Responsive multipath TCP in SDN-based datacenters

Conference Theme: Smart City & Smart WorldA basic need in datacenter networks is to provide high throughput for large flows such as the massive shuffle traffic flows in a MapReduce application. Multipath TCP (MPTCP) has been investigated as an effective approach toward this goal, by spreading one TCP flow onto multiple paths. However, the current MPTCP implementation has two major limitations: (1) a fixed number of subflows are used without reacting to the actual traffic condition; (2) the routing of subflows of a multipath TCP connection relies heavily on the ECMP-based random hashing. The former may lead to a waste of both the server and network resources, while the latter can cause throughput degradation when multiple subflows collide on the same path. This paper proposes a responsive MPTCP system to resolve the two limitations simultaneously. Our system employs a centralized controller for intelligent subflow route calculation and a monitor running on each server for actively adjusting the number of subflows. Working in synergy, the two modules enable MPTCP flows to respond to the traffic conditions and pursue high throughput on the fly, at very low computation and messaging overhead. NS3-based experiments show that our system achieves satisfactory throughput with less resource overhead, or better throughput at similar amounts of overhead, as compared to common alternatives.published_or_final_versio

Influence of uniaxial tensile stress on the mechanical and piezoelectric properties of short-period ferroelectric superlattice

Tetragonal ferroelectric/ferroelectric BaTiO3/PbTiO3 superlattice under uniaxial tensile stress along the c axis is investigated from first principles. We show that the calculated ideal tensile strength is 6.85 GPa and that the superlattice under the loading of uniaxial tensile stress becomes soft along the nonpolar axes. We also find that the appropriately applied uniaxial tensile stress can significantly enhance the piezoelectricity for the superlattice, with piezoelectric coefficient d33 increasing from the ground state value by a factor of about 8, reaching 678.42 pC/N. The underlying mechanism for the enhancement of piezoelectricity is discussed

Energy-momentum for Randall-Sundrum models

We investigate the conservation law of energy-momentum for Randall-Sundrum models by the general displacement transform. The energy-momentum current has a superpotential and are therefore identically conserved. It is shown that for Randall-Sundrum solution, the momentum vanishes and most of the bulk energy is localized near the Planck brane. The energy density is $\epsilon = \epsilon_0 e^{-3k \mid y \mid}$.Comment: 13 pages, no figures, v4: introduction and new conclusion added, v5: 11 pages, title changed and references added, accepted by Mod. Phys. Lett.

Chaotic Properties of Subshifts Generated by a Non-Periodic Recurrent Orbit

The chaotic properties of some subshift maps are investigated. These subshifts are the orbit closures of certain non-periodic recurrent points of a shift map. We first provide a review of basic concepts for dynamics of continuous maps in metric spaces. These concepts include nonwandering point, recurrent point, eventually periodic point, scrambled set, sensitive dependence on initial conditions, Robinson chaos, and topological entropy. Next we review the notion of shift maps and subshifts. Then we show that the one-sided subshifts generated by a non-periodic recurrent point are chaotic in the sense of Robinson. Moreover, we show that such a subshift has an infinite scrambled set if it has a periodic point. Finally, we give some examples and discuss the topological entropy of these subshifts, and present two open problems on the dynamics of subshifts

The extraction of nuclear sea quark distribution and energy loss effect in Drell-Yan experiment

The next-to-leading order and leading order analysis are performed on the differential cross section ratio from Drell-Yan process. It is found that the effect of next-to-leading order corrections can be negligible on the differential cross section ratios as a function of the quark momentum fraction in the beam proton and the target nuclei for the current Fermilab and future lower beam proton energy. The nuclear Drell-Yan reaction is an ideal tool to study the energy loss of the fast quark moving through cold nuclei. In the leading order analysis, the theoretical results with quark energy loss are in good agreement with the Fermilab E866 experimental data on the Drell-Yan differential cross section ratios as a function of the momentum fraction of the target parton. It is shown that the quark energy loss effect has significant impact on the Drell-Yan differential cross section ratios. The nuclear Drell-Yan experiment at current Fermilab and future lower energy proton beam can not provide us with more information on the nuclear sea quark distribution.Comment: 17 pages, 4 figure

