This dissertation describes a search for Z/{gamma}* boson pair production decaying into {mu}{mu}{mu}{mu}, {mu}{mu}ee, and eeee final states with approximately 1 fb{sup -1} of data at the Fermilab Tevatron Collider at {radical}s = 1.96 TeV. The small cross section times branching ratio for each channel mandated a thorough study of the acceptance and efficiencies. After optimization, 1.7 {+-} 0.1 events are expected for Standard Model production with a background of 0.13 {+-} 0.03 events. One event was found in the {mu}{mu}ee channel. A cross section limit of 4.4 pb is determined at a 95% confidence level for Standard Model production. Additionally, one parameter and two parameter 95% C.L. limits are found for the anomalous neutral trilinear gauge couplings ZZZ* and ZZ{gamma}*. The one parameter 95% C.L. coupling limits with a form factor scale of 1.2 TeV are: -0.28 < f{sub 40}{sup Z} < 0.28, -0.31 < f{sub 50}{sup Z} < 0.29, -0.26 < f{sub 40}{gamma} < 0.26, and -0.30 < f{sub 50}{sup {gamma}} < 0.28.

The Standard Model gives a satisfying description of subatomic processes at low energy (< 1 TeV). Beyond this energy scale, other models must be considered. Supersymmetry is one of them. It gives in an elegant way, solutions to several Standard Model short comings. This document reports the search for a supersymmetric signal characterized by the production of two stops decaying into two b-jets, one electron, one muon and missing energy. This study has been performed at the D0 experiment, located on the ring of Tevatron collider at FermiLab, (Chicago, USA), whose energy in the center of mass reaches {radical}s = 1.96 TeV. The data used for this analysis have been collected during Run IIa of D0 detector; from april 2003 to march 2006 ({approx} 1fb{sup -1}). The objects handled for this analysis require a good understanding of both calorimeters, muon detectors and trackers. As Tevatron is an hadronic collider and the number of Standard Model processes with the same signature as the signal is low, the background is thus dominated by QCD processes. After the selection cuts, no excess of data has been observed with respect to the Standard Model expectation. D0 experiment sensibility has been improved and the 95% …

Structural Health Monitoring (SHM) promises to deliver great benefits to many industries. Primarily among them is a potential for large cost savings in maintenance of complex structures such as aircraft and civil infrastructure. However, several large obstacles remain before widespread use on structures can be accomplished. The development of three components would address many of these obstacles: a robust sensor validation procedure, a low-cost active-sensing hardware and an integrated software package for transition to field deployment. The research performed in this thesis directly addresses these three needs and facilitates the adoption of SHM on a larger scale, particularly in the realm of SHM based on piezoelectric (PZT) materials. The first obstacle addressed in this thesis is the validation of the SHM sensor network. PZT materials are used for sensor/actuators because of their unique properties, but their functionality also needs to be validated for meaningful measurements to be recorded. To allow for a robust sensor validation algorithm, the effect of temperature change on sensor diagnostics and the effect of sensor failure on SHM measurements were classified. This classification allowed for the development of a sensor diagnostic algorithm that is temperature invariant and can indicate the amount and type of sensor failure. …

This thesis centers on the use of spectral modeling techniques on data from the Sloan Digital Sky Survey (SDSS) to gain new insights into current questions in galaxy evolution. The SDSS provides a large, uniform, high quality data set which can be exploited in a number of ways. One avenue pursued here is to use the large sample size to measure precisely the mean properties of galaxies of increasingly narrow parameter ranges. The other route taken is to look for rare objects which open up for exploration new areas in galaxy parameter space. The crux of this thesis is revisiting the classical Kennicutt method for inferring the stellar initial mass function (IMF) from the integrated light properties of galaxies. A large data set ({approx} 10{sup 5} galaxies) from the SDSS DR4 is combined with more in-depth modeling and quantitative statistical analysis to search for systematic IMF variations as a function of galaxy luminosity. Galaxy H{alpha} equivalent widths are compared to a broadband color index to constrain the IMF. It is found that for the sample as a whole the best fitting IMF power law slope above 0.5 M{sub {circle_dot}} is {Lambda} = 1.5 {+-} 0.1 with the error dominated by …

A RANS/DES numerical procedure with an extended Lax-Wendroff control-volume scheme and turbulence model is described for the accurate simulation of internal/external axisymmetric flow with and without strong rotation. This new procedure is an extension, from Cartesian to cylindrical coordinates, of (1) a second order accurate multi-grid, control-volume integration scheme, and (2) a k-{omega} turbulence model. This paper outlines both the axisymmetric corrections to the mentioned numerical schemes and the developments of techniques pertaining to numerical dissipation, multi-block connectivity, parallelization, etc. Furthermore, analytical and experimental case studies are presented to demonstrate accuracy and computational efficiency. Notes are also made toward numerical stability of highly rotational flows.

Performance-driven interface contract enforcement research aims to improve the quality of programs built from plug-and-play scientific components. Interface contracts make the obligations on the caller and all implementations of the specified methods explicit. Runtime contract enforcement is a well-known technique for enhancing testing and debugging. However, checking all of the associated constraints during deployment is generally considered too costly from a performance stand point. Previous solutions enforced subsets of constraints without explicit consideration of their performance implications. Hence, this research measures the impacts of different interface contract sampling strategies and compares results with new techniques driven by execution time estimates. Results from three studies indicate automatically adjusting the level of checking based on performance constraints improves the likelihood of detecting contract violations under certain circumstances. Specifically, performance-driven enforcement is better suited to programs exercising constraints whose costs are at most moderately expensive relative to normal program execution.

In this thesis we present a measurement of the relative fraction of t{bar t} events produced via gluon-fusion to the total number of t{bar t} events. Using the kinematics of the production and decay of the top and antitop quark pair, we trained a Neural Network to discriminate the gluon-fusion events. The Neural Network was then used as a template to fit for the gluon-fusion fraction in data. Using a total integrated luminosity of 955 pb{sup -1} we find {sigma}(gg{yields}t{bar t})/{sigma}(p{bar p}{yields}t{bar t}) < 0.33 at 68% confidence level and {sigma}(gg{yields}t{bar t})/{sigma}(p{bar p}{yields}t{bar t}) < 0.61 at 95% confidence level.