510 research outputs found

    Bash Cookbook

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    The key to mastering any Unix system, especially Linux and Mac OS X, is a thorough knowledge of shell scripting. Scripting is a way to harness and customize the power of any Unix system, and it's an essential skill for any Unix users, including system administrators and professional OS X developers. But beneath this simple promise lies a treacherous ocean of variations in Unix commands and standards.bash Cookbook teaches shell scripting the way Unix masters practice the craft. It presents a variety of recipes and tricks for all levels of shell programmers so that anyone can become a proficien

    A Comparison of Rainfall Estimation Techniques

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    This study compares two techniques that have been developed for rainfall and streamflow estimation with the aim of identifying strengths and weaknesses of each. The first technique utilises thin plate smoothing splines to develop rainfall surfaces for the catchment, which are then, in conjunction with daily point-wise rainfall data used to determine areal catchment estimates. The second technique develops a regression-based model relating elevation to total annual rainfall in order to scale rainfall for daily mean catchment rainfall estimates. Both approaches are compared in common catchments in the upper Murrumbidgee catchment. The comparison includes using the data from each of the approaches as input to a rainfall-runoff model and by comparison of the quality of modelled results to observed streamflow. The strengths, weaknesses and use for catchment managers in decision making are identified. The study results revealed that where rain station spatial density and data quality are high, both regression and the spline method perform equally as well in estimating long term rainfall trends. In conclusion, catchment managers could apply the simple regression technique over the sophisticated spline method to achieve the comparable results. This is particularly useful where an efficient yet simple method is required for assessing streamflow within similar catchments

    Land use change: implications for Australian Capital Territory Water use

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    Managing water resources to ensure environmental values are maintained, whilst allowing for continued economic development is a major challenge facing many areas including the Australian Capital Territory (ACT). This paper reports on a GIS based investigation of the implications of land use change on ACT water use. The paper describes a suite of tools that are collectively termed PLUCA (Platform for Land use Change Assessment). Areas with the potential for land use change were identified through land capability assessment and by investigation of the suitability of land for development of alternate industries. Spatial data including slope, aspect, a wetness index, climatic surfaces, geology and consideration of the minimum viable scale of industry were analysed in the study. A coarse land use class – water use relationship estimated for the ACT was used to determine the maximum potential water use resulting from land use change. Three scenarios, based on different levels of land use change were constructed to simulate high, medium and low levels of potential landuse change in the ACT. The estimated reduction in streamflow for the maximum development scenario, was around 6.8% of the average annual runoff from the ACT. This scenario represented modification of only 3.9% of the total land area. This study demonstrates the potential for the use of GIS in the optimisation of landuse from biophysical characteristics. The implications of such changes should they occur were calculated through investigation of the annual average reduction in streamflow. The study demonstrates the use of GIS techniques in quantifying interactions at appropriate scales for decision making. The development of improved decision support tools is also outlined. <br

    Comparison of landscape approaches to define spatial patterns of hillslope-scale sediment delivery ratio

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    A sediment delivery ratio (SDR) is that fraction of gross erosion that is transported from a given catchment in a given time interval. In essence, a SDR is a scaling factor that relates sediment availability and deposition at different spatial scales. In this paper, we focus on hillslope-scale SDR, i.e. the ratio of sediment produced from hillslopes to that delivered to the stream network. Factors that affect hillslope water movement, and thus entrainment or deposition of sediments, ultimately affecting the SDR, include upslope area, climate, topography, and soil cover. In erosion models, SDR is usually treated as a constant parameter. However, the use of spatially variable SDRs could improve the spatial prediction of the critical sources of sediment, i.e. identification of those areas directly affecting stream water quality. Such information would improve prioritisation of natural resource management effort and investment. Recent literature has described several landscape approaches to represent SDR variability in space, some of which account only for topography, whilst others consider topography and soil cover characteristics. The aim of this study was to evaluate four landscape approaches for their ability to depict spatial patterns of SDR in the Avon-Richardson catchment in the semi-arid Wimmera region (Victoria, South-east Australia). Erosion was assessed using a semi-distributed model (CatchMODS) with disaggregation based in subcatchments of around 40 km2 area. Hillslope gross erosion was assessed with a RUSLE approach. By applying the four landscape approaches using DEM and estimates of land use cover, four landscape index subcatchment distributions were calculated. These were normalised into standard distributions. Then, a sigmoid function was used to transform the standardised indices into SDR-index distributions ranging from zero to one. Finally, subcatchment SDRs were estimated as the product of the SDR-index by a whole-of-catchment SDR value that was estimated by calibration against sediment loads measured at five gauging stations of the study area. The major sources of hillslope erosion were modelled to be located in the southern hilly areas of the catchment. However, a topographic convergence approach predicted as well important contribution of hillslope-erosion sediment loads coming from the eastern flatter cropping land. The introduction of landscape-variable SDRs improved the overall goodness-of-fit of modelled versus observed sediment loads at five gauging stations located in the catchment for only the topographic convergence approach. However, the limited number of observations (11), the location of some gauging stations downstream of active gully erosion, and the lack of gauging stations monitoring the north-eastern part of the catchment hindered the assessment of which spatial distribution of hillslope erosion best represented the real catchment conditions. Further research is needed to define the relationship between landscape indices and SDR; and to evaluate the spatial distribution of erosion against more complete field evidence

