Abstract This thesis describes the development of high bandwidth (~1 GHz) TOF (time-of-flight) laser range finder techniques for industrial measurement applications in the measurement range of zero to a few dozen metres to diffusely reflecting targets. The main goal has been to improve single-shot precision to mm-level in order to shorten the measurement result acquisition time. A TOF laser range finder consists of a laser transmitter, one or two receivers and timing discriminators, and a time measuring unit. In order to improve single-shot precision the slew-rate of the measurement pulse should be increased, so the optical pulse of the laser transmitter should be narrower and more powerful and the bandwidth of the receiver should be higher without increasing the noise level too much. In the transmitter usually avalanche transistors are used for generating the short (3–10 ns) and powerful (20–100 A) current pulses for the semiconductor laser. Several avalanche transistor types were compared and the optimization of the switching circuit was studied. It was shown that as high as 130 A current pulses are achievable using commercially available surface mount avalanche transistors. The timing discriminator was noticed to give the minimum walk error, when high slew rate measurement pulses and a high bandwidth comparator were used. A walk error of less than +/- 1 mm in an input amplitude dynamic range higher than 1:10 can be achieved with a high bandwidth receiver channel. Adding an external offset voltage between the input nodes of the comparator additionally minimized the walk error. A prototype ~1 GHz laser range finder constructed in the thesis consists of a laser pulser and two integrated ASIC receiver channels with silicon APDs (avalanche photodiodes), crossover timing discriminators and Gilbert cell attenuators. The laser pulser utilizes an internal Q-switching mode of a commercially available SH-laser and produces optical pulses with a pulse peak power and FWHM (full-width-at-half-maximum) of 44 W and 74 ps, respectively. Using single-axis optics and 1 m long multimode fibres between the optics and receivers a total accuracy of +/-2 mm in the measurement range of 0.5–34.5 m was measured. The single-shot precision (σ-value) was 14 ps–34 ps (2–5 mm) in the measurement range. The single-shot precision agrees well with the simulations and is better with a factor of about 3-5 as compared to earlier published pulsed TOF laser radars in comparable measuring conditions.

A relatively new application for the laser is in fluorescence microscopes. The fluo- rescence microscope needs a high power light source input. Using a laser source improves the precision of the microscope. A pulsed laser source enhances the performance of the fluorescence microscope and a laser diode can be overdriven without being damaged. The thesis investigates which properties of the laser pulses are needed regarding pulse width, pulse period and waveform. The thesis also investigates which properties are desired for the electrical pulses driving the laser, and how they can be generated using electrical components. The desired laser pulse should have a pulse width of 100 ps and a pulse period of 50 ns. The laser pulse should also have a well-defined wavelength, stable output power and it should be able to quickly turn on and off. To achieve this laser pulse, the desired input to the laser diode should have an input voltage of 5 V, an input current of 250 mA, a pulse width of 100 ps and a pulse period of 50 ns. For generating this pulse the chosen pulse generator, an SRD, should have low junction capacitance, low package capacitance and low package inductance. The chosen amplifier, a MESFET, desires low drain current and should have high transconductance and a large negative threshold voltage.

This laboratory project has been done to evaluate pressure pulsing as an Enhanced Oil Recovery (EOR) technique. To perform the study, a consistent laboratory methodology was developed, including the construction of a Consistent Pulsing Source (CPS). Tests compared pulsed and non-pulsed waterfloods in a paraffin or crude oil saturated medium, which also contained connate water (an irreducible water saturation). Results revealed that pulsed tests had maximum flow rates 2. 5--3 times higher, greater oil recovery rates, and final sweep efficiencies that were more than 10% greater than non-pulsed tests. The CPS design has proven very successful, and has since been copied by a major oil corporation. However, there are two limitations, both caused by fluctuating water reservoir levels. Longer pulsed tests (reservoir-depletion tests) were periodically paused to refill the water reservoir, resulting in reservoir depressurization and lower flow rates. The final effect of this was impossible to quantify without correcting the problem. The second CPS limitation was the change in pulse shape with time. However, it is not expected that this had any major effect on the results. The pulse pressure and period studies were limited by early tests, which did not have the necessary time duration. Both increasing pulse pressure and decreasing pulse period were found to increase the final sweep efficiency. Slightly decreasing porosity (0. 4% lower) was found to lower sweep efficiencies. However, the 34. 9% porosity results were not done until reservoir depletion, so it is difficult to quantitatively compare results. An emulsion appeared after water breakthrough when using the CPS on light oils (mineral oil). This may have been the result of isolated oil ganglia being torn apart by the sharp pulses. Although it is difficult to apply laboratory results to the field, this study indicates that pressure pulsing as an EOR technique would be beneficial. Doubled or tripled oil recovery rates and 10% more oil recovery than waterflooding would be significant numbers in a field operation. A valuable application would be in pulsing excitation wells to both pressurize the reservoir and enhance the conformance of the displacing fluid over a long-term period. It would also be valuable for short-term chemical injections, where mixing with the largest volume possible is desirable.

