52,028 research outputs found

    Latest Results on g1g_1 and g2g_2 at high xx

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    Recent progress from Jefferson Lab has significantly improved our understanding of the nucleon spin structure in the high-xx region. Results of a precision measurement of the neutron spin asymmetry, A1nA_1^n, in the high-xx (valence quark) region are discussed. The up and down quark spin distributions in the nucleon were extracted. A2nA_2^n was also measured. The results were used, in combination with existing data, to extract the second moment, d2nd_2^n. Preliminary results on A1pA_1^p and A1dA_1^d in the high-xx region have also become available. Finally, the results of a precision measurement of the g2g_2 structure function to study higher twist effects will be presented.Comment: 4 pages, 2 figures, to appear in the DIS2005 Proceedings (AIP

    Optimal Power Allocation for A Massive MIMO Relay Aided Secure Communication

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    In this paper, we address the problem of optimal power allocation at the relay in two-hop secure communications under practical conditions. To guarantee secure communication during the long-distance transmission, the massive MIMO (M-MIMO) relaying techniques are explored to significantly enhance wireless security. The focus of this paper is on the analysis and design of optimal power assignment for a decode-and-forward (DF) M-MIMO relay, so as to maximize the secrecy outage capacity and minimize the interception probability, respectively. Our study reveals the condition for a nonnegative the secrecy outage capacity, obtains closed-form expressions for optimal power, and presents the asymptotic characteristics of secrecy performance. Finally, simulation results validate the effectiveness of the proposed schemes