Mathematics

  2010 MAY 4 - (VerticalNews.com) -- "Leucaena leucocephala is cultivated at close spacings that do not permit intercropping. This has been a discouraging factor for small landholders who need regular income to establish leucaena plantations and benefit horn the rapidly expanding market for wood," scientists in Hyderabad, India report.

  "Therefore, on-farm experiments were conducted near Bhadrachalam, Khammam district, Andhra Pradesh, India, from August 2001 to January 2006, to study the effect of reducing tree density and modifying tree geometry on the growth of leucaena and productivity of intercrops. The inter-row spacing of 1.3 m in farmers' practice was increased up to 13 m to examine whether wide-row planting and grouping of certain rows would facilitate extended intercropping without sacrificing wood yield. Tree density treatments tried were 1.3 x 1.3 m, 3 x 0.75 m, 3 x 1 m, 5 x 0.8 m and 3 x 2 m which gives densities 5919, 4444, 3333, 2500 and 1666 trees ha(-1), respectively. Tree geometry treatments tested were 7 x 1 in paired row spacing (7 x 1 PR), 10 x 1 m triple row spacing (10 x 1 TR) and 13 x 1 m four rows (13 x 1 FR) with a constant tree population of 2500 trees ha I. Cowpea (Vigna unguiculata) was the intercrop. While changes in tree density affected diameter at breast height (DBH) significantly, modification of tree geometry did not affect tree height and DBH. Marketable wood and dry biomass productivity was highest with 3 x 0.75 m spacing, and reducing tree density and alteration of tree geometry reduced the biomass considerably. In 2001, 2002 and 2003 seasons, respectively, tree spacing at 3 m produced mean yields of 97, 23 and 11% of the sole clop cowpea yield whereas modified tree geometry treatments produced mean yields of 97, 61 and 20% of sole crop yield. The widest spacing (13 x 1 FR) recorded 95, 73 and 30% of the sole crop yields during 2001, 2002 and 2003, respectively. Net returns from intercropping of leucaena in 3 x 0.75 m spacing was 36% higher than that of the farmers' practice. Although wider tree geometry treatments recorded lower net returns, they provided higher intercrop yields and returns in the first two years of plantation establishment," wrote J.V.N.S. Prasad and colleagues ...read more

  2010 MAY 4 - (VerticalNews.com) -- "The cognitive radio (CR) is known as a radio that can reconfigure its transceiver parameters based on the environmental awareness. The opportunistic radio (OR) is considered in this work, with a narrower definition where the awareness is limited to the spectrum knowledge," scientists in Guildford, the United Kingdom report.

  "The decision making framework is employed as a crucial entity to control the behaviour of the OR. The main purpose is to enable an efficient spectrum usage while avoiding the interference to other users. This study describes the proposed OR decision making framework including the flow of context information as an input process to the decision making engine, the context filtering and the reasoning mechanisms in which the decision optimisation is achieved using a genetic algorithm (GA)-based approach. The system stability of the GA-based reasoning engine is tested through simulations. Then, the experimental study is performed on a test platform for a practical proof of the concept. The test platform is based on the Ettus USRP (Universal Software Radio Peripheral) hardware and the GNU Radio open source software. Several tests were carried out to observe the OR capabilities of the proposed decision making framework," wrote S. Chantaraskul and colleagues, University of Surrey ...read more

  2010 MAY 4 - (VerticalNews.com) -- "Subglacial lakes in Antarctica influence to a large extent the flow of the ice sheet. In this study we use an idealised lake geometry to study this impact," investigators in Munich, Germany report.

  "We employ a) an improved three-dimensional full-Stokes ice flow model with a nonlinear rheology, b) a three-dimensional fluid dynamics model with eddy diffusion to simulate the basal mass balance at the lake-ice interface, and c) a newly developed coupler to exchange boundary conditions between the two individual models. Different boundary conditions are applied over grounded ice and floating ice. This results in significantly increased temperatures within the ice on top of the lake, compared to ice at the same depth outside the lake area. Basal melting of the ice sheet increases this lateral temperature gradient. Upstream the ice flow converges towards the lake and accelerates by about 10% whenever basal melting at the ice-lake boundary is present," wrote M. Thoma and colleagues ...read more