Browsing by Subject "CMS"
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Item Adapting a Beam-Based Rotordynamics Model to Accept a General Three-Dimensional Finite-Element Casing Model(2011-08-08) James, Stephen M.The subject of this thesis is an extension of a two-dimensional, axisymmetric, Timoshenko-beam finite-element rotordynamic code to include a three-dimensional non-axisymmetric solid-element casing model. Axisymmetric beams are sufficient to model rotors. Spring and damper forces provide the interface between the rotor and its casing and capture the dynamics of the full model. However, axisymmetric beams limit the modeling of real-case machine structures, where the casing is not axisymmetric. Axisymmetric and non-axisymmetric 3D finite element casing structures are modeled. These structures are then reduced using a technique called substructuring. Modal equations are developed for axisymmetric and non-axisymmetric casing models. In a 3D non-axisymmetric model, structural dynamics modes can be modeled by lateral modes in two orthogonal planes. Modal information of the complex 3D casing structures are generated, and then incorporated into the 2D code after a series of pre-processing steps. A reduction method called Component Mode Synthesis (CMS) is used to reduce the large dimensionality involved in calculation of rotordynamic coefficients. The results from the casing structures are merged with the rotor model to create a combined rotor-casing model. The analysis of the combined structure shows that there is a difference in the natural frequencies and unbalance response between the model that uses symmetrical casing and the one that uses non-axisymmetric casing. XLTRC2 is used as an example of a two-dimensional axisymmetric beam-element code. ANSYS is used as a code to build three-dimensional non-axisymmetric solid-element casing models. The work done in this thesis opens the scope to incorporate complex non-axisymmetric casing models with XLTRC2.Item Classifying learning management platforms by examining features and educational affordances(2011-08) Sung, Woon Hee; Liu, Min, Ed. D.; Veletsianos, GeorgeLearning management systems(LMSs) have become one of the most common computer systems adopted at universities, colleges and distance learning organizations. In order to identify different features and accordance of each LMS, LMSs’ features were compared by using four different categories; communication tools, productivity and student involvement tools, course delivery tools, and administration tools. Based upon the comparison of the different features affecting different usage patterns, this paper proposes a classification of seven selected LMSs; ANGEL, Blackboard, Moodle, Sakai, WebCT, Ning and Elgg. These seven LMSs are classified into three groups according to systems’ pedagogical adaptability and technological usability. The classification seeks to understand the possibilities and limitations of what these classified groups of LMSs can accomplish and is used to suggest a suitable usage in order to support teaching and learning. The proposed classification implies the need of future exploratory case study analyzing teaching and learning practices according to the classification.Item Search for New Heavy Resonances Decaying To t+t^- Pairs at the LHC with Square Root S= 7 TEV (L = 5.0 FB^-1)(2015-01-22) Suarez, IndaraThe Standard Model (SM) describes the known fundamental particles and their interactions due to the electromagnetic, weak, and strong forces through vector boson exchange. Although the SM has had major success in predicting a wealth of experimental measurements, astrophysical evidence for dark matter the observation of neutrino oscillations, and the matter-antimatter asymmetry in the universe indicate that the SM is not a complete theory. In addition to these experimental observations, problems stemming from the failure to incorporate the gravitational force and the quantum instability of the mass of the Higgs Boson have also contributed to the motivation to search for physics beyond the SM. Multiple theoretical scenarios, including those inspired by Grand Unified Theories (GUTs), models with extra spatial dimensions, and Supersymmetry (SUSY), have been proposed to address the shortcomings of the SM. In many of these models, the new symmetries that extend the SM gauge structure require the existence of new heavy neutral gauge bosons. Regardless of the exact nature or production mechanism of the hypothesized heavy bosons, they may be observed by studying dilepton final states at high energy colliders. As many models of physics beyond the SM predict enhanced couplings to third generation particles, searches for the new heavy bosons decaying into two ? -leptons are particularly well motivated. We present a direct search for high mass neutral resonances decaying into two opposite sign ?-leptons using data from proton-proton collisions at the LHC with center-of-mass energy square root of s = 7 TeV. The search has been conducted using data recorded by the Compact Muon Solenoid (CMS) experiment, corresponding to an integrated luminosity of 4.94 fb?1 and includes final states with leptonic and hadronic decays of the ?-lepton. The data has been found to be consistent with the background-only hypothesis within the sensitivity of the measurement. Using the Sequential Standard Model Z?-boson as a benchmark, we set a 95% confidence-level upper limit on the mass of Z?-bosons decaying to pairs of ?-leptons.Item Search for Supersymmetry in the Jets + Met + TAUS Final State Using the CMS Detector at the LHC(2013-02-28) Montalvo, Roy JoaquinIn this dissertation results are presented from a search for the pair production of heavy colored particles (gluinos, squarks) in R-parity conserving supersymmetric models, in which the lightest supersymmetric particle is a stable and neutral object. The search was performed for events with at least two tau leptons, two highly energetic jets and large missing transverse momentum in the final state on a data sample of proton-proton collisions at sqrt(s) = 7 TeV. The data sample was collected by the Compact Muon Solenoid detector at the Large Hadron Collider in 2011, and it corresponds to an integrated luminosity of 5fb^?1. The tau isolation variable was optimized for this search. The number of events corresponding to standard model processes in the final selection was estimated to be 7.49 ? 0.74 using background estimation techniques based on data. Nine observed events are found to be in agreement with the standard model prediction, and exclusion limits on gluino mass are obtained in the context of supersymmetric models at the 95% confidence level.