4,586 research outputs found

    Checking-in on Network Functions

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    When programming network functions, changes within a packet tend to have consequences---side effects which must be accounted for by network programmers or administrators via arbitrary logic and an innate understanding of dependencies. Examples of this include updating checksums when a packet's contents has been modified or adjusting a payload length field of a IPv6 header if another header is added or updated within a packet. While static-typing captures interface specifications and how packet contents should behave, it does not enforce precise invariants around runtime dependencies like the examples above. Instead, during the design phase of network functions, programmers should be given an easier way to specify checks up front, all without having to account for and keep track of these consequences at each and every step during the development cycle. In keeping with this view, we present a unique approach for adding and generating both static checks and dynamic contracts for specifying and checking packet processing operations. We develop our technique within an existing framework called NetBricks and demonstrate how our approach simplifies and checks common dependent packet and header processing logic that other systems take for granted, all without adding much overhead during development.Comment: ANRW 2019 ~ https://irtf.org/anrw/2019/program.htm

    Estimation of unsteady lift on a pitching airfoil from wake velocity surveys

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    The results of a joint experimental and computational study on the flowfield over a periodically pitched NACA0012 airfoil, and the resultant lift variation, are reported in this paper. The lift variation over a cycle of oscillation, and hence the lift hysteresis loop, is estimated from the velocity distribution in the wake measured or computed for successive phases of the cycle. Experimentally, the estimated lift hysteresis loops are compared with available data from the literature as well as with limited force balance measurements. Computationally, the estimated lift variations are compared with the corresponding variation obtained from the surface pressure distribution. Four analytical formulations for the lift estimation from wake surveys are considered and relative successes of the four are discussed

    Warm and dense stellar matter under strong magnetic fields

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    We investigate the effects of strong magnetic fields on the equation of state of warm stellar matter as it may occur in a protoneutron star. Both neutrino free and neutrino trapped matter at a fixed entropy per baryon are analyzed. A relativistic mean field nuclear model, including the possibility of hyperon formation, is considered. A density dependent magnetic field with the magnitude 101510^{15} G at the surface and not more than 3×10183\times 10^{18} G at the center is considered. The magnetic field gives rise to a neutrino suppression, mainly at low densities, in matter with trapped neutrinos. It is shown that an hybrid protoneutron star will not evolve to a low mass blackhole if the magnetic field is strong enough and the magnetic field does not decay. However, the decay of the magnetic field after cooling may give rise to the formation of a low mass blackhole.Comment: 17 pages, 10 figures, 3 tables, submitted to Phys. Rev.

    Spin Observables in Transition-Distribution-Amplitude Studies

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    Exclusive hadronic reactions with a massive lepton pair (l^+l^-) in the final state will be measured with PANDA at GSI-FAIR and with Compass at CERN, both in p+p-bar -> l^+l^-+pi and pi+N -> N'+l^+l^-. Similarly, electroproduction of a meson in the backward region will be studied at JLAB. We discuss here how the spin structure of the amplitude for such processes will enable us to disentangle various mechanisms. For instance, target-transverse-spin asymmetries are specific of a partonic description, where the amplitude is factorised in terms of baryon to meson or meson to baryon Transition Distribution Amplitudes (TDAs) as opposed to what is expected from baryon-exchange contributions.Comment: Contributed to the 19th International Spin Physics Symposium (SPIN 2010), September 27 - October 2, 2010, Juelich, Germany. 8 pages, 7 figures, uses jpconf.cls, jpconf11.clo, iopams.sty (included

    Phase Transition and Hybrid Star in a Nonlinear σ−ω\sigma - \omega model

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    The phase transition between the nuclear matter and the quark matter is examined. The relativistic mean field theory(RMF) is consider with interacting nucleons and mesons using TM1 parameter set for the nuclear matter equations of state. It is found that the trasition point depends on coupling constant αs\alpha_s and bag pressure. From the study of the structure of a hybrid neutron star, it is observed that the star contains quark matter in the interior and neutron matter on the outer perifery.Comment: 8 pages, 7 figures, to appear in Int. J. Mod. Phy.

    Self-consistent quantum effects in the quark meson coupling model

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    We derive the equation of state of nuclear matter including vacuum polarization effects arising from the nucleons and the sigma mesons in the quark-meson coupling model which incorporates explicitly quark degrees of freedom with quark coupled to the scalar and vector mesons. This leads to a softer equation of state for nuclear matter giving a lower value of incompressibility than would be reached without quantum effects. The {\it in-medium} nucleon and sigma meson masses are also calculated in a self-consistent manner.Comment: 10 pages, latex, 5 figure
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