7,052 research outputs found

    Mobile integrated conditional access system

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    This paper presents design of a novel security architecture integrating mobile and broadcasting technologies in the Pay-TV system. The security architecture proposed herein is a state-of-the-art solution to tackle well-known problems challenging current Pay-TV systems including but not limited to interoperability amongst service providers, relatively high cost of the service deployment, the security compromise, limited interactivity and bespoken services offered to subscribers. It also proposes the Follow-me service that enables subscribers to access their entitlements via an arbitrary set-top box

    Secondary instability and tertiary states in rotating plane Couette flow

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    AbstractRecent experimental studies have shown rich transition behaviour in rotating plane Couette flow (RPCF). In this paper we study the transition in supercritical RPCF theoretically by determination of equilibrium and periodic orbit tertiary states via Floquet analysis on secondary Taylor vortex solutions. Two new tertiary states are discovered which we name oscillatory wavy vortex flow (oWVF) and skewed vortex flow (SVF). We present the bifurcation routes and stability properties of these new tertiary states and, in addition, we describe a bifurcation procedure whereby a set of defected wavy twist vortices is approached. Further to this, transition scenarios at flow parameters relevant to experimental works are investigated by computation of the set of stable attractors which exist on a large domain. The physically observed flow states are shown to share features with states in our set of attractors.C.A.D. gratefully acknowledges EPSRC PhD studentship funding.This is the accepted manuscript. The final version is available from CUP at http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9418750&fileId=S0022112014006090

    Global MHD simulation of flux transfer events at the high-latitude magnetopause observed by the cluster spacecraft and the SuperDARN radar system

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    A global magnetohydrodynamic numerical simulation is used to study the large-scale structure and formation location of flux transfer events (FTEs) in synergy with in situ spacecraft and ground-based observations. During the main period of interest on the 14 February 2001 from 0930 to 1100 UT the Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the postnoon sector on an outbound trajectory. Throughout this period the magnetic field, electron, and ion sensors on board Cluster observed characteristic signatures of FTEs. A few minutes delayed to these observations the Super Dual Auroral Radar Network (SuperDARN) system indicated flow disturbances in the conjugate ionospheres. These “two-point” observations on the ground and in space were closely correlated and were caused by ongoing unsteady reconnection in the vicinity of the spacecraft. The three-dimensional structures and dynamics of the observed FTEs and the associated reconnection sites are studied by using the Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) MHD code in combination with a simple open flux tube motion model (Cooling). Using these two models the spatial and temporal evolution of the FTEs is estimated. The models fill the gaps left by measurements and allow a “point-to-point” mapping between the instruments in order to investigate the global structure of the phenomenon. The modeled results presented are in good correlation with previous theoretical and observational studies addressing individual features of FTEs

    Constraints on the Cluster Environments and Hot Spot Magnetic Field Strengths of the Radio Sources 3C254 and 3C280

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    We present new Chandra Observatory observations with archival HST and radio observations of 3C254, a radio quasara at z=0.734, and 3C280, a radio galaxy at z=0.996. We report the detection of X-ray and possible HST optical counterparts to the radio hot spots in 3C280 and of an X-ray counterpart to the radio hot spot in 3C254. We present constraints on the presence of X-ray clusters and on the magnetic field strengths in and around the radio hot spots. The spatial resolution of Chandra allows us to show that these sources are not in hot, massive clusters. The extended emission seen in ROSAT observations is resolved into point sources. The IGM around these sources is demonstrably not dense and hot. We conclude that radio sources are not reliable signposts of massive clusters at moderate redshifts. X-ray synchrotron emission could explain the radio, optical, and X-ray hot spot fluxes in 3C280, but it would require continuous acceleration of electrons to high Lorentz factors, since the synchrotron lifetime required to produce the X-ray emission is of order a human lifetime. SSC with or without IC scattering of the CMB can also explain the X-ray emission, but not the optical. We review all of the physical mechanisms and summarize our current constraints on the magnetic field strengths in andaround the hot spots of 3C254 and 3C280.Comment: accepted, ApJ, Feb 20, 2003 publication date estimate

    Programming Protocol-Independent Packet Processors

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    P4 is a high-level language for programming protocol-independent packet processors. P4 works in conjunction with SDN control protocols like OpenFlow. In its current form, OpenFlow explicitly specifies protocol headers on which it operates. This set has grown from 12 to 41 fields in a few years, increasing the complexity of the specification while still not providing the flexibility to add new headers. In this paper we propose P4 as a strawman proposal for how OpenFlow should evolve in the future. We have three goals: (1) Reconfigurability in the field: Programmers should be able to change the way switches process packets once they are deployed. (2) Protocol independence: Switches should not be tied to any specific network protocols. (3) Target independence: Programmers should be able to describe packet-processing functionality independently of the specifics of the underlying hardware. As an example, we describe how to use P4 to configure a switch to add a new hierarchical label

    Development of PARcific Approach: Participatory Action Research Methodology for Collectivist Health Research.

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    This article explores the evolution of a novel approach designed to advance qualitative methods in cross-cultural health research. This methodology was developed by synthesising several research methods and involved in-depth stakeholder consultation with participants of a Pacific-based nursing and midwifery health leadership program. Many of these participants played a crucial role in creating, exploring and evaluating several research methods and implementing and evaluating this co-designed research methodology. Starting with a Participatory Action Research framework, the research methodology evolved as it was informed by the local Pacific methodologies (in particular Talanoa and Kakala frameworks), where researchers, co-researchers and participants alike, working from within their own collectivist/individualist paradigms, negotiated cultural differences. Finally, a methodological framework of 'best practice' for future health research methods was developed for use with capacity building research. The new methodology could provide a foundation for future co-designed cross-cultural research in collectivist cultures

    The effect of root exudates on rhizosphere water dynamics

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    L.J.C. and N.K. are funded by BBSRC SARISA BB/L025620/1, L.J.C. is also funded by EPSRC EP/P020887/1. K.R.D. is funded by ERC 646809DIMR. P.D.H. and T.S.G. are funded by BBSRC BB/J00868/1. The James Hutton Institute receives funding from the Scottish Government. T.R. is funded by BBSRC SARISA BB/L025620/1, EPSRC EP/M020355/1, ERC 646809DIMR, BBSRC SARIC BB/P004180/1 and NERC NE/L00237/1. Data supporting this study are available on request from the University of Southampton repository at https://doi.org/10.5258/SOTON/D0609 [35].Peer reviewedPublisher PD

    Biodegradation of the Alkaline Cellulose Degradation Products Generated during Radioactive Waste Disposal.

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    The anoxic, alkaline hydrolysis of cellulosic materials generates a range of cellulose degradation products (CDP) including α and β forms of isosaccharinic acid (ISA) and is expected to occur in radioactive waste disposal sites receiving intermediate level radioactive wastes. The generation of ISA's is of particular relevance to the disposal of these wastes since they are able to form complexes with radioelements such as Pu enhancing their migration. This study demonstrates that microbial communities present in near-surface anoxic sediments are able to degrade CDP including both forms of ISA via iron reduction, sulphate reduction and methanogenesis, without any prior exposure to these substrates. No significant difference (n = 6, p = 0.118) in α and β ISA degradation rates were seen under either iron reducing, sulphate reducing or methanogenic conditions, giving an overall mean degradation rate of 4.7×10−2 hr−1 (SE±2.9×10−3). These results suggest that a radioactive waste disposal site is likely to be colonised by organisms able to degrade CDP and associated ISA's during the construction and operational phase of the facility
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