PBUF: Sharing buffer to mitigate flooding attacks

Software defined networking (SDN) is a promising network architecture, which decouples the control plane and data plane of a network. However, SDN opens some security challenges, such as man-in-the-middle attacks, spoofing attacks, flooding attacks and so on. In this paper, we focus on flooding attacks which consume the switch buffer and controller resource resulting in SDN framework resource overloaded. To prevent SDN framework from flooding attack, we present a defense approach called PBUF (Packet forwarding based on BUFfer sharing), which pools the idle switches to mitigate threat issues. This approach consists of buffer management and packet forwarding modules. The buffer management module gleans the statistics of incoming packets and then analyzes these statistics to estimate the buffer size by network calculus. Considering that a lot of table-miss packets will be generated and stored in buffer when the flooding attack is happening, the packet forwarding module is designed to forward these table-miss packets to idle switches to prevent the switch or controller to be overloaded. These table-miss packets will be buffered in idle switches and then sent to controller in a limited rate by generating packet-in messages. The simulation results show that PBUF is effective and only introduces a little overhead in SDN framework.Indexing terms: Flooding Attack; Security; Performance; SDN</p

Magnetosome Gene Duplication as an Important Driver in the Evolution of Magnetotaxis in the Alphaproteobacteria

The evolution of microbial magnetoreception (or magnetotaxis) is of great interest in the fields of microbiology, evolutionary biology, biophysics, geomicrobiology, and geochemistry. Current genomic data from magnetotactic bacteria (MTB), the only prokaryotes known to be capable of sensing the Earth’s geomagnetic field, suggests an ancient origin of magnetotaxis in the domain Bacteria. Vertical inheritance, followed by multiple independent magnetosome gene cluster loss, is considered to be one of the major forces that drove the evolution of magnetotaxis at or above the class or phylum level, although the evolutionary trajectories at lower taxonomic ranks (e.g., within the class level) remain largely unstudied. Here we report the isolation, cultivation, and sequencing of a novel magnetotactic spirillum belonging to the genus Terasakiella (Terasakiella sp. strain SH-1) within the class Alphaproteobacteria. The complete genome sequence of Terasakiella sp. strain SH-1 revealed an unexpected duplication event of magnetosome genes within the mamAB operon, a group of genes essential for magnetosome biomineralization and magnetotaxis. Intriguingly, further comparative genomic analysis suggests that the duplication of mamAB genes is a common feature in the genomes of alphaproteobacterial MTB. Taken together, with the additional finding that gene duplication appears to have also occurred in some magnetotactic members of the Deltaproteobacteria, our results indicate that gene duplication plays an important role in the evolution of magnetotaxis in the Alphaproteobacteria and perhaps the domain Bacteria

Large-sample estimation and inference in multivariate single-index models

By optimizing index functions against different outcomes, we propose a multivariate single-index model (SIM) for development of medical indices that simultaneously work with multiple outcomes. Fitting of a multivariate SIM is not fundamentally different from fitting a univariate SIM, as the former can be written as a sum of multiple univariate SIMs with appropriate indicator functions. What have not been carefully studied are the theoretical properties of the parameter estimators. Because of the lack of asymptotic results, no formal inference procedure has been made available for multivariate SIMs. In this paper, we examine the asymptotic properties of the multivariate SIM parameter estimators. We show that, under mild regularity conditions, estimators for the multivariate SIM parameters are indee

Viewpoint: Spinning Black Holes May Grow Hair

<p>Lane 1–11, Water control, Little Club, Monogenic <i>Sr28</i>, Jing 04–6, Jing 0202, Jingmai 14, Jingmai 11, Jingmai 10, Jingmai 8, Yunza 7, Yunza 6, Yunxuan 2, Yunmai 54, Yunmai 53, Yunmai 52, Yunmai 47, and Yunmai 39. ‘M’ indicates 1000 bp DNA ladder and white arrow indicates the position of the specific band.</p

Stimuli-responsive 2D polyelectrolyte photonic crystals for optically encoded pH sensing.

A versatile photonic crystal sensing motif based on a twodimensional (2D) inverse opal monolayer of stimuli-responsive polyelectrolyte gel with tunable optical properties is reported. The photonic membrane shows prompt response to pH and can be readily read out from either its optical spectra or interference colours

Analysis and synthesis of randomly switched systems with known sojourn probabilities

In this paper, a new approach is proposed and investigated for the stability analysis and stabilizing controller design of randomly switched linear discrete systems. The approach is based on sojourn probabilities and it is assumed that these probabilities are known a prior. A new Lyapunov functional is constructed and two main theorems are proved in this paper. Theorem 1 gives a sufficient condition for a switched system with known sojourn probabilities to be mean square stable. Theorem 2 gives a sufficient condition for the design of a stabilizing controller. The applications of these theorems and the corresponding corollary and lemma are demonstrated by three numerical examples. Finally, some future research is proposed

Effects of Multiple Sintering Parameters on the Thermal Performance of Bi-porous Nickel Wicks in Loop Heat Pipes

This document is the Accepted Manuscript version of the following article: Y. Qu, K. Zhou, K. F. Zhang and Y. Tian, ‘Effects of multiple sintering parameters on the thermal performance of bi-porous nickel wicks in Loop Heat Pipes’, International Journal of Heat and Mass Transfer, Vol. 99: 638-646, August 2016, doi: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.04.005. This manuscript version is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.The thermal performance of a water-saturated Loop Heat Pipe (LHP) with bi-porous nickel wicks has been examined theoretically and experimentally, based on five key influencing factors including the content of foaming agent, compacting pressure, incubation time at suitable temperature, sintering temperature and particle size of foaming agent. Comparison was made among a total number of 20 tests with each influencing factor allocated by four different values, where porosity, permeability, capillary suction head and effective thermal conductivity (ETC) were examined. ETC is an important parameter of thermal performance, and its experimental values were compared with eleven theoretical models. The results showed that ETC was mostly affected by the content of foaming agent: 1.9-2.2 times compared to the effect of compacting pressure and incubation time, with the effect of sintering temperature and particle size of foaming agent ata underestimated the true ETC values. In the porosity range of 0.5-0.7, an average of the Chernysheva & Maydanik model and the Chaudhary & Bhandari model was found to be the best fit to the experimental data, providing an accurate method to predict ETC values of water-saturated LHP with bi-porous nickel wicks.Peer reviewedFinal Accepted Versio