http://hdl.handle.net/1947/24 Search the Channel search http://dspace.dsto.defence.gov.au/dspace/simple-search http://hdl.handle.net/1947/10003 Title: User Guide to the Aircraft Cumulative Probability Chart Template.<br/><br/>Authors: Murtagh, B.; Maxfield, K.<br/><br/>Abstract: To ensure aircraft structural integrity is maintained to an acceptable level, probabilistic approaches may be used to calculate the risk of cracking (or failure) over the life of the aircraft or fleet. One such risk analysis technique employs a lognormal probability distribution to model the likelihood of cracking (or failure) in the fleet with respect to hours. This technique was programmed into Microsoft Excel to create a simple and easy to use template. An outline of the theory behind the probabilistic approach is provided as well as a comprehensive user guide to the template. This template allows the quick and simple determination of probability distributions of cracking (or failure) which may be used to assess the life of aircraft structures.<br/><br/>Executive summary: To ensure aircraft structural integrity is maintained to an acceptable level, probabilistic approaches may be used to calculate the risk of cracking (or failure) over the life of the aircraft or fleet. One such risk analysis technique employs a lognormal probability distribution to model the likelihood of cracking (or failure) in the fleet with respect to hours. This technique was programmed into Microsoft Excel to create a simple and easy to use template. An outline of the theory behind the probabilistic approach is provided as well as a comprehensive user guide to the template. This template allows the quick and simple determination of probability distributions of cracking (or failure) which may be used to assess the life of aircraft structures. http://hdl.handle.net/1947/10002 Title: Fractal Effects in Lanchester Models of Combat.<br/><br/>Authors: Perry, N.<br/><br/>Abstract: Lanchester’s Equations are one of the most misunderstood and misused models of combat, yetthey remain in widespread use as the combat mechanism behind many simulation systems.Previous work by the author examined the impact of a fractal distribution of forces onLanchester’s theory of combat. The present work extends that examination to conceptual issues regarding interpretation of Lanchester's Equations and to additional parameters beyond those examined previously.<br/><br/>Executive summary: Lanchester’s Equations are one of the most misunderstood and misused models of combat,yet they remain in widespread use as the combat mechanism behind many simulationsystems. Previous work by the author examined the impact of a fractal distribution offorces on Lanchester’s theory of combat. The present work extends that examination toconceptual issues regarding interpretation of Lanchester's Equations and to additionalparameters beyond those examined previously.A fractal model for the distribution of each side’s forces in space is shown to producegeneral force on force attrition expressions which describe the ability of each side to apply its strength effectively, due to battlefield congestion and finite engagement ranges. This is reflected in the logarithmic dependence of the Combat Intensity, Relative Effectiveness and Defender’s Advantage parameter on the initial force ratio.It confirms the functional form for the equation of state which had previously beenderived for a few special cases. This is consistent with previous derivations of thatexpression, which had also linked the functional form to limiting a force’s ability to apply its strength, and agrees well with historical data analysis.It concludes that spatial effects in combat are necessary to obtain this equation of stateinstead of Lanchester’s original equation of state, which would suggest that the majorshortfall of Lanchester’s combat model is the lack of a mechanism describing the effects of movement and spatial limitations on interaction between forces.An important consequence of the model proposed as a force on force attrition modelincorporating battlefield congestion, is that all the previously derived quantities from the original Lanchester model still apply if the simple attrition coefficients are replaced by the force level attrition coefficients that are developed. This work appears to be the first report that the force level Combat Intensity and Relative Effectiveness, both of which are key parameters in the results of Lanchester’s combat model, have a logarithmic dependence onforce ratio. This has yet to be investigated using available historical data.The major shortcoming of the present work is the lack of processes to determine theattrition rate coefficients and fractal dimensions. However, it should be realised that theselimitations apply not only to Lanchester models of combat but to all models of combat. Inspite of all these issues, the model developed here is useful as a combat metamodel toillustrate relationships between select combat parameters and facilitate comparisonbetween model and historical data, as indeed are all “Lanchester like” models. http://hdl.handle.net/1947/10001 Title: Application of Black Scholes Complexity Concepts to Combat Modelling.