5,426 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
Special studies of AROD system concepts and designs
Signal to noise ratios in airborne range and orbit determination system, and carrier and range loop performance analyse
Spatially encoded light for Large-alphabet Quantum Key Distribution
Most Quantum Key Distribution protocols use a two-dimensional basis such as
HV polarization as first proposed by Bennett and Brassard in 1984. These
protocols are consequently limited to a key generation density of 1 bit per
photon. We increase this key density by encoding information in the transverse
spatial displacement of the used photons. Employing this higher-dimensional
Hilbert space together with modern single-photon-detecting cameras, we
demonstrate a proof-of-principle large-alphabet Quantum Key Distribution
experiment with 1024 symbols and a shared information between sender and
receiver of 7 bit per photon.Comment: 9 pages, 6 figures, Added references, Updated Fig. 1 in the main
text, Updated Fig.1 in supplementary material, Added section Trojan-horse
attacks in supplementary material, title changed, Added paragraphs about
final key rate and overfilling the detector to result sectio
Initial surface deformations during impact on a liquid pool
A tiny air bubble can be entrapped at the bottom of a solid sphere that
impacts onto a liquid pool. The bubble forms due to the deformation of the
liquid surface by a local pressure buildup inside the surrounding gas, as also
observed during the impact of a liquid drop on a solid wall. Here we perform a
perturbation analysis to quantitatively predict the initial deformations of the
free surface of the liquid pool as it is approached by a solid sphere. We study
the natural limits where the gas can be treated as a viscous fluid (Stokes
flow) or as an inviscid fluid (potential flow). For both cases we derive the
spatio-temporal evolution of the pool surface, and recover some of the recently
proposed scaling laws for bubble entrapment. When inserting typical
experimental values for the impact parameters, we find that the bubble volume
is mainly determined by the effect of gas viscosity
Bubble Pinch-Off in a Rotating Flow
We create air bubbles at the tip of a “bathtub vortex” which reaches to a finite depth. The bathtub vortex is formed by letting water drain through a small hole at the bottom of a rotating cylindrical container. The tip of the needlelike surface dip is unstable at high rotation rates and releases bubbles which are carried down by the flow. Using high-speed imaging we find that the minimal neck radius of the unstable tip decreases in time as a power law with an exponent close to 1/3. This exponent was found by Gordillo et al. [Phys. Rev. Lett. 95, 194501 (2005)] to govern gas flow driven pinch-off, and indeed we find that the volume oscillations of the tip creates a considerable air flow through the neck. We argue that the Bernoulli pressure reduction caused by this air flow can become sufficient to overcome the centrifugal forces and cause the final pinch-off
Universal mechanism for air entrainment during liquid impact
When a mm-sized liquid drop approaches a deep liquid pool, both the interface
of the drop and the pool deform before the drop touches the pool. The build up
of air pressure prior to coalescence is responsible for this deformation. Due
to this deformation, air can be entrained at the bottom of the drop during the
impact. We quantify the amount of entrained air numerically, using the Boundary
Integral Method (BIM) for potential flow for the drop and the pool, coupled to
viscous lubrication theory for the air film that has to be squeezed out during
impact. We compare our results to various experimental data and find excellent
agreement for the amount of air that is entrapped during impact onto a pool.
Next, the impact of a rigid sphere onto a pool is numerically investigated and
the air that is entrapped in this case also matches with available experimental
data. In both cases of drop and sphere impact onto a pool the numerical air
bubble volume V_b is found to be in agreement with the theoretical scaling
V_b/V_{drop/sphere} ~ St^{-4/3}, where St is the Stokes number. This is the
same scaling that has been found for drop impact onto a solid surface in
previous research. This implies a universal mechanism for air entrainment for
these different impact scenarios, which has been suggested in recent
experimental work, but is now further elucidated with numerical results
Incorporating Vibration Test Results for the Advanced Stirling Convertor into the System Dynamic Model
The U.S. Department of Energy (DOE), Lockheed Martin Corporation (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Convertors (ASC) at NASA GRC undergo a vibration test sequence intended to simulate the vibration history that an ASC would experience when used in an ASRG for a space mission. During these tests, a data system collects several performance-related parameters from the convertor under test for health monitoring and analysis. Recently, an additional sensor recorded the slip table position during vibration testing to qualification level. The System Dynamic Model (SDM) integrates Stirling cycle thermodynamics, heat flow, mechanical mass, spring, damper systems, and electrical characteristics of the linear alternator and controller. This Paper presents a comparison of the performance of the ASC when exposed to vibration to that predicted by the SDM when exposed to the same vibration
Balancing roles: bridging the divide between HRM, employee participation and learning in the Dutch knowledge economy.
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