4,812 research outputs found
GHG emissions of green coffee production : toward a standard methodology for carbon footprinting : report
In this project, the scope for product specific rules for carbon footprinting of (green) coffee is investigated and a proposal is drafted for further work toward actual definition and implementation of such a standard
Are negative index materials achievable with surface plasmon waveguides? A case study of three plasmonic geometries
We present a theoretical analysis of planar plasmonic waveguides
that support propagation of positive and negative index modes. Particular
attention is given to the modes sustained by metal-insulator-metal (MIM),
insulator-metal-insulator (IMI), and insulator-insulator-metal (IIM)
geometries at visible and near-infrared frequencies. We find that all three
plasmonic structures are characterized by negative indices over a finite
range of visible frequencies, with figures of merit approaching 20.
Moreover, using finite-difference time-domain simulations, we demonstrate
that visible-wavelength light propagating from free space into these
waveguides can exhibit negative refraction. Refractive index and figure-ofmerit
calculations are presented for Ag/GaP and Ag/Si3N_4 - based structures
with waveguide core dimensions ranging from 5 to 50 nm and excitation
wavelengths ranging from 350 nm to 850 nm. Our results provide the design
criteria for realization of broadband, visible-frequency negative index
materials and transformation-based optical elements for two-dimensional
guided waves. These geometries can serve as basic elements of threedimensional
negative-index metamaterials
De koolzaden aan de wilgen hangen:rijden op biobrandstoffen uit energieteelt : een onderzoek met behulp van strategic niche management en de toekomstscenariomethodiek naar het telen van energiegewassen in Wielkopolska in Polen om hier biotransportbrandstoffen van te maken
Design of an integrated shallow water wave experiment
The experimental design and instrumentation for an integrated shallow-water surface gravity wave experiment is discussed. The experiment required the measurement of the water surface elevation, meteorological parameters, and directional spectra at a number of locations on a shallow lake. In addition, to acquire data under a wide range of conditions, an experimental period of three years was required. A system of telephone and radio modem links were installed to enable real-time monitoring of instrument performance at eight separate measurement locations on the lake. This system also enabled logging sessions to be optimized to ensure the maximum possible data return from this extended experimentIEEE Oceanic Engineering Societ
Innovative financing mechanisms for sustainable ecosystem management
The increasing human influence on ecosystems and the ensuing unsustainable exploitation and degradation has led in many places to depletion and loss of function of these ecosystems. These problems cannot be solved by (innovative) financing mechanisms, as the causes do not lie in a lack of financing mechanisms. Although decifit in funding in general is an important issue - the amount of finance available for ecosystems and biodiversity falls short of the funding neede
Perturbing open cavities: Anomalous resonance frequency shifts in a hybrid cavity-nanoantenna system
The influence of a small perturbation on a cavity mode plays an important
role in fields like optical sensing, cavity quantum electrodynamics and cavity
optomechanics. Typically, the resulting cavity frequency shift directly relates
to the polarizability of the perturbation. Here we demonstrate that particles
perturbing a radiating cavity can induce strong frequency shifts that are
opposite to, and even exceed, the effects based on the particles'
polarizability. A full electrodynamic theory reveals that these anomalous
results rely on a non-trivial phase relation between cavity and nanoparticle
radiation, allowing back-action via the radiation continuum. In addition, an
intuitive model based on coupled mode theory is presented that relates the
phenomenon to retardation. Because of the ubiquity of dissipation, we expect
these findings to benefit the understanding and engineering of a wide class of
systems.Comment: 15 pages, 12 figure
Electric and magnetic dipole coupling in near-infrared split ring metamaterial arrays
We present experimental observations of strong electric and magnetic
interactions between split ring resonators (SRRs) in metamaterials. We
fabricated near-infrared (1.4 m) planar metamaterials with different
inter-SRR spacings along different directions. Our transmission measurements
show blueshifts and redshifts of the magnetic resonance, depending on SRR
orientation relative to the lattice. The shifts agree well with a simple model
with simultaneous magnetic and electric near-field dipole coupling. We also
find large broadening of the resonance, accompanied by a decrease in effective
cross section per SRR with increasing density. These effects result from
superradiant scattering. Our data shed new light on Lorentz-Lorenz approaches
to metamaterials.Comment: 4 pages, 4 color figure
The new control system of the SPS injection kicker
The SPS accelerator will be used as injector for the LHC and has to be adapted to the LHC requirements. The tight specification on beam blow-up and bunch spacing in the SPS has required an upgrade program of the SPS injection kicker in order to obtain a reduction of the magnetic field ripple to less than ± 0.5% and of the magnet current rise time to less than 145 ns. In this context, the slow control part has been entirely rebuilt on the basis of off-the-shelf industrial components. A hierarchical architecture based on a SIEMENS S7-400 master programmable logic controller interconnected through PROFIBUS-DP to S7-300 deported and decentralised I/Os has been implemented. Integration of in-house specific G-64 hardware systems inside this industrial environment has been done through a PROFIBUS-DP to G-64 intelligent interface based on an OEM fieldbus mezzanine board on one side and an FPGA implementing the required functionality on the other. Simultaneously, the fast timing system has been completely reshuffled in order to provide the required SPS multi-cycling functionality and a synchronisation of the 16 magnets to 5ns. This modular architecture has been successfully integrated inside the new SPS accelerator control infrastructure and will be duplicated in the future for the control of the different SPS extraction channels
- …