Non-classical transport with angular-dependent path-length distributions. 2: Application to pebble bed reactor cores

We describe an analysis of neutron transport in the interior of model pebble bed reactor (PBR) cores, considering both crystal and random pebble arrangements. Monte Carlo codes were developed for (i) generating random realizations of the model PBR core, and (ii) performing neutron transport inside the crystal and random heterogeneous cores; numerical results are presented for two different choices of material parameters. These numerical results are used to investigate the anisotropic behavior of neutrons in each case and to assess the accuracy of estimates for the diffusion coefficients obtained with the diffusion approximations of different models: the atomic mix model, the Behrens correction, the Lieberoth correction, the generalized linear Boltzmann equation (GLBE), and the new GLBE with angular-dependent path-length distributions. This new theory utilizes a non-classical form of the Boltzmann equation in which the locations of the scattering centers in the system are correlated and the distance-to-collision is not exponentially distributed; this leads to an anisotropic diffusion equation. We show that the results predicted using the new GLBE theory are extremely accurate, correctly identifying the anisotropic diffusion in each case and greatly outperforming the other models for the case of random systems.Comment: 24 pages, 11 figures; Version 3: shortened title, corrected typo

Non-classical transport with angular-dependent path-length distributions. 1: Theory

This paper extends a recently introduced theory describing particle transport for random statistically homogeneous systems in which the distribution function p(s) for chord lengths between scattering centers is non-exponential. Here, we relax the previous assumption that p(s) does not depend on the direction of flight \Omega; this leads to an extended generalized linear Boltzmann equation that includes angular-dependent cross sections, and to an extended generalized diffusion equation that accounts for anisotropic behavior resulting from the statistics of the system.Comment: 22 pages; Version 3: shortened title; corrected typo

A review of the characteristics of 108 author-level bibliometric indicators

An increasing demand for bibliometric assessment of individuals has led to a growth of new bibliometric indicators as well as new variants or combinations of established ones. The aim of this review is to contribute with objective facts about the usefulness of bibliometric indicators of the effects of publication activity at the individual level. This paper reviews 108 indicators that can potentially be used to measure performance on the individual author level, and examines the complexity of their calculations in relation to what they are supposed to reflect and ease of end-user application.Comment: to be published in Scientometrics, 201

A MARKET OPPORTUNITY STUDY FOR THE DEVELOPMENT OF A NEW SPORT HORSE SERVICE AT THE MSU VETERINARY TEACHING HOSPITAL

The potential need for several new services within the Veterinary Teaching Hospital (VTH) is unknown. However, based on focus groups and practitioner surveys conducted over the last several years, potential new services were identified: overnight emergency, behavior medicine, equine sports medicine, dentistry, oncology and exotic animal medicine. Michigan State University's College of Veterinary Medicine (MSU-CVM) has recently expanded its equine research, diagnostic and therapy capabilities with the addition of the new Mary Anne McPhail Equine Performance Center. As a result of this expansion, a study was conducted to determine whether the VTH should also broaden its clinical offerings with a new complement of services targeted specifically toward sport horse care.Teaching/Communication/Extension/Profession,

PROJECT REPORT: A MARKET OPPORTUNITY STUDY FOR THE DEVELOPMENT OF A NEW ONCOLOGY SERVICE IN THE VETERINARY TEACHING HOSPITAL

Current trends in veterinary medicine indicate the potential need for several new services within the VTH. Based on focus groups and practitioner surveys conducted in late 1998 and early 1999, potential new services could include oncology, overnight emergency, behavior medicine, dentistry, equine sports medicine and exotic animal medicine. Of these, an oncology service is currently being considered based on internal staff recommendations coupled with survey and focus group information supporting demand for the service. Different from past new services, the oncology service was also earmarked to undergo a formal market study to determine the full potential of the opportunity and to more clearly establish the goals and objectives within the service.Teaching/Communication/Extension/Profession,

Asymptotic Derivation and Numerical Investigation of Time-Dependent Simplified Pn Equations

The steady-state simplified Pn (SPn) approximations to the linear Boltzmann equation have been proven to be asymptotically higher-order corrections to the diffusion equation in certain physical systems. In this paper, we present an asymptotic analysis for the time-dependent simplified Pn equations up to n = 3. Additionally, SPn equations of arbitrary order are derived in an ad hoc way. The resulting SPn equations are hyperbolic and differ from those investigated in a previous work by some of the authors. In two space dimensions, numerical calculations for the Pn and SPn equations are performed. We simulate neutron distributions of a moving rod and present results for a benchmark problem, known as the checkerboard problem. The SPn equations are demonstrated to yield significantly more accurate results than diffusion approximations. In addition, for sufficiently low values of n, they are shown to be more efficient than Pn models of comparable cost.Comment: 32 pages, 7 figure

Chaotic string-capture by black hole

We consider a macroscopic charge-current carrying (cosmic) string in the background of a Schwarzschild black hole. The string is taken to be circular and is allowed to oscillate and to propagate in the direction perpendicular to its plane (that is parallel to the equatorial plane of the black hole). Nurmerical investigations indicate that the system is non-integrable, but the interaction with the gravitational field of the black hole anyway gives rise to various qualitatively simple processes like "adiabatic capture" and "string transmutation".Comment: 13 pages Latex + 3 figures (not included), Nordita 93/55

The Non-Classical Boltzmann Equation, and Diffusion-Based Approximations to the Boltzmann Equation

We show that several diffusion-based approximations (classical diffusion or SP1, SP2, SP3) to the linear Boltzmann equation can (for an infinite, homogeneous medium) be represented exactly by a non-classical transport equation. As a consequence, we indicate a method to solve diffusion-based approximations to the Boltzmann equation via Monte Carlo, with only statistical errors - no truncation errors.Comment: 16 pages, 3 figure