supposed to be applied in many ferroelectric devices of MEMS such as micro-actuators, sensor, and ultrasonic motors. Thus, to deposit high quality PZT films is necessary. But in most research results, the deposition temperature must be raise to 550-700℃ to obtain ferroelectric perovskite structure. Such high deposition temperature causes many detrimental effects in the device producing process inducing inter-diffusion between layers and thermal stress etc. Progress has been made to obtain PZT thin film at low deposition temperature using PZT growth on seed layer, laser ablation and rapid thermal annealing etc. In this study, the PZT thin films were deposited by using a dual-target (PZT/PbO) sputter system, with intensified plasma enhanced by using thermionic electron emission technique. The processing temperature is expected to be decreased while maintaining high quality PZT thin film. The influence of the intensified plasma to the microstructure of PZT film will be investigated and correlated to its ferroelectric properties. The result show: without/with thermionic enhance sputtering PZT thin films, the deposition temperature must be upon 580 ℃ to obtain perovskite structure. Deposition rate of PZT thin film is higher at low deposition temperature and obtain PZT thin film growth rate increasing 1.72 times with thermionic. The polarization values of PZT thin film deposited by without thermionic and with thermionic sets are Pr=13 µC/cm2，Ps=31 µC/cm2 and Pr=18 µC/cm2，Ps=45 µC/cm2 respectively.
44
Teng, Siang-ling, and 鄧湘霖. "Ionic Interaction in Fluorescent Complexes with Aggregation-Enhanced Emission." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/43ea53.
Abstract:
碩士國立中山大學
材料與光電科學學系研究所
102
Abstract-1 A fluorescent biological sensor utilizing aggregation-enhanced emission (AEE) property was developed in our laboratory. First, anAIE-active fluorescent tetraphenylthiophene (TP) unit was synthetically connected to poly(N-isopropylacrylamide) by covalent and ionic bonds, resulting in the respective c- and i-TP-PNIPAM for the detection and quantification of the bovine serum albumin (BSA) model protein. When bind to BSA, the ionic i-TP-PNIPAM shows much better fluorescence (FL) sensitivity compared to c-TP-PNIP AM. The fluorescence (FL) intensity of i-TP-PNIAPM displays a good linear dependence on concentration of BSA (0 – 1 mg/mL), indicating quantitative fluorimetric protein detection can be achieved. Further addition of anionic surfactant ofsodium dodecylsulfate (SDS) considerably raised the FL intensity of the complexsolution. All the FL response was discussed in term of conformational freedom of the TP unit under different environmental constraints. Abstract-2 A water-soluble fluorophore containing four anionicsulfonated groups, sodium tetraphenylthiophenesulfonate (TPS), was sythesizedand characterized to have aggregation-enhanced emission (AEE) property. One the other hand, acidified Jeffamine (diammonium-terminated poly(propylene glycol) and Jeffamine-included β-cyclodextrin (β-CD) were separatedly prepared. Through the facile ionic interaction between sulfonate anion in TPS and ammonium cation in Jeffamine (or in Jeffamine-included β-CD), fluorescent ionic complex of iTP-JA (or iTP-CD-JA) can be prepared and their emission behavior was correlated with the degree of restricted intramolecular rotation (RIR), as the main mechanism responsible for AEE phenomenon, in each system of different molecular structures. When bind to polymeric Jeffamine, iTP-JA complex emits with higher intensity than the small-mass TPS. Use of β-CD rigidify the flexible Jeffamine, therefore, iTP-CD-JA complex is the most efficient emitter among all three samples.
45
Hsiao, Tai-Shen, and 蕭待森. "Organic and polymeric Schiff-base with Crystallization-enhanced emission." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/2zny75.
