Vegetation fires in urban and peri-urban (human) landscapes damage property and infrastructure, threaten lives and incur considerable suppression costs. This study investigated the timing of fires ...burning in vegetation within and around the city of Perth, Western Australia. The timing of fires from 16 different cause types were investigated at hourly, daily, monthly and annual scales, and using fire danger indices and fuel moisture. Ignitions from most causes were shown to have hourly and monthly profiles that reflect fire danger and fuel availability. Some causes with low heat outputs, such as cigarettes and sparks from cutting and welding, were more sensitive to fire danger and fuel availability than others. Causes related to arson and recreational activities, such as camp fires, were more likely to occur on weekends and public holidays. Arson prevention measures appear to have reduced the incidence of deliberately lit fires, and may have reduced the number of fires occurring on days of total fire ban, although these days have much higher rates of ignition than other days. High profile fire events also increase public awareness and reduce ignition rates. Lessons learned from analyses of fire occurrence can help fire agencies more effectively apply prevention and mitigation programs.
• The timing of vegetations fires were investigated with regard to their cause.• Arson and recreational caused fires are more frequent on weekends and holidays.• Total fire bans have a moderate effect on reducing ignitions.• High profile fire events lead to a noticeable reduction in ignition rates.
There is currently no fundamental understanding of the effects of topography on the behaviour of fires burning over a landscape. While a number of empirical models are employed operationally around ...the world, the effects of negative slopes on fire spread are ignored in all but one prediction system which may result in incorrect predictions. The general observation that large fires burning for some time over undulating topography can be approximated by assuming fire spread over flat ground is used to construct a quasi-empirical model framework for downslope rate of spread correction called kataburn. Kataburn is formulated for two alternative interpretations of slope spread–planar and linear–and can be applied to any empirical upslope spread correction model. Versions of kataburn derived using such models from Australia, the US and Canada are compared against experimental downslope data from the literature and found to better represent downslope spread than the existing operational downslope function.
•Topography has a significant effect on the spread of fire across the landscape.•Appropriate treatment of negative (lee) slope fire spread effects is important.•A new model framework, kataburn, is developed from functional considerations of fire spread across the landscape.•Kataburn can be used to construct negative slope spread corrections for any fire spread prediction system.•Kataburn is shown to perform much better than the only existing operational downslope model.
We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn→dπ(0)π(0) over the full energy region of the ABC effect, a pronounced ...low-mass enhancement in the ππ-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ΔΔ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m=2.37 GeV, Γ≈70 MeV and I(J(P))=0(3(+)) in both pn and ΔΔ systems. Necessary further tests of the resonance interpretation are discussed.
Data from bushfire incidents in south-west Western Australia from the Departments of Parks and Wildlife and Fire and Emergency Services were used to develop models that predict the number of ...human-caused bushfires within 10 management areas. Fire incident data were compiled with weather variables, binary classifications of day types (e.g. school days) and counts of the number of fires that occurred over recent days. Models were developed using negative binomial regression with a dataset covering 3 years and evaluated using data from an independent year. A common model form that included variables relating to fuel moisture content, the number of recent human-caused bushfires, work day (binary classification separating weekends and public holidays from other days) and rainfall was applied to all areas. The model had reasonable fit statistics across all management areas, but showed enough day-to-day prediction variability to be of practical use only in the more densely populated management areas, which were dominated by deliberate ignitions. The findings of this study should be of interest to fire managers in Mediterranean climatic regions where a variety of practices are used to manage wildfires.
Fire behaviour and spread predictions guides suppression strategies and public warnings during wildfires. The scientific understanding of fire behaviour forms the core of these predictions, but is ...incomplete, and expert judgement and experience are required to augment the evidence based knowledge. Amicus is a new decision support system that implements contemporary, published and operationalised bushfire behaviour models (e.g. rate of spread, flame height, fireline intensity, spotting distance) in the Australian bushfire context. It enables the inclusion of expert judgement and local knowledge, allows users to analyse temporal trends and uncertainty in inputs, and facilitates reliable and practical predictions. This paper provides a comprehensive overview of Amicus, including its operation and functionality, identifies the boundaries of the current understanding of fire science, discusses the major limitations in existing knowledge, and provides a framework for allowing deterministic and anecdotal/local knowledge to be incorporated into formal fire behaviour predictions.
•Fire behaviour predictions inform suppression strategies and public warnings.•Expert judgement and experience can augment fire science.•Amicus combines science and expert knowledge for robust transparent predictions.•Amicus highlights operational domains and the limits of model reliability.•Users can investigate the impact of uncertainty in input data on outputs.
The performance of wildfire suppression is often monitored using statistics related to area burned and time to contain a fire. Potential factors affecting the probability of initial attack (IA) ...success and the probability of large fires were examined in a data set composed of 334 Australian wildfires that burned in forest and shrubland vegetation and used aerial- and tanker-based suppression during the IA phase. Logistic regression analysis was used to determine the most significant predictor variables for a range of area- and time-based definitions for these measures. The variables that were found to be the best predictors of IA success were fire area at IA, fuel hazard, and aircraft response time. The probability of large fires was related to fuel hazard, area at IA, and the Forest Fire Danger Index. Fire area at IA was strongly linked with aerial suppression time delay and was also influenced by weather and fuel hazard score. Fire management practices can influence IA area, response timing, and fuel hazard. IA area and response times can be minimized through efficient fire detection and by deploying appropriate suppression resources rapidly from bases in locations that provide optimized geographical coverage. Fuel hazard can be moderated through management actions such as fuel reduction burning.
•The new method for 3D numerical modelling of multi-layered curved shells is proposed.•The modelling is performed with exact geometry description.•For calculations only 2D mesh is applied.•The method ...is called FEM23: 2D FEM for 3D analysis.•Examples are presented in which shells are composed with thick and thin layers.
The article presents a full three-dimensional (3D) numerical analysis of curved laminated shell structures using only a two-dimensional (2D) planar finite element mesh. The applied numerical method is called FEM23, which stands for the 2D finite element method for a full 3D analysis. FEM23 makes it possible to perform a numerical analysis of a multi-layered shell, utilising a numerical model based on a 2D finite element mesh. FEM23 ensures exact shell geometry since a pure mathematical description of a geometry is applied in the numerical model. Examples provided in the following paper prove FEM23 to be accurate and flexible. They involve the analysis of a special laminated structure - laminated glass, which comprises of glass panes bonded by thin polymer films. A full 3D description is provided for the glass panes as well as polymer films, even though the film thickness is over ten times smaller than the glass layers. The results are verified by the analytical solution and those obtained by standard 3D FEM. A unique post-processing procedure developed specially for FEM23 enables visualisation of the full 3D results.
The paper presents the efficient application of discontinuous Galerkin (DG) method on polygonal meshes. Three versions of the DG method in which the approximation is constructed using sets of ...arbitrary basis functions are under consideration. The analysed approach does not require definition of nodes or construction of shape functions. The shape of a polygonal finite element (FE) can be quite arbitrary. It can have arbitrary number of edges and can be non-convex. In particular, a single FE can have a polygonal hole or can even consist of two or more completely separated parts. The efficiency, flexibility and versatility of the presented approach is illustrated with a set of benchmark examples. The paper is restricted to two-dimensional case. However, direct extension of the algorithms to three-dimensions is possible.
•Discontinuous Galerkin (DG) method is applied for arbitrary polygonal elements.•Three versions of (DG) method are regarded.•In the formulation arbitrary basis functions can be used.•Element can have holes or consists of few separated parts.•The approach is illustrated with a set of two-dimensional benchmark examples.
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