Nous étudions l’influence d’une rétroaction optique à conjugaison de phase dans une diode laser. Ce type de rétroaction a été peu étudié et nous montrons ici qu’il donne des résultats intéressants, permettant de débloquer du contenu à haute fréquence. Cela pourrait mener à de meilleures performances dans des systèmes de génération de nombres aléatoires utilisant du chaos optique. / We study the influence of phase-conjugate feedback in a laser diode. This type of feedback has not been studied a lot and yet we show here that it can give interesting results. It unlocks oscillations at high frequencies. This could lead to an improvement in the performance of random number generators based on optical chaos.

This laboratory project has been done to evaluate pressure pulsing as an Enhanced Oil Recovery (EOR) technique. To perform the study, a consistent laboratory methodology was developed, including the construction of a Consistent Pulsing Source (CPS). Tests compared pulsed and non-pulsed waterfloods in a paraffin or crude oil saturated medium, which also contained connate water (an irreducible water saturation). Results revealed that pulsed tests had maximum flow rates 2. 5--3 times higher, greater oil recovery rates, and final sweep efficiencies that were more than 10% greater than non-pulsed tests. The CPS design has proven very successful, and has since been copied by a major oil corporation. However, there are two limitations, both caused by fluctuating water reservoir levels. Longer pulsed tests (reservoir-depletion tests) were periodically paused to refill the water reservoir, resulting in reservoir depressurization and lower flow rates. The final effect of this was impossible to quantify without correcting the problem. The second CPS limitation was the change in pulse shape with time. However, it is not expected that this had any major effect on the results. The pulse pressure and period studies were limited by early tests, which did not have the necessary time duration. Both increasing pulse pressure and decreasing pulse period were found to increase the final sweep efficiency. Slightly decreasing porosity (0. 4% lower) was found to lower sweep efficiencies. However, the 34. 9% porosity results were not done until reservoir depletion, so it is difficult to quantitatively compare results. An emulsion appeared after water breakthrough when using the CPS on light oils (mineral oil). This may have been the result of isolated oil ganglia being torn apart by the sharp pulses. Although it is difficult to apply laboratory results to the field, this study indicates that pressure pulsing as an EOR technique would be beneficial. Doubled or tripled oil recovery rates and 10% more oil recovery than waterflooding would be significant numbers in a field operation. A valuable application would be in pulsing excitation wells to both pressurize the reservoir and enhance the conformance of the displacing fluid over a long-term period. It would also be valuable for short-term chemical injections, where mixing with the largest volume possible is desirable.

The efficacy of injection-driven remediation techniques for non-aqueous phase liquid (NAPL) source zones is limited by the principle that fluid flow is focused along paths of least hydraulic resistance. The pressure pulse technology stands among a number of innovative methods that have been developed with the aim of overcoming or mitigating this limitation. The objective of this research was to observe and document differences in saturated groundwater flow and solute transport between an injection using a conventional or continuous pressure delivery approach and an injection using a pressure pulsing instrument. The underlying motivation was to identify engineering opportunities presented by pressure pulsing with the potential to improve remediation efficiency at contaminated sites. A series of tracer injections were conducted in the unconfined aquifer at the University of Waterloo Groundwater Research Facility at Canadian Forces Base (CFB) Borden near Alliston, ON (homogeneous fine sand), and in the shallow aquifer at a groundwater research site located on the North Campus at the University of Waterloo (moderately heterogeneous with discrete layers varying from fine sand to silt). A single injection well was used at each site for both the conventional and pressure pulsing injections. Different tracers were used for consecutive injections. Bromide, Lithium, Chloride, and fluorescent dyes (Rhodamine WT and Sulforhodamine B) were used. Formation pressurization data was captured by pressure transducers. The spatial distribution of the injected tracers was monitored at a series of multilevel wells. A groundwater flow and solute transport modeling exercise (MODFLOW and MT3DMS numerical engines) simulating the rapid boundary pressure modulation that occurs in association with pressure pulsing was conducted to complement the field injections. A two-dimensional domain was used to conduct a parametric investigation of pressure modulation and its effect on flow and transport. A three-dimensional domain served to scale-up the two-dimensional results and for benchmarking against field observations. Pressure pulsing simulation results reveal that repeated sudden onset of injection cessation produces brief periods of gradient reversal near the injection well and the development of a mixing zone around the injection well. The spatial extents of this mixing zone are highly dependent upon the hydraulic diffusivity of the medium. Greater heterogeneity in combination with presence of high hydraulic diffusivity pathways maximized the extent of the mixing zone and the magnitude of transverse and reversal hydraulic gradients. Lower pulsing frequency and higher pulsing amplitude favoured a more significant mixing zone, though these effects were secondary to geologic properties. Use of the pressure pulsing tool did not manifest into distinct changes in tracer breakthrough at either field research site. Comparison between tracer tests was complicated by sorption of fluorescent dyes and ongoing well development. Solute transport simulation results demonstrated augmentation of dispersion arising from the mixing zone phenomenon, but no distinct changes in advection.

