.

Cette thèse a traité trois différents aspects ayant trait à la recherche du boson de Higgs dans le canal de désintégration en deux photons avec le détecteur ATLAS. Le premier est une étude sur l'uniformité intrinsèque du calorimètre électromagnétique (EM) d'ATLAS en utilisant la mesure du temps de dérive des électrons d'ionisation. Environs 500 000 signaux provenant de rayons cosmiques sont enregistrés et sont comparés à la forme du signal prédite en utilisant la méthode FPM (pour First Principle Method). L'ajustement de la forme prédite à celle mesurée permet de mesurer le temps de dérive des électrons d'ionisation de l'argon liquide. L'uniformité du temps de dérive dans le compartiment Middle calculée par blocs de taille 0.1 x 0.1 dans le plan (η,φ) est estimée à 1.27 ± 0.03%. L'impact de la variation du temps de dérive sur l'uniformité de la réponse du calorimètre est estimée à 0.29 ± 0.01%. En tenant compte de la variation de l'épaisseur des plaques de plomb qui constituent le milieu passif et qui ont été mesurées par ailleurs, l'uniformité intrinsèque du calorimètre est estimée à 0.34%. La vitesse de dérive des électrons mesurée dans les différents compartiments du calorimètre est en moyenne V_{D(E = 1 kV/mm) = 4.58 ± 0.07 mm.μ s^-1 en bon accord avec des mesures antérieures de la vitesse de dérive des électrons dans l'argon liquide à la température de 88.5K. Le second aborde la question de l'estimation de la matière en amont du calorimètre, utilisant une cartographie du détecteur interne. Cette mesure est faite relativement au nombre de conversions dans le tube à vide (beam pipe) de manière à être indépendante du flux initial de photons. Une connaissance précise de la matière en amont du calorimètre est essentielle à la calibration en énergie des électrons et photons reconstruits dans le calorimètre. Puisqu'une large fraction des photons proviennent de mésons π^0, le flux initial de photons qui intervient dans le taux de conversions dans le beam pipe est normalisé aux désintégrations Dalitz du π^0. L'observable qui permet de comparer les données aux simulations Monte-Carlo (MC) est le rapport du nombre de conversions reconstruites dans le beam pipe et du nombre de Dalitz reconstruits. Ce rapport estimé avec les données de collision à une énergie de 7 TeV dans le centre de masse donne un bon accord sur la mesure de la matière dans le beam pipe avec la prédiction du MC : X/X_0 = 0.669 ± 0.033(stat) ^+0.013_-0.080(syst)%, X/X_0 = 0.709 ± 0.028(syst) %, et X/X_0 = 0.709 ± 0.028(syst) %respectivement. Le dernier est l'étude de la normalisation du signal et du bruit de fond ainsi que l'analyse du potentiel discriminant dans l'analyse inclusive du canal H → γγ. Différentes simulations MC sont utilisées pour estimer une normalisation à l'ordre NLO du signal et du bruit de fond irréductible (γγ) ainsi que les erreurs systématiques associées. Celles-ci représentent respectivement 16% et 26% de la section efficace totale. Le pouvoir discriminant de l'impulsion transverse du système diphoton et du cosθ* est aussi étudié. En particulier, une forte corrélation entre le cosθ* et la masse invariante diphoton est observée. Le bruit de fond semi-réductible (γ-jet) est normalisé à NLO avec 27% d'erreurs systématiques. Une nouvelle normalisation qui s'applique après l'identification des photons est proposée. Elle prend en compte la différente réjection des jets provenant de quark ou de gluon et est estimée à 1.9 ± 0.6. Les perspectives d'exclusion du boson de Higgs dans le canal diphoton à 10 TeV et l'extrapolation à 7 TeV pour un luminosité intégrée de 1 f b^−1 sont présentées. Dans le dernier scénario, environ 5 fois le Modèle Standard est exclu à 95% de niveau de confiance pour une masse du boson de Higgs autour de 120 GeV/c^2 .

