Impact ionization in GaAs: a screened exchange density functional approach

Results are presented of a fully ab-initio calculation of impact ionization rates in GaAs within the density functional theory framework, using a screened-exchange formalism and the highly precise all-electron full-potential linearized augmented plane wave (FLAPW) method. The calculated impact ionization rates show a marked orientation dependence in {\bf k} space, indicating the strong restrictions imposed by the conservation of energy and momentum. This anisotropy diminishes as the impacting electron energy increases. A Keldysh type fit performed on the energy-dependent rate shows a rather soft edge and a threshold energy greater than the direct band gap. The consistency with available Monte Carlo and empirical pseudopotential calculations shows the reliability of our approach and paves the way to ab-initio calculations of pair production rates in new and more complex materials.Comment: 11 pages, 4 figures, Submitted to Phys. Rev.

Some aspects of the electronic structure and photoemission studies of tetrahedral semiconductors

SIGLELD:D46258/83 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

An integrated testing programme for a near field radionuclide migration code

The DRINK code is a 2D, biogeochemical transport code developed as a research tool to simulate the long term evolution of near surface LLW disposal sites and to generate gaseous and liquid source terms for far field studies. The code was recently upgraded to provide a more generic modelling tool with wider application to radionuclide migration scenarios. During the development of this code, the Generalised Repository Model (GRM), an integrated strategy has been employed to ensure the production of a fully tested, verified and quality assured product. This strategy is based around a code development protocol with three main components: quality assurance and documentation, verification and realism testing. Realism testing includes both peer review and model testing, with the latter including: experimental test cases; natural and anthropogenic analogues; field observations and finally uncertainty and sensitivity analysis. This paper describes the successful application of the protocol to the development and testing of the GRM code with specific emphasis upon verification and realism testing

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Not AvailableDry season rice, popularly called as boro rice, has the potential to bridge the gap of production and consumption in the eastern India. High salinity of surface water in this area during the dry season however limits the cultivation of boro rice. Farmers have to resort to pumping ground water for dry season irrigation. Indiscriminate ground water pumping may lead to ground water depletion, salinity intrusion into the aquifers and increased cost of pumping. Judicious and conservative use of precious irrigation water is essential to enable boro rice and sustain the productivity of this fragile ecosystem. This study aimed at reducing irrigation water and increasing irrigation water productivity (Wp) in boro rice by optimizing the date of sowing and the use of suitable rice varieties. The experiment was conducted in 2012 – 2013 and 2013 – 2014 boro rice seasons at Central Soil Salinity Research Institute, Canning Town, India. Eight tested rice varieties, including 4 from Bangladesh, were sown during the first week (early sowing) and the last week of November (late sowing). Twenty one day seedlings of early sown and late sown crops were transplanted in adjacent fields. In each field, rice varieties were randomized with three replications. For both two cropping seasons, and under early sowing, yields of BINA dhan 8 (6.04t ha-1), BRRI dhan 47(5.89 t ha-1), CSR 22 (5.95 t ha-1), and IR 10206-29-2-1-1 (5.87 t ha-1) did not differ significantly and were significantly higher than those of other varieties. Under late sowing, BINA dhan 8 produced significantly the highest grain yield (5.86 t ha-1). In both sowings, CSRC(S) 50-2-1-1-4-B produced significantly the lowest yield. Irrigation water input for different varieties increased with their growth durations. Depth of irrigation water was lowest (117 cm for early sowing; 145 cm for late sowing) in the variety BRRI dhan 47, followed by IR 10206-29-2-1-1. Varieties CSR 34 and CSR 22 had the highest irrigation water inputs. For all cultivars, early sowing consumed 17% less irrigation water than late sown crop. The difference was due to higher water inputs for land soaking, land preparation and puddling in the late sown crop. The grain yields of late sown crops (4.92 t ha-1) were 13% less than those of early sown crops (5.56 t ha-1).WP under early sowing (41-45 kg grain/ha-cm) was about 30% higher than that under late sowing (31-35 kg grain/ha-cm) during both the years of study. Among the varieties, highest WP was recorded in BRRI dhan 47 under early sowing and in BINA dhan 8 in case of late sowing.International Rice Research Institut

The Internet of Things and value co-creation in a Service Dominant logic perspective

The new capacities of pervasive and ubiquitous computing are defining new horizons for human creativity and connectivity. This is also because pervasive and ubiquitous computing is very often linked with other emerging technologies, such as the semantic Web, cloud computing, and affective computing. At the same time, there has been a rapid development in 3G and 4G networks as well as in the use of feature-rich smartphones. This means that everyone can be connected at anytime and anywhere. In the near future, the development of specific hardware as well as software will enable everyone to be in touch with everything and everywhere, thus closing the “circle of pervasiveness.” The Internet of the future promises to connect our mobile devices with everything (from the fridge in our homes to special sensors in our cars or even in our bodies), whenever and whereverwe are