    Lower body acceleration and muscular responses to rotational and vertical whole-body vibration of different frequencies and amplitudes

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    This is the final version. Available on open access from SAGE Publications via the DOI in this recordThe aim of this study was to characterise acceleration transmission and neuromuscular responses to rotational (RV) and vertical (VV) vibration of different frequencies and amplitudes. Methods - 12 healthy males completed 2 experimental trials (RV vs. VV) during which vibration was delivered during either squatting (30°; RV vs. VV) or standing (RV only) with 20, 25, 30 Hz, at 1.5 and 3.0 mm peak-to-peak amplitude. Vibration-induced accelerations were assessed with triaxial accelerometers mounted on the platform and bony landmarks at ankle, knee, and lumbar spine. Results At all frequency/amplitude combinations, accelerations at the ankle were greater during RV (all p < 0.03) with the greatest difference observed at 30 Hz 1.5 mm. Transmission of RV was also influenced by body posture (standing vs. squatting, p < 0.03). Irrespective of vibration type vibration transmission to all skeletal sites was generally greater at higher amplitudes but not at higher frequencies, especially above the ankle joint. Acceleration at the lumbar spine increased with greater vibration amplitude but not frequency and was highest with RV during standing. Conclusions/Implications - The transmission of vibration during WBV is dependent on intensity and direction of vibration as well as body posture. For targeted mechanical loading at the lumbar spine, RV of higher amplitude and lower frequency vibration while standing is recommended. These results will assist with the prescription of WBV to achieve desired levels of mechanical loading at specific sites in the human body.London South Bank UniversityAge U

    A robust, semi-automated approach for counting cementum increments imaged with synchrotron X-ray computed tomography

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    Cementum, the tissue attaching mammal tooth roots to the periodontal ligament, grows appositionally throughout life, displaying a series of circum-annual incremental features. These have been studied for decades as a direct record of chronological lifespan. The majority of previous studies on cementum have used traditional thin-section histological methods to image and analyse increments. However, several caveats have been raised in terms of studying cementum increments in thin-sections. Firstly, the limited number of thin-sections and the two-dimensional perspective they impart provide an incomplete interpretation of cementum structure, and studies often struggle or fail to overcome complications in increment patterns that complicate or inhibit increment counting. Increments have been repeatedly shown to both split and coalesce, creating accessory increments that can bias increment counts. Secondly, identification and counting of cementum increments using human vision is subjective, and it has led to inaccurate readings in several experiments studying individuals of known age. Here, we have attempted to optimise a recently introduced imaging modality for cementum imaging; X-ray propagation-based phase-contrast imaging (PPCI). X-ray PPCI was performed for a sample of rhesus macaque (Macaca mulatta) lower first molars (n = 10) from a laboratory population of known age. PPCI allowed the qualitative identification of primary/annual versus intermittent secondary increments formed by splitting/coalescence. A new method for semi-automatic increment counting was then integrated into a purpose-built software package for studying cementum increments, to count increments in regions with minimal complications. Qualitative comparison with data from conventional cementochronology, based on histological examination of tissue thin-sections, confirmed that X-ray PPCI reliably and non-destructively records cementum increments (given the appropriate preparation of specimens prior to X-ray imaging). Validation of the increment counting algorithm suggests that it is robust and provides accurate estimates of increment counts. In summary, we show that our new increment counting method has the potential to overcome caveats of conventional cementochronology approaches, when used to analyse three-dimensional images provided by X-ray PPCI.Peer reviewe
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