The purpose of this thesis is to design a robust test facility for a small space nuclear power system and model its physical behavior under different scenarios. The test facility will be used to simulate a 1-10kWe nuclear reactor, its electrical generation, and heat removal capabilities. This simulator will be used to explore, test and understand the steady-state and transient operation capabilities of small space nuclear power systems. Currently, the system is planned to operate on a variable, electrical heat source directly connected to heat pipes. The heat pipes are to be stainless steel with a water working fluid. These heat pipes will then be connected to a power conversion simulator or actual power conversion technologies. The power conversion simulator is connected to a radiator using a water based heat pipe network using fins and connecting plates in a cylindrical geometry. Modeling of the facility was performed using two different analysis programs, STELLA and SolidWorks. STELLA was used as a lumped sum heat transport code, and SolidWorks was used as a more accurate system to verify the validity of STELLA's results. Both programs were used to analyze startup, heat pipe failures, and loss of power conversion with the end goal of finding safe operational transient scenarios for the transient test facility. / Graduation date: 2013

The damaging impact of continuous utility cuts on flexible pavement performance has been shown to be a major problem for urban roads and pavement mangers due to high reconstruction and maintenance costs. Horizontal Directional Drilling (HDD) is a trenchless construction method that does not require continuous trenching. HDD pipe installation techniques can reduce reinstatement costs, shorten construction periods, and lower social costs due to reduced user traffic delays. In this thesis, a detailed field study and numerical investigations was completed to quantify pavement deterioration and polyethylene (PE) pipe performance when pipelines are installed under flexible pavements using both traditional open-cut and HDD construction methods. Two 200mm SDR-17 DIPS HDPE pipes were installed 1.5m below a flexible pavement using open-cut and HDD construction technique. A state-of-the-art instrumentation and data acquisition systems were developed to measure HDD drill rig, PE pipes and pavement responses during pipe installations and for a period of about three years afterwards. Field data from (GPR) surveys, falling weight deflectometer (FWD) tests, surface distress surveys, and ground surface elevation survey were used to evaluate pavement deterioration due to the pipeline installations. The mechanisms of ground deformations during HDD and open-cut pipe installation were numerically investigated with FLAC3D, a commercial finite difference program. A hybrid constitutive model consisting of the traditional Duncan-Chang hyperbolic model and Mohr-Coulomb perfectly plastic model was developed and implemented in FLAC3D to simulate the non-linear stress-strain and stress dependent behavior of granular materials. Field test results show that the HDD installed pipe have significantly lower construction induced strains and ring deflections when compared to the open cut-and-cover installation and the mechanism of pipe deformation differs for the two construction techniques. The two pipes performed satisfactory over the long-term monitoring period as deflections and strain levels were below acceptable limits and there was no apparent deterioration of the pipe. Pipe deflections resulting from environmental effects (freeze and thaw) were found to be more significant than those due to material creep. Furthermore, the modified Iowa’s and Plastic Pipe Institute’s (PPI) ring deflection equations were found to over estimate pipe deflection for the open-cut and HDD installed pipes by about 114 and 50 percent, respectively. Results from field tests found that the HDD installation did not results in any observable change in the condition of the pavement structure performance, while the structure and integrity of pavement section in the vicinity of the open-cut was adversely impacted by utility cut excavation. It was determined numerically that when an unsupported excavation is created within a typical flexible pavement structure, distress zones that extend laterally from the face of the excavation to a distance of approximately 80% of the depth of excavation is developed. The results of the analyses suggests that better restoration techniques are required to eliminate the adverse effect caused by the stress relief within the pavement structure during a utility cut. Furthermore, the area of potential pavement deterioration should be extended beyond the edge of the utility cut to encompass the ‘distress zones’ when determining fees to cover pavement damage and restoration costs. Results obtained from numerical simulations advanced the understanding of the mechanism, magnitude, and extent of deformation within the pavement structure during HDD pipe installation in frictional and cohesive subgrade soils. Relationship between HDD annular bore pressures and displacements have been incorporated into design Charts and Tables for use in estimating maximum allowable bore pressures for HDD installation beneath flexible pavements. Critical bore pressures that would limit ground deformations and prevent excessive pavement deformations are presented. Critical bore pressures were compared to estimated allowable bore pressures obtained from the widely used Delft Geotechnics equation. The Delft Geotechnics equation was found to over estimate allowable bore pressure for HDD installation beneath flexible pavement. HDD pipeline installations under flexible pavement were found to have significantly lower restoration costs, social costs and maintenance cost than open-cut pipeline installations.

