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Three-phase dc/dc converters have the superior characteristics including lower current rating of switches, the reduced output filter requirement, and effective utilization of transformers. To further reduce the voltage stress on switches, three-phase three-level (TPTL) dc/dc converters have been investigated recently; however, numerous active power switches result in a complicated configuration in the available topologies. Therefore, a novel TPTL dc/dc converter adopting a symmetrical duty cycle control is proposed in this paper. Compared with the available TPTL converters, the proposed converter has fewer switches and simpler configuration. The voltage stress on all switches can be reduced to the half of the input voltage. Meanwhile, the ripple frequency of output current can be increased significantly, resulting in a reduced filter requirement. Experimental results from a 540-660-V input and 48-V/20-A output are presented to verify the theoretical analysis and the performance of the proposed converter.

The effect of hydrated alumina and triphenyl phosphate on the flame-retardance and thermal stability of the acid anhydride-cured epoxy resin was studied by thermogravimetry and limiting oxygen index determination. The results show that both the hydrated alumina and triphenyl phosphate act as flame-retardants for epoxy resin in gas phase and display condensed phase flame-retardant synergism when they are used together. However, they have little influence on the cured resin’s thermal stability.

In this paper, a low complexity adaptive EM-based channel estimation algorithm is proposed for Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems in slow time-varying frequency selective environment. The proposed algorithm was an adaptive channel estimation technique based on an expectation maximization (EM) algorithm for space-time block coded (STBC) MIMO OFDM systems. Simulation results show that in slow fading environment there was no degradation in normalized mean square error (MSE) as we increased the number of users. Comparing the Recursive Least-Squares(RLS) algorithm, the proposed algorithm exploits the structure of Alamouti STBC codes to reduce computational complexity.

In this paper, we propose a low complexity algorithm for channel estimation of Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems in slow time-varying frequency selective environment. The proposed algorithm was an adaptive channel estimation technique based on an expectation maximization (EM) algorithm for space-time block coded (STBC) MIMO OFDM systems. Simulation results show that in slow fading environment there was no degradation in normalized mean square error (MSE) as we increased the number of users. Comparing the Recursive Least-Squares (RLS) algorithm, the proposed algorithm exploits the structure of Alamouti STBC codes to reduce computational complexity.