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Sihai Zhou,Yun Zhang,Pan, A.V.,Shixue Dou,Koochae Chung,Jaimoo Yoo IEEE 2009 IEEE transactions on applied superconductivity Vol.19 No.3
<P>MgB<SUB>2</SUB> superconductors were made with two processes in this work. In one case, the SiC doped MgB<SUB>2</SUB> pellets were sintered in excessive Mg medium. It is found that the samples sintered in excessive Mg medium present Mg-rich composition comparing with the one sintered in Ar gas. The density is higher and the resistance is lower due to the penetration of the Mg into the pores and grain boundary of MgB<SUB>2</SUB>, which is beneficial to the J<SUB>c</SUB> improvement. In the other case, a two-step process was employed to make MgB<SUB>2</SUB>. J<SUB>c</SUB> of the sample with the composition of MgB<SUB>4</SUB> is very low after the first sintering. The J<SUB>c</SUB> was dramatically improved after the second sintering, but J<SUB>c</SUB> of the two-step made sample is still poorer than the MgB<SUB>2</SUB> made with general one step sintering due to the connectivity deterioration caused by the pulverization prior to the second sintering.</P>
Proportional-Fair Downlink Resource Allocation in OFDMA-Based Relay Networks
Liu, Chang,Qin, Xiaowei,Zhang, Sihai,Zhou, Wuyang The Korea Institute of Information and Commucation 2011 Journal of communications and networks Vol.13 No.6
In this paper, we consider resource allocation with proportional fairness in the downlink orthogonal frequency division multiple access relay networks, in which relay nodes operate in decode-and-forward mode. A joint optimization problem is formulated for relay selection, subcarrier assignment and power allocation. Since the formulated primal problem is nondeterministic polynomial time-complete, we make continuous relaxation and solve the dual problem by Lagrangian dual decomposition method. A near-optimal solution is obtained using Karush-Kuhn-Tucker conditions. Simulation results show that the proposed algorithm provides superior system throughput and much better fairness among users comparing with a heuristic algorithm.
Proportional-Fair Downlink Resource Allocation in OFDMA-Based Relay Networks
Chang Liu,Xiaowei Qin,Sihai Zhang,Wuyang Zhou 한국통신학회 2011 Journal of communications and networks Vol.13 No.6
In this paper, we consider resource allocation with proportional fairness in the downlink orthogonal frequency division multiple access relay networks, in which relay nodes operate in decode-and-forward mode. A joint optimization problem is formulated for relay selection, subcarrier assignment and power allocation. Since the formulated primal problem is nondeterministic polynomial time-complete, we make continuous relaxation and solve the dual problem by Lagrangian dual decomposition method. A near-optimal solution is obtained using Karush-Kuhn-Tucker conditions. Simulation results show that the proposed algorithm provides superior system throughput and much better fairness among users comparing with a heuristic algorithm.