7,090 research outputs found
XMILE:An XML-based approach for programmable networks
In this paper we describe an XML-based platform for dynamic active node policy updates. XML supports the definitionof specific policy languages, their extension to satisfy new needs and the management of deployed policies on differentactive nodes. We show an example of the management of router packet forwarding policies where the XML policiesthat drive the packet routing are updated at run-time on the active nodes depending on the network status. The platformdecouples policy management, which is handled through XML interpretation, from packet forwarding that, forperformance reasons has to be implemented in more efficient languages
Asymptotic inference for nearly unstable AR(p) processes
In this paper nearly unstable AR( p) processes (in other words, models with characteristic roots near the unit circle) are studied. Our main aim is to describe the asymptotic behavior of the least-squares estimators of the coefficients. A convergence result is presented for the general complex-valued case, The limit distribution is given by the help of some continuous time AR processes. We apply the results for real-valued nearly unstable AR(p) models. In this case the limit distribution can be identified with the maximum likelihood estimator of the coefficients of the corresponding continuous time AR processes
Medisch ethische beschouwingen over orgaantransplantatie
De medische kennis is in de laatste decennia aanzienlijk vergroot. Deze kennistoeneming is gepaard gegaan met een vermeerdering van het medisch kunnen. Nieuwe theorieƫn gingen vergezeld van nieuwe mogelijkheden. Zo is ook de orgaantransplantatie tot grote bloei gekomen door beheersing van de heelkundige techniek, maar vooral ook van de immunologische afweermechanismen. Een geheel.nieuw veld is opengelegd. Het is geboden om naast het juichen over deze vorderingen ook kritisch stil te staan en zich af te vragen: wat doen wij? Is het in medisch-ethisch opzicht geoorloofd om zo te handelen? En overschrijden wij de grenzen van het toelaatbare niet? In een aantal hoofdstukjes zullen wij ons hierop bezinnen
Evolution of a beam dynamics model for the transport lines in a proton therapy facility
Despite the fact that the first-order beam dynamics models allow an
approximated evaluation of the beam properties, their contribution is essential
during the conceptual design of an accelerator or beamline. However, during the
commissioning some of their limitations appear in the comparison against
measurements. The extension of the linear model to higher order effects is,
therefore, demanded. In this paper, the effects of particle-matter interaction
have been included in the model of the transport lines in the proton therapy
facility at the Paul Scherrer Institut (PSI) in Switzerland. To improve the
performance of the facility, a more precise model was required and has been
developed with the multi-particle open source beam dynamics code called OPAL
(Object oriented Particle Accelerator Library). In OPAL, the Monte Carlo
simulations of Coulomb scattering and energy loss are performed seamless with
the particle tracking. Beside the linear optics, the influence of the passive
elements (e.g. degrader, collimators, scattering foils and air gaps) on the
beam emittance and energy spread can be analysed in the new model. This allows
for a significantly improved precision in the prediction of beam transmission
and beam properties. The accuracy of the OPAL model has been confirmed by
numerous measurements.Comment: 17 pages, 19 figure
Bifurcation at nonsemisimple 1: - 1 resonance
In this paper a description is given of the bifurcation of periodic solutions occurring when a Hamiltonian system of two degrees of freedom passes through nonsemisimple 1ā1 resonance at an equilibrium. A bifurcation like this is found in the planar circular restricted problem of three bodies at the Lagrange equilibriumL 4 when the mass parameter passes through the critical value of Routh. Gegenstand dieses Artikels ist die Verzweigung periodischer Lƶsungen in Hamilton''schen Systemen mit zwei Freiheitsgraden beim Durchgang durch eine nicht-einfache 1ā1-Resonanz an einem Gleichgewicht. Ein Beispiel ist das ebene restringierte Dreikƶrperproblem am Lagrange-PunktL 4, wenn die Masse durch den kritischen Wert von Routh hindurchgeht
Spontaneous Ratchet Effect in a Granular Gas
The spontaneous clustering of a vibrofluidized granular gas is employed to
generate directed transport in two different compartmentalized systems: a
"granular fountain" in which the transport takes the form of convection rolls,
and a "granular ratchet" with a spontaneous particle current perpendicular to
the direction of energy input. In both instances, transport is not due to any
system-intrinsic anisotropy, but arises as a spontaneous collective symmetry
breaking effect of many interacting granular particles. The experimental and
numerical results are quantitatively accounted for within a flux model.Comment: 4 pages, 5 figures; Fig. 4 has been reduced in size and qualit
An Alternate Method for Fourier Transform Infrared (FTIR) Spectroscopic Determination of Soil Nitrate Using Derivative Analysis and Sample Treatments
This study aimed at examining effective sample treatments and spectral processing for an alternate method of soil nitrate determination using the attenuated total reflectance (ATR) of Fourier transform infrared (FTIR) spectroscopy. Prior to FTIR measurements, soil samples were prepared as paste to enhance adhesion between the ATR crystal and sample. The similar nitrate peak heights of soil pastes and their supernatants indicated that the nitrate in the liquid portion of the soil paste mainly responded to the FTIR signal. Using a 0.01-M CaSO4 solution for the soil paste, which has no interference bands in the characteristic spectra of the analyte, increased the concentration of the nitrates to be measured. Second-order derivatives were used in the prediction model to minimize the interference effects and enhance the performance. The second-order derivative spectra contained a unique nitrate peak in a range of 1,400-1,200 cm(-1) without interference of carbonate. A partial least square regression model using second-order derivative spectra performed well (R (2) = 0.995, root mean square error (RMSE) = 23.5, ratio of prediction to deviation (RPD) = 13.8) on laboratory samples. Prediction results were also good for a test set of agricultural field soils with a CaCO3 concentration of 6% to 8% (R (2) = 0.97, RMSE = 18.6, RPD = 3.5). Application of the prediction model based on soil paste samples to nitrate stock solution resulted in an increased RMSE (62.3); however, validation measures were still satisfactory (R (2) = 0.99, RPD = 3.0
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