171,356 research outputs found

    Effect of distribution of stickers along backbone on temperature-dependent structural properties in associative polymer solutions

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    Effect of distribution of stickers along the backbone on structural properties in associating polymer solutions is studied using self-consistent field lattice model. Only two inhomogeneous morphologies, i.e., microfluctuation homogenous (MFH) and micelle morphologies, are observed. If the system is cooled, the solvent content within the aggregates decreases. When the spacing of stickers along the backbone is increased the temperature-dependent range of aggregation in MFH morphology and half-width of specific heat peak for homogenous solutions-MFH transition increase, and the symmetry of the peak decreases. However, with increasing spacing of stickers, the above three corresponding quantities related to micelles behave differently. It is demonstrated that the broad nature of the observed transitions can be ascribed to the structural changes which accompany the replacement of solvents in aggregates by polymer, which is consistent with the experimental conclusion. It is found that different effect of spacing of stickers on the two transitions can be interpreted in terms of intrachain and interchain associations.Comment: 10 pages, 4 figures. arXiv admin note: text overlap with arXiv:1202.459

    Spectral Theory of Time Dispersive and Dissipative Systems

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    We study linear time dispersive and dissipative systems. Very often such systems are not conservative and the standard spectral theory can not be applied. We develop a mathematically consistent framework allowing (i) to constructively determine if a given time dispersive system can be extended to a conservative one; (ii) to construct that very conservative system -- which we show is essentially unique. We illustrate the method by applying it to the spectral analysis of time dispersive dielectrics and the damped oscillator with retarded friction. In particular, we obtain a conservative extension of the Maxwell equations which is equivalent to the original Maxwell equations for a dispersive and lossy dielectric medium.Comment: LaTeX, 57 Pages, incorporated revisions corresponding with published versio

    Measurement and Analysis of Multiband Bistatic and Monostatic Radar Signatures of Wind Turbines

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    This paper presents the results of recent measurements taken with two radar systems to measure the simultaneous monostatic and bistatic signature of wind turbines, at S-band and X-band. Coherent monostatic and bistatic data was collected with the University College London (UCL) NetRAD 2.4 GHz radar, and the Cranfield University CW radar operating at X-band. This initial analysis shows the bistatic Doppler signature of wind turbines and informs on the key differences seen at modest bistatic angles. Polarimetric variations are also analysed via data gathered using co-polarised VV and HH and cross-polarised VH components

    Parton Distributions at Hadronization from Bulk Dense Matter Produced at RHIC

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    We present an analysis of Ω\Omega, Ξ\Xi, Λ\Lambda and ϕ\phi spectra from Au+Au collisions at sNN=200\sqrt{s_{NN}}=200 GeV in terms of distributions of effective constituent quarks at hadronization. Consistency in quark ratios derived from various hadron spectra provides clear evidence for hadron formation dynamics as suggested by quark coalescence or recombination models. We argue that the constituent quark distribution reflects properties of the effective partonic degrees of freedom at hadronization. Experimental data indicate that strange quarks have a transverse momentum distribution flatter than that of up/down quarks consistent with hydrodynamic expansion in partonic phase prior to hadronization. After the AMPT model is tuned to reproduce the strange and up/down quark distributions, the model can describe the measured spectra of hyperons and ϕ\phi mesons very well where hadrons are formed through dynamical coalescence.Comment: 5 pages, 3 figures, two more paragraph added to address the referee's comment, figure updated to include the KET scale. Accepted version to appear in Phys. Rev.

    Dynamic Transitions for Quasilinear Systems and Cahn-Hilliard equation with Onsager mobility

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    The main objectives of this article are two-fold. First, we study the effect of the nonlinear Onsager mobility on the phase transition and on the well-posedness of the Cahn-Hilliard equation modeling a binary system. It is shown in particular that the dynamic transition is essentially independent of the nonlinearity of the Onsager mobility. However, the nonlinearity of the mobility does cause substantial technical difficulty for the well-posedness and for carrying out the dynamic transition analysis. For this reason, as a second objective, we introduce a systematic approach to deal with phase transition problems modeled by quasilinear partial differential equation, following the ideas of the dynamic transition theory developed recently by Ma and Wang

    Extended Hylleraas three-electron integral

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    A closed form expression for the three-electron Hylleraas integral involving the inverse quadratic power of one inter-particle coordinate is obtained, and recursion relations are derived for positive powers of other coordinates. This result is suited for high precision calculations of relativistic effects in lithium and light lithium-like ions.Comment: Submited to Phys. Rev.

    Preserving Our Collective Memory: The Case of HK Magazine

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    Founded in 1991, HK Magazine was one of the major English-language publications on local affairs, social issues and entertainment listings published weekly in Hong Kong for a quarter of a century. Apart from providing local entertainment information, it also witnessed the rapid social and political changes of Hong Kong when Britain handed over sovereignty of Hong Kong to China in 1997. In July 2013, HK Magazine was sold to the South China Morning Post (SCMP) Group which was subsequently purchased by Alibaba Group in December 2015. However, the SCMP Group announced on 28 September 2016 that the magazine's final issue would be released on 7 October 2016. The closure of the magazine was viewed by many as the loss of a “fun, independent and free-thinking' publication. In response to the huge reaction from the community, the SCMP Group agreed that the content of HK Magazine would be migrated to the SCMP website before the HK Magazine website was removed. It was however revealed that the SCMP website did not preserve the full archive of HK Magazine as promised. A public appeal was launched to help preserve the collective memory of Hong Kong by archiving the back issues of the magazine. Apart from reviewing the discussion arising from the close down of HK Magazine, this paper also addresses the critical role of the library in long term preserving HK Magazine on one hand and providing access to its digital content on the other
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