22,022 research outputs found

    Fluctuations in Shear-Jammed States: A Statistical Ensemble Approach

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    Granular matter exists out of thermal equilibrium, i.e. it is athermal. While conventional equilibrium statistical mechanics is not useful for characterizing granular materials, the idea of constructing a statistical ensemble analogous to its equilibrium counterpart to describe static granular matter was proposed by Edwards and Oakshott more than two decades ago. Recent years have seen several implementations of this idea. One of these is the stress ensemble, which is based on properties of the force moment tensor, and applies to frictional and frictionless grains. We demonstrate the full utility of this statistical framework in shear jammed (SJ) experimental states [1,2], a special class of granular solids created by pure shear, which is a strictly non-equilbrium protocol for creating solids. We demonstrate that the stress ensemble provides an excellent quantitative description of fluctuations in experimental SJ states. We show that the stress fluctuations are controlled by a single tensorial quantity: the angoricity of the system, which is a direct analog of the thermodynamic temperature. SJ states exhibit significant correlations in local stresses and are thus inherently different from density-driven, isotropically jammed (IJ) states.Comment: 6 pages, 4 figure

    Asteroseismic analysis of solar-mass subgiants KIC 6442183 and KIC 11137075 observed by Kepler

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    Asteroseismology provides a powerful way to constrain stellar parameters. Solar-like oscillations have been observed on subgiant stars with the \emph{Kepler\/} mission. The continuous and high-precision time series enables us to carry out a detailed asteroseismic study for these stars. We carry out data processing of two subgiants of spectral type G: KIC 6442183 and KIC 11137075 observed with the \emph{Kepler} mission, and perform seismic analysis for the two evolved stars. We estimate the values of global asteroseismic parameters: Δν=64.9±0.2\Delta\nu=64.9\pm 0.2 μ\muHz and νmax=1225±17\nu_{\rm max}=1225 \pm 17 μ\muHz for KIC 6442183, Δν=65.5±0.2\Delta\nu=65.5\pm 0.2 μ\muHz and νmax=1171±8\nu_{\rm max}=1171 \pm 8 μ\muHz for KIC 11137075, respectively. In addition, we extract the individual mode frequencies of the two stars. We compare stellar models and observations, including mode frequencies and mode inertias. The mode inertias of mixed modes, which are sensitive to the stellar interior, are used to constrain stellar models. We define a quantity dνmpd\nu_{\rm m-p} that measures the difference between the mixed modes and the expected pure pressure modes, which is related to the inertia ratio of mixed modes to radial modes. Asteroseismic together with spectroscopic constraints provide the estimations of the stellar parameters: M=1.040.04+0.01MM = 1.04_{-0.04}^{+0.01} M_{\odot}, R=1.660.02+0.01RR = 1.66_{-0.02}^{+0.01} R_{\odot} and t=8.650.06+1.12t=8.65_{-0.06}^{+1.12} Gyr for KIC 6442183, and M=1.000.01+0.01MM = 1.00_{-0.01}^{+0.01} M_{\odot}, R=1.630.01+0.01RR = 1.63_{-0.01}^{+0.01} R_{\odot} and t=10.360.20+0.01t=10.36_{-0.20}^{+0.01} Gyr for KIC 11137075. Either mode inertias or dνmpd\nu_{\rm m-p} could be used to constrain stellar models.Comment: 9 pages, 8 figures, 5 tables A&A accepte

    The tyrosine kinase and mitogen-activated protein kinase pathways mediate multiple effects of estrogen in hippocampus

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    Shear-induced rigidity of frictional particles: Analysis of emergent order in stress space

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    Solids are distinguished from fluids by their ability to resist shear. In traditional solids, the resistance to shear is associated with the emergence of broken translational symmetry as exhibited by a non-uniform density pattern, which results from either minimizing the energy cost or maximizing the entropy or both. In this work, we focus on a class of systems, where this paradigm is challenged. We show that shear-driven jamming in dry granular materials is a collective process controlled solely by the constraints of mechanical equilibrium. We argue that these constraints lead to a broken translational symmetry in a dual space that encodes the statistics of contact forces and the topology of the contact network. The shear-jamming transition is marked by the appearance of this broken symmetry. We extend our earlier work, by comparing and contrasting real space measures of rheology with those obtained from the dual space. We investigate the structure and behavior of the dual space as the system evolves through the rigidity transition in two different shear protocols. We analyze the robustness of the shear-jamming scenario with respect to protocol and packing fraction, and demonstrate that it is possible to define a protocol-independent order parameter in this dual space, which signals the onset of rigidity.Comment: 14 pages, 17 figure

    Reputation-based network selection solution in heterogeneous wireless network environments

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    The significant developments in terms of both mobile computing device (e.g., smartphones, tablets, laptops, etc.) and the wireless communication technologies (e.g., LTE, LTE-Advanced, WiMAX, etc.), lead towards a converged heterogeneous wireless environment. In this context, the user will be facing the problem of selecting from a number of Radio Access Networks that differ in technology, coverage, pricing scheme, bandwidth, latency, etc. In order to provide high quality of service (QoS) to the user in this heterogeneous wireless environment, a network selection solution is required that will efficiently facilitate the vertical handover between different wireless access networks in a seamless manner. In this paper, we propose a reputation-based network selection solution which aims to select the best value network for the user. We propose a network profiling algorithm that used to compute the reputation of each of the available networks based on the joint collaboration of the users within the network. The network with the best reputation value is recommended for selection and handover
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