2 results for Bowden, Alice Therese, Masters

  • Wind Resource Assessment in Waitati, Otago, New Zealand.

    Bowden, Alice Therese (2011)

    Masters thesis
    University of Otago

    The coastal Otago community of Waitati (45°45”S, 170°34”E, 19 km north of Dunedin) is considering renewable energy sources to help offset their electricity consumption. The Waitati Energy Project is focussed on the installation of a wind turbine for energy generation, and also for a visual testament to community achievement. The purpose of this research was to investigate the climatological viability of wind power in the Waitati area, with the assistance of boundary layer theory for understanding the interactions between synoptic scale air flow and land surface influences. This study utilised a combination of field work and numerical modelling to understand the local wind regime by characterising its spatial and temporal variability, determining the atmospheric and topographical influences on wind speed and direction, and predicting suitable locations for wind turbine sites. For the observations, twelve months of wind data from two automatic weather stations in Waitati (AWS1 and AWS2, located to the east and west of the township), as well as a 35 year wind record from Taiaroa Head were used. The numerical modelling was generated by the meteorological component of The Air Pollution Model (TAPM), to give three-dimensional numerical predictions of the Waitati wind regime at a 1 km resolution. The average wind speed in Waitati over the study period (June 5 2009 to May 31 2010) was 4.34 m s-1 at AWS1 and 2.46 m s-1 at AWS2. This variation in average wind speed was attributed to a sheltering effect at AWS2. At the more exposed Taiaroa AWS, average wind speeds reached 6.71 m s-1. The 35 year record of average wind speed from Taiaroa Head allowed the data from the study period to be put into a longer temporal context. Seasonal analysis of the observational data revealed spring and autumn as the windiest periods, with west to southwest airflow the predominant flow direction. These data were supplemented by seasonal TAPM predictions across the Waitati area. Areas of higher elevation were more exposed to high wind speeds, and the eastern side of the Waitati valley was largely sheltered from gradient winds by high topography to the south and west. Week-long case study analyses of cyclonic and anticyclonic systems revealed the ability of TAPM to predict wind speeds in different conditions. During the cyclonic conditions wind speeds were well predicted for Waitati, and the model estimated topographical channelling of the southerly through the hills to the south of Waitati. During the anticyclonic conditions nocturnal drainage flows and daytime sea breezes were predicted to modify the weak synoptic northeasterly wind. Of the four wind turbines featured in this research, the three larger, commercial ones were found to be climatologically unviable for this low wind speed environment. Their cut-in wind speeds of 4 to 5.5 m s-1 were so close to the (observed and modelled) average annual wind speed that it could be predicted that these turbines would only be operational for half of any given year. In contrast, the locally designed Thinair102 turbine, which is made for operation at the household level, would be more suitable with a cut-in wind speed of 3.5 m s-1.

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  • Normalisation, Evaluation and Verification of the New Zealand Hearing Screening Test.

    Bowden, Alice Therese (2013)

    Masters thesis
    University of Canterbury Library

    Presbycusis, or age-related hearing loss, is one of the most common chronic conditions to affect adults. On average individuals wait seven years from the time they notice a hearing impairment to the time they seek help from a hearing professional. This delay may have wide reaching implications for public health in the coming decades, as aging populations become more prevalent and as further research assesses the relationship between hearing loss and mental health conditions such as depression and dementia. The development of the New Zealand Hearing Screening Test (NZHST) aims to fulfil a need for a robust hearing screening test that individuals can access from home. This digit triplet test (DTT) will be particularly valuable for those in rural areas where audiological services are sparse and for those who have mobility issues which restrict attendance at clinical appointments. In order to accommodate as many New Zealanders as possible, the NZHST will have two versions, an internet version and a land-line telephone version; both of which can be delivered into their home in either New Zealand English or Te Reo Māori. This research is the third instalment in the development of the NZHST. The current research is divided into three parts; the verification of the New Zealand English DTT for the internet version, the pilot study for the Te Reo Māori DTT for the internet version, and the normalisation of the New Zealand English DTT for the telephone version. In the verification process, 50 individuals with various audiometric thresholds listened to 3 lists of 27 New Zealand English digit triplets, presented in three conditions; binaurally and to each ear separately via an internet interface. In the pilot study, 27 participants with various audiometric thresholds listened to 3 lists of 27 Te Reo Māori digit triplets via a software interface on a laptop computer. The normalisation process involved 10 individuals with normal hearing (average air-conduction pure tone thresholds of ≤ 20 dB HL) listening to 168 New Zealand English digit triplets under two different noise conditions; one as continuous speech noise and the other a noise with spectral and temporal gaps (STG noise) presented via a software interface on a laptop computer. Four conditions of the 168 digits were presented; once to each ear for the continuous noise, and once to each ear for the STG noise. Significant correlations were found between the binaural DTT and PTA (R = 0.66), and between the monaural ear DTT and PTA (R = 0.73) for the verification. The binaural DTT had a test sensitivity of 94% and a specificity of 88%. Pilot study correlation between binaural DTT and PTA was R = 0.61, and was R = 0.63 between monaural DTT and PTA; while the binaural sensitivity (100%) and specificity (100%) of the Te Reo DTT was affected by the very small number of participants with hearing loss (n = 4). The normalisation revealed that detection of the digit triplets was easier when STG noise (Lmid = -11.5 dB SNR, SD = 1.6 dB) was used as a masker, rather than continuous noise (Lmid = -8.9 dB SNR, SD = 1.4 dB).

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