Abstract:
碩士國立中山大學
材料與光電科學學系研究所
102
Restricted intramolecular rotation (RIR) of the non-coplanar aromatic fluorophores has been proven in several instances as the operative mechanism leading to the aggregation-enhanced emission (AEE) property. Besides using the bulky substituent as structural moiety of AEE-active materials, crystallization is also considered to be effective in reinforcing RIR. In chapter 1, An organic azine derivative of CN4OH, containing both of the para- and the ortho-hydroxyl (p- and o-OH) groups, is a fluorescent material with its emission efficiency dependent on the degree of crystallinity. With inherent hydroxyl groups, CN4OH can be homogeneously blended with different amounts of poly(4-vinyl pyridine) (PVP) through intermolecular hydrogen-bond (H-bond) interactions. With the incorporations of one and two molar equivalents of PVP, the solid CN4OH/PVP(4/1) and (2/1) blends emit strongly with intensity larger than the pure CN4OH. Nevertheless, further increase of the PVP content considerably reduced the crystallinity and the emission efficiency of the blend. Initially, PVP was preferably H-bonded to the p-OHs of CN4OH, resulting in the beneficial crystallization-enhanced emission (CEE); nevertheless, the PVP added in the later step started to bond to the o-OHs of CN4OH, reducing the crystallinity and the CEE-related fluorescence. With appropriate H-bond interaction, the CN4OH/PVP(2/1) blend emits with a high quantum yield (ɸF) of 88%, in contrast to the low ɸF of 15% for pure CN4OH. In chapter 2, Polymeric luminogen with Aggregation-enhanced emission (AEE) and crystallization-enhanced emission (CEE) behavior was prepared and characterized in this study. Schiff-base polymeric luminogen was prepared via the ring opening polymerization. First, we synthesized different molecule weight of Polymeric luminogen to observed crystallinity relative emission impact. Then the emission behavior of the CN-PLLA(n)s in heat treatment and solvent annealing was shown to correlate with CEE behavior, We was prepared a amorphous film by heat treatment then comparison with crystalline film, the crystal film emission is better than amorphous film. Then we will amorphous film do solvent annealing, after solvent fuming process, we check WAXD. In WAXD, have displays sharp reflection peaks and emission was gradually enhanced with increasing exposure time. Therefore, CN-PLLA(n)s is a fluorophore with CEE character.
46
Neal, Terrell Demetris. "Surface Plasmon Enhanced Light Emission from Organic Light Emitters." Thesis, 2006. https://thesis.library.caltech.edu/3698/1/Terrell_D_Neal.pdf.
Abstract:
We have experimentally verified that visible light emission for various organic light emitters can be enhanced through the use of surface plasmon coupling layers. By matching the plasmon frequency of a thin unpatterned silver film to the emission of a dye-doped polymer deposited onto this metal surface, we have observed an 11-fold enhancement of light emission. By patterning the silver layer, we estimate that the plasmon frequency can be tuned to match dye-doped polymer emission frequencies, and even larger emission enhancements as well as extraction efficiencies are expected. Carrier dynamics of such plasmon-enhanced organic light emitters were studied and a recombination rate increase due to surface plasmon polaritons was experimentally observed. Internal quantum efficiency data from the polyfluorenes studied follow the trend supported by the time-resolved photoluminescence measurements. Also, we have presented a way to extend the lifetime of organic light emitters by reducing the photodegredation effects from photo-oxidation using surface plasmon coupling.
47
Dangwal, Arti [Verfasser]. "Enhanced field emission from metallic surfaces and nanowires / Arti Dangwal." 2007. http://d-nb.info/986360023/34.
48
Sokolowski, James Kurt. "The formation of enhanced, low-ionization emission in galactic halos." Thesis, 1992. http://hdl.handle.net/1911/16590.
Abstract:
Recent observations have discovered pervasive, low-ionization gas with unusual excitation in the halos of nearby spiral galaxies. This has led to speculation concerning the excitation mechanisms operating at high galactic latitudes, including exotic processes involving nonequilibrium physics, local grain destruction and decaying dark matter. We demonstrate that the excitation conditions of the diffuse ionized media (DIMs) in several such objects, NGC 891, the Galaxy and NGC 1068, can be understood in terms of photoionization by the dominant radiation fields in their halos, if proper consideration is given to the spatial distributions of their stellar populations, the relative importance of nuclear continuum sources and subsequent radiative transfer.
Estimation of the stellar populations in NGC 891 and the Galaxy indicates that OB stars, and the central stars of planetary nebulae dominate the excitation of their DIMs. Photoionization models require local DIM electron densities of order unity to reproduce the observed emission characteristics of the high-$\vert z\vert$ gas. The DIM filling factor in NGC 891 is therefore restricted to the range 10$\sp{-3.5}\ \sbsp{\sim}{<}\ \phi\ \sbsp{\sim}{<}\ 10\sp{-1.5}$, while in the Galaxy $\phi\ \sbsp{\sim}{<}\ 10\sp{-1.2}$ is suggested. Ionization equilibrium indicates that only $\sim$5% of the total number of ionizing photons from OB stars escape the neutral disk, highlighting the importance of radiative transfer through the multiphase ISM.
