Near-surface distributions of soil water and water repellency under three effluent irrigation schemes in a blue gum (Eucalyptus globulus) plantation

Water repellent soils are difficult to irrigate and susceptible to preferential flow, which enhances the potential for accelerated leaching to groundwater of hazardous substances. Over 5 Mha of Australian soil is water repellent, while treated municipal sewage is increasingly used for irrigation. Only if a critical water content is exceeded will repellent soils become wettable. To avoid excessive loss of water from the root zone via preferential flow paths, irrigation schemes should therefore aim to keep the soil wet enough to maintain soil wettability. Our objective was to monitor the near-surface water content and water repellency in a blue gum (Eucalyptus globulus) plantation irrigated with treated sewage. The plantation's sandy soil surface was strongly water repellent when dry. For 4 months, three rows of 15 blue gum trees each received no irrigation, three other rows received 50% of the estimated potential water use minus rainfall, and three more rows received 100%. During this period, 162 soil samples were obtained in three sampling rounds, and their water content (% dry mass) and degree of water repellency determined. Both high and low irrigation effectively wetted up the soil and eliminated water repellency after 2 (high) or 4 (low) months. A single-peaked distribution of water contents was observed in the soil samples, but the water repellency distribution was dichotomous, with 44% extremely water-repellent and 36% wettable. This is consistent with a threshold water content at which a soil sample changes from water repellent to wettable, with spatial variability of this threshold creating a much wider transition zone at the field scale. We characterized this transition zone by expressing the fraction of wettable samples as a function of water content, and demonstrated a way to estimate from this the wettable portion of a field from a number of water content measurements. To keep the plantation soil wettable, the water content must be maintained at a level at which a significant downward flux is likely, with the associated enhanced leaching. At water contents with negligible downward flux, the field is water repellent, and leaching through preferential flow paths is likely. Careful management is needed to resolve these conflicting requirements.

An empirical study of encoding schemes and search strategies in discovering causal networks

Efficiently inducing precise causal models accurately reflecting given data sets is the ultimate goal of causal discovery. The algorithm proposed by Wallace et al. [10] has demonstrated its ability in discovering Linear Causal Models from data. To explore the ways to improve efficiency, this research examines three different encoding schemes and four searching strategies. The experimental results reveal that (1) specifying parents encoding method is the best among three encoding methods we examined; (2) In the discovery of linear causal models, local Hill climbing works very well compared to other more sophisticated methods, like Markov Chain Monte Carto (MCMC), Genetic Algorithm (GA) and Parallel MCMC searching.

Supporting user evaluation of IT security certification schemes

IT Security Certification is an increasingly important qualification for information technology (IT) professionals seeking employment in IT security. Yet currently there is a lack of rigorously developed approaches to support the evaluation and selection by key stakeholders of the most appropriate IT security certification scheme from among hundreds of vendor-neutral and vendor-specific schemes. This paper develops a framework based on categories, characteristics and criteria to support user evaluation and selection of an (IT) Security Certification scheme that satisfies user priorities and requirements. The paper illustrates the use of the framework to support an experienced IT Professional’s evaluation. Theoretical and practical implications of the framework and trial evaluation are discussed.

An evaluation of the viability of photovoltaics in residential schemes managed by UK registered social landlords

Global demands on fossil fuels require the investigation of renewable and viable alternative energy supplies. The Intergovernmental Panel on Climate Change (IPCC) has concluded that current consumption of fossil fuels is untenable as atmospheric emissions of gases, in particular carbon dioxide (CO²), is having a significant and worsening effect on global climate change (IPCC 1992).

25% of UK CO² emissions are generated in the housing sector (UKCCP 2000). As major providers of UK social housing, Registered Social Landlords (RSLs), indirectly make a significant contribution to UK CO² emissions. In delivering UK Government policies, RSLs are required to meet national social and economic targets, as well as environmental targets. Clearly, social, environmental and economic issues combine in the arena of energy efficiency and social housing.