<br/><br/>Authors: Perry, N.<br/><br/>Abstract: Lanchester’s equations are commonly used as the basis for force-on-force combat models, even if only as a metamodel for a more complex combat simulation. This report examines whether attrition is adequately modelled by such Markov processes. It shows that the distribution of historical battle casualties is consistent with that obtained when attrition is modelled as an Ito process. The additional Wiener term can be regarded as representing the impact of the wider environment on attrition rates.<br/><br/>Executive summary: Lanchester’s equations are commonly used as the basis for force-on-force combat models, even if only as a metamodel for a more complex combat model. These equations define a system with the strengths of the forces involved comprising its internal parameters. Many systems are adequately described using just their internal parameters, without consideration of any interactions between that system and its wider environment. However, it is apparent from the work on extending combat models based on Lanchester’s equations to include additional parameters such as morale, spatial force dispersion and movement, that such quantities do affect attrition rates. The inclusion of additional parameters also results in additional complexity and the loss of insight that a simple model provides. ideally what is desired is a means to include the effect of the wider environment on attrition rates without also increasing the model’s complexity.The standard model for the behaviour of stock prices in time assumes they are a continuous Markov process with a constant fractional drift rate. The Black and Scholes model of stock prices treats price volatility as resulting from the action of the rest of the market on the system comprised of the one stock price being modelled. Furthermore, it does not attempt to model the processes by which the market might affect the stock price, arguing that the mechanisms are too complex to model or are not known.Lanchester’s Equations are similar to the starting point for the derivation of the Black Scholes Equation. This suggests an obvious approach for including the effect of the wider environment in the evaluation of combat attrition rates, through the addition of a Wiener process, turning Lanchester’s Markov process into an Ito process.The present work has used an existing database of historical battle results to show that the frequency distribution of battle casualties is consistent with that expected when Lanchester’s equations are augmented to form an Ito Process rather than the conventional Markov Process. The additional Wiener term can be regarded as representing the impact of the wider environment on attrition rates. The shape of the casualty frequency distribution was not observed in the initial force strength distribution. This supports the contention that such distributions result from the attrition process itself and are not artefacts of the sampling or analysis procedure.The database used, and indeed all such databases, was shown to include an inherent bias which under-represents the number of small battles. While the effect of such bias was observed, by incorporating strata sampling concepts it was possible to confine the effects of such bias into a single stratum and a small number of data points, which can then be allowed for. http://hdl.handle.net/1947/10000 Title: A Review of Australian and New Zealand Investigations on Aeronautical Fatigue During the Period April 2007 to March 2009.<br/><br/>Authors: Clark, G.; Saunders, D.<br/><br/>Abstract: This document has been prepared for presentation to the 31st Conference of the International Committee on Aeronautical Fatigue scheduled to be held in Rotterdam, the Netherlands, 25th and 26 May 2009. Brief summaries and references are provided on the aircraft fatigue research and associated activities of research laboratories, universities, and aerospace companies in Australia and New Zealand during the period April 2007 to March 2009. The review covers fatigue–related research programs as well as fatigue investigations on specific military and civil aircraft.<br/><br/>Executive summary: The Australasian delegate to the International Committee on Aeronautical Fatigue (ICAF) is responsible for preparing a review of aeronautical fatigue research in Australia and New Zealand for presentation at the biennial ICAF conference. The Defence Science and Technology Organisation (DSTO) supports the Australasian delegate to ICAF by publishing the review as a DSTO document. This document later forms a chapter of the ICAF conference minutes published by the conference host nation. The format of the review reflects ICAF requirements. This review of research activities in the period April 2007 to March 2009 was undertaken by the Australasian National Delegate, Prof Graham Clark, of RMIT University, and Dr David Saunders, Research Leader Air Vehicles Division, DSTO.