33 resultados para Breakdown Probability


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 Aim: We investigated how the probability of burning is influenced by the time since fire (TSF) and gradients of climate, soil and vegetation in the fire-prone mediterranean-climate mallee woodlands of south-eastern Australia. This provided insight into the processes controlling contemporary fuel dynamics and fire regimes across biogeographical boundaries, and the consequent effects of climate change on potential shifts in boundaries between fuel systems and fire regimes, at a subcontinental scale. Location: South-eastern Australia. Methods: A desktop-based GIS was used to generate random sampling points across the study region to collect data on intersecting fire interval, rainfall, vegetation and soil type. We used a Bayesian framework to examine the effects of combinations of rainfall, vegetation and soil type on the hazard-of-burning and survival parameters of the Weibull distribution. These analyses identify the nature of environmental controls on the length of fire intervals and the age-dependence of the hazard of burning. Results: Higher rainfall was consistently associated with shorter fire intervals. Within a single level of rainfall, however, the interaction between soil and vegetation type influenced the length of fire intervals. Higher-fertility sands were associated with shorter fire intervals in grass-dominated communities, whereas lower-fertility sands were associated with shorter fire intervals in shrub-dominated communities. The hazard of burning remained largely independent of TSF across the region, only markedly increasing with TSF in shrub-dominated communities at high rainfall. Main conclusions: Rainfall had a dominant influence on fire frequency in the mediterranean-climate mallee woodlands of south-eastern Australia. Predicted changes in the spatial distribution and amount of rainfall therefore have the potential to drive changes in fire regimes, although the effects of soil fertility and rainfall on fire regimes do not align on a simple productivity gradient. Reduced soil fertility may favour plant traits that increase the rate of woody litter fuel accumulation and flammability, which may alter the overriding influence of rainfall gradients on fire regimes.

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Locating the real source of the Internet attacks has long been an important but difficult problem to be addressed. In the real world, attackers can easily hide their identities and evade punishment by relaying their attacks through a series of compromised systems or devices called stepping stones. Currently, researchers mainly use similar features from the network traffic, such as packet timestamps and frequencies, to detect stepping stones. However, these features can be easily destroyed by attackers using evasive techniques. In addition, it is also difficult to implement an appropriate threshold of similarity that can help justify the stepping stones. In order to counter these problems, in this paper, we introduce the consistent causality probability to detect the stepping stones. We formulate the ranges of abnormal causality probabilities according to the different network conditions, and on the basis of it, we further implement to self-adaptive methods to capture stepping stones. To evaluate our proposed detection methods, we adopt theoretic analysis and empirical studies, which demonstrate accuracy of the abnormal causality probability. Moreover, we compare our proposed methods with previous works. The result shows that our methods in this paper significantly outperform previous works in the accuracy of detection malicious stepping stones, even when evasive techniques are adopted by attackers.

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The management of its people defines the way in which an organisation develops the capabilities to successfully compete in the market environment. Since the 1950s, approaches to staff management have evolved from traditional bureaucratic foundations to strategic planning exercises. This article uses a case study approach to investigate the way in which the process of organisational learning evolved in the development of personnel management practices. It suggests that although old and new practices were often overlaid on each other, ‘bridges’ developed which allowed the progressive development of new managerial processes.