4,720 research outputs found
Network service chaining using segment routing in multi-layer networks
Network service chaining, originally conceived in the network function virtualization (NFV) framework for software defined networks (SDN), is becoming an attractive solution for enabling service differentiation enforcement to microflows generated by data centers, 5G fronthaul and Internet of Things (IoT) cloud/fog nodes, and traversing a metro-core network. However, the current IP/MPLS-over optical multi-layer network is practically unable to provide such service chain enforcement. First, MPLS granularity prevents microflows from being conveyed in dedicated paths. Second, service configuration for a huge number of selected flows with different requirements is prone to scalability concerns, even considering the deployment of a SDN network. In this paper, effective service chaining enforcement along traffic engineered (TE) paths is proposed using segment routing and extended traffic steering mechanisms for mapping micro-flows. The proposed control architecture is based on an extended SDN controller encompassing a stateful path computation element (PCE) handling microflow computation and placement supporting service chains, whereas segment routing allows automatic service enforcement without the need for continuous configuration of the service node. The proposed solution is experimentally evaluated in segment routing over an elastic optical network (EON) network testbed with a deep packet inspection service supporting dynamic and automatic flow enforcement using Border Gateway Protocol with Flow Specification (BGP Flowspec) and OpenFlow protocols as alternative traffic steering enablers. Scalability of flow computation, placement, and steering are also evaluated showing the effectiveness of the proposed solution
Phase-Tunable Temperature Amplifier
Coherent caloritronics, the thermal counterpart of coherent electronics, has
drawn growing attention since the discovery of heat interference in 2012.
Thermal interferometers, diodes, transistors and nano-valves have been
theoretically proposed and experimentally demonstrated by exploiting the
quantum phase difference between two superconductors coupled through a
Josephson junction. So far, the quantum-phase modulator has been realized in
the form of a superconducting quantum interference device (SQUID) or a
superconducting quantum interference proximity transistor (SQUIPT). Thence, an
external magnetic field is necessary in order to manipulate the heat transport.
Here, we theoretically propose the first on-chip fully thermal caloritronic
device: the phase-tunable temperature amplifier. Taking advantage of a recent
thermoelectric effect discovered in spin-split superconductors coupled to a
spin-polarized system, by a temperature gradient we generate the magnetic flux
controlling the transport through a temperature biased SQUIPT. By employing
commonly used materials and a geometry compatible with state-of-the-art
nano-fabrication techniques, we simulate the behavior of the temperature
amplifier and define a number of figures of merit in full analogy with voltage
amplifiers. Notably, our architecture ensures infinite input thermal impedance,
maximum gain of about 11 and efficiency reaching the 95%. This device concept
could represent a breakthrough in coherent caloritronic devices, and paves the
way for applications in radiation sensing, thermal logics and quantum
information.Comment: 7 pages, 3 figure
Phase-Tunable Thermal Logic: Computation with Heat
Boolean algebra, the branch of mathematics where variables can assume only
true or false value, is the theoretical basis of classical computation. The
analogy between Boolean operations and electronic switching circuits,
highlighted by Shannon in 1938, paved the way to modern computation based on
electronic devices. The grow of computational power of such devices, after an
exciting exponential -Moore trend, is nowadays blocked by heat dissipation due
to computational tasks, very demanding after the chips miniaturization. Heat is
often a detrimental form of energy which increases the systems entropy
decreasing the efficiency of logic operations. Here, we propose a physical
system able to perform thermal logic operations by reversing the old
heat-disorder epitome into a novel heat-order paradigm. We lay the foundations
of heat computation by encoding logic state variables in temperature and
introducing the thermal counterparts of electronic logic gates. Exploiting
quantum effects in thermally biased Josephson junctions (JJs), we propound a
possible realization of a functionally complete dissipationless logic. Our
architecture ensures high operation stability and robustness with switching
frequencies reaching the GHz
Phase-tunable Josephson thermal router
Since the the first studies of thermodynamics, heat transport has been a
crucial element for the understanding of any thermal system. Quantum mechanics
has introduced new appealing ingredients for the manipulation of heat currents,
such as the long-range coherence of the superconducting condensate. The latter
has been exploited by phase-coherent caloritronics, a young field of
nanoscience, to realize Josephson heat interferometers, which can control
electronic thermal currents as a function of the external magnetic flux. So
far, only one output temperature has been modulated, while multi-terminal
devices that allow to distribute the heat flux among different reservoirs are
still missing. Here, we report the experimental realization of a phase-tunable
thermal router able to control the heat transferred between two terminals
residing at different temperatures. Thanks to the Josephson effect, our
structure allows to regulate the thermal gradient between the output electrodes
until reaching its inversion. Together with interferometers, heat diodes and
thermal memories, the thermal router represents a fundamental step towards the
thermal conversion of non-linear electronic devices, and the realization of
caloritronic logic components.Comment: 9 pages, 5 figure
Redox Mediation at 11-Mercaptoundecanoic Acid Self-Assembled Monolayers on Gold
Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and digital simulation techniques were used to investigate quantitatively the mechanism of electron transfer (ET) through densely packed and well-ordered self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid on gold, either pristine or modified by physically adsorbed glucose oxidase (GOx). In the presence of ferrocenylmethanol (FcMeOH) as a redox mediator, ET kinetics involving either solution-phase hydrophilic redox probes such as [Fe(CN)6]3-/4- or surface-immobilized GOx is greatly accelerated: [Fe(CN)6]3-/4- undergoes diffusion-controlled ET, while the enzymatic electrochemical conversion of glucose to gluconolactone is efficiently sustained by FcMeOH. Analysis of the results, also including the digital simulation of CV and EIS data, showed the prevalence of an ET mechanism according to the so-called membrane model that comprises the permeation of the redox mediator within the SAM and the intermolecular ET to the redox probe located outside the monolayer. The analysis of the catalytic current generated at the GOx/SAM electrode in the presence of glucose and FcMeOH allowed the high surface protein coverage suggested by X-ray photoelectron spectroscopy (XPS) measurements to be confirmed.
- …