Ph.D., Faculty of Science, University of the Witwatersrand, 1999

Tsui Lung Kwan = 致密星的準簡正模 : 以微擾方程為基礎之研究 / 徐隆焜. / Thesis submitted in: August 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 98-100). / Text in English; abstracts in English and Chinese. / Tsui Lung Kwan = Zhi mi xing de zhun jian zheng mo : yi wei rao fang cheng wei ji chu zhi yan jiu / Xu Longkun. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Oscillating Stars and Gravitational Waves --- p.1 / Chapter 1.2 --- Outline of the Thesis --- p.3 / Chapter 2 --- Stellar Structure and Mode Classifications --- p.5 / Chapter 2.1 --- Relativistic Stars --- p.5 / Chapter 2.2 --- Equation of State --- p.6 / Chapter 2.3 --- Mode Classifications --- p.9 / Chapter 3 --- Axial w-mode Oscillations --- p.16 / Chapter 3.1 --- Equations of Stellar Oscillations --- p.16 / Chapter 3.2 --- Evaluation of QNMs --- p.18 / Chapter 3.3 --- General features of QNMs --- p.20 / Chapter 4 --- Universal behavior of axial QNMs --- p.22 / Chapter 4.1 --- BBF universal curve --- p.22 / Chapter 4.2 --- Scaled Coordinates --- p.26 / Chapter 4.3 --- Universality of Vrw(r*) inside stars --- p.29 / Chapter 4.3.1 --- Searching for the universality inside stars --- p.29 / Chapter 4.3.2 --- Simple analysis --- p.35 / Chapter 4.3.3 --- The importance of R* --- p.38 / Chapter 5 --- Scaled Coordinates Logarithmic Perturbation Theory --- p.40 / Chapter 5.1 --- The scaled axial oscillation equations --- p.41 / Chapter 5.2 --- The Formalism of SCLPT --- p.41 / Chapter 5.2.1 --- Perturbation parameter --- p.42 / Chapter 5.2.2 --- Perturbation-dependent boundary condition --- p.43 / Chapter 5.2.3 --- The first order perturbation --- p.44 / Chapter 5.2.4 --- The second order perturbation --- p.48 / Chapter 6 --- Cubic-Quintic Model of Neutron Stars --- p.53 / Chapter 6.1 --- Cubic-Quintic Model (CQM) --- p.53 / Chapter 6.2 --- The fluid functions --- p.54 / Chapter 6.3 --- The metric coefficients --- p.56 / Chapter 6.4 --- The tortoise radius R* --- p.58 / Chapter 6.5 --- The QNM frequencies --- p.60 / Chapter 7 --- The Chain of Approximations --- p.63 / Chapter 8 --- Inversion of QNMs --- p.72 / Chapter 8.1 --- The modified SCLPT --- p.72 / Chapter 8.2 --- The Inverting Scheme --- p.76 / Chapter 8.3 --- Application of the Inverting Scheme --- p.79 / Chapter 8.4 --- Improved Inverting Scheme --- p.80 / Chapter 9 --- Conclusion --- p.87 / Chapter 9.1 --- Summary of Our Work --- p.87 / Chapter 9.2 --- Outlook --- p.88 / Chapter A --- Linear and Quadratic Models --- p.90 / Chapter A.1 --- Linear Model (LM): Mass oc r --- p.90 / Chapter A.2 --- Quadratic Model (QM): Mass oc r2 --- p.93 / Chapter B --- The relationship between R* and the mass distribution --- p.96 / Bibliography --- p.98

