Latest Results on g1g_1 and g2g_2 at high xx

Recent progress from Jefferson Lab has significantly improved our understanding of the nucleon spin structure in the high-$x$ region. Results of a precision measurement of the neutron spin asymmetry, $A_1^n$, in the high-$x$ (valence quark) region are discussed. The up and down quark spin distributions in the nucleon were extracted. $A_2^n$ was also measured. The results were used, in combination with existing data, to extract the second moment, $d_2^n$. Preliminary results on $A_1^p$ and $A_1^d$ in the high-$x$ region have also become available. Finally, the results of a precision measurement of the $g_2$ 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

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