6,874 research outputs found
Evaluation of greenwaste mulch to control runoff quality from landfill sites during frequent storms
This paper describes a preliminary evaluation of two types of greenwaste (fresh and aged) used as a mulch layer to control runoff from disturbed landfill areas. Fresh greenwaste refers to woody and herbaceous garden waste that has been recently collected, chopped and shredded. Aged greenwaste is greenwaste which has been stockpiled for 18 months. We used rainfall simulator tests to investigate two aspects: (1) the performance of greenwaste mulch in reducing runoff during designed storm events with a high frequency of occurrence and (2) the release of pollutants via runoff as total suspended solids (TSS) and total organic carbon (TOC) during rain. Rainfall of <5-year average recurrence interval (ARI) was generally applied, consistent with stormwater compliance requirements for many Australian landfills. TOC released from fresh greenwaste material was higher in concentration than from aged greenwaste. However when used as a 10cm-deep mulch layer, fresh greenwaste was able to completely prevent runoff, even when tested under rainfalls up to 50 year ARI duration. An equivalent mulch layer of aged greenwaste was also effective in reducing runoff volume and TSS concentration compared with the bare soil during a 3.5-year ARI rainfall, but mean TOC concentration was higher. Based on these preliminary results, fresh greenwaste mulching of bare soils is an attractive option to control runoff and erosion from areas subject to intermittent landfill operations and worthy of further investigations
Estimation of soil water deficit in an irrigated cotton field with infrared thermography
Plant growth and soil water deficit can vary spatially and temporally in crop fields due to variation in soil properties and/or irrigation and crop management factors. We conducted field experiments with cotton (Gossypium hirsutum L.) over two seasons during 2007-2009 to test if infrared thermography can distinguish systematic variation in deficit irrigation applied to various parts of the field over time. Soil water content was measured with a neutron probe and thermal images of crop plants were taken with a thermal infrared camera. Leaf water potential and stomatal conductance were also measured on selected occasions. All measurements were made at fixed locations within three replicate plots of an irrigation experiment consisting of four soil-water deficit treatments. Canopy temperature related as well with soil water within the root zone of cotton as the stomatal conductance index derived from canopy temperature, but it neglected the effect of local and seasonal variation in environmental conditions. Similarities in the pattern of spatial variation in canopy temperature and soil water over the experimental field indicates that thermography can be used with stomatal conductance index to assess soil water deficit in cotton fields for scheduling of irrigation and to apply water in areas within the field where it is most needed to reduce water deficit stress to the crop. Further confidence with application of infrared thermography can be gained by testing our measurement approach and analysis with irrigation scheduling of other crops
Flux enhancement in the inner region of a geometrically and optically thick accretion disk
The surface flux (and the corresponding observed flux) of a geometrically
thick ``funnel'' shaped disk is computed taking into account the radiation
impinging on the surface from other parts of the disk. It is found that the
ratio of the maximum apparent luminosity to the real luminosity of the disk is
only a factor even when the opening angle of the disk is small
(). Thus, geometrically beamed emission from ``funnel'' shaped
sub-Eddington disks around stellar mass black holes, cannot explain the
Ultra-Luminous X-ray sources detected in nearby galaxies.Comment: accepted for publication in Ap
Modulational instability of ion-acoustic wave packets in quantum pair-ion plasmas
Amplitude modulation of quantum ion-acoustic waves (QIAWs) in a quantum
electron-pair-ion plasma is studied. It is shown that the quantum coupling
parameter (being the ratio of the plasmonic energy density to the Fermi
energy) is ultimate responsible for the modulational stability of QIAW packets,
without which the wave becomes modulational unstable. New regimes for the
modulational stability (MS) and instability (MI) are obtained in terms of
and the positive to negative ion density ratio . The growth rate of MI
is obtained, the maximum value of which increases with and decreases
with . The results could be important for understanding the origin of
modulated QIAW packets in the environments of dense astrophysical objects,
laboratory negative ion plasmas as well as for the next generation laser solid
density plasma experiments.Comment: 4 pages, 2 figures (to appear in Astrophysics and Space Science
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