Wu Jun = 中子星的極性w-模振盪 / 吳俊. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 100-102). / Text in English; abstracts in English and Chinese. / Wu Jun = Zhong zi xing de ji xing w-mo zhen dang / Wu Jun. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background introduction and historical review --- p.1 / Chapter 1.2 --- Outline of the thesis --- p.3 / Chapter 1.3 --- Notations and conventions --- p.4 / Chapter 2 --- Equilibrium and oscillations of Relativistic stars --- p.5 / Chapter 2.1 --- Relativistic stars --- p.5 / Chapter 2.1.1 --- Equilibrium configuration --- p.6 / Chapter 2.1.2 --- Equation of state --- p.7 / Chapter 2.2 --- Oscillations of relativistic stars --- p.9 / Chapter 2.2.1 --- Families of fluid modes --- p.10 / Chapter 2.2.2 --- Families of spacetime modes (w-mode) --- p.11 / Chapter 3 --- Polar oscillations of neutron stars --- p.14 / Chapter 3.1 --- Axial oscillations of neutron stars --- p.14 / Chapter 3.2 --- LD formulation --- p.16 / Chapter 3.2.1 --- Equations inside star --- p.17 / Chapter 3.2.2 --- Boundary conditions at r = 0 and r = R --- p.19 / Chapter 3.2.3 --- Perturbations outside star --- p.21 / Chapter 3.3 --- AAKS formulation --- p.22 / Chapter 3.3.1 --- Equations inside the star --- p.23 / Chapter 3.3.2 --- Behavior at the center and the stellar surface --- p.25 / Chapter 3.3.3 --- Evolution outside star --- p.28 / Chapter 3.3.4 --- Connection formula --- p.29 / Chapter 4 --- QNMs of polar oscillations --- p.31 / Chapter 4.1 --- Solution outside star --- p.31 / Chapter 4.2 --- LD approach --- p.32 / Chapter 4.3 --- Hamiltonian constraint --- p.33 / Chapter 4.4 --- Boundary conditions a.t r = R --- p.37 / Chapter 4.5 --- Direct integration scheme (DIS) --- p.42 / Chapter 4.6 --- Two-way integration scheme (TIS) --- p.43 / Chapter 4.7 --- Connect the interior and exterior solutions --- p.45 / Chapter 4.8 --- Numerical results --- p.46 / Chapter 5 --- Polar oscillations without fluid motions --- p.50 / Chapter 5.1 --- Zero pressure variation approximation (ZPVA) --- p.51 / Chapter 5.1.1 --- Evolution formulas --- p.51 / Chapter 5.1.2 --- Boundary conditions --- p.53 / Chapter 5.1.3 --- Approximate QNMs --- p.55 / Chapter 5.2 --- Zero density variation approximation (ZDVA) --- p.55 / Chapter 5.2.1 --- Single equation formulas --- p.58 / Chapter 5.2.2 --- Numerical results --- p.61 / Chapter 5.2.3 --- Summary --- p.62 / Chapter 5.3 --- Application of ZDVA --- p.65 / Chapter 5.3.1 --- Relation between axial and polar w-modes --- p.65 / Chapter 5.3.2 --- Analysis --- p.66 / Chapter 6 --- Universal behavior of polar QNMs --- p.69 / Chapter 6.1 --- Universal behavior of polar w-modes --- p.70 / Chapter 6.2 --- Ordinary CQM of neutron stars --- p.71 / Chapter 6.2.1 --- TOV parameters of a CQM star --- p.71 / Chapter 6.2.2 --- Stability problem of CQM --- p.73 / Chapter 6.2.3 --- EOS near the surface --- p.75 / Chapter 6.3 --- Scaling behavior of polar oscillations --- p.78 / Chapter 6.3.1 --- Scaling behavior of fluid motions --- p.79 / Chapter 6.3.2 --- Scaled wave equations --- p.80 / Chapter 6.4 --- Scaled Cubic-Quintic Model (SCQM) --- p.82 / Chapter 7 --- Conclusion --- p.85 / Chapter 7.1 --- Summary of Our Work --- p.85 / Chapter 7.2 --- Outlook --- p.86 / Chapter A --- Expansion of Hamiltonian constraint around the center --- p.88 / Chapter B --- Factorization integration scheme (FIS) --- p.92 / Chapter C --- Equivalence of two definitions of the Zerilli function --- p.96

No description available.

A self-powered neutron detector (SPND) is a device that, coupled with a current meter, provides a readout proportional to neutron population. This thesis discusses the design parameters of an array of such devices, their characteristics, and the use of these devices as a self-powered neutron spectrometer (SPNS) to provide information about the energy distribution in a neutron radiation field. Neutron absorption in an appropriate material produces subsequent beta emissions. In a SPND, some of these beta particles will cross a non-conducting region and stop in a collector material. A net exchange of charge between these regions can be read as a current flowing between the emission region and the collector region. One potential SPNS design was modeled using a Monte Carlo simulation of the device's interaction with a radiation field. The Monte Carlo program used predicts the beta flux which is proportional to the current that would be produced by an actual device. Various beta emitting materials were considered for this device, and a sensitivity study of each was included. The design considered is comprised of a concentric set of these cylindrical SPND detector elements which, in themselves, are currently available technology. / Graduation date: 1999

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Mar. 13, 2007). PDF text: xiii, 159 p. : ill. (some col.) UMI publication number: AAT 3223008. Includes bibliographical references. Also available in microfilm, microfiche and paper format.

