Axially-moving materials arise in problems associated with spacecraft antennas, pipes conveying fluid and telescopic robotic manipulators. Flexible extendible beams are a special class of axially-moving materials, in which the axially-moving material is modelled as a slender beam and the mechanism of elastic deformation is transverse bending. Hamilton's principle is used to derive the governing differential equation of motion and system invariant properties of a flexible extendible beam protruding from a rigid wall with prescribed extrusion profile. The mass of the system is not constant and the general analytical solution to the equation of motion is not known. In this study, numerical solutions are obtained using finite-element analysis. However, instead of following the obvious (but cumbersome) approach of using fixed-size elements and increasing their number, in a stepwise fashion, as mass elements enter the domain of interest, a more elegant approach is followed wherein the number of elements is fixed, while the sizes of the elements change with time. To this end, a variable-domain beam finite element whose size is a prescribed function of time is formulated. The accuracy of this variable-domain beam element is demonstrated through the time-integration of equations of motion using various extrusion profiles. Additional verification is performed by the evaluation of the system's invariant quantities, comparison with a special analytical solution, and the dynamic stability analysis of pipes conveying fluid. The effects of wall flexibility, tip mass, and high-frequency axial-motion perturbations to the transverse response of the flexible extendible beam are also examined. In order to gain a deeper insight into the mechanics of this system, the dynamic stability characteristics of the flexible extendible beam are also investigated using various extrusion profiles. The effects of physical damping, tip mass, tip support and wall flexibility on the stability characteristics of this system are examined. The power and versatility of this finite-element formulation is demonstrated in a simulation of an extruding flexible extendible beam which carries a tip mass and protrudes from a flexible envelope beam which imparts three-dimensional rigid-body rotations to the system. / Graduate

abstract: The theory of quantum electrodynamics predicts that beta decay of the neutron into a proton, electron, and anti-neutrino should be accompanied by a continuous spectrum of photons. A recent experiment, RDK I, reported the first detection of radiative decay photons from neutron beta decay with a branching ratio of (3.09 ± 0.32) × 10-3 in the energy range of 15 keV to 340 keV. This was achieved by prompt coincident detection of an electron and photon, in delayed coincidence with a proton. The photons were detected by using a single bar of bismuth germanate scintillating crystal coupled to an avalanche photodiode. This thesis deals with the follow-up experiment, RDK II, to measure the branching ratio at the level of approximately 1% and the energy spectrum at the level of a few percent. The most significant improvement of RDK II is the use of a photon detector with about an order of magnitude greater solid angle coverage than RDK I. In addition, the detectable energy range has been extended down to approximately 250 eV and up to the endpoint energy of 782 keV. This dissertation presents an overview of the apparatus, development of a new data analysis technique for radiative decay, and results for the ratio of electron-proton-photon coincident Repg to electron-proton coincident Rep events. / Dissertation/Thesis / Ph.D. Physics 2012

Desenvolvemos uma nova técnica de equações de movimento para excitações nucleares partícula-partícula. Para isso, foi estendido o formalismo de duplos-comutadores de Rowe, relaxando-se a condição de aniquilação do estado-pai, violada no presente caso. As equações foram testadas para estados com senioridade nula de 2, 4 e 6 partículas sujeitas a uma força de emparelhamento, estando os resultados em excelente concordância com a solução exata. Foram também calculados, usando-se as novas equações e uma hamiltoniana realística, os estados de baixa energia com J = 0+, 2+, 4+, 6+ e 8+ para o 210,212,214Pb e 0+, 2+, 4+ e 6+ para o 206,204,202Pb. Tanto as energias de excitação como as taxas de transição (t,p) ou (p ,t) para esses estados concordam bem com as obtidas por um cálculo convencional de modelo de camadas de McGrory e Kuo e com os dados experimentais. O formalismo deverá ser útil para a análise de reações de transferência de dois núcleons. / A new equations-of-motion technique for particle-particle excitations in nuclei is developed. To this end Rowe\'s double-commutator formalism was extended, relaxing the condition of annihilation of the parent state, which is violated in the present case. The new equations were tested for seniority-zero states of 2, 4 and 6 particles interacting with a pairing force, and the results are in excellent agreement with the existing exact solution. Also computed, using the new equations and a realistic Hamiltonian, were the low energy states with J = 0+, 2+, 4+, 6+ and 8+ the case of 210,212,214 Pb and 0+, 2+, 4+ and 6+ in the case of 206, 204,202Pb. Both the excitation energies and the transition rates for the (t,p) or (p,t) \"reaction leading to those states are in as good an agreement with the experimental data as those obtained in a conventional shell-model calculation performed by McGrory and Kuo for some the above isotopes. The present formalism should be of interest for the analysis of two-nucleon transfer reactions.