An investigation was conducted to determine and compare the effect of cell current pulsing and "self-oxidation" in increasing the CO tolerance of a PEM fuel cell. The most effective pulsing parameter values were also determined. Current pulsing involves periodically demanding positive current pulses from the fuel cell to create an anode over-potential, while "self-oxidation" or sustained potential oscillations is achieved when the anode catalyst becomes so saturated with CO that the anode over-potential increases to a value at which CO is oxidized from the catalyst surface. The CO tolerance of a fuel cell system with a Pt-Ru anode was tested using 50 and 496 ppm CO in the anode fuel. The performance of the system declined with an increase in CO concentration. Current pulses of various amplitude, frequency, and duty cycle were applied to the cell while CO was present in the anode fuel. With 50 ppm CO in the anode fuel, the most effective pulse in increasing CO tolerance while maintaining normal cell operation was 1.0 A/cm2, 0.25 Hz, and a 5% duty cycle. A pulse (120 Hz, 50% duty cycle) similar to the ripple current often generated when converting DC to single-phase 60 Hz AC had a positive effect on the CO tolerance of the system, but at frequencies that high, the pulse duration was not long enough to completely oxidize the CO from the catalyst surface. With 496 ppm CO in the anode fuel, a pulse of 1.0 A/cm2, 0.5 Hz, and a 20% duty cycle proved most effective. When the cell was exposed to 496 ppm CO, without employing pulsing, "self-oxidation" occurred and CO was periodically oxidized from the catalyst surface. However, pulsing allowed the cell to operate at the desired voltage and power a higher percentage of the time than "self-oxidation"; hence, pulsing was more effective.

The efficacy of injection-driven remediation techniques for non-aqueous phase liquid (NAPL) source zones is limited by the principle that fluid flow is focused along paths of least hydraulic resistance. The pressure pulse technology stands among a number of innovative methods that have been developed with the aim of overcoming or mitigating this limitation. The objective of this research was to observe and document differences in saturated groundwater flow and solute transport between an injection using a conventional or continuous pressure delivery approach and an injection using a pressure pulsing instrument. The underlying motivation was to identify engineering opportunities presented by pressure pulsing with the potential to improve remediation efficiency at contaminated sites. A series of tracer injections were conducted in the unconfined aquifer at the University of Waterloo Groundwater Research Facility at Canadian Forces Base (CFB) Borden near Alliston, ON (homogeneous fine sand), and in the shallow aquifer at a groundwater research site located on the North Campus at the University of Waterloo (moderately heterogeneous with discrete layers varying from fine sand to silt). A single injection well was used at each site for both the conventional and pressure pulsing injections. Different tracers were used for consecutive injections. Bromide, Lithium, Chloride, and fluorescent dyes (Rhodamine WT and Sulforhodamine B) were used. Formation pressurization data was captured by pressure transducers. The spatial distribution of the injected tracers was monitored at a series of multilevel wells. A groundwater flow and solute transport modeling exercise (MODFLOW and MT3DMS numerical engines) simulating the rapid boundary pressure modulation that occurs in association with pressure pulsing was conducted to complement the field injections. A two-dimensional domain was used to conduct a parametric investigation of pressure modulation and its effect on flow and transport. A three-dimensional domain served to scale-up the two-dimensional results and for benchmarking against field observations. Pressure pulsing simulation results reveal that repeated sudden onset of injection cessation produces brief periods of gradient reversal near the injection well and the development of a mixing zone around the injection well. The spatial extents of this mixing zone are highly dependent upon the hydraulic diffusivity of the medium. Greater heterogeneity in combination with presence of high hydraulic diffusivity pathways maximized the extent of the mixing zone and the magnitude of transverse and reversal hydraulic gradients. Lower pulsing frequency and higher pulsing amplitude favoured a more significant mixing zone, though these effects were secondary to geologic properties. Use of the pressure pulsing tool did not manifest into distinct changes in tracer breakthrough at either field research site. Comparison between tracer tests was complicated by sorption of fluorescent dyes and ongoing well development. Solute transport simulation results demonstrated augmentation of dispersion arising from the mixing zone phenomenon, but no distinct changes in advection.

