Lachlan Thompson

Complex Dielectric Measurements of Forest Fire Ash at X-Band Frequencies

Dielectric measurements of powdered forest fire ash have been investigated and presented using the Nicholson-Ross-Weir method within a WR-90 waveguide (X-band 8-12 GHz). The dielectric measurements of five samples have been outlined and taken at a room temperature of 22.8 °C. Permittivity ε for five different species has been presented within this letter. These include Eucalypt, Bracken Fern, She Oak, Wattle, and Cypress. The Eucalypt sample was tested dry and with a 30% moisture content by weight. The dry Eucalypt sample was found to have a permittivity value of approximately 2.32 ± 0.025 with a loss tangent of 0.005 ± 0.0025.

A Complex Dielectric Mixing Law Model for Forest Fire Ash Particulates

This letter presents an empirical mixing law for forest fire ash over X-Band (8-12 GHz). Six different species of Australian flora were tested. These include eucalypt, bracken fern, she oak, wattle, cypress, and pine. The investigation highlighted the discrepancies of mixing laws based on a spherical mixing phase to those measured. By optimizing the dimensionless parameter (v) of the unified mixing law formula, a good match was achieved. An average value of v = 10 was achieved over all six samples. The effective solid complex permittivities “εi ” for all the samples were determined. These were eucalypt (6.30 + 0.06 j), bracken fern (4.85 + 0.51 j), she oak (10.05 + 1.76 j), wattle (11.44 + 0.1.71 j), cypress (8.68 + 0.85 j), and pine (16.99 + 3.51 j).

The Nature of Fire Ash Particles: Microwave Material Properties, Dynamic Behavior, and Temperature Correlation

This paper focuses on the investigation of a number of physical and electromagnetic properties of fire generated ash particles, with relation to radar observations of forest fire smoke columns. Emphasis is placed on understanding the physical properties of the ash, which have direct effects on their scattering ability. Coupled with the electromagnetic properties, these physical properties describe the scatter generated when a number of dispersed ash particles are volumetrically interacting with radar signals. Due to their planar geometry, a study of ash particles originating from the eucalyptus genus has been conducted. Particular focus is placed on this genus due to its high population and role in fueling large bushfires within the Australian continent. The fundamental scattering mechanisms required for describing the radar reflectivity in horizontal, vertical, and cross-polarization have been explored by breaking down and analyzing three distinct properties of an individual ash particle. These include its geometric, dynamic, and electromagnetic properties. Statistical distributions from all three areas have been included to aid in the development of modeling tools.

Holistic Analysis of the Evolutionary Limits of Free Flight Application

The future of Free Flight, an air traffic control system where aircrews have the freedom and responsibility of selecting their trajectory and resolving it with others, is bright. The work performed by international Air Traffic Management (ATM) community is bringing Free Flight ever closer to reality. Also, due to technologies that have been accepted by the community, it has become easier to develop progressive simulations that can reasonably and logically map possible methods of evolution or progress from the post NextGen & SESAR implementation all the way to entirely Free Flight based ATM, and thereby understand the limits such a system would adhere to. In order to ensure the accuracy of these progressive simulations it becomes necessary to analyze unique results, and by replicating them, verify how they were created in the first place. This paper describes one such analysis, where a trend in decreasing pilot preference for direct flight paths was found, replicated, and verified. It also shows the possibility to take chaotic (i.e. discrete particles simulations with Monte Carlo adjustments and large numbers of linear relationships for high fidelity) simulations and verify them to a level that would allow the propagation and harvest of emergent properties for the purposes of holistically analyzing the limits of Free Flight.