2,995 research outputs found
Magneto-optical transport properties of monolayer phosphorene
The electronic properties of monolayer phosphorene are exotic due to its
puckered structure and large intrinsic direct band gap. We derive and discuss
its band structure in the presence of a perpendicular magnetic field. Further,
we evaluate the magneto-optical Hall and longitudinal optical conductivities,
as functions of temperature, magnetic field, and Fermi energy, and show that
they are strongly influenced by the magnetic field. The imaginary part of the
former and the real part of the latter exhibit regular {\it interband}
oscillations as functions of the frequency in the range
eV. Strong {\it intraband} responses in the latter
and week ones in the former occur at much lower frequencies. The
magneto-optical response can be tuned in the microwave-to-terahertz and visible
frequency ranges in contrast with a conventional two-dimensional electron gas
or graphene in which the response is limited to the terahertz regime. This
ability to isolate carriers in an anisotropic structure may make phosphorene a
promising candidate for new optical devices.Comment: 7 pages and 8 figure
Distributed Optimization in Energy Harvesting Sensor Networks with Dynamic In-network Data Processing
Energy Harvesting Wireless Sensor Networks (EH- WSNs) have been attracting increasing interest in recent years. Most current EH-WSN approaches focus on sensing and net- working algorithm design, and therefore only consider the energy consumed by sensors and wireless transceivers for sensing and data transmissions respectively. In this paper, we incorporate CPU-intensive edge operations that constitute in-network data processing (e.g. data aggregation/fusion/compression) with sens- ing and networking; to jointly optimize their performance, while ensuring sustainable network operation (i.e. no sensor node runs out of energy). Based on realistic energy and network models, we formulate a stochastic optimization problem, and propose a lightweight on-line algorithm, namely Recycling Wasted Energy (RWE), to solve it. Through rigorous theoretical analysis, we prove that RWE achieves asymptotical optimality, bounded data queue size, and sustainable network operation. We implement RWE on a popular IoT operating system, Contiki OS, and eval- uate its performance using both real-world experiments based on the FIT IoT-LAB testbed, and extensive trace-driven simulations using Cooja. The evaluation results verify our theoretical analysis, and demonstrate that RWE can recycle more than 90% wasted energy caused by battery overflow, and achieve around 300% network utility gain in practical EH-WSNs
Clay addition to sandy soil - effect of clay concentration and ped size on microbial biomass and nutrient dynamics after addition of low C/N ratio residue
Addition of clay-rich subsoil to sandy soil has been shown to increase crop production on sandy soils. The added clay is present as peds ranging in size from a millimetre to several centimetre. In thisexperiment clay soil (73% clay) was added to sandy soil (3% clay) at 10 and 20% clay w/w as 1, 3 and 5 mm peds. Shoots of young Kikuyu grass (C/N 20) were ground and added at 10g kg-1, and soils were incubated for 45 days at 80% of water holding capacity.The study confirmed that clay addition to sandy soil increased soil organic carbon retention but decreased cumulative respiration and available P compared to sandy soil alone. Ped size had little effect on respiration and nutrient availability. Over the course of 45 days peds broke down and organic C was bound to the < 53 μm fraction. The greatest proportion of peds and total organic carbon (54-67%) was in the initially added ped size. The TOC content of < 53 μm fraction of initially added peds was 0.38% and at the end of the experiment (after 45 days) the TOC had increased by 24, 19 and 10% in 1, 3 and 5 mm peds respectively.Shermeen Tahir and Petra Marschne
Comment on "Deuterium--tritium fusion reactors without external fusion breeding" by Eliezer et al
Inclusion of inverse Compton effects in the calculation of
deuterium-deuterium burn under the extreme conditions considered by Eliezer et
al. [Phys. Lett. A 243 (1998) 298] are shown to decrease the maximum burn
temperature from about 300 keV to only 100--150 keV. This decrease is such that
tritium breeding by the DD --> T + p reaction is not sufficient to replace the
small amount of tritium that is initially added to the deuterium plasma in
order to trigger ignition at less than 10 keV.Comment: 6 pages, 1 tabl
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Integrated Arable Farming Systems and their potential uptake in the UK
Integrated Arable Farming Systems are examined from the perspective of the farmer considering the use of such techniques, and data are presented which suggest that the uptake of the approach may expose the manager to a greater degree of risk. Observations are made about the possible uptake of such systems in the UK and the implications this may have for agricultural and environmental policy in general
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