Strategies for maximizing sugarcane yield with limited water in the Bundaberg district

Between 1995 and 2003 sugarcane farmers in Bundaberg had access to limited irrigation water. Over this time water allocations were effectively a quarter of the requirements for a fully irrigated crop. In response to this problem irrigation strategies were developed to assist farmers. Field investigations focused on the performance of water winch and furrow irrigation systems, which make up 91 percent of the irrigated area in the district. As most of these application systems have insufficient capacity to meet crop demands, opportunities to schedule irrigations were limited to start up after rain. Improvements in irrigation system performance were found to provide the greatest potential to increase sugarcane yield under conditions of limited water. Investigations identified that irrigation performance could be significantly improved through relatively minor adjustment. Timing of irrigation start up after rain influenced how much water could be applied to the field. Even with relatively low allocations delayed start up strategies could lead to a situation where water was left over at the end of the season

Assessing Alternatives for Directional Detection of a WIMP Halo

The future of direct terrestrial WIMP detection lies on two fronts: new, much larger low background detectors sensitive to energy deposition, and detectors with directional sensitivity. The former can large range of WIMP parameter space using well tested technology while the latter may be necessary if one is to disentangle particle physics parameters from astrophysical halo parameters. Because directional detectors will be quite difficult to construct it is worthwhile exploring in advance generally which experimental features will yield the greatest benefits at the lowest costs. We examine the sensitivity of directional detectors with varying angular tracking resolution with and without the ability to distinguish forward versus backward recoils, and compare these to the sensitivity of a detector where the track is projected onto a two-dimensional plane. The latter detector regardless of where it is placed on the Earth, can be oriented to produce a significantly better discrimination signal than a 3D detector without this capability, and with sensitivity within a factor of 2 of a full 3D tracking detector. Required event rates to distinguish signals from backgrounds for a simple isothermal halo range from the low teens in the best case to many thousands in the worst.Comment: 4 pages, including 2 figues and 2 tables, submitted to PR

Acoustic Metamaterials for Enhanced Wave Control

Acoustic metamaterials have redefined the limits of acoustic wave control with composite structures that realize effective material properties that go beyond those of natural materials. These extraordinary material properties enable imaging beyond the diffraction limit, negative effective sound speeds, and acoustic cloaking. Metamaterials continue to be a hot topic in the scientific community, as these resonant structures push the boundaries of acoustic wave control with unprecedented functionality. The primary goal of this work is to advance the prevalence, practicality, and scope of acoustic metamaterial research with novel materials that uniquely tailor wave fields for a variety of acoustic-based applications. Each chapter uses foundational metamaterial physics to advance our understanding of acoustic wave control with composite structures. The first section develops the theory and performs simulations for a non-Hermitian complementary metamaterial (NHCMM) with tunable active feedback loop circuits that improve the acoustic transmission through an intact human skull. This lays the foundation for ultrasonic brain imaging and neural therapies that require high frequency acoustic waves to penetrate deep within the brain. With a similarly designed metamaterial, we compare the accessible range of the effective density and bulk modulus for unit cells with symmetric and asymmetric feedback loop circuits. The asymmetric circuits result in a Willis coupled response that dramatically broadens the metamaterial’s attainable parameter range. We also demonstrate asymmetric wave transmission at high efficiency with passive Willis coupled metagratings for acoustic beam steering at extreme angles. Lastly, we use transformation acoustics to correct focused and self-bending acoustic beams that become distorted in anisotropic media. These developments advance acoustic-based technologies for biomedical imaging, noise control, underwater communication, and structural acoustic applications.Ph.D

The Impact of Motivation on Continued VFR into IMC: Another Perspective to an On-Going Problem

Continued flight under visual flight rules into instrument meteorological conditions remains the predominant cause for fatal accidents by percentage for general aviation aircraft operations. There are gaps in the research in determining how motivation might influence the decision-making process. Therefore, the purpose of this study was to determine how motivation and meteorological conditions might affect a pilot’s willingness to persist in flight into meteorological conditions. Four hundred and fifty-four general aviation pilots participated in a mixed factorial experiment to assess their willingness to persist in varying weather conditions. Participants were randomly assigned into one of three motivation groups (intrinsic, extrinsic, or no motivation) and were subjected to all three meteorological conditions (visual, marginal, and instrument) that were randomized in order of appearance. They were then asked to indicate their willingness to persist in each condition via a slider scale, scaled from 0 to 100. The results indicated the main effect of meteorological condition has a significant effect on willingness to persist, while the main effect of motivation did not. The interaction between meteorological condition and motivation resulted in a significant effect, particularly in the marginal meteorological condition

Impacts of Invasive Plants on Sandhill Crane (\u3ci\u3eGrus canadensis\u3c/i\u3e) Roosting Habitat

Invasive plants continue to spread in riparian ecosystems, causing both ecological and economic damage. This research investigated the impacts of common reed, purple loosestrife, riparian shrubland, and riparian woodlands on the quality and quantity of sandhill crane roosting habitat in the central Platte River, Nebraska, using a discrete choice model. A more detailed investigation of the impacts of common reed on sandhill crane roosting habitat was performed by forecasting a spread or contraction of this invasive plant. The discrete choice model indicates that riparian woodlands had the largest negative impact on sandhill crane roosting habitat. The forecasting results predict that a contraction of common reed could increase sandhill crane habitat availability by 50%, whereas an expansion could reduce the availability by as much as 250%. This suggests that if the distribution of common reed continues to expand in the central Platte River the availability of sandhill crane roosting habitat would likely be greatly reduced