Concrete structures can often be modeled as plates, for example, bridges, tunnel walls and pipes. Near-surface damage in concrete structures mostly takes the form of cracking. Surface-breaking cracks affect concrete properties and structural integrity; therefore, the nondestructive evaluation of crack depth is important for structural monitoring, strengthening and rehabilitation. On the other hand, material damping is a fundamental parameter for the dynamic analysis of material specimens and structures. Monitoring damping changes is useful for the assessment of material conditions and structural deterioration. The main objective of this research is to develop new methodologies for depth evaluation of surface-breaking cracks and the evaluation of damping in concrete plates. Nondestructive techniques based on wave propagation are useful because they are non-intrusive, efficient and cost effective. Previous studies for the depth evaluation of surface-breaking cracks in concrete have used diffracted compressional waves (P-waves). However, surface waves exhibit better properties for the characterization of near surface defects, because (a) surface waves dominate the surface response, they carry 67% of the wave propagation energy, and present lower geometrical attenuation because the propagating wave front is cylindrical; and (b) the penetration depth of Rayleigh waves (R-waves) depends on their frequency. Most of the R-wave energy concentrates at a depth of one-third of their wavelengths. The transmission of R-waves through a surface-breaking crack depends on the crack depth; this depth sensitivity is the basis for the so-called Fourier transmission coefficient (FTC) method. R-waves only exist in a half-space (one traction-free surface); whereas in the case of a plate (two traction-free surfaces), Lamb modes are generated. Fundamental Lamb modes behave like R-waves at high frequencies, because their wavelengths are small relative to the plate thickness. Lamb modes are not considered in the standard FTC method, and the FTC method is also affected by the selected spacing between receivers. The FTC calculation requires the use of an explicit time window for the identification of the arrival of surface waves, and the selection of a reliable frequency range. This research presents theoretical, numerical and experimental results. Theoretical aspects of Lamb modes are discussed, and a theoretical transfer function is derived, which can be used to study changes of Lamb modes in the time and frequency domains as a function of distance. The maximum amplitude of the wavelet transform varies with distance because of the dispersion of Lamb modes and the participation of higher Lamb modes in the response. Numerical simulations are conducted to study the wave propagation of Lamb modes through a surface-breaking crack with different depths. The surface response is found to be dominated by the fundamental Lamb mode. Using the 2D Fourier transform, the incident, transmitted and reflected fundamental Lamb modes are extracted. A transmission ratio between the transmitted and incident modes is calculated, which is sensitive to crack depths (d) normalized to the wavelength (λ) in a range (d / λ) = 0.1 to 1/3. A new wavelet transmission coefficient (WTC) method for the depth evaluation of surface-breaking cracks in concrete is proposed to overcome the main limitations of the FTC method. The WTC method gives a global coefficient that is correlated with the crack depth, which does not require time windowing and the pre-selection of a frequency bandwidth. To reduce the effects of wave reflections, which are present in the FTC method because of the non-equal spacing configuration, a new equal spacing configuration is used in the WTC method. The effects of Lamb mode dispersion are also reduced. In laboratory tests, an ultrasonic transmitter with central frequency at 50kHz is used as a source; the 50kHz frequency is appropriate for the concrete plate tested (thickness 80mm), because the fundamental Lamb modes have converged to the Rayleigh wave mode. The new method has also been used in-situ at Hanson Pipe and Precast Inc., Cambridge, Ontario, Canada, and it shows potential for practical applications. In general, the evaluation of material damping is more difficult than the measurement of wave velocity; the dynamic response and attenuation of structural vibrations are predominantly controlled by damping, and the damping is typically evaluated using the modal analysis technique, which requires considerable efforts. The existing methods based on surface waves, use the Fourier transform to measure material damping; however, an explicit time window is required for the spectral ratio method to extract the arrival of surface wave; in addition, a slope of the spectral ratio varies for different frequency ranges, and thus a reliable frequency range needs to be determined. This research uses the wavelet transform to measure material damping in plates, where neither an explicit time window nor the pre-selection of a frequency bandwidth are required. The measured material damping represents an average damping for a frequency range determined by source. Both numerical and experimental results show good agreement and the potential for practical applications.