This research investigates the use of a PETtrace cyclotron produced by General Electric (GE) as a neutron source for boron neutron capture therapy (BNCT). The GE PETtrace was chosen for this investigation because this type of cyclotron is popular among nuclear pharmacies and clinics in many countries; it is compact and reliable; it produces protons with energies high enough to produce neutrons with appropriate energy and fluence rate for BNCT and it does not require significant changes in design to provide neutrons. In particular, the standard PETtrace 18O target is considered. The cyclotron efficiency may be significantly increased if unused neutrons produced during radioisotopes production could be utilized for other medical modalities such as BNCT at the same time. The resulting dose from the radiation emitted from the target is evaluated using the Monte Carlo radiation transport code MCNP at several depths in a brain phantom for different scattering geometries. Four different moderating materials of various thicknesses were considered: light water, carbon, heavy water, and FluentalTM. The fluence rate tally was used to calculate photon and neutron dose, by applying fluence rate-to-dose conversion factors. Fifteen different geometries were considered and a 30-cm thick heavy water moderator was chosen as the most suitable for BNCT with the GE PETtrace cyclotron. According to the Brookhaven Medical Research Reactor (BMRR) protocol, the maximum dose to the normal brain is set to 12.5 RBEGy, which for the conditions of using a heavy water moderator, assuming a 60 ??A beam current, would be reached with a treatment time of 258 min. Results showed that using a PETtrace cyclotron in this configuration provides a therapeutic ratio of about 2.4 for depths up to 4 cm inside a brain phantom. Further increase of beam current proposed by GE should significantly improve the beam quality or the treatment time and allow treating tumors at greater depths.

The need for characterization of the Germania unit has emerged as a first step in the review, understanding and enhancement of the production practices applicable within the unit and the trend area in general. Petrophysical characterization of the Germania Spraberry units requires a unique approach for a number of reasons ?? limited core data, lack of modern log data and absence of directed studies within the unit. In the absence of the afore mentioned resources, an approach that will rely heavily on previous petrophysical work carried out in the neighboring ET O??Daniel unit (6.2 miles away), and normalization of the old log data prior to conventional interpretation techniques will be used. A log-based rock model has been able to guide successfully the prediction of pay and non-pay intervals within the ET O??Daniel unit, and will be useful if found applicable within the Germania unit. A novel multiple regression technique utilizing non-parametric transformations to achieve better correlations in predicting a dependent variable (permeability) from multiple independent variables (rock type, shale volume and porosity) will also be investigated in this study. A log data base includes digitized formats of gamma ray, cased hole neutron, limited resistivity and neutron/density/sonic porosity logs over a considerable wide area.

The delayed neutron emission rates of U-235 and Pu-239 samples were measured accurately from a thermal fission reaction. A Monte Carlo calculation using the Geant4 code was used to demonstrate the neutron energy independence of the detector used in the counting station. A set of highly purified actinide samples (U-235 and Pu-239) was irradiated in these experiments by using the Texas A&M University Nuclear Science Center Reactor. A fast pneumatic transfer system, an integrated computer control system, and a graphite-moderated counting system were constructed to perform all these experiments. The calculated values for the five-group U-235 delayed neutron parameters and the six-group Pu-239 delayed neutron parameters were compared with the values recommended by Keepin et al. (1957) and Waldo et al. (1981). These new values differ slightly from literature values. The graphite-moderated counting station and the computerized pneumatic system are now operational for further delayed neutron measurement.

The purpose of this research is to design and optimize the performance of a unique, inexpensive 6Li neutron-capture pulse-mode ion chamber (LiPMIC) for neutron detection that overcomes the fill-gas contamination stemming from outgas of detector components. This research also provides a demonstration of performance of LiPMICs. Simulations performed with GARFIELD, a drift-chamber simulation package for ion transport in an electrostatic field, have shown that argon-methane mixtures of fill-gas allow maintenance of electron drift velocity through a surprisingly wide range of fill-gas content. During the design stage of LiPMIC development, the thicknesses of lithium metallization layer, the neutron energy conversion site of the detector, and the thickness of neutron moderator, the high-density polyethylene body, are optimized through analytical and MCNPX calculations. Also, a methodology of obtaining the suitable combination of electric field strength, electron drift velocity, and fill-gas mixtures has been tested and simulated using argon-methane gas mixtures. The LiPMIC is shown to have comparable efficiency to 3He proportional counters at a fraction of cost. Six-month long baseline measurements of overall detector performance shows there is a 3% reduction in total counts for 252Cf sources, which provides a good indicator for the longevity of the detector.