Brookhaven National Laboratory experiment E949 was designed to search for the rare K meson decay K⁺ → π⁺ , neutrino, and anti-neutrino, a decay sensitive to physics beyond the Standard Model. While previous data analyses dealt with the high π⁺ momentum region accessible for this reaction, this thesis concentrates on the lower range between 140 and 199 MeV/c. Analysis of this low π⁺ momentum region was performed to search for additional evidence of the process K⁺ → π⁺, neutrino, and anti-neutrino. A blind analysis technique was used to avoid bias when developing the selection criteria used to suppress the competing background processes. The blind analysis technique was based on identifying background sources a priori and only examining the signal region once all selection criteria and background estimates had been finalized. The background estimates were performed using a technique known as a "bifurcation method", which relied on using two uncorrelated selection criteria to suppress each background source. The analysis of an exposure of 1.71 x 10¹² K⁺ decays resulted in an observation of three events with an estimated background of 0.927 ± 0.168(stat.)⁺³²⁰-₀.₂₃₇(sys.) events and a single event sensitivity of (4.28 ± 0.43)x 10-¹⁰. Using a likelihood method, the three candidate events observed here were combine with the previous E787 and E949 results, yielding a branching ratio of ϐ(K⁺ → π⁺, neutrino, and anti-neutrino decay of (1.73+1.15-1.05) x 10⁻¹⁰ at the 68% confidence level. This branching ratio is consistent with the prediction of the Standard Model, (0.85 ± 0.07) x 10⁻¹⁰. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis describes a new method for simulating high Reynolds number turbulence which requires much less computing power. This involved both theoretical work - to understand and model the important processes - and computational work, to implement the model efficiently. There are 'many different techniques for modelling particle dispersion in turbulent flow (e.g. K-theory and Random Flight) but they make assumptions about the fluid-particle interaction and require empirical coefficients. Theoretical work on the motion of bubbles and varticles in idealised flows has shown that the instantaneous structure of the velocity field is important in determining particle trajectories, and that particle motion cannot currently be modelled reliably in terms of time- or ensemble-averaged fluid velocities. Therefore the solution of many practical problems requires the simulation of the instantaneous structure of a turbulent velocity field. This can now be provided with the very large computers and large amounts of computer time; even then, only low Reynolds number turbulence can be simulated. In the method developed here, the velocity field of homogeneous isotropic turbulence is simulated by a large number of random Fourier modes varying in space and time. They are chosen so that the flow field has certain properties, namely (i) it satisfies continuity, (ii) the two point Eulerian spatial spectra have known form (e.g. the Kolmogorov inertial subrange), (iii) the time dependence is modelled by dividing the turbulence into large- and small-scales eddies, and by assuming that the large eddies advect the small eddies which also decorrelate as they are advected, (iv) the large- and small-scale Fourier modes are each statistically independent and Gaussian. Computations of the streamlines in a sequence of realisations of the flow show that they have a similar structure to that obtained from direct numerical simulations. New results for the statistics of high Reynolds number turbulent flows are obtained, for the velocity and pressure fields . Particle statistics are obtained by computing the trajectories of many particles and taking the ensemble average. Particle dispersion has been computed for a range of particle parameters and the results agree well with experimental measurements such as those of Snyder and Lumley; this enables us to compute empirical coefficients (e.g. Lagrangian timescales) for use in simpler models such as Random Flight, and for modelling other processes such as combustion and mixing. Rapid Distortion Theory is used to investigate the effects of high shear rate on the structure of homogeneous turbulence in chapter 4. The results show that an important effect of the shear acting on initially isotropic turbulence is the selective amplification of structures having large length scale in the mean flow direction.

In this thesis we examine the method of counting BB events produced in the BaBar experiment. The original method was proposed in 2000, but improvements to track reconstruction and our understanding of the detector since that date make it appropriate to revisit the B Counting method. We propose a new set of cuts designed to minimize the sensitivity to time-varying backgrounds. We find the new method counts BB events with an associated systematic uncertainty of ±0.6%. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

