2016 James R. Browning Symposium Keynote

2016 Browning Symposium Keynot

Adaptive Smoothing for Trajectory Reconstruction

Trajectory reconstruction is the process of inferring the path of a moving object between successive observations. In this paper, we propose a smoothing spline -- which we name the V-spline -- that incorporates position and velocity information and a penalty term that controls acceleration. We introduce a particular adaptive V-spline designed to control the impact of irregularly sampled observations and noisy velocity measurements. A cross-validation scheme for estimating the V-spline parameters is given and we detail the performance of the V-spline on four particularly challenging test datasets. Finally, an application of the V-spline to vehicle trajectory reconstruction in two dimensions is given, in which the penalty term is allowed to further depend on known operational characteristics of the vehicle.Comment: 25 pages, submitte

Part 2: is population growth good or bad for economic development?

In our previous post we described the shifting views of economists and demographers regarding the relationship between population growth and economic development. In short, rapid population growth in developing countries was thought to be a problem in the 1950s and 1960s, irrelevant (or even positive) in the 1970s and 1980s, and again an obstacle to robust economic growth from the mid-1990s up until today. Moreover, these changing views were very much in line with the evidence available for each period. How can we explain this

Part 1: is population growth good or bad for economic development?

This post is the first in a two part series exploring the relationship between population growth and economic development – a relationship that appears to have changed over time. See here for part tw

Interpreting Dark Matter Direct Detection Independently of the Local Velocity and Density Distribution

We demonstrate precisely what particle physics information can be extracted from a single direct detection observation of dark matter while making absolutely no assumptions about the local velocity distribution and local density of dark matter. Our central conclusions follow from a very simple observation: the velocity distribution of dark matter is positive definite, f(v) >= 0. We demonstrate the utility of this result in several ways. First, we show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form factor), such as from ordinary elastic scattering, can be "mocked up" by any mass of dark matter above a kinematic minimum. As an example, we show that dark matter much heavier than previously considered can explain the CoGeNT excess. Specifically, m_chi < m_Ge} can be in just as good agreement as light dark matter, while m_\chi > m_Ge depends on understanding the sensitivity of Xenon to dark matter at very low recoil energies, E_R ~ 6 keVnr. Second, we show that any rise in the deconvoluted recoil spectrum represents distinct particle physics information that cannot be faked by an arbitrary f(v). As examples of resulting non-trivial particle physics, we show that inelastic dark matter and dark matter with a form factor can both yield such a rise

Generalised Swan modules and the D(2) problem

We give a detailed proof that, for any natural number n, each algebraic two complex over C_n \times C_\infty is realised up to congruence by a geometric complex arising from a presentation for the group.Comment: This is the version published by Algebraic & Geometric Topology on 24 February 200

Investigation of processing conditions of melded parts to determine process boundaries

Melding, a novel method for producing seamless joints in thermosetting composites utilising the Quickstep&trade; process, is explored in this paper. The effect of processing conditions on the quality of melded joins is examined and a set of processing boundaries defined so that the strength of melded joints is optimized. HexPly&reg; 914c pre-preg material was exposed to a range of processing temperatures prior to joining via the melding process. Differential Scanning Calorimetry analysis was carried out to investigate the degree of cure of material prior to final joining, and it was found that minimal cure occurs at temperatures below 120&deg;C. After consolidation and cure of the melded parts, short beam shear testing was conducted to evaluate the strength of the melded interface. Exposure temperatures between 65&deg;C and 120&deg;C were found to optimize short beam shear join strength. Mode I double cantilever beam and mode II end notched flexural tests showed no detrimental effect of elevated exposure temperatures prior to joining. <br /