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Brisbane, Australia

Rahman A.,Griffith University | Chattopadhyay G.,Cardno | Hossain M.J.,Griffith University
IEEE Transactions on Power Delivery | Year: 2016

Timber poles are widely used for distributing electricity in rural areas, mainly in developing countries. The improved reliability of timber poles is extremely important as the breakdown or failure of any one of these poles can result in millions of dollars in lost revenue and restoration costs. The losses can include production loss, loss of property, or even loss of life. The reliability of such poles depends on a complex combination of age, usage, durability of timber, environmental factors influencing the deterioration process, and most important, maintenance actions carried out through the lifecycle of the poles. This paper focuses on developing an optimal maintenance model that predominantly captures the inground decay of timber poles, and on developing a mechanism for measuring these factors. The developed maintenance model is then illustrated with numerical examples. Analysis of failure data shows that most of the failures of timber poles are due to a decrease in timber strength and peripheral dimensions at or below ground level. The results from this research could be useful for maintenance and replacement decisions regarding inground timber components used in the utility, construction, railway, and transportation sectors. © 1986-2012 IEEE. Source

Parsons G.R.,University of Delaware | Myers K.,Cardno
Ecological Economics | Year: 2016

A yes-response function in a contingent valuation study is said to have fat tails if it has a high and slowly declining yes-response rate at high bid levels. Truncated bids refer to the practice of dropping high bid offers before a yes-response rate of near zero is reached. This is a common practice in contingent valuation. We explore the extent and implications of fat tails and truncated bids in a study of an endangered shorebird species. We find, among other things, that mean willingness to pay is quite sensitive to the highest bid offered – so much so that the choice of highest bid nearly dictates outcomes. © 2016 Elsevier B.V. Source

Branson P.,Cardno
Australian Coasts and Ports 2015 Conference | Year: 2015

Quinns Beach is situated within the City of Wanneroo on the south western Australian coast, approximately 40km north of Perth. The beach is fronted by a series of three limestone barrier reefs, which in contrast to coral reefs, are highly perforated resulting in a strongly modified nearshore wave climate that is responsible for the undulating planform character of the beaches in the City of Wanneroo; with numerous salients and cuspate forelands. Quinns Beach is situated on one such large cuspate foreland and has been experiencing ongoing erosion since at least the 1940's. Despite several engineering interventions over the past 30 years erosion is continuing at Quinns Beach. The present best estimate is that the 4 km length of beach has an average annual sediment deficit of approximately 20,000 m3. From an engineering perspective, Quinns Beach presents a challenging problem due to the importance of both longshore and cross shore transport at both seasonal and individual storm timescales. This, combined with existing coastal structures, results in a particular sensitivity to antecedent conditions that causes the locations of erosion to change between storms and seasons. In an effort to better understand the sediment transport pathways and support the assessment of options to improve management of the erosion issue, the XBeach model was set-up and calibrated to observed nearshore currents and morphological changes for a storm in September 2014. The extensive reefs (the furthest located 5km offshore) presented a significant challenge for developing a model domain that successfully resolved beach morphological changes around coastal structures and had sufficient spatial extent to suitably capture important areas of wind and wave set-up on reefs that drive the nearshore circulation. Modelling this complex environment provides important lessons for future coastal engineering on coasts with fringing reefs more generally. Source

Provis D.,Cardno | Provis D.,Swinburne University of Technology
Australian Coasts and Ports 2015 Conference | Year: 2015

Waves have been observed in Port Phillip Heads propagating at right angles to the direction of the dominant swell which comes from around the south west. These waves have the same period as the incoming swell. Analysis of radar images (WaMoS) shows that the secondary waves only exist in a relatively confined area. Examination of directional wave spectra from bottom-mounted acoustic gauges also demonstrates a localised area of occurrence. Analysis of the directional spectra show clear dual peaks at the same frequency but different directions, but only at specific sites. A numerical model (SWAN) has been used to investigate the location of the reflective area and the mechanism of reflection. The directional spectra from the model can be compared with those from the measured data. The most likely explanation is that the incoming swell is being reflected off a section of the wall of the canyon, the Entrance Deep, which runs through Port Phillip Heads. This phenomenon occurs through "total internal reflection" as the swell approaches the southern end of the canyon at greater than the critical angle for such reflection. Source

Gray C.A.,WildFish Research | Barnes L.M.,Cardno
Journal of Applied Ichthyology | Year: 2015

The dusky flathead (Platycephalus fuscus) is an important teleost harvested by recreational and commercial fishers throughout its endemic distribution along eastern Australia. This study indicates that the species has an extended spawning period throughout the austral summer, with females in spawning condition occurring in lower estuarine and coastal waters. Total length (L50) and age (A50) at which 50% (±1 SE) of the population was mature was 31.72 (±1.08) cm TL and 1.22 (±0.44) years for males and 56.75 (±0.60) cm TL and 4.55 (±0.13) years for females. The von Bertalanffy growth parameters differed significantly between sexes; females grew faster and attained a greater maximum TL and age than males. The largest female was 98.5 cm TL (7.5 kg), and the oldest 16 years, whereas the largest male was 61.5 cm TL (1.58 kg) and 11 years of age. A tag-and-release study identified the exchange of sub-adult and mature-sized individuals among estuaries. Determinations of length-based management regulations for the species are compounded by the large gender-based differences in growth and length-at-maturity. Current minimum legal lengths of 30-40 cm TL protect approximately 3-9% of the female spawning population. Alternative management options, including harvest slot sizes, need to be investigated and tested. © 2015 Blackwell Verlag GmbH. Source

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