In this dissertation, we explore the cosmological sensitivity of well-motivated extensions of the Standard Model (SM) of particles. We focus on two specific models, the vector portal and the Higgs portal, that can connect the SM to a dark sector of new hidden particles. We find that both portals have sensitivity in the ultra-weak coupling regime, where the relic abundance is set by the freeze-in mechanism. Provided that the mediators of the portal interactions decay into the SM, we derive the constraints on masses and couplings of such states from precision cosmology. As a primary source of constraints, we use Big Bang Nucleosynthesis (BBN), the Cosmic Microwave Background (CMB) and the diffuse X-ray background. For the Higgs portal scalar, we improve the relic abundance calculation in the literature and provide an estimate of thermal corrections to the freeze-in yield. We find that the cosmological bounds are relatively insensitive to improvements in the abundance accuracy, and a full finite-temperature calculation is not needed. We also investigate the BBN constraints for hypothetical long-lived metastable scalars particles $S$ that can be produced at the Large Hadron Collider from decays of the Higgs boson. We find that for viable branching ratios Br($h \to SS$), the early universe metastable abundance of $S$, regulated by its self-annihilation through the Higgs portal, is so large that the lifetime of $S$ is strongly constrained to $\tau_S < 0.1$~s to maintain the consistency of BBN predictions with observations. This provides a useful upper bound on the lifetimes of $S$ particles that a purposely-built detector, such as the one suggested in the MATHUSLA proposal, seek to discover. We also investigate the viability and detectability of freeze-in self-interacting fermionic dark matter communicating with the SM via a vector portal. We focus on the parameter where the $\chi \bar{\chi} \to A'A'$ is negligible, as required by a variety of indirect detection constraints. We find that planned upgrades to the direct detection experiments will be able to probe the region of parameter space that can alleviate small scale structure problems of dark matter via self-interactions for a dark fine structure constant as small as $\alpha_d =10^{-4}$. We forecast the sensitivity for Lux-ZEPLIN, XENONnT and PandaX-4T. / Graduate

This thesis contains studies of phenomenological aspects of new physics at hadron colliders, such as the Large Hadron Collider (LHC). After a general introduction in chapter 1, in chapter 2 we outline the main features of the Standard Model (SM) of particle physics and the theoretical motivations for going beyond it. We subsequently provide brief descriptions of a few popular models that aim to solve the issues that arise within the SM. In chapter 3 we describe the general Monte Carlo method for evaluating multidimensional integrals and show how it can be used to construct a class of computational tools called Monte Carlo event generators. We describe the main generic features of event generators and how these are implemented in the HERWIG++ event generator. By applying resummation techniques, we provide, in chapter 4, analytical calculations of two types of hadron collider observables. The first, global inclusive variables, are observables that make use of all measured particle momenta and can provide useful information on the scale of new physics. The second observable is the transverse energy of the QCD initial state radiation (ET ), associated with the either Drell-Yan gauge boson production or Higgs boson production. In both cases we provide comparisons to results obtained from Monte Carlo event generators. In chapter 5 we examine two well-motivated models for new physics: one of new heavy charged vector bosons (W prime), similar to the SM W gauge bosons, and a model motivated by strong dynamics electroweak symmetry breaking that contains new resonances, leptoquarks, that couple primarily to quarks and leptons of the third generation. In the prior model, we improve the current treatment of the W' by considering interference effects with the SM W and construct an event generator accurate to next-to-leading order which we use to conduct a phenomenological analysis. For the leptoquark model, starting from an effective Lagrangian for production and decay, we provide an implementation in the HERWIG++ event generator and use it to form a strategy for mass reconstruction. The thesis ends with some conclusions and suggestions for extensions of the work presented. Further details and useful formulæ are given in the appendices.

An ion accelerator has been constructed which, is capable of accelerating very intense monoenergetic beams of protons or deuterons up to 50 KEV energy. Total ion currents of 500 µ amps containing 30 to 40% atomic ions have been obtained. The intensity and high definition of the beam makes it possible to collimate after magnetic analysis, 50 µ amps of protons or deuterons at 30 KEV energy into a 1/16 inch diameter spot on a target. This deuteron beam incident on a heavy ice target is capable of producing a neutron flux of 3 x 10⁸ neutrons/sec from the "D on D" reaction at 50 KEV bombarding energy or the equivalent of the neutrons from 20 curies of radium used in a Ra-Be source. The intrinsic interest of the D-D reactions to nuclear physics had prompted the construction of a scattering chamber to be used in conjunction with the accelerator. An experimental arrangement has been designed and constructed for the measurement of the energy dependent characteristics of the companion reactions, D(d,n)He³ and D(d,p)H³, which has a potential accuracy considerably greater than previously reported. As well, the extension of studies to much lower energies has been made possible by the large ion currents available. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

With the development of mechanical fault diagnosis technology, complex mechanical systems do not need to be shut down periodically for the maintenance. The working condition of the mechanical systems can be monitored by analyzing the wear metal particles in the systems' lubricating oil. However, the output signals of the monitoring sensor are non-stationary. In some case the particle signals are overlapped with each other. The goal of this thesis is to find a method to decompose those overlapped particle signals, and then count the particle number in the lubricating oil. At the beginning EMD method was introduced in the experiment because of the character of the sensor signals. In this project, because EMD method is sensitive to the noise in the original signals, an improved version of EMD, EEMD method was implemented. Finally, a post processing method was used to get a better result.