The damaging impact of continuous utility cuts on flexible pavement performance has been shown to be a major problem for urban roads and pavement mangers due to high reconstruction and maintenance costs. Horizontal Directional Drilling (HDD) is a trenchless construction method that does not require continuous trenching. HDD pipe installation techniques can reduce reinstatement costs, shorten construction periods, and lower social costs due to reduced user traffic delays. In this thesis, a detailed field study and numerical investigations was completed to quantify pavement deterioration and polyethylene (PE) pipe performance when pipelines are installed under flexible pavements using both traditional open-cut and HDD construction methods. Two 200mm SDR-17 DIPS HDPE pipes were installed 1.5m below a flexible pavement using open-cut and HDD construction technique. A state-of-the-art instrumentation and data acquisition systems were developed to measure HDD drill rig, PE pipes and pavement responses during pipe installations and for a period of about three years afterwards. Field data from (GPR) surveys, falling weight deflectometer (FWD) tests, surface distress surveys, and ground surface elevation survey were used to evaluate pavement deterioration due to the pipeline installations. The mechanisms of ground deformations during HDD and open-cut pipe installation were numerically investigated with FLAC3D, a commercial finite difference program. A hybrid constitutive model consisting of the traditional Duncan-Chang hyperbolic model and Mohr-Coulomb perfectly plastic model was developed and implemented in FLAC3D to simulate the non-linear stress-strain and stress dependent behavior of granular materials. Field test results show that the HDD installed pipe have significantly lower construction induced strains and ring deflections when compared to the open cut-and-cover installation and the mechanism of pipe deformation differs for the two construction techniques. The two pipes performed satisfactory over the long-term monitoring period as deflections and strain levels were below acceptable limits and there was no apparent deterioration of the pipe. Pipe deflections resulting from environmental effects (freeze and thaw) were found to be more significant than those due to material creep. Furthermore, the modified Iowa’s and Plastic Pipe Institute’s (PPI) ring deflection equations were found to over estimate pipe deflection for the open-cut and HDD installed pipes by about 114 and 50 percent, respectively. Results from field tests found that the HDD installation did not results in any observable change in the condition of the pavement structure performance, while the structure and integrity of pavement section in the vicinity of the open-cut was adversely impacted by utility cut excavation. It was determined numerically that when an unsupported excavation is created within a typical flexible pavement structure, distress zones that extend laterally from the face of the excavation to a distance of approximately 80% of the depth of excavation is developed. The results of the analyses suggests that better restoration techniques are required to eliminate the adverse effect caused by the stress relief within the pavement structure during a utility cut. Furthermore, the area of potential pavement deterioration should be extended beyond the edge of the utility cut to encompass the ‘distress zones’ when determining fees to cover pavement damage and restoration costs. Results obtained from numerical simulations advanced the understanding of the mechanism, magnitude, and extent of deformation within the pavement structure during HDD pipe installation in frictional and cohesive subgrade soils. Relationship between HDD annular bore pressures and displacements have been incorporated into design Charts and Tables for use in estimating maximum allowable bore pressures for HDD installation beneath flexible pavements. Critical bore pressures that would limit ground deformations and prevent excessive pavement deformations are presented. Critical bore pressures were compared to estimated allowable bore pressures obtained from the widely used Delft Geotechnics equation. The Delft Geotechnics equation was found to over estimate allowable bore pressure for HDD installation beneath flexible pavement. HDD pipeline installations under flexible pavement were found to have significantly lower restoration costs, social costs and maintenance cost than open-cut pipeline installations.