Made available in DSpace on 2014-06-11T19:28:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-09-18Bitstream added on 2014-06-13T18:57:49Z : No. of bitstreams: 1 depietro_j_me_jabo.pdf: 1424480 bytes, checksum: fd0d58d73de3ddb09b7b417a5389737f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Face à carência de estudos relacionados à fisiologia pós-colheita de flores, a presente pesquisa teve como finalidade estudar a fisiologia e conservação póscolheita de flores cortadas de rosas cv. Vega, considerando os fatores associados à senescência floral e perda de vida decorativa. Os experimentos foram conduzidos em delineamento inteiramente casualizado, em esquema fatorial. Em todos os experimentos, as rosas foram mantidas em ambiente de laboratório com 20±2ºC e 67±3% UR, padronizadas em 50 cm e realizadas as seguintes avaliações (exceto para o experimento 5): perda de massa fresca, massa seca, taxa respiratória, notas de qualidade (escurecimento, turgescência e curvatura), conteúdo relativo de água, carboidratos solúveis e redutores, antocianina e coloração. Para o experimento 5 foi avaliada a quantidade de água absorvida e transpirada das rosas. No primeiro experimento, as flores foram colocadas dentro de uma câmara hermética e expostas ao 1-MCP, por um período de seis horas, nas seguintes concentrações: 1) Água destilada (controle); 2) 1-MCP 100 a ppb; 3) 1-MCP a 250 ppb; 4) 1-MCP a 500 ppb. Ao contrário do tratamento com água destilada, todas as concentrações de 1-MCP foram eficientes para retardar a senescência das flores, com destaque para a de 500 ppb que melhor manteve a qualidade, além de prolongar a vida de vaso das rosas até 19 dias. No segundo experimento, as flores permaneceram nas seguintes soluções de manutenção: 1) Água destilada (Controle); 2) 8-HQC (200 mg.L-1); 3) Sacarose (2%) + 8-HQC (200 mg.L-1); 4) Ácido Cítrico (75 mg.L-1); 5) Sacarose (2%) + Ácido Cítrico (75 mg.L-1); 6) 6- BA (60 mg.L-1); 7) Sacarose (2%) + 6-BA (60 mg.L-1). As rosas foram muito sensíveis à 6-benziladenina, associada ou não à sacarose, e perderam a qualidade aos seis dias de vida de vaso. Em contrapartida, o tratamento com 8-hidroxiquinolina... / Given the lack of studies on postharvest physiology of flowers, this research aims to study the postharvest physiology and keeping quality of Vega cut rose, were observed the factors associated with floral senescence and loss of decorative life. The experiments followed complete randomized design, in factorial arrangement. In all experiments, the roses were kept at room temperature with 20 ± 2ºC and 67±3% UR, standardized at 50 cm and it were analysis (except the fifth experiment): weight loss, dry weight, rate respiratory, quality (browning, turgidity and curvature), relative water content, soluble and reducing carbohydrates, anthocyanin, color and longevity. On the fifth experiment was to evaluation the water absorbed and transpired roses. On the first experiment, the flowers were placed inside an airtight chamber and exposed to 1-MCP for a period of six hours, in these concentrations: 1) Distilled water (control); 2) 1-MCP (100 ppb); 3) 1-MCP ( 250 ppb); 4) 1-MCP (500 ppb). Unlike treatment with distilled water, all concentrations of 1-MCP were effective in delaying the senescence of flowers, however, the concentration of 500 ppb of 1-MCP induced better maintenance of quality and extended vase life of roses to 19 days. On the second experiment, the flowers remained in these following holding solutions: 1) Distilled water (Control); 2) 8-HQC (200 mg.L-1); 3) Sucrose (2%) + 8-HQC (200 mg.L-1); 4) Citric Acid (75 mg.L-1); 5) Sucrose (2%) + Citric Acid (75 mg.L-1); 6) 6-BA (60 mg.L-1); 7) Sucrose (2%) + 6-BA (60 mg.L-1). The roses were very sensitive to 6-benzyladenine, with or without sucrose, and lost quality of six days of vase life. In contrast, treatment with 8-hydroxyquinoline has proved the most promising to maintain the quality of the flowers, for ten days. On the third experiment, the roses were treated this way: 1) Distilled water (Control), 2) STS (1 mM) ... (Complete abstract click electronic access below)

Nous étudions l’influence d’une rétroaction optique à conjugaison de phase dans une diode laser. Ce type de rétroaction a été peu étudié et nous montrons ici qu’il donne des résultats intéressants, permettant de débloquer du contenu à haute fréquence. Cela pourrait mener à de meilleures performances dans des systèmes de génération de nombres aléatoires utilisant du chaos optique. / We study the influence of phase-conjugate feedback in a laser diode. This type of feedback has not been studied a lot and yet we show here that it can give interesting results. It unlocks oscillations at high frequencies. This could lead to an improvement in the performance of random number generators based on optical chaos.