6,468 research outputs found
Direct Observation of Propagating Gigahertz Coherent Guided Acoustic Phonons in Free Standing Single Copper Nanowires
We report on gigahertz acoustic phonon waveguiding in free-standing single
copper nanowires studied by femtosecond transient reflectivity measurements.
The results are discussed on the basis of the semianalytical resolution of the
Pochhammer and Chree equation. The spreading of the generated Gaussian wave
packet of two different modes is derived analytically and compared with the
observed oscillations of the sample reflectivity. These experiments provide a
unique way to independently obtain geometrical and material characterization.
This direct observation of coherent guided acoustic phonons in a single
nano-object is also the first step toward nanolateral size acoustic transducer
and comprehensive studies of the thermal properties of nanowires
Optical Network Virtualisation using Multi-technology Monitoring and SDN-enabled Optical Transceiver
We introduce the real-time multi-technology transport layer monitoring to
facilitate the coordinated virtualisation of optical and Ethernet networks
supported by optical virtualise-able transceivers (V-BVT). A monitoring and
network resource configuration scheme is proposed to include the hardware
monitoring in both Ethernet and Optical layers. The scheme depicts the data and
control interactions among multiple network layers under the software defined
network (SDN) background, as well as the application that analyses the
monitored data obtained from the database. We also present a re-configuration
algorithm to adaptively modify the composition of virtual optical networks
based on two criteria. The proposed monitoring scheme is experimentally
demonstrated with OpenFlow (OF) extensions for a holistic (re-)configuration
across both layers in Ethernet switches and V-BVTs
NFV Based Gateways for Virtualized Wireless Sensors Networks: A Case Study
Virtualization enables the sharing of a same wireless sensor network (WSN) by
multiple applications. However, in heterogeneous environments, virtualized
wireless sensor networks (VWSN) raises new challenges such as the need for
on-the-fly, dynamic, elastic and scalable provisioning of gateways. Network
Functions Virtualization (NFV) is an emerging paradigm that can certainly aid
in tackling these new challenges. It leverages standard virtualization
technology to consolidate special-purpose network elements on top of commodity
hardware. This article presents a case study on NFV based gateways for VWSNs.
In the study, a VWSN gateway provider, operates and manages an NFV based
infrastructure. We use two different brands of wireless sensors. The NFV
infrastructure makes possible the dynamic, elastic and scalable deployment of
gateway modules in this heterogeneous VWSN environment. The prototype built
with Openstack as platform is described
The effect of light assisted collisions on matter wave coherence in superradiant Bose-Einstein condensates
We investigate experimentally the effects of light assisted collisions on the
coherence between momentum states in Bose-Einstein condensates. The onset of
superradiant Rayleigh scattering serves as a sensitive monitor for matter wave
coherence. A subtle interplay of binary and collective effects leads to a
profound asymmetry between the two sides of the atomic resonance and provides
far bigger coherence loss rates for a condensate bathed in blue detuned light
than previously estimated. We present a simplified quantitative model
containing the essential physics to explain our experimental data and point at
a new experimental route to study strongly coupled light matter systems.Comment: 10 pages, 4 figure
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