Concrete structures can often be modeled as plates, for example, bridges, tunnel walls and pipes. Near-surface damage in concrete structures mostly takes the form of cracking. Surface-breaking cracks affect concrete properties and structural integrity; therefore, the nondestructive evaluation of crack depth is important for structural monitoring, strengthening and rehabilitation. On the other hand, material damping is a fundamental parameter for the dynamic analysis of material specimens and structures. Monitoring damping changes is useful for the assessment of material conditions and structural deterioration. The main objective of this research is to develop new methodologies for depth evaluation of surface-breaking cracks and the evaluation of damping in concrete plates. Nondestructive techniques based on wave propagation are useful because they are non-intrusive, efficient and cost effective. Previous studies for the depth evaluation of surface-breaking cracks in concrete have used diffracted compressional waves (P-waves). However, surface waves exhibit better properties for the characterization of near surface defects, because (a) surface waves dominate the surface response, they carry 67% of the wave propagation energy, and present lower geometrical attenuation because the propagating wave front is cylindrical; and (b) the penetration depth of Rayleigh waves (R-waves) depends on their frequency. Most of the R-wave energy concentrates at a depth of one-third of their wavelengths. The transmission of R-waves through a surface-breaking crack depends on the crack depth; this depth sensitivity is the basis for the so-called Fourier transmission coefficient (FTC) method. R-waves only exist in a half-space (one traction-free surface); whereas in the case of a plate (two traction-free surfaces), Lamb modes are generated. Fundamental Lamb modes behave like R-waves at high frequencies, because their wavelengths are small relative to the plate thickness. Lamb modes are not considered in the standard FTC method, and the FTC method is also affected by the selected spacing between receivers. The FTC calculation requires the use of an explicit time window for the identification of the arrival of surface waves, and the selection of a reliable frequency range. This research presents theoretical, numerical and experimental results. Theoretical aspects of Lamb modes are discussed, and a theoretical transfer function is derived, which can be used to study changes of Lamb modes in the time and frequency domains as a function of distance. The maximum amplitude of the wavelet transform varies with distance because of the dispersion of Lamb modes and the participation of higher Lamb modes in the response. Numerical simulations are conducted to study the wave propagation of Lamb modes through a surface-breaking crack with different depths. The surface response is found to be dominated by the fundamental Lamb mode. Using the 2D Fourier transform, the incident, transmitted and reflected fundamental Lamb modes are extracted. A transmission ratio between the transmitted and incident modes is calculated, which is sensitive to crack depths (d) normalized to the wavelength (λ) in a range (d / λ) = 0.1 to 1/3. A new wavelet transmission coefficient (WTC) method for the depth evaluation of surface-breaking cracks in concrete is proposed to overcome the main limitations of the FTC method. The WTC method gives a global coefficient that is correlated with the crack depth, which does not require time windowing and the pre-selection of a frequency bandwidth. To reduce the effects of wave reflections, which are present in the FTC method because of the non-equal spacing configuration, a new equal spacing configuration is used in the WTC method. The effects of Lamb mode dispersion are also reduced. In laboratory tests, an ultrasonic transmitter with central frequency at 50kHz is used as a source; the 50kHz frequency is appropriate for the concrete plate tested (thickness 80mm), because the fundamental Lamb modes have converged to the Rayleigh wave mode. The new method has also been used in-situ at Hanson Pipe and Precast Inc., Cambridge, Ontario, Canada, and it shows potential for practical applications. In general, the evaluation of material damping is more difficult than the measurement of wave velocity; the dynamic response and attenuation of structural vibrations are predominantly controlled by damping, and the damping is typically evaluated using the modal analysis technique, which requires considerable efforts. The existing methods based on surface waves, use the Fourier transform to measure material damping; however, an explicit time window is required for the spectral ratio method to extract the arrival of surface wave; in addition, a slope of the spectral ratio varies for different frequency ranges, and thus a reliable frequency range needs to be determined. This research uses the wavelet transform to measure material damping in plates, where neither an explicit time window nor the pre-selection of a frequency bandwidth are required. The measured material damping represents an average damping for a frequency range determined by source. Both numerical and experimental results show good agreement and the potential for practical applications.