Potentially, the use of photovoltaics (PV) in social housing could assist the UK government in meeting targets in terms of affordable housing, providing "free" electricity to low income tenants, and with minimal environmental impact in urban areas. However, uptake of PV amongst RSLs in the UK has been minimal to date. This paper explores the factors that act as barriers to energy efficiency in this market.

A framework for assessing certification schemes for IT security professionals

This research develops a framework which allows the many IT security certifications to be compared by stakeholders, such as IT security professionals, employers, universities and governments. The framework employs a novel approach which allow users to tailor the comparison based on their own weightings, whilst taking advantage of standardised research.

Reliable algorithms and attack detection schemes for network systems

Network and Information security and reliability is still a key issue in information technology. This thesis develops two algorithms to improve the reliability and stability of content delivery systems, and proposes three attack detection schemes with high effectiveness and accuracy in detecting network attacks.

Authentication in public key encryption schemes

This thesis analyses authentication in public key encryption and makes contributions in two areas. Firstly, Compressed Nested PKI is proposed which improves the certificate validation process. Then an implicitly certified encryption scheme, Authenticated Public Key Encryption, which makes keys easier to manage, is introduced.

The place of place : case studies of place in Victorian planning schemes

Built environment and lived experience are inextricably interwoven. The Australian State of Victoria’s planning framework prioritises the physical characteristics of space above their socio-psychological correlates, as reflected in the relatively limited remit of ‘place’ in formal decision-making. The Victorian planning model struggles to accommodate the uniqueness of specific places in the process of development, despite the driving role it plays in expansion. A literature review investigating definitions of place and place identity determined that although place has been defined variously, and at times with some contradiction, there is broad consensus that it can be understood as the interrelation between the physical characteristics of a landscape and the sensory faculties of an individual and an individual’s experience. This interrelationship is in turn determined by social constructs. Depending on an individual’s length of residence in a particular physical location, place influences individual and social psychology through both the formation of place attachment and identity. While place attachment to landscapes has been described using a variety of complex methodologies, translation of this work into architectural and planning practice has been limited within Australia in general and Victoria in particular. The Victorian Shires of Surf Coast and Frankston are considered as examples of current best practice in integrating place into planning. Key issues highlighted in the conclusion include: the difficulties of incorporating qualitative information within the Victorian Planning Scheme; the importance of correctly measuring place attachment, rather than landscape preference; and the complexities, costs and ethical implications of describing place attachment for integration within the planning system.

Properties of series feature aggregation schemes

Feature aggregation is a critical technique in content-based image retrieval (CBIR) that combines multiple feature distances to obtain image dissimilarity. Conventional parallel feature aggregation (PFA) schemes failed to effectively filter out the irrelevant images using individual visual features before ranking images in collection. Series feature aggregation (SFA) is a new scheme that aims to address this problem. This paper investigates three important properties of SFA that are significant for design of systems. They reveal the irrelevance of feature order and the convertibility of SFA and PFA as well as the superior performance of SFA. Furthermore, based on Gaussian kernel density estimator, the authors propose a new method to estimate the visual threshold, which is the key parameter of SFA. Experiments, conducted with IAPR TC-12 benchmark image collection (ImageCLEF2006) that contains over 20,000 photographic images and defined queries, have shown that SFA can outperform conventional PFA schemes.

Properties of series feature aggregation schemes

Feature aggregation is a critical technique in content-based image retrieval (CBIR) that combines multiple feature distances to obtain image dissimilarity. Conventional parallel feature aggregation (PFA) schemes failed to effectively filter out the irrelevant images using individual visual features before ranking images in collection. Series feature aggregation (SFA) is a new scheme that aims to address this problem. This paper investigates three important properties of SFA that are significant for design of systems. They reveal the irrelevance of feature order and the convertibility of SFA and PFA as well as the superior performance of SFA. Furthermore, based on Gaussian kernel density estimator, the authors propose a new method to estimate the visual threshold, which is the key parameter of SFA. Experiments, conducted with IAPR TC-12 benchmark image collection (ImageCLEF2006) that contains over 20,000 photographic images and defined queries, have shown that SFA can outperform conventional PFA schemes.