The DIM in NGC 1068 demonstrates a bipolar asymmetry common among active galaxies, with high-excitation emission confined to two diametric sectors aligned along the radio jet axis and low-excitation emission uniformly distributed over the disk. We show that this bipolar morphology can be understood using the developing picture of NGC 1068, in which its burried Type 1 Seyfert nucleus is visible only through scattered polarized light. The DIM excitation is therefore anisotropic, with high-excitation gas along the jet axis photoionized by direct nuclear continuum and low-excitation gas away from the axis, illuminated by indirect nuclear emission scattered into it. Photoionization models using power-law continua, indicate that the filling factor of this DIM is restricted to the range $10\sp{-5} \ \sbsp{\sim}{<}\ \phi\ \sbsp{\sim}{<}\ 10\sp{-4}$ in order to reproduce the observed DIM emission characteristics.
49
Chen, Tai Lin, and 陳泰霖. "Aggregation Enhanced Emission and Piezochromism of Nitrogen Containing Heterocyclic Luminogen." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/42063937618355335109.
Abstract:
碩士國立中山大學
材料與光電科學學系研究所
101
Abstract - 1 Two tri-armed piezofluorochromic compounds of tris(4-(4-phenylquinolin-2-yl)phenyl)amine (TPA-3Qu) and tris(4-(6-(9H-carbazol-9yl)-4-phenylquinolin-2-yl)phenyl)amine (TPA-3QuCz) were prepared and found to exhibit keen fluorescence responses toward pressurization. With the framework of a twisted, pyramidal triphenylamine (TPA) center connecting to three large quinolinecarbazole (QuCz) arms, TPA-3QuCz is amorphous material exhibiting a large bathochromic shift of 112 nm under gentle grinding forces, which is in widely contrast to the small shift of 32 nm for TPA-3Qu when subjected to a high pressure load of 10 MPa. By heating to high temperatures, both TPA-3QuCz and TPA-3Qu also exhibited the same bathochromic shifts as pressurization did. Conformational transformations involving planarization of the arms were proposed to account for the observed fluorescence responses of TPA-3QuCz and TPA-3Qu towards pressure and heating. Abstract -2 In this study, organic molecules of 4,4''-((1E,1''E)-((3,4-diphenylthiophene-2,5-diyl)bis(4,1-phenylene))bis(ethene-2,1-diyl))dipyridine (TP-2Py) with smaller substituent and 4,4''-((1E,1''E)-((3,4-diphenylthiophene-2,5-diyl)bis(4,1-phenylene))bis(ethene-2,1-diyl))bis(N,N-diphenylaniline) (TP-2TPA) with stronger substituent were prepared and characterized to identify their photoluminescent (PL) responses toward the effect of aggregation emission enhancement (AEE). Comparing the fluorescence intensity for TP-2Py and TP-2TPA , no matter in the solid or solution state, the fluorescence of TP-2TPA is stronger than the TP-2Py. By the study influence of temperature on solution emissions of TP-2Py and TP-2TPA, and computer simulation, we realized the compound of TP-2TPA which could effective restriction on molecular rotation than the compound of TP-2Py. With the effector of effective restriction on molecular rotation, TP-2TPA can block the non-radiative energy loss, to enhance the efficiency of luminescence. In another way, we also blends with hydroxyl-containing components (poly( vinyl alcohol) (PVA)) on both compounds,TP-2Py and tp-2TPA,. After blending with the hydroxyl components, the fluorescence can be further intensified due to the further restricted molecular rotation, though the facile intermolecular hydrogen-bond (H-bond) interactions between the nitrogen containing heterocyclic and the hydroxyl functions.
50
Su, Chuan-Tsung, and 蘇傳宗. "Enhanced Radiative Emission in Carbon-based Nanomaterials Decorated GaN nanorods." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/52899208664580385342.
Abstract:
碩士國立臺灣海洋大學
光電科學研究所
101
We report the study on the enhancement of the photoluminescence (PL) in the nanocomposites including reduced graphene oxide nanoflakes (RGO)/GaN nanorods (NRs) and carbon nanodots (CNDs)/GaN NRs using 266 nm Nd:YAG laser excitation. We show that the enhanced PL emission in RGO/GaN NRs can be attributed to the coupling between the optical transition of GaN NRs and the surface plasmon resonance of the reduced graphene oxide nanoflakes, induced by the GaN NRs surface roughness. Moreover, the random lasing of CNDs/GaN NRs was observed because of the enhanced light scattering processes resulted from the CNDs. The approach we describe here will be useful for the future development of efficient optoelectronic devices and offers an alternative route for application of reduced graphene oxide and carbon nanodots.