In this study, the aim is to investigate the stiffness, longitudinal tensile strength and circumferential tensile strength of short fiber reinforced polyester composite pipes produced by centrifugal casting production method. To achieve this aim, theoretical calculation of modulus of elasticity of pipes was done and then test program was carried out on pipe samples produced with three different resin types which were orthophthalic, isophthalic and vinyl ester resin and three different fiber types which were E glass fiber, ECR glass fiber and basalt fiber. The tests were performed according to ISO (International Organization for Standardization) standards. When resin type and fiber type effect on the fiber reinforced polyester pipe samples were evaluated, calculated elastic modulus values were in accordance with the test results. According to the experimental test data, which were used to evaluate the effect of resin type on fiber reinforced polyester pipe properties, there is not a significant difference was observed in the stiffness, longitudinal and circumferential tensile strength test results of pipes having different resin types. In other words, there was not a significant effect of resin type on the stiffness, longitudinal tensile strength and circumferential tensile strength of short fiber reinforced pipes produced by centrifugal casting method. According to the experimental test data, which were used to evaluate the effect of fiber type on the properties of fiber reinforced polyester pipe, basalt fiber reinforced pipe samples showed higher mechanical performance over E glass fiber and ECR glass fiber reinforced pipes. However, the test results of basalt reinforced polyester pipe were not as good as the individual properties of basalt fiber. Finally, by comparing the basalt fiber reinforced pipe samples having almost the same stiffness and tensile test results as E glass fiber reinforced pipe samples, the gain in fiber and resin amount were investigated. Basalt fiber reinforced pipes were slightly lighter and thinner than E glass fiber reinforced pipes. However, the decrease in the amount of the fiber and resin in basalt reinforced pipe did not result in an overall cost reduction.

In this study, the effect of pipe-soil relative stiffness on the behaviour of buried flexible pipes was investigated considering the pipe size, material type, stiffness, pipe-soil and natural soil-backfill interfaces and geometry of the trench using the finite element method. For this purpose, a parametric study was conducted to examine the effect of different variables on the resulting earth loads and deformations imposed on the buried pipes. Various types of trench pipe-soil cases were analysed for a certain natural ground and backfill material by the PLAXIS finite element code which allows simulating non-linear soil behaviour, the stages of construction as well as the pipe-soil interaction aspects of the problem. Loads and deformations obtained by the finite element method were compared with those calculated by the conventional approaches for different pipe-soil stiffness ratios. The finite element results obtained for the deformation of typically flexible Polyethylene pipes were then used to back-calculate the range of modulus of soil reaction, E&#039 / , values for various pipe-soil relative stiffness and they were compared with the suggested value proposed by Howard (1977).

The present study describes the flow characteristics of swirling flows induced by twisted tape inserts in circular pipes. The study is focused on the secondary flow which is investigated experimentally and with numerical models. The results are expected to improve the paper manufacturing process by identifying and removing the detrimental secondary flow. Experimental tests show for the first time the existence of two co-rotating helical vortices superimposed over the main swirling flow, downstream of twisted tapes. The close proximity of the two co-rotating vortices creates a local counter-rotating flow at the pipe centerline. The flow is analyzed using LDV measurements and high speed camera visualization with fine air bubbles seeding which confirm that the helical vortices are stable. After extracting the characteristic tangential velocity profiles of the main vortex and of the two secondary vortices, it was observed that the maximum tangential velocity of all three vortices is the same, approximately half of the bulk velocity. The winding of the helical vortices is in the swirl direction and the pitch of the helical vortices is found to be independent of the inlet velocity. The experimental findings are confirmed by numerical simulations. The numerical results show that the helical vortices originate inside the swirler and evolve from single co-rotating vortices on each side of the tape. The flow characteristics are analyzed in detail. Swirlers with multiple twists and multiple chambers are shown to have less stable secondary motion and could be employed in applications were the secondary motion is detrimental.