The influence of collective neutrino oscillations on a supernova r-process

Recently, it has been demonstrated that neutrinos in a supernova oscillate collectively. This process occurs much deeper than the conventional matter-induced MSW effect and hence may have an impact on nucleosynthesis. In this paper we explore the effects of collective neutrino oscillations on the r-process, using representative late-time neutrino spectra and outflow models. We find that accurate modeling of the collective oscillations is essential for this analysis. As an illustration, the often-used "single-angle" approximation makes grossly inaccurate predictions for the yields in our setup. With the proper multiangle treatment, the effect of the oscillations is found to be less dramatic, but still significant. Since the oscillation patterns are sensitive to the details of the emitted fluxes and the sign of the neutrino mass hierarchy, so are the r-process yields. The magnitude of the effect also depends sensitively on the astrophysical conditions - in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. A more definitive understanding of the astrophysical conditions, and accurate modeling of the collective oscillations for those conditions, is necessary.Comment: 27 pages, 10 figure

Disentangling effects of abiotic factors and biotic interactions on cross-taxon congruence in species turnover patterns of plants, moths and beetles

High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments

Monitoring based on time-frequency tracking of estimated harmonic series and modulation sidebands

International audienceThe installation of a Condition Monitoring System (CMS) on a mechanical machine (e.g., on a wind turbine) aims to reduce the operating costs by applying a predictive maintenance strategy. The CMS is composed of sensors acquiring signals from which system health indicators are computed and monitored. Part of those indicators are predefined depending on the monitored system kinematic and are computed by averaging large or narrow spectral bands. The averaging and the need for predefined thresholds for default detection may induce lots of false alarms while reducing the ability to detect the default early. To get precise health indicators reflecting each local meaningful spectral content, the AStrion software proposes a new data-driven monitoring strategy without any a priori on the measured signals. First, an automatic spectral analysis is applied to detect, characterize and classify the different spectral structures of the successive measured signals. These spectral structures can be either single spectral peaks, either peaks grouped in harmonic series or in modulation sidebands [1]. Second, these spectral structures are characterized by several features, including for example the number of peaks, the characteristic frequencies and the energy. This gives a snapshot of the system health at the signal acquisition time. To perform an automatic diagnosis of the system, the spectral evolution should be tracked along the time snapshots. In this paper, we propose a time tracking method based on McAulay & Quatieri algorithm [2] which has been designed originally for speech signals acquired on a continuous temporal basis. We have adapted [2] in order to account not only for single spectral peak evolution but also for the evolution of more complex structures such as harmonic series or modulation sidebands, even in the case of signals acquired on a non-regular temporal basis, as it is often the case. Moreover, an added sleep state makes the proposed method robust against nondetected spectral structures at a given time. Finally, the temporal evolution of the spectral structure features can be monitored and used as precise health indicators. The following figure is a result of the proposed method applied on real signals coming from a test bench designed in KAStrion project for simulating a wind turbine operation and for which the inner race of the main bearing has been damaged. Above, the time frequency map displays a zoom of the spectral peaks detected (around 20.000 per snapshot, represented by circles) and shows in blue the tracking from 44 to 189 operating hours of a spectral peak at 3.45 Hz. This particular peak evolves at 129 hours to become an harmonic series with more and more peaks and energy. Its energy evolution (plotted below) shows an increase which mirrors out a failure. In a following step [3], this spectral structure has been associated with the ball pass frequency of the inner ring of the main bearing. A dismantling of this bearing has confirmed the failure. This result shows the potential of the proposed data-driven method to create automatically relevant health indicators